Bis(tert‐butylpyrene) Nanotweezers and Nanocalipers: Enhanced Extraction and Recognition Abilities for Single‐Walled Carbon Nanotubes

We developed a host–guest methodology for separation of single‐walled carbon nanotubes (SWNTs) according to the handedness, diameter and metallicity by the use of diporphyrin nanotweezers and nanocalipers. Although the pyrene has been frequently used to replace porphyrin, due to a similar affinity to the surface of SWNTs and better availability, the extraction and recognition abilities of dipyrene nanotweezers were not so good as those of diporphyrin ones as we reported previously. However, introduction of a tert‐butyl substituent at the 7′‐position of 2‐pyrene is found to enhance the extraction and recognition abilities of dipyrene nanotweezers and nanocalipers. That is, (6,5)‐SWNTs were obtained in high purity by use of bis(tert‐butylpyrene) nanotweezers with a phenanthrene spacer and metallic SWNTs were highly enriched by use of bis(tert‐butylpyrene) nanocalipers with a carbazole–anthracene–carbazole spacer.     

Approximate nonreflecting inflow-outflow boundary conditions for the calculation of navier-stokes equations in internal flows

In this paper, the nonreflecting boundary conditions based upon fundamental ideas of the linear analysis are developed for gas dynamic equations, and the modified boundary conditions for Navier-Stokes equations are proposed as a substitute of the nonreflecting boundary conditions inside boundary layers near rigid walls. These derived boundary conditions are then applied to calculations both for the Euler equations and the Navier-Stokes equations to determine if they can produce acceptable results for the subsonic flows in channels. The numerical results obtained by an implicit second-order upwind difference scheme show the effectiveness and generality of the boundary conditions. Furthermore, the formulae and the analysis performed here may be extended to three dimensional problems. recommended by Prof. Cui Erjie     

Transient non-Darcy free convection between parallel vertical plates in a fluid saturated porous medium

Transient non-Darcy free convection between two parallel vertical plates in a fluid saturated porous medium is investigated using the generalized momentum equation proposed by Vafai and Tien. The effects of porous inertia and solid boundary are considered in addition to the Darcy flow resistance. Exact solutions are found for the asymptotic states at small and large times. The large time solutions reveal that the velocity profiles are rather sensitive to the Darcy number Da when Da<1. It has also been found that boundary friction alters the velocity distribution near the wall, considerably. Finite difference calculations have also been carried out to investigate the transient behaviour at the intermediate times in which no similarity solutions are possible. This analytical and numerical study reveals that the transient free convection between the parallel plates may well be described by matching the two distinct asymptotic solutions obtained at small and large times.Nomenclature C empirical constant for the Forchheimer term - f velocity function for the small time solution - F velocity function for the large time solution - g acceleration due to gravity - Gr* micro-scale Grashof number - H a half distance between two infinite plates - K permeability - Nu Nusselt number - Pr Prandtl number - t time - T temperature - u, v Darcian velocity components - x, y Cartesian coordinates - effective thermal diffusivity - coefficient of thermal expansion - porosity - dimensionless time - similarity variable - dimensionless temperature - viscosity - kinematic viscosity - density - the ratio of heat capacities     

Cavitation phenomena in extracorporeal microexplosion lithotripsy

An experimental investigation was made of cavitation phenomena induced by underwater shock wave focusing applied to the extracorporeal microexplosion lithotripsy (microexplosion ESWL). Firstly an underwater microexplosion generated by detonation of a 10 mg silver azide pellet was studied and secondly underwater shock focusing and its induced cavitation phenomena were investgated. Underwater shock wave was focused by using a semi-ellipsoidal reflector in which a shock wave generated at the first focal point of the reflector was reflected and focused at the second focal point. It is found that an explosion product gas bubble did not produce any distinct rebound shocks. Meantime cavitation appeared after shock focusing at the second focal point where expansion waves originated at the exit of the reflector were simultaneously collected. A shock/bubble interaction is found to contribute not only to urinary tract stone disintegration but also tissue damage. The cavitation effect associated with the microexplosion ESWL was weaker in comparison with a spark discharge ESWL. The microexplosion ESWL is an effective method which can minimize the number of shock exposures hence decreasing tissue damage by conducting precise positioning of urinary tract stones.This article was processed using Springer-Verlag T_EX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society.     

Effect of ion beam irradiation on magnetism of Fe(100) outermost surfaces studied by spin-polarized ion scattering spectroscopy

We study the effect of 2 keV Ar⁺ ion beam irradiation (IBI) on the outermost surface magnetism of an Fe(100) film by spin-polarized ion scattering spectroscopy (SP-ISS). We found that the coercivity of the outermost surface is enhanced with IBI. On the other hand, spin polarization is independent of IBI. These effects of IBI on surface magnetism are discussed in terms of morphology and atomic arrangement of the surface analyzed by ISS and reflection high-energy electron diffraction. The variation of coercivity with respect to the average iron film thickness d followed a power law d^? n with the assumption that d is linearly dependent on the IBI time.     

