An energy-based model for swing hammer mills

An energy-based swing hammer mill model has been developed for coke oven feed preparation. it comprises a mechanistic power model to determine the dynamic internal recirculation and a perfect mixing mill model with a dual-classification function to mimic the operations of crusher and screen. The model parameters were calibrated using a pilot-scale swing hammer mill at various operating conditions. The effects of the underscreen configurations and the feed sizes on hammer mill operations were demonstrated through the fitted model parameters. Relationships between the model parameters and the machine configurations were established. The model was validated using the independent experimental data of single lithotype coal tests with the same BJD pilot-scale hammer mill and full operation audit data of an industrial hammer mill. The outcome of the energy-based swing hammer mill model is the capability to simulate the impact of changing blends of coal or mill configurations and operating conditions on product size distribution. Alternatively, the model can be used to select the machine settings required to achieve a desired product. (C) 2003 Elsevier Science B.V. All rights reserved.

Critical comparison of Julius Kruttschnitt Mineral Research Centre (JKMRC) blast fragmentation models

Blast fragmentation can have a significant impact on the profitability of a mine. An optimum run of mine (ROM) size distribution is required to maximise the performance of downstream processes. If this fragmentation size distribution can be modelled and controlled, the operation will have made a significant advancement towards improving its performance. Blast fragmentation modelling is an important step in Mine to Mill™ optimisation. It allows the estimation of blast fragmentation distributions for a number of different rock mass, blast geometry, and explosive parameters. These distributions can then be modelled in downstream mining and milling processes to determine the optimum blast design. When a blast hole is detonated rock breakage occurs in two different stress regions - compressive and tensile. In the-first region, compressive stress waves form a 'crushed zone' directly adjacent to the blast hole. The second region, termed the 'cracked zone', occurs outside the crush one. The widely used Kuz-Ram model does not recognise these two blast regions. In the Kuz-Ram model the mean fragment size from the blast is approximated and is then used to estimate the remaining size distribution. Experience has shown that this model predicts the coarse end reasonably accurately, but it can significantly underestimate the amount of fines generated. As part of the Australian Mineral Industries Research Association (AMIRA) P483A Mine to Mill™ project, the Two-Component Model (TCM) and Crush Zone Model (CZM), developed by the Julius Kruttschnitt Mineral Research Centre (JKMRC), were compared and evaluated to measured ROM fragmentation distributions. An important criteria for this comparison was the variation of model results from measured ROM in the-fine to intermediate section (1-100 mm) of the fragmentation curve. This region of the distribution is important for Mine to Mill™ optimisation. The comparison of modelled and Split ROM fragmentation distributions has been conducted in harder ores (UCS greater than 80 MPa). Further work involves modelling softer ores. The comparisons will be continued with future site surveys to increase confidence in the comparison of the CZM and TCM to Split results. Stochastic fragmentation modelling will then be conducted to take into account variation of input parameters. A window of possible fragmentation distributions can be compared to those obtained by Split . Following this work, an improved fragmentation model will be developed in response to these findings.

Amylases in enzyme detergents and their effects on a simulated long-life dairy dessert

Enzyme detergents used in the food industry contain proteinase as the major enzyme but amylase may be present, either by design or inadvertently. Three commercial enzyme detergents and 3 enzyme preparations used in detergents were assayed for alpha-amylase activity by the Ceralpha method using the Megazyme kits. The amylase activities of the detergents varied from 3.2x 10(-6) to 32x 10(-6) mumoles ml(-1) h(-1) while the enzyme preparations had much higher activities ranging from 0.05 to 8.06 mumoles ml(-1) h(-1). When added aseptically to a simulated dairy dessert (2% starch solution) and stored for 42 days, the enzyme detergents caused an increase in viscosity; enzyme preparations at low concentrations caused an initial increase in viscosity followed by a decrease; and enzyme preparations at high concentrations caused an immediate decrease in viscosity. The increase in viscosity corresponded to formation of a distinct network of starch granules while the decrease in viscosity was characterised by a marked decrease in size of the granules and little or no network of granules. Decreases in viscosity corresponded to increases in reducing sugars but samples which increased in viscosity showed no measurable reducing sugars. The amylase activity in all sources was destroyed by heating at 75degreesC for 15 min at pH 1.8.

