Studies of the effect of tracer activity on time-averaged positron emission particle tracking measurements on tumbling mills at PEPT Cape Town

The statistical uncertainties associated with time-averaged positron emission particle tracking (PEPT) measurements of the position, velocity and acceleration of a small tracer particle have been investigated. Experiments were undertaken using the ECAT ‘EXACT3D’ PET scanner recently installed at the facilities of PEPT Cape Town at iThemba LABS, South Africa. Small “button” sources of ⁶⁸Ga were attached to the outer shell of a small mill and PEPT data were recorded over several half-lives, for the cases of the mill being empty and entirely filled with steel balls. The effect of tracer activity on the statistical uncertainties in the positions, velocities and accelerations derived from the measurements was investigated, as a first step towards fully quantifying the uncertainties associated with tracking particles via PEPT in laboratory-scale tumbling mills.     

The tapered matrix amplifier: a low-power high-gain broadband amplifier

A new distributed amplifier topology that offers greatly reduced power consumption is presented. The tapered matrix amplifier (TMA) originates from the combination of transmission line tapering and matrix cascading of distributed amplifiers. The design of a TMA is however complicated by contrasting requirements of the tapered lines, the lumped line approximation and the parasitics of the circuit components. Therefore, a pragmatic design approach leveraging circuit optimization is proposed to handle these complexities. As a proof of concept, a prototype broadband amplifier was implemented in a 90 nm bulk CMOS process. It features an average gain of 15.8 dB over the pass-band, stretching from DC to 22 GHz, while consuming only 12.9 mW of DC power. The average noise figure in the pass-band is 5.4 dB, and the average IIP3 is ?7.3 dBm. The die area occupied by the amplifier is only 0.31 mm². In addition, it is shown that the prototype design can be easily adapted for high linearity while keeping the increase in power consumption to a minimum.     

Regional cardiac motion and strain estimation in three-dimensional echocardiography: a validation study in thick-walled univentricular phantoms

Automatic quantification of regional left ventricular deformation in volumetric ultrasound data remains challenging. Many methods have been proposed to extract myocardial motion, including techniques using block matching, phase-based correlation, differential optical flow methods, and image registration. Our lab previously presented an approach based on elastic registration of subsequent volumes using a B-spline representation of the underlying transformation field. Encouraging results were obtained for the assessment of global left ventricular function, but a thorough validation on a regional level was still lacking. For this purpose, univentricular thick-walled cardiac phantoms were deformed in an experimental setup to locally assess strain accuracy against sonomicrometry as a reference method and to assess whether regions containing stiff inclusions could be detected. Our method showed good correlations against sonomicrometry: r(2) was 0.96, 0.92, and 0.84 for the radial (ε(RR)), longitudinal (ε(LL)), and circumferential (ε(CC)) strain, respectively. Absolute strain errors and strain drift were low for ε(LL) (absolute mean error: 2.42%, drift: -1.05%) and ε(CC) (error: 1.79%, drift: -1.33%) and slightly higher for ε(RR) (error: 3.37%, drift: 3.05%). The discriminative power of our methodology was adequate to resolve full transmural inclusions down to 17 mm in diameter, although the inclusion-to-surrounding tissue stiffness ratio was required to be at least 5:2 (absolute difference of 39.42 kPa). When the inclusion-to-surrounding tissue stiffness ratio was lowered to approximately 2:1 (absolute difference of 22.63 kPa), only larger inclusions down to 27 mm in diameter could still be identified. Radial strain was found not to be reliable in identifying dysfunctional regions.     

Overview of Debug Standardization Activities

The semiconductor industry is disaggregated, with a complex web of suppliers and consumers. Standards help to facilitate and simplify the debug process. This article provides an overview of current standardization activity. One area in need of such standardization is that of on-chip debug processes and instruments. The debug area particularly exhibits limited commonality between different IP providers in terms of interfaces and methods for complex SoCs. The problem becomes even greater with more SoC integrators using diverse IP from different vendors, requiring an increasing range of debug, analysis, and optimization capabilities. This article describes the goals and ongoing activities of five debug standardization bodies: the Nexus 5001, MIPI (Mobile Industry Processor Interface) Test and Debug, IEEE PI149.7, IEEE P1687, and OCP-IP (Open Core Protocol International Partnership) Debug working groups.     

On the Fastest Vickrey Algorithm

We investigate the algorithmic performance of Vickrey-Clarke-Groves mechanisms in the single item case. We provide a formal definition of a Vickrey algorithm for this framework, and give a number of examples of Vickrey algorithms. We consider three performance criteria, one corresponding to a Pareto criterion, one to worst-case analysis, and one related to first-order stochastic dominance. We show that Pareto best Vickrey algorithms do not exist and that worst-case analysis is of no use in discriminating between Vickrey algorithms. For the case of two bidders, we show that the bisection auction stochastically dominates all Vickrey algorithms. We extend our analysis to the study of weak Vickrey algorithms and winner determination algorithms. For the case of two bidders, we show that the One-Search algorithm stochastically dominates all column monotonic weak Vickrey algorithms and that a suitably adjusted version of the bisection algorithm, the WD bisection algorithm, stochastically dominates all winner determination algorithms. The WD bisection algorithm Pareto dominates all column monotonic winner determination algorithms in the n bidder case.     

