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Time-accurate Experimental Investigation of Hypersonic Inlet Buzz at Mach 5
No full textHypersonic inlet buzz is investigated experimentally in a ramjet intake at Mach 5. A twodimensional planar inlet featuring a double-compression ramp with 10° and 22° inclination to the freestream direction and a rectangular cross section duct is tested. A solenoid is used to raise a barrier into the flow and initiate buzz at high throttling ratios. Static pressure is measured at a data sample rate of 10 kHz and Schlieren images are collected at an image frame rate of 30 kHz. Oscillations in the flow not linked to buzz are present both at zero and full throttle and they cause a high-amplitude pressure peak at very high frequency (higher than 3 kHz). At full throttle, buzz is spotted, in the contemporary presence of shear layers being ingested by the intake (Ferri criterion) and of separated flow lying on the second compression ramp (Dailey criterion). Both features are analyzed by means of the standard deviation of the frames captured. The kind of buzz hereby observed activates highamplitude pressure oscillations both at low frequencies and high frequencies. The unstarted flow field is largely subsonic inside the intake and allows for the use of linear acoustic theory. Indeed, one of the peaks recorded matches the quarter-wave resonator frequency (1411 Hz) of the inlet, suggesting that the barrier acts as a solid wall and that the inlet model behaves as a duct with a closed end
The British Women's Suffrage Movement and the Practice of Petitioning, 1890-1914
No full textThrough an examination of the women’s suffrage movement, this article reassesses the place of petitioning within late nineteenth and early twentieth-century British political culture. While critical of their Victorian predecessors reliance on petitions, the Edwardian women’s suffrage movement did not abandon petitioning, but reinvented it. Rather than presenting a polarized view of relations between suffragettes and suffragists, the article shows how both operated on a spectrum of direct action politics through petitioning. Militants and constitutionalists pioneered new, although different, modes of petitioning that underpinned broader repertoires of popular politics, adapting this venerable practice to a nascent mass democracy. The article then situates suffrage campaigners’ reinvention of petitioning within a broader political context. The apparent decline of petitioning, long noted by scholars, is reframed as the waning of the classic model of mass petitioning Parliament associated with Victorian pressure groups. The early twentieth century was a crucial period for the reshaping of petitioning as a tool for political participation and expression through myriad subscriptional forms, rather than primarily through the medium of parliamentary petitions
TENSOR STRUCTURE FOR NORI MOTIVES
No full textWe construct a tensor product on Freyd's universal abelian category Ab(C) attached to an additive tensor category or a ⊗-quiver and establish a universal property. This is used to give an alternative construction for the tensor product on Nori motives.<br/
O2 activation by non-heme thiolate-based dinuclear Fe complexes
No full textIron centers featuring thiolates in their metal coordination sphere (as ligands or substrates) are well known to activate dioxygen. Both heme and non-heme centers that contain iron-thiolate bonds are found in nature. Investigating the ability of iron-thiolate model complexes to activate O2 is expected to improve the understanding of the key factors that direct reactivity to either iron or sulfur. We report here the structural and redox properties of a thiolate-based dinuclear Fe complex, [FeII2(LS)2], (LS2- = 2,2’-(2,2’-bipyridine-6,6’-iyl)bis(1,1diphenylethanethiolate) and its reactivity with dioxygen, in comparison with its previously reported protonated counterpart, [FeII2(LS)(LSH)]+. When reaction with O2 occurs in the absence of protons or in the presence of one equivalent of proton (i.e. from [FeII2(LS)(LSH)]+), unsupported μ-oxo or μ-hydroxo FeIII dinuclear complexes ([FeIII2(LS)2O] and [FeIII2(LS)2(OH)]+, respectively) are generated. [FeIII2(LS)2O], reported previously but isolated here for the first time from O2 activation, is characterized by single crystal X-ray diffraction and Mössbauer, Resonance Raman and NMR spectroscopies. The addition of protons leads to the release of water and the generation of a mixture of two Fe-based "oxygen-free" species. DFT-calculations provide insight into the formation of the μ-oxo or μ-hydroxo FeIII dimers, predicting that a dinuclear μ-peroxo FeIII intermediate is key to reactivity, and the structure of which changes as a function of protonation state. Compared to previously reported Mn-thiolate analogues, the evolution of the peroxo intermediates to the final products is different and involves a comproportionation vs a dismutation process for the Mn and Fe derivate, respectively. <br/
Is it usual to be unusual? An investigation into molecular conformations in organic crystals
No full textMolecular conformations can influence the structure and properties of crystalline solids. Important solid-state phenomena such as conformational polymorphism arise from the ability of compounds to crystallise in different conformers. A method to readily identify whether or not a crystal conformation is highly adjusted or may correspond to a rare conformer is, thus, very desirable. We present a new way of identifying unusual conformations in molecular crystals from distributions of torsions in the Cambridge Structural Database (CSD). Our method allows for identification of torsion unusualness with regards to conformational adjustment and conformational change. As part of this method, two new parameters derived from CSD distributions are calculated: Padjust and Pchange. These parameters were tested against DFT calculations for the derivation of meaningful CSD probability thresholds which allow for the identification of unusual torsions. The developed method was then used to investigate unusual torsions in molecular crystals. We found that between 10-13% of torsions in the CSD are unusual and that unusual conformational adjustment is significantly more common than unusual conformational change