Heat resistance of Bacillus spores when adhered to stainless steel and its relationship to spore hydrophobicity

Twenty-one strains of Bacillus (10 B. stearothermophilus, 3 B. cereus, and 8 B. licheniformis strains) were assayed for spore surface hydrophobicity on the basis of three measures: contact angle measurement (CAM), microbial adhesion to hydrocarbons (MATH), and hydrophobic interaction chromatography (HIC). On the basis of the spore surface characteristics obtained from these assays, along with data on the heat resistance of these spores in water, eight strains of Bacillus (three B. stearothermophilus, three B. cereus, and two B. licheniformis strains) either suspended in water or adhering to stainless steel were exposed to sublethal heat treatments at 90 to 110degreesC to determine heat resistance (D-value). Significant increases in heat resistance (ranging from 3 to 400%) were observed for the eight strains adhering to stainless steel. No significant correlation was found between these heat resistance increases and spore surface characteristics as determined by the three hydrophobicity assays. There was a significant positive correlation between the hydrophobicity data obtained by the MATH assay and those obtained by the HIC assay, but these data did not correlate with those obtained by the CAM assay.

Diagnosing the cause of proteolysis in UHT milk

Proteolysis of UHT milk during storage at room temperature is a major factor limiting its shelf-life through changes in its flavour and texture. The latter is characterised by increases in viscosity leading in some cases to gel formation. The enzymes responsible for the proteolysis are the native milk alkaline proteinase, plasmin, and heat-stable, extracellular bacterial proteinases produced by psychrotrophic bacterial contaminants in the milk prior to heat processing. These proteinases react differently with the milk proteins and produce different peptides in the UHT milk. In order to differentiate these peptide products, reversed-phase HPLC and the fluorescamine method were used to analyse the peptides soluble in 12% trichloroacetic acid (TCA) and those soluble at pH 4.6. The TCA filtrate showed substantial peptide peaks only if the milk was contaminated by bacterial proteinase, while the pH 4.6 filtrate showed peptide peaks when either or both bacterial and native milk proteinases caused the proteolysis. Results from the fluorescamine test were in accordance with the HPLC results whereby the TCA filtrate exhibited significant proteolysis values only when bacterial proteinases were present, but the pH 4.6 filtrates showed significant values when the milk contained either or both types of proteinase. A procedure based on these analyses is proposed as a diagnostic test for determining which type of proteinase-milk plasmin, bacterial proteinase, or both-is responsible for proteolysis in UHT milk. (C) 2003 Swiss Society of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.

Effect of storage time and conditions on the seed coat colour of Australian adzuki beans

Two varieties of adzuki beans (Vigna angularis), Bloodwood and Erimo, were stored at temperatures of 10, 20 or 30degreesC, and relative humidities (RH) 40 or 65%, and samples were analysed at 0, 1.5, 3 and 6 months. Storage at 30degreesC for > 1.5 months caused a significant decrease in the a(star) and b(star) colour values and darkening of the seed coat. Beans stored at 65% RH had lower L-star but higher a(star) and b(star) colour values than those stored at 40% RH. Bloodwood and Erimo samples showed similar trends in colour during storage. The best storage conditions for the preservation of the adzuki colour were 10degreesC and 65% RH. The Australian beans had lower L-star, a(star) and b(star) colour values than Japanese Erimo-shouzu beans and storage increased the difference.

Effect of storage time and conditions on the cotyledon cell wall of the adzuki bean (Vigna angularis)

Two varieties of adzuki grown in Australia, Bloodwood and Erimo, were stored for up to 6 months at three temperatures (10, 20 and 30 degreesC), and two relative humidities (RH; 40 and 65%). The amount of cell wall material increased with time under all storage conditions. This increase was greatest at 30 degreesC and 40% RH. Storage time and conditions did not affect the total pectin levels in the cell wall. Erimo constantly exhibited a higher total pectin level than Bloodwood. The Bloodwood soluble pectin, Ca++ and Mg++ and Erimo Ca++ in the cell wall remained stable during storage, while the Erimo soluble pectin and Mg++ exhibited a slight decrease at 20 and 30 degreesC after 3 months of storage. (C) 2002 Elsevier Science Ltd. All rights reserved.

Ventricular performance and Na+-K+ ATPase activity are reduced early and late after myocardial infarction in rats

