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D L Jacobson

Publications and source records attributed to D L Jacobson.

16 recordsLinked to original sources
PubMed2004

Thermal and cold neutron phase-contrast radiography.

In this paper, we will discuss a phase-contrast imaging method that avoids the complications of interferometry to provide phase contrast in weakly absorbing samples. A transversely coherent neutron beam is used with the traditional radiography scheme. Images taken with this scheme show dramatic intensity variations due to sharp changes in the neutron wave refractive index. With some numerical processing these images may be used to reconstruct a quantitative phase radiograph of specimens imaged with this technique.

Journal Article↗
PubMed2003

Quantitative phase radiography with polychromatic neutrons.

We develop and experimentally demonstrate a formalism that allows accurate phase imaging using neutron sources producing highly polychromatic beams. The results of measurements from a rectangular block of silicon compare favorably with theoretical simulations based upon the known composition and geometry of the block. The increased flux and reduced exposure times will permit a simple extension of the technique to tomographic phase imaging.

Journal Article↗
PubMed2003

Precision neutron interferometric measurement of the nd coherent neutron scattering length and consequences for models of three-nucleon forces.

We have performed the first high precision measurement of the coherent neutron scattering length of deuterium in a pure sample using neutron interferometry. We find b(nd)=(6.665+/-0.004) fm in agreement with the world average of previous measurements using different techniques, b(nd)=(6.6730+/-0.0045) fm. We compare the new world average for the nd coherent scattering length b(nd)=(6.669+/-0.003) fm to calculations of the doublet and quartet scattering lengths from several modern nucleon-nucleon potential models with three-nucleon force (3NF) additions and show that almost all theories are in serious disagreement with experiment. This comparison is a more stringent test of the models than past comparisons with the less precisely determined doublet scattering length of (2)a(nd)=(0.65+/-0.04) fm.

Journal Article↗
PubMed2002

Changes in lean body mass and total body weight are weakly associated with physical functioning in patients with HIV infection.

CONTEXT: For clinicians managing weight loss in patients with HIV, it would be useful to understand how changes in lean body mass (LBM) effect physical functioning, and whether LBM is more strongly related to physical functioning than total body weight (TBW). OBJECTIVE: To determine the relationship of changes in LBM and changes in total body weight (TBW) to changes in self-reported physical functioning in men and women with HIV infection. METHODS: Study design was longitudinal analysis of 1474 patient-intervals (each interval was approximately 6 months long) in 486 persons. Patients were participants in Nutrition for Healthy Living, a cohort study of HIV positive persons in Massachusetts and Rhode Island. The main outcome measure was change in self-reported physical functioning. RESULTS: Of the 1,474 intervals, 1,165 were contributed by men and 309 by women. The mean CD4 count for the 1,474 intervals was 383 cells/ micro L. In men, 5 kg changes in LBM and TBW were associated with 2.2 (95% confidence interval, 0.9, 3.4, P= 0.001) and 2.6 (95% confidence interval, 1.3, 3.9, P= 0.0002) point changes in physical functioning (on a 100-point scale), respectively, after adjusting for covariates. The relationships of changes in LBM and TBW to changes in physical functioning were linear. In women, there were no significant relationships between changes in LBM or TBW to changes in physical functioning. CONCLUSIONS: In this longitudinal analysis of relatively healthy persons with HIV infection, changes in LBM and TBW were significantly related to changes in physical functioning in men, but the magnitude of the relationship was small. In women, changes in LBM and TBW were not related to changes in physical functioning. Our data suggest that it is not necessary to measure body composition (lean and fat compartments) to understand the impact of changes in weight on physical functioning - it is sufficient to follow total body weight.

Adult↗
PubMed2000

Concordance of human papillomavirus in the cervix and urine among inner city adolescents.

