Purely radiative perfect fluids

We study `purely radiative' (div E = div H = 0) and geodesic perfect fluids with non-constant pressure and show that the Bianchi class A perfect fluids can be uniquely characterized --modulo the class of purely electric and (pseudo-)spherically symmetric universes-- as those models for which the magnetic and electric part of the Weyl tensor and the shear are simultaneously diagonalizable. For the case of constant pressure the same conclusion holds provided one also assumes that the fluid is irrotational.Comment: 12 pages, minor grammatical change

Report on workshop A1: Exact solutions and their interpretation

I report on the communications and posters presented on exact solutions and their interpretation at the GRG18 Conference, Sydney.Comment: 9 pages, no figures. Many typos corrected. Report submitted to the Proceedings of GR18. To appear in CQ

Index Cohesive Force Analysis Reveals That the US Market Became Prone to Systemic Collapses Since 2002

BACKGROUND: The 2007-2009 financial crisis, and its fallout, has strongly emphasized the need to define new ways and measures to study and assess the stock market dynamics. METHODOLOGY/PRINCIPAL FINDINGS: The S&P500 dynamics during 4/1999-4/2010 is investigated in terms of the index cohesive force (ICF--the balance between the stock correlations and the partial correlations after subtraction of the index contribution), and the Eigenvalue entropy of the stock correlation matrices. We found a rapid market transition at the end of 2001 from a flexible state of low ICF into a stiff (nonflexible) state of high ICF that is prone to market systemic collapses. The stiff state is also marked by strong effect of the market index on the stock-stock correlations as well as bursts of high stock correlations reminiscence of epileptic brain activity. CONCLUSIONS/SIGNIFICANCE: The market dynamical states, stability and transition between economic states was studies using new quantitative measures. Doing so shed new light on the origin and nature of the current crisis. The new approach is likely to be applicable to other classes of complex systems from gene networks to the human brain

Institutions and Poverty: A Critical Comment Based on Evolving Currents and Debates

Tebaldi & Mohan (2010, JDS) have established an empirical nexus between institutions and monetary poverty. We first, reflect their findings in light of recent development models, debates and currents in post-2010 literature. We then re-examine their results with a non-monetary and multidimensional poverty indicator first published in 2010. Our findings confirm the negative relationship and the nexus disappears with control for average income. Hence, confirming the conclusions of the underlying study that institutions could have an indirect effect on multidimensional poverty. In other words, the poverty eradication effect of institutions is through income-average as opposed to income-inequality. We discuss the confirmed findings in light of implications to: (1) debates over preferences in economic rights; (2) China’s development/outlook; (3) the Chinese model versus sustainable development; (4) the Fosu conjectures; (5) Piketty’s & Kuznets’ celebrated literatures and (6) future research to ascertain the inequality mechanism

Preliminary Results on Artificial Insemination of Cattle in Suriname. Case Study : Commewijne District

In 1990 and with the help of the European Development Fund, a new and completely equipped Al-station was set up in an attempt to improve the genetic basis of the dairy herd in Suriname. Countering the dramatic decrease in local milkproduction being the main consideration. The author reviews the technical results of three years of Al in the eastern district of Commewijne. The Al-service which was directed from the capital in 1992 and 1993, was decentralised towards the regional veterinary service early 1994. The effects of this decentralisation are also discussed. Technical results realised during the first three years, of Al in the Commewijne district are in general disappointing. Only a small number of dairy farmers makes use of Al, while conception rates are low. The results clearly indicate that heat detection is a major problem, leading to long calving intervals. The kind (breed) of semen used does not influence conception rates. On the other hand, the technical skills of the inseminators involved do influence conception rates. So does the ethnie origin of the farmers involved, although this parameter is closely linked to the scale of the farms and the management level. At first sight, it would seem that decentralisation had a positive effect on technical results. Due to an increase in the number of inseminations performed, the number of Al-calves born increased substantially. Technical results however were inferior to those prior to decentralisation

Ovine toxoplasmosis in Suriname and its possible impact on human infection

This paper reports on the results of a serological survey on toxoplasmosis of sheep in the district of Commewijne, Suriname. A modified agglutination test showed the presence of specifie IgG antibodies to Toxoplasma gondii in 67 % of the 106 samples examined. The seroprevalence was not affected by the origin of the samples, the sex and the breed of the sheep and neither by the presence or absence of cats on the premises. It appears from earlier work that an important proportion of the human population in Suriname is seronegative and thus susceptible to this disease. The results of this survey on sheep are discussed with regard to the zoonotic properties of the disease