Passive Vapor Research Articles

Effect of chronic vapor nicotine exposure on affective and cognitive behavior in male mice

Nicotine use is a leading cause of preventable deaths worldwide, and most of those who attempt to quit will relapse. While electronic cigarettes and other electronic nicotine delivery systems (ENDS) were presented as a safer alternative to traditional cigarettes and promoted as devices to help traditional tobacco smokers reduce or quit smoking, they have instead contributed to increasing nicotine use among youths. Despite this, ENDS also represent a useful tool to create novel preclinical animal models of nicotine exposure that more accurately represent human nicotine use. In this study, we validated a chronic, intermittent, ENDS-based passive vapor exposure model in mice, and then measured changes in multiple behaviors related to nicotine abstinence. First, we performed a behavioral dose curve to investigate the effects of different nicotine inter-vape intervals on various measures including body weight, locomotor activity, and pain hypersensitivity. Next, we performed a pharmacokinetic study to measure plasma levels of nicotine and cotinine following chronic exposure for each inter-vape interval. Finally, we utilized a behavior test battery at a single dosing regimen that produces blood levels equivalent to human smokers in order to characterize the effects of chronic nicotine, vehicle, or passive airflow and identified nicotine-induced impairments in cognitive behavior.

Evaluation of Passive Vapor Diffusion Samplers to Quantify Acetylene, Ethene, and Ethane in Groundwater

AbstractAcetylene, ethene, and ethane are products from the degradation of trichloroethene (TCE) in contaminated aquifers. However, the volatility of these gases makes it challenging to avoid excessive losses during sampling. The objective of this study was to compare the quantification of acetylene, ethene, and ethane using passive vapor diffusion (PVD) samplers vs. conventional low‐flow groundwater collection. Samples were obtained from 8 to 13 monitoring wells at three sites that show potential for biotic and abiotic degradation of TCE in fractured rock aquifers. Method reporting limits (MRLs) for the PVD samplers were 0.25 μg/L for acetylene (0.0094 μM) and 0.28 μg/L for ethene and ethane (0.0099 and 0.0092 μM, respectively); the MRLs for conventional low‐flow groundwater samples were ~40% higher. For two of the sites, the maximum concentrations of acetylene, ethene, and ethane obtained with the PVD samplers were comparable to the conventional low‐flow samples. The frequency of detection for these gases with the PVD samplers was also comparable to conventional low‐flow groundwater sampling. For one of the sites with higher levels of acetylene (maximum of 13 μg/L), the concentrations from the PVD samplers were approximately twofold higher than those with conventional low‐flow groundwater sampling. Based on robust detection of acetylene, ethene, and/or ethane, it appears likely that degradation of TCE is occurring at the three sites that were sampled. The use of PVD samplers can reduce the possibility of false negative results to provide another line of evidence in support of natural attenuation.

Asymmetric Sawtooth Microstructure-Induced Vapor Mobility for Suppressed Buoyancy Conditions: Terrestrial Experiment and Design for ISS Experiments

The lack of buoyancy forces in microgravity stagnates vapor bubbles on heated electronic surfaces, raising local surface temperatures above device operating limits. Though flow boiling can help dissipate higher heat fluxes, the addition of pumps and regulated flow loops increases design complexity for electronic systems. Passive directional motion of the fluid using an asymmetric sawtooth microstructure has demonstrated motion along the surface due to viscous forces. The current study explores the sawtooth microstructure in the nucleate boiling regime for a horizontal upward- and downward-facing orientation with varying sawtooth profiles (60°–30° and 75°–15°) in terrestrial gravity conditions as a precursor to the International Space Station (ISS) experiments. A laser powder bed fusion metal additive manufacturing technique was used to fabricate the test surfaces with 250- $\mu \text{m}$ nucleation sites located on the long slopes. For the test surface with cavities spaced 2-mm apart, the wall superheat was ~4 K lower compared to cavities spaced 1 mm apart in the upward-facing orientation. The downward-facing surface induced passive vapor mobility in the direction of the long slope, and a thin liquid film was observed between the vapor mass and microstructure. This liquid film thickness was predicted using a simplified force balance model modified from a prior parabolic flight experiment. The model predicted a uniform liquid film thickness of $49~\mu \text{m}$ for a vapor slug moving at 13.7 mm/s with the input heat flux at 1.25 W/cm2. These terrestrial tests in the adverse orientation suggest that the sawtooth microstructure will successfully induce vapor mobility in upcoming ISS microgravity experiments. Elements of the final flight ampoule, including the cooling zone, the two-stage pressure relief system, and the high-speed imagery setup, are discussed.

