Elucidating the polycyclic aromatic hydrocarbons involved in soot inception.

Polycyclic aromatic hydrocarbons are the main precursors to soot particles in combustion systems. A lack of direct experimental evidence has led to controversial theoretical explanations for the transition from gas-phase species to organic soot clusters. This work focuses on sampling infant soot particles from well-defined flames followed by analysis using state-of-the-art mass spectrometry. We found that PAH molecules present in soot particles are all stabilomers. Kinetic Monte Carlo simulations and thermodynamic stability calculations further identify the detected PAHs as peri-condensed and without aliphatic chains. Van der Waals forces can easily link PAHs of such size and shape to form PAH dimers and larger clusters under the specified flame conditions. Our results provide direct experimental evidence that soot inception is initiated by a physical process under typical flame conditions. This work improves our understanding of aerosol particulates, which has implications for their environmental and climate change impacts.

Impact of Methanol and Butanol on Soot Formation in Gasoline Surrogate Pyrolysis: A Shock-Tube Study.

The influence of methanol and butanol on soot formation during the pyrolysis of a toluene primary reference fuel mixture with a research octane number (RON) of 91 (TPRF91) was investigated by conducting shock-tube experiments. The TPRF91 mixture contained 17 mol % n-heptane, 29 mol % iso-octane, and 54 mol % toluene. To assess the contribution of individual fuel compounds on soot formation during TPRF91 pyrolysis, the pyrolysis of argon diluted (1) toluene, (2) iso-octane, and (3) n-heptane mixtures were also studied. To enable the interpretation of the TPRF91 + methanol and TPRF91 + butanol experiments, the influence of both alcohols on soot formation during the thermal decomposition of toluene and iso-octane was also investigated in a separate series of measurements. Pyrolysis was monitored behind reflected shock waves at pressures between 2.1 and 4.2 bar and in the temperature range of 2060-2815 K. Laser extinction at 633 nm was used to determine the soot yield as a function of reaction time. For selected experiments, the temporal variation in temperature was also measured via time-resolved two-color CO absorption using two quantum-cascade lasers at 4.73 and 4.56 µm. It was found that soot formed during TPRF91 pyrolysis is primarily caused by the thermal decomposition of toluene. Adding methanol to TPRF91 results in a slight reduction of soot formation, whereas admixing butanol results in shifting soot formation to higher temperatures, but in that case, no overall soot reduction was observed during TPRF91 pyrolysis. Measured soot yields were compared to simulations based on a previous and an updated version of a detailed reaction mechanism from the CRECK modeling group [Nobili, A.; Cuoci, A.; Pejpichestakul, W.; Pelucchi, M.; Cavallotti, C.; Faravelli, T. Combust. Flame 2022; 10.1016/j.combustflame.2022.112073]. Rate-of-production analyses for reactions involving BINS at different experimental conditions were carried out. Although in the case of TPRF91 and toluene pyrolysis, no quantitative agreement was obtained between the experiment and simulation, the comparison nevertheless shows that the new version of the CRECK mechanism is a significant improvement over the previous one. In the case of n-heptane decomposition and iso-octane pyrolysis with and without alcohols, the updated reaction mechanism shows excellent agreement between simulation and measured soot yields.

Application of Change Point Analysis of Response Time Data to Detect Test Speededness.

Computer-based and web-based testing have become increasingly popular in recent years. Their popularity has dramatically expanded the availability of response time data. Compared to the conventional item response data that are often dichotomous or polytomous, response time has the advantage of being continuous and can be collected in an unobstrusive manner. It therefore has great potential to improve many measurement activities. In this paper, we propose a change point analysis (CPA) procedure to detect test speededness using response time data. Specifically, two test statistics based on CPA, the likelihood ratio test and Wald test, are proposed to detect test speededness. A simulation study has been conducted to evaluate the performance of the proposed CPA procedure, as well as the use of asymptotic and empirical critical values. Results indicate that the proposed procedure leads to high power in detecting test speededness, while keeping the false positive rate under control, even when simplistic and liberal critical values are used. Accuracy of the estimation of the actual change point, however, is highly dependent on the true change point. A real data example is also provided to illustrate the utility of the proposed procedure and its contrast to the response-only procedure. Implications of the findings are discussed at the end.

