Assessing the degree of preservation of landscape,natural and cultural–historical values in river dike reinforcement planning in the Netherlands

The Dutch river district is highly valued for its landscape, natural and cultural–historical elements (also called LNC values). According to the current Dutch policy on river dike reinforcements, these values should be safeguarded in planning and executing river dike reinforcement projects by following the ‘selective smart design strategy’. This paper presents an audit model, consisting of 20 modules, assessing the extent to which LNC values are taken into account in the planning process. The model was tested on eight projects and appeared to fit the objectives very well. The assignment of weighting constants used to interconnect the individual modules, however, would be improved if all parties involved could achieve consensus on this issue. The test results showed that in five of the eight projects examined, LNC values were sufficiently taken into consideration. Aspects that were insufficiently taken into account concerned, in particular, fauna surveys, valuation of LNC elements and effects valuation. Moreover, LNC values were often restored or compensated for, rather than preserved. Large differences were found between individual river dike reinforcement projects. The method can also be applied in river dike reinforcement plans in other countries. Copyright © 1999 John Wiley & Sons, Ltd.     

Repeatable and Realistic Experimentation in Mobile Wireless Networks

Experimenting with mobile and wireless networks is challenging because testbeds lack repeatability and existing simulation models are unrealistic for real-world settings. We present practical models for the physical and MAC layer behavior in mobile wireless networks in order to address this challenge. Our models use measurements of a real network rather than abstract radio propagation and mobility models as the basis for accuracy in complex environments. We develop an adaptive measurement technique in order to maximize the accuracy of our models in dynamic environments. The models then predict the packet delivery, deferring, and collision probability in the same network for an arbitrary set of transmitters. This allows to explore the performance of different network and higher layer protocols in simulation or emulation under identical and realistic conditions. We evaluate the accuracy of our models empirically by comparing them to benchmark measurements. We find that our models are effective at reproducing mobile scenarios in various environments. Across many experiments in realistic environments, we are able to reproduce link delivery probabilities with RMS error below 12 percent, and the simulated throughput of data flows in the presence of interfering transmitters with an error that is below 10 percent.     

In vivo hypothalamic release and synthesis of catecholamines in spontaneously hypertensive rats

Juvenile spontaneously hypertensive rats (SHR) have higher plasma levels of catechols and markedly larger catechol responses to yohimbine than do normotensive Wistar-Kyoto rats, indicating increased sympathoadrenal outflow and increased alpha 2-adrenergic receptor-mediated restraint of peripheral catecholamine release during hypertension development in SHR. Yohimbine-induced catecholamine release and metabolism in the posterolateral hypothalamus of the brain were assessed in juvenile (6 to 7 weeks) and adult (15 to 16 weeks) SHR and Wistar-Kyoto rats. In vivo microdialysis was used to obtain samples for measurements of norepinephrine, dihydroxyphenylglycol, methoxyhydroxyphenylglycol, and dihydroxyphenylacetic acid in conscious animals before and after yohimbine injection (1 mg/kg IV) beginning 24 hours after probe implantation. Catecholamine synthesis was examined from elevations of 3,4-dihydroxyphenylalanine levels after probe perfusion with NSD-1015, an inhibitor of L-aromatic acid decarboxylase. In adults, SHR had higher dialysate norepinephrine (277 +/- 38 versus 181 +/- 35 pg/mL), dihydroxyphenylglycol (3260 +/- 509 versus 2231 +/- 201 pg/mL), methoxyhydroxyphenylglycol (2659 +/- 369 versus 1890 +/- 144 pg/mL), and dihydroxyphenylacetic acid (46,312 +/- 5512 versus 13,187 +/- 1963 pg/mL) levels and markedly larger increases in 3,4-dihydroxyphenylalanine levels after NSD-1015 than Wistar-Kyoto rats. In juveniles, SHR had larger proportionate increments in microdialysate norepinephrine levels after yohimbine than Wistar-Kyoto rats (85% versus 25%). Although juvenile SHR and Wistar-Kyoto rats had similar NSD-1015-elicited increments in 3,4-dihydroxyphenylalanine levels, systemic yohimbine enhanced the NSD-1015-elicited 3,4-dihydroxyphenylalanine elevations in juvenile SHR but not in Wistar-Kyoto rats. These findings suggest augmented norepinephrine release and catecholamine synthesis in the posterolateral hypothalamus of adult SHR and augmented alpha 2-adrenergic receptor restraint of both norepinephrine release and catecholamine synthesis in juvenile SHR.     

Plasma metanephrines are markers of pheochromocytoma produced by catechol-O-methyltransferase within tumors

This study examined whether the high sensitivity of plasma free metanephrines for diagnosis of pheochromocytoma may result from production of free metanephrines within tumors. Presence in pheochromocytomas of catechol-O-methyltransferase (COMT), the enzyme responsible for conversion of catecholamines to metanephrines, was confirmed by Western blot analysis, enzyme assay, and immunohistochemistry. Western blot analysis and enzyme assay indicated that membrane-bound and not soluble COMT was the predominant form of the enzyme in pheochromocytoma. Immunohistochemistry revealed colocalization of COMT in the same chromaffin cells where catecholamines are translocated into storage vesicles by the vesicular monoamine transporter. Levels of free metanephrines in pheochromocytoma over 10,000 times higher than plasma concentrations in the same patients before removal of tumors indicated production of metanephrines within tumors. Comparisons of the production of metanephrines in patients with pheochromocytoma with production from catecholamines released or infused into the circulation indicated that more than 93% of the consistently elevated levels of circulating free metanephrines in patients with pheochromocytoma are derived from metabolism before and not after release of catecholamines into the circulation. The data indicate that the elevated plasma levels of free metanephrines in patients with pheochromocytoma are derived from catecholamines produced and metabolized within tumors. Some tumors do not secrete catecholamines, but all appear to metabolize catecholamines to free metanephrines, thus explaining the better sensitivity of plasma free metanephrines over other tests for diagnosis of pheochromocytoma.