Release Phenomenon Research Articles

Adaptability of enhanced bioretention cell for nitrogen and phosphorus removal under two antibiotics stress

The overuse of antibiotics in the medical and aquaculture industries has led to the frequent detection of antibiotics in wastewater. Considering antibiotics would have an unknown impact on wastewater treatment in the future, the long-term effects of sulfamethoxazole (SMX) and tetracycline (TC) stress on the performance, functional genes and microbial community in three bioretention cells were investigated. The results showed that during the experiment, 0.8–1.2 mg/L of SMX would not destroy the water treatment capacity of the bioretention cells, and had a promoting effect on total nitrogen and ammonia nitrogen. 1.6 mg/L of SMX would cause the reduction of nitrogen removal efficiency and the phenomenon of phosphorus release, but it could be restored after a period of operation. TC of 0.8–1.2 mg/L did not have a significant impact on the removal of nutrients in AC-BRC (activated carbon-bioretention cell) and ACI-BRC (activated carbon and iron-bioretention cell), but TC of 1.2 mg/L caused the phenomenon of phosphorus release in BRC and the decrease of total nitrogen removal rate, 1.6 mg/L TC could make the bioretention cell lose its water treatment capacity. qPCR analysis of denitrification genes showed that the abundance of nirS, nirK, nosZ, and hzo had varying degrees of decrease before and after antibiotic stress, which meant the two antibiotics significantly inhibited the reduction of nitrite and nitrous oxide. But for the total number of bacteria, the relative abundance of the four genes has increased. The results of microbial community analysis also found that Proteobacteria, Bacteroidetes, Chloroflexi, and BIrii41, Denitratisoma, Ferritrophicum, Thiobacillus occupied the dominant species at the phylum level and the genus level respectively, which included most of the denitrifying bacteria. During the experiment, the nitrogen and phosphorus removal efficiency of AC-BRC and ACI-BRC were enhanced obviously, but ammonia nitrogen accumulated in ACI-BRC in the early stage of the reaction.

Release behaviour of a high-pressure vapor vessel with condensation: Test and modeling study

• The vapor release test with condensation is conducted with three micro-cracks. • The ideal dropwise condensation and wall heat conduction are considered. • A six-equation vapor leakage model is presented with a bubbly flow assumption. • A blowdown model coupling with a leakage model is employed to simulate vapor release. A phenomenon of accidental release from a high-pressure containment into a low-pressure environment is significant in several industrial systems such as chemical reactors and pipeline transportation and storage. The paper aims to investigate the vapor release with condensation, and to develop a vapor release model coupling a blowdown model with a critical flow model. Vapor release tests of the pressurized vessel are performed with micro-cracks, and the fluid pressure and temperature evolutions are recorded. The theory of ideal dropwise condensation is used to describe the interfacial heat transfer, and the wall heat transfer is regarded as the heat conduction in a blowdown model. A six-equation model allowing the vapor leakage simulation with condensation is presented with a bubbly flow regime assumption. The vapor release model is composed of a critical flow model in conjunction with a vessel blowdown model, including the treatment of the vapor condensation, interfacial heat transfer, and interfacial force during the depressurization. The proposed model predictions exhibit strong similarities with the measured evolutions of the fluid pressure, temperature, and the total weight of the released fluid. Finally, the qualitative analysis of the vapor release with a heat transfer/adiabatic process is conducted. The vapor condensation occurs during the release process when the initial pressure is increased, while the condensation is reduced for a heat transfer process. The release time and vapor condensation of the pressurized vessel are significantly affected by the vessel volume and break area.

A study of thermal effect depending on temperature field adjacent to turbulent premixed flames using DNS

Turbulent premixed flames are heat release phenomena in the turbulent flow with premixed fuel and oxidiser. Turbulent premixed flames form the temperature field and are affected by the interaction between flow and heat. This study focused the temperature field adjacent to the flames and considered the effect of the interaction between flow and heat on the flames using DNS (Direct numerical simulation). In the development of planar flame in the turbulence field, the results show that spread of the flame zone leads to enhancement of the effect of turbulence field on the isosurface of temperature upstream of flames, and that the distribution of heat conduction does not deviate from the isosurface of temperature in the case of small wrinkles on the isosurface of temperature.

