Study on Formation of Interstellar C7H from Reactions C4 + C3H2 and C4H + C3H.

We interrogated C7H produced from reactions C4 + C3H2/C4H + C3H → C7H + H using both translational and photoionization spectroscopy. Reactants C3H, C3H2, C4, and C4H were synthesized in two crossed beams of 1% C2H2/He ignited by pulsed high-voltage discharge. The individual contributions of reactions C4 + C3H2 and C4H + C3H to product C7H were evaluated as 17:83 from reactant concentrations in both molecular beams. The translational energy distribution, the angular distribution, and the photoionization efficiency curve of product C7H were unraveled. C7H was identified as the most stable linear isomer by its photoionization efficiency curve that features two ionization thresholds corresponding to separate transitions to singlet and triplet states of l-C7H+. The quantum-chemical calculations indicate that the associations of C4 with C3H2 and C4H with C3H incur no entrance barriers, and the most favorable exit channel leads to product l-C7H + H. It is the first time demonstrating that C7H is producible from reactions 1,3C4 + 1C3H2 and 2C4H + 2C3H on the lowest-lying singlet and triplet potential energy surfaces of 1,3C7H2. This work implies that the reactions of C4 + C3H2 and C4H + C3H might have contributions to interstellar C7H to some extent as compared with the C + C6H2 reaction commonly adopted in an astrochemical model.

Formations of C6H from reactions C3 + C3H2 and C3H + C3H and of C8H from reactions C4 + C4H2 and C4H + C4H.

We interrogated C6H and C8H produced separately from the reactions C3 + C3H2/C3H + C3H/C3H2 + C3 → C6H + H and C4 + C4H2/C4H + C4H/C4H2 + C4 → C8H + H using product translational and photoionization spectroscopy. Individual contributions of the three reactions to the product C6H or C8H were evaluated with reactant concentrations. Translational-energy distributions, angular distributions, and photoionization efficiency curves of products C6H and C8H were unraveled. The product C6H (C8H) was recognized as the most stable linear isomer by comparing its photoionization efficiency curve with that of l-C6H (l-C8H), produced exclusively from the reaction C2 + C4H2 → l-C6H + H (C2 + C6H2 → l-C8H + H). The ionization threshold after deconvolution was determined to be 9.3 ± 0.1 eV for l-C6H and 8.9 ± 0.1 eV for l-C8H, which is in good agreement with theoretical values. Quantum-chemical calculations indicate that the reactions of C3 + C3H2 and C3H + C3H (C4 + C4H2 and C4H + C4H) incur no energy barriers that lie above the corresponding reactant and the most stable product l-C6H (l-C8H) with H on the lower-lying potential-energy surfaces. The theoretical calculation is in accord with the experimental observation. This work implies that the reactions of C3 + C3H2/C3H + C3H and C4 + C4H2/C4H + C4H need to be taken into account for the formation of interstellar C6H and C8H, respectively.

Systematic review and meta-analysis of nutrient supplements for treating sarcopenia in people with chronic obstructive pulmonary disease.

Individuals with chronic obstructive pulmonary disease (COPD) are prone to malnutrition and sarcopenia as a result of nutritional deficiencies and increased energy metabolism. However, the effects of nutrient supplements (NS) on treating sarcopenia in patients with COPD are not well established from systematic evidence. This meta-analysis examined the effect of NS on sarcopenia in patients with COPD. A systematic search of multiple databases was conducted, and 29 randomized controlled trials involving 1625 participants (age, mean [SD] = 67.9 [7.8] years) were analyzed. NS demonstrated significant improvements in body weight (MD,1.33 kg; 95% CI, 0.60, 2.05 kg; P = 0.0003; I2 = 87%), fat-free mass index (MD, 0.74 kg/m2; 95% CI, 0.21, 1.27 kg/m2; P = 0.007; I2 = 75%), and 6-min walk test (MD, 19.43 m; 95% CI, 4.91, 33.94 m; P = 0.009; I2 = 81%) compared with control. However, NS had nonsignificant effects on handgrip strength (SMD, 0.36; 95% CI, - 0.15, 0.88; P = 0.16; I2 = 87%) and quadriceps muscle strength (SMD, 0.11; 95% CI, -  0.06, 0.27; P = 0.20; I2 = 25%) compared with the control. In conclusion, NS may be an effective treatment for improving body composition and physical performance in COPD. Future studies should explore the effects of intervention durations, specific NS types, or combined training in patients with COPD and sarcopenia.

