In-field Studies Research Articles

Positive matrix factorization of organic aerosol: insights from a chemical transport model

Abstract. Factor analysis of aerosol mass spectrometer measurements (organic aerosol mass spectra) is often used to determine the sources of organic aerosol (OA). In this study we aim to gain insights regarding the ability of positive matrix factorization (PMF) to identify and quantify the OA sources accurately. We performed PMF and multilinear engine (ME-2) analysis on the predictions of a state-of-the-art chemical transport model (PMCAMx-SR, Particulate Matter Comprehensive Air Quality Model with extensions – source resolved) during a photochemically active period for specific sites in Europe in an effort to interpret the diverse factors usually identified by PMF analysis of field measurements. Our analysis used the predicted concentrations of 27 OA components, assuming that each of them is “chemically different” from the others. The PMF results based on the chemical transport model predictions are quite consistent (same number of factors and source types) with those of the analysis of AMS measurements. The estimated uncertainty of the contribution of fresh biomass burning is less than 30 % and of the other primary sources less than 40 %, when these sources contribute more than 20 % to the total OA. The PMF uncertainty increases for smaller source contributions, reaching a factor of 2 or even 3 for sources which contribute less than 10 % to the OA. One of the major questions in PMF analysis of AMS measurements concerns the sources of the two or more oxygenated OA (OOA) factors often reported in field studies. Our analysis suggests that these factors include secondary OA compounds from a variety of anthropogenic and biogenic sources and do not correspond to specific sources. Their characterization in the literature as low- and high-volatility factors is probably misleading, because they have overlapping volatility distributions. However, the average volatility of the one often characterized as a low-volatility factor is indeed lower than that of the other (high-volatility factor). Based on the analysis of the PMCAMx-SR predictions, the first oxygenated OA factor includes mainly highly aged OA transported from outside Europe, but also highly aged secondary OA from precursors emitted in Europe. The second oxygenated OA factor contains fresher secondary organic aerosol from volatile, semivolatile, and intermediate volatility anthropogenic and biogenic organic compounds. The exact contribution of these OA components to each OA factor depends on the site and the prevailing meteorology during the analysis period.

The Role of the Midfoot in Drop Landings.

The midfoot is instrumental to foot function; however, quantifying its roles in human movement has been difficult. A forceful dynamic activity like landing may help elucidate the midfoot's contribution to foot energetics and function. The main purpose of this study was to measure midtarsal joint kinematics and kinetics during a barefoot single-leg landing task. A secondary aim of this study was to explore the relationship between static foot posture and dynamic midfoot function. In a cross-sectional study design, 48 females (age = 20.4 ± 1.8 yr, body mass index = 21.6 ± 1.7 kg·m) performed drop landings from a height of 0.4 m onto split force platforms. Subjects hung from wooden rings and landed on their dominant leg. Midtarsal joint kinematic and kinetic data were recorded using a 14-camera optical motion capture system in conjunction with two in-ground force platforms and a custom kinetic three-segment foot model. Foot structure was measuring using the arch height index (AHI) and the static midtarsal joint angle from motion capture. Kinematic data revealed an average sagittal plane midtarsal joint range of motion of 27° through the landing phase. Kinetic data showed that between 7% and 22% of the total lower extremity joint, work during the landing was performed by the midtarsal joint. Both standing AHI and static midtarsal joint angle (static MA) were correlated with sagittal plane midtarsal joint range of motion (standing AHI: r = -0.320, P = 0.026; static MA: r = 0.483, P < 0.001) and with midtarsal joint work (standing AHI: r = 0.332, P = 0.021; static MA: r = -0.323, P = 0.025). The midfoot contributes substantially to landing mechanics during a barefoot single-leg landing task. Static foot posture measures have limited value in predicting midfoot kinematics and kinetics during sportlike landings.

