Sol Plaatje: in the spirit of the man

Paper presented at the Wits History Workshop: Myths, Monuments, Museums; New Premises? 16-18 July, 199

High-Isolation Antenna Technique for CubeSat-Borne, Continuous-Waveform Radar

Radar is important in target tracking, imaging, and weather prediction applications. As technology is increasingly miniaturized, there is a push for smaller radar. Research and exploration in outer space also benefit from small, low-power technologies. The NASA Jet Propulsion Laboratory’s RainCube was the first successful CubeSat-borne radar. A CubeSat is a type of small satellite that conforms to specific size and weight standards. Radar technology benefits from additional research on how to further miniaturize radar payloads. Integrating the transmit and receive antennas on the solar panels removes the need for antenna-deployment mechanisms, preserving space on the CubeSat. This thesis also demonstrates that implementing a radar that transmits and receives continuously and simultaneously (continuous-waveform) on the CubeSat improves the sensitivity, size, weight, and power consumption of the radar. Continuous-waveform radar suffers from self-interference because the transmitter and receiver are on at the same time. To overcome the self-interference, the transmitter and receiver must be isolated. Physically separating the antennas helps provide the isolation required for continuous-waveform radar, but is limited by the small size of the CubeSat. Isolation can be further increased by designing the antennas with opposite circular polarizations. The interfering signal traveling directly between the antennas has a different polarization than the receive antenna is designed for, so the interference is suppressed. The signal that hits a target reflects with the opposite circular polarization, so when it arrives at the receiver it has the proper polarization, so it is not suppressed. Combining physical-separation and different-polarization isolation enables a novel solution to implement a continuous-waveform radar on a small platform like a CubeSat

Roles and Ethics of the Practicing Criminologist

Academic criminologists, most trained as social and behavioral scientists, have not, for the most part, considered themselves as viable experts with skills and expertise which can be sold in the market place. Concomitantly, those professions and organizations which rely on professional experts and consultants have generally not considered academic criminologists as suited for their purpose. Part of this problem is derived from the very nature or orientation of graduate education. Doctorate programs concentrate on those skills that criminologists will need for university positions. We argue that the roles of criminologists in applied settings are essentially the same as for criminologists in academic settings. What differentiates applied criminologists from academic criminologists are not roles but the settings or contexts where they work. In this paper, we explore the application of criminological theories, methodologies, data analytic techniques and literature reviews in the applied setting. We outline so me of the typical activities and roles of criminologists in legal settings and show the applications of criminology in the practice of law and in court. We use examples from our consulting practice to show how these roles and accompanying skills are applied in the legal setting. We also consider some of the ethical questions associated with various roles and situation

The G protein-gated potassium current I(K,ACh) is constitutively active in patients with chronic atrial fibrillation

Background— The molecular mechanism of increased background inward rectifier current (IK1) in atrial fibrillation (AF) is not fully understood. We tested whether constitutively active acetylcholine (ACh)-activated IK,ACh contributes to enhanced basal conductance in chronic AF (cAF). Methods and Results— Whole-cell and single-channel currents were measured with standard voltage-clamp techniques in atrial myocytes from patients with sinus rhythm (SR) and cAF. The selective IK,ACh blocker tertiapin was used for inhibition of IK,ACh. Whole-cell basal current was larger in cAF than in SR, whereas carbachol (CCh)-activated IK,ACh was lower in cAF than in SR. Tertiapin (0.1 to 100 nmol/L) reduced IK,ACh in a concentration-dependent manner with greater potency in cAF than in SR (−logIC50: 9.1 versus 8.2; P<0.05). Basal current contained a tertiapin-sensitive component that was larger in cAF than in SR (tertiapin [10 nmol/L]-sensitive current at −100 mV: cAF, −6.7±1.2 pA/pF, n=16/5 [myocytes/patients] versus SR, −1.7±0.5 pA/pF, n=24/8), suggesting contribution of constitutively active IK,ACh to basal current. In single-channel recordings, constitutively active IK,ACh was prominent in cAF but not in SR (channel open probability: cAF, 5.4±0.7%, n=19/9 versus SR, 0.1±0.05%, n=16/9; P<0.05). Moreover, IK1 channel open probability was higher in cAF than in SR (13.4±0.4%, n=19/9 versus 11.4±0.7%, n=16/9; P<0.05) without changes in other channel characteristics. Conclusions— Our results demonstrate that larger basal inward rectifier K+ current in cAF consists of increased IK1 activity and constitutively active IK,ACh. Blockade of IK,ACh may represent a new therapeutic target in AF