Video-enhanced microscopy with a computer frame memory

Video-enhanced microscopy combined with the use of a computer frame memory extends considerably the useful range of our video enhanced contrast (AVEC) methods for polarizing, double-beam interference and differential interference contrast microscopy. Increased visual contrast is achieved by two stages of amplifications: the first optical, by using high bias retardation settings, and the second electronic. These steps are followed by a reduction of background brightness by means of a clamp voltage applied to a DC restoration circuit of the video camera. One of the limitations of the AVEC method alone is the inevitable appearance under high gain conditions of a pattern of mottle due to inaccessible dirt and defects in the lenses even of high quality. This limitation has been circumvented by storing the mottle pattern in the frame memory (frame store) and continuously subtracting it from each succeeding frame to clear the image. A major gain in image quality has resulted. In polarizing microscopy, the frame memory can be used also to subtract the image at one compensator setting from that at the equivalent setting of opposite sign, thus removing from the final image not only most of the mottle pattern but also the contrast due to the bright-field contrast. In the polarizing microscope, these manipulations of the raw video image make it possible to observe and measure the birefringence of various organelles and elements such as microtubules, intermediate filaments and bundles of as few as a half dozen actin filaments. Since scattered light is also removed from the image, features hidden from view in the unprocessed image become visible. In differential interference microscopy, the AVEC method makes visible (i.e. detectable) many linear elements and particles that are an order of magnitude smaller than the resolution limit and not visible in the optical image. Such features are inflated by diffraction, however, to Airy disk size.     

Dietary unsaturated fatty acids increase plasma glucagon-like peptide-1 and cholecystokinin and may decrease premeal ghrelin in lactating dairy cows

Previous reports have indicated that dietary unsaturated fat can decrease energy intake of lactating dairy cattle. However, the mechanism for this response is unclear. To evaluate the potential role of gut peptides, periprandial concentrations of cholecystokinin (CCK), glucagon-like peptide 1 (GLP-1), and ghrelin were measured. From a replicated 4 × 4 Latin square experiment, 4 cows from a single square were selected for analysis of responses to 3 treatments: a control diet (5.5% total fatty acids, 65% unsaturated), a diet with added saturated fat (SAT, 8.3% fatty acids, 47% unsaturated), and a diet with added unsaturated fat (UNS, 7.8% fatty acids, 63% unsaturated). The SAT treatment increased duodenal flow of saturated fatty acids compared with UNS and control and, despite the fact that ruminal biohydrogenation altered fatty acid profiles of digesta, UNS increased duodenal flow of unsaturated fatty acids compared with SAT and control. Blood samples were collected at 8-min intervals through the first 2 meals of the day and analyzed by commercial radioimmunoassays. The UNS treatment increased plasma CCK concentration relative to SAT and control, and increased plasma GLP-1 concentration compared with control. Furthermore, fat treatments tended to suppress the prandial ghrelin surge that was evident for control. Suppression of feed intake by unsaturated fats is likely mediated in part by increased secretion of CCK and GLP-1, and dietary fat may also inhibit ghrelin release before conditioned meals.     

Alternate and new brominated flame retardants detected in U.S. house dust

Due to the voluntary withdrawals and/or bans on the use of two polybrominated diphenyl ether (PBDE) commercial mixtures, an increasing number of alternate flame retardant chemicals are being introduced in commercial applications. To determine if these alternate BFRs are present in indoor environments, we analyzed dust samples collected from 19 homes in the greater Boston, MA area during 2006. Using pure and commercial standards we quantified the following brominated flame retardant chemicals using GC/ECNI-MS methods: hexabromocyclododecane (sigma HBCD), bis(2,4,6,-tribromphenoxy)ethane (BTBPE), decabromodiphenyl ethane (DBDPE), and the brominated components found in Firemaster 550 (FM 550): 2-ethylhexyl 2,3,4,5-tetrabromobenzoate (TBB) and (2-ethylhexyl)tetrabromophthalate (TBPH), the latter compound being a brominated analogue of di(2-ethylhexyl)phthalate (DEHP). The concentrations of all compounds were log-normally distributed and the largest range in concentrations was observed for HBCD (sum of all isomers), with concentrations ranging from <4.5 ng/g to a maximum of 130,200 ng/g with a median value of 230 ng/g. BTBPE ranged from 1.6 to 789 ng/g with a median value of 30 ng/g and DBDPE ranged from <10.0 to 11,070 ng/g with a median value of 201 ng/g. Of the FM 550 components, TBB ranged from <6.6 to 15,030 ng/g with a median value of 133 ng/g; whereas TBPH ranged from 1.5 to 10,630 ng/g with a median value of 142 ng/g. Furthermore, the ratio of TBB/TBPH present in the dust samples ranged from 0.05 to 50 (average 4.4), varying considerably from the ratio observed in the FM 550 commercial mixture (4:1 by mass), suggesting different sources with different chemical compositions, and/or differential fate and transport within the home. Analysis of paired dust samples collected from different rooms in the same home suggests HBCD, TBB, and TBPH are higher in dust from the main living area compared to dust collected in bedrooms; however, BTBPE and DBDPE levels were comparable between rooms. This study highlights the fact that numerous types of brominated flame retardants are present in indoor environments, raising questions about exposure to mixtures of these contaminants.     

