Clinical profile of arterial hypertension in patients with cerebrovascular diseases

The aim this work was to assess retrospectively the history of hypertension in patients admitted for cerebrovascular diseases. Two hundred and forty eight patients were studied (69% with ischemic strokes, 24% with hemorrhagic strokes and 7% with transient ischemic attacks. 76% of cases had a history hypertension with an evolution of ten years or more in 81% of cases. No differences in the prevalence of hypertension was observed among the different types of strokes. Of the 139 patients in whom the severity of hypertension was registered, 37% had mild, 45% moderate, 15% severe and 3% systolic hypertension. Those with severe hypertension had a higher incidence of hemorrhagic stroke. Fundoscopic examination was abnormal in 81% of the 64 patients in whom it was performed, left ventricular hypertrophy was found in 62% of the 146 patients in whom it was investigated. 51% of patients were receiving anti hypertensive treatment and it was effective in 26% of them. Thirty one percent of subjects had old lesions in the CAT scan; these subjects had a similar prevalence of hypertension and effectiveness of treatment than patients without old lesions. It is concluded that a history of more than ten years of hypertension is a risk factor for cerebrovascular disease, that severe hypertension is mostly associated to hemorrhagic strokes and that only 26% of patients with stroke had and adequate anti hypertensive treatment.     

A CONTROL VECTOR SIMPLEX APPROACH TO VARIABLE STRUCTURE CONTROL OF NONLINEAR SYSTEMS

An effective way to extend to the multi-input case the variable structure control philosophy is the method based on a set of m+1 control vectors forming a simplex in ℛ^m, and on the corresponding switching of the controlled system from one to another of m+1 different structures. In this paper, the basic method is briefly recalled and conditions for the possible extension of its validity to the case of uncertain nonlinear systems affine in the control law are sought. The possibility of guaranteeing the convergence of the simplex method also in the case of nonlinear systems non-affine in the control law is investigated. © 1997 by John Wiley & Sons, Ltd.     

Behavior of variable-structure control systems near the sliding manifold

A new definition of well-posedness, called generalized approximability, is introduced for variable-structure control systems described by ordinary differential equations. This definition isolates the following basic property: states fulfilling only approximately the sliding condition converge toward some well-defined sliding state, as the perturbations preventing exact sliding disappear. Approximability rules out ambiguous systems, which defy successful implementation of sliding feedback controls. The existence of the equivalent control is not required. It is shown that approximability is in essence of a form of uniqueness of the Filippov sliding state. Explicit criteria for approximability are obtained.     

River bed evolution due to channel expansion: general behaviour and application to a case study (Kugart River,Kyrgyz Republic)

We study the effect of spatial variations of river width on bed aggradation and degradation processes, making use of a one‐dimensional numerical model of channel morphodynamics. We refer to a peculiar case, the downstream reach of the Kugart River (Kyrgyzstan). The river has been partly channelized in the recent past with the aim of reducing the flooding risk for the surrounding villages; the consequent reduction of channel width in some reaches was also expected to improve channel conveyance with respect to the high sediment load produced in the upper river basin. The resulting longitudinal sequence of relatively sharp channel expansions and contractions has, however, triggered rapid siltation rates, especially in the narrowest reaches. This motivated the application of a 1‐D numerical model of river morphodynamics. Abrupt channel expansions are found to be the main driving forces for aggrading processes, which may extend for long distances from where they are generated. In order to obtain a thorough understanding of the morphodynamics of channel expansions, we first apply the model to simple test cases. This allows us to characterize the basic features of the problem and the dependence of bed evolution on the upstream Froude number Fr and on the expansion ratio r_b, which are the most relevant controlling parameters. We invariably find that deposition occurs in expansion regions with bed aggradation observed both upstream and downstream. The deposition prism progressively increases its height and lengthens both in the upstream and downstream directions. The deposition process is particularly intense, in terms of deposition prism height, in super‐critical conditions. Moreover, it is found that higher values of Fr strongly reduce the time scale of morphological processes and faster deposition rates are further facilitated by abrupt expansions. The present outcomes are relevant for assessing the expected altimetric response of river bed to the implementation of localized channelization works and to local river widening, a practise which is increasingly being employed within river restoration projects, with the aim of enhancing habitat diversity. Copyright © 2008 John Wiley & Sons, Ltd.     

