Periodically driven Taylor-Couette turbulence

We study periodically driven Taylor-Couette turbulence, i.e. the flow confined between two concentric, independently rotating cylinders. Here, the inner cylinder is driven sinusoidally while the outer cylinder is kept at rest (time-averaged Reynolds number is $Re_i = 5 \times 10^5$). Using particle image velocimetry (PIV), we measure the velocity over a wide range of modulation periods, corresponding to a change in Womersley number in the range $15 \leq Wo \leq 114$. To understand how the flow responds to a given modulation, we calculate the phase delay and amplitude response of the azimuthal velocity. In agreement with earlier theoretical and numerical work, we find that for large modulation periods the system follows the given modulation of the driving, i.e. the system behaves quasi-stationary. For smaller modulation periods, the flow cannot follow the modulation, and the flow velocity responds with a phase delay and a smaller amplitude response to the given modulation. If we compare our results with numerical and theoretical results for the laminar case, we find that the scalings of the phase delay and the amplitude response are similar. However, the local response in the bulk of the flow is independent of the distance to the modulated boundary. Apparently, the turbulent mixing is strong enough to prevent the flow from having radius-dependent responses to the given modulation.Comment: 12 pages, 6 figure

Carbon monoxide transfer in pig lungs during mechanical ventilation

This thesis comprises studies of gas transfer in the lungs during mechanical ventilation, which have been obtained in healthy pigs. The objectives of this thesis were: I) to adapt the breath-holding teclmique, as used during spontaneous breathing for estimation of gas transfer, to conditions of mechanical ventilation; and 2) to evaluate the effect of changes in lung volume on pulmonary gas transfer and capillary blood volume

The Flynn effect in Korea: large gains

Secular gains in IQ test scores have been reported for many Western countries. This is the first study of secular IQ gains in South Korea, using various datasets. The first question is what the size of the Flynn effect in South Korea is. The gains per decade are 7.7 points for persons born between 1970 and 1990. These gains on broad intelligence batteries are much larger than the gains in Western countries of about 3 IQ points per decade. The second question is whether the Korean IQ gains are comparable to the Japanese IQ gains with a lag of a few decades. The gains in Japan of 7.7 IQ points per decade for those born approximately 1940 1965 are identical to the gains per decade for Koreans born 1970 1990. The third question is whether the Korean gains in height and education lag a few decades behind the Japanese gains. The Koreans reach the educational levels the Japanese reached 25 30 years before, and the gains in height for Koreans born 1970 1990 are very similar to gains in height for Japanese born 1940 1960, so three decades earlier. These findings combined strongly support the hypothesis of similar developmental patterns in the two countries

Are cognitive differences between immigrant and majority groups diminishing?

A review is given of scores on various cognitive measures, comparing groups of ethnic Dutch and non-Western immigrants using a large number of datasets. The research shows that there are large group differences in school results, work proficiency, and g for Turks, Moroccans, Surinamese, Netherlands Antilleans, and Indonesians from the Moluccans compared with ethnic Dutch. However, South-East Asians score higher, and persons with one immigrant and one ethnic Dutch parent score only slightly below the mean of the Dutch. When comparing first-generation disadvantaged immigrant groups with later generations the data show substantial improvements for g, a remarkable stability of educational differences for younger children, and a clear improvement in educational achievement at the end of primary school. Indirect data on intergenerational improvements in work proficiency appear suggestive of a trend of closing gaps. Some of the data reflect higher cognitive capacities over time, and this enhances integration of immigrants into Dutch society. Causes of group differences and improvements in mean level of g are discussed. Copyright © 2004 John Wiley & Sons, Ltd

The Myth of the Stupid Believer: The Negative Religiousness–IQ Nexus is Not on General Intelligence (g) and is Likely a Product of the Relations Between IQ and Autism Spectrum Traits

Numerous studies have found a negative relationship between religiousness and IQ. It is in the region of −0.2, according to meta-analyses. The reasons for this relationship are, however, unknown. It has been suggested that higher intelligence leads to greater attraction to science, or that it helps to override evolved cognitive dispositions such as for religiousness. Either way, such explanations assume that the religion–IQ nexus is on general intelligence (g), rather than some subset of specialized cognitive abilities. In other words, they assume it is a Jensen efect. Two large datasets comparing groups with diferent levels of religiousness show that their IQ diferences are not on g and must, therefore, be attributed to specialized abilities. An analysis of the specialized abilities on which the religious and non-religious groups difer reveals no clear pattern. We cautiously suggest that this may be explicable in terms of autism spectrum disorder traits among people with high IQ scores, because such traits are negatively associated with religiousness

Does cultural background influence the intellectual performance of children from immigrant groups?