Creating Multi-Temporal Composites of Airborne Imaging Spectroscopy Data in Support of Digital Soil Mapping

An increasing demand for full spatio-temporal coverage of soil information drives the growing use of soil spectroscopy. Soil spectroscopy application performed under laboratory conditions or in-field studies in semi-arid areas have shown promising results. However, when acquiring data in temperate zones, limitations by vegetation-free coverage, variation in soil moisture and management are driving coherent spatio-temporal data collection. This study explores the use of multi-temporal imaging spectroscopy data to increase the total mapping area of bare soils in a heterogeneous agricultural landscape. Spectrally and spatially high-resolution data from the Airborne Prism Experiment (APEX) were collected in September 2013, April 2014 and April 2015. Bare soils in all acquisitions were identified. To eliminate short-term differences in soil moisture and soil surface roughness, the empirical line method was used to calibrate the reflectance values of the singular images (2013 and 2015) towards the singular image with most bare soil pixels (2014). Difference indicators show that the calibration was successful (decrease in root mean square difference and angle difference, increase in R2 and gain and offset close to one and zero). Finally, the multi-temporal composite image contained more than double the amount of bare soil pixels as compared to a singular acquisition. Summary statistics show that reflectance values of the multi-temporal composite approximate the single image data of 2014 (mean and standard deviation of 2014: 24.2 ± 8.9 vs. 24.0 ± 9.5 for the multi-temporal composite of 2013, 2014 and 2015). This indicates that global differences in soil moisture and land management have been corrected for. As a result, an improved spatial representation of soil parameters can be retrieved from the composite data. Spatial distribution of the correction factors and analysis of the spatial variability of all images, however, indicate that non-linear, short-term differences like variation in soil moisture and land management largely influence the result of the multi-temporal composite. Quantification and attribution of those factors will be required in the future to allow correcting for them.

Mining waste dumps – modern monitoring of thermal and gas activities

Abstract Mining waste dumps are permanently incorporated in the landscape of the mining areas and exert an impact on the environment in many ways. The presence in the massif of a dump of carbonaceous substances often leads to the formation of fire hazards. Monitoring the activity of a newly created coal waste dump or of one under fire plays an extremely important role in fire prevention activity. Under the current regulations it must be carried out both during the exploitation process and for many years afterwards. Monitoring a dump is targeted, among others, at detecting thermal and gas anomalies already at the initial stage of development and to undertake preventive measures to eliminate and minimize the impact and load of a dump for the environment and the health and life of humans. In the article selected results of a research project (Raport 2011) are shown; a method of monitoring fire hazards at dump wastes was proposed, which includes thermal scanning and thermal-gas monitoring by a borehole method aimed at fixed points in the dump. Monitoring the large area of a dump requires exploration of the thermal state of a significant area hence the accepted scanning of the area is with a precision thermal imaging camera during an air raid. Then at selected sites of the dump, long-term in-field studies were conducted using the wireless data collection system from scattered test holes, made of perforated pipes and equipped with temperature and gas probes (CO, CO2, O2). At the same time the changes of environmental conditions and changes in atmospheric state parameters were observed around the dump, the so-called wind rose, based on data recorded by the weather station.

Wild deer as potential vectors of anthelmintic-resistant abomasal nematodes between cattle and sheep farms

Gastrointestinal (GI) nematodes are among the most important causes of production loss in farmed ruminants, and anthelmintic resistance is emerging globally. We hypothesized that wild deer could potentially act as reservoirs of anthelmintic-resistant GI nematodes between livestock farms. Adult abomasal nematodes and faecal samples were collected from fallow (n = 24), red (n = 14) and roe deer (n = 10) from venison farms and areas of extensive or intensive livestock farming. Principal components analysis of abomasal nematode species composition revealed differences between wild roe deer grazing in the areas of intensive livestock farming, and fallow and red deer in all environments. Alleles for benzimidazole (BZ) resistance were identified in β-tubulin of Haemonchus contortus of roe deer and phenotypic resistance confirmed in vitro by an egg hatch test (EC50 = 0.149 µg ml−1 ± 0.13 µg ml−1) on H. contortus eggs from experimentally infected sheep. This BZ-resistant H. contortus isolate also infected a calf experimentally. We present the first account of in vitro BZ resistance in wild roe deer, but further experiments should firmly establish the presence of phenotypic BZ resistance in vivo. Comprehensive in-field studies should assess whether nematode cross-transmission between deer and livestock occurs and contributes, in any way, to the development of resistance on livestock farms.

