Home About us Contact
|
Home About us Contact | ||
|
|
||
Various Wavelengths (various + wavelength)
Selected AbstractsPhototropism of Thalli and Rhizoids Developed from the Thallus Segments of Bryopsis hypnoides LamourouxJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 6 2006Nai-Hao Ye Abstract Newly regenerated thalli were used to study the phototropism of Bryopsis hypnoides Lamouroux under different qualities of light. Positive phototropism in the thalli and negative phototropism in the rhizoids of B. hypnoides were investigated and analyzed in terms of bending. Both thalli and rhizoids developed from thallus segments exhibited typical tip growth, and their photoreceptive sites for phototropism were also restricted to the apical hemisphere. The bending curvature of rhizoids and thalli were determined with unilateral lights at various wavelengths and different fluence rates after a fixed duration of illumination. The trends of bending from the rhizoid and thallus were coincident, which showed that the action spectrum had a large range, from ultraviolet radiation (366.5 nm) to green light (524 nm). Based on the bending curvatures, blue light had the highest efficiency, while the efficiency of longer wavelengths (>500 nm) was significantly lower. External Ca2+ had no effect on the bending curvature of thalli and rhizoids. Blue light (440 nm) induced thallus branching from rhizoids, while red light (650 nm) had no such effect. Fast-occurring chloroplast accumulation in the outermost cytoplasmic layer of the blue light (440 nm)-irradiated region in the rhizoid was observed, from which protrusions (new thalli) arose after 4 h of the onset of illumination, and this action was thought to be driven by the dynamics of actin microfilaments. (Managing editor: Wei Wang) [source] Influence of electron correlations on strong field ionization of calciumLASER PHYSICS LETTERS, Issue 1 2004E. Charron Abstract Non-perturbative time-dependent calculations of single and double ionization of a one-dimensional model of atomic calcium by short and intense laser pulses were performed at various wavelengths. The comparison of the probabilities calculated within a two-active electron (TAE) approach with those obtained using a single-active electron (SAE) approximation clearly demonstrates the crucial role played by the electronic correlation and by doubly excited states within this model, even for the formation of Ca+. Experimental and calculated energy spectra of the singlet states of Ca. The experimental values (b) are taken from [20], and the calculated values (a) on the left and (c) on the right correspond to the present SAE and TAE models respectively. (© 2004 by HMS Consultants. Inc. Published exclusively by WILEY-VCH Verlag GmbH & Co.KGaA) [source] Blood Flow in Snake Infrared Organs: Response-Induced Changes in Individual VesselsMICROCIRCULATION, Issue 2 2007RICHARD C. GORIS ABSTRACT Objective: In the past the microkinetics of blood flow in the infrared pit organs of pit vipers has been studied with Doppler flowmetry using various infrared stimuli such as a human hand or soldering iron at various distances, lasers of various wavelengths, etc. Quick-acting variations in blood flow were recorded, and interpreted as a cooling mechanism for avoiding afterimage in the infrared receptors. However, the Doppler measurements provided only the summation of blood flow in a number of vessels covered by the sensing probe, but did not give data on flow in individual vessels. Methods: In the present work the authors introduced into the bloodstream of Gloydius and Trimeresurus pit vipers fluorescent microspheres labeled with fluorescein isothiocyanate (FITC) contained in a solution of FITC-dextran in physiological saline. They observed the passage of the microspheres through individual pit organ vessels with a fluorescent microscope to which was attached a high-speed video camera and image intensifier. Output of the camera was recorded before, during, and after stimulus with a 810-nm diode laser. Recording was done at 250 frames/s on high-speed video apparatus and downloaded to a hard disk. Disk files were loaded into proprietary software and particles were tracked and average velocities calculated. The data were then tested for significance by ANOVA with post hoc tests. Results: A significant (p < .05) increase in blood velocity was found at the focal point of the stimulus laser, but not anywhere removed from this point. Proximal severing of the pit sensory nerves caused degeneration of the pit receptor terminals and abolished stimulus-induced blood flow changes, but did not affect normal blood flow. Conclusions: The authors conclude that the receptors themselves are directly and locally controlling the smooth muscle elements of the blood vessels, in response to heating of the receptors by infrared radiation. They speculate that the heavy vascularization constitutes a cooling system for the radiation-encoding receptors, and further that the agent of control may be a volatile neuromediator such as nitric oxide. [source] The bactericidal effect of ultraviolet and visible light on Escherichia coliBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2008Natasha Vermeulen Abstract The bactericidal radiation dosages at specific wavelengths in the ultraviolet (UV),visible spectrum are not well documented. Such information is important for the development of new monochromatic bactericidal devices to be operated at different wavelengths. In this study, radiation dosages required to cause mortality of an Escherichia coli strain, ATCC 25922, at various wavelengths between 250 and 532 nm in the UV and visible spectrum were determined. Radiation at 265 nm in the UV region was most efficient in killing the E. coli cells and 100% mortality was achieved at a dose of 1.17 log mJ/cm2. In the visible spectrum, the radiation dosages required for a one-log reduction of the E. coli cell density at 458 and 488 nm were 5.5 and 6.9 log mJ/cm2, respectively. However, at 515 and 532 nm, significant killing was not observed at radiation dosage up to 7 log mJ/cm2. Based on the cell survival data at various radiation dosages between 250 and 488 nm, a predictive equation for the survival of E. coli cells is derived, namely log(S/S0),=, ,(1.089,×,107 e,0.0633,)D. The symbols, S0, S, ,, and D, represent initial cell density, cell density after irradiation, wavelength of the radiation and radiation dosage, respectively. The proportion of the surviving E. coli cells decreases exponentially with the increase in radiation dosage at a given wavelength. In addition, the radiation dose required for killing a certain fraction of the E. coli cells increases exponentially as the wavelength of radiation increases. Bioeng. 2008;99: 550,556. © 2007 Wiley Periodicals, Inc. [source] | ||||||||||