Formation and IR spectrum of monobridged Si2H4 isolated in solid argon.

The infrared (IR) spectrum of monobridged Si2H4 (denoted as mbr-Si2H4) isolated in solid Ar was recorded, and a set of lines (in the major matrix site) observed at 858.3 cm-1, 971.5 cm-1, 999.2 cm-1, 1572.7 cm-1, 2017.7 cm-1, 2150.4 cm-1, and 2158.4 cm-1 were characterized. The species was produced by the electron bombardment of an Ar matrix sample containing a small proportion of SiH4 during matrix deposition. Upon photolysis of the matrix samples using 365 nm and 160 nm light, the content of mbr-Si2H4 increased. The band positions, relative intensity ratios, and D-isotopic shift ratios of the observed IR features are generally in good agreement with those predicted by the B3LYP/aug-cc-pVTZ method. In addition, the photochemistry of the observed products was discussed.

Flow artifact removal in carotid wall imaging based on black and gray-blood dual-contrast images subtraction.

PURPOSE: To develop and validate a dual-contrast image subtraction (DCIS) strategy for eliminating the flow artifacts in black-blood carotid MRI. METHODS: Twelve patients with carotid stenosis and eight healthy volunteers were imaged using the black and gray-blood dual-contrast imaging based on the relaxation-enhanced compressed sensing three-dimensional motion-sensitizing driven equilibrium prepared rapid-gradient-echo (RECS-3D MERGE) sequence. Subtraction of black-blood images (BBIs) and gray-blood images (GBIs), together with a preweighting procedure, was performed to eliminate the residual blood signal in BBIs. A wavelet denoising procedure was applied to offset the noise amplification. In addition to the lumen signal-to-noise ratio (SNR) and wall-lumen contrast-to-noise ratio (CNR), the signal variance ratio (SVR) and contrast variance ratio (CVR) were also used to evaluate the blood suppression efficiency. RESULTS: By choosing the weighting factor of one, the lumen SNR of DCIS images was approximately 1% of that of the original BBIs, and the CNR showed a 91.4% improvement as compared with the BBIs. The median of the lumen SVR decreased to zero, and the CVR increased to 123% of that of the BBIs. CONCLUSIONS: DCIS is demonstrated to be an effective strategy for sufficiently removing the residual flow signal from black-blood carotid MRI. Magn Reson Med 77:1612-1618, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

An improved automated type-based method for area assessment of wound surface.

Accurate and precise wound measurements are a critical component of wound detection and assessment. Digital cameras are convenient and objective tools that are being increasingly used worldwide to assist with wound measurements and assessments. However, heterogeneous wounds and poor lighting conditions continue to be obstacles to wound area recognition. This study, therefore, provides an improved automated type-based wound area assessment method that is robust to lighting conditions and can distinguish between different wound tissues based on wound colors. The results of both laboratory and clinical applications of the proposed method show excellent consistency of manual area measurements. This proposed technology is expected to provide wound care specialists with more clinical information about heterogeneous wounds, thereby enabling prospective cost savings for therapy and treatment.

Formation of C9H2 and C10H2 from Reactions C3H + C6H2 and C4H + C6H2.

