Infrared Spectroscopy of Matrix-Isolated Neutral and Ionized Anthracoronene in Argon.

The matrix-isolated mid-IR (MIR) spectrum of neutral and ionized anthracoronene (C36H18, AnthCor) in argon has been measured experimentally, compared to the spectrum of its parent molecules, coronene and anthracene, and analyzed by comparison to a theoretical spectrum computed using density functional theory (DFT). The experimental and theoretical band positions generally agree within 0-10 cm-1. Anthracoronene exhibits extremely intense cation and anion bands around 1330 and 1318 cm-1. The intensity of these two bands approaches what is traditionally observed over the entire 1000-1600 cm-1 range for a typical PAH cation or anion. The matrix-isolated near-IR (NIR) through overlap region (OVR) spectrum of ionized AnthCor in argon has been reported for the first time and compared to the spectrum of its parent molecules, coronene and anthracene. The spectrum of AnthCor contains a very strong electronic transition around 6175 cm-1, placing it outside the range of the electronic transitions typically observed for PAHs. Anthracoronene is one of the few PAHs studied to date which has exhibited the formation of anions upon UV photolysis.

Parity is associated with a longer time to reach irreversible disability milestones in women with multiple sclerosis.

BACKGROUND: Multiple sclerosis (MS) frequently affects women of childbearing age. While short-term effects of pregnancy on MS course are well-known, whether pregnancy may influence long-term disability progression is debated. METHODS: A two-centre retrospective study to investigate long-term effect of pregnancy on disability was performed in a population of MS women. Survival analyses and multivariate Cox proportional regression models (including early predictors of MS severity and exposure to disease-modifying treatments) were performed to compare time to reach well-established disability milestones in nulliparous women and in those with pregnancies after MS onset ('parous'). Women with pregnancies before MS onset were excluded from analyses as they represent a heterogeneous group. RESULTS: Data about 445 women (261 nulliparous, 184 'parous') were analysed. A longer time to reach Expanded Disability Status Scale (EDSS) 4.0 and 6.0 was observed in parous women; Cox regression models revealed a lower risk for 'parous' than nulliparous women in reaching EDSS 4.0 and 6.0 (HR = 0.552, p = 0.008 and HR = 0.422, p = 0.012 respectively). CONCLUSION: Our findings suggest that pregnancy after MS onset is associated with a slower long-term disability progression. Whether this represents a biological/immunological effect, or reflects a higher propensity toward childbearing in women with milder disease, it remains uncertain deserving further investigations.

Multiple sclerosis relapses: a multivariable analysis of residual disability determinants.

BACKGROUND: Recovery from multiple sclerosis (MS) relapses is variable. The factors influencing persistence of residual disability (RD) after a relapse are still to be thoroughly elucidated. AIMS OF STUDY: To assess RD after MS relapses and to define the factors associated with persistence of RD. METHODS: Data were retrospectively collected for all relapses in a population of relapsing-remitting MS patients during 3 years. Relapse severity and RD after 1 year were calculated on Expanded Disability Status Scale basis. A multivariable analysis for factors influencing RD and relapse severity was performed (variables: age, gender, disease duration, oligoclonal bands, relapse severity, monosymptomatic/polysymptomatic relapse, immunomodulating treatment, incomplete recovery at 1 month). RESULTS: A total of 174 relapses were assessed. RD after 1 year was observed in 54.5% of the relapses. Higher risk of RD was associated with occurrence of a severe relapse (P = 0.024). Incomplete recovery at 1 month was highly predictive of RD at 1 year (P < 0.0001). Risk of a severe relapse was associated with age

Infrared spectroscopy of matrix-isolated neutral polycyclic aromatic nitrogen heterocycles: The acridine series.

The matrix-isolated, mid-infrared spectra of seven acridine-based polycyclic aromatic nitrogen heterocycles (PANHs) have been measured and compared to their non-nitrogen containing parent molecule. The acridine species investigated include acridine, benz[a]acridine, benz[c]acridine, dibenz[a,j]acridine, dibenz[c,h]acridine, dibenz[a,h]acridine and dibenz[a,c]acridine. The previously reported results for 1 and 2-azabenz[a]anthracenes are included for comparison. The experimentally determined band frequencies and intensities are compared with their B3LYP/6-31G(d) values. The overall agreement between experimental and theoretical values is good and in line with our previous investigations. Shifts, typically to the blue, are noted for the C-H out-of-plane (CHoop) motions upon insertion of a nitrogen atom. The formation of a bay region upon addition of additional benzene rings to the anthracene/acridine structure splits the solo hydrogen motions into a bay region solo and an external solo hydrogen, with the bay region solo hydrogen coupling to the quartet hydrogen motions and the external solo hydrogen coupling with the duo hydrogen motions resulting in an extreme decrease in intensity for the CHoop solo hydrogen band when the external hydrogen is replaced by a nitrogen atom. The C-C and C-H in-plane region of this acridine series exhibits the characteristic two fold increase in intensity, noted previously for PANHs. The strong ≈1400cm-1 band, which was identified in the previous PANH study, is noted in several molecular species as well as another strong PANH feature between 1480 and 1515cm-1 for several molecules. The presence of these strong bands appear to be primarily responsible for the two-fold increase in the C-H in-plane region's (1100-1600cm-1) intensity. The C-H stretching region can be characterized by contributions from the solo (bay or external), duo and quartet hydrogens, similar to what was observed in the dibenzopolyacene compounds.

Photochemistry of coronene in cosmic water ice analogs at different concentrations.

This work presents the photochemistry of ultraviolet (UV) irradiated coronene in water ices at 15 K, studied using mid-infrared Fourier transform (FTIR) spectroscopy for C24H12:H2O at concentrations of (1:50), (1:150), (1:200), (1:300) and (1:400). Previous UV irradiation studies of anthracene:H2O, pyrene:H2O and benzo[ghi]perylene:H2O ices at 15 K have shown that aromatic alcohols and ketones, as well as CO2 and H2CO are formed at very low temperatures. Like-wise, here, in addition to the coronene cation, hydroxy-, keto-, and protonated coronene (coronene-H+) are formed. The rate constants for the decay of neutral coronene and for the formation of photoproducts have been derived. It is shown that PAHs and their UV-induced PAH:H2O photoproducts have mid-infrared spectroscopic signatures in the 5-8 µm region that can contribute to the interstellar ice components described by Boogert et al. (2008) as C1-C5. Our results suggest that oxygenated and hydrogenated PAHs could be in UV-irradiated regions of the ISM where water-rich ices are important.