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Ortho-vanillin derived Al(III) and Co(III) catalyst systems for switchable catalysis using ε-decalactone, phthalic anhydride and cyclohexene oxide
No full textSwitchable catalysis is a useful one-pot method to prepare block polyesters utilising a single catalyst exposed to a mixture of monomers. The catalyst is switched between lactone ring-opening polymerization (ROP) and epoxide/anhydride ring-opening copolymerization (ROCOP) by controlling its chain-end chemistry. Here, novel aluminium(III) (1) and cobalt(III) complexes (2), coordinated by ortho-vanillin derived salen ligands, show excellent switchable catalytic activity and selectivity for the preparation of poly(ε-decalactone-block-cyclohexene phthalate-block-ε-decalactone) [PDL-b-PCHPE-b-PDL]. Both complexes have competitive activities with a commercial chromium salen catalyst for epoxide/anhydride ROCOP (TOFCr(III) = 1200 h−1 vs. TOFAl(III) = 350 h−1, 1 mol% catalyst loading vs. anhydride, 100 °C) and are significantly more active than the commercial catalyst for lactone ROP (TOFcr(III) = 3 h−1 vs. TOFAl(III) = 300 h−1; 0.5 mol% catalyst loading vs. lactone, T = 100 °C). The catalysts are tolerant to low loadings (0.1 mol% vs. anhydride, 0.05% vs. lactone) and produce high molar mass triblock polyesters (Mn = 6–57 kg mol−1). The efficient production of high molar mass polyesters allows for future optimization of the block polyester thermal–mechanical properties and applications
Using item response theory (IRT) to improve the efficiency of the Simple Clinical Colitis Activity Index (SCCAI) for patients with ulcerative colitis
No full textBackground
The SCCAI was designed to facilitate assessment of disease activity in ulcerative colitis (UC). We aimed to interrogate the metric properties of individual items of the SCCAI using item response theory (IRT) analysis, to simplify and improve its performance.
Methods
The original 9-item SCCAI was collected through TrueColours, a real-time software platform which allows remote entry and monitoring of patients with UC. Data were securely uploaded onto Dementias Platform UK Data Portal, where they were analysed in Stata 16.1 SE. A 2-parameter (2-PL) logistic IRT model was estimated to evaluate each item of the SCCAI for its informativeness (discrimination). A revised scale was generated and re-assessed following systematic removal of items.
Results
SCCAI data for 516 UC patients (41 years, SD = 15) treated in Oxford were examined. After initial item deletion (Erythema nodosum, Pyoderma gangrenosum), a 7-item scale was estimated. Discrimination values (information) ranged from 0.41 to 2.52 indicating selected item inefficiency with three items
Conclusion
Reduction of the SCCAI from the original 9-item scale to a 4-item scale provides optimum trait information that will minimise response burden. This new 4-item scale needs validation against other measures of disease activity such as faecal calprotectin, endoscopy and histopathology
A multirate variational approach to simulation and optimal control for flexible spacecraft
No full textWe propose an optimal control method for simultaneous slewing and vibration control of flexible spacecraft. Considering dynamics on different time scales, the optimal control problem is discretized on micro and macro time grids using a multirate variational approach. The description of the system and the necessary optimality conditions are derived through the discrete Lagrange-d’Alembert principle. The discrete problem retains the conservation properties of the continuous model and achieves high fidelity simulation at a reduced computational cost. Simulation results for a single-axis rotational maneuver demonstrate vibration suppression and achieve the same accuracy as the single rate method at reduced computational cost
Pen portraits of presidents - Professor Raymond Hide, CBE, ScD, FRS
No full textWe describe the life and scientific accomplishments of Professor Raymond Hide. He was a past President of the Royal Meteorological Society and a supreme example of a geophysicist much honoured in his lifetime. He covered a wide area of geophysics from geomagnetism, meteorology, geodesy, oceanography and related aspects of planetary physics. Raymond Hide was particularly known in meteorology as a founding father of geophysical fluid dynamics, especially for his experiments using a rotating cylindrical annulus to study atmospheric dynamics
Moral dilemmas in slave-owning societies: evidence from early legal texts
No full textSlavery is not a natural state. It arises when people or classes in a society assume the right to treat others as their property. And yet the status of slaves has rarely been defined by law, even when slavery was an accepted social fact. This publication examines the laws that did deal with slavery, from the earliest written rules in Mesopotamia, India, China, Rome, and the Islamic world, to medieval Europe and Tibet. It is evident that, rather than offering comprehensive definitions, the lawmakers were dealing with the complications that arose from the instability of the state, including issues of manumission, legal capacity, and the status of children. People could become slaves without the need for legal intervention, as a result of warfare or debt, but many slaves acquired freedoms, presenting complications that the lawmakers tried to address. They also, in many cases, hint at moral discomfort, suggesting that the act of lawmaking forced slave-owners to face up to the fact that they were treating other people as property
The differing physiology of nitrogen and tracer gas multiple-breath washout techniques
No full textBackground Multiple-breath washout techniques are increasingly being used to assess lung function. The principal statistic obtained is the lung clearance index (LCI), but values obtained for LCI using the N2-washout technique are higher than those obtained using an exogenous tracer gas such as SF6. This study explored whether the pure O2 used for the N2
washout could underlie these higher values.
