Neurochemical characterization of the alterations in the noradrenergic afferents to the cerebellum of adult rats exposed to X-irradiation at birth

A single dose of x-irradiation was applied on the cephalic end of newborn rats, and the alterations in the noradrenergic afferents to the cerebellum were studied 180 days later. A net increase in the noradrenaline content of cerebellum was found (122% of nonirradiated controls). The response of noradrenaline content to reserpine injection (0.9 mg/kg, i.p.) was similar in exposed and control rats. Likewise, the 3H release induced by Ro 4-1284 from cerebellar cortex slices labeled with [3H]noradrenaline was unmodified by x-rays, although a mild increase in the spontaneous efflux of 3H was found. The retention of 3H by the slices was reduced in exposed animals (58% of controls). Both the in vitro activity of tyrosine hydroxylase and the accumulation of L-3,4-dihydroxyphenylalanine (L-DOPA) were not significantly different between x-treated rats and controls. In contrast, monoamine oxidase activity was markedly reduced in x-irradiated cerebellum (38% of controls). The x-ray-induced decrease in cerebellar weight (-60%) resulted in marked increases in noradrenaline concentration (223%), tyrosine hydroxylase activity per milligram of protein (206%), and 3H retention (50%). The accumulation of L-DOPA per gram of tissue was also increased at every time considered. These data indicate that x-irradiation at birth produces a cerebellar loss not completely shared by the noradrenergic afferents, and a permanent imbalance between the noradrenergic afferent input and its target cells might eventually result.(ABSTRACT TRUNCATED AT 250 WORDS)     

Automotive observers based on multibody models and the extended Kalman filter

This work is part of a project aimed to develop automotive real-time observers based on detailed nonlinear multibody models and the extended Kalman filter (EKF). In previous works, a four-bar mechanism was studied to get insight into the problem. Regarding the formulation of the equations of motion, it was concluded that the state-space reduction method known as matrix-R is the most suitable one for this application. Regarding the sensors, it was shown that better stability, accuracy and efficiency are obtained as the sensored magnitude is a lower derivative and when it is a generalized coordinate of the problem. In the present work, the automotive problem has been addressed, through the selection of a Volkswagen Passat as a case-study. A model of the car containing fifteen degrees of freedom has been developed. The observer algorithm that combines the equations of motion and the integrator has been reformulated so that duplication of the problem size is avoided, in order to improve efficiency. A maneuver of acceleration from rest and double lane change has been defined, and tests have been run for the “prototype,” the “model” and the “observer,” all the three computational, with the model having 100 kg more than the prototype. Results have shown that good convergence is obtained for position level sensors, but the computational cost is high, still far from real-time performance.     

Author Index, Volume 5 (2000)

Authors Index

Author Index, Volume 5 (2000)     

Kinetic of epoxy resin formation by high‐performance liquid chromatography

This article is focused on the following of the cure of an epoxy resin by high‐performance liquid chromatography (HPLC) and the comparison of the data obtained with those obtained by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) techniques usually employed for characterize curing processes. A reversed‐phase HPLC method with UV detection is developed to study the kinetic of the curing reaction of diglycidyl ether of bisphenol A (DGEBA) with 1,3‐cyclohexanebismethylamine (1,3‐BAC) at 60, 70, and 80°C, before and after gelation. The limits of quantification obtained permit the application of the proposed method until the last steps of the formation kinetic. HPLC and DSC analysis show a good correlation. The gel conversions obtained by HPLC and DMA agree well. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 497–504, 2003     

A block-symmetric linearization of odd degree matrix polynomials with optimal eigenvalue condition number and backward error

The standard way of solving numerically a polynomial eigenvalue problem (PEP) is to use a linearization and solve the corresponding generalized eigenvalue problem (GEP). In addition, if the PEP possesses one of the structures arising very often in applications, then the use of a linearization that preserves such structure combined with a structured algorithm for the GEP presents considerable numerical advantages. Block-symmetric linearizations have proven to be very useful for constructing structured linearizations of structured matrix polynomials. In this scenario, we analyze the eigenvalue condition numbers and backward errors of approximated eigenpairs of a block symmetric linearization that was introduced by Fiedler (Linear Algebra Appl 372:325–331, 2003) for scalar polynomials and generalized to matrix polynomials by Antoniou and Vologiannidis (Electron J Linear Algebra 11:78–87, 2004). This analysis reveals that such linearization has much better numerical properties than any other block-symmetric linearization analyzed so far in the literature, including those in the well known vector space \(\mathbb {DL}(P)\) of block-symmetric linearizations. The main drawback of the analyzed linearization is that it can be constructed only for matrix polynomials of odd degree, but we believe that it will be possible to extend its use to even degree polynomials via some strategies in the near future.     