Vapor condensation with daytime radiative cooling

Significance Traditionally, the cooling for passive vapor condensation is mainly provided by convection and conduction. However, these mechanisms do not work when the vapor temperature is near the ambient air temperature. At such temperatures, radiative condensation remains effective. However, existing radiative vapor condensers must operate during the nighttime. Here, a novel radiative-cooling technique is applied to extend radiative condensation to both daytime and nighttime. The technique uses engineered thermal radiators that do not require lithography or other costly fabrication techniques and can be manufactured to cover large areas. When combined with traditional convective and conductive condensers, this passive technology can potentially double the water production rate for passive water technologies.

Appetitive, antinociceptive, and hypothermic effects of vaped and injected Δ-9-tetrahydrocannabinol (THC) in rats: exposure and dose-effect comparisons by strain and sex

Advances in drug vapor exposure systems have enabled evaluation of Δ-9-tetrahydrocannabinol (THC) vapor effects in laboratory animals. The purpose of this study was to 1) establish a range of parameters of THC vapor exposure in rats sufficient to produce a behavioral dose-effect curve in a battery of tasks sensitive to THC; and 2) to investigate sex differences in the effects of THC vapor exposure and THC injection (intraperitoneal, IP) on these behaviors in two strains of outbred rats. Male and female Sprague Dawley and Wistar rats (N = 22, 5–6/sex per group) received THC via passive vapor exposure (200 mg/mL; 5 conditions) and IP injection (1–20 mg/kg) in a within subject design. The effects of vaped and injected THC on appetite was determined using progressive ratio responding for food pellets. THC effects on nociception, measured using the tail withdrawal assay, and body temperature were also assessed during a 5-h test period for evaluation of time course of effects. Plasma THC concentrations were assessed after THC vapor and 10 mg/kg IP THC. THC vapor produced exposure-related increases and decreases in motivation to obtain food under the progressive ratio schedule. IP THC (3–20 mg/kg) reduced breakpoints. Vaped and injected THC produced exposure and dose-dependent antinociception and hypothermia. Sex and strain differences in THC effects were also observed. Plasma THC concentrations were higher after 10 mg/kg IP THC (152 ng/mL) compared to the highest vapor exposure condition tested (38 ng/mL), but magnitude of behavioral effects were comparable. THC vapor exposure produced reliable, dose orderly effects on food-maintained behavior, nociception, and body temperature that are comparable to effects of IP THC, although there were differences in the time course of behavioral outcomes.

Ultrahigh-efficiency desalination via a thermally-localized multistage solar still

Passive vapor generation systems combining interfacial solar heating and vaporization enthalpy recycling enable high-efficient low-cost desalination.

Modeling of passive vapor feed alkaline membrane direct methanol fuel cell

A two-dimensional model for passive vapor feed alkaline anion membrane direct methanol fuel cell (AAEM-DMFC) is developed to investigate the effects of open ratio, carbon dioxide (CO2) exit length, micro-porous layer (MPL) and porous layer’s hydrophobicity. The results show that decreasing the open ratio and enlarging the CO2 exit can relieve the methanol crossover. The fuel utilization efficiency can be significantly improved with the help of methanol recovery. The back-flow water direction shifts toward anode at low current density. The anode MPL (AMPL) can effectively mitigate the methanol intake from the tank and methanol crossover, however, the cathode MPL (CMPL) enhances the methanol intake and crossover at low current density. Moreover, the minimum methanol crossover can be achieved under an appropriate AMPL contact angle at high current density. Increasing the ACL hydrophobicity and vapor transport layer (VTL) hydrophilicity contributes to reducing methanol crossover. Overall, good water management and low methanol crossover can be achieved by optimizing porous layer structure, open ratio and carbon dioxide (CO2) exit length. The simulation results presented in this study can provide further guidance on the optimization of passive vapor feed AAEM-DMFC.

