An efficient method for network topology identification based on an SOM algorithm

In this paper we consider a large number of wireless terminals that are interconnected by a multihop wireless network called an ad hoc network. Design of routing protocols is a crucial problem in ad hoc networks. Location information of wireless terminals is an effective measure for ad hoc network routing. This paper presents a method to identify network topology implying terminal location and connections among terminals. A modified Self‐Organizing Map (SOM) algorithm is proposed to apply to the network topology identification. This method exploits information of the received power levels of the signals that are transmitted by other terminals. This paper has evaluated how network topology is identified by means of an example graph made by random numbers. The results show that only one bit information about the received power level in each terminal can identify network topology accurately with a mean error of about 10% for more terminals than a certain value. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 142(4): 34–44, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10100     

Vibration-based automatic power-generation system

Two types of electric power generator systems that automatically extract power from oscillating motion of a human body or vibration of machines and structures are proposed and studied. The first system utilizes self-excited rotation of an eccentric rotor that rotates in one direction in synchronization with the applied oscillating motion. Connecting an electrical load to the generator increases the damping about the rotor axis, and numerical analysis shows that there exists an upper limit to this damping to maintain the self-excited rotation mode. Excessive damping reduces the rotor to a swinging motion, resulting in decreased power output. The second type utilizes resonant vibration of a permanent magnet unit suspended by a set of springs. In order to maximize the output power, a micro controller changes the connection of the generator coils, which in effect changes the electro-mechanical damping, to keep the vibration amplitude within the allowable stroke. Theoretical analysis and experimental results are presented for both systems.     

Limb salvage and survival rates among elderly patients with advanced limb ischemia

Beta-Thalassemia hemoglobin E (beta-thal/Hb E) is the commonest form of hemoglobinopathy in Thailand. Shortened red cell life span, rapid iron turnover and tissue deposition of excess iron are major factors responsible for functional and physiological abnormalities found in various forms of thalassemia. Increased deposition of iron had been found in renal parenchyma of thalassemic patients, but no systematic study of the effect of the deposits on renal functions has been available. The purpose of this study is to describe the functional abnormalities of the kidney in patients with beta-thal/Hb E and provide evidence that increased oxidative stress might be one of the factors responsible for the damage. Urine and serum samples from 95 patients with beta-thal/Hb E were studied comparing with 27 age-matched healthy controls. No difference in the creatinine clearance was observed. beta-thal/Hb E patients excreted significantly more urinary protein (0.8+/-0.5 vs. 0.3+/-0.1 g/day, p < 0.001). Aminoaciduria was found in 16 % of the patients. Analysis of urinary protein by SDS-PAGE electrophoresis and silver staining revealed abnormal pattern of protein with increased small molecular weight (<45 kD) bands. Morning urine analysis showed significant lower urine osmolality (578.3+/-164.6 vs. 762.4+/-169.9 mosm/kg, p < 0.001) in patients. Patients excreted more NAG (N-acetyl beta-D-glucosaminidase, 26.3+/-41.3 vs. 8.4+/-3.9 U/g Cr, p < 0.0001) and beta2-microglobulin, 124.3+/-167 vs. 71+/-65.5 microg/g Cr, p = 0.001. Plasma and urine MDA (malonyldialdehyde) levels were both raised (p < 0.0001). Nine patients were selected for renal acidification study. All were found to be normal, but showed poor response to DDAVP challenge (urine osmolality 533+/-71). This is the first report of renal tubular defects found associated with beta-thal/Hb E disease. The mechanism leading to the damage is not known but it might be related to increased oxidative stress secondary to tissue deposition of iron, as indicated by the raised levels of serum and urine MDA. It is not known whether these functional defects would have any long-term effects on the patients. Further studies are warranted and means of prevention of these defects should urgently be sought.     

Effect of percutaneous transvenous mitral commissurotomy on postexercise breathlessness as determined by ventilation during recovery from constant workload exercise

We evaluated the effect of percutaneous transvenous mitral commissurotomy (PTMC) on ventilatory variables and dyspnea during recovery from a 6-minute submaximal constant workload exercise, and showed that the decrease in postexercise ventilation after PTMC was closely related to improvement in postexercise dyspnea after PTMC. Ventilation during recovery from submaximal constant workload exercise is related to postexercise breathlessness and can be used to assess the effectiveness of therapeutic interventions.     

Synthesis of new members of Pb-based 1222 superconductors containing sulfur: (Pb0.75S0.25)Sr2(RE1.6Ce0.4)Cu2O z (RE = Sm,Gd, Dy,and Ho)

We have discovered new members of the Pb-based 1222 layered cuprates containing sulfur of (Pb_0.75S_0.25)Sr₂(RE_1.6Ce_0.4)Cu₂O _z with RE = Sm, Gd, Dy, and Ho. All the samples are of almost-single 1222 phase. From the ρ–T and χ–T measurements, they are found to be superconductors after annealing under 125 atm O₂ atmosphere at 400 °C. Among them, the sample with RE = Gd is found to show superconductivity at the highest temperature of 30 K.     

