Identification and characterisation of chloramine decaying proteins and control of impact in chloraminated systems

Chloramine is the second most popular disinfectant behind chlorine used in water distribution systems. The main advantages of using chloramine over chlorine are; it provides a longer lasting disinfectant residual and forms a less amount of the regulated halogenated disinfection by-products. However, at times, microbial chloramine decay can overwhelm stability and is identified as one of the serious problems that needs addressing. One of the mechanisms of microbial chloramine decay is by production of soluble microbial products (SMP), which substantially affects the chloramine decay. The SMP are usually composed of proteins, polysaccharides, humic acids, fulvic acids, nucleic acids, enzymes and structural compounds, but it was suspected that the chloramine decaying SMP could be protein(s) due to the catalytic effect that was noted in the samples. It was noted in soluble form in water after the onset of nitrification in a chloraminated system. When the SMP was filtered out of the water and was run on the SDS page to identify the compound 25 different proteins were seen with weaker signals. Therefore, the identity of chloramine decaying soluble microbial products (SMP), which microbes produce them and how to control them are not known. If SMP was produced by nitrifiers and since nitrifiers could be inhibited by higher organic carbon levels when changing dissolved organic carbon (DOC) level in the water, it could alter the production of chloramine decaying SMP. Therefore, batch rechloramination tests were conducted for reactor sets with variable DOC levels to understand their effect on the impact of SMP. The results revealed as the highest production of SMP had been stimulated with low DOC level (0-1mg-C.L-1) compared to other DOC levels (2-3, 4-5 and 7-8 mg-C.L-1). To recognize microbial community variations with the impression of identifying CDP producing micro-organisms, microbial community analysis was also carried out in the same reactor sets. Significant differences in bacterial types against DOC variations could not be detected. However, some of the bacterial types such as Micobacterium, AOB, Bradyrhizobium sp., Methylobacterium and family Sphingomonadaceae recognized in this study are known to produce extracellular polymeric substances (EPS). My early work has identified that SMP are proteins; hence, named as chloramine decaying proteins (CDP). In Relation to the context of these experiments, the proteins consisting within EPS can be considered as CDP. Questioning if nitrifiers always produce CDP, two nitrified reactors - one with chloramine (chloraminated reactor) and the other with ammonia (ammoniated reactor) - were operated using nutrient added Milli-Q water as the feed water in a way nitrification occurs within the reactor. MilliQ was selected since it produced the highest concentration of CDP. It was expected that CDP could be easily separated amongst 25 previously found proteins. Therefore, nitrified bulk water and biofilm samples from both reactors were subjected to protein separation (2-dimensional gel electrophoresis and SDS-polyacrylamide gel electrophoresis) and protein identification (mass spectrometry-MS). Furthermore, bacterial community variations on ammoniated and chloraminated reactors were characterised by sequencing of 16S RNA. The batch rechloramination results obtained from the reactors for the first time established the production of CDP as a microbial response to chloramine stress. The bacterial community characterisations on each of the reactors did not show major differences in identified bacterial strains. However, the EPS producing bacterial strains (AOB, Bradyrhizobium sp. and family Sphingomonadaceae) identified in chloraminated reactors were suspected to be responsible for CDP production. Chloraminated and ammoniated bulk water samples were not resulting in enough concentrations, therefore, for comparison of protein spots and MS analysis, the biofilm samples (which are believed to have more CDP) were analysed. The major proteins detected were ammonia monooxygenase subunit A and putative porin related to Nitrosomonas sp. and Bradyrhizobium sp., respectively. However, their relation to CDP has to be further investigated. Conclusively, every aspect of this study is directing towards discovering a better control mechanism for the microbial/ CDP induced accelerated chloramine decay. Silver is a known inhibitor for several micro-organisms. Therefore, experiments were conducted to reveal the optimum dose of silver on inactivating nitrifying microbes and CDP for controlling the fast decay of chloramine. Interestingly, 2 μg-Ag.L-1 silver (which is far lower than the recommended level- 0.1 mg-Ag.L-1) was found to be effective for improving chloramine residuals in tested bulk waters. This study concludes by further emphasising the need for extensive study/research in further identification of CDP and bacteria communities responsible for chloramine decay in chloraminated drinking water distribution systems

