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Blue luminescence (BL) has been observed in various astrophysical environments, such as the inner region of the Red Rectangle Nebula. It has been previously linked to small polycyclic aromatic hydrocarbons. In this study, we explore the potential of N- and O-doped graphene material as carriers of BL. Using vacuum ultraviolet irradiation, pristine single-layer graphene films were exposed to solid N _2 and O _2 at low temperatures, resulting in the formation of N- or O-doped graphene. The photoluminescence (PL) spectrum of the synthesized N-doped graphene exhibits an asymmetrical peak at 378 nm, which is nearly identical to the BL observed in the Red Rectangle. In contrast, the synthesized O-doped graphene shows a symmetrical PL band at 414 nm. Further Raman and X-ray photoelectron spectroscopy analyses reveal that nitrogen atoms substitute carbon atoms in the graphene lattice, introducing structural defects and sp ^2 regions responsible for the observed luminescence. The simplicity of the bonding structures in the N-doped graphene, dominated by pyrrolic-N and pyridinic-N groups, further supports its potential as a model system for studying BL.

Background: Acute gastroenteritis (AGE) accompanied by seizures is not a rare scenario in childhood. We investigated the clinical features of children with febrile or afebrile seizures during AGE and aimed to identify the impact of fever in this situation-related seizure.Methods: We retrospectively reviewed the medical charts of children admitted due to seizures associated with mild AGE between January 2008 and December 2017. These consecutive patients were divided into two groups: an “afebrile group” whose diagnosis was compatible with “benign convulsion with mild gastroenteritis (CwG)” and a “febrile group” who had a fever within 24 h of the onset of an AGE-related seizure. We compared the two groups' clinical and laboratory characteristics, electroencephalograms (EEG), neuroimaging, and outcomes.Results: Of the children suffering from AGE and seizures, 41 were afebrile and 30 were febrile, with a mean age of 32.2 ± 27.6 months. The gender, seizure semiology, frequency, duration of seizures, the time interval between AGE symptoms onset and first seizure, and levels of serum sodium, and hepatic enzymes were significantly different between the two groups. The most frequently identified enteropathogen was rotavirus (33%), especially in the male and febrile subjects. Afebrile patients had more EEG abnormalities initially, but all returned to normal later. All cases had an uneventful outcome. Of note, seizure clusters (≥2 episodes) occurred more frequently in the afebrile patients who had a duration of AGE symptoms lasting 2 days or more, or white blood cell counts ≥ 10,000/μL (p-values: 0.05 and 0.04, respectively). In comparison with seven similar studies, all showed more seizure clusters, partial seizures, and a shorter interval between AGE onset and seizures in afebrile patients than in febrile patients. Contrarily, afebrile patients had longer seizure duration and lower serum hepatic transaminases than febrile patients.Conclusion: Although fever partially influenced the clinical features of AGE-related seizures, febrile CwG might have pathophysiology distinctly different from that of febrile seizures. Comprehensive knowledge in discerning febrile and afebrile CwG can help to avoid unnecessary diagnostics tests, and anticonvulsants use.

In recent years, the development of autonomous surface vehicles has been a field of increasing research interest. There are two major areas in this field: control theory and path planning. This study focuses on path planning, and two objectives are discussed: path planning for Unmanned Surface Vehicles (USVs) and implementation of path planning in a real map. In this paper, satellite thermal images are converted into binary images which are used as the maps for the Finite Angle A * algorithm (FAA *), an advanced A * algorithm that is used to determine safer and suboptimal paths for USVs. To plan a collision-free path, the algorithm proposed in this article considers the dimensions of surface vehicles. Furthermore, the turning ability of a surface vehicle is also considered, and a constraint condition is introduced to improve the quality of the path planning algorithm, which makes the traveled path smoother. This study also shows a path planning experiment performed on a real satellite thermal image, and the path planning results can be used by an USV

In this study, numerical analysis was carried out by using the finite element method to construct the first mode shape of damaged stiffened plates, and the damage locations were detected with two-dimensional discrete wavelet analysis. In the experimental analysis, four different damaged stiffened structures were observed. Firstly, each damaged structure was hit with a shaker, and then accelerometers were used to measure the vibration responses. Secondly, the first mode shape of each structure was obtained by using the wavelet packet, and the location of cracks were also determined by two-dimensional discrete wavelet analysis. The results of the numerical analysis and experimental investigation reveal that the proposed method is applicable to detect single crack or multi-cracks of a stiffened structure. The experimental results also show that fewer measurement points are required with the proposed technique in comparison to those presented in previous studies.

Postobstructive pulmonary edema is life-threatening, and results from a sudden episode of upper airway obstruction. Croup is generally thought to be a benign condition, but occasionally it can develop into postobstructive pulmonary edema. We present a case of a 5-year-old boy with recurrent croup, who was diagnosed with postobstructive pulmonary edema. Our experience alerts pediatricians to this easily misdiagnosed disease.