A Macrocyclic Peptide Library with a Structurally Constrained Cyclopropane‐containing Building Block Leads to Thiol‐independent Inhibitors of Phosphoglycerate Mutase

Here we report the construction of an mRNA‐encoded library of thioether‐closed macrocyclic peptides by using an N‐chloroacetyl‐cyclopropane‐containing exotic initiator whose structure is more constrained than the ordinary N‐chloroacetyl‐α‐amino acid initiators. The use of such an initiator has led to a macrocycle library with significantly suppressed population of lariat‐shaped species compared with the conventional libraries. We previously used a conventional library and identified a small lariat thioether‐macrocycle with a tail peptide with a C‐terminal free Cys whose sidechain plays an essential role in potent inhibitory activity against a parasitic model enzyme, phosphoglycerate mutase. On the other hand, the cyclopropane‐containing macrocycle library has yielded a larger thioether‐macrocycle lacking a free Cys residue, which exhibits potent inhibitory activity to the same enzyme with a different mode of action. This result indicates that such a cyclopropane‐containing macrocycle library would allow us to access mechanistically distinct macrocycles.     

Design of Advanced Functional Materials Using Nanoporous Single‐Site Photocatalysts

Nanoporous silica solids can offer opportunities for hosting photocatalytic components such as various tetra‐coordinated transition metal ions to form systems referred to as “single‐site photocatalysts”. Under UV/visible‐light irradiation, they form charge transfer excited states, which exhibit a localized charge separation and thus behave differently from those of bulk semiconductor photocatalysts exemplified by TiO₂. This account presents an overview of the design of advanced functional materials based on the unique photo‐excited mechanisms of single‐site photocatalysts. Firstly, the incorporation of single‐site photocatalysts within transparent porous silica films will be introduced, which exhibit not only unique photocatalytic properties, but also high surface hydrophilicity with self‐cleaning and antifogging applications. Secondary, photo‐assisted deposition (PAD) of metal precursors on single‐site photocatalysts opens up a new route to prepare nanoparticles. Thirdly, visible light sensitive photocatalysts with single and/or binary oxides moieties can be prepared so as to use solar light, the ideal energy source.     

Silver Nanoparticles Supported on CeO2‐SBA‐15 by Microwave Irradiation Possess Metal–Support Interactions and Enhanced Catalytic Activity

Metal–support interactions (MSIs) and particle size play important roles in catalytic reactions. For the first time, silver nanoparticles supported on CeO₂‐SBA‐15 supports are reported that possess tunable particle size and MSIs, as prepared by microwave (MW) irradiation, owing to strong charge polarization of CeO₂ clusters (i.e., MW absorption). Characterizations, including TEM, X‐ray photoelectron spectroscopy, and extended X‐ray absorption fine structure, were carried out to disclose the influence of CeO₂ contents on the Ag particle size, MSI effect between Ag nanoparticles and CeO₂‐SBA‐15 supports, and the strong MW absorption of CeO₂ clusters that contribute to the MSIs during Ag deposition. The Ag particle sizes were controllably tuned from 1.9 to 3.9 nm by changing the loading amounts of CeO₂ from 0.5 to 2.0 wt %. The Ag nanoparticle size was predominantly responsible for the high turnover frequency (TOF) of 0.41 min^?1 in ammonia borane dehydrogenation, whereas both particle size and MSIs contributed to the high TOF of 555 min^?1 in 4‐nitrophenol reduction for Ag/0.5CeO₂‐SBA‐15, which were twice as large as those of Ag/SBA‐15 without CeO₂ and Ag/CeO₂‐SBA‐15 prepared by conventional oil‐bath heating.     

Analysis of carcinogenic mechanisms of liver cancers induced by chronic exposure to alpha-particles from internally deposited Thorotrast

For the successful space traveling, the possibility for the detrimental effects on health including cancer caused by exposure to cosmic rays is a major concern. Thorotrast is a 25% colloidal solution of natural -emitter, thorium dioxide used as a radiological contrast medium during World War II. It caused hepatic malignant tumors by the local exposure to -particles decades after administration. Thorotrast-induced liver tumors consist of hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (ICC), and angiosarcoma (AS) at nearly the same instance. We analyzed mutations of the p53 and the K-ras genes, microsatellite instability (MSI), and loss of heterozygosity (LOH) in Thorotrast ICC. The major p53 mutation observed in Thorotrast ICC was the transition type, suggesting that reactive oxygen species are not likely involved in gene mutations of Thorotrast cancers. MSI frequency in Thorotrast ICC was significantly higher than that in non-Thorotrast ICC. MSI was partly attributed to the inactivation of the hMLH1 mismatch repair gene via methylation of the promoter region and to monoclonal expansion of cells with mutations. Thorotrast ICC shared LOH pattern with non-Thorotrast HCC and ICC. Furthermore, we could assess the distribution and the quantity of deposited thorium using an imaging plate and a BAS image analyzer. The distribution of thorium deposits was not always consistent with that of apoptotic cells. We conclude that Thorotrast ICC is developed through complex carcinogenic steps including genomic instability and mutations of crucial genes during remodeling of the liver architecture. We emphasize how pathological specimens from Thorotrast patients are valuable for assessing the relevance of long-term exposure to low dose -particles to radiation carcinogenesis.