Formulation and Evaluation of Controlled Release Matrix Tablets of Cefixime Trihydrate

Abstract: The main objective of the present work was to develop sustained release matrix tablets of Cefixime Trihydrate were prepared by direct compression techniques and evaluates the effect of formulation variables such as lubricant, binder, polymer content and viscosity grades of HPMC on the behavior of Cefixime Trihydrate release. The prepared tablets were evaluated for various physico-chemical parameters. In vitro release profile was check to evaluate the sustained release matrix tablet of Cefixime Trihydrate. The drug release from the optimized formulation was found to follow zero order kinetics. Thus the phenomenon of drug release showed that the release of optimized formulation is controlled by diffusion. Administration of Cefixime Trihydrate in a sustained release dosage would be more desirable for bacterial infections effects by maintaining the plasma concentrations of the drug well above the therapeutic concentration. From In vitro dissolution profile, Formulation S3 was prepared with Hydroxypropyl methylcellulose (K15M) combination where drug release was about 99.14% at the end of 24 hrs and followed zero order with non-Fickian diffusion method. It is selected as the best formulation.

Influence of temperature on secretion and functionality of lupin seed γ-conglutin.

Basic 7S globulins, a group of proteins commonly found in legumes, undergo the intriguing phenomenon of release from the seeds into hot water. γ-Conglutin is a representative of this group of proteins found in lupin seeds. The physiological significance and the molecular mechanism of the selective release of γ-conglutin from lupin seeds remain unknown. Therefore, the presented study aimed to determine changes in the functionality of this protein in response to the high temperature occurring during lupin seed incubation. It was confirmed that the main protein fraction released from the seeds during high-temperature incubation was γ-conglutin. The incubation condition favours the occurrence of this protein in a monomeric form, and the temperature used corresponds to its midpoint unfolding temperature. Subsequent analysis carried out on the γ-conglutin monomer revealed changes in its functionality after heat shock. The thermally treated protein shows a considerable increase in its interaction strength with flavonoids. Moreover, the inhibitory activity against glycoside hydrolases was enhanced when γ-conglutin monomer was exposed to specific temperatures. The results of the present study provide a potential explanation of the physiological relevance of γ-conglutin and shed new light on a possible mechanism of its activation upon specific heat treatment. This knowledge will help characterise homologous proteins, which are commonly found in other legumes and undergo a similar heat-induced secretion phenomenon. © 2021 Society of Chemical Industry.

Effect of the Influent Substrate Concentration on Nitrogen Removal from Summer to Winter in Field Pilot-Scale Multistage Constructed Wetland–Pond Systems for Treating Low-C/N River Water

The quality of micropolluted water is unstable and its substrate concentration fluctuates greatly. The goal is to predict the concentration effect on the treatment of nitrogen in a river with an actual low C/N ratio for the proposed full-scale Xiaoyi River estuary wetland, so that the wetland project can operate stably and perform the water purification function effectively in the long term. Two pilot-scale multistage constructed wetland–pond (MCWP) systems (S1 and S2, respectively) based on actual engineering with the same “front ecological oxidation ponds, two-stage horizontal subsurface flow constructed wetlands and surface flow constructed wetlands (SFCWs) as the core and postsubmerged plant ponds” as the planned process were constructed to investigate the effect of different influent permanganate indexes (CODMn) and total nitrogen (TN) contents on nitrogen removal from micropolluted river water with a fixed C/N ratio from summer to winter in the field. The results indicate that the TN removal rate in the S1 and S2 systems was significant (19.56% and 34.84%, respectively). During the process of treating this micropolluted water with a fixed C/N ratio, the influent of S2 with a higher CODMn concentration was conducive to the removal of TN. The TN removal rate in S2 was significantly affected by the daily highest temperature. There was significant nitrogen removal efficiency in the SFCWs. The C/N ratio was a major determinant influencing the nitrogen removal rate in the SFCWs. The organic matter release phenomenon in SFCWs with high-density planting played an essential role in alleviating the lack of carbon sources in the influent. This research strongly supports the rule that there is seasonal nitrogen removal in the MCWPs under different influent substrate concentrations, which is of guiding significance for practical engineering.

