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PubMed1996

Inertial and interceptional deposition of fibers in a bifurcating airway.

A computer model of a three-dimensional bifurcating airway was constructed in which the parent and daughter airways had different lengths but equal diameters. A diameter of 0.6 cm was chosen for the airways based on the third generation of Weibel's symmetric lung model. Different bifurcation angles of 60 degrees, 90 degrees, and 120 degrees were studied. Airflow fields in the airway were obtained by a finite-element method (FIDAP, Fluid Dynamics International, Evanston, IL) for Reynolds numbers of 500 and 1000, assuming uniform parent inlet velocities. The equations of motion for fiber transport in the airways were obtained, and deposition by the combined mechanisms of impaction and interception was incorporated. A computer code was developed that utilized the flow field data and calculated fiber transport in the airways using the equations of motion for fibers. Deposition efficiency was obtained by simulating a large number of fibers of various sizes. Fiber entering the daughter airways tended to orient themselves parallel to the flow. A site of enhanced deposition (or hot spot) was observed at the carina. The dominant parameter for the deposition was the fiber Stokes number. Flow Reynolds number and airway bifurcation angle were also found to affect the deposition.

Airway Resistance↗
PubMedDate not supplied

Oral fluid testing for drugs of abuse: positive prevalence rates by Intercept immunoassay screening and GC-MS-MS confirmation and suggested cutoff concentrations.

Draft guidelines for the use of oral fluid for workplace drug testing are under development by the Substance Abuse and Mental Health Services Administration (SAMHSA) in cooperation with industry and researchers. Comparison studies of the effectiveness of oral fluid testing versus urine testing are needed to establish scientifically reliable cutoff concentrations for oral fluid testing. We present the results of the first large scale database on oral fluid testing in private industry. A total of 77,218 oral fluid specimens were tested over the period of January through October 2001 at LabOne. Specimens were screened by Intercept immunoassay at manufacturer's recommended cutoff concentrations for the five SAMHSA drug categories (marijuana, cocaine, opiates, phencyclidine, and amphetamines). Presumptive positive specimens were confirmed by gas chromatography-tandem mass spectrometry. A total of 3908 positive tests were reported over the 10-month period, representing a positive rate of 5.06%. Of the five drug categories, marijuana and cocaine accounted for 85.75% of the positives. The pattern and frequency of drug positives showed remarkable similarity to urine drug prevalence rates reported for the general workforce according to the Quest Diagnostics' Drug Testing Index over the same general period, suggesting that oral fluid testing produces equivalent results to urine testing. The data on oral fluid testing also revealed a surprisingly high 66.7% prevalence of 6-acetylmorphine confirmations for morphine positives suggesting that oral fluid testing may be superior in some cases to urine testing. Comparison of oral fluid drug concentrations to SAMHSA-recommended cutoff concentrations in Draft Guidelines indicated that adoption of the screening and confirmation cutoff concentrations of Draft Guidelines #3 would produce the most consistent reporting results for all drug classes except amphetamines. Consequently, it is suggested that the final Guidelines adopt the screening and cutoff concentrations listed in Draft Guidelines #3 with the exception of lowering the amphetamines cutoff concentrations (screening/confirmation) to 50/50 ng/mL for amphetamine and methamphetamine.

Gas Chromatography-Mass Spectrometry↗
PubMed2000

Effects on the growth of carrots (Daucus carota L.), cabbage (Brassica oleracea var. capitata L.) and onion (Allium cepa L.) of restricting the ability of the plants to intercept resources.

