Asp-89: a critical residue in maintaining the oligomeric structure of sheep liver cytosolic serine hydroxymethyltransferase

Aspartate residues function as proton acceptors in catalysis and are involved in ionic interactions stabilizing subunit assembly. In an attempt to unravel the role of a conserved aspartate (D89) in sheep-liver tetrameric serine hydroxymethyltransferase (SHMT), it was converted into aspargine by site-directed mutagenesis. The purified D89N mutant enzyme had a lower specific activity compared with the wild-type enzyme. It was a mixture of dimers and tetramers with the proportion of tetramers increasing with an increase in the pyridoxal-5′-phosphate (PLP) concentration used during purification. The D89N mutant tetramer was as active as the wild-type enzyme and had similar kinetic and spectral properties in the presence of 500 μM PLP. The quinonoid spectral intermediate commonly seen in the case of SHMT was also seen in the case of D89N mutant tetramer, although the amount of intermediate formed was lower. Although the purified dimer exhibited visible absorbance at 425 nm, it had a negligible visible CD spectrum at 425 nm and was only 5% active. The apo-D89N mutant tetramer was a dimer unlike the apo-form of the wild-type enzyme which was present predominantly as a tetramer. Furthermore the apo mutant dimer could not be reconstituted to the holo-form by the addition of excess PLP, suggesting that dimer-dimer interactions are weak in this mutant. The recently published crystal structure of human liver cytosolic recombinant SHMT indicates that this residue (D90 in the human enzyme) is located at the N-terminal end of the fourth helix of one subunit and packs against K39 from the second N-terminal helix of the other symmetry related subunit forming the tight dimer. D89 is at the interface of tight dimers where the PLP 5'-phosphate is also bound. Mutation of D89 could lead to weakened ionic interactions in the tight dimer interface, resulting in decreased affinity of the enzyme for the cofactor

Fabrication, Mechanical and Wear Properties of Aluminum (Al6061)-Silicon Carbide-Graphite Hybrid Metal Matrix Composites

In recent times, the use of aluminum alloy-based Hybrid Metal Matrix Composites (HMMCs) is being increased in aerospace and automotive applications. HMMCs compensate for the low desirable properties of each filler used. However, the mechanical properties of HMMCs are not well understood. In particular, microstructural investigations and wear optimization studies of HMMCs are not clear. Therefore, further studies are required. The present study is aimed at fabricating and mechanical and wear characterizing and microstructure investigating of Silicon Carbide (SiC) and Graphite (Gr) added in Aluminum (Al) alloy Al6061 HMMCs. The addition of SiC particles was in the range from 0 to 9 weight percentage (wt.%) in steps of 3, along with the addition of 1 wt.% Gr in powder form. The presence of alloying elements in the Al6061 alloy was identified using the Energy Dispersive X-Ray Analysis (EDX). The dispersion of SiC and Gr particles in the alloy was investigated using metallurgical microscope and Scanning Electron Microscopy (SEM). The gain in strength can be attributed to the growth in dislocation density. The nature of fracture was quasi-cleavage. The microstructure examination reveals the uniform dispersion of the reinforcement. Density, hardness, and Ultimate Tensile Strength values observed to be increased with increased contents of SiC reinforcement. Besides, wear studies were performed in dry sliding conditions. Optimization studies were performed to investigate the effect of parameters that affecting the wear. The sliding wear resistance was noticed to be improved concerning higher amounts of reinforcement leading to a decrease in delamination and adhesive wear. The predicted values for the wear rate have also been compared with the experimental results and good correlation is obtained

Towards sustainable sanitation management: Establishing the costs and willingness to pay for emptying and transporting sludge in rural districts with high rates of access to latrines