Assessing occupational mercury exposures and behaviours of artisanal and small-scale gold miners in Burkina Faso using passive mercury vapour badges

Artisanal and small-scale gold mining (ASGM) is a crucial economic activity in Burkina Faso, however it is associated with significant mercury exposure and health concerns. The aim of the present study was to assess the level of mercury (Hg) vapour exposures and occupational behaviours at a representative site using Hg vapour monitor badges and questionnaires. To our knowledge this is the first time that personal exposure to Hg vapour during ASGM activities has been reported. The study population were ASGM workers who completed a questionnaire (n=100) or participated with an occupational exposure assessment using commercially available passive Hg vapour samplers (n=44). Occupational exposure to Hg was high during open-air burn events with a time weighted average (TWA) exposure of 7026±6857µg/m3 for burners, and 1412±2870µg/m3 for bystanders. Most (82%) of the people present at the burn exceeded the Permissible Exposure Limit (PEL) of 100µg/m3, and 11% exceeded the level considered to be Immediately Dangerous to Life and Health (IDLH) of 10,000µg/m3. Even control workers who were not present at the burn exceeded the PEL (24%), likely due to legacy Hg contamination producing latent Hg releases to the atmosphere. Similarly, 86% of the miners at the burn and 59% of control workers had an 8-h TWA that exceeded the Recommended Exposures Limit (REL). Several occupational behaviours that may contribute to Hg exposures were documented. This study corroborates previous studies suggesting that Hg exposure during amalgam burning is very high, and demonstrates the plausibility of using passive vapour monitoring badges rather than costly and logistically difficult biomonitoring methods. Mercury reduction and elimination interventions are strongly needed to reduce Hg exposure in ASGM communities, particularly as countries come into compliance with the Minamata Convention.

Chronic intermittent ethanol inhalation increases ethanol self-administration in both C57BL/6J and DBA/2J mice

Inbred mouse strains provide significant opportunities to understand the genetic mechanisms controlling ethanol-directed behaviors and neurobiology. They have been specifically employed to understand cellular mechanisms contributing to ethanol consumption, acute intoxication, and sensitivities to chronic effects. However, limited ethanol consumption by some strains has restricted our understanding of clinically relevant endpoints such as dependence-related ethanol intake. Previous work with a novel tastant-substitution procedure using monosodium glutamate (MSG or umami flavor) has shown that the procedure greatly enhances ethanol consumption by mouse strains that express limited drinking phenotypes using other methods. In the current study, we employ this MSG-substitution procedure to examine how ethanol dependence, induced with passive vapor inhalation, modifies ethanol drinking in C57BL/6J and DBA/2J mice. These strains represent ‘high’ and ‘low’ drinking phenotypes, respectively. We found that the MSG substitution greatly facilitates ethanol drinking in both strains, and likewise, ethanol dependence increased ethanol consumption regardless of strain. However, DBA/2J mice exhibited greater sensitivity dependence-enhanced drinking, as represented by consumption behaviors directed at lower ethanol concentrations and relative to baseline intake levels. DBA/2J mice also exhibited significant withdrawal-associated anxiety-like behavior while C57BL/6J mice did not. These findings suggest that the MSG-substitution procedure can be employed to examine dependence-enhanced ethanol consumption across a range of drinking phenotypes, and that C57BL/6J and DBA/2J mice may represent unique neurobehavioral pathways for developing dependence-enhanced ethanol consumption.

