The double dipole model of theta rhythm generation: Simulation of laminar field potential profiles in dorsal hippocampus of the rat

A set of compartmental models of CA1 pyramidal, granular and polymorph cells of the dorsal hippocampus have been used to simulate membrane potentials generated by synaptic activation at various levels along these cells. From the membrane potential distributions the field potentials in dorsal CA1 and the dorsal blade of the dentate area have been simulated using a model based on volume conduction theory. Field potential profiles similar to laminar profiles, found experimentally in the dorsal hippocampus during theta rhythm, could only be simulated by assuming (almost) simultaneous synaptic excitation of the 3 cell types at given sites. The results lead to 2 alternative models for the simultaneous excitation of CA1 pyramidal cells and dentate granular cells during theta rhythm. Other electrophysiological evidence favours the model in which the two neuronal populations are activated distally near the fissure

Letters to the Editor

Epilepsia. 1999 Oct;40(10):1464-5. Letters to the Editor about Relationship between cysticercosis and epilepsy. Monteiro L, Lopes J, Martins da Silva A. Comment on: Epilepsia. 1998 Oct;39(10):1025-40. PMID: 10528946 [PubMed - indexed for MEDLINE

Rheological study into the ageing process of high methoxyl pectin/sucrose aqueous gels

The ageing process of high methoxyl pectin (HMP)/sucrose gels was followed at different ageing temperatures by small amplitude oscillatory experiments. Dynamic mechanical measurements allowed the characterisation of the point at which the system undergoes the sol/gel transition. The HMP/sucrose system is extremely sensitive to temperature variation during ageing, especially in the lower temperature range. The viscoelastic behaviour through the gel point changes with the ageing temperature, probably due to variations in mobility of the pectin chains, and consequently, in the lifetime of junction zones. Weaker pectin networks are formed under thermal conditions unfavourable to the development of hydrophobic interactions. Gel time and elastic modulus have a complex dependence on temperature, which could be attributed to the different thermal behaviour of the intermolecular interactions that stabilise the nonpermanent cross links of these physical networks

Implementation of six sigma methodology for the elimination of contamination in Fine Pitch connectors

Quality drives companies to evolve, providing what customers need or even exceeding their expectations through products and services that play their functions properly during their lifetime. From this perspective, this study aims to solve a concrete defect that occurs during the assembly process of an electronic product for the automotive industry. One of the new challenges in the electronics industry is the contamination issue in Printed Circuit Boards (PCB). Contamination can be defined as any type of particles (residues) that are deposited on PCB surface or within a component, causing unwanted behaviours in the electronic device. In the present study, the investigated contamination is organic in nature and is originated by the solder flux. The solder flux is released during the welding process, being deposited inside the PCB Fine Pitch connectors. The DMAIC method was adopted as a Problem Solving tool. This method was selected to ensure the elimination of this type of defect. To support the investigation, the 5W2H and Is/Is Not quality tools were used. The investigation was developed by a multidisciplinary team. After the root-cause identification, the connectors provider was involved to assist in the development of an effective and low cost solution. The final solution resulted in the placement in the connectors of a protective cap. This solution, besides protecting the connectors, allowed a new collaborative relationship along the supply chain

Influence of temperature on the dynamic and steady-shear rheology of pectin dispersions

The influence of temperature on the dynamic and steady-shear rheology of ionic polysaccharides, high-methoxyl and low-methoxyl pectins, has been studied and compared with the behaviour of locust bean gum, a virtually neutral biopolymer. Using the time-temperature superposition principle, the rheological parameters were reduced to an arbitrary reference temperature. Activation energies were calculated and their dependence on temperature and shear rate analysed. Concerning the viscosity dependence on temperature, two approaches have been considered: one associated with the theory of absolute reaction rates leading to an Arrhenius type equation, and the other associated with the free volume theory, expressed by the Williams-Landel-Ferry equation. The difficulties encountered in the superposition of the dynamic properties of the pectin dispersions, the high activation energies, yield values and elastic plateau at low oscillatory frequency, are consistent with a macromolecular organization of these polymers dominated by important aggregation phenomena, which could be attributed to important intermolecular interactions like hydrogen bonding and hydrophobic interactions, especially in conditions of low degree of ionization of the carboxylic groups

Irrigação na cultura da bucha vegetal.