Atmospheric emission of reactive nitrogen during biofuel ethanol production

This paper evaluates emissions to the atmosphere of biologically available nitrogen compounds in a region characterized by intensive sugar cane biofuel ethanol production. Large emissions of NH3 and NOx, as well as particulate nitrate and ammonium, occur at the harvest when the crop is burned, with the amount of nitrogen released equivalent to approximately 35% of annual fertilizer-N application. Nitrogen oxides concentrations show a positive association with fire frequency, indicating that biomass burning is a major emission source, with mean concentrations of NOx doubling in the dry season relative to the wetseason. During the dry season biomass burning is a source of NH3, with other sources (wastes, soil, biogenic) predominant during the wet season. Estimated NO2-N, NH3-N, NO3- -N and NH4+ -N emission fluxes from sugar cane burning in a planted area of ca. 2.2 x 10(6) ha are 11.0, 1.1, 0.2, and 1.2 Gg N yr(-1), respectively.     

Effects of dilution on fine particle mass and partitioning of semivolatile organics in diesel exhaust and wood smoke

Experiments were conducted to examine the effects of dilution on fine particle mass emissions from a diesel engine and wood stove. Filter measurements were made simultaneously using three dilution sampling systems operating at dilution ratios ranging from 20:1 to 510:1. Denuders and backup filters were used to quantify organic sampling artifacts. For the diesel engine operating at low load and wood combustion, large decreases in fine particle mass emissions were observed with increases in dilution. For example, the PM2.5 mass emission rate from a diesel engine operating at low load decreased by 50% when the dilution ratio was increased from 20:1 to 350:1. Measurements of organic and elemental carbon indicate that the changes in fine particle mass with dilution are caused by changes in partitioning of semivolatile organic compounds. At low levels of dilution semivolatile species largely occur in the particle phase, but increasing dilution reduces the concentration of semivolatile species, shifting this material to the gas phase in order to maintain phase equilibrium. Emissions of elemental carbon do not vary with dilution. Organic sampling artifacts are shown to vary with dilution because of the combination of changes in partitioning coupled with adsorption of gas-phase organics by quartz filters. The fine particle mass emissions from the diesel engine operating at medium load did not vary with dilution because of the lower emissions of semivolatile material and higher emissions of elemental carbon. To measure partitioning of semivolatile materials under atmospheric conditions, partitioning theory indicates that dilution samplers need to be operated such that the diluted exhaust achieves atmospheric levels of dilution. Too little dilution can potentially overestimate the fine particle mass emissions, and too much dilution (with clean air) can underestimate them.     

A terrestrial biotic ligand model. 1. Development and application to Cu and Ni toxicities to barley root elongation in soils

A Terrestrial Biotic Ligand Model (TBLM) was developed using noncalcareous soils from Europe based on Cu and Ni speciation and barley (Hordeum vulgare cv. Regina) root elongation bioassays. Free metal ion (M2+) activity was computed by the WHAM VI model using inputs of soil metal, soil organic matter, and alkali and alkaline earth metals concentrations, and pH in soil solution. The TBLM assumes that metal in soil and in the solution are in equilibrium. Metal ions react with the biotic ligand, the receptor site, and inhibit root elongation. Other ions, principally H+, Ca2+ and Mg2+, compete with M2+ and, therefore, affect its toxicity. Toxicity is correlated only to the fraction of the total biotic ligand sites occupied by M2+. Compared to other models using either the soil metal concentration or M2+ activity as the toxic dose, the TBLM provides a more consistent method to normalize and compare Cu and Ni toxicities to root elongation among different soils. The TBLM was able to predictthe EC50 soil Cu and Ni concentrations generally within a factor of 2 of the observed values, a level of precision similar to that for the aquatic Biotic Ligand Model, indicating its potential utility in metals risk assessment in soils.     

Contribution of first- versus second-generation products to secondary organic aerosols formed in the oxidation of biogenic hydrocarbons

