Applying discrete element modelling to vertical and horizontal shaft impact crushers

The PFC3D (particle flow code) that models the movement and interaction of particles by the DEM techniques was employed to simulate the particle movement and to calculate the velocity and energy distribution of collision in two types of impact crusher: the Canica vertical shaft crusher and the BJD horizontal shaft swing hammer mill. The distribution of collision energies was then converted into a product size distribution for a particular ore type using JKMRC impact breakage test data. Experimental data of the Canica VSI crusher treating quarry and the BJD hammer mill treating coal were used to verify the DEM simulation results. Upon the DEM procedures being validated, a detailed simulation study was conducted to investigate the effects of the machine design and operational conditions on velocity and energy distributions of collision inside the milling chamber and on the particle breakage behaviour. (C) 2003 Elsevier Ltd. All rights reserved.

The mental health country profile: Background, design and use of a systematic method of appraisal

This article describes the construction and use of a systematic structured method of mental health country situation appraisal, in order to help meet the need for conceptual tools to assist planners and policy makers develop and audit policy and implementation strategies. The tool encompasses the key domains of context, needs, resources, provisions and outcomes, and provides a framework for synthesizing key qualitative and quantitative information, flagging up gaps in knowledge, and for reviewing existing policies. It serves as an enabling tool to alert and inform policy makers, professionals and other key stakeholders about important issues which need to be considered in mental health policy development. It provides detailed country specific information in a systematic format, to facilitate global sharing of experiences of mental health reform and strategies between policy makers and other stakeholders. Lastly, it is designed to be a capacity building tool for local stakeholders to enhance situation appraisal, and multisectorial policy development and implementation.

Applying the results of a systematic review in general practice

Objective: To assess how general practitioners might interpret and apply the results of a systematic review relevant to general practice. Design: Cross-sectional postal survey of general practitioners in August 1997. Participants: 51 general practitioners in the Southern Division of General Practice in Adelaide and 11 professors or heads of departments of general practice. Main outcome measures:Extent to which comments on the implications for practice and implications for research coincided with the evidence presented in a systematic review of antibiotics for the treatment of acute otitis media in children; and reported probability that respondents would prescribe antibiotics in three brief case scenarios. Results: There was considerable variation in the comments made by general practitioners on the implications of the review for clinical practice. After reading the review, respondents with training in critical appraisal were more likely to state that children with acute otitis media would usually recover spontaneously and reported a lower probability of prescribing antibiotics in two of the three case scenarios. Conclusions: Providing systematic reviews is not sufficient for the results of such evidence to be translated:into clinical practice. There is an association between critical appraisal skills and the application of evidence-based practice.

Effect of coinfection with STDs and of STD treatment on HIV shedding in genital-tract secretions - Systematic review and data synthesis

Objective: To determine whether coinfection with sexually transmitted diseases (STD) increases HIV shedding in genital-tract secretions, and whether STD treatment reduces this shedding. Design: Systematic review and data synthesis of cross-sectional and cohort studies meeting. predefined quality criteria. Main Outcome Measures: Proportion of patients with and without a STD who had detectable HIV in genital secretions, HIV toad in genital secretions, or change following STD treatment. Results: Of 48 identified studies, three cross-sectional and three cohort studies were included. HIV was detected significantly more frequently in participants infected with Neisseria gonorrhoeae (125 of 309 participants, 41%) than in those without N gonorrhoeae infection (311 of 988 participants, 32%; P = 0.004). HIV was not significantly more frequently detected in persons infected with Chlamydia trachomatis (28 of 67 participants, 42%) than in those without C trachomatis infection (375 of 1149 participants, 33%; P = 0.13). Median HIV load reported in only one study was greater in men with urethritis (12.4 x 10(4) versus 1.51 x 10(4) copies/ml; P = 0.04). In the only cohort study in which this could be fully assessed, treatment of women with any STD reduced the proportion of those with detectable HIV from 39% to 29% (P = 0.05), whereas this proportion remained stable among controls (15-17%), A second cohort study reported fully on HIV load; among men with urethritis, viral load fell from 12.4 to 4.12 x 10(4) copies/ml 2 weeks posttreatment, whereas viral load remained stable in those without urethritis. Conclusion: Few high-quality studies were found. HIV is detected moderately more frequently in genital secretions of men and women with a STD, and HIV load is substantially increased among men with urethritis, Successful STD treatment reduces both of these parameters, but not to control levels. More high-quality studies are needed to explore this important relationship further.