High-Harmonic Generation Approaching the Quantum Critical Point of Strongly Correlated Systems.

By employing the exact diagonalization method, we investigate the high-harmonic generation (HHG) of the correlated systems under the strong laser irradiation. For the extended Hubbard model on a periodic chain, HHG close to the quantum critical point (QCP) is more significant compared to two neighboring gapped phases (i.e., charge-density-wave and spin-density wave states), especially in low frequencies. We confirm that the systems in the vicinity of the QCP are supersensitive to the external field and more optical-transition channels via excited states are responsible for HHG. This feature holds the potential of obtaining high-efficiency harmonics by making use of materials approaching QCP. Based on the two-dimensional Haldane model, we further propose that the even- or odd-order components of generated harmonics can be promisingly regarded as spectral signals to distinguish the topologically ordered phases from locally ordered ones. Our findings in this Letter pave the way to achieve ultrafast light source from HHG in strongly correlated materials and to study quantum phase transition by nonlinear optics in strong laser fields.

Noncatalytic Oxidative Coupling of Methane (OCM): Gas-Phase Reactions in a Jet Stirred Reactor (JSR).

Oxidative coupling of methane (OCM) is a promising technique for converting methane to higher hydrocarbons in a single reactor. Catalytic OCM is known to proceed via both gas-phase and surface chemical reactions. It is essential to first implement an accurate gas-phase model and then to further develop comprehensive homogeneous-heterogeneous OCM reaction networks. In this work, OCM gas-phase kinetics using a jet-stirred reactor are studied in the absence of a catalyst and simulated using a 0-D reactor model. Experiments were conducted in OCM-relevant operating conditions under various temperatures, residence times, and inlet CH4/O2 ratios. Simulations of different gas-phase models related to methane oxidation were implemented and compared against the experimental data. Quantities of interest (QoI) and rate of production analyses on hydrocarbon products were also performed to evaluate the models. The gas-phase models taken from catalytic reaction networks could not adequately describe the experimental gas-phase performances. NUIGMech1.1 was selected as the most comprehensive model to describe the OCM gas-phase kinetics; it is recommended for further use as the gas-phase model for constructing homogeneous-heterogeneous reaction networks.

Analysis of risk factors of non-suicidal self-harm behavior in adolescents with depression.

BACKGROUND: Adolescents are a high-risk group for non-suicidal self-injury (NSSI), which seriously affects their physical and mental health. This study aimed to explore the risk factors for depressive adolescents with NSSI. METHODS: A total of 153 adolescents with depression were divided into the NSSI group (n=65) and non-NSSI group (n=88) according to the criteria stipulated by Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5). The Beck scale for suicidal ideation (BSS), adolescent self-rating life events checklist (ASLEC), family adaptability and cohesion evaluation scale II-Chinese version (FACES II-CV), childhood trauma questionnaire short form (CTQ SF), and multidimensional scale of perceived social support (MSPSS) were applied to evaluate suicidal ideation, frequency and intensity of stressful life events, family functions, childhood trauma, and perceived support, respectively. We applied two-dimensional logistic regression to identify risk factors for NSSI. RESULTS: Female gender ratio, suicidal ideation, and attempted suicide were significantly higher in the NSSI group than in the non-NSSI group (all P<0.05). Scores of interpersonal relationships in ASLEC, emotional abuse, and emotional neglect in the CTQ-SF were significantly higher in the NSSI group than those in the non-NSSI group (all P<0.001). The scores of family cohesion (P=0.001) and family adaptability (P=0.01) were significantly lower in the NSSI group than in the non-NSSI group. The MSPSS was used to assess support from the family, and the index was significantly lower in the NSSI group (P<0.001). After adjusting for age and gender, BSS score, interpersonal relationship score, emotional abuse score, and emotional neglect score were identified as independent risk factors for NSSI. CONCLUSIONS: The rate of NSSI in adolescents with depression is high. Higher scores of BSS, interpersonal relationship, emotional abuse, and neglect were independently associated with NSSI.

