Spectral properties of selected UV-blocking and UV-transmitting covering materials with application for production of high-value crops in high tunnels

The spectral properties of selected UV-blocking and UV-transmitting covering materials were characterized by means of a UV-VIS spectroradiometer or a UV-VIS spectrometer to provide researchers and growers with guidelines for selecting suitable materials for use in studying the effects of ambient solar UV radiation on the production of tomatoes and other high-value crops in high tunnels. A survey was made of a wide range of plastic covering materials to identify commercially available products that had the desired characteristics of transmitting high levels of photosynthetically active radiation and of being stable under ambient solar UV radiation. The study was focused on evaluating films that either blocked or transmitted UV wavelengths below 380 nm to determine comparative growth, yield and market quality and to provide a tool for integrated pest management. Based on this survey, two contrasting covering materials of similar thickness (0.152 mm) and durability (4-year polyethylene), one a UV-blocking film and the other a UV-transmitting film, were selected and used to cover two high tunnels at Beltsville, MD. Spectroradiometric measurements were made to determine comparative spectral irradiance in these two high tunnels covered with these materials and under ambient solar UV radiation. Comparative measurements were also made of selected glass and plastic materials that have been used in UV exclusion studies.     

Influence of PAR and UV-A in determining plant sensitivity and photomorphogenic responses to UV-B radiation

The role of photosynthetically active radiation (400-700 nm) (PAR) in modifying plant sensitivity and photomorphogenic responses to ultraviolet-B (280-320 nm) (UV-B) radiation has been examined by a number of investigators, but few studies have been conducted on ultraviolet-A (320-400 nm) (UV-A), UV-B and PAR interactions. High ratios of PAR-UV-B and UV-A-UV-B have been found to be important in ameliorating UV-B damage in both terrestrial and aquatic plants. Growth chamber and greenhouse studies conducted at low PAR, low UV-A and high UV-B often show exaggerated UV-B damage. Spectral balance of PAR, UV-A and UV-B has also been shown to be important in determining plant sensitivity in field studies. In general, one observes a reduction in total biomass and plant height with decreasing PAR and increasing UV-B. The protective effects of high PAR against elevated UV-B may also be indirect, by increasing leaf thickness and the concentration of flavonoids and other phenolic compounds known to be important in UV screening. The quality of PAR is also important, with blue light, together with UV-A radiation, playing a key role in photorepair of DNA lesions. Further studies are needed to determine the interactions of UV-A, UV-B and PAR.     

Experimental study of clay deformability in terms of initial fabric and soil-water potential

Summary Included in this paper are the results of an experimental study directed toward improving our understanding of the complex relationship between the stress-strain behavior of clay and its initial fabric and soil-water potential. Three blocks of a kaolinite clay were consolidated from a slurry under controlled conditions of pore fluid chemistry and stress path, and the fabrics of these samples were evaluated by use of scanning electron microscopy, optical microscopy, andX-ray diffraction. Upon completion of consolidation, test specimens trimmed from these samples were placed under air pressure in an extractor and brought to equilibrium at soil-water potentials up to 15 bars. Fabric changes during this phase are expressed in terms of changes in dry density. Then, these specimens were subjected to a constant strain rate uniaxial compression test, and empirical relationships among the undrained modulus,Poisson's ratio, strength parameter, initial fabric, and soil-water potential at the beginning of the test are presented.With 9 figures     

Nonobtuse Tetrahedral Partitions that Refine Locally Towards Fichera-Like Corners

Linear tetrahedral finite elements whose dihedral angles are all nonobtuse guarantee the validity of the discrete maximum principle for a wide class of second order elliptic and parabolic problems. In this paper we present an algorithm which generates nonobtuse face-to-face tetrahedral partitions that refine locally towards a given Fichera-like corner of a particular polyhedral domain. The first author was supported by the Swedish Foundation for Strategic Research, the second author was supported by Grant No. 49051 of the Academy of Finland, the third author was supported by Grant No. A 1019201 of the Academy of Sciences of the Czech Republic and by Institutional Research Plan AV0Z 10190503.     

