Cold adaptation and replicable microbial community development during long-term low temperature anaerobic digestion treatment of synthetic sewage

The development and, activity of a cold-adapting microbial community was monitored during low temperature anaerobic digestion (LtAD) treatment of wastewater. Two replicate hybrid anaerobic sludge bed-fixed-film reactors treated a synthetic sewage wastewater at 12°C, at organic loading rates of 0.25–1.0 kg Chemical Oxygen Demand (COD) m−3 d−1, over 889 days. The inoculum was obtained from a full-scale AD reactor, which was operated at 37˚C. Both LtAD reactors readily degraded the influent with COD removal efficiencies regularly exceeding 78% for both the total and soluble COD fractions. The biomass from both reactors was sampled temporally and tested for activity against hydrolytic and methanogenic substrates at 12˚C and 37˚C. Data indicated that significantly enhanced low-temperature hydrolytic and methanogenic activity developed in both systems. For example, the hydrolysis rate constant (K) at 12°C had increased 20–30-fold by comparison to the inoculum by day 500. Substrate affinity also increased for hydrolytic substrates at low temperature. Next generation sequencing demonstrated that a shift in community structure occurred over the trial, involving a 1-log-fold change in 25 SEQS (OTU-free approach) from the inoculum. Microbial community structure changes and process performance were replicable in the LtAD reactors

Mapping of water-related ecosystem services in the uMngeni catchment using a daily time-step hydrological model for prioritisation of ecological infrastructure investment – Part 1: Context and modelling approach

South Africa is a semi-arid country which frequently faces water shortages, and experienced a severe drought in the 2016 and 2017 rainfall seasons. Government is under pressure to continue to deliver clean water to the growing population at a high assurance of supply. Studies now show that the delivery of water may be sustained not only through built infrastructure such as dams and pipelines, but also through investment in ecological infrastructure (EI). A daily time-step hydrological model was used to map areas which should be prioritised for protection or rehabilitation to sustain the delivery of water-related ecosystem services within the uMngeni catchment. We focused on three water-related ecosystem services, i.e.: water supply, sustained baseflow, erosion control/avoidance of excessive sediment losses. The two key types of degradation were modelled, namely, overgrazing and the invasion of upland areas by Black Wattle (Acacia mearnsii). This, Part 1 of a paper in 2 parts, provides a discussion on the role of EI in delivering water-related ecosystem services, describes the motivation for the study, and the methods used in modelling and mapping the catchment. The results of this modelling exercise are presented in Part 2, which also explores and illustrates the potential hydrological benefits of rehabilitation and protection of EI in the uMngeni Catchment.Keywords: water, ecosystem services, hydrological modelling, ecological infrastructure, water securit

Understanding the diverse needs of subtitle users in a rapidly evolving media landscape.

Audiences are increasingly using services such as video on demand and the web to watch television programmes. Broadcasters need to make subtitles available across all these new platforms. These platforms also create new design opportunities for subtitles along with the ability to customise them to an individual's needs. To explore these new opportunities for subtitles we have begun the process of reviewing the guidance for subtitles on television and evaluating the original user research. We have found that existing guidelines have been shaped by a mixture of technical constraints, industry practice and user research, constrained by existing technical standards. This paper provides an overview of the subtitle research at BBC R&D over the past two years. Our research is revealing significant diversity in the needs and preferences of frequent subtitle users, and points to the need for personalisation in the way subtitles are displayed. We are developing a new approach to the authoring and display of subtitles that can respond to the user requirements by adjusting the subtitle layout in the client device

The thermal regime around buried submarine high voltage cables

The expansion of offshore renewable energy infrastructure and the need for trans-continental shelf power transmission require the use of submarine High Voltage (HV) cables. These cables have maximum operating surface temperatures of up to 70°C and are typically buried 1–2 m beneath the seabed, within the wide range of substrates found on the continental shelf. However, the heat flow pattern and potential effects on the sedimentary environments around such anomalously high heat sources in the near surface sediments are poorly understood. We present temperature measurements from a 2D laboratory experiment representing a buried submarine HV cable, and identify the thermal regimes generated within typical unconsolidated shelf sediments—coarse silt, fine sand and very coarse sand. We used a large (2 × 2.5 m) tank filled with water-saturated spherical glass beads (ballotini) and instrumented with a buried heat source and 120 thermocouples, to measure the time-dependent 2D temperature distributions. The observed and corresponding Finite Element Method (FEM) simulations of the steady state heat flow regimes, and normalised radial temperature distributions were assessed. Our results show that the heat transfer and thus temperature fields generated from submarine HV cables buried within a range of sediments are highly variable. Coarse silts are shown to be purely conductive, producing temperature increases of >10°C up to 40 cm from the source of 60°C above ambient; fine sands demonstrate a transition from conductive to convective heat transfer between c. 20°C and 36°C above ambient, with >10°C heat increases occurring over a metre from the source of 55°C above ambient; and very coarse sands exhibit dominantly convective heat transfer even at very low (c. 7°C) operating temperatures and reaching temperatures of up to 18°C above ambient at a metre from the source at surface temperatures of only 18°C. These findings are important for the surrounding near surface environments experiencing such high temperatures and may have significant implications for chemical and physical processes operating at the grain and sub-grain scale; biological activity at both micro-faunal and macro-faunal levels; and indeed the operational performance of the cables themselves, as convective heat transport would increase cable current ratings, something neglected in existing standards

In situ measurements of near-surface hydraulic conductivity in engineered clay slopes

