James A Greenberg

Isoprene emission estimates and uncertainties for the central African EXPRESSO study domain

A global three-dimensional (3-D) chemistry and transport model was used to demonstrate that a factor of 2 decrease in isoprene and monoterpene emissions results in significant (10–30%) changes in predicted concentration distributions of compounds such as OH, MPAN, NOx, H2O2, O3, and CO. Isoprene and monoterpenes were predicted to have a particularly strong impact on tropical regions, including central Africa. The 1996 Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO) study included a number of experiments that improved our ability to predict isoprene and monoterpene emissions from central Africa. The results of these experiments have been incorporated into an isoprene emission model that predicts hourly emissions on a spatial scale of about 1 km2. The model uses procedures that are suitable for estimating global emissions but uses regional measurements to accurately parameterize the model. Comparisons with above-canopy aircraft and tower flux measurements demonstrate that the model can estimate emissions within a factor of 2 for regions where ground measurements of model inputs are available. The annual central African isoprene emission predicted by our revised model (35 Tg C) is only 14% less than that predicted by our earlier model, but there are considerable differences in estimates of individual model variables. The models differ by more than a factor of 5 for specific times and locations, which indicates that there are large uncertainties in emission estimates for at least some locations and seasons. The good agreement obtained for the EXPRESSO study field sites, however, suggests that the model can predict reasonable estimates if representative field measurements are used to parameterize the model.

Birth weight as a predictor of brachial plexus injury

Objective To examine the relationship between birth weight and brachial plexus injury and estimate the number of cesareans needed to reduce such injuries. Methods All 80 neonatal records coded for brachial plexus injury from October 1985 to September 1993 at the Brigham and Womens Hospital in Boston, Massachusetts, were studied along with linked maternal files. Birth weight, method of delivery, presence or absence of shoulder dystocia, and any diagnosis of maternal gestational or nongestational diabetes were abstracted. Data for the group with brachial plexus injury were compared with data for live-born infants without this injury during the same period. The sensitivity and specificity of birth weight as a predictor of brachial plexus injury were calculated. Further, the number of cesarean deliveries necessary to prevent a single brachial plexus injury was estimated using various weight cutoffs (4000, 4500, and 5000 g) for elective cesarean delivery. Results Among 77,616 consecutive deliveries, there were 80 brachial plexus injuries identified, for an incidence of 1.03 per 1000 live births. The incidence of brachial plexus injury increased with increasing birth weight, operative vaginal delivery, and the presence of glucose intolerance. In the group of women without diabetes, between 19 and 162 cesarean deliveries would have been necessary to prevent a single immediate brachial plexus injury. Among women with diabetes, between five and 48 additional cesareans would have been required. Conclusion Although birth weight is a predictor of brachial plexus injury, the number of cesarean deliveries necessary to prevent a single injury is high at most birth weights. Because of the large number of cesarean deliveries needed to prevent a single brachial plexus injury in infants born to women without diabetes, it is difficult to recommend routine cesarean delivery for suspected macrosomia in these women.

Estimates of regional natural volatile organic compound fluxes from enclosure and ambient measurements

Natural volatile organic compound (VOC) emissions were investigated at two forested sites in the southeastern United States. A variety of VOC compounds including methanol, 2-methyl-3-buten-2-ol, 6-methyl-5-hepten-2-one, isoprene and 15 monoterpenes were emitted from vegetation at these sites. Diurnal variations in VOC emissions were observed and related to light and temperature. Variations in isoprene emission from individual branches are well correlated with light intensity and leaf temperature while variations in monoterpene emissions can be explained by variations in leaf temperature alone. Isoprene emission rates for individual leaves tend to be about 75% higher than branch average emission rates due to shading on the lower leaves of a branch. Average daytime mixing ratios of 13.8 and 6.6 ppbv C isoprene and 5.0 and 4.5 ppbv C monoterpenes were observed at heights between 40 m and 1 km above ground level the two sites. Isoprene and monoterpenes account for 30% to 40% of the total carbon in the ambient non-methane VOC quantified in the mixed layer at these sites and over 90% of the VOC reactivity with OH. Ambient mixing ratios were used to estimate isoprene and monoterpene fluxes by applying box model and mixed-layer gradient techniques. Although the two techniques estimate fluxes averaged over different spatial scales, the average fluxes calculated by the two techniques agree within a factor of two. The ambient mixing ratios were used to evaluate a biogenic VOC emission model that uses field measurements of plant species composition, remotely sensed vegetation distributions, leaf level emission potentials determined from vegetation enclosures, and light and temperature dependent emission activity factors. Emissions estimated for a temperature of 30°C and above canopy photosynthetically active radiation flux of 1000 μmol m−2 s−1 are around 4 mg C m−2 h−1 of isoprene and 0.7 mg C m−2 h−1 of monoterpenes at the ROSE site in western Alabama and 3 mg C m−2 h−1 of isoprene and 0.5 mg C m−2 h−1 of monoterpenes at the SOS-M site in eastern Georgia. Isoprene and monoterpene emissions based on land characteristics data and emission enclosure measurements are within a factor of two of estimates based on ambient measurements in most cases. This represents reasonable agreement due to the large uncertainties associated with these models and because the observed differences are at least partially due to differences in the size and location of the source region (“flux footprint”) associated with each flux estimate.

