Assessing the self-heating behaviour of Callide coal using a 2-metre column

A 2-m, adiabatic column has been successfully refurbished and recommissioned for coal self-heating research at The University of Queensland. Subbituminous coal from the Callide Coalfields reached thermal runaway in just under 19 days from a starting temperature of 20-22 degreesC. The coal was loaded as two layers, with an R-70 index of 2.73 degreesC h(-1) and 5.90 degreesC h(-1) for the upper layer and lower layer respectively. Initially, a hotspot developed in the upper layer between 120 and 140 cm from the air inlet due to moisture adsorption. After 7 days, self-heating in the lower half of the column began to take over, consistent with the higher R-70 index of this coal. The location of the final hotspot was approximately 60 cm from the air inlet. Further tests on Australian coals, with the column, will enable a better understanding of coal self-heating under conditions closely resembling mining, transport and storage of coal. The results from the column will also provide industry with the information needed to manage the coal self-heating hazard. (C) 2002 Elsevier Science Ltd. All rights reserved.

Alternative technologies for producing sterile low acid food products

Four emerging high-energy non-thermal technologies may replace or augment heating for producing sterile low-acid food products. High pressure, high-voltage pulsed electric field, high-energy ultrasound and high-intensity pulsed light are all capable of reducing bacterial spore counts under certain conditions. However, only non-continuous high pressure treatments, at temperatures higher than ambient, are currently capable of completely inactivating spores and producing sterile food products. The first three technologies also reduce the resistance of spores to inactivation by heat.

Ultra-high-temperature (UHT) treatment of milk: comparison of direct and indirect modes of heating

UHT processing of milk and its subsequent storage causes several changes which affect the shelf-life of UHT milk although it remains 'commercially sterile'. These changes include whey protein denaturation, protein-protein interaction, lactose-protein interaction, isomerisation of lactose, Maillard browning, sulphydryl compound formation, formation of a range of carbonyl and other flavoursome compounds, and formation of insoluble substances. They ultimately reduce the quality and limit the shelf life of UHT milk through development of off-flavours, fat separation, age gelation and sedimentation. The extent of these changes depends on many factors, a major one being the type of UHT heating. This review compares the effect heating milk by direct and indirect modes on various aspects of processing and quality of UHT milk.

Are tryptophan and 5-hydroxytryptophan effective treatments for depression? A meta-analysis

Objective: To review the literature regarding the effectiveness of 5-hydroxytryptophan (5-HT) and L-tryptophan in the treatment of unipolar depression. Methods: A systematic review of the literature from 1966 to 2000 using the search terms 'tryptophan', 5-hydroxytryptophan', '5-HTP', '5-HT' and 'depression'. We extracted and grouped data for meta-analysis by pooling odds ratios (OR) and relative risks where possible. Results: One hundred and eight studies were located of which only two studies, one of 5-HT and one of L-tryptophan, with a total of 64 patients met sufficient quality criteria to be included. These studies suggest 5-HT and L-tryptophan are better than placebo at alleviating depression (Peto OR = 4.1, 95% CI = 1.3-13.2). However, the small size of the studies, and the large number of inadmissible, poorly executed studies, casts doubt on the result from potential publication bias, and suggests that they are insufficiently evaluated to assess their effectiveness. Conclusions: A large body of evidence was subjected to very basic criteria for assessing reliability and validity, and was found to largely be of insufficient quality to inform clinical practice. More well-designed studies are urgently required to enable an assessment of what may be an effective class of agents.

Evaluation of various pre-treatments for the dehydration of banana and selection of suitable drying models

The thin-layer drying behaviour of bananas in a beat pump dehumidifier dryer was examined. Four pre-treatments (blanching, chilling, freezing and combined blanching and freezing) were applied to the bananas, which were dried at 50 degreesC with an air velocity of 3.1 m s(-1) and with the relative humidity of the inlet air of 10-35%. Three drying models, the simple model, the two-term exponential model and the Page model were examined. All models were evaluated using three statistical measures, correlation coefficient, root means square error, and mean absolute percent error. Moisture diffusivity was calculated based on the diffusion equation for an infinite cylindrical shape using the slope method. The rate of drying was higher for the pre-treatments involving freezing. The sample which was blanched only did not show any improvement in drying rate. In fact, a longer drying time resulted due to water absorption during blanching. There was no change in the rate for the chilled sample compared with the control. While all models closely fitted the drying data, the simple model showed greatest deviation from the experimental results. The two-term exponential model was found to be the best model for describing the drying curves of bananas because its parameters represent better the physical characteristics of the drying process. Moisture diffusivities of bananas were in the range 4.3-13.2 x 10(-10) m(2)s(-1). (C) 2002 Published by Elsevier Science Ltd.

