Vd Values Research Articles

Minimally invasive estimation of ventricular dead space volume through use of Frank-Starling curves.

This paper develops a means of more easily and less invasively estimating ventricular dead space volume (Vd), an important, but difficult to measure physiological parameter. Vd represents a subject and condition dependent portion of measured ventricular volume that is not actively participating in ventricular function. It is employed in models based on the time varying elastance concept, which see widespread use in haemodynamic studies, and may have direct diagnostic use. The proposed method involves linear extrapolation of a Frank-Starling curve (stroke volume vs end-diastolic volume) and its end-systolic equivalent (stroke volume vs end-systolic volume), developed across normal clinical procedures such as recruitment manoeuvres, to their point of intersection with the y-axis (where stroke volume is 0) to determine Vd. To demonstrate the broad applicability of the method, it was validated across a cohort of six sedated and anaesthetised male Pietrain pigs, encompassing a variety of cardiac states from healthy baseline behaviour to circulatory failure due to septic shock induced by endotoxin infusion. Linear extrapolation of the curves was supported by strong linear correlation coefficients of R = 0.78 and R = 0.80 average for pre- and post- endotoxin infusion respectively, as well as good agreement between the two linearly extrapolated y-intercepts (Vd) for each subject (no more than 7.8% variation). Method validity was further supported by the physiologically reasonable Vd values produced, equivalent to 44.3–53.1% and 49.3–82.6% of baseline end-systolic volume before and after endotoxin infusion respectively. This method has the potential to allow Vd to be estimated without a particularly demanding, specialised protocol in an experimental environment. Further, due to the common use of both mechanical ventilation and recruitment manoeuvres in intensive care, this method, subject to the availability of multi-beat echocardiography, has the potential to allow for estimation of Vd in a clinical environment.

Population pharmacokinetics analysis of intravenous busulfan in Chinese patients undergoing hematopoietic stem cell transplantation.

There are several reports describing population pharmacokinetic (popPK) models of busulfan (BU). However, limited information is available in Chinese hematopoietic stem cell transplantation (HSCT) patients. The present study aimed to establish a popPK model of intravenous BU in Chinese HSCT patients for individualized drug therapy. The popPK model of BU was developed from a total of 284 concentration-time points from 53 patients. The effects of demographic and biochemical covariates were investigated by nonlinear mixed effect model (NONMEM) software. Plots, visual predictive check (VPC), bootstrap and normalized prediction distribution error (NPDE) were performed to determine the stability and the reliability of the final model. A one-compartment model with first-order elimination process was confirmed as the final structural model for BU. For a typical patient whose body surface area (BSA) is 1.7m2 , the population typical values of CL and Vd were 11.86L/h, and 48.2L, respectively. The result suggested BSA showed significant influence on CL and Vd (P<.001). Plots revealed the final model was performing a goodness fit. The steady rate verified by bootstrap was 100%, relative deviation was less than 4.00%, estimated value of final model was in the 95% confidence interval (CI). The VPC results showed the observed values were almost all positioned within the 5th and 95th CIs. The mean and variance of the NPDE were 0.0363 (Wilcoxon signed-rank test, 0.298) and 0.877 (Fisher variance test, 0.134; SW test of normality, 0.108), respectively. The global adjusted P value was 0.305, which indicated that the prediction of the BU popPK model was adequate. A physician-friendly Microsoft Excel-base tool was implemented using the final popPK model for designing individualized dosing regimens.

