Biomedical subjects

J W Ager

Publications and source records attributed to J W Ager.

At least 19 recordsLinked to original sources

PubMed2006

Optical detection and ionization of donors in specific electronic and nuclear spin States.

We resolve the remarkably sharp bound exciton transitions of highly enriched 28Si using a single-frequency laser and photoluminescence excitation spectroscopy, as well as photocurrent spectroscopy. Well-resolved doublets in the spectrum of the 31P donor reflect the hyperfine coupling of the electronic and nuclear donor spins. The optical detection of the nuclear spin state, and selective pumping and ionization of donors in specific electronic and nuclear spin states, suggests a number of new possibilities which could be useful for the realization of silicon-based quantum computers.

Journal Article↗

PubMed2006

Large melting-point hysteresis of Ge nanocrystals embedded in SiO2.

The melting behavior of Ge nanocrystals embedded within SiO2 is evaluated using in situ transmission electron microscopy. The observed melting-point hysteresis is large (+/-17%) and nearly symmetric about the bulk melting point. This hysteresis is modeled successfully using classical nucleation theory without the need to invoke epitaxy.

Journal Article↗

PubMed2006

Evidence for p-type doping of InN.

The first evidence of successful p-type doping of InN is presented. It is shown that InN:Mg films consist of a p-type bulk region with a thin n-type inversion layer at the surface that prevents electrical contact to the bulk. Capacitance-voltage measurements indicate a net concentration of ionized acceptors below the -type surface. Irradiation with 2 MeV He+ ions is used to convert the bulk of InN:Mg from p to n-type, at which point photoluminescence is recovered. The conversion is well explained by a model assuming two parallel conducting layers (the surface and the bulk) in the films.

Journal Article↗

PubMed2005

Effects of polar solvents on the fracture resistance of dentin: role of water hydration.

Although healthy dentin is invariably hydrated in vivo, from a perspective of examining the mechanisms of fracture in dentin, it is interesting to consider the role of water hydration. Furthermore, it is feasible that exposure to certain polar solvents, e.g., those found in clinical adhesives, can induce dehydration. In the present study, in vitro deformation and fracture experiments, the latter involving a resistance-curve (R-curve) approach (i.e., toughness evolution with crack extension), were conducted in order to assess changes in the constitutive and fracture behavior induced by three common solvents-acetone, ethanol and methanol. In addition, nanoindentation-based experiments were performed to evaluate the deformation behavior at the level of individual collagen fibers and ultraviolet Raman spectroscopy to evaluate changes in bonding. The results indicate a reversible effect of chemical dehydration, with increased fracture resistance, strength, and stiffness associated with lower hydrogen bonding ability of the solvent. These results are analyzed both in terms of intrinsic and extrinsic toughening phenomena to further understand the micromechanisms of fracture in dentin and the specific role of water hydration.

Animals↗

PubMed2000

Age-related changes in initiation and maintenance of sleep: a meta-analysis.

The purpose of this meta-analysis was to determine the magnitude of change over the adult life span in four key sleep characteristics and to explore research design features that may account for variability in reported age-related sleep change. Forty-one published studies (combined N = 3293) provided 99 correlational effect sizes. Waking frequency and duration increased with age as previously concluded by narrative reviewers. Although narrative reviewers were less certain whether nighttime sleep amount or the ability to initiate sleep decreased with age, the meta-analysis suggested that both decreased. When sleep variables were measured by polysomnography rather than self-report, larger age-related changes were found. Few researchers who studied normal sleep controlled for important health moderators or studied women.

Adult↗

PubMed1998

Relation of maternal age and pattern of pregnancy drinking to functionally significant cognitive deficit in infancy.