The reactions of C3H and C4H radicals with C6H2 were investigated for the first time. Reactants C3H, C4H, and C6H2 were synthesized in two beams of C2H2 diluted with helium by pulsed high-voltage discharge. We measured translational-energy distributions, angular distributions, and photoionization-efficiency spectra of C9H2 and C10H2 produced from the title reactions in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet photoionization. The C3H (C4H) + C6H2 reaction releases 42% (33%) of available energy into the translational degrees of freedom of product C9H2 (C10H2) + H and scatters products into a nearly isotropic angular distribution. The photoionization-efficiency spectrum of C9H2 (C10H2) is in good agreement with that of C9H2 (C10H2) produced from the C7H (C8H) + C2H2 reaction. The ionization threshold, after deconvolution, was determined as 8.0 ± 0.1 eV for C9H2 and 8.8 ± 0.1 eV for C10H2. The combination of measurements of product translational-energy release and photoionization-efficiency spectra indicates productions of 3HC9H/c-1HC3(C)C5H/c-1HC7(C)CH + H and 1HC10H + H in the two title reactions, which are supported also by quantum-chemical calculations. Ratios branching to the three isomers of C9H2 remain unknown. This work demonstrates that long carbon-chain molecules (e.g., C9H2 and C10H2) can be synthesized from reactions of CmH (e.g., m = 3 and 4) radicals with polyynes (e.g., HC6H) and gives some valuable implications to planetary, interstellar, and combustion chemistry.

Formation of C3H2, C5H2, C7H2, and C9H2 from reactions of CH, C3H, C5H, and C7H radicals with C2H2.

The Cm+2H2 family can be classified into two categories - C2n+1H2 and C2n+2H2. Cm+2H2 are important intermediates in the syntheses of large carbonaceous molecules. An understanding of the formation mechanisms of both odd and even carbon-numbered Cm+2H2 is beneficial to atmospheric, astronomical, and combustion chemistry. HC2n+2H (polyynes) are believed to be producible from C2nH + C2H2 and C2H + C2nH2 reactions but C2n+1H2 (n≥ 2) attract less attention to their formation mechanisms. In the present study, we make up for the lack of knowledge on C2n+1H2 formation mechanisms by investigating the reactions C2n-1H + C2H2→ C2n+1H2 + H with n = 1-4. The dynamics of reactions of C2n-1H radicals with C2H2 are explored in crossed molecular beams using products C2n+1H2. The translational-energies and angular distributions of the hydrogen-loss channels of products are unraveled by measuring time-of-flight spectra and photoionization-efficiency spectra of C2n+1H2 with tunable synchrotron vacuum-ultraviolet ionization. The C2n+1H2 product includes two isomers, c-(1)HC2n-1(C)CH and (3)HC2n+1H, which are identified by the maximal translational-energy release and the photoionization threshold. Furthermore, quantum-chemical calculations indicate that the title reactions incur a small or negligible entrance barrier and are nearly isoergic except for the barrierless exothermic reaction CH + C2H2→ C3H2 + H. We demonstrate for the first time that C5H2, C7H2, and C9H2 are producible from the title reactions. In conjunction with studies on the C2nH + C2H2 reactions, a brief picture for the CmH (m = 1-8) + C2H2→ Cm+2H2 + H reactions can be outlined.

High-mobility group box 1 exacerbates CCl4-induced acute liver injury in mice.

High-mobility group box 1 (HMGB1) is a nuclear factor that can also serve as an imflammatory mediator once released into extracellular milieu. Therefore, HMGB1 has been recognized to play a pivotal role in inflammatory diseases such as sepsis, acute lung injury, ischemia reperfusion injury and type 1 diabetes. Nevertheless, its impact on carbon tetrachloride (CCl4)-induced hepatic injury is yet to be elucidated. In the present report, we demonstrated evidence indicating that high levels of HMGB1 were not only present in the necrotic area of liver but also in the serum after CCl4 challenge. In line with these observations, administration of exogenous recombinant HMGB1 exacerbated CCl4-induced hepatic injury, while HMGB1 blocking antibody provided protection for mice against CCl4-induced acute liver injury as evidenced by the decrease of serum transaminase and reduction of hepatic tissues necrosis. Mechanistic studies revealed that blockade of HMGB1 attenuated CCl4-induced MDA accumulation along with improved SOD and GSH activity. Treatment of mice with HMGB1 neutralizing antibody also significantly inhibited the production of proinflammatory mediators TNF-α and IL-6 along with attenuated HMGB1 expression and its extracellular release. Together, our data suggest an essential role for HMGB1 in CCl4-induced acute liver injury, while HMGB1 neutralizing antibody could be served as an effective regimen for preventing CCl4-induced acute liver injury.

