Dark matter-rich early-type galaxies in the CASSOWARY 5 strong lensing system

We study the strong gravitational lensing system number 5 identified by the CASSOWARY survey. In this system, a source at redshift 1.069 is lensed into four detected images by two early-type galaxies at redshift 0.388. The observed positions of the multiple images are well reproduced by a model in which the total mass distribution of the deflector is described in terms of two singular isothermal sphere profiles. By modelling the lens galaxy spectral energy distributions, we measure the lens luminous masses and stellar mass-to-light ratios. These values are used to disentangle the luminous and dark matter components in the vicinity of the multiple images. We estimate that the dark over total mass ratio projected within a cylinder centred on the primary lens and with a radius of 12.6 kpc is 0.8 +/- 0.1. We contrast these measurements with the typical values found at similar distances (in units of the effective radius) in isolated lens galaxies and show that the amount of dark matter present in these lens galaxies is almost a factor four larger than in field lens galaxies with comparable luminous masses. Data and models are therefore consistent with interpreting the lens of this system as a galaxy group. We infer that the overdense environment and dark matter concentration in these galaxies must have affected the assembly of the lens luminous mass components. We conclude that further multi-diagnostics analyses on the internal properties of galaxy groups have the potential of providing us a unique insight into the complex baryonic and dark-matter physics interplay that rules the formation of cosmological structures.Comment: 9 pages, 6 figures; accepted for publication in MNRA

STUDENTS’ PERCEPTIONS OF THE EFFECTS OF INTERNSHIPS ON CONFIDENCE AND POST-GRADUATION OUTCOMES IN HIGHER EDUCATION

Internships as a form of experiential learning have been consistently considered a “high impact educational experience” because of the value that it provides students during their college careers (O’Neill, 2010, p. 7). Administrators and faculty professionals in colleges and universities are in positions to encourage student engagement by creating experiential learning opportunities for students that will aid them in navigating their academic major and intended career trajectory. This study focused on how a stronger emphasis on internships could influence confidence among college students, as well as play a part in their decision-making process when considering post-graduation plans. The researcher explored the various engagement means and opportunities that college students utilized in off-campus settings. The researcher conducted a qualitative study using a narrative methodology and narrowed the focus to a population of students who have participated in internship opportunities. The study was conducted at a private institution, and the researcher interviewed eight participants. The interviews were semi-structured, and three rounds of interviews took place for each participant. The participants consisted of five female and three male undergraduate students with varying academic majors Purposive and convenience sampling was used to select all participants. Findings revealed that student engagement through internships will continue to be important to the higher education landscape because it shapes students’ experience and influences their confidence, while also allowing students to experience a professional environment and make sense of their post-graduation outcomes. Future research could build upon this study by exploring how remote internships are influencing how students make sense of the workplace and whether these internships influence their confidence or post-graduation outcomes

The Optimum Design of a Vacuum-Compatible Manipulator to Calibrate Space Based Ultraviolet Imagers

Recent discoveries in geospace science have necessitated the design of compact UV imaging instruments to make space-based observations from multiple vantage points. The miniaturized ultraviolet imager (MUVI) instrument from the Space Sciences Laboratory (SSL) at UC Berkeley is under development to facilitate such discoveries on a wider scale. This thesis documents the design, integration, and characterization of a vacuum compatible manipulator to calibrate the MUVI instrument inside the UV thermal vacuum chamber at SSL. Precision linear and rotation stages were implemented with custom mounting plates to achieve four degrees of freedom. Optical components were installed to imitate the MUVI instrument for testing purposes. A customized PCB was fabricated to control the stages and receive position feedback data. A Graphical User Interface was programmed and utilized to position the manipulator during experimental validation. Field of View sweeps were conducted using visible light and a monochromatic CMOS sensor to track the coordinates of a laser\u27s centroid. An analytical model of the optics assembly was developed and later refined from the experimental results. Using this model, the translation stages successfully compensated for optical misalignments. Analysis of the performance data showed the pointing resolution of the manipulator was less than 1 arcmin, which satisfied the calibration requirement for the MUVI imager

Influence of nucleus deformability on cell entry into cylindrical structures

The mechanical properties of cell nuclei have been demonstrated to play a fundamental role in cell movement across extracellular networks and micro-channels. In this work, we focus on a mathematical description of a cell entering a cylindrical channel composed of extracellular matrix. An energetic approach is derived in order to obtain a necessary condition for which cells enter cylindrical structures. The nucleus of the cell is treated either (i) as an elastic membrane surrounding a liquid droplet or (ii) as an incompressible elastic material with Neo-Hookean constitutive equation. The results obtained highlight the importance of the interplay between mechanical deformability of the nucleus and the capability of the cell to establish adhesive bonds and generate active forces in the cytoskeleton due to myosin action