Mechanism and characteristics of protein release from lactitol-based cross-linked hydrogel

Lactitol-based cross-linked hydrogel was synthesized, and model proteins (alpha-chymotrypsin, beta-lactoglobulin, bovine serum albumin (BSA), and gamma-globulin) were incorporated into the cross-linked hydrogel. The larger-molecular-weight proteins have lower diffusivity (D(e)) in the hydrogel. Increasing temperature accelerated the diffusion rate of proteins; however, the diffusion did not follow the Arrhenius equation at temperatures above 37 degrees C. The swelling ratio of the hydrogel was slightly decreased after heating for 2 h at 37 and 45 degrees C, and significantly reduced after 1 h at 60 degrees C. Therefore, diffusion of beta-lactoglobulin and BSA may be decreased by hydrogel shrinking at temperature over 37 degrees C. The model proteins have high affinities to buffer solution compared to the hydrogel network structure, resulting in high partition coefficients (K > 1) which do not affect the calculation of D(e) values. Incorporated protein release follows the theory of hindered diffusion.     

Toxic Effect of Certain Metals Mixture on Some Physiological and Morphological Characteristics of Freshwater Algae

The toxic effect of multi metals mixture which exist simultaneously in aquatic ecosystem on natural phytoplankton assemblages (green algae, blue-green algae and diatoms) was studied. For this purpose a laboratory scale unit was designed to evaluate the effect of continuous flow metals mixture in forms if triple and penta metals in Nile water algae. Clear changes in algal biomass in terms of chlorophyll a (chl a) took place when subjected to metals combination. The rise or decline in chl a was in relation with other algal pigments (chl b, chl c, carotenoides and phenophytin), protein and carbohydrate content of algal cells. Substantial changes in phytoplankton community structure was detected and the most tolerant group was blue-green algae followed by green algae while diatoms was the most sensitive group. The most dominant species in all cases were blue-green alga Oscillatoria mougeotii and green alga Scenedesmus quadricauda. In addition clear changes in morphological shape was observed for tolerant species belonging to the three algal groups. Nile water algae has ability to remove and accumulate metals in the following order therefore Zn > Cd > Ni > Cu > Cr. In addition, phytoplankton has ability to recovered from the stress of metals when eliminated from the media and the recovered biomass was nearly equivalent to that before exposing to metals stress. The overall effect of metals mixture depending on the type and number of metals, the algal community structure and ratio between different morphological forms of algae (unicellular, colonial and filamentous).     

Microcomputer controlled titration for determination of protein nitrogen in feeds and wheat.

The determination of protein nitrogen in feeds and wheat by microcomputer controlled titration is described. The method involves direct titration of ammonia with standard hypochlorite titrant in the presence of bromide. The titrant is delivered by an automatic buret, and the microcomputer controlled, automatically computed potentiometric end points are precise to 0.1% over a 5-fold concentration range of nitrogen. Digestions performed with both mercury and copper catalysts show comparable results. Samples are weighed before digestion by an electronic balance interfaced to the computer which records sample number and weight. An automatic pipet aliquots, dilutes, and buffers samples directly from the digestion tubes; the samples can be immediately titrated with the automatic titrator. The results for protein in NBS standards and check feed samples from an offical testing program compare closely with average values reported for these standards. Results show that feed and wheat samples contained 10-100% protein. Precision for successive aliquots of the same digests is 0.1-0.4%relative standard deviation; precision for multiple digestions of the same sample is 0.1-0.8%.     

Oxidation-reduction regimes in some Oxisols of tropical China

The oxidation-reduction regimes of some Oxisols of tropical China were investigated on the basis of the Eh values and the amounts of reducing substances, both measured by newly devised methods. The Eh values in the surface layers of soil profiles under natural forest and commercial forest were 400–550 mV, lower by 100–200 mV than the deeper horizons. The concentrations of reducing substances in the surface layers corresponded to 0.5–5.0 · 10^?5M of Mn²⁺. In the cultivated layer of a submerged paddy soil the concentration of reducing substances was as high as 13·10^?5M, with an Eh value of less than 100 mV. There was a negative correlation between the Eh value and the logarithm of the concentration of reducing substances, showing that the intensity aspect and the capacity aspect of the oxidation-reduction status of a soil are closely interrelated.     