Biogenic hydrocarbons emitted by vegetation are important contributors to secondary organic aerosol (SOA), but the aerosol formation mechanisms are incompletely understood. In this study, the formation of aerosols and gas-phase products from the ozonolysis and photooxidation of a series of biogenic hydrocarbons (isoprene, 8 monoterpenes, 4 sesquiterpenes, and 3 oxygenated terpenes) are examined. By comparing aerosol growth (measured by Differential Mobility Analyzers, DMAs) and gas-phase concentrations (monitored by a Proton Transfer Reaction Mass Spectrometer, PTR-MS), we study the general mechanisms of SOA formation. Aerosol growth data are presented in terms of a "growth curve", a plot of aerosol mass formed versus the amount of hydrocarbon reacted. From the shapes of the growth curves, it is found that all the hydrocarbons studied can be classified into two groups based entirely on the number of double bonds of the hydrocarbon, regardless of the reaction systems (ozonolysis or photooxidation) and the types of hydrocarbons studied: compounds with only one double bond and compounds with more than one double bond. For compounds with only one double bond, the first oxidation step is rate-limiting, and aerosols are formed mainly from low volatility first-generation oxidation products; whereas for compounds with more than one double bond, the second oxidation step may also be rate-limiting and second-generation products contribute substantially to SOA growth. This behavior is characterized by a vertical section in the growth curve, in which continued aerosol growth is observed even after all the parent hydrocarbon is consumed.     

Rheological characterization and electrokinetic phenomena of charged whey protein dispersions of defined sizes

A multi-step processing technique produced large colloidal particles from whey proteins, prompting instantaneous thickening upon hydration. Analysis of the rheological characteristics and zeta potential of the modified whey suspensions of defined particle sizes allowed investigation into the role of size on ingredient functionality. Preliminarily, the modified protein powders were sieved to achieve three size ranges, and analyzes were conducted on each of the three distributions and the non-sieved fractions. Following hydration, steady and oscillatory shear analyzes were performed using a controlled stress rheometer to determine rheological characteristics. Intrinsic viscosity was determined with a capillary viscometer and application of the Huggins equation. Zeta potential was calculated from colloidal electrophoretic mobility, measured with a ZetaPALS analyser. After thorough hydration, particle-size analysis revealed a size increase of >1.3 times for each fraction. When analysed on a protein basis, increasing particle size yielded an increase to intrinsic viscosity, flow behavior index, zero shear viscosity, and a decreased zeta potential and consistency coefficient. Knowledge of the interrelationship between zeta potential, rheological properties, and particle size of the modified whey ingredient will further advance an understanding of the functionality of this protein ingredient.     

Pelleted beet pulp substituted for high-moisture corn: 3. Effects on ruminal fermentation, pH, and microbial protein efficiency in lactating dairy cows

The effects of increasing concentrations of dried, pelleted beet pulp substituted for high-moisture corn on ruminal fermentation, pH, and microbial efficiency were evaluated using eight ruminally and duodenally cannulated multiparous Holstein cows in a duplicated 4 x 4 Latin square design with 21-d periods. Cows were 79 +/- 17 (mean +/- SD) DIM at the beginning of the experiment. Experimental diets with 40% forage (corn silage and alfalfa silage) and 60% concentrate contained 0, 6.1, 12.1, or 24.3% beet pulp substituted for high-moisture corn on a DM basis. Diet concentrations of NDF and starch were 24.3 and 34.6% (0% beet pulp), 26.2 and 30.5% (6% beet pulp), 28.0, and 26.5% (12% beet pulp), and 31.6 and 18.4% (24% beet pulp), respectively. Substituting beet pulp for corn did not affect daily mean or minimum ruminal pH but tended to reduce pH range. Ruminal acetate:propionate responded in a positive exponential relationship to added beet pulp. Rate of valerate absorption from the rumen was not affected by treatment. Substituting beet pulp for corn up to 24% of diet DM did not affect efficiency of ruminal microbial protein production, expressed as microbial N flow to the duodenum as a percentage of OM truly digested in the rumen. Microbial efficiency was not correlated to mean pH or daily minimum pH. While microbial efficiency was not directly related to concentration of beet pulp fed, it was positively correlated with passage rate of particulate matter, as represented by starch and indigestible NDF, probably due to reduced turnover of microbial protein in the rumen.     

Separation of fine particulate matter emitted from gasoline and diesel vehicles using chemical mass balancing techniques

Samples of fine particulate matter were collected in a roadway tunnel near Houston, TX over a period of 4 days during two separate sampling periods: one sampling period from 1200 to 1400 local time and another sampling period from 1600 to 1800 local time. During the two sampling periods, the tunnel traffic contained roughly equivalent numbers of heavy-duty diesel trucks. However, during the late afternoon sampling period, the tunnel contained twice as many light-duty gasoline-powered vehicles. The effect of this shift in the vehicle fleet affects the overall emission index (grams pollutant emitted per kilogram carbon in fuel) for fine particles and fine particulate elemental carbon. Additionally, this shift in the fraction of diesel vehicles in the tunnel is used to determine if the chemical mass balancing techniques used to track emissions from gasoline-powered and diesel-powered emissions accurately separates these two emission categories. The results show that the chemical mass balancing calculations apportion roughly equal amounts of the particulate matter measured to diesel vehicles between the two periods and attribute almost twice as much particulate matter in the late afternoon sampling period to gasoline vehicles. Both of these results are consistent with the traffic volume of gasoline and diesel vehicles in the tunnel in the two separate periods and validate the ability for chemical mass balancing techniques to separate these two primary sources of fine particles.