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 propose interferometric methods capable of measuring either the total angular momentum, or simultaneously measuring the spin and orbital angular momentum of single photons. This development ...enables the measurement of any angular momentum eigenstate of a single photon. The work allows the investigation of single-photon two-qubit entangled states and has implications for high density information transfer.
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
.
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.
The aim of this study was to assess the effects of changes to the stable environment on exhaled markers of respiratory inflammation in six horses with clinical histories of recurrent airway ...obstruction. The horses were maintained for two weeks under conventional stable management (straw bedding and hay) and for two weeks on a reduced-dust regimen (paper bedding and ensiled grass), in a crossover study design. Exhaled ethane and carbon monoxide (CO) and exhaled breath condensate hydrogen peroxide (H2O2) were measured every three days under each regimen. The presence of clinical signs of airway inflammation (nasal discharge and cough) was monitored daily. The reduced-dust regimen was associated with fewer clinical signs of airway inflammation than the conventional regimen. Exhaled ethane and CO were significantly lower on the reduced-dust regimen and these markers were correlated with clinical signs of respiratory inflammation, but exhaled H2O2 was not affected by the management regimen.
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.