Simultaneous steady state and dynamic design of process systems using structural indicators

The simultaneous design of the steady-state and dynamic performance of a process has the ability to satisfy much more demanding dynamic performance criteria than the design of dynamics only by the connection of a control system. A method for designing process dynamics based on the use of a linearised systems' eigenvalues has been developed. The eigenvalues are associated with system states using the unit perturbation spectral resolution (UPSR), characterising the dynamics of each state. The design method uses a homotopy approach to determine a final design which satisfies both steady-state and dynamic performance criteria. A highly interacting single stage forced circulation evaporator system, including control loops, was designed by this method with the goal of reducing the time taken for the liquid composition to reach steady-state. Initially the system was successfully redesigned to speed up the eigenvalue associated with the liquid composition state, but this did not result in an improved startup performance. Further analysis showed that the integral action of the composition controller was the source of the limiting eigenvalue. Design changes made to speed up this eigenvalue did result in an improved startup performance. The proposed approach provides a structured way to address the design-control interface, giving significant insight into the dynamic behaviour of the system such that a systematic design or redesign of an existing system can be undertaken with confidence.

A time-harmonic inverse methodology for the design of RF coils in MRI

An inverse methodology is described to assist in the design of radio-frequency (RF) coils for magnetic resonance imaging (MRI) applications. The time-harmonic electromagnetic Green's functions are used to calculate current on the coil and shield cylinders that will generate a specified internal magnetic field. Stream function techniques and the method of moments are then used to implement this theoretical current density into an RF coil. A novel asymmetric coil operating for a 4.5 T MRI machine was designed and constructed using this methodology and the results are presented.

Ecological interface design for pasteurizer II: A process description of semantic mapping

Ecological interface design (EID) is proving to be a promising approach to the design of interfaces for complex dynamic systems. Although the principles of EID and examples of its effective use are widely available, few readily available examples exist of how the individual displays that constitute an ecological interface are developed. This paper presents the semantic mapping process within EID in the context of prior theoretical work in this area. The semantic mapping process that was used in developing an ecological interface for the Pasteurizer II microworld is outlined, and the results of an evaluation of the ecological interface against a more conventional interface are briefly presented. Subjective reports indicate features of the ecological interface that made it particularly valuable for participants. Finally, we outline the steps of an analytic process for using EID. The findings presented here can be applied in the design of ecological interfaces or of configural displays for dynamic processes.

Whispered voice test for screening for hearing impairment in adults and children: systematic review

Objective To determine the accuracy of the whispered voice test in detecting hearing impairment in adults and children. Design Systematic review of studies of test accuracy. Data sources Medline, Embase, Science Citation Index, unpublished theses, manual searching of bibliographies of known primary and review articles, and contact with authors. Study selection Two reviewers independently selected and extracted data on study characteristics, quality, and accuracy of studies. Studies were included if they had cross sectional designs, at least one of the index tests was the whispered voice test, and the reference test (audiometry) was performed on at least 80% of the participants. Data extraction Data were used to form 2x2 contingency tables with hearing impairment by audiometry as the reference standard. Data synthesis The eight studies that were found used six different techniques. The sensitivity in the four adult studies was 90% or 100% and the specificity was 70% to 87%. The sensitivity in the four childhood studies ranged from 80% to 96% and specificity ranged from 90% to 98%. Conclusion The whispered voice test is a simple and accurate test for detecting hearing impairment. There is some concern regarding the lower sensitivity in children and the overall reproducibility of the test, particularly in primary care settings. Further studies should be conducted in primary care settings to explore the influence of components of the testing procedure to optimise test sensitivity and to promote standardisation of the testing procedure.

