Time-delayed models of gene regulatory networks

We discuss different mathematical models of gene regulatory networks as relevant to the onset and development of cancer. After discussion of alternativemodelling approaches, we use a paradigmatic two-gene network to focus on the role played by time delays in the dynamics of gene regulatory networks. We contrast the dynamics of the reduced model arising in the limit of fast mRNA dynamics with that of the full model. The review concludes with the discussion of some open problems

An Issue Worth Tackling: Chronic Traumatic Encephalopathy in the National Football League

America has become a sports empire over the past century. As the movie Concussion put it, the National Football League has single-handedly taken over the day that used to belong to the church–but this comes at a price. Chronic traumatic encephalopathy, or CTE, is a life-altering disease associated with high impact and contact sports that has created a heated debate in our sports-driven society. A study published in 2017 discovered CTE in 177 of 202 former football players–or a staggering 87%. Why do the players continue to play in the NFL if their longevity and well-being are jeopardized? Why has the NFL not taken action to protect the athletes? This review, focused on American football, works to shed light on this serious and complex issue while approaching it from a multitude of intriguing and provoking angles

Design flood peak determination in the rural catchments of the Eastern Cape, South Africa

Includes bibliographical references.Rainfall is a natural occurring phenomenon, and is usually a welcome event, nourishing the earth and with it the fauna and flora. When the runoff is high, flooding occurs, leading to damage to the environment, property and even to loss of life. Flooding is becoming more common. The reasons for this are complex, and include social expansion, urbanization and may also result from global warming. These flooding events have significant implications to the engineering profession and the affected communities. The estimation of peak design floods is necessary for the planning and design of civil engineering projects. Over the past century standard methods for flood peak estimation have been developed for most countries, and are usually categorized in the literature as direct statistical analyses, regional statistical analyses, empirical methods and deterministic methods. Some of these methods are easy to apply, while others require an in-depth analysis of the catchment and other parameters. Each method has its limitations. In rural gauged catchments, design engineers in the workplace typically use statistical methods while in rural un-gauged catchments, they use empirical or deterministic methods, even although the reliability of these methods to estimate the design flood peak have never been verified in South Africa. The objective of this study was to identify the most reliable statistical, deterministic and empirical method(s) of flood peak determination in the rural catchments of the Eastern Cape, South Africa. In this investigation the recorded annual peak runoff from 18 river flow gauging stations in the Eastern Cape were statistically analysed using the statistical distributions commonly used in South Africa. These statistical analyses were used to establish a benchmark for evaluating the deterministic and empirical methods. The catchments of all the stations were then analysed using the deterministic and empirical methods. Finally, the empirical and deterministic methods were compared against the best-fit statistical method. This highlighted which empirical and deterministic method(s) under- and over-estimated peak floods when compared with the statistical analyses of recorded annual peak runoff. The finding from the statistical analyses was that the Log Pearson Type 3 (LP3) distribution performed the best, generally fitting the recorded data well. In the comparison of deterministic methods it was found that the Standard Design Flood (SDF) method was the most conservative deterministic method at the higher Recurrence Intervals (RIs) while the Rational Method-Alternative was the most conservative at the lower RIs. In the final comparison between the LP 3 distribution and the empirical and deterministic methods, it was found that in the higher RI range, the SDF estimated runoff values similar to that estimated by the LP3 distribution, while in the lower RI range, the Rational Method-Alternative variation proved to be the most consistent. The other deterministic methods generally under-estimated runoff values when compared to the LP3 distribution. Generally, the Regional Maximum Flood method appeared to have a RI about 1000 years, although it was as low as 1 :200 years in some of the smaller sized catchments. In rural catchments of all sizes in the Eastern Cape of SA, design engineers in the workplace should analyse a catchment using all of the statistical, deterministic and empirical methods available and then select the most conservative result

Urban School Violence Prevention: A Suggested Intervention Utilizing Liberation Psychology