In situ measurements of near-saturated hydraulic conductivity in fine grained soils have been made at six exemplar UK transport earthwork sites: three embankment and three cutting slopes. This paper reports 143 individual measurements and considers the factors that influence the spatial and temporal variability obtained. The test methods employed produce near-saturated conditions and flow under constant head. Full saturation is probably not achieved due to preferential and by-pass flow occurring in these desiccated soils. For an embankment, hydraulic conductivity was found to vary by five orders of magnitude in the slope near-surface (0 to 0.3 metres depth), decreasing by four orders of magnitude between 0.3 and 1.2 metres depth. This extremely high variability is in part due to seasonal temporal changes controlled by soil moisture content, which can account for up to 1.5 orders of magnitude of this variability. Measurements of hydraulic conductivity at a cutting also indicated a four orders of magnitude range of hydraulic conductivity for the near-surface, with strong depth dependency of a two orders of magnitude decrease from 0.2 to 0.6 metres depth. The main factor controlling the large range is found to be spatial variability in the soil macro structure generated by wetting/drying cycle driven desiccation and roots. The measurements of hydraulic conductivity reported in this paper were undertaken to inform and provide a benchmark for the hydraulic parameters used in numerical models of groundwater flow. This is an influential parameter in simulations incorporating the combined weather/vegetation/infiltration/soil interaction mechanisms that are required to assess the performance and deterioration of earthwork slopes in a changing climate

Metric trees of generalized roundness one

Every finite metric tree has generalized roundness strictly greater than one. On the other hand, some countable metric trees have generalized roundness precisely one. The purpose of this paper is to identify some large classes of countable metric trees that have generalized roundness precisely one. At the outset we consider spherically symmetric trees endowed with the usual combinatorial metric (SSTs). Using a simple geometric argument we show how to determine decent upper bounds on the generalized roundness of finite SSTs that depend only on the downward degree sequence of the tree in question. By considering limits it follows that if the downward degree sequence $(d_{0}, d_{1}, d_{2}...)$ of a SST $(T,\rho)$ satisfies $|\{j \, | \, d_{j} > 1 \}| = \aleph_{0}$, then $(T,\rho)$ has generalized roundness one. Included among the trees that satisfy this condition are all complete $n$-ary trees of depth $\infty$ ($n \geq 2$), all $k$-regular trees ($k \geq 3$) and inductive limits of Cantor trees. The remainder of the paper deals with two classes of countable metric trees of generalized roundness one whose members are not, in general, spherically symmetric. The first such class of trees are merely required to spread out at a sufficient rate (with a restriction on the number of leaves) and the second such class of trees resemble infinite combs.Comment: 14 pages, 2 figures, 2 table

How does the early life environment influence the oral microbiome and determine oral health outcomes in childhood?

The first 1000 days of life, from conception to 2 years, are a critical window for the influence of environmental exposures on the assembly of the oral microbiome, which is the precursor to dental caries (decay), one of the most prevalentmicrobially induced disorders worldwide. While it is known that the human microbiome is susceptible to environmental exposures, there is limited understanding of the impact of prenatal and early childhood exposures on the oral microbiome trajectory and oral health. A barrier has been the lack of technology to directly measure the foetal "exposome", which includes nutritional and toxic exposures crossing the placenta. Another barrier has been the lack of statistical methods to account for the high dimensional data generated by-omic assays. Through identifying which early life exposures influence the oral microbiome and modify oral health, these findings can be translated into interventions to reduce dental decay prevalence.Christina Jane Adler, Kim-Anh Lê Cao, Toby Hughes, Piyush Kumar, Christine Austi

Concepção de novos materiais para catálise heterogénea e outras aplicações

Tese de doutoramento, Química (Química Inorgânica), Universidade de Lisboa, Faculdade de Ciências, 2012Fundação para a Ciência e a Tecnologia (FCT, SFRH/BD/48640/2008

The Atacama Cosmology Telescope: Physical Properties of Sunyaev-Zel'dovich Effect Clusters on the Celestial Equator

We present the optical and X-ray properties of 68 galaxy clusters selected via the Sunyaev-Zel'dovich Effect at 148 GHz by the Atacama Cosmology Telescope (ACT). Our sample, from an area of 504 square degrees centered on the celestial equator, is divided into two regions. The main region uses 270 square degrees of the ACT survey that overlaps with the co-added ugriz imaging from the Sloan Digital Sky Survey (SDSS) over Stripe 82 plus additional near-infrared pointed observations with the Apache Point Observatory 3.5-meter telescope. We confirm a total of 49 clusters to z~1.3, of which 22 (all at z>0.55) are new discoveries. For the second region the regular-depth SDSS imaging allows us to confirm 19 more clusters up to z~0.7, of which 10 systems are new. We present the optical richness, photometric redshifts, and separation between the SZ position and the brightest cluster galaxy (BCG). We find no significant offset between the cluster SZ centroid and BCG location and a weak correlation between optical richness and SZ-derived mass. We also present X-ray fluxes and luminosities from the ROSAT All Sky Survey which confirm that this is a massive sample. One of the newly discovered clusters, ACT-CL J0044.4+0113 at z=1.1 (photometric), has an integrated XMM-Newton X-ray temperature of kT_x=7.9+/-1.0 keV and combined mass of M_200a=8.2(-2.5,+3.3)x10^14 M_sun/h70 placing it among the most massive and X-ray-hot clusters known at redshifts beyond z=1. We also highlight the optically-rich cluster ACT-CL J2327.4-0204 (RCS2 2327) at z=0.705 (spectroscopic) as the most significant detection of the whole equatorial sample with a Chandra-derived mass of M_200a=1.9(-0.4,+0.6)x10^15 M_sun/h70, comparable to some of the most massive known clusters like "El Gordo" and the Bullet Cluster.Comment: 18 pages, 12 figures. Accepted to the Astrophysical Journal. New version includes minor changes in the accepted pape