A survey into the prevalence of parasitic helminths in broiler breeders

A survey was conducted to determine the prevalence of helminth infections in spent broiler breeders. Intestinal tracts from 10 birds from each of five farms were obtained and examined for parasite identification and quantification. Heterakis gallinarum infections were the most common, followed in order of decreasing incidence by Capillaria obsignata, Ascaridia galli, and Raillietina cesticillus. Peak worm burdens for individual birds were 121 (A. galli), 535 (H. gallinarum), 215 (C. obsignata) and 125 (R. cesticillus). Significant farm-to-farm variation in worm burdens was observed

Low-volume wet-process sprayed concrete : pumping and spraying

This paper, which reports on part of a three-year research project into wet-process sprayed concrete for repair, examines the influence of rheology on the pumping and spraying of fine concretes. The performance of ten laboratory-designed fine concretes were examined using a rotational viscometer, the slump test, a build test and a vane shear strength test. Visual grading and a sorptivity test were used to quantify the degree of reinforcement encasement which is a crucial factor in long term performance. Taken together, these tests form a rheological audit of each concrete which can help guide the design of sprayable, but also durable concretes. The two-point apparatus was successful for determining the flow resistance and torque viscosity of fine aggregate concretes, including those with air entrainment. The vane shear strength test was successful in providing an instantaneous reading of the shear strength of the concretes and is compared with their slump. The concretes were pumped and sprayed through a piston pump to assess their suitability and to measure their adhesion to a substrate by build thickness. This value is a measure of sprayability and is converted into values of maximum shear and tensile stress which are then compared with the workability parameters in order to determine their inter-relationship. These relationships are also compared with those obtained from a separated study of mortars. On its own, the sorptivity test did not accurately assess the encapsulation of the reinforcement. However, when considered with a visual grading of the cores, a more reliable indication can be obtained of the potential durability of the finished concrete, as well as the degree of encapsulation of the reinforcement. We demonstrate the conflict in selecting mix proportions that satisfy requirements for both installation and product quality

Doing it the wet way – sprayed concrete for repair

Doing it the wet way – sprayed concrete for repai

Low-volume wet-process sprayed concrete: hardened properties

This paper, which reports on part of a 3-year research project into wet-process sprayed mortars and concretes for repair, investigates the hardened performance of wet-process sprayed fine concretes. It follows on from an earlier paper by the authors on the performance of hardened wet-process sprayed mortars and some comparisons with these are made here (Austin SA, Robins PJ, Goodier CI (2000). Magz Concr Res 52:195–208). Work has also been completed by the authors on the pumping and rheology of the fine concrete mixes presented here (Austin SA, Goodier, CI, Robins PJ (2005). Mater Struc, RILEM 38:229–237). Nine laboratory-designed fine concretes were pumped and sprayed through a wet-process piston pump and one through a dry-process pump. The properties measured included compressive and flexural strength, tensile bond strength, hardened density, elastic modulus, sorptivity and drying and restrained shrinkage. In situ test specimens were extracted from 500 × 500 × 100 mm deep sprayed panels. Hardened property tests were also conducted on corresponding cast specimens and, where possible, on specimens that had been sprayed directly into a cube or beam mould. The compressive strengths of the cast cubes, although very similar, were usually slightly greater than the in␣situ cubes, the opposite of what was found for wet-sprayed mortars (Austin SA, Robins PJ, Goodier CI (2000). Magz Concr Res 52:195–208). Inconsistent results for compressive and flexural strengths obtained from spraying directly into a steel mould suggest that this method is not as reliable when using a piston pump as it is when using a low-output worm pump (Austin SA, Robins PJ, Goodier CI (2000). Magz Concr Res 52:195–208). The bond strength of all the mixes exceeded 2.1 MPa at 7 days. The values for modulus of elasticity, when compared with the compressive strength, were similar to published data for this relationship. The sorptivity values showed only a slight relationship with the compressive strength. The mixes exhibited a wide range of drying shrinkage, but the data from the restrained specimens suggest an actual repair is influenced as much by ambient conditions as it is by the mix proportions

An evaluation of repair mortars installed by worm-pump spraying

This paper examines the fresh and hardened performance of wet-process sprayed mortars and the influence of rheology on the pumping and spraying of these mortars. Seven commercially available preblended repair mortars designed for hand application, together with a laboratory-designed fine mortar, were investigated using the Tattersall two-point rotational viscometer, the pressure bleed test, the slump test, and a vane shear strength test. The mortars were pumped and sprayed with a small diameter worm pump and the build thickness determined. Hardened properties measured include compressive strength, tensile bond strength, hardened density and drying shrinkage. Tests were conducted on cast and in-situ specimens and, where possible, on specimens produced by spraying directly into a cube or beam mould. Initial findings for predicting the pumpability and sprayability of the mortars are presented and this is linked together with the hardened performance. These results show that the majority of proprietary pre-blended repair mortars designed for hand application are suitable for wet-process application with a worm pump

