The synthesis of a hardware scheduler for Non-Manifest Loops

This paper addresses the hardware implementation of a dynamic scheduler for non-manifest data dependent periodic loops. Static scheduling techniques which are known to give near optimal scheduling-solutions for manifest loops, fail at scheduling non-manifest loops, since they lack the run time information needed which makes a static schedule feasible. In this paper a dynamic scheduling approach was chosen to circumvent this problem. We present a case study using VHDL where the focus lies on implementations with minimal memory usage and low communication overhead between various components of the architecture. This has resulted in an efficient and synthesisable system

Design citeria for applications with non-manifest loops

In the design process of high-throughput applications, design choices concerning the type of processor architecture and appropriate scheduling mechanism, have to be made. Take a reed-solomon decoder as an example, the amount of clock cycles consumed in decoding a code is dependent on the amount of errors within that code. Since this is not known in advance, and the environment in which the code is transmitted can cause a variable amount of errors within that code, a processor architecture which employs a static scheduling scheme, has to assume the worst case amount of clock cycles in order to cope with the worst case situation and provide correct results. On the other hand a processor that employs a dynamic scheduling scheme, can gain wasted clock cycles, by scheduling the exact amount of clock cycles that are needed and not the amount of clock cycles needed for the worst case situation. Since processor architectures that employ dynamic scheduling schemes have more overhead, designers have to make their choice beforehand. In this paper we address the problem of making the correct choice of whether to use a static or dynamic scheduling scheme. The strategy is to determine whether the application possess non-manifest behavior\ud and weigh out this dynamic behavior against static scheduling solutions which were quite common in the past. We provide criteria for choosing the correct scheduling architecture for a high throughput application based upon the environmental and algorithm-specification constraints. Keywords¿ Non-manifest loop scheduling, variable latency functional units, dynamic hardware scheduling, self\ud scheduling hardware units, optimized data-flow machine architecture

Advanced signal processing methods for plane-wave color Doppler ultrasound imaging

Conventional medical ultrasound imaging uses focused beams to scan the imaging scene line-by-line, but recently however, plane-wave imaging, in which plane-waves are used to illuminate the entire imaging scene, has been gaining popularity due its ability to achieve high frame rates, thus allowing the capture of fast dynamic events and producing continuous Doppler data. In most implementations, multiple low-resolution images from different plane wave tilt angles are coherently averaged (compounded) to form a single high-resolution image, albeit with the undesirable side effect of reducing the frame rate, and attenuating signals with high Doppler shifts. This thesis introduces a spread-spectrum color Doppler imaging method that produces high-resolution images without the use of frame compounding, thereby eliminating the tradeoff between beam quality, frame rate and the unaliased Doppler frequency limit. The method uses a Doppler ensemble formed of a long random sequence of transmit tilt angles that randomize the phase of out-of-cell (clutter) echoes, thereby spreading the clutter power in the Doppler spectrum without compounding, while keeping the spectrum of in-cell echoes intact. The spread-spectrum method adequately suppresses out-of-cell blood echoes to achieve high spatial resolution, but spread-spectrum suppression is not adequate for wall clutter which may be 60 dB above blood echoes. We thus implemented a clutter filter that re-arranges the ensemble samples such that they follow a linear tilt angle order, thereby compacting the clutter spectrum and spreading that of the blood Doppler signal, and allowing clutter suppression with frequency domain filters. We later improved this filter with a redesign of the random sweep plan such that each tilt angle is repeated multiple times, allowing, after ensemble re-arrangement, the use of comb filters for improved clutter suppression. Experiments performed using a carotid artery phantom with constant flow demonstrate that the spread-spectrum method more accurately measures the parabolic flow profile of the vessel and outperforms conventional plane-wave Doppler in both contrast resolution and estimation of high flow velocities. To improve velocity estimation in pulsatile flow, we developed a method that uses the chirped Fourier transform to reduce stationarity broadening during the high acceleration phase of pulsatile flow waveforms. Experimental results showed lower standard deviations compared to conventional intensity-weighted-moving-average methods. The methods in this thesis are expected to be valuable for Doppler applications that require measurement of high velocities at high frame rates, with high spatial resolution

Incorporating Domain Knowledge in Deep Neural Networks for Discrete Choice Models