The objective of this paper is to assess the size and penetration of edge effects in carrot, cabbage and onion field crops and the extent to which these edge effects are modified by the presence of aerial or soil competition between the crop rows. In all three crops, large weight differences developed between the plants in the edge rows and those in the central rows. There was no indication of plant weight fluctuating between large and small values with each successive row in from the edge, as suggested by others. In carrot and onion, edge effects were greatly reduced by the presence of either white reflective aerial partitions or soil partitions, indicating that these species competed for both light and soil resources in UK field conditions. In cabbage, the mere presence of clear aerial partitions between rows reduced edge effects and there was little effect of soil partitions. This indicates the predominance of shoot over root competition in this species. The differences between species are possibly related to the architectural flexibility of their shoots. These results suggest that, within crops, carrot and onion plants compete for light over a distance of about 20 cm in each direction and for below-ground resources over a distance of about 50 cm in each direction. For cabbage, interactions between plants appeared to be dominated by the requirement for sufficient space to deploy the shoots for efficient light interception.

Brassica↗
PubMedDate not supplied

Dependence of light interception efficiency of Scots pine shoots on structural parameters.

The ratio of shoot silhouette area to total needle area (STAR) is one means of quantifying the light interception efficiency of a coniferous shoot. The silhouette area (or STAR) of a shoot depends on various structural characteristics of the shoot, and also varies with the direction of the shoot relative to the direction of radiation (sun angle). The mean STAR taken over all directions in space is the mean ratio of shoot silhouette area to total needle area in an isotropic radiation field. It also represents a mean STAR with respect to a spherical shoot orientation. In this study, equations for the relationship between mean STAR and easily measurable shoot characteristics were developed. The STAR values in different directions were determined from photographically measured shoot silhouette areas. Mean STAR varied between 0.079 and 0.308, and averaged 0.146. A clear increase in mean STAR with age was found. The material consisted of 305 Scots pine (Pinus sylvestris L.) shoots from Sweden and Finland, representing shoots of different age and a wide variation in site fertility. The needle area density in the shoot cylinder, together with the diameters of the shoot cylinder and the twig explained 87% of the variation in mean STAR.

Journal Article↗
PubMed1996

Hydraulic conductance, light interception and needle nutrient concentration in Scots pine stands and their relations with net primary productivity.

Aboveground xylem hydraulic conductance was determined in Scots pine (Pinus sylvestris L.) trees and stands from 7 to about 60 years of age. At the stand scale, leaf area index and net primary productivity (NPP, above- plus belowground) increased and reached a plateau at about 25-30 and 15-20 years, respectively; both parameters declined in mature stands. Stand hydraulic conductance followed a similar trend to NPP, with a maximum at about 15-20 years and a pronounced reduction in old stands. At the tree scale, annual biomass growth per unit of leaf area (growth efficiency) declined with tree age, whereas aboveground sapwood volume per unit leaf area, which is linearly related to maintenance respiration costs, steadily increased. Radiation interception per unit leaf area increased significantly with reduced leaf area index of mature stands, despite increased foliage clumping in the canopies of mature trees. Needle nutrient concentration did not change in the chronosequence. Tree hydraulic conductance per unit leaf area was strongly and positively correlated with growth efficiency. We discuss our findings in the context of growth reductions in mature and old trees, and suggest that increased hydraulic resistance and maintenance respiration costs may be the main causes of reduced carbon gain in mature and old trees.

Journal Article↗
PubMed2001

Effects of thinning on wood production, leaf area index, transpiration and canopy interception of a plantation subject to drought.

We conducted thinning trials in a 5-year-old Eucalyptus globulus ssp. globulus Labill plantation near Warrenbayne, northeastern Victoria, Australia, where soil salinization and waterlogging are common, and assessed treatment effects on tree growth, water use and survival. Half-hectare plots were thinned from the original density of 1100 stems ha(-1) to densities of 800, 600 and 400 stems ha(-1), and stem diameter increment, leaf area index, transpiration, canopy interception and depth of tree water source monitored for 21 months. Two drought periods occurred during the study, rainfall was 30% below the long-term average and there was severe mortality in all three plots. Analysis of deuterium abundance in soil and xylem water indicated that the trees accessed water only from the top meter of the soil profile. Transpiration rates were higher in the most heavily thinned plot than in the least thinned plot, which underwent a reduction in basal area during the study. The most heavily thinned plot increased in basal area by 10% during the study. Edge trees had significantly greater diameters than trees from the middle of the plots.