Liquid chromatographic determination of barbaloin (aloin) in foods

A simple and rapid liquid chromatographic method is described for the determination of barbaloin (aloin, 10-D-glucopyranosyl-1,8-dihydroxy-3-(hydroxymethyl)-9(10H)-anthraceno ne) in foods. Barbaloin is extracted with water from foods containing aloe and the extract is cleaned up on a disposable cartridge by using methanol-water (55 + 45) as eluant. The eluted barbaloin is separated by liquid chromatography on a YMC A-302 column with methanol-water (50 + 50) mobile phase, and detected at 293 nm. Recoveries of barbaloin added to foods at the levels of 0.05 and 0.50 mg/g were 94.4-100%. Assay results for commercial food samples indicated that the present method is applicable to a variety of foods supplemented with aloe.     

Theoretical effect of wheel loads on subsoil stresses

This study highlights the previously expressed concerns of soil researchers who have indicated that compaction pressures or stresses in the deeper layers of soil are determined by the amount of surface load. Modifications of Boussinesq theory by Froelich and further modification of Froelich's equations by Soehne were used to predict and develop graphical relationships for maximum allowable loads and/or mean surface contact pressures beneath loaded farm machinery tyres. Vertical compressive stresses at different subsoil depths were calculated and design loads for a currently used high flotation tyre were examined for comparative purposes. For highly compactible soils the results indicate that mean surface contact pressures should not exceed maximum allowable stresses in the subsoil for individual wheel loads which exceed approximately 30 kN. Thus, it appears that future designs based upon limited ground contact pressures are essential. This will require limitations on vehicle wheel loads and the use of more tyres and axles on heavy equipment.     

Radiometrische Untersuchungen zu Sorptionsverhalten und Abbau von 14C-PCB sowie 14C-Picloram in verschiedenen Böden

Radiometric analyses of sorption and degradation of ¹⁴C-PCB and ¹⁴C-Picloram in different soils Adsorption - desorption isothermes with ¹⁴C-PCB (2,3,4-trichlorodiphenyl) and ¹⁴C-picloram (4-amino-3,5,6-trichloropyridin-carbonic acid) were determined on 15 different soils. The rates of decomposition were determined on 3 soils. The adsorption of PCB was very intense with K-factors according to Freundlich (soil:solution = 1:20) varying from 16 to 9861. Adsorption increased with increase of organic matter and Fe-content. Picloram showed low adsorption rates, with K-factors varying from 0,01 to 18 (soil:solution = 1:4). The chemical is adsorbed by the organic matter. Decrease of pH increases the adsorption. The correlation of the K-factors with %C, % clay, pH, CEC and %0Fe_o was computed. The decomposition tests were monitored over a period of 183 days (25°C, 80% water capacity) and yielded decomposition rates of < 0,1% PCB and < 2% picloram. This difference might be due to the structure of the substance. The decomposition of PCB depends most likely on the degree of sorption. No relation between the decomposition of picloram and sorption or soil properties was found.     

Changes in fish populations in southernmost Norway during the last decade

Up to 1978 51% of brown trout populations and 27% of perch populations in the four southernmost counties of Norway were lost. During 1983 the fish status of lakes in the two southernmost counties which in the period 1974 to 1978 still had fish were updated. During the period 1978 to 1983, 30% of the remaining brown trout populations and 12% of the perch populations were lost. By 1983 71% of brown trout populations and 43% of perch populations in this area have been lost. In October 1983, 623 (77%) of the lakes were sampled for analyses of water quality. The status and change in fish populations during the period from 1974–78 to 1983 were highly related to water quality status.     

An assessment of the core-break method for estimating rooting density of different crops in the field

Most of the methods available for plant rooting studies in field soil are very tedious and time-consuming. Several investigations have shown that the core-break technique, in which roots are counted that appear at the faces of a broken core of soil, provides acceptable estimates of root length density in some situations. We investigated the usefulness of the core-break technique for evaluating rooting density of four plant species in two soil types. We encountered several problems, but recommend the core-break method to researchers who wish to quantify root development rapidly under various soil tillage practices.     

Adsorption of sulphate and fluoride by variable charge soils

The adsorption of sulphate and fluoride by three variable charge soils was studied. Adsorption increased with increase in the amount of sulphate added at constant _pH, and decreased with increase of _pH.
The ratios of the amount of released OH⁻to that of the adsorbed SO^2-₄ at pH 5–0 were 0.12, 0.14 and 0.20 for the three soils, respectively, much lower than the corresponding OH⁻/F⁻ ratios which ranged from 0.3 to 1.0. For a ferric acrisol the OH⁻ released accounted, on average, for only 15% of the SO^2-₄ adsorbed, leaving more than 60% to be explained by the decrease in positive charge and the increase in negative charge carried by the soil.