Prospective studies of the effects of prenatal alcohol exposure on development have focused primarily on the detection of subtle deficits. This study was designed to extend those findings by evaluating dose-response, functional significance, and pattern of drinking in greater detail. 480 African-American infants, recruited to overrepresent prenatal exposure at moderate-to-heavy levels, were assessed. For the five outcomes tested, nonparametric and hockey stick regression analyses both indicated essentially no relation between pregnancy drinking and developmental outcome below a median threshold of 0.5 oz absolute alcohol/day, with the impact of the exposure increasing gradually above threshold. Functional deficit was defined in terms of performance in the bottom 10th percentile of the distribution. For four of the five outcomes tested, there was no increased incidence of functionally significant deficit in infants born to moderate-to-heavy drinking mothers <30 years old, whereas those born to older drinking mothers were 2 to 5 times more likely to be functionally impaired. Among the infants exposed above threshold, functionally significant deficits were seen primarily in those whose mothers averaged at least 5 drinks/occasion on an average of at least once/week. By contrast, a history of alcohol abuse was not related to functional deficit. These data suggest that efforts to reduce the incidence of alcohol-related functional impairment should specifically target the older mother who engages in intermittent heavy drinking during pregnancy.

Adult↗

PubMed1996

Autoimmunity to collagen in human lung cancer.

Autoantibodies have been described in human cancer patients as well as in animal models of malignancy. The extracellular matrix and especially basement membranes act as barriers for tumor cell invasion. Collagen, particularly types I, III, and IV, are major constituents of the extracellular matrix. We tested the hypothesis that autoimmunity to collagen antigens is present in lung cancer. Sera from 67 patients with lung cancer and 50 reference subjects were tested for anticollagen antibodies by using purified human collagen types I-V and for antibodies binding human cartilage aggrecan proteoglycan. Antibody levels were determined by using ELISA. The relationship of serum levels of these antibodies to patient survival, histology, treatment response, disease stage, and pack years of smoking was examined by using multiple regression and discriminant function analyses. A subgroup of 45 patients in whom a smoking history was available was analyzed separately. Within 1 month of the initiation of therapy, mean serum levels of antibodies binding fibrillar collagen types I-III and V were significantly higher (P < 0.025) than were those in control sera (43.2% of patients positive for one or more anticollagen antibodies). Antibodies binding aggrecan proteoglycan were not different between patients and control sera. In the lung cancer patients, the levels of serum antibodies binding types IV and V collagens contributed to the variance of progression-free survival days, survival days, and the duration of favorable response in opposite directions. Histological cell type contributed to the variance in the level of serum antibody binding collagen types IV and V. Lower levels of antibody binding type IV and higher levels of antibody binding type V were associated with small cell carcinoma. The pack-years of smoking only contributed to the variance in the level of serum antibody binding type V collagen. We conclude that autoantibodies to fibrillar collagen antigens are present frequently in lung cancer patients, and their levels may be related to histological cell type and to the duration of the response to treatment.

Adolescent↗

PubMed1996

Has awareness of the alcohol warning label reached its upper limit?

Has awareness of the alcoholic beverage warning label reached its maximum? This study tracks changes in the level of awareness among a sample of 7334 inner-city African-American gravidas seeking prenatal care between May 1989 and June 1993. Previously, we found that a significant increase in awareness of the warning label occurred in March 1990. In the current analysis over a 50-month period, the level of awareness continued to increase through December 1992 and then leveled off, suggesting a negatively accelerated growth function. The logistic function fitted to the awareness curve predicts that the upper limit of awareness in this population has been reached (the predicted upper limit being 81.5%). In addition a logit regression analysis showed that women who did not know about the warning label were more likely to be over 29 years of age. Heavier drinkers were 1.25 times more likely to be aware of the label. Among those drinkers who were not aware of the label, 30% drank at both conception and antenally, thus putting their fetus at high risk for alcohol-related birth defects.

Adult↗

PubMed1996

Heeding the alcoholic beverage warning label during pregnancy: multiparae versus nulliparae.

