Theoretical and experimental studies of error in square-law detector circuits

Square law detector circuits to determine errors from the ideal input/output characteristic function were investigated. The nonlinear circuit response is analyzed by a power series expansion containing terms through the fourth degree, from which the significant deviation from square law can be predicted. Both fixed bias current and flexible bias current configurations are considered. The latter case corresponds with the situation where the mean current can change with the application of a signal. Experimental investigations of the circuit arrangements are described. Agreement between the analytical models and the experimental results are established. Factors which contribute to differences under certain conditions are outlined

Seasonal Diets of Newfoundland Martens, Martes americana atrata

We analyzed scats (n = 679) and stomach contents (n = 25) collected from 1980-2003 to assess the relative frequencies of food types utilized by Newfoundland Marten (Martes americana atrata) during summer and winter. Meadow Voles (Microtus pennsylvanicus) were the most prevalent food item occurring in 80% and 47.5% of samples from summer and winter, respectively. Apart from Snowshoe Hares (Lepus americana), which occurred in 28% of winter samples, all other food types occurred in <16% of samples during each season. Diet breadth was widest during winter and may be related to a lower availability of Meadow Voles during this time of year. Erratum included

A new two-dimensional lattice model that is "consistent around a cube"

For two-dimensional lattice equations one definition of integrability is that the model can be naturally and consistently extended to three dimensions, i.e., that it is "consistent around a cube" (CAC). As a consequence of CAC one can construct a Lax pair for the model. Recently Adler, Bobenko and Suris conducted a search based on this principle and certain additional assumptions. One of those assumptions was the "tetrahedron property", which is satisfied by most known equations. We present here one lattice equation that satisfies the consistency condition but does not have the tetrahedron property. Its Lax pair is also presented and some basic properties discussed.Comment: 8 pages in LaTe

A study of the effects of interference-rejection filters on feedback radiometer sensitivity

The trade-offs between sensitivity and interference immunity resulting from input bandpass filter losses in a noise-injection feedback radiometer are examined. Data are provided to permit the selection of an optimum filter configuration based on the independent variables of percentage bandwidth, q-factors, and desired band-edge rejection

COMBINING INDIVIDUAL KINETIC AND KINEMATIC PROFILES: A NOVEL APPROACH TO INJURY PREVENTION

ABSTRACT Darren William Hearn: Combining Individual Kinetic and Kinematic Profiles: A Novel Approach to Injury Prevention(Under the direction of Darin Anthony Padua) Musculoskeletal injury related to fitness and training represent an extraordinary burden to the individual, the workplace, and the healthcare system. Though injury incidence can exceed 79% for some training, our ability to identify those at greatest risk for sustaining injury is limited. The validity of screening techniques appears dependent on the population and have come under recent scrutiny. The purpose of this dissertation was to investigate how demographic, performance, and biomechanical variables, both individually and in combination, correlate with survival time to and hazard of musculoskeletal injury during cadet basic training at the United States Military Academy (USMA). We hypothesized that females, those with a history of injury, greater BMI, lesser cadence, those who move poorly, and those with poor performance on their physical fitness test would exhibit greater hazard of injury during training. Subjects were cadets entering cadet basic training in Summer, 2018. Data were collected using questionnaires, physical fitness tests, kinematic software, and wearable accelerometers. Injury surveillance was conducted over the first 60 days of training. Descriptive statistics and time to event analyses including the derivation of Kaplan Meier curves, Log Rank tests, and Cox proportional hazard regression modeling were used to address the research questions. A total of 595 participants met inclusion criteria and 97 sustained injury during the follow up period. Key observations included that most injuries occurred during weeks three and four of training; greater hazard for musculoskeletal injury was observed in females, those with a history of injury, poor movement and a poor physical fitness test score. However, hazards were unique to the individual based on modifiable and non-modifiable characteristics. Our observations suggest that multivariable risk modeling using survival analysis is an effective means of identifying those at greatest risk for sustaining musculoskeletal injury risk during training. Using carefully selected variables including demographic, movement, and performance variables appears to produce the most precise models. However, model precision is dependent upon individualized factors and care should be taken to understand how the presence of unmodifiable variables influence risk.Doctor of Philosoph