MOTIVATION: Proper management of fecal sludge has significant positive health and environmental externalities. Most research on managing onsite sanitation so far either simulates the costs of, or the welfare effects from, managing sludge in situ in pit latrines. Thus, designing management strategies for onsite rural sanitation is challenging, because the actual costs of transporting sludge for treatment, and sources for financing these transport costs, are not well understood. METHODS: In this paper we calculate the actual cost of sludge management from onsite latrines, and identify the contributions that latrine owners are willing to make to finance the costs. A spreadsheet-based model is used to identify a cost-effective transport option, and to calculate the cost per household. Then a double-bound contingent valuation method is used to elicit from pit-latrine owners their willingness-to-pay to have sludge transported away. This methodology is employed for the case of a rural subdistrict in Bangladesh called Bhaluka, a unit of administration at which sludge management services are being piloted by the Government of Bangladesh. RESULTS: The typical sludge accumulation rate in Bhaluka is calculated at 0.11 liters/person/day and a typical latrine will need to be emptied approximately once every 3 to 4 years. The costs of emptying and transport are high; approximately USD 13 per emptying event (circa 14% of average monthly income); household contributions could cover around 47% of this cost. However, if costs were spread over time, the service would cost USD 4 per year per household, or USD 0.31 per month per household-comparable to current expenditures of rural households on telecommunications. CONCLUSION: This is one of few research papers that brings the costs of waste management together with financing of that cost, to provide evidence for an implementable solution. This framework can be used to identify cost effective sludge management options and private contributions towards that cost in other (context-specific) administrative areas where onsite sanitation is widespread

VeSV- Value at the end of the Sanitation Value Chain: Final Report

Bangladesh is no stranger to composting projects using both green waste and faecal sludge (FS). There have been many initiatives over the years with varying degrees of success. Similarly there have been hundreds, if not thousands of projects to improve access to latrines, latrine use and latrine management. Again there has been a great deal of success, especially in increasing the number of latrines being built. However, a key gap regarding the safe collection and processing of the waste from the pit still remains. In cases where projects have attempted addressing this, the solution has rarely been viable on a large scale. That is where this project—VeSV—is different. The aim of this project is to provide scientific evidence to support the commercial viability of collecting and composting faecal sludge for use in agriculture and horticulture. The gap between a good idea and commercial success is bridged on this project by producing primary scientific data based on qualitative and quantitative research methods and by engaging a number of stakeholders across sectors. A rigorous research was conducted to characterize raw faecal sludge material from single pit latrines in rural Bangladesh, as the starting point to develop value across the sanitation chain from processing FS material, through adding value by recovering nutrient and finally by assessing the potential commercialization of the final product in the fertilizer market. Crucially academics, NGOs, business groups and existing fertilizer, composting and latrine management companies were involved as part of our Reference Group, which helped to develop practical engineering solutions in harmony with the right and relevant context in rural Bangladesh. Our research outcomes include the development of safe methodologies for pit emptying; the assessment of people's intentions to change current operation and maintenance practices of pit latrines at household level and their willingness to participate in commercially viable and sustainable methods for FS management; the assessment of optimised engineering process for FS stabilisation and the production of a safe, high quality fertilizer that is desirable to farmers; and the identification of potential hurdles that may obstruct the widespread adoption of business models for FS fertiliser

A systems perspective on water markets: barriers, bright spots, and building blocks for the next generation

Unidad de excelencia María de Maeztu CEX2019-000940-

Incisional hernia following colorectal cancer surgery according to suture technique: Hughes Abdominal Repair Randomized Trial (HART).

BACKGROUND: Incisional hernias cause morbidity and may require further surgery. HART (Hughes Abdominal Repair Trial) assessed the effect of an alternative suture method on the incidence of incisional hernia following colorectal cancer surgery. METHODS: A pragmatic multicentre single-blind RCT allocated patients undergoing midline incision for colorectal cancer to either Hughes closure (double far-near-near-far sutures of 1 nylon suture at 2-cm intervals along the fascia combined with conventional mass closure) or the surgeon's standard closure. The primary outcome was the incidence of incisional hernia at 1 year assessed by clinical examination. An intention-to-treat analysis was performed. RESULTS: Between August 2014 and February 2018, 802 patients were randomized to either Hughes closure (401) or the standard mass closure group (401). At 1 year after surgery, 672 patients (83.7 per cent) were included in the primary outcome analysis; 50 of 339 patients (14.8 per cent) in the Hughes group and 57 of 333 (17.1 per cent) in the standard closure group had incisional hernia (OR 0.84, 95 per cent c.i. 0.55 to 1.27; P = 0.402). At 2 years, 78 patients (28.7 per cent) in the Hughes repair group and 84 (31.8 per cent) in the standard closure group had incisional hernia (OR 0.86, 0.59 to 1.25; P = 0.429). Adverse events were similar in the two groups, apart from the rate of surgical-site infection, which was higher in the Hughes group (13.2 versus 7.7 per cent; OR 1.82, 1.14 to 2.91; P = 0.011). CONCLUSION: The incidence of incisional hernia after colorectal cancer surgery is high. There was no statistical difference in incidence between Hughes closure and mass closure at 1 or 2 years. REGISTRATION NUMBER: ISRCTN25616490 (http://www.controlled-trials.com)

