The ATPase cycle of PcrA helicase and its coupling to translocation on DNA.

The superfamily 1 bacterial helicase PcrA has a role in the replication of certain plasmids, acting with the initiator protein (RepD) that binds to and nicks the double-stranded origin of replication. PcrA also translocates single-stranded DNA with discrete steps of one base per ATP hydrolyzed. Individual rate constants have been determined for the DNA helicase PcrA ATPase cycle when bound to either single-stranded DNA or a double-stranded DNA junction that also has RepD bound. The fluorescent ATP analogue 2'(3')-O-(N-methylanthraniloyl)ATP was used throughout all experiments to provide a complete ATPase cycle for a single nucleotide species. Fluorescence intensity and anisotropy stopped-flow measurements were used to determine rate constants for binding and release. Quenched-flow measurements provided the kinetics of the hydrolytic cleavage step. The fluorescent phosphate sensor MDCC-PBP was used to measure phosphate release kinetics. The chemical cleavage step is the rate-limiting step in the cycle and is essentially irreversible and would result in the bound ATP complex being a major component at steady state. This cleavage step is greatly accelerated by bound DNA, producing the high activation of this protein compared to the protein alone. The data suggest the possibility that ADP is released in two steps, which would result in bound ADP also being a major intermediate, with bound ADP.P(i) being a very small component. It therefore seems likely that the major transition in structure occurs during the cleavage step, rather than P(i) release. ATP rebinding could then cause reversal of this structural transition. The kinetic mechanism of the PcrA ATPase cycle is very little changed by potential binding to RepD, supporting the idea that RepD increases the processivity of PcrA by increasing affinity to DNA rather than affecting the enzymatic properties per se

The composition and friction-reducing properties of leaf layers

Every autumn rail networks across the world suffer delays, accidents and schedule changes due to low friction problems caused by leaves landing on the rails. These leaves form a layer that can reduce the friction between the wheel and the rail to a similar level as that between ice and an ice-skate (μ=0.01–0.05). Previous works have generated several hypotheses for the chemical reactions and low friction mechanism associated with these layers. In this work, the reaction between an aqueous extract of sycamore leaves and metallic iron is investigated. This reaction has been shown to produce a black precipitate, which matches field observations of leaf layers, while friction tests with these extracts produce characteristic ultra low friction. The reaction is investigated through FTIR, XPS, CHNS and ICP-MS analysis as well as wet chemical testing. The impact of the reaction on friction is investigated through three rounds of tribological testing. The results indicate that the black precipitate produced is iron tannate, formed by complexation of tannins with dissolved iron ions. Friction testing showed that eliminating tannins from the leaf extract resulted in a significant increase in the friction coefficient compared with the control

The influence of tool coating on the length of the normal operating region (steady-state wear) for micro end mills

Increasing miniaturisation has significantly increased demand for highly accurate small parts to be machined. Micro milling presents a viable method for series machining parts such as miniature heat exchangers or fuel injectors. Micro end mill tool wear, however, is considerably more difficult to monitor than its macro counterpart, and the tools often fail due to chipping or shaft failure. High tool breakage rates make costs unpredictable and machining times inefficient. Conversely, macro end mill wear is well characterised, and the typical wear curve well understood. The aim of this work is to elongate the steady state region (SSR) of the wear curve for micro end mills, as this is the practical life of the tool. Coatings can be applied to achieve this, improving wear rates and cutting performance. This study examines the wear that took place during straight-slot machining with 500 μm micro end mills. This was then compared with observed wear mechanisms on the macro scale. The length of the SSR was used to evaluate the ability of various new coatings to extend the working tool life. The relative predictability in the SSR allows tool paths to be modified to account for changing tool geometry. The results demonstrate that for micro-mills, the SSR could be elongated, in spite of less predictable wear mechanisms. Overall, this work presents a successful attempt to manipulate the wear curve for micro end mills and highlights the importance of developing an understanding of the wear mechanisms taking place for micro-mills as compared with macro-mills

Congenital Nephrotic Syndrome in IL7Rα-SCID: A Rare Feature of Maternofetal Graft-Versus-Host Disease

info:eu-repo/semantics/publishedVersio

Conditioning regimens for haematopoietic cell transplantation in primary immunodeficiencies

Purpose of ReviewHematopoietic cell transplantation (HCT) is an established curative treatment for children with primary immunodeficiencies. This article reviews the latest developments in conditioning regimens for primary immunodeficiency (PID). It focuses on data regarding transplant outcomes according to newer reduced toxicity conditioning regimens used in HCT for PID.Recent FindingsConventional myeloablative conditioning regimens are associated with significant acute toxicities, transplant-related mortality, and late effects such as infertility. Reduced toxicity conditioning regimens have had significant positive impacts on HCT outcome, and there are now well-established strategies in children with PID. Treosulfan has emerged as a promising preparative agent. Use of a peripheral stem cell source has been shown to be associated with better donor chimerism in patients receiving reduced toxicity conditioning. Minimal conditioning regimens using monoclonal antibodies are in clinical trials with promising results thus far.SummaryReduced toxicity conditioning has emerged as standard of care for PID and has resulted in improved transplant survival for patients with significant comorbidities.</div

Learning tethered perching for aerial robots

Aerial robots have a wide range of applications, such as collecting data in hard-to-reach areas. This requires the longest possible operation time. However, because currently available commercial batteries have limited specific energy of roughly 300 W h kg -1 , a drone's flight time is a bottleneck for sustainable long-term data collection. Inspired by birds in nature, a possible approach to tackle this challenge is to perch drones on trees, and environmental or man-made structures, to save energy whilst in operation. In this paper, we propose an algorithm to automatically generate trajectories for a drone to perch on a tree branch, using the proposed tethered perching mechanism with a pendulum-like structure. This enables a drone to perform an energy-optimised, controlled 180° flip to safely disarm upside down. To fine-tune a set of reachable trajectories, a soft actor critic-based reinforcement algorithm is used. Our experimental results show the feasibility of the set of trajectories with successful perching. Our findings demonstrate that the proposed approach enables energy-efficient landing for long-term data collection tasks

The role of private rental brokerage in housing outcomes for vulnerable Australians: Final report

This Final Report outlines the findings of research investigating the role of private rental brokerage in supporting housing outcomes for vulnerable households in the private rental market. In the last two decades the private rental market has become increasingly important in providing homes for Australians. It has also become increasingly competitive, particularly at the lower-end, where supply has fallen significantly behind demand. Given the lack of affordable ownership options in many local housing markets, and the contraction of public housing, many households with low or moderate means must now look to the private rental sector for their housing over the longer term. Government policy has encouraged renters who would otherwise be eligible for social housing to move into the private rental market. This tenure shift has been supported by the provision of several assistance measures for private renters. Those best known and understood are Commonwealth Rent Assistance (CRA) and state and territory Private Rent Assistance (PRA) programs, which provide bond and rent loans to eligible people. Two other elements also exist alongside the best known private rental supports: the National Rental Affordability Scheme (NRAS) (although as the planned further expansion of this scheme was halted by the newly elected Abbott Government in budget 2014/15 thereby limiting its future potential as a supply-side private rental assistance measure) and private rental brokerage. This report is concerned specifically with private rental brokerage; a previously underresearched measure among private rental supports nationally. Conceptually, we describe private rental brokerage as the 'third pillar' of supports nationally, sitting alongside the much larger CRA measure and, as the research findings reported here note, reinforcing the reach and impact of PRA.Selina Tually, Michele Slatter, Debbie Faulkner and Susan Oakley for the Australian Housing and Urban Research Institute at The University of Adelaid