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  • Author: Chuan Liu x
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Abstract

Accurate measurements of cigarette coal temperature are essential to understand the thermophysical and thermo-chemical processes in a burning cigarette. The last system-atic studies of cigarette burning temperature measurements were conducted in the mid-1970s. Contemporary cigarettes have evolved in design features and multiple standard machine-smoking regimes have also become available, hence there is a need to re-examine cigarette combustion. In this work, we performed systematic measurements on gas-phase temperature of burning cigarettes using an improved fine thermocouple technique. The effects of machine-smoking parameters (puff volume and puff duration) and filter ventilation levels were studied with high spatial and time resolutions during single puffs. The experimental results were presented in a number of differ-ent ways to highlight the dynamic and complex thermal processes inside a burning coal. A mathematical distribution equation was used to fit the experimental temperature data. Extracting and plotting the distribution parameters against puffing time revealed complex temperature profiles under different coal volume as a function of puffing intensities or filter ventilation levels. By dividing the coal volume prior to puffing into three temperature ranges (low-temperature from 200 to 400 °C, medium-temperature from 400 to 600 °C, and high-temperature volume above 600 °C) by following their development at different smoking regimes, useful mechanistic details were obtained. Finally, direct visualisation of the gas-phase temperature through detailed temperature and temperature gradient contour maps provided further insights into the complex thermo-physics of the burning coal. [Beitr. Tabakforsch. Int. 26 (2014) 191-203]

Summary

A previously established method based on headspace solidphase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography (GC×GC) coupled to time-of-flight mass spectrometry (TOFMS) has been used to evaluate and compare the profiles of semi-volatile compounds present in mainstream tobacco smoke particulate matter trapped on glass fibre filters for two types of cigarettes differing only in filter design. In the first cigarette, the filter cavity contained approximately 60 mg of a weakly basic macroporous polystyrene resin cross-linked with divinyl benzene and with surface amine functionality (CR20), whereas in the second cigarette, it was empty.

Relative quantitative analysis, chemical identification, and chemical grouping allowed the use of both parametric and non-parametric analyses to identify differences in the chemical composition of the smokes from these cigarettes. The analysis demonstrated that in addition to the selective partial removal of volatile carbonyls and HCN demonstrated previously, CR20 selectively, but incompletely removed 316 compounds from the particulate phase of cigarette smoke, mainly aryl and aromatic hydrocarbons as well as other more volatile species. In contrast, the relative proportion of amines, hydroxylated aromatic compounds and less volatile species was increased in the smoke from the cigarette containing CR20 in the filter.

Our findings show that high resolution GC techniques combined with mass spectrometry and chemometric approaches are powerful tools for deconvoluting the complexity of combustion aerosols, as well as helping to identify changes in chemical composition resulting from modifications to cigarette designs. [Beitr. Tabakforsch. Int. 28 (2019) 231–249]

Summary

To study the effects of tobacco rod circumference on cigarette combustion status, cigarettes were made with three different circumferences of 24 mm, 20 mm, 17 mm and otherwise identical construction. Their combustion characteristics, including combustion coal volume, characteristic temperature distribution, heating rate, instantaneous burn rate, and yields of selected mainstream smoke chemicals, were systematically measured. The results indicated that the cigarettes with the lowest circumference of 17 mm showed higher combustion temperatures with a smaller coal volume. The maximum instantaneous burn rate was distinctly different for the three cigarettes, from 1.84 mm/s to 2.48 mm/s, when their circumference was reduced from 24 mm to 17 mm. The tobacco mass consumption per puff showed a negative trend when the circumference decreased. The majority of the chemical compounds (16 of 21) measured in mainstream smoke decreased when the circumference was reduced, except for formaldehyde, while the yields of the chemical compounds produced per weight of cut tobacco, consumed during puffing, showed an obverse trend.

Abstract

Background

The aim of the study was to evaluate short-term safety and efficacy of simultaneous modulated accelerated radiation therapy (SMART) delivered via helical tomotherapy in patients with nasopharyngeal carcinoma (NPC).