FINITE ELEMENT APPROXIMATION OF A NONLINEAR STEADY-STATE HEAT CONDUCTION PROBLEM

1. Introduction Anciellt Chinese mathematicians have done many fund~al discoveries, even thoughmad of them are now usually called by western names, e.g., the Pascal triangle, the HornerIcheme, the Gaussian elimination, see [231. In the modern era3 Chinese mathematiciare have.jalso got many priorities. For instance, the fast Proof Of convergence of the finite element methodfor a linear elliptic boundary vajue problem was done in the pioneering work [61 by K. Feng in1965 (for the English tra…     

MULTIPLE EFFECTS OF UV RADIATION (265–330 NM) ON FUNGAL SPORE EMERGENCE

We have investigated the influence of narrow-band UV radiation, 265–330 nm. on germination of spores of the fungus Cladosporium cucumerinum Ellis and Arth., using a Xe arc lamp and filters. Reciprocity of time and dose rate was demonstrated when fungal spores were subjected to UV radiation at 325 nm but failed to hold at 265 nm. Based on these findings, data on fluence response, and partial action spectra, we propose that there are two biologically active sites in this organism that are affected by radiation between 265 and 330 nm and that might be influenced by changes in the stratospheric ozone layer: a short-wave-sensitive site (265–295 nm) and a long-wave-sensitive site (300–330 nm). Data obtained with narrow-band interference filters confirmed previous reports of damage to nucleic acid from UV at 265–295 nm and in addition demonstrated significant inhibition by UV at 300–320 nm. Further studies of the 300 330 nm portion of the spectrum, using combinations of plastic and glass filters, showed that the influence of UV radiation in this region was primarily to produce a non-photoreactivable delay in germ-tube emergence.     

USE OF REGRESSION ANALYSIS TO ESTIMATE UV SPECTRAL IRRADIANCE FROM BROAD BAND RADIOMETER READINGS UNDER FS-40 FLUORESCENT SUNLAMPS FILTERED WITH CELLULOSE ACETATE

Abstract— Weighted and unweighted UV spectral irradiances were measured under a 2-lamp fluorescent fixture containing Westinghouse FS-40 fluorescent sunlamps filtered with (6 h aged) 0.127 mm (0.005 in.) cellulose acetate by use of newly developed broadband UV radiometers and an automated UV spectro-radiometer. Measurements were taken at 10-cm intervals between 20 and 110 cm from the lamps. Correlations were determined between sets of data measured with the broadband radiometers and the UV spectroradiometer.
By use of linear regression analyses on the weighted and unweighted spectral data, regression equations were developed for predicting UV-B irradiance (unweighted mWm-²), biologically effective UV (BUV) (weighted mWm) in the 280–320 nm (UV-B) region, UV-B sun equivalents, and incident flux density in the UV-B region in photons m-²× 10²¹ integrated over a 6-h exposure. Examination of the correlation coefficients ( r values) indicated that agreement was excellent between measured and predicted values for all comparisons (r values from 0.9972 to 0.9998).
Use of regression equations should permit accurate. rapid estimation of both weighted and unweighted UV irradiances at any location in an experimental set-up and provide a useful means for intra- and inter-laboratory comparisons of spectral measurements, made in the interagency BACER program under FS-40 fluorescent sunlamps filtered with 0.127 mm cellulose acetate (aged for 6h).     

Evaluating UV-B effects and EDU protection in soybean leaves using fluorescence

A growth-chamber experiment was conducted to evaluate whether ethylenenediurea (EDU), a chemical shown to be protective against ozone pollution, could ameliorate foliar damage induced by ultraviolet-B (UV-B) radiation exposure in 'Roanoke' soybean (Glycine max L.), a UV-B-sensitive cultivar, and whether these effects could be discriminated using fluorescence (F) observations. The experiment had four treatment groups: control; biologically effective UV-B (18 kJ m(-2) day(-1)); EDU (500 micromol mol(-1)); and both UV-B and EDU (UV/EDU). Measurements included photosynthetic pigments, F image system (FIS) images of adaxial surfaces in four spectral regions (blue, green, red and far-red) and F emission spectra of the pigment extracts produced at two excitation wavelengths, 280 nm (280EX) and 380 nm (380EX). Several F ratios from 280EX, 380EX and the FIS images successfully separated the low UV vs high EDU group responses based on means alone, with intermediate values for controls and the combined UV/EDU groups. A UV-B/blue emission ratio, F315/F420 (280EX), was correlated with chlorophyll content (microg cm(-2))(R = 0.88, P < 0.001), as was a ratio of emissions at two UV-A wavelengths: F330/F385 (280EX) (R = 0.87). These two 280EX ratios were also linearly correlated with emission ratios produced by 380EX, such as the far-red/green ratio, F730/F525 (380EX) (R = 0.92, P < 0.001), and clearly distinguished the UV-B and EDU groups separately, and which bracketed the similar intermediate responses of the UV/EDU and control groups. The FIS images additionally captured the following anatomical spatial patterns across the leaf surfaces: (1) emissions of UV-B-irradiated leaves were more uniform but lower in intensity than those of other groups; and (2) emissions of EDU-treated leaves exhibited the greatest variation in spatial patterns because veins had elevated blue F and leaf edges had enhanced red and far-red F. This experiment supports the hypothesis that EDU substantially ameliorated UV-B damage to foliage, a result that relied on the combined use of FIS images and emission spectra.