Parity properties of Costas arrays defined via finite fields

A Costas array of order $n$ is an arrangement of dots and blanks into $n$ rows and $n$ columns, with exactly one dot in each row and each column, the arrangement satisfying certain specified conditions. A dot occurring in such an array is even/even if it occurs in the $i$-th row and $j$-th column, where $i$ and $j$ are both even integers, and there are similar definitions of odd/odd, even/odd and odd/even dots. Two types of Costas arrays, known as Golomb-Costas and Welch-Costas arrays, can be defined using finite fields. When $q$ is a power of an odd prime, we enumerate the number of even/even odd/odd, even/odd and odd/even dots in a Golomb-Costas array. We show that three of these numbers are equal and they differ by $\pm 1$ from the fourth. For a Welch-Costas array of order $p-1$, where $p$ is an odd prime, the four numbers above are all equal to $(p-1)/4$ when $p\equiv 1\pmod{4}$, but when $p\equiv 3\pmod{4}$, we show that the four numbers are defined in terms of the class number of the imaginary quadratic field $\mathbb{Q}(\sqrt{-p})$, and thus behave in a much less predictable manner.Comment: To appear in Advances in Mathematics of Communication

Herbert Anderson - A Tribute

Tribute to Herbert Anderson for his years of service as the Editor of Reflective Practice

Watershed Prioritization

The overall objective of this two-year study was to evaluate the water quality in the thirty-seven sub-basin watersheds in the Illinois River in Arkansas and to arrive at a watershed prioritization list to use in targeting non-point source activities. A water quality monitoring program was conducted with sampling in all thirty-seven sub-basins during both storm and base flow events and more intensive sampling in eight representative sub-basins during stOffil events. Each sub-basin was sampled seasonally during low flow (base-flow) conditions and during high flow storm (storm flow) conditions. In addition to the regular sampling, the intensive sub-basins were sampled approximately 20 additional times during high flow

The Role of Students\u27 Professional Experience in Online Learning: Analysis of Asynchronous Participation

This paper reports on a causal-comparative study that investigated potential differences in students\u27 participation in asynchronous online learning environments according to their professional experience. In the study, 893 messages from 77 students in an online master\u27s program in human resource development (HRD) at a large U.S. university were analyzed. The research shed light on an important component of online education by illuminating ways in which novices and experienced students tend to relate to each other, the instructor, and the content of specific topics. Findings show evidence of both novices and experienced students using this medium in a very similar way when dealing with asynchronous tools. Discussion and recommendations are presented

Prospectus, September 17, 2014

THE PYGMALION FESTIVAL CELEBRATES 10 YEARS; Service learing and volunteerism through Parkland; Listen and learn with the Free Music Series; What\u27s happening? Events around campus that you don\u27t want to miss out on; Women\u27s Soccer beat Lewis and Clark 1-0; Statistics still show gender gap in STEM fields; Hookah smoking a hot trend but clouded by health concerns; It\u27s Here! Football on Television; The College Football Playoff: A reminder; Parkland Men\u27s Soccer start season strong; Why video game sound is so powerfully bondinghttps://spark.parkland.edu/prospectus_2014/1025/thumbnail.jp

Control of electron, ion and neutral heating in a radio-frequency electrothermal microthruster via dual-frequency voltage waveforms

The development of low power micro-propulsion sources is of recent interest for application on miniature satellite platforms. Radio-frequency. (rf) plasma electrothermal microthrusters can operate without a space-charge neutralizer and provide increased control of spatiotemporal power deposition. Further understanding of how the phase-resolved rf plasma heating mechanisms affect the phase-averaged bulk plasma properties, e.g. neutral gas temperature, could allow for in-flight tailoring of plasma thrusters. In this work, experimentally validated two-dimensional fluid-kinetic simulations were employed to study the spatially resolved electron and ion power deposition and neutral gas heating in a dual-frequency rf electrothermal microthruster operating at 1.5. Torr plenum pressure in argon. Experimental validation was performed through a comparison of the measured and simulated phase resolved Ar(2p(1)) excitation rates, showing close agreement. Two types of dual-frequency voltage waveforms were investigated, and comprise the combination of a 13.56 MHz voltage waveform with 27.12 MHz and 40.68 MHz waveforms, respectively. Varying the phase offset of the higher harmonic relative to the fundamental 13.56. MHz voltage waveform was found to modulate the dc self-bias voltage by 11% and 3% of the maximum applied peak-to-peak voltage, respectively. The 13.56. MHz, 27.12. MHz dual-frequency voltage waveform provided the highest degree of control, where the fraction of total rf power deposited into Ar+ ions was found to vary from 57% to 77%, modulating the on-axis neutral gas temperature by 35%. This control is attributed to the variation in the fraction of the rf phase cycle for which the sheath is collapsed, altering the phase-averaged electric field strength adjacent to the radial wall. The application of dual-frequency waveforms provides the ability to optimize the particle heating mechanisms with application to electrothermal propulsion.The work presented herein was funded by the Engineering and Physical Sciences Research Council (EPSRC, EP/M508196/1)

ACTH Prevents Deficits in Fear Extinction Associated with Early Life Seizures

Objective: Early life seizures (ELS) are often associated with cognitive and psychiatric comorbidities that are detrimental to quality of life. In a rat model of ELS, we explored long-term cognitive outcomes in adult rats. Using ACTH, an endogeneous HPA-axis hormone given to children with severe epilepsy, we sought to prevent cognitive deficits. Through comparisons with dexamethasone, we sought to dissociate the corticosteroid effects of ACTH from other potential mechanisms of action. Results: Although rats with a history of ELS were able to acquire a conditioned fear learning paradigm and controls, these rats had significant deficits in their ability to extinguish fearful memories. ACTH treatment did not alter any seizure parameters but nevertheless was able to significantly improve this fear extinction, while dexamethasone treatment during the same period did not. This ACTH effect was specific for fear extinction deficits and not for spatial learning deficits in a water maze. Additionally, ACTH did not alter seizure latency or duration suggesting that cognitive and seizure outcomes may be dissociable. Expression levels of melanocortin receptors, which bind ACTH, were found to be significantly lower in animals that had experienced ELS than in control animals, potentially implicating central melanocortin receptor dysregulation in the effects of ELS, and suggesting a mechanism of action for ACTH. Interpretation: Taken together, these data suggest that early treatment with ACTH can have significant long-term consequences for cognition in animals with a history of ELS independently of seizure cessation and may act in part through a CNS melanocortin receptor pathway