Diameter of orientations of graphs with given order and number of blocks

A strong orientation of a graph $G$ is an assignment of a direction to each edge such that $G$ is strongly connected. The oriented diameter of $G$ is the smallest diameter among all strong orientations of $G$. A block of $G$ is a maximal connected subgraph of $G$ that has no cut vertex. A block graph is a graph in which every block is a clique. We show that every bridgeless graph of order $n$ containing $p$ blocks has an oriented diameter of at most $n-\lfloor \frac{p}{2} \rfloor$. This bound is sharp for all $n$ and $p$ with $p \geq 2$. As a corollary, we obtain a sharp upper bound on the oriented diameter in terms of order and number of cut vertices. We also show that the oriented diameter of a bridgeless block graph of order $n$ is bounded above by $\lfloor \frac{3n}{4} \rfloor$ if $n$ is even and $\lfloor \frac{3(n+1)}{4} \rfloor$ if $n$ is odd.Comment: 15 pages, 2 figure

A qualitative evaluation of healthy weight services in a local authority in England

Objective The purpose of this study was to evaluate the healthy weight services in one local authority in England, where obesity levels have been above the national average since 2006. Design We conducted process and outcome evaluation using a qualitative methodology. Data were generated in focus group discussions and semi-structured interviews with clients, practitioners, healthcare professionals and volunteers. Results Ninety-one individuals from six services participated in the evaluation. Staff competencies and empowerment outcomes were identified as areas of strength. However, despite examples of excellent practice and enthusiastic recommendations from clients, access and referral processes were areas of weakness. Conclusion In England, local authorities have an important role to play in tackling obesity. It is crucial that they are provided with the tools to be able to implement healthy weight interventions effectively. A whole-systems approach presents a real opportunity for staff in local authorities and public health to work collaboratively and innovatively towards the same goal of continuous improvement in obesity management

Waste-derived inosilicate carrier for antimicrobial Zn2+ and Ag+ ions

Recent research by the authors has demonstrated that the inosilicate, lithium metasilicate (Li2SiO3), can be prepared by hydrothermal synthesis from waste green container glass (GCG) [1,2]. This study investigated the potential of this material to be ion-exchanged with antimicrobial Zn2+ or Ag+ ions for use as a filler in polymer composites. Antimicrobial polymer composites are an advantage in applications where the communication of pathogenic bacteria poses a problem, such as hospitals, abattoirs and food-processing factories. The naturally-occurring biodegradable mucopolysaccharide derivative, chitosan, was used as a model polymer in this study. The lithium metasilicate product was synthesised from GCG in LiOH(aq) and ion-exchanged with either Zn2+ or Ag+ ions via batch sorption. The in vitro antibacterial properties of solvent-cast metasilicate-chitosan composite membranes were then evaluated by zone of inhibition against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus

Fluoride occurrence in the lower East African Rift System, Southern Malawi

Countries located on the East African Rift System (EARS) are vulnerable to fluoride in their groundwater; a vulnerability for the developing country of Malawi at the southern rift periphery that is not well characterised. Groundwater fluoride occurrence in Malawi is documented here to better understand and manage fluoride risks posed. Available literature and Gov't of Malawi archive fluoride data spanning some fifty years have been collated and augmented by our own 2016–18 surveys of groundwater quality in Southern Malawi, targeting deep-sourced springs. In total, fluoride data for 1365 borehole, spring and hot spring samples were assembled. Statistically, 83% of samples were below the 1.5 mg/l WHO limit, concentrations in the 1.5–6 mg/l range between former (pre-1993) and current WHO guidelines at 14%, and those with fluoride above the current Malawi (former WHO) 6 mg/l guideline, at 3%. A lower occurrence than in other zones of the EARS, but indicative of a need for a Malawi Gov't management policy revision and associated management strategies endorsed by several documented incidences of dental fluorosis in proximity to high fluoride groundwater. Increased fluoride is related to increased groundwater temperatures signifying the importance of geothermal groundwater provenance. Temperature data may indeed be used as a proxy indicator of fluoride risk; samples with a temperature >32 °C, contained >6 mg/l fluoride. Structural geological controls appear to allow deep geothermal groundwaters to come to the near surface, as evidenced by increased fluoride in springs and boreholes close to faulted areas. Hydrochemical evaluation shows that fluoride concentrations are influenced by fluorite equilibration and sensitivity to calcium and pH. Recommendations are made to further document the occurrence of fluoride and enhance management of risks due to fluoride in drinking water in Malawi. With fluoride as a key indicator within Sustainable Development Goal number 6, the current Malawi standard and waters with concentration between 1.5 and 6 mg/l will come under increased scrutiny and pose a key challenge to assessment and management efforts

