The capacity of an in vitro gastrointestinal (IVG) method to predict relative bioavailable Cd from soil ingestion was evaluated. Bioaccessible Cd determined by the IVG method was compared with relative bioavailable Cd measured from dosing trials using juvenile swine for 10 soils contaminated with Cd from 23.8 to 465 mg kg -1 . The effect of the food-dosing vehicle (i.e., dough) in the IVG method was evaluated. Bioaccessible Cd was measured in the gastric extraction and intestinal extraction steps of the IVG method. Means for bioaccessible Cd, in parentheses, fell in the following order: gastric extraction step without dough (63.0%) > intestinal extraction step without dough (39.1%) > gastric extraction step with dough (38.2%) > intestinal extraction step with dough (12.9%). It is possible that phytic acid associated with the addition of dough decreased bioaccessible Cd. In vivo relative bioavailable Cd ranged from 10.4 to 116% with a mean of 63.4%. Linear relationships between the IVG gastric extraction step without dough (r ) 0.86), the IVG intestinal extraction step with dough (r ) 0.80), and the in vivo relative bioavailable Cd were found. Inexpensive in vitro methods might be useful in estimating the relative biovailability of Cd in soils from contaminated sites.

The effect of the dosing vehicle (e.g., dough) on the ability of an in vitro gastrointestinal (IVG) method to predict relative bioavailable Pb associated with soil ingestion was evaluated. Bioaccessible Pb determined by the IVG method was compared with relative bioavailable Pb measured from dosing trials using juvenile swine for 18 contaminated soils ranging from 1270 to 14200 mg Pb kg(-1). Bioaccessible Pb was measured in the IVG gastric extraction (GE) and intestinal extraction (IE) solutions. Mean bioaccessible Pb values were 32.2% for GE without dough, 23.0% for GE with dough, 1.06% for IE without dough, and 0.56% for IE with dough. It is possible that phytic acid associated with the dough addition decreased bioaccessible Pb. In vivo relative bioavailable Pb ranges for different swine tissues were 1 to 87% for blood, 0 to 110% for liver, 1 to 124% for kidney, and 0.04 to 94% for bone. Strong linear relationships between IVG GE Pb with dough (r > 0.76, P < 0.0002), IVG IE Pb with dough (r > 0.56, P < 0.015), and IVG GE Pb without dough (r > 0.81, P < 0.0001) and in vivo bioavailable Pb as estimated with blood, kidney, liver, and bone were found. Inexpensive in vitro methods may be useful in providing an estimate of the variability in relative bioavailable Pb at a single study site. The IVG method can be used to estimate relative bioavailable Pb, As, and Cd in contaminated soil.

In this paper, a new approach for designing the virtual topology of optical multihop networks has been developed. The considerations when designing an optical multihop network, such as wavelength assignment and traffic routing problem have been investigated. The objective function of designing virtual topology is the propagation delay and/or transmission delay of the optical multihop traffics. The optical networks with 8 nodes have been designed based on different types of traffic demands. The design approach is based on the Hopfield neural network (HNN) model. With this method, the optimal solutions for designing optical multihop network have been obtained. All the solutions are compared with results of the previous researchers and good agreement has been observed, thus establishing the validity of the method developed.

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The design of virtual topology of multihop lightwave networks belongs to multivariable and multidimensional optimization problem. It requires selection of the connectivity diagram among all the communication nodes. In this paper, this optimization problem is converted to a problem of finding optimal path among all the nodes and Kohonen's Self Organizing Feature Mapping (SOFM) algorithm is used as the optimization approach. The main objective of the design is to minimize a function which combines both average delay and throughput. Simulation experiments are carried out and results are obtained from 8-node to 20-node optical multihop networks based on different fixed traffic demands. The results obtained are in good agreement with previous research work.