Improving User Experience for Passenger Information Systems. Prototypes and Reference Objects

Research problem: This study explores how established patterns, means, and services influence the users' first experience when encountering a novel self-service application. The application (DB Cairo) is a passenger information system for public transportation running on mobile phones. Research questions: Is the users' first experience with the application influenced by established communicative patterns, means, and services? Are they used as reference objects? Which attributes of the application are relevant? Is there a leading reference object (prototype)? Do reference objects vary depending on the personal factors age and gender? Literature review: Little is known about user experience in first contact situations regarding passenger information systems. For our investigations, we used a theoretical framework combining Linguistic Evaluation Theory, Prototype Theory, and Linguistic Genre Theory: Evaluations are regarded as an integral part of user experience. Evaluation is conceptualized as an act where a subject evaluates an object with a certain purpose at a certain time by comparing it with other objects. Every object has various attributes-some are relevant for the evaluation, and others are not. Communication quality is seen as a crucial complex attribute for the evaluation of communicative applications. Methodology: We conducted a qualitative study: Data from two user test series (n = 12)with thinking-aloud protocols and retrospective interviews were analyzed with qualitative content analysis procedures. The participants were male and female, age 25-35 or 55-65, mobile-phone users, and multimodal travellers. The tests were conducted in a laboratory with a computer-based mobile-phone emulator. Results and conclusions: Results show that the participants explore the application by comparing its attributes with attributes of reference objects. Reference objects vary depending on attributes of the application. Regarding topic-related attributes, participants rely on established artifacts, which form a topic-related multimedia network. Within this network, the website of German Railways functions as prototype. Age- and gender-specific differences were not detected. The findings indicate that research into user experience and development practice could benefit from reconstructing and analyzing topic-related artifacts. Limitations of the study were a small sample size, the test location, and environment. Future challenges are the investigation of influencing factors and the development of new methods/tools for data collection infield studies.

Halophyte crop cultivation: The case for Salicornia and Sarcocornia

Increasing soil salinization and the growing scarcity of fresh water dictate the need for a creative solution to attain sustainable crop production. To accomplish this aim, the domestication of inherently salt tolerant plant species with economic value is proposed as a straightforward methodology. Most studies investigating salt tolerance mechanisms are linked to small, experimental systems that cannot be generalized to the real agricultural context. The crops Salicornia and Sarcocornia, however, with their extreme salt tolerance and long history of consumption by humans, make the ideal model plants on which to base a halophyte growth strategy. New applied technologies were developed for leafy vegetable production using small-scale greenhouse and in-field studies. Several cultivation systems adapted to the irrigation water salinity and the available soil conditions are described. Daylength manipulation and a repetitive harvest regime partially elucidated the flowering patterns of Salicornia and Sarcocornia and showed that flowering should be prevented for maximal vegetable production. Additionally, the beneficial effect of saline irrigation on quality parameters via the enhancement of stress-induced secondary metabolites with antioxidant capacity should be considered during cultivation. This review summarizes the recent developments in growing halophytes for food production with saline irrigation, using Salicornia and Sarcocornia as a case study.

