Design and Construction of a Computer Controlled Astronomical Spectropolarimeter

A theoretical description of a simple optical train, modulated signal based spectropolarimeter is discussed. The design includes, after the telescope optical tube (in this case, a 9.25” Schmidt Cassegrain), a rotating quarter waveplate (compensator), a fixed linear polarizer (analyzer), and transmission grating of 100l/mm, with a ZWO ASI290mm astronomical camera. The practical constraints on implementing such an instrument are discussed, and the construction of the spectropolarimeter is detailed, including the necessary optics, optomechanics, and electromechanics. The rotation and recording of the rotating compensator is facilitated by a motorized connection with proportional feedback control, and the uncertainty in measuring the angle is discussed. Calibration data from measurements with linear and circular polarizations was collected and analyzed, and exhibited close to the expected theoretical performance. Full analysis of the light in terms of the 4 Stoke’s parameters was hindered by lack of knowledge of the relative angle between analyzer and compensator, leading to ambiguity in the S1 and S2 parameters; however, even with this ambiguity, degrees of polarization can be determined. Astronomical data was collected on the Moon, Arcturus, and Vega. The analyzed moonlight exhibited clear linear polarization, with a degree of polarization of 4.13%. The polarimetric analysis of Vega and Arcturus suggested potential for polarization, but more analysis is needed. Spectroscopic performance was confirmed by measuring the hydrogen Balmer lines in Vega, leading to a plate scale of 0.6434 nm px . In summary, a low cost, low complexity spectropolarimeter capable of measuring all 4 Stoke’s parameters of stellar spectra has been constructed and tested on known generated polarization signals and astronomical objects

Simulations of bulk and confined bubble nucleation

The present thesis investigates, with atomistic simulations, vapor nucleation and liquid dynamics under nanoscale confinement. The main objective of this work is to go beyond the quasi-static classical picture of liquid-vapor phase transition, including kinetic and inertial effects. The performed simulations provide an accurate description of the phenomenon and a framework to interpret experimental observations. The dynamics of vapor nucleation is investigated in the pure bulk liquid and in confined conditions. In the last case, also wetting transition is studied. Particular attention is devoted to surfaces that combine textured geometries with an hydrophobic chemistry. These are able to stabilize vapor phase within surfaces asperities, producing a state in which liquid is suspended above the entrapped vapor pockets. In these conditions, remarkable properties arise that are collectively known as superhydropobicity. In this suspended state, known also as Cassie-Baxter state, the contact area between solid and liquid is reduced with respect to a flat surface and with respect to the textured surface in which the corrugations are flooded with the liquid. Moreover, the liquid presents a higher contact angle (CA), with a lower CA hysteresis and a reduced liquid-solid friction. Due to these properties, superhydrophobic surfaces are suitable for applications such as self-cleaning glass, window, andwallpaint. Theypreventmoistureaccumulation, helpanti-icing, andallowdropwisecondensationtoincreasetheheattransferefficiencyandwaterharvesting. These are all in-air applications. However, the presence of a large shear free liquid/gas interface suggested that super-hydrophobic surfaces can be used in many submerged applications, e.g. drag reduction, anti-friction, anti-adhesive, anti-corrosion, and boiling heat transfer. Cassie-Baxter state can be destabilized by changes in pressure and temperature, that produce the intrusion of the liquid within surface defects. The corresponding state in which the surface is completely wetted is known as Wenzel state. The loss of super-hydrophobic properties (Cassie-Baxter to Wenzel transition) has proved to be experimentally irreversible. It is therefore crucial to characterize both wetting and recovery mechanisms in order understand how to design surfaces supporting a robust Cassie-Baxter state, i.e. a suspended state that can resist to temperature and pressure fluctuations. Wetting transition and recovery of superhydrophobic state take place via vapor/liquid and liquid/vapor phase transitions occurring under confinement at the nanoscale within geometric defects. Over the last decades, a significant amount of experimental and theoretical work has been devoted to the study of confined liquidvapor transition. In spite of this, not much is known yet about the kinetics of the process. The contribution to the topic obtained during the three years of my PhD is presented in this thesis. The first part of the work has been devoted to develop and test Molecular Dynamics and Monte Carlo methods able to properly simulate multiphase systems. Indeed, it has been demonstrated that serious issues arise when the standard global barostats, developed to simulate bulk systems, are straightforwardly applied to systems with subdomains at different pressures, e.g. liquid and vapor domains during nucleation. A solution to overcome these artifacts has been proposed, consisting in the implementation of a local barostat that imposes a local force balance between a piston and the contacting liquid. With this approach, a more accurate prediction of the vapor nucleation barrier in a super-heated liquid has been obtained. Secondly, the simulation techniques developed at the first stage of my PhD work have been employed to study homogeneous bubble nucleation. At the liquid pressure andtemperaturehereinvestigated, thisphenomenonisarareevent: thewaitingtime to observe the inception of vapor formation is order of magnitude longer than the typical time that can be explored by atomistic simulations. This issue, that causes waste of computational resources, has been tackled by carefully selecting special techniques able to preserve kinetic and inertial effects during bubbles growth. With this approach, “dynamical” quantities have been estimated, e.g. the nucleation rate. Other two essential aspects have been addressed: the limits of theoretical expressions routinely used to evaluate the kinetic prefactor in Eyring equation for vapor nucleation; the relation between successful nucleation events and relevant observables, such as temperature and liquid velocity, at beginning and during bubble expansion. The last section of this thesis is focused on heterogeneous nucleation and wetting of super-hydrophobic surfaces. Recent theoretical and experimental studies have produced conflicting results in the characterization of the pathways by which liquid intrudes in pores. The disagreement resides, specifically, in the symmetry properties expected for the advancing meniscus shape. Experiments show a symmetric pathways, in which the liquid penetrates in the surface pores with an essentially flat meniscus, while quasi-static theories predict that the asymmetric pathway is more probable, in which the liquid entering in the surface cavities bend forming a bubble in a corner. My simulations have proved that inertial effects change the wetting and recovery path with respect the predictions of quasi-static approaches. This reconcile theory and experiments: when the transition is barrierless, as expected in experimental conditions in which only nearly spontaneous processes can be addressed, the more complete theory developed here predicts a symmetric wetting as observed in the experiments