Effectiveness of indoor plants for passive removal of indoor ozone

Indoor vegetation is often proposed as a passive approach for improving indoor air quality. While studies of outdoor environments indicate that vegetation can be an important sink of outdoor ozone, there is scant data in the literature concerning the dynamics of ozone uptake by indoor plants. This study determined ozone deposition velocities (vd) for five common indoor plants (Peace Lily, Ficus, Calathia, Dieffenbachia, Golden Pothos). The transient vd was calculated, using measured leaf areas for each plant, for exposures mimicking three diurnal cycles where ozone concentrations in chamber tests were elevated for 8 h followed by 16 h in the absence of ozone. Estimates of vd at the end of the first exposures ranged from 5.6 m h−1 for Golden Pothos to 0.9 m h−1 for Peace Lily. Values of vd were approximately 50% and 66% lower at the end of a second exposure and third exposure, respectively. Estimates of vd were also made for a range of photosynthetic active radiation (PAR) levels typically observed indoors. An increase in PAR from 0.6 to 41.2 μmol m−2 sec−1 resulted in increases in vd ranging from a factor of 1.7 (Diffenbachia) to 4.7 (Peace Lily). For deposition velocities measured in this study, the ozone removal effectiveness ranges from 0.9% to 9% for leaf surface area to room volume ratio of 0.06 m−1 (approximately one plant for every 1.8 m2 of floor area) when accounting for values of air exchange and background loss typical of a residential environment.

Anatomical characteristics in 20-year-old Zelkova serrata trees from eight half-sib families

Zelkova serrata (Thunb.) Makino (“keyaki” in Japanese) is an important broad-leaved species for the wood industry in Japan. To analyze the among-family variation of anatomical characteristics in Z. serrata, wood fiber length (WFL), vessel element length in earlywood (VEL), fiber wall thickness (FWT), and vessel diameter in earlywood (VD) were investigated for 20-year-old trees from eight half-sib families. Mean values of WFL, VEL, FWT, and VD ranged from 1.31 to 1.51 mm, 0.19 to 0.22 mm, 1.2 to 2.1 µm, and 131 to 188 µm, respectively. Relatively higher F values were obtained by analysis of variance for WFL and VEL, suggesting that these characteristics might be improved though the selection of mother trees under tree breeding programs. In addition, growth characteristics were not significantly correlated with anatomical characteristics, except for FWT.

Method to predict length dependency of negative bias temperature instability degradation in p-MOSFETs

We propose a method to predict the length dependency of the magnitude of degradation caused by negative bias temperature instability (NBTI) stress applied to a p-MOSFET. Threshold voltage degradation ΔVth varied according to the drain bias Vd, during the measurement of drain current Id. The depletion length Ldep into the channel was calculated based on a particular Vd value and the channel doping concentration. Ldep was used to extract the channel edge region length Ledge, then the center channel region length Lcen was obtained by subtracting Ledge from the gate length Lgate. We proposed an equation that uses Ldep, Lcen, Ledge and degree of ΔVth variation to calculate ΔVth according to Lgate while the p-MOSFET is under NBTI stress. Equation estimates of ΔVth at different Lgate were similar to measurements.

An UPLC-MS/MS Method for Determination of Vicenin-2 and Lychnopholic Acid in Rat Plasma and its Application to a Pharmacokinetic Study

Vicenin-2 (VIC) and lychnopholic acid (LA) are present in large amounts in hydroalcoholic extract from leaves of Lychnophora salicifolia, commonly known in the Brazilian Cerrado as arnicao, a plant applied as topic anti-inflammatory and as a flavoring agent for the traditional spirit (cachaca). A new ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for quantification of LA and VIC in plasma samples in order to evaluate their pharmacokinetic profiles in rats. The method was linear in the range of 10-2500 ng mL-1, acceptable precision accuracies were obtained and no significant matrix effect was observed. The validated method was successfully applied to pharmacokinetic study. LA presented very low t1/2 (half-time), high Cl (serum clearance) and Vd (volume of distribution), and for VIC, the t1/2 value was slightly larger, but still rather low, whereas Cl and Vd values were slightly lower, indicating that both substances are instantaneous and well distributed in the body, and quickly eliminated.

Dry deposition of O3 and SO2 estimated from gradient measurements above a temperate mixed forest

Vertical profiles of O3 and SO2 concentrations were monitored at the Borden Forest site in southern Ontario, Canada from May 2008 to April 2013. A modified gradient method (MGM) was applied to estimate O3 and SO2 dry deposition fluxes using concentration gradients between a level above and a level below the canopy top. The calculated five-year mean (median) dry deposition velocity (Vd) were 0.35 (0.27) and 0.59 (0.54) cm s−1, respectively, for O3 and SO2. Vd(O3) exhibited large seasonal variations with the highest monthly mean of 0.68 cm s−1 in August and the lowest of 0.09 cm s−1 in February. In contrast, seasonal variations of Vd(SO2) were smaller with monthly means ranging from 0.48 (May) to 0.81 cm s−1 (December). The different seasonal variations between O3 and SO2 were caused by the enhanced SO2 uptake by snow surfaces in winter. Diurnal variations showed a peak value of Vd in early morning in summer months for both O3 and SO2. Canopy wetness increased the non-stomatal uptake of O3 while decreasing the stomatal uptake. This also applied to SO2, but additional factors such as surface acidity also played an important role on the overall uptake.

