Synthesis and Conformational Studies of Lower Rim Cyanomethyl Substituted Calix[4]arenes

The conformational inversion characteristics of calix[4]arenes carrying cyanomethyl groups on the lower rim have been investigated. Complete conversion from a 1,3-alternate to a partial cone conformation was observed for the 1,3-dicyanomethyl ether of calix[4]arene at room temperature, while at higher temperatures further inversion to a 1:1 mixture of partial cone and cone conformers occurred.     

Stabilization of a multiwavelength erbium-doped fiber laser using a nonlinear silicon waveguide

We propose and demonstrate a multiwavelength erbium-doped fiber laser stabilized by four-wave mixing (FWM) in a nonlinear silicon-on-insulator (SOI) waveguide. The optical gain was provided by an erbium-doped fiber amplifier, and the wavelength selectivity was achieved by a Fabry–Pérot comb filter in the ring cavity. The FWM in the SOI waveguide was enhanced by applying a reverse-biased p-i-n diode structure to reduce free-carrier absorption. Making use of the nonlinearity of the SOI waveguide, a multiwavelength laser with six output wavelengths at 0.8 nm spacing was achieved. The power difference among modes was equalized within a range of 1.8 dB. The power fluctuation of each mode was stabilized to <0.65 dB during 20 min observation at room temperature.     

CD133 and CD133‐regulated nucleophosmin linked to 5‐fluorouracil susceptibility in human colon cancer cell line SW620

Cancer stem cells (CSCs) are known to be resistant to conventional chemotherapy and radiotherapy. Specific CSC targeting and eradication is therefore a therapeutically important challenge. CD133 is a colorectal CSC marker with unknown function(s). Assessing proteomic changes induced by CD133 may provide clues not only to new CD133 functions but also to the chemotherapy and radiation susceptibility of colon cancer cells. To identify the proteins affected by CD133, CD133‐positive (CD133+), and CD133‐negative (CD133–) human colon cancer cells were obtained by cell sorting. Whole proteomes were profiled from SW620/CD133+ and SW620/CD133– cells and analyzed by 2D‐based proteome analysis. Nucleophosmin (NPM1) was identified as a protein regulated by CD133. CD133 protein level was not affected by NPM1, and an interaction between the two proteins was not observed. CD133 and NPM1 protein levels were positively correlated in 11 human colon cancer cell lines. The CD133+ subpopulation percentage or its value normalized against CD133 protein level was only linked to intrinsic susceptibility of human colon cancer cells to 5‐fluorouracil (5‐FU). However, either suppression of CD133 or NPM1 significantly increased 5‐FU susceptibility of SW620. The present study suggests that CD133‐regulated NPM1 protein level may provide a clue to novel CD133 function(s) linked to human colon cancer cell susceptibility to chemotherapy.     

Development of a new casting method to fabricate U–Zr alloy containing minor actinides

Metal fuel slugs of U–Zr alloys for a sodium-cooled fast reactor (SFR) have conventionally been fabricated using an injection casting method. However, casting alloys containing volatile radioactive constituents, such as Am, are problematic in a conventional injection casting method. As an alternative fabrication method, low pressure gravity casting has been developed. Casting soundness, microstructural characteristics, alloying composition, density, and fuel losses were evaluated for the following as-cast fuel slugs: U–10 wt% Zr, U–10 wt% Zr–5 wt% RE, and U–10 wt% Zr–5 wt% RE–5 wt% Mn. The U and Zr contents were uniform throughout the matrix, and impurities such as oxyen, carbon, and nitrogen satisfied the specification of total impurities less than 2,000 ppm. The appearance of the fuel slugs was generally sound, and the internal integrity was shown to be satisfactory based on gamma-ray radiography. In a volatile surrogate casting test, the U–Zr–RE–Mn fuel slug showed that nearly all of the manganese was retained when casting was done under an inert atmosphere.     

Preparation of various well-organized porous silica impregnated with calcium chloride and their water uptake

A variety of ordered (macro)mesoporous silica ((M)MPS) was prepared, impregnated with calcium chloride (CC) and finally tested for water uptake. Liquid-grown MPS (LMPS) were in the short tube bundles, aerosol-made MPS (AMPS) were the spheres having the pores in parallel with their surface, and dip-coated MPS (DMPS) were in a form of 2-D hexagonal film. Ordered macropores were introduced to AMPS and DMPS by using polystyrene latexes as templates. Post impregnation of CC on these (M)MPS, obeying Langmuir isotherm, increased with the chemical activity and BET specific area of the host surface, in the order of AMPS < LMPS ~ AMMPS < DMPS < DMMPS. The salt, once loaded above ~ 0.06 g CC/g (M)MPS, continued to uptake water until they formed the salt solution in equilibrium with the prevailing water vapor at the given temperature. However, the CC, in situ impregnated in AMPS, was not all available for water uptake, due to some chemical deterioration. For the given host materials, the particle-to-particle voids, if any, and CC loading retarded the rate of water uptake. For the given salt loading, the internal uptake rate increased in the order of AMPS < LMPS ~ AMMPS < DMPS < DMMPS.     