Disasters↗
PubMed1990

Architectural distribution of foliage in individual Pinus radiata D. Don crowns and the effects of clumping on radiation interception.

The architectural arrangement and leaf area of representative branch units, on one branch complex from each cluster on the stem, were measured on six trees in a widely spaced 7-year-old Pinus radiata D. Don plantation. There was a linear relationship between leaf area and the basal area of branch complexes. Assuming similarity in the arrangement of branch units within concomitant branch complexes at each cluster, the 3-dimensional distribution of leaf area density (leaf area per unit volume) in an array of cubic cells, each 10(-3) m(3), comprising the volume of each tree crown, was reconstructed. The fraction of cells in which foliage was present varied from 0.08 to 0.23 in the crowns with the highest (Tree 4) and lowest (Tree 3) degree of clumping, respectively. This difference was related to the number, length, and leaf area per unit length of Order 3 branch units, in particular. The actual distributions of leaf area density were used with a simple radiative transfer model to estimate the probability of penetration of beam and diffuse photosynthetically active radiation (PAR) through individual tree crowns. The average probability of beam penetration was greater for the tree with the most clumped foliage than for the tree with the least clumped foliage. For both trees, the average probabilities of penetration were greater than the values that would have resulted if a random distribution of foliage had been assumed. The negative binomial model was used to estimate an index of foliage dispersion for the tree crowns. For beam PAR, the index of foliage dispersion was 3.3 and 2.3 for the trees with the most, and the least clumped foliage, respectively. These results were supported by analysis of the architectural arrangement of foliage in the tree crowns. For two days in summer, the assumption that leaf area density was randomly distributed would have resulted in a 20 to 30% overestimation of intercepted PAR flux by the tree crowns.

Journal Article↗
PubMed1990

Effects of leaf display on light interception and apparent photosynthesis in two contrasting Populus cultivars during their second growing season.

Effects of the contrasting leaf display of poplar cultivars Eugenei (Populus x euramericana) and Tristis (P. tristis x P. balsamifera) on light interception and photosynthesis were studied in the second year of growth in an irrigated plantation near Rhinelander, Wisconsin, USA (lat. 45 degrees N). Leaves on the current terminal (CT) and on proleptic branches were measured between 0900 and 1500 h on five clear days from June to September 1980. Leaf orientation-based differences between these cultivars were evident as the second growing season progressed and the crowns of the trees in the plantation grew together. Leaves of Eugenei are erectophile or tilted from the horizontal. In this cultivar light penetrated throughout the crown; many leaves on the lowest branches were illuminated as fully as those on the upper CT and had higher photosynthetic rates than equivalent leaves in Tristis. However, by early September many of the lower branches on Eugenei trees had abscised. In the planophile Tristis, adaxial photon flux densities (PPFD) of leaves on the lower portion of the CT and on branches were only a fraction of those measured on the upper CT. This pattern became more extreme as the season progressed. Few of the lower branches of Tristis abscised during the growing season. Photosynthesis rates, especially on a whole-leaf basis, were closely related to incident PPFDs in both cultivars. The ecological significance of these results are discussed, as well as the hypothesized effect of leaf inclination on crop productivity.

Journal Article↗
PubMed1989

The accuracy of some simple models for predicting particulate interception and retention in agricultural systems.

