Far-UV absorption spectra of SiH2 and dibridged Si2H2 isolated in solid argon.

We employ electron bombardment during the deposition of an Ar matrix containing a small proportion of SiH4 to generate various silicon hydrides. Subsequently, the irradiation of a matrix sample at 365 nm decomposes SiH2 and dibridged Si2H2 in solid Ar, which we identify through infrared spectroscopy. We further recorded the corresponding ultraviolet absorption spectra at each experimental stage. An intense band observed in the range of 170-203 nm is largely destroyed upon 365-nm photolysis, which is assigned to the C1B2 â† X1A1 transition of SiH2. Moreover, a moderate band observed in the region of 217-236 nm is reduced slightly, which is assigned to the 31B2 â† X1A1 transition of dibridged Si2H2. These assignments are made based on the observed photolytic behavior, and the prediction of the vertical excitation energies with the corresponding oscillator strengths by using time-dependent density functional theory and equation-of-motion coupled cluster theory.

IR absorption spectra of aniline cation, anilino radical, and phenylnitrene isolated in solid argon.

Electron bombardment of aniline (PhNH2) in an Ar matrix mainly generated the aniline cation (PhNH2+), anilino (PhNH) and phenyl (Ph) radicals, and phenylnitrene (PhN). Further irradiation of the electron-bombarded matrix sample at 365 nm depleted PhNH2+ and PhN, and resulted in the formation of PhNH2, PhNH, and Ph. In separate experiments, irradiation of the PhNH2/Ar matrix samples at 265 or 160 nm mainly generated PhNH and Ph radicals, but without the formation of PhNH2+ and PhN. According to the observed photochemical behaviors, quantum-chemically predicted harmonic vibrational wavenumbers of each species, and the information reported in previous photodissociation studies, we unambiguously characterized the IR features of the aromatic species. The information of the vibrational fundamentals of PhNH is new and the formation mechanism is discussed.

Comparison of Clinical Characteristics Between Febrile and Afebrile Seizures Associated With Acute Gastroenteritis in Childhood.

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.

Triplet vs πσ* state mediated N-H dissociation of aniline.

UV-excited aromatic molecules with N-H/O-H moieties often possess an important nonradiative relaxation pathway, from an optically bright ππ* state to a dark dissociative πσ* state. We apply a new time-selected photofragment translational spectroscopy method to disclose a previously unknown triplet-mediated N-H dissociation of aniline prevented by the multiphoton dissociative ionization in conventional methods. We further determined the branching fractions of aniline dissociated in the πσ*, triplet, and ground states at 248 nm. Additionally, we selectively captured the population changes in the singlet and triplet states with ionization from different laser wavelengths, 355 or 266 nm, in time-resolved photoion yields. The combination of experimental data enables us to uniquely determine the relative ionization cross sections of the singlet and triplet states at an ionization laser wavelength of 266 nm and allows us to extensively measure the rate constants of intersystem crossing and the branching fractions at various excitation wavelengths.

Temporal Analysis of Conformers in the Course of pH Scan Directed by Urea-Urease Reaction-A "Protein Clock".

We demonstrate an analytical approach to monitor the effect of pH on protein tertiary structure. An autocatalytic enzyme reaction is used to stimulate refolding of proteins during real-time analysis. The method takes advantage of a nonlinear pH ramp generated by the urea-urease clock reaction. In this study, alterations to the structures of model proteins were monitored by mass spectrometry (charge pattern shift) and fluorometry (tryptophan fluorescence quenching). The pH measurements were conducted at different points of the sample flow line by different methods to minimize artifacts. Interestingly, different protein ions (corresponding to native and unfolded proteins) show distinct temporal mass spectral profiles, which reveal gradual refolding and concomitant deprotonation of higher charge state ions in the course of the clock reaction. Every multiply charged ion of a protein is characterized with its own "clock time". This approach does not require major modification of standard instrumentation. It enables determination of "high sensitivity" pH intervals for small and large molecules within a single experiment. Thus, it can be useful for characterizing the protein folding in response to pH change.

Communication: Mode-dependent excited-state lifetime of phenol under the S1/S2 conical intersection.