Intraperitoneal drain placement and outcomes after elective colorectal surgery: international matched, prospective, cohort study

Despite current guidelines, intraperitoneal drain placement after elective colorectal surgery remains widespread. Drains were not associated with earlier detection of intraperitoneal collections, but were associated with prolonged hospital stay and increased risk of surgical-site infections.Background Many surgeons routinely place intraperitoneal drains after elective colorectal surgery. However, enhanced recovery after surgery guidelines recommend against their routine use owing to a lack of clear clinical benefit. This study aimed to describe international variation in intraperitoneal drain placement and the safety of this practice. Methods COMPASS (COMPlicAted intra-abdominal collectionS after colorectal Surgery) was a prospective, international, cohort study which enrolled consecutive adults undergoing elective colorectal surgery (February to March 2020). The primary outcome was the rate of intraperitoneal drain placement. Secondary outcomes included: rate and time to diagnosis of postoperative intraperitoneal collections; rate of surgical site infections (SSIs); time to discharge; and 30-day major postoperative complications (Clavien-Dindo grade at least III). After propensity score matching, multivariable logistic regression and Cox proportional hazards regression were used to estimate the independent association of the secondary outcomes with drain placement. Results Overall, 1805 patients from 22 countries were included (798 women, 44.2 per cent; median age 67.0 years). The drain insertion rate was 51.9 per cent (937 patients). After matching, drains were not associated with reduced rates (odds ratio (OR) 1.33, 95 per cent c.i. 0.79 to 2.23; P = 0.287) or earlier detection (hazard ratio (HR) 0.87, 0.33 to 2.31; P = 0.780) of collections. Although not associated with worse major postoperative complications (OR 1.09, 0.68 to 1.75; P = 0.709), drains were associated with delayed hospital discharge (HR 0.58, 0.52 to 0.66; P < 0.001) and an increased risk of SSIs (OR 2.47, 1.50 to 4.05; P < 0.001). Conclusion Intraperitoneal drain placement after elective colorectal surgery is not associated with earlier detection of postoperative collections, but prolongs hospital stay and increases SSI risk

Can cash incentives modify groundwater pumping behaviors? Evidence from an experiment in Punjab

As groundwater levels steadily decline in India, authorities are concerned about reducing extraction for irrigation purposes without jeopardizing food security. Very low or zero prices for electricity and water in agriculture is partly responsible for overextraction, but charging higher prices is politically not feasible. In this study, we describe the results of a pilot scheme implemented in Punjab, India, where farmers who enrolled were allocated a monthly entitlement of electricity units and compensated for unused electricity. Eight hours of uninterrupted daytime electricity supply were also provided under the scheme instead of the usual mix of daytime and night-time supply. Analyzing data from a cross-sectional farm household survey and instrumenting for enrollment, we find that self-reported hours of irrigation for enrolled farmers were significantly lower than for non-enrolled ones, with no impact on rice yields. We also find a reduction in monthly electricity consumption at electricity-feeder level due to the pilot scheme using the synthetic control method. Our results suggest that the combination of daytime electricity provision and cash incentives for unused electricity has the potential to incentivize farmers to reduce electricity consumption and irrigation hours by at least 7.5% and up to 30% without impacting paddy yields

A phenomenological treatment of cation distribution in spinels: System (Ni(1-x)Alx)(t)[NixAl2-x](0) O-4

Presented in this paper is a phenomenological model for cation distribution between crystallographically non-equivalent sites of the spinel structure at high temperature. Interactions between ions on each site are characterized by enthalpy parameters. A regular solution model is assumed for mixing of the species on tetrahedral and octahedral sites, independent of the nature of bonding in the solid. The model provides an equation which is functionally similar to that proposed by O'Neill and Navrotsky /15/ based on electrostatic considerations. However, the phenomenological model gives a more realistic interpretation of the constants involved in the equation. Recent experimental data on temperature dependence of cation distribution in NiAl2O4 are used to test the validity of the different models. Since Ni2+ ion in tetrahedral coordination exhibits Jahn-Teller distortion, an entropy corresponding to randomization of the distortion in the cubic phase has been incorporated in the model. Inclusion of the Jahn-Teller entropy in the expression for the cation distribution appears to be as important as introduction of quadratic dependence of enthalpy of disordering (Delta H-D) on cation distribution. Best statistical fit to experimental data is obtained when both Jahn-Teller entropy and energetics of interaction of ions are incorporated in the model