MR monitoring of focused ultrasonic surgery of renal cortex: experimental and simulation studies

The aim of the study was to test the hypothesis that magnetic resonance (MR) imaging-guided and -monitored noninvasive ultrasonic surgery can be performed in highly perfused tissues from outside the body. A simulation study was performed to evaluate the optimal sonication parameters. An MR-compatible positioning device was then used to manipulate a focused ultrasound transducer in an MR imager, which was used to sonicate kidneys of five rabbits at various power levels and different durations. Temperature elevation during sonication was monitored with a T1-weighted spoiled gradient-echo sequence. The simulation study demonstrated that a sharply focused transducer and relatively short sonication times (30 seconds or less) are necessary to prevent damage to the overlying skin and muscle tissue, which have a much lower blood perfusion rate than kidney. The experiments showed that the imaging sequence was sensitive enough to show temperature elevation during sonication, thereby indicating the location of the beam focus. Histologic evaluations showed that kidney necrosis could be consistently induced without damage to overlying skin and muscle. The study demonstrated that highly perfused tissues such as the renal cortex can be coagulated from outside the body with focused ultrasound and that MR imaging can be used to guide and monitor this surgery.     

Excited state absorption of pump radiation as a loss mechanism insolid-state lasers

The characteristics of optical pumping dynamics in laser-pumped, rare-earth-doped, solid-state laser materials are investigated by using a tunable alexandrite laser to pump Y₃Al₅O₁₂ :Nd³⁺ in an optical cavity. It is found that the slope efficiency of the Nd laser operation depends strongly on the wavelength of the pump laser. For pump wavelengths resulting in low slope efficiencies, intense fluorescence emission is observed from the sample in the blue-green spectral region. This is attributed to the excited-state absorption of pump photons which occurs during radiationless relaxation from the pump band to the metastable state. This type of process is an important loss mechanism for monochromatic pumping of laser systems at specific pump wavelengths     

Should we be surprised at expert system success ?

Abstract. Expert systems proliferate. They are now a usable and used tool in a variety of organizations. However, little research has been undertaken on the quantification of success or failure of expert system projects. By and large the only test carried out for expert system validation is one of comparison of the conclusions of the system with those of an expert or team of experts. While questioning the validity, this paper accepts that this method is being used and analyses whether or not the results obtained from this type of test should be a surprise. That is, what sort of results should be expected and to what extent do the reported ones live up to these expectations? Earlier research from the field of human information processing casts doubts on the success claims made for current expert systems. The implications of this research are then analysed in order to explore the possible redeeming features of expert systems which are not taken into account in such comparisons. The use of linear models as comparators for expert systems may prove beneficial.     

Eruption times of third molars in young rural Nigerians

The mechanical stability of proximal femoral osteotomies fixed by the tension band wire technique was studied in flexion-compression and torsion tests. The fixation consisted in crossing the section with two Kirschner wires and with a wire cerclage applied to the tension surface. The study was conducted in three steps. First, cyclinders of wood were cut either transversely or at 30 degrees of inclination in relation to the long axis of the specimen, and fixed with two Kirschner wires and a wire cerclage. We concluded that the inclination of the plane of section significantly increased the stability of fixation. No significant difference was observed when oblique sections were made in the reverse orientation. Second, 30 degrees subtrochanteric varus osteotomies were performed in dog femurs, so that the section plane was transverse in one group and oblique in another, after closing the osteotomy. In both groups the fixation was achieved by two Kirschner wires that crossed the osteotomy and a wire cerclage placed on the lateral cortex (tension surface). We concluded that inclination of the osteotomy plane increased the stability of osteosynthesis in bone specimens, as already seen with the wood pieces. Third, the stability of tension band wire fixation was compared with that provided by the AO/ASIF paediatric angled plate. Varus osteotomies (30 degrees) were created at the subtrochanteric level of paired dog femurs. On one side, the femur was fixed with Kirschner wires and a wire cerclage as described previously. For the other femur, the osteotomy was fixed with the angled plate. We found that both types of fixation presented the same stability in flexion-compression tests. However, under torsion the tension band wire fixation was 30%-50% less stable than the plate fixation.     

A human homologue of the Drosophila Toll protein signals activation of adaptive immunity

Induction of the adaptive immune response depends on the expression of co-stimulatory molecules and cytokines by antigen-presenting cells. The mechanisms that control the initial induction of these signals upon infection are poorly understood. It has been proposed that their expression is controlled by the non-clonal, or innate, component of immunity that preceded in evolution the development of an adaptive immune system in vertebrates. We report here the cloning and characterization of a human homologue of the Drosophila toll protein (Toll) which has been shown to induce the innate immune response in adult Drosophila. Like Drosophila Toll, human Toll is a type I transmembrane protein with an extracellular domain consisting of a leucine-rich repeat (LRR) domain, and a cytoplasmic domain homologous to the cytoplasmic domain of the human interleukin (IL)-1 receptor. Both Drosophila Toll and the IL-1 receptor are known to signal through the NF-kappaB pathway. We show that a constitutively active mutant of human Toll transfected into human cell lines can induce the activation of NF-kappaB and the expression of NF-kappaB-controlled genes for the inflammatory cytokines IL-1, IL-6 and IL-8, as well as the expression of the co-stimulatory molecule B7.1, which is required for the activation of naive T cells.     

Respiratory symptoms and bronchial responsiveness are related to dietary salt intake and urinary potassium excretion in male children

Six men were accidentally exposed to NO2 when they were changing a propeller using a gas burner in the poorly ventilated hold of a ship. All of them were admitted to hospital with shortness of breath and cough. Chest X-ray on admission revealed diffuse, patchy and infiltrative shadows, leading to the diagnosis of pulmonary edema in all five patients. Steroid therapy was effective and followed by a quick recovery in all patients. None developed third phase manifestations characterized pathologically by bronchiolitis obliterans.     

Dental evidence for the peopling of the New World: some methodological considerations

Turner (1985b) and Greenberg et al. (1986) proposed that New World populations originated in northern Asia and entered the Americas in three migratory waves: Macro-Indian, Aleut-Eskimo, and Na-Dene. Biological support for this model comes from Turner's unweighted pair group (UPGMA) cluster analysis of discrete dental traits in world populations. Unfortunately, UPGMA analysis often creates suspect clusters and may not be valid as a method for displaying evolutionary relationships because it assumes that rates of evolution are equal among all populations. To test whether Turner's results are an artifact of his analytical method, I analyzed his published data (Turner 1985b) using two alternative techniques that do not assume homogeneous rates of change: a Wagner distance algorithm employing the Fitch-Margoliash criterion for goodness of fit and a maximum parsimony analysis using segment-coded dental trait frequencies. Both alternative methods produce trees that are similar to the UPGMA analysis results, supporting Turner's original results and basic conclusions. Comparisons of tree topology demonstrate that there is strong congruence between trees produced by all three methods, although the placement of certain populations, such as Na-Dene, depends on the method of analysis employed.