Overflow Characteristics of Circular Weirs : Effect of Inflow Conditions

The most common types of weirs are the broad-crested weir, the sharp-crested weir, the circular-crested weir and nowadays the ogee crest weir. Advantages of the cylindrical weir shape include the stable overflow pattern, the ease to pass floating debris, the simplicity of design compared to ogee crest design and the associated lower costs. In this study, the authors describe new experiments of circular weir overflows, with eight cylinder sizes, for several weir heights and for five types of inflow conditions : partially-developed inflow, fully-developed inflow, upstream ramp, upstream undular hydraulic jump and upstream (breaking) hydraulic jump. Within the range of the experiments, the cylinder size, the weir height D/R and the presence of an upstream ramp had no effect on the discharge coefficient, flow depth at crest and energy dissipation. But the inflow conditions had substantial effects on the discharge characteristics and flow properties at the crest. Practically the results indicate that discharge measurements with circular weirs are significantly affected by the upstream flow conditions

Characteristics of Undular Hydraulic Jumps: Experimental Apparatus and Flow Patterns

In open channels, the transition from supercritical to subcritical flows is called a hydraulic jump. For low upstream Froude numbers, free-surface undulations develop downstream of the jump and the hydraulic jump is called an undular jump. New experiments on undular hydraulic jumps were performed in a rectangular channel in which the upstream flows were fully developed turbulent shear flows. In this paper, the main flow patterns are described. Visual and photographic observations indicate five types of undular jumps. One of the main flow characteristics is the presence of lateral shock waves for Froude numbers larger than 1.2. The results show that the disappearance of undular jump occurs for Froude numbers ranging from 1.5 to 2.9 and that the wave length and amplitude of the free-surface undulations are functions of the upstream Froude number and the aspect ratio yc/W

Overflow Characteristics of Cylindrical Weirs

The most common types of weirs are the broad-crested weir, the sharp-crested weir, the circular-crested weir and nowadays the ogee crest weir. Advantages of the cylindrical weir shape include the stable overflow pattern, the ease to pass floating debris, the simplicity of design compared to ogee crest design and the associated lower costs. Related applications include roller gates and inflated rubber dams. In this report, the authors describe new experiments of circular weir overflows, with eight cylinder sizes, for several weir heights and for five types of inflow conditions : partially-developed inflow, fully-developed inflow, upstream ramp, upstream undular hydraulic jump and upstream (breaking) hydraulic jump. Within the range of the experiments, the cylinder size, the weir height D/R and the presence of an upstream ramp had no effect on the discharge coefficient, flow depth at crest and energy dissipation. But the inflow conditions had substantial effects on the discharge characteristics and flow properties at the crest

Characteristics of Undular Hydraulic Jumps. Experimental Apparatus and Flow Patterns

The authors thank the discussers for their interest on the topic and for some new photographic information. They wish to highlight some important points and indicate that additional photographic evidence on their work can be found in CHANSON (1993,1995a,1995b)

Dynamics of two interacting particles in classical billiards

The problem of two interacting particles moving in a d-dimensional billiard is considered here. A suitable coordinate transformation leads to the problem of a particle in an unconventional hyperbilliard. A dynamical map can be readily constructed for this general system, which greatly simplifies calculations. As a particular example, we consider two identical particles interacting through a screened Coulomb potential in a one-dimensional billiard. We find that the screening plays an important role in the dynamical behavior of the system and only in the limit of vanishing screening length can the particles be considered as bouncing balls. For more general screening and energy values, the system presents strong non-integrability with resonant islands of stability.Comment: REVTEX manuscript, 4 figures (1 ps + 3 gif, Postscript versions available upon request). Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.htm

Análisis ecológica y comparativa de parásitos en juveniles de Mugil liza (Pisces, Mugilidae) de dos sitios en la baía Samborombón, Argentina

