The international trade as the sole engine of growth for an economy

Can international trade act as the sole engine of growth for an economy? If yes, what are the mechanisms through which trade operates in transmitting permanent growth? This paper answers these questions with two simple two-country models, in which only one country enjoys sustained growth in autarky. The models differ in the assumptions on technical change, which is either labour- or capital-augmenting. In both cases, the stagnant economy imports growth by trading. In the first model, growth is transmitted because of permanent increases in the trade volume. In the alternative framework, the stagnant economy imports sustained growth because its terms of trade permanently improve.international trade; stagnant economies; growth transmission; mechanisms of transmission.

A new hybrid distribution paradigm: Integrating drones in medicines delivery

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

Change of sea level trend in the Mediterranean and Black seas

Sea level anomaly (SLA) data in the Mediterranean and Black seas obtained by ocean radar altimetry missions (TOPEX/Poseidon, Jason, ERS-1/2 and ENVISAT) are studied in conjunction with corresponding sea-surface temperature (SST) data. The studied time span is 11 years long, 1993-2003. Besides confirming previously published results, we report a significant, but enigmatic, abrupt change in the SLA trend that took place in mid-1999 which has been corroborated by independent tide gauge data. Results obtained from an Empirical Orthogonal Function (EOF) analysis show that the change in 1999 is not uniform in the Mediterranean Sea, which can thus be divided into 6 sub-regions. This 1999 kink in the rate-of-change happened in four of these sub-regions as well as in the Black Sea. Upon splitting the time series at mid-1999, we see a good spatial correlation for the first period between SLA and SST trend maps in both the Mediterranean Sea and the Black Sea, while for the second period such correlation virtually disappeared in the Mediterranean and is greatly reduced in the Black Sea. It implies that prior to 1999 the steric effect was a major factor in interannual variability of sea level in the Mediterranean and Black seas, but after the time the SLA inverted its trend in mid-1999, this steric effects became less important as a forcing factor. It is premature to draw conclusions about the physical processes involved based on the data sets we study, but it appears that the Mediterranean Sea might be seeing a restoration of Adriatic as the main source of deep water in the eastern basin, while the Black Sea level has been largely controlled by an interannual or interdecadal steric effect

An exact approach for the vehicle routing problem with two-dimensional loading constraints

We consider a special case of the symmetric capacitated vehicle routing problem, in which a fleet of K identical vehicles must serve n customers, each with a given demand consisting in a set of rectangular two-dimensional weighted items. The vehicles have a two-dimensional loading surface and a maximum weight capacity. The aim is to find a partition of the customers into routes of minimum total cost such that, for each vehicle, the weight capacity is taken into account and a feasible two-Dimensional allocation of the items into the loading surface exists. The problem has several practical applications in freight transportation, and it is -hard in the strong sense. We propose an exact approach, based on a branch-and-cut algorithm, for the minimization of the routing cost that iteratively calls a branch-and-bound algorithm for checking the feasibility of the loadings. Heuristics are also used to improve the overall performance of the algorithm. The effectiveness of the approach is shown by means of computational results

Cardiovascular Endurance Among College Students: How is it Related to Overall Fitness?

Please see the pdf version of the abstract

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

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

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

Owner and animal factors predict the incidence of, and owner reaction towards, problem behaviors in companion dogs

Unwelcome behaviors in pet dogs may have serious implications for the quality of life of both the animals and their owners. We investigated owners\u2019 perceptions about their dogs\u2019 behavioral issues as well as other factors that might be predictive of potential canine problem behaviors. We distinguished between \u201cundesirable behaviors\u201d (behaviors that were unpleasant to the owners) and \u201cproblematic behaviors\u201d (behaviors that the owners found difficult to overcome). We designed an on-line survey eliciting information about owners, their dogs, their relationship with their dogs and whether the animals exhibited any of 15 potentially problematic behaviors. The largest proportion of respondents (65%) reported that their dogs exhibited undesirable, but not problematic, behaviors and were not interested in their modification. Only 32% of the respondents considered the behavior to be both undesirable and problematic and wished to change it. The owners\u2019 perception of a problem was associated with reports of fear- and anxiety-related behaviors. The owner\u2019s gender, marital status and attitude towards the dog as his/her child as well as the dog\u2019s age, size, age at acquisition and breed emerged as robust predictors. Compared to all other behavioral categories, reported aggressive canine behaviors were three times more likely to elicit an owner\u2019s wish to address them. This study revealed that the behaviors of dogs may be perceived differently by their owners and the type of perception may influence the owner\u2019s actual willingness to change those behaviors. Moreover, we identified the most robust set of factors that, either individually or combined, would help predict a dog\u2019s potential problem behaviors and an owner\u2019s attitude towards them, which will be useful in improving rational prevention and treatment strategies