Effect of Mulligan’s Pain Release Phenomenon on Ted in Subjects with Subacute Lateral Epicondylitis

Introduction: Lateral Epicondylitis is a overuse syndrome usually seen in people who perform repeated extension and supination movement of elbow against resistance. Tissue Extensibility Dysfunction (TED) is a term which suggests apparent tightness of the muscle which has occurred due to spasm, lactic acid accumulation, inflammation or over use.
 Need of The Study: Many Studies involving manual therapy with different techniques have already demonstrated manual therapy is effective in reducing pain in subjects with lateral epicondylitis. Very few studies have focused on Mulligan’s Pain Release Phenomenon (PRP) which is established to reduce pain and improving range of motion. Also, there is dirth in literature related to tissue extensibility dysfunction occurring in subacute variant of tennis elbow and the effect of PRP on TED. Hence this study is been undertaken. 
 Methodology: A total of 50 sample size was randomized into 25 per group. Group A consisted of Conventional therapy and Group B consisted of Conventional therapy with Mulligan’s PRP. Outcome measures were noted pre therapy and on the 7th day that is post therapy and results were tabulated.
 Results: The results declare that pain (0.05 and 0.001), grip strength (0.001, 0.001) and disability (0.001, 0.001) showed significant improvement in the scores in both the group whereas muscle stiffness (0.341 and 0.001) significantly improved only in Group B.
 Conclusion: Mulligan’s Pain Release Phenomenon technique can be used to treat Subacute tennis elbow effectively and is known to reduce the muscle stiffness along with pain and disability and improving strength.

Layer-by-Layer Fabrication of Hydrogel Microsystems for Controlled Drug Delivery From Untethered Microrobots.

Targeted drug delivery from untethered microrobots is a topic of major interest in current biomedical research. The possibility to load smart materials able to administer active principles on remotely in vivo guidable microdevices constitutes one of the most attractive opportunities to overcome the drawbacks of classical untargeted delivery methodologies. Hydrogels, in particular, are ideal candidates as drug-carrying materials due to their biocompatibility, low cost, and ease of manufacturing. On the other hand, these polymers suffer from poor control over release rate and overall released amount. Starting from these premises, the present article demonstrates the possibility to tune the release of hydrogels applied on magnetically steerable microrobots by fabricating microsystems via layer-by-layer self-assembly. By doing this, the diffusion of chemicals from the hydrogel layers to the external environment can be optimized and the phenomenon of burst release can be strongly limited. The microrobotic platforms employed to transport the hydrogel active material are fabricated by employing 3D printing in combination with wet metallization and present a gold layer on their surface to enhance biocompatibility. The maneuverability of microdevices coated with both thin and thick multilayers is investigated, individuating optimized parameters for efficient actuation.

Phosphate removal from simulated wastewater using industrial calcium-containing solid waste

Anthropogenic solid waste can serve as a reactive substrate to adsorb and immobilize PO43- to enhance the sustainability of the water-energy-food nexus due to nutrient streams being recovered and recycled into the food chain as slow-release fertilizers. However, the structural complexity of solid waste presents significant hurdles identifying its ultimate potential to efficiently adsorb PO43- from wastewater streams while its rich chemical composition – obtaining usable, heavy metal-free products to be reused in a highly regulated environment. In this study, two types of calcium-rich solid waste, biomass combustion bottoms ash (BA) and lime kiln dust (LKD), were evaluated for their propensity to adsorb PO43- from simulated wastewater streams. Batch adsorption studies showed maximum adsorption (PO43- removal) taking place at 2200 ppm of BA and 1800 ppm LKD with the sorption kinetics obeying well second order behavior. Estimated sorption capacity was 55.6 and 35.3 mg P/g LKD and BA, respectively, comparable or higher than for other natural Ca-containing natural minerals reported in the literature. PO43- ion adsorption was shown to be inhibited to below 50% as organic acid concentration increased in simulated wastewater solution. Importantly, heavy metal release into the simulated wastewater was assessed and it was concluded that only BA released Zn concentrations which were higher than those regulated by EPA. Mechanistically, the underlying metal release phenomena were observed and explained by the significant initial material dissolution rather than by any competing processes, such as organic acid competitive adsorption with PO43- ion.

Stereoscopic high-speed imaging of iron microexplosions and nanoparticle-release.

