Light Energy Levels Research Articles

ENERGY LEVELS OF QUARKONIA IN POTENTIAL MODELS

We review the subject of the energy levels of light and heavy quark-antiquark bound states in potential models, with emphasis on potentials which are motivated from quantum chromodynamics. In addition to pointing out the successes of potential models, we discuss problems with the potential approach, including uncertainties in the form of the potential, its spin dependence, its transformation properties, and its nondiagonal terms. We consider two-body wave equations with both nonrelativistic and relativistic kinematics, pointing out that in the latter case, a wide variety of different wave equations have been used in the literature.

Activity of phthalocyanine photosensitizers against human glioblastoma in vitro.

In vitro studies utilizing an established human glioblastoma cell line (U87MG) were undertaken to compare the light absorption spectra and photocytotoxicity characteristics of hematoporphyrin derivative (HpD), metal-free phthalocyanine tetrasulfonate (PcS), and aluminum phthalocyanine tetrasulfonate (AlPcS). The peak absorption wavelengths for the compounds studied were: HpD = 630 nm, PcS = 630 nm, AlPcS = 677 nm. Seven different concentrations of each compound (0 to 20 micrograms/ml) were subjected to five different energy levels (40 to 640 joules/cm2) of broad band light (wavelength = 650 +/- 40 nm). Control experiments employing each drug alone and photoactivation alone were also performed. HpD showed a consistent dose-dependent photoactivated cytotoxicity with an abrupt decrease in cell survival when energies of 160 joules/cm2 or more were administered and a drug concentration dependency that resulted in a progressive decline in cell survival beginning at 1.0 microgram/ml. The metal-free PcS had a 10 times greater absorption of light at 675 nm, but only a very weak cytotoxic effect, which occurred at concentrations in excess of 10.0 micrograms/ml and energy levels greater than 320 joules/cm2. AlPcS, however, displayed a 100-fold increase in light absorption at 675 nm when compared to HpD. This was coupled with a decrease in cell survival similar to the HpD curves, but with a much steeper slope of percentage cell kill at lower drug concentrations and energy dosages. The control studies did not result in any appreciable cytotoxic effect. The data suggest that AlPcS holds promise as a second generation photosensitizer in the photodynamic treatment of human gliomas.

Control of Oxidative Sulfur Metabolism of Chlorobium limicola forma thiosulfatophilum

A metered blend of anaerobic-grade N(2), CO(2), and H(2)S gases was introduced into an illuminated, 800-ml liquid volume, continuously stirred tank reactor. The system, described as an anaerobic gas-to-liquid phase fed-batch reactor, was used to investigate the effects of H(2)S flow rate and light energy on the accumulation of oxidized sulfur compounds formed by the photoautotroph Chlorobium limicola forma thiosulfatophilum during growth. Elemental sulfur was formed and accumulated in stoichiometric quantities when light energy and H(2)S molar flow rate levels were optimally adjusted in the presence of nonlimiting CO(2). Deviation from the optimal H(2)S and light energy levels resulted in either oxidation of sulfur or complete inhibition of sulfide oxidation. Based on these observations, a model of sulfide and sulfur oxidases electrochemically coupled to the photosynthetic reaction center of Chlorobium spp. is presented. The dynamic deregulation of oxidative pathways may be a mechanism for supplying the photosynthetic reaction center with a continuous source of electrons during periods of varying light and substrate availability, as in pond ecosystems where Chlorobium spp. are found. Possible applications for a sulfide gas removal process are discussed.

