Autoignition characteristics of
n-heptane/air, gasoline/air, and ternary surrogate/air mixtures were studied behind reflected shock waves in a high-pressure, low-temperature regime similar to that ...found in homogeneous charge compression ignition (HCCI) engine cycles. The range of experiments covered combustion of fuel in air for lean, stoichiometric, and rich mixtures (
Φ
=
0.5
, 1.0, 2.0), two pressure ranges (15–25 and 45–60 atm), temperatures from 850 to 1280 K, and exhaust gas recirculation (EGR) loadings of (0, 20, and 30%). The ignition delay time measurements in
n-heptane are in good agreement with the shock tube study of Fieweger et al. (Proc. Combust. Inst. 25 (1994) 1579–1585) and support the observation of a pronounced, low-temperature, NTC region. Strong agreement was seen between ignition delay time measurements for RD387 gasoline and surrogate (63% iso-octane/20% toluene/17%
n-heptane by liquid volume) over the full range of experimental conditions studied. Ignition delay time measurements under fuel-lean
(
Φ
=
0.5
)
mixture conditions were longer than with
Φ
=
1.0
mixtures at both the low- (15–25 atm) and high- (45–60 atm) pressure conditions. Ignition delay times in fuel-rich
(
Φ
=
2.0
)
mixtures for both gasoline and surrogate were indistinguishable in the low-pressure (15–25 atm) range, but were clearly shorter at high-pressures (45–60 atm). EGR loading affected the ignition delay times similarly for both gasoline and surrogate, with clear trends indicating an increase in ignition delay time with increased EGR loading. This data set should provide benchmark targets for detailed mechanism validation and refinement under HCCI conditions.
Ignition delay times and ethylene concentration time-histories were measured behind reflected shock waves during decalin oxidation and pyrolysis. Ignition delay measurements were conducted for ...gas-phase decalin/air mixtures over temperatures of 769–1202K, pressures of 11.7–51.2atm, and equivalence ratios of 0.5, 1.0, and 2.0. Negative-temperature-coefficient (NTC) behavior of decalin autoignition was observed, for the first time, at temperatures below 920K. Current ignition delay data are in good agreement with past shock tube data in terms of pressure dependence but not equivalence ratio dependence. Ethylene mole fraction and fuel absorbance time-histories were acquired using laser absorption at 10.6 and 3.39μm during decalin pyrolysis for mixtures of 2200–3586ppm decalin/argon at pressures of 18.2–20.2atm and temperatures of 1197–1511K. Detailed comparisons of these ignition delay and species time-history data with predictions based on currently available decalin reaction mechanisms are presented, and preliminary suggestions for the adjustment of some key rate parameters are made.
Omega-3 fatty acids are important to pregnancy and neonatal development and health. One mechanism by which omega-3 fatty acids exert their protective effects is through serving as substrates for the ...generation of specialized pro-resolving lipid mediators (SPM) that potently limit and resolve inflammatory processes. We recently identified that SPM levels are increased in maternal blood at delivery as compared to umbilical cord blood, suggesting the placenta as a potential site of action for maternal SPM. To explore this hypothesis, we obtained human placental samples and stained for the SPM resolvin D2 (RvD2) receptor GPR18 via immunohistochemistry. In so doing, we identified GPR18 expression in placental vascular smooth muscle and extravillous trophoblasts of the placental tissues. Using in vitro culturing, we confirmed expression of GPR18 in these cell types and further identified that stimulation with RvD2 led to significantly altered responsiveness (cytoskeletal changes and pro-inflammatory cytokine production) to lipopolysaccharide inflammatory stimulation in human umbilical artery smooth muscle cells and placental trophoblasts. Taken together, these findings establish a role for SPM actions in human placental tissue.
Omega-3 and omega-6 fatty acids are important for neonatal development and health. One mechanism by which omega-3 and omega-6 fatty acids exert their effects is through their metabolism into ...oxylipins and specialized pro-resolving mediators. However, the influence of oxylipins on fetal growth is not well understood. Therefore, the objective of this study was to identify oxylipins present in maternal and umbilical cord plasma and investigate their relationship with infant growth. Liquid chromatography-tandem mass spectrometry was used to quantify oxylipin levels in plasma collected at the time of delivery. Spearman's correlations highlighted significant correlations between metabolite levels and infant growth. They were then adjusted for maternal obesity (normal body mass index (BMI: ≤30 kg/m
) vs. obese BMI (>30 kg/m
) and smoking status (never vs. current/former smoker) using linear regression modeling. A
-value < 0.05 was considered statistically significant. Our study demonstrated a diverse panel of oxylipins from the lipoxygenase pathway present at the time of delivery. In addition, both omega-3 and omega-6 oxylipins demonstrated potential influences on the birth length and weight percentiles. The oxylipins present during pregnancy may influence fetal growth and development, suggesting potential metabolites to be used as biomarkers for infant outcomes.