OBJECTIVES: To evaluate concordance for human papillomaviruses (HPVs) between cervix and urine in sexually active adolescents. METHODS: Cervical swabs and urine were collected from 80 adolescents in Baltimore, MD. Specimens were tested for 34 HPVs by PCR and for cancer-associated HPVs by Hybrid Capture (HC II) Probe B. Cervical vs. urine prevalence was evaluated by logistic regression with general estimating equations. Risk factors for prevalence and viral burden were evaluated by Fisher's exact and Kruskal-Wallis tests, respectively. RESULTS: HPV prevalence by PCR, for any HPV, was very high in the cervix (90.0%) and somewhat lower in urine (75.0%) (odds ratio, 1.07; 95% confidence interval 1.07 to 1.34). Only one adolescent was HPV-positive in urine alone. Among HPV-PCR positives at either or both sites, concordance was 82% for presence of any HPV and 40% for specific HPV types. Multiple infections were common at both sites. On an average, HC II viral burden (relative light unit ratio) was 9-fold higher in cervix than in urine (median, 47.3 vs. 4.9; P = 0.005) but correlated poorly between the two sites of the same individual (r = 0.14). Compared with normal adolescents, those with squamous intraepithelial lesions had a much higher prevalence of HPV by HC II in cervix (100% vs. 28.6, P<0.0001) as well as in urine (86.7% vs. 35.4%, P = 0.002) and a significantly higher viral burden in the cervix (median, 141.8 vs. 7.3, P = 0.0045) but not in urine (median, 22.7 vs. 4.38; P = 0.13). CONCLUSION: There was a very high prevalence of HPV in cervix and urine of sexually active adolescents. Testing urine for HPV may be useful in epidemiologic investigations and in monitoring of infected women.

Adolescent↗
PubMed2000

Histologic development of cervical ectopy: relationship to reproductive hormones.

BACKGROUND AND OBJECTIVES: Cervical ectopy has been proposed as a risk factor for chlamydial infection, HIV, and other sexually transmitted diseases (STDs). Ectopy is a histologic phenomenon resulting from a complex interplay of morphologic and hormonal processes. Reproductive hormones influence the production of ectopy during late fetal life, puberty, pregnancy, and with use of oral contraceptives. Ectopy is modified over time by squamous metaplasia and epitheliazation, low pH, trauma, and possibly by cervical infection. STUDY DESIGN: The authors review the histologic development of ectopy from late fetal life to menopause to understand STD risk. RESULTS: Ectopy is often assessed and quantified by direct, unaided observation during speculum examinations. This method may result in inaccurate estimates and misclassification with the transformation zone. CONCLUSION: Valid, reproducible measures of ectopy are necessary for epidemiologic studies to examine the impact of exogenous hormonal contraceptives on the development of ectopy and on potential infection risk.

Adolescent↗
PubMed2000

Relationship of hormonal contraception and cervical ectopy as measured by computerized planimetry to chlamydial infection in adolescents.

BACKGROUND: Adolescents are at increased risk for chlamydial infection and its sequelae. Hormonal contraception and cervical ectopy were previously suggested risk factors for chlamydia. GOAL: To determine if chlamydia is more prevalent in female participants with greater ectopy and in hormonal contraceptive users. STUDY DESIGN: Ninety-seven adolescent females aged 11 to 20 years were recruited from two Baltimore inner-city clinics. After administering a reproductive history questionnaire, endocervical specimens were tested for Chlamydia trachomatis by polymerase chain reaction. After acetic acid application to the cervix, cervical photographs were taken, the area of ectopy was quantified by computerized planimetry, and ectopy was categorized as none (0mm2), mild (< 22mm2), and moderate (> 22mm2). The likelihood of chlamydia by ectopy and type of hormonal contraceptive use was determined by logistic regression adjusted for age and sexual partners. RESULTS: The odds of chlamydial infection was similar in persons with mild ectopy compared with no ectopy (adjusted odds ratio [OR], 0.76; 95% CI, 0.14-4.03), and in persons with moderate ectopy compared with no ectopy (adjusted OR, 1.94; 95% CI, 0.40-9.39). The likelihood of chlamydia was higher in depot-medroxyprogesterone acetate users compared with nonhormone users (adjusted OR, 5.44; 95% CI, 1.25-23.6). Oral contraceptive users did not have an increased likelihood of chlamydia (adjusted OR, 0.92; 95% CI, 0.10-8.78). CONCLUSION: Using a new, reliable, and standardized technique to quantify cervical ectopy, the authors did not find an elevated prevalence of chlamydial infection in adolescents with cervical ectopy. Depot-medroxyprogesterone acetate use may increase the risk of chlamydial infection compared with combined estrogen-progestin oral contraceptives.

