Factorial design approach to fabricate and optimize floating tablets based on combination of natural polymer and rice bran wax

Background The aim of the present research work was to fabricate a novel gastroretentive drug delivery system in the form of tablets using a combination of natural polymer and rice bran wax with an intention to control drug delivery and to enhance the gastric residence time of the model drug Famotidine in the gastrointestinal tract. Results The results of the preliminary trial batches prepared by using the hot melt granulation technique resulting in six different formulations showed good physicochemical characteristics and tablets conformed to the Pharmacopoeial specifications. Gastroretentive tablets containing natural polymer showed prolonged drug release comparable to Methocel. The optimized formulation (C3) using 32 factorial design showed FLT 27 ± 2.47 s, SI 92.68 ± 1.36% and % CDR 98.89 ± 0.39% at 12 h. The stability studies indicated the stability of the formulation during storage. Conclusions It was concluded that the release profile fitted best to zero-order equation with non-Fickian diffusion mechanism of drug release which demonstrates swelling-controlled drug release mechanism. Thus, the formulated tablets have the potential for improved release and gastroretentive properties. Graphical Abstract

New insights in the mechanism of cation migration induced by cation-anion dynamic coupling in superionic conductors

Understanding the ion diffusion mechanism is one of the key preconditions for designing superionic conductors in solid state lithium batteries and many other energy devices. Besides single-cation vacancy/interstitial-assisted and multi-cation...

Evaluation of the Adsorption and Desorption Dynamics of Beet Juice Red Dye on Alginate Microbeads

The use of alginate microcapsules has often been mentioned as one of the ways to remove dyes from waste solvents, water and materials from the food industry. In addition, alginate can be used as a wall material for the microencapsulation of food dyes and their further application in the food industry. The aims of this study were to: (i) determine the effect of the alginate concentration (1, 2, 3 and 4%) on the ability of the adsorption and desorption of natural beetroot red dye and (ii) evaluate the kinetic parameters of the adsorption and desorption process, as well as the factors affecting and limiting those processes. According to the obtained results, the viscosity of alginate solutions increased with an increase in the alginate concentration. Based on k2 values (the pseudo-second order kinetic rate constant), when a more concentrated solution of alginate was used in the adsorption process, the beads adsorbed a smaller amount of dye. Furthermore, based on the values for n derived from the Korsmeyer–Peppas model, the dye release rates (k) were higher for beads made with lower alginate concentrations, and this release was governed by a pseudo-Fickian diffusion mechanism (n values ranged from 0.2709 to 0.3053).

The Diffusion Isotope Effect and Diffusion Mechanism in Liquid Cu-Ag and Cu-Ni Alloys

In this paper, the diffusion isotope effect and diffusion mechanism are investigated by means of molecular dynamics simulations in two liquid alloys, Ni-Ag and Ni-Cu. The values for the diffusion isotope effect parameter allow for the estimate of the number of atoms which are moving cooperatively in a basic diffusion event as experienced by a given atomic species. It is shown that the composition dependence of ND is typically very small. However, the temperature dependence of this parameter is much more pronounced. In addition, it is shown that, on average, in these alloys and temperatures considered, ND is limited to the range: 5<ND<17. This is consistent with results of molecular dynamics simulations on the average coordination number calculations. This would suggest that, together with a given atom, depending on temperature, the neighbouring atoms are all involved in the basic diffusion event.

Formulation and Evaluation of Cefaclor Extended-Release Tablet

Over past 30 years as the expanse and complication involved in marketing new drug entities have increased, with concomitant recognition of the therapeutic advantages of controlled drug delivery, greater attention has been focused on development of extended or controlled release drug delivery systems. In the present research work an attempt has been made to optimize, formulate and characterize extended-release tablet of Cefaclor. The preformulation studies were performed for the drug (e.g., physico-chemical properties, melting point, solubility etc.). The drug had shown the results under standard specifications. UV spectroscopic analytical method was also performed for quantitative determinations by plotting standard curve. Before this the pure drug was also scanned for the ƛ max value at different concentrations. The pre-compressions parameters and the post compression parameters for the nine formulated tablets were performed. The drug release study of the selected formulations EF3, EF6 and EF9 was performed as those formulations has shown the results within pharmacopoeia limits. The Formulation EF9 was then taken for release kinetic study as it has shown best results among the other three formulations. So, it confirms the drug release by Higuchi diffusion mechanism. From the results, conclusion can be drawn that the formulation consisting 10-12% concentration of hydroxypropyl methyl cellulose K4-M with 1% microcrystalline cellulose and 25% of lactose are considered as ideal for the optimized extended-release tablet formulation for Cefaclor. Keywords: Extended release, Cefaclor, Higuchi diffusion mechanism, PBP, bacterial cell wall synthesis.