Methods

Between August 2011 and September 2013, 132 newly diagnosed NPC patients were enrolled for a prospective phase II study. The prescription doses delivered to the gross tumor volume (pGTVnx) and positive lymph nodes (pGTVnd), the high risk planning target volume (PTV1), and the low risk planning target volume (PTV2), were 67.5 Gy (2.25 Gy/F), 60 Gy (2.0 Gy/F), and 54 Gy (1.8 Gy/F), in 30 fractions, respectively. Acute toxicities were evaluated according to the established RTOG/EORTC criteria. This group of patients was compared with the 190 patients in the retrospective P70 study, who were treated between September 2004 and August 2009 with helical tomotherapy, with a dose of 70-74 Gy/33F/6.5W delivered to pGTVnx and pGTVnd.

Results

The median follow-up was 23.7 (12–38) months. Acute radiation related side-effects were mainly problems graded as 1 or 2. Only a small number of patients suffered from grade 4 leucopenia (4.5%) or thrombocytopenia (2.3%). The local relapse-free survival (LRFS), nodal relapse-free survival (NRFS), local-nodal relapse-free survival (LNRFS), distant metastasis-free survival (DMFS) and overall survival (OS) were 96.7%, 95.5%, 92.2%, 92.7% and 93.2%, at 2 years, respectively, with no significant difference compared with the P70 study.

Conclusions

Smart delivered via the helical tomotherapy technique appears to be associated with an acceptable acute toxicity profile and favorable short-term outcomes for patients with NPC. Long-term toxicities and patient outcomes are under investigation.

Summary

A diffusion denuder apparatus has been used to investigate the gas-particle partitioning of formaldehyde, acetaldehyde, acrolein and crotonaldehyde in cigarette mainstream smoke (MS), compounds that are of interest owing to their toxicity and near quantitative retention in the body during cigarette smoking. Formaldehyde showed the best performance in denuder experiments with simple aldehyde-air mixtures owing to the relatively fast rate of the heterogeneous reaction formaldehyde(g) + dinitrophenylhydrazine(s) 6 hydrazone(s). Analysis with the GORMLEY-KENNEDY equation revealed that formaldehyde denuder removal approached, but did not attain, complete efficiency even under optimized operational conditions. Acetaldehyde, acrolein and crotonaldehyde were trapped with considerably lower efficiency than formaldehyde under the denuder conditions used, and more effective denuder wall coatings would be required to examine gas-particle partitioning of these other carbonyls. The proportion of form-aldehyde in the smoke particulate phase initially entering the denuder was > 99%, but loss of formaldehyde from the smoke particles was relatively rapid leading to 35%–61% deposition over the denuder length. The temperature dependence of formaldehyde deposition in the denuder was well predicted using Henry’s law constant for aqueous formaldehyde solutions. These observed properties of form-aldehyde are primarily due to reversible reactions of formaldehyde with water in cigarette smoke leading to the much less volatile species methanediol, its oligomers and hydrate. These data suggest that cigarette smoke inhalation is likely to expose the deeper-lung generations of smokers to greater relative formaldehyde exposure, and greater genotoxic risk at those generations than might occur through inhalation of formaldehyde vapour alone.

Risk assessments of formaldehyde in cigarette smoke should be updated to recognise this modified risk profile. [Beitr. Tabakforsch. Int. 29 (2020) 2–20]

Summary

The thermo-oxidative decomposition of lovage (Levisticum officinale) and davana (Artemisia pallens) essential oils has been studied by pyrolysis-gas chromatography/mass spectrometry in 9% oxygen and 91% nitrogen atmosphere at 300 °C to simulate low-temperature tobacco heating conditions. Both lovage and davana oils contain numerous chemical substances; the main components of both oils are various oxygen-containing compounds. Isobenzofuranones are the most important constituents of lovage oil, and their relative intensity changed significantly during oxidative pyrolysis. (Z)-ligustilide underwent two kinds of decomposition reactions: an aromatization reaction resulting in the formation of butylidenephthalide and the scission of the lactone ring with the elimination of carbon dioxide or carbon monoxide. Davanone is the main component of davana oil, which did not decompose considerably during low-temperature oxidative pyrolysis. However, the relative yield of the second most intensive component, bicyclogermacrene, reduced markedly due to bond rearrangement reactions. Davana ether underwent oxidation reactions leading to the formation of various furanic compounds. The changes in the composition of both essential oils could be interpreted in terms of bond splitting, intramolecular rearrangement mechanisms and oxidation reactions of several constituents during low-temperature oxidative pyrolysis. The applied thermo-oxidative method was found to be suitable to study the stability of the essential oils and monitor the decomposition products under simulated tobacco heating conditions. In spite of the complicated composition of the essential oils, no evidence for interaction between the oil components was found. [Beitr. Tabakforsch. Int. 29 (2020) 27–43]

Summary

Background: Combustion as well as pyrolysis of tobacco greatly affect the type and levels of toxicants in cigarette smoke. We previously developed an approach to combine simultaneous temperature and pressure measurements with fast in-situ microprobe chemical sampling inside a burning cigarette, producing a series of temperature and gas-flow velocity maps that characterize this dynamic system in response to externally applied air flow.