In this work, the combustion behavior of seeded iron particles (d50 = 70 µm) in a laminar diffusion flame was studied in a modified Mckenna flat-flame burner. Two high speed cameras in stereo configuration allowed 3D position and 3D velocity measurements of burning iron particles as well as 3D evaluation of particle microexplosions. Microexplosive processes are important since it can affect both combustion stability and formation of product components. The observed microexplosions happened before particle extinction resulting in change of trajectories, velocities, radiation intensities and fragmentation into smaller particles. It was observed for the first time that fragments of these microexplosions tend to produce planar structures. A frequent release phenomenon was observed during the iron particle combustion using magnified thermal radiation imaging and high-speed shadowgraphy. This release phenomenon was indirectly confirmed with scanning electron microscopy of combust products, revealing multiple cracked particle shells and hollow structures. Black body radiation characteristics was observed indicating the release being in condensed phase and emission spectroscopy identified FeO as intermediate species during combustion. The observed release is believed to mainly consist of iron-oxide nanoparticles formed in the homogenous reaction between vapor iron and oxidizers.

Parameter inversion and microscopic damage research on discrete element model of cement-stabilized steel slag based on 3D scanning technology

The macro- and micro-physical properties of cement-stabilized steel slag (CSS) base materials in a highway project were studied. A discrete element model of CSS with a real steel slag shape was constructed using Particle Flow Code 3D and 3D scanning technology. The sensitivity between the macro- and micro-parameters of the sample was explored, and a nonlinear regression equation was established to analyze the relationship between these parameters. Uniaxial compression simulation tests were conducted on CSS with steel slag contents of 0%, 10%, 30%, and 50%. By combining contact calculation, crack location, energy tracking, acoustic emission (AE) monitoring, and other program systems, the macro- and micro-mechanical properties and micro-crack evolution law of the samples in the failure process were analyzed in terms of strength, energy, and fracture damage. The damage mechanism of CSS was also revealed. Results showed that with the increase in steel slag content, the elastic modulus and peak stress of the samples increased, the Poisson’s ratio decreased, and the post-peak stress curve steepened, indicating obvious brittle failure characteristics. With the increase in steel slag content, the crack initiation stress, thickness of the fracture surface, and number of internal micro-cracks in CSS increased exponentially. In the uniaxial compression test, AE intensity underwent five stages, in which the peak moment of AE intensity exhibited hysteresis compared with the moment of the peak stress. Absorption and release phenomena of strain energy were observed in the process of specimen failure. When the steel slag content increased, the total strain energy absorbed by the specimen increased. When the absorbed energy exceeded the bond strength, the bond ruptured with the release of energy. The main crack of the sample penetrated and stretched to the direction of strain energy release to form a macroscopic fracture surface.

Effect of Free Volume on Curcumin Release from Various Polymer-Based Composite Films Analyzed Using Positron Annihilation Lifetime Spectroscopy.

This work reports the effects of free volume on curcumin release in various polymer-based composite films. Curcumin-reinforced biocomposite films were fabricated with natural biopolymers (carrageenan and chitosan) and bioplastics (poly(lactide) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT)) via the solvent casting method. The curcumin release test was performed using an aqueous medium, and it was found that it was released the fastest in the carrageenan film, followed by the chitosan, PLA, and PBAT films, presumably owing to the dissimilarity of the polymer matrix. The free volume of the polymer films was determined using positron annihilation lifetime spectroscopy (PALS) to understand the release phenomena of curcumin. The free volume fraction was varied and reliant on the type of polymer, with the highest in the PBAT-based film followed by the PLA-, chitosan-, and carrageenan-based films. The free volume method helps analyze the release of bioactive compounds in a polymer matrix and may help to achieve a better understanding of the release of bioactive compounds.

A Critical Review of Alien Limb-Related Phenomena and Implications for Functional Magnetic Resonance Imaging Studies.

Consensus criteria on corticobasal degeneration (CBD) include alien limb (AL) phenomena. However, the gist of the behavioral features of AL is still “a matter of debate.” CBD-related AL has so far included the description of involuntary movements, frontal release phenomena (frontal AL), or asomatognosia (posterior or “real” AL). In this context, the most frequent symptoms are language and praxis deficits and cortical sensory misperception. However, asomatognosia requires, by definition, intact perception and cognition. Thus, to make a proper diagnosis of AL in the context of CBD, cognitive and language dysfunctions must be carefully verified and objectively assessed. We reviewed the current literature on AL in CBD and now propose that the generic use of the term AL should be avoided. This catchall AL term should instead be deconstructed. We propose that the term AL is appropriate to describe clinical features associated with specific brain lesions. More discrete sets of regionally bound clinical signs that depend on dysfunctions of specific brain areas need to be assessed and presented when posing the diagnosis. Thus, in our opinion, the AL term should be employed in association with precise descriptions of the accompanying involuntary movements, sensory misperceptions, agnosia-asomatognosia contents, and the presence of utilization behavior. The review also offers an overview of functional magnetic resonance imaging-based studies evaluating AL-related phenomena. In addition, we provide a complementary set of video clips depicting CBD-related involuntary movements that should not mistakenly be interpreted as signs of AL.

