Resultados do programa experimental de fumagen de pescado

The fish smoking is a traditional process in most african countries and has been gradually improved to the light of changes in forms, techniques and materials. In Mozambique, in particular, this method is not as developed as expected, because it has more advantages in wetlands during rainy seasons, where there is no shortage of salt and in order to give a special taste to the dry fish. In many parts of the country, mainly in coastal areas, the smoking process is made manually by families: a small fire with any type of wood, close to a small amount of fish on a stick, tilted on fire in order to take smoke and heat for several hours. This process is used in the south (Inhaca Island), in central and northern regions (Beira, Nampula) and was also seen in Niassa Lake. This paper presents a program aimed at the application of existing knowledge about fish smoking process and at technology improvement.

Observations on the inhibitory effect of sodium chloride on molds met with in smoked fishery products

Even though smoke curing is a very elegant method of preserving fish, the resultant products have only a very restricted shelf-life, unless stored under refrigerated conditions. The main source of spoilage is the early setting in of a vigorous growth of moulds. This problem is of a serious nature even in temperate climatic conditions. In full and universal recognition of the gravity of the problem, the FAO conference on herring technology held in September 1950 at Bergen in Norway has recommended the problem of "means of prevention of mould growth in smoked products" for future research study. This note records an interesting observation made at this Laboratory on the inhibitory action of sodium chloride on the development of mould in smoked fishery products.

Studies on smoking of eel fillets

A procedure has been worked out to (hot) smoke eel fillets. Some of the important factors such as size of the fillets, brining, pre-drying, source of smoke, smoking period, final drying have been studied. Best quality of smoked product is obtained on smoking eel fillets with a mixture of coconut-husk and sag saw-dust in 1:1 proportion for 15 hours. Optimum moisture level of the final product was fixed in the range of 30 to 35% and it had a storage life of about 8 months at room temperature.

Canning of smoked sardine

A process for canning smoked oil sardine (Sardinella longiceps) is described. Cold blanching of dressed fish in brine, smoking followed by drying in hot air or cooking in steam to reduce the moisture content to the required level and subsequent canning yields product with good organoleptic properties. Coconut husk is used as source of smoke.

Influence of fat content on the quality and shelf life of cured sardines

The paper presents results of studies on the effect of seasonal variations in the fat content on the quality and shelf life of dry cured, pickle cured and smoke cured oil sardines. The merits and defects of each method of curing during different seasons are discussed.

The Gjerstad kiln: a combined hot and cold smoking kiln

A combined hot and cold smoking kiln has been constructed for use at Lake Turkana, Kenya. Used for cold smoking, the kiln's main advantages over the traditional kilns used in this area are its greater smoking capacity and lower firewood consumption. Having the option of using the same smoke house for cold and hot smoking reduces the total construction costs for an operator producing both types of smoke cured product. The hot smoking process was found to require markedly less firewood than cold smoking, a fact of considerable importance in desert or semi-desert areas with sparse vegetation.

Preparation and keeping quality of hot smoked mackerel

A method has been standardised for the production of smoke cured mackerel by dry salting in the ratio of 1:8 salt to fish followed by smoking in a traditional smoke chamber at 70±5°C for 5h. The smoke was generated by burning moist coconut husk and saw dust. The product obtained by this method had shelf-lives of 105, 95 and 6 days in chilled storage (0 to 2°C) refrigerated storage (10±2°C) and at room temperature (29±2°C) respectively.

The bacterial cytoskeleton modulates motility, type 3 secretion, and colonization in Salmonella.

Although there have been great advances in our understanding of the bacterial cytoskeleton, major gaps remain in our knowledge of its importance to virulence. In this study we have explored the contribution of the bacterial cytoskeleton to the ability of Salmonella to express and assemble virulence factors and cause disease. The bacterial actin-like protein MreB polymerises into helical filaments and interacts with other cytoskeletal elements including MreC to control cell-shape. As mreB appears to be an essential gene, we have constructed a viable ΔmreC depletion mutant in Salmonella. Using a broad range of independent biochemical, fluorescence and phenotypic screens we provide evidence that the Salmonella pathogenicity island-1 type three secretion system (SPI1-T3SS) and flagella systems are down-regulated in the absence of MreC. In contrast the SPI-2 T3SS appears to remain functional. The phenotypes have been further validated using a chemical genetic approach to disrupt the functionality of MreB. Although the fitness of ΔmreC is reduced in vivo, we observed that this defect does not completely abrogate the ability of Salmonella to cause disease systemically. By forcing on expression of flagella and SPI-1 T3SS in trans with the master regulators FlhDC and HilA, it is clear that the cytoskeleton is dispensable for the assembly of these structures but essential for their expression. As two-component systems are involved in sensing and adapting to environmental and cell surface signals, we have constructed and screened a panel of such mutants and identified the sensor kinase RcsC as a key phenotypic regulator in ΔmreC. Further genetic analysis revealed the importance of the Rcs two-component system in modulating the expression of these virulence factors. Collectively, these results suggest that expression of virulence genes might be directly coordinated with cytoskeletal integrity, and this regulation is mediated by the two-component system sensor kinase RcsC.

