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The libRadtran radiative transfer model was used to calculate examples of the amount of spectral radiation (250-2500 nm) incident on the eye. Simulations were run for every hour of four individual days (representing spring, summer, autumn and winter) and at three latitudes (from southern Spain to central Finland), in order to demonstrate diurnal and sea-sonal variations in directional photon flux density due to solar angle. The dataset also includes outputs under strong and weak aerosol optical density, three bidirectional re-flectance distribution functions (corresponding to a forested, urban and snowy ground surfaces), eight cardinal directions, and two tilt angles (either looking towards the horizon or 15 degrees downward). All simulations were parametrized accord-ing to local meteorological conditions (elevation, pressure, temperature) and atmospheric condition on the simulated day (aerosol optical density, water column, O 3 and NO2 con-centrations), at 170 cm above the ground (representing the average human height). Example data are presented for a 17 degrees field of view relevant to exposure of the macula (with-out correction for spectral transmission of ocular media). For each simulation, a file in ".csv" format is available contain-ing the radiance at each wavelength. The simulations were performed in batches via R software, from a template input parameter file modified for each simulation from a summary input table. The R code and input files are also available. By describing the amount and wavelength composition of direc-tional radiation incident on the eye, this dataset and future simulations will help parameterize research aimed at under-standing and mitigating eye-related diseases.(c) 2023 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)

Birds and reptiles typically have five spectral types of visual pigment: the rod pigment, plus four cone pigments, which probably gives them tetrachromatic color vision. This system, which was inherited from ancestral vertebrates, can vary under natural selection. Most obvious is the loss of visual pigments in nocturnal lineages including mammals. This review focuses on lineages that retain the ‘tetrachromatic’ retina. Here, photoreceptor spectral sensitivities and the relative numbers of different photoreceptor types can vary, as can the pigmented oil droplets that narrow cone spectral sensitivities to enhance color discrimination at the expense of absolute sensitivity. One can ask how color vision evolves to suit an animal’s ecology and behaviour. A key question is whether variation is attributable to the overall illumination intensity, the spectral composition of the illumination or to the reflectance spectra of objects of interest, such as the colorful communication signals of fruit, flowers and other animals. Overall the picture is of limited variation, which suggests that a common retinal bauplan is well adapted for color vision of diurnal vertebrates in terrestrial environments, while the selection due species-specific uses of color is comparatively weak.

Modern lifestyle is characterized by constant exposure to artificial light, which is associated with alterations in biological rhythms, abnormalities to reproductive cycles and metabolic changes. In this study, we aimed to evaluate the effects of four different lighting patterns on puberty timing and on possible metabolic changes in female Wistar rats. Additionally, we developed a machine learning algorithm to automatically classify the stages of the estrous cycle. Adult Wistar rats mated during a week at a photoperiod station where they were exposed to combined red-green-blue lights (RGB) during the photoperiod that varied its spectral composition (i.e., variable color temperature) during the day (RGB-v; N = 14), RGB during the photoperiod with a fixed light color temperature (RGB-f; N = 13) during the whole photoperiod; constant darkness (DD; N = 13) and constant fixed light (LL; N = 15). Experiments were performed only on female litters from postnatal day (PND) 22 to 50. Body weight, puberty onset, estrous cyclicity and serum metabolic parameters were measured. We also collected pictures of vaginal smears to create a dataset of 15,936 images to construct an automatic classifier based on convolutional neural networks. No significant differences were found in the age of vaginal opening; however, the RGB-v group showed a significantly lower number of complete and consecutives cycles. Also, the RGB-f group showed the first complete estrous cycle significantly earlier than the RGB-v group. Female rats housed in LL condition presented significantly lower mean body weight from PND 33 to PDN 47 compared to the other groups. Furthermore, higher levels of plasma triglycerides were found in the DD group compared to RGB-f and RGB-v. HDL levels were significantly lower in RGB-v compared to RGB-f and LL groups. Total cholesterol was significantly lower in RGB-v compared to all groups. Visceral fat was significantly higher in RGB-f compared to the LL group. These results suggest that both changes in photoperiod and lighting quality affect pubertal development and alter lipid profiles and visceral fat accumulation.

