Proton-neutron correlations in nuclei with N = 30

Structure of the nuclei with N = 30 and Z = 20–28 is investigated by the nuclear shell model within the proton-neutron configurations (1f_{$\text{7}\text{2}$})^z?20_p × (2p_{$\text{3}\text{2}$}, 2p_{$\text{case1}\text{2}$}, 1f_{$\text{case5}\text{2}$})²_n. Effective proton-neutron interactions determined by a least-squares fit to the observed spectra of N = 29 nuclei are adopted. Agreement of the calculated spectra with experimental spectra is satisfactory. Strong correlations between protons and neutrons break down the pairing scheme and lower the first J = 2 levels in doubly even nuclei, which is shown from the resultant wave functions. A relation between the shell model and collective rotational model is discussed concerning the calculated rotation-like spectrum of ⁵⁶Fe. Electromagnetic properties and spectroscopic factors of single-nucleon transfer reactions are calculated. They are in good agreement with experiments.     

Dichloropentafluoropropanes as solvents for size exclusion chromatography

We have found that HCFC225s (HCFC225ca: 3,3-dichloro-1,1,1,2,2-pentafluoropropane, HCFC225cb: 1,3-dichloro-1,1,2,2,3-pentafluoropropane) are superior mobile phases for size exclusion chromatography (SEC). As alternatives of CFC113, they have been shown to possess a number of excellent properties, such as low flammability, low viscosity, low cost, high purity, and environmental and operational friendliness. In addition, they have distinct advantages for the SEC measurement, because they solubilize some kinds of acrylate such as poly(methyl methacrylate) (PMMA) and commercial monodispersed PMMA can be used to prepare calibration curves necessary for the measurement of equivalent molecular weight of some polymers. Furthermore, we propose an HCFC225/1,1,1,3,3,3-hexafluoroisopropanol mixed solvent for use in the SEC of poly(ethylene terephthalate) (PET) and polyamides. Poly(2-(perfluorooctyl)ethyl acrylate), whose PMMA equivalent weight average molecular weight was 118,100 Da, was evaluated by a multi-angle laser light scattering (MALLS) detector to have an absolute molecular weight of 439,000 Da. The difference can be attributed to the molecular size of the polyfluorinated polymer compared to the non-fluorinated one. The possible application of this novel mobile phase system for molecular size and molecular weight characterization of perfluoropolyethers, PET, nylon 6 and nylon 6,6 are also discussed.     

An entirely new methodology for synthesizing perfluorinated compounds: synthesis of perfluoroalkanesulfonyl fluorides from non-fluorinated compounds

A new synthetic procedure for the preparation of perfluoroalkanesulfonyl fluorides utilizing liquid-phase direct fluorination with elemental fluorine has been developed. Direct fluorination of a partially fluorinated ester, which has alkanesulfonyl fluoride in the end, was synthesized from non-fluorinated counterparts and perfluorinated acid fluoride according to the PERFECT process, gave the desired perfluorinated product in moderate yield as well as by-products arising from CS bond cleavage. The results of the direct fluorination of some model substrates suggest that the CS bond cleavage occurred due to radical formation at the α-position rather than the β-position.     

Catalytic cyclization of o-alkynylbenzaldehyde acetals and thioacetals. Unprecedented activation of the platinum catalyst by olefins. Scope and mechanism of the reaction

A general protocol for the synthesis of functionalized indenes from o-alkynylbenzaldehyde acetals and thioacetals has been elaborated. Acetals uniformly give cyclization products having the alkyl group from the starting acetylene migrated to the alpha-position, whereas the cyclization of the corresponding thioacetals proceeds without alkyl migration. Optimization of the catalytic system for the cyclization of o-alkynylbenzaldehyde acetals revealed an unknown activation effect: PtCl(2) was found to be a better catalyst for the cyclization of acetals in the presence of olefins than without. A similar catalytic system (PtCl(2)/benzoquinone) has been found to be appropriate for the cyclization of cyclic acetals, whereas the optimal catalyst for the reaction of thioacetals is PdI(2). NMR monitoring of two reactions, acetal 3a + Pd(CH(3)CN)Cl(2) in CD(3)CN and thioacetal 5j + PdI(2) in CD(2)Cl(2), revealed that in both reactions similar cationic species are formed at the early stage of the transformation. Computational data (B3LYP/SDD level of theory) suggest that the difference in the reaction pathways for acetals and thioacetals can be rationalized by taking into account the relative stabilities of the corresponding vinylpalladium intermediates (22 vs 20 and 19 vs 21), which suggests a reversible thermodynamically controlled alkyl migration in the intermediate vinylcationic species.     

