Specifying and Monitoring Market Mechanisms Using Rights and Obligations

We provide a formal scripting language to capture the semantics of market mechanisms. The language is based on a set of well-defined principles, and is designed to capture an agent’s rights, as derived from property, and an agent’s obligations, as derived from restrictions placed on its actions, either voluntarily or as a consequence of other actions. Rights and obligations are viewed as first-class goods, from which we define fundamental axioms about well-functioning market-oriented worlds. Coupled with the scripting language is a run-time system that is able to monitor and enforce rights and obligations. Our treatment extends to represent a variety of market mechanisms, ranging from simple two-agent single-good exchanges to complicated combinatorial auctions.Engineering and Applied Science

Time-to-Contact and Collision-Detection Estimations as Measures of Driving Safety in Old and Dementia Drivers

The paper discusses the importance of Time-to-Contact (TTC) and collision occurrence (CD) estimations for safe driving. It describes a computerised testing tool that requires TTC and CD estimations while dividing attention and discusses the association between performance on this task and several measures of driving safety. We report four studies showing that the task is sensitive to age effects and dementia effects, that the accuracy of Time-to-Contact estimations differentiates between old and dementia drivers recently involved in accidents and those not involved. We also found an association between performance on this task and that on navigation and car following tasks in a driving simulator

The 2.3 kW Ion Thruster Wear Test

A 30-cm diameter xenon ion thruster is under development at NASA to provide an ion propulsion option for auxiliary and primary propulsion on missions of national interest. Specific efforts include thruster design optimizations, component life testing and validation, and performance characterizations. Under this program, the ion thruster will be brought to engineering model development status. This paper describes the results of a 2.3-kW 2000-hour wear test performed to identify life limiting phenomena, measure the performance and characterize the operation of the thruster, and obtain wear, erosion, and surface contamination data. These data are being using as a data base for proceeding with additional life validation tests, and to provide input to flight thruster design requirements

Strategic Liquidity Provision in Uniswap v3

Uniswap v3 is the largest decentralized exchange for digital currencies. A novelty of its design is that it allows a liquidity provider (LP) to allocate liquidity to one or more closed intervals of the price of an asset instead of the full range of possible prices. An LP earns fee rewards proportional to the amount of its liquidity allocation when prices move in this interval. This induces the problem of {\em strategic liquidity provision}: smaller intervals result in higher concentration of liquidity and correspondingly larger fees when the price remains in the interval, but with higher risk as prices may exit the interval leaving the LP with no fee rewards. Although reallocating liquidity to new intervals can mitigate this loss, it comes at a cost, as LPs must expend gas fees to do so. We formalize the dynamic liquidity provision problem and focus on a general class of strategies for which we provide a neural network-based optimization framework for maximizing LP earnings. We model a single LP that faces an exogenous sequence of price changes that arise from arbitrage and non-arbitrage trades in the decentralized exchange. We present experimental results informed by historical price data that demonstrate large improvements in LP earnings over existing allocation strategy baselines. Moreover we provide insight into qualitative differences in optimal LP behaviour in different economic environments

Plasma contactor technology for Space Station Freedom

Hollow cathode plasma contactors were baselined for Space Station Freedom (SSF) to control the electrical potentials of surfaces to eliminate/mitigate damaging interactions with the space environment. The system represents a dual-use technology which is a direct outgrowth of the NASA electric propulsion program and in particular the technology development effort on ion thruster systems. Specific efforts include optimizing the design and configuration of the contactor, validating its required lifetime, and characterizing the contactor plume and electromagnetic interference. The plasma contact or subsystems include the plasma contact or unit, a power electronics unit, and an expellant management unit. Under this program these will all be brought to breadboard and engineering model development status. New test facilities were developed, and existing facilities were augmented, to support characterizations and life testing of contactor components and systems. The magnitude, scope, and status of the plasma contactor hardware development program now underway and preliminary test results on system components are discussed

The kinetics and product state distributions from gas-phase reactions of small atomic and molecular cations with C₂H₄, C₂H₃F, 1,1-C₂H₂F₂, C₂HF₃ and C₂F₄

