Experimental investigation of transitional flow in a toroidal pipe

The flow instability and further transition to turbulence in a toroidal pipe (torus) with curvature (tube-to-coiling diameter) 0.049 is investigated experimentally. The flow inside the toroidal pipe is driven by a steel sphere fitted to the inner pipe diameter. The sphere is moved with constant azimuthal velocity from outside the torus by a moving magnet. The experiment is designed to investigate curved pipe flow by optical measurement techniques. Using stereoscopic particle image velocimetry, laser Doppler velocimetry and pressure drop measurements, the flow is measured for Reynolds numbers ranging from 1000 to 15000. Time- and space-resolved velocity fields are obtained and analysed. The steady axisymmetric basic flow is strongly influenced by centrifugal effects. On an increase of the Reynolds number we find a sequence of bifurcations. For Re=4075 a supercritical bifurcation to an oscillatory flow is found in which waves travel in the streamwise direction with a phase velocity slightly faster than the mean flow. The oscillatory flow is superseded by a presumably quasi-periodic flow at a further increase of the Reynolds number before turbulence sets in. The results are found to be compatible, in general, with earlier experimental and numerical investigations on transition to turbulence in helical and curved pipes. However, important aspects of the bifurcation scenario differ considerably

The Airplane in Unit Sampling of Mule Deer Populations in Harding County, South Dakota

The prairie deer region of South Dakota extends west from the Missouri River to the Black Hills. The region borders the states of Nebraska, Wyoming, Montana, and North Dakota, and is approximately 40,000 square miles in extent. Biologists believe that present deer numbers on these prairies are similar to those of pre-homestead days. The present large numbers of deer in certain counties have given many prairie ranchers and farmers cause for concern. The region\u27s first deer season (bucks only) in 1952 resulted from earlier increases in mule and whitetail herds. After a closed season in 1953, a hunter\u27s choice of any deer for 9 days was in force in 1954, and nearly 5,000 deer were killed throughout the region. This type of hunt was changed to bucks only in 1955 for the same length season. The 3 recent harvests on the prairies increased South Dakota\u27s big-game hunting area from about 3,500 square miles in the Black Hills to nearly 30,000 square miles. Some counties had no open season during the 3 previous harvests

Subcritical versus supercritical transition to turbulence in curved pipes

Transition to turbulence in straight pipes occurs in spite of the linear stability of the laminar Hagen--Poiseuille flow if the amplitude of flow perturbations as well as the Reynolds number exceed a minimum threshold (subcritical transition). As the pipe curvature increases centrifugal effects become important, modifying the basic flow as well as the most unstable linear modes. If the curvature (tube-to-coiling diameter $d/D$) is sufficiently large a Hopf bifurcation (supercritical instability) is encountered before turbulence can be excited (subcritical instability). We trace the instability thresholds in the $Re-d/D$ parameter space in the range $0.01\leq\ d/D \leq0.1$ by means of laser-Doppler velocimetry and determine the point where the subcritical and supercritical instabilities meet. Two different experimental setups were used: a closed system where the pipe forms an axisymmetric torus and an open system employing a helical pipe. Implications for the measurement of friction factors in curved pipes are discussed

European populations of Diabrotica virgifera virgifera are resistant to aldrin, but not to methyl-parathion

The western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of cultivated corn in North America and has recently begun to invade Europe. In addition to crop rotation, chemical control is an important option for D. v. virgifera management. However, resistance to chemical insecticides has evolved repeatedly in the USA. In Europe, chemical control strategies have yet to be harmonized and no surveys of insecticide resistance have been carried out. We investigated the resistance to methyl-parathion and aldrin of samples from nine D. v. virgifera field populations originating from two European outbreaks thought to have originated from two independent introductions from North America. Diagnostic concentration bioassays revealed that all nine D. v. virgifera field populations were resistant to aldrin but susceptible to methyl-parathion. Aldrin resistance was probably introduced independently, at least twice, from North America into Europe, as there is no evident selection pressure to account for an increase of frequency of aldrin resistance in each of the invasive outbreaks in Europe. Our results suggest that organophosphates, such as methyl-parathion, may still provide effective control of both larval and adult D. v. virgifera in the European invasive outbreaks studied