Classical plume theory: 1937-2010 and beyond

Developing a theoretical description of turbulent plumes, the likes of which may be seen rising above industrial chimneys, is a daunting thought. Plumes are ubiquitous on a wide range of scales in both the natural and the man-made environments. Examples that immediately come to mind are the vapour plumes above industrial smoke stacks or the ash plumes forming particle-laden clouds above an erupting volcano. However, plumes also occur where they are less visually apparent, such as the rising stream of warmair above a domestic radiator, of oil from a subsea blowout or, at a larger scale, of air above the so-called urban heat island. In many instances, not only the plume itself is of interest but also its influence on the environment as a whole through the process of entrainment. Zeldovich (1937, The asymptotic laws of freely-ascending convective flows. Zh. Eksp. Teor. Fiz., 7, 1463-1465 (in Russian)), Batchelor (1954, Heat convection and buoyancy effects in fluids. Q. J. R. Meteor. Soc., 80, 339-358) and Morton et al. (1956, Turbulent gravitational convection from maintained and instantaneous sources. Proc. R. Soc. Lond. A, 234, 1-23) laid the foundations for classical plume theory, a theoretical description that is elegant in its simplicity and yet encapsulates the complex turbulent engulfment of ambient fluid into the plume. Testament to the insight and approach developed in these early models of plumes is that the essential theory remains unchanged and is widely applied today. We describe the foundations of plume theory and link the theoretical developments with the measurements made in experiments necessary to close these models before discussing some recent developments in plume theory, including an approach which generalizes results obtained separately for the Boussinesq and the non-Boussinesq plume cases. The theory presented - despite its simplicity - has been very successful at describing and explaining the behaviour of plumes across the wide range of scales they are observed. We present solutions to the coupled set of ordinary differential equations (the plume conservation equations) that Morton et al. (1956) derived from the Navier-Stokes equations which govern fluid motion. In order to describe and contrast the bulk behaviour of rising plumes from general area sources, we present closed-form solutions to the plume conservation equations that were achieved by solving for the variation with height of Morton's non-dimensional flux parameter Γ - this single flux parameter gives a unique representation of the behaviour of steady plumes and enables a characterization of the different types of plume. We discuss advantages of solutions in this form before describing extensions to plume theory and suggesting directions for new research. © 2010 The Author. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

Use of 2G coated conductors for efficient shielding of DC magnetic fields

This paper reports the results of an experimental investigation of the performance of two types of magnetic screens assembled from YBa2Cu3O7-d (YBCO) coated conductors. Since effective screening of the axial DC magnetic field requires the unimpeded flow of an azimuthal persistent current, we demonstrate a configuration of a screening shell made out of standard YBCO coated conductor capable to accomplish that. The screen allows the persistent current to flow in the predominantly azimuthal direction at a temperature of 77 K. The persistent screen, incorporating a single layer of superconducting film, can attenuate an external magnetic field of up to 5 mT by more than an order of magnitude. For comparison purposes, another type of screen which incorporates low critical temperature quasi-persistent joints was also built. The shielding technique we describe here appears to be especially promising for the realization of large scale high-Tc superconducting screens.

Gasoline fuelled partially premixed compression ignition in a light duty multi cylinder engine: A study of low load and low speed operation

The objective of this study was to examine the operating characteristics of a light duty multi cylinder compression ignition engine with regular gasoline fuel at low engine speed and load. The effects of fuel stratification by means of multiple injections as well as the sensitivity of auto-ignition and burn rate to intake pressure and temperature are presented. The measurements used in this study included gaseous emissions, filter smoke opacity and in-cylinder indicated information. It was found that stable, low emission operation was possible with raised intake manifold pressure and temperature, and that fuel stratification can lead to an increase in stability and a reduced reliance on increased temperature and pressure. It was also found that the auto-ignition delay sensitivity of gasoline to intake temperature and pressure was low within the operating window considered in this study. Nevertheless, the requirement for an increase of pressure, temperature and stratification in order to achieve auto-ignition time scales small enough for combustion in the engine was clear, using pump gasoline. Copyright © 2009 SAE International.