Investigation of Re(VII) diffusion in Tamusu clayrock core by through-diffusion method

Tamusu area is the primary pre-selection site of clayrock disposal repository for high-level radioactive waste (HLW) in China. However, the research on the migration behavior of nuclides in Tamusu clayrock is still in its infancy. For the first time in laboratory, the diffusion behavior of Re(VII) in Tamusu clayrock core was studied by means of through-diffusion method. The effects of pH, ionic strength and humic acid on the diffusion behavior of Re(VII) in clayrock were studied. The effective diffusion coefficient, apparent diffusion coefficient and rock capacity factor value were obtained. All the experimental conditions of Re(VII) diffusion in Tamusu clayrock are compared with other geological samples under the same conditions in literature data. The diffusion mechanism of radionuclide in Tamusu clay is discussed, which can provide experimental data for site selection and safety assessment of high-level radioactive waste repository in China. The experimental results showed an effective application and reference for the countries disposed HLW in mudrocks or clayrocks, such as France, Belgium etc. in Europe. Moreover, this research can provide the original data support for the metallogenic regularity and prospecting prognosis of rare element rhenium in different geological environments.

Experimental process and kinetic behavior of carbothermal reduction of lithium cobaltate as a cathode for waste lithium batteries

Lithium cobaltate as a cathode material has great recycling value in the recycling process of spent lithium-ion batteries, To promote the thermal reduction process of lithium cobaltate and recover high-value cobalt and lithium metals, we studied the process of lithium cobaltate reduction by carbon under different conditions and its thermal reaction kinetics. The effects of calcination temperature, raw material ratio, pelletizing pressure and holding time on the reduction rate of lithium cobaltate were investigated by controlling variables. The results showed that the optimum experimental conditions were as follows: mass ratio of carbon and lithium cobaltate was 1:1, pelletizing pressure was 45 MPa, calcination temperature was 800 °C, and calcination time was 6 h. Under these conditions, lithium cobaltate could be converted into cobalt and lithium carbonate, and the recovery rate of cobalt and lithium was 97% and 95%, respectively. A kinetic study on the carbothermal reduction reaction of LiCoO2 showed that the average activation energy of the carbothermal reaction of LiCoO2 under nitrogen protection was 280.6851 kJ/mol, and the mechanism model of the thermal decomposition reaction of LiCoO2 was controlled by chemicals, showing a deceleration curve. The corresponding process conforms to the threedimensional diffusion mechanism of the inverse Jander equation, which lays a theoretical foundation for the high-efficiency separation and recovery of LiCoO2 cathode material for waste lithium-ion batteries.

Revisiting the chevrel phase: Impact of dispersion corrections on the properties of Mo6S8 for cathode applications

While the Mo6S8 chevrel phase is frequently used as cathode material in Mg--ion batteries, theoretical studies on this material are comparatively scarce. The particular structure of the Mo6S8 phase, with rather loosely connected cluster entities, points to the important role of dispersion forces in this material. However, so far this aspect has been completely neglected in the discussion of Mo6S8 as cathode material for mono- and multivalent-ion batteries. In this work we therefore have studied the impact of dispersion forces on stability and kinetics of Mo6S8 intercalation compounds. For this purpose, a series of charge carriers (Li, Na, K, Mg, Ca, Zn, Al) has been investigated. Interestingly, dispersion forces are observed to only slightly affect the lattice spacing of the chevrel phase, nevertheless having a significant impact on insertion voltage and in particular on the charge carrier mobility in the material. Moreover, upon varying the charge carriers in the chevrel phase, their diffusion barriers are observed to scale linearly with the ion size, almost independent of the charge of the considered ions. This indicates a rather unique and geometry dominated diffusion mechanism in the chevrel phase. The consequences of these findings for the ion mobility in the chevrel phase will be carefully discussed.

Self-generated oxygen gradients control collective aggregation of photosynthetic microbes

For billions of years, photosynthetic microbes have evolved under the variable exposure to sunlight in diverse ecosystems and microhabitats all over our planet. Their abilities to dynamically respond to alterations of the luminous intensity, including phototaxis, surface association and diurnal cell cycles, are pivotal for their survival. If these strategies fail in the absence of light, the microbes can still sustain essential metabolic functionalities and motility by switching their energy production from photosynthesis to oxygen respiration. For suspensions of motile C. reinhardtii cells above a critical density, we demonstrate that this switch reversibly controls collective microbial aggregation. Aerobic respiration dominates over photosynthesis in conditions of low light, which causes the microbial motility to sensitively depend on the local availability of oxygen. For dense microbial populations in self-generated oxygen gradients, microfluidic experiments and continuum theory based on a reaction–diffusion mechanism show that oxygen-regulated motility enables the collective emergence of highly localized regions of high and low cell densities.