Artificial light at night (ALAN) is increasingly recognised as a major threat to conservation, causing physiological and behavioural impacts on species adapted to a predictable day-night cycle, including the disruption of reproductive processes. This study investigates the influence of spectral composition of ALAN on Amphiprion ocellaris reproductive success. We compared spawning frequency, clutch size, embryo quality and hatching success of A. ocellaris exposed to ALAN with warm-white and cool-white spectra to fish held in control (12 h day: 12 h night) conditions. The presence of ALAN, regardless of light colour treatment, increased the interval (number of days) between spawning events, and eggs developing under ALAN were smaller than eggs developing under control conditions. Hatching success was influenced by both the presence of ALAN and spectral composition of the light, with fewer embryos hatching under cool-white light compared to warm-white light treatments. As light pollution continues to spread, more research is needed to understand the extent of the impacts of ALAN on marine organisms and to identify effective management strategies.

In broadband light, longitudinal chromatic aberration (LCA) provides emmetropization signals from both wavelength defocus and the resulting chromatic cues. Indoor illuminants vary in their spectral output, potentially limiting the signals from LCA. Our aim is to investigate the effect that artificial illuminants with different spectral outputs have on chick emmetropization with and without low temporal frequency modulation. In Experiment 1, two-week-old chicks were exposed to 0.2 Hz, square-wave luminance modulation for 3 days. There were 4 spectral conditions: LED strips that simulated General Electric (GE) LED "Soft" (n = 13), GE LED "Daylight" (n = 12), a novel "Equal" condition (n = 12), and a novel "High S" condition (n = 10). These conditions were all tested at a mean level of 985 lux. In Experiment 2, the effect of intensity on the "Equal" condition was tested at two other light levels (70 lux: n = 10; 680 lux: n = 7). In Experiment 3, the effect of temporal modulation on the "Equal" condition was tested by comparing the 0.2 Hz condition with 0 Hz (steady). Significant differences were found in axial growth across lighting conditions. At 985 lux, birds exposed to the "Equal" condition showed a greater reduction in axial growth (both p 0.01) and a greater hyperopic shift compared to "Soft" and "Daylight" (both p 0.01). The "High S" birds experienced more axial growth compared to "Equal" (p 0.01) but less than in "Soft" and "Daylight" (p 0.01). Axial changes in "Equal" were only observed at 985 lux with 0.2 Hz temporal modulation, and not with lower light levels or steady light. We conclude that axial growth and refraction were dependent on the lighting condition in a manner predicted by wavelength defocus signals arising from LCA.

Since the discovery of non-visual effect of light, consequences on human psychology and physiology have been investigated; however, effects on cognition of exposure to different spectral composition have been partially explored. Aim of this paper is an overview on researches developed in this field to compare general approaches and measurements protocols: the scarce knowledge of the physiological mechanisms, as well as the lack of shared methods, techniques, tools and procedures represent the weak point of this research. The impact of different procedures and experimental settings on results is shown, evidencing the need for scientifically consistent and internationally agreed procedures.

Communication plays a central role in the behavioral ecology of many animals, yet the background noise generated by large breeding aggregations may impair effective communication. A common behavioral strategy to ameliorate noise interference is gap detection, where signalers display primarily during lulls in the background noise. When attempting gap detection, signalers have to deal with the fact that the spacing and duration of silent gaps is often unpredictable, and that noise varies in its spectral composition and may thus vary in the degree in which it impacts communication. I conducted playback experiments to examine how male treefrogs deal with the problem that refraining from calling while waiting for a gap to appear limits a male's ability to attract females, yet producing calls during noise also interferes with effective sexual communication. I found that the temporal structure of noise (i.e., duration of noise and silent gap segments) had a stronger effect on male calling behavior than the spectral composition. Males placed calls predominantly during silent gaps and avoided call production during short, but not long, noise segments. This suggests that male treefrogs use a calling strategy that maximizes the production of calls without interference, yet allows for calling to persist if lulls in the background noise are infrequent.