Soil respiration rate and its sensitivity to temperature in pasture systems of dry-tropics

Tree clearing is a topical issue the world over. In Queensland, the high rates of clearing in the past were mainly to increase pasture production. The present research evaluates the impact of clearing on some soil biological properties, i.e. total soil respiration, root respiration, microbial respiration, and microbial biomass (C and N), and the response of soil respiration to change in temperature. In-field and laboratory (polyhouse) experiments were undertaken. For in-field studies, paired cleared and uncleared pasture plots were selected to represent three major tree communities of the region, i.e. Eucalyptus populnea, E. melanophloia, and Acacia harpophylla. The cleared sites were chosen to represent three different time-since-clearing durations (5, 11–13, and 33 years; n=18 for cleared and uncleared plots) to determine the temporal impact of clearing on soil biological properties. Experiments were conducted in the polyhouse to study in detail the response of soil respiration to changes in soil temperature and soil moisture, and to complement in-field studies for estimating root respiration. The average rate of CO2 emission was 964 g CO2/m2/yr, with no significant difference (P<0.05) among cleared and uncleared sites. Microbial respiration and microbial biomass were greater at uncleared compared with those at cleared sites. The Q 10-value of 1.42 (measured for different seasons in a year) for in-field measurements suggested a small response of soil respiration to soil temperature, possibly due to the limited availability of soil moisture and/or organic matter. However, results from the polyhouse experiment suggested greater sensitivity of root respiration to temperature change than for total soil respiration. Since root biomass (herbaceous roots) was greater at the cleared than at uncleared sites, and root respiration increased with an increase in temperature, we speculate that with rising ambient temperature and consequently soil temperature, total soil respiration in cleared pastures will increase at a faster rate than that in uncleared pastures.

John Caddy, Review of “Marine Habitat and Cover: Their Importance for Productive Coastal Fishery Resources”

Overfishing has depleted many fish stocks to histor-ically low levels. The goal of fisheries management isto rebuild commercially valuable marine biomass.Recently a shift has occurred away from singlespecies management towards ecosystem-based man-agement. A major aspect of ecosystem managementis identifying and protecting ‘critical habitat’. Despitethis focus on habitat, it has received little attention infield studies. Marine Habitat and Cover attempts toaddress this need for future research by exploring theuse of habitat as cover in marine systems. The author,John Caddy, makes use of his extensive backgroundand a review of primary literature to present topicsrelevant to habitat use and restoration. This reviewwas performed as part of a graduate aquatic ecologyclass.The book is organized into nine chapters withmultiple sub-sections within each chapter. The intro-duction provides the reader with some background onthe laws and regulations that govern human impactson marine habitat. It finishes with a bulleted list offactors affecting the ability of fish stocks to recover,with the final four bullets dealing directly with habitatand its use by fish as cover. Chapter 1 introduces thereader to the subject matter with some generaldefinitions of key words and an overview of habitatconstraints on fishes. We are also introduced to theauthor’s method of using conceptual models toillustrate his points. Chapter 2 seeks to create adialog about critical habitat and its place in stockrecovery. The author argues that a structural bottle-neck exists as a result of limited suitable cover, wherethe survival of a juvenile fish is most vulnerable.Caddy further suggests that this lack of ideal covercould play a more vital role in juvenile survival thanfood abundance. He also introduces the concept offractality for measuring the efficiency of habitat ascover.Chapter 3 begins with a description of the structureof cover and introduces the notion that preferredcover varies ontogenetically and becomes morelimiting with increasing body size. The fractalcoefficient is defined, but a more detailed descriptionof the fractal concept in addition to proper expressionof all terms would have permitted better comprehen-sion of the equations provided. The chapter closeswith two interesting examples of how cover depen-dent species may experience higher predationmortality with size due to displacement. The nextchapter outlines the influence of cover on behavior.Caddy expands on the concept of fractality todescribe the holding capacity of habitat. The holdingcapacity dictates how the habitat is utilized as well asthe size distribution of fishes present. He alsointroduces the idea of cover corridors that extendfrom one habitat to another during different stages ofa fish’s life history. Within these cover corridors are

Evaluation of Papanicolaou Stain for Studying Micronuclei in Buccal Cells Under Field Conditions