Pneumomediastinum, the leakage of air or gas into the mediastinum, can be a primary or secondary diagnosis. Although spontaneous pneumomediastinum (SPM) is uncommon in pediatric respiratory disorders, it is potentially life-threatening. In this study, we investigated the associations between various etiologies and clinical presentations, hospital length-of-stay, and clinical outcomes of SPM. From January 2004 to December 2007, we collected medical records and chest films from 23 pediatric patients with SPM. Results showed that increased hospital length-of-stay was significantly associated with asthma (p = 0.035), dyspnea/tachypnea (p = 0.01), and emergent visit (p = 0.04). Dysphagia was associated with shorter hospital stay (p = 0.058). Besides, the disorder was misdiagnosed initially in 21% of patients. In conclusion, there may be close relationships between the predisposing factors of SPM and its clinical manifestations. The high rate of misdiagnosis highlights the importance of careful examination and history taking in pediatric patients with chest pain.

Lower respiratory tract infections associated with wheezing are not uncommon in infants and young children. Among the wheezing-associated disorders, allergic etiologies are more commonly encountered than anatomic anomalies. We present a 3-year-old girl with a sudden attack of asthmatic symptoms including dyspnea, cyanosis and diffuse wheezing. Based on a history of choking, and atelectasis in the right upper lobe detected by chest films, flexible tracheobronchoscopy was arranged and incidentally detected a stenotic orifice in the right upper lobe bronchus. Multidetector-row spiral computed tomography and pulmonary scintigraphy subsequently also disclosed the focal stenosis. She suffered from recurrent wheezing, pneumonia and lung atelectasis during 1 year of follow-up. We emphasize the diagnosis, clinical course and management of focal stenosis in the right upper lobe bronchus.

Multimass ion imaging techniques were used to study the photodissociation of p-methylphenol, p-ethylphenol and p(2-aminoethyl)phenol which are chormophores of the amino acid tyrosine. The chromophores of amino acid tyrosine show side-chain size-dependent dissociation properties and one dissociation channel, H atom elimination is seen for p-methylphenol and p-ethylphenol.

The original ion imaging technique has low velocity resolution, and currently, photodissociation is mostly investigated using velocity map ion imaging. However, separating signals from the background (resulting from undissociated excited parent molecules) is difficult when velocity map ion imaging is used for the photodissociation of large molecules (number of atoms ≥ 10). In this study, we used the photodissociation of phenol at the S1 band origin as an example to demonstrate how our multimass ion imaging technique, based on modified spatial map ion imaging, can overcome this difficulty. The photofragment translational energy distribution obtained when multimass ion imaging was used differed considerably from that obtained when velocity map ion imaging and Rydberg atom tagging were used.We used conventional translational spectroscopy as a second method to further confirm the experimental results, and we conclude that data should be interpreted carefully when velocity map ion imaging or Rydberg atom tagging is used in the photodissociation of large molecules. Finally, we propose a modified velocity map ion imaging technique without the disadvantages of the current velocity map ion imaging technique. [ABSTRACT FROM AUTHOR]

Matrix-assisted laser desorption ionization (MALDI) has been widely used in the mass analysis of biomolecules; however, there are a lot of debates about the ionization mechanisms. Previous studies have indicated that S1-S1 annihilation might be a key process in the generation of primary ions. This study investigates S1-S1 annihilation by examining the time-resolved fluorescence spectra of 12 matrices. No S1-S1 annihilation was observed in six of these matrices (3-hydroxy-picolinic acid, 6-aza-2-thiothymine, 2,4-dihydroxy-acetophenone, 2,6-dihydroxy-acetophenone, 2,4,6-trihydroxyacetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S1) in five of these matrices (2,5-dihydroxybenzoic acid, a-cyano-4-hydroxycinnamic acid, 2,5-dihydroxy-acetophenone, 2,3-dihydroxybenzoic acid, and 2,6-dihydroxybenzoic acid), and S1-S1 annihilation was a possible reaction. Among these five matrices, no S1-S1 annihilation was observed for 2,3-dihydroxybenzoic acid in typical peak power region of nanosecond laser pulses in MALDI, but a very small value of reaction rate constant was observed only in the high peak power region. The excited-state lifetime of sinapinic acid was too short to determine whether the molecules reacted in an electronically excited state. No correlation was observed between the ion generation efficiency of MALDI and S1-S1 annihilation. The results indicate that the proposal of S1-S1 annihilation is unnecessary in MALDI and energy pooling model for MALDI ionization mechanism has to be modified. [ABSTRACT FROM AUTHOR]

Photodissociation of amino acid tryptophan in a molecular beam at wavelengths of 212.8 and 193 nm, corresponding to excitation to the second and third absorption bands, was investigated using multimass ion imaging techniques. The respective wavelengths also represent excitation to the edge of a positive circular dichroism band and the center of a negative circular dichroism band of L-tryptophan. Only one dissociation channel was observed at both photolysis wavelengths: C8NH6CH2CHNH2COOH→C8NH6CH2+CHNH2COOH. Dissociation rates were found to be 1.3×106 and 5×106 s-1 at the respective wavelengths. Comparison to theoretical calculation indicates that dissociation occurs on the ground state after internal conversion. Implication of asymmetric photolysis is discussed. [ABSTRACT FROM AUTHOR]