Adolescent↗
PubMed1999

Cervical ectopy and the transformation zone measured by computerized planimetry in adolescents.

OBJECTIVE: To determine whether cervical ectopy and the transformation (T) zone were larger in adolescents using oral contraceptives (OCs) compared to depot medroxyprogesterone acetate (DMPA). METHOD: Cervical photographs were taken on 91 adolescents in Baltimore, Maryland. Ectopy and T zone size were measured using computerized planimetry. Patients provided reproductive and sexual history. Correlates of ectopy and T zone size were identified by proportional odds and linear regression models, respectively. RESULT: Twenty-five women had no ectopy. Parity was independently associated with greater ectopy (OR 3.9, 95% CI 1.37-11.11). Predictors of smaller ectopy were douching (OR 0.23, 95% CI 0.09-0.65), and shorter sexual history (OR 0.20, 95% CI 0.05-0.74). Neither OC or DMPA were associated with ectopy. Predictors of greater T zone size were years since menarche (13.8 mm2/year, P = 0.003) and OCs (54.7 mm2, P = 0.05). DMPA predicted a smaller T zone (-67.0 mm2, P = 0.01). CONCLUSION: Computerized planimetry provides standardized measurements. Douching and sexual activity may decrease ectopy through increased squamous metaplasia. Hormonal contraceptives were not associated with ectopy in adolescents. However, long-term progestin use may decrease T zone size.

Adolescent↗
PubMed1997

Epidemiology and estimated population burden of selected autoimmune diseases in the United States.

Autoimmune diseases cause significant and chronic morbidity and disability. The actual number of persons in the United States that are affected by autoimmune diseases and the resultant magnitude of their impact on the public's health are limited to a few specific diseases. In order to understand the clinical, public health and economic importance of these diseases it is necessary to have estimates of incidence and prevalence rates in the population. In this analysis, we estimate the number of persons affected by 24 autoimmune diseases in the United States by applying mean weighted prevalence and incidence rates obtained from published articles to U. S. Census data. The study was restricted to 24 autoimmune predefined diseases for which there was direct or indirect evidence for autoimmune pathogenesis. Subsequently, we used computerized search software and ancestry searching (bibliographies) to conduct a comprehensive search of articles published from 1965 to the present. Eligible studies included those which adhered to standard disease definitions and which included population-based estimates of incidence or prevalence rates. Mean weighted incidence and prevalence rates were calculated from eligible published studies with greater weight proportionately given to larger studies. The mean rates were then applied to the U.S. Census population figures to estimate the number of persons currently afflicted with each disease and the number of new cases occurring each year in the United States. Only U.S. and European studies were used to estimate prevalence and incidence rates when there were at least six eligible studies available for a disease. When there were fewer than six studies, all available studies were included, regardless of country of origin. The number of eligible incidence and prevalence studies found in the literature varied considerably between the 24 autoimmune diseases selected. The largest number of eligible prevalence studies were conducted on multiple sclerosis (MS), rheumatoid arthritis, and systemic lupus erythematosus (SLE) (>/=23), followed by insulin-dependent diabetes (IDDM), myasthenia gravis, primary biliary cirrhosis, and scleroderma (>/=7). There were only one to four eligible studies done on 11 other diseases, and no prevalence studies on 6 diseases. Incidence studies were less frequent but the largest number of studies were conducted on IDDM (n = 37) and MS (n = 28), followed by Graves' disease/hyperthyroidism, glomerulonephritis, primary biliary cirrhosis, rheumatic fever, rheumatoid arthritis, scleroderma, and SLE (>/=9). On the other 11 diseases, there were one to six eligible studies, and no studies on 5 diseases. There were no eligible incidence or prevalence studies on Goodpasture's syndrome, idiopathic thrombocytopenia purpura, or relapsing polychondritis. Overall we estimate that 8,511,845 persons in the United States or approximately 1 in 31 Americans are currently afflicted with one of these autoimmune diseases. The diseases with the highest prevalence rates were Graves'/hyperthyroidism, IDDM, pernicious anemia, rheumatoid arthritis, thyroiditis, and vitiligo, comprising an estimated 7,939, 280 people or 93% of the total number estimated. Glomerulonephritis, MS, and SLE added an estimated 323,232 people. The prevalence of the other diseases reviewed were rare, less than 5.14/100,000. Most diseases were more common in women. From the incidence data we estimate that 237,203 Americans will develop an autoimmune disease in 1996 and that approximately 1,186,015 new cases of these autoimmune diseases occur in the United States every 5 years. Women were at 2.7 times greater risk than men to acquire an autoimmune disease. After reviewing the medical literature for incidence and prevalence rates of 24 autoimmune diseases, we conclude that many autoimmune diseases are infrequently studied by epidemiologists. As a result the total burden of disease may be an underestimate. (ABSTRACT TRUNCATED)

