Opponent color cells in the cat lateral geniculate nucleus

A microelectrode survey of the cat lateral geniculate has uncovered an infrequent new type of lateral geniculate cell in layer B with "on" center responses to short wavelengths and "off" center responses to long wavelengths. The short wavelength responses are mediated by cones with peak sensitivity at about 450 nanometers, and the long wavelength responses by cones with peak sensitivity at 556 nanometers. Two of double opponent color cells also had double opponent features.     

Microspectrophotometry of photoreceptor organelles from eyes of the prawn Palaemonetes

Microspectrophotometric measurements of individual dark-adapted rhabdoms of the prawn Palaemonetes vulgaris reveal the presence of two light-sensitive pigments. A pigment with maximum absorbancy at 555 nanometers is converted by light to a long-lived intermediate with wavelength of maximum absorbancy at 496 nanometers. A second pigment with wavelength of maximum absorbancy at 496 nanometers bleaches in the light, seemingly without forming detectable products at wavelengths longer than 375 nanometers. Both pigments occur in each layer of microvilli.     

Prolonged color blindness induced by intense spectral lights in rhesus monkeys

Prolonged exposure of rhesus monkeys to intense blue light produces long-term changes which are consistent with loss of response of those cones that contain a photopigment with peak absorption at 445 nanometers. The 90 percent reduction of spectral sensitivity in the blue region has lasted more than 5 months. Reduced sensitivity to long wavelengths is produced by adaptation to light of 520 nanometers. This reduced sensitivity, which lasts no more than 30 days, is attributed to a temporary loss of response of the cones containing a photopigment with peak absorption at 535 nanometers.     

Evidence for large upward trends of ultraviolet-B radiation linked to ozone depletion

Spectral measurements of ultraviolet-B radiation made at Toronto since 1989 indicate that the intensity of light at wavelengths near 300 nanometers has increased by 35 percent per year in winter and 7 percent per year in summer. The wavelength dependence of these trends indicates that the increase is caused by the downward trend in total ozone that was measured at Toronto during the same period. The trend at wavelengths between 320 and 325 nanometers is essentially zero.     

Direct observation of the femtosecond excited-state cis-trans isomerization in bacteriorhodopsin

Femtosecond optical measurement techniques have been used to study the primary photoprocesses in the light-driven transmembrane proton pump bacteriorhodopsin. Light-adapted bacteriorhodopsin was excited with a 60-femtosecond pump pulse at 618 nanometers, and the transient absorption spectra from 560 to 710 nanometers were recorded from -50 to 1000 femtoseconds by means of 6-femtosecond probe pulses. By 60 femtoseconds, a broad transient hole appeared in the absorption spectrum whose amplitude remained constant for about 200 femtoseconds. Stimulated emission in the 660- to 710-nanometer region and excited-state absorption in the 560- to 580-nanometer region appeared promptly and then shifted and decayed from 0 to approximately 150 femtoseconds. These spectral features provide a direct observation of the 13-trans to 13-cis torsional isomerization of the retinal chromophore on the excited-state potential surface. Absorption due to the primary ground-state photoproduct J appears with a time constant of approximately 500 femtoseconds.     

Ecosystem response to solar ultraviolet-B radiation: influence of trophic-level interactions

Solar ultraviolet radiation (UVR) can reduce the photosynthesis and growth of benthic diatom communities in shallow freshwater. Nevertheless, greater amounts of algae accumulate in UVR-exposed habitats than in UVR-protected environments. Near-ultraviolet (UVA wavelengths of 320 to 400 nanometers) and mid-ultraviolet (UVB, wavelengths of 280 to 320 nanometers) radiation also inhibit algal consumers (Diptera: Chironomidae). Larval chironomids are more sensitive to UVB than sympatric algae. Differential sensitivity to UVB between algae and herbivores contributes to counterintuitive increases in algae in habitats exposed to UVB. These mesocosm experiments illustrate that predictions of the response of entire ecosystems to elevated UVB cannot be made on single trophic-level assessments.     

The ultraviolet receptor of bird retinas

The eyes of 15 species of birds from 10 families have some cones maximally sensitive at 370 nanometers in the near-ultraviolet. Spectral sensitivity was measured by recording extracellularly in opened eyecups , and a maximum in the ultraviolet was revealed by selectively adapting the retina with yellow background lights. The 370-nanometer spectral sensitivity function is attributed to receptors because its spectral position does not vary with the strength of adaptation and because it is present when the receptor potentials are isolated from the contributions of higher order retinal neurons by exposing the retina to sodium aspartate. These measurements demonstrate the basis for the ultraviolet sensitivity of birds that has been seen in behavioral experiments, and they provide further evidence that many vertebrates share with insects vision in the near-ultraviolet.     

