All-optical method for maintaining a fixed intensity level of a light signal in optical computation

In data and image processing the role of optics is already well established. Due to inherent parallelism the optical systems run faster than its electronic counterparts. Optical nonlinear material can be used as a successful optical switch. The primary requirement for proper functioning of such nonlinear material based logic devices is a fixed intensity level of the optical signal against a specific logic state. In this communication, the authors propose a new concept to obtain a fixed intensity level of optical signal against a specific logic state for data processing. The scheme may extend a tremendous application not only to the area of all-optical computation, but also to optical communication process.     

Two Photon Spectroscopy Can Serve as a Marker of Protein Denaturation Pathway

Rhodamine group of molecules are widely used dyes for imaging of biological molecules. Application of these dyes however includes a limitation that these molecules absorb in the visible range of the spectrum, which does not fall in the ‘biologically transparent window’ (BTW). Two photon absorption (TPA) process could come up with an alternate solution to this as these dyes could be excited in the near infrared (NIR) window to extract similar information. To validate this we have investigated TPA cross section (TPACS, σ₂) of two rhodamine dyes, namely Rhodamine 6G (R6G), Rhodamine B (RhB), site selectively bound with a model protein, bovine serum albumin (BSA), by exciting at 800 nm. Two photon spectroscopy and imaging confirms the binding of the dye to the protein. The decreases in TPACS with increasing temperature at a fixed BSA concentration excellently follows the temperature induced structural transition of BSA as the protein transforms from a molten globule to unfolded conformation beyond 60 °C, which has previously been established through circular dichroism (CD) measurements. The thus established resemblance in TPACS and CD measurement trends thus strongly affirms the suitability of TPA process in protein imaging and as an alternative marker to tracking its conformational transformations using NIR radiation.     

Organocatalyzed Double C(sp3)−H Alkylation of Cyclic N-Sulfonyl Ketimines with 3-Chloropropiophenones: Selective Access to 2,3,6-Trisubstituted Pyridines

An efficient sequential one-pot, two-step pseudo-four-component reaction between 3/4-methyl N-sulfonyl ketimines with 3-chloropropiophenones triggered by DIPEA/NaHCO₃ as a cooperative base and subsequent aza-cyclization using NH₄OAc is reported. This transition-metal-oxidant-free technique concocts new C−C/C=C/C=N−C bonds selectively, guaranteeing acceptable yields of 2,3,6-trisubstituted pyridines possessing ortho-hydroxyaryl/benzenesulfonamide and propiophenone moieties at C2 and C3 positions, respectively. Interestingly, while replacing methyl-substituents with straight alkyl chains of N-sulfonyl ketimines, only a monoalkylation reaction happened with in situ-generated vinyl ketones to deliver promising yields of 3-picoline derivatives. Moreover, the synthetic transmutation of prepared pyridine derivative led to several important classes of pyridocoumarin, 5H-chromenopyridine, and di(pyridin-3-yl) methane derivatives.     

Zinc ionomer based on sulfonated maleated styrene-ethylene/butylene-styrene block copolymer

A new ionomer, containing both carboxylated and sufonated groups, was obtained by sulfonating a maleated styrene-ethylene/butylene-styrene (m-SEBS) block copolymer, followed by its neutralization with zinc acetate. Dielectric thermal analyses show that the incorporation of ionic groups in m-SEBS is responsible for the occurrence of the high temperature ionic relaxation in addition to the relaxations of the base polymer. Formation of the ionomer causes a significant improvement in stress-strain properties compared to the corresponding base polymer.     

Melting temperature and debye temperature of ternary chalcopyrite semiconductors

Band state concept has been used for the first time to explain the Melting temperature and Debye temperature of ternary chalcopyrite semiconductors. The experimental results agree quite well with those evaluated from this model. Finally we derive a correlation between the two termperatures.     

Synthesis and Catalytic Studies of Thermoresponsive Copper (I) Complex towards Click Reactions

Click reaction or copper-assisted azide–alkyne cycloaddition (CuAAC) reaction can conveniently synthesize desired organic molecules or functionalize biological macromolecules. In many cases, trace amounts of residual copper from the reaction mixture are not trivial to remove when the exhaustive purification step is avoided to fulfill the essential criteria of a click reaction. It is often detrimental, particularly for biochemical applications or when it involves biological macromolecules. Herein, we have reported the synthesis of a new type of copper (I) complex as a smart catalyst for click reaction, which can be separated from the reaction mixture very easily by the slight elevation of temperature, thanks to its thermoresponsive behavior. The click reactions using a thermoresponsive catalyst were first studied in an aqueous medium using various organic molecules containing alkyne and azide functional groups. Later, the strategy was extended to biological macromolecules like collagen.