Total and acid-soluble fluoride content of infant cereals, beverages and biscuits from Brazil

Total fluoride (TF) and HCl 0.01 M ('gastric juice')-soluble fluoride (SF) were analysed in infant foods, beverages and calcium-rich biscuits. Samples were divided into seven categories: children cereals (A), chocolate-flavoured milk (B), soy beverages (C), filled biscuits (D), non-filled biscuits (E), wafer biscuits (F) and corn starch biscuits (G). Mean TF concentrations ± SD (amplitude, unit µg F ml^-1 or µg F g^-1) were: (A) 4.25 ± 3.04 (0.20 - 7.84, n = 6); (B) 0.34 ± 0.47 (0.05-1.27, n = 6); (C) 0.15 ± 0.07 (0.09-0.29, n = 8); (D) 8.44 ± 1.76 (7.65-10.47, n = 4); (E) 12.41 ± 1.15 (10.69-13.68, n = 4); (F) 0.35 ± 0 (0.34-0.36, n = 4) and (G) 7.77 ± 1.12 (6.86-8.68, n = 2). Five samples of cereals, one sample of chocolate-flavoured milk and 10 samples of biscuits were analysed for SF. In cereals analysed for SF, all fluoride was soluble, while for the chocolate-flavoured milk, approximately 50% of TF was soluble. Regarding the biscuits analysed for SF approximately 20% of TF was soluble. It was observed that some of the cereals and beverages, and most of the biscuits analysed, might be important contributors to total daily fluoride intake. When consumed just once per day, cereals and beverages might supply up to 25% of the maximum recommended daily fluoride intake (0.07 mg F kg^-1 body weight) for a 2-year-old child (12 kg). For the filled, non-filled and corn starch biscuits, when 3, 32 or 20 units of them, respectively, are consumed just once per day, they may supply up to 16% of the maximum recommended daily fluoride intake. However, only approximately 25% of fluoride absorption occurs from the stomach and 75% from the small intestine. Therefore, a higher fluoride bioavailability is possible.     

High-T/sub c/ superconducting planar filter with pseudo-Chebyshev characteristic

This paper presents design and measurement results of a high-T/sub c/ superconducting planar filter based on a pair of coupled modified hairpin resonators considered to be a key constituent of the filter structure. This provides the filter characteristics, which are very close to the Chebyshev prototype of the same order.     

Deterministic Chaos during First-Order Phase Transitions in a Liquid–Vapor System

A model is developed in which the theory of deterministic chaos for the interface layer is used to treat both homophase and heterophase fluctuations of density (volume) and the fluctuations of pressure, whose duration increases as the critical point is approached. This approach, based on the transition from continuous differential equations to mappings, leads to a number of important consequences in theoretical analysis of high-temperature processes of evaporation and condensation, including the loss of information on the initial conditions, the alternation, and the presence of branching points on bifurcation diagrams.     

Modeling of the Sorption Dynamics in Multicomponent Ion-Exchange Systems with Consideration of Complexation Reactions on the Basis of the Surface Complexation Theory

The sorption dynamics in multicomponent ion-exchange systems with consideration of complexation reactions in solution is theoretically described by solving (on a computer) nonlinear material balance equations and kinetic equations of internal diffusion. Equilibria in multicomponent ion-exchange systems are characterized using the surface complexation theory. According to this theory, fixed groups of an ion exchanger and counterions form complexes located in different layers (Stern layers) at different distances from the surface. These layers constitute a circuit of series-connected capacitors. The fundamental advantage of such an approach is the fact that equilibria in multicomponent systems can be described in terms of a set of parameters obtained for binary systems. Additional account is taken of complexation reactions in the solution in the space between sorbent grains in an ion-exchange column. The H⁺–A–B three-component metal-ion exchange in various systems (A, B = Zn²⁺, Co²⁺, Ni²⁺, Cd²⁺, Ca²⁺, and Na⁺) is studied. Comparison is made between the results of numerical calculations of the characteristics of the H⁺–A ^{n +}–B ^{n +} ion exchange in multicomponent systems containing metal ions with and without consideration of chemical reactions.     

Screw Machines with Longitudinal Circulating Liquid. Communication 1. Pressure-Flow Rate Characteristics

The possibility of organizing longitudinal circulation of polymeric fluids along the channels of screw machines is demonstrated; it levels out the concentrations of additives, required because of the imprecise operation of metering systems in time, and averaging of the temperature of the fluid along the length of the screw. The pressure-flow rate characteristics of screw machines with longitudinal fluid circulation are investigated and the operating conditions in the presence and absence of longitudinal circulation are determined. The region of geometric screw dimensions where longitudinal circulation of polymeric fluid cannot be organized is determined.     

Results from the monitoring of pesticide residues in fruit and vegetables on the Danish market, 2000-01

To check compliance with the maximum residue levels in foods and to monitor the residue levels to enable an evaluation of the exposure of the Danish population to pesticides, a monitoring programme for pesticides residues in fruit and vegetables was performed. Sampling plans were designed based on previous findings and on consumption data. Samples (n = 4404) of mainly fresh conventionally and organically grown fruit and vegetables were collected at wholesalers and importers and at food processing companies. Of the samples, 3% were frozen products and 5% organically grown. Of the samples, 34% were of Danish origin, with 66% from other countries. Two accredited laboratories performed analyses of the samples using capillary gas chromatography, liquid chromatography and a spectrophotometric method. Reporting levels were set at the lowest calibration level or at the limit of determination. Residues were found in 60% of the samples of fruit but in only 18% of the vegetable samples. Residues above the maximum residue levels were found in 6% of all samples of fruit and in 2% of the vegetable samples.