Single-Element and Competitive Metal Mobility Measured with Column Infiltration and Batch Tests

The distribution coefficient, K-d, is often used to quantify heavy metal mobility in soils. Batch sorption or column infiltration tests may be used to measure K-d. The latter are closer to natural soil conditions, but are difficult to conduct in clays. This difficulty can be overcome by using a laboratory centrifuge. An acceleration of 2600 gravities was applied to columns of London Clay, an Eocene clay sub-stratum, and Cu, Ni, and Zn mobility was measured in centrifuge infiltration tests, both as single elements and in dual competition. Single-element K-d values were also obtained from batch sorption tests, and the results from the two techniques were compared. It was found that K-d values obtained by batch tests vary considerably depending on the metal concentration, while infiltration tests provided a single K-d value for each metal. This was typically in the lower end of the range of the batch test K-d values. For both tests, the order of mobility was Ni > Zn > Cu. Metals became more mobile in competition than when in single-element systems: Ni K-d decreased 3.3 times and Zn K-d 3.4 times when they competed with Cu, while Cu decreased only 1.2 times when in competition with either Ni or Zn. Our study showed that competitive sorption between metals increases the mobility of those metals less strongly bound more than it increases the mobility of more strongly bound metals.

Study of fibre distribution and orientations in UHPFRC by electrical resistivity and mechanical tests

This paper presents experimental tests carried out on steel fibre reinforced concrete samples, including mechanical tests as well as non-destructive technique (electrical resistivity) and non destructive technique on cores (X-ray). Electrical resistivity measurements are done as a blind test, to characterise the electrical anisotropy and deduce the distribution and the orientation of fibres. These results are compared to X-ray imaging to check the quality of the non destructive evaluation. Then, flexural and compressive strength are measured on specimens to assess the influence of fibre distribution on the concrete properties.

Field and Laboratory Tests of Flow-Proportional Passive Samplers for Determining Average Phosphorus and Nitrogen Concentration in Rivers

Flow responsive passive samplers offer considerable potential in nutrient monitoring in catchments; bridging the gap between the intermittency of grab sampling and the high cost of automated monitoring systems. A commercially available passive sampler was evaluated in a number of river systems encapsulating a gradient in storm response, combinations of diffuse and point source pressures, and levels of phosphorus and nitrogen concentrations. Phosphorus and nitrogen are sequestered to a resin matrix in a permeable cartridge positioned in line with streamflow. A salt tracer dissolves in proportion to advective flow through the cartridge. Multiple deployments of different cartridge types were undertaken and the recovery of P and N compared with the flow-weighted mean concentration (FWMC) from high-resolution bank-side analysers at each site. Results from the passive samplers were variable and largely underestimated the FWMC derived from the bank-side analysers. Laboratory tests using ambient river samples indicated good replication of advective throughflow using pumped water, although this appeared not to be a good analogue of river conditions where flow divergence was possible. Laboratory tests also showed good nutrient retention but not elution and these issues appeared to combine to limit the utility in ambient river systems at the small catchment scale.

Is Use of Optional Attributes and Associations in Conceptual Modeling Always Problematic? Theory and Empirical Tests

Prior research has argued that use of optional properties in conceptual models results in loss of information about the semantics of the domains represented by the models. Empirical research undertaken to date supports this argument. Nevertheless, no systematic analysis has been done of whether use of optional properties is always problematic. Furthermore, prior empirical research might have deliberately or unwittingly employed models where use of optionality always causes problems. Accordingly, we examine analytically whether use of optional properties is always problematic. We employ our analytical results to inform the design of an experiment where we systematically examined the impact of optionality on users’ ability to understand domains represented by different types of conceptual models. We found evidence that use of optionality undermines users’ ability to understand the domain represented by a model but that this effect weakens when use of mandatory properties to replace optional properties leads to more-complex models.

FE simulation and experimental tests of high-strength structural bolts under tension

Experimental tests have been completed for high-strength 8.8 bolts for studying their mechanical performance subjected to tensile loading. As observed from these tests, failure of structural bolts has been identified as in one of two ways: threads stripping and necking of the threaded portion of the bolt shank, which is possibly due to the degree of fit between internal and external threads. Following the experimental work, a numerical approach has been developed for demonstration of the tensile performance with proper consideration of tolerance class between bolts and nuts. The degree of fit between internal and external threads has been identified as a critical factor affecting failure mechanisms of high-strength structural bolts in tension, which is caused by the machining process. In addition, different constitutive material laws have been taken into account in the numerical simulation, demonstrating the entire failure mechanism for structural bolts with different tolerance classes in their threads. It is also observed that the bolt capacities are closely associated with their failure mechanisms.

Cold-formed steel sections with web openings subjected to web crippling under two-flange loading conditions - part I: Tests and finite element analysis

The results of 82 web crippling tests are presented, with 20 tests conducted on channel sections without web openings and 62 tests conducted on channel sections with web openings. The tests consider both end-two-flange and interior-two-flange loading conditions. In the case of the tests with web openings, the hole was located directly under the concentrated load. The concentrated load was applied through bearing plates; the effect of different bearing lengths is investigated. In addition, the cases of both flanges fastened and unfastened to the support is considered. A non-linear elasto-plastic finite element model is described, and the results compared against the laboratory test results; a good agreement was obtained in terms of both strength and failure modes.

