Thermodynamics of an attractive 2D Fermi gas

Thermodynamic properties of matter are conveniently expressed as functional relations between variables known as equations of state. Here we experimentally determine the compressibility, density and pressure equations of state for an attractive 2D Fermi gas in the normal phase as a function of temperature and interaction strength. In 2D, interacting gases exhibit qualitatively different features to those found in 3D. This is evident in the normalized density equation of state, which peaks at intermediate densities corresponding to the crossover from classical to quantum behaviour.Comment: Contains minor revision

The initial development of a jet caused by fluid, body and free surface interaction with a uniformly accelerated advancing or retreating plate. Part 1. The principal flow

The free surface and flow field structure generated by the uniform acceleration (with dimensionless acceleration σ) of a rigid plate, inclined at an angle α ∈ (0, π/2) to the exterior horizontal, as it advances (σ > 0) or retreats (σ < 0) from an initially stationary and horizontal strip of inviscid, incompressible fluid under gravity, are studied in the small-time limit via the method of matched asymptotic expansions. This work generalises the case of a uniformly accelerating plate advancing into a fluid as studied in Needham et al. (2008). Particular attention is paid to the innermost asymptotic regions encompassing the initial interaction between the plate and the free surface. We find that the structure of the solution to the governing initial boundary value problem is characterised in terms of the parameters α and μ (where μ = 1+σ tan α), with a bifurcation in structure as μ changes sign. This bifurcation in structure leads us to question the well-posedness and stability of the governing initial boundary value problem with respect to small perturbations in initial data in the innermost asymptotic regions, the discussion of which will be presented in the companion paper Gallagher et al. (2016) . In particular, when (α, μ) ∈ (0, π/2) × R+, the free surface close to the initial contact point remains monotone, and encompasses a swelling jet when (α, μ) ∈ (0, π/2)×[1,∞), or a collapsing jet when (α, μ) ∈ (0, π/2) × (0, 1). However, when (α, μ) ∈ (0, π/2) × R−, the collapsing jet develops a more complex structure, with the free surface close to the initial contact point now developing a finite number of local oscillations, with near resonance type behaviour occurring close to a countable set of critical plate angles α = α∗n ∈ (0, π/2) (n = 1, 2, . . .)

Statistical characterization of the forces on spheres in an upflow of air

The dynamics of a sphere fluidized in a nearly-levitating upflow of air were previously found to be identical to those of a Brownian particle in a two-dimensional harmonic trap, consistent with a Langevin equation [Ojha {\it et al.}, Nature {\bf 427}, 521 (2004)]. The random forcing, the drag, and the trapping potential represent different aspects of the interaction of the sphere with the air flow. In this paper we vary the experimental conditions for a single sphere, and report on how the force terms in the Langevin equation scale with air flow speed, sphere radius, sphere density, and system size. We also report on the effective interaction potential between two spheres in an upflow of air.Comment: 7 pages, experimen

Significance of the pericardium in human subjects: Effects on left ventricular volume, pressure and ejection

To assess the effect of the pericardium, left ventricular systolic function and diastolic compliance were studied in 15 patients before and after pericardiotomy during coronary artery surgery. Using first pass radionuclide angiography, curves for left ventricular systolic function (stroke work versus end-diastolic volume) and a measure of diastolic compliance (pulmonary capillary wedge pressure versus end-diastolic volume) were generated by changing body position to alter venous return. Left ventricular end-diastolic volume ranged from 41 to 111 ml/m2and pulmonary capillary wedge pressure from 0 to 24 mm Hg.No significant changes were found in blood pressure (150/83 to 148/82 mm Hg), heart rate (66.7 to 67.1 beats/min), cardiac index (2.38 to 2.41 liters/min per m2), ejection fraction (0.56 to 0.54), end-systolic volume index (31.4 to 32.2 ml/m2), end-diastolic volume index (65.9 to 69.5 ml/m2) or pulmonary capillary wedge pressure (7.5 to 7.3 mm Hg). The pericardium did not affect the curves relating stroke work and end-diastolic volume or those relating pulmonary capillary wedge pressure and end-diastolic volume. Thus, when filling pressure and volume are normal or only moderately elevated, the pericardium does not appear to affect left ventricular systolic function or diastolic compliance in patients

Adjustable Prone Trolley Design for People Suffering from Spinal Cord Injuries in Nepal

For people suffering from spinal cord injuries, it is important to stay active. However, with spinal cord injuries, the use of a wheelchair isn’t feasible. These patients require a prone trolley. A prone trolley is a horizontal pad with four wheels that a patient can maneuver and control while lying in a prone position. Our partner, International Nepal Fellowship (INF), deals directly with patients who suffer from spinal cord injuries on a daily basis. INF, a Christian, medical organization, manages a hospital in Pokhara, Nepal which specializes in treating patients with spinal cord injuries. The Nepal Prone Trolley Team’s goal is to provide our partner with a sustainable prone trolley design and create the required manufacturing documentation to enable them to produce the prone trolleys in country at their Green Pastures hospital. The team began our work by researching what a prone trolley is, how it functions and what is currently available. During the research, the team discovered that there weren’t many examples of a manually powered prone trolley or critical dimensions for ergonomics for manually powered trolleys. This drove the team to develop testing methods and preliminary designs specifically for INF. Various basic designs were considered, but, through communication with INF, a single design was chosen. Computer modeling of this design was used to decrease the overall weight of the trolley and simplify the frame. With most of the design finalized, the team is ready to begin prototyping next semester.https://mosaic.messiah.edu/engr2021/1012/thumbnail.jp