Myocardial infarction leads to compensatory ventricular remodeling. Disturbances in myocardial contractility depend on the active transport of Ca2+ and Na+, which are regulated by Na+-K+ ATPase. Inappropriate regulation of Na+-K+ ATPase activity leads to excessive loss of K+ and gain of Na+ by the cell. We determined the participation of Na+-K+ ATPase in ventricular performance early and late after myocardial infarction. Wistar rats (8-10 per group) underwent left coronary artery ligation (infarcted, Inf) or sham-operation (Sham). Ventricular performance was measured at 3 and 30 days after surgery using the Langendorff technique. Left ventricular systolic pressure was obtained under different ventricular diastolic pressures and increased extracellular Ca2+ concentrations (Ca2+e) and after low and high ouabain concentrations. The baseline coronary perfusion pressure increased 3 days after myocardial infarction and normalized by 30 days (Sham 3 = 88 ± 6; Inf 3 = 130 ± 9; Inf 30 = 92 ± 7 mmHg; P < 0.05). The inotropic response to Ca2+e and ouabain was reduced at 3 and 30 days after myocardial infarction (Ca2+ = 1.25 mM; Sham 3 = 70 ± 3; Inf 3 = 45 ± 2; Inf 30 = 29 ± 3 mmHg; P < 0.05), while the Frank-Starling mechanism was preserved. At 3 and 30 days after myocardial infarction, ventricular Na+-K+ ATPase activity and contractility were reduced. This Na+-K+ ATPase hypoactivity may modify the Na+, K+ and Ca2+ transport across the sarcolemma resulting in ventricular dysfunction.

Effects of mercury on the arterial blood pressure of anesthetized rats

The available data suggests that hypotension caused by Hg2+ administration may be produced by a reduction of cardiac contractility or by cholinergic mechanisms. The hemodynamic effects of an intravenous injection of HgCl2 (5 mg/kg) were studied in anesthetized rats (N = 12) by monitoring left and right ventricular (LV and RV) systolic and diastolic pressures for 120 min. After HgCl2 administration the LV systolic pressure decreased only after 40 min (99 ± 3.3 to 85 ± 8.8 mmHg at 80 min). However, RV systolic pressure increased, initially slowly but faster after 30 min (25 ± 1.8 to 42 ± 1.6 mmHg at 80 min). Both right and left diastolic pressures increased after HgCl2 treatment, suggesting the development of diastolic ventricular dysfunction. Since HgCl2 could be increasing pulmonary vascular resistance, isolated lungs (N = 10) were perfused for 80 min with Krebs solution (continuous flow of 10 ml/min) containing or not 5 µM HgCl2. A continuous increase in pulmonary vascular resistance was observed, suggesting the direct effect of Hg2+ on the pulmonary vessels (12 ± 0.4 to 29 ± 3.2 mmHg at 30 min). To examine the interactions of Hg2+ and changes in cholinergic activity we analyzed the effects of acetylcholine (Ach) on mean arterial blood pressure (ABP) in anesthetized rats (N = 9) before and after Hg2+ treatment (5 mg/kg). Using the same amount and route used to study the hemodynamic effects we also examined the effects of Hg2+ administration on heart and plasma cholinesterase activity (N = 10). The in vivo hypotensive response to Ach (0.035 to 10.5 µg) was reduced after Hg2+ treatment. Cholinesterase activity (µM h-1 mg protein-1) increased in heart and plasma (32 and 65%, respectively) after Hg2+ treatment. In conclusion, the reduction in ABP produced by Hg2+ is not dependent on a putative increase in cholinergic activity. HgCl2 mainly affects cardiac function. The increased pulmonary vascular resistance and cardiac failure due to diastolic dysfunction of both ventricles are factors that might contribute to the reduction of cardiac output and the fall in arterial pressure.

Ativação da enzima conversora de angiotensina no coração após infarto do miocárdio e suas repercussões no remodelamento ventricular

Objetivo: Determinar as alterações de atividade da enzima conversora de angiotensina (ECA) no coração com infarto do miocárdio (IM) e comparar os efeitos do captopril e losartan em parâmetros morfológicos e funcionais de ratos com IM. Métodos: O IM foi produzido em ratos Wistar por ligadura de ramos da artéria coronária esquerda. Os controles (Con) foram submetidos a uma cirurgia fictícia. Animais com IM e Con foram tratados com captopril (30mg/kg/dia) ou losartan (15mg/kg/dia) e estudados 30 dias após, determinando-se a atividade da ECA nos ventrículos direito (VD) e esquerdo (VE), as alterações hemodinâmicas e as concentrações de hidroxiprolina (OH-Pro) e proteína total no VD e VE. Resultados: A atividade da ECA aumentou no VD (+25%) e VE (+70%) após IM. A maior atividade foi observada na cicatriz fibrótica, onde atingiu cerca de 4,5 vezes a do músculo do VE que sobreviveu ao IM (420±68 vs 94±8nmoles/g/min; P<0,01). O IM determinou aumento da pressão diastólica final e hipertrofia do VD e VE. Captopril e losartan foram igualmente eficazes em atenuar a hipertrofia e o aumento da pré-carga. O captopril também atenuou o aumento de OH-Pro no VD e VE após IM. O IM reduziu a concentração de proteína principalmente no músculo de VE, efeito esse acentuado pelo captopril. Conclusão: A grande atividade da ECA na cicatriz deve produzir altas concentrações de angiotensina II (AII) no sangue que drena da cicatriz. Os efeitos dos inibidores da ECA seriam decorrentes, principalmente, da redução de geração local de AII, e não de aumento de cininas, uma vez que captopril e losartan exerceram efeitos similares no remodelamento pós-infarto.

