Pollutant source or sink? Adsorption and mobilization of PFOS and PFOA from sediments in a large shallow lake with extended reed belt.

In this study, we i) assessed the occurrence of perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) in sediments, pore water, and bulk water from three different areas in Lake Neusiedl, Austria, and ii) investigated mechanisms regulating adsorption and remobilization of these substances under different conditions via multiple lab-scale experiments. The adsorption capacity was mainly influenced by sediments' organic matter content, oxide composition, and pre-loading. Results suggest that a further increase of PFAS-concentrations in the open lake can be partly buffered by sediment transport to the littoral zone and adsorption to sediments in the extended reed belt. But, under current conditions, the conducted experiments revealed a real risk for mobilization of PFOS and PFOA from reed belt sediments that may lead to their transport back into the lake. The amount of desorbed PFAS is primarily dependent on water/sediment- or pore water/water-ratios and the concentration gradient. In contrast, water matrix characteristics and oxygen levels played a minor role in partitioning. The highest risk for remobilizing PFOS and PFOA was observed in experiments with sediments taken near the only major tributary to the lake (river Wulka), which had the highest pre-loading. The following management advice for water transport between high and low polluted areas can be derived based on the results. First, to reduce emissions into Lake waters from polluted tributaries like the Wulka river, we recommend diffuse pathways through the reed belt in the lake's littoral to reduce pollutant transport into the Lake and avoid high local sediment loadings. Second, water exchange with dried-up areas with probable higher loadings should be carefully handled and monitored to avoid critical back transport in the open lake. And third, general work in the reed belt or generally in the reed should be accompanied by monitoring to prevent uncontrolled remobilization in the future.

Slow relaxation in a {Tb2Ba(α-fur)8}n polymer with Ln = Tb(iii) non-Kramers ions.

We report the synthesis, crystal structure and magnetic properties of a new heteronuclear polymeric complex based on non-Kramers Tb ions and carboxylic α-fur = C4H3OCOO ligands: {[Tb2Ba(α-fur)8(H2O)4]·2H2O}n. The α-furoate ligands consolidate 1D zig-zag chains running along the c-axis, formed by Tb2 dimers separated by Ba ions. Ab initio calculations, in combination with the fit of experimental data, predict that the single-ion magnetic ground state is highly anisotropic () and consists of a quasi-doublet with a ΔTb/kB = 3.22 K gap, well separated from the next excited state, while the gap for the Tb2 dimer is Δ2Tb/kB = 2.58 K. Static magnetization and heat capacity measurements show that, magnetically, the system can be modeled as dimers of non-Kramers Tb ions, coupled by an antiferromagnetic intradimer interaction J'*/kB = -1.6 K. Dipolar interactions couple the Tb ions in the dimer with their first neighbour ions along the chain, with J''*/kB = -0.15 K, and with the surrounding ions out of the chain, with maximum J'''*/kB = -0.03 K. Ac susceptibility measurements in H = 0 performed down to 50 mK temperatures have enabled us to observe slow relaxation of magnetization, with an Orbach-like activation energy of U/kB = 1.1 K. It is assigned to the sluggish response of the 3D spin system due to a short-range ordering, possibly enhanced by the presence of disorder caused by defects in the polymeric chains. Under the application of a magnetic field, the system slowly relaxes by two distinct direct processes, strongly affected by a phonon bottleneck effect. We discuss the different relaxational phenomenology of the new complex in comparison with that of the isostructural {[Dy2Ba(α-fur)8(H2O)4]·2H2O}n, differing only in the Kramers nature of the ions, and the mononuclear {Ln(α-fur)3(H2O)3}n (Ln = Tb, Dy) complexes, previously reported.

Surfing the High Energy Output Branch of Nonlinear Energy Harvesters.

Hysteresis and multistability are fundamental phenomena of driven nonlinear oscillators, which, however, restrict many applications such as mechanical energy harvesting. We introduce an electrical control mechanism to switch from the low to the high energy output branch of a nonlinear energy harvester by exploiting the strong interplay between its electrical and mechanical degrees of freedom. This method improves the energy conversion efficiency over a wide bandwidth in a frequency-amplitude-varying environment using only a small energy budget. The underlying effect is independent of the device scale and the transduction method and is explained using a modified Duffing oscillator model.