Infrared thermographic assessment of heat release phenomena in steel parts subjected to quasi-static deformation

The paper describes the mechanism of heat release during deformation and main features of passive infrared thermographic diagnostics of steel parts subjected to elastic, elastic–plastic and plastic deformation under quasi-static loading. A basic equation for evaluating temperature signals caused by quasi-static deformation is derived. It is stated that the evaluation of steel structures by passive thermal methods should be performed when the heat is generated by mechanical stresses appearing in structures subjected to mechanical loading. The analysis of the loading kinetics and temperature anomalies has shown that thermal nondestructive testing technique is a useful tool for determining stress state in steel structures during the initiation and evolution of fracture. It is shown that the quasi-static deformation of steel structures is accompanied by the formation of elastic clusters separated by shear bands, and the plastic deformation in shear bands causes heat release resulting in a temperature increase of 4–12.5 °C.

Experimental study of accidental leakage behaviour of liquid CO2 under shipping conditions

CO2 shipping is a viable transport alternative when pipelines are impractical. Lack of experience in large-scale CO2 shipping projects implies uncertainty in selecting optimal cargo conditions and operational safety procedures. The risk of uncontrolled release of CO2 arises in case of mechanical failure of storage or cargo vessels, and a thorough understanding of the discharge phenomena, including the propensity for solid formation, is necessary to develop safety protocols. A refrigerated experimental setup is established in this study to investigate the release phenomena of liquid CO2 under shipping conditions. The rig features a dome-ended cylindrical pressure vessel, a discharge pipe section and a liquid nitrogen refrigeration system that enables conditioning near the triple point – at ∼0.7 MPa, 223 K - and higher liquid pressures (∼2.6 MPa, 263 K). Pressure, temperature and mass monitoring were considered to enable an extensive observation of the leakage behaviour under typical operation scenarios. Three different sets of experiments were considered to inform the designer in the selection of optimal process conditions, with low-pressure (0.7 – 0.94 MPa, 223–228 K), medium-pressure (1.34–1.67 MPa, 234–245 K) and high-pressure tests (1.83–2.65 MPa, 249–259 K) demonstrating distinct behaviours relative to phase transitions, leakage duration and solidification of inventory.

Study of Earthquake Effects on Structures and Mitigation Measures: A Literature Review

Earthquake is the phenomenon of sudden release of built-up energy due to the tectonic plate’s movement induces tremors along the lithospheric surface of Earth in the form of waves called seismic wave. Soil liquefaction, structural instability, surface faults and uplifts, triggering landslides and tsunami are some of its causes. These induce changes in the terrain of the concerned areas. Earthquake is commonly of four types, namely tectonic, collapse, volcanic and explosion and are classified based on cause of origin, depth of focus and intensity. The effects produced by action of earthquake on structures can be reduced by following certain measures such as verifying structure of the terrain and history of seismic activity, analyzing seismic performance of structure, design verification and utilization of available preventive and corrective techniques. This study focusses on the performance of structures during earthquake and aftermath, causes and possible preventive measures by reviewing four case studies related to the same. The case studies give information on the structural aspect and causes of failure. The paper emphases the importance of seismic consideration, methodical analysis, mitigation and incorporation of the same into designing strategies.