Effect of total light energy on symptoms and growth of ring rot-infected Red Pontiac potato plants

The effect of total light energy levels on development of bacterial ring rot symptoms caused byCorynebacterium sepedonicum (Spieck. and Kotth.) Skapt. and Burkh., and growth (plant height) of cv. Red Pontiac was investigated by growing inoculated and uninoculated rooted stem cuttings under different pre-inoculation and post-inoculation total light energy levels. Infected plants grown under a 45 mW cm−2 hr pre-inoculation total light energy level had a higher (P< 0.01) mean ring rot severity rating than plants grown under 103 mW cm−2 hr. Disease severity increased as the postinoculation total light energy decreased. Plants inoculated withC. sepedonicum showed little growth under a post-inoculation total light energy of 45 mW cm−2 hr, however, under 103 mW cm−2 hr; significantly greater growth occurred. Uninoculated plants grew more rapidly than infected plants under all pre-and post-inoculation total light energy level combinations, except those grown at pre-inoculation levels of 45 mW cm−2 hr.

The influence of micro-algae on the oxygen dynamics in a brackish ditch

Seasonal changes in the activity of phytoplankton and benthic algae in relation to diurnal oxygen pulses were investigated in a 120 cm deep, brackish hypertrophic ditch. A vertical chloride gradient was built up by saline seepage and drain-water effluent. The stable chloride gradient could lead to oxygen stratification near the sediment, and to oxygen gradients towards the water surface. The oxygen gradients were rather unstable, depending on the chloride gradient and the wind velocity. Light was limiting photosynthesis both in summer and in winter. Surface oxygen maxima increased with solar radiation during summer. In summer the diatomCyclotella caused surface oxygen maxima at light saturation in the late afternoon. Simultaneously, the dominant flagellatesPeridinium andChlamydomonas produced oxygen in dim light, probably choosing their favourite light energy level by vertical migration. Oxygen fluctuations ranged from 0 to 34 mg O2.l−1 in a 100 cm vertical profile above a 20 cm anoxic layer. The amplitude of the diurnal oxygen maxima varied from 10 to 34 mg O2.l−1. In winter the water became very clear. The oxygen gradient was inverted during the day showing a characteristic oxygen maximum above the bottom, produced by benthicAchnanthes colonies.

Development of photobehavioural responses in young rainbow trout, Salmo gairdneri Richardson

The photobehaviour of young rainbow trout was studied from the time of hatching to completed emergence using an artificial turf substrate incubation system. At all light energies tested, free‐embryos initiated a substantial downward movement and rates of fish descent did not appear to reflect the order of light energy levels. A nocturnal activity rhythm was established early in the downward phase. The occurrence of a rapid photoresponse shift 21 days after hatching coincided with the synchronous onset of emergence in all fish groups and the depletion of 85% (by volume) of the yolk reserve. Concurrent morphological observations indicated that the photoresponse change occurred when fish were about 25 mm long, and when paired and median fins were fully developed.

Rose bengal induced corneal swelling: relation to inciting wavelength.

Cornea endothelial cells sensitized with rose bengal and exposed to light demonstrated a wavelength dependent alteration in physiological response. Corneas exposed to 549 millimicron swelled at rates similar to controls exposed to identical energy levels of incandescent light. Corneas exposed to 451, 500, 612, and 651 millimicron swelled at rates less rapid than corneas exposed to similar energy levels of incandescent light. The photodynamically induced physiological alteration of cornea endothelial cells approximately paralleled the spectral curve of rose bengal with its peak at 550 millimicron.

Effect of ovarian hormones on synchrony of hamster circadian rhythms

Adult ovariectomized hamsters which were implanted with Silastic capsules containing estradiol benzoate (EB), progesterone (P) or nothing (Blank) were exposed to prolonged constant light (LL) with free access to running wheels. Freerunning locomotor rhythms were recorded on an event recorder. Light energy levels averaged 12.2 uwatts/cm 2 or 48.3 Lux. Rhythm splitting occurred in 1 7 animals given EB, 5 7 given P and 5 11 Blank implanted animals. Altogether, 1 7 EB, 6 7 P and 8 11 Blank implanted animals showed some form of splitting or other rhythm anomaly such as desynchrony of endogenous oscillations. There was a high incidence ( 10 11 ) of animals showing an additional transient rhythmical component running across the split condition. The study supports the concept that a multi-oscillatory system normally generates a cohesive circadian behavioral rhythm. Estradiol appears to facilitate the synchrony of these oscillations.

