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Background and purpose Theoretical considerations and the results of animal studies indicate that manual lymphatic drainage ( MLD) might have an impact on intracranial pressure ( ICP). There is a lack of clinically qualitative investigations on patients with severe cerebral diseases. Methods Between April 2013 and January 2015 a prospective observational study was performed on patients who were undergoing intracranial pressure measurement and treatment with MLD. ICP, cerebral perfusion pressure, mean arterial pressure ( MAP), heart rate and oxygen saturation were recorded continuously 15 min before the procedure, during MLD (22 min) and for 15 min after the procedure. For analysis the data treatment units were divided into two groups: patients with a mean baseline ICP <15 mmHg (group 1) and patients with a mean ICP ≥15 mmHg before MLD (group 2). Results A total of 133 treatment units (61 patients) were analysed (group 1 n = 99; group 2 n = 34). The mean baseline ICP was 10.4 mmHg overall, and 8.3 mmHg and 18.6 mmHg respectively in group 1 and group 2; ICP significantly decreased during therapy with MLD and this persisted during the follow-up period in group 2. MAP did not show any significant differences between the different periods. Conclusions Our data showed a significant reduction of ICP during therapy with craniocervical MLD in patients with severe cerebral diseases. [ABSTRACT FROM AUTHOR]

Measurements of HONO were carried out at an urban background site near central London as part of the Clean air for London (ClearfLo) project in summer 2012. Data were collected from 22 July to 18 August 2014, with peak values of up to 1.8 ppbV at night and non-zero values of between 0.2 and 0.6 ppbV seen during the day. A wide range of other gas phase, aerosol, radiation, and meteorological measurements were made concurrently at the same site, allowing a detailed analysis of the chemistry to be carried out. The peak HONO=NOx ratio of 0.04 is seen at ~02:00 UTC, with the presence of a second, daytime, peak in HONO=NOx of similar magnitude to the night-time peak, suggesting a significant secondary daytime HONO source. A photostationary state calculation of HONO involving formation from the reaction of OH and NO and loss from photolysis, reaction with OH, and dry deposition shows a significant underestimation during the day, with calculated values being close to 0, compared to the measurement average of 0.4 ppbV at midday. The addition of further HONO sources from the literature, including dark conversion of NO2 on surfaces, direct emission, photolysis of ortho-substituted nitrophenols, the postulated formation from the reaction of HO2×H2O with NO2, photolysis of adsorbed HNO3 on ground and aerosols, and HONO produced by photosensitized conversion of NO2 on the surface increases the daytime modelled HONO to 0.1 ppbV, still leaving a significant missing daytime source. The missing HONO is plotted against a series of parameters including NO2 and OH reactivity (used as a proxy for organic material), with little correlation seen. Much better correlation is observed with the product of these species with j(NO2), in particular NO2 and the product of NO2 with OH reactivity. This suggests the missing HONO source is in some way related to NO2 and also requires sunlight. Increasing the photosensitized surface conversion rate of NO2 by a factor of 10 to a mean daytime first-order loss of ~6×10-5 s-1 (but which varies as a function of j(NO2)) closes the daytime HONO budget at all times (apart from the late afternoon), suggesting that urban surfaces may enhance this photosensitized source. The effect of the missing HONO to OH radical production is also investigated and it is shown that the model needs to be constrained to measured HONO in order to accurately reproduce the OH radical measurements. [ABSTRACT FROM AUTHOR]

The article offers information on the measurement of trophospheric ozone (O3), nitric oxide (NO), and nitrogen dioxide (NO2) fluxes and its interaction over a bare soil through aerodynamic gradient method. It adds the use of eddy-covariance and automatic chambers for ozone and NO fluxes. It states that chemical interactions of the gasses resulted only to small ozone flux divergence.

The article presents a study which compares the efficiency of different techniques using various instruments in measuring interferences of commercial nitrogen dioxide (NO2) in the urban atmosphere and in a smog chamber. Chemiluminescence instruments with molybdenum or photolytic converters, Luminol based instrument and a proposed NO 2 Long Path Absorption Photometer (LOPAP) were compared with spectroscopic techniques. The methods and results of the study are discussed.

The article presents a study on the development of a compact and simple instrument, Long Path Absorption Photometer (LOPAP), to detect nitrous oxide in the atmosphere. The study states that significant interferences against nitrous acid (HONO) and oxide are suppressed using a HONO/oxide scrubber. The study states that LOPAP allows absolute calibration that can be quickly performed with liquid nitrite standards, and has been validated against chemiluminescence technique.

The article presents a study which measures nitric oxide (NO), tropospheric ozone (O3), and nitrogen dioxide (NO2) fluxes and chemical interactions over an agricultural field. The study assessed NO, O3, and NO2 using the aerodynamic gradient method and vertical mixing ratio profile measurements. Results show that uncertainties of the friction velocity have caused flux uncertainties while O3 are accounted for about 10% on average.

The article presents a study which compares the performances of different commercial nitrogen dioxide (NO2) instruments and a NO2-LOPAP in the urban atmosphere and in a smog chamber in Santiago de Chile. A field experiment was conducted wherein chemiluminescence instruments with molybdenum or photolytic converters were compared to NO2-LOPAP with spectroscopic techniques to detect interferences. Results show strong interferences and agreements in all instruments.