Starch degradation in 'Kensington' mango fruit following heat treatments

Changes in carbohydrate metabolism of 'Kensington' mango fruit from 2 major production regions in Queensland were measured after conditioning fruit with hot air at 40degreesC for 0, 2, 4, 8 and 16 h or at 22degreesC for 16 h (control) followed by hot-water treatment at either 45degreesC fruit-core temperature for 30 min or 47degreesC fruit-core temperature held for 15 min. Advancing physiological maturity of 'Kensington' mango fruit was correlated with increased starch concentration within the mesocarp. An alpha-amylase inhibitor was present in unripe 'Kensington' mesocarp. alpha-Amylase activity was promoted by conditioning fruit at 40degreesC for 8 h, and this enhanced enzyme activity persisted until the fruit were ripe. Consequently, starch degradation was accelerated and the concentration of total soluble solids was higher in fruit conditioned at 40degreesC for 8 h than in fruit left at the lower temperature of 22degreesC for 16 h or not conditioned. Immediately on removal of fruit from hot-water treatment, activities of alpha-amylase and phosphorylase were inhibited. This inhibition was correlated with higher starch concentration and starch layer and starch spot injuries in these fruit. A positive correlation was also found between increased sucrose concentration and greater starch loss in 40degreesC conditioned 'Kensington' fruit. It is proposed that increased sugar concentration in the mesocarp increased the level of fruit heat tolerance.

Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis

Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibility, dating very-fined supergene manganese oxides by Ar-40/(39) Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily Ar-40(atm), Ar-38(atm), and Ar-36(atm), (atmospheric Ar isotopes). The second sites yield predominantly Ar-40* (radiogenic Ar-40), Ar-39(K), and Ar-38(K) (nucleogenic components), at similar to0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of Ar-40*, Ar-39(K), and Ar-38(K) suggests that these isotopes occupy the same crystallographic sites and that Ar-39(K) loss from the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric Ar-40 nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geo-chronological information by analyzing supergene manganese oxides minerals.

Kinetic parameters associated with self-heating of New Zealand coals under adiabatic conditions

Adiabatic self-heating tests were carried out on five New Zealand coal samples ranging in rank from lignite to high-volatile bituminous. Kinetic parameters of oxidation were obtained front the self-heating curves assuming Arrhenius behaviour. The activation energy E (kJ mol(-1)) and the pre-exponential factor A (s(-1)) were determined in the temperature range of 70-140 degreesC. The activation energy exhibited a definite rank relationship with a minimum E of 55 kJ mol(-1) occurring at a Suggate rank of similar to6.2 corresponding to subbituminous C. Either side of this rank there was a noticeable increase in the activation energy indicating lower reactivity of the coal. A similar rank trend was also observed in the R-70 self-heating rate index values that were taken from the initial portion of the self-heating curve front 40 to 70 degreesC. From these results it is clear that the adiabatic method is capable of providing reliable kinetic parameters of coal oxidation.

Heat-induced changes in UHT milks - Part 1

Raw milk was stored for 0, 2 and 4 days and processed in a UHT pilot plant by either direct or indirect heating. The unstored raw milk was also pasteurised. The thermally induced changes resulting from these treatments were investigated by examining a number of indices of heat damage. Lactulose, furosine, total and free hydroxymethylfurfural (HMF) and acid-soluble beta-lactoglobulin were analysed by high performance liquid chromatography (HPLC) while soluble tryptophan was examined by fluorescence spectroscopy. The directly heated UHT milk showed less heat damage than the indirectly heated milk, while the pasteurised milk displayed the least heat damage. During storage of the UHT milk for 12 weeks at similar to20degreesC, the levels of lactulose remained constant, while the furosine concentration increased. Both the total HMF and undenatured beta-lactoglobulin contents showed a general decrease during storage; however free HMF values initially rose but then decreased after four weeks' storage. As the age of the milk at the time of UHT processing increased, the levels of some of the indicators decreased. It is concluded that lactulose is the most reliable index of heat treatment, as it is virtually unaffected by refrigerated storage of the milk before or ambient storage after UHT processing. Reliance on other indicators may give misleading information on the heat load that UHT milk has received during processing.