Autoimmune Diseases↗
PubMed1997

The effect of mode of administration on medical outcomes study health ratings and EuroQol scores in AIDS.

Brief measures of health-related quality of life are being used with increased frequency in AIDS clinical trials. Self-administration of questionnaires can reduce costs in this setting because they require little time. However, the equivalence between self- and interview-administered responses in clinical trials is not known. We evaluated patient and proxy responses to the Medical Outcomes Study HIV Health Survey (MOS-HIV) and the EuroQol. We randomized 68 patients with advanced HIV disease on (1) mode of administration (self vs. interview); (2) type of interview (face-to-face vs. telephone); (3) questionnaire order (MOS-first vs. EuroQol-first); and (4) 2- vs. 3-item response categories for physical limitations. There were few differences in scores between self and interview administration and type of interview. Proxy respondents viewed patients as more impaired than did patients themselves on subjective aspects of health including mental health (63.8 vs. 75.7, p < 0.001), health distress (67.3 vs. 77.1, p = 0.007), pain (64.4 vs. 70.0, p = 0.04), and vitality (48.4 vs. 55.5, p = 0.04). Results concerning questionnaire order and number of response categories were not conclusive. Our results suggest that for patients with advanced HIV disease, data from the MOS-HIV and the EuroQol collected using different modes may be pooled, but that proxy responses should be calibrated.

Adult↗
PubMed1993

A factor analysis of the Klein sexual orientation grid in two disparate samples.

Many researchers interested in sexual orientation can be separated into two camps: The "lumpers," who try to reduce sexual classifications to as small a number of categories as possible, and the "splitters," who try to show differences among groups and individuals that make classification schemes increasingly difficult and/or intricate. We report factor analyses of the Klein Grid (a questionnaire with 21 sexual orientation items) to see how many factors emerge in two samples of strikingly different origins. In both samples, the first factor to emerge loaded substantially on all of the Klein Grid's 21 items. This factor accounted for a majority of the variance. In both samples, a second, correlated factor emerged which indexed a separation between most of the items and those having to do with social and/or emotional preferences. In both samples, a third correlated factor also emerged, but this factor differed between the two populations: one refined the social/emotional distinction and the other distinguished ideal behavior from past and current behavior. We conclude on the basis of our analysis that both the lumpers and the splitters are correct.

Bisexuality↗
PubMed1992

Effects of recalled childhood gender nonconformity on adult genitoerotic role and AIDS exposure. HNRC Group.

