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  • Artikel: DFG Deutsche Nationallizenzen  (48)
  • Chemistry  (43)
  • Stomach  (5)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Annals of biomedical engineering 26 (1998), S. 859-869 
    ISSN: 1573-9686
    Schlagwort(e): Spectral analysis ; Matching pursuit ; Stomach ; Gastric motility ; Electrogastrography ; Evolutionary programming ; Signal analysis ; Electrogastrogram
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract The electrogastrogram (EGG) is a surface measurement of gastric myoelectrical activity. The normal frequency of gastric myoelectrical activity in humans is 3 cycles/min. Abnormal frequencies in gastric myoelectrical activity have been found to be associated with functional disorders of the stomach. The aim of this article was, therefore, to develop new time-frequency analysis methods for the detection of gastric dysrhythmia from the EGG. A concept of overcomplete signal representation was used. Two algorithms were proposed for the optimization of the overcomplete signal representation. One was a fast algorithm of matching pursuit and the other was based on an evolutionary program. Computer simulations were performed to compare the performance of the proposed methods in comparison with existing time-frequency analysis methods. It was found that the proposed algorithms provide higher frequency resolution than the short time Fourier transform and Wigner-Ville distribution methods. The practical application of the developed methods to the EGG is also presented. It was concluded that these methods are well suited for the time-frequency analysis of the EGG and may also be applicable to the time-frequency analysis of other biomedical signals. © 1998 Biomedical Engineering Society. PAC98: 8780+s, 0705Kf
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Annals of biomedical engineering 27 (1999), S. 88-95 
    ISSN: 1573-9686
    Schlagwort(e): Electrogastrography ; Gastric motility ; Stomach ; Filter banks ; Neural networks
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract Dysrhythmia in gastric myoelectrical activity has been frequently observed in patients with gastric motor disorders and gastrointestinal symptoms. The assessment of the regularity of gastric myoelectrical activity is of great clinical significance. The aim of this study was to develop an automated assessment method for the regularity of gastric myoelectrical activity from the surface electrogastrogram (EGG). The method proposed in this paper was based on the filter bank and neural network. First, the EGG signal was divided into frequency subbands using filter bank analysis. Second, a parameter called the subband energy ratio (SER) was computed for each subband signal. A multilayer perceptron neural network was then used to automatically classify the EGG signal into four categories: bradygastria, normal, tachygastria, and arrhythmia, using the SER as the input. The EGG recording was made using the standard method of electrogastrography by placing electrodes on the abdominal surface. The study was performed in 40 patients with various gastric motor disorders, ten healthy adults, and ten healthy children. The neural network was trained and tested using the EGG data obtained from the patients. The regularity of gastric myoelectrical activity was assessed based on the classification of the minute-by-minute EGG segments. Using the running spectral analysis method as a gold standard, the proposed automated method had an accuracy of 100% for the training set and 97% for the test set. It was concluded that the proposed method provides an accurate and automatic assessment of the regularity of gastric myoelectrical activity from the EGG. © 1999 Biomedical Engineering Society. PAC99: 8780-y, 8717-d, 0705Mh, 0270Hm
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1481-1490 
    ISSN: 0887-624X
    Schlagwort(e): ibuprofen ; ketoprofen ; naproxen ; copolymer reactivity ; thermal stability ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Three nonsteroidal antiinflammatory drugs, 2-(4-isobutylphenyl)-propionic acid (ibuprofen), 2-(3-benzoylphenyl)-propionic acid (ketoprofen), and 2-(6-methoxy-2-naphthyl)-propionic acid (naproxen), were covalently linked with 2-hydroxyethyl methacrylate (HEMA). The drug-linked HEMA (M1) (ibuprofen-linked HEMA abbreviated as HI; ketoprofen-linked HEMA as HK, and naproxen-linked HEMA as HN), were respectively copolymerized with methacrylic acid (M2), MA, to obtain macromolecular prodrugs. The compositions of the copolymers were determined by means of a 1H-NMR spectroscopy and monomer reactivity ratios were estimated using the Kelen-Tüdös linear differential equation. The reactivity ratios are: r1 = 0.101 ± 0.012, r2 = 1.071 ± 0.065 for HI-MA; r1 = 0.344 ± 0.066, r2 = 0.966 ± 0.032 for HN-MA, and r1 = 0.650 ± 0.182, r2 = 1.032 ± 0.106 for HK-MA, respectively. The monomer reactivity toward to MA radical estimated from 1/r2 values is almost same for all three monomers (1/r2 ∼ 1). The glass transition temperatures of three drug-linked homopolymers go hand in hand with the steric hindrance of three drugs, i.e., ketoprofen 〉 naproxen ≫ ibuprofen calculated the minimum energy by computer molecular modeling. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1481-1490, 1998
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 27 (1989), S. 3799-3809 
    ISSN: 0887-624X
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Plasma polymerization of some cyano-containing organic compounds was carried out at 13.56 MHz from the gas phase. The resulting polymer films were smooth and pinhole free. The electrical conductivities of the polymer films varied from 10-12 to 10-7 S cm-1 depending upon which cyano-containing monomer was used. The Al/polymer film/ITO (indium-tin oxide) sandwich cells made from the films demonstrated a photovoltaic effect, and some of them showed good rectifying behavior. Infrared spectroscopy (IR) and ultraviolet spectroscopy (UV) were utilized to characterize the structure of the product polymers. The effects of the original structure in the starting monomers on the structure of the resulting polymers are investigated. The influence of incident light intensity on the photovoltaic characteristics was also investigated.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Medical & biological engineering & computing 29 (1991), S. 339-350 