How well does B-type natriuretic peptide predict death and cardiac events in patients with heart failure: systematic review

Objective To assess how well B-type natriuretic peptide (BNP) predicts prognosis in patients with heart failure. Design Systematic review of studies assessing BNP for prognosis m patients with heart failure or asymptomatic patients. Data sources Electronic searches of Medline and Embase from January 1994 to March 2004 and reference lists of included studies. Study selection and data extraction We included all studies that estimated the relation between BNP measurement and the risk of death, cardiac death, sudden death, or cardiovascular event in patients with heart failure or asymptomatic patients, including initial values and changes in values in response to treatment. Multivariable models that included both BNP and left ventricular ejection fraction as predictors were used to compare the prognostic value of each variable. Two reviewers independently selected studies and extracted data. Data synthesis 19 studies used BNP to estimate the relative risk of death or cardiovascular events in heart failure patients and five studies in asymptomatic patients. In heart failure patients, each 100 pg/ml increase was associated with a 35% increase in the relative risk of death. BNP was used in 35 multivariable models of prognosis. In nine of the models, it was the only variable to reach significance-that is, other variables contained no prognostic information beyond that of BNP. Even allowing for the scale of the variables, it seems to be a strong indicator of risk. Conclusion Although systematic reviews of prognostic studies have inherent difficulties, including die possibility of publication bias, the results of the studies in this review show that BNP is a strong prognostic indicator for both asymptomatic patients mid for patients with heart failure at all stages of disease.

A study of the interaction between operator style and machine capability for a hydraulic mining excavator

This paper presents a case study that explores how operator digging style juxtaposes with mechanical capability for a class of hydraulic mining excavators. The relationships between actuator and digging forces are developed and these are used to identify the excavator's capability to apply forces in various directions. Two distinct modes of operation are examined to see how they relate to the mechanical capabilities of the linkage and to establish if one has merit over the other. It is found that one of these styles results in lower loading of the machine.

Design analysis for refolding monomeric protein

Renaturation of protein expressed as inclusion bodies within Escherichia coli is a key step in many bioprocesses. Operating conditions for the refolding step dramatically affect the amount of protein product recovered, and hence profoundly influence the process economics. The first systematic comparison of refolding conducted in batch, fed-batch and continuous stirred-tank reactors is provided Refolding is modeled as kinetic competition between first-order refolding (equilibrium reaction) and irreversible aggregation (second-order). Simulations presented allow direct comparison between different flowsheets and refolding schemes using a dimensionless economic objective. As expected from examination of the reaction kinetics, batch operation is the most inefficient merle. For the base process considered, the overall cost of fed-batch and continuous refolding is virtually identical (less than half that of the batch process). Reactor selection and optimization of refolding using overall economics are demonstrated to be vitally important.

Prolotherapy injections for chronic low back pain - A systematic review

Study Design. A systematic review of randomized and quasi-randomized controlled trials. Objectives. To determine the efficacy of prolotherapy injections in adults with chronic low back pain. Summary of Background Data. Prolotherapy is an injection-based treatment for chronic low back pain. Proponents of prolotherapy suggest that some back pain stems from weakened or damaged ligaments. Repeatedly injecting them with irritant solutions is thought to strengthen the ligaments and reduce pain and disability. Prolotherapy protocols usually include co-interventions to enhance the effectiveness of the injections. Methods. The authors searched MEDLINE, EMBASE, CINAHL, and Science Citation Index up to January 2004, and the Cochrane Controlled Trials Register 2004, issue 1, and consulted content experts. Both randomized and quasi-randomized controlled trials comparing prolotherapy injections to control injections, either alone or in combination with other treatments, were included. Studies had to include measures of pain and disability before and after the intervention. Two reviewers independently selected the trials and assessed them for methodologic quality. Treatment and control group protocols varied from study to study, making meta-analysis impossible. Results. Four studies, all of high quality and with a total of 344 participants, were included. All trials measured pain and disability levels at 6 months, three measured the proportion of participants reporting a greater than 50% reduction in pain or disability scores from baseline to 6 months. Two studies showed significant differences between the treatment and control groups for those reporting more than 50% reduction in pain or disability. Their results could not be pooled. In one, cointerventions confounded interpretation of results; in the other, there was no significant difference in mean pain and disability scores between the groups. In the third study, there was little or no difference between groups in the number of individuals who reported more than 50% improvement in pain and disability. The fourth study reporting only mean pain and disability scores showed no differences between groups. Conclusions. There is conflicting evidence regarding the efficacy of prolotherapy injections in reducing pain and disability in patients with chronic low back pain. Conclusions are confounded by clinical heterogeneity among studies and by the presence of co-interventions. There was no evidence that prolotherapy injections alone were more effective than control injections alone. However, in the presence of co-interventions, prolotherapy injections were more effective than control injections, more so when both injections and co-interventions were controlled concurrently.