64 research outputs found
How to assess the role of transcranial magnetic stimulation in nicotine addiction
No full text[No abstract available]Daskalakis ZJ, 2006, EXP BRAIN RES, V174, P403, DOI 10.1007-s00221-006-0472-0; Fiore MC, 2008, TREATING TOBACCO USE; Koob GF, 2008, AM PSYCHIAT PUBLISHI, P3; Li XB, 2013, BIOL PSYCHIAT, V73, P714, DOI 10.1016-j.biopsych.2013.01.003; Nahas Z, 2001, BIOL PSYCHIAT, V50, P712, DOI 10.1016-S0006-3223(01)01199-4; O'Reardon JP, 2007, BIOL PSYCHIAT, V62, P1208, DOI 10.1016-j.biopsych.2007.01.018; Paterson NE, 2007, NEUROTOX RES, V11, P1; Perkins KA, 2001, EXP CLIN PSYCHOPHARM, V9, P243, DOI 10.1037--1064-1297.9.3.243; Strafella AP, 2001, J NEUROSCI, V21; Wing VC, 2012, BRAIN STIMUL0
Experimental Validation of a Computational Fluid Dynamics Model of The Upper Respiratory Airways Utilizing a Heat Transfer Approach
No full textTobacco smoking is one of the leading causes of death and disease globally. E-CIGS (e-cigarettes) were introduced in 2004 and marketed as a safer alternative. However, there is growing concern that instead of displacing combustible cigarette use, E-CIGS are attracting large numbers of nicotine-naïve youth who may not have smoked otherwise. Factors such as attractive flavors, advertising targeting youth, and the introduction of nicotine salts are responsible for the rise in prevalence among youth. Unlike free-base nicotine, nicotine salts are nonvolatile and do not induce throat harshness when inhaled. One regulatory approach that has been proposed is to set a floor on the throat harshness of electronic cigarette aerosols to deter previously nicotine-naïve youth from using them. However, the relationship between throat harshness and various electronic cigarette variables, including nicotine concentration, nicotine salt fraction, electrical power, and inhalation patterns, has not been closely examined. Recently, a theoretical model was developed to quantify nicotine deposition and throat harshness from key electronic cigarette variables. This model is partly derived from a computational fluid dynamics simulation of flow through the upper respiratory airways.
This thesis aims to experimentally validate the CFD simulations used in the 1-D model derivation of the segmental heat transfer correlations. The study involved the construction of a physical model that replicates the complex geometry of the human airway used in CFD computations and measuring the temperature at various points in the model. At the same time, air was drawn through it at different flow rates (1 SLPM to 20 SLPM ). Then, temperature measurements, appropriately non-dimensionalized, were compared to the CFD-predicted temperatures at the same flow rates. An experimental setup was developed to mimic the idealized boundary conditions used in the CFD model. The setup rigorously treated measurement uncertainty and optimized temperature measurement locations in the flow path. Key measurement outcomes included temperature, relative temperature change across locations, and relative temperature change across flow rates.
Experimental results aligned with the CFD predictions after optimizing for the dominant source of uncertainty, the position of the thermocouples. This experimental set-up was deemed a working approach to validating this computational fluid dynamic simulation across the upper respiratory tract. However, to improve this setup, a more precise method is needed to locate the thermocouples inside the physical model after its construction
Does mechanical vibration optimize macro interlock in cemented arthroplasty?
No full textBackground Cemented total hip replacement has a high success rate. However, failure is still a problem, and the major reason for failure is aseptic loosening. Current surgical methods to insert prosthetic stems into a cement filled bone cavity are purely manual. Our hypothesis was that the use of vibration can improve the quality of cement interdigitation for implantation of the femoral component in cemented total hip replacement. Methods We investigated the effect that mechanical vibration during insertion has on the area of interlock of the cement with the bone, the depth of cement penetration and the required insertion force. A reusable mold was used to simulate the femoral cavity and enabled quantification of these parameters under vibrated and nonvibrated conditions. Results Our results showed that the area of interlock of cement and mold together was increased by 2.25%, and the force required to insert the stem was decreased by around 30N when the stem was vibrated at a frequency of 36 Hz and an amplitude of 2mm. Conclusion Our results indicated that vibration of the femoral stem has a beneficial effect on the cement-bone interface and that vibrating the prosthesis during insertion into the cement significantly lowers the force needed for insertion
Reactive oxygen species emissions from supra- and sub-ohm electronic cigarettes