Two simultaneously excited fireballs in front of two positively biased electrodes immersed in plasma were investigated by emission spectroscopy under different experimental conditions (gas and pressure, plasma density). Experimental results were obtained regarding the spectral composition of the light emitted by the fireballs, the influence of the appearance of the second fireball on the spectrum of the light emitted by the first fireball, the electron temperature and density, as well as on the elementary processes involved in the appearance and dynamics of the fireballs.

With their good energy efficiency and characteristics that allow the adjustment of light intensity and spectral composition, light emitting diodes (LEDs) have opened up new research prospects for nutrition supply, pollution control as well as energy conversion and conservation. The potentials of LED as an effective light source for studies conducted in aquatic environment such as disinfection, fish behavior, biomass production, and photocatalyst activation have been explored to a greater extent since 1980׳s. As the third paper of a series that reviews LEDs׳ applications in scientific researches, this work concentrates in the researches on red, yellow, green, blue, and ultraviolet LEDs׳ applications published since mid-1990. The review is composed to demonstrate that LEDs are well qualified to succeed its more energy demanding counterparts in the research performed in aquatic environment. In addition, the authors have compiled a table that includes the findings covered in their previous works, which list some common types of LEDs and their respective usages in scientific researches.

Ensemble empirical mode decomposition (EEMD) is investigated to decompose the impact echo (IE) testing data into different spectral composition for defect signal extraction. The effects of critical EEMD parameters are studied. As IE signals have strong surface waves with wide bandwidth, the amplitude of the added white noise is larger than that normally used for other applications to successfully decompose all interested modes. The number of ensemble trials increases with increasing noise amplitude. The influence of the frequency of the signal to be extracted on the EEMD performance is also analyzed. The results show that the high frequency resonance mode is easier to be extracted than the low frequency resonance mode from the IE signal. The effectiveness of the EEMD method for IE signal decomposition is demonstrated using both numerical simulations and experimental tests.

The main parameters of the ion-photon emission (IPE) arising from the bombardment of yttrium–iron garnets (YIG) samples with Ar + -ions were studied. The essential difference in the spectral composition, quantum yield of emissions, and spatial distribution of radiation registered from YIG to that from samples of pure metal iron was determined. Such difference in parameters of IPE is due to contribution of new mechanisms of formation of excited particles leaving the sample during ion bombardment YIG compared with emission from a metal. It was suggested the excited atoms are formed during the decay of Me m O n complexes ejected from solids.

SummaryMigrating monarch butterflies (Danaus plexippus) use a time-compensated sun compass to navigate from eastern North America to their overwintering grounds in central Mexico. Here we describe the neuronal layout of those aspects of the butterfly's central complex likely to establish part of the internal sun compass and find them highly homologous to those of the desert locust. Intracellular recordings from neurons in the monarch sun compass network reveal responses tuned to specific E-vector angles of polarized light, as well as azimuth-dependent responses to unpolarized light, independent of spectral composition. The neural responses to these two stimuli in individual neurons are mediated through different regions of the compound eye. Moreover, these dual responses are integrated to create a consistent representation of skylight cues in the sun compass throughout the day. The results advance our understanding of how ambiguous sensory signals are processed by the brain to elicit a robust behavioral response.Video Abstract

The transformation of natural tidal sea-level and currents is studied resulting from large-scale tidal power plant (TPP) dams in bays of the Sea of Okhotsk (SO). Some effects due to this transformation are estimated based on predictive modelling and a number of expected changes in amplitudes and phases, and spectral composition of tidal oscillations are described. Changes of morphometric properties of basins change the character of tidal motions even on significant distance from a dam. That is why, it is impossible to estimate this impact as usual boundary-value problems. The problem is solved based on “impedance” conditions on the open boundary of the model area, allowing to take into account the radiation of the additional perturbations induced by both waves reflected from the dam and nonlinear effects inside the area. In general, the transformation effects are proportional to the dam size and depend essentially on the dam location, the creation of which can change dissipative and resonance properties of the bays. The changes in tidal energetics of SO due to the dam construction are also considered to show noticeable reconstruction of horizontal energy fluxes and changes in the energy dissipation. Possible environmental consequences are related mainly to the transformation of tidal currents.

