Photoreactions of β-aziridinylacrylonitriles and acrylates with alkenes: the substituent effects on the formation of [3+2] cycloadducts

The photochemical C,C-bond cleavage of trisubstituted aziridines 3-6 and consequent [3+2] cycloaddition with electron-deficient alkenes afforded the novel head-to-head adducts (1,2,3,5-tetrasubstituted pyrrolidines) selectively and efficiently. The aziridines 3 and 5 reacted with molecular oxygen, affording dioxazolidine 26 and cleaved products, respectively. The results may suggest that the C,C-bond of aziridine cleaves biradically. The photoreactions of N-tritylaziridines 7-9 possessing diester, dinitrile, and butadiene groups in the side chain with electron-deficient alkenes yielded 2,3-cis-pyrrolidine derivatives 29, 30, and 33 exclusively. In particular, the dinitrile 8 also reacted with non-electron-deficient alkenes. The formal synthesis of the indolizidine fragment 10 of stellettamides starting from the pyrrolidine (E)-33 was achieved in a convenient manner.     

Charge states of Ca atoms in β-dicalcium silicate

In order to study the crystal structure of β‐Ca₂SiO₄, time-of-flight neutron powder diffraction experiments were carried out at temperatures between room temperature (RT) and 600 °C. Rietveld refinement at RT has shown that β‐Ca₂SiO₄ is monoclinic based on P2₁/n symmetry and two different types of Ca sites, Ca(1) and Ca(2). All interatomic distances within 3 Å were calculated, with the valences of Ca(1) with seven CaO bonds and Ca(2) with eight were estimated to be 1.87+ and 2+ by the Zachariasen-Brown-Altermatt formula (bond valence sum). Applying charge neutrality the two charge states of Ca in β‐Ca₂SiO₄ are [Ca(1)SiO₄]²⁻ and Ca(2)²⁺, respectively. Furthermore, the [Ca(1)SiO₄]²⁻ unit has the shortest Ca-O distance, and its length kept constant at 2.23 Å at all temperatures. In the short-range structure analysis at RT, the shortest Ca-O bond was also observed in a radial distribution function. These results imply that the [Ca(1)SiO₄]²⁻ unit has covalency on the shortest Ca-O in addition to Si-O.     

Stereoselective total synthesis of atpenins a4 and b, harzianopyridone, and NBRI23477 B

The stereoselective total synthesis of atpenins A4 (2) and B (3), harzianopyridone (4), and NBRI23477 B (5) have been developed using a convergent approach involving the coupling reaction of a common iodopyridine with an aldehyde corresponding to the appropriate side chain of the desired compound. Furthermore, the absolute configurations of atpenin B (3), harzianopyridone (4), and NBRI23477 B (5) have been unambiguously determined.     

An interface capturing method with a continuous function: The THINC method with multi-dimensional reconstruction

An interface capturing method with a continuous function is proposed within the framework of the volume-of-fluid (VOF) method. Being different from the traditional VOF methods that require a geometrical reconstruction and identify the interface by a discontinuous Heaviside function, the present method makes use of the hyperbolic tangent function (known as one of the sigmoid type functions) in the tangent of hyperbola interface capturing (THINC) method [F. Xiao, Y. Honma, K. Kono, A simple algebraic interface capturing scheme using hyperbolic tangent function, Int. J. Numer. Methods Fluids 48 (2005) 1023–1040] to retrieve the interface in an algebraic way from the volume-fraction data of multi-component materials. Instead of the 1D reconstruction in the original THINC method, a multi-dimensional hyperbolic tangent function is employed in the present new approach. The present scheme resolves moving interface with geometric faithfulness and compact thickness, and has at least the following advantages: (1) the geometric reconstruction is not required in constructing piecewise approximate functions; (2) besides a piecewise linear interface, curved (quadratic) surface can be easily constructed as well; and (3) the continuous multi-dimensional hyperbolic tangent function allows the direct calculations of derivatives and normal vectors. Numerical benchmark tests including transport of moving interface and incompressible interfacial flows are presented to validate the numerical accuracy for interface capturing and to show the capability for practical problems such as a stationary circular droplet, a drop oscillation, a shear-induced drop deformation and a rising bubble.     

Fabrication of high aspect ratio subwavelength gratings based on X-ray lithography and electron beam lithography

In this paper, we present two nano-fabrication technologies that provide effective approaches for low-cost, large-scale manufacturing of nano-gratings. One grating is fabricated on polymethylmethacrylate (PMMA) with the pitch of 500 nm, and height of 2000 nm, and the other is fabricated on silicon wafer with the pitch of 666 nm, and height of 200 nm. High aspect ratio PMMA nanostructures which use X-ray lithography and electron beam lithography (EBL) are reported in this paper. These gratings can be used as molds, making it possible for industrial nano-imprinting technology to significantly cut cost and shorten process time.     

Relationships between power-law long-range interactions and fractional mechanics

We investigate the relationships between models of power-law long-range interactions and mechanics based on fractional derivatives. We present the fractional Lagrangian density which gives the Euler–Lagrange equation that serves as the equation of motion for fractional-power-law long-range interactions. We derive this equation by the fractional variational method. In addition, we derive a Noether-like current from the fractional Lagrangian density.     

Large-aperture focusing of x rays with micropore optics using dry etching of silicon wafers

Large-aperture focusing of Al K(α) 1.49 keV x-ray photons using micropore optics made from a dry-etched 4 in. (100 mm) silicon wafer is demonstrated. Sidewalls of the micropores are smoothed with high-temperature annealing to work as x-ray mirrors. The wafer is bent to a spherical shape to collect parallel x rays into a focus. Our result supports that this new type of optics allows for the manufacturing of ultralight-weight and high-performance x-ray imaging optics with large apertures at low cost.