High-temperature passive direct methanol fuel cells operating with concentrated fuels

Conventionally, passive direct methanol fuel cells (DMFC) are fed with diluted methanol solutions and can hardly be operated at elevated temperatures (>120 °C) because the ionic conductivity of Nafion-type proton exchange membranes depends strongly on water content. Such a system design would limit its energy density and power density in mobile applications. In this communication, a passive vapor feed DMFC capable of operating with concentrated fuels at high temperatures is reported. The passive DMFC proposed in this work consists of a fuel reservoir, a perforated silicone sheet, a vapor chamber, two current collectors and a membrane electrode assembly (MEA) based on a phosphoric acid doped polybenzimidazole (PBI) membrane. The experimental results reveal that the methanol crossover through a PBI membrane is substantially low when compared with the Nafion membranes and the PBI-based passive DMFC can yield a peak power density of 37.2 mW cm−2 and 22.1 mW cm−2 at 180 °C when 16 M methanol solutions and neat methanol are used respectively. In addition, the 132 h discharge test indicates that the performance of this new DMFC is quite stable and no obvious performance degradation is observed after activation, showing its promising applications in portable power sources.

On-Site Vapor-Phase Analysis as a Novel Approach for Monitoring Groundwater Wells

The results of comprehensive field testing of on-site vapor-phase-based groundwater monitoring methods are presented to demonstrate their utility as a robust and cost-effective approach for rapidly obtaining volatile organic compounds (VOCs) concentration data from a monitoring well. These methods—which rely on sensitive, commercially available field equipment to analyze vapor in equilibrium with groundwater—proved easy to implement and can be tailored to site-specific needs, including multilevel sampling. During field testing, low-flow groundwater concentrations could be reasonably estimated using submerged passive vapor diffusion samplers or field equilibration of collected groundwater (R2 = 0.85 to 0.96). These two methods are not as reliant on in-well mixing to overcome vertical stratification within wells as simpler headspace methods. The importance of well and aquifer-specific factors on concentration data (and therefore method selection) is highlighted, including the effect of changing in-well patterns due to seasonal temperature gradients. Results indicated that vertical stratification was relatively limited within the set of wells included in these studies, resulting in similar performance for short depth-discrete passive vapor diffusion samplers (constructed from 40-mL vials) and longer samplers (2.5 to 5 feet in length) designed to cover a larger portion of the screened interval. A year-long, multi-event evaluation demonstrated that vapor-phase-based monitoring methods are no more variable than conventional groundwater monitoring methods, with both types subject to similar spatial and temporal variability that can be difficult to reduce. Vapor sampling methods represent a promising approach for estimation of groundwater concentrations by reducing the cost liabilities associated with monitoring while providing a more sustainable approach.

Review on utilization of the pervaporation membrane for passive vapor feed direct methanol fuel cell

The Direct Methanol Fuel Cell (DMFC) is a promising portable power source for mobile electronic devices because of its advantages including easy fuel storage, high energy density, low temperature operation and compact structure. In DMFC, methanol is used as a fuel source where it can be fed in liquid or vapor phase. However, the vapor feed DMFC has an advantage over the liquid feed system as it has the potential to have a higher operating temperature to increase the reaction rates and power outputs, to enhance the mass transfers, to reduce methanol crossover, reliable for high methanol concentration and it can increase the fuel cell performance. Methanol vapor can be delivered to the anode by using a pervaporation membrane, heating the liquid methanol or another method that compatible. Therefore, this paper is a review on vapor feed DMFC as a better energy source than liquid feed DMFC, the pervaporation membrane used to vaporize methanol feed from the reservoir and its applications in vapor feed DMFC.

Study on a Passive Vapor Feed Direct Methanol Fuel Cell with High Methanol Concentration

Abstrac t—An extensive research has been carried out to improve the performance of direct methanol fuel cells (DMFCs) using low methanol concentration below 5 M either in active or passive conditions due to methanol crossover (MCO) problem which the methanol crosses over the membrane and reacts directly with oxygen at cathode. However, a low methanol concentration leads to a low energy density of the fuel cell system and a short runtime which cannot meet the requirement of commercialization. Therefore, it is important to use a high concentration of methanol in DMFC to achieve a high energy density. This study was done to improve the performance of passive vapor feed DMFC by using high methanol concentrations from 12 M (molarity) to neat methanol. From the results obtained, it was showed that the performance of passive vapor feed DMFC that used high methanol concentration improved. It was a linear dependence of current density on methanol concentration which is the current density increased when the methanol concentration increased up to neat. The linear dependence of current density on the concentration suggested that the cell operation was under the rate controlling by the methanol transport. Therefore, it can conclude that high methanol concentration can leads to high energy density achieved by the DMFCs.