Discrete choice models (DCM) are widely employed in travel demand analysis as a powerful theoretical econometric framework for understanding and predicting choice behaviors. DCMs are formed as random utility models (RUM), with their key advantage of interpretability. However, a core requirement for the estimation of these models is a priori specification of the associated utility functions, making them sensitive to modelers' subjective beliefs. Recently, machine learning (ML) approaches have emerged as a promising avenue for learning unobserved non-linear relationships in DCMs. However, ML models are considered "black box" and may not correspond with expected relationships. This paper proposes a framework that expands the potential of data-driven approaches for DCM by supporting the development of interpretable models that incorporate domain knowledge and prior beliefs through constraints. The proposed framework includes pseudo data samples that represent required relationships and a loss function that measures their fulfillment, along with observed data, for model training. The developed framework aims to improve model interpretability by combining ML's specification flexibility with econometrics and interpretable behavioral analysis. A case study demonstrates the potential of this framework for discrete choice analysis

Electrophoretic NMR characterisation of charged sidechain cationic polyelectrolytes and their interaction with the anionic surfactant, sodium dodecyl sulfate

Oppositely charged polymers and surfactants show a complex phase behaviour, with large regions of solubility and insolubility dependent on the concentrations of the species present. Here, a series of quaternized hydroxyethyl cellulose (cationic) polymers have been characterised by pulsed-gradient spin-echo NMR (PGSE-NMR) and electrophoretic NMR (eNMR) in simple aqueous (D2O) solutions and in combination with the oppositely charged (anionic) surfactant, sodium dodecyl sulfate (SDS). Analysis of the effective charge on the polymer derived from both the eNMR and PGSE-NMR results yields a readily interpretable insight into the polymer behaviour – the effective charge on the polymer at infinite dilution shows a linear relationship with the degree of modification. On addition of low concentrations of SDS, typically Csurf < 5mM, the surfactant interacts with the charged polymers, leading to substantial changes in the dynamics of the system (polymer diffusion, viscosity). At these levels of surfactant addition, there is no macroscopic phase separation. Further, the absence of an interaction with the parent, uncharged polymer strongly suggests that the SDS only interacts with the charged moieties present on the functionalized side-groups, and not the polymer backbone. Ultimately, the charge on the soluble polymer/surfactant complex was found to depend linearly on the level of surfactant binding, across a series of polymers with differing levels of modification, with the charge becoming effectively zero at the macroscopic phase separation boundary

Comparison of the 2005 growth charts for Saudi children and adolescents to the 2000 CDC growth charts

Background and objectives: The 2000 CDC growth charts for the United States, a revision of the National Center for Health Statistics/World Health Organization (NCHS/WHO) growth charts, were released in 2002 to replace the NCHS/WHO charts. We evaluated the differences between the CDC growth charts and the Saudi 2005 reference to determine the implications of using the 2000 CDC growth charts in Saudi children and adolescents. Subjects and methods: The Saudi reference was based on a cross-sectional representative sample of the Saudi population of healthy children and adolescents from birth to 19 years of age. Measurements of the length/ stature, weight and head circumference were performed according to expert recommendations. The CDC charts from birth to 20 years were based on a cross-sectional representative national sample from five sources collected between 1963 and 1994. The data from the CDC study including the 3rd, 5th, 50th, 95th, and 97th percentiles were plotted against the corresponding percentiles on the Saudi charts for the weight for age, height for age, weight for height for children from 0 to 36 months and weight for age, stature for age and body mass index for children 2 to 19 years of age. Results: There were major differences between the two growth charts. The main findings were the upward shift of the lower percentiles of the CDC curves and the overlap or downward shift of the upper percentiles, especially for weight, weight for height, and BMI. Conclusions: The use of the 2000 CDC growth charts for Saudi children and adolescents increases the prevalence of undernutrition, stunting, and wasting, potentially leading to unnecessary referrals, investigations and parental anxiety. The increased prevalence of overweight and obesity is alarming and needs further investigation

Association between sodium-glucose cotransporter 2 (SGLT2) inhibitors and lower extremity amputation: A systematic review and meta-analysis

