Accurate Q value for the Se double-electron-capture decay

The Q   value of the neutrinoless double-electron-capture (0νECEC$0\nu \text{ECEC}$) decay of ⁷⁴Se was measured by using the JYFLTRAP Penning trap. The determined value is 1209.169(49) keV, which practically excludes the possibility of a complete energy degeneracy with the second ²⁺$2^{+}$ state (1204.205(7) keV) of ⁷⁴Ge in a resonant 0νECEC$0\nu \text{ECEC}$ decay. We have also computed the associated nuclear matrix element by using a microscopic nuclear model with realistic two-nucleon interactions. The computed matrix element is found to be quite small. The failure of the resonant condition, combined with the small nuclear matrix element and needed p-wave capture, suppresses the decay rate strongly and thus excludes ⁷⁴Se as a possible candidate to search for resonant 0νECEC$0\nu \text{ECEC}$ processes.     

Development of Counting Skills: Role of Spontaneous Focusing on Numerosity and Subitizing-Based Enumeration

Children differ in how much they spontaneously pay attention to quantitative aspects of their natural environment. We studied how this spontaneous tendency to focus on numerosity (SFON) is related to subitizing-based enumeration and verbal and object counting skills. In this exploratory study, children were tested individually at the age of 4–5 years on these skills. Results showed 2 primary relationships in children's number skills development. Performance in a number sequence production task, which is closely related to ordinal number sequence without reference to cardinality, is directly associated with SFON. Second, the association of SFON and object counting skills, which require relating cardinal and ordinal aspects of number, is mediated by subitizing-based enumeration. This suggests that there are multiple pathways to enumeration skills during development.     

Thioflavin T hydroxylation at basic pH and its effect on amyloid fibril detection

The fluorescent dye thioflavin T (ThT) is commonly used for in situ amyloid fibril detection. In this work, we focused on the spectroscopic properties and chemical stability of ThT in aqueous solution as a function of pH, temperature, and dye concentration. A reversible hydroxylation process occurs in alkaline solutions, which was characterized using a combination of UV-vis absorption spectroscopy, proton NMR, and density functional theory (DFT). On the basis of these studies, we propose a chemical structure for the hydroxylated form. Finally, by means of fluorescence spectroscopy, ThT hydroxylation effects on in situ amyloid detection have been investigated, providing new insights on the efficiency of the ThT assay for quantitative fibril evaluation at basic pH.     

Site selectivity in the protonation of a phosphinito bridged Pt(I)-Pt(I) complex: a combined NMR and density-functional theory mechanistic study

The protonation of the dinuclear phosphinito bridged complex [(PHCy2)Pt(mu-PCy2){kappa(2)P,O-mu-P(O)Cy2}Pt(PHCy2)] (Pt-Pt) (1) by Br?nsted acids affords hydrido bridged Pt-Pt species the structure of which depends on the nature and on the amount of the acid used. The addition of 1 equiv of HX (X = Cl, Br, I) gives products of formal protonation of the Pt-Pt bond of formula syn-[(PHCy2)(X)Pt(mu-PCy2)(mu-H)Pt(PHCy2){kappaP-P(O)Cy2}] (Pt-Pt) (5, X = Cl; 6, X = Br; 8, X = I), containing a Pt-X bond and a dangling kappa P-P(O)Cy2 ligand. Uptake of a second equivalent of HX results in the protonation of the P(O)Cy2 ligand with formation of the complexes [(PHCy2)(X)Pt(mu-PCy2)(mu-H)Pt(PHCy2){kappaP-P(OH)Cy2}]X (Pt-Pt) (3, X = Cl; 4, X = Br; 9, X = I). Each step of protonation is reversible, thus reactions of 3, 4, with NaOH give, first, the corresponding neutral complexes 5, 6, and then the parent compound 1. While the complexes 3 and 4 are indefinitely stable, the iodine analogue 9 transforms into anti-[(PHCy2)(I)Pt(mu-PCy2)(mu-H)Pt(PHCy2)(I)] (Pt-Pt) (7) deriving from substitution of an iodo group for the P(OH)Cy2 ligand. Complexes 3 and 4 are isomorphous crystallizing in the triclinic space group P1 and show an intramolecular hydrogen bond and an interaction between the halide counteranion and the POH hydrogen. The occurrence of such an interaction also in solution was ascertained for 3 by (35)Cl NMR. Multinuclear NMR spectroscopy (including (31)P-(1)H HOESY) and density-functional theory calculations indicate that the mechanism of the reaction starts with a prior protonation of the oxygen with formation of an intermediate (12) endowed with a six membered Pt(1)-X...H-O-P-Pt(2) ring that evolves into thermodynamically stable products featuring the hydride ligand bridging the Pt atoms. Energy profiles calculated for the various steps of the reaction between 1 and HCl showed very low barriers for the proton transfer and the subsequent rearrangement to 12, while a barrier of 29 kcal mol(-1) was found for the transformation of 12 into 5.     

