Apparent contrast of molecularly thin films of water at ionic crystal surfaces

We focus the apparent contrast of water islands formed at ionic crystal surfaces in air at room temperature (RT) using the non-contact monitoring mode of a scanning force microscope (SFM). Their apparent heights of water islands formed on LiF(001), CaF₂(111) and BaF₂(111) surfaces have been measured to be about 2, 1 and 1 nm, respectively. The water growth of a NaF(001) surface has two phases (phase I and phase II). The apparent heights of phase I and phase II have been measured to be about 2 and 1.5 nm, respectively. The apparent height of water films is shown to be strongly modified by the dielectric constant of sample and water, and the true thickness of water islands is discussed.     

Chiral Space Formed by (+)‐(1S)‐1,1′‐Binaphthalene‐2,2′‐diyl Phosphate: Recognition of Aliphatic L‐α‐Amino Acids

(+)‐(1S)‐1,1′‐Binaphthalene‐2,2′‐diyl hydrogen phosphate (bnppa) is one of the useful optical selectors. To disclose the molecular mechanism by which bnppa recognizes aliphatic L ‐α‐amino acids and separates them by fractional crystallization, X‐ray analyses of bnppa and of its salts with L ‐alanine, L ‐valine, L ‐norvaline, and L ‐norleucine have been undertaken. All the amino acids adopt energetically favorable conformations in the crystal structures. The conformations and the packing patterns of bnppa in these crystal structures are very similar. The bnppa molecules are packed in a specific way to form hydrophobic and hydrophilic layers that are well separated. Between bnppa molecules, at the interface of these hydrophobic and hydrophilic layers, a space with chirality is formed. This space, designated as chiral space, recognizes the optically active amino acids. The packing of bnppa is mainly governed by intermolecular CH⋅⋅⋅π interactions between naphthalene moieties. The chiral space is responsible for the molecular recognition by bnppa allowing fractional crystallization of the L ‐α‐amino acids.     

SURFACE RHEOLOGY OF POLYMERIC SOLIDS

Surface molecular motions of amorphous polymeric solids have been directly measured on the basis of scanningviscoelasticity microscopic (SVM) and lateral force microscopic (LFM) measurements. SVM and LFM measurements werecarried out for films of conventional monodisperse polystyrene (PS) with sec-butyl and proton-terminated end groups atroom temperature. In the case of the number-average molecular weight, M_n, less than ca. 4.0×10~4, the surface was in a glass-rubber transition state even though the bulk glass transition temperature, T_g was far above room temperature, meaning thatthe surface molecular motion was fairly active compared with that in the bulk. LFM measurements of the, monodisperse PSfilms at various scanning rates and temperatures revealed that the time-temperature superposition was applicable to thesurface mechanical relaxation behavior and also that the surface glass transition temperature, T_g~σ, was depressed incomparison with the bulk one even though the magnitude of M_n was fairly high at 1.40×10~5. The surface molecular motionof monodisperse PS with various chain end groups was investigated on the basis of temperature-dependent scanningviscoelasticity microscopy (TDSVM). The T_g~σs for the PS films with M_n of 4.9×10~6 to 1.45×10~6 measured by TDSVMwere smaller than those for the bulk one, with corresponding M_ns, and the T_g~σs for M_ns smaller than ca. 4.0×10~4 were lowerthan room temperature (293 K). The active thermal molecular motion at the polymeric solid surface can be interpreted interms of an excess free volume near the surface region induced by the surface localization of chain end groups. In the case ofM_n=ca. 5.0×10~4, the T_g~σs for the α, ω-diamino-terminated PS (α,ω-PS(NH_2)_2) and α, ω-dicarboxy-terminated PS (α, ω-PS(COOH)_2) films were higher than that of the PS film. The change of T_g~σ for the PS film with various chain end groups canbe explained in terms of the depth distribution of chain end groups at the surface region depending on the relativehydrophobicity.     

Tau neutrinos favored over sterile neutrinos in atmospheric muon neutrino oscillations

The previously published atmospheric neutrino data did not distinguish whether muon neutrinos were oscillating into tau neutrinos or sterile neutrinos, as both hypotheses fit the data. Using data recorded in 1100 live days of the Super-Kamiokande detector, we use three complementary data samples to study the difference in zenith angle distribution due to neutral currents and matter effects. We find no evidence favoring sterile neutrinos, and reject the hypothesis at the 99% confidence level. On the other hand, we find that oscillation between muon and tau neutrinos suffices to explain all the results in hand.     

Determination of 210Po in Reagent Samples by Alpha-Ray Spectrometry Using Extraction Chromatographic Resin

The determination of ²¹⁰Po in phosphoric acid reagent by alpha-ray spectrometry using extraction chromatographic resin is presented. The decontamination factors of interference elements were measured. It was observed that HCl, HNO₃, ascorbic acid, thioacetamide and Cu were free from ²¹⁰Po but Pb contain small amounts of ²¹⁰Po. ²¹⁰Po in phosphoric acid samples was ranged from <8 to 2.4 Bq/l. The detection limit of ²¹⁰Po in 50 ml of phosphoric acid is 8 mBq/l with a counting time of 1 day undercounting efficiency of 30%.     

Iridium‐Catalyzed Direct C4‐ and C7‐Selective Alkynylation of Indoles Using Sulfur‐Directing Groups

Indoles and their analogues have been one of the most ubiquitous heterocycles during the past century, and extensive studies have been conducted to establish practical synthetic methods for their derivatives. In particular, selective functionalization of the poorly reactive benzenoid core over the pyrrole ring has been a great challenge. Reported herein is an iridium‐catalyzed direct alkynylation of the indole C4‐ and C7‐positions with the assistance of sulfur directing groups. This transformation shows a wide range of functional‐group tolerance with exceptional site selectivity. The directing group can be either easily removed or transformed after catalysis. The synthetic utility of the alkyne fragment is demonstrated by the derivatization into the core structure of natural indole alkaloids.     

Negative muon capture ratios for nitrogen oxide molecules

Journal of Radioanalytical and Nuclear Chemistry - Per-atom muon capture ratios are precisely determined from characteristic muonic X-ray measurements of three nitrogen oxide samples (NO, N2O, and...