A novel large conductance, nonselective cation channel in pheochromocytoma (PC12) cells

Nasal blockage is one of the most habitual symptoms in otolaryngologist office and the concha nasalis inferior hypertrophy the commonest cause of the trouble. Cases in which medical treatment is refractory, surgery could be an optional resort in accordance of a great deal of specialists. The possibility of give rise to atrophic rhinitis or even ozenatous lesions has been refraining this surgery lately. In our series are contemplated the outcomes of several surgical procedures as mode of management of the hypertrophy of the lower turbinal. In the article are assessed the results of several surgical techniques dealing with hypertrophy of concha nasalis inferior. 75 patients were operated under endoscopic control. Some underwent a submucous decompression (SD) other partial resection (PR). Results at half and long term of both techniques-the conservative one (SD) and that a little more aggressive (PR)-are compared, and so are the factors conditioning the selection of the surgical procedure done. We consider the partial resection of the inferior concha, under endoscopic vision, as the best way for improving the nose obstruction due to inferior concha hypertrophy, provided conservative measures are not wise at all. Furthermore because with our own hands we reach very good outcomes, both in breathing and nasal comfort. Only the patient's age may influence the last decision.     

Eigenvalue condition numbers and pseudospectra of Fiedler matrices

The aim of the present paper is to analyze the behavior of Fiedler companion matrices in the polynomial root-finding problem from the point of view of conditioning of eigenvalues. More precisely, we compare: (a) the condition number of a given root \({\lambda }\) of a monic polynomial p(z) with the condition number of \({\lambda }\) as an eigenvalue of any Fiedler matrix of p(z), (b) the condition number of \({\lambda }\) as an eigenvalue of an arbitrary Fiedler matrix with the condition number of \({\lambda }\) as an eigenvalue of the classical Frobenius companion matrices, and (c) the pseudozero sets of p(z) and the pseudospectra of any Fiedler matrix of p(z). We prove that, if the coefficients of the polynomial p(z) are not too large and not all close to zero, then the conditioning of any root \({\lambda }\) of p(z) is similar to the conditioning of \({\lambda }\) as an eigenvalue of any Fiedler matrix of p(z). On the contrary, when p(z) has some large coefficients, or they are all close to zero, the conditioning of \({\lambda }\) as an eigenvalue of any Fiedler matrix can be arbitrarily much larger than its conditioning as a root of p(z) and, moreover, when p(z) has some large coefficients there can be two different Fiedler matrices such that the ratio between the condition numbers of \({\lambda }\) as an eigenvalue of these two matrices can be arbitrarily large. Finally, we relate asymptotically the pseudozero sets of p(z) with the pseudospectra of any given Fiedler matrix of p(z), and the pseudospectra of any two Fiedler matrices of p(z).     

Real-time state observers based on multibody models and the extended Kalman filter

This work is a preliminary study on the use of the extended Kalman filter (EKF) for the state estimation of multibody systems. The observers based on the EKF are described by first-order differential equations, with independent, non-constrained coordinates. Therefore, it should be investigated how to formulate the equations of motion of the multibody systems so that efficient, robust and accurate observers can be derived, which can serve to develop advanced real-time applications. In the paper, two options are considered: a state-space reduction method and the penalty method. Both methods are tested on a four-bar mechanism with a linear spring-damper. The results enable us to analyze the pros and cons of each method and provide clues for future research.     

Commercial biodegradable material for food contact: methodology for assessment of service life

Control of the durability of commercial biodegradable materials when used as food packaging is relevant to guarantee the safety of food. The service life performance of a commercial material based on poly(lactic acid) was assessed through an aging test which mimics its real use (immersion in water at 40 °C for up to 6.5 months). The ability of different techniques for the evaluation of polymer decomposition was investigated and two types of degradation were shown, a reversible physical aging and a permanent deterioration due to hydrolysis. Physical aging was reflected in differential scanning calorimetry scans by increased glass transition temperature and corresponding enthalpy. A gradual decrease of crystallization temperature and increase of melting temperature and crystallinity were also observed. The progressive loss of mechanical properties reflected the sum of both types of degradation. Hardness, flexural modulus and flexural strength were more sensitive to deterioration than strain. The highest toughness of the material was achieved at two months. The cleavage of polymer chains and release of substances caused increased migration levels, especially marked for long time periods. Water uptake and migration levels followed a concordant pattern and experienced the highest increases. A simple protocol for quality control based on the obtained results is suggested. Copyright © 2012 Society of Chemical Industry