A self-interacting partially directed walk subject to a force

We consider a directed walk model of a homopolymer (in two dimensions) which is self-interacting and can undergo a collapse transition, subject to an applied tensile force. We review and interpret all the results already in the literature concerning the case where this force is in the preferred direction of the walk. We consider the force extension curves at different temperatures as well as the critical-force temperature curve. We demonstrate that this model can be analysed rigorously for all key quantities of interest even when there may not be explicit expressions for these quantities available. We show which of the techniques available can be extended to the full model, where the force has components in the preferred direction and the direction perpendicular to this. Whilst the solution of the generating function is available, its analysis is far more complicated and not all the rigorous techniques are available. However, many results can be extracted including the location of the critical point which gives the general critical-force temperature curve. Lastly, we generalise the model to a three-dimensional analogue and show that several key properties can be analysed if the force is restricted to the plane of preferred directions.Comment: 35 pages, 14 figure

Superheating fields of superconductors: Asymptotic analysis and numerical results

The superheated Meissner state in type-I superconductors is studied both analytically and numerically within the framework of Ginzburg-Landau theory. Using the method of matched asymptotic expansions we have developed a systematic expansion for the solutions of the Ginzburg-Landau equations in the limit of small $\kappa$, and have determined the maximum superheating field $H_{\rm sh}$ for the existence of the metastable, superheated Meissner state as an expansion in powers of $\kappa^{1/2}$. Our numerical solutions of these equations agree quite well with the asymptotic solutions for $\kappa<0.5$. The same asymptotic methods are also used to study the stability of the solutions, as well as a modified version of the Ginzburg-Landau equations which incorporates nonlocal electrodynamics. Finally, we compare our numerical results for the superheating field for large-$\kappa$ against recent asymptotic results for large-$\kappa$, and again find a close agreement. Our results demonstrate the efficacy of the method of matched asymptotic expansions for dealing with problems in inhomogeneous superconductivity involving boundary layers.Comment: 14 pages, 8 uuencoded figures, Revtex 3.

Adjustable Prone Trolley Design for People Suffering from Spinal Cords Injuries in Nepal

For people who suffer from spinal cord injuries in Nepal, rehabilitation and care are often difficult to receive, especially for those for whom fewer resources are available. Thankfully, International Nepal Fellowship (INF), a non-profit serving Nepal for nearly 70 years, aids patients with spinal cord injuries at Green Pastures Hospital and Rehabilitation Centre in Pokhara, Nepal. A crucial part of any rehabilitation is adequate exercise to improve circulation and prevent sores and muscular atrophy. Yet, due to the nature of the injury, using a traditional wheelchair is not an option to fulfill this need for those with spinal cord injuries. Therefore, Green Pastures uses prone trolleys so that these patients can exercise. A prone trolley is a horizontal cushioned board where the patient lies flat on their stomach and is able to move themselves using the wheels attached to the cushioned board. Despite the importance of the prone trolley, the trolleys at Green Pastures Hospital have a few critical issues. The major issue is that the prone trolleys are internationally imported, which not only means that delivery can take months, but also that the trolleys are also difficult to repair when damaged. Both these factors severely hamper Green Pastures Hospital’s ability to provide spinal cord injured patients with the care they need. The Nepal Prone Trolley team, a part of Messiah University Collaboratory, seeks to develop and design a fundamentally better prone trolley for INF. The goal of our project is to design a prone trolley that can be fabricated by the INF staff with locally sourced materials. The advantage of this new design is that it will be easier to obtain and can easily be repaired when needed. After creating a design that satisfies our goal and fulfills the criteria of a functional prone trolley as defined by INF, we were able to fabricate a prototype of the prone trolley using resources and techniques available in Pokhara. Moving forward, we will conduct testing and redesign the trolley so that our finalized prone trolley design will be able to transform how Green Pastures Hospital aids their spinal cord injury patients. Funding for this work provided by The Collaboratory for Strategic Partnerships and Applied Research.https://mosaic.messiah.edu/engr2022/1011/thumbnail.jp

Renewing Criminalized and Hegemonic Cultural Landscapes

The Mafia's long historical pedigree in Mezzogiorno, Southern Italy, has empowered the Mafioso as a notorious, uncontested, and hegemonic figure. The counter-cultural resistance against the mafiosi culture began to be institutionalized in the early 1990s. Today, Libera Terra is the largest civil society organization in the country that uses the lands confiscated from the Mafia as a space of cultural repertoire to realize its ideals. Deploying labor force through volunteer participation, producing biological fruits and vegetables, and providing information to the students on the fields are the principal cultural practices of this struggle. The confiscated lands make the Italian experience of anti-Mafia resistance a unique example by connecting the land with the ideals of cultural change. The sociocultural resistance of Libera Terra conveys a political message through these practices and utters that the Mafia is not invincible. This study draws the complex panorama of the Mafia and anti-Mafia movement that uses the ‘confiscated lands’ as cultural and public spaces for resistance and socio-cultural change. In doing so, this article sheds new light on the relationship between rural criminology and crime prevention policies in Southern Italy by demonstrating how community development practice of Libera Terra changes the meaning of landscape through iconographic symbolism and ethnographic performance

Equation level matching: An extension of the method of matched asymptotic expansion for problems of wave propagation

We introduce an alternative to the method of matched asymptotic expansions. In the "traditional" implementation, approximate solutions, valid in different (but overlapping) regions are matched by using "intermediate" variables. Here we propose to match at the level of the equations involved, via a "uniform expansion" whose equations enfold those of the approximations to be matched. This has the advantage that one does not need to explicitly solve the asymptotic equations to do the matching, which can be quite impossible for some problems. In addition, it allows matching to proceed in certain wave situations where the traditional approach fails because the time behaviors differ (e.g., one of the expansions does not include dissipation). On the other hand, this approach does not provide the fairly explicit approximations resulting from standard matching. In fact, this is not even its aim, which to produce the "simplest" set of equations that capture the behavior