Maser Flares Driven by Variations in Pumping and Background Radiation
No full textWe simulate maser flares by varying either the pump rate or the background level of radiation in a 3D model of a maser cloud. We investigate the effect of different cloud shapes, saturation levels and viewpoints. Results are considered for clouds with both uniform and internally variable unsaturated inversion. Pumping and background variations are represented by several different driving functions, some of which are light curves drawn from observations.We summarise the pumping variability results in terms of three observable parameters, the maximum flux density achieved, a variability index and duty cycle.We demonstrate typical ranges of the flux density that may result from viewing an aspherical object from random viewpoints. The best object for a flare is a prolate cloud, viewed close to its long axis and driven from unsaturated conditions to at least modest saturation. Results for variation of the background level are qualitatively different from the variable pumping results in that they tend to produce short intervals of low flux density under conditions of moderate saturation and sufficient variability to be consistent with strong flaring. Variable backgroundmodels typically have a significantly higher duty cycle than those with variable pumping
Are negative beliefs about psychosis associated with emotional distress in adults and young people with such experiences? A meta-analysis.
No full textObjective: Emotional distress, including depression and anxiety is commonly reported amongst individuals experiencing psychosis. The beliefs individuals hold about the meaning of their psychosis may explain the distress they experience. The current meta-analysis aimed to review the association between beliefs about psychosis experiences and emotional distress. Method: Three electronic databases (PsycINFO, Medline and CINAHL) were searched using keywords and controlled vocabulary (e.g., Medical Subject Headings) from date of inception to August 2019. A total of 19 eligible papers were identified.Results: Our random-effects meta-analysis revealed that depression and anxiety held moderate association with psychosis beliefs, with perceptions concerning a lack of control over experiences having the strongest association with distress. Longitudinal studies suggest that negative beliefs at baseline are associated with depressive symptoms at follow-up. Conclusions: The results suggest that the endorsement of negative beliefs about psychosis is associated with current level of depression and anxiety. The results are consistent with theories of emotional distress in psychosis. However, the small number of longitudinal papers limits what can be concluded about the direction or other temporal characteristics of these relationships. Therapies that target unhelpful beliefs about psychosis may beneficial.<br/
Rethinking energy use in distillation processes for a more sustainable chemical industry
No full textThe need for greater sustainability for the production of fuels and chemicals has spurred significant research to rethink energy use in the chemical industry, and eventually substitute fossil fuel sources by renewable sources. Nowadays, the chemical industry is responsible for about one third of the total energy used - and the associated CO2 emissions - in the industrial sector. Among the energy intensive operations, distillation alone is responsible for about 40% of the energy used in the chemical industry, but there is clearly much room for improvement.This paper aims to provide an informative perspective on the current energy use in the chemical industry, with a focus on distillation – the undisputed king of industrial separation processes – and potential improvements for a more sustainable future. There is clearly an increasing need and scope for advanced distillation technologies (e.g. reactive distillation, dividing-wall columns, thermal coupling, cyclic distillation, heat pump assisted distillation, and heat integrated distillation columns) that can significantly reduce the energy usage and the carbon footprint of modern chemical plants. However, these advanced distillation technologies must be considered, along with conventional distillation operations, in the context of the process as a whole. Based on the overview provided, several challenges and opportunities for research directions are highlighted towards rethinking the energy use for a more sustainable chemical industry
DESIGNING SATISFYING SERVICE ENCOUNTERS: WEBSITE VERSUS STORE TOUCHPOINTS
No full textThis study investigated how touchpoints moderate the antecedents of customer satisfaction with service encounters by comparing online and in-store encounters. Construal level theory was used within the Touchpoint, Context, Qualities (TCQ) Framework (De Keyser et al. 2020) to integrate a comprehensive model of how touchpoints—websites or stores—influence the magnitude of customer responses to qualities of service encounters. A hierarchical linear model (HLM) was estimated using survey data describing the service encounters of 2.4 million customers with a global retailer. Online customers weighed cognitive and behavioral qualities more heavily than in-store customers, whereas they weighed emotional and sensorial qualities less heavily. Moreover, random effects in the HLM model indicated that each country and store would have unique clientele effects for specific qualities. Since each firm has limited resources, this research offers guidance on key qualities in designing satisfying service encounters for each touchpoint and how qualities should be standardized and customized in global omnichannel environments