The photodissociation of jet-cooled α-fluorotoluene and 4-fluorotoluene at 193 and 248 nm was studied using vacuum ultraviolet (vuv) photoionization/multimass ion imaging techniques as well as electron impact ionization/photofragment translational spectroscopy. Four dissociation channels were observed for α-fluorotoluene at both 193 and 248 nm, including two major channels C6H5CH2F→C6H5CH2 (or C7H7)+F and C6H5CH2F→C6H5CH (or C7H6)+HF and two minor channels C6H5CH2F→C6H5CHF+H and C6H5CH2F→C6H5+CH2F. The vuv wavelength dependence of the C7H7 fragment photoionization spectra indicates that at least part of the F atom elimination channel results from the isomerization of α-fluorotoluene to a seven-membered ring prior to dissociation. Dissociation channels of 4-fluorotoluene at 193 nm include two major channels C6H4FCH3→C6H4FCH2+H and C6H4FCH3→C6H4F+CH3 and two minor channels C6H4FCH3→C6H5CH2 (or C7H7)+F and C6H4FCH3→C6H5CH (or C7H6)+HF. The dissociation rates for α-fluorotoluene at 193 and 248 nm are 3.3×107 and 5.6×105 s-1, respectively. The dissociation rate for 4-fluorotoluene at 193 nm is 1.0×106 s-1. An ab initio calculation demonstrates that the barrier height for isomerization from α-fluorotoluene to a seven-membered ring isomer is much lower than that from 4-fluorotoluene to a seven-membered ring isomer. The experimental observed differences of dissociation rates and relative branching ratios between α-fluorotoluene and 4-fluorotoluene may be explained by the differences in the six-membered ring to seven-membered ring isomerization barrier heights, F atom elimination threshold, and HF elimination threshold between α-fluorotoluene and 4-fluorotoluene. [ABSTRACT FROM AUTHOR]

Photodissociation of pyrimidine at 193 and 248 nm was investigated separately using vacuum ultraviolet photoionization at 118.4 and 88.6 nm and multimass ion imaging techniques. Six dissociation channels were observed at 193 nm, including C4N2H4→C4N2H3+H and five ring opening dissociation channels, C4N2H4→C3NH3+HCN, C4N2H4→2C2NH2, C4N2H4→CH3N+C3NH, C4N2H4→C4NH2+NH2, and C4N2H4→CH2N+C3NH2. Only the first four channels were observed at 248 nm. Photofragment translational energy distributions and dissociation rates indicate that dissociation occurs in the ground electronic state after internal conversion at both wavelengths. The dissociation rates were found to be >5×107 and 1×106 s-1 at 193 and 248 nm, respectively. Comparison with the potential energies from ab initio calculations have been made. [ABSTRACT FROM AUTHOR]

Photodissociation of indole at 193 and 248 nm under collision-free conditions has been studied in separate experiments using multimass ion imaging techniques. H atom elimination was found to be the only dissociation channel at both wavelengths. The photofragment translational energy distribution obtained at 193 nm contains a fast and a slow component. Fifty-four percent of indole following the 193 nm photoexcitation dissociate from electronically excited state, resulting in the fast component. The rest of 46% indole dissociate through the ground electronic state, giving rise to the slow component. A dissociation rate of 6×105 s-1, corresponding to the dissociation from the ground electronic state, was determined. Similar two-component translational energy distribution was observed at 248 nm. However, more than 80% of indole dissociate from electronically excited state after the absorption of 248 nm photons. A comparison with the potential energy surfaces from the ab initio calculation has been made. [ABSTRACT FROM AUTHOR]

Photodissociation of pyridine, 2,6-d2-pyridine, and d5-pyridine at 193 and 248 nm was investigated separately using multimass ion imaging techniques. Six dissociation channels were observed at 193 nm, including C5NH5→C5NH4+H (10%) and five ring opening dissociation channels, C5NH5→C4H4+HCN, C5NH5→C3H3+C2NH2, C5NH5→C2H4+C3NH, C5NH5→C4NH2+CH3 (14%), and C5NH5→C2H2+C3NH3. Extensive H and D atom exchanges of 2,6-d2-pyridine prior to dissociation were observed. Photofragment translational energy distributions and dissociation rates indicate that dissociation occurs in the ground electronic state after internal conversion. The dissociation rate of pyridine excited by 248-nm photons was too slow to be measured, and the upper limit of the dissociation rate was estimated to be 2×103 s-1. Comparisons with potential energies obtained from ab initio calculations and dissociation rates obtained from the Rice-Ramsperger-Kassel-Marcus theory have been made. [ABSTRACT FROM AUTHOR]

Several multimass ion-imaging techniques are employed to study the photodissociation dynamics of phenol at different wavelengths. The dissociation channels, as well as the vibrational and rotational energies of the product are found to be consistent with the potential energy surfaces.

Photodissociation of phenol at 248 nm was studied using multimass ion imaging techniques. Photofragment translational energy distribution of H atom elimination was measured. The results demonstrate that H atom elimination occurs on the πσ* excited state which has repulsive potential-energy functions with respect to the stretching of OH bond. It supports the recent ab initio calculation. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]