Exhaled methane concentration profiles during exercise on an ergometer.

Exhaled methane concentration measurements are extensively used in medical investigation of certain gastrointestinal conditions. However, the dynamics of endogenous methane release is largely unknown. Breath methane profiles during ergometer tests were measured by means of a photoacoustic spectroscopy based sensor. Five methane-producing volunteers (with exhaled methane level being at least 1 ppm higher than room air) were measured. The experimental protocol consisted of 5 min rest--15 min pedalling (at a workload of 75 W)--5 min rest. In addition, hemodynamic and respiratory parameters were determined and compared to the estimated alveolar methane concentration. The alveolar breath methane level decreased considerably, by a factor of 3-4 within 1.5 min, while the estimated ventilation-perfusion ratio increased by a factor of 2-3. Mean pre-exercise and exercise methane concentrations were 11.4 ppm (SD:7.3) and 2.8 ppm (SD:1.9), respectively. The changes can be described by the high sensitivity of exhaled methane to ventilation-perfusion ratio and are in line with the Farhi equation.

Experimental classification of dynamical regimes in optically injected lasers.

We present a reliable and fast technique to experimentally categorise the dynamical state of optically injected two mode and single mode lasers. Based on the experimentally obtained time-traces locked, unlocked and chaotic states are distinguished for varying injection strength and detuning. For the two mode laser, the resulting experimental stability diagram provides a map of the various single mode and two mode regimes and the transitions between them. This stability diagram is in strong agreement with the theoretical predictions from low-dimensional dynamical models for two mode lasers. We also apply our method to the single mode laser and retain the close agreement between theory and experiment.

A review of the volatiles from the healthy human body.

A compendium of all the volatile organic compounds (VOCs) emanating from the human body (the volatolome) is for the first time reported. 1840 VOCs have been assigned from breath (872), saliva (359), blood (154), milk (256), skin secretions (532) urine (279), and faeces (381) in apparently healthy individuals. Compounds were assigned CAS registry numbers and named according to a common convention where possible. The compounds have been grouped into tables according to their chemical class or functionality to permit easy comparison. Some clear differences are observed, for instance, a lack of esters in urine with a high number in faeces. Careful use of the database is needed. The numbers may not be a true reflection of the actual VOCs present from each bodily excretion. The lack of a compound could be due to the techniques used or reflect the intensity of effort e.g. there are few publications on VOCs from blood compared to a large number on VOCs in breath. The large number of volatiles reported from skin is partly due to the methodologies used, e.g. collecting excretions on glass beads and then heating to desorb VOCs. All compounds have been included as reported (unless there was a clear discrepancy between name and chemical structure), but there may be some mistaken assignations arising from the original publications, particularly for isomers. It is the authors' intention that this database will not only be a useful database of VOCs listed in the literature, but will stimulate further study of VOCs from healthy individuals. Establishing a list of volatiles emanating from healthy individuals and increased understanding of VOC metabolic pathways is an important step for differentiating between diseases using VOCs.

Correlations between blood glucose and breath components from portable gas sensors and PTR-TOF-MS.

Acetone is one of the most abundant volatile compounds in the human breath and might be important for monitoring diabetic patients. Here, a portable acetone sensor consisting of flame-made, nanostructured, Si-doped WO3 sensing films was used to analyse the end tidal fraction of the breath (collected in Tedlar bags) from eight healthy volunteers after overnight fasting (morning) and after lunch (afternoon). After breath sampling, the gaseous components were also analysed by proton transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS), and each person's blood glucose level was measured. The portable sensor accurately detected the presence of acetone with fast response/recovery times (<12 s) and a high signal-to-noise ratio. Statistical analysis of the relationship between the PTR-TOF-MS measurements of breath gases (e.g., acetone, isoprene, ethanol and methanol), sensor response and the blood glucose level was performed for both sampling periods. The best correlations were found after overnight fasting (morning): in particular, between blood glucose level and breath acetone (Pearson's 0.98 and Spearman's 0.93). Whereas the portable sensor response correlated best with the blood glucose (Pearson's 0.96 and Spearman's 0.81) and breath acetone (Pearson's 0.92 and Spearman's 0.69).

