High performance channel injection sealant invention abstract

High performance channel sealant is based on NASA patented cyano and diamidoximine-terminated perfluoroalkylene ether prepolymers that are thermally condensed and cross linked. The sealant contains asbestos and, in its preferred embodiments, Lithofrax, to lower its thermal expansion coefficient and a phenolic metal deactivator. Extensive evaluation shows the sealant is extremely resistant to thermal degradation with an onset point of 280 C. The materials have a volatile content of 0.18%, excellent flexibility, and adherence properties, and fuel resistance. No corrosibility to aluminum or titanium was observed

'The UK is not innocent' : Black Lives Matter, policing and abolition in the UK

Purpose: The purpose of this article is to show that racism is not only a US problem. Rather, racism is endemic and pervasive in the UK context, manifesting at every level of policing. From stop and search, to deaths after police contact, the authors highlight long-standing and widespread racist disparities in UK policing. The authors therefore pierce through any delusions of UK “post-racialism” in order to show that, as protesters have reminded us, “the UK is not innocent”. Design/methodology/approach: In this piece, the authors reflect on the Black Lives Matter protests of 2020. Whilst the catalyst was the death of George Floyd in the United States, the authors explore what the protests mean in the UK context. To do so, the authors draw upon recent high-profile examples of police racism, before situating those events within a wider landscape of racist policing. Findings: Demonstrating that UK policing has to be understood as institutionally racist, the authors suggest that responses to police racism need to be radical and uncompromising – tweaks to the system are not enough. The authors therefore look towards defunding and abolition as ways in which one can begin to seek change. Originality/value: The piece takes up the challenges set by this Black Lives Matter moment and offers a critical take on policing that seeks to push beyond reformism whilst also highlighting the realities of UK racism

Gauge transformations in the Lagrangian and Hamiltonian formalisms of generally covariant theories

We study spacetime diffeomorphisms in Hamiltonian and Lagrangian formalisms of generally covariant systems. We show that the gauge group for such a system is characterized by having generators which are projectable under the Legendre map. The gauge group is found to be much larger than the original group of spacetime diffeomorphisms, since its generators must depend on the lapse function and shift vector of the spacetime metric in a given coordinate patch. Our results are generalizations of earlier results by Salisbury and Sundermeyer. They arise in a natural way from using the requirement of equivalence between Lagrangian and Hamiltonian formulations of the system, and they are new in that the symmetries are realized on the full set of phase space variables. The generators are displayed explicitly and are applied to the relativistic string and to general relativity.Comment: 12 pages, no figures; REVTeX; uses multicol,fancyheadings,eqsecnum; to appear in Phys. Rev.

Decoherence induced by Smith-Purcell radiation

The interaction between charged particles and the vacuum fluctuations of the electromagnetic field induces decoherence, and therefore affects the contrast of fringes in an interference experiment. In this article we show that if a double slit experiment is performed near a conducting grating, the fringe visibility is reduced. We find that the reduction of contrast is proportional to the number of grooves in the conducting surface, and that for realistic values of the parameters it could be large enough to be observed. The effect can be understood in terms of the Smith-Purcell radiation produced by the surface currents induced in the conductor.Comment: 10 pages, 3 figures. Improved discussion on experimental perspectives. References added. Version to appear in Phys. Rev.

The issue of time in generally covariant theories and the Komar-Bergmann approach to observables in general relativity

Diffeomorphism-induced symmetry transformations and time evolution are distinct operations in generally covariant theories formulated in phase space. Time is not frozen. Diffeomorphism invariants are consequently not necessarily constants of the motion. Time-dependent invariants arise through the choice of an intrinsic time, or equivalently through the imposition of time-dependent gauge fixation conditions. One example of such a time-dependent gauge fixing is the Komar-Bergmann use of Weyl curvature scalars in general relativity. An analogous gauge fixing is also imposed for the relativistic free particle and the resulting complete set time-dependent invariants for this exactly solvable model are displayed. In contrast with the free particle case, we show that gauge invariants that are simultaneously constants of motion cannot exist in general relativity. They vary with intrinsic time