The article focuses on the development of a Long Path Absorption Photometer (LOPAP) instrument for the detection of NO2 in the atmosphere. The instrument is considered more sensitive than known instruments as it has an accuracy of 10 percent and a precision of 0.5 percent for three minutes time resolution. It is also deemed easier to apply than other methods. Its use is validated by intercomparison with chemiluminescence instrument with photolytic NO2 converter.

The article discusses the measurement of nitrogen oxide concentrations in the atmosphere simulation chamber by using various instruments. It highlights the analytical methods used including pulsed cavity ring-down spectroscopy (CRDS), laser-induced fluorescence (LIF) and broadband cavity ring-down spectroscopy (BBCRDS). It also notes that all of the absorption spectrometers were optimized to discover the main target species during the NO3Comp Campaign.

The oxidation capacity of the highly polluted urban area of Santiago, Chile has been evaluated during a summer measurement campaign carried out from 8-20 March 2005. The hydroxyl (OH) radical budget was evaluated employing a simple quasi-photostationary-state model (PSS) constrained with simultaneous measurements of HONO, HCHO, O3, NO, NO2, j(O¹D), j(NO2), 13 alkenes and meteorological parameters. In addition, a zero dimensional photochemical box model based on the Master Chemical Mechanism (MCMv3.1) has been used to estimate production rates and total free radical budgets, including OH, HO2 and RO2. Besides the above parameters, the MCM model has been constrained by the measured CO and volatile organic compounds (VOCs) including alkanes and aromatics. Both models simulate the same OH concentration during daytime indicating that the primary OH sources and sinks included in the simple PSS model predominate. Mixing ratios of the main OH radical precursors were found to be in the range 0.8- 7 ppbv (HONO), 0.9-11 ppbv (HCHO) and 0-125 ppbv (O3). The alkenes average mixing ratio was ∼58 ppbC accounting for ∼12% of the total identified non-methane hydrocarbons (NMHCs). During the daytime (08:00 h-19:00 h), HONO photolysis was shown to be the most important primary OH radical source comprising alone ∼55% of the total initial production rate, followed by alkene ozonolysis (∼24%) and photolysis of HCHO (∼16%) and O3 (∼5%). The calculated average and maximum daytime OH production rates from HONO photolysis was 1.7 ppbv h-1 and 3.1 ppbv h-1, respectively. Based on the experimental results a strong photochemical daytime source of HONO is proposed. A detailed analysis of the sources of OH radical precursors has also been carried out. [ABSTRACT FROM AUTHOR]

In the present pilot study, an optimized LOPAP instrument (LOng Path Absorption Photometer) for the detection of nitrous acid (HONO) in the atmosphere (DL 0.2 pptV) was tested at the high alpine research station Jungfraujoch at 3580m altitude in the Swiss Alps under conditions comparable to polar regions. HONO concentrations in the range <0.5-50 pptV with an average of 7.5 pptV were observed at the Jungfraujoch. The diurnal profiles obtained exhibited clear maxima at noon and minima with very low concentration during the night supporting the proposed photochemical production of HONO. In good agreement with recent measurements at the South Pole, it was demonstrated, that interferences of chemical HONO instruments can significantly influence the measurements and lead to considerable overestimations, especially for low pollution level. Accordingly, the active correction of interferences is of paramount importance for the determination of reliable HONO data. [ABSTRACT FROM AUTHOR]

The degradation mechanism of 1,3,5-trimethylbenzene (TMB) as implemented in the Master Chemical Mechanism version 3.1 (MCM) was evaluated using data from the environmental chamber at the Paul Scherrer Institute. The results show that the MCM provides a consistent description of the photo-oxidation of TMB/NOx mixtures for a range of conditions. In all cases the agreement between the measurement and the simulation decreases with decreasing VOC-NOx ratio and in addition with increasing precursor concentration. A significant underestimation of the decay rate of TMB and thus underestimation of reactivity in the system, consistent with results from previous appraisals of the MCM, was observed. Much higher nitrous acid (HONO) concentrations compared to simulations and expected from chamber characterization experiments were measured during these smog chamber experiments. A light induced NO2 to HONO conversion at the chamber walls is suggested to occur. This photoenhanced NO2 to HONO conversion with subsequent HONO photolysis enhances the reactivity of the system. After the implementation of this reaction in the model it describes the decay of TMB properly. Nevertheless, the model still overpredicts ozone at a later stage of the experiment. This can be attributed to a too slow removal of NO2. It is also shown that this photo-enhanced HONO formation is not restricted to TMB photo-oxidation but also occurs in other chemical systems (e.g. α-pinene). However, the influence of HONO as a source of OH radicals is less important in these more reactive systems and therefore the importance of the HONO chemistry is less obvious. [ABSTRACT FROM AUTHOR]