Experimental Characterization of Capillary-Fed Carbon Nanotube Vapor Chamber Wicks

The thermal performance of passive vapor chamber heat spreaders can be improved by enhancing evaporation from the internal wick structure. A wick structure that integrates conventional copper screen mesh and carbon nanotubes (CNTs) is developed and characterized for increased heat transport capability and reduced thermal resistance. The high-permeability mesh provides for a low-resistance liquid flow path while the carbon nanotubes, with their high thermal conductivity and large surface area, help reduce conduction and phase-change resistances. The wicks are fabricated by sintering a copper mesh on a multilayer substrate consisting of copper and molybdenum. CNTs are grown on to this mesh and a submicron layer of copper is evaporated on to the CNTs to improve wettability with water and wicking. Samples grown under varying degrees of positive bias voltage and varying thicknesses of post-CNT-growth copper evaporation are fabricated to investigate the effect of surface morphology variations. The resultant boiling curves indicate that micro/nano-integrated wicks fabricated with higher positive bias voltages during CNT synthesis coupled with thicker copper coatings produce lower wick thermal resistances. Notably, heat fluxes at the heater surface of greater than 500 W/cm2 were supported without a critical heat flux condition being reached.

Abstract 4474: Occupational exposure to benzene and leukocyte telomere length

Abstract Benzene is an important industrial solvent and a ubiquitous environmental contaminant. IARC has classified benzene as a human leukemogen (Group 1) and a possible lymphomagen. We have previously demonstrated that exposure to benzene results in hematotoxic effects in a cross-sectional study, and that longer telomere length may be associated with non-Hodgkin lymphoma (NHL) in a prospective study conducted in the general population. To further explore the biologic plausibility that benzene may be a lymphomagen, we tested if leukocyte telomere length was altered in a cross-sectional biomarker study of workers occupationally exposed to benzene in Shanghai, China. Forty-four benzene-exposed workers were enrolled from factories that used benzene, along with 44 age and gender-matched controls from two workplaces in the same geographic area that did not use benzene or other chemicals associated with bone marrow toxicity. Personal exposure measurements were obtained for each exposed worker using passive 3M organic vapor monitoring badges. Blood samples were collected from each worker, and leukocyte telomere length was measured using a quantitative PCR procedure. Linear regression using the natural logarithm of telomere length and adjusting for potential confounders was used to test for differences in telomere length between exposed workers and controls. The median benzene personal air level was 31 ppm in the exposed workers. Compared to unexposed workers, the mean leukocyte telomere length was increased by about 8% in all benzene-exposed workers (p=0.05). There was a 4% increase in workers exposed to < 31 ppm and a 12% increase in workers exposed to > 31 ppm and a statistically significant dose-dependent increase in telomere length with increasing levels of benzene exposure in air (ptrend = 0.01). Some preliminary evidence has suggested that benzene exposure may stimulate telomerase expression in lymphocytes and other cell lines. Given that longer telomere length has been associated with risk of NHL, our findings provide some support for the biologic plausibility that benzene is a lymphomagen but require replication in larger studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4474. doi:1538-7445.AM2012-4474

Analytical model for uni-directional flow passive soil vapour extraction system

An analytical one-dimensional model has been developed to examine the uni-directional barometric pumping in passive Soil Vapour Extraction (SVE) system. The model is applicable to a special case in which a radial flow field is insignificant. The system considered contains two unsaturated zone layers, an upper contaminated low permeability layer and a lower high permeability layer contains a well screens. The numerical simulations results show that an increase in upper layer thickness results in increase in cumulative displacement. It is clear that to extract relatively effective amount of air, upper layer thickness should be at least few tens meters.