An Examination of Oral Fed Post-Trauma Patients for Calorie and Protein Consumption as a Percentage of Estimated Needs, and How it Impacts Length of Hospital Stay and Wound Healing

Due to rising costs of healthcare, clinicians are responsible for decreasing costs by providing care that moves the patient from injury, to recovery, to discharge within a matter of just a few days. The Registered Dietitian is responsible for the nutrition assessment and nutrition diagnosis, nutrition prescription and plan, and for monitoring the patient to achieve nutritional repletion within this short time frame. Concerns for patients who require nursing staff and caregivers for feeding are evident, especially when increased demands are being placed on the nursing staff. This study aims to determine whether or not “feeder patients” are at a higher risk for malnutrition, which could potentially result in delayed discharge, poor rate of wound healing, and increased costs to the institution

Are credit unions in Ecuador achieving economies of scale?

This study tests the assertion that membership growth in credit unions is constrained by their unique structural features, such as their non-profit mission and member-based ownership. Although these features enhance inclusiveness, existing theory suggest that they work against efficiency when membership grows too diffuse. To address this issue, this study uses a model that takes into account existing theory on constrained-optimization in credit unions and theory on the adverse effects of diffuse ownership. Using data on 36 public credit unions in Ecuador, the empirical analysis finds evidence that credit unions can achieve economies of scale despite their problematic structural features. One possible explanation for this result may stem from the level of formality in Ecuador’s financial system including its level of prudential regulation, information technology, and capital market formation. Moreover, the optimal credit union size may be a function of institutional and technological development in addition to their unique structural features. This conclusion has important implications on policies aimed at expanding credit access in developing financial markets

Qualitative Analysis of the Saltwater Aquarium Trade: The Process of Specialization Promotes Science as a Leisure Activity

Aquariums adorning the homes of hobbyists are ecosystems, specifically oriented to add a visual component to the living space. This hobby and trade utilizes animals that humans do not connect with on a regular basis. Home aquarium keeping, specifically the saltwater form of participation, requires daily contact (i.e., care) with the system and the organisms within. The captive environment facilitates contact with aquatic organisms. The main premise of this study was to investigate, using ethnographic methods, the interaction between saltwater aquarium hobbyists and the activity of at-home aquarium keeping. The serious leisure and specialization frameworks provide a guide to this study. These constructs delineate various forms of participation in other resource-oriented leisure activities such as birdwatching and boating. These hobbies affect wild resources, and when explored using specialization, managerial recommendations become evident. Due to increased focus on the aquarium industry as an under-regulated wildlife trade, these two constructs provided the opportunity to not only understand the participants in the aquarium hobby, but also identify sustainable management techniques. This study found saltwater aquarists are serious in their hobby from the onset. In addition, the ability to keep aquatic organisms alive requires the hobbyist to continuously gather information in order to maintain participation. Knowledge is obtained through research (i.e., sources) or second-hand information. Both modes rely heavily on the aquarium keeping social world. Furthermore, this study indicates saltwater aquarists are motivated to continue participation towards the pinnacle of participation, an aesthetically pleasing miniature reef display. A “mini reef” requires perseverance through stages of involvement, each building on the last. Most notably, progression towards a reef aquarium requires the aquarist to increasingly think, and act, like a scientist. In fact, a major result of this study delineated several scientifically oriented niches of specialization in which a hobbyist could demonstrate expertise. Niches provide reef hobbyists to find a place of distinction, and personal identity, within a challenging hobby populated by a number of other capable participants. In many ways, these niches resemble scientific specialties or branches of study. Further studies should aim to untangle this connection, the potential for aesthetic motivation to mediate the two, and the ability of the hobby to create scientific niches that facilitate scientific careers