Aim: Two cigarette types differing only in diameter were puffed under ISO 3308 and Health Canada Intense (HCI) regimes to further understand the dynamic interaction of air flow and cigarette design parameters on tobacco combustion and pyrolysis by applying the thermophysical and thermo-chemical mapping approach.

Methods: Three types of sampling probes were inserted, which are thermocouple arrays for gas-phase temperature, quartz tubes for pressure measurement, and a heated sampling microprobe coupled to a single-photon soft ionisation mass spectrometer for chemical analysis. Two kinds of similarly constructed cigarettes with the same blend were analysed: superslim (17 mm circumference) and king-size (24 mm circumference).

Synchronization among the sampled signals was achieved by mapping two probes (e.g., temperature/chemistry or temperature/pressure) at a time. The physical and chemical events were visualised and compared between the cigarettes and puffing regimes.

Results: A series of temperature, pressure, and chemical maps were obtained for the superslim and king-size cigarettes under ISO and HCI conditions. The pressure in the burning cigarette was higher in the superslim cigarette, and the temperature distribution differed between the two cigarette formats. As expected, temperatures and pressures were higher under HCI puffing than under ISO puffing for both cigarette formats. Thermochemical maps for e.g., benzene and nitric oxide formation were qualitatively similar between the superslim and king-size cigarettes. For other substances the distribution was markedly different.

Conclusion: The application of multi-probe in-situ chemical sampling is suitable to analyse highly dynamic combustion and pyrolysis processes occurring inside the two types of cigarettes. Ultimately, a direct comparison of cigarette circumferences on the complex combustion processes and formation of smoke constituents was achieved. [Beitr. Tabakforsch. Int. 29 (2020) 44–54]

Abstract

Three quartz samples extracted from different origins were collected for ESR evaluation to appreciate the optical bleaching characteristics of the E1’ centre in a long time scale. After exposure of about 400 hours to artificial sunlight, the E1’ centre were bleached to a steady increasing level, about 2.5 times of its natural level, and the increase level also exhibit a small variability among different sample origins. The constant increasing level provide a significantly evidence for the potential use of the natural signal intensities of quartz E1’ centre in tracing sediment provenance. The results show that the signal intensity of E1’ centre increased within beginning 84 h and decreased after 202 h as previous researches have partly predicted. After long time exposed to sunlight, there is no correlation between irradiated samples’ dose rate and its E1’ centre ESR signal intensity. Thus, no new convenient indication shed light on the possible use of the E1’ centre for ESR sediment dating.

Abstract

Human bocavirus 1 (HBoV1) is a parvovirus recently found to be a possible aetiologic agent of acute respiratory disease in children. We conducted the first clinical and molecular study on this virus in Latvia (LV) and Lithuania (LT). The aim of the study was to determine the occurrence of HBoV1 in respiratory tract samples taken from hospitalised children with acute respiratory tract infections in LV and LT. In total 186 children with age one to 50 months, and who fulfilled criteria of acute respiratory tract infection, including lower respiratory tract infections, with or without fever, were included in this study. A nasopharyngeal aspirate was obtained from each patient on admission. DNA was isolated and polimerase chain reaction (PCR) performed targeting the HBoV1 NS1sequence. HBoV1 positive samples were sequenced and phylogenetic analysis was performed. HBoV1 sequence was detected in 42 (32%) of 130 LV and in 8 (14%) of 56 LT samples. In LV the majority of patients with HBoV1 infection were observed in February while in LT in October. The phylogenetic tree for HBoV1 indicated that isolates of HBoV1 cluster closely and include almost all of the isolates in this study. HBoV1 is common in Latvia and Lithuania and might be a significant pathogen that contributes to acute respiratory tract infections in children.