Pulse shape analysis of second harmonic and difference-frequency generation

A computer model has been used to investigate the pulse shape evolution of interacting waves during second harmonic generation and difference-frequency generation processes. Using general assumption and coupled equations theory we describe in detail the back and forth energy transfer in connection with pulse shape. Two type of phase-match (modal phase-match and quasi-phase-match) with experimental relevance are discussed. In the case of quasi-phase-match uniform and chirped grating are discussed. The connection of the model with material properties and non-linear optical (NLO) strength is presented. The proposed model have allowed us to derive the essential feature of pulse shaping and compressing that rely on NLO process only.     

Development of injectable high molecular weight hyaluronic acid hydrogels for cartilage regeneration

The study focuses on developing hyaluronic acid (1200 kilo Dalton) hydrogels for cartilage regeneration. In spite of being highly biocompatible; a large amount of water absorption and easily degrading nature restricts the use of hyaluronic acid in the field of tissue regeneration. This can be rectified by crosslinking hyaluronic acid with a crosslinking agent such as divinyl sulfone; which results in a biocompatible hydrogel with superior rheological properties. Different amounts of divinyl sulfone have been used for crosslinking hyaluronic acid to get three types of hydrogels with differing properties. Swelling studies, rheology analysis, enzymatic degradation and scanning electron microscopic analysis were conducted on all the different types of hydrogels prepared. Viscoelastic properties of the hydrogel were analyzed so that a hydrogel with better elastic property and stability is obtained. Scanning electron microscopy was used to study the morphology of the HA hydrogels. The cytotoxicity testing was conducted to prove the non-toxic nature of the hydrogels and cell culture studies using adipose mesenchymal stem cells showed better adhesion and proliferation properties in all the three hydrogels. Thus hyaluronic acid hydrogel makes a promising material for cartilage regeneration.     

Linear viscoelastic behavior of copper phthalocyanine dispersions used in printing inks

In this paper we describe the linear viscoelastic properties of copper phthalocyanine (CuPCN) dispersions that are used in the manufacturing of offset lithographic printing inks. Transmission electron microscopy shows that the primary pigment particles are rod-like and have sizes in the range of 10 to 300 nm. Steady shear measurements show that the dispersions are Newtonian at a pigment volume fraction of 0.073 and become increasingly shear thinning as the pigment volume fraction is increased. The strong shear-thinning nature of these dispersions can be attributed to the highly flocculated nature of the dispersions, which is due to interparticle attractions. The structural complexity of the dispersions also results in an unexpected linear viscoelastic response. While at low frequencies (0.1 and 1.0 Hz) the ex tent of the linear region decreases with increasing pigment concentration, at a higher frequency (10 Hz) the extent of the linear region increases with increasing pigment concentration. This increase in the linear region with increasing pigment concentration suggests that at higher frequencies the dispersion is less brittle, and that the rheological behavior is dominated by intra-aggregate associations. In addition, frequency sweeps show that the dispersions behave like a viscoelastic liquid at low pigment concentrations. However, at higher pigment concentrations (yet significantly lower than the maximum packing fraction) the dispersions behave like a cross-linking polymer at its gel point.     

Thermal stability of magnesium-rich primers based on glycidyl carbamate resins

Coatings of outstanding thermal stability were obtained by the combination of two novel technologies, that of a magnesium-rich primer and a silane-modified glycidyl carbamate binder. While conducting a study to evaluate the new binder system with respect to properties of the magnesium-rich primer, during thermogravimetric analysis of samples, previously unobserved and unexpected properties were noted. The samples transformed into an intact solid residue, with the amount of the residual char ranging between 40 and 90% weight depending on the pigment volume concentration (PVC) of the magnesium particles in the composition. It appears that the hitherto unobserved property is essentially a function of the metallic pigment particles in the coating. The discovery of the exceptional thermal stability potentially increases the range of application for these primers and these can be further developed for use as a thermal barrier coating.     