The accuracy of three radionuclide transfer models for predicting the interception and retention of airborne particles by agricultural crops was tested using Pu-bearing aerosols released to the atmosphere from nuclear fuel facilities on the U.S. Department of Energy's Savannah River Plant, near Aiken, SC. The models evaluated were: 1) NRC, the model defined in U.S. Nuclear Regulatory Guide 1.109; 2) FOOD, a model similar to the NRC model that also predicts concentrations in grains; and 3) AGNS, a model developed from the NRC model for the southeastern United States. Plutonium concentrations in vegetation and grain were predicted from measured deposition rates and compared to concentrations observed in the field. Crops included wheat, soybeans, corn and cabbage. Although predictions of the three models differed by less than a factor of 4, they showed different abilities to predict concentrations observed in the field. The NRC and FOOD models consistently underpredicted the observed Pu concentrations for vegetation. The AGNS model was a more accurate predictor of Pu concentrations for vegetation. Both the FOOD and AGNS models accurately predicted the Pu concentrations for grains.

Aerosols↗
PubMed2005

Spiders that decorate their webs at higher frequency intercept more prey and grow faster.

Many orb-weaving spiders decorate their webs with extra, bright white, ultraviolet light reflecting silk. Previous studies suggest that these decorations increase a spider's foraging efficiency by improving web attractiveness, which is known as the prey-attraction hypothesis. One assumption of this hypothesis is that individuals which decorate their webs at a higher frequency are expected to have a higher growth rate. Using a decoration-building orb-weaving spider, Argiope versicolor, I show a strong positive relationship between the growth rate in terms of weight gain and the frequency of decoration-building, as well as the rate of insect interception. This is the first study to reveal a fitness consequence of decorating behaviour in spiders.

Analysis of Variance↗
PubMed2004

Implementation of the INTERCEPT Blood System for Platelets into routine blood bank manufacturing procedures: evaluation of apheresis platelets.

BACKGROUND AND OBJECTIVES: The INTERCEPT Blood System for Platelets utilizes amotosalen-HCl (S-59) in combination with ultraviolet A (UVA) light to inactivate viruses, bacteria, protozoa and leucocytes that may contaminate platelet concentrates (PCs). To facilitate implementation of this technique into routine blood bank manufacturing procedures, this study evaluated the impact of different time settings of photochemical treatment on in vitro platelet function. MATERIALS AND METHODS: Platelets derived from apheresis (6.5-7.0 x 10(11) platelets) were resuspended in 240 ml of autologous plasma and 360 ml of platelet additive solution (PAS III) and split into two equal-sized PC units. Whereas one unit was not treated, the other was treated with 150 microm amotosalen and 3 J/cm2 UVA light followed by a compound adsorption device (CAD) step for reduction of residual amotosalen and photoproducts. In a first series of experiments (arm A, n = 7), PC units were photochemically treated after an overnight storage period of 16-23 h followed by a CAD step of 4 h. In a second series (arm B, n = 8), photochemical treatment occurred after a short storage time of 4 h with a subsequent CAD step of 16 h. Platelet function was evaluated by assaying blood gas analysis, glucose and lactate concentration, lactate dehydrogenase (LDH), hypotonic shock response (HSR) and the expression of CD62p, over a period of 7 days. RESULTS: Neither of the photochemical treatment procedures showed differences for pH, pCO2, pO2, HCO3, glucose consumption or platelet activation until the end of day 7. Increased lactate values detected for the treated units of arm A at the end of the storage period were independent from the PCT time setting. CONCLUSIONS: Photochemical pathogen inactivation with different initial resting periods between 4 and 23 h, and different CAD steps of 4 and 16 h, had no influence on the platelet in vitro function during 7 days of storage.

Adsorption↗
PubMed2005

Flavohaemoglobin HmpX from Erwinia chrysanthemi confers nitrosative stress tolerance and affects the plant hypersensitive reaction by intercepting nitric oxide produced by the host.

