Maximal Instantaneous Mitral Valve Velocities Measured with a Digital Echocardiographic Tracking System

Analysis of the motion of various cardiac structures is attaining increasing clinical significance. By coupling a digital tracking system to a commercially available echocardiograph, continuous position and velocity data from selected intracardiac structures were obtained. This tracking system, which employs a dynamic range gate, has been designed to isolate and lock on to a selected target within the heart. Position of the target is calculated every 8 ms; velocity is obtained by determining the difference between consecutive positions. This system has been used to study mitral valve motion in 20 normal subjects. Maximal instantaneous velocities of the anterior leaflet of the mitral valve were recorded. These instantaneous velocities are to be distinguished from the average velocities obtained by manually measuring the slopes of the curve segments. This system demonstrates a new technique for obtaining more detailed information about the dynamic characteristics of selected cardiac structures.     

Use of microhardness as a simple means of estimating relative wear resistance of carbide thermal spray coatings: Part 2. wear resistance of cemented carbide coatings

A selection of WC-Co and Cr₃C₂-25%NiCr coatings produced by plasma spray and high velocity oxygen fuel (HVOF) deposition techniques were subjected to various wear tests designed to simulate abrasion, cavitation, sliding, and particle erosion type wear mechanisms. All of the coatings were at least 200 μm thick and were deposited onto stainless steel substrates. In Part 1 of this contribution, the microstructures of the coatings were characterized and their mechanical properties were assessed using microindentation procedures. In this second part of the article, the behavior of the coatings when subjected to the various wear tests is reported and the utility of microhardness testing as an indication of relative wear resistance is discussed. It is shown that correctly performed, appropriate microhardness measurements are a good indication of abrasion resistance and sliding wear resistance, and also correlate well with cavitation resistance in Cr₃C₂-NiCr. The measurements were less useful for predicting erosion resistance for both Cr₃C₂-NiCr and WC-Co, however, and for abrasion resistance when WC-Co was ground against SiC. Here the contribution of micromechanisms involving fracturing and brittle failure is greater than that indicated by the coating microhardness, which is essentially a measurement of resistance to plastic deformation under equilibrium conditions.     

Determination of protein concentration in raw milk by mid-infrared fourier transform infrared/attenuated total reflectance spectroscopy

This study investigates the potential use of attenuated total reflectance spectroscopy in the mid-infrared range for determining protein concentration in raw cow milk. The determination of protein concentration is based on the characteristic absorbance of milk proteins, which includes 2 absorbance bands in the 1500 to 1700 cm(-1) range, known as the amide I and amide II bands, and absorbance in the 1060 to 1100 cm(-1) range, which is associated with phosphate groups covalently bound to casein proteins. To minimize the influence of the strong water band (centered around 1640 cm(-1)) that overlaps with the amide I and amide II bands, an optimized automatic procedure for accurate water subtraction was applied. Following water subtraction, the spectra were analyzed by 3 methods, namely simple band integration, partial least squares (PLS) and neural networks. For the neural network models, the spectra were first decomposed by principal component analysis (PCA), and the neural network inputs were the spectra principal components scores. In addition, the concentrations of 2 constituents expected to interact with the protein (i.e., fat and lactose) were also used as inputs. These approaches were tested with 235 spectra of standardized raw milk samples, corresponding to 26 protein concentrations in the 2.47 to 3.90% (weight per volume) range. The simple integration method led to very poor results, whereas PLS resulted in prediction errors of about 0.22% protein. The neural network approach led to prediction errors of 0.20% protein when based on PCA scores only, and 0.08% protein when lactose and fat concentrations were also included in the model. These results indicate the potential usefulness of Fourier transform infrared/attenuated total reflectance spectroscopy for rapid, possibly online, determination of protein concentration in raw milk.     

NIRS Detection of Moldy Core in Apples

Moldy core of apples is undetectable until the fruit is cut open or bitten into, therefore it can pose serious problems to both producer and consumer. Removal of diseased fruits prior to storage would be most desirable. The objective of this study was to evaluate the ability of VIS-NIR minispectrometers to detect moldy core in apples, on line. An apparatus which is qualified for on-line Near-Infrared Spectroscopy (NIRS) measurements was developed based on an off-the-shelf minispectrometer. Apples, cv. Red Delicious, were collected from several orchards before and during the commercial harvest, and were stored at 0°C pending the tests. The data were analyzed by chemometric procedures, specifically, by partial least squares regression (PLSR), and were classified by means of canonical discriminant analysis. The canonical variables were represented by the latent variables of PLS models based on the spectra. The accuracy of the classification results was high, in light of doubts regarding the moldy fraction threshold of 5%; in such a case the mold covers only the seed carpals of the fruit, where it might remain without really damaging the fruit. Improvements should aim to reduce errors in classifying low-level damage, and also in misclassifying some healthy fruits. The rate of testing (1 s per fruit) is acceptable for quality-control purposes, but should be accelerated for future packing-line implementation.     