Blood flow velocity waveforms in the middle cerebral artery during cycle exercise and recovery

The blood flow velocity waveforms in the middle cerebral artery (MCA) were measured under incremental cycle exercises and following recovery using the transcranial Doppler ultrasound velocimeter. At rest, the flow waveform in the MCA is characterized by a high forward flow at end-diastole, which is as much as half peak-systolic velocity. The peak-systolic velocity Vs was found to markedly rise in proportion with exercise intensity under mild and moderate intensities (up to 110 W) of exercise, while it tended to keep constant values under higher exercise intensities (above 110 W). The end-diastolic velocities Vd showed no significant change under mild exercise intensity and gradually increased under moderate exercise intensities. It was also found that the Vd values decreased more rapidly than Vs in the recovery phase. Such nonlinear changes in Vs and Vd indicate that the influence of exercise on cerebral blood flow is more complicated than previously thought.

Population pharmacokinetics and dosing simulations of cefepime in septic shock patients receiving continuous renal replacement therapy

The aim of this study was to describe the population pharmacokinetics of cefepime in septic shock patients requiring continuous renal replacement therapy and to determine whether current or alternative dosing regimens can achieve PK/PD targets. In this observational PK study, 62 samples from 13 patients were analysed using non-linear mixed-effects modelling. Different dosing regimens were evaluated using Monte Carlo simulations with ultrafiltration flow rates (UFRs) of 1000, 1500 and 2000mL/h. The probability of target attainment was calculated against a conservative (60% T>MIC) and a higher PK/PD target (100% T>MIC) against an MIC of 8mg/L, the clinical susceptibility breakpoint for Pseudomonas aeruginosa. A one-compartment model with between-subject variability (BSV) on clearance and volume of distribution (Vd) described the data adequately. UFR was supported as a covariate on both parameters. Typical values for clearance and Vd were 4.4L/h (BSV 37%) and 40.9L (BSV 20%), respectively. Dosing simulations showed failure to achieve both a conservative and a higher PK/PD target using a dose of 1g q12h for patients treated with a high UFR (≥1500mL/h). The dose of 2g q8h or 1g q6h leads to optimal target attainment for high UFR. One gram q8h is optimal for low UFR (≤1000mL/h). We found important variability in PK parameters. Dosing simulations show that a dose of 2g q8h or 1g q6h is needed to ensure rapid achievement of adequate levels if the UFR is ≥1500mL/h and 1g q8h for low UFR (≤1000mL/h).

Influence of systemic inflammatory response syndrome on the pharmacokinetics of vancomycin

Therapeutic drug monitoring (TDM) of vancomycin (VCM) is recommended to minimize its nephrotoxicity and maximize efficacy. Recently, the concept of systemic inflammatory response syndrome (SIRS) has been introduced to describe a clinical state resulting from the actions of complex intrinsic mediators in an acute-phase systemic response. However, there are few reports on the pharmacokinetics of VCM in patients with SIRS. This study investigated the effect of SIRS on the pharmacokinetics of VCM by analyzing the predictability of TDM and pharmacokinetic parameters in 31 non-SIRS patients and 52 SIRS patients, with stratification by SIRS score. The mean prediction error (ME) and mean absolute prediction error in SIRS score 2 and 3 patients differed from those in non-SIRS patients. The ME in the score 4 group showed a negative value. In the comparison of pharmacokinetic parameters by SIRS score, a significantly lower CL(vcm) value was observed at score 4 compared with scores 2 and 3, a higher Vd value was observed at score 4 compared with non-SIRS and at score 3, and a longer T1/2 was observed at score 2. In the comparison of patient characteristics by SIRS score, albumin, aspartate aminotransferase, and alanine aminotransferase levels showed differences among the scores. However, no correlation was observed between VCM pharmacokinetics and these three laboratory parameters. These findings suggest that the pharmacokinetics of VCM may be affected by the pathology of SIRS rather than by patient characteristics.

