Towards standardisation in breathomics

Exhaled breath VOCs analysis is safe and non-invasive method of monitoring for human metabolic profiles and has the potential to become diagnostic tool in clinical practise. This thesis first describe in detail the different aspects of exhaled breath VOCs and its use as diagnostic tool in respiratory diseases. The current exhaled breath analysis work-flow including breath sampling, analysis and data processing is also described. A single exhaled breath sample can contain in excess of 500 different chemical species. There is a wide range of factors that can cause the variability to individual breath profiles. In order to detect small changes in breath profiles, a standardised and reproducible approach to exhaled breath analysis methodology is required. The long term storage of exhaled breath samples using multi-sorbent tubes is investigated, the optimum storage protocol and condition is discussed. A portable breath sampling system was also developed for remote sampling. The introduction of this new feature enables breath sampling to be carried out outside the designated laboratory with no location restriction. This feature combined with the easy to use and non-invasive original sampling unit designed for subjects with impaired lung function minimise participant stress level and discomfort. It also utilises the custom developed air supply filtration assembly to create a standardised purified breathable air that can minimise the method variability and improve standardisation to breath samples collected. This methodology is tested in an excise induced bronchoconstriction (EIB) study where two groups of participants: healthy and excise induced bronchoconstriction (EIB) positive undergo high intensity cardiopulmonary exercise testing (CPET). The data from two groups of participants is analysed and three markers which shown correlation with EIB positive participants are determined

Allometric models for aboveground biomass of ten tree species in northeast China

China contains 119 million hectares of natural forest, much of whichis secondary forest. An accurate estimation of the biomass of these forests is imperative because many studies conducted in northeast China have only used primary forest and this may have resulted in biased estimates. This study analyzed secondary forest in the area using information from a forest inventory to develop allometric models of the aboveground biomass (AGB). The parameter values of the diameter at breast height (DBH), tree height (H), and crown length (CL) were derived from a forest inventory of 2,733 trees in a 3.5 ha plot. The wood-specific gravity (WSG) was determined for 109 trees belonging to ten species. A partial sampling method was also used to determine the biomass of branches (including stem, bark and foliage) in 120 trees, which substantially ease the field works. The mean AGB was110,729 kg ha–1. We developed four allometric models from the investigation and evaluated the utility of other 19 published ones for AGB in the ten tree species. Incorporation of full range of variables with WSG-DBH-H-CL, significantly improved the precision of the models. Some of models were chosen that best fitted each tree species with high precision (R2 ≥ 0.939, SEE 0.167). At the latitude level, the estimated AGB of secondary forest was lower than that in mature primary forests, but higher than that in primary broadleaf forest and the average level in other types of forest likewise

How long may a breath sample be stored for at −80 °C? A study of the stability of volatile organic compounds trapped onto a mixed Tenax:Carbograph trap adsorbent bed from exhaled breath

Thermal desorption is used extensively in exhaled breath volatile organic compound (VOC) analysis, and it is often necessary to store the adsorbent tube samples before analysis. The possible introduction of storage artefacts is an important potential confounding factor in the development of standard methodologies for breath sampling and analysis. The stability of VOCs trapped from breath samples onto a dual bed Tenax® TA:Carbograph adsorbent tube and stored  −80°C was studied over 12.5 month. 25 samples were collected from a single male participant over 3 h and then stored at  −80 °C. Randomly selected adsorbent tubes were subsequent analysed by thermal desorption-gas chromatography-mass spectrometry at 5 times points throughout the 12.5 month of the study. Toluene-d8, decane-d22 and hexadecane-d34 internal standards were used to manage the instrument variability throughout the duration of the study. A breath-matrix consisting of 161 endogenous and 423 exogenous VOC was created. Iterative orthogonal partial least squared discriminant analysis (OPLS-DA) and principal components analysis (PCA) indicated that it was not possible to detect storage artefacts at 1.5 month storage. By 6 month storage artefacts were discernible with significant changes observed for 27% of the recovered VOC. Endogenous VOC were observed to be more susceptible to storage. A paired two-tailed t-test on the endogenous compounds indicated that the maximum storage duration under these conditions was 1.5 month with 94% of the VOCs stable. This study indicates that a prudent approach is best adopted for the storage of adsorbent samples; storage times should be minimised, and storage time examined as a possible discriminatory factor in multivariate analysis