Free oscillations in the period range from 9 to 40 h and their corresponding adjoint solutions are used to synthesize semidiurnal and diurnal tides of second degree. The free oscillations are determined with explicit consideration of frictional terms and the full loading and self-attraction effect. This allows for a detailed analysis of the loading and self-attraction effect on the dynamics of ocean tides, e.g. a physical explanation is given for the induced phase delay computed by ocean tide models. Further, the synthesis gives a spectral composition of certain well known tidal features and pairs of free oscillations are identified, diminishing their contribution either on a global or local scale.

We investigated the effects of overlap between the advertisement calls of two closely related and often-sympatric species of grey treefrogs on female phonotactic behaviour and signal selectivity. The tetraploid H. versicolor and the diploid H. chrysoscelis have advertisement calls consisting of trains of stereotyped pulses that are similar in their spectral composition. All females of H. versicolor from a population sympatric with H. chrysoscelis approached a speaker broadcasting synthetic advertisement calls modelled after conspecific calls when the calls of the two species alternated from speakers with a 90° angular separation with respect to the release point. Surprisingly, the same females almost exclusively approached the source of synthetic calls modelled after the heterospecific advertisement calls when these calls completely overlapped the conspecific stimuli. Female H. chrysoscelis from the same sympatric population approached the source of synthetic conspecific calls even when these calls were overlapped by the heterospecific stimuli, indicating that females in these closely related species may differ in their susceptibility to the negative consequences of call overlap. When female H. versicolor were presented with conspecific advertisement calls that were completely overlapped by those of H. chrysoscelis, many females failed to approach either signal source. Response times of females that did respond were also longer, and the direction of phonotaxis was shifted in the direction of the heterospecific signal source. These negative influences of acoustic interference were reduced or eliminated as the degree of overlap between the calls of the two species was reduced. The results demonstrate that the effects of signal overlap on female phonotactic behaviour may be complex.

In a car, acoustic comfort has become a sales point. Due to the fact that the main noises have been reduced, the secondary sounds which could not be heard before suddenly became annoying. Such is the case of rattle noise, caused by repeated impacts between unloaded gears in the gear box, as they are driven by the engine acyclism. This publication presents a new method of study of the rattle noise. Our test bench is original, given that the gear box is not operated but is submitted to small angular oscillations. This allows us to control the angular acceleration applied on the primary shaft. We first distinguished and reviewed various kinds of rattling depending on the acyclism level produced. Then, we simulated real engine excitation by applying an acceleration made up of a sum of harmonics rather than a simple sine. Our aim being to measure the influence of the spectral composition and the waveform of the gear box input torque on the rattle threshold.

Measurements of cloudless direct, global, and diffuse solar radiations, taken over a one year period at Helwan, are analyzed in terms of global index and diffuse fraction for clear-sky conditions. The dependence of the diffuse fraction on the global index was represented by a polynomial. These results support the use of routine instantaneous surface meteorological data to calculate global and diffuse radiations on a horizontal surface in the absence of any other radiation measurements. The spectral composition of the global solar-radiation was found to be 4.3% UV band, 32.5% band range 250–630 nm, 13.74% red band, 52.75% infrared band and 29.7% diffuse solar-radiation. The spectral distribution of direct solar-radiation ratio of the extraterrestrial solar radiation was found to be: 0.69% green and blue band, 47.5% yellow and orange band 45% red band, and 52.7% infra-red band.

The biologically important process of endogenous synthesis of vitamin D under UV solar irradiation is widespread in the biosphere and inherent to most animals and plants. A new method of biological dosimetry of UV radiation based on an in vitro model of vitamin D synthesis ('D-dosimeter') is discussed. Unlike the vast majority of biodosimeters, the action of which depends on the UV sensitivity of DNA and thus reflects damaging effects of UV radiation, the process of vitamin D synthesis is beneficial by its nature. To date, the complex network of photo- and thermoreactions of vitamin D synthesis in vitro is well understood, and an adequate mathematical model is available, ensuring a link between biological and physical units. Original spectral analysis of the multicomponent photoisomer mixture has been specially designed to provide the most effective use of the D-dosimeter in situ. Spectral selectivity (exceptional sensitivity of certain parameters to the spectral composition of UV radiation) extends the usefulness of the method.