The rheological performance of wet-process sprayed mortars

This paper, which reports on part of a three year research project into wet-process sprayed concrete for repair, examines the influence of rheology on the pumping and spraying of mortars. The performance of seven commercially available pre-packaged repair mortars and six laboratory designed fine mortars was examined using the Tattersall two-point and Viskomat rotational viscometers, the pressure bleed test, the slump test, a build test and a vane shear strength test. These tests were used to form a rheological audit of each mortar. The two-point apparatus was successful with low-workability mortars and their flow resistance and torque viscosities were determined. These parameters were also obtained with the Viskomat, although problems were encountered due to their low workability. The pressure bleed test measured both the rate and the total volume of liquid emitted from the mixes whilst the vane shear strength test provided an instantaneous reading of the shear strength of the mortars and is compared with their slump. The mortars were pumped and sprayed through a worm pump to assess their suitability and to measure their adhesion to a substrate by build thickness. This value is a measure of sprayability and is converted into values of maximum shear and bending stress which are then compared with the workability parameters in order to determine their inter-relationship

Workability, shear strength and build of wet-process sprayed mortars

This paper, which reports on part of a three year research project into wetprocess sprayed concrete for repair, examines the influence of rheology on the pumping and spraying of sprayed mortars. The workability properties of seven commercially available prepackaged repair mortars and six laboratory designed fine mortars were examined using the Tattersall Two-point viscometer, the slump test, a build test and a vane shear strength test. The Two-point apparatus was successful with low-workability mortars and the flow resistance and torque viscosity of the mortars was determined. The vane shear strength test provided an instantaneous reading of the shear strength of the mortars and is compared with their slump. The build value, a measure of sprayability, is then compared with these two workability parameters and the flow resistance in order to determine their inter-relationship

Locally Efficient Estimation of Regression Parameters Using Current Status Data

In biostatistics applications interest often focuses on the estimation of the distribution of a time-variable T. If one only observes whether or not T exceeds an observed monitoring time C, then the data structure is called current status data, also known as interval censored data, case I. We consider this data structure extended to allow the presence of both time-independent covariates and time-dependent covariate processes that are observed until the monitoring time. We assume that the monitoring process satisfies coarsening at random. Our goal is to estimate the regression parameter beta of the regression model T = Z*beta+epsilon where the conditional density of the error epsilon given Z is assumed to have location parameter equal to zero. Because of the curse of dimensionality no globally-efficient nonparametric estimator with good practical performance at moderate sample sizes exists. We present an estimator of the parameter beta that attains the semiparametric efficiency bound if we correctly specify (a) a model for the monitoring mechanism and (b) a lower dimensional model for the conditional distribution of T given the covariates. In addition, our estimator is robust to model misspecification. If only (a) is correctly specified, the estimator remains consistent and asymptotically normal. We conclude with a simulation experiment and a data analysis

Construction and repair with wet-process sprayed concrete and mortar

Construction and repair with wet-process sprayed concrete and morta

Importance of size representation and morphology in modelling optical properties of black carbon: comparison between laboratory measurements and model simulations

Black carbon (BC) from incomplete combustion of biomass or fossil fuels is the strongest absorbing aerosol component in the atmosphere. Optical properties of BC are essential in climate models for quantification of their impact on radiative forcing. The global climate models, however, consider BC to be spherical particles, which causes uncertainties in their optical properties. Based on this, an increasing number of model-based studies provide databases and parameterization schemes for the optical properties of BC, using more realistic fractal aggregate morphologies. In this study, the reliability of the different modelling techniques of BC was investigated by comparing them to laboratory measurements. The modelling techniques were examined for bare BC particles in the first step and for BC particles with organic material in the second step. A total of six morphological representations of BC particles were compared, three each for spherical and fractal aggregate morphologies. In general, the aggregate representation performed well for modelling the particle light absorption coefficient σabs, single-scattering albedo SSA, and mass absorption cross-section MACBC for laboratory-generated BC particles with volume mean mobility diameters dp,V larger than 100nm. However, for modelling Ångström absorption exponent AAE, it was difficult to suggest a method due to size dependence, although the spherical assumption was in better agreement in some cases. The BC fractal aggregates are usually modelled using monodispersed particles, since their optical simulations are computationally expensive. In such studies, the modelled optical properties showed a 25% uncertainty in using the monodisperse size method. It is shown that using the polydisperse size distribution in combination with fractal aggregate morphology reduces the uncertainty in measured σabs to 10% for particles with dp,V between 60-160nm. Furthermore, the sensitivities of the BC optical properties to the various model input parameters such as the real and imaginary parts of the refractive index (mre and mim), the fractal dimension (Df), and the primary particle radius (app) of an aggregate were investigated. When the BC particle is small and rather fresh, the change in the Df had relatively little effect on the optical properties. There was, however, a significant relationship between app and the particle light scattering, which increased by a factor of up to 6 with increasing total particle size. The modelled optical properties of BC are well aligned with laboratory-measured values when the following assumptions are used in the fractal aggregate representation: mre between 1.6 and 2, mim between 0.50 and 1, Df from 1.7 to 1.9, and app between 10 and 14nm. Overall, this study provides experimental support for emphasizing the importance of an appropriate size representation (polydisperse size method) and an appropriate morphological representation for optical modelling and parameterization scheme development of BC