1,086 research outputs found

    A new hybrid distribution paradigm: Integrating drones in medicines delivery

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    This paper analyses a new hybrid paradigm resulting from the integration of unmanned aerial vehicles (UAV), commonly referred to as drones, in logistics and distribution processes. This work is motivated by a real application, where the company Connect Robotics, the first drone delivery provider in Portugal, made a partnership with a pharmacy located at a rural region to start implementing the delivery of medicines by drone. The pharmacy receives orders throughout the day and has to deliver in the same day with tight lead-times. The resulting problem is modelled as a Dynamic Parallel Drone Scheduling Vehicle Routing Problem with Lead-Time. A solution method is devised to solve it, thus helping the pharmacist to plan the car and drone delivery routes during the day. The results obtained on real instances revealed that the solution method is effective when compared to the optimal solutions of the static version of the problem, since the dynamic solution only differs, on average, about 7% from the static one. Moreover, some managerial insights about the impact of adding drones to the distribution operation are discussed, namely the economic and environmental impacts with cost savings up to 41% and reduction of monthly CO2 emissions of 310 kg, the use of spare batteries which increase the benefit from 16% to 41%, and same-day versus next-day delivery

    Barium alginate capsules for 3D immobilisation of living cells: morphology, membrane properties and permeability

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    Encapsulation in a barium alginate membrane is a promising strategy to obtain a three dimensional culture of living cells: membrane properties are crucial for a realistic clinical application. A one-step encapsulation technique, recently developed for controlled release of boar semen, was employed to prepare barium alginate and protamine-alginate membranes: permeability to two model molecules (haemoglobin and glucose) was evaluated. Capsules were evaluated for technological properties and scanning electron microscopy was used to examine the external morphology of the capsules and the 3D distribution of the cells within the core. The results indicate that 3D arrangement and cell shape are maintained, capsule dimensions and mechanical properties can be modulated, as well as their permeability to model molecules such as haemoglobin and glucose

    The Two-Echelon Capacitated Vehicle Routing Problem

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    Multi-echelon distribution systems are quite common in supply-chain and logistic systems. They are used by public administrations in their transportation and traffic planning strategies as well as by companies to model their distribution systems. Unfortunately, the literature on com- binatorial optimization methods for multi-echelon distribution systems is very poor. The aim of this paper is twofold. Firstly, it introduces the family of Multi-Echelon Vehicle Routing Problems. Second, the Two-Echelon Capacitated Vehicle Routing Problem, is presented. The Two-Echelon Capacitated Vehicle Routing Problem (2E-CVRP) is an extension of the classical VRP where the delivery passes through intermediate depots (called satellites). As in the classical VRP, the goal is to deliver goods to customers with known demands, minimizing the total delivery cost while considering vehicle and satellites capacity constraints. A mathematical model for 2E-CVRP is presented and some valid in- equalities given, which are able to significantly improve the results on benchmark tests up to 50 customers and 5 satellites. Computational re- sults under different realistic scenarios are presented

    5'-deiodinase activity and circulating thyronines in lactating cows.

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    To investigate the correlation between lactation and thyroid hormone metabolism, the authors studied concentrations of total and free thyroxine (T4 and fT4), triiodothyronine (T3 and fT3), and reverse triiodothyronine (rT3) in plasma and milk, as well as liver and mammary gland 5'-deiodinase (5'D) activity in dry, early, middle, and late lactating dairy cows. Cows in early lactation show lower plasma levels of T4 and rT3 than dry, middle, and late lactating animals, whereas T3 shows the lowest plasma levels in the dry period; free T4 and T3 show a similar pattern. In early lactation there is a clear decrease in liver 5'D associated with a notable increase in mammary 5'D. Concentrations of T4 and T3 in milk drop significantly in the first few days after delivery, whereas rT3 increases up to the fourth month. The findings suggest a relationship between the hypothyroid status of lactating cows and the rearrangement of organ-specific 5'-deiodinase activity related to the maintenance of the udder's function

    Intense beam of metastable Muonium

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    Precision spectroscopy of the Muonium Lamb shift and fine structure requires a robust source of 2S Muonium. To date, the beam-foil technique is the only demonstrated method for creating such a beam in vacuum. Previous experiments using this technique were statistics limited, and new measurements would benefit tremendously from the efficient 2S production at a low energy muon (<20<20 keV) facility. Such a source of abundant low energy μ+\mathrm{\mu^+} has only become available in recent years, e.g. at the Low-Energy Muon beamline at the Paul Scherrer Institute. Using this source, we report on the successful creation of an intense, directed beam of metastable Muonium. We find that even though the theoretical Muonium fraction is maximal in the low energy range of 252-5 keV, scattering by the foil and transport characteristics of the beamline favor slightly higher μ+\mathrm{\mu^+} energies of 7107-10 keV. We estimate that an event detection rate of a few events per second for a future Lamb shift measurement is feasible, enabling an increase in precision by two orders of magnitude over previous determinations
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