1. 1. Thermoregulatory set points — i.e. the body temperatures at which heat-seeking or cooling behaviour are initiated — of the lacertid lizard Podarcis muralis were measured by infra-red thermography in animals exposed to light of different spectral compositions. 2. 2. Exposing intact lizards to light from which wavelength < 540 or < 600 nm had been filtered out resulted in persistent but reversible decreases in the values of both thermoregulatory set points. Mean heating rates and bask durations were also affected. 3. 3. Light from which wavelengths < 480 nm had been removed had no effect on any of these variables.

Upon exposure of polymers to ionizing radiation, such products as the exited molecules, cations, anions, trapped electrons and free radicals are generated. These intermediates absorb light efficiently in UV, visible and IR regions of the spectrum. The mechanism and efficiency of photoradiation reactions depend on the nature of the intermediates, temperature and spectral composition of light. Photoradiation reaction differs from a purely radiation reaction, in particular, the type and amount of products depend on the dose rate and light intensity, highly inhomogeneous spatial distribution of products caused by chain mechanism of the photoradical reactions.

Dishabituation of visual attention by infant- and adult-directed (ID and AD) speech was investigated in four experiments. Four-month-olds received 12 10-s presentations of a checkerboard pattern with a speech segment compounded only on the ninth trial. Recovery of visual attention was observed on the compound trial in response to both ID and AD speech, but only ID speech dishabituated visual attention during the following pattern-alone retest (a Thompson-Spencer dishabituation effect, observed in the first two experiments). Synthetic analogs of these speech segments' fundamental frequencies (Fos) elicited equivalent increases in attention on the compound trial, but neither elicited Thompson-Spencer dishabituation (Experiment 3). A synthetic version of the intact ID signal elicited Thompson-Spencer dishabituation, but synthetic stimuli simulating the F0 only, the F0 plus the first harmonic above the F0, and the harmonics only did not (Experiment 4). These data have implications for the acoustic characteristics of ID speech that increase infant attention and arousal.

Stomatal responses to light spectral composition have generally been investigated in the laboratory. This study was carried out in the field on a cotton (Gossypium hirsutum, cv. Acala SJ2) crop to compare the effects of light spectral composition on stomatal conductance under two water stress regimes. Results showed that leaf conductance increased more when blue light irradiance increased than when red light irradiance increased, both in non-stress and stress conditions. The sum of the total leaf conductances under blue and red light irradiance, as normally measured in the shade, closely approximated the shaded leaf conductance measured outdoors in white light during non-stress conditions. Water stress diminished the leaf conductance in both blue and red light. Under non-stress conditions, the abaxial stomatal conductance in blue and red light exhibited a steeper slope than that of the adaxial. Blue light accentuated the difference between abaxial and adaxial stomatal conductance compared with red light in non-stress conditions. In stress conditions, the abaxial conductance was virtually equal to the adaxial conductance under both blue and red light, respectively.

The spectral content of the Doppler signal (as revealed by spectral analysis) provides useful diagnostic information about local hemodynamic conditions. Changes in these conditions are used to diagnose atherosclerotic lesions in arteries accessible to ultrasound. Extremely high frequencies, as found in and distal to a tight stenosis, indicate the presence of a jet, while Doppler signals with a wide bandwidth are related to regions with wide velocity ranges and/or disturbed flow patterns. However, the random interactions of the scatterers, the dimensions of the sample volume, the velocity of the scatterers and the method of signal processing used affect the displayed spectral composition of the Doppler signal. This article reviews the basic mechanisms and cautions the investigator against a quick and superficial interpretation of the results obtained without a proper appreciation of the random fluctuations due to the methods used to record and process the signals.

Theoretical examination shows that the information on crystal properties and phase transitions in PbTiO 3 may be obtained from the observation of channeling radiation. Measurements of the channeling radiation intensity and the spectral composition may be used to locate the displaced light atoms and to check the ferroelectric models.

