77 research outputs found
The role of mathematical modeling in VOC analysis using isoprene as a prototypic example
Isoprene is one of the most abundant endogenous volatile organic compounds
(VOCs) contained in human breath and is considered to be a potentially useful
biomarker for diagnostic and monitoring purposes. However, neither the exact
biochemical origin of isoprene nor its physiological role are understood in
sufficient depth, thus hindering the validation of breath isoprene tests in
clinical routine.
Exhaled isoprene concentrations are reported to change under different
clinical and physiological conditions, especially in response to enhanced
cardiovascular and respiratory activity. Investigating isoprene exhalation
kinetics under dynamical exercise helps to gather the relevant experimental
information for understanding the gas exchange phenomena associated with this
important VOC.
A first model for isoprene in exhaled breath has been developed by our
research group. In the present paper, we aim at giving a concise overview of
this model and describe its role in providing supportive evidence for a
peripheral (extrahepatic) source of isoprene. In this sense, the results
presented here may enable a new perspective on the biochemical processes
governing isoprene formation in the human body.Comment: 17 page
Monitoring of oxidative and metabolic stress during cardiac surgery by means of breath biomarkers: an observational study
Research articl
Laser spectroscopy for breath analysis : towards clinical implementation
Detection and analysis of volatile compounds in exhaled breath represents an attractive tool for monitoring the metabolic status of a patient and disease diagnosis, since it is non-invasive and fast. Numerous studies have already demonstrated the benefit of breath analysis in clinical settings/applications and encouraged multidisciplinary research to reveal new insights regarding the origins, pathways, and pathophysiological roles of breath components. Many breath analysis methods are currently available to help explore these directions, ranging from mass spectrometry to laser-based spectroscopy and sensor arrays. This review presents an update of the current status of optical methods, using near and mid-infrared sources, for clinical breath gas analysis over the last decade and describes recent technological developments and their applications. The review includes: tunable diode laser absorption spectroscopy, cavity ring-down spectroscopy, integrated cavity output spectroscopy, cavity-enhanced absorption spectroscopy, photoacoustic spectroscopy, quartz-enhanced photoacoustic spectroscopy, and optical frequency comb spectroscopy. A SWOT analysis (strengths, weaknesses, opportunities, and threats) is presented that describes the laser-based techniques within the clinical framework of breath research and their appealing features for clinical use.Peer reviewe
Cavity-enhanced direct frequency comb spectroscopy
Cavity-enhanced direct frequency comb spectroscopy combines broad spectral
bandwidth, high spectral resolution, precise frequency calibration, and
ultrahigh detection sensitivity, all in one experimental platform based on an
optical frequency comb interacting with a high-finesse optical cavity. Precise
control of the optical frequency comb allows highly efficient, coherent
coupling of individual comb components with corresponding resonant modes of the
high-finesse cavity. The long cavity lifetime dramatically enhances the
effective interaction between the light field and intracavity matter,
increasing the sensitivity for measurement of optical losses by a factor that
is on the order of the cavity finesse. The use of low-dispersion mirrors
permits almost the entire spectral bandwidth of the frequency comb to be
employed for detection, covering a range of ~10% of the actual optical
frequency. The light transmitted from the cavity is spectrally resolved to
provide a multitude of detection channels with spectral resolutions ranging
from a several gigahertz to hundreds of kilohertz. In this review we will
discuss the principle of cavity-enhanced direct frequency comb spectroscopy and
the various implementations of such systems. In particular, we discuss several
types of UV, optical, and IR frequency comb sources and optical cavity designs
that can be used for specific spectroscopic applications. We present several
cavity-comb coupling methods to take advantage of the broad spectral bandwidth
and narrow spectral components of a frequency comb. Finally, we present a
series of experimental measurements on trace gas detections, human breath
analysis, and characterization of cold molecular beams.Comment: 36 pages, 27 figure
Stability and Thermal Conductivity Characteristic of Carbon Nanotube Based Nanofluids
Heat transfer fluids such as water, ethylene glycol and engine oil are commonly used in heat exchanger applications. However these fluids posses low thermal conductivity. The technology advancement in nanotechnology has enabled the nano size particles to be included in a base fluid. This new generation of fluid is known as nanofluids. Producing a stable nanofluid with improved thermal conductivity is a challenging process. The suspended nanoparticles tend to sediment with respect to time. In the present study, multiwall carbon nanotubes (MWCNT) based nanofluids with or without surfactant were investigated in the aspect of stability and thermal conductivity. Study implies that nanofluids added with polyvinylpyrrolidone (PVP) surfactant exhibit better stability compared to nanofluids without surfactant. About 22.2% thermal conductivity improvement was observed for water containing 0.5wt% of MWCNT and 0.1wt% of PVP surfactant. The thermal conductivity also increases with the increasing of MWCNT’s weight fraction
Optimisation of the Hardness AZ31B Reinforced with Lead and Carbon Nanotubes using the Response Surface Method
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