Subharmonic resonance

Thesis (M.A.)--Boston University, 1949. This item was digitized by the Internet Archive

An analysis and extension of Eddington's unified theory of physics

Thesis (Ph.D.)--Boston UniversityThis thesis is divided into three parts. In the first part Eddington's algebra of E-numbers is outlined and the Dirac matrices are introduced. At this point .it becomes possible to relate specific entities that the two men treat in common. In particular, the derivation of the interchange operator from the point of view of wave tensor calculus is given in full. The reason for this method of treatment is that Eddington's interchange operator is more general than Dirac's, since it contains Dirac's interchange operator as one factor. The additional factor in Eddington's operator helps to form the basis of his nuclear theory. With the introduction of Lorentz rotations it becomes possible to show that many of the E-numbers have their exact counterpart in the work of Dirac. Part Two deals with certain general relationships which are shown to exist between the wave tensor calculus and the bra and ket vector algebra. Tho Heisenberg and Schrödinger formulations are presented. against the more general background or Dirac's algebra. Procedures are then set up to relate the bra and ket vectors to Eddington's wave vectors. Within the wave tensor algebra it is possible to build wave tensors of higher order from a group of wave vectors. One can, in turn, relate the elements of a second-rank wave tensor with a vector, and the element of a fourth-rank wave tensor with a second-rank tensor. This means that Dirac's bra and ket vectors can be related to a second-rank tensor. This is illustrated through the tenaors of electromagnetic theory and the Einstein law of gravitation. The purpose of Part Two is to show the tremendous scope possessed by the E-numbers. Part Three contains a more general type of discussion. Here, for example, the concept of an observable ia scrutinized from both Dirac's and Eddington's point of view. Although at first they look entirely different, they can be shown to be compatible. Eddington's argument for an absolute standard of length is also discussed. Here the particular application of Eddington's concept of a basic uncertainty in position appears. This argument applies to the field of quantum electrodynamics when one deals with an electron of zero dimensions. If the basic uncertainty in position is of the order of 10^-13 cm, then distances of less than this value cease to have physical significance, as their measurements cannot be taken. This helps to remove certain of the divergences inherent in a point particle theory. A step by step analysis leading to Eddington's exclusion principle is given, starting from the Pauli exclusion principle, because it gives insight as to the vantage point from which Eddington views physical theory

Point-of-use Water Treatment for Private Wells in North Carolina: Risks and Solutions for Lead, Per- and Polyfluoroalkyl Substances (PFASs), and Microbial Contaminants

Almost 50 million people across the United States and Canada rely on privately-owned wells for their domestic water needs. Private well users are legally responsible for maintaining their own water quality as no enforceable drinking water standards nor monitoring and treatment requirements exist for private wells as they do for public water systems. As a result, private well users are potentially exposed to a range of chemical and microbial contaminants through their drinking water. Point-of-use (POU) water treatment represents one potential solution to reduce harmful exposures through well water, but well users frequently do not adopt any household treatment even after the results of a water test indicate some form of contamination. Additionally, the effectiveness of consumer POU treatment products for removing certain contaminants from private well water, including lead and per- and polyfluoroalkyl substances (PFASs), is largely unknown, as very few studies have tested their performance over time in household settings. This research thus aims to advance knowledge around POU water treatment for private well water to reduce the barriers to these solutions for well users. An under-sink activated carbon block POU filter was installed in the homes of 18 well users across North Carolina and tested monthly for eight months for metals, PFASs, and microbial indicator organisms. Filters removed 98% of all influent lead on average for the entire study duration and significantly improved the safety and effectiveness of faucet flushing, reducing levels at the tap to below the American Academy of Pediatrics recommendation of 1 µg/L of lead in drinking water. Additionally, filters consistently removed 97-99% of all influent PFASs, including emerging short-chain perfluoroalkyl ether acids, even up to two months beyond the manufacturer recommended lifetime of the device. Filters did not result in increased microbial risk of drinking water at the tap under normal conditions of use, but the results emphasized the need for additional well protections and maintenance to ensure the microbial safety of private well water, regardless of the decision to implement POU treatment. Finally, the experiences of participants in this study highlighted the need for strengthened well outreach and support programs that provide technical assistance and financial support to private well users around POU treatment in addition to well testing. The results of this study may thus be used by state and local health departments to provide evidence-based recommendations around the use of POU filters for private well users that may significantly reduce lead and PFAS exposures among this population.Doctor of Philosoph