Nature of X(3872)X(3872) from its radiative decay

We study the radiative decay of $X(3872)$ based on the assumption that $X(3872)$ is regarded as a $c\overline{c}$ charmonium with quantum number $J^{PC}=1^{++}$ ($J,\,P,\,C$ stand for spin, parity and charge conjugation, respectively) in accordance with the Particle Data Group assignment. The form factors of $X(3872)$ transitions to $J/\psi\gamma$ and $\psi'\gamma$ ($\psi'$ denotes $\psi(2S)$ throughout the paper) are calculated in the framework of the covariant light-front quark model. The phenomenological wave function of a meson depends on the parameter $\beta$ which inverse essentially describes the confinement scale. In the present work, the parameters $\beta$ for the vector $J/\psi$ and $\psi'$ mesons will be determined through their decay constants which are from the experimental values of their partial decay widths to electron-positron pair. As for $X(3872)$ we determine the value of $\beta$ by the decay width of $X(3872)\rightarrow \psi'\gamma$. Then we examine the width of $X(3872)\to J/\psi\gamma$ in a manner of parameter-free prediction and confront it with the experimental value. Both of the hypothesises that $X(3872)$ is the $1P$ state or $2P$ state are considered, although the predicted $1P$ charmonium mass is significantly lower than the mass of $X(3872)$. It is found that one will encounter the inconsistency or contradiction between the widths of $X(3872)\to J/\psi\gamma$ and $X(3872)\to \psi'\gamma$ if interpreting $X(3872)$ as a pure charmonium. We thus conclude that $X(3872)$ can not be a pure $c\overline c$ resonance and other components are necessary in its wave function.Comment: 12 pages, 1 figur

The Correspondence between Convergence Peaks from Weak Lensing and Massive Dark Matter Haloes

The convergence peaks, constructed from galaxy shape measurement in weak lensing, is a powerful probe of cosmology as the peaks can be connected with the underlined dark matter haloes. However the capability of convergence peak statistic is affected by the noise in galaxy shape measurement, signal to noise ratio as well as the contribution from the projected mass distribution from the large-scale structures along the line of sight (LOS). In this paper we use the ray-tracing simulation on a curved sky to investigate the correspondence between the convergence peak and the dark matter haloes at the LOS. We find that, in case of no noise and for source galaxies at $z_{\rm s}=1$, more than $65\%$ peaks with $\text{SNR} \geq 3$ (signal to noise ratio) are related to more than one massive haloes with mass larger than $10^{13} {\rm M}_{\odot}$. Those massive haloes contribute $87.2\%$ to high peaks ($\text{SNR} \geq 5$) with the remaining contributions are from the large-scale structures. On the other hand, the peaks distribution is skewed by the noise in galaxy shape measurement, especially for lower SNR peaks. In the noisy field where the shape noise is modelled as a Gaussian distribution, about $60\%$ high peaks ($\text{SNR} \geq 5$) are true peaks and the fraction decreases to $20\%$ for lower peaks ($3 \leq \text{SNR} < 5$). Furthermore, we find that high peaks ($\text{SNR} \geq 5$) are dominated by very massive haloes larger than $10^{14} {\rm M}_{\odot}$.Comment: 13 pages, 11 figures, 4 tables, accepted for publication in MNRAS. Our mock galaxy catalog is available upon request by email to the author ([email protected]

Age-dependent effects of chronic amphetamine on prelimbic-nucleus accumbens circuit function and goal-directed behavior

Non-medial amphetamine (AMPH) use is prevalent in the adolescent population. Empirical evidence suggests that individuals starting using drugs during adolescence have a higher chance of developing drug-related problems. It is hypothesized that adolescents may have a heightened vulnerability to drug induced plasticity such as cognitive deficits and neuroadaptations. My pilot studies suggested that the high frequency stimulation (HFS)-induced long-term depression (LTD) in the prelimbic cortex (PL) is likely to be a target influenced by repeated AMPH in an age-of-exposure dependent manner, which results in abnormalities in the reward circuit function and goal-directed behavior. Using a rat model, this hypothesis was tested with three specific aims: (1) to investigate the ontogeny of this LTD function (Experiment 1), (2) to assess the effect of adolescent and adult amphetamine on HFS-induced LTD in the PL and the potential mechanisms underlying AMPH-induced changes (Experiment 2) and (3) to determine whether AMPH-induced changes in the PL and in the reward circuit are associated with impaired cognitive flexibility (Experiment 3). In Experiment 1, field potentials in brain slices from male naive rats were assessed to test the effect of age on the expression of this LTD. The role of GABA and dopamine receptors in the HFS-induced LTD was investigated using respective agonist or antagonist. In Experiment 2, brain slices from male rats pre-exposed to repeated 3.0 mg/kg AMPH i.p injections were used in field potential and patch-clamp recordings to assess AMPH’s effect on the expression of LTD and dopamine’s modulation of inhibition. In Experiment 3, male and female rats were treated as in Experiment 2 and subjected to a strategy set-shifting task to assess AMPH’s effect on cognitive flexibility. Upon finishing the behavioral testing, each rat was sacrificed for slice recordings to assess AMPH’s effect on HFS-induced plasticity in the PL-nucleus accumbens circuit. These studies revealed unique behavioral changes and neuroadaptations following adolescent AMPH exposure. Our results are consistent with the hypothesis that adolescent brain is more vulnerable to the detrimental effect of drugs