When measuring ΔΦ with the Kelvin method, stray capacities can cause considerable error. By evaluating the spectral composition of the Kelvin signal, we were able to show that phase sensitive detection of an overtone instead of the usually used fundamental frequency results in a very effective suppression of these effects. The thus modified Kelvin method was successfully applied to the system SO2-Pt(111). Isothermal and temperature programmed ΔΦ experiments combined with TPD results indicate the existence of molecular and dissociative SO2 adsorption states.

We report on gain profile and spectral composition of stimulated emission from an optically excited MOVPE GRINSCH ZnCdSe-ZnSe quantum well.

Summary Fluorescence spectra were determined at -196° in chloroplasts of greening maize leaves in order to analyse the structural characteristics of the spectra. Digitonin-treated mature chloroplasts were also investigated. Difference spectra calculated from the emission spectra measured at different stages of greening revealed the presence of six fluorescence forms with approximate band positions at 675, 685, 695, 705, 720, and 738 nm respectively. With progressing greening, the minor forms became less discernible, since the spectral composition reached a steady-state. With exception of the form at 705 nm the components reappeared in mature chloroplasts when treated with digitonin.

The light distribution in a diffraction pattern produced by a sequence of ultrasonic pulses depends on a number of parameters characterizing the pulse shape, modulation and sequencing as well as changes in the spectral composition due to non-linearities in the propagation medium. Based on calculations of such light diffraction patterns it is possible to consider the inverse problem, i.e. the determination of parameters mentioned above by evaluating certain features of the diffraction pattern produced by the pulses. A number of examples are given to illustrate these possibilities.

Geologically-formed calcite is a suitable material for dating, using thermoluminescence (TL) and electron-spin-resonance. However, many problems preclude accurate age determination. Some of these problems stem from different sample pre-treatment procedures, such as grinding, drilling or pre-heating. It has long been known that grinding can introduce spurious TL in calcite, but there have been wide differences of opinion as to the magnitude of the influence and its importance. Therefore, various grinding and acid-washing procedures have been suggested to avoid spurious thermoluminescence. Various models have been developed to explain the mechanism. We have studied the changes in thermoluminescence (TL) and cathodoluminescence (CL) properties as well as in the spectral composition of the glow from calcite and MgO due to surface defects and heat treatment. It is found that both laboratory heat treatment and surface indents give rise to changes in TL efficiency.

Atlantic salmon parr, Salmo salar, were reared in dark green or light grey tanks under a dual photoperiod, consisting of a constant background illumination (LD 24:0) from incandescent bulbs and additional light simulating a natural photoperiod (LDN). Additional light was either yellow light from incandescent bulbs or artificial daylight from fluorescent tubes. There were no significant differences in growth between groups in green or grey tanks, or between groups receiving additional light of different spectral composition. There were strong indications of smoltification in grey tanks, whereas in the green tanks the fish were not considered to be smolts.

It is found that natural zircon, which has suffered a low degree of damage from the decay of its uranium and thorium impurities, displays a TL spectrum with peaks at ≈480 nm (blue-green) and ≈600 nm (yellow-orange); whereas for severely damaged zircon the spectral composition exhibits only a broad peak centred at ≈600 nm. When annealed, the severely damaged zircon reverts to displaying—in response to a test dose—a TL spectrum similar to that of the less damaged crystals. Moreover, when the completely annealed zircon is subsequently subjected to intense artificial damage, it once again shows a TL spectrum with a broad peak centred at ≈600 nm. These observations clearly link the TL spectral composition with the degree of radiation damage sustained by zircon. By measuring the TL spectra after various storage times at room temperature, it is found that the long-wavelength parts of the spectra fade faster than the shorter-wavelength parts.

Groups of Atlantic salmon (Salmo salar) parr were reared under indoor light sources of different spectral composition. A control group was reared under outdoor light conditions. Growth rate was not significantly different among the indoor groups, whereas the outdoor group had a significantly lower growth rate. All groups developed the external appearance and experienced the reduced condition factor and increased salinity tolerance normally associated with the parr-smolt transformation. Fish from all groups were successfully acclimated to seawater in early May. The subsequent 6-month growth period in seawater did not reveal any differences in growth potential of fish from the different experimental groups. It was concluded that the parr-smolt transformation was completed under light sources of different spectral composition.