    ISSN: 1741-0444
    Schlagwort(e): Bio-potential ; Electrogastrography ; Gastric motility ; Myoelectrical activity ; Signal analysis ; Slow wave ; Stomach
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Electrogastrography (EGG), the cutaneous recording of the myoelectrical activity of the stomach using surface electrodes, is attractive due to its non-invasiveness and its correlation with gastric motility. Since the first measurement of the EGG, a great deal of research effort has been expended on investigating its relationship with specific activities of the stomach in question. In this review, we discuss how to measure the EGG, what information is available in the EGG, how to extract useful information from the EGG and the prospective applications of the EGG. After a brief historic evolution of the EGG, we first discuss the measurement of the EGG, the importance of localisation of the stomach and the characteristics of the EGG. The most commonly used EGG data-analysis methods, both power spectral analysis and waveform analysis, are then outlined. Some of prospective applications of the EGG in clinical diagnosis and medical research are described, mainly concerning the correlation between EGG amplitude and gastric motility and that between EGG rhythmic variations and motility disorders. Specifically, we present studies on pre- and postprandial EGGs, observation of the propagation direction of the gastric slow wave and gastric electrical dysrhythmias and their correlation with gastric motility.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Medical & biological engineering & computing 29 (1991), S. 351-357 
    ISSN: 1741-0444
    Schlagwort(e): Bioelectric potential ; Electrogastrogram ; Electromyography ; Gastric motility ; Slow wave ; Stomach
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract The gastric electric activity paces the contractions of the stomach and can be measured noninvasively using surface electrodes placed on the abdomen. In this paper, response of the gastric electric activity to water and a solid meal was investigated using surface electrodes. Applying an improved recording technique, power spectral analysis and statistical analysis methods, the gastric electric activity in preprandial, postwater and postprandial states was measured and analysed from ten healthy volunteers. To more convincingly show the effect of water and the solid meal on the gastric slow wave and gastric motility, simultaneous recordings of the cutaneous EGG and manometric activities in the stomach were performed in three gastroparetic patients. It was found that water does not induce contractions of the stomach, but the gastric slow wave amplitude increases (p〈0·05) and frequency decreases (p〈0·05). The solid meal results in an increase in both the amplitude (p〈0·01) and the frequency (p〈0·02) of the gastric slow wave. It appears that the postprandial EGG amplitude increases because of a combination of stomach contractions and gastric distension bringing the stomach closer to the recording electrodes. The slow wave frequency, however, correlates well with stomach contractions.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Medical & biological engineering & computing 30 (1992), S. 564-567 
    ISSN: 1741-0444
    Schlagwort(e): Electrogastrography ; Milk ; Myoelectrical activity ; Slow wave ; Spectrum analysis ; Stomach
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 42 (1991), S. 1501-1507 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The process of depolymerization of PET resin by EG glycolysis under pressure is investigated. The kinetics of this pressurized depolymerization of PET resin is discussed. It was found that the rate of depolymerization is dependent of temperature, pressure, and concentration ratio of EG to PET. The rate of depolymerization is proportional to the square of EG concentration and faster than that under atmospheric pressure. Glycolyzed products under pressure consist of the PET monomer, BHET, and oligomers, mostly dimer and trimer. An equilibrium between BHET and oligomers is attained quickly soon after the depolymerization step is completed in the case of a higher ratio of EG/PET used. In the case of lower ratio of EG/PET, the final product now consists of higher molecular weight of oligomers rather than monomer, dimer, and trimer.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 209-214 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: A new class of all organic sol-gel second-order nonlinear optical (NLO) materials based on hexa(methoxymethyl) melamine (HMM) was developed. Two NLO active chromophores, 4 (4′-nitrophenylazo) aniline (DO3) and 4-amino-4′-nitrobiphenyl (ANB), were incorporated into the melamine matrices. The samples exhibited second-order optical nonlinearity after poling and curing at 220°C for 30 min. DO3/HMM and ANB/HMM samples showed a second harmonic coefficient, d33 of 10.7 and 1.8 pm/V at 1064 nm, respectively. The temporal stability of both systems was studied at room temperature as well as at 100°C. Waveguide optical losses of samples at 633 and 830 nm were found. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 10
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The interfacial tensions of immiscible binary blends of poly(dimethyl siloxane) (PDMS) and polybutadiene (PBD) have been determined as a function of molecular weight and temperature. The technique employed for these measurements takes advantage of recent advances in the determination and analysis of pendant fluid drop profiles. The experimental data are compared to the predictions of square gradient theories and theories based on the diffusion equation approach as developed by Helfand and co-workers. Qualitative agreement is obtained with both types of theory when the Flory-Huggins interaction parameter is taken to be comprised of two terms: a temperature independent term of entropic origin; and an enthalpic term that is inversely dependent upon the temperature.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
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