Phenol can serve as a model for examining the deactivation of the aromatic amino acid tyrosine following UV excitation, which mainly occurs through a repulsive πσ* state along the O-H bond. The reaction barrier formed by the conical intersection between the optically bright S1 (ππ*) state and the dissociative S2 (πσ*) state does not inhibit O-H bond rupture even though the excitation energy is below the barrier height. To examine the O-H bond-rupture dynamics in association with the initial excited vibrational modes, we used a picosecond laser to investigate the vibrational-mode-dependent excited-state lifetime of phenol under the S1/S2 conical intersection. Unexpectedly short lifetimes were observed in the S1 state for a″ symmetric vibrational modes (including v4, v16a, τOH, and v5). These results clarify recent theoretical calculations showing that the relaxation from S1 to S2 either occurs via symmetry-allowed non-adiabatic transitions or is topographically linked to a lower energy minimum on the multidimensional potential energy surface.

Health Education and Symptom Flare Management Using a Video-based m-Health System for Caring Women With IC/BPS.

OBJECTIVE: To assess effectiveness of the video-based m-health system providing videos dictated by physicians for health education and symptom self-management for patients with Interstitial cystitis/bladder pain syndrome (IC/BPS). METHODS: An m-health system was designed to provide videos for weekly health education and symptom flare self-management. O'Leary-Sant index and visual analogue scale as well as SF-36 health survey were administrated to evaluate the disease severity and quality of life (QoL), respectively. A total of 60 IC/BPS patients were recruited and randomly assigned to either control group (30 patients) or study group (30 patients) in sequence depending on their orders to visit our urological clinic. Patients in both control and study groups received regular treatments, while those in the study group received additional video-based intervention. Statistical analyses were conducted to compare the outcomes between baseline and postintervention for both groups. The outcomes of video-based intervention were also compared with the text-based intervention conducted in our previous study. RESULTS: After video-based intervention, patients in the study group exhibited significant effect manifested in all disease severity and QoL assessments except the pain visual analogue scale, while no significance was found in the control group. Moreover, the study group exhibited more significant net improvements than the control group in 7 SF-36 constructs, except the mental health. The limitations include short intervention duration (8 weeks) and different study periods between text-based and video-based interventions. CONCLUSION: Video-based intervention is effective in improving the QoL of IC/BPS patients and outperforms the text-based intervention even in a short period of intervention.

Excited-state dissociation dynamics of phenol studied by a new time-resolved technique.

Phenol is an important model molecule for the theoretical and experimental investigation of dissociation in the multistate potential energy surfaces. Recent theoretical calculations [X. Xu et al., J. Am. Chem. Soc. 136, 16378 (2014)] suggest that the phenoxyl radical produced in both the X and A states from the O-H bond fission in phenol can contribute substantially to the slow component of photofragment translational energy distribution. However, current experimental techniques struggle to separate the contributions from different dissociation pathways. A new type of time-resolved pump-probe experiment is described that enables the selection of the products generated from a specific time window after molecules are excited by a pump laser pulse and can quantitatively characterize the translational energy distribution and branching ratio of each dissociation pathway. This method modifies conventional photofragment translational spectroscopy by reducing the acceptance angles of the detection region and changing the interaction region of the pump laser beam and the molecular beam along the molecular beam axis. The translational energy distributions and branching ratios of the phenoxyl radicals produced in the X, A, and B states from the photodissociation of phenol at 213 and 193 nm are reported. Unlike other techniques, this method has no interference from the undissociated hot molecules. It can ultimately become a standard pump-probe technique for the study of large molecule photodissociation in multistates.

Advantage of spatial map ion imaging in the study of large molecule photodissociation.

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.

Posterior Reversible Encephalopathy Syndrome With Spinal Cord Involvement in Children.

We characterized a cohort of patients with posterior reversible encephalopathy syndrome with spinal cord involvement. We encountered 2 children and identified an additional 19 patients from the internet databases. Of the 21 patients analyzed, 8 were children. The mean peak systolic blood pressure in adults was significantly higher than in children (221.8 ± 14.3 vs 191.4 ± 31.3 mm Hg; P < .01). Regardless of age, the most common clinical symptom was headache (90%) and the least common clinical symptom was seizures (28%). Atypical neuroimaging was more common in children (63%) than in adults (8%). Abnormal cerebrospinal fluid results were frequently found in children (83%). All children recovered uneventfully, but 3 adults had sequelae. A broader clinicoradiologic spectrum makes the diagnosis of children more complex than in adults. Awareness of the atypical features with a meticulous management of hypertension is imperative to avoid unnecessary invasive workups and to achieve an uneventful recovery.

Fluorescence spectroscopy of UV-MALDI matrices and implications of ionization mechanisms.

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-trihydroxy-acetophenone, and ferulic acid). We observed two matrix molecules reacting in an electronically excited state (S1) in five of these matrices (2,5-dihydroxybenzoic acid, α-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.