Potássio : fontes alternativas, tratamentos térmicos e disponibilidade para plantas de milho (Zea Mays L.)

Nosso país é um dos principais produtores agrícolas do mundo e altamente dependente da importação de fertilizantes, principalmente o potássio. Visando reduzir essa dependência, materiais provenientes de rochas para fornecimento desse elemento estão sendo testados. Este estudo foi divido em dois experimentos: um experimento em laboratório e um em casa de vegetação. O experimento em laboratório teve por objetivo avaliar os diferentes tipos de tratamentos térmicos e extratores, associados a fontes alternativas de potássio, no aumento da disponibilidade de K. O ensaio foi realizado num delineamento experimental inteiramente casualizado num esquema fatorial 4 x 5 x 3, com quatro repetições. Os fatores estudados foram: quatro fontes alternativas de potássio (verdete, fonolito, gnaisse e granito); cinco tratamentos térmicos (radiação em forno micro-ondas; autoclavagem; aquecimento em forno mufla com resfriamento rápido; aquecimento em forno mufla com resfriamento lento; e o material in natura); e três extratores: água, ácido cítrico 2 % e solução Mehlich-1. As extrações foram realizadas utilizando 4 g das fontes alternativas, adicionando-se 40 mL de cada extrator, as amostras foram agitadas, centrifugadas, filtradas e avolumadas. Foram realizadas seis extrações sucessivas e determinada a concentração de potássio nos extratos. Os dados obtidos foram submetidos à análise de variância, sendo seus efeitos desdobrados em contrastes ortogonais. O experimento em casa de vegetação teve por objetivo avaliar o efeito da utilização de fontes alternativas de potássio, submetidas a tratamentos térmicos, no fornecimento de potássio para plantas de milho (Zea mays L.). O delineamento experimental adotado foi em blocos casualizados, em um esquema fatorial (3 x 5) + 1, sendo três fontes alternativas de K (verdete, fonolito e granito), submetidas à cinco diferentes tratamentos (aquecimento em forno mufla com resfriamento lento, aquecimento em forno mufla com resfriamento rápido, radiação em forno micro-ondas, autoclavagem, e o material in natura). As fontes alternativas foram comparadas com o cloreto KCl. Amostras de solo contendo 2 dm³ de TFSA, foram incubadas durante 20 dias. Após a adubação, em cada vaso foram aplicadas as fontes alternativas de potássio. Realizou-se o plantio com cinco sementes de milho e posterior desbaste, deixando três plantas por vaso. Decorridos 40 dias da semeadura, foi realizado o corte da parte aérea das plantas, a coleta de amostras de solo para análise dos teores de potássio e separação das raízes. Os dados obtidos foram submetidos à análise de variância e desdobrados em contrastes ortogonais. Observando os resultados obtidos nos experimentos de laboratório e casa de vegetação, podemos concluir que a fonte alternativa e proporcionou melhores resultados e que possui potencial agronômico para ser utilizada como fonte alternativa de potássio foi o fonolito. Utilizando o fonolito como fonte alternativa de nutrientes, o tratamento térmico que proporcionou melhores resultados foi o com aquecimento em forno mufla, principalmente quando o resfriamento foi realizado lentamente.

Modification of MOR by desilication treatments: Structural, textural and acidic characterization

The effect of several desilication experimental parameters (base concentration, temperature and time) on the characteristics of MOR zeolite was studied. The samples were characterized by X-ray diffraction, Al-27 and Si-29 MAS-NMR, chemical analysis, and FTIR (framework vibration region). The textural characterization was made by N-2 adsorption and the acidity was evaluated by pyridine adsorption followed by FTIR and by the catalytic model reaction of n-heptane cracking. The alkaline treatments promoted the Si extraction from the zeolite framework, without considerable loss of crystallinity and, as it was envisaged, an important increase of the mesoporous structure was attained. A linear correlation between the number of framework Si per unit cell. N-Si and the asymmetric stretching wavenumber, nu(i), was observed. The acidity characterization shows that the desilicated samples exhibit practically the same acid properties than the parent HMOR zeolite. The optimum desilication conditions were those used to obtain sample M/0.2/85/2, i.e., sample treated with 0.2 M NaOH solution at 85 degrees C for 2 h.