Weight Gain in College Freshmen: Emerging Adulthood and Health Responsibility

Background and Purpose: College freshmen gain weight at double the rate of same-age peers, and personal, interpersonal, and situational factors play a role in this phenomenon. The objectives of the study were to quantify weight change in first semester college students and to identify predictors of weight gain. Methods: In fall 2011, 76 unmarried freshmen, living in dormitories at a public, southwestern U.S. university, participated in the study. Heights and weights were measured at the beginning and end of the semester, and an on-line survey was administered at both times. Results: In the first semester of college, 43% gained clinically significant weight (> 3.5 pounds) and 15% gained more than 10 pounds. The group at highest risk was students with a normal BMI; 50% of this cohort gained clinically significant weight. Two variables predicted 12% of weight gain: a low level of health responsibility and a normal BMI. Conclusion: For college freshmen at highest risk of precipitous weight gain, health promotion strategies aimed at maximizing health responsibility is needed. Additionally, an integration of mediating influences related to the developmental stage of emerging adulthood, such as perceived social norms, positive peer influence and self-efficacy may result in improved long-term lifestyle practices

Releases and first recovery of Lathrolestes ensator (Hymenoptera: Ichneumonidae) in North America, a parasitoid of Hoplocampa testudinea (Hymenoptera: Tenthredinidae)

The European apple sawfly, Hoplocampa testudinea (Klug), is a pest of apple, Malus pumila Bork. (Rosaceae), in orchards. Introduced from Europe onto Long Island, New York, in 1939, it gradually invaded the New England states (Pyenson 1943). Downes and Andison (1942) also reported the apple sawfly on Vancouver Island in 1940. In 1979, H. testudinea was discovered for the first time in southern Quebec (Paradis 1980), after which it spread throughout the apple-growing areas of this province (Vincent and Mailloux 1988). There are no published records on any natural enemies of H. testudinea in North Americ

Assessing flood risk for a rural detention area

International audienceFlood detention areas serve the primary purpose of controlled water storage during large flood events in order to decrease the flood risk downstream along the river. These areas are often used for agricultural production. While various damage estimation methods exist for urban areas, there are only a few, most often simpler approaches for loss estimation in rural areas. The loss assessment can provide an estimate of the financial provisions required for the farmers' compensation (e.g., in the context of cost-benefit analyses of detention measures). Flood risk is a combination of potential damage and probability of flooding. Losses in agricultural areas exhibit a strong seasonal pattern, and the flooding probability also has a seasonal variation. In the present study, flood risk is assessed for a planned detention area alongside the Elbe River in Germany based on two loss and probability estimation approaches of different time frames, namely a monthly and an annual approach. The results show that the overall potential damage in the proposed detention area amounts to approximately 40 000 ? a?1, with approximately equal losses for each of the main land uses, agriculture and road infrastructure. A sensitivity analysis showed that the probability of flooding (i.e., the frequency of operation of the detention area) has the largest impact on the overall flood risk

Experimental investigation of transitional flow in a toroidal pipe

The flow instability and further transition to turbulence in a toroidal pipe (torus) with curvature ratio (tube-to-coiling diameter) 0.049 is investigated experimentally. The flow inside the toroidal pipe is driven by a steel sphere fitted to the inner pipe diameter. The sphere is moved with constant azimuthal velocity from outside the torus by a moving magnet. The experiment is designed to investigate curved pipe flow by optical measurement techniques. Using stereoscopic particle image velocimetry, laser Doppler velocimetry and pressure drop measurements, the flow is measured for Reynolds numbers ranging from 1000 to 15 000. Time- and space-resolved velocity fields are obtained and analysed. The steady axisymmetric basic flow is strongly influenced by centrifugal effects. On an increase of the Reynolds number we find a sequence of bifurcations. For $\mathit{Re}= 4075\pm 2\hspace{0.167em} \%$ a supercritical bifurcation to an oscillatory flow is found in which waves travel in the streamwise direction with a phase velocity slightly faster than the mean flow. The oscillatory flow is superseded by a presumably quasi-periodic flow at a further increase of the Reynolds number before turbulence sets in. The results are found to be compatible, in general, with earlier experimental and numerical investigations on transition to turbulence in helical and curved pipes. However, important aspects of the bifurcation scenario differ considerabl

Affective-semantic integration of bivalent words

Single words have affective and aesthetic properties that influence their processing. Here we investigated the processing of a special case of word stimuli that are extremely difficult to evaluate, bivalent noun-noun-compounds (NNCs), i.e. novel words that mix a positive and negative noun, e.g. ‘Bombensex’ (bomb-sex). In a functional magnetic resonance imaging (fMRI) experiment we compared their processing with easier-to-evaluate non-bivalent NNCs in a valence decision task (VDT). Bivalent NNCs produced longer reaction times and elicited greater activation in the left inferior frontal gyrus (LIFG) than non-bivalent words, especially in contrast to words of negative valence. We attribute this effect to a LIFG-grounded process of semantic integration that requires greater effort for processing converse information, supporting the notion of a valence representation based on associations in semantic networks