Multichannel detection in high-performance liquid chromatography

A linear photodiode array has been used as the photodetector element in a new ultraviolet-visible detection system for high-performance liquid chromatography. This array allows simultaneous acquisition of light intensity data at all wavelengths between 190 and 600 nanometers. By use of a computer network concept in the electronics, this detection system can process eight different chromatographic signals simultaneously in real time and acquire spectra manually or automatically. Detector response times are variable and can be as low as 0.040 second, and bandwidth selection is variable from 4 to 400 nanometers. These characteristics permit fast chromatographic techniques and user-selectable signal-to-noise ratio enhancement. Spectra can be acquired in 10 milliseconds, permitting qualitative characterization at several different points on a single peak without destroying chromatographic signal integrity. Examples illustrate applications in fast high-performance liquid chromatography peak purity determination, and postanalysis data reduction.     

Far red bioluminescence from two deep-sea fishes

Spectral measurements of red bioluminescence were obtained from the deep-sea stomiatoid fishes Aristostomias scintillans (Gilbert) and Malacosteus niger (Ayres). Red luminescence from suborbital light organs extends to the near infrared, with peak emission at approximately 705 nanometers in the far red. These fishes also have postorbital light organs that emit blue luminescence with maxima between 470 and 480 nanometers. The red bioluminescence may be due to an energy transfer system and wavelength-selective filtering.     

Photoactivated fluorescence from individual silver nanoclusters

Fluorescence microscopy of nanoscale silver oxide (Ag2O) reveals strong photoactivated emission for excitation wavelengths shorter than 520 nanometers. Although blinking and characteristic emission patterns demonstrate single-nanoparticle observation, large-scale dynamic color changes were also observed, even from the same nanoparticle. Identical behavior was observed in oxidized thin silver films that enable Ag2O particles to grow at high density from silver islands. Data were readily written to these films with blue excitation; stored data could be nondestructively read with the strong red fluorescence resulting from green (wavelengths longer than 520 nanometers) excitation. The individual luminescent species are thought to be silver nanoclusters that are photochemically generated from the oxide.     

分光光度法测定小球藻数量的方法研究

[目的]确定用分光光度法测定小球藻藻液浓度的适宜波长。[方法]在不同波长下对不同浓度普通小球藻藻液的吸光度进行测定,对有关数据进行生物统计分析。[结果]在8．7×10^6～8．7×10^8个／ml的浓度范围内,小球藻藻液的最大吸收波长在680nm左右,较高浓度小球藻藻液的吸光度超出了测定范围。显著性测验表明,9种波长下小球藻藻液浓度与藻液吸光度呈极显著直线相关。680nm波长下的测定灵敏度最高,其最高藻液浓度最低,为3．79×10^8个／ml;700nm波长下的测定灵敏度最低,其最高藻液浓度最高,为7．7×10^8个／ml;560nm波长下的测定灵敏度仅高于700nm波长下的,其最高藻液浓度为6．9×10^8个／ml;540nm波长下的测定灵敏度高于560nm波长下的,其最高藻液浓度为6．5×10^8个／ml。[结论]在680nm波长下测定小球藻藻液浓度,其灵敏度高、数据更精确。     

Unusual retinal cells in the dolphin eye

By comparison to the cellular constituents of the retinas of certain other diving mammals, the elements of the dolphin retina include an unusually large number of specialized cells. Both cone and rod receptors may be identified. An unusual amacrine cell may be seen which produces a process that spans the cells between the inner plexiform and outer plexiform layers. Most unusual is a layer of giant ganglion cells which appears to serve most of the central retina. The giant ganglion cells support giant dendrites and optic nerve fibers which range up to 8 micrometers in diameter.     

Hydroxyl radical photoproduction in the sea and its potential impact on marine processes

Photochemical production rates and steady-state concentrations of hydroxyl radicals (.OH) were measured in sunlight-irradiated seawater. Values ranged from 110 nanomolar per hour and 12 x 10(-18) molar in coastal surface water to 10 nanomolar per hour and 1.1 x 10(-18) molar in open ocean surface water. The wavelengths responsible for this production are in the ultraviolet B region (280 to 320 nanometers) of the solar spectrum. Dissolved organic matter (DOM) appears to be the main source for .OH over most of the oceans, but in upwelling areas nitrite and nitrate photolysis may also be important. DOM in the deep sea is degraded more readily by .OH (and its daughter radicals), by a factor of 6 to 15, than is DOM in open-ocean surface water. This finding may in part bear on major discrepancies among current methods for measuring dissolved organic carbon in seawater.     