Estudo técnico/económico da instalação de uma central de cogeração numa serração de madeira

O pinheiro tem um papel importante na ecologia e economia nacional. O Pinheiro sofre de uma praga severa, denominada por doença da murchidão dos pinheiros, causada pelo nemátodo da madeira do pinheiro (NMP). Apresenta-se como um verme microscópico, invertebrado, medindo menos de 1,5 mm de comprimento. O contágio entre árvores deve-se a vectores biologicamente conhecidos por longicórneo e capricórnio do pinheiro. Os produtores de madeira de pinho são desta forma obrigados a efectuar tratamentos térmicos (HT), de eliminação do NMP e dos seus vectores para que a exportação da madeira serrada cumpra com a norma NP 4487. De modo a manter a competitividade internacional das empresas nacionais, o impacto dos custos do HT deve ser minimizado. O objectivo desta dissertação é efectuar o estudo técnico-económico da implementação de um sistema de cogeração capaz produzir calor para efectuar o tratamento ao NMP e simultaneamente energia eléctrica para vender à rede pública. As receitas da venda de energia eléctrica poderão contribuir para a minimização dos custos do HT. Tendo em conta que os resíduos das serrações de madeira podem ser usados como combustível consideraram-se para avaliação duas tecnologias de cogeração, um sistema de turbina a vapor clássico (ciclo Rankine) e um sistema Organic Rankine Cycle (ORC), permitindo ambas a queima dos resíduos das serrações de madeira. No que diz respeito à avaliação económica, foi desenvolvido um simulador de tecnologia/modalidade de remuneração que efectua cálculos consoante as necessidades térmicas de cada produtor, a potência eléctrica a instalar e indicadores económicos, VAL, TIR e PAYBACK da instalação do sistema de cogeração. O simulador desenvolvido aplica a nova legislação que enquadra o sistema jurídico e remuneratório da cogeração (DL 23/2010), na qual se consideram duas modalidades, geral e especial. A metodologia desenvolvida foi aplicada num caso real de uma serração de madeira e os principais resultados mostram que as soluções apresentadas, turbina a vapor e sistema ORC, não apresentam viabilidade económica. Através da análise de sensibilidade, conclui-se que um dos factores que mais influência a viabilidade económica do projecto é o tempo de funcionamento reduzido. Sendo uma das soluções apresentada a criação de uma central de cogeração para vários produtores de madeira. Uma possível solução para o problema do reduzido tempo de utilização seria o fornecimento do serviço de tratamentos térmicos a outros produtores de paletes de madeira que não possuem estufa própria.

Dimensionless analysis of constrained damping treatments

One of the most effective ways of controlling vibrations in plate or beam structures is by means of constrained viscoelastic damping treatments. Contrary to the unconstrained configuration, the design of constrained and integrated layer damping treatments is multifaceted because the thickness of the viscoelastic layer acts distinctly on the two main counterparts of the strain energy the volume of viscoelastic material and the shear strain field. In this work, a parametric study is performed exploring the effect that the design parameters, namely the thickness/length ratio, constraining layer thickness, material modulus, natural mode and boundary conditions have on these two counterparts and subsequently, on the treatment efficiency. This paper presents five parametric studies, namely, the thickness/length ratio, the constraining layer thickness, material properties, natural mode and boundary conditions. The results obtained evidence an interesting effect when dealing with very thin viscoelastic layers that contradicts the standard treatment efficiency vs. layer thickness relation; hence, the potential optimisation of constrained and integrated viscoelastic treatments through the use of properly designed thin multilayer configurations is justified. This work presents a dimensionless analysis and provides useful general guidelines for the efficient design of constrained and integrated damping treatments based on single or multi-layer configurations. (C) 2012 Elsevier Ltd. All rights reserved.

Structural, physical, and chemical modifications induced by microwave heating on native agar-like galactans

Native agars from Gracilaria vermiculophylla produced in sustainable aquaculture systems (IMTA) were extracted under conventional (TWE) and microwave (MAE) heating. The optimal extracts from both processes were compared in terms of their properties. The agars’ structure was further investigated through Fourier transform infrared and NMR spectroscopy. Both samples showed a regular structure with an identical backbone, β-D-galactose (G) and 3,6-anhydro-α-L-galactose (LA) units; a considerable degree of methylation was found at C6 of the G units and, to a lesser extent, at C2 of the LA residues. The methylation degree in the G units was lower for MAEopt agar; the sulfate content was also reduced. MAE led to higher agar recoveries with drastic extraction time and solvent volume reductions. Two times lower values of [η] and Mv obtained for the MAEopt sample indicate substantial depolymerization of the polysaccharide backbone; this was reflected in its gelling properties; yet it was clearly appropriate for commercial application in soft-texture food products.