Times In Distilled Water Research Articles

A model for erosion kinetics of a hydrogel matrix

We have observed that the weight of κ-carrageenan hydrogel decreases in an oscillatory manner with time in distilled water. In order to explain this observation, a kinetic model for an oscillatory erosion of hydrogel is proposed in which two coefficients, α and β, are introduced for the initiation and the termination of the hydrogel erosion. Analysis of erosion data on κ-carrageenan hydrogel is attempted via the present model. Hydrogel starts to swell when transferred into an aqueous solution. The swelling continues until the weight W( t) of water in the hydrogel reaches αP( t), where P( t) is the polymer weight in the hydrogel. When W( t) = αP( t), erosion, that is, liberation of both polymer and water from the hydrogel, starts. The erosion process is terminated when the water weight in the hydrogel decreases to βP( t). The swelling and erosion take place alternately and the swelling/erosion cycle continues repeatedly until all the polymer molecules are liberated from the hydrogen matrix. It is found that these two parameters, α and β, affect both the amplitude and frequency of the oscillation. Further, the amplitude and the frequency of the oscillation depend on the water influx and efflux rates.

Consumer vinegar test for determining calcium disintegration

A consumer test and standardized methods were compared for measuring the disintegration of calcium tablets, and the disintegration results were compared with results of dissolution testing to determine the ability of the consumer test of disintegration to predict bioavailability of calcium. Disintegration of 17 calcium supplement products, in tablet form, was studied in Simulated Gastric Fluid Test Solution, USP, without pepsin (GF), in distilled water, and in white distilled vinegar. For disintegration testing with GF and with distilled water, six tablets of each product were placed in an apparatus and immersed in the solution at 37 degrees C for 60 minutes. Six tablets of each product were tested in 200 mL of vinegar at room temperature for 30 minutes. Disintegration was determined by visual observation. Seven products were tested for dissolution in GF or water. Three samples of each product were tested at intervals over 120 minutes for calcium content. Results of testing with an ion-selective electrode were converted to milligrams and compared with the calcium content of the tablets (as claimed on the package label). The mean disintegration times of various calcium products in vinegar ranged from 1.8 to greater than 30 minutes. The mean time in distilled water and GF ranged from 1.6 to greater than 60 minutes and from 1.0 to greater than 60 minutes, respectively. Results were in agreement in 87% to 93% of cases between the consumer vinegar test and the standardized disintegration test methods, a significant correlation. No correlation was found between disintegration time and the extent of dissolution. The disintegration and dissolution of commercially available calcium tablets was highly variable.(ABSTRACT TRUNCATED AT 250 WORDS)

Correlated confocal laser scanning microscopy with high-voltage electron microscopy of focal contacts in 3T3 cells stained with napthol blue black

We used the MRC-500 confocal laser scanning microscope (LSM) in the reflecting mode, rather than the fluorescent mode, to produce high-resolution images of cytoskeletal structures in 3T3 cells stained with Napthol Blue Black (NBB). High voltage electron microscopy CHVEM) of the same cells confirmed that structures at the cell/substratum interface imaged with the LSM are “focal contacts,” regions of cell attachment to the substratum.Swiss 3T3 cells were cultured on Formvar/carbon-coated gold finder grids in Dulbecco's Modified Eagles medium containing 10% calf serum in saturated humidity and 10% CO2at 37°C. Preconfluent cultures growing on the grids were fixed in a detergent/glutaraldehyde fixative for 10 minutes, stained with 0.2% NBB in methanol/acetic acid/water for 30 minutes, rinsed several times in distilled water, mounted in simple chambers in distilled water and examined in the LSM operated in the reflecting mode.

Scanning Electron Microscopy of the Palp Sense Organs of the Harvestman Leiobunum townsendi (Arachnida: Opiliones)

Scanning Electron Microscopy of the Palp Sense Organs of the Harvestman Leiobunum townsendi (Arachnida: Opiliones)

The hydrolytic durability of two high-level waste oxide borosilicate glasses (GP [formula omitted] and GP [formula omitted

Two glasses containing 15 wt.% simulated high-level liquid waste (HLLW) oxides were leached several times in distilled water, Asse rock salt brine, and carnallite-containing quinary solution at normal pressure (Soxhlet: 100 °C) and at 130 bars (autoclave: 100, 150 and 200 °C). The leach rates are relatively high during the first few days, but decrease rapidly, and after 10 to 15 days approach a constant value. The leach rates increase with temperature and show only a slight difference between water and brine but a decrease in the case of quinary solution. Leaching at elevated pressure and 100 °C is less than at normal pressure and the same temperature. The crystallization of the glass products (annealing time 100 days at 750 °C) has no effect on the leach resistance as determined in Soxhlet tests.

Identification of L forms by polyacrylamide-gel electrophoresis.

Crude membranes were obtained from L forms by allowing the cells to lyse in distilled water. The crude membranes were washed several times in distilled water, lyophilized, and extracted with phenol-acetic acid-water. The membrane proteins were separated electrophoretically in polyacrylamide gels run at pH 4.5. Electrophoretic patterns and densitometric tracings of the gels showed distinct, reproducible intergeneric differences among L forms of Proteus, Streptobacillus, Staphylococcus, and Streptococcus. Differences within a genus could not be detected except between the group A streptococcal L forms and the one group D F-24 L form. This electrophoretic method offers possibilities for ready identification of L forms through the use of standard reference strains.

Permanent mounting of unstained and aceto-orcein stained cells in the water-soluble medium, Abopon.

