Value of transcranial Doppler indices in predicting raised ICP in infantile hydrocephalus. A study with review of the literature

Cerebral hemodynamic changes in infants with progressive hydrocephalus have been studied with the transcranial Doppler (TCD) technique. Several authors have referred to the correlation between the hemodynamic changes and increased intracranial pressure (ICP). Despite conflicting conclusions on the value of pulsatility index (PI) and resistance index (RI) measurements for monitoring infantile hydrocephalus, these pulsatility indices are the most commonly used for this purpose. Although clinical signs of raised ICP are highly variable and unreliable in infants, assumptions have been made in most of the studies about the presence of elevated ICP on the basis of the patient's clinical state. Few studies have reported on actual ICP values, however, and a direct relationship between ICP and TCD changes has never been adequately demonstrated. In the present study, this relationship was investigated in long-term simultaneous TCD/ICP measurements, in an attempt to develop a noninvasive method of monitoring the effect of ICP on intracranial hemodynamics. Two groups of data sets were established. Group I consisted of pre- and postoperative (shunt implantation) TCD/ICP measurements. Group II were long-term simultaneous TCD/ICP recordings showing significant ICP variations. In most of the postoperative measurements there was a decrease in the average PI and RI values. The correlation between PI or RI and ICP in the long-term simultaneous recordings, however, was generally poor. The risk of obtaining false positive or false negative PI or RI values in short-term measurements was also demonstrated. It can be concluded from our results, besides the wide range of reference values for the Doppler indices and extracranial influences upon them, that the present Doppler indices are inadequate for monitoring the complex intracranial dynamic responses in patients with raised ICP.     

Neurocontrol for lateral vehicle guidance

A solution to autonomous lateral vehicle guidance using a neurocontroller that can learn from measured human-driving data without knowledge of the physical car parameters is discussed. Simulations and practical tests confirm that a small-size feedforward autonomous neural network (21 neurons) can learn to steer a vehicle at high speeds only from looking at human-driving examples. In this way, the network learns the total closed-loop behavior, including the nonlinear dynamics of the vehicle and the driver's individual driving style. The main result of practical investigations is that the neutral controller trained on human-driving examples exhibits an aperiodic behavior that does not vanish at higher speeds (tests performed up to 130 km/h) and produces fewer lateral deviations than the linear state controller     

Modeling of fast pulse responses in the Multitrack: an advanced TAP reactor

A detailed transport model for the Multitrack setup, a TAP-like system, has been developed, which allows further analysis of adsorption, diffusion and catalysis phenomena. This includes the transport in the void part between the pulse valve and the reactor inlet. The effects of viscous flow and thermal transpiration, aspects that have not been studied in detail before for this type of setup, have been analyzed. A new expression for the modeling of the output signal is proposed depending on the positioning of the MS detector used in the study. The transport parameters of the model have been estimated by the analysis of the experimental pulse responses of the empty reactor system and the reactor charged with an inert packed bed. The proposed model reproduces the experimental pulse responses very well, and therefore can be extended to study systems with reacting or adsorbing beds by including the corresponding rate equations for the processes occurring in the bed of particles.     

Inactivation of Staphylococcus hyicus lipase by hexadecylsulfonyl fluoride: evidence for an active site serine

The Staphylococcus hyicus lipase is an acyl hydrolase with broadsubstrate specificity including neutral glycerides and phospholipids.To obtain further insight into the mechanism of action of thisenzyme, we tested several sulfonyl fluorides as active site-directedinhibitors. The enzyme is resistant to the well-known serineprotease/esterase inhibitor phenylmethanesulfonyl fluoride (PMSF),but is rapidly inactivated by hexadecylsulfonyl fluoride. Thekinetics of inactivation were studied in Triton X-100 micelles.Inactivation is fast and the rate of inactivation is constantover the pH range where this lipase is active. Metal ions likeCa²⁺ and Sr²⁺ do not appreciably influence the rate of inactivation,although the enzymatic activity is significantly increased,suggesting a structural role for these ions. The S.hyicus lipasecontains a consensus sequence G-H/Y-S-X-G. Substitution by site-directedmutagenesis of this serine (Ser369) by a cysteine resulted ina mutant with only 0.2% residual activity. The activity of thismutant could not be inhibited with water-soluble sulfhydrylreagents either in the presence or absence of Triton X-100 micelles.In the presence of Triton X-100 micelles, inactivation of themutant occurred with 4-nitrophenylhexadecyl disulfide (t_1/2= 125 min) while the wild-type enzyme does not react at all.We conclude that Ser369 is the active site residue and thatin water this residue is inaccessible. Only after interfacialactivation Ser369 (or Cys369) becomes exposed and reacts withirreversible inhibitors.     

Metabolite interactions in prostatic fluid mimics assessed by 1H NMR

Magnetic Resonance Materials in Physics, Biology and Medicine - Molecular interactions in prostatic fluid are of biological interest and may affect MRI and MRS of the prostate. We investigated the...     

Developments in proton MR spectroscopic imaging of prostate cancer

Magnetic Resonance Materials in Physics, Biology and Medicine - In this paper, we review the developments of 1H-MR spectroscopic imaging (MRSI) methods designed to investigate prostate cancer,...     

Comparing Syntactic and Semantic Action Refinement

The semantic definition of action refinement on labelled configuration structures is compared with the notion ofsyntactic substitution, which can be used as another notion of action refinement in a process algebraic setting. The comparison is done by studying a process algebra equipped with sequential composition, parallel composition with an explicit synchronisation set, and an operator for action refinement. On the one hand, the language (including the refinement operator) is given a configuration structure semantics. On the other hand, a reduction procedure transforms a process termPinto aflatterm (i.e., with the refinement operator not occurring in it)red(P) by means of syntactic substitution, defined in a structural inductive way. The main aim of the paper is to investigate general conditions under which the termsPandred(P) have the same semantics. The results we present are essentially dependent on the question whether the refined action can be synchronised or not. In the latter case,Pandred(P) give rise to isomorphic configuration structures under mild assumptions. The former case is considerably more difficult, since then refinement cannot be expected to distribute over parallel composition. We give necessary and sufficientsemanticconditions under which distribution still holds up to semantic equivalence. Subsequently, we also give sufficient (but not necessary)syntacticconditions for reducible terms. Finally, we generalise these results to a language with recursion.