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A Review of Gas-Surface Interaction Models for Orbital Aerodynamics Applications
No full textRenewed interest in Very Low Earth Orbits (VLEO) - i.e. altitudes below 450km - has led to an increased demand for accurate environment characterisationand aerodynamic force prediction. While the former requires knowledgeof the mechanisms that drive density variations in the thermosphere, thelatter also depends on the interactions between the gas-particles in the residualatmosphere and the surfaces exposed to the flow. The determination ofthe aerodynamic coefficients is hindered by the numerous uncertainties thatcharacterise the physical processes occurring at the exposed surfaces. Severalmodels have been produced over the last 60 years with the intent of combiningaccuracy with relatively simple implementations. In this paper the mostpopular models have been selected and reviewed using as discriminating factors relevance with regards to orbital aerodynamics applications and theoreticalagreement with gas-beam experimental data. More sophisticated modelswere neglected, since their increased accuracy is generally accompanied by asubstantial increase in computation times which is likely to be unsuitable formost space engineering applications. For the sake of clarity, a distinction wasintroduced between physical and scattering kernel theory based gas-surfaceinteraction models. The physical model category comprises the Hard Cubemodel, the Soft Cube model and the Washboard model, while the scatteringkernel family consists of the Maxwell model, the Nocilla-Hurlbut-Shermanmodel and the Cercignani-Lampis-Lord model. Limits and assets of eachmodel have been discussed with regards to the context of this paper. Whereverpossible, comments have been provided to help the reader to identifypossible future challenges for gas-surface interaction science with regards toorbital aerodynamic applications
Impact of COVID-19 lockdown on flash and real-time glucose sensor users with type 1 diabetes in England
No full textAims People with type 1 diabetes (T1D) face the daily task of implementing self-management strategies to achieve their glycaemic goals. The UK COVID-19 lockdown has had an impact on day-to-day behaviour, which may affect diabetes self-management and outcomes. We assessed whether sensor-based outcomes pre- and during lockdown periods were different in a cohort of glucose sensor users with T1D. Methods Data were collected from Freestyle Libre (FSL) or Dexcom G6 sensor users who remotely shared their data with the diabetes clinic web-platform. Sensor metrics according to international consensus were analysed and compared between pre-lockdown period, and two and six weeks into lockdown (Period 1 and 2). Results Two hundred and sixty-nine T1D patients (baseline HbA1c 57±14mmol/mol) were identified as FSL (n=190) or Dexcom G6 (n=79) users. In patients with sensor use>70% (N=223), compared to prelockdown period percentage TIR 3.9 to 10mM (TIR) significantly increased during Period 1 (59.6±18.2 vs. 57.5±17.2%, p=0.002) and Period 2 (59.3±18.3 vs. 57.5±17.2%, p=0.035). The proportion of patients achieving TIR ≥70% increased from 23.3% pre-lockdown, to 27.8% in Period 1 and 30.5% in Period 2. A higher proportion also achieved the recommended time below and above range, and coefficient of variation in Period 1 and 2. Dexcom G6 users had significantly lower % time below range (<3.9mM) compared to FSL users during both lockdown periods (Period 1: Dexcom G6 vs. FSL: 1.8% vs. 4%; Period 2: 1.4% vs. 4%, P< 0.005 for both periods). Conclusion Sensor-based glycaemic outcomes in people with T1D in the current cohort improved during COVID19 lockdown, which may be associated with positive changes in self-management strategies. Further work is required to evaluate long term sustainability and support
Combining Alkali Metals and Zinc to Harness Heterometallic Cooperativity in Cyclic Ester Ring-Opening Polymerisation
No full textHeterometallic cooperativity is an emerging strategy to elevate polymerisation catalyst performance. Here, we report the first heterotrimetallic Na/Zn2 and K/Zn2 complexes supported by a ProPhenol ligand, which deliver “best of both” in cyclic ester ring-opening polymerisation, combining the outstanding activity (Na/K) and good control (Zn2) of homometallic analogues. Detailed NMR studies and density-functional theory calculations suggest that the Na/Zn2 and K/Zn2 complexes retain their heterometallic structures in the solution-state. To the best of our knowledge, the K/Zn2 analogue is the most active heterometallic catalyst reported for rac-lactide polymerisation (kobs = 1.7 x 10-2 s-1), giving activities five times faster than the Na/Zn2 complex. These versatile catalysts also display outstanding performance in ε-caprolatone and δ-valerolactone ring-opening polymerisation. These studies provide underpinning methodologies for future heterometallic polymerisation catalyst design, both in cyclic ester polymerisation and other ring-opening (co)polymerisation reactions
Incentivising bioenergy with carbon capture and storage (BECCS) responsibly: Comparing stakeholder policy preferences in the United Kingdom and Sweden
No full textBioenergy with carbon capture and storage (BECCS) plays a central role in scenario pathways that limit global warming in line with the objectives of the Paris Agreement. Yet deliberate policy efforts to incentivise BECCS—whether through amending existing climate policies or introducing entirely new ones—remain rare. In this paper, we contend that BECCS must be incentivised responsibly, through policy-making processes which account for diverse and geographically varying societal values and interests. More specifically, we make the case for responsible incentivisation by undertaking a comparative analysis of stakeholder attitudes to four idealised policy scenarios for BECCS, including representatives of government, business, nongovernmental and academic communities, in the UK and Sweden. The scenarios were: business as usual; international policy reform; national BECCS policy; and national policy for negative emissions technologies. Based on our findings, we recommend that policymakers 1) recognise the need to develop new incentives and make enabling reforms to existing policy instruments; 2) consider the risk of mitigation deterrence in their real world (and not abstracted) contexts; 3) employ multi-instrument approaches to incentivisation that do not overly rely on carbon pricing or 4) force a choice between technology specific or technology neutral policies; and 5) attend to the diversity of stakeholder and wider public perspectives that will ultimately determine the success—or failure—of their policy designs