Predicting groundwater vulnerability to geogenic fluoride risk : a screening method for Malawi and an opportunity for national policy redefinition

Fluoride concentrations in Malawi’s groundwater are primarily controlled by geogenic sources that are highly variable and may cause a heterogeneous fluoride occurrence and local-to-regional variations in fluorosis health risks posed. Our aim was to address the challenge of developing a national solution to predicting groundwater vulnerability to geogenic fluoride risk in the country of Malawi where incidences of fluorosis are reported and typical developing world problems of limited data and resources abound. Previously there have only been sporadic, local-scale studies linking fluoride occurrence with health risks in Malawi with no attempts to tackle the issue nationally. We hence develop a screening method for predicting groundwater vulnerability to geogenic fluoride in the form of detailed risk maps developed from statistical relationships shown between groundwater fluoride occurrence and known geogenic fluoride sources. The approach provides for dynamic update and informed acquisition of new data and hence on-going improving capacity to manage fluoride risks in Malawi. Our screening method provides a technical basis for redefining national fluoride policy to ensure commensurate management of health risks posed. Specifically, the approach provides a pathway for stepped progression from the current 6 mg/L Malawian standard for fluoride in drinking water to adoption of the World Health Organisation 1.5 mg/L guideline standard

Identifying groundwater fluoride source in a weathered basement aquifer in central Malawi : human health and policy implications

Consumption of groundwater containing fluoride exceeding World Health Organization (WHO) 1.5 mg/L standard leaves people vulnerable to fluorosis: a vulnerability not well characterised in Malawi. To evaluate geogenic fluoride source and concentration, groundwater fluoride and geology was documented in central Malawi where groundwater supplies are mainly sourced from the weathered basement aquifer. Lithological composition was shown as the main control on fluoride occurrence. Augen gneiss of granitic composition posed the greatest geological fluoride risk. The weathered basement aquifer profile was the main factor controlling fluoride distributions. These results and fluoride-lithology statistical analysis allowed the development of a graded map of geological fluoride risk. A direct link to human health risk (dental fluorosis) from geological fluoride was quantified to support science-led policy change for fluoride in rural drinking water in Malawi. Hazard quotient (HQ) values were calculated and assigned to specific water points, depending on user age group; in this case, 74% of children under six were shown to be vulnerable to dental fluorosis. Results are contrary to current standard for fluoride in Malawi groundwater of 6 mg/L, highlighting the need for policy change. Detailed policy recommendations are presented based on the results of this stud

Quantum decision making by social agents

The influence of additional information on the decision making of agents, who are interacting members of a society, is analyzed within the mathematical framework based on the use of quantum probabilities. The introduction of social interactions, which influence the decisions of individual agents, leads to a generalization of the quantum decision theory developed earlier by the authors for separate individuals. The generalized approach is free of the standard paradoxes of classical decision theory. This approach also explains the error-attenuation effects observed for the paradoxes occurring when decision makers, who are members of a society, consult with each other, increasing in this way the available mutual information. A precise correspondence between quantum decision theory and classical utility theory is formulated via the introduction of an intermediate probabilistic version of utility theory of a novel form, which obeys the requirement that zero-utility prospects should have zero probability weights.Comment: This paper has been withdrawn by the authors because a much extended and improved version has been submitted as arXiv:1510.02686 under the new title "Role of information in decision making of social agents

Paleo-geohydrology of Lake Chilwa, Malawi is the source of localised groundwater salinity and rural water supply challenges

