Formation pathways of HO2 and OH changing as a function of temperature in photolytically initiated oxidation of dimethyl ether

The time resolved product formation in oxidation of dimethyl ether (DME) has been studied between 298-625 K and 20-90 torr total pressure. Near-infrared frequency modulation spectroscopy (FMS) with Herriott type multi pass optics and UV absorption spectroscopy (UV) were conducted in the same cell. The reaction was initiated by pulsed photolysis in a mixture of Cl₂, O₂, and DME via CH₃OCH₂ radical formation. The reaction process was investigated through FMS measurement of HO₂ and OH, and UV measurement of CH₃OCH₂O₂. The yields of HO₂ and OH are obtained by comparison with reference mixtures, Cl₂, O₂, and CH₃OH for HO₂, and Cl₂, O₂, CH₃OH, and NO for OH, which convert 100% of initial Cl to HO₂ and OH. The CH₃OCH₂O₂ yield is also obtained. It was found that the HO₂ yield increases sharply over 500 K mainly with a longer time constant than that of R + O₂ reaction, while a prompt component exists throughout the temperature range at a few percent yield. OH was found to be produced promptly at a yield considerably larger than that known for the simplest alkanes. The CH₃OCH₂O₂ profile has a prompt rise followed by a gradual decay whose rate is consistent with the slow HO₂ formation. The species profiles were successfully predicted with a model constructed by modifying the existing one to suit the reduced pressure condition. After modification, it was inferred that the HO₂ formation over 500 K is secondary from HCHO + OH and HCO + O₂ and a part of HCO is formed directly from the O₂ adduct, whereas the HO₂ formation below 500 K is governed by CH₃OCH₂O₂ chemistry. The HCO forming pathway via isomerization-decomposition of the O₂ adduct, which was not included in the former models, was supported by our quantum-chemical calculations.     

Low-intensity pulsed ultrasound (LIPUS) and cell-to-cell communication in bone marrow stromal cells

Low-intensity pulsed ultrasound (LIPUS) is an established therapy for fracture repair and has been used widely in the clinics, but its underlying mechanism of action remains unclear. The aim of the current research was to determine the effect of LIPUS on gap junctional cell-to-cell intercellular communication in rat bone marrow stromal cells (BMSC) in vitro and to determine whether the ability of BMSCs to communicate by gap junctions would affect their response to LIPUS. Single or daily-multiple LIPUS treatment at 1.5 MHz, 30 mW/cm², for 20 min was applied to BMSC. We demonstrated that BMSC form functional gap junctions and single LIPUS treatment significantly increased the intracellular dye transfer between BMSC. In addition, activated phosphorylation of ERK1/2 and p38 by LIPUS stimulation was diminished when cells were treated with a gap junction inhibitor 18β-glycyrrhetinic acid (18β). We further demonstrated that 18β diminished the significant increase in alkaline phosphatase activity following LIPUS stimulation. These results suggest a potential role of gap junctional cell-to-cell intercellular communication on the effects of LIPUS in BMSC.     

Rigorous Treatment of the Liquid-Vapor Transition in a Polydisperse System with Kac Interaction

Within the canonical formalism, we consider a polydisperse lattice-gas model and a polydisperse continuous system interacting with the Kac potential. We obtain rigorous expressions for free energy densities. We also exhibit phase diagrams of the bidisperse lattice-gas model.     

Interplay between the Diradical Character and Third‐Order Nonlinear Optical Properties in Fullerene Systems

To reveal new structure–property relationships in the nonlinear optical (NLO) properties of fullerenes that are associated with their open‐shell character, we investigated the interplay between the diradical character (y_i) and second hyperpolarizability (longitudinal component, γ_zzzz) in several fullerenes, including C₂₀ , C₂₆ , C₃₀ , C₃₆ , C₄₀ , C₄₂ , C₄₈ , C₆₀ , and C₇₀ , by using the broken‐symmetry density functional theory (DFT; LC‐UBLYP (μ=0.33)/6‐31G*//UB3LYP/6‐31G*). We found that the large differences between the geometry and topology of fullerenes have a significant effect on the diradical character of each fullerene. On the basis of their different diradical character, these fullerenes were categorized into three groups, that is, closed‐shell (y_i=0), intermediate open‐shell (0<y_i<1), and almost pure open‐shell compounds (y_i?1), which originated from their diverse topological features, as explained by odd‐electron‐density and spin‐density diagrams. For example, we found that closed‐shell fullerenes include C₂₀ , C₆₀ , and C₇₀ , whereas fullerenes C₂₆ and C₃₆ and C₃₀ , C₄₀ , C₄₂ , and C₄₈ are pure and intermediate open‐shell compounds, respectively. Interestingly, the γ_zzzz enhancement ratios between C₃₀ / C₃₆ and C₄₀ / C₆₀ are 4.42 and 11.75, respectively, regardless of the smaller π‐conjugation size in C₃₀ and C₄₀ than in C₃₆ and C₆₀ . Larger γ_zzzz values were obtained for other fullerenes that had intermediate diradical character, in accordance with our previous valence configuration interaction (VCI) results for the two‐site diradical model. The γ_zzzz density analysis shows that the large positive contributions originate from the large γ_zzzz density distributions on the right‐ and left‐extended edges of the fullerenes, between which significant spin polarizations (related to their intermediate diradical character) appear within the spin‐unrestricted DFT level of theory.     