OBJECTIVE: We compared the impact of the Federal Alcoholic Beverage Warning Label on multiparae (women with at least one previous live birth) and nulliparae (women with no previous live births). The label, implemented on November 18, 1989, urges women not to drink during pregnancy because of the risk of birth defects. If multiparae drank during prior pregnancies, delivering apparently normal babies, we hypothesized that the warning might be less salient for them. METHOD: We studied 17,456 inner city black gravidas seen between September 1986 and September 1993 at one antenatal clinic. Time series analysis (ARIMA) examined trends in monthly means of antenatal drinking scores (alcohol consumption adjusted for weeks' gestation, age, parity and periconceptional drinking). RESULTS: For nulliparae (n = 7,349), reported drinking began to show a significant decline in June 1990, 7 months after the implementation of the warning label (t = 2.00, p < .04). In contrast, multiparae (n = 10,107) showed no change in reported drinking (t = 1.23) postlabel. CONCLUSIONS: Given previous results that multiparae drink more and that heavier drinkers are ignoring the warning label, these data are very distressing and suggests the importance of targeting multiparae for intensive prevention efforts.

Adolescent↗

PubMed1996

Effects of case management on retention in prenatal substance abuse treatment.

Participation in substance abuse treatment during pregnancy is associated with improved pregnancy outcomes. Case management has been proposed as one way to reduce barriers to receiving and continuing treatment. An evaluation was conducted on a case management program to retain pregnant women in drug treatment. Two hundred twenty-five pregnant women received case management services consisting of home visits, telephone counseling, transportation, and referral. All women contacted a substance abuse treatment center and most (56%) obtained treatment during pregnancy. Sociodemographic factors, personal and family history of substance use and drug treatment, protective services involvement, history of physical and sexual abuse, and need for tangible resources were assessed. Charts were reviewed at the substance abuse treatment center for number of visits and urine toxicology reports, and at the hospital for pregnancy outcome. Data were analyzed by LISREL path analysis. Five factors had significant path correlations to prenatal attendance at the substance abuse treatment center: history of protective services involvement, number of drugs ever used, currently receiving methadone, intensity of case management, and receiving transportation to drug treatment appointments. We conclude that case management, including providing transportation, contributes significantly to retention in substance abuse treatment during pregnancy.

Adult↗

PubMed1995

MOMs (multiples of the median) and DADs (discriminant aneuploidy detection): improved specificity and cost-effectiveness of biochemical screening for aneuploidy with DADs.

OBJECTIVE: Our purpose was to assess the efficacy of double- and triple-screening paradigms for Down syndrome and to develop a more logical, statistical approach to risk prediction that will decrease the cost of screening and allow the incorporation of new parameters appropriately weighted for their contribution. STUDY DESIGN: Data from 24,504 patients who had biochemical screening for Down syndrome by single (alpha-fetoprotein), double (alpha-fetoprotein, beta-human chorionic gonadotropin), or triple screening (alpha-fetoprotein, beta-human chorionic gonadotropin, unconjugated estriol) who had complete outcome information were analyzed by (1) existing gaussian-based methods, (2) the Glasgow ratio method, and (3) a new statistical approach (i.e., directly adjusted data sets for discriminant aneuploidy detection [DADs]) RESULTS: By use of individual risk-based thresholds for "at risk" status, both double and triple screening performed far better than single screening, but the percentages of patients at risk varied widely. When the percentages at risk were held constant, the sensitivity of double and triple screenings was similar, suggesting that there are no benefits of using estriol as a third marker. For 25,000 patients the use of only alpha-fetoprotein and beta-human chorionic gonadotropin would save about $500,000, with no decrease in sensitivity. With the DADs approach a statistically sound model giving more stable estimates was developed that permits each factor to be analyzed for its own explained proportion of variance and allows each parameter to have different weighting. For this data set the same sensitivity was seen with, conservatively, a 1% reduction in the percentage of patients at risk, which would reduce by 250 the number of amniocenteses, at a further savings of about $400,000. CONCLUSIONS: By use of existing methods, double screening is equally as effective as triple screening, so that the expense of estriol is unnecessary. The DADs approach, by allowing for variable weighting of parameters, lowers the at risk percentage and will permit a much more flexible approach as new parameters become available. Changing to DADs and eliminating estriol should achieve higher specificity for the same sensitivity and save, conservatively, about $900,000 in this series. Extrapolated nationally, if confirmed, the annual savings could approach $72,000,000.

