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Trypanosoma cruzi Discrete Typing Units in Chagas disease patients from endemic and non-endemic regions of Argentina
- C. I. CURA, R. H. LUCERO, M. BISIO, E. OSHIRO, L. B. FORMICHELLI, J. M. BURGOS, S. LEJONA, B. L. BRUSÉS, D. O. HERNÁNDEZ, G. V. SEVERINI, E. VELAZQUEZ, T. DUFFY, E. ANCHART, R. LATTES, J. ALTCHEH, H. FREILIJ, M. DIEZ, C. NAGEL, C. VIGLIANO, L. FAVALORO, R. R. FAVALORO, D. E. MERINO, S. SOSA-ESTANI, A. G. SCHIJMAN
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- Journal:
- Parasitology / Volume 139 / Issue 4 / April 2012
- Published online by Cambridge University Press:
- 06 February 2012, pp. 516-521
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Genetic diversity of Trypanosoma cruzi may play a role in pathogenesis of Chagas disease forms. Natural populations are classified into 6 Discrete Typing Units (DTUs) Tc I-VI with taxonomical status. This study aimed to identify T. cruzi DTUs in bloodstream and tissue samples of Argentinean patients with Chagas disease. PCR-based strategies allowed DTU identification in 256 clinical samples from 239 Argentinean patients. Tc V prevailed in blood from both asymptomatic and symptomatic cases and Tc I was more frequent in bloodstream, cardiac tissues and chagoma samples from immunosuppressed patients. Tc II and VI were identified in a minority of cases, while Tc III and Tc IV were not detected in the studied population. Interestingly, Tc I and Tc II/VI sequences were amplified from the same skin biopsy slice from a kidney transplant patient suffering Chagas disease reactivation. Further data also revealed the occurrence of mixed DTU populations in the human chronic infection. In conclusion, our findings provide evidence of the complexity of the dynamics of T. cruzi diversity in the natural history of human Chagas disease and allege the pathogenic role of DTUs I, II, V and VI in the studied population.
Inconsistencies in bioelectrical impedance and anthropometric measurements of fat mass in a field study of prepubertal children
- Mareike Mast, A. Sönnichsen, K. Langnäse, K. Labitzke, U. Bruse, U. Preuß, M. J. Müller
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- Journal:
- British Journal of Nutrition / Volume 87 / Issue 2 / February 2002
- Published online by Cambridge University Press:
- 09 March 2007, pp. 163-175
- Print publication:
- February 2002
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The present study examined the consistency of bioelectrical impedance analysis (BIA) and anthropometric measurements in body composition analysis in a field study of prepubertal children using a representative group of 2286 5–7-year-old children from Kiel, north-west Germany. Body composition was assessed using anthropometric measures (A; four skinfolds) and BIA. Various published algorithms (according to and for A, , and for BIA and for a combined approach) were used to estimate body composition. Using A resulted in a sum of four skinfolds varying between age-dependent median values of 24·0 and 28·2 mm in boys and 30·5 and 33·3 mm in girls. When fat mass (FM) was calculated from A, age- and algorithm-dependent differences in median values were observed, with values varying between 8·5 and 14·6 % for boys and 11·1 and 14·9 % for girls. Using different algorithms ( v. ) only minor inconsistencies were observed. BIA-derived resistance index (height2/resistance) varied between 18·8 and 24·4 cm2/Ω for boys and 17·1 and 19·0 cm2/Ω for girls. Using four different algorithms to estimate FM from BIA data resulted in high intra-individual variances in percentage FM (from 13·8 to 33·4) as well as in the prevalence of overweight (from 14·7 to 98·4 % for boys and from 42·3 to 98·5 % for girls). Data obtained using the different BIA algorithms showed some, or even marked, inconsistencies as well as systematic deviations (an overestimation of FM at low percentage FM, v. ). When comparing BIA with A, BIA systematically overestimated FM. The differences between the results were influenced by BMI, gender and height. Considerable inconsistencies were observed at low BMI (<10th percentile) for girls and for small children. Although the within-observer as well as between-observer CV for both techniques are acceptable, we recommend caution in relation to the algorithms used for data analysis. The use of an interchange table of percentage FM derived from different algorithms for different percentile groups of skinfold thicknesses is recommended.
Experiments on drag-reducing surfaces and their optimization with an adjustable geometry
- D. W. BECHERT, M. BRUSE, W. HAGE, J. G. T. VAN DER HOEVEN, G. HOPPE
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- Journal:
- Journal of Fluid Mechanics / Volume 338 / 10 May 1997
- Published online by Cambridge University Press:
- 10 May 1997, pp. 59-87
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Previous research has established that surfaces with tiny ribs (riblets) aligned in the streamwise direction can reduce the turbulent wall-shear stress below that of a smooth surface. Typical skin-friction reductions have been found to be about 5%. The results of the present investigation, however, demonstrate a considerable improvement over this value. This improvement is achieved by a systematic experimental optimization which has been guided by theoretical concepts.
A key feature of our experiments is the utilization of an oil channel. Previous experiments in wind tunnels had to contend with very small riblet dimensions which typically had a lateral rib spacing of about 0.5 mm or less. By contrast, in our oil channel, the ribs can have a lateral spacing of between about 2 and 10 mm. This increased size of the surface structures enables test surfaces to be manufactured with conventional mechanical methods, and it also enables us to build test surfaces with adjustable geometry. In addition, the Berlin oil channel has a novel shear stress balance with an unprecedented accuracy of ±0.3%. This latter feature is a prerequisite for a systematic experimental optimization.
In the present investigation, surfaces with longitudinal ribs and additional slits are studied. The experiments cover a fairly large range of parameters so that the drag reduction potential of a surface with ribs and/or slits is worked out conclusively. A large parameter range is made possible because of the adjustability of the surfaces as well as the automatic operation of the oil channel. In particular, the following tests were run:
(i) Shear stress measurements with conventional riblet configurations, i.e. with triangular and semi-circular grooves, have been carried out. These measurements were necessary in order to establish the connection between our oil channel data and previous data from wind tunnels. As was previously established, we found a drag reduction of about 5%.
(ii) An adjustable surface with longitudinal blade ribs and with slits was built and tested. Both groove depth and slit width could be varied separately and continuously during the experiment. It turned out, that slits in the surface did not contribute to the drag reduction. Nevertheless, these investigations show how perforated surfaces (e.g. for boundary-layer control) can be designed for minimal parasitic drag. On the other hand, with closed slits, an optimal groove depth for the rib surface could be determined, i.e. half of the lateral rib spacing. For this configuration, we found an 8.7% skin-friction reduction. By carefully eliminating deleterious effects (caused by little gaps, etc.), the skin-friction reduction could be improved to a record value of 9.9%.
(iii) A quantitative comparison between theory and experiment was carried out. The theory is based on the assumption that riblets impede the fluctuating turbulent crossflow near the wall. In this way, momentum transfer and shear stress are reduced. The simplified theoretical model proposed by Luchini (1992) is supported by the present experiments.
(iv) For technological applications of riblets, e.g. on long-range commercial aircraft, the above thin-blade ribs are not practical. Therefore, we have devised a surface that combines a significantly improved performance (8.2 %) with a geometry which exhibits better durability and enables previously developed manufacturing methods for plastic riblet film production to be used. Our riblet geometry exhibits trapezoidal grooves with wedge-like ribs. The flat floor of the trapezoidal grooves permits an undistorted visibility through the transparent riblet film which is essential for crack inspection on aircraft.