High Background Levels of Urinary Benzene Metabolites Found in a Volunteer Study

AbstractThe formation of carbonyls and epoxides in e-cigarette (EC) aerosol is possible due to heating of the liquid constituents. However, high background levels of these compounds have inhibited a clear assessment of exposure during use of ECs. An EC containing an e-liquid replaced with 10% of 13C-labeled propylene glycol and glycerol was used in a controlled use clinical study with 20 EC users. In addition, five smokers smoked cigarettes spiked with the described e-liquid. Seven carbonyls (formaldehyde, acetaldehyde, acrolein, acetone, crotonaldehyde, methacrolein, propionaldehyde) were measured in the aerosol and the mainstream smoke. Corresponding biomarkers of exposure were determined in the user’s urine samples. 13C-labeled formaldehyde, acetaldehyde and acrolein were found in EC aerosol, while all seven labeled carbonyls were detected in smoke. The labeled biomarkers of exposure to formaldehyde (13C-thiazolidine carboxylic acid and 13C-N-(1,3-thiazolidine-4-carbonyl)glycine), acrolein (13C3-3-hydroxypropylmercapturic acid) and glycidol (13C3-dihydroxypropylmercapturic acid) were present in the urine of vapers indicating an EC use-specific exposure to these toxicants. However, other sources than vaping contribute to a much higher extent by several orders of magnitude to the overall exposure of these toxicants. Comparing data for the native (unlabeled) and the labeled (exposure-specific) biomarkers revealed vaping as a minor source of user’s exposure to these toxicants while other carbonyls and epoxides were not detectable in the EC aerosol.

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Stress profile influences learning approach in a marine fish

PeerJ ◽

10.7717/peerj.3445 ◽

2017 ◽

Vol 5 ◽

pp. e3445 ◽

Cited By ~ 6

Author(s):

Vincent Raoult ◽

Larissa Trompf ◽

Jane E. Williamson ◽

Culum Brown

Keyword(s):

Food Reward ◽

Coping Styles ◽

High Stress ◽

Proactive Coping ◽

Stress Profile ◽

Activity Levels ◽

High Background ◽

Background Levels ◽

Low Levels ◽

The Cost

The spatial learning skills of high and low stress juvenile mulloway (Argyrosomus japonicus) were tested in a dichotomous choice apparatus. Groups of fish were formed based on background blood cortisol levels and required to learn the location of a food reward hidden in one of two compartments. Low stress fish characterised by low background levels of the stress hormone cortisol had higher activity levels and entered both rewarded and unrewarded rooms frequently. Within the first week of exposure, however, their preference for the rewarded room increased, indicative of learning. Fish that had high background levels of cortisol, in contrast, showed low levels of activity but when they chose between the two rooms they chose the rewarded room most often but showed less improvement over time. After 12 days in the apparatus, both low and high stress fish had similar ratios of rewarded vs unrewarded room entrances. Our results suggest that proactive coping styles may increase exposure to novel contexts and thus favour faster learning but at the cost of reduced initial accuracy.

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High background levels compromise the use of cardiac troponin I RNA detection in peripheral blood as a diagnostic tool in cardiology

International Journal of Clinical & Laboratory Research ◽

10.1007/s005990070027 ◽

2000 ◽

Vol 30 (1) ◽

pp. 13-15 ◽

Cited By ~ 2

Author(s):

P. Tschentscher ◽

C. Heeschen ◽

C. Hamm ◽

C. Wagener

Keyword(s):

Diagnostic Tool ◽

Peripheral Blood ◽

Cardiac Troponin ◽

Troponin I ◽

Cardiac Troponin I ◽

Rna Detection ◽

High Background ◽

Background Levels

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Scattering-angle dependence of signal/background ratio of inner-shell electron excitation loss in EELS

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100075701 ◽

1983 ◽

Vol 41 ◽

pp. 390-391

Author(s):

T. Oikawa ◽

M. Inoue ◽

T. Honda ◽

Y. Kokubo

Keyword(s):