No full textElectronic cigarettes (ECIGs) are battery-powered devices that heat and vaporize solutions containing propylene glycol (PG) and/or vegetable glycerin (VG), nicotine and possible trace flavorants to produce an inhalable aerosol. The heating process can lead to the formation of reactive oxygen species (ROS), which are linked to various oxidative damage-initiated diseases. Several studies in the literature have addressed ROS emissions in ECIG aerosols, but the effects of power, ECIG device design and liquid composition on ROS are relatively unknown. In addition, ROS emissions have not been examined in the emerging high power, sub-Ohm device (SOD) category. In this study, an acellular 2',7'-dichlorofluorescin (DCFH) probe technique was optimized to measure ROS in ECIG aerosols. The technique was deployed to measure ROS emissions in SOD and supra-Ohm ECIGs while varying power, heater coil head design and liquid composition (PG/VG ratio and nicotine concentration). Liquids were made from analytical standards of PG, VG and nicotine and contained no flavorants. At high powers, ROS emissions in ECIGs and combustible cigarettes were similar. Across device designs, ROS emissions were uncorrelated with power (R 2 = 0.261) but were highly correlated with power per unit area (R 2 = 0.78). It was noticed that an increase in the VG percentage in the liquid yielded higher ROS flux, and nicotine did not affect ROS emissions. ROS emissions are a function of device design and liquid composition at a given power. For a given liquid composition, a promising metric for predicting ROS emissions across device designs and operating conditions is power per unit area of the heating coil. Importantly, ROS formation is significant even when the ECIG liquid consists of pure analytical solutions of PG and VG; it can therefore be viewed as intrinsic to ECIG operation and not solely a by-product of particular flavorants, contaminants or additives. © The Author(s) 2018
Direct dripping: A high-temperature, high- formaldehyde emission electronic cigarette use method
No full textIntroduction: Electronic cigarettes (ECIGs) electrically heat and vaporize a liquid solution to produce an inhalable nicotine-containing aerosol. Normally the electrical heater is fed the liquid via an automatic wick system. Some ECIG users, however, elect to directly drip liquid onto an exposed heater coil, reportedly for greater vapor production and throat hit. Use of such direct drip atomizers (DDAs) may involve greater exposure to non-nicotine toxicants due to the potentially higher temperatures reached by the coil. In this study we examined nicotine and volatile aldehyde (VA) emissions from one type of DDA under various use scenarios, and measured heater temperature. Methods: Aerosols were machine-generated from an NHALER 510 Atomizer powered by an eGo-T battery (Joyetech), using a common PG-based liquid and a fixed puffing regimen. Inter-drip interval, the number of puffs drawn between replenishing the liquid on the coil, was varied from 2-4 puffs/drip. Total particulate matter, nicotine, and VA yields were quantified. Heater temperature was monitored using an infrared camera. Results: Depending on the condition, VA emissions, including formaldehyde, greatly exceeded values previously reported for conventional ECIGs and combustible cigarettes, both per puff and per unit of nicotine yield. Increasing the inter-drip interval resulted in greater VA emissions, and lower total particulate matter and nicotine yields. Maximum heater coil temperature ranged from 130°C to more than 350°C. Conclusions: Due to the higher temperatures attained, DDAs are inherently likely to produce high toxicant emissions. The diversity of ECIG use methods, including potential off-label methods, should be considered as ECIG regulatory efforts proceed. © The Author 2015
Mechanistic Analysis of the Pyrolysis of Vegetable Glycerin: A Reactive Force Field – Molecular Dynamics Study
No full textVegetable glycerin (VG, C3H8O3) is a triol found as an additive in food, pharmaceutical, and vaping products. Studying the pyrolysis of VG with the resulting species and their rates of formation is crucial in further understanding the underlying effects on human health. In this paper, we utilize molecular dynamics (MD) and the reactive force field (ReaxFF) to investigate VG pyrolysis. VG decomposed at a rate of activation energy Es = 204.3 kJ/mol and pre-exponential factor A0= 1.42E+14 s-1. The main products were formaldehyde (FA), acetaldehyde (Ace), propanal (PA), acrolein (Acr), and glyoxal (GA). Both MD concentration profiles and transition state searches showed that FA, followed by AA, were the favored products. VG underwent several cracking mechanisms, with the cleavage of the hydroxyl group from the middle carbon having the lowest energy barrier (ΔG‡ = 259.97 kJ/mol). Longer-chained species formed via side reactions, resulting in methacrolein, crotonaldehyde, and pentanal, along with benzene and ethylbenzene intermediates. VG decomposition was found to be endothermic where the reaction rate increased with increasing system temperature. The Ea value for decomposition and formation reactions reached a threshold at a system density of 0.13 g/mL, while the collision factor generally increased. © Engineered Science Publisher LLC 202
Characteristics and toxicant emissions of JUUL electronic cigarettes
