Study of the effects of particle-phase carbon on the gas/particle partitioning of semivolatile organic compounds in the atmosphere using controlled field experiments

A controlled field experiment (CFE) methodology with a filter/sorbent sampler was used to minimize artifact effects when measuring values of the gas/particle (G/P) partitioning constant (Kp, m3 microg(-1)) for semivolatile organic compounds (SOCs) in the atmosphere. CFE sampling was conducted at three different locations (Beaverton, OR; Denver, CO; and Hills, IA). Kp values were measured for a series of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs). To examine the possible effects on the G/P partitioning of the amounts of organic material (om) phase, organic carbon (OC), and elemental carbon (EC) in the sampled particulate material, the measured Kp values were normalized by the aerosol mass fractions f(om), f(OC), and f(EC) according to Kp/ f(om), Kp/f(OC), and Kp/f(EC). Using a log-log format, the resulting normalized values were all found to be more highly correlated with the subcooled liquid vapor pressure p(L)o than were the unnormalized Kp values. For the PAHs,the one-parameter model assuming Kp = Kp,OC f(OC) yielded only slightly less variability in the predicted Kp values than did the one-parameter model Kp = Kp,EC f(EC). The two-parameter model Kp = Kp,OC f(OC) + Kp,EC f(EC) was found to provide only small improvements over each of the one-parameter models. Overall, the data are more consistent with an absorptive mechanism of partitioning to the particulate material but do not rule out some role for adsorption to particle surfaces. The data suggest that small amounts of organic carbon (f(OC) approximately 0.02) can have significant effects on the G/P partitioning of SOCs.     

Heritability of changes in genetic evaluations of dairy bulls from first to later records of daughters

Objectives of this study were to investigate changes in predicted transmitting abilities (PTA) of yields from evaluations based on first records to evaluations based on first and later records of daughters and determine whether these changes are heritable. Data were USDA sire evaluations of July 1989 through May 2000 on Holstein bulls in standard progeny testing programs. Changes in PTA for milk, fat, and protein from evaluations based on first records of daughters to evaluations on first and second were obtained on 2001 bulls. These were divided into two sets: subset 1 (n = 889) included bulls first evaluated before 1995 and subset 2 (n = 1112) included bulls first evaluated in 1995 and later. Changes in PTA from first-record evaluation to most recent evaluation (May 2000) were obtained on 2524 bulls first evaluated in 1995 or later. Mean changes in PTA for bulls first evaluated in 1995 and later were smaller than mean changes for bulls evaluated earlier but standard deviations were similar. Regressions of changes in PTA on changes in parent average showed that a change of 1.0 kg in parent average resulted in 1.1 to 1.2 kg change in PTA. Heritabilities estimated with animal model ranged from 0.14 to 0.23 for changes from first-record evaluation to evaluation on first and second, and 0.27 to 0.35 for changes from first-record evaluation to most recent evaluation. Heritabilities of this magnitude allow for identifying bulls that decrease in PTA.     

Finite element analysis of underwater capacitor micromachined ultrasonic transducers

A simple electromechanical equivalent circuit model is used to predict the behavior of capacitive micromachined ultrasonic transducers (cMUT). The equivalent circuit model of the cMUT lacks important features such as coupling to the substrate and the ability to predict crosstalk between elements of an array of transducers. To overcome these deficiencies, a finite element model of the cMUT is constructed using the commercial code ANSYS(R). Calculation results of the complex load impedance seen by single capacitor cells are presented, then followed by a calculation of the plane wave real load impedance seen by a parallel combination of many cells that are used to make a transducer. Crosstalk between 1-D array elements is found to be due to two main sources: coupling through a Stoneley wave propagating at the transducer-water interface and coupling through Lamb waves propagating in the substrate. To reduce the crosstalk level, the effect of structural variations of the substrate are investigated, which includes a change of its thickness and etched trenches or polymer walls between array elements     

Capacitive micromachined ultrasonic transducers: next-generation arrays for acoustic imaging?

Piezoelectric materials have dominated the ultrasonic transducer technology. Recently, capacitive micromachined ultrasonic transducers (CMUTs) have emerged as an alternative technology offering advantages such as wide bandwidth, ease of fabricating large arrays, and potential for integration with electronics. The aim of this paper is to demonstrate the viability of CMUTs for ultrasound imaging. We present the first pulse-echo phased array B-scan sector images using a 128-element, one-dimensional (1-D) linear CMUT array. We fabricated 64- and 128-element 1-D CMUT arrays with 100% yield and uniform element response across the arrays. These arrays have been operated in immersion with no failure or degradation in performance over the time. For imaging experiments, we built a resolution test phantom roughly mimicking the attenuation properties of soft tissue. We used a PC-based experimental system, including custom-designed electronic circuits to acquire the complete set of 128 x 128 RF A-scans from all transmit-receive element combinations. We obtained the pulse-echo frequency response by analyzing the echo signals from wire targets. These echo signals presented an 80% fractional bandwidth around 3 MHz, including the effect of attenuation in the propagating medium. We reconstructed the B-scan images with a sector angle of 90 degrees and an image depth of 210 mm through offline processing by using RF beamforming and synthetic phased array approaches. The measured 6-dB lateral and axial resolutions at 135 mm depth were 0.0144 radians and 0.3 mm, respectively. The electronic noise floor of the image was more than 50 dB below the maximum mainlobe magnitude. We also performed preliminary investigations on the effects of crosstalk among array elements on the image quality. In the near field, some artifacts were observable extending out from the array to a depth of 2 cm. A tail also was observed in the point spread function (PSF) in the axial direction, indicating the existence of crosstalk. The relative amplitude of this tail with respect to the mainlobe was less than -20 dB.     

