An interferometric study of molecular emission around ngc 7538 at millimeter wavelengths

A basic premise of this thesis is to use the techniques of millimeter interferometry to probe the high density regions around newly formed stars. The technique is invaluable since the spatial resolution of an interferometer allows the study of small scale density enhancements in the molecular cloud that could provide the conditions for maser excitation. In addition to the detailed density structure, the millimeter continuum observations provide a tool for modeling the H II region and for calculating parameter~ such as electron density, electron temperature, and emission measure, which are useful in determining the excitation mechanism for the maser emission.Ope

First Interferometric Images of the 36 GHz Methanol Masers in the DR21 Complex

Class I methanol masers are believed to be produced in the shock-excited environment around star-forming regions. Many authors have argued that the appearance of various subsets of class I masers may be indicative of specific evolutionary stages of star formation or excitation conditions. Until recently, however, no major interferometer was capable of imaging the important 36 GHz transition. We report on Expanded Very Large Array observations of the 36 GHz methanol masers and Submillimeter Array observations of the 229 GHz methanol masers in DR21(OH), DR21N, and DR21W. The distribution of 36 GHz masers in the outflow of DR21(OH) is similar to that of the other class I methanol transitions, with numerous multitransition spatial overlaps. At the site of the main continuum source in DR21(OH), class I masers at 36 and 229 GHz are found in virtual overlap with class II 6.7 GHz masers. To the south of the outflow, the 36 GHz masers are scattered over a large region but usually do not appear coincident with 44 GHz masers. In DR21W we detect an "S-curve" signature in Stokes V that implies a large value of the magnetic field strength if interpreted as due to Zeeman splitting, suggesting either that class I masers may exist at higher densities than previously believed or that the direct Zeeman interpretation of S-curve Stokes V profiles in class I masers may be incorrect. We find a diverse variety of different maser phenomena in these sources, suggestive of differing physical conditions among them.Comment: 8 pages, accepted for publication in Ap

Health Risks of Limited-Contact Water Recreation

Background: Wastewater-impacted waters that do not support swimming are often used for boating, canoeing, fishing, kayaking, and rowing. Little is known about the health risks of these limited-contact water recreation activities

Entity-Enriched Neural Models for Clinical Question Answering

We explore state-of-the-art neural models for question answering on electronic medical records and improve their ability to generalize better on previously unseen (paraphrased) questions at test time. We enable this by learning to predict logical forms as an auxiliary task along with the main task of answer span detection. The predicted logical forms also serve as a rationale for the answer. Further, we also incorporate medical entity information in these models via the ERNIE architecture. We train our models on the large-scale emrQA dataset and observe that our multi-task entity-enriched models generalize to paraphrased questions ~5% better than the baseline BERT model

Information Security and Privacy in the Digital World: Some Selected Topics

In the era of generative artificial intelligence and the Internet of Things, while there is explosive growth in the volume of data and the associated need for processing, analysis, and storage, several new challenges are faced in identifying spurious and fake information and protecting the privacy of sensitive data. This has led to an increasing demand for more robust and resilient schemes for authentication, integrity protection, encryption, non-repudiation, and privacy-preservation of data. The chapters in this book present some of the state-of-the-art research works in the field of cryptography and security in computing and communications.Comment: Published by IntechOpen, London Uk in Nov 2023, the book contains 8 chapters spanning over 131 pages. arXiv admin note: text overlap with arXiv:2307.02055, arXiv:2304.0025

Multispecific Antibody Development Platform Based on Human Heavy Chain Antibodies

Heavy chain-only antibodies (HCAbs) do not associate with light chains and their VH regions are functional as single domains, forming the smallest active antibody fragment. These VH regions are ideal building blocks for a variety of antibody-based biologics because they tolerate fusion to other molecules and may also be attached in series to construct multispecific antibodies without the need for protein engineering to ensure proper heavy and light chain pairing. Production of human HCAbs has been impeded by the fact that natural human VH regions require light chain association and display poor biophysical characteristics when expressed in the absence of light chains. Here, we present an innovative platform for the rapid development of diverse sets of human HCAbs that have been selected in vivo. Our unique approach combines antibody repertoire analysis with immunization of transgenic rats, called UniRats, that produce chimeric HCAbs with fully human VH domains in response to an antigen challenge. UniRats express HCAbs from large transgenic loci representing the entire productive human heavy chain V(D)J repertoire, mount robust immune responses to a wide array of antigens, exhibit diverse V gene usage and generate large panels of stable, high affinity, antigen-specific molecules