Energy Loss ◽

Electron Excitation ◽

Heavy Elements ◽

Background Intensity ◽

Light Elements ◽

Energy Analyzer ◽

High Background ◽

Scattering Angle ◽

Angle Dependence ◽

Shell Electron

EELS allows us to make analysis of light elements such as hydrogen to heavy elements of microareas on the specimen. In energy loss spectra, however, elemental signals ride on a high background; therefore, the signal/background (S/B) ratio is very low in EELS. A technique which collects the center beam axial-symmetrically in the scattering angle is generally used to obtain high total intensity. However, the technique collects high background intensity together with elemental signals; therefore, the technique does not improve the S/B ratio. This report presents the experimental results of the S/B ratio measured as a function of the scattering angle and shows the possibility of the S/B ratio being improved in the high scattering angle range.Energy loss spectra have been measured using a JEM-200CX TEM with an energy analyzer ASEA3 at 200 kV.Fig.l shows a typical K-shell electron excitation edge riding on background in an energy loss spectrum.

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Correction of the contrast transfer function to determine the radial density distribution of frozen-hydrated tobacco mosaic virus

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100123088 ◽

1992 ◽

Vol 50 (1) ◽

pp. 536-537

Author(s):

Michael F. Smith ◽

John P. Langmore

Keyword(s):

Transfer Function ◽

Phase Contrast ◽

Heavy Atom ◽

Biological Molecules ◽

Frequency Compensation ◽

Contrast Transfer Function ◽

High Background ◽

Low Contrast ◽

Radial Density Distribution ◽

Excellent Preservation

The purpose of image reconstruction is to determine the mass densities within molecules by analysis of the intensities within images. Cryo-EM offers this possibility by virtue of the excellent preservation of internal structure without heavy atom staining. Cryo-EM images, however, have low contrast because of the similarity between the density of biological material and the density of vitreous ice. The images also contain a high background of inelastic scattering. To overcome the low signal and high background, cryo-images are typically recorded 1-3 μm underfocus to maximize phase contrast. Under those conditions the image intensities bear little resemblance to the object, due to the dependence of the contrast transfer function (CTF) upon spatial frequency. Compensation (i.e., correction) for the CTF is theoretically possible, but implementation has been rare. Despite numerous studies of molecules in ice, there has never been a quantitative evaluation of compensated images of biological molecules of known structure.

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Acquisition of EELS spectra for high-resolution spectroscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100148721 ◽

1993 ◽

Vol 51 ◽

pp. 578-579

Author(s):

Maoxu Qian ◽

Mehmet Sarikaya ◽

Edward A. Stern

Keyword(s):

Energy Loss ◽

Detection System ◽

High Resolution Spectroscopy ◽

High Signal ◽

Short Report ◽

Edge Structure ◽

High Background ◽

Gain Variation ◽

Sufficient Energy ◽

On Line

It is difficult, in general, to perform quantitative EELS to determine, for example, relative or absolute compositions of elements with relatively high atomic numbers (using, e.g., K edge energies from 500 eV to 2000 eV), to study ELNES (energy loss near edge structure) signal using the white lines to determine oxidation states, and to analyze EXELFS (extended energy loss fine structure) to study short range ordering. In all these cases, it is essential to have high signal-to-noise (S/N) ratio (low systematical error) with high overall counts, and sufficient energy resolution (∽ 1 eV), requirements which are, in general, difficult to attain. The reason is mainly due to three important inherent limitations in spectrum acquisition with EELS in the TEM. These are (i) large intrinsic background in EELS spectra, (ii) channel-to-channel gain variation (CCGV) in the parallel detection system, and (iii) difficulties in obtaining statistically high total counts (∽106) per channel (CH). Except the high background in the EELS spectrum, the last two limitations may be circumvented, and the S/N ratio may be attained by the improvement in the on-line acquisition procedures. This short report addresses such procedures.

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