The connections between childhood gender nonconformity (assessed by the Freund Feminine Gender Identity Scale, or FGI) and adult genitoerotic role (assessed by a sex history) were examined. The core sample was a group of 106 men who had sex with other men before 1980 and who are currently enrolled in two longitudinal studies of AIDS. Although other workers have cautioned against assuming a priori that childhood gender role is inherently related to adult preferences for particular sexual acts, our data suggest that there is at least a statistical association between these two concepts. In particular, the FGI (and many of its factors and items) are significantly associated with preferences for receptive anal intercourse and, less clearly, with oral-anal contact--but not with oral-genital intercourse or insertive and intercourse. Suggestions for AIDS prevention and safe-sex awareness are made on the basis of these findings. The data also suggest that in sex research involving homosexual men, the correct genitoerotic role distinction is not insertive vs. receptive behaviors, or even insertive vs. receptive and intercourse, but receptive anal intercourse vs. all other behaviors.

Acquired Immunodeficiency Syndrome↗
PubMed1991

The evolution of lymphadenopathy and hypergammaglobulinemia are evidence for early and sustained polyclonal B lymphocyte activation during human immunodeficiency virus infection.

To examine whether polyclonal activation of B lymphocytes as measured by hypergammaglobulinemia contributes to lymphadenopathy in human immunodeficiency virus (HIV) infection, correlates of adenopathy were examined in 240 homosexual men. Lymph node size was measured in 12 sites semiannually over 4 years. Both adenopathy and hyperglobulinemia developed within 1 year after seroconversion and persisted at high levels. Adenopathy declined near diagnosis of AIDS whereas serum IgG decreased 8-16 months after diagnosis. Adenopathy attributable to HIV occurred in all palpable node groups. By logistic regression, HIV-positive men were best discriminated from HIV-negative men by size of posterior cervical nodes and the number of sites with enlarged nodes. In a repeated measures model of covariance, adenopathy in HIV-positive men was associated with more CD4+ cells (P less than .002), elevated serum globulins (P less than .01), and lower platelet counts (P less than .05). Adenopathy declined over time (P less than .001) and with diagnosis of AIDS or AIDS-related complex (P less than .03). Thus, adenopathy and hypergammaglobulinemia are correlated and follow a similar course through various stages of HIV infection, suggesting that both are caused by polyclonal B cell activation.

AIDS-Related Complex↗
PubMed1986

Hepatitis A antibody in an isolated Amerindian tribe fifty years after exposure.

Antibody to hepatitis A in an Amerindian tribe was found in everyone over 50 years old but in no one younger. We suggest that the tribe had become infected with hepatitis A virus during the period, about 50 years earlier, when they engaged in raids on Luso-Brasilian settlers, that the virus failed to persist in the tribe when they withdrew into isolation, and that those who had been infected maintained antibody titers without boosting since that time.

Adolescent↗
PubMed1986

Geographic variation in infant loss of maternal measles antibody and in prevalence of rubella antibody.

Maternal and cord measles and rubella antibodies were compared in 15 populations from Brazil, Ecuador, Chile, India, Jordan, Nigeria, South Africa, Taiwan, and the United States. Review of the literature concerning these countries showed that a higher proportion of children 6-12 months of age responded immunologically to measles vaccine in areas with low per capita product than in wealthier populations. The authors show that this difference reflects differences in maternal antibody titer and differences in efficiency of transport of measles immunity across the placenta. No variation in the half-life of passive measles immunity in the infant was found in comparing three geographic areas. When these biologic factors are fully evaluated, it should be possible to predict the response to be expected from vaccination at any particular age without directly testing the vaccine in children below and above generally recommended ages for vaccination. With regard to rubella, high antibody prevalence rates were found in most of the developing countries, as well as in the United States, and these countries are therefore unlikely to encounter widespread problems with congenital rubella. However, Taiwan, and all of four areas of Brazil have prevalence rates which are no higher than those which pertained in the United States prior to establishment of the rubella immunization program. The authors believe that protection of the infants in these countries is a matter of high priority, but that, if approached hastily, it could exacerbate the problem.

Adult↗