The Relationship Between Physical Activity and Executive Control Functioning as Modified by Genotype

As we age, the structure of the brain deteriorates and cognitive functioning declines. The region of the brain that begins to age the fastest is the frontal lobe, in which the dorsal-lateral prefrontal cortex is involved in executive control functions such as planning, organizing, initiating behaviors, and working memory. For some individuals, the brain declines more rapidly with age because of genetic factors. Apolipoprotein E (APOE) is a gene that assists in the transport of cholesterol and repair of the brain when it is damaged. Presence of the ε4 allele impairs cholesterol transport and puts its carriers at risk for increased cognitive decline and possibly dementia of the Alzheimer's type (DAT). Physical activity can slow the aging process of the brain and delay the onset and severity of cognitive decline and DAT as it increases oxygenation and blood flow, neuronal growth and synaptogenesis, and it increases the expression of genes helpful to the functioning of the brain such as brain-derived neurotrophic factor (BDNF). Therefore, individuals at greater genetic risk for age-related cognitive decline (i.e., ε4 carriers) should receive increased benefit from physical activity. Accordingly, this study examined the relationship between physical activity and executive control functioning, assessed by the Wisconsin Card Sort Test (WCST) in middle-aged APOE ε4 carriers and non-carriers. High-active participants were predicted to perform better than their low-active counterparts, and this difference should be even greater among APOE ε4 carriers. While most research studies on this topic have focused on general cognitive performance, the present study is specific in its focus on executive control functioning. Sixty-seven cognitively normal middle-aged adults between the ages of 50 - 70 years were assessed on medical history, overall cognitive functioning, APOE genotype, level of physical activity, and executive control functioning (WCST). Using hierarchical regression, seven WCST variables were regressed on age, genotype, physical activity, and the interaction between genotype and physical activity. Analysis revealed that as level of physical activity increased, performance significantly improved on all seven WCST variables for APOE ε4 carriers, but not for non-carriers. These results reveal that the benefits of physical activity to cognitive performance in this age group are specific to those who are genetically at-risk for cognitive decline

An exact solution of the metric-affine gauge theory with dilation, shear, and spin charges

The spacetime of the metric-affine gauge theory of gravity (MAG) encompasses {\it nonmetricity} and {\it torsion} as post-Riemannian structures. The sources of MAG are the conserved currents of energy-momentum and dilation, shear and spin. We present an exact static spherically symmetric vacuum solution of the theory describing the exterior of a lump of matter carrying mass and dilation, shear and spin charges.Comment: 13 pages, RevTe

New Complexity Results and Algorithms for the Minimum Tollbooth Problem

The inefficiency of the Wardrop equilibrium of nonatomic routing games can be eliminated by placing tolls on the edges of a network so that the socially optimal flow is induced as an equilibrium flow. A solution where the minimum number of edges are tolled may be preferable over others due to its ease of implementation in real networks. In this paper we consider the minimum tollbooth (MINTB) problem, which seeks social optimum inducing tolls with minimum support. We prove for single commodity networks with linear latencies that the problem is NP-hard to approximate within a factor of $1.1377$ through a reduction from the minimum vertex cover problem. Insights from network design motivate us to formulate a new variation of the problem where, in addition to placing tolls, it is allowed to remove unused edges by the social optimum. We prove that this new problem remains NP-hard even for single commodity networks with linear latencies, using a reduction from the partition problem. On the positive side, we give the first exact polynomial solution to the MINTB problem in an important class of graphs---series-parallel graphs. Our algorithm solves MINTB by first tabulating the candidate solutions for subgraphs of the series-parallel network and then combining them optimally