Plasma assisted thin film formation

Thin films of fluorocarbon-based polymers can be deposited by plasma assisted polymerisation of various perfluorocarbons. The chemical natures of plasma polymers of hexafluoropropene and perfluorohexane were examined as a function of power, flow rate and position in reactor. Polymerised hexafluoropropene displayed increased fluorine contents at high powers; this is at odds with perfluorohexane which demonstrated lower fluorine contents. Differing reaction mechanisms between saturated and unsaturated perfluorocarbons were proposed to explain this. Both perfluorocarbons were found to give increased CF(_2) contents out of the plasma glow region. This was demonstrated to be a function of distance from the monomer inlet, and was ascribed to the production of long lived polymer forming species in the gas phase. Plasma oxidation of low density polyethylene, polystyrene and poly (ether ether ketone) with oxygen and carbon dioxide was modelled by corresponding photooxidation reactions. Correlations between the structure of the polymer, the treatment used, and the final products were drawn. Aliphatic components tended to give carbon-oxygen single bonds, phenyl rings were oxidised to carbonyl and acid groups, and carbonyl groups to acids. Metal-containing polymeric thin films were produced from plasmas of zinc acetylacetonate and aluminium tri-sec -butoxide. The products from each monomer were different, with the zinc compound resulting in a high proportion of zinc carboxylate and the aluminium compound giving the oxide or hydroxide. Incorporation of these compounds into a perfluorohexane plasma resulted in the formation of metal fluoride containing thin films

Chitosan nanoparticles as Carrier of Immunorestoratory plant extract: synthesis, characterization and Immunorestoratory efficacy

Various medicinal plants are rich in certain bioactive compounds that can help in restoration of immune system but these compounds may be unstable in gastro intestinal tract due to elevated pH and harsh conditions that render the biotherapeutic compound ineffective in GI tract. Various particulate systems such as nanoparticles had been used to improve the pharmacokinetic and pharmacodynamic properties of various drugs. In our present research we have used chitosan, a biodegradable polymer as carrier of plant extract (i.e Ethanolic extract of leaves of Ziziphus mauritiana) having immunomodulatory property and checked its immunorestorative efficacy in immunosuppressed hostIt was found that the oral administration of leaf extract of plant loaded in chitosan nanoparticles is an efficient immunorestorer in Swiss albino mice whose immune system had been suppressed by giving intraperitoneal injection of hydrocortisone(10mg/Kg body weight).The nanoparticles system enhances stability in harsh conditions in GI tract and may be a better vehicle in future for efficient drug delivery.Keywords: Chitosan, nanoparticles, immunorestoration, Ziziphus mauritiana, Hydrocortisone, Immunosuppressio

Optimization and effects of physico-chemical parameters on synthesis of Chitosan Nanoparticles by Ionic Gelation Technique

Background. Biopolymers are used as vehicles for the carrying drugs to their site of action. These polymers are less toxic and can even protect the drug entity from degradation in physiological conditions of the body. Large number of techniques are employed to prepare the nanoformulation of these polymers but ionic gelation is of great interest because no harsh and incompatible chemicals are used during the process. Chitosan nanoparticles are good drug carriers because of their good biocompatibility and biodegradability. As a new drug delivery system they have attracted attention due to their applications in loading protein, drugs etc.  In the present research ionic gelation technique have been optimized for the preparation of chitosan nanoparticles. Various physico-chemical parameters of Nanoparticles such as size, Zeta potential and poly dispersity index were evaluated under different process parameters. Result: In current study ionic gelation technique had been optimized for the preparation of chitosan nanoparticles. We have evaluated the effect of various physico-chemical parameters such as type of polyanion, Sonication, surfactant etc and their effect on size and zeta potential of nanoparticles had been studied. Conclusion: A novel Nanoparticle system composed of low molecular weight chitosan was successfully prepared in the present study by simple ionic-gelation techniques under aqueous-based conditions. It was observed that there was considerable effect of various physico- chemical parameters on size, zeta potential and polydispersity index of Nanoparticles prepared. Results shows that the size of Nanoparticles decreases with the increase in concentration of  Chitosan. Polyvinyl alcohol was found to be the best surfactant because it was very effective in decreasing the surface tension without increasing viscosity. Intermittent sonication during the process decreases the size of Nanoparticles considerably.Controled use of polyanions under different conditions can develop  negatively charged Nanoparticles that can be used for delivery of positively charded drugs and therapeutic molecules

مدى توافر أبعاد رأس المال البشري في القطاع المصرفي

يهدف البحث إلى تحديد مدى توافر أبعاد رأس المال البشري: المعارف, والخبرات, والمهارات, والقدرات في فروع المصارف التجارية الخاصة في الساحل السوري. اعتمد البحث على المنهج الوصفي, وشمل مجتمع البحث جميع المسؤولين (مدير, معاون مدير, رئيس قسم, رئيس شعبة أو دائرة) لدى فروع المصارف التجارية الخاصة في الساحل السوري, وبالاعتماد على طريقة الحصر الشامل تمّ توزيع (120) استبانة على كافة المسؤولين في فروع المصارف التجارية الآنفة الذكر, واسترجع منها (111) استبانة, وتمّ استبعاد (4) استبانات لعدم صلاحيتها للتحليل الإحصائي, وبذلك يكون عدد الاستبانات المستردة والصالحة للتحليل الإحصائي (107) استبانات, وبنسبة استجابة (89.92%). أظهرت النتائج أنّ أبعاد رأس المال البشري متوفرة وبدرجة كبيرة في المصارف محل الدراسة, وبأهمية نسبية (79.1%).

