Effect of Rate and Quantum Yield of 1-alkyl-2-(arylazo) Imidazoles on the Surface of Silver Nps

1-Alkyl-2-(arylazo)imidazole(RaaiR/) exists in trans-structure about –N=N- bond at ambient condition. Upon optical excitation in UV region the trans-RaaiR/ isomerises to cis-RaaiR/. The photochromism is very susceptible to internal substituents and external environment like solvent polarity, viscosity and presence of innocent foreign molecule. The changes from cis-to-trans occurs slowly in visible light excitation it has significantly faster rate at higher temperature. In this work we have studied the effect of silver nanoparticle on the photochromic activity of RaaiR/. The quantum yield of the photoisomerisation is dropped by 9-27% in inclusion phase AgNPs@RaaiR/ than free state and the order of rate is: free state > silver nano particle. The activation energy (Ea) of cis to trans isomerisation is also diminished compared to free state of photochrome.

Pollen Allergy; Mechanism and Etiology

The term allergy refers to an exaggerated immune response to a foreign molecule. In a normal healthy individual, this foreign molecule will act as a harmless antigen, as it will be recognized & cleared by the immune system without causing any significant damage to host tissues. In certain individuals, such antigens stimulate immune system in such a way that a series of exaggerated immune response are generated against it, leading to significant tissue injury and damage to the host. Such as exaggerated immune response may also cause death of the patient. Such antigen is termed as an allergen. Allergy is categorised under Immunoglobulin E (IgE) mediated type I hypersensitivity reactions. These reactions occur when an antigen acting as an allergen attacks the immune system of the host and causes excessive stimulation of mast cells and basophils. This is followed by the release of allergy mediators which are responsible for causing local or systemic anaphylaxis, allergic asthma, allergic rhinitis, conjuctivitis. Type I allergens are of various types, the mechanism of action is same; however underlying factors may differ in each type. This article is about pollen allergens, in specific & will discuss the common sources of pollen allergens in Pakistan, the relevance and the factors behind pollen allergy.

COMMENTS ON THE ELASTIC PROPERTIES IN SOLID SOLUTIONS OF SILVER HALIDES

Recently first principles microscopic calculations, using the generalized gradient approximation, appeared for the solid mixed system AgCl x Br 1-x at various compositions. Here, we suggest a model that can estimate the compressibility of the mixed crystals in terms of the compressibilities of the end members alone. This model makes use of a single parameter, i.e. the compressibility of a defect volume, when considering the volume variation produced by the addition of a "foreign molecule" to a host crystal as a defect volume.

An Adenosinetriphosphate-Activated Hemolytic System

Lysis of human red cells in vitro by an enzyme obtained from rabbit red cell hemolysates and the inhibition of this lytic activity by human stroma have been shown to require Mg++ and ATP, and ATP utilization has been demonstrated in both reactions. We find that sodium or potassium ions are also required for the lytic phenomenon and that they enhance the inhibition. The rate of hemolysis is not affected by the internal concentrations of these ions but depends only on the external concentration. The rate of influx and efflux of Na22Cl and K42Cl in surviving red cells is greatly enhanced both during and after treatment with rabbit hemolytic factor whereas the entry of C24-sucrose, a small foreign molecule, is mediated only in the presence of hemolytic factor. Glycolysis neither protects against lysis nor enhances the activity of this system, and cardiac glycosides which are known inhibitors of active transport of ions also have no effect. It appears that lysis in this system is not brought about by increased active transport of ions into the cell but that the rabbit factor degrades or combines with some membrane component, altering permeability and resulting in increased diffusion, first of sodium and potassium ions and other small molecules, and finally of large molecules (hemoglobin) out of the cell.