A Constraint Programming Approach to the Hospitals / Residents Problem

An instance I of the Hospitals / Residents problem (HR) involves a set of residents (graduating medical students) and a set of hospitals, where each hospital has a given capacity. The residents have preferences for the hospitals, as do hospitals for residents. A solution of I is a stable matching, which is an assignment of residents to hospitals that respects the capacity conditions and preference lists in a precise way. In this paper we present constraint encodings for HR that give rise to important structural properties. We also present a computational study using both randomly-generated and real-world instances. Our study suggests that Constraint Programming is indeed an applicable technology for solving this problem, in terms of both theory and practice

Optical angular momentum in air core fibers

As data consumption continues to grow, the backbone of the internet, comprising single mode fiber (SMF)-based infrastructure, is fundamentally limited by nonlinear optical effects. One strategy to address this bottleneck, space division multiplexing (SDM), utilizes multiple modes in a single fiber as independent data channels. Orbital Angular Momentum (OAM) carrying modes, which have twisting phase fronts tracing out helices as the beams propagate, have recently received tremendous attention as a means of achieving low-crosstalk, digital signal processing (DSP)-free transmission with enhanced capacity. Terabit-scale transmission using 4 OAM modes over 1.1km has been demonstrated, but questions remain – how many OAM modes can fibers support, and how stable is propagation over longer lengths? In this thesis, we investigate angular momentum carrying modes in a novel class of fibers featuring an air core. We find that high-order OAM states, although arising in degenerate pairs, counterintuitively resist mode coupling due to OAM conservation, pointing to a unique stability inherent to OAM modes in fibers. We achieve OAM propagation up to 13.4km lengths, and achieve mode purities greater than 15dB at data-center length-scales. We use these fibers to transmit wavelength-division multiplexed data with 25 GHz channel spacing, 10 GBaud rates and quadrature-phase-shift keyed modulation formats in 12 modes simultaneously, over 1.2km, and over a large number of wavelengths across the C-band (1530-1565nm). However, transmission over every mode in every channel of the C-band was prevented by the accidental degeneracy of OAM states with undesired modes. To achieve a larger ensemble of stable modes over a larger wavelength range, we study new fiber designs that avoid this accidental degeneracy problem. We find that the most scalable modal eigenbasis is a set of states that carry non-integer amounts of average OAM, also called spin-orbit coupled modes in analogy with similar effects observed in atomic physics. We demonstrate excitation and transmission of 24 such modes over device lengths (10m). The achievement of a record number of uncoupled modes in fibers confirms the viability of angular momentum states as data carriers, and potential applications include links in data centers, high capacity optical amplifiers, and quantum communications links.2017-09-09T00:00:00

Interview of John P. Rossi, Ph.D.

Dr. John Patrick Rossi was born in Philadelphia in 1936 to Gabriel (Al) and Muriel Rossi. He was raised by two aunts, an uncle, and his grandfather in lower Olney. He attended La Salle College High School, received his B. A. in history from La Salle College in 1958, his M. A. from Notre Dame in 1960, and his Ph.D. in History from the University of Pennsylvania in 1965. His dissertation was on the British Liberal Party from 1874 to 1880. He began teaching at La Salle College in 1962; was associate editor of Four Quarters ; received the Lindback Award; developed popular classes on World War II, baseball history, and George Orwell; and served as History Department chair. He has published many works on the British Liberal Party, baseball history, Orwell, and other topics. After retiring, he received the honorable title Professor Emeritus

The Relational Exchange Model for Academic Partnerships (REMAP): A Transition from Transactional to Transformational Relationships Between PK-12 School Districts and Institutions of Higher Education

Education is in an incredible time of transition. Even prior to the COVID-19 pandemic, there was mounting importance on the need for professional development to meet the ever-increasing demands of students, families, and communities along with ongoing accountability and improvement measures. This increased need of professional development for educators in PK-12 school districts has only accelerated in the wake of COVID-19. Considering this need, a new model for sustainable, mutually beneficial, relationships between PK-12 school districts and Institutions of Higher Education (IHE) is critical. A movement from the currently existing, singularly beneficial, transactional finite relationships to a sustained, mutually beneficial, transformational dyadic relationship will provide growth opportunities for both PK-12 districts and IHE’s. The proposed Relational Exchange Model for Academic Partnerships provides a conceptual framework for how PK-12 school districts and IHE’s can establish and maintain meaningful, and transformational, relationships at the organizational level

Habitat Use by Juvenile Gag, Mycteroperca microlepis (Pisces: Serranidae), in Subtropical Charlotte Harbor, Florida (USA)

Estuaries play a key role in the juvenile stage of gag (Myeteroperca microlepis). The use of estuarine habitats by juvenlle gag has been examined in temperate estuaries, which are at the northern limits of the range of this species, but the importance of subtropical estuaries during the early life history of this species has not been studied extensively. Gag were collected in subtropical Charlotte Harbor, Florida, during routine monthiy sampling from January 1996 to Decemher 2002. Juvenlle gag were collected using a 21.3-m seine, a 183-m haul seine, and a 183-m purse seine. A total of 738 individuals ranging from 30 to 489 mm standard length (SL) were collected in 4,480 samples. Most gag (96%) were probably young-of-the-year (\u3c 288 mm SL). The majority of juveniles were collected in polyhaline Gasparilla and Pine Island sounds from April to December, with a few larger individuals captured year-round. The observed period of gag settlement was similar to thet reported in other subtropical and temperate estuaries, but gag in Charlotte Harbor remained in the estuary longer and egressed at a larger size than did gag in other estuaries. Relative abundance of juvenile gag within Charlotte Harbor was greatest on shallow seagrass shoals but was also high along flinging mangrove shorelines, which is a habitat not previously reported for gag