Transcriptomic analysis of polyketide synthases in a highly ciguatoxic dinoflagellate, Gambierdiscus polynesiensis and low toxicity Gambierdiscus pacificus, from French Polynesia.

Marine dinoflagellates produce a diversity of polyketide toxins that are accumulated in marine food webs and are responsible for a variety of seafood poisonings. Reef-associated dinoflagellates of the genus Gambierdiscus produce toxins responsible for ciguatera poisoning (CP), which causes over 50,000 cases of illness annually worldwide. The biosynthetic machinery for dinoflagellate polyketides remains poorly understood. Recent transcriptomic and genomic sequencing projects have revealed the presence of Type I modular polyketide synthases in dinoflagellates, as well as a plethora of single domain transcripts with Type I sequence homology. The current transcriptome analysis compares polyketide synthase (PKS) gene transcripts expressed in two species of Gambierdiscus from French Polynesia: a highly toxic ciguatoxin producer, G. polynesiensis, versus a non-ciguatoxic species G. pacificus, each assembled from approximately 180 million Illumina 125 nt reads using Trinity, and compares their PKS content with previously published data from other Gambierdiscus species and more distantly related dinoflagellates. Both modular and single-domain PKS transcripts were present. Single domain β-ketoacyl synthase (KS) transcripts were highly amplified in both species (98 in G. polynesiensis, 99 in G. pacificus), with smaller numbers of standalone acyl transferase (AT), ketoacyl reductase (KR), dehydratase (DH), enoyl reductase (ER), and thioesterase (TE) domains. G. polynesiensis expressed both a larger number of multidomain PKSs, and larger numbers of modules per transcript, than the non-ciguatoxic G. pacificus. The largest PKS transcript in G. polynesiensis encoded a 10,516 aa, 7 module protein, predicted to synthesize part of the polyether backbone. Transcripts and gene models representing portions of this PKS are present in other species, suggesting that its function may be performed in those species by multiple interacting proteins. This study contributes to the building consensus that dinoflagellates utilize a combination of Type I modular and single domain PKS proteins, in an as yet undefined manner, to synthesize polyketides

Simulation method for investigating the use of transition-edge sensors as spectroscopic electron detectors

Transition-edge sensors (TESs) are capable of highly accurate single particle energy measurement. TESs have been used for a wide range of photon detection applications, particularly in astronomy, but very little consideration has been given to their capabilities as electron calorimeters. Existing electron spectrometers require electron filtering optics to achieve energy discrimination, but this step discards the vast majority of electrons entering the instrument. TESs require no such energy filtering, meaning they could provide orders of magnitude improvement in measurement rate. To investigate the capabilities of TESs in electron spectroscopy, a simulation pipeline has been devised. The pipeline allows the results of a simulated experiment to be compared with the actual spectrum of the incident beam, thereby allowing measurement accuracy and efficiency to be studied. Using Fisher information, the energy resolution of the simulated detectors was also calculated, allowing the intrinsic limitations of the detector to be separated from the specific data analysis method used. The simulation platform has been used to compare the performance of TESs with existing X-ray photoelectron spectroscopy (XPS) analysers. TESs cannot match the energy resolution of XPS analysers for high-precision measurements but have comparable or better resolutions for high count rate applications. The measurement rate of a typical XPS analyser can be matched by an array of 10 TESs with 120 microsecond response times and there is significant scope for improvement, without compromising energy resolution, by increasing array size

3D ToF-SIMS imaging of polymer multilayer films using argon cluster sputter depth profiling

ToF-SIMS imaging with argon cluster sputter depth profiling has provided detailed insight into the three-dimensional (3D) chemical composition of a series of polymer multilayer structures. Depths of more than 15 μm were profiled in these samples while maintaining uniform sputter rates. The 3D chemical images provide information regarding the structure of the multilayer systems that could be used to inform future systems manufacturing and development. This also includes measuring the layer homogeneity, thickness, and interface widths. The systems analyzed were spin-cast multilayers comprising alternating polystyrene (PS) and polyvinylpyrrolidone (PVP) layers. These included samples where the PVP and PS layer thickness values were kept constant throughout and samples where the layer thickness was varied as a function of depth in the multilayer. The depth profile data obtained was observed to be superior to that obtained for the same materials using alternative ion sources such as C60 n+. The data closely reflected the “as manufactured” sample specification, exhibiting good agreement with ellipsometry measurements of layer thickness, while also maintaining secondary ion intensities throughout the profiling regime. The unprecedented quality of the data allowed a detailed analysis of the chemical structure of these systems, revealing some minor imperfections within the polymer layers and demonstrating the enhanced capabilities of the argon cluster depth profiling technique

Effects of temperature and ammonia flow rate on the chemical vapour deposition growth of nitrogen-doped graphene

We doped graphene in situ during synthesis from methane and ammonia on copper in a low-pressure chemical vapour deposition system, and investigated the effect of the synthesis temperature and ammonia concentration on the growth. Raman and X-ray photoelectron spectroscopy was used to investigate the quality and nitrogen content of the graphene and demonstrated that decreasing the synthesis temperature and increasing the ammonia flow rate results in an increase in the concentration of nitrogen dopants up to ca. 2.1% overall. However, concurrent scanning electron microscopy studies demonstrate that decreasing both the growth temperature from 1000 to 900 1C and increasing the N/C precursor ratio from 1/50 to 1/10 significantly decreased the growth rate by a factor of six overall. Using scanning tunnelling microscopy we show that the nitrogen was incorporated mainly in substitutional configuration, while current imaging tunnelling spectroscopy showed that the effect of the nitrogen on the density of states was visible only over a few atom distances