In the present pilot study, an optimized LOPAP instrument for the detection of nitrous acid (HONO) in the atmosphere (DL 0.2 pptV) was tested at the high alpine research station "Jungfraujoch" at 3580m altitude in the Swiss Alps under conditions comparable to polar regions. HONO concentrations in the range <0.5-50 pptV with an average of 7.5 pptV were observed at the "Jungfraujoch". The diurnal profiles obtained exhibited clear maxima at noon and minima with very low concentration during the night supporting the proposed photochemical production of HONO. In good agreement with recent measurements at the South Pole, it was demonstrated, that interferences of chemical HONO instruments can significantly influence the measurements and lead to considerable overestimations, especially for low pollution level. Accordingly, the correction of interferences is of paramount importance for those instruments, which sample HONO on aqueous or humid surfaces. [ABSTRACT FROM AUTHOR]

The interactions of aerosols consisting of humic acids with gaseous nitrogen dioxide (NO2) were investigated under different light conditions in aerosol flow tube experiments at ambient pressure and temperature. The results show that NO2 is converted on the humid acid aerosol into nitrous acid (HONO), which is released from the aerosol and can be detected in the gas phase at the reactor exit. The formation of HONO on the humic acid aerosol is strongly activated by light: In the dark, the HONO-formation was below the detection limit, but it was increasing with the intensity of the irradiation with visible light. Under simulated atmospheric conditions with respect to the actinic flux, relative humidity and NO2-concentration, reactive uptake coefficients γrxn for the NO2→HONO conversion on the aerosol between γrxn <10-7 (in the dark) and γrxn=6x10-6 were observed. The observed uptake coefficients decreased with increasing NO2- concentration in the range from 2.7 to 280 ppb and were dependent on the relative humidity (RH) with slightly reduced values at low humidity (<20% RH) and high humidity (>60% RH). The measured uptake coefficients for the NO2→HONO conversion are too low to explain the HONO-formation rates observed near the ground in rural and urban environments by the conversion of NO2→HONO on organic aerosol surfaces, even if one would assume that all aerosols consist of humic acid only. It is concluded that the processes leading to HONO formation on the Earth surface will have a much larger impact on the HONO-formation in the lowermost layer of the troposphere than humic materials potentially occurring in airborne particles. [ABSTRACT FROM AUTHOR]

HONO formation has been proposed as an important OH radical source in simulation chambers for more than two decades. Besides the heterogeneous HONO formation by the dark reaction of NO2 and adsorbed water, a photolytic source has been proposed to explain the elevated reactivity in simulation chamber experiments. However, the mechanism of the photolytic process is not well understood so far. As expected, production of HONO and NOx was also observed inside the new atmospheric simulation chamber SAPHIR under solar irradiation. This photolytic HONO and NOx formation was studied with a sensitive HONO instrument under reproducible controlled conditions at atmospheric concentrations of other trace gases. It is shown that the photolytic HONO source in the SAPHIR chamber is not caused by NO2 reactions and that it is the only direct NOy source under illuminated conditions. In addition, the photolysis of nitrate which was recently postulated for the observed photolytic HONO formation on snow, ground, and glass surfaces, can be excluded in the chamber. A photolytic HONO source at the surface of the chamber is proposed which is strongly dependent on humidity, on light intensity, and on temperature. An empirical function describes these dependencies and reproduces the observed HONO formation rates to within 10%. It is shown that the photolysis of HONO represents the dominant radical source in the SAPHIR chamber for typical tropospheric O3/H2O concentrations. For these conditions, the HONO concentrations inside SAPHIR are similar to recent observations in ambient air. [ABSTRACT FROM AUTHOR]

In the present study, the heterogeneous conversion of nitrogen oxide (NO) and nitrogen dioxide (NO2) was studied at atmospheric humidity levels on flame soot surfaces treated with gaseous nitric acid (HNO3). In addition, the heterogeneous reaction of HNO3 on soot was investigated at atmospheric humidity. For the treatment of soot by pure HNO3 only reversible uptake with a surface coverage of ∼1-2×1014 HNO3 cm-2 was observed for HNO3 mixing ratios in the range 250-800 ppbv. Only for higher HNO3 mixing ratios of >800 ppbv the formation of NO and NO2 was observed. The results were not affected by the addition of NO. In none of the experiments with HNO3 the formation of nitrous acid (HONO) was observed. For HNO3 mixing ratios <600 ppbv the upper limit yields for HONO, NO2 and NO were found to be <0.2%, <0.5% and <1%, respectively. Compared to untreated soot, the product formation of the reaction of NO2 with soot was not significantly affected when the soot surface was treated with gaseous HNO3 prior to the experiment. Only for high surface coverage of HNO3 the formation of HONO was suppressed in the initial phase of the reaction, probably caused by the blocking of active sites by adsorbed HNO3. Under the assumption that the experimental findings for the used model flame soot can be extrapolated to atmospheric soot particles, the results show that the reactions of HNO3 and HNO3+NO on soot surfaces are unimportant for a "renoxification" of the atmosphere and do not represent an atmospheric HONO source. In addition, the integrated HONO yield of ca. 1014 cm-2 in the reaction of NO2 with soot is not significantly influenced by simulated atmospheric processing of the soot surface by HNO3, and is still too small to explain HONO formation in the atmosphere. [ABSTRACT FROM AUTHOR]