Effect of web holes on web crippling strength of cold-formed steel channel sections under end-one-flange loading condition – Part I: Tests and finite element analysis

Web openings could be used in cold-formed steel beam members, such as wall studs or floor joints, to facilitate ease of services in buildings. In this paper, a combination of tests and non-linear finite element analyses is used to investigate the effect of such holes on web crippling under end-one-flange (EOF) loading condition; the cases of both flanges fastened and unfastened to the bearing plates are considered. The results of 74 web crippling tests are presented, with 22 tests conducted on channel sections without web openings and 52 tests conducted on channel sections with web openings. In the case of the tests with web openings, the hole was either located centred above the bearing plates or having a horizontal clear distance to the near edge of the bearing plates. A good agreement between the tests and finite element analyses was obtained in term of both strength and failure modes.

Examining architects' performance in Nigeria private and public sectors building projects

Abstract: Purpose – The aim of this paper is to examine and compare the performance of architects with respect to clients' rating of importance over a set of performance criteria in Nigerian public and private sector building projects. Design/methodology/approach – A survey involving clients from both public and private sectors of recently completed building projects in Nigeria was undertaken. Data analysis includes comparing similarities and differences using standardised ratio, Mann Whitney U and Wilcoxon tests. Findings – The results show that private sector clients are likely to be more concerned with cost, while public sector clients are more concerned with buildability of design. A total of 79 per cent of the criteria were similarly selected by both sectors with respect to importance of the criteria. Architects need to improve their performance significantly in about 82 per cent of the whole set of 28 criteria. The architects performed better in the public sector than the private sector and 14 per cent of the criteria were indicated as being statistically different in terms of architects' performance. Originality/value – The results provide feedback which can be incorporated in architects' future projects so as to ensure successful project implementation in the building delivery process.

Comparison of LIMPET contra-rotating wells turbine with theoretical and model test predictions

The performance of the contra-rotating Wells turbine installed in the LIMPET wave power station is compared to the predicted performance from theoretical analysis and model tests. A reasonable agreement was found between the predicted and measured turbine damping characteristic, however the turbine efficiency was found to be poorly predicted. It is postulated that this is due to the unsteady nature and mal-distribution of flow through the LIMPET turbine, which were not considered in the predictions. It is suggested that the reduced performance of the contra-rotating Wells turbine makes biplane or monoplane Wells turbines with guide vanes better solutions for OWC's.

Effect of Loading, Voltage Difference and Phase Angle on the Synchronisation of a Small Alternator

Synchronisation of small distributed generation, 30 kVA–2 MVA, employing salient-pole synchronous machines is normally performed within a narrow range of tolerances for voltage, frequency and phase angle. However, there are situations when the ability to synchronise with non-ideal conditions would be beneficial. Such applications include power system islanding and rapid generator start-up. The physical process and effect of out-of-phase synchronisation is investigated both through simulation and experimental tests on a salient-pole alternator. There are many factors that affect synchronisation, but particular attention is given to synchronisation angle, voltage difference and, as generators will be loaded during islanding, the load angle. The results suggest that it would be acceptable for the maximum synchronisation angle of distributed generation to exceed that of current practice. Interesting observations on the nature of out-of-phase synchronisation are made, including some specific to small salient-pole synchronous machines. Furthermore, recommendations are made for synchronisation under different system conditions.

In vitro testing of chitosan in gentamicin-loaded bone cement No antimicrobial effect and reduced mechanical performance

Background and purpose Efforts to prevent infection of arthroplasties, including the use of antibiotic-loaded bone cement, are not always successful. We investigated whether the incorporation of chitosan in gentamicin-loaded bone cement increases antibiotic release, and prevents bacterial adherence and biofilm formation by clinical isolates of Staphylococcus spp. In addition, we performed mechanical and degradation tests.

Unite and conquer: univariate and multivariate approaches for finding differentially expressed gene sets

Motivation: Recently, many univariate and several multivariate approaches have been suggested for testing differential expression of gene sets between different phenotypes. However, despite a wealth of literature studying their performance on simulated and real biological data, still there is a need to quantify their relative performance when they are testing different null hypotheses.

Results: In this article, we compare the performance of univariate and multivariate tests on both simulated and biological data. In the simulation study we demonstrate that high correlations equally affect the power of both, univariate as well as multivariate tests. In addition, for most of them the power is similarly affected by the dimensionality of the gene set and by the percentage of genes in the set, for which expression is changing between two phenotypes. The application of different test statistics to biological data reveals that three statistics (sum of squared t-tests, Hotelling's T2, N-statistic), testing different null hypotheses, find some common but also some complementing differentially expressed gene sets under specific settings. This demonstrates that due to complementing null hypotheses each test projects on different aspects of the data and for the analysis of biological data it is beneficial to use all three tests simultaneously instead of focusing exclusively on just one.

Attention deficits in Alzheimer's disease and vascular dementia

OBJECTIVE:

To compare the performance of patients with mild-moderate Alzheimer's disease (AD) and vascular dementia (VaD) on tests of information processing and attention.

METHOD:

Patients with AD (n=75) and VaD (n=46) were recruited from a memory clinic along with dementia-free participants (n=28). They underwent specific tests of attention from the Cognitive Drug Research battery, and pen and paper tests including Colour Trails A and B and Stroop. All patients had a CT brain scan that was independently scored for white-matter change/ischaemia.

RESULTS:

Attention was impaired in both AD and VaD patients. VaD patients had more impaired choice reaction times and were less accurate on a vigilance test measuring sustained attention. Deficits in selective and divided attention occurred in both patient groups and showed the strongest correlations with Mini Mental State Examination scores.

CONCLUSION:

This study demonstrates problems with the attentional network in mild-moderate AD and VaD. The authors propose that attention should be tested routinely in a memory clinic setting.