To compare Papanicolaou (Pap) and May-Grünwald Giemsa (MGG) stain as 2 techniques for staining for buccal mucosal cells to detect micronuclei (MN) infield studies.Eighty cytologic smears (2 per individual) were taken from the buccal mucosa of 40 cigarette smokers recruited at a rural village in Egypt. Forty smears were stained with Pap stain and 40 with MGG stain. All were assessed for cellularity and scored for MN.Pap stain was faster and easier to process and transport in the field study than was MGG stain. Regarding MGG smears, bacteria and cell debris masked the MN as compared to Pap smears, in which the fixative destroyed the bacteria and made the cell boundaries clearly demarcated. Using Pap stain, MN were seen easily in transparent cytoplasm.Pap stain is the preferred method infield studies for scoring and detecting MN in cells of buccal mucosa.

Preliminary investigation of maximal fetlock extension during jump landing phase on two arena surfaces; two dimensional motion analysis

Surface type has a recognised effect on the biomechanics of a horse, yet suitability of surfaces to discipline has not been fully substantiated. Ideal exercise surface conditions should be a balance of energy absorption to minimise concussion and energy return to aid performance (Barrey et al., 1999) and these conditions vary according to type of work. Greater force on a particular limb will increase the probability of injury, especially in sports that are repetitive in nature, such as show jumping. It is well known that high impact forces occur during the landing phase of jumping (Meershoek et al., 2001); investigation of this phase is therefore integral to understanding the effect that surface has on horses that jump. Maximal fetlock extension may be useful as an indicator of magnitude of ground reaction forces (Clayton, 1997). This means that in-field studies can be used to measure maximal fetlock extension as a guide to forces placed on the limb.

Supercooling Point of Bean Leaf Beetle (Coleoptera: Chrysomelidae) in Minnesota and a Revised Predictive Model for Survival at Low Temperatures

Abstract Integrated pest management (IPM) programs for the bean leaf beetle, Cerotoma trifurcata (Forster), could benefit from an ability to forecast the magnitude and timing of early-season infestations. The objectives of this study were to examine the supercooling point (SCP) of adult C. trifurcata as an index of its cold hardiness, monitor overwintering survival, and revise an existing model used to predict the overwintering survival of this pest in wooded areas as a function of low-temperature accumulation. Within a year, the mean SCP of C. trifurcata ranged from −8.9 to −6.0°C. Soil temperatures dropped below the lowest mean SCP (i.e., −8.9°C) in only 2 of 11 yr (1994–2004). In-field survivorship studies showed that adult C. trifurcata successfully overwintered in Minnesota (34–59% survival). This species survived well in years when the existing model predicted zero or low survival. In contrast, our revised model predicted more closely the overwintering survival of this species in southern Minnesota....

Magnetic properties of nanostructured spinel ferrites and nanocomposite Nd2Fe114B/α-Fe permanent magnets

This paper presents some of the important magnetic properties of the nanostructured spinel ferrites such as Ni0.5Zn0.5Fe2O4 and Mn0.67Zn0.33Fe2O4 and also that of the nanocomposite Nd2Fe14B/α-Fe permanent magnetic material. The increase in the magnetic transition temperature of Ni-Zn ferrite from 538 K in the bulk state to 592 K when the grain size is reduced to 16 nm is correlated to the enhancement in the AB superexchange interaction strength because of an increase in the magnetic ion concentration in the A-site on milling, as shown by the EXAFS and in-field Mossbauer studies. The particle size has been tailor-made by varying the concentration of the oxidant in the case of Mn-Zn ferrite. The critical particle size for the superparamagnetic limit has been found to be 25 nm with an effective magnetic anisotropy constant of 7.78 kJ m−3 which is about an order of magnitude higher than that of the bulk ferrite. The exchange coupling is found to be strengthened in the nanocomposite magnet Nd2Fe14B/α-Fe, when the grain boundary anisotropy is removed by thermal annealing and thus facilitating the enhancement of the energy product

Effect of Alloying on Maximum Depth of Pits in Mild Steel in Marine Immersion Environments