Chemical transformation of 3-bromo-2,2-bis(bromomethyl)-propanol under basic conditions

The mechanism of the spontaneous decomposition of 3-bromo-2,2-bis(bromomethyl)propanol (TBNPA) and the kinetics of the reaction of the parent compound and two subsequent products were determined in aqueous solution at temperatures from 30 to 70 degrees C and pH from 7.0 to 9.5. TBNPA is decomposed by a sequence of reactions that form 3,3-bis(bromomethyl)oxetane (BBMO), 3-bromomethyl-3-hydroxymethyloxetane (BMHMO), and 2,6-dioxaspiro[3.3]-heptane (DOH), releasing one bromide ion at each stage. The pseudo-first-order rate constant of the decomposition of TBNPA increases linearlywith the pH. The apparent activation energy of this transformation (98+/-2 KJ/mol) was calculated from the change of the effective second-order rate constant with temperature. The pseudoactivation energies of BBMO and BMHMO were estimated to be 109 and 151 KJ/mol, respectively. Good agreement was found between the rate coefficients derived from changes in the organic molecules concentrations and those determined from the changes in the Br- concentrations. TBNPA is the most abundant semivolatile organic pollutant in the aquitard studied, and together with its byproducts they posess an environmental hazard. TBNPA half-life is estimated to be about 100 years. This implies that high concentrations of TBNPA will persist in the aquifer long after the elimination of all its sources.     

Modulation of cocaine- and methamphetamine-induced behavioral sensitization by inhibition of brain nitric oxide synthase

Evidence suggests the existence of multiple interactions between dopamine, glutamate and nitric oxide (NO) in brain structures associated with psychomotor stimulation. The present study was undertaken to investigate the effect of the relatively selective inhibitor of the neuronal nitric oxide synthase (NOS) isoform, 7-nitroindazole (7-NI), on the development of sensitization to the locomotor stimulating effect of cocaine and methamphetamine (METH). Male Swiss Webster mice that received 15 mg/kg cocaine once a day for 5 days developed a marked locomotor sensitization to a challenge cocaine (15 mg/kg) or cross-sensitization to a challenge METH (0.5 mg/kg) injection given after a 10-day drug-free period. This treatment also produced a context-dependent sensitization as evident by the sensitized response to a challenge saline injection. Pretreatment with 7-NI (25 mg/kg) 30 min before cocaine administration (5 days) completely blocked the induction of sensitization to cocaine, the cross-sensitization to METH and the conditioned locomotion induced by cocaine. 7-NI when given alone, either acutely or for 5 days, had no significant effect on the locomotor activity of animals. Animals treated with METH (1.0 mg/kg) for 5 days developed marked sensitization to challenge METH (0.5 mg/kg), cross-sensitization to challenge cocaine (15 mg/kg) and context-dependent locomotion. Pretreatment with 7-NI (25 mg/kg) attenuated the sensitized response to METH and the cross-sensitization to cocaine as revealed after a 10-day drug-free period. However, the METH-induced conditioned locomotion was unaffected by the pretreatment with 7-NI. The present study supports the role of brain NO in the development of sensitization to both psychostimulants, cocaine and METH. However, it appears that the inability of 7-NI to completely abolish the sensitized responses induced after METH administration is the result of the resistible conditioned locomotion caused by METH, but not by cocaine.     

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) decreases glutamate uptake in cultured astrocytes

The deleterious effect of the parkinsonian neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on dopaminergic neurons of the substantia nigra is well established. In addition, increased glutamatergic drive to basal ganglia output nuclei is considered a likely contributor to the pathogenesis of Parkinson's disease. One possibility for the increased excitatory tone may be related to an impairment in glutamate uptake. As astrocytes possess efficient transport mechanisms for both MPTP and glutamate, we have examined the effect of this agent on D-aspartate uptake into these cells. Treatment of cultures with 50 microM MPTP for 24 h decreased uptake by 39%. Kinetic analysis revealed that this effect was due to a 35% decrease in Vmax with no change in the Km. Treatment with deprenyl, a monoamine oxidase B inhibitor, produced a complete reversal of MPTP-induced uptake inhibition, but was ineffective following exposure of cells to the MPTP metabolite, 1-methyl-4-phenylpyridinium (MPP+). Removal of MPTP from cultures resulted in a complete restoration of glutamate uptake after 24 h. These results show that MPTP reversibly compromises glutamate uptake in cultured astrocytes, which is dependent on the conversion of MPTP to MPP+. Such findings suggest that the glutamate transporter in astrocytes plays an important role in MPTP-induced neurotoxicity and possibly in parkinsonism.     