Sleep quality is linked to disordered eating, obesity, depression, and weight-related functioning. Most research, however, has focused on clinical populations. The current study investigated ...relationships between sleep quality, disordered eating, and patterns of functioning in a community sample to better understand relationships among modifiable health behaviors. Participants (
N
= 648) recruited from Amazon Mechanical Turk completed assessments of eating, depression, weight-related functioning, and sleep. Self-reported height and weight were used to calculate body mass index (
M
= 27.3,
SD
= 6.9). Participants were on average 37.6 years (
SD
= 12.3), primarily female (65.4%), and White, not Hispanic (72.7%). Over half of participants endorsed poor sleep quality, and average sleep scores were above the clinical cutoff for poor sleep quality. Sleep scores were significantly positively correlated with disordered eating, depression, and weight-related functioning, even after adjusting for age, body mass index, and sex. Multivariate regression models predicting weight-related functioning and depression showed that both sleep quality and disordered eating independently predicted depression. Sleep quality did not independently predict weight-related functioning; however, disordered eating did. To the best of our knowledge, this is the first study to assess sleep behaviors, disordered eating, and weight-related functioning in a community sample of weight diverse participants. Results indicate that most participants endorsed poor sleep quality, which was associated with disordered eating patterns, including binge eating and poorer weight-related functioning, even after controlling for body mass index, highlighting that this relationship exists across the weight spectrum. These results speak to the importance of health behavior assessment and intervention within nonclinical samples.
Level of evidence
Level III: evidence obtained from well-designed cohort or case–control analytic studies
We report the first application of cavity-enhanced absorption spectroscopy (CEAS) using a coherent light source for sensitive and rapid gaseous species time-history measurements in a shock tube. ...Off-axis alignment and fast scanning of the laser wavelength were used to minimize coupling noise in a low-finesse cavity. An absorption gain factor of 83 with a measurement time resolution of 20 µs was demonstrated for C2H2 detection using a near-infrared transition near 1537 nm, corresponding to a noise-equivalent detection limit of 20 ppm at 296 K and 76 ppm at 906 K at 50 kHz. This substantial gain in signal, relative to conventional single-pass absorption, will enable ultra-sensitive species detection in shock tube kinetics studies, particularly useful for measurements of minor species and for studies of dilute reactive systems.
The rate constant of the H-abstraction reaction of formaldehyde (CH2O) by hydrogen atoms (H), CH2O + H = H2 + HCO, has been studied behind reflected shock waves with use of a sensitive mid-IR laser ...absorption diagnostic for CO, over temperatures of 1304–2006 K and at pressures near 1 atm. C2H5I was used as an H atom precursor and 1,3,5-trioxane as the CH2O precursor, to generate a well-controlled CH2O/H reacting system. By designing the experiments to maintain relatively constant H atom concentrations, the current study significantly boosted the measurement sensitivity of the target reaction and suppressed the influence of interfering reactions. The measured CH2O + H rate constant can be expressed in modified Arrhenius from as k CH2O+H(1304–2006 K, 1 atm) = 1.97 × 1011(T/K)1.06 exp(−3818 K/T) cm3 mol–1s–1, with uncertainty limits estimated to be +18%/–26%. A transition-state-theory (TST) calculation, using the CCSD(T)-F12/VTZ-F12 level of theory, is in good agreement with the shock tube measurement and extended the temperature range of the current study to 200–3000 K, over which a modified Arrhenius fit of the rate constant can be expressed as k CH2O+H(200–3000 K) = 5.86 × 103(T/K)3.13 exp(−762 K/T) cm3 mol–1 s–1.
We evaluated a multiplexed PCR panel for the detection of 16 bacterial, viral, and fungal pathogens in cerebrospinal fluid. Panel results were compared to routine testing, and discrepancies were ...resolved by additional nucleic acid amplification tests or sequencing. Overall, the positive and negative agreements across methods were 92.9% and 91.9%, respectively.
Arbuscular mycorrhizal (AM) fungi facilitate inorganic N (NH₄ ⁺ or NO₃ ⁻) uptake by plants, but their role in N mobilization from organic sources is unclear. We hypothesized that arbuscular ...mycorrhizae enhance the ability of a plant to use organic residues (ORs) as a source of N. This was tested under controlled glasshouse conditions by burying a patch of OR in soil separated by 20-μm nylon mesh so that only fungal hyphae can pass through it. The fate of the N contained in the OR patch, as influenced by Glomus claroideum, Glomus clarum, or Glomus intraradices over 24 weeks, was determined using ¹⁵N as a tracer. AM fungal species enhanced N mineralization from OR to different levels. N recovery and translocation to Russian wild rye by hyphae reached 25% of mineralized N in G. clarum, which was most effective despite its smaller extraradical development in soil. Mobilization of N by G. clarum relieved plant N deficiency and enhanced plant growth. We show that AM hyphae modify soil functioning by linking plant growth to N mineralization from OR. AM species enhance N mineralization differentially leading to species-specific changes in the quality of the soil environment (soil C-to-N ratio) and structure of the soil microbial community.
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