Wind-Induced Vibration Energy Harvesting Using Piezoelectric Transducers Coupled with Dynamic Magnification

Flexible cylindrical structures subjected to wind loading experience vibrations from periodic shedding of vortices in their wake. Vibrations become excessive when the natural frequencies of the cylinder coincide with the vortex shedding frequency. In this study, cylinder vibrations are transmitted to a beam inside the structure via dynamic magnifier system. This system amplifies the strain experienced by piezoelectric patches bonded to the beam to maximize the conversion from vibrational energy into electrical energy. Realworld applicability is tested using a wind tunnel to create vortex shedding and comparing the results to finite element modeling that shows the structural vibrational modes. A crucial part of this study is conditioning and storing the harvested energy, focusing on theoretical modeling, design parameter optimization, and experimental validation. The developed system is helpful in designing wind-induced energy harvesters to meet the necessity for novel energy resources

Evaluation of the feasibility, diagnostic yield, and clinical utility of rapid genome sequencing in infantile epilepsy (Gene-STEPS): an international, multicentre, pilot cohort study

BACKGROUND: Most neonatal and infantile-onset epilepsies have presumed genetic aetiologies, and early genetic diagnoses have the potential to inform clinical management and improve outcomes. We therefore aimed to determine the feasibility, diagnostic yield, and clinical utility of rapid genome sequencing in this population. METHODS: We conducted an international, multicentre, cohort study (Gene-STEPS), which is a pilot study of the International Precision Child Health Partnership (IPCHiP). IPCHiP is a consortium of four paediatric centres with tertiary-level subspecialty services in Australia, Canada, the UK, and the USA. We recruited infants with new-onset epilepsy or complex febrile seizures from IPCHiP centres, who were younger than 12 months at seizure onset. We excluded infants with simple febrile seizures, acute provoked seizures, known acquired cause, or known genetic cause. Blood samples were collected from probands and available biological parents. Clinical data were collected from medical records, treating clinicians, and parents. Trio genome sequencing was done when both parents were available, and duo or singleton genome sequencing was done when one or neither parent was available. Site-specific protocols were used for DNA extraction and library preparation. Rapid genome sequencing and analysis was done at clinically accredited laboratories, and results were returned to families. We analysed summary statistics for cohort demographic and clinical characteristics and the timing, diagnostic yield, and clinical impact of rapid genome sequencing. FINDINGS: Between Sept 1, 2021, and Aug 31, 2022, we enrolled 100 infants with new-onset epilepsy, of whom 41 (41%) were girls and 59 (59%) were boys. Median age of seizure onset was 128 days (IQR 46-192). For 43 (43% [binomial distribution 95% CI 33-53]) of 100 infants, we identified genetic diagnoses, with a median time from seizure onset to rapid genome sequencing result of 37 days (IQR 25-59). Genetic diagnosis was associated with neonatal seizure onset versus infantile seizure onset (14 [74%] of 19 vs 29 [36%] of 81; p=0·0027), referral setting (12 [71%] of 17 for intensive care, 19 [44%] of 43 non-intensive care inpatient, and 12 [28%] of 40 outpatient; p=0·0178), and epilepsy syndrome (13 [87%] of 15 for self-limited epilepsies, 18 [35%] of 51 for developmental and epileptic encephalopathies, 12 [35%] of 34 for other syndromes; p=0·001). Rapid genome sequencing revealed genetic heterogeneity, with 34 unique genes or genomic regions implicated. Genetic diagnoses had immediate clinical utility, informing treatment (24 [56%] of 43), additional evaluation (28 [65%]), prognosis (37 [86%]), and recurrence risk counselling (all cases). INTERPRETATION: Our findings support the feasibility of implementation of rapid genome sequencing in the clinical care of infants with new-onset epilepsy. Longitudinal follow-up is needed to further assess the role of rapid genetic diagnosis in improving clinical, quality-of-life, and economic outcomes. FUNDING: American Academy of Pediatrics, Boston Children's Hospital Children's Rare Disease Cohorts Initiative, Canadian Institutes of Health Research, Epilepsy Canada, Feiga Bresver Academic Foundation, Great Ormond Street Hospital Charity, Medical Research Council, Murdoch Children's Research Institute, National Institute of Child Health and Human Development, National Institute for Health and Care Research Great Ormond Street Hospital Biomedical Research Centre, One8 Foundation, Ontario Brain Institute, Robinson Family Initiative for Transformational Research, The Royal Children's Hospital Foundation, University of Toronto McLaughlin Centre