Dynamics of the reaction of C3(a³Πu) radicals with C2H2: a new source for the formation of C5H.

The reaction C3(a(3)Πu) + C2H2 → C5H + H was investigated at collision energy 10.9 kcal mol(-1) that is less than the enthalpy of ground-state reaction C3(X(1)Σg (+)) + C2H2 → C5H + H. C3(a(3)Πu) radicals were synthesized from 1% C4F6/He by pulsed high-voltage discharge. The title reaction was conducted in a crossed molecular-beam apparatus equipped with a quadrupole-mass filter. Product C5H was interrogated with time-of-flight spectroscopy and synchrotron vacuum-ultraviolet ionization. Reactant C3(a(3)Πu) and product C5H were identified using photoionization spectroscopy. The ionization thresholds of C3(X(1)Σg(+)) and C3(a(3)Πu) are determined as 11.6 ± 0.2 eV and 10.0 ± 0.2 eV, respectively. The C5H product is identified as linear pentynylidyne that has an ionization energy 8.4 ± 0.2 eV. The title reaction releases translational energy 10.6 kcal mol(-1) in average and has an isotropic product angular distribution. The quantum-chemical calculation indicates that the C3(a(3)Πu) radical attacks one of the carbon atoms of C2H2 and subsequently a hydrogen atom is ejected to form C5H + H, in good agreement with the experimental observation. As far as we are aware, the C3(a(3)Πu) + C2H2 reaction is investigated for the first time. This work gives an implication for the formation of C5H from the C3(a(3)Πu) + C2H2 reaction occurring in a combustion or discharge process of C2H2.

Dynamics of the reaction of C2 with C6H2: an implication for the formation of interstellar C8H.

The reaction C2 + C6H2 → C8H + H was investigated for the first time. Reactant C2 (C6H2) was synthesized from 1% C3F6/He (5% C2H2/He) by pulsed high-voltage discharge. We measured the translational-energy distribution, the angular distribution, and the photoionization spectrum of product C8H in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. This reaction released average translational energy of 8.5 kcal mol(-1) corresponding to a fraction of 0.37 in translation. C8H was identified as octatetranyl based on the maximal translational-energy release 23 ± 2 kcal mol(-1) and the ionization threshold 8.9 ± 0.2 eV. Kinematic constraints can qualitatively account for the nearly isotropic angular distribution. The quantum-chemical calculations indicate that the exothermic reactions C2 (X (1)Σg (+)/a (3)Πu) + HC6H → C8H + H can proceed without entrance and exit barriers, implying the importance in the cold interstellar medium. This work verifies that interstellar C8H can be formed through the C2 + C6H2 reaction.

Extracellular Water Ratio and Phase Angle as Predictors of Exacerbation in Chronic Obstructive Pulmonary Disease.

BACKGROUND: Chronic obstructive pulmonary disease (COPD), characterized by high-energy metabolism, often leads to malnutrition and is linked to exacerbations. This study investigates the association of malnutrition-related body composition and handgrip strength changes with exacerbation frequencies in COPD patients. METHODS: We analyzed 77 acute exacerbation COPD (AECOPD) patients and 82 stable COPD patients, categorized as frequent and infrequent exacerbators. Assessments included body composition, handgrip strength, nutritional risk, dyspnea scale, and COPD assessment. RESULTS: Among AECOPD patients, there were 22 infrequent and 55 frequent exacerbators. Infrequent exacerbators showed better muscle parameters, extracellular water ratio, phase angle, and handgrip strength. Significant differences in intracellular water, total cellular water, protein, and body cell mass were observed between groups. Logistic regression indicated that extracellular water ratio (OR = 1.086) and phase angle (OR = 0.396) were independently associated with exacerbation risk. Thresholds for exacerbation risk were identified as 0.393 for extracellular water ratio and 4.85° for phase angle. In stable COPD, 13 frequent and 69 infrequent exacerbators were compared, showing no significant differences in weight, muscle, and adipose parameters, but significant differences in extracellular water ratio, phase angle, and handgrip strength. CONCLUSIONS: These findings suggest that increased exacerbations in COPD patients correlate with higher extracellular water ratios and lower phase angles.

