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  • 11
    Electronic Resource
    Electronic Resource
    Springer
    Discrete & computational geometry 20 (1998), S. 333-357 
    ISSN: 1432-0444
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. Every convex polytope can be represented as the intersection of a finite set of halfspaces and as the convex hull of its vertices. Transforming from the halfspace (resp. vertex) to the vertex (resp. halfspace) representation is called vertex enumeration (resp. facet enumeration ). An open question is whether there is an algorithm for these two problems (equivalent by geometric duality) that is polynomial in the input size and the output size. In this paper we extend the known polynomially solvable classes of polytopes by looking at the dual problems. The dual problem of a vertex (resp. facet) enumeration problem is the facet (resp. vertex) enumeration problem for the same polytope where the input and output are simply interchanged. For a particular class of polytopes and a fixed algorithm, one transformation may be much easier than its dual. In this paper we propose a new class of algorithms that take advantage of this phenomenon. Loosely speaking, primal—dual algorithms use a solution to the easy direction as an oracle to help solve the seemingly hard direction.
    Type of Medium: Electronic Resource
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  • 12
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The IAH1 gene of Saccharomyces cerevisiae encodes an esterase that preferentially acts on isoamyl acetate; however, the enzyme has not yet been completely purified from the yeast S. cerevisiae. We constructed the IAH1 gene expression system in Escherichia coli, and purified the IAH1 gene product (Iah1p). The amount of Iah1p produced by recombinant E. coli was more than 40% of total cellular proteins. The molecular size of Iah1p was 28 kDa by SDS-polyacrylamide gel electrophoresis. Judging from the molecular weight estimation by gel filtration of purified Iah1p, the enzyme was thought to be a homodimer. The K m values for isoamyl acetate and isobutyl acetate were 40.3 mM and 15.3 mM, respectively. The enzyme activity was inhibited by Hg2+, p-chloromercuribenzoate, and diisopropylfluorophosphate.
    Type of Medium: Electronic Resource
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  • 13
    ISSN: 1432-0630
    Keywords: 81.15 ; 82.80 ; 42.62
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Laser-ionization Time-Of-Flight (TOF) mass-spectrometric studies have been carried out on the 532 nm and 1064 nm laser ablation products from a nitrogen-rich polymer. The polymer used had an elemental composition of C6.0N8.9H3.4 and consisted of C=N, C-N, and N-H chemical bonds. The TOF mass spectra observed were composed of various peaks (≤150 amu) depending on the ablation laser wavelength. The primary peaks were assigned to C+, CN+, CHnN+ 2 (n=1−3) and C2H2N+ 3 for 532 nm ablation, and C+, C+ 3, HCN+, HCCN+, CH2NH+, HNCN+, H3NCN+, and C4H4N+ 7 for 1064 nm ablation. The flight velocity distributions with peak velocities ranging from ≈8.6×103 cm/s to ≈3.8×104 cm/s were measured for these products. The distinct velocity distributions observed between small and large products indicate the presence of two origins in the fragment ejection process from the polymer for both 532 nm and 1064 nm ablation. Furthermore, we suggest an importance of the translational energy of the fragments for the product generation in the laser plume.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    European radiology 6 (1996), S. 358-361 
    ISSN: 1432-1084
    Keywords: Stomach ; Neoplasms ; Computed tomography ; Staging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to evaluate usefulness of right lateral position CT in determining invasion of gastric cancer into adjacent organs. We assessed whether position shift, a change in the relative location of a gastric tumor and adjacent organs between the supine position and right lateral position CT, was a useful sign for absence of invasion into perigastric organs. In 37 patients with advanced gastric cancer with doubtful invasion into adjacent organs by conventional CT after 500 ml water oral intake, additive right lateral CT was performed. Of 24 cases of lesions in the gastric body, 16 had a position shift and no invasion into adjacent organs at surgery (T3), and 8 had no position shift and invasion (T4). The accuracy was 100%. Six gastric cardial and 7 pyloric tumors showed no position shift, and 3 cardial and 2 pyloric tumors were proved to be noninvasive (T3). The accuracy of cardial and pyloric tumor was 50 and 71%. We concluded that position shift may be useful in the diagnosis of invasion of adjacent organs by gastric cancer, limited to in cases with gastric body cancer.