Adolescent↗

PubMed1994

Effects of alcohol use, smoking, and illicit drug use on fetal growth in black infants.

STUDY OBJECTIVES: To compare the effects of prenatal exposure to alcohol, smoking, and illicit drugs on birth size. DESIGN: Prospective, longitudinal correlational study, with statistical control for confounding. PARTICIPANTS: Four hundred seventeen black infants. Mothers recruited at first prenatal clinic visit on the basis of moderate-to-heavy use of alcohol or cocaine or both, plus a 5% random sample of lower-level drinkers and abstainers. MAIN RESULTS: Alcohol, smoking, opiates, and cocaine were each correlated with smaller birth weight, length, and head circumference (median r = -0.21; p < 0.001). However, when all four substances, gestational age, and six covariates were controlled statistically, birth weight related only to alcohol and smoking (p < 0.05), length only to alcohol (p < 0.05), and head circumference only to opiates (p < 0.01). Although smoking affected birth weight at all levels of exposure, a larger deficit was seen in relation to heavy drinking (509 gm) than to heavy smoking (269 gm). Alcohol and smoking did not affect birth size synergistically, and their effects were seen primarily in infants of women more than 30 years of age. CONCLUSIONS: The association of reduced birth weight and length with illicit drug use may be a consequence of simultaneous exposure of the fetus to alcohol and smoking. Opiate exposure is specifically related to reduced head circumference, and the effect of cocaine on birth size is primarily an indirect consequence of shorter gestation and poorer maternal nutrition.

Adolescent↗

PubMed1994

History of in utero cocaine exposure in language-delayed children.

To determine whether children with language delays are more likely to have been exposed to cocaine in utero than children with normal language development, a case-control study was undertaken. Based on routine office screening in our primary-care clinic over a 1-year period, we identified 29 consecutive children, aged 24 to 48 months, as language-delayed. They were compared with an approximate 2:1 match of children without language delay who had been seen in the clinic on the same days and who were of similar age. There was more reported cocaine use during pregnancy (six of 29, 21%) among the language-delayed children than among the controls (five of 71, 7%). This difference is statistically significant (P < 0.05, chi 2 = 3.92; odds ratio = 3.4 +/- 2.2). Discriminant analysis revealed that both cocaine and nicotine exposure were associated with delayed language development--with an unexpected negative, i.e., an antagonistic, protective, interactive effect (F[3,96] = 4.66, R2 = 12.7%, P < .005); neither gender nor caretaker contributed to language development in this sample. These results suggest that children with language delay detected in a clinical setting are more likely to have been exposed in utero to cocaine than children with normal language development. Prenatal cocaine exposure should be a risk factor in monitoring development in children.

Case-Control Studies↗

PubMed1993

Relationship between the fetal biophysical profile score, umbilical artery Doppler velocimetry, and fetal blood acid-base status determined by cordocentesis.