In the past decades, numerous programs have been developed in attempts to reduce the rates of violence facing students in American schools. The spotlight on these programs have increased since horrific mass shooting events have taken place throughout the country. Many of these programs have utilized varied methods in their attempt to reduce school-based violence, from the implementation of hardline policies meant to act as violence deterrents to the development of risk assessment teams aimed at identifying and intervening against potential threats; however, few of the existing programs have shown substantial efficacy rates. Additionally, several of the violence prevention programs have demonstrated substantial negative impacts for minority students. This paper suggests a violence prevention program aimed at addressing the unique and overlooked needs of urban, minority school students with an emphasis on community-based, culturally informed interventions. The suggested program separates itself in its focus on the community rather than just the school, operating from the belief that schools are mirrors of both the strengths and challenges of the whole community; therefore, violence prevention programming must be community rather than solely school-based. Liberation psychology and participatory action research form the foundation for the recommended program with the community identifying the problems contributing to violence and determining the appropriate interventions to meet the specified goals

Rydberg-State-Resolved Resonant Energy Transfer in Cold Electric-Field-Controlled Intrabeam Collisions of NH3 with Rydberg He Atoms

The resonant transfer of energy from the inversion sublevels in NH3 to He atoms in triplet Rydberg states with principal quantum number n = 38 has been controlled using electric fields below 15 V/cm in intrabeam collisions at translational temperatures of ∼1 K. The experiments were performed in pulsed supersonic beams of NH3 seeded in He at a ratio of 1:19. The He atoms were prepared in the metastable 1s2s 3S1 level in a pulsed electric discharge in the trailing part of the beams. The velocity slip between the heavy NH3 and the lighter metastable He was exploited to perform collision studies at center-of-mass collision speeds of ∼70 m/s. Resonant energy transfer in the atom–molecule collisions was identified by Rydberg-state-selective electric-field ionization. The experimental data have been compared to a theoretical model of the resonant dipole–dipole interactions between the collision partners based on the impact parameter method

Scales of the Extra Dimensions and their Gravitational Wave Backgrounds

Circumstances are described in which symmetry breaking during the formation of our three-dimensional brane within a higher-dimensional space in the early universe excites mesoscopic classical radion or brane-displacement degrees of freedom and produces a detectable stochastic background of gravitational radiation. The spectrum of the background is related to the unification energy scale and the the sizes and numbers of large extra dimensions. It is shown that properties of the background observable by gravitational-wave observatories at frequencies $f\approx 10^{-4}$ Hz to $10^3$ Hz contain information about unification on energy scales from 1 to $10^{10}$ TeV, gravity propagating through extra-dimension sizes from 1 mm to $10^{-18}$mm, and the dynamical history and stabilization of from one to seven extra dimensions.Comment: 6 pages, Latex, 1 figure, submitted to Phys. Re

SAO/NASA joint investigation of astronomical viewing quality at Mount Hopkins Observatory: 1969-1971

Quantitative measurements of the astronomical seeing conditions have been made with a stellar-image monitor system at the Mt. Hopkins Observatory in Arizona. The results of this joint SAO-NASA experiment indicate that for a 15-cm-diameter telescope, image motion is typically 1 arcsec or less and that intensity fluctuations due to scintillation have a coefficient of irradiance variance of less than 0.12 on the average. Correlations between seeing quality and local meteorological conditions were investigated. Local temperature fluctuations and temperature gradients were found to be indicators of image-motion conditions, while high-altitude-wind conditions were shown to be somewhat correlated with scintillation-spectrum bandwidth. The theoretical basis for the relationship of atmospheric turbulence to optical effects is discussed in some detail, along with a description of the equipment used in the experiment. General site-testing comments and applications of the seeing-test results are also included

Interplanetary propulsion using inertial fusion

Inertial fusion can be used to power spacecraft within the solar system and beyond. Such spacecraft have the potential for short-duration manned-mission performance exceeding other technologies. We are conducting a study to assess the systems aspects of inertial fusion as applied to such missions, based on the conceptual engine design of Hyde (1983) we describe the required systems for an entirely new spacecraft design called VISTA that is based on the use of DT fuel. We give preliminary design details for the power conversion and power conditioning systems for manned missions to Mars of total duration of about 100 days. Specific mission performance results will be published elsewhere, after the study has been completed