Excited singlet absorption in 1,2-benzanthracene by the use of nanosecond laser photolysis and spectroscopy

Using the technique of laser photolysis and spectroscopy, we have observed excited singlet state absorption bands in 1,2-benzanthracene at 560 and 520 nanometers. The bands decay in less than 50 nanoseconds and are replaced by the known absorption spectrum of the lowest triplet state.     

Exponential gain and saturation of a self-amplified spontaneous emission free-electron laser

Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent x-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational x-ray free-electron laser.     

3种扁谷盗对不同波长光趋性研究

【目的】研究锈赤扁谷盗Cryptolestes ferrugineus成虫、土耳其扁谷盗Cryptolestes turcicus和长角扁谷盗Cryptolestes pusillus雌成虫对不同波长光的趋性。【方法】室内应用光行为反应装置测试3种扁谷盗羽化1、11、21和31日龄(雌)成虫对试验波长303、320、330、340、351、368、400、445、460、480、520、525、545、560、575和580 nm的趋光率。【结果】锈赤扁谷盗羽化1、11、21和31日龄成虫趋光率最高的刺激光波长分别为351、351、400、480 nm,对锈赤扁谷盗成虫诱集效果较好的光波长有351、400和445 nm,随着日龄的增加,对锈赤扁谷盗成虫诱集率大于20%的光波数增加;土耳其扁谷盗羽化1、11、21和31日龄趋光率分别为16%~51%、11%~46%、7%~37%和4%~28%,雌成虫趋光率最高的刺激光波长分别为351(368)、368、330和351 nm,对土耳其扁谷盗雌成虫诱集效果较好的光波长有368、351和303 nm;长角扁谷盗羽化1、11、21和31日龄趋光率分别为1.11%~75.56%、18.89%~70.00%、33.33%~62.22%和22.22%~71.11%,雌成虫趋光率最高的刺激光波长分别为575、320、400(445)和320(560)nm,对长角扁谷盗雌成虫诱集效果较好的光波长有320、575和330 nm。【结论】锈赤扁谷盗成虫的趋光性随着日龄的增加而增强,土耳其扁谷盗雌成虫的趋光性随着日龄的增加而下降,长角扁谷盗雌成虫的趋光性随着日龄的增加略为下降。     

Oxygen isotopes in biogenic silica: global changes in ocean temperature and isotopic composition

A record of oxygen isotopes in biogenic silica from a deep-sea sediment core from the Southern Ocean reveals that marine diatoms retain their primary isotopic composition after burial. As a result, the marine diatom record can be combined with data on coexisting planktonic foraminifera to monitor past surface temperature and isotopic composition of seawater. The coupling of these two records allows the solution of two paleotemperature equations for each core interval. Data from a South Atlantic core show that the average delta(18)O during the glacial period at this site was higher by about 1.3 per mil than average Holocene values, and that average glacial-age temperatures were not significantly different from average Holocene values.     

Identification of specific transducin alpha subunits in retinal rod and cone photoreceptors

Transducin is a guanyl nucleotide-binding protein that couples rhodopsin photolysis to hydrolysis of guanosine 3',5'-monophosphate in rod photoreceptor cells of vertebrate retinas. Several complementary DNA clones encoding transducin subunits have recently been characterized. One clone, isolated from a bovine retina complementary DNA library, encodes a previously unidentified polypeptide with an amino acid sequence 78% identical to the sequence of the alpha subunit of bovine rod outer segment transducin. Antibodies to a synthetic peptide with amino acid sequence derived specifically from this novel polypeptide recognize a 41-kilodalton polypeptide in homogenates of bovine retina. Localization of this polypeptide in bovine retina by indirect immunofluorescence demonstrates that it is expressed only in cone outer segments. Antibodies to specific sequences found only in the rod transducin alpha subunit recognize a polypeptide localized only in the rod outer segment. Therefore, bovine rod and cone cells each express structurally related yet significantly different forms of transducin.     

Photo-tautomerization of acetaldehyde to vinyl alcohol: a potential route to tropospheric acids

Current atmospheric models underestimate the production of organic acids in the troposphere. We report a detailed kinetic model of the photochemistry of acetaldehyde (ethanal) under tropospheric conditions. The rate constants are benchmarked to collision-free experiments, where extensive photo-isomerization is observed upon irradiation with actinic ultraviolet radiation (310 to 330 nanometers). The model quantitatively reproduces the experiments and shows unequivocally that keto-enol photo-tautomerization, forming vinyl alcohol (ethenol), is the crucial first step. When collisions at atmospheric pressure are included, the model quantitatively reproduces previously reported quantum yields for photodissociation at all pressures and wavelengths. The model also predicts that 21 ± 4% of the initially excited acetaldehyde forms stable vinyl alcohol, a known precursor to organic acid formation, which may help to account for the production of organic acids in the troposphere.