Quantum transport in Josephson junctions

Josephson junctions consist of two superconductors separated by some barrier, be it superconducting, ferromagnetic, or semiconducting. The striking feature of Josephson junctions is that for a phase difference between the two superconducting reservoirs, electrical current will flow between them. To study this transport we utilise the techniques of non-equilibrium Green’s functions; capable of probing the interplay between coherent quantum effects over macroscopic distances. We begin by broadly discussing the quantum mechanical techniques required in this work, before deriving the relevant equations to be solved. We then introduce numerical discretisation and explore how in lattice systems spin-orbit coupling can produce intricate fractals in an electron’s bandstructure. We then introduce a numerical algorithm which, although creates numerical instabilities, improves the speed of conventional Green’s function calculations. Finally, we study the electrical current, and the bound states which carry this current, in various Josephson junction architectures. We first compare our calculations with previous results in the literature to verify our results and demonstrate the generality of the non-equilibrium Green’s functions technique. We then explore numerically the anomalous Josephson effect, where current flows even in the absence of a phase bias between the two junctions. We provide a universal condition to be satisfied for Josephson junctions to exhibit anomalous current before modelling some experimental data concerning this effect.Thesis (Ph.D.) -- University of Adelaide, School of Physical Sciences, 202

Youth and the communication of Risk: developing connections between cancer council Australia and contemporary online youth culture

Through two focus groups, the project investigated how youth culture perceives online communication of risk. In two 90-minute sessions, investigators gaged the range of online activities that nine 18 - 24 year old university students engaged with. Through a guided discussion the participants explored how they would relate to the communication of health risk more generally and cancer risk more specifically.Participants’ online activity is very high and a range of social media forms are part of their everyday lives. In contrast, their use of traditional media is almost non-existent. Their relationship to accessing and being aware of health information demonstrated a range of views that pointed to quite new and different relationships to health and health professionals. To intersect with their online movements in the communication of health risk demands a sophisticated knowledge of their own searching patterns.Key ideas generated from the focus groups include: that it might be advantageous to group health risk beyond the specificity of cancer for online success; that an online persona would be useful to provide a face for the communication of risk; that a multi-platform campaign to raise the profile of a persona would be useful; and that success means moving between the serious and the light-hearted in a way that makes the persona a complete person of interest for them

Mass transfer in eccentric binaries: the new Oil-on-Water SPH technique

To measure the onset of mass transfer in eccentric binaries we have developed a two-phase SPH technique. Mass transfer is important in the evolution of close binaries, and a key issue is to determine the separation at which mass transfer begins. The circular case is well understood and can be treated through the use of the Roche formalism. To treat the eccentric case we use a newly-developed two phase system. The body of the donor star is made up from high-mass "water" particles, whilst the atmosphere is modelled with low-mass "oil" particles. Both sets of particles take part fully in SPH interactions. To test the technique we model circular mass-transfer binaries containing a 0.6 Msun donor star and a 1 Msun white dwarf; such binaries are thought to form cataclysmic variable (CV) systems. We find that we can reproduce a reasonable CV mass-transfer rate, and that our extended atmosphere gives a separation that is too large by aproximately 16%, although its pressure scale height is considerably exaggerated. We use the technique to measure the semi-major axis required for the onset of mass transfer in binaries with a mass ratio of q=0.6 and a range of eccentricities. Comparing to the value obtained by considering the instantaneous Roche lobe at pericentre we find that the radius of the star required for mass transfer to begin decreases systematically with increasing eccentricity.Comment: 9 pages, 8 figures, accepted by MNRA

Long-Term Outcomes in Anterior Cruciate Ligament Reconstruction: A Systematic Review of Patellar Tendon Versus Hamstring Autografts.

BACKGROUND: Much controversy still exists surrounding graft choice in anterior cruciate ligament (ACL) reconstruction. Over the past decade, an increase in comparative studies with longer follow-up has enhanced our understanding of current graft options and outcomes. PURPOSE: To describe the long-term comparative outcomes of ACL reconstruction with autograft bone-patellar tendon-bone (BPTB) versus autograft hamstring (HS) ACL reconstruction with regard to clinical and radiographic outcomes. STUDY DESIGN: Systematic review; Level of evidence, 2. METHODS: A search of the PubMed, MEDLINE, Cochrane, and Scopus databases was performed to identify studies in the English language with outcome data comparing ACL reconstruction utilizing autograft BPTB and autograft HS; only studies with a minimum 5-year follow-up were included. Outcome data included failure and complications, manual and instrumented laxity, patient-reported outcomes, and radiographic risk of osteoarthritis. RESULTS: Twelve studies with a total of 953 patients met the inclusion criteria. Of these studies, 8 were level 1 evidence and 2 were level 2. Mean follow-up was 8.96 years (range, 5-15.3 years). No differences in graft failure or manual or instrumented laxity were seen in any studies. Lower clinical outcomes scores and greater motion loss were seen in BPTB patients in 1 and 2 studies, respectively. Two of 4 studies reporting on anterior knee pain, and 3 of 7 that recorded kneeling pain found it more frequently among BPTB patients. One study found significantly increased reoperation rates in HS patients, while another found a similar result in BPTB, and 1 study reported a significant increase in contralateral ACL tears in BPTB patients. Three of 5 studies reporting on radiographic evidence of osteoarthritis noted significantly increased rates in BPTB patients. CONCLUSION: This systematic review comparing long-term outcomes after ACL reconstruction with either autograft BPTB or autograft HS suggests no significant differences in manual/instrumented laxity and graft failures between graft types. An increase in long-term anterior knee pain, kneeling pain, and higher rates of osteoarthritis were noted with BPTB graft use