    Type of Medium: Electronic Resource
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  • 15
    ISSN: 1432-1084
    Keywords: Key words: Deep neck abscess ; Cervical fascial anatomy ; Anterior cervical space ; CT ; MRI
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The aim of this study was to determine the pathway of infrahyoid extension of the oropharyngeal abscess considering the anatomy of the fascial spaces by cross-sectional imaging. CT scans and MR images were retrospectively reviewed in ten patients with known infrahyoid extension of oropharyngeal abscesses (eight with acute tonsillitis, two with acute phlegmonous oropharyngitis). In seven of eight patients tonsillar abscesses descended along the deep cervical fascia converging on the hyoid bone and further accumulated in the anterior cervical space through which extension to the mediastinum took place in four patients. In seven patients the abscesses involved the retropharyngeal space at the infrahyoid neck. In two of these seven patients the abscesses directly extended down into the upper mediastinum through the retropharyngeal space. In one patients of the seven mediastinal spread of an abscess occurred through the posterior cervical space, not through the retropharyngeal space. Cross-sectional imaging is valuable in the evaluation of deep neck abscesses and the pathway of spread. The anterior cervical space in the infrahyoid neck is important for mediastinal extension of pharyngeal abscesses.
    Type of Medium: Electronic Resource
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  • 16
    ISSN: 1432-1076
    Keywords: Cleidocranial dysplasia syndrome ; Atresia ani ; Urogenital anomalies ; Psoriasis ; Autosomal recessive inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A cleidocranial dysplasia syndrome associated with atresia ani, urogenital anomalies, and psoriasis-like skin lesions is reported in two siblings (1 boy, 1 girl) in a family of Japanese descent. There is no family history of cleidocranial dysplasia syndrome and/or psoriasis. Consanguinity is denied.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 105-110 (Jan. 1992), p. 1229-1232 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 1198-1199 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 8703-8708 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reactions of N(4S) atoms with NO and H2 have been investigated using direct detection of N atoms by the atomic resonance absorption technique in a shock tube apparatus, where N(4S) is generated by photodecomposition of NO by 193 nm laser radiation behind reflected shock waves. The rate constant of the reaction, N+NO→N2+O (1) has been determined using pseudo first-order kinetic analysis to be k1=(1.3±0.3)×1013 (cm3 mol−1 s−1) over 1600–2300 K temperature range, which agrees very well with the estimation by Baulch et al. [Evaluated Kinetic Data for High Temperature Reactions (Butterworths, London, 1973), Vol. 2]. No (or very small) activation energy of this process was confirmed. Also, the rate constant of the reaction, N+H2→NH+H (2) has been decided by adding H2 to NO–Ar mixtures; it is k2=(2.8±0.2)×1014 exp(−Ea/RT) (cm3 mol−1 s−1), where Ea =33±7 kcal/mol. A quantum mechanical calculation performed in order to determine the mechanism of this reaction suggests that the reaction N(4S)+H2→NH+H proceeds via a direct abstraction of H atom from H2, and it gives calculated activation energy which is in good agreement with the present experiment.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 4077-4092 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ultraviolet photoelectron spectroscopy (UPS) has been applied to the investigation of the electronic structure of oligothiophenes with 4–8 thiophene rings. In a series of α-linked oligomers (αn with n being the number of rings), a systematic evolution of the π band is observed. Several peaks which correspond to the π band are observed in the region of 0.7–3 eV below the Fermi level (EF), and the bandwidth becomes broader with increasing n. The nonbonding π band is observed at 3.5 eV below EF and its energy is almost independent of the number of thiophene units. UPS spectra of α7 and α8 are fairly similar to the spectra of polythiophene, showing that these oligomers are good model compounds of the polymer. The ionization threshold energy of α7 and polythiophene was observed to be 5.3 eV. The effect of irregularity on the π-electron system was also studied by using oligomers which contain a β linkage or a vinylene group at the middle of the molecule. The UPS spectra showed that the β linkages significantly affect the electronic structure of polythiophene, while the vinylene group does not. In order to analyze the UPS spectra and to investigate the electronic structures of oligomers, the orbital energies and the geometries of these oligomers are calculated by the semiempirical MNDO-SCF-MO (modified neglect of diatomic overlap self-consistent-field molecular orbital) method. Theoretically simulated spectra of these oligothiophenes derived from the obtained orbital energies by Gaussian broadening are compared with the observed ones. The agreement between the observed and calculated spectra is very good, particularly in the π region. It is shown from the optimized geometry that (1) αn 's have planar structure and π electrons are delocalized, (2) the oligomer with β linkages has nonplanar structure leading to limited delocalization of π electrons, and (3) the oligomers with a vinylene group are almost planar and the disturbance by the vinylene group on the delocalization is small.
    Type of Medium: Electronic Resource
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