Simulation Comparison of Self-Heating Effects in Junctionless Nanowire Transistors and FinFET Devices

I. Introduction In order to reduce the short channel effects, junctionless nanowire transistors (JNT) can be a very interesting option once it avoids the lateral diffusion of impurities from source and drain regions to the channel. In addition, as they are a multiple gate devices it is possible to improve the electrostatic control over the channel charges [1-4]. While the channel in state-of-art nFinFET devices is undoped or lightly doped with p-type impurities, n-type JNT have a uniform heavy concentration of donor impurities from source to drain, which simplifies the device fabrication, once it dispenses complicated annealing techniques [5-6]. A schematic view and a longitudinal-section of n-type JNT and FinFET devices are shown on Fig. 1. As demonstrated in Fig. 1 JNT and FinFET are made using Silicon-On-Insulator (SOI) substrates. The thermal resistance associated to the buried oxide is in order of 100 times larger than silicon. Thus, both device alternatives can suffer from the difficulty of dissipating the heating of the silicon film caused by the Joule effect thanks to the current conduction, the so-called self-heating effect (SHE). This paper aims at comparing the self-heating effects (SHE) between FinFET and JNT devices using three-dimensional simulation. II. Devices Characteristics The comparison of SHE between JNT and FinFET devices by means of three-dimensional numerical simulations has been performed with Synopsys Sentaurus Device simulator [10]. Both JNT and FinFET devices have been simulated with gate oxide thickness of 2nm, channel length (L) of 0.5 µm and 1 µm, fin width (Wfin ) of 10 nm and 20nm, fin height (Hfin ) of 60 nm and 10nm. For the JNT P+ polysilicon was used as gate material. The JNT has been doped uniformly with 5x1018 cm-3 and 1x1019 cm-3 with n-type impurities, while the channel region of FinFET has been doped with 1x1015 cm-3with p-type impurities. In order to avoid the series resistance, the drain and source extensions were simulated with 5nm. The buried oxide thickness is 100 nm. The simulations have been done with isothermal grid at 300K where there is no self-heating effect (hereafter mentioned as without SHE) as well as with thermal contact at the buried oxide allowing the thermal generation to be accounted in the several grid points (hereafter mentioned as with SHE). III. Results and analysis Fig.2 and Fig. 3 present the behavior of the drain current as a function of gate voltage for FinFET and JNT. It is possible to compare the simulations with and without SHE, which present the same behavior i.e., there is no clear SHE due to the lower VD (50mV) resulting in lower static power (P = VD.ID ). According to the results obtained for lower VD, it is possible to confirm that those simulations are calibrated for analysis with higher VD values since their behavior are the same, independently if accounting or not the silicon film heating. On the other hand, when the VD increased to 1.5V, it is clearly visible the presence of the SHE in both JNT and FinFET as the current with non-isothermal grid is smaller than with isothermal one, thanks to the mobility degradation due to temperature rise. Finally, Fig. 4 shows the curves for the difference between drain current without SHE and with SHE (ΔID ), for the same VGT as a function of the power with SHE. The results show that, for the same power level, the ΔID is higher in FinFET devices i.e, the self-heating effect degrades the drain current much more than compared in JNT. Conclusions According to the results simulated, JNT suffer less self-heating effect when compared with a similar FinFET devices due to the decreasing of the mobility variation with temperature. acknoledgment The authors acknowledge CAPES, FAPESP and CNPq for the financial support. References D. Hisamoto et al., IEEE Transactions on Electron Devices, vol.47 , pp. 2320-2325, 2000. J. T. Park et al., IEEE Electron Device Letters, vol.22, pp. 405-406, 2001. J. P. Colinge et al., IEEE Electron Device Letters, vol.24, pp. 515-517, 2003. J. P. Colinge et al., Proceeding of IEEE International SOI Conference, pp. 1, 2009. C. W. Lee et al., Appl. Phys. Lett., vol. 94, no. 5, p. 053 511, Feb. 2009. J. P. Colinge et al., Nat. Nanotechnol., vol. 5, no. 3, pp. 225–229, Mar. 2010. G. Mariniello et al., Symposium on Microelectronics Technology and Devices (SBMICRO) 2013 v.1 p1-4. A. Kranti et al., Solid-State Electronics, vol. 65-66, pp. 33-37, Dec. 2011. S. Zimin et al., Proc. ICSICT, 1998, pp. 572-574. Sentaurus Device User’s Manual, Synopsys, 2013. Figure 1