Surface functionalization of titanium substrates with Deoxyribonuclease I inhibit peri-implant bacterial infection.

This study aimed to investigate the effect of Deoxyribonuclease I (DNase I) coating on initial adhesion and biofilm formation of peri-implant bacteria. Titanium (Ti), Ti-polydopamine (Ti-PDOP), Ti-PDOP-DNase I and Ti-PDOP-inactivated DNase I samples were studied. The FE-SEM, EDS and XPS were used to confirm that DNase I was coated onto Ti. The initial adhesion and biofilm formation of Aggregatibacter actinomycetemcomitans (A.a) and Fusobacterium nucleatum (F.n) were observed by CLSM. The osteogenic induction of Ti-PDOP-DNase I on MC3T3-E1 cells was investigated by ALP activity and RT-PCR. The adhesion clearance rate of viable bacteria on the surfaces of Ti-PDOP-DNase I was 91.95% for A.a, and 96.37% for F.n, and the 24 h biofilm formation of the bacteria was significantly inhibited. In addition, on DNase I coating, the mRNA level of osteogenic marker genes (alp, opn, bsp, sp7) and the activity of ALP were both up-regulated. Therefore, DNase I coating could be an alternative approach for preventing implant-related infection.

Patient Satisfaction with Navigator Interpersonal Relationship (PSN-I): item-level psychometrics using IRT analysis.

BACKGROUND: Patient navigation (PN) is a promising intervention to eliminate cancer health inequities. Patient navigators play a critical role in the navigation process. Patients' satisfaction with navigators is important in determining the effectiveness of PN programs. We applied item response theory (IRT) analysis to establish item-level psychometric properties for the Patient Satisfaction with Interpersonal Relationship with Navigators (PSN-I). METHODS: We conducted a confirmatory factor analysis (CFA) to establish unidimensionality of the 9-item PSN-I in 751 cancer patients (68% female) between 18 and 86 years old. We fitted unidimensional IRT models-unconstrained graded response model (GRM) and Rasch model-to PSN-I data, and compared model fit using likelihood ratio (LR) test and information criteria. We obtained item parameter estimates (IPEs), item category/operating characteristic curves, and item/test information curves for the better fitting model. RESULTS: CFA with diagonally weighted least squares confirmed that the one-factor model fit the data (RMSEA = 0.047, 95% CI = 0.033-0.060, and CFI ≈ 1). Responses to PSN-I items clustered into the 4th and 5th categories. We aggregated the first three response categories to provide stable parameter estimates for both IRT models. The GRM fit the data significantly better than the Rasch model (LR = 80.659, df = 8, p < 0.001). Akaike's information coefficient (6384.978 vs. 6320.319) and Bayesian information coefficient (6471.851 vs. 6443.771) were lower for the GRM. IPEs showed substantial variation in items' discriminating power (1.80-3.35) for GRM. CONCLUSIONS: This IRT analysis confirms the latent structure of the PSN-I and supports its use as a valid and reliable measure of latent satisfaction with PN.

Analyzing the solid soot particulates formed in a fuel-rich flame by solvent-free matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry.

