The behavioral responses of the fiddler crab, UCA PUGILATOR, to ionizing irradiation

Thesis (M.A.)--Boston University. Note: Page 24 is missing.Many animals, invertebrates as well as vertebrates, have demonstrated an ability to somehow sense ionizing irradiation. This recognition is often apparent by a behavioral response which can be correlated with the x-ray stimulus in some way. The fiddler crab, Uca pugilator, was found to exhibit a behavioral response to ionizing irradiation. When the x-ray machine was turned off, the animal would respond instantaneously by a marked hesitation in its general movement after which it would resume its normal activity. This response suggests the animal's ability to somehow be aware of irradiation. Previous work in this area suggested that the photoreceptors were the primary site of stimulation. The fiddler crab's photoreceptors, located at the ends of protruding eye-stalks, are particularly easily excised. When the eye stalks were rer1oved, the response to x-rays was no longer evident. A parallel series of experiments were done with ltght as the stimulus. With intact eyestalks, the animal showed the same off response, and with the eyestalk removed, the subject exhibited no such response. The possibility of a direct stimulation of nervous structures as well as that of an indirect activation by the x-ray evoked release of bioactive substances is discussed. After considering the sinus gland, which was also removed along with the photoreceptors, as a possible site of x-ray reception, a strong implication that the photoreceptors are the primary locus of x-ray sensitivity in the fiddler crab was stated. The marked dose rate dependency of the animal's response to x-rays was noted, and a possible explanation was suggested

ENCOMPASS: A SAGA based environment for the compositon of programs and specifications, appendix A

ENCOMPASS is an example integrated software engineering environment being constructed by the SAGA project. ENCOMPASS supports the specification, design, construction and maintenance of efficient, validated, and verified programs in a modular programming language. The life cycle paradigm, schema of software configurations, and hierarchical library structure used by ENCOMPASS is presented. In ENCOMPASS, the software life cycle is viewed as a sequence of developments, each of which reuses components from the previous ones. Each development proceeds through the phases planning, requirements definition, validation, design, implementation, and system integration. The components in a software system are modeled as entities which have relationships between them. An entity may have different versions and different views of the same project are allowed. The simple entities supported by ENCOMPASS may be combined into modules which may be collected into projects. ENCOMPASS supports multiple programmers and projects using a hierarchical library system containing a workspace for each programmer; a project library for each project, and a global library common to all projects

Manual pages for SAGA software tools, appendix H

Several pages from the SAGA UNIX programmer's manual are presented. These pages are for SAGA software tools

SAGA: A project to automate the management of software production systems

The SAGA system is a software environment that is designed to support most of the software development activities that occur in a software lifecycle. The system can be configured to support specific software development applications using given programming languages, tools, and methodologies. Meta-tools are provided to ease configuration. The SAGA system consists of a small number of software components that are adapted by the meta-tools into specific tools for use in the software development application. The modules are design so that the meta-tools can construct an environment which is both integrated and flexible. The SAGA project is documented in several papers which are presented

Structure of the Mg-Chelatase Cofactor GUN4 Reveals a Novel Hand-Shaped Fold for Porphyrin Binding

In plants, the accumulation of the chlorophyll precursor Mg-protoporphyrin IX (Mg-Proto) in the plastid regulates the expression of a number of nuclear genes with functions related to photosynthesis. Analysis of the plastid-to-nucleus signaling activity of Mg-Proto in Arabidopsis thaliana led to the discovery of GUN4, a novel porphyrin-binding protein that also dramatically enhances the activity of Mg-chelatase, the enzyme that synthesizes Mg-Proto. GUN4 may also play a role in both photoprotection and the cellular shuttling of tetrapyrroles. Here we report a 1.78-Å resolution crystal structure of Synechocystis GUN4, in which the porphyrin-binding domain adopts a unique three dimensional fold with a “cupped hand” shape. Biophysical and biochemical analyses revealed the specific site of interaction between GUN4 and Mg-Proto and the energetic determinants for the GUN4 • Mg-Proto interaction. Our data support a novel protective function for GUN4 in tetrapyrrole trafficking. The combined structural and energetic analyses presented herein form the physical-chemical basis for understanding GUN4 biological activity, including its role in the stimulation of Mg-chelatase activity, as well as in Mg-Proto retrograde signaling

Environmental changes and the rise and fall of civilizations in the northern Horn of Africa: an approach combining δD analyses of land-plant derived fatty acids with multiple proxies in soil

