160. Urgent Care Prescriber Perspectives on Antibiotic Prescribing During the COVID-19 Pandemic

Background Urgent care practices were significantly impacted by the COVID-19 pandemic. Studies conducted early in the pandemic demonstrated dramatic decreases in outpatient antibiotic prescribing, particularly amongst agents typically used for respiratory infections. We observed a 33% decline in urgent care antibiotics prescribing during the COVID-19 pandemic in our urgent care clinics. We investigated the prescriber experience to elucidate factors influencing antibiotic use for respiratory conditions during the COVID-19 pandemic at two academic urgent care clinics. Methods We employed a mix method approach, first distributing a survey to all full-time prescribers. We then followed up with qualitative interviews (12 of 22 prescribers) which was conducted by a single, trained interviewer using a standardized guide. Interviews were recorded and transcribed verbatim. Each transcription was independently reviewed and coded by two blinded investigators using standardized themes and adjudicated by a third investigator for stability, robustness, and interrater reliability. Individually, researchers identified and coded key themes and statements. These themes were then discussed as a group and combined where they shared meaning. This project was reviewed and deemed to be non-human subjects research by the Stanford University School of Medicine Panel on Human Subjects in Medical Research. Results A total of 20 of the 22 prescribers (13 MDs and 9 APPs) completed the survey (91% response rate). Notably, only 25% of prescribers agreed that COVID-19 had changed their antibiotic prescribing practices for patients with respiratory infections despite objective data that all prescribed less. In the qualitative interviews, we identified four major themes impacting the appropriateness of antibiotic prescribing practices as shown in Table 1. Conclusion Urgent care prescribers attributed a decrease in antibiotic prescribing during COVID-19 to changes in patient expectations and knowledge base, a switch to telemedicine-based encounters, and changing epidemiology. These shifts could be utilized by outpatient antimicrobial stewardship efforts to sustain low prescribing rates for conditions in which antibiotics are generally not indicated. Disclosures Marisa Holubar, MD, MS, Nothing to disclose

Multivariable State-Feedback Controller Design for PV Inverter Connected to a Weak Grid

This paper presents a robust multi-input multi-output (MIMO) state-feedback control scheme for a photovoltaic (PV) inverter connected to a weak grid. For a weak grid, the point of common coupling (PCC) voltage is very sensitive to the power disturbances and it is dynamically coupled to the PLL dynamics. So far, most of the control methods do not take into accounts these couplings. Therefore, in this paper, the MIMO controller was designed taking into account the dynamics of the phase-locked loop (PLL) and coupling effects between PCC voltage and the active power to enhance the system’s robustness. As result, the robust performance of the PV inverter interfaced to a weak grid was yielded. In addition, the sensitivity of the system to PLL was eliminated, allowing the use of larger PLL bandwidth even in a very weak grid. Based on the eigenvalues analysis method, a comparative study between the proposed control method and the conventional vector control method was performed. The proposed method is verified with simulations in PLECS and real-time simulations in the RT Box. The results show that the proposed MIMO control method preserves the system stability robustness against any change of grid strength, generated power and PLL bandwidth.

DEVELOPMENT AND VALIDATION OF THE PROCEDURE FOR QUANTITATIVE DETERMINATION OF IMPURITIES IN TABLETS “RANOLAZIN-NAN”

The article presents the results of the research on the development of the procedure for determining related impurities by high-performance reversed-phase chromatography in the tablets “Ranolazin-NAN”. The conditions for samples preparation of ranolazine tablets, optimal conditions for the gradient mode of chromatography were selected using Zorbax Eclipse Plus C18 column: eluent A - 0,1% triethylamine buffer with pH 6,0 ± 0,1 (diluted with orthophosphoric acid) and acetonitrile in a ratio 70:30 v / v and eluent B - acetonitrile. The effect of pH medium (2,0, 6,0 and 9,0) on the efficiency of the column while studying the solutions of ranolazine and identified impurities was established. The suitability of the chromatographic system was proven and the specificity of the method for determining unidentified and identified impurities was proven. Linearity in the entire range of the procedure usage (from the quantitation limit to 125% (of the content of a single impurity)), correctness as well as precision at the level of reproductivity and intermediate precision, and the stability (robustness) of the method with small changes in the flow rate and column temperature were proven for the procedure of related impurities determination in Ranolazin-NAN tablets.

