Optical image asymmetric cryptosystem using fingerprint based on iterative fraction Fourier transform

A novel asymmetric cryptosystem for optical image is proposed using fingerprint based on iterative fractional Fourier transform. To enhance the security, a hyperchaotic phase generated by a 4D Lorenz system is considered as the public key in the proposed encryption system, while the private key is emerged by the retrieved phase and fingerprint. In the encryption process, the secret information is hid into the hyperchaotic phase. Subsequently, the private key can be obtained by a reversible operation. To decrypt the original image, the ciphertext and private key are imported into the input plane of fractional Fourier system. This system is also applicable for information authentication because the fingerprint is used both in encryption and decryption approach. Some numerical simulations have been done to test the validity and capability of the encryption system.     

A Convenient,Large-Scale Preparation of 2,4-Dichlorophenyl-4-bromomethyl-phenoxyacetate Suitable for Resin Anchorage of the First Fmoc Amino Acid

2,4-dichlorophenyl-4-bromomethyl-phenoxyacetate 3 was prepared by NBS treatement of 2,4-dichlorophenyl-4-methylphenoxyacetate 2. This ester is a key intermediate in the preparation of 2,4-dichlorophenyl-N^α-Fmoc-aminoacyl-4-oxymethylphenoxy-acetates suitable for anchorage of the first amino acid on amine-functionalized polymers.     

Local shrinkage and stress induced by thermo-oxidation in composite materials at high temperatures

The paper is concerned with the modelling, simulation and experimental characterisation of local shrinkage strains and stresses induced by thermo-oxidation phenomena in the IM7/977-2 carbon/epoxy composite material at elevated temperatures. The oxygen concentration and mechanical fields were established through a coupled model constructed from a unified multiphysical approach and the thermodynamics of irreversible processes. The model was implemented in the ABAQUS^® finite element commercial code. Simulations of thermo-oxidation-induced matrix shrinkage were run at a local scale, i.e., the scale of the elementary constituents of the composite, the fibre and the matrix. The experimental assessment was done at the same scale, and the local matrix shrinkage profiles were measured by confocal interferometric microscopy.A good agreement was found between the simulated and measured profiles, validating the unified model. The thermo-oxidation induced stress field was analysed to understand the influence of the environment on the onset of damage in composite materials at elevated temperature.     

Spin‐State Ordering on One Sub‐lattice of a Mononuclear Iron(III) Spin Crossover Complex Exhibiting LIESST and TIESST

The two‐step spin crossover in mononuclear iron(III) complex [Fe(salpm)₂]ClO₄ ? 0.5 EtOH ( 1 ) is shown to be accompanied by a structural phase transition as concluded from ⁵⁷Fe Mössbauer spectroscopy and single crystal X‐ray diffraction, with spin‐state ordering on just one of two sub‐lattices in the intermediate magnetic and structural phase. The complex also exhibits thermal‐ and light‐induced spin‐state trapping (TIESST and LIESST), and relaxation from the LIESST and TIESST excited states occurs via the broken symmetry intermediate phase. Two relaxation events are evident in both experiments, that is, two T(LIESST) and two T(TIESST) values are recorded. The change in symmetry which accompanies the TIESST effect was followed in real time using single crystal diffraction. After flash freezing at 15 K the crystal was warmed to 40 K at which temperature superstructure reflections were observed to appear and disappear within a 10 000 s time range. In the frame of the international year of crystallography, these results illustrate how X‐ray diffraction makes it possible to understand complex ordering phenomena.     

Synthesis,Photophysics and Nonlinear Optical Properties of Stilbenoid Pyrimidine‐Based Dyes Bearing Methylenepyran Donor Groups

The nonlinear properties and the photophysical behavior of two π‐conjugated chromophores that incorporate an electron‐deficient pyrimidine core (A) and γ‐methylenepyrans as terminal donor (D) groups have been thoroughly investigated. Both dipolar and quadrupolar branching strategies are explored and rationalized on the basis of the Frenkel exciton model. Even though a cooperative effect is clearly observed if the dimensionality is increased, the nonlinear optical (NLO) response of this series is moderate if one considers the nature of the D/A couple and the size of the chromophores (as measured by the number of π electrons). This effect was attributed to a disruption in the electronic conjugation within the dyes’ scaffold for which the geometry deviates from planarity owing to a noticeable twisting of the pyranylidene end‐groups. This latter structural parameter also has a strong influence on the excited‐state dynamics, which leads to a very efficient fluorescence quenching.     

Evaluation of image quality of DWIBS versus DWI sequences in thoracic MRI at 3 T

Purpose

To compare diffusion weighted imaging with background suppression (DWIBS) sequence with classic spectral diffusion sequence (DWI) with and without respiratory gating in mediastinal lymph node analysis at 3 T.