For cellular morphology, mammalian cells were grown on cover slips in Leigh ton tubes, fixed in 1% osmic acid vapor for 2 min, decolorized with 30% H2O2 in 5% ammonium oxalate solution (1:7) for 2 min, then washed thoroughly, and finally mounted in a water-soluble medium consisting of a saturated solution of Abopon in 0.2 M phosphate buffer, pH 7.0. For chromosomal analysis of similarly cultured cells, aceto-orcein preparations were made by conventional methods, with the following minor modifications: following pretreatment with colchicine and hypotonic expansion, the cells on the cover slips were fixed in acetic-alcohol (1:3), air dried, incubated at 37° C for 15 min in 2% orcein in 45% acetic acid, rinsed in 45% acetic acid, washed several times in distilled water, and finally mounted in Abopon mounting medium. Both kinds of preparations were allowed to harden for 24 hr before being handled. Such slides will keep for years at room temperature. Studies requiring frequent comparisons of cellular and chromosomal morphology of cultured cells can thus be extended over long periods of time.

SALT ABSORPTION AND ACCUMULATION IN VARIOUS REGIONS OF ROOTS

THIS STUDY was made to provide more information concerning the relative amounts of salt accumulated in various regions of roots and the amounts translocated to the shoot from various regions of roots. For soine years it was believed that the greatest amount of salt always is accumulated near the root tip and that this also is the region through which most of the salt absorbed enters the plant (Prevot and Steward, 1936; Steward et al., 1942; Overstreet and Jacobson, 1946), Kramer and Wiebe (1952) found, however, that in roots of barley, tomato, and pine there is as much acicumulation of P32 in a region one to several centimeters behind the root tips as in the apical region, and there is typically a region of low accumulation a few millimeters behind the tip. This appears to be in the region of cell enlargement. Later Wiebe and Kramer (1954) found that very little of the salt accumulated in the root tips of barley seedlings was translocated to the shoots, but considerable translocation occurred from the regions 10-60 mm. behind the tip. This was true for Rb86, Is3 and S35, as well as for P32, when roots were exposed to the isotopes for a period of 6 hr. In view of the results obtained with barley seedlings it was decided to study accumulation in and translocation out of various zones of the roots of several other species of plants. MATERIALS AND METHODS.-The plants used were Golden Cross Bantam sweet corn, Thomas Laxton peas, and Pima S-1 cotton. The seeds were surface sterilized for 15 min. in a 5 per cent solution of Clorox (a commercial preparation of sodium hypochlorite) and rinsed several times in distilled water before starting germination. The corn was germinated on moist filter paper in finger bowls in darkness at 25?C. for 48 hr. The cotton seeds were soaked in water for 30 min. and then germinated on moist paper in an incubator at 35?C. for 48 hr. The peas were soaked in water over-night and germinated in dilute nutrient solution (0.02 per cent Hoagland solution) at 25?C. in darkness for 48 hr. The full strength Hoagland solution contained 5 mM. of KNO3, 5 mM. of Ca(NO3)2, 2mM. Of MgSO4, and one mM. of KH2PO4 per liter. After germination the seeds were laid on lucite plates provided with holes through which the roots projected downward into jars of dilute nutrient solution. The jars were wrapped in aluminum foil and the lucite plates were painted with black asphalt to exclude light. Dilute, aerated nutrient solution

THE EFFECT OF FURFURAL UPON THE GERMINATION AND RESPIRATION OF ASCOSPORES OF NEUROSPORA TETRASPERMA

THE WORK of Emerson (1948) showed for the first time that chemical treatment, as well as the application of heat (Goddard 1935, 1939), could activate ascospores of Neurospora. She reported that furfural and furfuryl alcohol in very low concentrations effectively induced germination, but the mechanism of this activating effect was not investigated. Since that time, Sussman (1953) has reported that 11 other heterocyclics also serve as activators of ascospores. The purpose of the following experiments was to follow up these observations with an investigation of the metabolic effects of chemical activators. MATERIALS AND METHODS.-Ascospores were obtained by crossing strains 374 and 377 of Neurospora tetrasperma which were then grown as outlined by Goddard (1935). Since Emerson (personal communication, 1951) has shown that ascospores rapidly lose their sensitivity to chemical activators, these were used within a month after harvesting (fresh spores). In the experiments wherein the ageing effect or loss of sensitivity was studied, old spores were used: these had been harvested at least 6 mo. before use. Both fresh and old ascospores were stored at 40 C. at 65 per cent relative humidity. Respiratory measurements were made in Warburg vessels of 7 ml. capacity with a fluid volume of 1.1 ml. Standard Warburg manometers were used at a shaking rate of 120 oscillations per minute, while the temperature of the bath was maintained at, 260 C. except when otherwise stated. Anaerobic conditions were obtained by flushing the vessels with nitrogen which had been passed through alkaline pyrogallol and then over a heated copper coil to remove contaminant CO2 and 02. Spore suspensions for the respirometric determinations were made up by determining the volume of a weighed sample of spores after centrifuging in a hematocrit tube. The spores were then washed with a 1:4 dilution of sodium hypochlorite (Fishers reagent grade) to kill contaminant conidia, rinsed several times in distilled water, and finally resuspended in 30 parts of distilled water (by volume). Controls of dormant spores suspended in water were always run. The rate of oxygen uptake remained constant; therefore, it was assumed that contamination was controlled effectively. Spores were heat activated by suspending them in distilled water at 600 C. for 30 min. in a constant temperature oil bath. Chemical activation was usu-