Physiology and biochemistry of human subjects during entrapment.

A classification of various categories of entrapped people under the ruins of collapsed buildings after earthquakes, technical failures or explosions is proposed. Type and degree of injury at the moment of building collapse and duration of entrapment are the two basic parameters in this classification. The aim is to provide sources and types of volatile organic compounds (VOCs) that can be used for establishing a new method for locating entrapped victims based on human chemical signatures. Potential target compounds, among others, are ammonia, acetone, isoprene, dimethylsulfide, dimethyldisulfide and trimethylamine. In this context, the possible neuroendocrine, metabolic and physical responses of potential victims during the different types of entrapment are correlated with the sources of VOCs such as expired air, urine, blood and sweat. The proposed classification scheme was developed as part of an integrated research project which investigates the use of combined audio, video and chemical methods for the early location of entrapped people under the ruins of collapsed buildings.

On-off intermittency in an optically injected semiconductor laser.

We report on the observation of on-off intermittency in an optically injected dual-mode semiconductor laser. It is shown that quasi-single-mode chaotic dynamics of the injected mode are accompanied by intermittent and irregular bursts of the intensity of the uninjected mode. We define a threshold intensity of the uninjected mode to distinguish laminar and bursting states of the system. For small values of the threshold parameter we observe excellent agreement with the predictions of theory for the distribution of the laminar phase durations. For larger values of the threshold parameter, a gap appears in the distribution of laminar phase durations. Numerical simulations demonstrate that this gap is a consequence of the fact that in this case the on states of the system define large intensity spikes, which can belong either to the same or to distinct bursts away from the single-mode manifold.

Dependence of exhaled breath composition on exogenous factors, smoking habits and exposure to air pollutants.

Non-invasive disease monitoring on the basis of volatile breath markers is a very attractive but challenging task. Several hundreds of compounds have been detected in exhaled air using modern analytical techniques (e.g. proton-transfer reaction mass spectrometry, gas chromatography-mass spectrometry) and have even been linked to various diseases. However,the biochemical background for most of compounds detected in breath samples has not been elucidated; therefore, the obtained results should be interpreted with care to avoid false correlations. The major aim of this study was to assess the effects of smoking on the composition of exhaled breath. Additionally, the potential origin of breath volatile organic compounds (VOCs) is discussed focusing on diet, environmental exposure and biological pathways based on other's studies. Profiles of VOCs detected in exhaled breath and inspired air samples of 115 subjects with addition of urine headspace derived from 50 volunteers are presented. Samples were analyzed with GC-MS after preconcentration on multibed sorption tubes in case of breath samples and solid phase micro-extraction (SPME) in the case of urine samples. Altogether 266 compounds were found in exhaled breath of at least 10% of the volunteers. From these, 162 compounds were identified by spectral library match and retention time (based on reference standards). It is shown that the composition of exhaled breath is considerably influenced by exposure to pollution and indoor-air contaminants and particularly by smoking. More than 80 organic compounds were found to be significantly related to smoking, the largest group comprising unsaturated hydrocarbons (29 dienes, 27 alkenes and 3 alkynes). On the basis of the presented results, we suggest that for the future understanding of breath data it will be necessary to carefully investigate the potential biological origin of volatiles, e.g., by means of analysis of tissues, isolated cell lines or other body fluids. In particular, VOCs linked to smoking habit or being the results of human exposure should be considered with care for clinical diagnosis since small changes in their concentration profiles(typically in the ppt(v)­ppb(v) range) revealing that the outbreak of certain disease might be hampered by already high background.

Breath isoprene: muscle dystrophy patients support the concept of a pool of isoprene in the periphery of the human body.

