Ultrasound-assisted synthesis of block copolymers of chitosan and <Emphasis Type="Italic">D</Emphasis>,<Emphasis Type="Italic">L</Emphasis>-lactide: Structure and properties

The block copolymers of chitosan with D,L-lactide are synthesized under UV irradiation of the homogeneous solution of the corresponding homopolymers with the yield of the main product being 96 wt %. The polyblock structure of copolymer chains, in which the size of polylactide blocks is varied in the range of (2.9–22.0) × 10³ depending on the synthesis conditions, is demonstrated. The incorporation of polylactide blocks into the structure of chitosan leads to development of the material structure close to the structure of polylactide. The films of the block copolymers containing 16 wt % polylactide and having a molecular mass of its blocks of 22.0 × 10³ have increased values of breaking stress (47 MPa) and ultimate strain (20%) compared to chitosan (24 MPa and 1.9%, respectively). The obtained block copolymers possess bactericidal properties.     

The intramolecular Diels-Alder vinylthiophen (IMDAV) reaction: An easy approach to thieno[2,3-f]isoindole-4-carboxylic acids

The reaction of readily accessible 3-(thien-2-yl)allylamines with maleic anhydride, followed by a domino sequence involving successive acylation/[4+2] cycloaddition steps, leads to the formation of the thieno[2,3-f]isoindole core. The key step, the intramolecular Diels-Alder vinylaren (IMDAV) reaction, proceeds with high level of diastereoselectivity and with formation of a single diastereoisomer of the target product 4,4a,5,6,7,7a-hexahydro-3aH-thieno[2,3-f]isoindole-4-carboxylic acids in excellent yields. If the reaction is carried out at room temperature, it occurs in 2–3 days and the proton migration (H-shift) does not take place at the last stage. In boiling benzene, the reaction is complete after three hours, but in this case a slight impurity of byproducts bearing aromatic thiophene ring – 4a,5,6,7,7a,8-hexahydro-4H-thieno[2,3-f]isoindole-4-carboxylic acids is formed.     

Terahertz Microscope Based on Solid Immersion Effect for Imaging of Biological Tissues

Optics and Spectroscopy - We propose a new method of terahertz microscopy for imaging of biological tissues with a subwavelength spatial resolution. It makes it possible to surmount the Abbe...     

An Experimentally Trained Noise Filtration Method of Optical Coherence Tomography Signals

Optics and Spectroscopy - A method for wavelet filtration procedure training for optical coherence tomography (OCT) images using the experimental measurements of test objects that were constructed...     

Differentiation of Pigmented Skin Lesions Based on Digital Processing of Optical Images

Optics and Spectroscopy - A method for differentiation of pigmented skin lesions is proposed that is based on digital processing of optical images. The optical images are detected using a digital...     

Studying the effect of flap angle on the noise of interaction of a high-bypass jet with a swept wing in a co-flow

Jet–flap interaction noise for a small-scale swept wing model of a trendsetter plane has been studied experimentally, with a double-stream nozzle installed nearby. The effect of the flap angle on the noise of jet–wing interaction has been analyzed. It has been discovered that the flap angle considerably affects the interaction noise in a wide frequency range in such a way that the noise intensity in each frequency band grows exponentially as the flap edge approaches the shear-layer boundary (on a logarithmic scale, this corresponds to linear scaling of the spectrum depending on the flap angle). The exponential noise reduction as the flap angle decreases agrees with the known theoretical simplified-configuration models that are based on the effect of interaction of the near field of instability wave with the edge. Not only does this agreement show that noise increase/reduction mechanism may be associated with similar processes, it also provides an effective tool for controlling the interaction noise.