An optical communications link

Includes bibliographical references.The thesis describes the development of a specification for, and prototypes of, an opto-electric voice communications link. The introductory sections deal with the generalised optical communications channel, the available hardware, and some of the research that has been done in the field. The information presented is used to motivate the type of system to be developed. The emphasis is placed on cost, though not as an overriding consideration. Modulation systems are examined, and frequency modulation of an m.f. subcarrier is chosen. The development of the practical system is covered in detail, in particular the receiver frontend circuitry. Considerable discrepancies between the design figures and actual measured performance are analysed, and their causes located. A practical mechanical design is presented, with suggested modifications for production. In conclusion, future developments in the field are examined

Optimal Estimation of Several Linear Parameters in the Presence of Lorentzian Thermal Noise

In a previous article we developed an approach to the optimal (minimum variance, unbiased) statistical estimation technique for the equilibrium displacement of a damped, harmonic oscillator in the presence of thermal noise. Here, we expand that work to include the optimal estimation of several linear parameters from a continuous time series. We show that working in the basis of the thermal driving force both simplifies the calculations and provides additional insight to why various approximate (not optimal) estimation techniques perform as they do. To illustrate this point, we compare the variance in the optimal estimator that we derive for thermal noise with those of two approximate methods which, like the optimal estimator, suppress the contribution to the variance that would come from the irrelevant, resonant motion of the oscillator. We discuss how these methods fare when the dominant noise process is either white displacement noise or noise with power spectral density that is inversely proportional to the frequency ($1/f$ noise). We also construct, in the basis of the driving force, an estimator that performs well for a mixture of white noise and thermal noise. To find the optimal multi-parameter estimators for thermal noise, we derive and illustrate a generalization of traditional matrix methods for parameter estimation that can accommodate continuous data. We discuss how this approach may help refine the design of experiments as they allow an exact, quantitative comparison of the precision of estimated parameters under various data acquisition and data analysis strategies.Comment: 16 pages, 10 figures. Accepted for publication in Classical and Quantum Gravit

Respiration cycle duration and seawater flux through open blowholes of humpback (Megaptera novaeangliae) and North Atlantic right (Eubalaena glacialis) whales

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Martins, M. C. I., Miller, C., Hamilton, P., Robbins, J., Zitterbart, D. P., & Moore, M. Respiration cycle duration and seawater flux through open blowholes of humpback (Megaptera novaeangliae) and North Atlantic right (Eubalaena glacialis) whales. Marine Mammal Science, (2020): 1-20, doi:10.1111/mms.12703.Little is known about the dynamics of baleen whale respiratory cycles, especially the mechanics and activity of the blowholes and their interaction with seawater. In this study, the duration of complete respiration cycles (expiration/inhalation events) were quantified for the first time in two species: North Atlantic right whale (NARW) and humpback whale (HW) using high resolution, detailed imagery from an unoccupied aerial system (UAS). The mean duration of complete respiration cycles (expiration/inhalation event) in the NARW and HW were 3.07 s (SD = 0.503, n = 15) and 2.85 s (SD = 0.581, n = 21), respectively. Furthermore, we saw no significant differences in respiration cycle duration between age and sex classes in the NARW, but significant differences were observed between age classes in the HW. The observation of seawater covering an open blowhole was also quantified, with NARW having 20% of all breaths with seawater presence versus 90% in HW. Seawater incursion has not been described previously and challenges the general consensus that water does not enter the respiratory tract in baleen whales. Prevalent seawater has implications for the analysis and interpretation of exhaled respiratory vapor/mucosa samples, as well as for the potential inhalation of oil in spills.Samples were collected under NMFS NOAA Permits 17355, 17355‐01, and 21371, and with approval from the Woods Hole Oceanographic Institution Institutional Animal Care and Use Committee. Funding by Ocean Life Institute of the Woods Hole Oceanographic Institution, NOAA NA14OAR4320158 and University College London Master of Research in Biodiversity, Evolution and Conservation program

Entanglements of North Atlantic right whales increase as their distribution shifts in response to climate change: The need for a new management paradigm [poster]

