Polycyclic aromatic hydrocarbons (PAHs) in the atmospheres of two French alpine valleys: sources and temporal patterns

International audienceAlpine valleys represent some of the most important crossroads for international heavy-duty traffic in Europe, but the full impact of this traffic on air quality is not known due to a lack of data concerning these complex systems. As part of the program "Pollution des Vallées Alpines" (POVA), we performed two sampling surveys of polycyclic aromatic hydrocarbons (PAHs) in two sensitive valleys: the Chamonix and Maurienne Valleys, between France and Italy. Sampling campaigns were performed during the summer of 2000 and the winter of 2001, with both periods taking place during the closure of the "Tunnel du Mont-Blanc". The first objective of this paper is to describe the relations between PAH concentrations, external parameters (sampling site localization, meteorological parameters, sources), and aerosol characteristics, including its carbonaceous fraction (OC and EC). The second objective is to study the capacity of PAH profiles to accurately distinguish the different emission sources. Temporal evolution of the relative concentration of an individual PAH (CHR) and the PAH groups BghiP+COR and BbF+BkF is studied in order to differentiate wood combustion, gasoline, and diesel emissions, respectively. The results show that the total particulate PAH concentrations were higher in the Chamonix valley during both seasons, despite the cessation of international traffic. Seasonal cycles, with higher concentrations in winter, are also stronger in this valley. During winter, particulate PAH concentration can reach very high levels (up to 155 ng.m-3) in this valley during cold anticyclonic periods. The examination of sources shows the impact during summer of heavy-duty traffic in the Maurienne valley and of gasoline vehicles in the Chamonix valley. During winter, Chamonix is characterized by the strong influence of wood combustion in residential fireplaces, even if the temporal evolution of specific PAH ratios are difficult to interpret. Information on sources given by PAH profiles can only be considered in qualitative terms

Sharp transition for single polarons in the one-dimensional Su-Schrieffer-Heeger model

We study a single polaron in the Su-Schrieffer-Heeger (SSH) model using four different techniques (three numerical and one analytical). Polarons show a smooth crossover from weak to strong coupling, as a function of the electron-phonon coupling strength $\lambda$, in all models where this coupling depends only on phonon momentum $q$. In the SSH model the coupling also depends on the electron momentum $k$; we find it has a sharp transition, at a critical coupling strength $\lambda_c$, between states with zero and nonzero momentum of the ground state. All other properties of the polaron are also singular at $\lambda = \lambda_c$, except the average number of phonons in the polaronic cloud. This result is representative of all polarons with coupling depending on $k$ and $q$, and will have important experimental consequences (eg., in ARPES and conductivity experiments)

The new control system of the SPS target sector

The SPS, the Super Proton Synchrotron at CERN, is an accelerator originally designed and commissioned in 1976 for protons. The control system of the SPS target stations, beam absorbers and other aperture limiting devices was developed in the seventies. It was mainly based on home made electronics and equipment dependent software. With time, this electronics has become obsolete, difficult to maintain in operation and not suitable for integration into a modern control system. In 1997, a project was set up to modernise the electronics and the related software. The new control system is largely based on standard industrial hardware and software components. SIEMENS Simatic S7-300 programmable logic controllers have been used as equipment controllers and connected through PROFIBUS to a Windows-NT front-end PC running the SIEMENS WinCC SCADA package which acts as local controller and remote access gateway. This fully industrial solution has been successfully integrated into the actual SPS accelerator control infrastructure and is open to other industrial communication protocols. The design, development and realisation of the selected solution have been outsourced to industry

Estimation of running capacity can likely be removed from questionnaires estimating walking impairment in patients with claudication

OBJECTIVE: The Estimating Ambulation Capacity by History-Questionnaire (EACH-Q) and the Walking Impairment Questionnaire (WIQ) are used to estimate maximal walking distance (MWD). The EACH-Q and WIQ included 4 and 14 items respectively, among which one item dealing with running capacity. We hypothesised that this item was of little interest in patients with claudication. DESIGN: The WIQ and EACH-Q were self-completed and corrected before a constant load (3.2 km h(-1); 10% slope) treadmill tests, maximised to 15 min. PATIENTS: 371 patients (298 males/73 females, 62.9 +/- 11.2 years). METHODS: The number of errors (duplicate, absent or paradoxical answers to one item) and correlation of questionnaire scores with MWD on treadmill were calculated, before and after skipping the answer to the running item. RESULTS: The proportion of questionnaires with errors was 27% with the EACH-Q and 48% with the WIQ. Two-hundred and twenty-one (59.6%) and 245 (66%) out of 371 patients reported to be unable to run, for the EACH-Q and WIQ, respectively. The rate of errors was reduced by 15% for the EACH-Q (p < 0.05) when skipping the running item for scoring. The correlation coefficients between the MWD and the questionnaire scores were 0.449 and 0.485 for the EACH-Q and were 0.571 and 0.572 for the WIQ, before and after skipping the running item, respectively. CONCLUSION: Most of our patients reported to be unable to run and skipping the running item reduce the rate of errors in self-completing the questionnaires without impairing the correlation of questionnaire scores with treadmill results. It is likely that the running item could be removed from the WIQ and EACH-Q questionnaires

