Progress towards an improved quasiparticle camera In superfluid 3He-B

The superfluid state, often obtained in the laboratory using liquid helium at very low temperatures, provides the basis for a wide range of interesting experiments. One large field of research relates to the study of turbulence in a superfluid, referred to as quantum turbulence due to the importance of quantum mechanical behaviour in the description of this phenomenon. An important experimental tool in the study of quantum turbulence is the mechanical resonator, with many different types of oscillator seeing use. Variations in the resonance can be related to the properties of the fluid through an understanding of the drag applied to the object. The many seemingly disparate measurements reported here were performed in the hope of providing background for future development of improved experimental techniques. In an effort to develop an improved method for determining oscillator properties, measurements have been made using a multifrequency lock-in amplifier in superfluid 4He. The results obtained show that the multifrequency lock-in can be used to obtain results equivalent to the traditional method while reducing the time required. Due to the possibility of vastly increased sensitivity to changes in effective mass, tests were performed in 4He using a new form of oscillator with a 100 nm by 100 nm square cross-section, significantly smaller than other available devices. The resonant frequency of these resonators, referred to as nanobeams, was varied from 0.6 MHz to 8.5 MHz by using beams of different length. Measurements of the resonator response as a function of temperature show that the beams can successfully probe the fluid, though the current theory is found to be insufficient to exactly quantify the dependence seen. A possible observation of turbulence generated by a nanobeam is also reported. Despite an observed critical velocity significantly different to theoretical predictions, all other measurements are consistent with a turbulent transition. As the eventual goal is to use nanobeams for measurements in 3He-B, the drag on high frequency oscillators in 3He-B was also studied. Measurements on 4 devices of different frequencies found that the current model of damping remains adequate beyond the expected frequency limit for this model. Observations of anomalous increases in the damping for a single resonator in 3He-B are also discussed. As this unexpected damping is only seen for small, sensitive resonators there is concern that similar effects could hinder interpretation of future nanobeam measurements in 3He-B. Efforts were made to understand the source of this damping, and hence explain why it is seen for only one of three nominally identical oscillators, though no conclusive explanation could be found

Can incentive-based spatial management work in the Eastern tuna and billfish fishery?

The Eastern tuna and billfish fishery (ETBF) is currently managed through an input quota system based on individual transferable effort units (the number of hooks) and a total allowable effort level (i.e. total number of hooks) A spatial management policy based on a series of differential hook-penalties has been proposed as a flexible tool to discourage vessels operating in certain areas (e.g. those with high bycatch potential) and encourage operating in other areas (e.g. with less bycatch potential). In this study, the importance of catch rates per hook to location choice is assessed through the estimation of a nested multinomial logit model. Other variables in the model include distance to the location, prices of the main species, fuel prices and vessel characteristics. The effects of increasing hook penalties in key areas on fishing effort in those areas and elsewhere are assessed. Implications for vessel economic performance are also assessed.Resource /Energy Economics and Policy,

Younger Federal District Court Judges Favor Presidential Power

From 1960 to 2015, Federal District Court opinions involving challenges to Executive Branch authority show that U.S. Federal District Court judges (trial judges) support such authority less as they age, with a sharp decline beginning near age 57. We argue that District judges know that elevation to the Federal Circuit Court of Appeals becomes increasingly improbable, and hence have less reason to ‘cooperate’ with the Executive, with advancing age. Political variables (and other variables) introduced as extra regressors do not reverse our main results. When there are contemporaneous vacancies on their Circuit courts, District judges in the eleven State Circuits (but not the District of Columbia circuit) are also more likely to favor the Executiv

The Effects of Surgical Antiseptics and Time Delays on RNA Isolated From Human and Rodent Peripheral Nerves

Peripheral Nerve Injury (PNI) is common following blunt or penetrating trauma with an estimated prevalence of 2% among the trauma population. The resulting economic and societal impacts are significant. Nerve regeneration is a key biological process in those recovering from neural trauma. Real Time-quantitative Polymerase Chain Reaction (RT-qPCR) and RNA sequencing (RNA seq) are investigative methods that are often deployed by researchers to characterize the cellular and molecular mechanisms that underpin this process. However, the ethical and practical challenges associated with studying human nerve injury have meant that studies of nerve injury have largely been limited to rodent models of renervation. In some circumstances it is possible to liberate human nerve tissue for study, for example during reconstructive nerve repair. This complex surgical environment affords numerous challenges for optimizing the yield of RNA in sufficient quantity and quality for downstream RT-qPCR and/or RNA seq applications. This study characterized the effect of: (1) Time delays between surgical liberation and cryopreservation and (2) contact with antiseptic surgical reagents, on the quantity and quality of RNA isolated from human and rodent nerve samples. It was found that time delays of greater than 3 min between surgical liberation and cryopreservation of human nerve samples significantly decreased RNA concentrations to be sub-optimal for downstream RT-qPCR/RNA seq applications (<5 ng/μl). Minimizing the exposure of human nerve samples to antiseptic surgical reagents significantly increased yield of RNA isolated from samples. The detrimental effect of antiseptic reagents on RNA yield was further confirmed in a rodent model where RNA yield was 8.3-fold lower compared to non-exposed samples. In summary, this study has shown that changes to the surgical tissue collection protocol can have significant effects on the yield of RNA isolated from nerve samples. This will enable the optimisation of protocols in future studies, facilitating characterisation of the cellular and molecular mechanisms that underpin the regenerative capacity of the human peripheral nervous system

P1_8 Escaping the Moons of Mars using a Pogo Stick

The objective of this paper was to investigate the gravitational field strengths of the Martian Moons; Deimos and Phobos’ effect on a pogo stick and it’s rider. It was hypothesised that spring required to escape Deimos would be smaller due to the gravitational field strength being lower. This hypothesis was tested using Hooke’s Law and the Newtonian Laws of gravity to calculate the spring size needed to propel the pogo stick and its rider to a point where it was no longer under the effects of the respective moons gravitational pull. We found this value for the spring decompression to be 1.56 m on Deimos and 5.1 m on Phobos. These values confirmed the hypothesis we made and therefore it would be possible to use a pogo stick to escape the Martian Moons’ gravity

P1_7 Solar-Powered Superhero: What’s Superman’s Power Consumption?

In this paper, we assess the viability of Superman being powered by solar energy. We do this by calculating the energy that he would be able to absorb in a day - 3 × 107J - and comparing it to the energy that he requires to carry out certain superhuman activities. We find that he could leap the Empire State Building 75 times using the energy he acquires in a day, but he requires 3 days worth of energy to match the energy output of a train for one second

P1_2 Using Trebuchets for Lunar Satellites

In this paper we investigated the possibility of launching a 10 kg satellite into lunar orbit from the surface of the Moon, using a trebuchet. We found that the mass of the counterweight required would be 330 tonnes. We also discussed how the kinetic energy required for the speed of the orbit and the gravitational energy needed to be overcome changed as a result of the orbital radius

P1_5 Martian muon decay

One of the first pieces of evidence for Einstein's theory of special relativity was the apparent detection of muons at the surface of earth. We consider the same effect but using a Martian atmosphere. We calculate that the time taken to traverse the Troposphere is $t_{actual} = 1.3\times 10^{-5}$s after allowing for relativity. Lastly, we find that the number of muon's detectable is $\sim0.26\%$