An interferometric study of molecular emission around NGC 7538 at millimeter wavelengths

NGC 7538 is a visible H II region with an associated molecular cloud, situated in the Perseus arm of the Galaxy. A group of infrared sources, IRS 1, IRS 2, and IRS 3, is situated at the interface between the molecular cloud and the visible nebula. Maser emission from OH, H\sb2O, H\sb2CO, CH\sb3OH, and NH\sb3 has been detected toward IRS 1. In order to examine the model for the excitation of the formaldehyde (H\sb2CO) maser, proposed by Boland and de Jong (1981), interferometric observations of the cloud around IRS 1 have been made in the J = 1-0 transitions of HCN, HCO\sp{+}, and \sp{13}CO. The HCN and HCO\sp{+} maps show the presence of a cavity around IRS 1 which is not seen in the \sp{13}CO maps. Since HCN and HCO\sp{+} trace densities $>$10\sp5 cm\sp{-3}, the cavity indicates a lack of high density material around the H II region. Continuum observations at 88 GHz and 110 GHz result in a 2-component model for the H II region. There is a cool, extended component toward which all the masers are seen. The parameters calculated for this component, along with the H\sb2 densities ($\sim$10\sp4 cm\sp{-3}) from the molecular observations, were put into the H\sb2CO master model. The results show that the H\sb2CO gas must be at a distance of 0.011 pc from the H II region for maximum inversion in the H\sb2CO transition and the abundance of H\sb2CO relative to H\sb2 must be $\sim$4 $\times$ 10\sp{-7}.The molecular observations also show that the molecular cloud is extremely clumpy. These clumps around IRS 1 could provide the varying densities required for the other masers observed in the region. The HCO\sp{+} results also indicate the presence of a high density molecular outflow which originates about 15" south of IRS 1. The position angle of the outflow agrees with that of a CO outflow detected toward this source. The results imply that there may be another source powering the outflow which is situated south of IRS 1. The new source appears to be situated at the center of an elongated structure, also seen in HCO\sp{+}, which is oriented perpendicular to the direction of the outflow.U of I OnlyETDs are only available to UIUC Users without author permissio

Radio Astronomy: A Strong Link Between Undergraduate Education and Research

The program at the MIT Haystack Observatory has added a new opportunity for students as part of our overall national effort to encourage research by undergraduates. Radio astronomy complements other branches of astronomy, augments science education broadly, and serves to promote interdisciplinary research and education. In the past 2 years, we have conducted a successful pilot program to develop and test a program that facilitates the linking of undergraduate research and education through radio astronomy. As a result of this effort, ² a small radio telescope has been developed and can be used as a hands-on introduction to radio astronomical techniques and instrument calibration. The telescope is presently being commercialized so that it can be purchased as a low-cost kit for assembly. ² Remote access to the Haystack 37-m antenna has made it possible for students nationwide to access a research grade facility and we invite faculty everywhere who are interested in this possibility to use our facility. Undergraduate students can participate in the exciting world of research by performing experiments with the telescope. ² Radio astronomy materials for faculty, students, and interested amateurs have been developed are posted on our web site (http://www.haystack.mit.edu). The materials will continue to be upgraded and enhanced, and the contributions from participating teachers and students nationwide will be added to the project files. We hope to make this not only a resource for someone using our facility but also for the community in general. We are now bringing the Haystack telescopes and radio astronomy to the broad undergraduate community. Based on our pilot experiences, we envision students everywhere being able to exploit the opportunity to strengthen their education through practical research using radio astronomy

The Educational Role of Small Telescopes in Radio Astronomy

Radio astronomy provides an excellent educational opportunity for students since it exposes them to multi-disciplinary principles found in engineering, physics and mathematics. Motivated by the potential for exciting discovery through astronomical observations, students learn through the process of making measurements, analyzing the data, and interpreting the observations. Observing tools in radio astronomy, however, have not been generally or easily accessible to students, particularly at the undergraduate or pre-college levels, since the number of radio telescopes and the availability of time on these telescopes have been limited. In order to resolve this problem, the MIT Haystack Observatory has developed a small radio telescope (SRT) that can be assembled as a kit by students and used in basic observations that help train them in the techniques of radio astronomy. The Haystack SRT and the experiments that can be conducted with it are described in this chapter, and its important role in training students in the use of larger telescopes for research is discussed