On Voxel-by-voxel Accumulated Dose for Prostate Radiation Therapy using Deformable Image Registration

Since delivered dose is rarely the same with planned, we calculated the delivered total dose to ten prostate radiotherapy patients treated with rectal balloons using deformable dose accumulation (DDA) and compared it with the planned dose. The patients were treated with TomoTherapy using two rectal balloon designs: five patients had the Radiadyne balloon (balloon A), and five patients had the EZ-EM balloon (balloon B). Prostate and rectal wall contours were outlined on each pre-treatment MVCT for all patients. Delivered fractional doses were calculated using the MVCT taken immediately prior to delivery. Dose grids were accumulated to the last MVCT using DDA tools in Pinnacle3 TM (v9.100, Philips Radiation Oncology Systems, Fitchburg, USA). Delivered total doses were compared with planned doses using prostate and rectal wall DVHs. The rectal NTCP was calculated based on total delivered and planned doses for all patients using the Lyman model. For 8/10 patients, the rectal wall NTCP calculated using the delivered total dose was less than planned, with seven patients showing a decrease of more than 5% in NTCP. For 2/10 patients studied, the rectal wall NTCP calculated using total delivered dose was 2% higher than planned. This study indicates that for patients receiving hypofractionated radiotherapy for prostate cancer with a rectal balloon, total delivered doses to prostate is similar with planned while delivered dose to rectal walls may be significantly different from planned doses. 8/10 patients show significant correlation between rectal balloon anterior-posterior positions and some VD values.

Pharmacokinetic/pharmacodynamic profiling of imipenem in patients admitted to an intensive care unit in India: A nonrandomized, cross-sectional, analytical, open-labeled study.

Background and Aim:Widespread use of imipenem in intensive care units (ICUs) in India has led to the development of numerous carbapenemase-producing strains of pathogens. The altered pathophysiological state in critically ill patients could lead to subtherapeutic antibiotic levels. Hence, the aim of this study was to investigate the variability in the pharmacokinetic and pharmacodynamic profile of imipenem in critically ill patients admitted to an ICU in India.Materials and Methods:Plasma concentration of imipenem was determined in critically ill patients using high performance liquid chromatography, at different time points, by grouping them according to their locus of infection. The elimination half-life (t΍) and volume of distribution (Vd) values were also computed. The patients with imipenem trough concentration values below the minimum inhibitory concentration (MIC) and 5 times the MIC for the isolated pathogen were determined.Results:The difference in the plasma imipenem concentration between the gastrointestinal and the nongastrointestinal groups was significant at 2 h (P = 0.015) following drug dosing; while the difference was significant between the skin/cellulitis and nonskin/cellulitus groups at 2 h (P = 0.008), after drug dosing. The imipenem levels were above the MIC and 5 times the MIC for the isolated organism in 96.67% and 50% of the patients, respectively.Conclusions:The pharmacokinetic profile of imipenem does not vary according to the locus of an infection in critically ill patients. Imipenem, 3 g/day intermittent dosing, maintains a plasma concentration which is adequate to treat most infections encountered in patients admitted to an ICU. However, a change in the dosing regimen is suggested for patients infected with organisms having MIC values above 4 mg/L.