Host cells respond to infection by generating nitric oxide (NO) as a cytotoxic weapon to facilitate killing of invading microbes. Bacterial flavohaemoglobins are well-known scavengers of NO and play a crucial role in protecting animal pathogens from nitrosative stress during infection. Erwinia chrysanthemi, which causes macerating diseases in a wide variety of plants, possesses a flavohaemoglobin (HmpX) whose function in plant pathogens has remained unclear. Here we show that HmpX consumes NO and prevents inhibition by NO of cell respiration, indicating a role in protection from nitrosative stress. Furthermore, infection of Saintpaulia ionantha plants with an HmpX-deficient mutant of E. chrysanthemi revealed that the lack of NO scavenging activity causes the accumulation of unusually high levels of NO in host tissue and triggers hypersensitive cell death. Introduction of the wild-type hmpX gene in an incompatible strain of Pseudomonas syringae had a dramatic effect on the hypersensitive cell death in soya bean cell suspensions, and markedly reduced the development of macroscopic symptoms in Arabidopsis thaliana plants. These observations indicate that HmpX not only protects against nitrosative stress but also attenuates host hypersensitive reaction during infection by intercepting NO produced by the plant for the execution of the hypersensitive cell death programme.

Bacterial Proteins↗
PubMed2006

Assessment of the economic value of the INTERCEPT blood system in Belgium.

Emerging pathogens continue to threaten blood safety, requiring novel safety approaches. INTERCEPT Blood System for platelets (IBSP) inactivates pathogens, aiming at eliminating the risk of transmitting current and emerging pathogens. The objective was to evaluate the incremental cost-effectiveness ratio (ICER) for IBSP in Belgium. A decision model comparing a 'world with IBSP' to a 'world without IBSP' calculates lifetime costs and 'quality adjusted life years' (QALYs) following platelet transfusion in different indications. Disease-specific life expectancy and consequences of transfusion-transmitted infections were obtained from literature. Transfusion safety and costs were obtained from official sources. Hepatitis C virus-like emerging pathogen was simulated. A wide range of ICERs was observed, highly sensitive to the risk of emerging pathogen trans- mission, underlying disease and age. In the most conservative approach, ICER ranged from 3,459,201 Euro/QALY in absence of emerging pathogen to 195,364 Euro/QALY. The mean threshold of emerging infection risk for IBSP dominance (saving money and producing health gains) ranged from 1/1,079 to 1/2,858 transfusions. Considering the high value authorities appear to place on preventing accidental injury, and ICER of recent implementations in transfusion medicine (NAT: up to 2.3 million Euro per lifeyear), IBSP can be considered cost-effective, taking into account the potential risk of emerging pathogens.

Belgium↗
PubMedDate not supplied

Monitoring well interception with fractures in clayey till.

When using monitoring wells for investigation of contaminant sources in clayey till, there is a high risk that fractures may cause mobile contaminants to bypass the monitoring wells. This paper indicates that the probability of interception between monitoring wells and hydraulic conductive fractures is often significantly less than 50%. Based on a field experiment and application of a calibrated discrete fracture matrix diffusion numerical model (FRAC3Dvs), the paper also evaluates pesticide-monitoring results for different positions of monitoring well screen relative to fractures. For well screens situated 0.25 and 2 m from a conductive fracture, the first concentrations of the pesticide metabolite (2,6 dichlorobenzamide, "BAM") would be measured two years and 18 years, respectively, after the contaminant had been transported into an underlying aquifer. In this way, underlying aquifers may be subjected to contamination by downward moving contamination without being observed in monitoring wells in the till.

Aluminum Silicates↗
PubMed1983

Pregnancy interception with a combination of prostaglandins: studies in monkeys.

Treatment with combinations of synthetic prostaglandins, one with an ovarian site of action and one with a uterine site of action, terminated pregnancy in all rhesus monkeys given the injection on day 28 of fertile menstrual cycles. Single prostaglandins, even at higher doses, interrupted pregnancy in only one-third of the monkeys. The most effective treatment, 5-oxa-17-phenyl-18,19,20-trinor prostaglandin F1 alpha methyl ester plus 9-deoxo-16,16-dimethyl-9-methylene prostaglandin E2, promptly intercepted early pregnancy after a single administration and without side effects.

