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  • 1
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Functional magnetic resonance imaging (fMRI) in macaque monkeys is emerging as a potent candidate to bridge the gap between data from human fMRI studies and data from anatomy, electrophysiology and lesion studies in monkeys. The primary (SI) and secondary (SII) somatosensory cortices are the principal regions for somatosensory information processing and contain systematic representations of the body surface map (somatotopy). To examine the functional organization of the somatosensory cortices in anaesthetized macaque monkeys with fMRI, we asked whether focal and differential activation could be observed in SI and SII in response to tactile stimulation with two parameters: body sides (right and left) and body regions (hand and face). We found that changes in stimulus parameters elicited differential focal activation in both SI and SII in two ways. First, the hand and face stimulation activated SI and SII in the contralateral, but not in the ipsilateral, hemisphere. Second, the hand and face stimulation differentially activated two adjacent regions in both SI and SII. These fMRI results appear to correlate with previous mapping studies by other methods in the macaque somatosensory cortices. This study shows the feasibility of fMRI studies in mapping multiple sensory areas in monkeys by which we can distinguish between adjacent functionally distinct regions.
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  • 2
    ISSN: 1613-9674
    Keywords: Antro-oral fistula ; Maxillary sinusitis ; Radiography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Fifty-two patients who developed antro-oral fistula following tooth extraction were examined clinically and radiographically. Of these, 39 patients had only perforation of the antral floor and the other 13 had the tooth root pushed into the maxillary sinus. Maxillary sinusitis was present in 43 cases. The most frequent site of antro-oral fistula was the upper first molar, and the palatal root of the upper first molar was pushed into the antrum the most frequently. Our study suggested that most of the patients with antro-oral fistula had associated maxillary sinusitis before the extraction of the tooth. The highest risk of the occurrence of antro-oral fistula appeared to be at the time of extraction of the upper first molar associated with periapical and periodontal lesions.
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  • 3
    ISSN: 1613-9674
    Keywords: Osteomyelitis ; Mandible ; Radiograph ; Inflammatory extension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It is thought that the phase of inflammatory extension in osteomyelitis of the mandible varies according to the primary site of infection, that is, the causative tooth. This study was conducted to analyze the relationship between the extension phase of inflammatory bone changes and the causative tooth in patients with radiographically diagnosised osteomyelitis of the mandible. Between 1983 and 1993, a total of 219 patients with osteomyelitis of the mandible were seen in our department. In the age distribution, 135 cases occurred in men and 98 cases in women. Osteomyelitis was most prevalent in patients in their sixties (39 cases) followed by patients in their forties and fifties (38 cases each). The causative tooth was identified in 97 cases of osteomyelitis in the mandible. In the 39 cases in which the primary infection was caused by the third mandibular molar, distal extension was most prevalent (30 cases). In the 58 cases in which a tooth other than the third mandibular molar was the cause (front tooth, premolar, deciduous tooth and other molars), equal extension in the mesio-distal direction was most prevalent (40 cases). In the upper-lower extension phase, lower extension beyond the mandibular canal was most prevalent in the first, second and third molar teeth. In the cases involving teeth other than the mandibular molars, the inflammatory bone changes were rather limited to the upper part of the mandibular canal.
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  • 4
    ISSN: 1613-9674
    Keywords: Three-dimensional CT ; Fracture ; Jaw ; High resolution CT
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to evaluate the diagnostic value of three-dimensional (3-D) image reconstruction of jaw bone fractures in comparison with high-resolution CT scanning. Assessment was made using a simple scoring system and analyzing the effects of factors like slice thickness, fracture site, and displacement of bone fragments. 3-D images proved especially useful in patients with complicated maxillary fractures. Images reconstructed from CT scans obtained with a 2-mm slice thickness were much better than those reconstructed from scans with a 5-mm slice. 3-D images provided very useful data regarding fractures with marked displacement. 3-D images not only outlined the extent of the fractures but revealed differences of the mechanism of injury between the maxilla and the mandible. Although 3-D images do not provide any information that is not already present in the original CT sections, they do present selected volume data in an easily assimilated and familiar anatomical format. The findings suggest that the high-resolution CT scanning and 3-D image reconstruction are complementary procedures.
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  • 5
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Knowledge or experience is voluntarily recalled from memory by reactivation of the neural representations in the cerebral association cortex. In inferior temporal cortex, which serves as the storehouse of visual long-term memory, activation of mnemonic engrams through electric stimulation ...
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  • 6
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    Electronic Resource
    Springer
    Skeletal radiology 16 (1987), S. 216-222 
    ISSN: 1432-2161
    Keywords: Bone tumors ; Chondroblastoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Chondroblastoma is a relatively rare benign bone tumor of cartilage origin. Roentgenologically it presents usually as a region of lytic destruction of bone with a thin sclerotic rim in the epiphysis of long tubular bone. Less than 9% occur in the pelvic bones but show a tendency to arise from the triradiate cartilage. We present two cases of chondroblastoma originating in the triradiate cartilage, each showing extensive lytic bony destruction and an intrapelvic soft tissue mass. A review of the literature suggests that chondroblastoma of the triradiate cartilage shows an aggressive radiological appearance.