Pharmacokinetics Of Zinc In Broiler Chickens After Single Intraingluvial Administration With Zinc Aspartate

Summary The pharmacokinetics of zinc was investigated in broiler chickens after single crop intubation of 50 mg/kg 5% zinc aspartate suspension in 2% carboxymethyl cellulose solution. Blood serum zinc concentrations were assayed on a biochemical analyzer. The pharmacokinetics of zinc was evaluated using two approaches – compartmental method and non-compartmental analysis using pharmacokinetic software (TopFit, v. 2.0). After the intraingluvial application, zinc was rapidly absorbed (t1/2abs. =0.1040.02 h) by the alimentary system of birds attaining Cmax of 63.603.94 mol/ml by hour 0.77 (compartmental method) and Cmax =69.274.35 mol/ml by hour 0.92 h (non-compartmental method). It is characterized with a long biological half-life (t1/2) of 13.821.63 h (compartmental analysis) and 15.961.73 h (non-compartmental analysis) and long mean residence times (MRT) 20.122.35 h and 23.002.50 h, respectively. The distribution in blood and extracellular fluid was good as seen from Vd(area) values 0.770.05 l/kg (compartmental analysis) and 0.650.05 l/kg (non-compartmental analysis).

Comparison of the radiation hardness of silicon and silicon carbide

The radiation hardness of silicon carbide and silicon are compared. It is shown that one of the main characteristics of the radiation hardness of a semiconductor, the carrier removal rate Vd, strongly depends on its measurement conditions in the case of wide-gap semiconductors. A conclusion is made that comparison of the values of Vd, obtained at room temperature for SiC and Si, is not fully adequate from the physical standpoint.

Irradiation of sublimation-grown p-SiC with 0.9-MeV electrons

Carrier removal rate Vd has been determined in three sublimation-grown p-type SiC polytypes under irradiation with 0.9-MeV electrons. Known published data are used to compare the values of Vd in silicon carbide at room temperature in relation to the polytype, conductivity type, and fabrication technology. A model that accounts for the difference between the values of Vd is suggested.

Fogwater deposition modeling for terrestrial ecosystems: A review of developments and measurements

Recent progress in modeling fogwater (and low cloud water) deposition over terrestrial ecosystems during fogwater droplet interception by vegetative surfaces is reviewed. Several types of models and parameterizations for fogwater deposition are discussed with comparing assumptions, input parameter requirements, and modeled processes. The relationships among deposition velocity of fogwater (Vd) in model results, wind speed, and plant species structures associated with literature values are gathered for model validation. Quantitative comparisons between model results and observations in forest environments revealed differences as large as 2 orders of magnitude, which are likely caused by uncertainties in measurement techniques over heterogeneous landscapes. Results from the literature review show that Vd values ranged from 2.1 to 8.0 cm s−1 for short vegetation, whereas Vd = 7.7–92 cm s−1 and 0–20 cm s−1 for forests measured by throughfall-based methods and the eddy covariance method, respectively. This review also discusses the current understanding of the impacts of fogwater deposition on atmosphere-land interactions and over complex terrain based on results from numerical studies. Lastly, future research priorities in innovative modeling and observational approaches for model validation are outlined.

Therapeutic monitoring of intravenous vancomycin in a pediatric critical care unit

In critically ill pediatric patients vancomycin distribution and elimination is altered underscoring the need for pharmacokinetic monitoring; however the therapeutic trough ranges have not been validated for children. To describe the pharmacokinetics of intravenous vancomycin in critically ill pediatric patients using plasmatic vancomycin monitoring. Retrospective, descriptive study performed in a paediatric critical care unit. Vancomycin serum levels (Cmin and Cpeak), t ½ and Vd were determined in 1 month to 12 year old patients receiving ≥ 40 mg per-kg-per day. Plasmatic levels were measured at therapy onset and during follow up, evaluating the proportion of trough level determinations within therapeutic range, the average trough concentration, and the Cpeak achieved. A total of 65 plasmatic vancomycin monitorings were analysed in 45 patients. The average values for Ctrough, Cpeak, t1/2 and Vd were 10.4 μg/mL, 22.7 μg/mL, 3,1 h and 0.7 L/kg, respectively. An average dose of 47,1 mg/kg/day achieved initial Ctrough levels < 10 mg/mL in 60% of patients (n = 27), between 10 and 14,9 μg/mL in 22,2% (n = 10), between 15 to 20 μg/mL in 4% (n: 2), and > 20 μg/mL in 13,3% (n: 6). Vancomycin doses of 40 mg/kg/day are insufficient for critically ill paediatric patients without renal failure. A higher starting dose and monitoring of plasma levels must be considered in this population.