Presented at 2019: World Marine Mammal Science Conference, Barcelona, Spain, December 9-12, 2019.Detection rate of severely injured or entangled NARWs began to increase around 2004 - 2007.We thank the North Atlantic Right Whale Consortium for data curation and dissemination, and the Atlantic Large Whale Disentanglement Network for entanglement sighting information

Fatally entangled right whales can die extremely slowly

Author Posting. © IEEE, 2006. This article is posted here by permission of IEEE for personal use, not for redistribution. The definitive version was published in Proceedings Oceans 2006, Boston, MA, USA, 3 pp, doi:10.1109/OCEANS.2006.306792.Unlike smaller marine mammals that lack the mass and power to break free from serious entanglements in fixed fishing gear, right whales can do so, but they are not always rope free. The remaining rope can gradually constrict one or more body parts and the resulting debilitation and ultimate death can take many months. Thus the practices that lead to these mortalities need to be viewed not only as a conflict between the cultural and socioeconomic value of a fishery versus a potential species extinction process, but also in terms of an extreme animal welfare issue.Supported by NOAA NA04NMF4720392, Woods Hole Oceanographic Institution Ocean Life Institute, and the North Pond Foundation

Larger females have more calves: influence of maternal body length on fecundity in North Atlantic right whales

© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Stewart, J., Durban, J., Europe, H., Fearnbach, H., Hamilton, P., Knowlton, A., Lynn, M., Miller, C., Perryman, W., Tao, B., & Moore, M. Larger females have more calves: influence of maternal body length on fecundity in North Atlantic right whales. Marine Ecology Progress Series, 689, (2022): 179–189, https://doi.org/10.3354/meps14040.North Atlantic right whales (NARW) are critically endangered and have been declining in abundance since 2011. In the past decade, human-caused mortalities from vessel strikes and entanglements have been increasing, while birth rates in the population are at a 40 yr low. In addition to declining abundance, recent studies have shown that NARW length-at-age is decreasing due to the energetic impacts of sub-lethal entanglements, and that the body condition of the population is poorer than closely related southern right whales. We examined whether shorter body lengths are associated with reduced fecundity in female NARW. We compared age-corrected, modeled metrics of body length with 3 metrics of fecundity: age at first reproduction, average inter-birth interval, and the number of calves produced per potential reproductive year. We found that body length is significantly related to birth interval and calves produced per reproductive year, but not age at first reproduction. Larger whales had shorter inter-birth intervals and produced more calves per potential reproductive year. Larger whales also had higher lifetime calf production, but this was a result of larger whales having longer potential reproductive spans, as body lengths have generally been declining over the past 40 yr. Declining body sizes are a potential contributor to low birth rates over the past decade. Efforts to reduce entanglements and vessel strikes could help maintain population viability by increasing fecundity and improving resiliency of the population to other anthropogenic and climate impacts.Funding to the New England Aquarium for curation of the photo-identification catalog is provided by NOAA Contract 1305M2- 18-P-NFFM-0108

Estimating the effects of stressors on the health, survival and reproduction of a critically endangered, long-lived species

Funding: Office of Naval Research (Grant Number(s): N000142012697, N000142112096); Strategic Environmental Research and Development Program (Grant Number(s): RC20-1097, RC20-7188, RC21-3091).Quantifying the cumulative effects of stressors on individuals and populations can inform the development of effective management and conservation strategies. We developed a Bayesian state–space model to assess the effects of multiple stressors on individual survival and reproduction. In the model, stressor effects on vital rates are mediated by changes in underlying health, allowing for the comparison of effect sizes while accounting for intrinsic factors that might affect an individual's vulnerability and resilience. We applied the model to a 50-year dataset of sightings, calving events and stressor exposure of critically endangered North Atlantic right whales Eubalaena glacialis. The viability of this population is threatened by a complex set of stressors, including vessel strikes, entanglement in fishing gear and fluctuating prey availability. We estimated that blunt and deep vessel strike injuries and severe entanglement injuries had the largest effect on the health of exposed individuals, reinforcing the urgent need for mitigation measures. Prey abundance had a smaller but protracted effect on health across individuals, and estimated long-term trends in survival and reproduction followed the trend of the prey index, highlighting that long-term ecosystem-based management strategies are also required. Our approach can be applied to quantify the effects of multiple stressors on any long-lived species where suitable indicators of health and long-term monitoring data are available.Publisher PDFPeer reviewe