Study of steady state and transient EGR behaviour of a medium duty diesel engine

It is well known that accurate EGR control is paramount to controlling engine out emissions during steady state and transient operation of a diesel engine. The direct measurement of EGR is however non-trivial and especially difficult in engines with no external EGR control where the intake manifold CO2 levels can be measured more readily. This work studies the EGR behaviour in a medium duty diesel engine with a passive EGR rebreathing strategy for steady state and transient operation. High speed (response time ∼1ms) in-cylinder sampling using modified GDI valves is coupled with high frequency response analysers to measure the cyclic in-cylinder CO2, from which the EGR rate is deduced. It was found that controlling the EGR using the passive rebreathing strategy during certain combined speed and load transients is challenging, causing high smoke and NO emissions. The in-cylinder sampling method coupled with fast CO2 measurement (time constant ∼8ms) in the exhaust port gave insights about the EGR rate during these transients. The complex interaction of the manifold pressures, turbo-charger operation and trapped charge composition from the previous cycle simply can cause high dilution and therefore high smoke levels. The steady state variation of NO emissions with respect to EGR is also studied using a fast NO analyzer (time constant ∼2ms) in the exhaust port. Cyclic variation was found to be up to ±5% at some load conditions. © 2008 SAE International.

Investigation into partially premixed combustion in a light-duty multi-cylinder diesel engine fuelled gasoline and diesel with a mixture of

Partially premixed compression ignition (PPCI) engines operating with a low temperature highly homogeneous charge have been demonstrated previously using conventional diesel fuel. The short ignition delay of conventional diesel fuel requires high fuel injection pressures to achieve adequate premixing along with high levels of EGR (exhaust gas recirculation) to achieve low NOx emissions. Low load operating regions are typified by substantial emissions of CO and HC and there exists an upper operating load limitation due to very high rates of in-cylinder gas pressure rise. In this study mixtures of gasoline and diesel fuel were investigated using a multi-cylinder light duty diesel engine. It was found that an increased proportion of gasoline fuel reduced smoke emissions at higher operating loads through an increase in charge premixing resulting from an increase in ignition delay and higher fuel volatility. The results of this investigation confirm that a combination of fuel properties, exhibiting higher volatility and increased ignition delay, would enable a widening of the low emission operating regime, but that consideration must be given to combustion stability at low operating loads. Copyright © 2007 SAE International.

A simple diesel engine air-path model to predict the cylinder charge during transients: Strategies for reducing transient emissions spikes

Simple air-path models for modern (VGT/EGR equipped) diesel engines are in common use, and have been reported in the literature. This paper addresses some of the shortcomings of control-oriented models to allow better prediction of the cylinder charge properties. A fast response CO2 analyzer is used to validate the model by comparing the recorded and predicted CO2 concentrations in both the intake port and exhaust manifold of one of the cylinders. Data showing the recorded NOx emissions and exhaust gas opacity during a step change in engine load illustrate the spikes in both NOx and smoke seen during transient conditions. The predicted cylinder charge properties from the model are examined and compared with the measured NOx and opacity. Together, the emissions data and charge properties paint a consistent picture of the phenomena occurring during the transient. Alternative strategies for the fueling and cylinder charge during these load transients are investigated and discussed. Experimental results are presented showing that spikes in both NOx and smoke can be avoided at the expense of some loss in torque response. Even if the torque response must be maintained, it is demonstrated that it is still possible to eliminate spikes in NOx emissions for the transient situation being examined. Copyright © 2006 SAE International.

Global civil aviation black carbon emissions.

Aircraft black carbon (BC) emissions contribute to climate forcing, but few estimates of BC emitted by aircraft at cruise exist. For the majority of aircraft engines the only BC-related measurement available is smoke number (SN)-a filter based optical method designed to measure near-ground plume visibility, not mass. While the first order approximation (FOA3) technique has been developed to estimate BC mass emissions normalized by fuel burn [EI(BC)] from SN, it is shown that it underestimates EI(BC) by >90% in 35% of directly measured cases (R(2) = -0.10). As there are no plans to measure BC emissions from all existing certified engines-which will be in service for several decades-it is necessary to estimate EI(BC) for existing aircraft on the ground and at cruise. An alternative method, called FOX, that is independent of the SN is developed to estimate BC emissions. Estimates of EI(BC) at ground level are significantly improved (R(2) = 0.68), whereas estimates at cruise are within 30% of measurements. Implementing this approach for global civil aviation estimated aircraft BC emissions are revised upward by a factor of ~3. Direct radiative forcing (RF) due to aviation BC emissions is estimated to be ~9.5 mW/m(2), equivalent to ~1/3 of the current RF due to aviation CO2 emissions.