Internet congestion control: From stochastic to dynamical models

Since its inception, control of data congestion on the Internet has been based on stochastic models. One of the first such models was Random Early Detection. Later, this model was reformulated as a dynamical system, with the average queue sizes at a router’s buffer being the states. Recently, the dynamical model has been generalized to improve global stability. In this paper we review the original stochastic model and both nonlinear models of Random Early Detection with a two-fold objective: (i) illustrate how a random model can be “smoothed out” to a deterministic one through data aggregation and (ii) how this translation can shed light into complex processes such as the Internet data traffic. Furthermore, this paper contains new materials concerning the occurrence of chaos, bifurcation diagrams, Lyapunov exponents and global stability robustness with respect to control parameters. The results reviewed and reported here are expected to help design an active queue management algorithm in real conditions, that is, when system parameters such as the number of users and the round-trip time of the data packets change over time. The topic also illustrates the much-needed synergy of a theoretical approach, practical intuition and numerical simulations in engineering.

Formulation and Characterization of Self-Microemulsifying Drug Delivery System of Tacrolimus

The present investigation aimed to formulate a liquid self-microemulsifying drug delivery system (SMEDDS) of tacrolimus to enhance its oral bioavailability by improving its dispersibility and dissolution rate. Four liquid SMEDDS were prepared using maisine CC as oil phase, labrasol ALF as surfactant and transcutol HP as co-surfactant based on the solubility studies of tacrolimus in these components. The phase behavior of the components and the area of microemulsion were evaluated using pseudoternary phase diagrams. The formulations were also assessed for thermodynamic stability, robustness to dilution, self-emulsification time, drug content, globule size and polydispersity index. The prepared SMEDDS formulations exhibited improved drug release compared to the pure drug powder. From this study, it was concluded that using a composition of 10% maisine CC, 67.5% labrasol ALF and 22.5% transcutol produced a liquid SMEDDS with good thermodynamic stability and enhanced in-vitro drug release profiles compared with pure tacrolimus powder. All which supports the use of self-micro emulsifying drug delivery systems as a promising approach to improve solubility, dissolution and stability of poorly soluble drugs like tacrolimus.

Robust Compensating Function Scheme for Adequate Electrical Power System Stabilization

This work centers on robust compensating function scheme for adequate electrical power system stabilization. There has been high level of disturbances in the power line and lack of adequate compensation technique to cancel the effects of the resultant instability which has caused power failures. The problem was addressed by the consideration of disturbances in the power line during the design of the compensating function for the improvement of the power system performance and stability. H-Infinity synthesis robust compensating function design method was used to design an adequate compensator that can improve the performance and stability of the power system. From the results, the H-infinity Synthesis Controlled Generating Plant (HCGP) recorded an overshoot of 0%, settling time of 1.04 seconds, tracking error of 0dB, gain margin of 21.7dB and phase margin of 79.6 degrees. The simulation was repeated by varying the value to k to -0.3, and the generating plant produced same results. This shows that the system can maintain performance and stability equilibrium even when there is change in its parameters. Since the HCGP satisfied the performance and stability robustness, therefore it was concluded that power system robust compensating function scheme for improved performance and stability robustness was achieved using H-Infinity synthesis method.

Development and Validation of HPLC Method for Diphenhydramine Hydrochloride

Aim: The aim of present method development for Diphenhydramine HCl performed on HPLC is to obtain specific, more accurate and precise results as compare to spectrophotometric method. Methods: HPLC analysis was performed according to USP method with wavelength detection at 220nm and 1.0ml/min flow rate. Wufeng thermo HPLC system UV -100detector was used having column C18(4.6mm*250mm) 5. Methanol and water (4:1) mixture was used as mobile phase and pH was adjusted at 7.4 with the help of triethanolamine. Validation parameters like linearity, accuracy, precision, solution stability, robustness, LOD, LOQ and system suitability were successfully evaluated. Results: The regression co-efficient for calibration curve was 0.991 and % recovery was in range (80-110%), whereas no robustness was observed in this reported method. Conclusion: In summary, the expected linearity, accuracy and % recovery indicating that HPLC is more precise method than spectrophotometry and suggested that present method qualifies the validation criteria.