Breathable and wearable graphene/waterborne polyurethane coated regenerated polyethylene terephthalate fabrics for motion sensing and thermal therapy.

The functional utilization of recycled polymers has emerged as a current prominent and timely subject. Flexible wearable devices with high sensitivity to conductivity have garnered significant attention in the fields of human healthcare monitoring and personal heat management. One significant obstacle that needs to be addressed is the simultaneous maintenance of both sensing functionality and durability in composite fabrics. In this paper, a collection of durable, breathable, and flexible smart fabric was produced using the scratch coating method. The fabrics were created by utilizing a regenerated polyethylene terephthalate fabric as a base material, incorporating graphene microsheets (G) as a conductive agent, and applying a waterborne polyurethane layer as a surface protective coating. Furthermore, an investigation was conducted to assess their sensing performance and electrothermal performance. The composite fabric exhibits significant advantages in terms of high conductivity (592 S/m), wide strain range, high sensitivity (Gauge factor = 6.04) and fantabulous dynamic stability (2000 cycles) at a mass ratio of Graphene/WPU loading of 8:2. These sensors were successfully utilized to monitor various degrees of real-time human body movements, ranging from significant deformation bending of elbows to slight deformation swallowing. Furthermore, the sensors also exhibit a significant electric heating effect. Specifically, when a voltage of 10 V is applied, the sensors can reach a steady state temperature of 53.3 °C within a mere 30 s. This discovery holds potential for the development of wearable heaters that can be used for on-demand thermal therapy, functional protective clothing, and medical electric heating wearables.

Migraine Duration as a Potential Amplifier of Obesity.

Purpose: Migraine is a complex neurovascular disorder with obesity as a notable risk factor. This study aimed to investigate an under-researched area of the association between migraine duration and body composition. Patients and Methods: Patients with migraine from a neurology outpatient department were enrolled and were categorized into four groups based on illness duration: 1 year, 1-5 years, 5-10 years, and >10 years. Patient demographics, blood biochemistry, and body composition data were collected and analyzed statistically. Results: Patients with migraine were predominantly female, with lower education levels, significant work stress, poor sleep, and limited exercise. Longer migraine duration corresponded to increased obesity metrics. Notably, those patients with under 1 year of illness showed elevated blood lipid and liver function levels, whereas those with >10 years showed increased weight, waist circumference, body mass index, and fat content, despite higher physical activity. Significant positive correlation between obesity metrics and migraine duration was seen in patients who had migraine for >1 year. Conclusion: Our findings indicate that protracted episodes of migraine could amplify obesity tendencies, underscoring the imperative of weight regulation in migraine intervention to diminish ensuing adiposity-associated hazards.

Examining the molecular mechanisms of topiramate in alleviating insulin resistance: A study on C2C12 myocytes and 3T3L-1 adipocytes.

PURPOSE: Migraine, a severely debilitating condition, may be effectively managed with topiramate, known for its migraine prevention and weight loss properties due to changes in body muscle and fat composition and improved insulin sensitivity. However, the mechanism of topiramate in modulating insulin response in adipocytes and myocytes remains elusive. This study aims to elucidate these molecular mechanisms, offering insights into its role in weight management for migraine sufferers and underpinning its clinical application. METHODS: Insulin resistance improvements were evaluated through glucose uptake measurements in C2C12 muscle cells and 3T3L-1 adipocytes, with Oil red O staining conducted on adipocytes. RNA-seq transcriptome analysis was used to identify the regulatory target genes of topiramate in these cells. The involvement of key genes and pathways was further validated through western blot analysis. RESULTS: Topiramate effectively reduced insulin resistance in C2C12 and 3T3L-1 cells. In C2C12 cells, it significantly lowered SORBS1 gene and protein levels. In 3T3L-1 cells, topiramate upregulated CTGF and downregulated MAPK8 and KPNA1 genes. Changes were notable in nuclear cytoplasmic transport and circadian signaling pathways. Furthermore, it caused downregulation of MKK7, pJNK1/ JNK1, BMAL1, and CLOCK proteins compared to the insulin-resistant model. CONCLUSION: This study provides preliminary insights into the mechanisms through which topiramate modulates insulin resistance in C2C12 myocytes and 3T3L-1 adipocytes, enhancing our understanding of its therapeutic potential in managing weight and insulin sensitivity in migraine patients.

