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991.
MG Fehlings T Errico P Cooper V Benjamin T DiBartolo 《Canadian Metallurgical Quarterly》1993,32(2):198-207; discussion 207-8
Although occipitocervical fusion is frequently used for instability of the upper cervical spine and the occipitocervical articulation, most currently used techniques have one or more of the following disadvantages: the necessity for sublaminar wires, the use of occipital screws, a fixed angle of instrumentation, or the necessity for routine postoperative halo immobilization. Moreover, many reported techniques are associated with a high rate of nonunion or instrumentation failure. We present our experience with a technically simple method of obtaining rigid occipitocervical arthrodesis using a 5-mm malleable rod that is fixed to the skull by a pair of wires passed through four suboccipital burr holes. Segmental spinal fixation is achieved with Wisconsin interspinous wires and is occasionally supplemented with sublaminar wires. Supplemental autogenous bone graft is used in all cases. A cervical collar is routinely used for postoperative immobilization. The results of treatment were retrospectively reviewed in 16 patients with an average age of 49.4 years (range, 9-69). Mean follow-up was 24 months (range, 12-36 mo). The indication for fusion was instability of the occiput-C1-C2 complex as a result of Chiari malformation, rheumatoid disease, skull base tumor resection, basilar invagination, ankylosing spondylitis, Down's syndrome, cervical laminectomy, and trauma. The average number of levels fused was 5.4 (range, O-C3 to O-T3). Successful occipitocervical arthrodesis was achieved in all but one of the surviving patients. The single patient with a pseudarthrosis was successfully managed with supplemental bone grafting and halo immobilization. There were two deaths from medical complications in chronically ill patients. Other complications included one postoperative instrumentation loosening, one myocardial infarction, and one superficial occipital decubitus. In conclusion, rodding and segmental interspinous wiring is an effective, technically simple method of obtaining rigid occipitocervical fixation, which obviates the need for bulky orthoses. 相似文献
992.
993.
994.
An algorithm is described for processing the results of two- coordinate measurements of a profile representing a partial circle. Information is presented on the instrument structure and on the functions executed by the microprocessor.Translated from Izmeritel'naya Tekhnika, No. 9, pp. 22–24, September, 1993. 相似文献
995.
996.
We show here for the first time that a stable parallel double helix with Hoogsteen pairing can exist independently of the triple helix of which it is a component part. The experiments employ DNA oligonucleotides with mixed sequences of normal bases. These duplexes are distinct from previously reported ribopolynucleotide helices containing bulky substituents which prevent Watson-Crick pairing as well as from parallel duplexes with Donohue, or reversed Watson-Crick, pairing. Stoichiometry is established by mixing curves and gel electrophoresis. Tm depends linearly upon pH, increasing with acidity because of the need to protonate N3 of C. The Tm of the 20-mer studied here is 52 degrees C at pH 5.2 and 0.1 M NaCl. At pH above 6, the molecule rearranges to form an antiparallel duplex with imperfect Watson-Crick pairing and loops, and the Tm is then independent of pH. The CD spectrum of the parallel duplex is very similar to that of the corresponding triple helix but quite different from that of the Watson-Crick helix. The infrared spectrum in the double bond region closely resembles that of the triple helix but, as with the CD, is quite different from that of the Watson-Crick duplex. The infrared spectra of the duplex and triple helix are also nearly identical in the region form 800 to 1000 cm-1, which is sensitive to backbone conformation. The only symmetry element present is a pseudorotational axis coincident with the helix axis of the parallel duplex as well as with the axis of the corresponding triple helix.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
997.
We address the problem of determining the topology and bridge-capacity assignments for a network connecting a number of token rings via source-routing bridges. The objective is to minimize the cost of bridge installations while meeting the network users' performance requirements. The problem is modeled as a mixed 0–1 integer program. A comparison is given between two solution algorithms: a simulated annealing algorithm using the flow-deviation algorithm for each routing subproblem, and a drop algorithm using the simplex method for the same subproblems to provide benchmark solutions. In the former algorithm, the routing subproblem is formulated as a nonlinear program with penalty functions to model node and link capacity constraints, and in the latter as a multicommodity flow model with the same capacity constraints. Computational results show that the simulated-annealing/flow-deviation algorithm produced substantially better solutions than the LP-based drop algorithm. 相似文献
998.
Lee V.V. Kuehne S.C. Nguyen C.T. Beiley M.A. Wong S.S. 《Electron Devices, IEEE Transactions on》1993,40(7):1223-1230
A local interconnection technology utilizing polysilicon strapped with selective-chemical-vapor-deposited (CVD) tungsten has been developed. Both n- and p-channel MOS transistors have been successfully fabricated using this technology. Tungsten deposited on polysilicon is an attractive gate shunt and local interconnection material because of its low resistivity, immunity to dopant segregation and diffusion, and resistance to electromigration. A potential problem of this technology is the excessive diode leakage current associated with strapping shallow source/drain diodes with tungsten. The leakage is attributed to defects induced by the heavy source/drain implant, which can be effectively eliminated with a proper annealing procedure 相似文献
999.
As the number of fuzzy logic applications increases, demand for faster architectures will grow. Our design for a VLSI fuzzy processor uses fuzzy inference techniques that optimize processing time. Preprocessing that reduces the number of rules to be processed, parallel computation of active rule degrees of activation, and scalability are major features of this architecture. The journal issue contains a concise summary of this article. The complete article is linked to Micro's home page on the World Wide Web (http://www.computer.org/pubs/micro/micro.htm) 相似文献
1000.
Marie-Angele De Looze R. Coronini Monique Legentil P. Jeannin Marie-Hélene Magri 《Scientometrics》1996,36(2):167-183
This paper analyses the determination of visibility of journals in which researchers of INRA (National Institute for Agricultural Research) publish. The corpus is comprised of 671 articles published over a period of four years in 258 journals. The advantage of the method applied for determining the visibility of journals is that it combines two approaches: a) bibliometric indicators (coverage by the ISI-publications and by two specific French databases) and b) experts' opinions (10 economists and sociologists). The main results are: a) There is a convergence between the opinion of the experts and «visibility» in the databases, b) The impact factor confirms the main opinions of the experts. The first journals ranked by the experts and JCR Social Sciences are the same but represent only 40 per cent of the total journals analysed. The other journals were revealed by the experts and French databases.«Whoever seeks to pass a balanced but lucid judgement on the general trends of the activity carried out by the profession to which he belongs, is liable to say either banalities or to hurt his colleagues»The notion which we retain of core is that which is successively and conjointly validated by the experts and by the major databases representative of the field.This study was financed by the Department of Rural Economy and Sociology of INRA. 相似文献