From Schrödinger’s equation to the quantum search algorithm

The quantum search algorithm is a technique for searching N possibilities in only O(√N) steps. Although the algorithm itself is widely known, not so well known is the series of steps that first led to it, these are quite different from any of the generally known forms of the algorithm. This paper describes these steps, which start by discretizing Schrödinger’s equation. This paper also provides a self contained introduction to quantum computing algorithms from a new perspective.     

Rapid determination of four polycyclic aromatic hydrocarbons by HPTLC using nano plates

Summary Reversed phase nano plates (HPTLC) have been used for a rapid analysis of a number of PAH (benzo(ghi) perylene, benzo(a)pyrene, benzofluoranthenes and benz(a) anthracene) regularly present in the ambient air. A definite volume of extract is applied to a silica gel column and eluated with cyclohexane. The concentrated eluat is spotted on plates in streak form. A twofold development with acetonitrile/dichloromethane/water (911) results in a complete distinct separation of the four components in 7 min. Evaluation of sample spots is accomplished by measuring the fluorescence intensity registered as a peak at 366 nm. The evaluated peak against benzo(b)fluoranthene is characterized as benzfluoranthenes since the benzfluoranthene isomers are not separated by this procedure. This method has a good reproducibility (rel. standard error 4.4%) and can be easily adopted to the quantitative determination of the four PAH in ambient air and in indoor air involving short sampling periods. The minimum detectable limits on these plates for benz(a) anthracene is 2 ng and 0.2 ng for the three other PAH.

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Schnelle Bestimmung von vier polycyclischen aromatischen Kohlenwasserstoffen durch HPTLC mit Nano-Platten

Zusammenfassung Für eine schnelle Bestimmung von einigen PAH, die stÄndig in der Au\enluft auftreten, werden Nano-Platten (HPTLC) mit reversed phase verwendet. Ein bestimmtes Extraktvolumen wird auf eine KieselgelsÄule gegeben und mit Cyclohexan eluiert. Das konzentrierte Eluat wird strichförmig auf der Platte aufgetragen. Eine zweifache horizontale Entwicklung mit Acetonitril/Dichlormethan/ Wasser (911) bedingt eine deutliche Auftrennung der vier Komponenten nach 7 min. Die Auswertung erfolgt durch Messung der FluorescenzintensitÄt bei 366 nm. Da bei diesem Verfahren die Isomere des Benzo(b)fluoranthens nicht getrennt werden, mu\ die dem Standard Benzo(b)fluoranthen zugeordnete PeakflÄche als Benzfluoranthene bezeichnet werden. Die Methode zeigt eine gute Reproduzierbarkeit (rel. Standardabweichung 4,4%) und kann zur Bestimmung dieser vier PAH in der Au\enluft als auch in der Raumluft bei kurzen Probenahmezeiten Anwendung finden. Die Nachweisgrenzen auf der Nano-Platte betragen für Benz(a) anthracen 2 ng, für die drei übrigen PAH 0,2 ng/Fleck.

     

Base catalyzed intramolecular transamidation of 2-aminoquinazoline derivatives on solid phase

A novel intramolecular cyclo-elimination via transamidation on the Rink Amide AM resin under mild basic conditions is presented. The methodology led to the synthesis of an important class of cardiotonic agents: imdiazo- and pyrimido-quinazolines from the corresponding 2-aminoquinazoline hydrobromide salt under mild basic conditions. NMR based titration studies revealed the role of hydrobromide as a molecular switch, which on removal triggers the cyclisation of aminoquinazoline to tricyclic structures. The main advantage of transamidation under basic conditions over the TFA cleavage is the recyclability of the resin obtained after cyclo-elimination. This has been demonstrated by successive synthesis of four structurally diverse imidazoquianzolin-2-ones using the same batch of resin without any cross contamination.     

Absence of first order electronic transitions in liquid metals

High pressure shock wave data on a wide variety of metals indicates that electronic transitions are continuously distributed in the liquid phase and accompanied by melting maxima. A qualitative explanation for this behavior is suggested.