Drone-Delivery Network for Opioid Overdose -- Nonlinear Integer Queueing-Optimization Models and Methods

We propose a new stochastic emergency network design model that uses a fleet of drones to quickly deliver naxolone in response to opioid overdoses. The network is represented as a collection of M/G/K queuing systems in which the capacity K of each system is a decision variable and the service time is modelled as a decision-dependent random variable. The model is an optimization-based queuing problem which locates fixed (drone bases) and mobile (drones) servers and determines the drone dispatching decisions, and takes the form of a nonlinear integer problem, which is intractable in its original form. We develop an efficient reformulation and algorithmic framework. Our approach reformulates the multiple nonlinearities (fractional, polynomial, exponential, factorial terms) to give a mixed-integer linear programming (MILP) formulation. We demonstrate its generalizablity and show that the problem of minimizing the average response time of a network of M/G/K queuing systems with unknown capacity K is always MILP-representable. We design two algorithms and demonstrate that the outer approximation branch-and-cut method is the most efficient and scales well. The analysis based on real-life overdose data reveals that drones can in Virginia Beach: 1) decrease the response time by 78%, 2) increase the survival chance by 432%, 3) save up to 34 additional lives per year, and 4) provide annually up to 287 additional quality-adjusted life years

Physicochemical Characterization of Inclusion Complex of Catechin and Glucosyl-β-Cyclodextrin

Purpose: To investigate the suitability of glucosyl-β-cyclodextrin (G-β-CD) to form inclusion complex with catechin, and characterize the physicochemical properties of the inclusion complex of catechin and G-β-CD.Methods: Catechin and G-β-CD was mixed in water at the same molar ratio, stirred at 20 °C for 48 h and lyophilized to obtain the complex. Its physicochemical properties were investigated by ultravioletvisible spectrometry (UV), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray diffractometry (XRD) and differential scanning calorimetry (DSC).Results: The characteristic UV absorption peaks for catechin, the physical mixture and the complex occurred at 279 nm. There was no significant difference between the IR spectra of the physical mixture and the complex. SEM and XRD data indicate that catechin was molecularly distributed in G-β-CD matrix and lost its crystallinity in the process. DSC indicate that the heat stability of catechin was significantly improved by complexing with G-β-CD.Conclusion: Catechin can efficiently interact with G-β-CD to form a complex by freeze-drying method. The complex of catechin and G-β-CD resulted in the changes in some of the characteristic spectral and thermal properties of the former. Furthermore, the heat stability of catechin is significantly improved.Keywords: Catechin, Glucosyl-β-cyclodextrin, Complex, Physicochemical propert

Multi-Agent Search for a Moving and Camouflaging Target

In multi-agent search planning for a randomly moving and camouflaging target, we examine heterogeneous searchers that differ in terms of their endurance level, travel speed, and detection ability. This leads to a convex mixed-integer nonlinear program, which we reformulate using three linearization techniques. We develop preprocessing steps, outer approximations via lazy constraints, and bundle-based cutting plane methods to address large-scale instances. Further specializations emerge when the target moves according to a Markov chain. We carry out an extensive numerical study to show the computational efficiency of our methods and to derive insights regarding which approach should be favored for which type of problem instance