Core excitation, specific dissociation, and the effect of the size of aromatic molecules connected to oxygen: phenyl ether and 1,3-diphenoxybenzene.

Near-edge X-ray absorption fine structure (NEXAFS) spectra of phenyl ether at the carbon K-edge and 1,3-diphenoxybenzene at both the carbon and oxygen K-edges were measured in the total ion yield mode using X-rays from a synchrotron and a reflectron time-of-flight mass spectrometer. Time-dependent density functional theory was adopted to calculate the carbon and oxygen K-edge NEXAFS spectra of phenol, phenyl ether, and 1,3-diphenoxybenzene. The assignments and a comparison of the experimental and calculated spectra are presented. The mass spectra of ionic products formed after X-ray absorption at various excitation energies are also reported. Specific dissociations were observed for the 1s → π* transition of phenyl ether. In comparison with phenol and phenyl ether, the dependence of the fragmentation on the excitation site and destination state was weak in 1,3-diphenoxybenzene, likely as a result of delocalization of the valence electrons and rapid randomization of energy.

Ion intensity and thermal proton transfer in ultraviolet matrix-assisted laser desorption/ionization.

The ionization mechanism of ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) was investigated by measuring the total cation intensity (not including sodiated and potasiated ions) as a function of analyte concentration (arginine, histidine, and glycine) in a matrix of 2,4,6-trihydroxyacetophenone (THAP). The total ion intensity increased up to 55 times near the laser fluence threshold as the arginine concentration increased from 0% to 1%. The increases were small for histidine, and a minimal increase occurred for glycine. Time-resolved fluorescence intensity was employed to investigate how analytes affected the energy pooling of the matrix. No detectable energy pooling was observed for pure THAP and THAP/analyte mixtures. The results can be described by using a thermal proton transfer model, which suggested that thermally induced proton transfer is crucial in the primary ion generation in UV-MALDI.

Near-edge X-ray absorption fine structure spectra and site-selective dissociation of phenol.

A time-of-flight mass spectrometer with orthogonal acceleration and soft X-rays from synchrotron radiation were utilized to measure near-edge X-ray absorption fine structure (NEXAFS) spectra of carbon and oxygen in phenol and the corresponding ionic fragments following core excitation. The photon energies were in the range of 284-298 eV for the carbon K-edge and 529.5-554.5 eV for the oxygen K-edge. The total ion yield, ion intensity for each ionic fragment, and ion intensity ratio, defined as ion intensity divided by total ion yield, were measured as a function of photon energy. Possible mechanisms of dissociation are proposed and enhancements of specific products of dissociation are reported. In general, the enhancement of these specific products is small in the carbon K-edge region but is clear for some products at the oxygen K-edge. In particular, elimination of the H atom from the hydroxyl group was observed only at the oxygen K-edge. One remarkable result is that an excitation of a core-level electron of oxygen greatly enhanced the cleavage of specific C-C bonds.

Spontaneous hemopneumothorax simulating acute abdominal affections.

Spontaneous hemopneumothorax (SHP) is a rare potentially life-threatening condition that occurs in predominantly young adolescents. The resultant massive hemorrhage leading to hypovolemic shock can be a surgical emergency. It constitutes 1-12% of all spontaneous pneumothoraces and presents with two cardinal features, chest pain and dyspnea. However, the pain of SHP may be confined to the abdomen secondary to the irritation of diaphragmatic pleura, which produces signs simulating an acute abdomen. SHP masquerading as an abdominal affection is apparently regarded as extremely rare. We present a case of a 16-year-old male with SHP presenting features simulating acute gallbladder disease. After prompt diagnosis with appropriate surgical intervention, he had an uneventful recovery. Our experience emphasizes the importance of careful and thorough chest examination for each child with atypical pictures for abdominal pain to exclude possible extra-abdominal lesions, even rare as SHP.

Is energy pooling necessary in ultraviolet matrix-assisted laser desorption/ionization?

RATIONALE: Energy pooling has been suggested as the key process for generating the primary ions during ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI). In previous studies, decreases in fluorescence quantum yields as laser fluence increased for 2-aminobenzoic acid, 2,5-dihydroxybenzoic acid (2,5-DHB), and 3-hydroxypicolinic acid were used as evidence of energy pooling. This work extends the research to other matrices and addresses whether energy pooling is a universal property in UV-MALDI. METHODS: Energy pooling was investigated in a time-resolved fluorescence experiment by using a short laser pulse (355 nm, 20 ps pulse width) for excitation and a streak camera (1 ps time resolution) for fluorescence detection. RESULTS: The excited-state lifetime of 2,5-DHB decreased with increases in laser fluence. This suggests that a reaction occurs between two excited molecules, and that energy pooling may be one of the possible reactions. However, the excited-state lifetime of 2,4,6-trihydroxyacetophenone (THAP) did not change with increases in laser fluence. The upper limit of the energy pooling rate constant for THAP is estimated to be approximately 100-500 times smaller than that of 2,5-DHB. CONCLUSIONS: The small energy pooling rate constant for THAP indicates that the potential contribution of the energy pooling mechanism to the generation of THAP matrix primary ions should be reconsidered.

