An algorithm for the design of generalized quantizers for detection

A procedure based on the generalized Lloyd algorithm approach using a sequence of independent noise samples to design M-region generalized quantizers for signal detection is presented. Included in this case are the conventional M-interval quantizer detectors. The quantizer parameters for S.A. Kassam's (1985) four-region generalized quantizer detector are computed using various sample sizes for the known sequence of independent noise samples. Two families of densities which cover a wide spectrum of possible nonGaussian densities are considered: the generalized Gaussian densities and the Johnson S_u family of densities. The performance of the quantizer detector is compared to that of the locally optimum detector, and the results are presented as the asymptotic relative efficiencies of the respective detectors. The case when the noise density is not known before analysis is considered, and the detection performance is examined using an estimate of the density. A mean-squared-error distortion criterion is used in the proposed algorithm to obtain quantizers that yield maximum efficacy. It is shown through numerical examples that the design procedure is simple, fast, and applicable to a wide range of nonGaussian distributions     

Identification and correction of water velocity measurement errors associated with ultrasonic Doppler flow monitoring

Ultrasonic Doppler flow monitoring (UDFM) is used to measure water flow in pipes and channels. However, a lack of scattering particles and signal noise can cause velocity errors, particularly for smaller discharges and surface water ('clean') flows. A postprocessing methodology is presented that identifies and corrects these errors, maximising the value of existing data. Test criteria are used to identify errors. The error correction procedure defines depth–velocity relationships from cleaned 'training data' representing the range of flow conditions (including backed up) and uses these relationships to replace erroneous velocities automatically. UDFM velocity errors have been successfully identified and corrected in example applications. Routine use allows early identification of changes in instrument or site behaviour. The methodology is practical, consistent and updateable. This is a significant advancement over previous methods for correcting velocity errors, improving the applicability of UDFM.     

Systemic inflammatory response syndrome treatment by powdered sorbent pheresis: the BioLogic-Detoxification Plasma Filtration System

Systemic inflammatory response syndrome (SIRS) is one of the most common causes of death in intensive care unit patients. The detoxification plasma filtration (DTPF) system (HemoCleanse, Inc., West Lafayette, IN) combines the DT hemodiabsorption system in series with a push-pull pheresis PF system (a suspension of powdered sorbents surrounding 0.5 microm plasma filter membranes). Bidirectional plasma flow (at 80-100 ml/min) across the PF membranes provides direct contact between plasma proteins and powdered sorbents, as well as clearance of cytokines (tumor necrosis factor-alpha, interleukin-1beta, and interleukin-6) at a rate of 15-25 ml/min, without evidence of saturation for 90 minutes. In a U.S. Food and Drug Administration approved study we treated eight patients with SIRS and organ failure with a single DTPF treatment, using powdered charcoal as sorbent in four patients and powdered charcoal and silica in four patients. Treatments proceeded for 6 hours with proper heparin anticoagulation (activated clotting time 250-300 sec) and appeared safe. All patients improved during the treatments and each had increased blood pressure and decreased need for pressor agents. Plasma cytokine levels stabilized or decreased during treatment and were significantly lower the morning after treatment. Multiple organ dysfunction (MOD) and Acute Physiology Chronic Health Evaluation II scores and organ function gradually improved in most patients, and two patients survived for more than 28 days and two for more than 14 days. The DTPF System may prove beneficial in treatment of patients with sepsis.     

Liver failure associated with mitochondrial DNA depletion

BACKGROUND/AIMS: Liver failure in infancy can result from several disorders of the mitochondrial respiratory chain. In some patients, levels of mitochondrial DNA are markedly reduced, a phenomenon referred to as mitochondrial DNA depletion. To facilitate diagnosis of this condition, we have reviewed the clinical and pathological features in five patients with mitochondrial DNA depletion. METHODS: Cases were identified by preparing Southern blots of DNA from muscle and liver, hybridising with appropriate probes and quantifying mitochondrial DNA relative to nuclear DNA. RESULTS: All our patients with mitochondrial DNA depletion died of liver failure. Other problems included hypotonia, hypoglycaemia, neurological abnormalities (including Leigh syndrome) and cataracts. Liver histology showed geographic areas of fatty change, bile duct proliferation, collapse of liver architecture and fibrosis; some cells showed decreased cytochrome oxidase activity. Muscle from three patients showed mitochondrial proliferation, with loss of cytochrome oxidase activity in some fibres but not in others; in these cases, muscle mitochondrial DNA levels were less than 5% of the median control value. The remaining two patients (from a single pedigree) had normal muscle histology and histochemistry associated with less severe depletion of mitochondrial DNA in muscle. CONCLUSIONS: Liver failure is common in patients with mitochondrial DNA depletion. Associated clinical features often include neuromuscular disease. Liver and muscle histology can be helpful in making the diagnosis. Mitochondrial DNA levels should be measured whenever liver failure is thought to have resulted from respiratory chain disease.     

Imperfect quarter-waveplate compensation in Sagnacinterferometer-type current sensors

We analyze scale factor errors associated with integrating imperfect quarter-waveplates into loop and in-line Sagnac interferometer fiber-optic current sensors. We show that relatively large imperfections in the quarter-waveplates can be tolerated in the loop version when the birefringence axes of the two quarter-waveplates are oriented 45° with respect to each other. For the in-line version, we demonstrate an electronic signal processing scheme that desensitizes the scale factor to imperfections in the quarter-waveplate     

COAL SWELLING AND CO-PROCESSING

Herrin No. 6 coal and the filter cake cleaned product from Pittsburgh No. 8 coal were co-processed with a liquid produced from the mild gasification of Wyodak coal. The co-processing studies were conducted in tubing bomb reactors and in a batch autoclave under hydrogen pressure. The reactants were thermally pretreated under helium to induce coal swelling and promote catalyst dispersion. Ferrocene and iron pentacarbonyl were used as catalyst precursors for these studies and were sulfided in situ to generate the active forms of the iron catalyst. Iron pentacarbonyl was found to form the better catalyst for conversion of these coals. Conversion of the filter cake product was found to be enhanced by pretreatment with the mild gasification liquid, because this treatment caused the coal to swell and promoted uniform dispersion of the catalyst. Higher coal conversion was observed from co-processing Herrin No. 6 coal compared to the filter cake product. This indicates the Herrin No. 6 coal would be the preferred coal to use in a commercial process. There was improvement in the quality of the oil product from co-processing Herrin No. 6 coal compared to the mild-gasification liquid.     