Thermodynamic Evolution of Solar Flare Supra-arcade Downflows

Abstract Solar flares are rapid energy release phenomena that appear as bright ribbons in the chromosphere and high temperature loops in the corona, respectively. Supra-arcade Downflows (SADs) are plasma voids that first come out above the flare loops and then move quickly toward the flare loop top during the decay phase of the flare. In our work, we study 20 SADs appearing in three flares. By differential emission measure (DEM) analysis, we calculate the DEM weighted average temperature and emission measure of the front region and the main body of SADs. It is found that the temperatures of the SAD front and body tend to increase during the course of SADs flowing downwards. The relationship between the pressure and temperature fits well with the adiabatic equation for both the SAD front and body, suggesting that the heating of SADs is mainly caused by adiabatic compression. Moreover, we also estimate the velocities of SADs via the Fourier Local Correlation Tracking method and find that increase of the temperature of the SAD front presents a correlation with the decrease of the SAD kinetic energy, while the SAD body does not, implying that the viscous process may also heat the SAD front in spite of a limited role.

Evaluation of drug release kinetics from polymeric nanoparticles loaded with poorly water-soluble APIs

Abstract The aim of this research was to investigate the release behavior of a combination of two poorly water-soluble active pharmaceutical ingredients (APIs) from poly (D,L-lactide-co-glycolide) (PLGA) nanoparticles. Amlodipine besylate - AML, a calcium channel blocker, and valsartan - VAL, an angiotensin II receptor antagonist drug, were used as poorly water-soluble model drugs. PLGA nanoparticles loaded with AML-VAL (1:16 w/w) were obtained by nanoprecipitation using an amphiphilic block copolymer - Pluronic F127 as stabilizer. The drugs release from the PLGA nanoparticles was determined by a dialysis membrane method under sink conditions. Nanoparticles provided a slow release for both APIs and an attenuated burst effect compared to free drug. Five kinetics models such as Zero-order, First-order, Korsmeyer-Peppas, Higuchi and Hixson-Crowell were applied to predict drug release profiles. The Higuchi and Korsmeyer-Peppas models (R2 > 0.97) best described physicochemical release phenomenon for each PLGA formulations.

Influence of Polyvinyl Alcohol Powder on the Mechanical Performance and Volume Stability of Sulfoaluminate–Portland Cement Composite

Cement quick repair materials generally have the defects of brittleness and early shrinkage. The modification of composite cement mortar by water-soluble glue powder—polyvinyl alcohol (PVA)—was studied in the condition of settled water cement ratio. At 90 days, the maximum flexural strength of mortar was 15.4 MPa, which was 1.3 times of the group without PVA and there was no strength shrinkage phenomenon. Through the analysis of the porosity, PVA improved the total porosity; high porosity could play a better role of buffering and absorbing the impact stress, effectively improving the toughness of mortar. At 28 days, the maximum impact resistance was 1.72 J/cm2, which was 1.75 times of the group without PVA. In addition, the increased total porosity also greatly absorbed the shrinkage stress at the early stage, and reduced the mortar self-shrinkage. When the PVA content was 1%, the volume self-shrinkage of mortar decreased from the initial 3360 μm·m−1 to 700 μm·m−1. According to the analysis of hydration heat, the addition of PVA effectively reduced the early hydration heat release rate and alleviated the concentrated heat release phenomenon to a certain extent. In this paper, the hydration reaction of composite cement and the action mechanism of PVA in composite cement were studied by means of X-ray diffraction, infrared spectrum and hydration heat analysis.

Studying Drug Release through Polymeric Controlled Release Formulations in United States Pharmacopoeia 2 Apparatus Using Multiphysics Simulation and Experiments.

In vitro dissolution of oral drug formulations is often studied using the United States Pharmacopoeia (USP) apparatus. Although a well-stirred vessel or a perfect sink assumption is often employed in the modeling of in vitro dissolution in USP apparatus, such a limit is usually not realized in actual experimental conditions. The interplay of hydrodynamics in the vessel and the swelling and erosion of dosage forms often results in substantial deviations from the dissolution behavior obtained under perfect sink approximation. We develop a multiphysics model of drug release from controlled release tablets of polymeric excipients with active pharmaceutical ingredients (APIs). Simulations are performed in COMSOL for the USP 2 (paddle) apparatus and the effects of stirring speed, drug loading, erosion rate, and polymer swelling and erosion are analyzed in detail. We demonstrate that the drug release phenomena can be conveniently interpreted using the Weibull equation to fit the simulation results. This is further confirmed using drug release experiments performed on mechanically compressed tablets of naproxen sodium as the API with poly-methyl-methacrylate-co-methacrylic acid as the excipient. We show that the API-to-polymer ratio may be varied to obtain different regimes of controlled release.