Mean Annual Reduction Research Articles

Tuberculin sensitivity trends in Hellenic army recruits during the period 1981-91

Setting: The tuberculin skin test is widely used to define the tuberculous infection in the community. Serial representative tuberculin surveys demonstrate the trend of the risk of tuberculous infection. Objective: The study of tuberculous infection in Hellenic army recruits for the purposes of BCG vaccination, which with chemoprophylaxis and early case-finding are the major strategies used for preventing tuberculosis (TB). Design: We investigated tuberculin skin sensitivity on 544210 Hellenic Armed Forces recruits during 1981–1991. The age of the subjects ranged between 18–28 years (mean 21 ± 1.5 years). We used the Mantoux technique with tuberculin PPD-RT 23 with Tween 80, dose 2 IU ( 1 5000 ) of the Hellenic Pasteur Institute. Tuberculin skin reactions were examined by two experienced readers after 48 hours. Indurations < 5 mm were considered as negative reactions, ≥ 10 mm as positive, and 5–9 mm as doubtful reactions. Results: The results of the present study were compared to other studies undertaken in recruits during the period 1934-80. We found a decrease of positive reactions from 14.2% in 1981 to 6.8% in 1991. The mean annual reduction was 0.74%. The decline has continued since 1947, as previous studies during the period 1934-80 have shown. Conclusion: We conclude that the tuberculin reactivity in recruits of the Hellenic army, although still high in relation to other European countries and North America, is declining steadily. We predict that the number of positive reactions will fall to about 1 % by the year 2000, assuming that the same trend continues.

A utility bill study of mobile home weatherization savings

This study analyzes utility bill data for 36 mobile homes retrofitted by Colorado Division of Housing Weatherization Assistance Program according to criteria developed specifically for mobile homes by the National Renewable Energy Laboratory (NREL). The post-retrofit energy savings were determined using PRISM, a regression method that provides weather normalization. The study indicated a mean annual reduction in total natural gas consumption of approximately 25% and a mean reduction in heating fuel usage of about 31%. These reductions far exceeded US national average weatherization savings for both mobile homes and site-constructed homes while remaining within weatherization program cost guidelines. These real-world savings were about 70% of what had been expected based on experiments conducted previously at NREL within a controlled environment.

A 10-year retrospective study of periodontal disease progression.

The purpose of this study was to record the rate of periodontal disease progression over a 10-year period with respect to individual subject, age and tooth type. 283 subjects, who had undergone a full-mouth radiographic examination in 1974-76 and at that time were 25-70 years old, were randomly selected from a larger patient sample for a new radiographic examination in 1985-86. 201 subjects (71%) agreed to participate. For each respondent, tooth loss over the 10-year period was calculated. The radiographic bone height at the mesial and distal aspect of all teeth was assessed by measuring the distance between the cemento-enamel junction and the bone crest. Difference in periodontal bone height between the 2 examinations was calculated for each tooth site. The results revealed that the mean number of teeth lost over the 10-year period was 3.8 (SD 4.6). Tooth mortality, expressed as a % of the no. of teeth present at the initial examination, increased with age and varied between 2.9%-28.5%. In all age groups, molars had the highest and canines the lowest rate of tooth mortality. The frequency of subjects with loss of greater than 10 teeth was highest for the initially 45-year old individuals (20%). 7 individuals (3%) had become edentulous. The mean annual reduction of alveolar bone height varied between 0.07-0.14 mm in the age groups 25-65 years. The initially 70-year old subjects showed a statistically significant higher annual rate of bone loss (0.28 mm).(ABSTRACT TRUNCATED AT 250 WORDS)

Biogeochemical cycling in an organic-rich coastal marine basin. 7. Sulfur mass balance, oxygen uptake and sulfide retention

Sulfur and oxygen fluxes were quantified in the seasonally varying anoxic marine sedimentary system of Cape Lookout Bight, N.C., U.S.A. Over the three year study period, 1981–1983, the mean annual sulfate reduction rate was determined to be 18.2 ± 1.6 moles · m−2 · y−1. This value, added to the estimate of the detrital sulfur input of 1.2 ± 4.4 gave a total sulfur input of 19.4 ± 4.7 moles · m−2 · y−1. The sulfide flux to the sediment-water interface, measured in anaerobic benthic chambers was 4.6 ± 0.5 moles · m−2 · y−1, and represented 37% of the annual oxygen uptake rate of 25.2 ± 2.8 moles · m−2 · y−1. The sulfide burial rate, determined to be 15.5 ± 3.1 moles · m−2 · y−1, was within 5% of the value predicted by summing the fluxes at the sediment-water interface. The CS weight ratio of sediment below the depth of diagenetic reaction was determined to be 2.75. The sulfide retention rate in these rapidly accumulating sediments (10 cm/yr) was 77 ± 19%. Comparison of this result with previous studies shows that rapid sediment accumulation and the lack of bioturbation control this unusually high degree of sulfide retention.

Evaluation of endosseous implant abutments as a base for fixed prosthetic appliances. A preliminary clinical study

In the present 2-year report nineteen Linkow blade implants with a total of twenty-seven perforating posts were assessed. All implants included were considered functionally successful and served as abutments for fixed prosthetic appliances. Periodontal probe and radiographic measurements of bone loss around the perforating implant posts, and registration of plaque and gingival index scores were performed every 6 months. During the first 4-6 weeks after implantation a vertical bone loss approximating an average of 1-2 mm occurred in the neck area of the implants. After this initial resorption, bone loss proceeded at a slower rate. The mean annual crest reduction was approximately 0.1 mm from the first to the fourth examination, as assessed from radiographic measurements. Periodontal probe measurements, showing a mean annual crest reduction of 0.2 mm, usually exhibited higher values than corresponding radiographic measurements at both implants and abutment teeth. At implants there was a significant positive correlation between plaque and gingivitis after 18 and 24 months, but not before that time. No correlation was seen between gingival index scores and the degree of bone resorption.