Posttraumatic stress disorder (PTSD) is more prevalent in women and associated with greater risk of major forms of cardiovascular disease, but physiological mechanisms underlying this association ...remain unknown. We hypothesized that abnormal sympathetic responses to sympathoexcitatory stimuli might predispose PTSD patients to a greater risk of cardiovascular disease. We examined changes in integrated muscle sympathetic nerve activity (MSNA) burst and multiunit action potential (AP) recruitment patterns as well as hemodynamic responses during cold pressor test (CPT) in 14 women with PTSD and 14 healthy control subjects. Data were collected during 1-min baseline, 2-min CPT, and 3-min recovery. At baseline, blood pressure (BP) was not different between groups; however, heart rate and sympathetic neural activity were greater in women with PTSD MSNA burst frequency (BF): 27 ± 13 vs. 18 ± 14 bursts/min (
= 0.04); AP frequency: 272 ± 152 vs. 174 ± 146 spikes/min (
= 0.03). In response to CPT, BP responses exhibited a significant group × time interaction (
= 0.01) highlighted by a significant diastolic BP main group effect (
= 0.048) despite the finding that increases in integrated MSNA burst responses were not different between groups (
> 0.05). However, compared with control subjects, AP firing frequency (group × time interaction
= 0.0001, group
= 0.02) and AP per burst (group × time interaction
= 0.03, group
= 0.03) were augmented in women with PTSD. Collectively, women with PTSD exhibited a greater pressor response and an exaggerated sympathetic neural recruitment pattern during sympathoexcitatory stimuli that may, in part, explain the propensity toward developing hypertension and cardiovascular disease later in life.
The novel findings of the present study are that women with posttraumatic stress disorder (PTSD) have an augmented pressor response to the sympathoexcitatory stimulus of a cold pressor test (CPT) compared with healthy control subjects. Although integrated muscle sympathetic nerve activity burst responses were not significantly different between groups, total sympathetic action potential discharge in response to the CPT was markedly elevated in women with PTSD exhibiting increased firing of low-threshold axons as well as the recruitment of latent subpopulations of larger-sized axons that are otherwise silent at baseline. Aberrant autonomic circulatory control in response to sympathoexcitatory stimulus may in part explain the propensity toward developing hypertension and cardiovascular disease in this population.
The Multiple Chamber Aerosol Chemical Aging Study (MUCHACHAS) tested the hypothesis that hydroxyl radical (OH) aging significantly increases the concentration of first-generation biogenic secondary ...organic aerosol (SOA). OH is the dominant atmospheric oxidant, and MUCHACHAS employed environmental chambers of very different designs, using multiple OH sources to explore a range of chemical conditions and potential sources of systematic error. We isolated the effect of OH aging, confirming our hypothesis while observing corresponding changes in SOA properties. The mass increases are consistent with an existing gap between global SOA sources and those predicted in models, and can be described by a mechanism suitable for implementation in those models.
NO2 concentrations were measured by various instruments during the NO3Comp campaign at the atmosphere simulation chamber SAPHIR at Forschungszentrum Jülich, Germany, in June 2007. Analytical methods ...included photolytic conversion with chemiluminescence (PC-CLD), broadband cavity ring-down spectroscopy (BBCRDS), pulsed cavity ring-down spectroscopy (CRDS), incoherent broadband cavity-enhanced absorption spectroscopy (IBB\-CEAS), and laser-induced fluorescence (LIF). All broadband absorption spectrometers were optimized for the detection of the main target species of the campaign, NO3, but were also capable of detecting NO2 simultaneously with reduced sensitivity. NO2 mixing ratios in the chamber were within a range characteristic of polluted, urban conditions, with a maximum mixing ratio of approximately 75 ppbv. The overall agreement between measurements of all instruments was excellent. Linear fits of the combined data sets resulted in slopes that differ from unity only within the stated uncertainty of each instrument. Possible interferences from species such as water vapor and ozone were negligible under the experimental conditions.
DPOAE input/output (I/O) functions were measured at 7f2 frequencies (1 to 8 kHz; f2/f1 = 1.22) over a range of levels (-5 to 95 dB SPL) in normal-hearing and hearing-impaired human ears. L1-L2 was ...level dependent in order to produce the largest 2f1-f2 responses in normal ears. System distortion was determined by collecting DP data in six different acoustic cavities. These data were used to derive a multiple linear regression model to predict system distortion levels. The model was tested on cochlear-implant users and used to estimate system distortion in all other ears. At most but not all f2's, measurements in cochlear implant ears were consistent with model predictions. At all f2 frequencies, the ears with normal auditory thresholds produced I/O functions characterized by compressive nonlinear regions at moderate levels, with more rapid growth at low and high stimulus levels. As auditory threshold increased, DPOAE threshold increased, accompanied by DPOAE amplitude reductions, notably over the range of levels where normal ears showed compression. The slope of the I/O function was steeper in impaired ears. The data from normal-hearing ears resembled direct measurements of basilar membrane displacement in lower animals. Data from ears with hearing loss showed that the compressive region was affected by cochlear damage; however, responses at high levels of stimulation resembled those observed in normal ears.
