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991.
The capacity of Shigella flexneri to act as a delivery system for stimulation of local immunity was investigated by use of an S. Flexneri 2a vaccine candidate (SC602). This vaccine strain was constructed by deletion of virulence genes responsible for dissemination (icsA) and survival (iuc:iut) of bacteria within the colonic mucosa. Among the most immunogenic S. flexneri 2a proteins inducing a local immunoglobulin A antibody response, the IpaC invasion was selected as a potential protein carrier. Overexpression of IpaC from a plasmid in trans within SC602 (SC602/pIpaC) was shown to be required for the induction of optimal anti-IpaC antibody response in the murine pulmonary infection model. A weak anti-IpaC antibody response was obtained after intranasal inoculations with SC602/pIpaC live bacteria. This response was enhanced by combining systemic priming with SC602/pIpaC killed bacteria and local boosting with SC602/pIpaC live bacteria. These results suggest that naive B cells primed systemically could account for local antibody production. This immunization protocol will allow further evaluation of the immunogenicity of IpaC hybrid proteins expresses in SC602. 相似文献
992.
S Ikezaki A Nishikawa F Furukawa T Imazawa M Mitsui T Enami M Takahashi 《Canadian Metallurgical Quarterly》1995,(113):44-50
A 13-week subchronic toxicity study of josamycin was performed in male and female F344 rats to determine the maximum tolerable dose (MTD) for subsequent investigation of the carcinogenicity. As animals refused to take diet containing 5.0% josamycin in our preliminary study, dose levels in the present study were determined as 0, 0.16, 0.32, 0.63, 125 and 2.5% in diet. Rats were randomly allocated to 6 groups, each consisting of 10 males and 10 females. No animal died during the administration period and no group showed significant changes in body weight gain. Definite toxicity of josamycin was not noted in hematological and serum biochemical examinations. Histopathological examinations revealed no particular findings related to josamycin administration except cecal enlargement in the 1.25 and 2.5% groups. based on the results of the present study, it was concluded that the MTD of josamycin in 2.5% in diet, because the dietary dose level of 2.5% proved to exert no significant toxicological signs. 相似文献
993.
S. Shaw 《Journal of Computer Assisted Learning》1993,9(2):93-99
Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained. 相似文献
994.
A version control mechanism is proposed that enhances the modularity and extensibility of multiversion concurrency control algorithms. The multiversion algorithms are decoupled into two components: version control and concurrency control. This permits modular development of multiversion protocols and simplifies the task of proving the correctness of these protocols. A set of procedures for version control is described that defines the interface with the version control component. It is shown that the same interface can be used by the database actions of both two-phase locking and time-stamp concurrency control protocols to access multiversion data. An interesting feature of the framework is that the execution of read-only transactions becomes completely independent of the underlying concurrency control implementation. Unlike other multiversion algorithms, read-only transactions in this scheme do not modify any version-related information, and therefore do not interfere with the execution of read-write transactions. The extension of the multiversion algorithms to a distributed environment becomes very simple 相似文献
995.
W. Claeys V. Quintard S. Dilhaire D. Lewis Y. Danto 《Quality and Reliability Engineering International》1994,10(4):289-295
We have recently developed an optical contactless method for testing the quality of solder joints during accelerated thermal cycling ageing processes.1 The method was based upon the measurement of the dynamic thermal behaviour of the joint to short bursts of Joule heating. It has proved to be efficient in revealing the formation of cracks at the lead-solder interface. We present a method to evaluate ageing at a much earlier stage in the cycling process. We have observed in earlier work,1 that before cracks appear, structural changes occur in the solder at the lead-solder interface. The thermal response of the solder joint is recorded over time to a Peltier heat perturbation produced by flowing a current pulse through the interface where structural changes occur. The key point in this method is to discriminate the Peltier effect from the Joule thermal response because both effects generate heat. The variation of the early Peltier response in the thermal cycling ageing tests is seen as a quantitative signature of the structural changes in the lead-solder interface. 相似文献
996.