RATIONALE: The compositional and structural information of soot particles is essential for a better understanding of the chemistry and mechanism during the combustion. The aim of the present study was to develop a method to analyze such soot particulate samples with high complexity and poor solubility. METHODS: The solvent-free sample preparation matrix-assisted laser desorption/ionization (MALDI) technique was combined with the ultrahigh-resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) for the characterization of solid soot particulates. Moreover, a modified iso-abundance plot (Carbon Number vs. Hydrogen Number vs. Abundance) was introduced to visualize the distributions of various chemical species, and to examine the agreement between the hydrogen-abstraction-carbon-addition (HACA) mechanism and the polycyclic aromatic hydrocarbon growth in the investigated flame system. RESULTS: This solvent-free MALDI method enabled the effective ionization of the solid soot particulates without any dissolving procedure. With the accurate m/z ratios from FTICR-MS, a unique chemical formula was assigned to each of the recorded mass signals. The combustion products were proven to be mainly large polycyclic aromatic hydrocarbons (PAHs), together with a small amount (<5%) of oxidized hydrocarbons. CONCLUSIONS: The developed method provides a new approach for the molecular characterization of soot particulates like carbonaceous materials. The investigated soot particulates are mainly PAHs with no or very short aliphatic chains. The growth mechanism of PAHs during combustion can be examined against the classic HACA mechanism.

Effects of DNase I coating of titanium on bacteria adhesion and biofilm formation.

The removal of mature biofilm from the surface of implant has been a formidable challenge in treating implant-associated infection. Prevention of biofilm formation rather than removal of existing biofilm is a more effective approach. Immobilization of biofilm-dispersing enzymes on material surfaces is regarded as one of the most promising strategies. Deoxyribonuclease I (DNase I) can degrade extracellular DNA (eDNA) and then destabilize biofilm. In this study, DNase I was immobilized on a titanium (Ti) surface by using dopamine as an intermediate. The water contact angle, SEM, EDS and XPS confirmed that DNase I was successfully coated to the bare Ti and the final coating was highly hydrophilic. The DNase I coating showed significant effects in preventing Streptococcus mutans (S. mutans) and Staphylococcus aureus (S. aureus) adhesion and biofilm formation over a time span of 24h. The favorable biocompatibility was demonstrated by cell study in vitro. In addition, cell adhesion results suggested that DNase I coating had the potential to facilitate MC3T3-E1 cell attachment. DNase I coating with anti-infection ability and biocompatibility has great potential for increasing success rates of implant applications.

Oxytocin is implicated in social memory deficits induced by early sensory deprivation in mice.

Early-life sensory input plays a crucial role in brain development. Although deprivation of orofacial sensory input at perinatal stages disrupts the establishment of the barrel cortex and relevant callosal connections, its long-term effect on adult behavior remains elusive. In this study, we investigated the behavioral phenotypes in adult mice with unilateral transection of the infraorbital nerve (ION) at postnatal day 3 (P3). Although ION-transected mice had normal locomotor activity, motor coordination, olfaction, anxiety-like behaviors, novel object memory, preference for social novelty and sociability, they presented deficits in social memory and spatial memory compared with control mice. In addition, the social memory deficit was associated with reduced oxytocin (OXT) levels in the hypothalamus and could be partially restored by intranasal administration of OXT. Thus, early sensory deprivation does result in behavioral alterations in mice, some of which may be associated with the disruption of oxytocin signaling.

The Mediated MIMIC Model for Understanding the Underlying Mechanism of DIF.

Due to its flexibility, the multiple-indicator, multiple-causes (MIMIC) model has become an increasingly popular method for the detection of differential item functioning (DIF). In this article, we propose the mediated MIMIC model method to uncover the underlying mechanism of DIF. This method extends the usual MIMIC model by including one variable or multiple variables that may completely or partially mediate the DIF effect. If complete mediation effect is found, the DIF effect is fully accounted for. Through our simulation study, we find that the mediated MIMIC model is very successful in detecting the mediation effect that completely or partially accounts for DIF, while keeping the Type I error rate well controlled for both balanced and unbalanced sample sizes between focal and reference groups. Because it is successful in detecting such mediation effects, the mediated MIMIC model may help explain DIF and give guidance in the revision of a DIF item.

Detection of Test Speededness Using Change-Point Analysis.