Unsupervised Part Discovery via Dual Representation Alignment.

Object parts serve as crucial intermediate representations in various downstream tasks, but part-level representation learning still has not received as much attention as other vision tasks. Previous research has established that Vision Transformer can learn instance-level attention without labels, extracting high-quality instance-level representations for boosting downstream tasks. In this paper, we achieve unsupervised part-specific attention learning using a novel paradigm and further employ the part representations to improve part discovery performance. Specifically, paired images are generated from the same image with different geometric transformations, and multiple part representations are extracted from these paired images using a novel module, named PartFormer. These part representations from the paired images are then exchanged to improve geometric transformation invariance. Subsequently, the part representations are aligned with the feature map extracted by a feature map encoder, achieving high similarity with the pixel representations of the corresponding part regions and low similarity in irrelevant regions. Finally, the geometric and semantic constraints are applied to the part representations through the intermediate results in alignment for part-specific attention learning, encouraging the PartFormer to focus locally and the part representations to explicitly include the information of the corresponding parts. Moreover, the aligned part representations can further serve as a series of reliable detectors in the testing phase, predicting pixel masks for part discovery. Extensive experiments are carried out on four widely used datasets, and our results demonstrate that the proposed method achieves competitive performance and robustness due to its part-specific attention. The code will be released upon paper acceptance.

NUSAP1 is Upregulated by Estrogen to Promote Lung Adenocarcinoma Growth and Serves as a Therapeutic Target.

Nucleolar and spindle-associated protein 1 (NUSAP1), a microtubule-associated protein, has been recently identified to exhibit aberrant expression patterns that correlate with malignant tumorigenesis and progression across various cancer types. However, the specific regulatory mechanisms and potential targeting therapies of NUSAP1 in lung adenocarcinoma (LUAD) remain largely elusive. In this study, by conducting bioinformatics analyses as well as in vitro and in vivo experiments, we identified that NUSAP1 was significantly upregulated in LUAD, with a notable correlation with poorer overall survival, higher scores for immunogenicity and immune infiltration, as well as increased sensitivity to conventional chemotherapeutic drugs such as paclitaxel, docetaxel and vinorelbine in LUAD. Functionally, NUSAP1 overexpression significantly promoted LUAD cell proliferation, while its knockdown markedly suppressed this process. Interestingly, our results revealed that NUSAP1 upregulation was mediated by estrogen via ERß activation. Furthermore, we identified entinostat as a novel inhibitor of NUSAP1. Pharmacological targeting ERß/NUSAP1 axis with fulvestrant (ERß antagonist) or entinostat (novel NUSAP1 inhibitor) significantly reduced LUAD growth both in vitro and in vivo, which may represent effective alternative therapeutic strategies for patients with LUAD.

Exploring the dynamics of C/H and C/Cl exchanges in the C(3P) + C2H3Cl reaction.