No full textIntroduction JUUL is an electronic cigarette (ECIG) with a compact form factor. It is prefilled with a liquid that is advertised to contain a high concentration of nicotine salt. JUUL commands 50% of the US ECIG market share, and its wide popularity with underage users has triggered unprecedented actions by the US FDA. Apart from its nicotine salt-containing liquid and compact form, a salient advertised design feature is a control circuit that limits the heating coil temperature, presumably reducing unwanted toxicants. In this study, several tobacco-flavoured JUUL devices were reverse engineered, and their aerosol emissions were studied. Methods Total nicotine and its partitioning (freebase and protonated), propylene glycol/vegetable glycerin (PG/VG) ratio, and carbonyls were quantified by gas chromatography (GC) and high performance liquid chromatography (HPLC). The temperature control functionality of JUUL was investigated using a temperature-controlled bath in which the coil was submerged. Results The liquid nicotine concentration was found to be 69 mg/mL, and the liquid and aerosol PG/VG ratio was found to be 30/70. In 15 puffs, JUUL emitted 2.05 (0.08) mg of nicotine, overwhelmingly in the protonated form. Carbonyl yields were significantly lower than those reported for combustible cigarettes, but similar to other closed-system ECIG devices. The heating coil resistance was 1.6 (0.66) Ohm, while the maximum power delivered by the JUUL device was 8.1 W. The control circuit limited the peak operating temperature to approximately 215C. Conclusions JUUL emits a high-nicotine concentration aerosol predominantly in the protonated form. JUUL's nicotine-normalised formaldehyde and total aldehyde yields are lower than other previously studied ECIGs and combustible cigarettes. © 2019 Author(s)
Effect of free-base and protonated nicotine on nicotine yield from electronic cigarettes with varying power and liquid vehicle
No full textNicotine in electronic cigarette (ECIG) liquids can exist in a free-base or protonated (or “salt”) form. Protonated nicotine is less aversive upon inhalation than free-base nicotine, and many ECIG manufacturers have begun marketing protonated nicotine products, often with high nicotine concentrations. Regulations intended to control ECIG nicotine delivery limit nicotine concentration but do not consider nicotine form. In this study, we systematically examined the effect of nicotine form on nicotine yield for varying powers and liquid vehicles. A Kanger Subox Mini-C tank ECIG (0.5 Ω) was used to generate aerosols at varying powers (5–45 W) from liquid solutions that contained either free-base or protonated nicotine at 15 mg/g concentration, with a liquid vehicle consisting of either propylene glycol (PG) or vegetable glycerin (VG), resulting in four different solutions (free-base/PG, free-base/VG, protonated/PG, and protonated/VG). Nicotine yield was quantified using gas chromatography-mass spectrometry. Nicotine yields were not influenced by nicotine form under any condition investigated. At each power level, PG-based liquids resulted in approximately double the nicotine yield of VG-based liquids. Nicotine concentrations in the aerosols matched those of the parent liquids for both the PG and VG conditions. Increasing power led to greater nicotine yield across all conditions. The amount of nicotine emitted by an ECIG is independent of whether the nicotine is free-base or protonated, however the liquid vehicle has a strong effect on yield. Regulations intended to limit nicotine emissions must consider not only nicotine concentration, but also liquid vehicle and device power. © 2020, The Author(s)
Free-Base and Total Nicotine, Reactive Oxygen Species, and Carbonyl Emissions from IQOS, a Heated Tobacco Product
No full textIntroduction: IQOS is an emerging heated tobacco product marketed by Philip Morris International (PMI). Because the tobacco in IQOS is electrically heated and not combusted, PMI claims that it generates significantly lower toxicant levels than combustible cigarettes. To date, a few independent studies have addressed IQOS toxicant emissions, and none have reported reactive oxygen species (ROS), and the form of the nicotine emitted by the device. Methods: In this study, IQOS aerosol was generated using a custom-made puffing machine. Two puffing regimens were used: Health Canada Intense and ISO. ROS, carbonyl compounds (CCs), and total nicotine and its partitioning between free-base and protonated forms were quantified in the IQOS aerosol by fluorescence, high-performance liquid chromatography, and gas chromatography, respectively. The same toxicants were also quantified in combustible cigarette aerosols for comparison. In addition, propylene glycol and vegetable glycerin were also measured in the IQOS tobacco and aerosol. Results: IQOS and combustible cigarettes were found to emit similar quantities of total and free-base nicotine. IQOS total ROS (6.26 ± 2.72 nmol H2O2/session) and CC emissions (472 ± 19 μg/session) were significant, but 85% and 77% lower than levels emitted by combustible cigarettes. Conclusions: IQOS emits harmful constituents that are linked to cancer, pulmonary disease, and addiction in cigarette smokers. For a given nicotine intake, inhalation exposure to ROS and CCs from IQOS is likely to be significantly less than that for combustible cigarettes. Implications: IQOS is PMI's new heated tobacco product. PMI claims that because IQOS heats and does not burn tobacco it generates low toxicant yields. We found that one IQOS stick can emit similar free-base and total nicotine yields as a combustible cigarette. A pack-A-day equivalent user of IQOS may experience significant inhalation exposure of ROS and CCs compared to background air. However, substituting IQOS for combustible cigarettes will likely result in far lower ROS and carbonyl inhalation exposure for a given daily nicotine intake. © 2018 The Author(s) 2018. Published by Oxford University Press on behalf of the Society for Research on Nicotine and Tobacco. All rights reserved. For permissions, please e-mail: [email protected]
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