OBJECTIVE: Fetal hypoxia-acidosis is part of the terminal pathway leading to intrauterine fetal death. A central premise of antepartum surveillance is that identification and timely delivery of the hypoxic or acidotic fetus will prevent intrauterine death and decrease long-term neurologic damage. The optimal method to identify fetal hypoxia-acidosis has not been determined. We attempted to compare the performance of the biophysical profile score and umbilical artery Doppler velocimetry in the identification of fetal acidemia, hypoxemia, and hypercarbia as determined by pH and gas analysis of fetal blood obtained by cordocentesis. STUDY DESIGN: Fetal biophysical profile and umbilical artery Doppler velocimetry studies were performed before cordocentesis in 24 patients (26 to 40 weeks). Umbilical vein pH and blood gas values were determined in all cases. The pulsatility index of the umbilical artery was obtained with pulsed Doppler equipment. Receiver-operator characteristic curve analysis and stepwise multiple logistic regression were performed to examine the relationship between biophysical profile score, umbilical artery Doppler velocimetry, and acid-base status. RESULTS: The prevalence of fetal acidemia (pH 2 SD below the mean for gestational age) was 41.7% (10/24). There was a significant relationship between the change in umbilical artery pulsatility index and fetal acidemia (chi 2 = 26.6, p < 0.001) and hypercarbia (chi 2 = 22.9, p < 0.001), but not hypoxemia (chi 2 = 1.0, p > 0.1), and between the biophysical profile score and fetal acidemia (chi 2 = 11.1, p < 0.001) and hypercarbia (chi 2 = 9.0, p < 0.005), but not hypoxemia (chi 2 = 2.3, p > 0.1). Stepwise multiple logistic regression demonstrated that umbilical artery Doppler velocimetry was a better explanatory variable for acidemia and hypercarbia than the biophysical profile score. CONCLUSION: A strong relationship between the degree of fetal acidemia and hypercarbia and the results of umbilical artery Doppler velocimetry and biophysical profile was found. However, umbilical artery Doppler velocimetry was a better explanatory variable for these outcome than the biophysical profile score.

Acid-Base Equilibrium↗

PubMed1993

Punishing pregnant drug users: enhancing the flight from care.

One hundred forty-two low income women were interviewed postpartum to determine their attitudes regarding the potential effects of a punitive law on the behavior of substance-using pregnant women. The convenience sample was primarily black (85.2%) and single (81%) and 14.8% admitted use of illicit drugs during pregnancy. A goodness-of-fit chi-square analysis revealed that subjects believed a punitive law would be a significant deterrent to substance-using gravida seeking prenatal care, drug testing or drug treatment (P < 0.01). Comments indicated that substance-using pregnant women would 'go underground' to avoid detection and treatment for fear of incarceration and loss of their children.

Alcohol Drinking↗

PubMed1993

Teratogenic effects of alcohol on infant development.

Results of previous studies of effects of drinking during pregnancy on standardized tests of infant development have varied, depending on level of exposure. This study of 382 Black, inner city infants confirmed effects of moderate-to-heavy prenatal alcohol exposure on Bayley Scale performance originally observed in a White, middle class cohort. Effects of second and third trimester drinking were as strong or stronger than those of drinking at the time of conception. New methods for reducing the Bayley Scale data suggested specific deficits relating to emergence of the ability to imitate modeled behavior and the development of standing and walking. The incidence of very poor performance (bottom 10th percentile) on the Bayley Mental Development Index more than doubled in children whose mothers averaged at least 0.5 oz absolute alcohol per day during pregnancy, indicating that this exposure has a clinically meaningful impact at markedly lower levels than those associated with full fetal alcohol syndrome. Clinically meaningful effects on the Psychomotor Development Index, by contrast, were seen only in the infants of heavy drinking mothers with overt symptomatology of alcohol abuse. Adverse effects on Bayley Scale performance were more prevalent in the infants of women more than 30 years of age.

Adult↗

PubMed1993

A time series analysis of the impact of the alcohol warning label on antenatal drinking.

In a sample of over 12,000 African-American gravidas, we tested the hypothesis that the Federal Beverage Labeling Act of 1988 has decreased antenatal drinking. Results of time series analysis indicated a 7-month lag in the impact of the alcohol warning label. Controlling for population changes, antenatal drinking began to fall as of June 1990. However, this decrease was small in size and did not impact on the heaviest drinkers. Seasonal trends in drinking were also detected, with peaks around the end of the year and the summer.

Adult↗

PubMed1993

The alcohol beverage warning label: when did knowledge increase?

This article presents data on the awareness of the alcohol beverage warning label among a sample of 5,169 inner city African-American gravidas seeking prenatal care. While the label law was implemented in November 1989, a significant increase in knowledge of the label did not occur until March 1990. Women who predominantly consumed wine coolers and beer, and those under age 30 were more likely to know about the label than their counterparts.

Adult↗