Coffee, tea and diabetes: the role of weight loss and caffeine

OBJECTIVE:To assess the effect of weight change on the relationship between coffee and tea consumption and diabetes risk.DESIGN:Prospective cohort study, using data from the First National Health and Nutrition Examination Survey Epidemiologic Follow Up Study. Survival analyses were conducted using 301 selfreported cases of diabetes and eight documented diabetes deaths during an 8.4-y follow-up.SUBJECTS:A total of 7006 subjects aged 32–88 y with no reported history of diabetes were included in the study.RESULTS:For all subjects combined, increases in consumption of ground-caffeinated coffee and caffeine at baseline were followed by decreases in diabetes risk during follow-up. There were significant statistical interactions between age and consumption of caffeine (P=0.02) and ground-caffeinated coffee (P=0.03). Age-stratified analysis showed that the decrease in diabetes risk only applied to ≤60-y-old subjects, for whom the decrease in diabetes risk also obtained for ground-decaffeinated coffee and regular tea. The multivariate hazard ratio (HR) and 95% confidence interval for a 2 cups/day increment in the intake of ground-caffeinated coffee, ground-decaffeinated coffee and regular tea was 0.86 (0.75–0.99), 0.58 (0.34–0.99) and 0.77 (0.59–1.00), respectively. The diabetes risk was negatively related to the consumption in a dose–response manner. There were strong statistical interactions between prior weight change and beverage consumption for ≤60-y-old subjects. Further analysis revealed that the decrease in diabetes risk only applied to those who had lost weight, and that there was a positive dose–response relationship between diabetes risk and weight change. For example, the multivariate HR and 95% confidence interval for >0 vs 0 cups/day of ground-decaffeinated coffee was 0.17 (0.04–0.74), 0.52 (0.19–1.42), 0.77 (0.30–1.96) and 0.91 (0.39–2.14) for subgroups with weight change of ≤0, 0–10, 10–20 and >20 lbs, respectively. There was no significant association between diabetes risk and consumption of instant-caffeinated coffee, instant-decaffeinated coffee or herbal tea. Caffeine intake appeared to explain some, but not all, of the diabetes-risk reduction and weight change.CONCLUSION:The negative relationship between diabetes risk and consumption of ground coffee and regular tea, observed for all NHEFS subjects, actually only applied to nonelderly adults who had previously lost weight.

The Use of Bidirectional Barbed Suture in Laparoscopic Myomectomy and Total Laparoscopic Hysterectomy

Bidirectional barbed suture is a new design that incorporates tiny barbs spaced evenly along the length of the suture cut facing in opposite directions from the midpoint. Unlike the smooth-textured traditional suture, the bidirectional barbs on this new product introduce a new paradigm in which wound tension is evenly distributed across the length of the suture line rather than at the knotted end. No knots are required with bidirectional barbed suture. We present a small case series with bidirectional barbed suture to close myometrial defects in laparoscopic myomectomies and vaginal cuffs in total laparoscopic hysterectomies. On the basis of our early experience, we are optimistic that this new suture material is a potentially valuable tool for gynecologic surgeons.

Canopy fluxes of 2-methyl-3-buten-2-ol over a ponderosa pine forest by relaxed eddy accumulation: Field data and model comparison

Canopy level flux measurements of 2-methyl-3-buten-2-ol (MBO) were made over a 7 year old ponderosa pine plantation in the Sierra Nevada range of California using the relaxed eddy accumulation method. Fluxes peaked in late afternoon (1600 LT), at an average rate of 1.11 mg C m-2 h-1. This corresponds to the time of peak temperatures. MBO fluxes were strongly correlated with both temperature and photosynthetically active radiation (PAR). Model calculations of MBO flux from this site using a model developed for isoprene provide an accurate simulation of the diurnal emissions pattern but overestimate the measured flux by a factor of 2. Discrepancies between the measurements and the model predictions are likely due to the uncertainties in choosing model inputs. These results indicate a significant flux of reactive carbon in the western United States where MBO-emitting pines are the dominant forest vegetation. Copyright 1999 by the American Geophysical Union.