Prioritizing reaches for restoration in a regulated Alpine river: Locally driven versus hydro‐morphologically based actions

We discuss the prioritization of river reaches to be selected for restoration measures under the constraints of financial resource limitation. We propose and apply a simple approach based on the quantification of major hydro‐morphological alterations and the critical comparison with locally proposed restoration actions. The available hydro‐morphological and ecological data for the approach do not go beyond the requirements posed by the implementation of the EU Water Framework and Floods Directives. We describe an example that refers to a heavily regulated Alpine river (Sarca River, NE Italy). The results indicate hydropower facilities as a key source of hydrological alteration, with sediment retention and grade control structures on lateral tributaries playing an additional relevant role in reducing sediment supply. The frequency and duration of sediment‐transporting floods have dramatically decreased, and the bed sediment composition has been markedly altered and become highly compacted. Habitat improvement has been achieved after the implementation of minimum environmental flows. The comparison between the results of the hydro‐morphological indicators and the locally proposed restoration actions highlights that reaches with lower degree of hydro‐morphological alterations do not coincide with the areas chosen for the locally planned actions, which often miss considerations of the relevant spatial scales. In a context of limited available financial resources and data compared to other flagship river restoration projects in the European Alps, the present work suggests viable options for the choice of target restoration reaches.     

The oral strontium load test in the assessment of intestinal calcium absorption

A close correlation between calcium and strontium intestinal absorption has been described. In this study, a test using Stable Strontium has been assessed in women without abnormal calcium or bone metabolism, with no history of drugs which might affect calcium or bone metabolism. Decreasing values of Strontium intestinal absorption, according to the length of the postmenopausal period, have been observed. Besides, the Stable Strontium Test has been given in postmenopausal women with osteoporotic femur fractures. In comparison with age matched healthy women, this latter group showed a significantly lower Strontium intestinal absorption. Analogous behaviour has been reported for Calcium intestinal absorption.     

Variable structure systems nonlinear in the control law

The most relevant results of Utkin's work obtained for variable structure systems linear in the control law which slide on suitable manifolds in the state space, are extended to some class of fully nonlinear plants. The equivalence between the Filippov solution concept is proved for this class. Further, the approximability property (convergence to the nonideal sliding motion to the ideal) is shown to hold for an important subclass.     

Biological and electrochemical oxidation of naphthalenesulfonates

A biofilm airlift suspension (BAS) reactor and an undivided flow cell equipped with a boron‐doped diamond (BDD) anode and a stainless‐steel cathode were used to investigate the effects of varying operating conditions on process performance in the biological and electrochemical oxidation of a mixture of naphthalenesulfonates contained in the infiltration water of a contaminated industrial site. The experiments were aimed at evaluating the feasibility of process integration and the criteria for optimization (i.e. how to maximize degradation efficiency with minimum energy consumption) in combined biological and electrochemical oxidation of scarcely biodegradable compounds. Because of high reactor biomass concentration and long biomass retention time, the BAS reactor achieved a high degradation capacity (up to 6.8 kg COD m^?3 d^?1). On the other hand, owing to the recalcitrant character of some of the aromatic sulfonates in the leachate, the overall degradation efficiency did not exceed 70% based on COD measurements. All naphthalene‐mono‐ and ‐disulfonates (except naphthalene‐1,5‐disulfonate) were completely degraded in the BAS reactor, whereas more complex molecules (e.g. naphthalenetrisulfonates) were more recalcitrant to biological oxidation. These compounds were completely mineralized by electrochemical oxidation using a boron‐doped diamond anode. The energy consumption and the time required for the complete mineralization of the infiltration water decreased from 80 kWh m^?3 and 4 h to 61 kWh m^?3 and 3 h for the oxidation of raw and biologically pretreated leachate, respectively. Copyright © 2005 Society of Chemical Industry     

Controlled release of vancomycin from cross-linked gelatine

This paper explores the possibility of using biodegradable cross-linked gelatines as antibiotic devices for a long-term elution (80 days). Capillary electrophoresis (CE) has been utilized to evaluate the mass percentage of vancomycin and gelatine contemporary released from differently cross-linked vancomycin loaded gelatine samples in an elution time ranging from 24 to 1920 h. While the solubilization kinetic of gelatine samples differently cross-linked can be very close described by the simplified Higuchi model, the vancomycin release kinetic is contemporary governed by both the Fickian diffusion process trough the gelatine matrix network and the dissolution process of the matrix due to its degradation. Comparing the antibiotic eluting kinetics from gelatine at diverse cross-linking degree we observed that the degradation of the proteic matrix appears to have a minor influence in the drug release control. Vancomycin released from all the gelatine partially cross-linked samples results active against Staphylococcus aureus and Streptococcus faecalis which represent the most pathogens commonly isolated in orthopaedic infections. Vancomycin overcomes the minimum inhibitory concentration for both the bacteria in the whole range of elution time. Cross-linked gelatine devices appear to represent a useful biodegradable delivery system for local anti-infective therapy in arthoplasty.     

The VSS approach to the model reference control of nonminimum phaselinear plants

A nontrivial application of the discontinuous control system theory, based on Filippov's solution concept, is presented. The problem addressed is the model reference output feedback control of linear plants with non-Hurwitzian numerator in the transfer function. A solution in the case of known systems is presented first. An error state equation, whose state is accessible, is then derived for the case in which the plant parameters are unknown. In the case in which some bounds on the plant characteristics are supposed known, a pair of discontinuous signals acting on both the plant and the model is chosen, causing the error state to vanish asymptotically