784 research outputs found
San Francisco Delta Risk Assessment Year 1 Report & Appendices
Get PDFThe Relative Contributions of Contaminants to Environmental Risk in the Upper San Francisco Estuary: Progress Report Year 1 and Appendices
Prepared for: The Metropolitan Water District of Southern California
Prepared by: Wayne G. Landis, Steven R. Eikenbary, Ethan A. Brown, Colter P. Lemons, Emma E. Sharpe, and April J. Markiewicz
Institute of Environmental Toxicology, Huxley College of the Environment
Western Washington University
Bellingham, WA 98225
June 30, 202
Ohio State University Law Class 1921 (group pose)
No full textFaculty: Adams, John J., Dean; Students: Beeman, Matthew G.; Bowers, Cary; Brown, Barrett F.; George, Jesse K.; Heald, Howard F.; Huston, Ernest H.; Landis, George E.; McNamara, J. Dale; Morton, E. Searles; Orr, Walter Albert; Overturf, Wayne; Paulin, Seth; Peiros, David A. ; Porter, W. Glover; Pretzman, Allen I.; Putnam, David W.; Roberts, Raymond H.; Spira, Frank; Vogelsang, Fre
A systems and molecular analysis of G protein-mediated signalling
Get PDFThe ability of cells to respond correctly to signals from their microenvironment is an
essential prerequisite of life. Many external signals are detected through G protein-coupled
receptor (GPCR) signalling pathways, which control all aspects of eukaryotic physiology.
Ligand-bound GPCRs initiate signalling by promoting exchange of GDP for GTP on the
Gα subunit of heterotrimeric G proteins, thereby facilitating activation of downstream
effectors. Signalling is terminated by the hydrolysis of GTP to GDP through intrinsic
GTPase activity of the Gα subunit, in a reaction catalysed by the regulator of G protein
signalling (RGS) proteins.
Due to the problem of complexity in higher eukaryotic GPCR signalling, the matingresponse
in Schizosaccharomyces pombe has been used to study GPCR signalling in isolation.
In vivo data from quantitative assays of reporter strains and live-cell
uorescence
microscopy informs the development of an ordinary differential equation model of the signalling
pathway, first described by Smith et al., 2009.
The rate of nucleotide exchange on the Gα (Gpa1) is a key molecular mechanism controlling
duration and amplitude of signalling response. The in
uence of this is investigated
through characterisation of Gpa1 nucleotide exchange mutants and perturbation of reaction
rate parameters in the computational model. Further, this thesis also presents data
relating to the temporal and spatial regulation of Rgs1 (the sole RGS protein for Gpa1).
Using an inter-disciplinary approach, evidence is provided to suggest that an interaction
between Rgs1 and the C-terminal tail of the GPCR (Mam2) tethers Rgs1 to the plasma
membrane to facilitate its function.
Finally, quantification of signalling at the single cell level is described. Time-lapse livecell
imaging of
uorescent reporter cells is optimised and single cell signalling response
quantified using image analysis software. Single cell quantification provides greater insight
into temporal dynamics, cell-to-cell variability, and highlights the existence of mechanisms
for cellular decision-making
The Origin, Development, Application, Lessons Learned, and Future Regarding the Bayesian Network Relative Risk Model for Ecological Risk Assessment
Get PDFIn 2012, a regional risk assessment was published that applied Bayesian networks (BN) to the structure of the relative risk model. The original structure of the relative risk model (RRM) was published in the late 1990s and developed during the next decade. The RRM coupled with a Monte Carlo analysis was applied to calculating risk to a number of sites and a variety of questions. The sites included watersheds, terrestrial systems, and marine environments and included stressors such as nonindigenous species, effluents, pesticides, nutrients, and management options. However, it became apparent that there were limits to the original approach. In 2009, the relative risk model was transitioned into the structure of a BN. Bayesian networks had several clear advantages. First, BNs innately incorporated categories and, as in the case of the relative risk model, ranks to describe systems. Second, interactions between multiple stressors can be combined using several pathways and the conditional probability tables (CPT) to calculate outcomes. Entropy analysis was the method used to document model sensitivity. As with the RRM, the method has now been applied to a wide series of sites and questions, from forestry management, to invasive species, to disease, the interaction of ecological and human health endpoints, the flows of large rivers, and now the efficacy and risks of synthetic biology. The application of both methods have pointed to the incompleteness of the fields of environmental chemistry, toxicology, and risk assessment. The low frequency of exposure‐ response experiments and proper analysis have limited the available outputs for building appropriate CPTs. Interactions between multiple chemicals, landscape characteristics, population dynamics and community structure have been poorly characterized even for critical environments. A better strategy might have been to first look at the requirements of modern risk assessment approaches and then set research priorities. Integr Environ Assess Manag 2021;17:79–94. © 2020 SETA
Άbdul-Ramān al-Şūfī and his Book of the Fixed Stars: a journey of re-discovery
No full textThe Book of the Fixed Stars was written by the Persian astronomer Άbdul-Ramān al-Şūfī around AD 964, and is one of the most important medieval Arabic treatises on astronomy. al-Şūfī's work contains an extensive star catalog as well as detailed star charts for the 48 classical constellations, and draws on material in Ptolemy's Almagest. At present no English translation of al-Şūfī's treatise exists. This paper summarizes a detailed study by the first author for a Ph.D. degree in the Center of Astronomy at James Cook University (Townsville, Australia) which will include for the first time a complete English translation of the main parts of al-Şūfī's major work.
This paper includes a brief biography of al-Şūfī, along with information on the extant manuscripts of the Book of the Fixed Stars, the structure of the book and star catalogue, and the star maps and charts. A major finding which we highlight in this paper is al-Şūfī's stellar magnitude estimates which were based upon a unique three-step intermediate magnitude system that he developed. al-Şūfī also identified and commented on more than one hundred new stars that were not listed in the Almagest or other early star catalogs. al-Şūfī's contribution to astronomy reverberated throughout history, extending to recent times
- …