The global radiation is recorded at several stations on the Earth. The information about its spectral composition is poor. In this paper the spectral composition means the ratio of spectral global radiation measured by coloured glass filter domes to the total global radiation. From the measurements made by Klein and Goldberg it follows that the monthly ratios vary significantly from place to place, while the variations from month to month at one place are significant only at the station which lies near to the North Pole. The Budapest data proved the dominant effect of cloudiness on the spectral composition of global radiation. This effect is in good statistical relationship with the relative global radiation. The regression constant tabulated in this paper do not contain the error of zero point elevation which is due to the overheating of glass filters by the absorbed solar radiation.

Laboratory culture studies on the salinity and light tolerance of Eugomontia sacculata Kornm, from different habitats suggest that the species has at least two physiological variants adapted to particular habitat conditions. Plants taken from a shallow estuary survived in culture under higher light intensities than plants collected from the sublittoral region, while sublittoral plants were unable to tolerate the reduced salinity in which the estuarine plants were able to live. The host shell may provide protection from unfavourable changes in the external conditions and will also modify some environmental factors such as light intensity and its spectral composition. The possible role of light in the morphogenesis of shell-boring algae is discussed.

The equivalent-background transformation developed by Crawford was used to examine the equivalence of adaptive states (dark and light adaptation) in long-term photopic adaptation using targets of varying duration. The critical feature of Crawford's transformation is that the threshold sensitivity of the eye to a variety of test-stimulus sizes and durations at a particular time in the dark is specified in terms of the light-adapted condition that produces the same threshold sensitivity. In the present investigation two target durations and four chromatic combinations of red and green adapting stimuli (red on red, green on green, red on green and green on red) were used to test for equivalence with respect to test-stimulus duration, area and chromatic composition. Equivalence between light-adapted and dark-adapted states was found not to exist for the stimulus variations employed. In particular, the degree of temporal summation was observed to vary importantly with the area of the test stimulus used; as well as with the spectral composition of the test and adapting fields. Thus more than one process was needed to explain the temporal integration of light in the photopic visual system and these were hypothesized to be excitatory and inhibitory processes of the visual receptive field. It was found, however, that when color-defective subjects were used to more completely isolate cone mechanisms and reduce the possibility of cone interactions equivalence between adaptive states was obtained.

Achromatic sensations for trichromatic mixtures were determined as a function of stimulus intensity with the spectral composition as a parameter. The result showed that the change in the achromatic locus with stimulus intensity was described in terms of a linear relation between the middleand long-wavelength components and of a nonlinear relation between the short- and longer-wavelength components.

A new broad absorption band at 365 nm with a shoulder at 378 nm appears in NaCl crystals with a high concentration of copper after a period of storage in air at room temperature. The spectral composition of fluorescence also altered. An explanation of some of the changes is given.

IN evaluating the radiation hazards of space flights it becomes necessary to calculate not only the risk of exceeding a given total dose of protons from solar flares [ll, but also the risk of exceeding the effective dose which reflects the presence of renewal processes in a living organism after irradiation, [21. It is shown in Ill that even in the case where the spectral composition of the solar protons is taken into account, in prolonged flights some average proton spectrum is realized. On this principle in the following calculations of the risk of exceeding the effective does we proceed from the assumption (used in [3, 41) that the protons in all the flares are characterized by the same spectrum and the same law for the decay of their protective does. Thus the dose of protons for protection is

This letter describes an experimental investigation of the spectral composition of the output of CS 2 /O 2 /N 2 O and CS 2 /O 2 /CO 2 flame lasers with nondispersive optical cavity. CO-additive V-V exchange probabilities were used to explain spectral composition of the laser power output.

The dependence of thresholds and SRS spectral composition of 22 salts of inorganic acids on the temperature and the content of crystalline water was studied. It has been found that the thresholds decrease with decreasing temperature and increase with increasing content of crystalline water. The results are treated with regard to the intermolecular interaction.