Reactions between atomic and small molecular ions with a series of fluorinated ethenes are studied in a selected ion flow tube. Kinetics and product state distributions are measured. The latter are compared with those from photoionisation.</p

Pre-school childcare and inequalities in child development

Centre-based childcare may benefit pre-school children and alleviate inequalities in early childhood development, but evidence on socio-emotional and physical health outcomes is limited. Data were from the UK Millennium Cohort Study (n=14,376). Inverse-probability weighting was used to estimate confounder-adjusted population-average effects of centre and non-centre-based childcare (compared to parental care only) between ages 26-31 months on (age 3): internalising and externalising symptoms, pro-social behaviour, independence, emotional dysregulation, vocabulary, school readiness, and body mass index. To assess impacts on inequalities, controlled direct effects of low parental education and lone parenthood on all outcomes were estimated under two hypothetical scenarios: 1) universal take-up of centre-based childcare; and 2) parental care only. On average, non-centre based childcare improved vocabulary and centre-based care improved school readiness, with little evidence of other benefits. However, socio-economic inequalities were observed for all outcomes and were attenuated in scenario 1 (universal take-up). For example, inequalities in externalising symptoms (according to low parental education) were reduced from a confounder-adjusted standard deviation difference of 7.8 (95% confidence intervals: 6.7-8.8), to 1.7 (0.6-2.7). Inequalities by parental education in scenario 2 (parental care only) were wider than in scenario 1 for externalising symptoms (at 3.4; 2.4-4.4), and for emotional dysregulation and school readiness. Inequalities by lone parenthood, which were smaller, fell in scenario 1, and fell further in scenario 2. Universal access to centre-based pre-school care may alleviate inequalities, while restricted access (e.g. during lockdown for a pandemic such as Covid-19) may widen some inequalities in socioemotional and cognitive development

Do Clinical Correlates of Knee Osteoarthritis Predict Outcome to Intra-Articular Steroid Injections?

OBJECTIVE:To determine if clinical correlates of knee osteoarthritis(OA) affect likelihood of outcome to intra-articular steroid injections(IASI) in symptomatic knee OA. METHODS:Men and women aged≥40 years with painful knee OA who participated in an open label trial of IASI completed questionnaires and clinical examination. OMERACT-OARSI criteria were used to assess response to therapy in the short-term(within 2-weeks). Among those who initially responded, those whose pain had not returned to within 20% of the baseline KOOS-pain score at 6-months were characterised as longer-term responders. Log binomial regression was used to examine factors associated with outcome. RESULTS:199 participants were included, of whom 146(73.4%) were short-term and 40(20.1%) longer-term responders. Compared to short-term non-responders, participants with medial joint-line tenderness(RR=1.42;1.10-1.82), medial & lateral joint-line tenderness(RR=1.38;1.03-1.84), patellofemoral tenderness(RR=1.27;1.04-1.55), anserine tenderness(RR=1.27;1.06-1.52) and a belief that treatment would be effective(RR/unit increase, [range 0-10]=1.05;1.01-1.09), were more likely to be short-term responders. Aspiration of joint fluid(RR=0.79;0.66-0.95) and previous ligament/meniscus injury(RR=0.63;0.44-0.91) were associated with a reduced risk of being a short-term responder. Compared to initial non-responders and those whose pain recurred within 6-months, participants with higher number of pain sites(RR/unit increase, [range 0-10]=0.83;0.72-0.97), chronic widespread pain(RR=0.32;0.10-0.98), perceived chronicity of disease(RR/unit increase, [range 0-10]=0.86;0.78-0.94) and a higher depression score(RR/unit increase, [range 0-21]=0.89;0.81-0.99) were less likely to be longer-term responders. CONCLUSION:Among patients with symptomatic knee OA, tenderness around the knee was associated with better short-term outcome to IASI. However, clinical-related factors did not predict longer-term response while those with chronic widespread pain and depressive symptoms were less likely to obtain longer-term benefit