Breath isoprene accounts for most of the hydrocarbon removal via exhalation and is thought to serve as a non-invasive indicator for assaying several metabolic effects in the human body. The primary objective of this paper is to introduce a novel working hypothesis with respect to the endogenous source of this compound in humans: the idea that muscle tissue acts as an extrahepatic production site of substantial amounts of isoprene. This new perspective has its roots in quantitative modeling studies of breath isoprene dynamics under exercise conditions and is further investigated here by presenting pilot data from a small cohort of late stage Duchenne muscle dystrophy patients (median age 21, 4 male, 1 female). For these prototypic test subjects isoprene concentrations in end-tidal breath and peripheral venous blood range between 0.09-0.47 and 0.11-0.72 nmol/l, respectively, amounting to a reduction by a factor of 8 and more as compared to established nominal levels in normal healthy adults. While it remains unclear whether isoprene can be ascribed a direct physiological mechanism of action, some indications are given as to why isoprene production might have evolved in muscle.

Decline of exhaled isoprene in lung cancer patients correlates with immune activation.

Isoprene (2-methylbuta-1,3-diene) represents a precursor molecule of isoprenoids (steroids, terpens), and available data suggest that isoprene is related to cholesterol biosynthesis. Breath concentrations of isoprene have been reported to be altered in a number of clinical conditions. However, the physiological meaning of isoprene changes has not yet been established. Utilizing proton-transfer-mass spectroscopy, we analyzed isoprene concentrations (m/z 69, tentatively identified as isoprene) in breath samples in Tedlar bags collected from 79 lung cancer patients (23 females, 56 males). Results were compared to the concentrations of immune activation marker neopterin (ELISA, BRAHMS, Hennigsdorf, Germany), lipid parameters (routine enzymology) and C-reactive protein (CRP). Isoprene concentrations were median 92.5 ppb (25th-75th percentile: 79-131 ppb). There was no relationship with staging, grading or age, but isoprene concentrations correlated significantly with total cholesterol (rs = 0.281, p < 0.01) and LDL cholesterol (rs = 0.236, p < 0.05). There was no significant relationship between exhaled isoprene concentrations and HDL cholesterol (rs = 0.048), triglycerides (rs = 0.164) and CRP (rs = -0.115; all not significant). A significant inverse correlation existed between isoprene and neopterin concentrations (rs = -0.215, p < 0.05); the latter also correlated with total cholesterol (rs = -0.343, p = 0.001), HDL cholesterol (rs = -0.273, p = 0.01), LDL cholesterol (rs = -0.236, p < 0.05) and CRP (rs = 0.230, p < 0.05) but not with triglycerides (rs = 0.035, not significant). Results suggest that immune activation might play a role in the decline of isoprene which is probably related to lipid metabolic changes. Interestingly, similar relationships between elevated neopterin and decreased lipid concentrations have been reported earlier in other clinical conditions, e.g. in patients with HIV-1 infection.

A modeling-based evaluation of isothermal rebreathing for breath gas analyses of highly soluble volatile organic compounds.

Isothermal rebreathing has been proposed as an experimental technique for estimating the alveolar levels of hydrophilic volatile organic compounds (VOCs) in exhaled breath. Using the prototypic test compounds acetone and methanol, we demonstrate that the end-tidal breath profiles of such substances during isothermal rebreathing show a characteristic increase that contradicts the conventional pulmonary inert gas elimination theory due to Farhi. On the other hand, these profiles can reliably be captured by virtue of a previously developed mathematical model for the general exhalation kinetics of highly soluble, blood-borne VOCs, which explicitly takes into account airway gas exchange as a major determinant of the observable breath output. This model allows for a mechanistic analysis of various rebreathing protocols suggested in the literature. In particular, it predicts that the end-exhaled levels of acetone and methanol measured during free tidal breathing will underestimate the underlying alveolar concentration by a factor of up to 1.5. Moreover, it clarifies the discrepancies between in vitro and in vivo blood-breath ratios of hydrophilic VOCs and yields further quantitative insights into the physiological components of isothermal rebreathing and highly soluble gas exchange in general.

Emerging meso- and macroscales from synchronization of adaptive networks.

We consider a set of interacting phase oscillators, with a coupling between synchronized nodes adaptively reinforced, and the constraint of a limited resource for a node to establish connections with the other units of the network. We show that such a competitive mechanism leads to the emergence of a rich modular structure underlying cluster synchronization, and to a scale-free distribution for the connection strengths of the units.