Change-point analysis (CPA) is a well-established statistical method to detect abrupt changes, if any, in a sequence of data. In this paper, we propose a procedure based on CPA to detect test speededness. This procedure is not only able to classify examinees into speeded and non-speeded groups, but also identify the point at which an examinee starts to speed. Identification of the change point can be very useful. First, it informs decision makers of the appropriate length of a test. Second, by removing the speeded responses, instead of the entire response sequence of an examinee suspected of speededness, ability estimation can be improved. Simulation studies show that this procedure is efficient in detecting both speeded examinees and the speeding point. Ability estimation is dramatically improved by removing speeded responses identified by our procedure. The procedure is then applied to a real dataset for illustration purpose.

Correlation between CYP4F2 gene rs2108622 polymorphism and susceptibility to ischemic stroke.

OBJECTIVE: To conduct a meta-analysis for the correlation between cytochrome P450 4F2 (CYP4F2) rs2108622 (V433M) gene polymorphism and ischemic stroke. METHODS: We retrieved the case-control studies on the correlation between CYP4F2 V433M polymorphism and ischemic stroke included in domestic and international databases before January 2015 and selected the best genetic model, using RevMan 5.2 software for meta-analysis. According to the heterogeneity test results of selected literature, the effect model of consolidated data was selected, and the combined OR and 95% CI were calculated. RESULTS: A total of six documents were included. Recessive model (VM + MM vs. VV) was selected as the best genetic model. The combined results showed that: compared with wild-type VV, there are significant association between ischemic stroke and CYP4F2 polymorphism (OR merge = 1.37, 95% CI: 1.21~1.54, P < 0.001). CONCLUSION: CYP4F2 V433M may be the susceptibility gene for ischemic stroke.

IL-17A G197A gene polymorphism contributes to susceptibility for liver cirrhosis development from patients with chronic hepatitis B infection in Chinese population.

BACKGROUND: IL-17A G197A and IL-17F A7488G gene polymorphisms are found to be associated with the risk of several diseases, however few studies have focused on their correlation with risk of liver cirrhosis (LC). AIMS: The aim of this study was to assess the impact of IL-17A G197A and IL-17F A7488G gene polymorphisms on development of LC from chronic hepatitis B (CHB) in Chinese patients. METHODS: A total of 163 HBV-related LC patients and 168 CHB patients were enrolled in the present study. IL-17A and IL-17F gene polymorphisms were analyzed using a polymerase chain reaction (PCR) restriction fragment length polymorphism assay (PCR-RFLP). RESULTS: Frequencies of IL-17A G197A genotype AA and allele A were significantly higher in LC patients compared with that in CHB patients (AA 42.33% vs 27.98%, P = 0.032; A 56.34% vs 46.15%, P=0.011, respectively); While no significant difference in frequencies of genotypes and alleles of IL-17F A7488G was found between the two groups. The AA genotype of IL-17A G197A significantly increased LC risk (OR 4.186, 95% CI: 1.479-11.844), while A allele carriers were also associated with an increased LC risk (OR 1.856, 95% CI: 1.161-2.967). CONCLUSION: IL-17A G197A is a candidate gene that confers the genetic susceptibility for LC development from CHB in Chinese population.

Investigating the role of CH2 radicals in the HACA mechanism.

Detailed mechanisms of PAH growth involving methylene (CH2) were studied using accurate ab initio density functional theory B3LYP/6-311+G(d,p) calculations, as well as approximate QCISD(T,full)/6-311++G(3df,2pd) calculations. The PAH growth can be divided into five essential reaction steps, namely, addition C2H2 → intramolecular hydrogen migration → addition CH2 → cyclization → H-elimination. The aliphatic species of indene and 1H-phenalene are found in the pathways of PAH growth, which is in accord with the experimental results that reveal the formation of aliphatic species in flames. It was found that the simultaneous removal of two H atoms in one reaction step is feasible in PAH evolution, and this can reasonably interpret the absence of a H atom in the post-flame region. The corresponding rate coefficients at 1 atm were evaluated by using TST and RRKM theory by solving the master equations in the temperature range of 500-2500 K. The calculated branching ratios suggest that the pathways involving CH2 are competitive in PAH growth.