In this study, we determined the limits and extent of hydrocarbon biodegradation, earthworm and plant toxicity, and waste leachability of crude oil-containing soils. Three oils (heavy, medium, and ...light of API gravity 14, 30, and 55, respectively) were mixed into silty loamy soils containing low (0.3%) or high (4.7%) organic carbon at 4000−27 000 mg/kg TPH. Hydrocarbon bioremediation in these artificially weathered oily soils usually followed first-order removal rates in which 50−75% and 10−90% of the total petroleum hydrocarbons (TPH) were degraded in 3−4 months for the low and high organic soils, respectively. Gas chromatographic profiles (simulated boiling point distillation of saturates and aromatic compounds) showed that, after bioremediation, hydrocarbons in oily soils decreased from 70 to 90%, from 40 to 60%, and from 35 to 60% for those carbon number species in the range of C11−C22, C23−C32, and C35−C44, respectively. Most oily soils were initially toxic to earthworms in which few animals survived 14-day bioassays. In a solid phase Microtox test, most oily soils had EC50 values that were ≤50%. Seed germination and plant growth (21-day test, wheat and oat but not corn) were also significantly reduced (0−25% of controls) in untreated soils containing the medium and light crude oils but not the heavy oil. Bioremediated soils were neither toxic to earthworms, inhibitory in the Microtox assay, nor inhibited seed germination after 5 (high organic soil) or 10−12 (low organic soil) months of treatment. Water-soluble hydrocarbons (e.g., O&G and BTEX) could leach from pretreated soils (medium and light crude oily soils) in column or batch extraction experiments. However, after bioremediation, most of the aromatic compounds were no longer leachable from the soils. These data demonstrate that treated oily soils lose their toxicity and potential to leach significant amounts of BTEX. These nontoxic soils contain 1000−8600 mg/kg residual hydrocarbons as TPH. Furthermore, these data suggest that the remaining petroleum compounds may be bound or unavailable in that they are not (a) biodegraded further, (b) toxic to soil-dwelling species (earthworms and plants), and (c) susceptible to leaching and subsequent impact to groundwater. These findings provide a basis for a framework in which petroleum hydrocarbon-containing soils can be evaluated by ecological assessment methods such as biodegradability, ecotoxicity, and leaching potential of regulated substances.
Traditionally, ecotoxicity quantitative structure–activity relationships (QSARs) for alcohol ethoxylate (AE) surfactants have been developed by assigning the measured ecotoxicity for commercial ...products to the average structures (alkyl chain length and ethoxylate chain length) of these materials. Acute
Daphnia magna toxicity tests for binary mixtures indicate that mixtures are more toxic than the individual AE substances corresponding with their average structures (due to the nonlinear relation of toxicity with structure). Consequently, the ecotoxicity value (expressed as effects concentration) attributed to the average structures that are used to develop the existing QSARs is expected to be too low. A new QSAR technique for complex substances, which interprets the mixture toxicity with regard to the “ethoxymers” distribution (i.e., the individual AE components) rather than the average structure, was developed. This new technique was then applied to develop new AE ecotoxicity QSARs for invertebrates, fish, and mesocosms. Despite the higher complexity, the fit and accuracy of the new QSARs are at least as good as those for the existing QSARs based on the same data set. As expected from typical ethoxymer distributions of commercial AEs, the new QSAR generally predicts less toxicity than the QSARs based on average structure.
Kinetic studies conducted in the new atmosphere simulation chamber SAPHIR at the Research Center Jülich allow a thorough investigation of oxidation of isoprene induced by O3 and the OH radical under ...atmospheric conditions. Rate coefficients for the O3‐isoprene and OH‐isoprene reaction are determined from measured concentration‐time profiles. For the reaction of O3 with isoprene the rate coefficient is determined to be (9.6 ± 0.7) × 10−18 cm3molecule−1 s−1 at 286 K. The rate coefficient for the reaction OH + isoprene is (10.0 ± 1.2) × 10−11 cm3molecule−1 s−1 at 294 K. The kinetic parameters determined in SAPHIR at atmospheric concentrations agree well with recent recommendations.