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 is 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. The first model for isoprene in exhaled breath has been developed by our research group. In this 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.

Dynamic profiles of volatile organic compounds in exhaled breath as determined by a coupled PTR-MS/GC-MS study.

In this phenomenological study we focus on dynamic measurements of volatile organic compounds (VOCs) in exhaled breath under exercise conditions. An experimental setup efficiently combining breath-by-breath analyses using proton transfer reaction mass spectrometry (PTR-MS) with data reflecting the behaviour of major hemodynamic and respiratory parameters is presented. Furthermore, a methodology for complementing continuous VOC profiles obtained by PTR-MS with simultaneous SPME/GC-MS measurements is outlined. These investigations aim at evaluating the impact of breathing patterns, cardiac output or blood pressure on the observed breath concentration and allow for the detection and identification of several VOCs revealing characteristic rest-to-work transitions in response to variations in ventilation or perfusion. Examples of such compounds include isoprene, methyl acetate, butane, DMS and 2-pentanone. In particular, both isoprene and methyl acetate exhibit a drastic rise in concentration shortly after the onset of exercise, usually by a factor of about 3-5 within approximately 1 min of pedalling. These specific VOCs might also be interpreted as potentially sensitive indicators for fluctuations of blood or respiratory flow and can therefore be viewed as candidate compounds for future assessments of hemodynamics, pulmonary function and gas exchange patterns via observed VOC behaviour.

Assessment of reperfusion following thrombolysis with mean fibrillation and amplitude spectrum area in patients with sustained ventricular fibrillation.

BACKGROUND: Improved microcirculatory reperfusion in patients with ventricular fibrillation (VF) enhances the electrical activity of the fibrillation process and increases the likelihood of successful defibrillation. METHODS: Changes in amplitude spectrum area (AMSA) and mean fibrillation (MF) in patients with sustained VF were analysed after administration of rt-PA variant tenecteplase in out-of-hospital cardiac arrest (OHCA) during cardiopulmonary resuscitation (CPR). RESULTS: A total of 69 ECG sequences from nine patients were evaluated. Patients who received tenecteplase showed significantly longer duration of VF (p = 0.016). While AMSA declined significantly during CPR (p = 0.001), MF did not differ between groups. There were two survivors in the treatment group and one in the control group. CONCLUSION: When tenecteplase was administered during CPR, VF lasted significantly longer than in controls. Changes in MF and AMSA did not indicate improved myocardial perfusion in patients who received tenecteplase during CPR.

All-optical memory based on the injection locking bistability of a two-color laser diode.

We study the injection locking bistability of a specially engineered two-color semiconductor Fabry-Pérot laser. Oscillation in the uninjected primary mode leads to a bistability of single mode and two-color equilibria. With pulsed modulation of the injected power we demonstrate an all-optical memory element based on this bistability, where the uninjected primary mode is switched with 35 dB intensity contrast. Using experimental and theoretical analysis, we describe the associated bifurcation structure, which is not found in single mode systems with optical injection.

3-Heptanone as a potential new marker for valproic acid therapy.

Breath gas samples from 27 patients with epilepsy (17 male and 10 female patients; mean age: 9.7 years, median age: 8.2 years, SD: ±4.2 years) were screened via proton transfer reaction mass spectrometry. The patients were treated with valproic acid (VPA) therapy, and blood samples for determination of VPA concentrations were surveyed. All patients showed significantly elevated concentrations of 3-heptanone (C(7)H(14)O) in exhaled breath gas (mean: 14.7 ppb, median: 13.8 ppb SD: ±5.7 ppb). In human breath, several hundred different volatile organic compounds can be detected. In breath of patients with valproic acid monotherapy, an increased concentration of 3-heptanone was measured. The objective of this study was to investigate if serum VPA concentrations correlate with 3-heptanone concentrations in exhaled breath. In conclusion, 3-heptanone in breath gas is significantly elevated in patients treated with the valproic acid, but does not correlate significantly with the VPA concentrations in serum or the daily dose of this drug.