Physics Commons^™

Probing High-Momentum Protons And Neutrons In Neutron-Rich Nuclei, M. Duer, C. L. A. S. Collaboration, O. Hen, E. Piasetzky, H. Hakobyan, L. B. Weistein, M. Braverman, Gerard P. Gilfoyle, Et. Al.

Physics Faculty Publications

The atomic nucleus is one of the densest and most complex quantum-mechanical systems in nature. Nuclei account for nearly all the mass of the visible Universe. The properties of individual nucleons (protons and neutrons) in nuclei can be probed by scattering a high-energy particle from the nucleus and detecting this particle after it scatters, often also detecting an additional knocked-out proton. Analysis of electron- and proton-scattering experiments suggests that some nucleons in nuclei form close-proximity neutron–proton pairs with high nucleon momentum, greater than the nuclear Fermi momentum. However, how excess neutrons in neutron-rich nuclei form such close-proximity pairs remains unclear. …

Modified Fault Tree Method For Vulnerability Analysis Of Nuclear Medicine Facility Security System Case Study: Radiotherapy Facility, Sardjito General Hospital, Haryono Budi Santosa

International Journal of Nuclear Security

Assessing the vulnerability of physical protection systems (PPS) in nuclear medicine facilities is needed to prevent a security incident that could lead to the malicious use of nuclear material. Theft and sabotage of nuclear materials is becoming globally recognized. The current methods of assessing vulnerability tend to be oriented toward complex nuclear security; consequently, it is excessive to use such methods in simple facilities (i.e., radiotherapy facilities in hospitals).

The fault tree analysis is a method to assess vulnerability for a simple nuclear facility. The method’s primary events (i.e., basic events and undeveloped events) are able to accommodate fault causes …

Direct Collapse To Supermassive Black Hole Seeds: Comparing The Amr And Sph Approaches, Yang Luo, Kentaro Nagamine, Isaac Shlosman

Physics and Astronomy Faculty Publications

We provide detailed comparison between the adaptive mesh refinement (AMR) code ENZO-2.4 and the smoothed particle hydrodynamics (SPH)/N-body code GADGET-3 in the context of isolated or cosmological direct baryonic collapse within dark matter (DM) haloes to form supermassive black holes. Gas flow is examined by following evolution of basic parameters of accretion flows. Both codes show an overall agreement in the general features of the collapse; however, many subtle differences exist. For isolated models, the codes increase their spatial and mass resolutions at different pace, which leads to substantially earlier collapse in SPH than in AMR cases due …

Supermassive Black Hole Seed Formation At High Redshifts: Long-Term Evolution Of The Direct Collapse, Isaac Shlosman, Jun-Hwan Choi, Mitchell C. Begelman, Kentaro Nagamine

Physics and Astronomy Faculty Publications

We use cosmological adaptive mesh refinement code enzo zoom-in simulations to study the long-term evolution of the collapsing gas within dark matter haloes at z. This direct collapse process is a leading candidate for rapid formation of supermassive black hole (SMBH) seeds. To circumvent the Courant condition at small radii, we apply the sink particle method, focusing on evolution on scales ∼0.01–10 pc. The collapse proceeds in two stages, with the secondary runaway happening within the central 10 pc. The sink particles form when the collapsing gas requires additional refinement of the grid size at the highest refinement level. …

Observational Properties Of Simulated Galaxies In Overdense And Average Regions At Redshifts Z ≃ 6–12, Hidenobu Yajima, Isaac Shlosman, Emilio Romano-Díaz, Kentaro Nagamine

Physics and Astronomy Faculty Publications

We use high-resolution zoom-in cosmological simulations of galaxies of Romano-Díaz et al., post-processing them with a panchromatic three-dimensional radiation transfer code to obtain the galaxy UV luminosity function (LF) at z ≃ 6–12. The galaxies are followed in a rare, heavily overdense region within a ∼5σ density peak, which can host high-z quasars, and in an average density region, down to the stellar mass of M_star ∼ 4 × 10⁷ M_⊙. We find that the overdense regions evolve at a substantially accelerated pace – the most massive galaxy has grown to M_star ∼ 8.4 …

Supermassive Black Hole Formation At High Redshifts Via Direct Collapse In A Cosmological Context, Jun-Hwan Choi, Isaac Shlosman, Mitchell C. Begelman

Physics and Astronomy Faculty Publications

We study the early stage of the formation of seed supermassive black holes via direct collapse in dark matter (DM) haloes, in the cosmological context. We perform high-resolution zoom-in simulations of such collapse at high z. Using the adaptive mesh refinement code enzo, we resolve the formation and growth of a DM halo, until its virial temperature reaches ∼10⁴ K, atomic cooling turns on, and collapse ensues. We demonstrate that direct collapse proceeds in two stages, although they are not well separated. The first stage is triggered by the onset of atomic cooling, and leads to rapidly increasing …

Partial Differential Equations, Nathaniel James Onnen

Honors Theses

This paper will discuss methods for solving many different partial differential equations, as well as real world applications in physics. We are interested in finding solutions to the wave and heat equations in one dimension, the wave equation in two dimensions, as well as a solution to Schrodinger’s equation. In order to do this, we will study different methods including Fourier series, Bessel functions, and Hermite polynomials. I will use these methods to derive solutions for the mentioned problems, as well as to produce visualizations for many of them.