Modeling burst channels using partitioned Fritchman's Markov models

Discrete models based on functions of Markov chains (also referred to as hidden Markov models or finite-state channel (FSC) models) have been used to characterize the error process in communication channels with memory. One important property of these models is that the probability of any observed sequence can be expressed as a linear combination of the probability of a finite set of sequences of finite length, the so-called basis sequences. In this paper, we express the parameters of a class of FSC models as a simple function of the probability of the basis sequences. Based on this approach, we propose a new method for the parameterization of the Fritchman (1967) channel with single-error state as well as the interesting cases of Fritchman channels with more than one error state and the Gilbert-Elliott channel ((GEC) nonrenewal models). To illustrate the method, FSC models for the nonfrequency-selective Rician fading channel are presented. The number of states and the probability of state transitions are estimated for a given set of fading parameters     

Ambient fine particulate air pollution triggers ST-elevation myocardial infarction, but not non-ST elevation myocardial infarction: a case-crossover study

Background

We and others have shown that increases in particulate air pollutant (PM) concentrations in the previous hours and days have been associated with increased risks of myocardial infarction, but little is known about the relationships between air pollution and specific subsets of myocardial infarction, such as ST-elevation myocardial infarction (STEMI) and non ST-elevation myocardial infarction (NSTEMI).

Methods

Using data from acute coronary syndrome patients with STEMI (n?=?338) and NSTEMI (n?=?339) and case-crossover methods, we estimated the risk of STEMI and NSTEMI associated with increased ambient fine particle (<2.5 um) concentrations, ultrafine particle (10-100 nm) number concentrations, and accumulation mode particle (100-500 nm) number concentrations in the previous few hours and days.

Results

We found a significant 18% increase in the risk of STEMI associated with each 7.1 μg/m³ increase in PM_2.5 concentration in the previous hour prior to acute coronary syndrome onset, with smaller, non-significantly increased risks associated with increased fine particle concentrations in the previous 3, 12, and 24 hours. We found no pattern with NSTEMI. Estimates of the risk of STEMI associated with interquartile range increases in ultrafine particle and accumulation mode particle number concentrations in the previous 1 to 96 hours were all greater than 1.0, but not statistically significant. Patients with pre-existing hypertension had a significantly greater risk of STEMI associated with increased fine particle concentration in the previous hour than patients without hypertension.

Conclusions

Increased fine particle concentrations in the hour prior to acute coronary syndrome onset were associated with an increased risk of STEMI, but not NSTEMI. Patients with pre-existing hypertension and other cardiovascular disease appeared particularly susceptible. Further investigation into mechanisms by which PM can preferentially trigger STEMI over NSTEMI within this rapid time scale is needed.     

3D Printed Anatomical Nerve Regeneration Pathways

A 3D printing methodology for the design, optimization, and fabrication of a custom nerve repair technology for the regeneration of complex peripheral nerve injuries containing bifurcating sensory and motor nerve pathways is introduced. The custom scaffolds are deterministically fabricated via a microextrusion printing principle using 3D models, which are reverse engineered from patient anatomies by 3D scanning. The bifurcating pathways are augmented with 3D printed biomimetic physical cues (microgrooves) and path‐specific biochemical cues (spatially controlled multicomponent gradients). In vitro studies reveal that 3D printed physical and biochemical cues provide axonal guidance and chemotractant/chemokinetic functionality. In vivo studies examining the regeneration of bifurcated injuries across a 10 mm complex nerve gap in rats showed that the 3D printed scaffolds achieved successful regeneration of complex nerve injuries, resulting in enhanced functional return of the regenerated nerve. This approach suggests the potential of 3D printing toward advancing tissue regeneration in terms of: (1) the customization of scaffold geometries to match inherent tissue anatomies; (2) the integration of biomanufacturing approaches with computational modeling for design, analysis, and optimization; and (3) the enhancement of device properties with spatially controlled physical and biochemical functionalities, all enabled by the same 3D printing process.     

Development and experimental characterization of a fuel cell powered aircraft

This paper describes the characteristics and performance of a fuel cell powered unmanned aircraft. The aircraft is novel as it is the largest compressed hydrogen fuel cell powered airplane built to date and is currently the only fuel cell aircraft whose design and test results are in the public domain. The aircraft features a 500 W polymer electrolyte membrane fuel cell with full balance of plant and compressed hydrogen storage incorporated into a custom airframe. Details regarding the design requirements, implementation and control of the aircraft are presented for each major aircraft system. The performances of the aircraft and powerplant are analyzed using data from flights and laboratory tests. The efficiency and component power consumption of the fuel cell propulsion system are measured at a variety of flight conditions. The performance of the aircraft powerplant is compared to other 0.5–1 kW-scale fuel cell powerplants in the literature and means of performance improvement for this aircraft are proposed. This work represents one of the first studies of fuel cell powered aircraft to result in a demonstration aircraft. As such, the results of this study are of practical interest to fuel cell powerplant and aircraft designers.