Decreased expression of IL-27 and its correlation with Th1 and Th17 cells in progressive multiple sclerosis.

Progressive multiple sclerosis (MS) is an immune-mediated demyelinating disease in which both imbalanced T helper (Th) subsets and aberrant cytokine profiles have been found. Interleukin-27 (IL-27), a cytokine with pro-inflammatory and anti-inflammatory effects, plays pleiotropic roles in immunomodulation. In the present study, plasma levels of IL-27, interferon-gamma (IFN-γ), IL-17 and frequencies of peripheral Th1, Th17 cells were determined by enzyme-linked immunosorbent assay (ELISA) and flow cytometry in 45 progressive MS and 25 healthy controls. mRNA expression levels of IL-27, IFN-γ, T-bet, IL-17 and RAR-related orphan receptor gamma t (RORγt) in peripheral blood mononuclear cells (PBMCs) were also quantified by real-time polymerase chain reaction. Plasma and mRNA levels of IL-27 in progressive MS patients were significantly lower than those in healthy controls, while plasma concentrations of IL-17, frequencies of circulating Th17, and mRNA expression levels of IL-17 as well as RORγt were all increased remarkably compared with healthy controls. No statistical significance was observed in IFN-γ and T-bet mRNA expression or plasma IFN-γ levels between progressive MS patients and healthy controls. Moreover, plasma levels of IL-27 were found to be negatively correlated to the percentages of circulating Th17 or plasma IL-17 concentrations in patients with progressive MS. Our data showed that progressive MS patients had decreased plasma and mRNA expression levels of IL-27, suggesting that it might be involved in the pathophysiological process of MS.

a-Stratified Computerized Adaptive Testing in the Presence of Calibration Error.

a-Stratified computerized adaptive testing with b-blocking (AST), as an alternative to the widely used maximum Fisher information (MFI) item selection method, can effectively balance item pool usage while providing accurate latent trait estimates in computerized adaptive testing (CAT). However, previous comparisons of these methods have treated item parameter estimates as if they are the true population parameter values. Consequently, capitalization on chance may occur. In this article, we examined the performance of the AST method under more realistic conditions where item parameter estimates instead of true parameter values are used in the CAT. Its performance was compared against that of the MFI method when the latter is used in conjunction with Sympson-Hetter or randomesque exposure control. Results indicate that the MFI method, even when combined with exposure control, is susceptible to capitalization on chance. This is particularly true when the calibration sample size is small. On the other hand, AST is more robust to capitalization on chance. Consistent with previous investigations using true item parameter values, AST yields much more balanced item pool usage, with a small loss in the precision of latent trait estimates. The loss is negligible when the test is as long as 40 items.

New insights into thermal decomposition of polycyclic aromatic hydrocarbon oxyradicals.

Thermal decompositions of polycyclic aromatic hydrocarbon (PAH) oxyradicals on various surface sites including five-membered ring, free-edge, zigzag, and armchair have been systematically investigated by using ab initio density functional theory B3LYP/6-311+G(d,p) basis set. The calculation based on Hückel theory indicates that PAHs (3H-cydopenta[a]anthracene oxyradical) with oxyradicals on a five-membered ring site have high chemical reactivity. The rate coefficients of PAH oxyradical decomposition were evaluated by using Rice-Ramsperger-Kassel-Marcus theory and solving the master equations in the temperature range of 1500-2500 K and the pressure range of 0.1-10 atm. The kinetic calculations revealed that the rate coefficients of PAH oxyradical decomposition are temperature-, pressure-, and surface site-dependent, and the oxyradical on a five-membered ring is easier to decompose than that on a six-membered ring. Four-membered rings were found in decomposition of the five-membered ring, and a new reaction channel of PAH evolution involving four-membered rings is recommended.