Crowding, housing and health: An exploratory study of Australian cities

Australian capital cities are among the most expensive in the world, and the persistent shortage of affordable housing is a significant driver of housing overcrowding, particularly in the private rental sector. Health and wellbeing issues arise from closer contact between household members including increased spread of communicable infections, sleep disruption, lack of privacy and an inability to care adequately for sick household members. The aim of this paper is to examine the extent and the spatial distribution of overcrowding in the five largest cities in Australia – Sydney, Melbourne, Brisbane, Perth and Adelaide, and consider its distribution in relation to socioeconomic disadvantage. The analysis begins by critically reviewing available standards for quantifying overcrowding – e.g. World Health Organisation, Eurostat, Canadian National Occupancy Standard for Housing Appropriateness and Proxy Occupancy Standards. Drawing from the above frameworks, the investigation extends to compute indicators of crowding using 2011 Australian Bureau of Statistics Census data. The chosen unit of analysis (i.e. SA2) enables local level geographies of overcrowding to be mapped within and across cities. We then compare incidence of overcrowding and the distribution of socio-economic disadvantage measured by Socio-Economic Index for Areas (SEIFA) - the Index of Relative Socio-Economic Disadvantage (IRSD).Our findings indicate Sydney and Melbourne have the highest incidence of crowding in housing amongst the largest five cities, accounting to 26% and 17% of residents living in such dwellings respectively. We also find a strong overlap of geographies of overcrowding and socioeconomic disadvantage and, contrary to the conventional wisdom, overcrowding seems to be most evident in middle-city areas in all the cities investigated except for Adelaide. The geographical analysis thus generates policy-relevant spatial knowledge about the locations and extent of crowding in specific Australian citie

New framework for simultaneous localization and mapping: Multi map SLAM

The main contribution of this paper arises from the development of a new framework, which has its inspiration in the mechanics of human navigation, for solving the problem of Simultaneous Localization and Mapping (SLAM). The proposed framework has specific relevance to vision based SLAM, in particular, small baseline stereo vision based SLAM and addresses several key issues relevant to the particular sensor domain. Firstly, as observed in the authors' earlier work, the particular sensing device has a highly nonlinear observation model resulting in inconsistent state estimations when standard recursive estimators such as the Extended Kalman Filter (EKF) or the Unscented variants are used. Secondly, vision based approaches tend to have issues related to large feature density, narrow field of view and the potential requirement of maintaining large databases for vision based data association techniques. The proposed Multi Map SLAM solution addresses the filter inconsistency issue by formulating the SLAM problem as a nonlinear batch optimization. Feature management is addressed through a two tier map representation. The two maps have unique attributes assigned to them. The Global Map (GM) is a compact global representation of the robots environment and the Local Map (LM) is exclusively used for low-level navigation between local points in the robot's navigation horizon. ©2008 IEEE

Simultaneous localisation and mapping: A stereo vision based approach

With limited dynamic range and poor noise performance, cameras still pose considerable challenges in the application of range sensors in the context of robotic navigation, especially in the implementation of Simultaneous Localisation and Mapping (SLAM) with sparse features. This paper presents a combination of methods in solving the SLAM problem in a constricted indoor environment using small baseline stereo vision. Main contributions include a feature selection and tracking algorithm, a stereo noise filter, a robust feature validation algorithm and a multiple hypotheses adaptive window positioning method in 'closing the loop'. These methods take a novel approach in that information from the image processing and robotic navigation domains are used in tandem to augment each other. Experimental results including a real-time implementation in an office-like environment are also presented. © 2006 IEEE

Investigation of the agricultural resources in Sri Lanka

The author has identified the following significant results. Several in-house capabilities were developed. The facilities to prepare color composites of excellent quality were developed, using bulk B/W 70 mm transparencies or 1:1,000,000 positive transparencies. These color composites were studied through optical devices on light tables. A zoom transfer scope was also added, enabling direct transfer of LANDSAT composite data on to base maps

Estimating rainfall distributions at high temporal resolutions using a multifractal model