This paper addresses both the construct validity and the criterion-related validity of the "Revisie Amsterdamse Kinder Intelligentie Test" (RAKIT), which is a cognitive ability test developed for primary school children. The present study compared immigrant primary school children (N = 559) and Dutch children (N = 604). The mean scores of Surinamese/Netherlands Antillean, Moroccan, and Turkish children differed from each other and were lower than those of the Dutch children. Comparison of the test dimensions showed that group differences with respect to the construct validity were small. We found some item bias, but the combined effects on the sum score were not large. The estimate of general intelligence (g) as computed with the RAKIT showed strong predictive validity for most school subjects and standardized achievement tests. Although some criteria revealed significant prediction bias, the effects were very small. Most of the analyses we performed on differences in test scores and differences in criterion scores supported Spearman's hypothesis that g is the predominant factor determining the size of the differences between two groups. The conclusion that the RAKIT can be used for the assessment of groups from various backgrounds seems warranted

The Role of Thrombin in Proliferative Vitreoretinopathy

PURPOSE. To determine the role of thrombin in the development of proliferative vitreoretinopathy (PVR). METHODS. Vitreous was collected from patients undergoing a vitrectomy (macular holes and puckers, n ¼ 11 [controls]; retinal detachment without PVR development following vitrectomy, n ¼ 15 [RRD1]; retinal detachment with PVR development within 6 months after vitrectomy, n ¼ 11 [RRD2]; and established PVR, n ¼ 14 [PVR]). Thrombin activity in vitreous was determined using a thrombin-specific chromogenic substrate. ARPE-19 cells were stimulated with 83 diluted vitreous samples in the presence and absence of hirudin. The samples were analyzed at t ¼ 0 and t ¼ 24 hours for the presence of 27 cytokines/ chemokines and growth factors using a multiplex approach. In comparable studies, ARPE-19 cells were stimulated for 2 hours, and mRNA expression levels for CCL2, CXCL8, GMCSF, IL6, and PDGFB were determined by real-time quantitative (RQ)-PCR. RESULTS. Thrombin activity was significantly (P < 0.05) higher in vitreous of the PVR group compared to the other groups. Proliferative vitreoretinopathy vitreous stimulated the production of chemokine (C-C motif) ligand (CCL)2, chemokine (C-X-C motif) ligand (CXCL)8, granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-6, and plateletderived growth factor (PDGF)-BB by ARPE-19 to significantly (P < 0.05) higher levels than vitreous from the RRD1 and RRD2 groups. These effects of PVR vitreous were significantly (P < 0.05) reduced by hirudin. These data were confirmed by mRNA studies. CONCLUSIONS. Thrombin activity is increased in vitreous of patients with established PVR and is involved in the activation of proinflammatory and profibrotic pathways in RPE cells. Inhibition of thrombin activity may therefore represent a potential treatment option for proliferative vitreoretinopathy

A fluorescence approach to investigate repartitioning of coalescing agents in acrylic polymer emulsions

Repartitioning of co-solvents between particles of latex emulsions was investigated by means of a fluorescence method based on the detection of the amount of co-solvent via the solvatochromic shift of the emission maximum of a fluorescent probe, copolymerized at a low concentration. Complete repartitioning of co-solvents between particles of latex materials with a low Tg (ca. 25 °C) occurred within minutes. For a hydrophilic latex with a Tg of 68 °C, equilibration was achieved within an hour. Repartitioning was faster for more hydrophobic co-solvents. For a hydrophobic latex of similar Tg, co-solvent repartitioning took place on the same time scale, but complete equilibration was not reached. Possibly, there is an additional slow component in the repartitioning, or the prolonged presence of co-solvent causes a structural change in the latex particles that affects the outcome of the experiment