Estimation of partial optical path length in the brain in subject-specific head models for near-infrared spectroscopy

Three-dimensional head models with the structures constructed from the MR head images of 40 volunteers were constructed to analyze light propagation in the subject-specific head models. The mean optical path length in the head and the partial optical path length in the brain at 13 fiducial points for each volunteer were estimated to evaluate the intersubject and spatial variability in the optical path lengths. Although the intersubject variability in the optical path lengths is very high, the spatial variability in the average of the mean optical path length and partial optical path length is similar to the previously reported data. The mean optical path length in the head increases, whereas the partial optical path length in the brain decreases with an increase in the depth of the brain surface. The partial optical path length is highly correlated with the depth of the brain surface in comparison to the mean optical path length in the head.     

Sulfonic acids as water‐soluble initiators for cationic polymerization in aqueous media with Yb(OTf)3

Aqueous sulfonic acids (HOSO₂R; R = CH₃, Ph‐p‐CH₃, and Ph‐p‐NO₂), coupled with a water‐tolerant Lewis acid, ytterbium triflate [Yb(OTf)₃; OTf =  OSO₂CF₃], initiate the cationic suspension polymerization of p‐methoxystyrene (pMOS) in heterogeneous aqueous media. They induce controlled polymerization of pMOS at 30 °C, and the molecular weights of the polymers (weight‐average molecular weight/number‐average molecular weight ∼ 1.7) increase with conversion. These suspension polymerizations are initiated by the entry of sulfonic acid from the aqueous phase into the organic phase and proceed via reversible activation of the sulfonyl terminus by the Lewis acid. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2728–2733, 2000     

Spaces of maps into topological group with the Whitney topology

Let X be a locally compact Polish space and G a non-discrete Polish ANR group. By C(X,G), we denote the topological group of all continuous maps endowed with the Whitney (graph) topology and by Cc(X,G) the subgroup consisting of all maps with compact support. It is known that if X is compact and non-discrete then the space C(X,G) is an l₂-manifold. In this article we show that if X is non-compact and not end-discrete then Cc(X,G) is an (R^∞×l₂)-manifold, and moreover the pair (C(X,G),Cc(X,G)) is locally homeomorphic to the pair of the box and the small box powers of l₂.     

Formal Total Synthesis of Fostriecin by 1,4‐Asymmetric Induction with an Alkyne–Cobalt Complex

The synthesis of a protected dephosphofostriecin, and thereby a formal synthesis of fostriecin, has been accomplished. The synthetic challenges were the construction of four stereogenic centers and the conformationally labile cis‐cis‐trans‐triene moiety. Previous total syntheses have employed at least two asymmetric reactions that required the use of an external chiral auxiliary. Although remote stereoinduction in a 1,4‐relationship is considered difficult, we have developed a notable 1,4‐asymmetric induction that utilizes an alkyne–cobalt complex for the control of C5 stereochemistry by the C8 stereogenic center. The stereochemistry at C11 was established by 1,3‐asymmetric induction with a higher‐order alkynyl‐zinc reagent. Thus, only one asymmetric reaction requiring an external chiral auxiliary was employed in this route. The labile cis‐cis‐trans‐triene unit was constructed at a late stage of the synthesis by diastereoselective coupling of a dienyne and an aldehyde unit, followed by reduction.     

2‐benzothiazolyl phenacyl sulfoxide,a new precursor for 2‐oxo‐2‐phenylethanethial

Previously, a facile formation of a thioaldehyde by the thermolysis of a heteroaryl phenacyl sulfoxide was confirmed by the detection of a cycloadduct with 2,3‐dimethyl‐1,3‐butadiene. The usefulness of benzothiazolyl phenacyl sulfoxide as a precursor for 2‐oxo‐2‐phenylethanethial was studied under the same conditions in the presence of various dienes and anthracene. In all cases, the Diels‐Alder cycloadducts were formed in moderate to good yields, and the addition of triethylamine as external base was revealed to be effective for carrying out the thermolysis under milder reaction conditions and for the improvement of yields. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 363–367, 1999