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Biomedical subjects

A P Jacobson

Publications and source records attributed to A P Jacobson.

17 recordsLinked to original sources
PubMed1992

A graphical method of estimating fatal radiation-induced cancers using the BEIR V method.

A method is presented that permits health physicists to estimate the risks of radiation-induced cancers in populations of males or females exposed to whole-body external irradiation at any age. Graphics are presented that may be used for either acute or chronic exposures. There is good agreement for chronic exposures when the cancer estimates determined here are compared with those prescribed in BEIR V. There are differences between the two when considering some acute exposures. In such circumstances, the method given here generally gives conservative results.

Environmental Exposure↗
PubMed1991

Analysis of repeated-measure multicycle unilateral mastication in children.

This study examined systematic and random errors associated with repeated-measure, multiple-cycle unilateral mastication in children during single recording sessions with the Replicator system. Twenty-six recording sessions with 17 children (10 boys, 7 girls) were examined. Nine of these children had a functional-shift unilateral crossbite malocclusion and were recorded before and after crossbite correction. Repeated recordings (trials) of mandibular movement during each session were made of right-side chewing of similar-sized pieces of cheese. The following variables were computed for each chewing cycle (stroke): time closed, maximum closure velocity, maximum opening velocity, chewing rate, vertical opening, and lateral deviation. From the multiple cycles of each trial, two pattern descriptors--the average and standard deviation--were determined for each variable. In addition, the mean and variance of these pattern descriptors were determined from the multiple trials of each recording session and were the dependent variables in a stepwise multiple regression analysis, with treatment status, sex, age, dentition stage, crossbite presence, and right side status the independent variables. The results disclosed bias in repeated measures of human chewing in response to adaptation to the recording session; this was evident in the average response but not in the variability of the measures. Sex and functional status of the subjects were associated with the mean and variance of measures describing the chewing pattern.

Adolescent↗
PubMed1982

Health effect of occupational exposure to steady magnetic fields.

An observational cross sectional study was conducted to determine if long term exposure to steady magnetic fields of up to 200 Oersteds could be related, on a dose-response basis, to findings of medical examinations. Health data were obtained for 320 workers who spent a major portion of their workday in the magnetic fields produced by the direct current through large electrolytic cells. These data were compared to those for a control group of 186 workers. The vertical and horizontal components of the magnetic fields were measured in each cell room and the time weighted average exposure to magnetic fields was calculated for each job classification. The leukocyte count and the monocyte percent were found to decrease, while the lymphocyte percent was found to increase with increased exposure to the horizontal component of the magnetic field. A slight tendency of both the systolic and diastolic blood pressures to increase with increasing exposure to the vertical component of the magnetic field was found in the black workers in the study. No such effect was found in the other racial groups. No other signs or symptoms were found to depend on magnetic field exposure.

Analysis of Variance↗
PubMed1981

Chewing patterns in normal children.

Chewing patterns are precisely plotted in deciduous, mixed and permanent dentitions. These show a progression from a large component in the opening movement with a more medial closing path in the deciduous dentition, to a more vertical overall pattern with the closing path lateral to the opening path in the early permanent dentition.

Adolescent↗
PubMed1978

Contamination of the home environment by patients treated with Iodine-131: initial results.

We have employed twin sodium iodide radiation detectors to analyze iodine-131 transfer from thyroid patients to their families. Unlike previous studies of this problem, we measured thyroid radioiodine activity directly and are able to detect as little as 92 pCi of iodine 131 in adult thyroids. As in previous studies, we have also measured direct radiation exposures of family members with wristband thermoluminescent dosimeters. Thus far, we have studied seven families with 17 persons. Eleven of these are children under age 16. Direct radiation exposure of family persons from proximity of these radioactive patients ranged from 0.17 to 126 mR per day (natural background radiation amounts to approximately 0.35 mR per day). The maximum activity of iodine-131 in family thyroids ranged from less than 92 pCi to as high as 110,000 pCi and resulted in thyroid dose equivalents of 4 to 1330 mrem. Based on recent estimates of thyroid cancer, the latter dose equivalent could possibly double the risk of thyroid malignancy in children over what is expected normally. Such a risk implies the addition of 10 induced cases to the 10 naturally occurring cases per million people per year.

Adolescent↗
PubMed1977

Radioresistance of mongolian gerbils. Fast neutrons.

Seventy-six 8 week old Mongolian gerbils were exposed to acute, whole-body fast neutrons produced by The University of Michigan 83-in. cyclotron. Groups of seven or eigth gerbils were given doses between 485 and 881 rad at 25 rad per minute. The LD 50/30 determined by probit analysis was 750 rad, with 95 per cent fiducial limits of 733 and 776. For the 50 per cent mortality level, an r.b.e. of fast neutrons compared with cobalt-60 of 1-45 was determined. For the same end-point, the r.b.e. for fast neutrons compared with X-rays is 1-33. Mortality data, body-weight and microhaematocrit changes are discussed.

Animals↗
PubMed1976

The role of natural radiations in human leukemogenesis.

Some 3 billion years ago, life arose from a warm pool of primordial ooze amid a constant drizzle of radiation. Steadily, man evolved from the lesser forms of life because of or in spite of his natural background-radiation environment. This study is an attempt to determine to what extent these background radiations are responsible for human disease, namely leukemia. Dose rate data were compared with data on all forms of leukemia in the 50 United States for four population subgroups. For the total U. S., no relation between background radiation and leukemia is apparent. A positive correlation appears, however, if various states are deleted from the analysis. It appears that conditions relative to populations and their environment could mask a radiation effect if in fact one is present.

Background Radiation↗
PubMedDate not supplied

Potential exposure to metal fumes, particulates, and organic vapors during radiotherapy shielding block fabrication.

The shielding-block fabrication areas of three hospitals were surveyed to assess inhalation exposure to lead (Pb), cadmium (Cd), bismuth (Bi), and tin (Sn) fumes, as well as styrene and methyl chloride vapors. Area and personal breathing zone samples were collected for various steps in the block fabrication process. Only 3 of 16 air samples for metals resulted in detectable levels of Pb and/or Cd. The levels were well below the Occupational Safety and Health Administration (OSHA) Permissible Exposure Limits, excluding a sample which contained a visible metal fragment. Bi and Sn were not detected in any samples. Methyl chloride and styrene vapors were not detected in any air samples during foam cutting procedures. Total particulates (TP) were measurable in 11 of 17 air samples (ranging from 0.01 to 2.1 mg/m3). TP values were below the OSHA federal standard for nuisance particulates, which is 15 mg/m3. The data suggest that the materials and procedures sampled do not present an inhalation hazard to employees who construct shielding blocks. Precautions should, however, be exercised to prevent exposure under extreme procedural conditions such as soldering or overheating of alloy, and by other means such as ingestion. Care should also be taken during cleanup or housekeeping to prevent re-entrainment into the work atmosphere of mechanically generated metal particles or materials condensed within melting pots (which may be high in metal content).

Air Pollutants, Occupational↗