CRYOGENIC FLUIDS IN NUCLEAR PROPULSION SYSTEMS

Nuclear rocket engines employ hydrogen, a cryogenic liquid, as a propellant in order to obtain a system with a high specific impulse. Since hydrogen is also an excellent moderator of neutrons, it provides a reactivity contribution which must be taken into consideration in the design of a reactor and in its programmed operation. The reactivity worth of hydrogen is a function of its density distribution. The prediction of this quantity was facilitated by heat transfer experiments, which were simulated on a digital computer. Pressure oscillations associated with the twophase flow of hydrogen were simulated by means of a spring-mass model. (auth

Lesbian and bisexual women's experiences of sexuality-based discrimination and their appearance concerns

Lesbian and bisexual women frequently experience sexuality-based discrimination, which is often based on others' judgements about their appearance. This short article aims to explore whether there is a relationship between lesbian and bisexual women's experiences of sexuality-based discrimination and their satisfaction with the way that they look. Findings from an online survey suggest that discrimination is negatively related to appearance satisfaction for lesbian women, but not for bisexual women. It is argued that this difference exists because lesbian appearance norms are more recognisable and distinctive than bisexual women's appearance norms

Professionalism, Golf Coaching and a Master of Science Degree: A commentary

As a point of reference I congratulate Simon Jenkins on tackling the issue of professionalism in coaching. As he points out coaching is not a profession, but this does not mean that coaching would not benefit from going through a professionalization process. As things stand I find that the stimulus article unpacks some critically important issues of professionalism, broadly within the context of golf coaching. However, I am not sure enough is made of understanding what professional (golf) coaching actually is nor how the development of a professional golf coach can be facilitated by a Master of Science Degree (M.Sc.). I will focus my commentary on these two issues

An additive manufactured CubeSat mirror incorporating a novel circular lattice

Additive Manufacturing (AM; 3D printing) for mirror fabrication allows for intricate designs that can combine lightweight structures and integrated mounting. Conventional lightweight structures utilise cubic or prismatic unit cells, which do not provide uniform support at the edge of curved mirrors. We present a new circular lattice based upon cylindrical coordinates and how this lattice has been incorporated within an 80 mm diameter mirror intended for use in a 3U CubeSat telescope. Several design iterations are explored, which include prototype mirrors produced in a titanium alloy and a finite element analysis of the one of the design iterations

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Los Alamos Omega West Reactor

A description is given of the Omega West Reactor and associated experimental facilities, followed by a brief discussion of recent usage, new experiments, and future prospects

CRYOGENIC FLUIDS IN NUCLEAR PROPULSION SYSTEMS

Nuclear rocket engines employ hydrogen, a cryogenic liquid, as a propellant in order to obtain a system with a high specific impulse. Since hydrogen is also an excellent moderator of neutrons, it provides a reactivity contribution which must be taken into consideration in the design of a reactor and in its programmed operation. The reactivity worth of hydrogen is a function of its density distribution. The prediction of this quantity was facilitated by heat transfer experiments, which were simulated on a digital computer. Pressure oscillations associated with the twophase flow of hydrogen were simulated by means of a spring-mass model. (auth