One of the Bloodiest Days: A Comparative Analysis of Open and Closed Television News

This article analyzes television news reports, from five countries, dealing with an incident that took place in the West Bank village of Nahalin in April 1989 during the Palestinian uprising. The analysis of both the verbal and visual texts attempts to explicate "open" and "closed" presentations of the incident by referring to three dimensions: the rhetoric of balance, the rhetoric of facticity, and the rhetoric of neutrality. The analysis suggests that the stories by both Israel Television and CBS are relatively "closed," with the Israeli case being "defensive" while that of CBS being "offensive." The other versions are appraised as lying somewhere between poetic closure and journalistic openness.     

Learning the structure of dynamic Bayesian networks from time series and steady state measurements

Dynamic Bayesian networks (DBN) are a class of graphical models that has become a standard tool for modeling various stochastic time-varying phenomena. In many applications, the primary goal is to infer the network structure from measurement data. Several efficient learning methods have been introduced for the inference of DBNs from time series measurements. Sometimes, however, it is either impossible or impractical to collect time series data, in which case, a common practice is to model the non-time series observations using static Bayesian networks (BN). Such an approach is obviously sub-optimal if the goal is to gain insight into the underlying dynamical model. Here, we introduce Bayesian methods for the inference of DBNs from steady state measurements. We also consider learning the structure of DBNs from a combination of time series and steady state measurements. We introduce two different methods: one that is based on an approximation and another one that provides exact computation. Simulation results demonstrate that dynamic network structures can be learned to an extent from steady state measurements alone and that inference from a combination of steady state and time series data has the potential to improve learning performance relative to the inference from time series data alone.     

Influence of autofrettage on fracture toughness

A specimen, called the ring specimen, was developed to determine the fracture toughnessK _tc, under conditions of autofrettage. Tests were carried out on standard arc shaped specimens and ring specimens without autofrettage to obtainK _tc values of a gun barrel steel chosen for study and seen to yield similar results. Tests were also performed on autofrettaged (100 percent overstrain) ring specimens at various crack lengths producing results with a dramatic decrease inK _tc of 60 per cent. From this, it may be inferred that the critical length of a crack in an autofrettaged gun barrel made of this material will be less than anticipated. Although cold work or autofrettage enhances fatigue life by decreasing crack propagation rate, it is seen to decreaseK _tc creating, from this point of view, more dangerous conditions. For a design which must guarantee long life, the accompanying decrease in critical crack size may indeed prove a liability. Of course, this is a result for one particular material with a specific heat treatment and therefore not general; other materials must be tested, as well.

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Résumé On a étudié une éprouvette, dénommée éprouvette en anneau, en vue de déterminer la ténacité à la ruptureK _tc sous des conditions d'auto-frettage. Des essais ont été effectués sur des éprouvettes standards en forme d'arc et sur des éprouvettes en anneau sans auto-frettage en vue d'obtenir les valeurs deK _tc dans le cas d'un acier pour âme de canon choisi pour l'étude. Ces essais ont conduit à des résultats similaires. Des essais ont également été effectués sur des échantillons en anneau auto-frettés à 100% de sur-dilatation correspondant à diverses longueurs de fissure. Les résultats ont montré une diminution deK _tc de l'ordre de 60%. On peut déduire de cette observation que la longueur critique relative à une fissure dans une âme d'un canon auto-fretté réalisé dans ce matériau sera plus faible que prévu. Bien que l'écrouissage où l'auto-frettage améliore l'endurance en fatigue par des croissances de la vitesse de propagation d'une fissure, on constate qu'elle diminue leK _tc, occasionnant de ce point de vue des conditions plus dangereuses. Dans le cas d'une construction qui doit garantir un service de longue durée, la décroissance de la dimension critique d'une fissure peut être pénalisante. Bien entendu, ceci n'est qu'un résultat pour un matériau particulier avec un traitement thermique spécifique, qui dès lors ne peut être généralisé. D'autres matériaux doivent être également testés.