Cost-effectiveness modelling of telehealth for patients with raised cardiovascular disease risk: evidence from a cohort simulation conducted alongside the Healthlines randomised controlled trial

OBJECTIVES: To investigate the long-term cost-effectiveness (measured as the ratio of incremental NHS cost to incremental quality-adjusted life years) of a telehealth intervention for patients with raised cardiovascular disease (CVD) risk. DESIGN: A cohort simulation model developed as part of the economic evaluation conducted alongside the Healthlines randomised controlled trial. SETTING: Patients recruited through primary care, and intervention delivered via telehealth service. PARTICIPANTS: Participants with a 10-year CVD risk ≥20%, as measured by the QRISK2 algorithm, and with at least 1 modifiable risk factor, individually randomised from 42 general practices in England. INTERVENTION: A telehealth service delivered over a 12-month period. The intervention involved a series of responsive, theory-led encounters between patients and trained health information advisors who provided access to information resources and supported medication adherence and coordination of care. PRIMARY AND SECONDARY OUTCOME MEASURES: Cost-effectiveness measured by net monetary benefit over the simulated lifetime of trial participants from a UK National Health Service perspective. RESULTS: The probability that the intervention was cost-effective depended on the duration of the effect of the intervention. The intervention was cost-effective with high probability if effects persisted over the lifetime of intervention recipients. The probability of cost-effectiveness was lower for shorter durations of effect. CONCLUSIONS: The intervention was likely to be cost-effective under a lifetime perspective. TRIAL REGISTRATION NUMBER: ISRCTN27508731; Results

Generally covariant theories: the Noether obstruction for realizing certain space-time diffeomorphisms in phase space

Relying on known results of the Noether theory of symmetries extended to constrained systems, it is shown that there exists an obstruction that prevents certain tangent-space diffeomorphisms to be projectable to phase-space, for generally covariant theories. This main result throws new light on the old fact that the algebra of gauge generators in the phase space of General Relativity, or other generally covariant theories, only closes as a soft algebra and not a a Lie algebra. The deep relationship between these two issues is clarified. In particular, we see that the second one may be understood as a side effect of the procedure to solve the first. It is explicitly shown how the adoption of specific metric-dependent diffeomorphisms, as a way to achieve projectability, causes the algebra of gauge generators (constraints) in phase space not to be a Lie algebra --with structure constants-- but a soft algebra --with structure {\it functions}.Comment: 22 pages, version to be published in Classical & Quantum Gravit

Oxygenated compounds in aged biomass burning plumes over the Eastern Mediterranean: evidence for strong secondary production of methanol and acetone

International audienceAirborne measurements of acetone, methanol, PAN, acetonitrile (by Proton Transfer Reaction Mass Spectrometry), and CO (by Tunable Diode Laser Absorption Spectroscopy) have been performed during the Mediterranean Intensive Oxidants Study (MINOS August 2001). We have identified ten biomass burning plumes from strongly elevated acetonitrile mixing ratios. The characteristic biomass burning signatures obtained from these plumes reveal secondary production of acetone and methanol, while CO photochemically declines in the plumes. Mean excess mixing ratios - normalized to CO - of 1.8%, 0.20%, 3.8%, and 0.65% for acetone, acetonitrile, methanol, and PAN, respectively, were found. By scaling to an assumed global annual source of 663-807Tg CO, biomass burning emissions of 25-31 and 29-35 Tg/yr for acetone and methanol are estimated, respectively. Our measurements suggest that the present biomass burning contributions of acetone and methanol are significantly underestimated due to the neglect of secondary formation within the plume. Median acetonitrile mixing ratios throughout the troposphere were around 150pmol/mol, in accord with current biomass burning inventories and an atmospheric lifetime of ~6 months

A Connection Approach to Numerical Relativity

We discuss a general formalism for numerically evolving initial data in general relativity in which the (complex) Ashtekar connection and the Newman-Penrose scalars are taken as the dynamical variables. In the generic case three gauge constraints and twelve reality conditions must be solved. The analysis is applied to a Petrov type \{1111\} planar spacetime where we find a spatially constant volume element to be an appropriate coordinate gauge choice.Comment: 17 pages, LaTe