The application of methods of non-linear dynamics for the improved and predictive recognition of patients threatened by sudden cardiac death

OBJECTIVES: This study introduces new methods of non-linear dynamics (NLD) and compares these with traditional methods of heart rate variability (HRV) and high resolution ECG (HRECG) analysis in order to improve the reliability of high risk stratification. METHODS: Simultaneous 30 min high resolution ECG's and long-term ECG's were recorded from 26 cardiac patients after myocardial infarction (MI). They were divided into two groups depending upon the electrical risk, a low risk group (group 2, n = 10) and a high risk group (group 3, n = 16). The control group consisted of 35 healthy persons (group 1). From these electrocardiograms we extracted standard measures in time and frequency domain as well as measures from the new non-linear methods of symbolic dynamics and renormalized entropy. RESULTS: Applying discriminant function techniques on HRV analysis the parameters of non-linear dynamics led to an acceptable differentiation between healthy persons and high risk patients of 96%. The time domain and frequency domain parameters were successful in less than 90%. The combination of parameters from all domains and a stepwise discriminant function separated these groups completely (100%). Use of this discriminant function classified three patients with apparently low (no) risk into the same cluster as high risk patients. The combination of the HRECG and HRV analysis showed the same individual clustering but increased the positive value of separation. CONCLUSIONS: The methods of NLD describe complex rhythm fluctuations and separate structures of non-linear behavior in the heart rate time series more successfully than classical methods of time and frequency domains. This leads to an improved discrimination between a normal (healthy persons) and an abnormal (high risk patients) type of heart beat generation. Some patients with an unknown risk exhibit similar patterns to high risk patients and this suggests a hidden high risk. The methods of symbolic dynamics and renormalized entropy were particularly useful measures for classifying the dynamics of HRV.     

Proximity of helices VIII (Ala273) and IX (Met299) in the lactose permease of Escherichia coli

Three double-Cys mutant pairs--Ala273-->Cys/Met299-->Cys, Thr266-->Cys/Ile303-->Cys, and Thr266-->Cys/Ser306-->Cys--were constructed in a functional lac permease construct devoid of Cys residues, and the excimer fluorescence or electron paramagnetic resonance (EPR) was studied with pyrene- or spin-labeled derivatives, respectively. After reconstitution into proteoliposomes, excimer fluorescence is observed with mutant Ala273-->Cys/Met299-->Cys, but not with the single-Cys mutants nor with mutants Thr266-->Cys/Ile303-->Cys or Thr266-->Cys/Ser306-->Cys. Furthermore, spin-spin interaction is also observed with mutant Ala273-->Cys/Met299-->Cys, but only after the permease is reconstituted into proteoliposomes. The results provide independent support for the conclusions that helix VIII is close to helix IX and that the transmembrane helices of the permease are more loosely packed in a detergent micelle as opposed to a phospholipid bilayer.     

Waves,currents, tides—problems and prospects

A quantitative estimation of the energy potential of ocean surface waves, ocean currents and tides and a review of the techniques for utilizing these renewable energy sources, their present state of development and their economic and environmental aspects are presented. The potential of wave power, which is in the order of 1–10 TW, could become a significant source of energy in regions of the world with favorable wave conditions, such as the United Kingdom and Japan. All wave-power schemes investigated today are in an early stage of development, and require more research to become commercially available. The prospects for utilizing ocean currents are relatively unattractive due to the small resource base and the possible environmental effects. Although tidal mills have been used since the eleventh century, today only one sizable tidal power plant has been built, the 240 MW_e Rance Tidal Power Station in France. The overall potential of tidal energy is about 3 TW, but only in certain locations of the world do the natural conditions promise technical and economic viability.     

Sequencing and analysis of 51·6 kilobases on the left arm of chromosome XI from Saccharomyces cerevisiae reveals 23 open reading frames including the FAS1 gene

We have sequenced two segments containing a total of 51·6 kb of the left arm from chromosome XI of Saccharomyces cerevisiae. The first segment of 38·5 kb contains 18 open reading frames (ORFs) of more than 100 amino acid residues. Five ORFs encode known yeast genes, including the fatty acid synthase gene (FAS1). Three new yeast genes were discovered with homologies to non-yeast genes and ten new genes without homologies to any known sequences. The second segment of 13 kb contains five ORFs with two known yeast genes and three unknown genes. The sequences from cosmid pUKG041 were obtained entirely with the walking primer strategy resulting in a very low overall sequence redundancy of 2·8 and an average reading length of 443 bases.     

The dilemma of colonic vasculitis: report of a unique case

A case is presented of a patient, diagnosed preoperatively as having cecal carcinoma, who was found, at operation, to have a pathologically selective vasculitis involving the right side of the colon which was unclassifiable in any of the known vasculitides. Problems of diagnosis and classification and their bearing on management are discussed.     

Frequencies of n-polygons in planar sections of polyhedrons

In geology and metallography thin or polished sections of crystalline aggregates are a main subject of microscopic investigations. It is important to know what kinds of polygons are generated by planar sections through polyhedrons. In recent years computer simulation was the common method to determine the frequencies of n-polygons. In this paper an integral geometric approach to derive exact formulas for these frequencies is described. For some families of simple polyhedrons results are given in analytical form and as numerical values.     

A quintic spline collocation procedure for solving the falkner-skan boundary-layer equation

A quintic spline collocation method is used to numerically solve the Falkner-Skan similarity boundary-layer equation for a wide range of pressure gradient parameter, both favorable and adverse, and wall mass transfer, both injection and suction. Through proper choice of the parameter in a constant ratio interval variable-grid system, extremely accurate solutions are obtained with as few as 7 grid points across the boundary layer. It is suggested that perhaps the method and grid system can be coupled to yield an optimal node distribution technique which will allow highly accurate solutions with few grid points and minimum discretion on the part of the user.