There is increasing interest in ethane (C
2H
6) in exhaled breath as a non-invasive marker of oxidative stress (OS) and thereby a potential indicator of disease. However, the lack of real-time ...measurement techniques has limited progress in the field. Here we report on a novel Tunable Diode Laser Spectrometer (TDLS) applied to the analysis of exhaled ethane in patients with lung cancer. The patient group (
n
=
5
2
) comprised randomly selected patients presenting at a respiratory clinic. Of these, a sub-group (
n
=
1
2
) was subsequently diagnosed with lung cancer. An age-matched group (
n
=
1
2
) corresponding to the lung cancer group was taken from a larger control group of healthy adults (
n
=
5
8
). The concentration of ethane in a single exhaled breath sample collected from all subjects was later measured using the TDLS. This technique is capable of real-time analysis of samples with accuracy 0.1 parts per billion (ppb), over 10 times less than typical ambient levels in the northern hemisphere.
After correcting for ambient background, ethane in the control group (26% smokers) ranged from 0 to 10.54
ppb (median of 1.9
ppb) while ethane in the lung cancer patients (42% smokers) ranged from 0 to 7.6
ppb (median of 0.7
ppb). Ethane among the non-lung cancer patients presenting for investigation of respiratory disease ranged from 0 to 25
ppb (median 1.45
ppb).
We conclude that, while the TDLS proved effective for accurate and rapid sample analysis, there was no significant difference in exhaled ethane among any of the subject groups. Comments are made on the suitability of the technique for monitoring applications.
We report on an experiment to develop a high power, large bandwidth, infra-red photodetection system for use with radio frequency optical modulation schemes in the generation of gravitational wave ...detectors now being constructed. The incident light is split into 16 components by a configuration of 50:50 beam splitters and directed towards an array of InGaAs PIN photodiodes. The radio frequency output from the diodes is combined using ferrite loaded broad-band hybrid coaxial couplers together with coaxial transformers in a cascade, totem-pole, arrangement. The photodetection system has a very wide bandwidth, being shot noise limited to over 100 MHz in less than 150 mA of photocurrent. It has a photocurrent capability of up to 1.5 A which corresponds to an incident light power of about 2.3 W after optical losses are taken into account. The noise contribution from the photodiode array with bias applied is around
1.4×10
−21
W/
Hz
.
We describe a high-resolution real-time spectroscopy system targeted to ethane gas with sensitivity > or = 70 ppt and response time from > or = 0.7 s. The measurement technique is based on a mid-IR ...lead-salt laser passing through a Herriott cell through which a gas sample flows. We compare wavelength scanning and locked configurations and discuss their relative merits. The technology has been motivated by clinical breath testing applications, ethane being widely regarded as the most important breath biomarker for cell damage via free-radical-mediated oxidative attack. We discuss preliminary human and animal studies in which ultrasensitive real-time ethane detection offers new diagnostic and monitoring potential.
We report a new oil and gas prospecting technique based on measurements of sub‐part‐per‐billion ethane concentration in the atmosphere and local wind data. The sensitivity of our sensor enables ...detection, from a range of several km, of the naturally occurring ethane seepages that accompany hydrocarbon reservoirs. Using the concentration and wind data, the gas dispersion process is inverted to provide maps of surface ethane flux over several hundred km2. Within a desert environment, we demonstrate the technique is capable of locating a controlled release and corresponds with the results from a geochemical soil sampling survey conducted over the same oil field.
There is growing evidence that oxidative stress is increased in haemodialysis patients and that dialysis per se is a contributory factor. The elevated oxidant stress, a result of increased production ...of reactive oxidant species (ROS), may be due to increased pro-inflammatory activity and reduced antioxidant mechanisms. ROS are transitory molecules and therefore surrogate markers of oxidant damage are required. Identification of potential causes of oxidative damage such as dialyser membranes or dialysate has been proposed and therefore assessment of oxidative damage during a single dialysis session would be of interest. We have used breath ethane, a widely accepted marker of oxidative stress, to investigate the cause and extent of the resulting oxidative damage during single dialysis sessions. Our study involved assessment of breath ethane levels during haemodialysis in an end-stage renal failure haemodialysis population (n = 24). Breath samples were collected using discrete sampling techniques and were subsequently analysed using laser spectroscopy. Each patient adopted the role of longitudinal control in this study and his or her breath ethane level was monitored regularly during the dialysis session. Significant breath ethane elevation was observed at the beginning (within the first 10 min) of each dialysis session. This paper provides an in-depth statistical analysis and clinical discussion of the recent findings. A regression analysis of the collected breath ethane data showed a trend towards increased ethane levels for patients on dialysis for a shorter duration of time (r = 0.656, R-Sq = 43.3%, p = 0.001). Multiple linear regression was undertaken to further assess these associations and revealed that peak ethane levels were significantly and independently associated with time period on dialysis (p < 0.000), vascular access (p = 0.013) and male sex (p = 0.005). However, whilst diabetes status had demonstrated a correlation with peak ethane levels (0.525, p = 0.008) this was not independent of vascular access status. This multivariate linear model was significantly associated with Ln peak ethane levels (S = 0.744, R-Sq = 80.8%). The observed rapid rise in oxidative stress during the first few minutes after commencement of dialysis gives new insight into the dynamics of the oxidative damage resulting from dialysis treatment.
We report on measurements of the frequency noise of a highly stabilised injection locked Nd:YAG laser. We use a nested loop frequency stabilisation scheme to achieve a loop gain of ∼1×10
6 at Fourier ...frequencies around 1 kHz with frequency actuation applied only to the master oscillator. A frequency noise level of ∼
2×10
−5
Hz
Hz
−1/2
was measured for the master laser around this frequency using an independent, narrow line width, suspended analyser cavity. Furthermore we demonstrate that the frequency noise performance of the injection locked slave laser is identical to that of the master oscillator to this level. This performance is very close to the frequency noise specification for gravitational wave detection by GEO 600.
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