Cohort Profile: Burden of Obstructive Lung Disease (BOLD) study

The Burden of Obstructive Lung Disease (BOLD) study was established to assess the prevalence of chronic airflow obstruction, a key characteristic of chronic obstructive pulmonary disease, and its risk factors in adults (≥40 years) from general populations across the world. The baseline study was conducted between 2003 and 2016, in 41 sites across Africa, Asia, Europe, North America, the Caribbean and Oceania, and collected high-quality pre- and post-bronchodilator spirometry from 28 828 participants. The follow-up study was conducted between 2019 and 2021, in 18 sites across Africa, Asia, Europe and the Caribbean. At baseline, there were in these sites 12 502 participants with high-quality spirometry. A total of 6452 were followed up, with 5936 completing the study core questionnaire. Of these, 4044 also provided high-quality pre- and post-bronchodilator spirometry. On both occasions, the core questionnaire covered information on respiratory symptoms, doctor diagnoses, health care use, medication use and ealth status, as well as potential risk factors. Information on occupation, environmental exposures and diet was also collected

Removal of N-Nitrosodimethylamine and Other Disinfection By-Product Precursors from Tertiary Wastewater Effluent by Activated Carbon

Organic constituents at the low to sub-microgram per liter level derived from wastewater effluents represent precursors to previously undetected disinfection by-products (DBPs) in drinking water utilities. N-nitrosodimethylamine (NDMA) is an emerging DBP of particular concern due to its suspected genotoxicity and carcinogenicity an order of magnitude greater than currently regulated DBPs. Granular activated carbon (GAC) has been shown to be a potential control technology for removing NDMA precursors from wastewater effluent, but adsorption behavior of specific precursor material is still poorly understood. The goal of this research is to expand knowledge of the GAC adsorption behavior of NDMA and other DBP precursors in wastewater effluent, including understanding the effect of different activated carbon types, the effect of varying GAC column Empty Bed Contact Time (EBCT), the effect of source water blending on NDMA precursor sorption, and the breakthrough of NDMA precursors relative to trihalomethane, haloacetic acid, and haloacetonitrile precursors. Lignite-based and wood-based activated carbon were found to remove NDMA precursors better than coconut-shell and bituminous carbons, presumably due to larger mesopore volumes. NDMA precursors are thought to be larger molecular weight compounds or behave in water such that adsorption occurs in the mesopore region. A distinct non-adsorbable fraction in powdered activated carbon batch tests suggests a range of different precursor compounds. In Rapid Small-Scale Column Tests (RSSCTs), a simulated 20-minute bench-scale EBCT performed better than a 10-minute column, thus longer EBCTs are suggested when optimizing GAC control for NDMA precursors in wastewater. NDMA precursors were also found to adsorb independently of bulk organic matter and other DBP precursors, suggesting its precursors are distinct from currently regulated and other nitrogenous DBPs. As a result, Overall Fluorescence Intensity was proposed as a possible surrogate for NDMA precursors due to its similar adsorption behavior in RSSCTs using blended influent waters. Evidence is also presented for considering NDMA precursors as similar to micropollutants due to rapid sorption in batch testing distinct from DOM, and diminished impacts of influent concentrations on fractional RSSCT breakthrough