First functionalized MRI contrast agent recognizing vascular lesions.

A new MRI-contrast agent, EB-DTPA-Gd, that has an Evans Blue analogue as a sensing unit for endothelium lesions, was designed and synthesized. The agent also has diethylenetriamine-N,N,N',N",N"-pentaacetic acid-Gd complex (Gadolinium-DTPA) units, which have been used as detection units for T1-weighted MRI. The EB-DTPA-Gd was able to recognize and adsorb to the vascular endothelium-denuded region of porcine aorta, and to decrease the relaxation time of circumferential water's protons, making possible MR imaging of the endothelium-denuded region. The compound can be employed as a contrast agent for the imaging of vascular lesions using MRI.     

2-hydroxymethyl-4-phenylthio-1-butene as a key compound for total synthesis of acyclic terpenoids

A new total synthesis of myrcene, citral, squalane, and isophytol employing 2-hydroxymethyl-4-phenylthio-1-butene as a starting material is described.     

Path-dependence of the forming limit stresses in a sheet metal

The effect of changing strain paths on the forming limit stresses of sheet metals is investigated using the Marciniak–Kuczyński model and a phenomenological plasticity model with non-normality effects [Kuroda, M., Tvergaard, V., 2001. A phenomenological plasticity model with non-normality effects representing observations in crystal plasticity. J. Mech. Phys. Solids 49, 1239–1263]. Forming limits are simulated for linear stress paths and two types of combined loading: a combined loading consisting of two linear stress paths in which unloading is included between the first and second loadings (combined loading A), and combined loading in which the strain path is abruptly changed without unloading (combined loading B). The forming limit stresses calculated for combined loading A agree well with those calculated for the linear stress paths, while the forming limit curves in strain space depend strongly on the strain paths. The forming limit stresses calculated for the combined loading B do not, however, coincide with those calculated for the linear stress paths. The strain-path dependence of the forming limit stress is discussed in detail by observing the strain localization process.     

Chemical properties of fatty acid derivatives as inhibitors of DNA polymerases

In this study, the chemical properties of organic acids as DNA polymerase inhibitors were examined. In total, we assayed the inhibitory activities of 23 compounds. We found that the DNA synthesis activity of DNA polymerase was usually reduced to less than 50% in the presence of 100 microM monoprotic acids, which have a Clog P value greater than 7.0 and a pK(a) value less than 5.4. With a minor modification these chemical properties applied to several organic fatty acids previously reported as DNA polymerase inhibitors. Moreover, we also examined the inhibitory activities of perfluorooctadecanoic acid (PFOdA) and perfluorooctanesulfonic acid (PFOS) against DNA polymerase beta in detail. These compounds inhibited the polymerase activity of pol beta competitively with template-primer DNA, and non-competitively with dNTPs. In addition, the 8 kDa domain-defective pol beta was also sensitive to these compounds. Our results suggest that the inhibitory mode of action of PFOdA and PFOS is different from that mediated by the classic fatty acid inhibitors against DNA polymerase beta.     

Energetics and volume changes in electron attachment to pyrazine in supercritical xenon

The attachment of electrons to pyrazine occurs reversibly over a wide range of pressures at and above room temperature in supercritical xenon. The rate constant for attachment increases with pressure at low pressures, passes through a maximum, and levels off at values of 1-3x10(12) m(-1) s(-1) at high pressure. The activation volumes for attachment (DeltaVa*) are quite small but show maxima near the compressibility maxima. In contrast, DeltaVa* is always negative for this reaction in sc-ethane and exhibits minima near the compressibility maxima. The rate constants for electron detachment change little with pressure but increase with temperature. Activation volumes for detachment are small. To explain the small volume change observed for this reaction, it is proposed that at the higher pressures clustering around the neutral pyrazine is comparable to that around the ion; i.e., the partial molar volumes are comparable. The free energy change (DeltaGr) of this reaction decreases between 40 and 60 bar and then is fairly constant at higher pressures. The dependence of DeltaGr on pressure is consistent with clustering around the neutral pyrazine at higher pressure. Also, the electron affinity of the clusters, pyrazineXen, increases with n to a few tenths of an eV.