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OBJECTIVES: The aim of this work was to present a preliminary numerical analysis of the integration process of dental implants using a finite element simulation of the dynamic response following impulse excitation. Assessment of the osseointegration process has been previously examined using a numerical approach by calculating the natural frequency of a cantilever attached to the implant. The methodology adopted in this work allows a direct measurement of the implant response following impulse loading and avoids the addition of a bulky cantilever set-up. METHODS: The geometric configuration was obtained by averaging the coordinate data from tomographic scans of 14 mandibles. The materials properties were approximated from experimental analysis performed on trabecular and cortical bone tissue. A load was applied to the top of the implant in one direction resulting in an initial displacement. The implant was then freed and allowed to vibrate over approximately 10 cycles. Three fixity conditions were assumed by changing the properties of the surrounding bone ranging from full integration to a poorly integrated implant typical of the situation during bone healing following surgery. The results of the three fixity conditions were compared by calculating the fundamental displacement amplitudes and frequencies of the vibrating impact. RESULTS: The calculated results indicated that the implant vibrated at a predominant frequency when partially integrated with a displacement principally in the direction of the applied impulse. However, when the implant was fully integrated a more complex vibration pattern ensued, suggesting the superposition of two or more fundamentals. SIGNIFICANCE: Attention has been paid to the formulation of the numerical model for validation purposes as well as a reliable reference for the optimum interpretation of the experimental data. In this way it was possible to establish a simulation procedure to investigate the response of the tissues surrounding the implant and their properties at different stages of healing. It should be pointed out that the numerical procedures represented a valid preliminary approach to the problem and were capable of indicating a guide to the optimum design of the experimental apparatus for measurement of displacement and frequency in vivo.  相似文献   

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OBJECTIVE: To investigate the contribution of HLA-DMA and DMB genes, which play a crucial role in the HLA class II restricted antigen presentation pathway, in susceptibility to rheumatoid arthritis (RA). METHODS: The distribution of DMA and DMB alleles was examined in patients with RA and in healthy subjects by oligotyping of PCR amplified genomic DNA with sequence specific oligonucleotide probes. RESULTS: There were no significant differences in the prevalence of DMA and DMB alleles in patients with RA as compared to healthy controls. In addition, no significant differences in frequencies of DMA and DMB alleles were observed in RA susceptibility epitope positive RA patients and controls. CONCLUSION: DMA and DMB genes do not appear to play a role in susceptibility to RA.  相似文献   

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The paper presents data on the differential fertility of schizophrenics and controls, and the fertility of their siblings. This study used several methodological procedures in the study of schizophrenia reproduction, which strengthens the validity of the findings. Firstly, both male and female rates were examined. Secondly, the method of selection of a control avoided the biases introduced by using census data or other non-matched controls. Third, a diagnostic criterion was used which minimizes the possibility of the inclusion of other psychiatric illnesses. The results obtained support prior reports of the lowered reproductive rates of schizophrenics. Further, the siblings of schizophrenics were found not to have a reproductive advantage when contrasted to control siblings. The failure to find a reproductive advantage conflicts with a hypothesis of a balanced polymorphism as the mechanism maintaining an apparent constant rate of schizophrenia.  相似文献   

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The results of 26 ankle arthrodeses performed for rheumatoid arthritis on 21 patients were reviewed. Tibiotalar arthrodesis was performed in 14 ankles, and tibiotalocalcaneal arthrodesis was performed in 12. External fixation was used in 20 ankles, and internal fixation was used in six. Followup was available in 24 of 26 ankles (19 patients), and averaged 5 years (range, 2-8 years). There was no pain experienced in 19 ankles; mild, occasional pain was experienced in four ankles; and moderate, daily pain was experienced in one ankle. Daily activities were limited in five patients and recreational activities were limited in 11. All patients reported some difficulty walking on uneven terrain. Nearly all patients were satisfied; two were satisfied with reservations and two were dissatisfied. Union was achieved in 25 of 26 (96%) ankles. Ankle arthrodesis is an effective operation in patients with rheumatoid arthritis. Unlike previous reports, union and complication rates in this series were comparable with rates for arthrodesis for posttraumatic and degenerative arthritis.  相似文献   

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Sixteen patients with severe rheumatoid arthritis, marked inflammation of the synonvial membrane and high rheumatoid titer were cannulated by the thoracic duct for a period rangin between 82 up to 100 days. The patients being not under any medication during that time. Quantitative and qualitative analysis of the lymphocytes were performed, as well as responses to mitogens, rheumatoid factor, circulating antibodies and delayed hypersensitivity. By the 14th day nearly all the patients had a partial or almost complete remission of their disease. No complications were observed. These results will be discussed.  相似文献   

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Some patients with rheumatoid arthritis (RA) as well as those with other collagen diseases are positive for antinuclear antibody (ANA). We investigated the frequency of positivity for ANA in 104 patients with RA and evaluated the clinical features and laboratory data in the ANA-positive and -negative groups. The presence of ANA in sera was studied by indirect immunofluorescence using HEp-2 cells as the antigen substrate. Sera with a positive fluorescence at a dilution of 1:20 were considered to be positive for ANA. Of the 104 patients, 39 (37.5%) were positive for ANA. The staining pattern in the positive cases varied, but most were speckled (64.1%) and homogeneous (48.7%). A small number showed a nucleolar (20.5%) or a centromere (10.3%) pattern. None showed a shaggy pattern. The ANA titer was lower in RA patients compared with those with other collagen-related diseases such as systemic lupus erythematosus or progressive systematic sclerosis. None of the patients positive for ANA with either a nucleolar or centromere staining pattern had progressive systemic sclerosis or the CREST syndrome. One patient each had Raynaud's phenomenon and pulmonary fibrosis. There was no correlation between ANA positivity and indicators of joint inflammation. The prevalence of ANA positivity in patients with advanced or prolonged disease was higher than those with early stages or short durations. There was no correlation with drug therapy.  相似文献   

