Blind source separation based on time-frequency signalrepresentations

Blind source separation consists of recovering a set of signals of which only instantaneous linear mixtures are observed. Thus far, this problem has been solved using statistical information available on the source signals. This paper introduces a new blind source separation approach exploiting the difference in the time-frequency (t-f) signatures of the sources to be separated. The approach is based on the diagonalization of a combined set of “spatial t-f distributions”. In contrast to existing techniques, the proposed approach allows the separation of Gaussian sources with identical spectral shape but with different t-f localization properties. The effects of spreading the noise power while localizing the source energy in the t-f domain amounts to increasing the robustness of the proposed approach with respect to noise and, hence, improved performance. Asymptotic performance analysis and numerical simulations are provided     

Roof-harvested rainwater for potable purposes: Application of solar collector disinfection (SOCO-DIS)

The efficiency of solar disinfection (SODIS), recommended by the World Health Organization, has been determined for rainwater disinfection, and potential benefits and limitations discussed. The limitations of SODIS have now been overcome by the use of solar collector disinfection (SOCO-DIS), for potential use of rainwater as a small-scale potable water supply, especially in developing countries. Rainwater samples collected from the underground storage tanks of a rooftop rainwater harvesting (RWH) system were exposed to different conditions of sunlight radiation in 2-L polyethylene terephthalate bottles in a solar collector with rectangular base and reflective open wings. Total and fecal coliforms were used, together with Escherichia coli and heterotrophic plate counts, as basic microbial and indicator organisms of water quality for disinfection efficiency evaluation. In the SOCO-DIS system, disinfection improved by 20–30% compared with the SODIS system, and rainwater was fully disinfected even under moderate weather conditions, due to the effects of concentrated sunlight radiation and the synergistic effects of thermal and optical inactivation. The SOCO-DIS system was optimized based on the collector configuration and the reflective base: an inclined position led to an increased disinfection efficiency of 10–15%. Microbial inactivation increased by 10–20% simply by reducing the initial pH value of the rainwater to 5. High turbidities also affected the SOCO-DIS system; the disinfection efficiency decreased by 10–15%, which indicated that rainwater needed to be filtered before treatment. The problem of microbial regrowth was significantly reduced in the SOCO-DIS system compared with the SODIS system because of residual sunlight effects. Only total coliform regrowth was detected at higher turbidities. The SOCO-DIS system was ineffective only under poor weather conditions, when longer exposure times or other practical means of reducing the pH were required for the treatment of stored rainwater for potable purposes.     

Antioxidant capacity of methanolic and water extracts prepared from food‐processing by‐products

This study aims to evaluate the antioxidant capacity of mango peel, roselle seed, okara (by‐product of soya milk industry), cocoa shell and pink guava (by‐product of pink guava industry) in comparison to 6‐hydroxy‐2,5,7,8‐tetramethylchroman‐2‐carboxylic acid (Trolox). The β‐carotene bleaching, 1,1‐diphenyl‐2‐picrylhydrazyl and reducing power assays were used to determine the antioxidant capacity of selected by‐products by measuring the absorbance at 470, 520 and 700 nm, respectively. The results showed that methanolic extracts of pink guava and cocoa shell exhibited the highest antioxidant activity and free radical scavenging activity compared to other studied samples. Roselle seed water extract exhibited the highest antioxidant activity and free radical scavenging when extracted with water. Pink guava possessed the highest reducing power in methanolic extract at a concentration of 0.16 mg mL^?1. At the same concentration, mango peel exhibited the highest reducing power when extracted with water. The present study shows that pink guava, roselle seed and cocoa shell are potential sources of antioxidant components that can be exploited as food preservative agents or nutraceuticals. Copyright © 2006 Society of Chemical Industry     

Mitogen-activated protein kinases (Erk1,2) phosphorylate Lys-Ser-Pro (KSP) repeats in neurofilament proteins NF-H and NF-M

Mammalian neurofilament proteins, particularly midsized (NF-M) and heavy (NF-H) molecular weight neurofilament proteins, are highly phosphorylated in axons. Neurofilament function depends on the state of phosphorylation of the numerous serine/threonine residues in these proteins. Most phosphorylation occurs in the lys-ser-pro (KSP) repeats in the C-terminal tail domains of NF-H and NF-M. In our previous study, cyclin-dependent kinase 5 (cdk5) was shown to phosphorylate specifically the KSPXK repeats in rat NF-H. Because 80% of the repeats are of the KSPXXXK type, it was of interest to determine which kinase phosphorylates these motifs. Using a synthetic KSPXXXK peptide to screen for a specific kinase, we fractionated rat brain extracts by column chromatography and identified extracellular signal-regulated kinase (Erk2) activated by an upstream activator, the mitogen-activated protein kinase kinase MAPKK (MEK), by Western blot analysis, sequence identification, and inhibition by a specific MEK inhibitor (PD 98059). The fraction containing Erk2, as well as bacterially expressed Erk1 and Erk2, phosphorylated all types of KSP motifs in peptides (KSPXK, KSPXXK, KSPXXXK, and KSPXXXXK) derived from NF-M and NF-H. They also phosphorylated an expressed 24 KSPXXXK repeat NF-H polypeptide, an expressed NF-H as well as dephosphorylated native rat NF-H, and NF-M proteins with accompanying decreases in their respective electrophoretic mobilities. A comparative kinetic study of Erk2 and cdk5 phosphorylation of KSPXK and KSPXXXK peptides revealed that, in contrast to cdk5, which phosphorylated only the KSPXK peptide, Erk2 could phosphorylate both. The preferred substrate for Erk2 was KSPXXXK peptide. The MEK inhibitor PD 98059 also inhibited phosphorylation of NF-H, NF-M, and microtubule-associated protein (MAP) in primary rat hippocampal cells and caused a decrease in neurite outgrowth, suggesting that Erk1,2 may play an important role in neurite growth and branching. These data suggest that neuronal Erk1 and Erk2 are capable of phosphorylating serine residues in diverse KSP repeat motifs in NF-M and NF-H.     

