Introduction of new functions to speed up sorption measurements

The procedure suggested by Jäntti enables estimation or calculation of the values of adsorption parameters in an early stage of adsorption measurements. The procedure may also give information about the validity of models used for the explanation of the measurements. In the present paper new functions are introduced to get results easier.     

Fast electromagnetic balance

Instead of reading the equilibrium value, the deflection of the balance as a function time can be measured and the equation of motion can be used to calculate the unknown torque T and to relate the other quantities in the equation to the actual instrument-constants. In this way, balance reading could be much faster and weighing errors due to faulty instrument and environmental influences can be smaller than those in equilibrium position. This enables the use of microbalances for the observation of fast chemical or thermal processes and to use it as fast checkweigher for control of sorting machines. In the present paper we present results from calculations of a simulation procedure.This revised version was published online in November 2005 with corrections to the Cover Date.     

Restoring of A balance by electric pulses

Restoring of the balance beam to its initial situation after a change of load can be effected by combination of forces of different kind. In former papers we discussed the possibility using the equation of motion of the balance to determine the mass to be measured. After the measurement the balance was restored by means of current pulses into the electromagnetic measuring system. In the present paper we discuss the application of electric pulses into an additional electrostatic system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Molecular diameter data from thermo molecular flow experiments

Based on the theory of thermo molecular flow forces at low gas pressures, an equation is evaluated which relates the thermo molecular flow effect at high gas pressures to the molecular diameters of the gas molecules. Our experimental results are compared with molecular diameters from other types of experiment.     

Application of Jäntti’s method for the explanation of adsorption onto rough surfaces

Jäntti introduced a method to calculate the final value of the adsorbed mass already in a very early stage of adsorption measurements. His method was restricted to gravimetric measurements and to adsorptions, which satisfy the simplest molecular model. One of the advantages of his method was that when more complicated molecular models were necessary, the curve resulting from Jäntti`s calculations showed discrepancies from the curve predicted for the simple situation. We used such deviations to evaluate the parameters of the models necessary for the explanation of the measurements. One of the examples we discussed concerned the influence of the occurrence of two parallel and simultaneous adsorptions. In the present paper we discuss the application of these results to adsorption onto a surface where roughness could be expected to play a part. If we consider a rough surface as the sum of two extra surfaces we can apply Jäntti’s method by using our former results of parallel adsorption. We characterise roughness by two parameters which we evaluated with Jäntti’s method. We emphasise that the existence of roughness is not demonstrated by Jäntti’s method, but that the method is useful for the evaluation of parameters introduced by other arguments or from other sources.     

Shelf Life Extension and Quality Improvement of Cucumber Slices Impregnated in Infusions of Edible Herbs

Abstract

Development of functional food through their enrichment with herbal extracts is gaining much attention from the food industry. The present study evaluates the benefits, such as the oxidative stability and quality retention, of the enrichment of cucumber (Cucumis sativus) with natural phenolic compounds through immersion into a variety of herbal infusions. After a preliminary experiment with gallic acid solutions, the beneficial effect of hypotonic solutions was observed and the optimal process conditions were defined. The second step of the study involved the immersion of cucumber in the herbal infusions for 2.5?h at 70?°C. The total phenolic content (TPC), antiradical and antioxidant activity of osmo-treated slices were determined to evaluate the extent of bioactive compounds’ impregnation. During the immersion, TPC, antioxidant and antiradical activity significantly increased irrespective of the type of the herbal infusion. The TPC varied greatly, ranging from 1.41 to 781.14?mg GAE/kg of cucumber. The highest total phenolics were found in cucumber treated with Origanum vulgare infusion, followed by Jasminum officinale and Mentha spicata infusions. The aforementioned osmo-treated slices were also highly appreciated by the sensory panel; therefore, for those best performing herbal infusions, the third phase of this work involved the study of quality degradation under subsequent storage of the osmo-treated slices vs. the untreated ones. The results regarding color, texture, and visual assessment demonstrated the superior quality retention of the osmo-treated samples that exhibited a shelf life extension ranging from two- to almost four-fold compared to the untreated tissue.     

Fundamental limits to the measurements of the gravitational constantG

An analysis is given of the limits set by the thermal noise to the accuracy of the measurements ofG with a torsion balance. The results are applied to measurements published recently. This shows that the uncertainty in modern measurements approaches the noise limit.     

Saving time when measuring BET isotherms

The measurement of adsorption isotherms and the determination of surface properties of a solid by means of the BET equation usually takes a lot of time as it involves measurement of several dynamic adsorption curves each at a given gas pressure. Two different timesaving approaches are suggested: (a) the beginning of a single dynamic curve is considered and (b) the beginnings of a number of different dynamic curves is considered. Approach (a) is less time consuming than approach (b), where approach (b) yields more accurate estimates of the BET-parameters. A discussion is given of the possibilities of using the time saving procedure of J?ntti for the two approaches.