Abortifacient Agents↗
PubMed2001

Interception of small particles by flocculent structures, sessile ciliates, and the basic layer of a wastewater biofilm.

We investigated attachment processes of hydrophobic and hydrophilic particles (diameter = 1 microm) to mature biofilms grown on clay marbles in a sequencing batch biofilm reactor. During a treatment cycle with filtered wastewater containing different fluorescent beads, the progression of particle density in various biofilm compartments (carrier biofilm, basic biofilm layer, biofilm flocs, and sessile ciliates) was determined by flow cytometry, confocal laser scanning microscopy and automated image analysis. Particles were almost completely removed from wastewater by typical processes of particle retention: up to 58% of particles attached to clay marbles, up to 15% were associated with suspended flocs, and up to 10% were ingested by sessile ciliates. Ingestion of particles by ciliates was exceptionally high immediately after wastewater addition (1,200 particles grazer(-1) x h(-1)) and continued until approximately 14% of the water had been cleared by ciliate filter feeding. Most probably, ciliate bioturbation increases particle sorption to the basic biofilm. Backwashing of the reactor detached pieces of biofilm and thus released approximately 50% of the particles into rinsing water. Clay marbles in the upper part of the reactor were more efficiently abraded than in the lower part. No indications for selective attachment of the applied hydrophobic and hydrophilic beads were found. As a consequence of interception patterns, organisms at elevated biofilm structures are probably major profiteers of wastewater particles; among them, ciliates may be of major importance because of their highly active digestive food vacuoles.

Animals↗
PubMed2002

Preload-adjusted maximal power of right ventricle: contribution of end-systolic P-V relation intercept.

To assess whether preload-adjusted maximal power (PAMP), which is calculated as W(max)/V (where W(max) is maximal power and V(ed) is end-diastolic volume with beta = 2) is an index of right ventricular (RV) contractility, we measured RV pressure (P) and volume (V) and pulmonary artery pressure and flow in 10 dogs at baseline and after inotropic stimulation. PAMP was derived from steady-state data, whereas the slope (E(es)) and intercept (V(d)) of the end-systolic P-V relationship were derived from data obtained during vena caval occlusion. Inotropic stimulation increased E(es) (from 0.96 +/- 0.25 to 1.62 +/- 0.28 mmHg/ml; P < 0.001) and V(d) (from -3.0 +/- 17.2 to 12.4 +/- 10.8 ml; P < 0.05) but not PAMP (from 0.24 +/- 0.10 to 0.36 +/- 0.22 mW/ml(2); P = 0.09). We found a strong relationship between the optimal beta-factor for preload adjustment and V(d). A corrected PAMP, PAMP(c) = W(max)/(V(ed) - V(d))(2), which incorporated the V(d) dependency, was sensitive to the inotropic changes (from 0.23 +/- 0.12 to 0.54 +/- 0.17 mW/ml(2); P < 0.001) with a good correlation with E(es) (r = 0.88; P < 0.001).

Animals↗
PubMed2005

Internal model of gravity for hand interception: parametric adaptation to zero-gravity visual targets on Earth.

Internal model is a neural mechanism that mimics the dynamics of an object for sensory motor or cognitive functions. Recent research focuses on the issue of whether multiple internal models are learned and switched to cope with a variety of conditions, or single general models are adapted by tuning the parameters. Here we addressed this issue by investigating how the manual interception of a moving target changes with changes of the visual environment. In our paradigm, a virtual target moves vertically downward on a screen with different laws of motion. Subjects are asked to punch a hidden ball that arrives in synchrony with the visual target. By using several different protocols, we systematically found that subjects do not develop a new internal model appropriate for constant speed targets, but they use the default gravity model and reduce the central processing time. The results imply that adaptation to zero-gravity targets involves a compression of temporal processing through the cortical and subcortical regions interconnected with the vestibular cortex, which has previously been shown to be the site of storage of the internal model of gravity.

Adaptation, Physiological↗