Optical-Faint, Far-Infrared-Bright Herschel Sources In The Candels Fields: Ultra-Luminous Infrared Galaxies At Z > 1 And The Effect Of Source Blending, Haojing Yan, Mauro Stefanon, Zhiyuan Ma, S. P. Willner, Rachel Somerville, Matthew L.N. Ashby, Romeel Davé, Pablo G. Pérez-González, Antonio Cava, Tommy Wiklind, Dale D. Kocevski, Marc Rafelski, Jeyhan Kartaltepe, Asantha Cooray, Anton M. Koekemoer, Norman A. Grogin

Physics and Astronomy Faculty Publications

The Herschel very wide field surveys have charted hundreds of square degrees in multiple far-IR (FIR) bands. While the Sloan Digital Sky Survey (SDSS) is currently the best resource for optical counterpart identifications over such wide areas, it does not detect a large number of Herschel FIR sources and leaves their nature undetermined. As a test case, we studied seven "SDSS-invisible," very bright 250 μm sources (S ₂₅₀ > 55 mJy) in the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey fields where we have a rich multi-wavelength data set. We took a new approach to decompose the FIR sources, using …

Getting Started With Research " Writing-Up The Results Of Your Research", Jacinta Browne

Articles

This paper gives an overview of the considerations and practical aspects of writing-up the results of your research which may be of interest to those beginning their research career or simply carrying out a research project for the first time as part of an academic qualification. It outlines practical steps for both writing-up the results of your research as an academic report and thereafter disseminating your results more widely as a peer-reviewed scientific publication.

Getting Started With Research " Beginning: Defining A Research Question And Preparing A Research Plan, Jacinta Browne

Articles

Research is the lifeblood of medicine with innovations being made in the different technologies used to diagnose and / or screen for the presence of disease or to deliver treatments with higher efficacy. Scientific publication is the network of vessels which delivers the lifeblood. The outputs of research provides us with tomorrows medicine. In this series of articles we will be discussing the different aspects of carrying out research from the conception of the research idea to publication in a peer reviewed journal with the cycle repeating again with new research ideas emerging from the research conducted.

Getting Started With Research "Carrying Out Your Research Project", Jacinta Browne

Articles

This paper gives an overview of the considerations and practical aspects of carrying out a research project which may be of use to those beginning their research career or simply carrying out a research project for the first time as part of an academic qualification. It outlines practical steps for consideration in the day to day management of a research project and highlights areas which require particular consideration for a project to be completed successfully.

High-Quality Broadband Bvri Photometry Of Benchmark Open Clusters, Michael Deloss Joner

Theses and Dissertations

Photometric techniques are often used to observe stars and it can be demonstrated that fundamental stellar properties can be observationally determined using calibrated sets of photometric data. Many of the most powerful techniques utilized to calibrate stellar photometry employ the use of stars in clusters since the individual stars are believed to have many common properties such as age, composition, and approximate distance. Broadband photometric Johnson/Cousins BVRI observations are presented for several nearby open clusters. The new photometry has been tested for consistency relative to archival work and shown to be both accurate and precise. The careful use of a …

Characteristics Cd_{0.3}Sn_{0.7}Se Thin Films As Absorber Materials For Solar Cell Devices, Salma Mahdi Shaban, Raad Mohammad Saleh, Ahmed Saleh Ahmed

Turkish Journal of Physics

Cadmium Tin Selenide compound Cd_{0.3}Sn_{0.7}Se was prepared by direct reaction of high-purity elemental Cadmium, Tin and selenium. Cd_{0.3}Sn_{0.7}Se thin films were prepared on to well-cleaned glass substrates by vacuum thermal evaporation technique at room temperature of different thicknesses. The X-ray diffraction studies revealed that all the deposited films are amorphous in nature and exhibiting polycrystalline structure when are annealed at 348 K and 373 K. The crystallites were found to have a preferred orientation along the (111) direction. The analysis of its optical characteristics indicated the ability of these films to absorb the visible light due to its graded energy …

A Review Of The Different Methods For Assessing Standing Balance, Jacinta Browne, N. J. O'Hare

Articles

This paper is a review of the balance assessment methods currently used to evaluate standing balance. Most of the presently available instrumentation appears to be more suited to research laboratories than to routine clinical situations. Functional assessments of balance appear to be the quickest test to administer and do not require expensive equipment however only gross changes in balance can be detected making them suitable as a screening tool for identifying subject’s needing more thorough evaluation. Force platforms appear to be most suited balance assessment instrumentation to the clinical situation since it produces a real time display and can detect …

Development Of A Novel Method For Assessing Balance: The Quantitative Posturography System, Jacinta Browne, Neil O'Hare

Articles

Balance is the ability to maintain equilibrium while sitting or standing. There are a number of different methods, which are used to assess balance: technical methods such as Sway Magnetometry, Ataxia Meter and Force Platforms and clinical methods such as Functional Reach Test, Berg Balance Test and Fall Risk Index. The most frequently used technical method is the force platform. There are two types of Force Platform a static and a dynamic Force Platform of which the dynamic Force Platform has been found to be more sensitive at detecting impaired balance. The Quantitative Posturography System (QPS) described in this paper …

Measured Stark Widths And Shifts Of Several Niii Sectral Lines: Temperature Dependence, Stevan Djenize, Vladimir Milosavljevic

Articles

Stark parameters (width and shift) of four doubly ionized nitrogen spectral lines, that belong to 3s-3p and 3p-3d transitions (lower multiplets), have been measured in a linear pulsed, low pressure, arc discharge in the nitrogen-oxygen and helium-nitrogen-oxygen plasmas in a (30 000 - 54 000) K electron temperature and a (0.75 10²³ - 2.8 10²³) electron density ranges. The measured values have been compared to the existing experimental and calculated data.