Field measurements of the atmospheric dry deposition fluxes and velocities of polycyclic aromatic hydrocarbons to the global oceans.

The atmospheric dry deposition fluxes of 16 polycyclic aromatic hydrocarbons (PAHs) have been measured, for the first time, in the tropical and subtropical Atlantic, Pacific, and Indian Oceans. Depositional fluxes for fine (0.7-2.7 μm) and coarse (>2.7 μm) aerosol fractions were simultaneously determined with the suspended aerosol phase concentrations, allowing the determination of PAH deposition velocities (vD). PAH dry deposition fluxes (FDD) bound to coarse aerosols were higher than those of fine aerosols for 83% of the measurements. Average FDD for total (fine + coarse) Σ16PAHs (sum of 16 individual PAHs) ranged from 8.33 ng m(-2)d(-1) to 52.38 ng m(-2)d(-1). Mean FDD for coarse aerosol's individual PAHs ranged between 0.13 ng m(-2)d(-1) (Perylene) and 1.96 ng m(-2)d(-1) (Methyl Pyrene), and for the fine aerosol fraction these ranged between 0.06 ng m(-2)d(-1) (Dimethyl Pyrene) and 1.25 ng m(-2)d(-1) (Methyl Chrysene). The estimated deposition velocities went from the highest mean vD for Methyl Chrysene (0.17-13.30 cm s(-1)), followed by Dibenzo(ah)Anthracene (0.29-1.38 cm s(-1)), and other high MW PAHs to minimum values of vD for Dimethyl Pyrene (<0.04 cm s(-1)) and Pyrene (<0.06 cm s(-1)). Dry depositional processes depend on the concentration of PAHs in the suspended aerosol, but also on physicochemical properties and environmental variables (vapor pressure, wind speed, and on the affinity of aerosols for depositing to the sea surface). Empirical parametrizations are proposed to predict the dry depositional velocities of semivolatile organic compounds to the global oceans.

Technical Note: An empirical algorithm estimating dry deposition velocity of fine, coarse and giant particles

Abstract. An empirical algorithm is developed for calculating bulk dry deposition velocity (Vd) of fine (PM2.5) – particles having a diameter of ≤ 2.5 μm), coarse (PM2.5−10 – particles having a diameter of 2.5–10 μm), and giant (PM10+ – particles having a diameter of &gt; 10 μm) atmospheric particles. The algorithm is developed from an empirical fit of Vd data calculated using the size-resolved Vd scheme of Zhang et al. (2001) with assumed lognormal size distributions of PM2.5, PM2.5−10 and PM10+. In the new algorithm, the surface deposition velocity (Vds) is parameterized as a simple linear function of friction velocity (u*) for PM2.5 and as a polynomial function of u* for both PM2.5−10 and PM10+ over all the 26 land use categories (LUCs). An adjustment factor as an exponential function of u* and leaf area index (LAI) is also applied to Vds of PM2.5−10 and PM10+ over 9 of the 26 LUCs that have variable LAI. Constant gravitational settling velocities are provided for PM2.5, PM2.5−10 and PM10+. Aerodynamic resistance between a reference height and the surface can be calculated using available analytical formulas from the literature. The bulk Vd of PM2.5, PM2.5−10 and PM10+ at the reference height can then be calculated by combining the gravitational settling velocity, aerodynamic resistance and the parameterized Vds. Vd values calculated using the new algorithm are within ±20% of those using the original size-resolved scheme for fine, coarse and giant particles. Uncertainties in Vd values from the new algorithm due to the pre-assumed size distributions are on the order of 20% for fine particles and on the order of a factor of 2.0 for coarse and giant particles. The new algorithm provides an alternative approach for calculating Vd of bulk aerosol particles. Vd of any particulate species can be simply estimated using this scheme as long as the mass fractions in fine, coarse and giant particles are known or can be assumed.