Observation of Interaction of Spin and Intrinsic Orbital Angular Momentum of Light

Interaction of spin and intrinsic orbital angular momentum of light is observed, as evidenced by length-dependent rotations of both spatial patterns and optical polarization in a cylindrically-symmetric isotropic optical fiber. Such rotations occur in straight few-mode fiber when superpositions of two modes with parallel and anti-parallel orientation of spin and intrinsic orbital angular momentum (IOAM=$2\hslash$) are excited, resulting from a degeneracy splitting of the propagation constants of the modes.Comment: 6 pages, 5 figures, and a detailed supplement. Version 3 corrects a typo and adds the journal referenc

Intergalactic Globular Clusters

We confirm and extend our previous detection of a population of intergalactic globular clusters in Abell 1185, and report the first discovery of an intergalactic globular cluster in the nearby Virgo cluster of galaxies. The numbers, colors and luminosities of these objects can place constraints on their origin, which in turn may yield new insights to the evolution of galaxies in dense environments.Comment: 2 pages, no figures. Talk presented at JD6, IAU General Assembly XXV, Sydney, Australia, July 2003, to appear in Highlights of Astronomy, Vol. 1

The role of spatial embedding in mouse brain networks constructed from diffusion tractography and tracer injections

Diffusion MRI tractography is the only noninvasive method to measure the structural connectome in humans. However, recent validation studies have revealed limitations of modern tractography approaches, which lead to significant mistracking caused in part by local uncertainties in fiber orientations that accumulate to produce larger errors for longer streamlines. Characterizing the role of this length bias in tractography is complicated by the true underlying contribution of spatial embedding to brain topology. In this work, we compare graphs constructed with ex vivo tractography data in mice and neural tracer data from the Allen Mouse Brain Connectivity Atlas to random geometric surrogate graphs which preserve the low-order distance effects from each modality in order to quantify the role of geometry in various network properties. We find that geometry plays a substantially larger role in determining the topology of graphs produced by tractography than graphs produced by tracers. Tractography underestimates weights at long distances compared to neural tracers, which leads tractography to place network hubs close to the geometric center of the brain, as do corresponding tractography-derived random geometric surrogates, while tracer graphs place hubs further into peripheral areas of the cortex. We also explore the role of spatial embedding in modular structure, network efficiency and other topological measures in both modalities. Throughout, we compare the use of two different tractography streamline node assignment strategies and find that the overall differences between tractography approaches are small relative to the differences between tractography- and tracer-derived graphs. These analyses help quantify geometric biases inherent to tractography and promote the use of geometric benchmarking in future tractography validation efforts

Spatial scaling metrics of mask-induced induced line-edge roughness

Mask contributors to line-edge roughness (LER) have recently been shown to be an issue of concern for both the accuracy of current resist evaluation tests as well the ultimate LER requirements for the 22-nm production node. Problems arise from mask absorber LER as well as mask reflector or surface roughness leading to random phase variations in the reflected beam. Not only do these mask contributors effect to total measured LER in resist, but they also effect LER spatial characteristic such as the LER power spectral density and related descriptors of correlation length and roughness exponent. Noting that these characteristics are important in the understanding of LER, it is crucial to understand how mask effects impact these parameters. Moreover, understanding how these metrics respond to mask effects may lead to an experimental mechanism for experimentally evaluating the importance of mask contributors to LER. Here we use computer modeling to study the LER spatial metrics arising from mask effects. We further describe the effects of illumination conditions and defocus on the metrics and compare the results to those expected from intrinsic resist LER

A Home Device for Vestibular Stimulation

The goal of this project, which was presented to the team by Kevin Maher (President of Advanced Therapeutic devices), was to develop a product prototype for safe, vestibular stimulation for children with developmental disabilities. Vestibular stimulation is a form of therapy that increases muscle coordination. It works by stimulating the canals and sacs within the inner ear that detect accelerations. The project targeted children from ages two to seven years old, under 48 inches tall, and less than 100 lbs. The production device also sought to differ from stimulation devices found in hospitals in a few respects: it would cost under $5000, reside in a patient’s home, be hand-powered, and be controlled by an average person. The final device needed to support a 200 lb. load at the edge of the structure and adjust for the center of gravities for the range of children. After sessions of brainstorming, the team produced three workable layouts, only one was adequate. The final setup had a structure of ¼ in. aluminum structural pipe similar to a football field goal. This structure mounted on a single bearing housing and steel shaft. The final design had two bars to mount weights in order to adjust the center of gravity. The prototype, however, used a swinging bar, lock, and a sliding weight. The final prototype had an adjustable footrest and a five-point restraint harness. The final cost and weight was$1700 and no more than 500 lb. The design met all of the requirements and had adequate safety for any child’s needs, but the team thought the design needed significant changes before it became a final product