Sferični kristali celekoksiba za poboljšanje topljivosti, oslobađanja i mikromeričnih svojstava

Celecoxib spherical agglomerates were prepared with polyvinylpyrrolidone (PVP) using acetone, water and chloroform as solvent, non-solvent and bridging liquid, respectively. The agglomerates were characterized by differential scanning calorimetry (DSC), X-ray diffraction (XRD), IR spectroscopic studies and scanning electron microscopy (SEM). The IR spectroscopy and DSC results indicated the absence of any interactions between drug and additives. XRD studies showed a decrease in crystallinity in agglomerates. The crystals exhibited significantly improved micromeritic properties compared to pure drug. The loading efficiency (% or mg drug per 100 mg crystals) was in the range of 93.9 ± 2.3 and 97.3 ± 1.3% (n = 3), with all formulations. The aqueous solubility and dissolution rate of the drug from crystals was significantly (p < 0.05) increased (nearly two times). The solubility and in vitro drug release rates increased with an increase in PVP concentration (from 2.5 to 10%). The SEM studies showed that the crystal possesses a good spherical shape with smooth and regular surface.U radu je opisana priprava sferičnih aglomerata sa celekoksibom koristeći polivinilpirolidon (PVP), aceton, vodu i kloroform. Aglomerati su karakterizirani diferencijalnom pretražnom kalorimetrijom (DSC), rentgenskom difrakcijom (XRD), IR spektroskopijom i pretražnom elektronskom mikroskopijom (SEM). IR i DSC su pokazale odsutnost bilo kakvih interakcija između ljekovite tvari i aditiva. XRD je pokazala smanjenje kristaliničnosti u aglomeratima. Aglomerati su pokazali značajno poboljšana mikromerična svojstva u odnosu na čisti lijek. Udio lijeka u njima bio je između 93.89 ± 2.26 i 97.32 ± 1.29%. Topljivost u vodi i oslobađanje ljekovite tvari iz aglomerata povećalo se skoro dva puta. Topljivost i in vitro oslobađanje se povećava s povećanjem koncentracije PVP (od 2,5 do 10%). SEM studije su pokazale da kristali imaju pravilan sferični oblik te glatku i pravilnu površinu

Optical Studies of InGaAs/GaAs Multiple Quantum Wells (MQW\u27s) and GaAs/Si Using Novel Scanning Electron Microscopy Based Techniques

The influence of defects on electron-hole plasma transport in nipi-doped in 0.2Ga0.8As/GaAs multiple quantum wells (MQWs) has been studied using a novel technique called electron beam induced absorption modulation (EBIA) imaging. Modulation doped MQW structures exhibit large optical nonlinearities and are important for the development of all-optical spatial light modulators used in optical computing and communication. The electron-hole plasma is generated by a high-energy electron beam in a scanning electron microscope and is used as a probe to study the MQW absorption modulation induced locally by the electron beam. The influence of structural defects on the diffusive transport of carriers is imaged with a μm-scale resolution. A strong spatial correlation between dark line defects observed in cathodoluminescence (CL) and absorption modulation steps in EBIA reveals the existence of strain-induced band edge fluctuations that are caused by misfit dislocations. The spatial variation of stress in metalorganic chemical vapor deposition grown GaAs/Si has been studied with linearly polarized cathodoluminescence (LPCL). GaAs grown on Si wafers in selective areas (10 to 1000 μm mesas) were studied. The large difference in thermal expansion coefficient between GaAs and Si results in thermal stress-induced microcracks and dislocations which can occur upon cooling from growth temperatures. Using LPCL, we have determined the spatial distribution of the stress tensor from the polarized CL strain-split peak positions and solutions to the orbital-strain Hamiltonian

Monitoring Cryptographic Strength of Wireless Sensor Networks using ZKP 1

Abstract The security mechanisms used for wired networks cannot be directly used in sensor networks as there is no user-controlling of each individual node, wireless environment, and more importantly, scarce energy resources. In this paper, we address some of the special security threats and attacks in Wireless Sensor Networks offer a powerful methodology to monitor environments, and have a lot of interesting applications, We propose a scheme for detection of distributed sensor cloning attack and use of zero knowledge protocol for verifying the authenticity of the sender sensor nodes. The cloning attack is addressed by attaching a unique fingerprint to each node that depends on the set of neighboring nodes and itself. The fingerprint is attached with every message a sensor node sends. The Zero knowledge protocol is used to ensure non transmission of crucial cryptographic information in the wireless network in order to avoid man-in-the middle attack and replay attack. The paper presents a detailed analysis for various scenarios and also analyzes the performance and cryptographic strength. Keywords Wireless Sensor Networks, Zero Knowledge Protocol Cloning Attack, Man-in-the-Middle Attack. I. Introduction Wireless sensor networks consist of large numbers of sensors that act cooperatively to provide &quot;usable chunks of predigested information rather than a confusing wash of number&quot