For international environmental problems involving many countries, such as, e.g., the climate problem, it is unlikely that all countries will participate in an international environmental agreement. If some countries commit themselves to cooperate, while the remaining countries act independently and in pure self-interest, it appears to be possible to achieve a Pareto improvement if the non-signatory countries reduce their emissions, in exchange for transfers from the countries which sign an agreement. However, the paper shows that the prospect of receiving a transfer for reducing one's emissions provided the country does not commit itself to cooperation, tends to reduce the incentive a country might have to commit itself to cooperation. Moreover, if the disincentive effect of such side payments is strong, total emissions will be higher in a situation with side payments than in a situation in which the signatory countries commit themselves to not give transfers to free riding countries. Copyright Kluwer Academic Publishers 1997international environmental agreement, cooperation, side payments,

Severe acute respiratory syndrome (SARS) of humans is caused by a novel coronavirus of zoonotic origin termed SARS-associated coronavirus (SARS-CoV). The virus induces severe injury of lung tissue, as well as lymphopenia and destruction of the architecture of lymphatic tissue by as-yet-unknown mechanisms. In this study, the interaction of SARS-CoV with dendritic cells (DCs), the key regulators of immune responses, was analysed. Monocyte-derived DCs were infected with SARS-CoV and analysed for viability, surface-marker expression and alpha interferon (IFN-a) induction. SARS-CoV infection was monitored by quantitative RT-PCR, immunofluorescence analysis and recovery experiments. SARS-CoV infected both immature and mature DCs, although replication efficiency was low. Immature DCs were activated by SARS-CoV infection and by UV-inactivated SARS-CoV. Infected DCs were still viable on day 6 post-infection, but major histocompatibility complex class I upregulation was missing, indicating that DC function was impaired. Additionally, SARS-CoV infection induced a delayed activation of IFN-a expression. Therefore, it is concluded that SARS-CoV has the ability to circumvent both the innate and the adaptive immune systems.

Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. This paper makes use of the regional variation in schooling legislation within the German secondary education system to estimate the causal effect of central exit examinations on student performance. We propose a difference-in-differences framework that exploits the quasi-experimental nature of the German TIMSS middle-school sample. The estimates show that students in federal states with central exit examinations clearly outperform students in other federal states, but that only part of the difference can be attributed to central exit examinations. Our results suggest that central examinations increase student achievement by about one third school year equivalent. Terms of use: Documents in EconStor mayJEL Code: I28.

After primary school, German pupils are given a secondary school track recommendation. This recommendation and the actual track choice are strongly associated with later life outcomes. Using data from the German PISA 2000 extension study, we analyze the effect of relative age on track recommendations and actual choice. Younger pupils and boys are less likely to be recommended to and enrolled in the academic track (Gymnasium), the most attractive track in terms of later life outcomes. Flexible enrollment and grade retention partly offset these effects. We find no convincing evidence that postponing the recommendation by lengthening primary school by 2 years reduces the age or gender bias.JEL classification: I21, I28.

An environmental tax reform might bring about gains over and above improved environmental quality. In particular, if tax revenues from environmental taxes are used to reduce the tax on wage income, positive employment effects can result in second-best economies. An efficiency wage model is used to analyze the impact of an ecological tax reform on involuntary unemployment. The government controls emissions by selling emission permits. Employment of labor and wages are determined endogenously. Conditions are identified under which an environmental tax reform reduces unemployment and increases welfare.

Applying the theory of yardstick competition to the schooling system, we show that it is optimal to have central tests of student achievement and to engage in benchmarking because it raises the quality of teaching. This is true even if teachers' pay (defined in monetary terms) is not performance related. If teachers value reputation, and if teaching output is measured so that it becomes comparable, teachers will increase their effort. The theory is tested using the German PISA-E data. Our estimates suggest that, despite the flat career profile of German teachers, the quality of teaching tends to be higher in federal states with central exams.JEL Code: I28.

Standard-Nutzungsbedingungen:Die Dokumente auf EconStor dürfen zu eigenen wissenschaftlichen Zwecken und zum Privatgebrauch gespeichert und kopiert werden.Sie dürfen die Dokumente nicht für öffentliche oder kommerzielle Zwecke vervielfältigen, öffentlich ausstellen, öffentlich zugänglich machen, vertreiben oder anderweitig nutzen.Sofern die Verfasser die Dokumente unter Open-Content-Lizenzen (insbesondere CC-Lizenzen) zur Verfügung gestellt haben sollten, gelten abweichend von diesen Nutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte. Terms of use: Documents in

Human dendritic cells (DCs) are the main antigen presenting cells (APC) and can be divided into two main populations, myeloid and plasmacytoid DCs (pDCs), the latter being the main producers of Type I Interferon. The vast majority of pDCs can be found in lymphoid organs, where the main pool of all immune cells is located, but a minority of pDCs also circulate in peripheral blood. Human cytomegalovirus (HCMV) employs multiple mechanisms to evade the immune system. In this study, we could show that pDCs obtained from lymphoid organs (tonsils) (tpDCs) and from blood (bpDCs) are different subpopulations in humans. Interestingly, these populations react in opposite manner to HCMV-infection. TpDCs were fully permissive for HCMV. Their IFN-α production and the expression of costimulatory and adhesion molecules were altered after infection. In contrast, in bpDCs HCMV replication was abrogated and the cells were activated with increased IFN-α production and upregulation of MHC class I, costimulatory, and adhesion molecules. HCMV-infection of both, tpDCs and bpDCs, led to a decreased T cell stimulation, probably mediated through a soluble factor produced by HCMV-infected pDCs. We propose that the HCMV-mediated impairment of tpDCs is a newly discovered mechanism selectively targeting the host's major population of pDCs residing in lymphoid organs.