Tuning the release rate of acidic degradation products through macromolecular design of caprolactone-based copolymers

Macromolecular engineering is presented as a tool to control the degradation rate and release rate of acidic degradation products from biomedical polyester ethers. Three different caprolactone/1,5-dioxepan-2-one (CL/DXO) copolymers were synthesized: DXO/CL/DXO triblock, CL/DXO multiblock, and random cross-linked CL/DXO copolymer. The relation of CL and DXO units in all three copolymers was 60/40 mol %. The polymer discs were immersed in phosphate buffer solution at pH 7.4 and 37 degrees C for up to 364 days. After different time periods degradation products were extracted from the buffer solution and analyzed. In addition mass loss, water absorption, molecular weight changes, and changes in thermal properties were determined. The results show that the release rate of acidic degradation products, a possible cause of acidic microclimates and inflammatory responses, is controllable through macromolecular design, i.e., different distribution of the weak linkages in the copolymers.     

ASAXS study of styrene‐grafted sulfonated poly(vinylidene fluoride) membranes

Small‐angle and wide‐angle X‐ray scattering and anomalous small‐angle X‐ray scattering were used to investigate proton‐conducting membranes prepared by radiation‐induced styrene grafting and sulfonation of commercial poly(vinylidene fluoride) (PVDF‐g‐PS) films. The membranes retain the lamellar and highly oriented structure of the original PVDF films even through excessive grafting and sulfonation. The sulfonate groups aggregate in the central part of the amorphous layers, where they form a weakly ordered structure that does not show any preferred orientation. This structure is suggested to be lamellar with alternate metal‐sulfonated hydrate and PVDF‐g‐PS layers. The lamellar period is 15.1 Å. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1734–1748, 2000     

空间分辨荧光分析技术

空间分辨荧光分析技术突破了传统荧光分析的局限,为获得空间定位信息提供了技术保障。系统地综述了构成该技术的共焦荧光法、全内反射荧光法、多光子荧光法以及近场荧光法等4种方法的原理、特点、发展及其应用,并且强调了其在单分子测定中的作用。引用文献64篇。     

Ca[Ag2(SCN)4]·2H2O

Calcium tetra­thio­cyanato­diargentate(I) dihydrate, Ca[Ag₂(SCN)₄]·2H₂O, contains eight‐membered Ag₄S₄ rings bonded together through shared atoms to form layers parallel to (100). The thio­cyanate groups link the layers to Ca–O chains running parallel to the c axis. The Ca atom is located on a twofold rotation axis parallel to b and is surrounded by four water molecules of crystallization and four thio­cyanate N atoms in a distorted square antiprism.     

Activation energy of the reaction between hexacyanoferrate (Ш) and thiosulfate ions catalyzed by platinum nanoparticles confined in nanometer space

Pt nanoparticles (NPs) have been successfully encapsulated in SBA-15 mesoporous silica support. The silica was firstly functionalized by polyaminoamine (PAMAM) dendrimers with various generations and provided different nanometer space for Pt NPs. The growth of Pt NPs is restricted by the double confinement effect of PAMAM dendrimers and SBA-15 mesopores. The Pt NPs can be precisely controlled to localize inter- or intradendrimeric within SBA-15 tunnels. The different pore structures of Gn-PAMAM-SBA-15 (Gn-PS15) support have great influence on the catalytic performance of the encapsulated Pt NPs. The blocking structure of higher generation Gn-PS15 support debased the catalytic performance and increased the activation energy of reaction between Fe(CN)(6)(3-) and S(2)O(3)(2-) in a certain degree.