Methods A model of a homogenous, reciprocally-ventilated acinus was constructed. Perfusion was kept constant, and ventilation adjusted by varying the swept volume during the breathing cycle. The blood
supplying the acinus had a standard mixed-venous composition. CO2
and O2 exchange between the blood and acinar gas proceeded to
equilibrium. The model was initialised with either air or air plus tracer
gas as the inspirate. Washouts were conducted with pure O2 for the N2
washout or with air for the tracer gas washout.
Results At normal ventilation-perfusion (V/Q) ratios, the rate of washout of N2 and exogenous tracer gas was almost indistinguishable. At low V/Q, the N2 washout lagged the tracer gas washout. At very low V/Q, N2
became trapped in the acinus. Under low V/Q conditions, breathing pure
O2 introduced a marked asymmetry between the inspiratory and
expiratory gas flow rates that was not present when breathing air.
Discussion The use of pure O2 to washout N2 increases O2 uptake in low V/Q units. This generates a background gas flow into the acinus thatopposes flow out of the acinus during expiration, and so delays the washout of N2
Co-attention for conditioned image matching
No full textWe propose a new approach to determine correspondences between image pairs in the wild under large changes in illumination, viewpoint, context, and material. While other approaches find correspondences between pairs of images by treating the images independently, we instead condition on both images to implicitly take account of the differences between them. To achieve this, we introduce (i) a spatial attention mechanism (a co-attention module, CoAM) for conditioning the learned features on both images, and (ii) a distinctiveness score used to choose the best matches at test time. CoAM can be added to standard architectures and trained using self-supervision or supervised data, and achieves a significant performance improvement under hard conditions, e.g. large viewpoint changes. We demonstrate that models using CoAM achieve state of the art or competitive results on a wide range of tasks: local matching, camera localization, 3D reconstruction, and image stylization
Climate change research and the search for solutions: rethinking interdisciplinarity
No full textGrowing political pressure to find solutions to climate change is leading to increasing calls for multiple disciplines, in particular those that are not traditionally part of climate change research, to contribute new knowledge systems that can offer deeper and broader insights to address the problem. Recognition of the complexity of climate change compels researchers to draw on interdisciplinary knowledge that marries natural sciences with social sciences and humanities. Yet most interdisciplinary approaches fail to adequately merge the framings of the disparate disciplines, resulting in reductionist messages that are largely devoid of context, and hence provide incomplete and misleading analysis for decision-making. For different knowledge systems to work better together toward climate solutions, we need to reframe the way questions are asked and research pursued, in order to inform action without slipping into reductionism. We suggest that interdisciplinarity needs to be rethought. This will require accepting a plurality of narratives, embracing multiple disciplinary perspectives, and shifting expectations of public messaging, and above all looking to integrate the appropriate disciplines that can help understand human systems in order to better mediate action
Skill transferability and the stability of transition pathways - a learning-based explanation for patterns of diffusion
No full textUnderstanding and governing technology transitions is essential to cope
with major challenges of the 21st century such as climate change or digitization.
In this paper, a learning-based approach is developed to explain the dynamics
of different transition pathways. Technological know-how is necessary to make
effective use of new machinery and capital goods. Firms and employees accumulate
technology-specific knowledge when working with specific machinery. Radical
innovation differs by technology type and pre-existing knowledge may be imperfectly
transferable across types. This paper addresses the implications of cross-technology
transferability of skills for firm-level technology adoption and its consequences for
the direction of macro-level technological change. A microeconomically founded
model of technological learning is introduced. The model is based on empirical
and theoretical insights from the innovation literature. In a simulation study using
the macroeconomic ABM Eurace@unibi-eco and applied to the context of green
technology diffusion, it is shown that a high transferability of knowledge has
ambiguous effects. It accelerates the diffusion process initially but comes at the cost
of long-term technological stability and specialization. For firms, it is easy to adopt
new technology, but also easy to switch back to the incumbent type. Technological
instability can be macroeconomically costly
Malaria infection and severe disease risks in Africa
No full textThe relationship between community prevalence of Plasmodium falciparum and the burden of severe, life-threatening disease remains poorly defined. To examine the three most common severe malaria phenotypes from catchment populations across East Africa, we assembled a dataset of 6506 hospital admissions for malaria in children aged 3 months to 9 years from 2006 to 2020. Admissions were paired with data from community parasite infection surveys. A Bayesian procedure was used to calibrate uncertainties in exposure (parasite prevalence) and outcomes (severe malaria phenotypes). Each 25% increase in prevalence conferred a doubling of severe malaria admission rates. Severe malaria remains a burden predominantly among young children (3 to 59 months) across a wide range of community prevalence typical of East Africa. This study offers a quantitative framework for linking malaria parasite prevalence and severe disease outcomes in children