School facilities and student achievements: evidence from the Timss

This paper studies the link between school facilities and student achievements in eight countries using data from the TIMSS 2003 database. OLS and propensity score matching is used to control for observable characteristics. Both methods indicate that poor school facilities may be negatively associated with student achievements, but the estimated coefficients are mainly insignificant. Significantly negative estimates are found in only three out of eight countries when using OLS. When using matching on propensity scores I only find significant coefficients in one of the countries.

School building conditions and student achievments: Norwegian evidence

This paper studies the effects from poor school building conditions on student achievements in Norwegian primary schools based on results from national tests in mathematics, English and Norwegian. The benchmark OLS results suggest a negative relationship, but the estimates are mostly insignificant. Further, a municipality fixed effects (MFE) and an instrumental variable approach (IV) is suggested as alternatives to OLS in order to battle potential endogeneity issues due to unobservable characteristics. The results from the OLS and IV procedures are mostly similar to the OLS results.

Temporal coherence length of light in semiclassical field theory models

The following work is motivated by the conceptual problems associated with the wave-particle duality and the notion of the photon. Two simple classical models for radiation from individual emitters are compared, one based on sines with random phasejumps, another based on pulse trains. The sum signal is calculated for a varying number of emitters. The focus lies on the final signal's statistical features quantified by means of the temporal coherence function and the temporal coherence length. We show how these features might be used to experimentally differentiate between the models. We also point to ambiguities in the definition of the temporal coherence length.Comment: 7 pages, 3 figures. The following article has been submitted to AIP Conference Proceedings: Advances in Quantum Theory, Vaxjo 201

The consequences of a hypothetical economic boycott on South Africa

African Studies Seminar series. Paper presented November 1977By a boycott we mean the refusal by persons to deal with one or more other persons. The purpose of the boycott is generally to punish, or induce abandonment of a course of action, by economic pressure. Likewise, an international boycott refers to the refusal of citizens of a state to trade, or enter into other economic relations with the citizens of another state, in order to manifest resentment or bring pressure. A boycott is to be distinguished from measures of economic retortion such as reprisals, sanctions, embargoes or blockades, which are initiated by a government to bring pressure upon a state guilty of unfriendly, reprehensible or illegal behaviour. Boycotts, however, merge into such official procedures if they are encouraged or organized by government....As far as South Africa is concerned, there has been a notable tendency for an increase in the calls for an economic boycott.... An articulate demand for an investment boycott was made last year in a joint statement issued by Chief Gatsha Buthelesi and Dr. C.F. Beyers Naude.... It is not the purpose of this paper to assess the validity of the theologians' reasoning. Suffice it to say that social and economic devastation is a most unlikely scenario from which South Africa will emerge as a peaceful multi-racial society. In my opinion it is rapid economic growth, and NOT the enforced abandonment of prosperous international economic links, which is best suited effectively to further the case of the South African Black. Be this as it may, let us look now at the consequences which a hypothetical economic boycott would have for South Africa

Frequency and phase relations of entangled photons observed by a two-photon interference experiment

An entangled photon experiment has been performed with a large variation of the temperature of the non-linear crystal generating the entangled pair by spontaneous downconversion. The photon pairs are separated by a nonpolarizing beamsplitter, and the polarization modes are mixed by half wave plates. The correlation function of the coincidences is studied as a function of the temperature. In the presence of a narrow interference filter we observe that the correlation changes between -1 and +1 about seven times within a temperature interval of about 30 degrees C. We show that the common simplified single-mode pair representation of entangled photons is insufficient to describe the results, but that the biphoton description that includes frequency and phase details gives close to perfect fit with experimental data for two different choices of interference filters. We explain the main ideas of the underlying physics, and give an interpretation of the two-photon amplitude which provides an intuitive understanding of the effect of changing the temperature and inserting interference filters.Comment: arXiv admin note: text overlap with arXiv:1309.108

Uitbreiding bevoegdheden ter handhaving van de openbare orde en veiligheid

De bevoegdheden van de burgemeester ter handhaving van de openbare orde en veiligheid zijn de laatste tijd fors uitgebreid en er is nog een aantal bevoegdheden in voorbereiding. Deze bevoegdheden moeten de burgemeester in staat stellen snel op te treden tegen ordeverstoringen en onveiligheid. Bijzonder is dat de burgemeester zijn nieuwe bevoegdheden, onder omstandigheden en voorwaarden, preventief kan gebruiken en toepassen op groepen ordeverstoorders. Ook kan hij de bewegingsvrijheid en privacy van betrokkenen flink inperken. Dit betekent dat hij terughoudend en zorgvuldig met die bevoegdheden moet omgaan. Als hij zich te veel profileert als crimefighter, verspeelt hij het vertrouwen als burgervader

Voorzorg en bestuurlijke handhaving

Inleiding In deze bijdrage belicht ik enkele bestuurlijke bevoegdheden ter handhaving van de openbare orde en veiligheid vanuit het perspectief van de voorzorgcultuur, zoals door Pieterman beschreven (Pieterman, 2008). Deze bevoegdheden, waaronder bestuurlijke ophouding, preventief fouilleren, cameratoezicht en gebieds-, samenscholings- en huisverboden, beantwoorden aan een sterke roep om orde en veiligheid in het publieke domein. Ze passen in zekere zin in het voorzorgdenken. Toepassing van deze bevoegdheden is effectief in relatie tot onzekere bedreigingen van de openbare orde en veiligheid. We betalen er wel een hoge prijs voor