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  • 7
    ISSN: 1573-4846
    Keywords: alkoxysilane ; tetramethylammonium ions ; hydrolysis and polycondensation ; trimethylsilylation ; 29Si n.m.r.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Tetracethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) have been co-hydrolyzed in methanolic solutions containing tetramethylammonium ions that only affect polymerization of silicate species (hydrolysis products of TEOS) to form the Si8O 20 8− cubic octameric silicate species. The effects of water content and TEOS-to-MTEOS molar ratio on the distribution of species formed in the solutions have been investigated with the trimethylsilylation technique and 29Si n.m.r. spectroscopy. Formation of Si8O 20 8− and the cubic octameric species consisting of both Si(O−)4 and CH3Si(O−)3 units, (CH3)nSi8O 20−n (8−n)− (n=1−5), is found in the solutions. The increase of water content in the solutions solely results in increasing yield of Si8O 20 8− in spite of the presence of hydrolysis products of MTEOS together with those of TEOS, suggesting that water in the solutions plays an important role in the formation of Si8O 20 8− with the aid of tetramethylammonium ions. The TEOS-to-MTEOS molar ratio varies the distribution that is kept under control by the water content, increasing yields of (CH3)nSi8O 20−n (8−n)− (n=1, 2). It is found that the water content and TEOS-to-MTEOS molar ratio determine the reaction conditions effective for the formation of CH3Si(O−)3 unit-containing cubic octameric species.
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  • 8
    ISSN: 1573-4846
    Keywords: lignin ; organic-inorganic hybrids ; fiber ; carbothermal reduction ; carbide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Lignin-silica-titania and lignin-titania hybrid fibers have been prepared by sol-gel processing from lignin, tetraethoxysilane, and titanium tetrakis(2,4-pentanedionate) using a mixture of 2,4-pentanedione and tetrahydrofuran as solvent and H2SO4 as catalyst. Amounts of H2O and H2SO4, to add to the solutions with the Si-to-Ti atomic ratios of 0–1.0, were determined for achieving favorable spinnability of fibers from the solutions. The FT-IR spectrum of the fibers indicated the formation of hybrid fibers. The hybrid fibers, cured in air to avoid coalescense, could be converted into Si–Ti–C and TiC fibers upon pyrolysis at 1500°C in Ar.
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  • 9
    ISSN: 1573-4846
    Keywords: alkoxysilane ; tetramethylammonium ions ; co-hydrolysis ; copolymerization ; 29Si NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract 29Si NMR peaks due to species with the double four-membered ring siloxane backbone composed of both Si(O−)4/2 and CH3Si(O−)3/2 units, (CH3) n Si8O 20 − n /(8 − n) − (n=1–3), formed by co-hydrolysis of tetraethoxysilane and methyltriethoxysilane in the presence of tetramethylammonium ions in methanol have been assigned. It has been found that 29Si NMR peaks due to Si(OSi)3(O−) units shift to lower frequencies by replacement of the adjacent Si(O−)4/2 units by CH3Si(O−)3/2 units, in other words, with increasing m value in Si[OSi(O−)3]3 − m [OSi(CH3) (O−)2] m (O−) (m=0–2). Peaks from CH3 Si(OSi)3 units in the species have also appeared as separated due to the kind of neighbor structural units. On the basis of the assignments, positions of CH3Si(O−)3/2 units in the cubic octameric siloxane framework of (CH3) n Si8O 20 − n /(8 − n) − (n=2, 3), for both of which three isomers are present, have been estimated.
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  • 10
    ISSN: 1573-4846
    Keywords: organic-inorganic hybrids ; carbothermal reduction ; silicon carbide ; fibers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Silica-phenolic resin hybrid fibers with carbon-to-silicon atomic ratios of 2.6 to 5.4 have been prepared from ethanol solutions of tetraethoxysilane, phenolic resins, water, and hydrochloric acid with a tetraethoxysilane-H2O−HCl molar ratio of 1:2:0.01 by sol-gel processing. The hybrid fibers have been heated at 1500°C in Ar for carbothermal reduction to convert them into silicon carbide fibers. The effects of the holding time at 1500°C and the carbon-to-silicon atomic ratio of the hybrid fibers on the free carbon content in the silicon carbide fibers have been investigated. It has been found that the conversion is complete by the heat-treatment for more than 2 h. The silicon carbide fibers with a free carbon content of ca. 2 wt% have been obtained from the hybrid fibers with the ratios of 2.6 to 4.3.
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