Abstract Laboratory studies have shown the influence of alloying on the pitting potential of modern mild- and low-alloy structural steels in a marine immersion environment. A similar effect would be expected infield studies, although these have not been able to isolate the effect of alloying on maximum pit depth as afunction of time, and correlation studies have been inconclusive. It is argued here that the reasons for this are twofold. One is that the nature of the pitting mechanics changes with time, from micropitting as typically observed in laboratory studies, to macropitting as seen in field studies. The second reason is that, so far, efforts at correlating field data have attempted to use a simplistic model for the growth of maximum pit depth as a function of time. A more realistic model that distinguishes between the corrosion mechanics in different phases has been introduced recently. This is applied to the literature data. It has been discovered that the effects of alloying depend on the corrosio...

Thermography as a tool for damage assessment

The use of infrared thermography (IRT) as a nondestructive evaluation technique is becoming increasingly attractive for the detection of sub-surface defects in composite structures. Extensive in-field studies have been performed that enable qualitative results to be obtained for simple structures. Unfortunately its application to complex geometries is not widely accepted. This study focuses on the use of finite element (FE) analysis to simulate the thermographic process for complex non-axisymmetric geometries. As a result of this study a suitably calibrated finite element simulation has been generated and validated. This process has the potential to be applied to composite structures with complex structural configurations.

Application of truss analysis for the quantification of changes in fish condition

Conservation of skeletal structure and uniquebody ratios in fishes facilitated thedevelopment of truss analysis as a taxonomictool to separate physically-similar species. The methodology is predicated on themeasurement of across-body distances from asequential series of connected polygons. Changes in body shape or condition amongmembers of the same species can be quantifiedwith the same technique, and we conducted afeeding experiment using yellow perch (Perca flavescens) to examine the utility ofthis approach. Ration size was used as asurrogate for fish condition, with fishreceiving either a high (3.0% body wt/d) or alow ration (0.5%). Sequentially over our11-week experiment, replicate ration groups offish were removed and photographed whilecontrol fish were repeatedly weighed andmeasured. Standard indices of condition (totallipids, weight-length ratios, Fulton'scondition) were compared to truss measurementsdetermined from digitized pictures of fish. Condition indices showed similarity betweenrations while truss measures from the caudalregion were important for quantifying changingbody shape. These findings identify trussanalysis as having use beyond traditionalapplications. It can potentially be used as acheap, accurate, and precise descriptor of fishcondition in the lab as shown here, and wehypothesize that it would be applicable infield studies.

In-Field Monitoring of Beneficial Insect Populations in Transgenic Corn Expressing a Bacillus thuringiensis Toxin

In 1998 and 1999, field studies were conducted near Rosemount, MN to assess the potential impact of transgenic sweet corn, transformed to express the Cry1Ab toxin from Bacillus thuringiensis Berliner var kurstaki (i.e., Bt corn), on several beneficial insects, including predatory coccinellids, chrysopids and anthocorids. Beneficial insects in both Bt and in non-Bt sweet corn were also monitored in field cages in 1999. Plants were visually sampled for beneficial insects by arbitrarily selecting 3 consecutive plants from each plot or 6 plants/cage. Rank transformed data were analyzed using the Kruskal-Wallis test, which indicated no significant within-year differences in the overall density of beneficial insect populations between Bt and non-Bt sweet corn. Coleomegilla maculata (DeGeer) was the dominant predator species detected in 1998 and 1999. A significant trend (P &amp;lt; 0.05) was found for C. maculata larvae in open plots, with non-Bt treatments having higher C. maculata levels than Bt. Also, C. maculata larval and adult densities, for caged plots, showed a significant trend for higher counts in the in non-Bt corn. No additional differences in species diversity of beneficial insects were detected using Hills N1. Neither Hippodamia convergens Guérin-Ménville, Adalia bipunctata (L.), nor Coccinella septempunctata L. were observed during 1999. Although our test detected significant trends for higher densities of C. maculata in non-Bt corn, the results also suggest that longer-term in-field studies with higher sample sizes are needed to further characterize what may be relatively subtle population effects in the field.

