Selective synthesis and crystal structure of [10]cycloparaphenylene

[10]Cycloparaphenylene ([10]CPP) was selectively synthesized in four steps in 13% overall yield from commercially available 4,4'-diiodobiphenyl by using mono-I-Sn exchange, Sn-Pt transmetalation, I-Pd exchange, and subsequent oxidative coupling reactions. The single-crystal X-ray structure of [10]CPP is described.     

A Stochastic Model for Block Segmentation of Images Based on the Quadtree and the Bayes Code for It

In information theory, lossless compression of general data is based on an explicit assumption of a stochastic generative model on target data. However, in lossless image compression, researchers have mainly focused on the coding procedure that outputs the coded sequence from the input image, and the assumption of the stochastic generative model is implicit. In these studies, there is a difficulty in discussing the difference between the expected code length and the entropy of the stochastic generative model. We solve this difficulty for a class of images, in which they have non-stationarity among segments. In this paper, we propose a novel stochastic generative model of images by redefining the implicit stochastic generative model in a previous coding procedure. Our model is based on the quadtree so that it effectively represents the variable block size segmentation of images. Then, we construct the Bayes code optimal for the proposed stochastic generative model. It requires the summation of all possible quadtrees weighted by their posterior. In general, its computational cost increases exponentially for the image size. However, we introduce an efficient algorithm to calculate it in the polynomial order of the image size without loss of optimality. As a result, the derived algorithm has a better average coding rate than that of JBIG.     

Synthesis of 1,3,4-thiadiazol-2-ylacetic acid derivatives

1,3,4-Thiadiazol-2-ylacetic acids 4 were prepared by lithiation of 2-methyl-1,3,4-thiadiazoles 1 , followed by treatment with carbon dioxide. Diethyl 1,3,4-thiadiazol-2-ylmalonates 6 were prepared by nucleophilic displacement reaction of the corresponding bromides 5 with diethyl malonate. Introduction of the amino group at the a-position of 4 or 6 was carried out via oximation or bromination to give the amino ester 9 or 4 . Attempts to prepare DL-α-amino-1,3,4-thiadiazol-2-ylacetic acids from 9 or 4 were unsuccessful because the amino acids were decarboxylated too rapidly to be isolated in the free form.     

Approaching over 10 000‐fold sensitivity increase in chiral capillary electrophoresis: Cation‐selective exhaustive injection and sweeping cyclodextrin‐modified micellar electrokinetic chromatography

A novel and simple method that combines an online concentration technique with an enantioseparation technique for capillary electrophoresis—namely, cation‐selective exhaustive injection and sweeping cyclodextrin‐modified micellar electrokinetic chromatography (CSEI‐sweeping CD‐modified MEKC)—realizes the effective enantioseparation of cationic analytes while keeping a significant increase of detection sensitivity. This technique consists of a slight modification of the basic CSEI‐sweeping MEKC. The main idea is to simply add an anionic CD as a chiral selector into the micellar buffer including sodium dodecyl sulfate, but not to change any other buffers in order to preserve the online concentration mechanism. When applied to analysis of the street drug, methamphetamine, the method achieved not only a baseline enantioseparation but also limits of detection (LODs; S/N = 3) of 70–90 pg/mL (ppt) for each isomer. This translates to a more than 10 000‐fold improvement compared to the LODs by the usual injection method. The present technique, which was made from a slight modification of CSEI‐sweeping MEKC, would give an attractive approach that is applicable to almost any analytes for which CSEI‐sweeping MEKC is applicable; all that is required is the selection of an appropriate anionic CD to be added to the micellar buffer.     

Non‐elementary speed‐ups in logic calculi

In this paper we show some non‐elementary speed‐ups in logic calculi: Both a predicative second‐order logic and a logic for fixed points of positive formulas are shown to have non‐elementary speed‐ups over first‐order logic. Also it is shown that eliminating second‐order cut formulas in second‐order logic has to increase sizes of proofs super‐exponentially, and the same in eliminating second‐order epsilon axioms. These are proved by relying on results due to P. Pudlák. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Corrosion analysis and monitoring of the environmental factors for the deterioration of chromium-bearing reinforcing steel in mortar

To understand environmental factors, Cl ion concentration and pH were monitored by inserting microelectrodes into artificial pores in the mortar. The corrosion behavior of reinforcing steels containing chromium were investigated with carbon steel (SM) by electrochemical impedance spectroscopy (EIS). From the EIS, the corrosion resistance of the Cr-bearing reinforcing steel was visibly higher than the SM reinforcing steel. Simultaneously, the Cl ion concentration in the mortar was obtained using Ag/AgCl microelectrodes, showing that this behavior is generally controlled by diffusion. Similarly, the pH in the mortar was obtained using W/WOx microelectrodes. With a 20-mm cover thickness, pH was limited to approximately pH 11, but with a 10-mm cover thickness, pH continued to decrease to around pH 9.5. Solutions were prepared simulating the condition in the pores in mortar and were used in EIS measurements. The charge transfer resistance, R _ct, in the simulated solutions showed good correspondence with that in the actual mortar. This is attributed to the fact that the corrosion of reinforcing steel was controlled by the solution conditions (mainly Cl concentration and pH) in mortar. Moreover, it was found that, as compared with SM, Cr-bearing steel could keep the passive film in severe condition, and have long incubation time until the passive film was destroyed.     

Structural order in perfluoropentacene thin films and heterostructures with pentacene

Synchrotron x-ray diffraction reciprocal space mapping was performed on perfluoropentacene (PFP) thin films on SiO2 in order to determine the crystal structure of a novel, substrate-induced thin film phase to be monoclinic with unit cell parameters of a = 15.76 +/- 0.02 A, b = 4.51 +/- 0.02 A, c = 11.48 +/- 0.02 A, and beta = 90.4 +/- 0.1 degrees . Moreover, layered and co-deposited heterostructures of PFP and pentacene (P) were investigated by specular and grazing-incidence x-ray diffraction, atomic force microscopy, and Fourier-transform infrared spectroscopy. For a ca. three-monolayers-thick PFP film grown on a P underlayer, slightly increased lattice spacing was found. In contrast, co-deposited P/PFP films form a new mixed-crystal structure with no detectable degree of phase separation. These results highlight the structural complexity of these technically relevant molecular heterojunctions for use in organic electronics.