Ambulatory blood pressure and Doppler echocardiographic indexes of borderline hypertensive men presenting an exaggerated blood pressure response during dynamic exercise

Borderline hypertension (BH) has been associated with an exaggerated blood pressure (BP) response during laboratory stressors. However, the incidence of target organ damage in this condition and its relation to BP hyperreactivity is an unsettled issue. Thus, we assessed the Doppler echocardiographic profile of a group of BH men (N = 36) according to office BP measurements with exaggerated BP in the cycloergometric test. A group of normotensive men (NT, N = 36) with a normal BP response during the cycloergometric test was used as control. To assess vascular function and reactivity, all subjects were submitted to the cold pressor test. Before Doppler echocardiography, the BP profile of all subjects was evaluated by 24-h ambulatory BP monitoring. All subjects from the NT group presented normal monitored levels of BP. In contrast, 19 subjects from the original BH group presented normal monitored BP levels and 17 presented elevated monitored BP levels. In the NT group all Doppler echocardiographic indexes were normal. All subjects from the original BH group presented normal left ventricular mass and geometrical pattern. However, in the subjects with elevated monitored BP levels, fractional shortening was greater, isovolumetric relaxation time longer, and early to late flow velocity ratio was reduced in relation to subjects from the original BH group with normal monitored BP levels (P<0.05). These subjects also presented an exaggerated BP response during the cold pressor test. These results support the notion of an integrated pattern of cardiac and vascular adaptation during the development of hypertension.

Hipertensão arterial e consumo de sal em população urbana

Objetivo: Avaliar o consumo de sal e a relação sódio/potássio urinário em amostra randomizada de população urbana etnicamente miscigenada. Métodos: Foi selecionada uma amostra randômica de 2.268 residentes de Vitória, ES, entre 25 e 64 anos de idade. Os indivíduos foram escolhidos por amostragem domiciliar realizada em 1999/2000, dos quais 1.663 (73,3%) compareceram ao hospital para a realização de exames padronizados. O consumo estimado de sal, Na+ e K+ foi determinado por meio da coleta de urina de 12h no período noturno (19h às 7h) e do gasto mensal de sal domiciliar referido durante a entrevista. A pressão arterial clínica foi medida duas vezes por diferentes pesquisadores treinados em condições padronizadas, usando esfignomamômetro de mercúrio. Para análise estatística foram utilizados o teste de Student e o teste de Tukey. Resultados: A excreção urinária de Na+ foi mais alta em homens e em indivíduos de menores condições socioeconômicas (P<0,000). Não foi observada diferença entre os grupos étnicos. A excreção de K+ não se relacionou com nível socioeconômico e raça, mas foi significativamente mais alta entre os homens (25±18 x 22±18 mEq/12h; P=0,002). Foi observada uma correlação linear positiva entre a excreção urinária de Na+ e pressão arterial sistólica (r=0,15) e diastólica (r=0,19). Indivíduos hipertensos apresentaram maior excreção urinária de Na+ e relação Na/K, quando comparados com indivíduos normotensos. O consumo de sal relatado foi aproximadamente 50% do consumo estimado pela excreção urinária de 12h (em torno de 45% da excreção urinária de 24h). Conclusões: A ingestão de sal é fortemente influenciada pelo nível socioeconômico e pode, parcialmente, explicar a alta prevalência de hipertensão arterial nas classes socioeconômicas mais baixas

Efeitos agudos do alongamento estático no desempenho da força dinâmica em homens jovens