Trichogramma releases in North Carolina cotton: why releases fail to suppress heliothine pests.

Field studies were conducted in 1996 and 1997 to determine the fate of naturally oviposited F3 heliothine eggs in cotton plots treated with augmentative releases of Trichogramma exiguum Pinto & Platner and nontreated plots. Four cohorts of newly oviposited eggs (< 24 h old) were followed in 1996 and two cohorts in 1997. In 1996, mean +/- SD percent parasitism, estimated by in-field studies following the fate of naturally oviposited eggs, ranged from 7 +/- 7 to 61 +/- 8% in T. exiguum release plots and 0 +/- 0 to 35 +/- 13% in control plots. The mean +/- SD percent of eggs hatched in T. exiguum release plots ranged from 1 +/- 2 to 11 +/- 4% and 7 +/- 4 to 28 +/- 10% in control plots. In 1997, mean +/- SD percent egg parasitism ranged from 27 +/- 4 to 40 +/- 3% in T. exiguum release plots and 15 +/- 18 to 25 +/- 8% in control plots. The mean +/- SD percent of eggs hatched in T. exiguum release plots ranged from 7 +/- 3 to 12 +/- 2% and 18 +/- 6 to 28 +/- 8% in control plots. Despite increased parasitism and reduced egg hatch in T. exiguum release plots, overall, there was no significant difference in larval density (all instars combined) between T. exiguum release and control plots. Combined analysis of the heliothine larval populations and egg fate data revealed that the additional egg mortality produced by released T. exiguum was offset by lower larval mortality in release plots. Because of the occurrence of compensatory mortality, the egg stage of heliothines is not an appropriate target for biological control using Trichogramma wasp releases.

Monitoring volatile organic compounds in ambient air inside and outside buildings with the use of a radio-frequency-based ion-mobility analyzer with a micromachined drift tube

A radio-frequency-based ion-mobility analyzer with a micromachined drift tube was operated continuously to monitor volatile organic compounds (VOCs) in ambient air inside a building and in an open space near the union of I-10 and I-25 at Las Cruces, New Mexico. Air was drawn directly, without enrichment or preseparation, through the analyzer, which was regulated to 35 °C. The ion source was a photo-discharge lamp at 10.6 eV, providing a preliminary level of selectivity in response to chemicals with low ionization potentials. The compensation voltage was scanned continuously from −40 to +20 V at rates of 60 V/s, providing profiles of ions obtained from VOCs in air. Solvents were detected at 1-ppm levels as fugitive emissions from other experiments under way in the laboratory from 8:00 a.m. to 6:00 p.m. However, patterns in VOC levels from 1 to 5 ppb between 6:00 p.m. and 7:00 a.m. and on weekends was attributed to air exchange between ambient air and the ventilation system of the building. The mobility analyzer results were consistent with VOCs from traffic on major city thoroughfare adjacent to the building. In-field studies near two interstate highways demonstrated that analyzer response could be correlated to traffic patterns and exhibited diurnal trends. These findings demonstrate the concept and practice of micromachined mobility analyzers as continuous monitors for VOCs as airborne vapors in buildings and on site. © 2000 John Wiley & Sons, Inc. Field Analyt Chem Technol 4: 297–308, 2000

A Brief Tutorial on the Development of Measures for Use in Survey Questionnaires

The adequate measurement of abstract constructs is perhaps the greatest challenge to understanding the behavior of people in organizations. Problems with the reliability and validity of measures used on survey questionnaires continue to lead to difficulties in interpreting the results of field research. Price and Mueller suggest that measurement problems may be due to the lack of a well-established framework to guide researchers through the various stages of scale development. This article provides a conceptual framework and a straightforward guide for the development of scales in accordance with established psychometric principles for use infield studies