Chirality Emergence in Thin Solid Films of Amino Acids by Polarized Light from Synchrotron Radiation and Free Electron Laser

One of the most attractive hypothesis for the origin of homochirality in terrestrial bioorganic compounds is that a kind of “chiral impulse” as an asymmetric excitation source induced asymmetric reactions on the surfaces of such materials such as meteorites or interstellar dusts prior to the existence of terrestrial life (Cosmic Scenario). To experimentally introduce chiral structure into racemic films of amino acids (alanine, phenylalanine, isovaline, etc.), we irradiated them with linearly polarized light (LPL) from synchrotron radiation and circularly polarized light (CPL) from a free electron laser. After the irradiation, we evaluated optical anisotropy by measuring the circular dichroism (CD) spectra and verified that new Cotton peaks appeared at almost the same peak position as those of the corresponding non-racemic amino acid films. With LPL irradiation, two-dimensional anisotropic structure expressed as linear dichroism and/or linear birefringence was introduced into the racemic films. With CPL irradiation, the signs of the Cotton peaks exhibit symmetrical structure corresponding to the direction of CPL rotation. This indicates that some kinds of chiral structure were introduced into the racemic film. The CD spectra after CPL irradiation suggest the chiral structure should be derived from not only preferential photolysis but also from photolysis-induced molecular structural change. These results suggest that circularly polarized light sources in space could be associated with the origin of terrestrial homochirality; that is, they would be effective asymmetric exciting sources introducing chiral structures into bio-organic molecules or complex organic compounds.     

Importance of specific purine-pyrimidine amino and hydroxyl groups for efficient cleavage by a hammerhead ribozyme

Subsequent of the discovery that RNA can have site specific cleavage activity, there has been a great deal of interest in the design and testing of trans-acting catalytic RNAs as therapeutic agents. We have chemically synthesized and experimentally analyzed chimeric DNA-RNA ribozymes in which the catalytic center remains as RNA.     

Identification and functional analysis of sulfonylurea receptor 1 variants in Japanese patients with NIDDM

The sulfonylurea receptor 1 (SUR1) is an essential regulatory subunit of the beta-cell ATP-sensitive K+ channel (K[ATP]). The possible role of SUR1 gene mutation(s) in the development of NIDDM remains controversial as both a positive association and negative linkage results have been reported. Therefore, we examined the SUR1 gene at the single nucleotide level with single strand conformation polymorphism analysis in 100 Japanese NIDDM patients. We identified a total of five amino acid substitutions and 17 silent mutations by examining all 39 exons of this gene. Two rare novel mutations, D811N in exon 20 and R835C in exon 21, were identified in the first nucleotide-binding fold (NBF), a functionally important region of SUR1, in one patient each, both heterozygotes. To analyze possible functional alterations, we reconstituted the mutant K(ATP) by coexpressing beta-cell inward rectifier (BIR) (Kir 6.2), a channel subunit of K(ATP), and mutant SUR1 in HEK293T and COS-7 cells. As demonstrated by the patch clamp technique and rubidium (Rb+) efflux studies, neither mutation alters the properties of channel activities. Two other rare missense mutations, R275Q in exon 6 and V560M in exon 12, were also identified. The R275Q substitution was not found in 67 control subjects, and V560M was present in three control subjects. Neither of these substitutions appeared to cosegregate with NIDDM in the probands' families. A previously reported S1370A substitution located in the second NBF was also common in the Japanese subjects (allelic frequency 0.37), and was found at an equal frequency in nondiabetic control subjects. In conclusion, SUR1 mutations impairing K(ATP) function do not appear to be major determinants of NIDDM susceptibility in Japanese.     

A new colorimetric method for the determination of free fatty acids with acyl-CoA synthetase and acyl-CoA oxidase

A rapid and sensitive spectrophotometric assay for free fatty acids using acyl-CoA synthetase and acyl-CoA oxidase is described. It is sensitive to as low as 5 nmol of free fatty acids, and the standard curve is linear up to 100 nmol. The assay consists of the measurement of H2O2 produced from free fatty acids by acyl-CoA synthetase and acyl-CoA oxidase. The quantity of H2O2 is determined by the absorbance at 550 nm in the presence of catalase and 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole (AHMT). This method shows a broad specificity to long-chain fatty acids and the recoveries of added fatty acids (C12-C18) are more than 90%. The presence or absence of serum components or Escherichia coli cell-free extracts has no significant effect on the recovery of added palmitic acid.