Kβ X-ray Emission Spectroscopy as a Probe of Cu(I) Sites: Application to the Cu(I) Site in Preprocessed Galactose Oxidase
No full textCu(I) active sites in metalloproteins are involved in O2 activation, but their O2 reactivity is difficult to study due to the Cu(I) d10 closed shell which precludes the use of conventional spectroscopic methods. Kβ X-ray emission spectroscopy (XES) is a promising technique for investigating Cu(I) sites as it detectsphotons emitted by electronic transitions from occupied orbitals. Here, we demonstrate the utility of Kβ XES in probing Cu(I) sites in model complexes and a metalloprotein. Using Cu(I)Cl, emission features from double ionization (DI) states are identified using varying incident X-ray photon energies and areasonable method to correct the data to remove DI contributions is presented. Kβ XES spectra of Cu(I) model complexes, having biologically relevant N/S ligands and different coordination numbers, are compared and analyzed, with the aid of density functional theory (DFT) calculations, to evaluate thesensitivity of the spectral features to the ligand environment. While the low-energy Kβ2,5 emission feature reflects the ionization energy of ligand np valence orbitals, the high-energy Kβ2,5 emission feature corresponds to transitions from molecular orbitals (MOs) having mainly Cu 3d character with the intensities determined by ligand-mediated d–p mixing. A Kβ XES spectrum of the Cu(I) site in preprocessed galactose oxidase (GOpre) supports the 1Tyr/2His structural model that was determined by our previous X-ray absorption spectroscopy and DFT study. The high-energy Kβ2,5 emission feature in the Cu(I)-GOpre data has information about the MO containing mostly Cu 3dx2−y2 character that is thefrontier molecular orbital (FMO) for O2 activation, which shows the potential of Kβ XES for probing the Cu(I) FMO associated with small molecule activation in metalloproteins
Effect of primary percutaneous coronary intervention on in-hospital outcomes among active cancer patients presenting with ST-elevation myocardial infarction: A propensity score matching analysis
No full textIntroduction: Primary percutaneous coronary intervention (pPCI) is the gold standard, guideline recommended revascularization strategy in patients presenting with ST-elevation myocardial infarction (STEMI). However, there are limited data on its use and effectiveness among patients with active cancer presenting with STEMI.Methods and Results: All STEMI hospitalizations between 2004 and 2015 from the National Inpatient Sample were retrospectively analysed, stratified by cancer type. Propensity score matching was performed to estimate the average treatment effect of pPCI in each cancer on in-hospital adverse events, including major adverse cardiovascular and cerebrovascular events (MACCE) and its individual components, and compare treatment effect between cancer and non-cancer patients. Out of 1,870,815 patients with STEMI, 38,932 (2.1%) had a current cancer diagnosis (haematological: 11,251 [28.9% of all cancers]; breast: 4,675 [12.0%]; lung: 9,538 [24.5%]; colon: 3,749 [9.6%]; prostate: 9,719 [25.0%]). Patients with cancer received pPCI less commonly than those without cancer (from 54.2% for lung cancer to 70.6% for haematological vs. 82.3% in no cancer). Performance of pPCI was strongly associated with lower adjusted probabilities of MACCE and all-cause mortality in the cancer groups compared with the no cancer group. There was no significant difference in estimated average pPCI treatment effect between the cancer groups and non-cancer group.Conclusion: pPCI is underutilized in STEMI patients with current cancer despite its significantly lower associated rates of in-hospital all-cause mortality and MACCE that is comparable to patients without cancer. Further work is required to assess the long-term benefit and safety of pPCI in this high-risk group
A Longitudinal Study of Pervasive Display Personalisation
No full textWidespread sensing devices enable a world in which physical spaces become personalised in the presence of mobile users. An important example of such personalisation is the use of pervasive displays to show content that matches the requirements of proximate viewers. Despite prior work on prototype systems that use mobile devices to personalise displays, no significant attempts to trial such systems have been carried out. In this paper we report on our experiences of designing, developing and operating the world’s first comprehensive display personalisation service for mobile users. Through a set of rigorous quantitative measures, and a detailed qualitative analysis of twelve user/stakeholder interviews, we demonstrate the success of the platform in realising display personalisation, and offer a series of reflections to inform the design of future systems
Offset-free IMC with generalized disturbance models
No full textIntegral action is an essential component for offset-free response inmany feedback control systems. Standard internal model control designrules ensure an offset-free response for open-loop stable plants. Inthis paper a linear feedback control structure is proposed thatcomprises an observer using an augmented plant model, state estimatefeedback and disturbance estimate feedback. This allows internal modelcontrol design principles to be applied to unstable and marginallystable plants. Conditions are given for both nominal internal stabilityand offset-free action even in the case of plant-model mismatch. TheYoula parameterization is recovered as a limiting case withreduced-order observers. The design is illustrated on a large scalenon-square model with marginally stable dynamics