Self-reported estimation of usual walking speed improves the performance of questionnaires estimating walking capacity in patients with vascular-type claudication

OBJECTIVE: Most questionnaires do not estimate the usual walking speed of the patient, although it is well known that patients may experience apparently different walking capacities if walking slow or fast. We hypothesized that correcting the self-reported estimated walking capacity by a coefficient issued from the self-reported estimation of usual walking speed would significantly improve the correlation between questionnaire-estimated and treadmill-measured walking capacity. METHODS: Three hundred ten consecutive patients complaining of vascular-type claudication were asked to estimate their usual walking speed in comparison to people of their age (or friends or relatives) with ratings ranging from much slower (1 pt) to much faster (5 pts), in addition to the filling out of the walking impairment questionnaire (WIQ) and the estimated ambulatory capacity by history questionnaire (EACH-Q). Corrected WIQ (WIQc) and corrected EACH-Q (EACH-Qc) scores were obtained by multiplying the scores of each questionnaire by the "usual-speed" coefficient and dividing by 5. Results for questionnaire scores were compared to maximal walking time (MWT) on a treadmill. RESULTS: All but four patients self-completed the usual-speed question. Median scores (25-75 centiles) were 41% (26-59) for the WIQ and 24% (11-41) for the EACH-Q. Coefficients of correlation of the three WIQ subscales and of the EACH-Q with treadmill results were significantly improved after correction by the "usual-speed" question. Overall, WIQ (mean of the three WIQ subscales) tended to improve but did not reach significance. CONCLUSION: Correcting the self-reported estimation of walking capacity by a self-reported estimation of usual walking pace significantly improves the correlation of all WIQ subscale scores and of the EACH-Q score with treadmill measurements of capacity. This confirms the interest of speed estimation in patients with peripheral arterial occlusive disease and claudication

Proximal ischemia is a frequent cause of exercise-induced pain in patients with a normal ankle to brachial index at rest

BACKGROUND: Excluding a vascular origin of exercise-related pain is often difficult in clinical practice. Recent papers have underlined the frequent association of concurrent lumbar spine degenerative disease and peripheral arterial disease. Furthermore, even when suspected, isolated exercise-induced proximal ischemia is difficult to diagnose. Measurement of transcutaneous oxygen pressure (tcpO2) is an interesting and accurate method to differentiate proximal (buttock) from distal (calf) regional blood flow impairment (RBFI) during exercise. OBJECTIVES: We searched for isolated proximal-without-distal RBFI as a possible cause of claudication, in patients with borderline (ABI-b: 0.91 - 0.99) or normal (ABI-n: 1.00 to 1.40) ankle to brachial index at rest. STUDY DESIGN: Retrospective cohort design study. We analyzed patients referred to our laboratory with symptom limiting claudication and an ankle brachial index within normal limits. SETTING: University-based exercise-investigation center. METHODS: Over a 12-year period, we identified 463 patients referred to our laboratory that had their lowest resting ABI between 0.90 and 1.40. The tcpO2 on chest, buttocks, and calves were recorded during treadmill walking tests (3.2 km/h, 10% slope) in 220 ABI-b and 243 ABI-n unique consecutive patients complaining of limiting claudication (each patient\u27s ABI was the lowest of the 2 legs). Limiting claudication was defined as the reported inability to walk 1 kilometer without stopping. A DROP index (limb tcpO2-changes minus chest tcpO2-changes from rest) below -15 mmHg was used to indicate a positive result (i.e. exercise-induced RBFI). RESULTS: Treadmill exercise showed evidence for proximal or distal RBFI, of at least one side, in 128 out of 220 patients (58.2%) and in 86 out of 243 (35.4%) patients with ABI-b and ABI-n, respectively. Isolated proximal-without-distal RBFI was found in 32 out of the 128 (25.0 %) positive tests in ABI-b and 32 out of the 86 (37.2%) positive tests in ABI-n patients. LIMITATIONS: Study limitations include the absence of systematic follow-up of diagnosed patients and absence of systematic search for cardio-respiratory co-morbid conditions. CONCLUSION: Isolated proximal-without distal RBFI is found in approximately one out of 7 patients complaining of symptom limiting claudication with a borderline or normal resting ABI. Exercise-tcpO2 may help to discriminate patients with arterial claudication that could benefit from invasive vascular investigations and procedures