The density and peculiar velocity fields of nearby galaxies

We review the quantitative science that can be and has been done with redshift and peculiar velocity surveys of galaxies in the nearby universe. After a brief background setting the cosmological context for this work, the first part of this review focuses on redshift surveys. The practical issues of how redshift surveys are carried out, and how one turns a distribution of galaxies into a smoothed density field, are discussed. Then follows a description of major redshift surveys that have been done, and the local cosmography out to 8,000 km/s that they have mapped. We then discuss in some detail the various quantitative cosmological tests that can be carried out with redshift data. The second half of this review concentrates on peculiar velocity studies, beginning with a thorough review of existing techniques. After discussing the various biases which plague peculiar velocity work, we survey quantitative analyses done with peculiar velocity surveys alone, and finally with the combination of data from both redshift and peculiar velocity surveys. The data presented rule out the standard Cold Dark Matter model, although several variants of Cold Dark Matter with more power on large scales fare better. All the data are consistent with the hypothesis that the initial density field had a Gaussian distribution, although one cannot rule out broad classes of non-Gaussian models. Comparison of the peculiar velocity and density fields constrains the Cosmological Density Parameter. The results here are consistent with a flat universe with mild biasing of the galaxies relative to dark matter, although open universe models are by no means ruled out.Comment: In press, Physics Reports. 153 pages. gzip'ed postscript of text plus 20 embedded figures. Also available via anonymous ftp at ftp://eku.ias.edu/pub/strauss/review/physrep.p

Use of Novel Strategies to Develop Guidelines for Management of Pyogenic Osteomyelitis in Adults: A WikiGuidelines Group Consensus Statement.

Importance Traditional approaches to practice guidelines frequently result in dissociation between strength of recommendation and quality of evidence. Objective To construct a clinical guideline for pyogenic osteomyelitis management, with a new standard of evidence to resolve the gap between strength of recommendation and quality of evidence, through the use of a novel open access approach utilizing social media tools. Evidence Review This consensus statement and systematic review study used a novel approach from the WikiGuidelines Group, an open access collaborative research project, to construct clinical guidelines for pyogenic osteomyelitis. In June 2021 and February 2022, authors recruited via social media conducted multiple PubMed literature searches, including all years and languages, regarding osteomyelitis management; criteria for article quality and inclusion were specified in the group's charter. The GRADE system for evaluating evidence was not used based on previously published concerns regarding the potential dissociation between strength of recommendation and quality of evidence. Instead, the charter required that clear recommendations be made only when reproducible, prospective, controlled studies provided hypothesis-confirming evidence. In the absence of such data, clinical reviews were drafted to discuss pros and cons of care choices. Both clear recommendations and clinical reviews were planned with the intention to be regularly updated as new data become available. Findings Sixty-three participants with diverse expertise from 8 countries developed the group's charter and its first guideline on pyogenic osteomyelitis. These participants included both nonacademic and academic physicians and pharmacists specializing in general internal medicine or hospital medicine, infectious diseases, orthopedic surgery, pharmacology, and medical microbiology. Of the 7 questions addressed in the guideline, 2 clear recommendations were offered for the use of oral antibiotic therapy and the duration of therapy. In addition, 5 clinical reviews were authored addressing diagnosis, approaches to osteomyelitis underlying a pressure ulcer, timing for the administration of empirical therapy, specific antimicrobial options (including empirical regimens, use of antimicrobials targeting resistant pathogens, the role of bone penetration, and the use of rifampin as adjunctive therapy), and the role of biomarkers and imaging to assess responses to therapy. Conclusions and Relevance The WikiGuidelines approach offers a novel methodology for clinical guideline development that precludes recommendations based on low-quality data or opinion. The primary limitation is the need for more rigorous clinical investigations, enabling additional clear recommendations for clinical questions currently unresolved by high-quality data