The dynamics of the C((3)P) + C2H3Cl reaction at collision energy 3.8 kcal mol(-1) was investigated in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. Time-of-flight spectra of products C3H2Cl, C3H3, and Cl were recorded at various laboratory scattering angles, from which translational-energy distributions and angular distributions of product channels C3H2Cl + H and C3H3 + Cl were derived. Cl correlates satisfactorily with C3H3 in linear momentum and angular distributions, which confirms the production of C3H3 + Cl. The H-loss (Cl-loss) channel has average translational-energy release 14.3 (8.8) kcal mol(-1) corresponding to a fraction 0.30 (0.14) of available energy into the translational degrees of freedom of product HCCCHCl + H (H2CCCH + Cl). The branching ratio of channel H to channel Cl was determined approximately as 12:88. The measurements of translational-energy releases and photoionization thresholds cannot distinguish HCCCHCl from H2CCCCl because both isomers have similar enthalpy of formation and ionization energy; nevertheless, the Rice-Ramsperger-Kassel-Marcus calculation prefers HCCCHCl. The measurement of photoionization spectra identifies product C3H3 as H2CCCH (propargyl). Both products C3H2Cl + H and C3H3 + Cl might correlate to the same triplet intermediate H2CCCHCl but have distinct angular distributions; the former is nearly isotropic whereas the latter is forward biased. A comparison with the C((3)P) + C2H3F reaction is stated.

Dynamics of carbon-hydrogen and carbon-methyl exchanges in the collision of 3P atomic carbon with propene.

We investigated the dynamics of the reaction of (3)P atomic carbon with propene (C3H6) at reactant collision energy 3.8 kcal mol(-1) in a crossed molecular-beam apparatus using synchrotron vacuum-ultraviolet ionization. Products C4H5, C4H4, C3H3, and CH3 were observed and attributed to exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3; their translational-energy distributions and angular distributions were derived from the measurements of product time-of-flight spectra. Following the addition of a (3)P carbon atom to the C=C bond of propene, cyclic complex c-H2C(C)CHCH3 undergoes two separate stereoisomerization mechanisms to form intermediates E- and Z-H2CCCHCH3. Both the isomers of H2CCCHCH3 in turns decompose to C4H5 + H and C3H3 + CH3. A portion of C4H5 that has enough internal energy further decomposes to C4H4 + H. The three exit channels C4H5 + H, C4H4 + 2H, and C3H3 + CH3 have average translational energy releases 13.5, 3.2, and 15.2 kcal mol(-1), respectively, corresponding to fractions 0.26, 0.41, and 0.26 of available energy deposited to the translational degrees of freedom. The H-loss and 2H-loss channels have nearly isotropic angular distributions with a slight preference at the forward direction particularly for the 2H-loss channel. In contrast, the CH3-loss channel has a forward and backward peaked angular distribution with an enhancement at the forward direction. Comparisons with reactions of (3)P carbon atoms with ethene, vinyl fluoride, and vinyl chloride are stated.

Dynamics of the C/H and C/F exchanges in the reaction of 3P carbon atoms with vinyl fluoride.

Two product channels C3H2F + H and C3H3 + F were identified in the reaction of C((3)P) atoms with vinyl fluoride (C2H3F) at collision energy 3.7 kcal mol(-1) in a crossed molecular-beam apparatus using selective photoionization. Time-of-flight (TOF) spectra of products C3H2F and C3H3 were measured at 12-16 laboratory angles as well as a TOF spectrum of atomic F, a counter part of C3H3, was recorded at single laboratory angle. From the best simulation of product TOF spectra, translational-energy distributions at seven scattering angles and a nearly isotropic (forward and backward peaked) angular distribution were derivable for exit channel C3H2F + H (C3H3 + F) that has average kinetic-energy release of 14.5 (4.9) kcal mol(-1). Products C3H2F + H and C3H3 + F were estimated to have a branching ratio of ~53:47. Furthermore, TOF spectra and photoionization spectra of products C3H2F and C3H3 were measured at laboratory angle 62° with photoionization energy ranging from 7 eV to 11.6 eV. The appearance of TOF spectra is insensitive to photon energy, implying that only single species overwhelmingly contributes to products C3H2F and C3H3. HCCCHF (H2CCCH) was identified as the dominant species based on the measured ionization threshold of 8.3 ± 0.2 (8.6 ± 0.2) eV and the maximal translational-energy release. The C/H and C/F exchange mechanisms are stated.