Chemical solver to compute molecule and grain abundances and non-ideal MHD resistivities in prestellar core collapse calculations

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.We develop a detailed chemical network relevant to the conditions characteristic of prestellar core collapse. We solve the system of time-dependent differential equations to calculate the equilibrium abundances of molecules and dust grains, with a size distribution given by size-bins for these latter. These abundances are used to compute the different non-ideal magneto-hydrodynamics resistivities (ambipolar, Ohmic and Hall), needed to carry out simulations of protostellar collapse. For the first time in this context, we take into account the evaporation of the grains, the thermal ionisation of Potassium, Sodium and Hydrogen at high temperature, and the thermionic emission of grains in the chemical network, and we explore the impact of various cosmic ray ionisation rates. All these processes significantly affect the non-ideal magneto-hydrodynamics resistivities, which will modify the dynamics of the collapse. Ambipolar diffusion and Hall effect dominate at low densities, up to n_H = 10^12 cm^-3, after which Ohmic diffusion takes over. We find that the time-scale needed to reach chemical equilibrium is always shorter than the typical dynamical (free fall) one. This allows us to build a large, multi-dimensional multi-species equilibrium abundance table over a large temperature, density and ionisation rate ranges. This table, which we make accessible to the community, is used during first and second prestellar core collapse calculations to compute the non-ideal magneto-hydrodynamics resistivities, yielding a consistent dynamical-chemical description of this process

An improved PKPD modeling approach to characterize the pharmacodynamic interaction over time between ceftazidime/avibactam and colistin from in vitro time-kill experiments against multidrug-resistant Klebsiella pneumoniae isolates.

In contrast to the checkerboard method, bactericidal experiments [time-kill curves (TKCs)] allow an assessment of pharmacodynamic (PD) interactions over time. However, TKCs in combination pose interpretation problems. The objective of this study was to characterize the PD interaction over time between ceftazidime/avibactam (CZA) and colistin (CST) using TKC against four multidrug-resistant Klebsiella pneumoniae susceptible to both antibiotics and expressing a widespread carbapenemase determinant KPC-3. In vitro TKCs were performed and analyzed using pharmacokinetic/pharmacodynamic (PKPD) modeling. The general pharmacodynamic interaction model was used to characterize PD interactions between drugs. The 95% confidence intervals (95%CIs) of the expected additivity and of the observed interaction were built using parametric bootstraps and compared to evaluate the in vitro PD interaction over time. Further simulations were conducted to investigate the effect of the combination at varying concentrations typically observed in patients. Regrowth was observed in TKCs at high concentrations of drugs alone [from 4 to 32× minimum inhibitory concentrations (MIC)], while the combination systematically prevented the regrowth at concentrations close to the MIC. Significant synergy or antagonism were observed under specific conditions but overall 95%CIs overlapped widely over time indicating an additive interaction between antibiotics. Moreover, simulations of typical PK profile at standard dosages indicated that the interaction should be additive in clinical conditions. The nature of the PD interaction varied with time and concentration in TKC. Against the four K. pneumoniae isolates, the bactericidal effect of CZA + CST combination was predicted to be additive and to prevent the emergence of resistance at clinical concentrations

On the distribution of high-frequency stock market traded volume: a dynamical scenario

This manuscript reports a stochastic dynamical scenario whose associated stationary probability density function is exactly a previously proposed one to adjust high-frequency traded volume distributions. This dynamical conjecture, physically connected to superstatiscs, which is intimately related with the current nonextensive statistical mechanics framework, is based on the idea of local fluctuations in the mean traded volume associated to financial markets agents herding behaviour. The corroboration of this mesoscopic model is done by modelising NASDAQ 1 and 2 minute stock market traded volume

Hydrogen production during the irradiation of gaseous organic compounds: advantage of an extracted beam

ACE, Accélérateur, NIMBInternational audienceThis paper presents a fundamental study of the radiolysis of gaseous organic molecules induced by proton beam. For that purpose, a specific extracted beam line associated with a gas irradiation cell was set up on the 4 MV facility of the Institut de Physique Nucléaire of Lyon. The first experiments have been performed with gaseous alkanes and alkenes. The gaseous species formed during irradiation are analysed by an on-line gas chromatography instrument equipped with two detectors. In order to test our experimental faiclity, we have studied the influence of irradiation parameters (duration, beam intensity, pressure) on the production of hydrogen. In the case of propane, the radiolytic yield value of hydrogen G(H$_2$) is equal to 3.7 for total does in the range of 0.4 to 2.3 MGy at atmospheric pressure