International trade in services. A growing contribution to Belgium’s current balance

Service activities hold an ambiguous position in the economy. Although they represent a dominant share of activity and employment, they have only a minor position in international trade. Generally speaking, trade in services has therefore attracted less interest than trade in goods in the context of competitiveness policy, and economic research has paid less attention to it. Yet despite the low gross volume of international trade in services, the services balance has grown in Belgium over the past fifteen years. Compensating in part for the deteriorating balance of trade in goods, net exports of services have gradually become the primary driver of the current account balance. Belgium’s central position in the European economic fabric is one of the main contributory factors in the good performance of Belgium’s trade in services. This has led to the development of trade and logistics services, particularly thanks to the importance of the port of Antwerp in maritime traffic. Given its central position combined with the quality of its human capital, Belgium is also the location for the headquarters of the European institutions and several multinational bodies, and that is another decisive factor in the growth of service exports. However, Belgium’s good general performance in trade in services is not seen in all service categories. In particular, services connected with information and communication technologies have not grown particularly strongly. Yet these services constitute a growth catalyst that could benefit the whole economy, and the human capital needed for such a development is available in Belgium.services, competitiveness, market share, transport, services for public authorities, business services

Minimal time problem for discrete crowd models with a localized vector field

In this work, we study the minimal time to steer a given crowd to a desired configuration. The control is a vector field, representing a perturbation of the crowd velocity, localized on a fixed control set. We characterize the minimal time for a discrete crowd model, both for exact and approximate controllability. This leads to an algorithm that computes the control and the minimal time. We finally present a numerical simulation

Minimal time for the continuity equation controlled by a localized perturbation of the velocity vector field

In this work, we study the minimal time to steer a given crowd to a desired configuration. The control is a vector field, representing a perturbation of the crowd velocity, localized on a fixed control set. We will assume that there is no interaction between the agents. We give a characterization of the minimal time both for microscopic and macroscopic descriptions of a crowd. We show that the minimal time to steer one initial configuration to another is related to the condition of having enough mass in the control region to feed the desired final configuration. The construction of the control is explicit, providing a numerical algorithm for computing it. We finally give some numerical simulations

Controllability and optimal control of the transport equation with a localized vector field

We study controllability of a Partial Differential Equation of transport type, that arises in crowd models. We are interested in controlling such system with a control being a Lipschitz vector field on a fixed control set $\omega$. We prove that, for each initial and final configuration, one can steer one to another with such class of controls only if the uncontrolled dynamics allows to cross the control set $\omega$. We also prove a minimal time result for such systems. We show that the minimal time to steer one initial configuration to another is related to the condition of having enough mass in $\omega$ to feed the desired final configuration

Controllability of a 2 × 2 parabolic system by one force with space-dependent coupling term of order one

International audienceThis paper is devoted to the controllability of linear systems of two coupled parabolic equations when the coupling involves a space dependent first order term. This system is set on an bounded interval I ⊂⊂ R, and the first equation is controlled by a force supported in a subinterval of I or on the boundary. In the case where the intersection of the coupling and control domains is nonempty, we prove null controllability at any time. Otherwise, we provide a minimal time for null controllability. Finally we give a necessary and sufficient condition for the approximate controllability. The main technical tool for obtaining these results is the moment method

Chronic helminth infection burden differentially affects haematopoietic cell development while ageing selectively impairs adaptive responses to infection

Throughout the lifespan of an individual, the immune system undergoes complex changes while facing novel and chronic infections. Helminths, which infect over one billion people and impose heavy livestock productivity losses, typically cause chronic infections by avoiding and suppressing host immunity. Yet, how age affects immune responses to lifelong parasitic infection is poorly understood. To disentangle the processes involved, we employed supervised statistical learning techniques to identify which factors among haematopoietic stem and progenitor cells (HSPC), and both innate and adaptive responses regulate parasite burdens and how they are affected by host age. Older mice harboured greater numbers of the parasites’ offspring than younger mice. Protective immune responses that did not vary with age were dominated by HSPC, while ageing specifically eroded adaptive immunity, with reduced numbers of naïve T cells, poor T cell responsiveness to parasites, and impaired antibody production. We identified immune factors consistent with previously-reported immune responses to helminths, and also revealed novel interactions between helminths and HSPC maturation. Our approach thus allowed disentangling the concurrent effects of ageing and infection across the full maturation cycle of the immune response and highlights the potential of such approaches to improve understanding of the immune system within the whole organism

Defense contracting

Thesis (M.B.A.)—Boston University

Price Updating in Production Networks. National Bank of Belgium Working Paper No. 352

This paper evaluates how firms change their prices in response to cost shocks and other price changes in their environment. We first document three new facts on the heterogeneity of firm-level producer prices and their relation-ship to buyers and suppliers in a production network. We then develop a non-parametric framework of how producers update their prices, taking into account this production network. The framework is very general, and accounts for the heterogeneity in price changes and the production network from the stylized facts. Moreover, the framework is consistent with various price setting mechanisms, and does not impose a particular market structure or demand func-tional form. Exploiting rich data on producer prices and the network structure of production in Belgium, we estimate the model to evaluate the importance of both channels in the data. We find that, on average, input price pass-through is incomplete and very much below one, while firms also strongly react to other prices in their environment. This implies that firms can adjust their markups in response to both cost shocks and prices of other firms. Furthermore, firms react differently to common shocks than to idiosyncratic shocks, on average completely passing through common shocks, but much less idiosyncratic shocks