Introdução: O alongamento muscular é frequentemente utilizado nas práticas desportivas, com o objetivo de aumentar a flexibilidade muscular e amplitude articular, assim como diminuir o risco de lesões e melhorar o desempenho atlético. Objetivo: Analisar o efeito agudo do alongamento com diferentes tempos no desempenho da força dinâmica de membros superiores e inferiores em homens jovens. Métodos: Participaram da amostra 14 voluntários do sexo masculino com idade de 23 ± 2 anos, peso corporal de 84 ± 10kg, estatura de178 ± 7cm, IMC de 26 ± 2kg/m2 e percentual de gordura de 11 ± 3%. Eles foram avaliados com o teste de 10RM em três situações distintas: condição sem alongamento (SA), aquecimento especifico seguido do teste de 10-RM; condição com oito minutos de alongamento (AL-8), uma sessão de alongamento estático com oito minutos de duração, seguido do aquecimento e teste de 10RM; e a condição alongamento 16 minutos (AL-16), 16 minutos de alongamento seguidos dos procedimentos descritos anteriormente. Os testes foram feitos no supino reto e leg-press 45º; os alongamentos foram selecionados de forma a atingir as musculaturas solicitadas nos respectivos exercícios. Resultados: Houve redução de 9,2% da força muscular dinâmica de membros superiores em comparação dos grupos SA e AL16, e entre os grupos AL8 e AL16 (p < 0,001). Em membros inferiores essa redução de força (p < 0,001) foi de 4,8% para AL-8 e de 14,3% para AL-16 em comparação com o grupo SA. Conclusão: Sessões de alongamentos estáticos efetuados antes de atividades que envolvam força dinâmica possuem a capacidade de alterar negativamente o desempenho dessa qualidade física, acarretando pior rendimento em longos períodos de alongamento.

Estado nutricional e estilo de vida em vegetarianos e onívoros, Grande Vitória-ES

Objetivo: Descrever e analisar o estado nutricional e aspectos do estilo de vida de vegetarianos e onívoros residentes na Grande Vitória/ES, na faixa etária de 35 a 64 anos de idade. Material E Métodos: Trata-se de estudo observacional híbrido de casos prevalentes com avaliação retrospectiva da exposição. Os grupos de expostos (134) e não expostos à dieta onívora típica ocidental (67) foram determinados no início da investigação. Foram coletados dados antropométricos, bioquímicos, de atividade física e alimentação através de questionário e 3 recordatórios de 24 horas e diagnosticados sobrepeso, Razão Cintura Quadril (RCQ) inadequada e hipercolesterolemia. Colesterol total e frações, triglicerídeos, ácido úrico, sódio e potássio urinários foram comparados entre os grupos, através do teste t de Student. Foi usado o teste qui-quadrado para comparar proporções, com =0,05. Resultados: Foram encontradas diferenças significativas em relação à ocupação. Duração da atividade física e tempo assistindo televisão e/ou utilizando computador foram maiores entre os onívoros. Os vegetarianos relataram práticas alimentares mais saudáveis e menor consumo de lipídios, proteínas e sódio. Os onívoros apresentaram maior risco de sobrepeso, RCQ inadequada e hipercolesterolemia (valores de P<0,0001). HDL-colesterol não foi diferente nos grupos. Conclusão: Os vegetarianos apresentaram perfil nutricional mais adequado e menor risco para os agravos crônicos estudados, apesar de pequena diferença no padrão de atividade física regular entre os grupos estudados.

Correlação entre a depuração plasmática de creatinina utilizando urina coletada durante 24 horas e 12 horas

Introdução: A concentração da creatinina no plasma é usada para avaliar a função renal, mas a depuração da creatinina plasmática (DCP) constitui método mais sensível para essa finalidade. Objetivo: Correlacionar a DCP em coleta urinária de 12 horas noturna com a de 24 horas. Métodos: Noventa e cinco voluntários (34-64 anos) coletaram urina durante 24 horas em dois frascos: diurno (das 7h às 19h) e noturno (das 19h às 7h do dia seguinte). A coleta de sangue se deu em jejum para medidas bioquímicas. A correlação entre as variáveis foi feita pelo teste Pearson (r) e a concordância de medidas, pelo teste de Bland-Altman. Resultados: Urinas de quatro indivíduos foram recusadas por erro de coleta. Na amostra final (n = 91; 42 homens), havia 23 hipertensos e cinco diabéticos. A DCP (mL/min/1,73 m2) foi menor no período noturno em mulheres (77,8 ± 22,7 versus 88,4 ± 23,6; p < 0,05) e similar em homens (91,2 ± 22,9 versus 97,3 ± 30,9; p > 0,05). As correlações entre a DCP na urina de 12 horas noturna ou diurna e a de 24 horas foram fortes (r = 0,85 e 0,83, respectivamente). Em 85 e 83 dos 91 indivíduos, a medida da DCP noturna e diurna, respectivamente, foi concordante com a de 24 horas. Conclusão: A urina de 12 horas, sobretudo quando coletada à noite, fornece valores de DCP similares àqueles obtidos em coleta de 24 horas. Como essa coleta é mais fácil de ser feita em pacientes ambulatoriais à noite, esse período deveria ser preferido para a medida da filtração glomerular.