Solid-state additive manufacturing for metallized optical fiber integration

The formation of smart, Metal Matrix Composite (MMC) structures through the use of solid-state Ultrasonic Additive Manufacturing (UAM) is currently hindered by the fragility of uncoated optical fibers under the required processing conditions. In this work, optical fibers equipped with metallic coatings were fully integrated into solid Aluminum matrices using processing parameter levels not previously possible. The mechanical performance of the resulting manufactured composite structure, as well as the functionality of the integrated fibers, was tested. Optical microscopy, Scanning Electron Microscopy (SEM) and Focused Ion Beam (FIB) analysis were used to characterize the interlaminar and fiber/matrix interfaces whilst mechanical peel testing was used to quantify bond strength. Via the integration of metallized optical fibers it was possible to increase the bond density by 20–22%, increase the composite mechanical strength by 12–29% and create a solid state bond between the metal matrix and fiber coating; whilst maintaining full fiber functionality

Additively manufactured lab-on-chip devices

3D printing of microfluidics is in its infancy but it is already demonstrating game-changing potential. The technology offers new capabilities in highly complex geometries that can be designed and printed to high resolutions in many iterations. At Loughborough University our goal is to create smart complex 3D printed bespoke reactors that can adhere to a variety of industrial applications. This work is highly interdisciplinary and is spearheaded by a cross-campus collaborative expert group from Manufacturing and Chemical Engineering, Biology and Chemistry. The presented work was based on the production of a variety of flow reactor Lab-on-Chip (LOC) devices, each possessing unique capabilities in regards to both sensing and particle manipulation techniques. Multiple applications are covered such as the embedding of metal coated optical fibres and electronics within a metal matrix for inline sensing capabilities; the manufacture of high pressure and high temperature metal matrix LOC devices for application in supercritical fluid chemistry and hostile sampling; and the design and optimisation of magnetic particle continuous flow separators. The results are demonstrated for all three of the above mentioned applications and the outcomes, to date, of the individual projects will be concluded with the expected further work

Exploring the mechanical strength of additively manufactured metal structures with embedded electrical materials

Ultrasonic Additive Manufacturing (UAM) enables the integration of a wide variety of components into solid metal matrices due to the process induced high degree of metal matrix plastic flow at low bulk temperatures. Exploitation of this phenomenon allows the fabrication of previously unobtainable novel engineered metal matrix components. The feasibility of directly embedding electrical materials within UAM metal matrices was investigated in this work. Three different dielectric materials were embedded into UAM fabricated aluminium metal-matrices with, research derived, optimal processing parameters. The effect of the dielectric material hardness on the final metal matrix mechanical strength after UAM processing was investigated systematically via mechanical peel testing and microscopy. It was found that when the Knoop hardness of the dielectric film was increased from 12.1 HK/0.01 kg to 27.3 HK/0.01 kg, the mechanical peel testing and linear weld density of the bond interface were enhanced by 15% and 16%, respectively, at UAM parameters of 1600 N weld force, 25 µm sonotrode amplitude, and 20 mm/s welding speed. This work uniquely identified that the mechanical strength of dielectric containing UAM metal matrices improved with increasing dielectric material hardness. It was therefore concluded that any UAM metal matrix mechanical strength degradation due to dielectric embedding could be restricted by employing a dielectric material with a suitable hardness (larger than 20 HK/0.01 kg). This result is of great interest and a vital step for realising electronic containing multifunctional smart metal composites for future industrial applications

Evaluating the Benefits of Restricted Grazing to Protect Wet Pasture Soils in Two Dairy Regions of New Zealand

Many dairy farms in the Manawatu and Southland regions of New Zealand have poorly drained soils that are prone to treading damage, an undesirable outcome on grazed pastures during the wetter months of the year. Removing cows to a stand-off pad during wet conditions can reduce damage, but incurs costs. The objective of this study was to evaluate the impact of different levels of restricted grazing (from 0 to 10 hours grazing time/day for lactating cows) on pasture yield, damage and wastage, feed and stand-off expenses, and farm operating profit. A simulated farm from each region was used in a farm systems model. This model simulated pasture-cow-management interactions, using site-specific climate data as inputs for the soil-pasture sub-models. Days to recover previous yield potential for damaged paddocks can vary widely. A sensitivity analysis (40 to 200 days to recover) was conducted to evaluate the effect of this parameter on results. Full protection when there is risk of damage (0 grazing hours/day) appeared to be less profitable compared with some level of grazing, because the advantages of reduced damage were outweighed by the disadvantages of managing infrequently grazed pastures. The differences in operating profit between full protection and some level of grazing became less as the recovery time increased, but for both regions grazing durations of 6-8 hours/day when a risk of damage is present appeared to be a sensible strategy irrespective of recovery time

Using the MitoB method to assess levels of reactive oxygen species in ecological studies of oxidative stress

In recent years evolutionary ecologists have become increasingly interested in the effects of reactive oxygen species (ROS) on the life-histories of animals. ROS levels have mostly been inferred indirectly due to the limitations of estimating ROS from in vitro methods. However, measuring ROS (hydrogen peroxide, H2O2) content in vivo is now possible using the MitoB probe. Here, we extend and refine the MitoB method to make it suitable for ecological studies of oxidative stress using the brown trout Salmo trutta as model. The MitoB method allows an evaluation of H2O2 levels in living organisms over a timescale from hours to days. The method is flexible with regard to the duration of exposure and initial concentration of the MitoB probe, and there is no transfer of the MitoB probe between fish. H2O2 levels were consistent across subsamples of the same liver but differed between muscle subsamples and between tissues of the same animal. The MitoB method provides a convenient method for measuring ROS levels in living animals over a significant period of time. Given its wide range of possible applications, it opens the opportunity to study the role of ROS in mediating life history trade-offs in ecological settings