Microfabricated passive vapor preconcentrator/injector designed for microscale gas chromatography

The design, fabrication, and preliminary testing of a micromachined-Si passive vapor preconcentrator/injector (μPPI) are described. Intended for incorporation in a gas chromatographic microsystem (μGC) for analyzing organic vapor mixtures, the μPPI captures vapors from the air at a known rate by means of passive diffusion (i.e., without pumping) and then desorbs the vapor sample thermally by means of an integrated heater and injects it downstream (with pumping). The μPPI chip comprises a 1.8 μL deep reactive-ion-etched (DRIE) Si cavity with a resistively heated membrane floor and a DRIE-Si cap containing >1500 parallel diffusion channels, each 54 × 54 × 200 μm. The cavity is packed with 750 μg of a commercial graphitized carbon adsorbent. Fluidic and heat-transfer modeling was used to guide the design process to ensure power-efficient sample transfer during thermal desorption. Experiments performed with toluene at concentrations of ~1 ppm gave a constant sampling rate of 9.1 mL min(-1) for up to 30 min, which is within 2% of theoretical predictions and corresponds to a linear dynamic mass uptake range of ~1 μg. The cavity membrane could be heated to 250 °C in 0.23 s with 1 W of applied power and, with 50 mL min(-1) of suction flow provided by a downstream pump, yielded >95% desorption/injection efficiency of toluene samples over an 8-fold range of captured mass.

Field Investigation of Vapor‐Phase‐Based Groundwater Monitoring

The use of in‐field analysis of vapor‐phase samples to provide real‐time volatile organic compound (VOC) concentrations in groundwater has the potential to streamline monitoring by simplifying the sample collection and analysis process. A field validation program was completed to (1) evaluate methods for collection of vapor samples from monitoring wells and (2) evaluate the accuracy and precision of field‐portable instruments for the analysis of vapor‐phase samples. The field program evaluated three vapor‐phase sample collection methods: (1) headspace samples from two locations within the well, (2) passive vapor diffusion (PVD) samplers placed at the screened interval of the well, and (3) field vapor headspace analysis of groundwater samples. Two types of instruments were tested: a field‐portable gas chromatograph (GC) and a photoionization detector (PID). Field GC analysis of PVD samples showed no bias and good correlation to laboratory analysis of groundwater collected by low‐flow sampling (slope = 0.96, R2 = 0.85) and laboratory analysis of passive water diffusion bag samples from the well screen (slope = 1.03; R2 = 0.96). Field GC analysis of well headspace samples, either from the upper portion of the well or at the water‐vapor interface, resulted in higher variability and much poorer correlation (consistently biased low) relative to laboratory analysis of groundwater samples collected by low‐flow sample or passive diffusion bags (PDBs) (slope = 0.69 to 0.76; R2 = 0.60 to 0.64). These results indicate that field analysis of vapor‐phase samples can be used to obtain accurate measurements of VOC concentrations in groundwater. However, vapor samples collected from the well headspace were not in equilibrium with water collected from the well screen. Instead, PVD samplers placed in the screened interval represent the most promising approach for field‐based measurement of groundwater concentrations using vapor monitoring techniques and will be the focus of further field testing.

A Key Factor for the Actual Application of a Vapor Feed Passive DMFC Operated with High Concentration of Methanol

The supply of water to the anode from the cathode through the electrolyte membrane is a critical factor for the operation of vapor feed DMFC at high methanol concentrations. A comparative study in a passive vapor feed DMFC employing a PCP on the anode surface had been carried out with and without a hydrophobic cathode filter. Compact and a noncompact cells were fabricated and used. The noncompact cell could be operated with high methanol concentrations of even 100 wt%, while the compact one could not be operated with 90 wt% methanol. This was related to the deficiency of water at the anode surface in the compact cell design, where heat dissipation was not enhanced. For the supply of water to the anode surface, the employment of a hydrophobic filter on the cathode surface was necessary, especially for the compact cell.

Analysis of a passive vapor feed direct methanol fuel cell

The passive fuel delivery systems presented thus far have utilized the liquid phase as a transport medium. However, since methanol is a highly volatile component, the vapor phase can be utilized to transport methanol to the fuel cell. A one-dimensional analysis of the transport of methanol from the fuel source to the fuel cell is developed here, with the goal of describing the key issues. Operation of the fuel cell is further characterized with a full numerical model that captures transience, and also addresses fuel, water, and thermal management issues. The results show that the condensation of water onto a methanol evaporation pad needs to be limited if the operation time of the fuel cell is to increase.