Crinine-type alkaloids from Hippeastrum aulicum and H. calyptratum

An ongoing search for alkaloids in the Amaryllidaceae species using GC MS resulted in the identification of two crinine-type alkaloids, aulicine (1) and 3-O-methyl-epimacowine, (2) from the indigenous Brazilian species Hippeastrum aulicum and Hippeastrum calyptratum, respectively. In addition, two alkaloids, 11-oxohaemanthamine (3) and 7-methoxy-O-methyllycorenine (4) were both isolated from H. aulicum. Furthermore, we provide here complete NMR spectroscopic data for the homolycorine analogues nerinine (5) and albomaculine (6). The absolute stereochemistry of the 5,10b-ethano bridge in the crinine variants was determined by circular dichroism and X-ray crystallographic analysis, thus presenting the first direct evidence for the presence of crinine-type alkaloids in the genus Hippeastrum

Pollutant dispersion in a developing valley cold-air pool

Pollutants are trapped and accumulate within cold-air pools, thereby affecting air quality. A numerical model is used to quantify the role of cold-air-pooling processes in the dispersion of air pollution in a developing cold-air pool within an alpine valley under decoupled stable conditions. Results indicate that the negatively buoyant downslope flows transport and mix pollutants into the valley to depths that depend on the temperature deficit of the flow and the ambient temperature structure inside the valley. Along the slopes, pollutants are generally entrained above the cold-air pool and detrained within the cold-air pool, largely above the ground-based inversion layer. The ability of the cold-air pool to dilute pollutants is quantified. The analysis shows that the downslope flows fill the valley with air from above, which is then largely trapped within the cold-air pool, and that dilution depends on where the pollutants are emitted with respect to the positions of the top of the ground-based inversion layer and cold-air pool, and on the slope wind speeds. Over the lower part of the slopes, the cold-air-pool-averaged concentrations are proportional to the slope wind speeds where the pollutants are emitted, and diminish as the cold-air pool deepens. Pollutants emitted within the ground-based inversion layer are largely trapped there. Pollutants emitted farther up the slopes detrain within the cold-air pool above the ground-based inversion layer, although some fraction, increasing with distance from the top of the slopes, penetrates into the ground-based inversion layer.Peer reviewe

Water Desalination in Solar Earth Stills: A Numerical Study

To simulate water desalination in solar earth stills, we developed a numerical one‐dimensional model, which considers four layers: cover, soil, enclosed, and external air. The soil layer is divided into thin homogeneous sublayers, whose thermal and hydraulic properties are computed, during the simulation, by taking into account their temperature and humidity. Given adequate photometric properties, any covering material can be simulated. The model was experimentally verified and applied to two different climatological regions in Israel, examining the influence of water table depth on the amount of collected fresh water in two different types of solar earth stills. The model is able to predict accurately the amount of drinking water collected in a solar earth still. This method of water desalination is applicable in regions where the water table is near the soil surface

A numerical simulation of the greenhouse microclimate

A numerical one-dimensional model was designed to simulate the diurnal changes of the greenhouse environment. The model takes into consideration a soil layer, a vegetation layer, an air layer and a cover. The thermal radiative, sensible, latent and conductive heat fluxes were modeled in each layer in terms of its unknown temperature and vapor pressure. The model was applied to the coastal region of Israel during the winter and summer seasons in order to assess the heating/cooling requirements of glass and polyethylene covered greenhouses

Mapping Frost-Sensitive Areas with a Three-Dimensional Local-Scale Numerical Model. Part I. Physical and Numerical Aspects

Abstract Radiative frost is one of the most severe weather conditions that affects agricultural activities in many parts of the world. Since various protective methods to reduce frost impact are available, refinements of frost forecasting methodologies should provide economical benefits. In the present study, a three-dimensional numerical local-scale model for the simulation of the microclimate near the ground surface of nonhomogeneous regions during radiative frost events was developed. The model is based on the equations of motion, heat, humidity and continuity in the atmosphere and the equations of heat and moisture diffusion in the soil. Emphasis was given in establishing a refined formulation of energy budget equations for soil surface and plant canopy Additionally, an improved finite difference scheme procedure for approximating horizontal derivatives in a terrain-following coordinate system was introduced. The sensitivity of the model to various parameters that way affect the nocturnal minimum temp..

Verification Study of a Numerical Greenhouse Microclimate Model

ABSTRACT A numerical one-dimensional model was designed to simulate the diurnal changes of the greenhouse en-vironment. The model consists of: a soil layer, a vegeta-tion layer, an air layer and a cover. The thermal radiative, sensible, latent and conductive heat fluxes were modeled in each layer in terms of its unknown temperature and vapor pressure. In order to obtain flexibility and accuracy of the model, sophisticated models were adopted to simulate each of the greenhouse sublayers and a theoretical method was proposed to describe the water diffusion through stomata as a function of the environmental parameters. Numerical experiments were conducted to test the sen-sitivity of the model to some parameters. The results in-dicate the necessity to properly initialize the model and to determine an accurate inside air transfer coefficient of sensible and latent heat. An observational study was performed in order to test the ability of the model to properly describe the greenhouse microclimate. Good agreement was obtained between predicted and observed temperatures and humidities