The results from a simulation chamber study on the formaldehyde (HCHO) absorption cross section in the UV spectral region are presented. We performed 4 experiments at ambient HCHO concentrations with ...simultaneous measurements of two DOAS instruments in the atmosphere simulation chamber SAPHIR in Jülich. The two instruments differ in their spectral resolution, one working at 0.2 nm (broad-band, BB-DOAS), the other at 2.7 pm (high-resolution, HR-DOAS). Both instruments use dedicated multi reflection cells to achieve long light path lengths of 960 m and 2240 m, respectively, inside the chamber. During two experiments HCHO was injected into the clean chamber by thermolysis of well defined amounts of para-formaldehyde reaching mixing rations of 30 ppbV at maximum. The HCHO concentration calculated from the injection and the chamber volume agrees with the BB-DOAS measured value when the absorption cross section of Meller and Moortgat (2000) and the temperature coefficient of Cantrell (1990) were used for data evaluation. In two further experiments we produced HCHO in-situ from the ozone + ethene reaction which was intended to provide an independent way of HCHO calibration through the measurements of ozone and ethene. However, we found an unexpected deviation from the current understanding of the ozone + ethene reaction when CO was added to suppress possible oxidation of ethene by OH radicals. The reaction of the Criegee intermediate with CO could be 240 times slower than currently assumed. Based on the BB-DOAS measurements we could deduce a high-resolution cross section for HCHO which was not measured directly so far.
N2O5 detection in the atmosphere has been accomplished using techniques which have been developed during the last decade. Most techniques use a heated inlet to thermally decompose N2O5 to NO3, which ...can be detected by either cavity based absorption at 662 nm or by laser-induced fluorescence. In summer 2007, a large set of instruments, which were capable of measuring NO3 mixing ratios, were simultaneously deployed in the atmosphere simulation chamber SAPHIR in Jülich, Germany. Some of these instruments measured N2O5 mixing ratios either simultaneously or alternatively. Experiments focused on the investigation of potential interferences from, e.g., water vapour or aerosol and on the investigation of the oxidation of biogenic volatile organic compounds by NO3. The comparison of N2O5 mixing ratios shows an excellent agreement between measurements of instruments applying different techniques (3 cavity ring-down (CRDS) instruments, 2 laser-induced fluorescence (LIF) instruments). Datasets are highly correlated as indicated by the square of the linear correlation coefficients, R2, which values were larger than 0.96 for the entire datasets. N2O5 mixing ratios well agree within the combined accuracy of measurements. Slopes of the linear regression range between 0.87 and 1.26 and intercepts are negligible. The most critical aspect of N2O5 measurements by cavity ring-down instruments is the determination of the inlet and filter transmission efficiency. Measurements here show that the N2O5 inlet transmission efficiency can decrease in the presence of high aerosol loads, and that frequent filter/inlet changing is necessary to quantitatively sample N2O5 in some environments. The analysis of data also demonstrates that a general correction for degrading filter transmission is not applicable for all conditions encountered during this campaign. Besides the effect of a gradual degradation of the inlet transmission efficiency aerosol exposure, no other interference for N2O5 measurements is found.
Theoretical, laboratory, and chamber studies have shown
fast regeneration of the hydroxyl radical (OH) in the photochemistry of isoprene,
largely due to unimolecular reactions which were previously ...thought not to
be important under atmospheric conditions. Based on early field
measurements, nearly complete regeneration was hypothesized for a wide range
of tropospheric conditions, including areas such as the rainforest where
slow regeneration of OH radicals is expected due to low concentrations of
nitric oxide (NO). In this work the OH regeneration in isoprene
oxidation is directly quantified for the first time through experiments
covering a wide range of atmospherically relevant NO levels (between 0.15
and 2 ppbv – parts per billion by volume) in the atmospheric simulation
chamber SAPHIR. These conditions cover remote areas partially influenced by
anthropogenic NO emissions, giving a regeneration efficiency of OH close to 1, and areas like the Amazonian rainforest with very low NO, resulting in
a surprisingly high regeneration efficiency of 0.5, i.e. a factor of 2 to 3
higher than explainable in the absence of unimolecular reactions. The
measured radical concentrations were compared to model calculations, and the
best agreement was observed when at least 50 % of the total loss of
isoprene peroxy radicals conformers (weighted by their abundance) occurs via
isomerization reactions for NO lower than 0.2 ppbv. For these levels of NO,
up to 50 % of the OH radicals are regenerated from the products of the 1,6
α-hydroxy-hydrogen shift (1,6-H shift) of Z-δ-RO2 radicals through the photolysis of an unsaturated hydroperoxy aldehyde (HPALD)
and/or through the fast aldehydic hydrogen shift (rate constant
∼10 s−1 at 300 K) in di-hydroperoxy carbonyl peroxy
radicals (di-HPCARP-RO2), depending on their relative yield. The
agreement between all measured and modelled trace gases (hydroxyl,
hydroperoxy, and organic peroxy radicals, carbon monoxide, and the sum of
methyl vinyl ketone, methacrolein, and hydroxyl hydroperoxides) is nearly
independent of the adopted yield of HPALD and di-HPCARP-RO2 as both
degrade relatively fast (<1 h), forming the OH radical and CO among
other products. Taking into consideration this and earlier isoprene studies,
considerable uncertainties remain on the distribution of oxygenated products,
which affect radical levels and organic aerosol downwind of unpolluted
isoprene-dominated regions.
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