Evaporation loss of dissolved volatile substances from ice surfaces

Volatile acidic solutes were used to make dilute solutions, which were frozen by various methods. The concentration of solutes and the pH of the samples were measured before and after being frozen. When the sample solution is frozen from the bottom to the top, solutes are concentrated into the unfrozen solution (i.e., the upper part of the sample) due to the freeze concentration effect. Thereafter, concentrated anions combine with protons to form acids, and the amount of acids in the unfrozen solution increase as the ice formation progresses. At the end of freezing, the acid is saturated at the ice surface, and if the formed acid is volatile, then evaporation occurs. Frozen solutions were allowed to stand below 0 degrees C, where evaporation rates were obtained in the following order: formate > acetate > propionate > n-butyrate > chloride > nitrate. Except for nitrate, evaporation rates were enough to take place in frozen water of the natural environment (e.g., ice crystal, graupel, snow crystal, and frozen droplets). The relationship between the evaporation rate of volatile acids and their physical properties demonstrate that the evaporation rates of weak acids are faster than those of strong acids, and the evaporation rates among weak acids are the same as the volatility of weak acids.     

Enantioselective total synthesis of isishippuric acid B via intramolecular Michael reaction

The first enantioselective total synthesis of isishippuric acid B bearing a novel 4,5-seco-6-norquadrane skeleton was accomplished from (R)-citronellal with use of a Diels-Alder cycloaddition and an intramolecular Michael addition as the ring-forming steps. Comparison of the optical rotation of the synthetic material with that of the natural product confirmed the absolute configuration of isishippuric acid B to be 1R, 2R, 8R, and 11R.     

Chemical kinetics of reactions in the unfrozen solution of ice

Some reactions are accelerated in ice compared to aqueous solution at higher temperatures. Accelerated reactions in ice take place mainly due to the freeze-concentration effect of solutes in an unfrozen solution at temperatures higher than the eutectic point of the solution. Pincock was the first to report an acceleration model for reactions in ice,1 which successfully simulated experimental results. We propose here a modified version of the model for reactions in ice. The new model includes the total molar change involved in reactions in ice. Furthermore, we explain why many reactions are not accelerated in ice. The acceleration of reactions can be observed in the cases of (i) second- or higher-order reactions, (ii) low concentrations, and (iii) reactions with a small activation energy. Reactions with a buffer solution or additives in order to adjust ion strength, zero- or first-order reactions, or reactions containing high reactant concentrations are not accelerated by freezing. We conclude that the acceleration of reactions in the unfrozen solution of ice is not an abnormal phenomenon.     

Effect of reaction vessel diameter on sonochemical efficiency and cavitation dynamics

The influence of reaction vessel diameter on the sonochemical yield was investigated by using reaction vessels with five different diameters. It was revealed that the formation of H₂O₂ and chloride ion, from the sonolysis of pure water and 1,2,4-trichlorobenzene aqueous solution, was affected by the reaction vessel diameter. That is, these yields increased as the reaction vessel diameter increased up to ø 90 mm and then decreased over ø 90 mm. From the analyses of the measurement of sonochemiluminescence and the calorimetry, it was suggested that active cavitation bubbles were formed at certain zones. In the case of a larger diameter reaction vessel, it was suggested that bubble nuclei that have not grown up to the resonance size, escaped from the sonication zone to the non-sonication zone and dissolved away. As a result, the number of active cavitation bubbles and the yields of H₂O₂ and chloride ion would decrease in the case of a larger diameter reaction vessel.     

Total synthesis of pteridic acids A and B

Pteridic acid A (1) is a spirocyclic octaketide produced by the phytoepiphytic actinomycete Streptomyces hygroscopicus TP-A0451 and possesses potent plant-growth-promoting activity comparable to that of indole-3-acetic acid. The enantioselective total synthesis of this natural product was achieved by employing the Sn(OTf)(2)-mediated Evans aldol reaction and the Fukuyama acetylenic coupling reaction as the key C--C bond-forming steps producing 1 through a 14-step sequence in 22 % overall yield from a known oxazolidinone derivative. MgBr(2)-mediated equilibration of an anomerically favored spirocyclic intermediate used for the synthesis of 1 brought about partial epimerization of the spirocenter to give the corresponding anomerically disfavored epimer, which was converted into pteridic acid B (11-epi-1), another plant-growth promoter of the same microbial origin.     

Background updating and shadow detection based on spatial, color, and texture information of detected objects

Background model updating is a vital process for any background subtraction technique. This paper presents an updating mechanism that can be applied efficiently to any background subtraction technique. This updating mechanism exploits the color and spatial features to characterize each detected object. Spatial and color features are used to classify each detected object as a moving background object, a ghost, or a real moving object. The starting position of each detected object is the cue for updating background images. In addition, this paper presents a hybrid scheme to detect and remove cast shadows based on texture and color features. The robustness of the proposed method and its effectiveness in overcoming challenging problems such as gradual and sudden illumination changes, ghost appearance, non-stationary background objects, the stability of moving objects most of the time, and cast shadows are verified quantitatively and qualitatively.     

Optical path-length matrix method for estimating skin spectrum

In this article, we propose a new method??the optical path-length matrix method (OPLM)??as a faster alternative to the Monte Carlo for multi-layered media (MCML), which is often used to simulate the skin spectrum. Theoretically, peripheral oxygen saturation can be estimated by iterating MCML, but it is not a realistic strategy because it requires huge computation time. The optical path-length matrix is obtained as the probabilistic density histograms of the optical path length in skin using MCML, and once the matrix is obtained, skin spectral reflectance can be calculated by accumulating all combinations of elements in the matrix and by setting an absorption coefficient based on the Beer-Lambert law. The computational time of OPLM was approximately 26,000 times faster than that of MCML.     

Noise Analysis of Duplicated Data on Microarrays Using Mixture Distribution Modeling

We propose a technique for estimating gene expression values for duplicated data on cDNA microarrays. In the scatter plots, the distribution is constructed from a mixture of normal two-dimensional distributions, which represent fluctuations in gene expression values due to noise. An expectation-maximization (EM) algorithm is used for estimating the modeling parameters. The probability that duplicated data is shifted by noise is calculated using Bayesian estimation. Six data sets of rice cDNA microarray assays were used to test the proposed technique. Genes in the data sets were subjected to clustering based on probability of true value. Clustering successfully identified candidate genes regulated by circadian rhythms in rice.