Experiment for Regional Sources and Sinks of Oxidants (EXPRESSO): An overview

This paper presents an overview of the Experiment for Regional Sources and Sinks of Oxidents (EXPRESSO) including the objectives of the project, a detailed description of the characteristics of the experimental region and of field instrumentation deployed, and a summary of the main results of all components of the experiment. EXPRESSO is an international, multidisciplinary effort to quantify and better understand the processes controlling surface fluxes of photochemical precursors emitted by vegetation and biomass burning along a tropical forest to savanna gradient in central Africa. The experiment was conducted at the beginning of the dry season in November-December 1996. Three main research tools were deployed during this period: (1) the French research aircraft (Avion de Recherche Atmospherique et de Teledetection, Fokker 27), instrumented for chemistry and flux measurements (CNRS- France), (2) two satellite receivers for in situ acquisition of National Oceanic and Atmospheric Administration-advanced very high resolution radiometer (NOAA-AVHRR) imagery for fire detection (EC-JRC, Ispra, Italy), and (3) a 65-m walkup tower installed at a tropical forest site in the Republic of Congo (National Center for Atmospheric Research, Boulder, Colorado). Average dynamic and turbulence characteristics over savanna and forest ecosystems were retrieved from aircraft measurements. They illustrate the complex atmospheric circulation occurring in this region in the vicinity of the Intertropical Convergence Zone. Satellite receivers were operated three times a day to produce maps of fire distribution. Statistics and mapping of burned surfaces from NOAA-AVHRR and ERS-Along Track Scanning Radiometer space systems have been developed. The influence of biogenic and biomass burning sources on the chemical composition of the lower atmosphere was studied through both aircraft and tower measurements. The EXPRESSO field campaign was followed by modeling efforts (regional and global scales) in which model components are evaluated using the experimental data.

Metabolic mass, metabolic rate, caloric restriction, and aging in male Fischer 344 rats

Previous investigators have found the metabolic rate to be the same in calorically-restricted and ad-libitum fed rodents, and hence concluded that the Rate of Living Theory does not help explain the longer lifespan of the calorically-restricted (CR) animal. However, these previous instigators may not have used reliable estimates of metabolic mass in their calculations of metabolic rate. Hence the present study investigated the reliability of ten different estimates of metabolic mass (MM) in 21-month-old male Fischer 344 rats fed three different diets to yield a wide range of body compositions. Two criteria were used to rank each estimate of metabolic mass: strong correlation with daily caloric intake (DCI); and zero Y-intercept on the regression curve of DCI versus the MM. The combined weight of the heart, liver, kidneys and brain (OW) was found to be the best estimate of MM. Statistical analysis of the differences in metabolic rate in the three groups of rats showed that the significance of these differences depended on the estimate of MM used. OW yielded different results than did fat-free mass (FFM), body weight (BW), BW(0.75), and BW(0.67). Therefore, because previous investigators used FFM, BW, BW(0.75), or BW(0.67), rather than a more reliable estimate such as OW, their finding that metabolic rate was not different in the CR and ad-lib groups, and their conclusion that the Rate of Living Theory does not help explain the longer lifespan of the CR animal, are called into question.

Volatile organic compounds and isoprene oxidation products at a temperate deciduous forest site

Biogenic volatile organic compounds (BVOCs) and their role in atmospheric oxidant formation were investigated at a forest site near Oak Ridge, Tennessee, as part of the Nashville Southern Oxidants Study (SOS) in July 1995. Of 98 VOCs detected, a major fraction were anthropogenic VOCs such as chlorofluorocarbons (CFCs), alkanes, alkenes and aromatic compounds. Isoprene was the dominant BVOC during daytime. Primary products from BVOC oxidation were methylvinylketone, methacrolein and 3-methylfuran. Other compounds studied include the BVOCs α-pinene, camphene, β-pinene, p-cymene, limonene and cis-3-hexenyl acetate and a series of light alkanes, aromatic hydrocarbons and seven of the CFCs. The correlation of meteorological parameters, with the mixing ratios of these different compounds, reveals information on atmospheric oxidation processes and transport. Long-lived VOCs show very steady mixing ratio time series. Regionally and anthropogenically emitted VOCs display distinct diurnal cycles with a strong mixing ratio decrease in the morning from the breakup of the nocturnal boundary layer. Nighttime mixing ratio increases of CFCs and anthropogenic VOCs are suspected to derive from emissions within the Knoxville urban area into the shallow nocturnal boundary layer. In contrast, the time series of BVOCs and their oxidation products are determined by a combination of emission control, atmospheric oxidation and deposition, and boundary layer dynamics. Mixing ratio time series data for monoterpenes and cis-3-hexenyl acetate suggest a temporarily emission rate increase during and after heavy rain events. The isoprene oxidation products demonstrate differences in the oxidation pathways during night and day and in their dry and wet deposition rates.

Vertical distribution of isoprene in the lower boundary layer of the rural and urban southern United States

An analysis is presented of vertical profiles of isoprene concentration and meteorological parameters measured in the boundary layer (BL) during the daylight hours at a rural site in Alabama and an urban site in Atlanta, Georgia, during the summer of 1990, as part of the Southern Oxidants Study. Of the 37 isoprene profiles recorded at the sites, 16 exhibited complex vertical structure with local maxima within the BL. This complex vertical structure appears to arise from a variety of turbulent processes fostered by horizontal inhomogeneities in the surface emissions of isoprene and by the transient appearance of layers of strong wind shear and/or vertical stability within the BL. A statistical analysis of the data suggests that the complex features observed in the individual profiles are stochastic in nature and tend to cancel out upon averaging over all profiles. Nevertheless, these complex structures can confound attempts to infer the BL abundance of a short-lived hydrocarbon like isoprene from a set of measurements at a single height. Our calculations suggest that measurements made at a height of 40–100 m above the surface will yield the most reliable measure of average BL concentrations of reactive hydrocarbons.