9 research outputs found
Linking a dermal permeation and an inhalation model to a simple pharmacokinetic model to study airborne exposure to di(n-butyl) phthalate
Six males clad only in shorts were exposed to high levels of airborne di(n-butyl) phthalate (DnBP) and diethyl phthalate (DEP) in chamber experiments conducted in 2014. In two 6 h sessions, the subjects were exposed only dermally while breathing clean air from a hood, and both dermally and via inhalation when exposed without a hood. Full urine samples were taken before, during, and for 48 h after leaving the chamber and measured for key DnBP and DEP metabolites. The data clearly demonstrated high levels of DnBP and DEP metabolite excretions while in the chamber and during the first 24 h once leaving the chamber under both conditions. The data for DnBP were used in a modeling exercise linking dose models for inhalation and transdermal permeation with a simple pharmacokinetic model that predicted timing and mass of metabolite excretions. These models were developed and calibrated independent of these experiments. Tests included modeling of the “hood-on” (transdermal penetration only), “hood-off” (both inhalation and transdermal) scenarios, and a derived “inhalation-only” scenario. Results showed that the linked model tended to duplicate the pattern of excretion with regard to timing of peaks, decline of concentrations over time, and the ratio of DnBP metabolites. However, the transdermal model tended to overpredict penetration of DnBP such that predictions of metabolite excretions were between 1.1 and 4.5 times higher than the cumulative excretion of DnBP metabolites over the 54 h of the simulation. A similar overprediction was not seen for the “inhalation-only” simulations. Possible explanations and model refinements for these overpredictions are discussed. In a demonstration of the linked model designed to characterize general population exposures to typical airborne indoor concentrations of DnBP in the United States, it was estimated that up to one-quarter of total exposures could be due to inhalation and dermal uptake
Hybrid Data Augmentation and Dual-Stream Spatiotemporal Fusion Neural Network for Automatic Modulation Classification in Drone Communications
Automatic modulation classification (AMC) is one of the most important technologies in various communication systems, including drone communications. It can be applied to confirm the legitimacy of access devices, help drone systems better identify and track signals from other communication devices, and prevent drone interference to ensure the safety and reliability of communication. However, the classification performance of previously proposed AMC approaches still needs to be improved. In this study, a dual-stream spatiotemporal fusion neural network (DSSFNN)-based AMC approach is proposed to enhance the classification accuracy for the purpose of aiding drone communication because SDDFNN can effectively mine spatiotemporal features from modulation signals through residual modules, long-short term memory (LSTM) modules, and attention mechanisms. In addition, a novel hybrid data augmentation method based on phase shift and self-perturbation is introduced to further improve performance and avoid overfitting. The experimental results demonstrate that the proposed AMC approach can achieve an average classification accuracy of 63.44%, and the maximum accuracy can reach 95.01% at SNR = 10 dB, which outperforms the previously proposed methods
Measurement of Phthalates in Skin Wipes: Estimating Exposure from Dermal Absorption
This study has determined the levels
of six phthalates (dimethyl
phthalate (DMP), diethyl phthalate (DEP), di(isobutyl) phthalate (DiBP),
di(<i>n</i>-butyl) phthalate (DnBP), butyl benzyl phthalate
(BBzP), and di(2-ethylhexyl) phthalate (DEHP)) in skin wipes; examined
factors that might influence the levels, including body location,
time of sampling, and hand-washing; and estimated dermal absorption
based on the measured levels. Skin wipes were collected from the forehead,
forearm, back-of-hand, and palm of 20 participants using gauze pads
moistened with isopropanol. DiBP, DnBP, and DEHP were most frequently
detected; DEHP levels were substantially higher than DnBP and DiBP
levels, and DnBP levels were somewhat lower than DiBP levels. The
levels differed at different body locations, with palm > back-of-hand
> forearm ≥ forehead. Repeated wipe sampling from six participants
over a 1 month period indicated that levels at the same body location
did not vary significantly. The estimated median total dermal absorption
from skin surface lipids on the palm, back-of-hand, arm, and head
are 0.48, 0.68, and 0.66 (μg/kg)/day for DiBP, DnBP, and DEHP,
respectively. These estimates are roughly 10–20% of the total
uptake reported for Chinese adults and suggest that dermal absorption
contributes significantly to the uptake of these phthalates. Washing
with soap and water removed more than 50% of the phthalates on the
hands and may be a useful tool in decreasing aggregate phthalate exposure
Impact of Clothing on Dermal Exposure to Phthalates: Observations and Insights from Sampling Both Skin and Clothing
Clothing can either
retard or accelerate dermal exposure to phthalates.
To investigate the impact of clothing on dermal exposure to six phthalates
(DMP/DEP/DiBP/DnBP/BBzP/DEHP) in real environments, two sets of experiments
have been conducted: (1) Skin wipes were collected from 11 adults
to examine the phthalate levels on both bare-skin (hand/forehead)
and clothing-covered body locations (arm/back/calf); (2) Five adults
were asked to wear just-washed jeans for 1 day (1<sup>st</sup> experiment),
5 days (2<sup>nd</sup> experiment), and 10 days (3<sup>rd</sup> experiment).
Phthalate levels on their legs were measured on selected days during
the wearing period, and phthalate levels in the jeans were measured
at the end of each experiment and again after washing. Measured phthalate
levels on body locations covered by clothing were lower than those
on uncovered locations, but still substantial. Dermal uptake would
be underestimated by a factor of 2 to 5 if absorption through body
locations covered by clothing were neglected. Phthalate levels in
the jeans and on the legs increased with the wearing time. However,
the levels in the jeans and on the legs were not strongly correlated,
indicating that other pathways, e.g, contact with bedding or bedclothes,
likely contribute to the levels on the legs. The efficiency with which
laundering washing removed phthalates from the jeans increased with
decreasing <i>K</i><sub>ow</sub>; median values ranged from
very low (<5%) for DEHP to very high (∼75%) for DMP