Filter-Based Fading Channel Modeling

A channel simulator is an essential component in the development and accurate performance evaluation of wireless systems. A key technique for producing statistically accurate fading variates is to shape the flat spectrum of Gaussian variates using digital filters. This paper addresses various challenges when designing real and complex spectrum shaping filters with quantized coefficients for efficient realization of both isotropic and nonisotropic fading channels. An iterative algorithm for designing stable complex infinite impulse response (IIR) filters with fixed-point coefficients is presented. The performance of the proposed filter design algorithm is verified with 16-bit fixed-point simulations of two example fading filters

A novel isolator-based system promotes viability of human embryos during laboratory processing

In vitro fertilisation (IVF) and related technologies are arguably the most challenging of all cell culture applications. The starting material is a single cell from which one aims to produce an embryo capable of establishing a pregnancy eventually leading to a live birth. Laboratory processing during IVF treatment requires open manipulations of gametes and embryos, which typically involves exposure to ambient conditions. To reduce the risk of cellular stress, we have developed a totally enclosed system of interlinked isolator-based workstations designed to maintain oocytes and embryos in a physiological environment throughout the IVF process. Comparison of clinical and laboratory data before and after the introduction of the new system revealed that significantly more embryos developed to the blastocyst stage in the enclosed isolator-based system compared with conventional open-fronted laminar flow hoods. Moreover, blastocysts produced in the isolator-based system contained significantly more cells and their development was accelerated. Consistent with this, the introduction of the enclosed system was accompanied by a significant increase in the clinical pregnancy rate and in the proportion of embryos implanting following transfer to the uterus. The data indicate that protection from ambient conditions promotes improved development of human embryos. Importantly, we found that it was entirely feasible to conduct all IVF-related procedures in the isolator-based workstations

Flexible Delivery Damaging to Learning? Lessons From the Canterbury

Abstract Preparing courses for flexible delivery and distance education is normally a time-consuming and expensive process. This paper describes the design and evaluation of a system that automatically captures and indexes audio and video streams of traditional university lectures without demanding any changes in the style or tools used by teachers. Using a 'wizard-of-oz' technique to simulate the automatic indexing, we ran a four month trial of the system in a large (746 students) first year Computer Studies course. The results reveal some surprising social implications of making flexible delivery available to students at a residential university. Early in the trial, many students expressed an intention to use the system, but few did. Late in the course, many students stated that they urgently needed the system for revision, but even fewer used it. At the same time, lecture attendance appeared to be lower than normal. We hypothesise that the availability of a flexible alternative to lectures removed the necessity of attending lectures, and that students deceived themselves about their intentions to catch up using the digital medium