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A study of 6 series of concentrated and purified -- by ultracentrifugation -- dry cultural rabies vaccine inactivated with ultra-voilet rays demonstrated that in case of a 31--316 increase of concentration immunogenicity of the preparation rose 3--13-fold. Purification of the vaccine took place with its concentration. Additional purification of the concentrated vaccine on aluminium oxide led to a partial loss of the viral protein and to reduction of immunogenicity.  相似文献   

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OBJECTIVE: To determine the effect on the uptake of breast screening of a personalized letter from the general practitioner recommending mammography, sent to coincide with an invitation from the NHS breast screening programme. DESIGN: Randomised control trial with stratification of prognostic variables. SETTING: A group practice in Hackney, east London. SUBJECTS: 473 women invited for breast screening by the City and East London Breast Screening Service. OUTCOME MEASURE: Attendance for mammography. RESULTS: All women in the randomised trial were followed up; 134 of 236 (57%) randomly allocated to receive the prompting letter attended for mammography compared with 120 of 234 (51%) controls This difference was not significant (chi 2 = 1.43, p = 0.23) CONCLUSION: Personal recommendation by a letter prompting attendance for mammography from the general practitioner known best to women due to be screened did not improve uptake of breast screening in this east London practice. Other strategies are needed to increase uptake of mammography in inner cities.  相似文献   

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OBJECTIVE: This study was performed to determine the compliance with the basic treatments for rheumatoid arthritis (RA; medication, physical therapy, and ergonomic measures), to study psychological factors that influence compliance in light of the social learning theory, to learn whether patient education positively influences compliance and health, and to find an approach to patient education that improves compliance. METHODS: A MEDLINE search of the English language literature was performed. RESULTS: Few studies have dealt with compliance in RA patients; levels of adherence are generally low. According to the social learning theory, human function involves a continuous interaction between behavior, personal factors, and external environment. Self-efficacy is a personal factor that refers to the belief in one's capabilities and opportunities for being compliant with treatment advice. Patient education may improve ergonomic performance and compliance with physical exercise programs. CONCLUSIONS: Compliance with medication was infrequently studied. Whether improved compliance leads to better health status could not be determined. Compliance with RA treatments are generally low. Systematic study of the effect of patient education on treatment and health is warranted. Self-efficacy enhancing techniques in patient education may improve compliance.  相似文献   

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A monoclonal antibody giving a dominant reaction with the group-specific polysaccharide of streptococcus group B in an ELISA test has been developed. The purified polysaccharide exhibited a high positivity with reference anti B streptococcal antiserum in the ELISA test. Cross-tests of antibodies with other groups of streptococci provided a minimum cross-reaction only in the case of G streptococci. Monoclonal antibodies were prepared using Streptococcus agalactiae S 589 MT strain isolated from a case of bovine mastitis which does not express Ia, Ib, II, III, IV and V type antigens, nor C, R and X protein antigens.  相似文献   

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This study was performed to verify and further characterize the role of neuroendocrine factors in the regulation of fetal adipose metabolism. On day 72 to 74 of gestation, pig fetuses in one uterine horn were hypophysectomized (hypoxed) by micro-cauterization, fetuses in the other horn served as sham controls. Fetuses were removed by laparotomy on day 110 of gestation. Slices of subcutaneous adipose tissue from control fetuses responded to lipolytic stimulation by norepinephrine alone (NE; 1 microgram/ml), NE plus adenosine deaminase (160 mUnits/ml) or dibutyryl cyclic AMP (5 mM). Adipose tissue from hypoxed fetuses, however, responded to lipolytic stimulation by only dibutyryl cyclic AMP, not NE. Lipogenesis in adipose tissue slices, as quantitated by 3H2O incorporation into triglyceride fatty acids, was increased 2.6 fold by hypophysectomy. These results demonstrate the necessity of a functioning pituitary in the normal regulation of fatty acid synthesis and receptor-mediated lipolytic response in developing fetal adipose tissue.  相似文献   

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A recent study conducted in Sweden reported that 1) leukemia risk in children who lived near 220 or 400 kV electric-power transmission lines was associated with calculated historical magnetic field levels; 2) children living within a distance of 50 m of transmission lines had an elevated risk of leukemia; and 3) there was no association between leukemia and residential magnetic fields measured many years after diagnosis. Subsequently, these investigators found through logistic regression analysis that disease was more strongly associated with calculated historical fields than with distance. Since the calculated historical fields in that study depended predominantly on distance and transmission-line load current, the logistic regression results suggest that historical load current plays an important role in the epidemiological results. Thus, we studied hourly 1974 load-current data for six transmission lines, and we examined 1958-1985 annual load-current data for 112 transmission lines. Most lines exhibited marked diurnal load-current rhythms during 1974, and all six showed systematic weekday-weekend differences. During 1958-1985, average loadings of Swedish 220 and 400 kV lines increased by about 1.3% year. Predictive-value and kappa-statistic analyses indicated that Swedish transmission-line load currents were not stable over long periods, so that contemporaneous load current (or a contemporary magnetic field measurement) was not a good surrogate for historical load current (or historical magnetic fields). The results provide a potential explanation of the failure of the Swedish Study to find an association between leukemia and contemporaneous magnetic field levels measured many years after the etiologic period, and suggest that the inclusion of load-current data could significantly improve the quality of historical field calculations.  相似文献   

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