Mugil liza Valenciennes, 1836 is an economically important food fish and has been recommended for aquaculture in South America. A total of 278 fishes were collected in the spring and summer of 2009 and 2010. These fish were sorted into sample groups according to their size class. We used Bayesian statistics and 95% credible intervals for each parameter tested were calculated. Fish studied harbored a total of 15 different species of parasites. Diversity of parasite species found on Mugilliza was greatest at the S.R.C. collection site, but evidenced a lower species richness than at A.R. site. The 1st size fishes of both sites evidenced greater parasite diversity than either 2nd or 3rd size fish. Differences observed could be explained by the different use of habitat types at the two sites or differential susceptibility to infection by parasites. The dominance of D. fastigata influenced observed results of lower community diversity indexes. New works elucidating different parasite life cycles within juvenile and adults of M. liza in Argentina, promise to be important for determining the risk of the parasitism by zoonotic metacercariae A. (P.) longa and use of this fish as food and an economic resource, and the possible use of mullet parasites in other promising fields as indicators of biodiversity, and/ or water contamination.Mugil liza, Valenciennes, 1836 es un pez de importancia comercial y ha sido recomendado en Sudamerica para la acuicultura. Los peces se distribuyeron en grupos de acuerdo con la talla. Usamos estadística Bayesiana e intervalos de credibilidad del 95% para cada parámetro calculado. Los peces alojaron un total de 15 especies parasitarias. La diversidad de las especies parásitas de M. liza fue mayor en el sitio de colecta S.R.C., pero evidencio una menor riqueza especifica que en A.R. La 1er talla de los peces de ambos sitios evidencio una mayor diversidad parasitaria que la 2da o 3er talla. Las diferencias observadas se pueden explicar por un uso diferente del hábitat en los dos sitios o a una susceptibilidad diferente a la infección por los parásitos. La influencia de la dominancia de D. fastigata resulta en el menor índice de diversidad de la comunidad. Nuevos trabajos que diluciden los diferentes ciclos de vida de los parásitos en los juveniles y adultos de M. liza en Argentina, prometen ser importantes para determinar el riesgo del parasitismo de la metacercaria zoonotica A. (P.) longa y el uso de este pez como alimento, una fuente económica y el posible uso de los parásitos de la lisa en otros promisorios campos como indicadores de biodiversidad y/o contaminación acuática.Centro de Estudios Parasitológicos y de Vectore

Un análisis bayesiano de la ecología parasitaria ein Jenynsia multidentata (Pisces: Anablepidae)

Jenynsia multidentata Jenyns, 1842 (one-sided livebearers) are euryhaline viviparous fish of small size, used in the laboratory experiment, important as resource for biological control of mosquito’s larva and a key species to recover eutrophic lakes. Works have been published dealing with parasite biodiversity of this host, but little has been studied about the parasite community ecology. From early 2009 to ends of 2010 specimens of J. multidentata were collected from two places, the Salado Relief Channel (S.R.C.) on Samborombon Bay and the Sauce Chico River near to the city of Bahia Blanca (B.B.). All fish were sexed, measured and grouped into sizes/age classes. The fishes from both sites harbored 16 parasitic species: nine digenean, one monogenean, one metacestode, one acanthocephalan, two nematode and two copepods. Lecithaster confusus Odhner, 1905, the metacercariae Hemiuridae gen. sp. indet., metacercariae Thylodelphys sp. (inside the eye), Glossocercus sp. nematode L4 (intestine) and Ergasilus sieboldii Nordmann, 1832 are new records for the host. The high number of larval stages made of this fish a link between micro and macroecosystems. The size 2 had the higher biodiversity in both sites, which could be the most suitable age to store the maximal number of parasite of the environment and have a more equitability in their distribution on the host. In B.B. some parasites had higher prevalence and mean abun dance due to the small size of the waterbody compared with the S.R.C. Despite that, in S.R.C. exist a higher specific richness and biodiversity due the daily flow of saline and freshwater and proximity of the sample site to the mouth of the channel in the bay. This is the first approximation to an analysis of the parasitic ecology on this host.Jenynsia multidentata Jenyns, 1842 (madrecitas) son peces viviparous, eurihalinos de pequeño tamaño usados en experimientos de laboratorio, como un recurso importante para el control biológico de larvas de mosquito y una especie clave para recuperar lagos eutrofizados. Han sido publicados varios trabajos acerca de la biodiversidad parasitaria de este pez pero poco es conocido acerca de la ecología de la comunidad parasitaria de este hospedador. pero poco se conoce acerca de su ecología parasitaria. Durante los meses de primavera y verano en el 2009 y 2010, especímenes de J. multidentata se colectaron del Canal Colector del Salado (S.R.C.) en la Bahía de Samborombon y del Rio Sauce Chico cercano a la ciudad de Bahía Blanca (B.B.), fueron sexados, medidos y agrupados en clases según su tamaño/edad. Los peces de los dos sitios albergaron 16 especies de parásitos: nueve digeneos, un monogeneo, un cestodo, un acantocéfalo, dos nematodos y dos copépodos. Lecithaster confusus Odhner, 1905, la metacercaria Hemiuridae gen. sp. indet., metacercaria Thylodelphys sp. (en el ojo), Glossocercus sp. nematode L4 (intestino) y de Ergasilus sieboldii Nordmann, 1832 son nuevas citas para el hospedador. El gran número de estadios larvales hacen de este pez un nexo entre micro y macroecosistemas. La talla 2 tuvo una mayor biodiversidad en ambos sitios, la cual puede ser la edad más apropiada para recolectar el máximo número de parásitos del ambiente y tener una distribución dentro del hospedador de mayor equitabilidad. En B.B. algunos parasitos tuvieron mayor pre valencia y abundancia media debido al menor tamaño del cuerpo de agua comparado con S.R.C. A pesar de esto, en S.R.C. existe una mayor riqueza específica y biodiversidad debido al flujo diario de agua dulce y salina y a la proximidad del sitio de muestreo a la desembocadura del canal en la Bahía. El gran número de parásitos en los machos puede deberse a un cambio en el uso de la energía que se focaliza en la reproducción. Esta es la primera aproximación a un análisis de la ecología parasitaria de este hospedador y, como resultado, podemos ver algún tipo de influencia del mismo que no debe ser ignorado y debería ser estudiado en el futuro considerando cada parasito como la interrelación entre ellos y el hospedador.Centro de Estudios Parasitológicos y de VectoresFacultad de Ciencias Naturales y Muse