International audienceRainfall data from 18 stations in the vicinity of Tokyo city, measured to a precision of 1 mm, were analysed for multifractal properties. A multifractal model based on the scaling properties of temporal distribution of rainfall intensities was formulated to investigate the intensity distribution relationships in the available scaling regime. Although conventional analysis did not provide encouraging results with these measurements, an alternative approach that could be applied to rainfall data of widely variable quality and duration was used to establish a scaling relationship between daily and hourly rainfall intensities. Using a discrete cascade algorithm based on the log-Lèvy generator, synthetic hourly rainfall series were generated from the multifractal statistics of daily-accumulated rainfall. Several properties of rainfall time series that are relevant to the use of rainfall data in surface hydrological studies were used to determine, statistically, the degree of agreement between the synthetic hourly series and observed hourly rainfall. Keywords: rainfall modelling, cascades, multifractal, downscalin

Natural ventilation in insect screened single span greenhouses under warm weather

The ventilation rates of different types of ridge vents in combination with insect-screened side vents were assessed in single greenhouses in terms of the difference in temperature and humidity inside and outside under tropical conditions. The A-frame (slanted roof) was comparatively advantageous over the conventional arch frame (curved roof) for keeping daytime temperature lower in single span greenhouse with insect-screenedside vents (mesh size: 1 by 1 mm) and without roof vents. The inclusion of ridge vents further reduced the internal temperature and relative humidity (RH) in the A-frame greenhouse during the daytime. The openingarea of the ridge vent within the range between 9.3% and 14% (of the floor area) did not significantly change the ventilation based internal temperature and RH when operated under low wind speeds (0.5±0.5 m s-1). Meanwhile the effect of ridge orientation, with respect to wind direction, on greenhouse ventilation was not obvious in terms of temperature or RH under inconsistent wind directions and low wind speeds. Greenhouse ventilation positively responded to low winds (0.25 m s-1) by reducing internal temperature as well as RH. However, the response to a further increase in wind speed from 0.25 to 0.5 m s-1 was not significant. Based on climate control characteristics an A-frame single-span greenhouse design with double sided alternate ridge vents and insect-screened side vents could be appropriate for tropical climates under low wind speeds and inconsistent wind directions as a cost effective and user-friendly greenhouse design. Particularly, it is highly applicable for the small-scale controlled environment vegetable production in mid and low elevations in the wet zone of Sri Lanka. Keywords: Alternate ridge vent, curved roof, continuous ridge vent, ridge orientation, wind effect

Reduced-rank Envelope Vector Autoregressive Models

The standard vector autoregressive (VAR) models suffer from overparameterization which is a serious issue for high-dimensional time series data as it restricts the number of variables and lags that can be incorporated into the model. Several statistical methods, such as the reduced-rank model for multivariate (multiple) time series (Velu et al., 1986; Reinsel and Velu, 1998; Reinsel et al., 2022) and the Envelope VAR model (Wang and Ding, 2018), provide solutions for achieving dimension reduction of the parameter space of the VAR model. However, these methods can be inefficient in extracting relevant information from complex data, as they fail to distinguish between relevant and irrelevant information, or they are inefficient in addressing the rank deficiency problem. We put together the idea of envelope models into the reduced-rank VAR model to simultaneously tackle these challenges, and propose a new parsimonious version of the classical VAR model called the reduced-rank envelope VAR (REVAR) model. Our proposed REVAR model incorporates the strengths of both reduced-rank VAR and envelope VAR models and leads to significant gains in efficiency and accuracy. The asymptotic properties of the proposed estimators are established under different error assumptions. Simulation studies and real data analysis are conducted to evaluate and illustrate the proposed method

Elevating the value of urban location: A consumer preference-based approach to valuing local amenity provision

Estimating the non-market monetary values of urban amenities has become commonplace in urban planning research, particularly following Rosen’s seminal article on hedonic theory in 1974. As a revealed preference method, the hedonic approach decouples the market price of a house into price components that are attributable to housing characteristics. Despite the potential contribution of this theory in a planning context, three main limitations exist in the conventional applications: (1) variable measurement issues, (2) model misspecification, and (3) the problematic common use of global regression. These flaws problematically skew our understanding of the urban structure and spatial distribution of amenities, leading to misinformed policy interventions and poor amenity planning decisions. In this article, we propose a coherent conceptual framework that addresses measurement, specification, and scale challenges to generate consistent economic estimates of local amenities. Finally, we argue that, by paying greater attention to the spatial equity of amenity values, governments can provide greater equality of opportunities in cities