Flower formation inChrysanthemum morifolium: the influence of light level

SummaryGroups of chrysanthemum plants were transferred from a constant light level of 63 J cm-2 day-1 to higher levels at the start of short days, and at weekly intervals thereafter. The plants remained in their new light regime for one or two weeks before they were returned to the lower level. The results showed that flower initiation began earliest if transfer was made to a light level of 125 J cm-2 day-1 for two weeks at the start of short days. This benefit was retained throughout the subsequent period of growth at the lower light level and resulted in earlier flowering.The average level of visible radiation received in glasshouses in winter, even on the South Coast of England, is only 67 J cm-2 day-1 in the worst two months. The data suggest that if artificial light is used during this period to supplement the natural light and to raise the level of light energy received to at least 125 J cm-2 day-1 for the first two weeks of short days, earlier and more uniform flowering should . be obtained.Further...

NET PHOTOSYNTHESIS AND LEAF AREA INDEX RELATIONSHIPS IN SWARDS OF DACTYLIS GLOMERATA UNDER CONTRASTING DEFOLIATION REGIMES

ABSTRACTNet photosynthesis per unit area of ground surface was determined at saturating light energy levels in Dactylis glonwrata swards over a wide range of leaf area indices (LAI). The relationship between net photosynthesis and LAI was influenced by the particular defoliation regime to which the sward was subjected. In most instances net photosynthesis and LAI were linearly related, with defoliation regime influencing both the slope and intercept of the regression. However, a defoliation regime which left leaves below 3 inches (7.5 cm) resulted in a curvilinear relation. The net photosynthesis‐LAI relationships were compared with the DM production of the swards on which they were obtained. Differences in these relationships did not entirely explain the differences in sward yield. The significance of these findings is discussed with reference to the theories of light interception and pasture growth.

Effective Interaction and Level Structure of Nuclei with Free Nucleon-Nucleon Interaction

Effective interaction and energy levels of light and intermediate nuclei ($^{6}\mathrm{He}$, $^{6}\mathrm{Li}$, $^{18}\mathrm{O}$, $^{18}\mathrm{F}$, and $^{58}\mathrm{Ni}$) are calculated using the interaction of Shakin and his collaborators derived from the Yale potential following the unitary-model-operator approach. Detailed comparison is made with works of Kuo-Brown and other authors. It is found that the differences in the approximations used by different groups of workers in the evaluation of the reaction matrix elements can lead to large differences in the spectra, indicating that it is very necessary to evaluate the reaction matrix elements more precisely before applying them to nuclear-structure calculations.

Action Spectrum of the Photoperiod Mechanism Controlling Sexual Maturation in the Threespine Stickleback, Gasterosteus aculeatus

Experiments in which groups of 80 threespine stickleback (Gasterosteus aculeatus) were exposed to four discrete segments of the visible spectrum (388–466, 455–518, 513–583, and 585–653 mμ) and compared with two control groups (experimental and wild) showed no major differences in seasonal rates of gonad maturation. This result contrasts with the narrower action spectra of the photoperiod mechanisms in some birds (600–750 mμ) and many insects (400–500 mμ). Light energy levels of &lt; 0.37 × 103 erqs/cm2-sec (equivalent to approximately 5 lux at 420 mμ) induced normal seasonal changes indicating a level of sensitivity for the photoperiod mechanism in this species comparable to that of certain birds and insects (approximately 1 lux). Histological comparisons of ovary development with the brook stickleback (Culaea inconstans) showed closely similar development patterns except for the final stage of yolk deposition. A further stage of yolk differentiation described for the threespine stickleback probably accounts for the larger egg size in this species.

Physiology of Growth in the Wheat Plant IV. Effects of Day Length And Light Energy Level

This study describes the effects of short- and long-day treatments at two light-energy levels on the growth of a spring wheat.