We present a method that is useful in the estimate and assessment of heat capacity data. The approach is based on an analysis of the logarithmic average of the phonon frequencies. In this quantity, that may be easily derived from experimental data on the vibrational entropy, the influence of atomic masses can be exactly accounted for even in polyatomic solids. Our method is applied to Li2O, Na2O, K2O, Rb2O, and Cs2O. In particular, literature data for K2O are critically examined. 相似文献
997.
Effect of alloying elements on the solidification characteristics and microstructure of Al- Si- Cu- Mg- Fe 380 alloy 总被引:1,自引:0,他引:1
The effect of varying the major alloying elements within the limits of specification on the solidification behavior, fluidity,
and microstructure of a 380 alloy has been studied at two cooling rates. The thermal analysis technique has been used to study
the solidification behavior. The alloying elements investigated ranged from 3.22 to 4.09 pct copper, 1.01 to 1.70 pct iron,
0.06 to 0.50 pct magnesium, 1.69 to 3.00 pct zinc, and 0.16 to 0.46 pct manganese. The results show that the solidification
behavior of the 380 alloys is complicated, and the cooling curve at 0.4 ‡C/s indicates six reactions taking place during the
process of solidification. Cooling curves obtained for each of the alloying element additions, their analysis, and the resultant
microstructures are discussed. 相似文献
998.
K Jaton-Ogay S Paris M Huerre M Quadroni R Falchetto G Togni JP Latgé M Monod 《Canadian Metallurgical Quarterly》1994,14(5):917-928
Aspergillus fumigatus secretes a serine alkaline protease (ALP) and a metalloprotease (MEP) when the fungus is cultivated in the presence of collagen as sole nitrogen and carbon source. The gene encoding ALP was isolated and characterized previously. We report here the cloning and the sequencing of the gene encoding MEP. Genomic and cDNA clones were isolated from A. fumigatus libraries using synthetic oligonucleotides as probes. Stretches of the deduced amino acid sequence were found to be in agreement with the N-terminal amino acid sequence of MEP and with internal peptide sequences. The amino acid sequence of the enzyme contains a putative active-site sequence HEYTH homologous to the active site of other bacterial and eukaryotic zinc metalloproteases. Sequence analysis reveals that MEP has a pre-proregion consisting of 245 amino acid residues preceding the 388 amino acid residues of the mature region (molecular mass of 42 kDa). An alp mep mutant, deficient in proteolytic activity at neutral pH in vitro, was constructed and tested for pathogenicity in a murine model. No difference in pathogenicity was observed between the wild-type strain and the alp mep double mutant, suggesting that ALP and MEP are not essential for the invasion of the lung tissues by A. fumigatus. 相似文献
999.
G Gaffney MV Squier A Johnson V Flavell S Sellers 《Canadian Metallurgical Quarterly》1994,70(2):F101-F106
Neuropathological examinations were carried out at necropsy on 274 cases of intrauterine death or neonatal death at or before three days after birth. Fifty six (20.4%) subjects had evidence of prenatal ischaemic brain damage. On review of the maternal case notes to ascertain antenatal clinical associations there was an increased incidence of intrauterine growth retardation, either based on birth weight for gestational age (odds ratio (OR) 2.0; 95% confidence interval (CI) 1.1 to 3.7) or diagnosed antenatally (OR 2.7; 95% CI 1.3 to 5.6). Oligohydramnios was also more common (OR 2.9; 95% CI 1.2 to 7.0). The association of intrauterine growth retardation and white matter damage remained after excluding fetuses with a major congenital anomaly (OR 2.4; 95% CI 1.1 to 5.1). The findings suggest that chronic intrauterine hypoxia may be associated with damage to cerebral white matter among fetuses and infants who die. The relation between ischaemic white matter damage and cerebral palsy among survivors remains speculative. 相似文献
1000.
S. I. Glinchak Yu. A. Egorov R. R. Aliev E. D. Radchenko B. K. Nefedov N. A. Grigor'ev 《Chemistry and Technology of Fuels and Oils》1992,28(3):175-177
Translated from Khimiya i Tekhonologiy Topliv i Masel, No. 3, pp. 33–34, March, 1992. 相似文献