Design of an Imaging Payload for Earth Observation from a Nanosatellite

A compact imaging payload consisting of visible-near infrared and short-wave infrared capability is being developed to demonstrate low-cost wildfire monitoring among other Earth observations. Iris is a 1U multispectral push-broom imager that is capable of generating spectral data pertinent for wildfire science and wildfire risk analysis from a CubeSat platform. This payload is slated to fly on-board Ex-Alta 2, the University of Alberta’s second CubeSat and Alberta’s contribution to the Canadian CubeSat Project, to be deployed from the International Space Station in 2022. Iris features four closely integrated designs: optical, structural, electronics, and firmware. The mechanical and electronic interfaces of Iris are suited for modular integration into 1U of other generic CubeSat structures. The design has significant constraints on mass, size, performance, and cost. The current optical design features two compact lightpaths within the housing for imaging in short-wave infrared, near-infrared, blue, and red bands (center wavelengths at 2100, 865, 490, and 665 nm, respectively). Design simulations suggest achievement of a signal-to-noise ratio greater than 20 dB across all bands and a spatial resolution of 360 mor better averaged across the field-of-view. Taken together, this demonstrates significant scientific value for minimized cost and instrument volume. This design uses exclusively commercially available lenses, providing significant overall cost savings. The structural housing of Iris consists of 6061 T6 Aluminum, which provides a light-tight optical path for the visible to near-infrared and short-wave infrared light paths, as well as mounting for the optics and printed circuit board to the CubeSat structure within the required tolerances. A 45-degree folding mirror is employed to provide an extended optical lightpath within 1U with no deployable optics. The lens and mirror mounts are fitted with manual adjustment mechanisms for post-assembly alignment of the optical elements. This feature allows the team to perform small modifications to the axial position of the lenses as well as the folding mirror plane without having to re-manufacture the structure, saving time and cost. Within Iris, a subsystem named Electra features a custom filtered CMV4000 CMOS detector from ams AG integrated alongside a custom filtered G11478-512WB InGaAs linear array from Hamamatsu. Electra is a custom printed circuit board which houses an Intel Cyclone V system-on-chip field-programmable gate array, 512 MB of DDR3 synchronous dynamic random-access memory, and other supporting infrastructure for controlling Iris imaging operations and handling spectral data. An in-house software and VHDL suite is implemented within Electra for sensor control, memory management, and all off-board communications. Software functionality includes data compression and a cloud detection algorithm, wherein images are ranked based on heuristic value of relative cloud content, together increasing scientific value per spacecraft link time. A full proto-flight model of Iris is scheduled for manufacturing and testing in Q4 2021. Following manufacturing, comprehensive validation analysis and characterization will be performed, confirming ability to meet mission requirements

Increased Microerythrocyte Count in Homozygous α+-Thalassaemia Contributes to Protection against Severe Malarial Anaemia

Karen Day and colleagues show that increased microcytic erythrocyte count may contribute substantially to the protection of α+-thalassaemia-homozygous children against severe malaria anaemia

Vitamin D and Its Role During Pregnancy in Attaining Optimal Health of Mother and Fetus

Despite its discovery a hundred years ago, vitamin D has emerged as one of the most controversial nutrients and prohormones of the 21st century. Its role in calcium metabolism and bone health is undisputed but its role in immune function and long-term health is debated. There are clear indicators from in vitro and animal in vivo studies that point to vitamin D’s indisputable role in both innate and adaptive immunity; however, the translation of these findings to clinical practice, including the care of the pregnant woman, has not occurred. Until recently, there has been a paucity of data from randomized controlled trials to establish clear cut beneficial effects of vitamin D supplementation during pregnancy. An overview of vitamin metabolism, states of deficiency, and the results of recent clinical trials conducted in the U.S. are presented with an emphasis on what is known and what questions remain to be answered

Effects of Aversive Stimuli on Prospective Memory. An Event-Related fMRI Study

Prospective memory (PM) describes the ability to execute a previously planned action at the appropriate point in time. Although behavioral studies clearly showed that prospective memory performance is affected by the emotional significance attributed to the intended action, no study so far investigated the brain mechanisms subserving the modulatory effect of emotional salience on PM performance. The general aim of the present study was to explore brain regions involved in prospective memory processes when PM cues are associated with emotional stimuli. In particular, based on the hypothesised critical role of the prefrontal cortex in prospective memory in the presence of emotionally salient stimuli, we expected a stronger involvement of aPFC when the retrieval and execution of the intended action is cued by an aversive stimulus. To this aim BOLD responses of PM trials cued by aversive facial expressions were compared to PM trials cued by neutral facial expressions. Whole brain analysis showed that PM task cued by aversive stimuli is differentially associated with activity in the right lateral prefrontal area (BA 10) and in the left caudate nucleus. Moreover a temporal shift between the response of the caudate nucleus that preceded that of aPFC was observed. These findings suggest that the caudate nucleus might provide an early analysis of the affective properties of the stimuli, whereas the anterior lateral prefrontal cortex (BA10) would be involved in a slower and more deliberative analysis to guide goal-directed behaviour