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Kinetics and thermal behaviour of the structure formation process in HMP/sucrose gelation

The concentration and temperature dependence of the gelation kinetics of high-methoxyl pectin (HMP; 60% sucrose, pH 3) was investigated using measurements of small-amplitude oscillatory shear. The rate of gelation close to the gel point can be described as a second-order rate process using the kinetic model of Ross-Murphy (Carbohydr. Polym. 1991, 14, 281) and a critical exponent close to that predicted by the percolation approach. The modulus after a long ageing time showed a power concentration dependence with an exponent around 3.1, higher than the classical square of concentration dependence, which was probably either due to the non-equilibrium state of the HMP gels even after long ageing times, or due to the proximity of the concentration range studied to the critical gelling concentration. The gelation rate of HMP/sucrose systems is strongly dependent on the temperature. An Arrhenius relationship was applied to describe this dependence. Two different processes are proposed to explain the discontinuity observed, each one having rates with different temperature dependence. The applicable kinetics at longer times are quite different, with a lower dependence on polymer concentration and ageing temperature. A non-isothermal kinetic model was used to describe the gelation process of the HMP/sucrose system during cooling

Relação entre mudanças no uso da terra e o relevo em uma área piloto da zona da mata sul de Pernambuco.

A identificação, a interpretação, a organização e a espacialização de características ambientais tais como: solos, relevo, clima, uso e ocupação, entre outras, numa escala adequada, são de fundamental importância quando se pretende elaborar uma estratégia de desenvolvimento rural em bases sustentáveis. A expansão da cultura da cana-de-açúcar na Zona da Mata Sul de Pernambuco, motivada pelo Proálcool, não atendeu a esses requisitos, principalmente, com relação ao relevo. Desta forma, o presente estudo tem como objetivos: 1) elaborar os mapas de relevo (altitude e declividade), cobertura ?recente? e cobertura ?pretérita?; 2) avaliar as mudanças na cobertura de mata Atlântica; 3) avaliar a adequação do uso da terra ao relevo de uma área piloto da Zona da Mata Sul de Pernambuco. A área selecionada (aproximadamente 75.000 ha) foi delimitada utilizando mapas planialtimétricos na escala 1:25.000. Esses mapas foram usados na obtenção do modelo digital de terreno (MDT) e extração das áreas com mata Atlântica no início da década de 1970. O mapa de uso e cobertura ?recente? foi obtido usando imagens do sensor Landsat 5 TM. Aproximadamente 50% da área apresenta relevo forte ondulado e montanhoso impróprias para o uso agropecuário. Apesar disso, a cana-de-açúcar ocupa 45% dessas áreas, cuja aptidão é para a preservação da fauna e da flora e recreação. Dos cerca de 24.000 ha de matas existentes na década de 70, 16.000 ha foram removidos. Dos atuais 11.907 ha de mata Atlântica, aproximadamente 4.052 ha são de novas formações

Characterization of requeijão and technological optimization of its manufacturing process

In attempts to characterize Portuguese whey cheese (Requeijão) and optimize the manufacture thereof I7 whey cheeses were produced according to a factorial design using heating time, heating temperature and fractional addition of ovinelcaprine milk as manipulated technological variables. Chemical analyses were carried out for the 17 cheeses, whereas sensorial and rheological analyses were carried out for eight selected whey cheeses and a reference (i.e. a whey cheese produced locally according to traditional procedures). A true local maximum exists for moisture content (at a temperature of about 93°C heating time of about 30 min and addition of about 17% ovine milk) which lies well within the range chosen for experimentation. Fat content of Requeijão was positively affected by heating temperature (especially via its quadratic effect) and, to a lesser extent, by heating time (especially via its linear effect); nitrogen content was especially affected by heating temperature (via its quadratic effect); and moisture content was affected especially by heating temperature (via its quadratic effect). The sensorial analyses showed that the eight whey cheeses produced were prefered with respect to the reference whey cheese. For rheological analyses the most significant observations pertain to the high strain dependence of the dynamic moduli, absence of a true equilibrium storage modulus, and relatively low difference between the loss and the storage modulus

Impact of brewery wastewater inhibitors in pure and mixed cultures of the yeast Rhodosporidium toruloides NCYC 921 and the microalga Tetradesmus obliquus ACOI 204/07

ABSTRACT: Brewery wastewater (BWW) is an appealing low-cost substrate for the production of single cell oils by oleaginous microorganisms. However, it may contain inhibitor compounds that may affect the microbial metabolism. This work investigated, for the first time, the presence of potential inhibitor compounds in primary brewery wastewater (PBWW) and secondary brewery wastewater (SBWW) for the pure and mixed cultivation of the yeast Rhodosporidium toruloides NCYC 921 and the microalga Tetradesmus obliquus ACOI 204/07. Three organic acids (OrgAc) were identified in the brewery effluents (acetic, propionic and butyric acids). Yeast and microalga pure and mixed cultivations were performed in PBWW and SBWW in order to understand the behaviour of the microorganisms, individually and together. Flow cytometry (FC) was used to monitor each microbial population during the mixed cultivations, and to study the yeast and microalga cell viability throughout all cultivations. The yeast cells in pure cultures grown in both effluents were severely affected by the OrgAc presence confirmed by the cell stress results obtained by FC. However, in the mixed cultures, the yeast cells were able to develop, and the levels of stress conditions were considerably lower. Only in microalga pure and mixed cultures efficient OrgAc removal was observed.info:eu-repo/semantics/publishedVersio