ProFound: an expert system for protein identification using mass spectrometric peptide mapping information

We describe the protein search engine "ProFound", which employs a Bayesian algorithm to identify proteins from protein databases using mass spectrometric peptide mapping data. The algorithm ranks protein candidates by taking into account individual properties of each protein in the database as well as other information relevant to the peptide mapping experiment. The program consistently identifies the correct protein(s) even when the data quality is relatively low or when the sample consists of a simple mixture of proteins. Illustrative examples of protein identifications are provided.     

Effects of dietary inclusion of chromium propionate and calcium propionate on glucose disposal and gastrointestinal development in dairy calves

In experiment 1, 21 male Holstein calves (43.9 kg) were fed only milk replacer at 1.4% of their body weight as dry matter for 6 wk. Dietary treatments included a commercial milk replacer (22% protein, 15% fat) containing (dry basis) either 6.4% Ca propionate or 6.4% dextrose (control) and either 0 or 0.5 mg/kg of supplemental Cr as Cr propionate. Neither Cr nor Ca propionate affected body weight gain; however, Ca propionate tended to increase the growth of the entire foregut measured after slaughter at 6 wk of age. A Minimal Model glucose tolerance test indicated that insulin sensitivity was not affected by treatment. However, calves fed Cr had higher glucose disappearance indexes than controls when propionate was not fed (0.013 vs. 0.019 units) but similar clearance when propionate was included (0.018 vs. 0.018 units, Cr x P interaction). The area under the glucose response curves after propionate-loading tests was much greater for calves fed the Cr versus control replacer when propionate was not present; however, when propionate was included, the response was less dramatic. In experiment 2, 25 Holstein calves were used to study performance and metabolic responses when milk replacer, and then postweaning starter, were supplemented with 0.5 mg/kg of Cr as Cr propionate. The metabolic responses of these calves were not affected by treatment. Overall, combined data suggested that supplemental Cr may improve glucose effectiveness; however, these responses seemed to be attenuated by supplemental propionate.     

Use of artificial neural networks to predict the gas chromatographic retention index data of alkylbenzenes on carbowax-20M

Quantitative structure-activity relationships (QSARs) quantify the connection between the structure and properties of molecules and allow the prediction of properties from structural parameters. Models of relationships between structure and retention index of alkylbenzenes were constructed by means of a multilayer neural network using extended delta-bar-delta (EDBD) algorithms. The 165 group data belong to 129 alkylbenzenes at different temperatures on carbowax-20M. We proposed a new method to describe the structure of the alkylbenzene with a simple set of six numeric code depending on its molecular formula. A set of six numbers and the temperature were used as input parameters to predict the retention indices. The performance of different order of structural coding was investigated. The networks' architecture and the learning times were optimized. The optimum ANNs could give excellent prediction results. In addition, the multiple linear regression (MLR) and nonlinear multivariate regression were applied. We have shown in our studies that, based on the structural numeric codes, ANNs give more accurate predictions of retention index data of alkykbenzenes than regression analysis.     

Simulation and experimental characterization of a 2-D capacitive micromachined ultrasonic transducer array element

In this letter, a 400-mumx400-mum 2-D capacitive micromachined ultrasonic transducer (cMUT) array element is experimentally characterised, and the results are found to be in good agreement with theoretical predictions. As a receiver, the transducer has a 1.8x10(-7) nm/ radical(Hz) displacement sensitivity, and, as a transmitter, it produces 16.4 kPa/V of output pressure at the transducer surface at 3 MHz. The transducer also has more than 100% fractional bandwidth around 3 MHz, which makes it suitable for ultrasound imaging.     

Measurements of the atmospheric carbon monoxide column with a ground-based length-modulated radiometer

A ground-based remote sounding instrument that uses a length-modulated radiometer to measure the total atmospheric carbon monoxide (CO) column has been built. Measurements made in Toronto during August and September of 1994 showed average CO concentrations of 125 to 150 parts per billion in volume (ppbv, parts in 10(9)). Similar measurements made in October at a rural site 80 km north of Toronto showed concentrations of approximately 100 ppbv. The latter measurements are shown to agree with other simultaneous ground- and satellite-based measurements. This instrument is an advanced prototype of the MOPITT (Measurements of Pollution in the Troposphere) satellite instrument.     

Design and operation of a very large ring laser gyroscope

The design and initial operation of a vertical square He-Ne ring laser G0 with a perimeter of 14 m is discussed. This builds on earlier demonstrations of the feasibility of large ring lasers (perimeter approximately 4 m) for single-mode gyroscope operation and with lesser pulling than navigation gyroscopes. With servoing of the rf excitation to yield single-mode operation, G0 gave a quality factor 1 x 10(12) and a Sagnac line with a frequency of 287.8 +/- 1.0 Hz induced by Earth rotation Omega(E). This has confirmed some vital questions over the feasibility of very large gyroscopes for geodetic measurements at the level of 10(-9) Omega(E).