BACKGROUND: The association between sodium-glucose cotransporter 2 inhibitors (SGLT2i\u27s) and lower extremity amputation is unclear. PURPOSE: To systematically review randomized control trials (RCTs) and observational studies quantifying risk of lower extremity amputations associated with SGLT2i use. DATA SOURCES AND STUDY SELECTION: We searched PubMed, EMBASE, Scopus, and the Cochrane Central Register of Controlled Trials from January 2011 to February 2020 for RCTs and observational studies including lower extremity amputation outcomes for individuals with type 2 diabetes mellitus treated with SGLT2i\u27s vs. alternative treatments or placebo. DATA EXTRACTION AND SYNTHESIS: Two reviewers independently extracted data. MAIN OUTCOMES AND MEASURES: Our primary outcome was risk of lower limb amputation. Secondary outcomes included peripheral arterial disease, peripheral vascular disease, venous ulcerations, and diabetic foot infections. We also evaluated the risk of bias. We conducted random and fixed effects relative risk meta-analysis of RCTs. RESULTS: After screening 2,006 studies, 12 RCTs and 18 observational studies were included, of which 7 RCTs and 18 observational studies had at least one event. The random effects meta-analysis of 7 RCTs suggested the absence of a statistically significant association between SGLT2i exposure with evidence of substantial statistical heterogeneity (n = 424/23,716 vs n = 267/18,737 in controls; RR 1.28, CI\u27s 0.93-1.76; I2 = 62.0%; p = 0.12) whereas fixed effects analysis showed an increased risk with statistical heterogeneity (RR 1.27, 1.09-1.48; I2 = 62%; p = 0.003). Subgroup analysis of canagliflozin vs placebo showed a statistically significantly increased risk in a fixed effects meta-analysis (n = 2 RCTs, RR 1.59, 1.26-2.01; I2 = 88%; p = 0.0001) whereas the meta-analysis of dapagliflozin or empagliflozin (n = 2 RCTs each) and a single RCT for ertugliflozin did not show a significantly increased risk. The findings from observational studies were too heterogeneous to be pooled in a meta-analysis and draw meaningful conclusions. Both randomized and observational studies were of generally good methodological quality. CONCLUSIONS: Overall, there was no consistent evidence of SGLT2i exposure and increased risk of amputation. The increased risk of amputation seen in the large, long-term Canagliflozin Cardiovascular Assessment Study (CANVAS) trial for canagliflozin, and select observational studies, merits continued exploration

Catheter intervention for branch and crossed pulmonary arteries

IntroductionOver the last decade, stent implantation has become a widely accepted, effective therapy for the treatment of pulmonary arterial (PA) stenoses. Stent implantation has proved to be a safe procedure with minimal complications.ObjectivesTo review our experience with branch PA stenting. We reviewed also catheter based interventions for patients with right aortic arch and crossed pulmonary arteries associated with branch PA stenosis.MethodRetrospective data analysis of all patients who had branch PA stenting at KACC, NGHA, Riyadh KSA, during the period from January 2006 till October 2009. Patients with pulmonary atresia VSD and MAPCAS were excluded.ResultsTwenty-one patients were identified to have PA stenting during the study period. 14 were females (66.7%). Six patients (29%) were syndromic (Alagile syndrome, DiGeorge syndrome, Down syndrome, Goldenhar Syndrome, and Noonan Syndrome). Five patients (24%) had crossed Pas. Seven patients (33%) had PA, VSD, PDA, Two had TOF, one had AVSD with TOF, one DORV, one TGA, one truncus arteriosus with IAA type B, and one had Bicuspid AV with aortic stenosis as a primary diagnosis. All of them had branch PA stenting as a secondary procedure (post surgical intervention). Six patients (29%) had PA stenting as a primary intervention with no prior surgical intervention. Six patients (29%) had Bilateral branch PAs stenting, 11 (52%) had LPA stenting and 4 (19%) had RPA stenting. The median age at branch PA stenting was 35months (range 2months to 45years). The median weight was 10.5kg (2.8–100kg). The median F/U period was 32months (40days to 61months). Ten patients (48%) required stent dilatation after a median period of 28months (12–38months). One patient had failed LPA stenting (stent embolized and parked into RPA) who later underwent another intervention with successful LPA stenting.ConclusionStent implantation has proved to be a safe procedure with minimal complications.Even in those with crossed Pas. Restenoses is long term concerns which are amenable to redilatation with excellent results