Meeting long-term rural community water supply needs requires diligent geohydrological conceptualisation. Study of Malawi’s Lake Chilwa Basin, including sampling of 330 water points in Phalombe District, enabled assessment of groundwater quality influence upon supply. The control of larger Lake Chilwa paleo-environments on current Basin groundwater quality is demonstrated. Lacustrine sediment deposition forming high-level deposits under open lake conditions and terrace deposits under open and closed lake conditions significantly control the groundwater major-ion quality and salinity now observed. Paleo-lake extent marks the transition between low-TDS (total dissolved solids) groundwater suitable for water supply at higher elevations and high-TDS brackish groundwater in areas overlain by lacustrine deposits closer to the current lake level. Low-TDS groundwater is limited to mid-to-low reach influent leakage of rivers incising terraces. Permeable fluvial deposits within the deeper paleo-river channel may possibly provide low-TDS water. The conceptual model, whereby paleo-lake controls groundwater salinity, provides science-based evidence to address policy to manage the significant water point functionality concerns quantified at the district and river basin scales. Targeting of the low-TDS groundwater alongside improved use of upland low-TDS stream/river sources with fewer, but larger capacity, and better maintained gravity-fed supply schemes are recommended. This study hence shows the value of paleo-geohydrology interpretation of the lake–groundwater system conceptualisation to inform Sustainable Development Goal 6 (SDG 6.5.1)—integrated water resources management policy for rural water supply

Nitrogen processes in aquatic ecosystems

Executive summary Nature of the problem (science/management/policy) • Freshwater ecosystems play a key role in the European nitrogen (N) cycle, both as a reactive agent that transfers, stores and processes N loadings from the atmosphere and terrestrial ecosystems, and as a natural environment severely impacted by the increase of these loadings. Approaches • This chapter is a review of major processes and factors controlling N transport and transformations for running waters, standing waters, groundwaters and riparian wetlands. Key findings/state of knowledge • The major factor controlling N processes in freshwater ecosystems is the residence time of water, which varies widely both in space and in time, and which is sensitive to changes in climate, land use and management. • The effects of increased N loadings to European freshwaters include acidification in semi-natural environments, and eutrophication in more disturbed ecosystems, with associated loss of biodiversity in both cases. • An important part of the nitrogen transferred by surface waters is in the form of organic N, as dissolved organic N (DON) and particulate organic N (PON). This part is dominant in semi-natural catchments throughout Europe and remains a significant component of the total N load even in nitrate enriched rivers. • In eutrophicated standing freshwaters N can be a factor limiting or co-limiting biological production, and control of both N and phosphorus (P) loading is oft en needed in impacted areas, if ecological quality is to be restored. Major uncertainties/challenges • The importance of storage and denitrifi cation in aquifers is a major uncertainty in the global N cycle, and controls in part the response of catchments to land use or management changes. In some aquifers, the increase of N concentrations will continue for decades even if efficient mitigation measures are implemented now. • Nitrate retention by riparian wetlands has oft en been highlighted. However, their use for mitigation must be treated with caution, since their effectiveness is difficult to predict, and side effects include increased DON emissions to adjacent open waters, N2O emissions to the atmosphere, and loss of biodiversity. • In fact, the character and specific spatial origins of DON are not fully understood, and similarly the quantitative importance of indirect N2O emissions from freshwater ecosystems as a result of N leaching losses from agricultural soils is still poorly known at the regional scale. • These major uncertainties remain due to the lack of adequate monitoring (all forms of N at a relevant frequency), especially – but not only – in the southern and eastern EU countries. Recommendations (research/policy) • The great variability of transfer pathways, buffering capacity and sensitivity of the catchments and of the freshwater ecosystems calls for site specific mitigation measures rather than standard ones applied at regional to national scale. • The spatial and temporal variations of the N forms, the processes controlling the transport and transformation of N within freshwaters, require further investigation if the role of N in influencing freshwater ecosystem health is to be better understood, underpinning the implementation of the EU Water Framework Directive for European freshwaters