Moderate ovarian hyperstimulation syndrome complicated by deep cerebrovascular thrombosis

This report describes two cases that developed moderate ovarian hyperstimulation syndrome (OHSS) without evidence of haemoconcentration. Both patients developed serious cerebrovascular thrombosis resulting in hemiparesis, and recovered after treatment with anticoagulants. This report emphasizes that other factors may contribute to vascular thrombosis, and illustrates that cerebrovascular accidents may complicate even moderate OHSS.     

Solar box cookers: Towards a decentralized sustainable energy strategy for sub-Saharan Africa

The continued economic decline of sub-Saharan Africa, and the African energy crisis in particular, have received considerable attention in recent literature. Little attention, however, has been given to the assessment of solar power as an environmentally sound and economically viable energy strategy. Considering the increasing fuelwood scarcity and debt incurred through petroleum imports, solar energy provides a welcome alternative to traditional biomass and fossil fuel energy sources. Research and development in solar energy has concentrated primarily on highly technical, capital intensive applications, leaving possibilities for small scale utilizations unexplored. This paper argues for small scale, decentralized development of solar power as a sustainable household fuel source for sub-Saharan Africa. Domestic cooking constitutes more than 60% of total energy use in the region and consumes scarce time, labor, income, and natural resources. Thus, the appropriate management of fuel and energy resources in the residential sector is crucial for significant development. This paper examines the economic viability of solar box cookers (SBCs), their costs and benefits both on the household and community levels, and how they may contribute to economic development. In arguing for the implementation of SBCs, policy implications in terms of financing and a comprehensive energy plan geared towards sustainable development are also presented.     

Meta-Heuristic Algorithms for Hydrologic Frequency Analysis

Meta-heuristic algorithms, such as the genetic algorithm and ant colony optimization, have received considerable attention in recent years due to their higher ability for solving difficult engineering optimization problems. This paper employs these techniques for estimating parameters of commonly used flood frequency distributions, and compares them with some conventional methods such as maximum likelihood, moments and probability weighted moments using annual maximum discharge data of 14 rivers from East-Azarbaijan, Iran. The results indicate that both the genetic algorithm and ant colony optimization are suitable parameter estimation alternatives. Also, the results of Monte Carlo simulation for various sample sizes, ranging from 20 to 100, demonstrate that the meta-heuristic algorithms yield accurate quantile estimates.     

Repair of coarctation with resection and extended end-to-end anastomosis

BACKGROUND: Our surgical strategy for infant coarctation changed from subclavian flap aortoplasty to resection with extended end-to-end anastomosis in 1991. The purpose of this review was to evaluate the results of that strategy. METHODS: From 1991 through 1997, 55 infants underwent repair of coarctation of the aorta using resection with extended end-to-end anastomosis. Isolated coarctation of the aorta was present in 26 patients, 20 patients had a ventricular septal defect, and 9 patients had other associated intracardiac lesions. Mean age at surgery was 0.20+/-0.24 years (median, 21 days). In 34 patients (62%), arch reconstruction was performed through a left thoracotomy. Twenty patients (36%) had median sternotomy with simultaneous repair of coarctation of the aorta and intracardiac repair of associated lesions. One patient had recoarctation repair through a median sternotomy. All coarctation and ductal tissue was resected and the anastomosis was constructed starting opposite the left carotid artery with running polypropylene suture. RESULTS: There was one early death 26 days after coarctation of the aorta and ventricular septal defect repair in a child on extracorporeal membrane oxygenation for meconium aspiration and 2 late deaths owing to pneumonia and pulmonary hypertension (1) and interventricular hemorrhage (1). There were no instances of paraplegia. Follow-up in survivors ranges from 10 to 76 months (mean, 39.8+/-17.2 months). Recoarctation has developed in 2 patients, who have had successful balloon dilation 6 and 14 months after the operation. This yields a low recoarctation rate of 3.6%. CONCLUSIONS: Resection with extended end-to-end anastomosis yields a low mortality and particularly a low recoarctation rate and is our procedure of choice for infants with coarctation of the aorta.     

North America's electricity infrastructure: are we ready for more perfect storms?

With the tragic events of 9/11 permanently etched in our minds, the massive 14 August power outage evoked eerie reminders of what shook our world 2 years ago. While preliminary reports indicate that there was no apparent evidence of terrorism, the cascading blackouts were a sudden illumination of our electricity infrastructure's vulnerable condition. This infrastructure affects us all - are we prepared for future storms?.