The adsorption properties of organic sulfur compounds on zeolite-based sorbents impregnated with rare-earth metals

Dimethyl disulfide (DMDS) and dimethyl sulfide (DMS) are non-polar, stable, organic sulfur compounds found in liquefied petroleum gas, and their oxidation in the atmosphere results in the formation of tropospheric sulfur dioxide, which is subsequently converted into sulfuric acid, as the main factor of acid rain. In the present study, adsorption processes were devised based on the use of modified zeolite impregnated with rare-earth metals (Ce, La or Pr) for the adsorption of DMDS and DMS, and their sorption capacities were compared with that of commercial zeolite [Zeolite-Y, Ultra Stable Y(USY)]. The adsorption capacities of adsorbents were tested using a micro liquid flow reactor at room temperature. USY impregnated with cerium oxide (UC-10) had excellent DMDS and DMS adsorption capacities as compared with the other adsorbents tested. It was found that impregnation of USY with rare-earth metal such as Ce improved the sulfur adsorption capacity of zeolite. The form of the Ce promoter impregnated into USY was determined by FT-Raman spectroscopy. Adsorbents were characterized by X-ray fluorescence spectrometer, X-ray diffraction, and BET and the results obtained are discussed.     

Loading Dynamics of a Sliding DNA Clamp

Sliding DNA clamps are loaded at a ss/dsDNA junction by a clamp loader that depends on ATP binding for clamp opening. Sequential ATP hydrolysis results in closure of the clamp so that it completely encircles and diffuses on dsDNA. We followed events during loading of an E. coli β clamp in real time by using single‐molecule FRET (smFRET). Three successive FRET states were retained for 0.3 s, 0.7 s, and 9 min: Hydrolysis of the first ATP molecule by the γ clamp loader resulted in closure of the clamp in 0.3 s, and after 0.7 s in the closed conformation, the clamp was released to diffuse on the dsDNA for at least 9 min. An additional single‐molecule polarization study revealed that the interfacial domain of the clamp rotated in plane by approximately 8° during clamp closure. The single‐molecule polarization and FRET studies thus revealed the real‐time dynamics of the ATP‐hydrolysis‐dependent 3D conformational change of the β clamp during loading at a ss/dsDNA junction.     

An Upconversion Nanoparticle with Orthogonal Emissions Using Dual NIR Excitations for Controlled Two‐Way Photoswitching

Developing multicolor upconversion nanoparticles (UCNPs) with the capability of regulating their emission wavelengths in the UV to visible range in response to external stimuli can offer more dynamic platforms for applications in high‐resolution bioimaging, multicolor barcoding, and driving multiple important photochemical reactions, such as photoswitching. Here, we have rationally designed single‐crystal core–shell‐structured UCNPs which are capable of orthogonal UV and visible emissions in response to two distinct NIR excitations at 808 and 980 nm. The orthogonal excitation–emission properties of such UCNPs, as well as their ability to utilize low‐power excitation, which attenuates any local heating from the lasers, endows the UCNPs with great potential for applications in materials and biological settings. As a proof of concept, the use of this UCNP for the efficient regulation of the two‐way photoswitching of spiropyran by using dual wavelengths of NIR irradiation has been demonstrated.     

Selective oxidation on metallic carbon nanotubes by halogen oxoanions

Chlorine oxoanions with the chlorine atom at different oxidation states were introduced in an attempt to systematically tailor the electronic structures of single-walled carbon nanotubes (SWCNTs). The degree of selective oxidation was controlled systematically by the different oxidation state of the chlorine oxoanion. Selective suppression of the metallic SWCNTs with a minimal effect on the semiconducting SWCNTs was observed at a high oxidation state. The adsorption behavior and charge transfer at a low oxidation state were in contrast to that observed at a high oxidation state. Density functional calculations demonstrated the chemisorption of chloro oxoanions at the low oxidation state and their physisorption at high oxidation states. These results concurred with the experimental observations from X-ray photoelectron spectroscopy. The sheet resistance of the SWCNT film decreased significantly at high oxidation states, which was explained in terms of a p-doping phenomenon that is controlled by the oxidation state.