Posterior Reversible Encephalopathy Syndrome in Children: Case Series and Systematic Review.

To study presentations and outcome of posterior reversible encephalopathy syndrome in children, we retrospectively analyzed 14 patients admitted to our pediatric intensive care unit. We further assessed 94 additional pediatric cases from a systematic review. Our patients had a mean age of 11.6 years. Their precipitating factors were hypertension (100%), immunosuppressants (71%), antineoplastic agents (21%), and hemodialysis (14%). Initial neurologic manifestations included seizures (100%), mental change (100%), headache (79%), and visual disturbance (57%). After prompt diagnosis by magnetic resonance imaging (MRI) with intensive management, all patients had complete clinical recovery with subsequent radiologic resolution. Systemic literature review indicated that seizures (90%), hypertension (85%), and atypical neuroimaging findings (80%) are common presentations in childhood posterior reversible encephalopathy syndrome. We conclude that in children presenting with seizures and hypertension, a pediatric neurologist should consider posterior reversible encephalopathy syndrome within a comprehensive differential diagnosis of acute encephalopathy. Early recognition and intensive care are essential to ensure complete neurologic recovery in children with posterior reversible encephalopathy syndrome.

Operating styles, working time and daily driving distance in relation to a taxi driver's speeding offenses in Taiwan.

This study explored the determinant factors of taxi drivers' speeding violations in Taiwan. Data were gathered from a nation wide survey and included 6923 professional taxi drivers in 2006. The results indicated that 96.6% were males and 92.5% had less than a college level education. Daily working hours were from 2.5 h to 15 h with a mean of 10.12 h. The data also indicated that taxi drivers worked approximately 27.35 days and only took 2.65 days rest per month. Of the observed taxi drivers, 25.6% reported at least one speeding violation in a one-year period. The results of a generalized linear model (GLM) revealed that the determinant factors associating with a taxi driver's speeding violation were not related to gender or educational level. However, age, job experience, operating styles, kilometers driven daily, driving late at night, and monthly off duty days were significantly associated with committing the speeding violations.

Modeling motivation and habit in driving behavior under lifetime driver's license revocation.

The purpose of the present study was to verify the motivational factors underlying the theory of planned behavior (TPB) predicting the driving behavior of lifetime driving license revoked offenders. Of a total of 639 drivers whose licenses had been permanently revoked, 544 offenders completed a questionnaire constructed to measure attitudes toward behaviors, subjective norms, perceived behavioral control, behavioral intentions (the key constructs of the TPB), and previous driving habit strength. The finding of the study revealed that an offenders' driving behavior after a lifetime license revocation was significantly correlated to behavioral intention (R=0.60, p<0.01), perceived behavioral control (R=0.61, p<0.01), previous driving habit (R=0.44, p<0.01), and attitude (R=0.41, p<0.01). There was no evidence that subjective norms including road regulation, society ethics, and people important to offenders had an influence on driving behavior (R=0.03). Low driving habit strength offenders are motivated to drive because of behavioral intention, whereas strong driving habit strength offenders are motivated to drive because of perceived behavioral control. Previous driving habit strength is a moderator in the intention-behavior relationship. The model appeared successful when previous habits were weak, but less successful when previous habits were strong.

A magnetic-bottle multi-electron-ion coincidence spectrometer.

A novel multi-electron-ion coincidence spectrometer developed on the basis of a 1.5 m-long magnetic-bottle electron spectrometer is presented. Electrons are guided by an inhomogeneous magnetic field to a detector at the end of the flight tube, while a set of optics is used to extract counterpart ions to the same detector, by a pulsed inhomogeneous electric field. This setup allows ion detection with high mass resolution, without impairing the high collection efficiency for electrons. The performance of the coincidence spectrometer was tested with double ionization of carbon disulfide, CS(2) → CS(2)(2+) + e(-) + e(-), in ultrashort intense laser fields (2.8 × 10(13) W/cm(2), 280 fs, 1030 nm) to clarify the electron correlation below the rescattering threshold.