New biochemical material laser emission in microdroplets using ribo-flavin and its enhancement by mixing highly scattering intralipid medium

New laser emission from a biochemical material, ribo-flavin (vitamin B₂), at 570 nm was observed for the first time in liquid microdroplets pumped at 475 nm using a pulsed optical parametric oscillator. Laser emission spectra from microdroplets containing ribo-flavin in water and glycerol solution exhibit periodic mode structures depending on the microdroplet diameter demonstrating the morphology-dependent resonances. Magnitude enhancement of lasing emission is confirmed experimentally from liquid microdroplets of ribo-flavin solution with appropriate mixture of the fat emulsion Intralipid-10% suspension as highly scattering medium. We believe that such biochemical-soft multiple light scatterer systems may allow a wide range lasing of other bio-materials and even lead to the discovery of some novel species as well as highly sensitive analysis and diagnosis for future applications.     

Calorimetric Investigation of the Monolayers Formed At Solid-liquid Interface

Heat capacity measurements have been made to investigate the formation of two solid monolayers each of n-pentane, n-heptane and n-dodecane adsorbed on graphite, one at submonolayer coverages and the other coexisting with the liquid. At submonolayer coverages the monolayers are found to melt respectively at 99.8, 151.6, and 217.3 K, well below the bulk melting points. The monolayers coexisting with the liquid melted at 205.6 for heptane and at 287.8 K for dodecane, whereas no evidence was obtained for pentane on the formation of such solid monolayer above the bulk melting point. The order persisting in the liquid near the interface depends upon the length of the molecules. The dodecane monolayers showed another transitions below the melting points both at submonolayer and multilayer coverages.This revised version was published online in November 2005 with corrections to the Cover Date.     

High-Resolution Reflectometry by Optical Multidigitized Coherence

We propose and confirm a novel technique of optical frequency domain reflectometry based on multidigitized coherence using a multimode laser. The proposed system can easily provide the potential for high resolution on the order of 10 μm without scanning frequencies as in frequency domain reflectometers of either continuous or stepwise sweep. The theoretical approach agrees well with the experimental results demonstrated using a commercially available multimode laser diode.     

Laser operation with output feedback pumping and first-order phase transition analogy

It is shown that by means of the newly proposed regime of output feedback pumping, a conventional laser exhibiting only second-order phase transition behavior generally displays the nonequilibrium analogue of a first-order phase transition. Optical bistability should also be achieved in the laser system under feedback pumping incorporated with an externally injected optical signal.     

A theoretical treatment of the line-intensity jump in a decaying argon-arc plasma

The line-intensity jump in decaying argon arcs has been investigated theoretically. The population density at the peak of the jump is in Saha-Boltzmann equilibrium. Using the Saha-Boltzmann relation, the influence of the change in electron density is clarified. As a criterion above which the change in electron density does not influence the amplitude of the jump, τ_N/τ_T ≧ 10₃ is derived, where τ_N and τ_T are, respectively, the density and temperature relaxation times for the electrons. This criterion is not satisfied in most arcs. An improved method is presented for the determination of the gas temperature in stationary arcs.     

Numerical simulation of facilitated transport of carbon dioxide in a condensate film

Numerical analysis was performed for the effects of chemical reactions on the behavior of carbon dioxide absorbed in a condensate film. A condensate film flowing on a vertical surface under the influence of the combined effects of the vapor shear and gravity was chosen as a model problem. Convective flux towards the wall surface played a significant role in the absorption characteristics. Concentrations of the carbon dioxide and bicarbonate ion in the film increased as the condensation proceeded. The difference between the two concentrations at a same longitudinal position decreased as the condensation proceeded. Resistivity of the condensate film was smaller for a thicker condensate film with larger concentration of carbon dioxide in the vapor phase.In einer numerischen Studie wurde der Einfluß chemischer Reaktionen auf das Verhalten von in einem Kondensationsfilm absorbierten Kohlendioxid untersucht. Als Modellfall wurde ein Kondensatfilm gewählt, der an einer vertikalen Wand unter dem kombinierten Einfluß von Schubspannung (bewirkt durch die Dampfströmung) und Schwerkraft abfließt. Die Konvektionsströmung zur Wand beeinflußt das Absorptionsverhalten entscheidend. Im Verlauf des Kondensationsprozesses steigt die Konzentration des Kohlendioxids und der Bikarbonationen im Film an. Der Unterschied zwischen den beiden Konzentrationen an der gleichen Längenkoordinate verringerte sich im Verlauf des Kondensationsvorganges. Der Widerstand des Kondensationsfilms war bei dickerem Film und höherer Konzentration des Kohlendioxids in der Dampfphase geringer.     

Development of an ultra-high sensitive photon counting system and its application to biomedical measurements

The sensitivity of the photon counting method for the detection of extra-weak optical intensity was improved on the introduction of the enhanced single photoelectron counting technique incorporated with a selected photomultiplier operated under optimum conditions. With this ultra-high sensitive photon counting system it has been possible to measure the difference between the luminescence of the blood of healthy and diseased human subjects (both have extremely weak values).