Materials and methods

26 patients scheduled for mediastinoscopic lymph node analysis, prospectively undergone a thoracic 3 T MRI with DWIBS (FatSat = STIR; TR/TE = 6674.1/44.7 ms; IR = 260 ms) and DWI sequences (FatSat = SPIR; TR/TE = 1291/59.6 ms) (b = 0-400-800 s/mm2) with and without (free breathing) respiratory gating.Images at b = 800 were analyzed by two radiologists. They performed qualitative analysis of fat-sat homogeneity and motion artifacts, rated from 0 to 4, and quantitative evaluation by studying signal to background (STB) of lymph nodes.

Results

Quality of fat suppression was significantly higher for DWIBS than for DWI both for free-breathing (score 3.48 ± 0.65 vs. 1.76 ± 0.96, p < 0.0001) and respiratory-gated scans (3.17 ± 0.77 vs. 1.72 ± 0.73, p = 0.0001). Similarly, artifacts were reduced with DWIBS (3.16 ± 0.47 vs. 1.76 ± 0.59, p < 0.0001; 3.0 ± 0.73 vs. 2.04 ± 0.53, p = 0.0001). Quantitative analysis showed higher STB with DWIBS (3.26 ± 1.83 vs. 0.98 ± 0.44, p < 0.0001; 3.56 ±, 2.09 vs. 0.92 ± 0.59, p < 0.0001). Gating did not improve image quality and STB on DWIBS (p > 0.05).

Conclusion

In thoracic MRI, ungated DWIBS sequence improves fat-sat homogeneity, reduces motion artifacts and increases STB of lymph nodes. Respiratory gating does not improve DWIBS image quality.     

Diastereoselective preparation of 2,4,6-trisubstituted-2'-cyanopiperidines: application to the construction of the carbon framework of perhydrohistrionicotoxin

The anodic cyanation of methanolic solutions of the 2-alkyl-N-phenylpiperidines 6b-d was performed in a flow cell equipped with a graphite felt anode. The reaction led to the formation of the 2-cyano-6-alkyl-N-phenylpiperidines 2b-d and proceeded with a high degree of regioselectivity. The 1H NMR spectra of the aminonitriles 2b-d showed an epimeric mixture at C-6. The major isomer has a trans configuration in which the cyano group is axial and the alkyl substituent is equatorial. Conversely, electrochemical oxidation of the 4-methyl-6-pentyl-N-phenylpiperidine 6e afforded the trisubstituted aminonitrile 2e as a single diastereomer (> 98% de). The 4-cyanobutyl side chain was incorporated in a two-step procedure to yield dinitrile 4e. This latter compound was directly converted into spiropiperidine 5e by using the Thorpe-Ziegler annulation procedure. The overall sequence (4 steps, 43%) allows the construction of the basic carbon framework of perhydrohistrionicotoxin.     

Versatile reactions of a para-bromophenylacetylide iron(II) derivative and X-ray structure of the fluoro analogue. Synthesis of new redox-active organoiron(II) synthons

The synthesis of the new (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,3-(C₆H₄X) (m-2a/2b; X=F/Br) and (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄I) (2c) complexes, as well as the solid-state structure of the known (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄F) (2a) complex are described. The catalytic coupling reactions of the bromo complexes with various alkynes were next investigated. Starting from the known (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄Br) complex (2b), the synthesis of the (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄)---CC---H complex (6d) and of the corresponding silyl-protected precursors (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄)CC---SiR₃ (6b/6c; R=ⁱPr/Me) are reported. By use of lithium---bromine exchange reactions on 2b, the silyl- (7a; E=Si; R=Me) and tin- (7b–7d; E=Sn; R=Me, Bu, Ph) substituted analogues (η²-dppe)(η⁵-C₅Me₅)Fe---CC---1,4-(C₆H₄)ER₃ are also isolated. The spectroscopic and electrochemical characterisations of all these new Fe(II)/Fe(III) redox-active building blocks are presented and the electronic substituent parameters for the “(η²-dppe)(η⁵-C₅Me₅)Fe---CC” group are determined by means of ¹⁹F-NMR.     

N-3 alkylation of uracils with unprotected amino alcohols using the Mitsunobu reaction

During our search for novel CGRP antagonists, we had great difficulty in accessing one of our key motifs. Herein, we communicate how we solved the problem by an unprecedented Mitsunobu alkylation using unprotected amino alcohols.     

Limit Cycle Stability

A method for determining the stability of limit cycles in non-linearsystems is presented. It is based on the describing functionmethod used in engineering, and is especially suitable for usewith single-loop feedback systems, though it can be used inits present form with autonomous sets of ordinary differentialor difference equations which can be transformed to single-loopfeedback form. The stability test uses a successive approximationmethod which is shown to be convergent; explicit error boundsare not given but a feature of the method is that it is apparentwhen a sufficiently high order approximation is being used.From a practical point of view, the stability criterion's mainadvantage appears to be that the nonlinear part of the systemis not greatly restricted—discontinuities and multiplebranches cause no difficulties, as evidenced by an example givenwhere the nonlinearity is a relay with hysteresis. Unlike earlierlimit cycle stability tests using describing functions, thisone includes its own reliability guide and allows a better approximationto be used if the current one is not good enough.