Objective: This study aimed to develop and optimize pH-responsive Eudragit S-100 coated chitosan Nanoparticles (NPs) for targeted curcumin delivery in Ulcerative Colitis (UC). The objectives included enhancing curcumin's bioavailability, achieving colon-specific release through mucoadhesive, pH-sensitive nanocarriers, and evaluating their long-term stability. Methods: Curcumin-loaded chitosan NPs were prepared via ionotropic gelation using Sodium Tripolyphosphate (STPP) and coated with Eudragit S-100 via solvent evaporation. Nine formulations (F1–F9) were optimized by varying chitosan (250–750 mg) and STPP (500–1000 mg) concentrations. The NPs were characterized for particle size, zeta potential, Entrapment Efficiency (EE), morphology (SEM), and in vitro drug release in simulated gastrointestinal pH (1.2 → 7.5). Release kinetics were analyzed using Zero-Order, Higuchi, and Korsmeyer-Peppas models. Stability studies were conducted at 4 °C, 28 °C/65% RH, and 40 °C/75% RH for 90 days to assess particle size and drug retention. Results: The optimized formulation (F4: 500 mg chitosan, 500 mg STPP) exhibited a mean particle size of 355.5 nm, high EE (76.65%), and a zeta potential of −36.32 mV, confirming colloidal stability. Coated NPs demonstrated pH-dependent release: minimal in acidic pH (2.32% at pH 1.2) and sustained in colonic pH (98.33% at pH 7.5). Release kinetics followed the Korsmeyer-Peppas model (R² = 0.9892, n = 0.62), indicating anomalous transport. Stability studies revealed excellent retention of particle size (≤361.4 nm) and drug content (>99%) under varied storage conditions, confirming long-term stability. Conclusion: Eudragit S-100 coated chitosan NPs successfully addressed curcumin's solubility and bioavailability challenges while ensuring pH-responsive, targeted colonic delivery. The optimized formulation (F4) exhibited robust stability, making it a promising candidate for UC therapy. Future studies should focus on in vivo efficacy and clinical translation.
AbstractMicroalgae, a group of photosynthetic microorganisms, are a promising feedstock for biodiesel production, but their biomass retrieval is a challenging task. Flocculation is a feasible method for dewatering and harvesting microalgae biomass. In the current study, the effect of alum flocculation on Chlorella vulgaris biomass retrieval has been studied. Alum structural changes with pH were led to a full factorial design to address the effect of this chemical structure changes at different pH values. It is observed that the best flocculation efficiency could be achieved in the natural pH value of C. vulgaris growth medium (8.2) with less than 0.5 g/L flocculant addition, which would lead to the flocculation efficiency of more than 90%. An ensemble architecture of neural networks successfully employed for flocculation modeling.
AbstractThe thermal degradation of saturated chlorinated polyethylene in powder and fiber form has been studied. Direct observations of fiber length variations have enabled us to prove the reactional mechanisms proposed. In the temperature range of 200°–300°C, the material exhibits some fluidity. Its degradation is explained by intrachain and interchain dehydrochlorination reactions, followed by an arrangement of conjugated double bonds obtained in the shape of polyacenic cycles. Between 300°C and 800°C, the polyacenic cycles react with each other to give a pregraphitic structure which is responsible for the increase in rigidity of the material. The fibers of saturated chlorinated polyethylene can be used as a precursor of carbon fiber.
AbstractThe activation energy (Ea) for the dehydrochlorination of PVC and PVC stabilized with an epoxide was determined by a method involving dynamic pH measurements. The Ea increase was 5 kcal/mole between unformulated PVC (Ea = 22.6 kcal/mole) and any of the other formulations (Ea = 27.7–28.6 kcal/mole). On the basis of this and data contained in the literature, research alternatives for the stabilization mechanism are proposed using model compounds.
The recent developments in nanosecond pulsed power supplies facilitate the emission of high density electron bursts but their safe operation demands avoiding breakdowns. Using the theoretical and numerical modeling of the electron emission phenomena from a tip (micro-protrusion), the breakdown threshold (pre-breakdown) is analyzed considering it as the highest value of the voltage preserving the system out of the thermo-emission instability regime. However, the space charge that builds up in front of the tip limits the performance of these electron sources by decreasing the local electric field and consequently the thermo-field emission as well as the temperature of the emissive surface. Hence, it is found that the system can safely hold higher voltages (without breakdown) in the presence of dense space charge. In direct current, for a titanium elliptic tip, the highest operation voltage increases by about 15%, whereas for a tungsten hyperbolic tip, it increases by 70%. Remarkably, the emitted current close to the pre-breakdown voltage stays unchanged with or without taking into account the space charge. Surprisingly, when very short pulses (3 ns) are applied to a tungsten hyperbolic tip, the pre-breakdown voltage additionally increases by 30%, and the Coulomb screening, very effective in front of the tip apex, enlarges the electron emission area by 60%, releasing about 1.3 times more electrons compared to vacuum emission (without the space charge). Moreover, the ring effect, experimentally discovered by Dyke and Trolan [Phys. Rev. 89, 799 (1953)] on the radial electron density distribution, can be microscopically observed and understood with your model.
The decomposition of metastable photoionized mass-selected alkali clusters is investigated using a tandem time-of-flight spectrometer. Na+n and K+n are found to decompose mainly by the evaporation of either a single neutral atom or a neutral dimer in a time scale of about 10 μs. The predominant fragmentation channels are found to follow the adiabatic dissociation channels associated with the lowest energies accordingly to our CI calculations. In the light of our experimental and theoretical results a comparison between the different calculations of the absolute atomization energies available in the literature is presented.
Bifurcations between thermal equilibria are studied in a slab radiating plasma at constant pressure. The thermal stability is discussed in connection with the behavior of the equilibrium solutions when the input power flux in the radiating layer is varied. A general necessary and sufficient stability criterion is demonstrated. In the case of a constant impurity concentration it leads to a simple stability condition in terms of the edge temperature only.
A mixture of commercially available carbon black powders and hydrogen uranyl phosphate (HUP) precipitate can be used as the electrode material for miniaturized double-layer capacitors. A solid cell of C-HUP‖HUP‖C-HUP has a capacitance of 1 F which, given the device area and thickness of 0.8 cm2 and 0.2 cm respectively, corresponds to an energy density of more than 5 J/cm3. The charge×voltage factor is higher than 5×10−6 s and the working voltage is over 1.6 V. The leakage current is lower than 3 μA at room temperature. The electrolyte can be operated up to about 120 °C if the device is hermetically sealed.
Time-resolved anisotropic magnetoresistance (AMR) measurements of the irreversible switching of the magnetization were performed on isolated Ni nanowires. The magnetization reversal was triggered by injection of high current densities in a static magnetic field. The detection was achieved by means of a Wheatstone bridge with a 1 GHz bandwidth. Time-resolved switching was obtained in single shot measurements. Nanowires with diameter of about 100 nm that present a uniform rotation in the reversible regime detected in quasistatic AMR measurements are found to have switching in about 14 ns. This value can be accounted for in the framework of an uniform rotation model with value of the Gilbert damping coefficient of 0.005–0.01. Nanowires with larger diameters (typ. 200 nm) that manifest inhomogeneous magnetization in quasistatic AMR measurements have a switching time of about 37 ns.