Individual and Environmental Factors Associated with Tobacco Smoking, Alcohol Abuse and Illegal Drug Consumption in University Students: A Mediating Analysis

[Abstract] Substance abuse is a major and prevalent public health concern among university students. Tobacco smoking, risky alcohol behavior, and illegal drug consumption may lead to health problems and behavioral and academic issues. Several individual and environmental factors associate with substance abuse in this population, and the mediating effect of alcohol abuse in the relationship between tobacco smoking and drug consumption is yet to be explored. The purposes of this study were to evaluate the association of individual and environmental factors and substance use, and to analyze the relationship between tobacco smoking, alcohol abuse, and drug consumption, considering alcohol abuse as a possible mediator. A total of 550 Spanish undergraduate and postgraduate students completed several questionnaires regarding their smoking status, alcohol use, and drug consumption during the last six months. Bivariate and multivariate analyses were conducted to explore associations between factors. Direct, indirect and mediating effects were tested using a partial least squares approach (PLS-SEM). The results indicated that substance abuse is associated with being male, living with other students, and combined substance consumption. PLS-SEM showed a significant effect of tobacco smoking and alcohol abuse on drug consumption. Alcohol abuse plays a mediating role in the relationship between tobacco smoking and drug use

Sensory processing patterns in developmental coordination disorder, attention deficit hyperactivity disorder and typical development

[Abstract] Background. Sensory processing difficulties (SPD) are present in children with Developmental Coordination Disorder (DCD) and Attention Deficit and Hyperactivity Disorder (ADHD). However, little is known about sensory processing variability in these disorders. Objective. The purpose of this study was to explore SPD among children with DCD, ADHD and co-occurring symptoms in comparison to children with typical development (TD) and to determine how potential social confounders may influence these associations. Methods. The study involved 452 children aged 6–12 years. The Short Sensory Profile-2 was used to assess sensory processing patterns. Multiple linear regressions were utilized to investigate the relationship between DCD, ADHD and co-occurring symptoms and sensory processing patterns, adjusting for social covariates. Results. Children with DCD and ADHD symptoms showed greater variability of atypical sensory processing patterns compared with TD children. Low registration and sensory sensibility issues were more prevalent in the DCD group. ADHD children showed higher rates of low registration, sensory sensibility and sensory seeking, and all children in the co-occurring symptoms group presented sensory sensibility. Conclusion. This study reports significant variability in sensory processing among children with DCD, ADHD and co-occurring symptoms using a population-based sample. These differences can contribute to understand how neurological and social factors correlates across diagnoses.Xunta de Galicia; ED481A-2018/15