The application of polymethylene waxes as conditioning agent in hair relaxers

Hair relaxers are harsh chemical treatments that leave the hair dull, dry and limp. There is a constant need for improvement of these products to make them milder and incorporate conditioning properties. Because of the high pH of relaxer or hair straightening systems, most quaternized (conditioning) ingredients are unstable and slowly break down to release ammonia over time, having no conditioning effects by the time the consumers use them. This paper discusses the partial substitution of the fatty alcohols that are traditionally used in relaxer systems with polymethylene wax and the benefits derived from using them. The study included the investigation of synergies among the ingredients, the stabilities of the various systems and comparisons with commercially available systems. The polymethylene wax, used in combination with the mineral oil gel and phosphate salt, coats the hair during the relaxing process, leaving it shiny, soft and conditioned as opposed to the poor condition of the hair relaxed by traditional, commercially available NaOH and LiOH relaxers. An additional benefit of using polymethylene wax in relaxer systems is that the conditioning agents that are normally added to the neutralizing shampoo to repair or mask the damage as a result of the relaxing process can be omitted.     

Molecular mechanism of cancer seeding: adhesion molecules and signal transduction networks

Cancer is a chronic and progressive disease characterised by disturbances of growth, cellular differentiation and maintenance of tissue integrity. The latter phenomenon leads to invasion. The transition from the noninvasive towards the invasive stage of the disease is crucial because it transforms a benign and easily curable lesion into a malignant and therapy-resistant disease. Tumour progression is the result of a number of genetic alterations, initiated by a single mutation without immediate clinical manifestations and ending with a metastatic cascade. Activation of tumour-promoter genes (oncogenes), by mutation or overexpression, and inactivation of tumour-suppressor genes, by mutation or deletion, favour oncogenesis. Separate genes are implicated in distinct steps of the tumour progression. Defects in DNA-repair genes influence all steps. Metastasis is a multistep process of invasion. At each step invasion occurs within a micro-ecosystem in which a continuous molecular crosstalk takes place between the cancer cells and the host cells that participate at the establishment of the tumour. The cancer cells carry the genetic alterations and act as the founders of the micro-ecosystem. We shall discuss the invasion-suppressor function of the E-cadherin/catenin complex. Inactivation of one element of this complex may initiate invasion in an appropriate genetic background. Such inactivation may take place at various levels: mutation in coding sequences; hypermethylation of the promoter; mRNA instability; tyrosine phosphorylation; proteolysis; extracellular interactions.     

Cardiorespiratory effects of O-isobutyl S-[2-(diethylamino)-ethyl] methylphosphonothioate -- a structural isomer of VX

O-Isobutyl S-[2-(diethylamino)ethyl]methylphosphonothioate (VR) is a structural isomer of a more well-known chemical warefare agent, O-ethyl S-[2(diisopropylamino)ethyl]methylphosphonothioate (code designation VX). In this study, cardiorespiratory and central nervous system (CNS) effects of VR (2LD50 or 22.6 microg kg(-1); s.c.) were evaluated in urethane-anesthetized (Group 1) and unanesthetized (Group 2) guinea pigs instrumented for concurrent recordings of electrocorticogram (ECoG) and a variety of cardiorespiratory activities. The first sign of intoxication was a state of progressive bradycardia, vascular hypotension and arrhythmia (Group 1, approximately 13 min post-VR; Group 2, approximately 6 min post-VR). Bradypnea, excessive salivation and compensatory changes in blood pressure typically did not emerge until 3-5 min prior to apnea (Group 1, approximately 28 min post-VR; Group 2, approximately 15 min post-VR). An idioventricular rhythm, which signalled a failing myocardium, appeared at the same time or shortly after the development of a bradypneic profile. Another notable toxicity component of VR, based on arterial pH, pO2/pCO2 and bicarbonate (HCO3-) level data, was a state of combined hypercapnia, acidemia and hypoxemia during the development of bradypnea. Taken together, findings from this study indicated that changes in medullary respiratory unit activity and ECoG data displayed little, if any, notable signs of CNS perturbation prior to the terminal stage (approximately 1 min prior to respiratory failure). Thus, in addition to displaying a greater sensitivity to perturbation by VR, the peripheral cardiorespiratory system components also appeared to play a more important role in precipitating a progressively dysfunctional cardiorespiratory status that ultimately led to collapse of central respiratory mechanisms and death.