International audienceThe domains of the ancient polities D'MT and Aksum in the Horn of Africa's highlands are a superior natural system for evaluating roles of environmental change on the rise and fall of civilizations. To compare environmental changes of the times of the two polities, we analyzed stable hydrogen isotopic ratios (δD) of land-plant derived fatty acids (n-C26-30) and other proxies from soil sequences spanning the Holocene from the region. Three results suggest that trends in δD values unambiguously reflect changes in rainfall. First, increases in δD coincide with dry periods inferred from studies of eastern African lakes. Second, changes in δD values were parallel among sections during overlapping time intervals. Third, consideration of vegetation history did not alter directions of trends in δD values over time. By unambiguously recording precipitation, the δD values also enhanced interpretations of proxies that are affected by both climate and land clearing. Both D'MT (ca 2750-2350 cal y BP) and the Aksumite (ca 2100-1250 cal y BP) rose during wetter intervals of the drier part of the Holocene (after ca 6000 cal y BP). Analyses of charred matter indicated that fire had been a common agent of land clearing in all sites. The influence of climate on fire varied, however. Prior to the emergence of D'MT, δD values were correlated with C4:C3 plant ratios estimated from δ13C values. There are no C4 trees and precipitation may have been the main influence on canopy openness. After ca 4300 cal y BP, there was no significant relationship between δD and C4:C3 plant ratios suggesting that factors such as fire influenced canopy openness regardless of climate. Furthermore, the impact of land clearance differed between sites and between D'MT and the Aksumite's times. In one site, the interval from 3550 cal y BP to the decline of D'MT had several anomalies that suggested dramatic increases in thermal severity of fire and human impact. Among these were a large contribution of charred matter to a high% total organic carbon that low hydrogen and oxygen indices suggest was severely altered by other factors than humification. These results support hypotheses about the rise of civilizations being favored by specific climatic conditions but suggest that patterns of land clearing differed during the declines of D'MT and the Aksumite

Supporting Undergraduate Research for Globally Distributed Students and Mentors

Undergraduate research is widely viewed as a high-impact practice. However, participation in undergraduate research among students completing degree programs exclusively online may be impeded due to barriers such as access limitations, time poverty, and adequate institutional support. Through an NSF I-USE project (#2021221), we formed a framework of support, including a research independent study course and a mentoring program, where we deliberately separated and defined the roles of research supervisor and research mentor. In this session, we will discuss interview data on the experiences of faculty and students in both the credit-bearing active research as well as the non-credit-bearing research mentoring program, highlighting both successes and growth areas. We will also share our ideas for moving forward with undergraduate research support for fully online students and our plans for navigating the hurdles we know are coming

Breeding Birds in Cedar Stands in the Great Dismal Swamp

The Great Dismal Swamp located in the coastal plain on the Virginia- North Carolina border, has long been recognized as a vegetationally distinctive region with many unusual geological and biological features. Formerly at least twice the currently estimated size of 85,000 hectares (Carter 1979), the Great Dismal Swamp is still shrinking because of a dropping water table caused by more than 200 years of logging, ditching, and other human activities. In 1973, the Union Camp Corporation donated a 19,871-hectare tract located near Suffolk, Virginia. to The Nature Conservancy, which transferred the land to the U.S. Fish and Wildlife Service. This parcel, all in Virginia and including the 1255-hectare Lake Drummond, became the core of the Great Dismal Swamp National Wildlife Refuge (hereafter, G.D.S.N.W.R.), established in 1974. The G.D.S.N.W.R. is still growing in size by the acquisition of land by purchase or by gift; by the end of 1980, it was 41,026 hectares, with 24 per cent (9866 hectares) in North Carolina

Undergraduate Research in a Fully Online Engineering Program: Building the Framework of Support

Undergraduate engineering programs often face low persistence and retention. Females and ethnic minorities are underrepresented and show lower persistence Certain minorities may be less likely to enroll in online programs Lower persistence and retention in online students across disciplines Undergraduate research may increase persistence and retention. Online students likely underrepresented due to access limitation

Guiding Undergraduate Researchers in the Virtual World: Mentoring Experiences of Globally Distributed Students

The advancement of technology has led to an increase in undergraduate students pursuing degrees online. The translation of undergraduate research to the online environment is relatively new, though gaining momentum, partly due to the COVID-19 pandemic. Mentoring is a key undergraduate research support, particularly for those engaged online, as it fosters a supportive environment for online students to develop their skills and knowledge in their field of study. This study aims to explore the positive impacts of mentoring undergraduate research for fully online students. A single case study methodology was used, with interview data collected from four research mentees completing their degrees fully online. While this study is exploratory and further research with a larger sample size is necessary, the preliminary findings suggest that virtual mentoring can lead to a stronger sense of belonging, enhanced understanding of research processes, professional development (including career path and transferable skills), and continuous personal growth. These results highlight the importance of providing research mentoring opportunities to online students