Mating Behavior of the Giant Waterbug Belostoma flumineum Say

Sexual selection theory predicts that in the few species where males make a larger parental investment than females and limit female reproduction, females should court and compete for males (i.e. we should observe sex-role reversal --Trivers, 1972). These predictions were tested in the laboratory with the giant waterbug Belostoma flumineum Say (Hemiptera: Belostomatidae) . Males of this species characteristically carry and brood eggs on their dorsa, thus making a substantial parental investment. The courtship sequence in one male:one female pairings began with the male pumping (rapidly raising and lowering his abdomen at the water\u27s surface). This presumably attracted the female, who then moved to and contacted the male. Placing his hind leg over the female\u27s back, the male positioned the female and copulation occurred. Oviposition invariably followed. After the female deposited approximately four eggs, the male forced the female back to copulate again. This cycle continued virtually uninterrupted until the male was approximately 80% encumbered (x̄=102 eggs) . Two male: one female trios were set up to simulate a situation in which access to females limited male reproduction. The same general courtship sequence was observed, with minor variations. The rate of male pumping (i.e. pumps per minute) was significantly higher than in any other sex ratio situation observed. Oviposition frequently did not follow copulation. Both components of sexual selection appeared to be observed: 1) intrasexual selection was seen in males striking at each other, and 2) intersexual selection (i.e. courtship competition) was observed in male pumping displays. A situation in which access to males limited female reproduction was simulated in one male:two female trios. Again, the same general courtship sequence was followed with minor variations. The rate of male pumping did not differ significantly from one male: one female pairings. Oviposition frequently did not follow copulation. Intrasexual selection was observed in the form of a pushing behavior, where one female would attempt to push another female off of the male\u27s back. However, no intersexual selection (i.e. no female courtship) was seen. Thus what is observed may be partial sex-role reversal. Sex roles may rely as much on proximate circumstances as on pre-programmed genetic behaviors. In order to assess preference for or dominance of partially-encumbered males and heavily-gravid females, additional trios were set up. Partially-encumbered males paired with unencumbered males and females did not breed significantly more than the unencumbered males. Heavily-gravid females paired with less-gravid females and males did breed significantly more than the less-gravid females. The manner in which these results relate to sexual selection theory are discussed

Mating Behavior of the Giant Waterbug Belostoma flumineum Say

Sexual selection theory predicts that in the few species where males make a larger parental investment than females and limit female reproduction, females should court and compete for males (i.e. we should observe sex-role reversal --Trivers, 1972). These predictions were tested in the laboratory with the giant waterbug Belostoma flumineum Say (Hemiptera: Belostomatidae) . Males of this species characteristically carry and brood eggs on their dorsa, thus making a substantial parental investment. The courtship sequence in one male:one female pairings began with the male pumping (rapidly raising and lowering his abdomen at the water\u27s surface). This presumably attracted the female, who then moved to and contacted the male. Placing his hind leg over the female\u27s back, the male positioned the female and copulation occurred. Oviposition invariably followed. After the female deposited approximately four eggs, the male forced the female back to copulate again. This cycle continued virtually uninterrupted until the male was approximately 80% encumbered (x̄=102 eggs) . Two male: one female trios were set up to simulate a situation in which access to females limited male reproduction. The same general courtship sequence was observed, with minor variations. The rate of male pumping (i.e. pumps per minute) was significantly higher than in any other sex ratio situation observed. Oviposition frequently did not follow copulation. Both components of sexual selection appeared to be observed: 1) intrasexual selection was seen in males striking at each other, and 2) intersexual selection (i.e. courtship competition) was observed in male pumping displays. A situation in which access to males limited female reproduction was simulated in one male:two female trios. Again, the same general courtship sequence was followed with minor variations. The rate of male pumping did not differ significantly from one male: one female pairings. Oviposition frequently did not follow copulation. Intrasexual selection was observed in the form of a pushing behavior, where one female would attempt to push another female off of the male\u27s back. However, no intersexual selection (i.e. no female courtship) was seen. Thus what is observed may be partial sex-role reversal. Sex roles may rely as much on proximate circumstances as on pre-programmed genetic behaviors. In order to assess preference for or dominance of partially-encumbered males and heavily-gravid females, additional trios were set up. Partially-encumbered males paired with unencumbered males and females did not breed significantly more than the unencumbered males. Heavily-gravid females paired with less-gravid females and males did breed significantly more than the less-gravid females. The manner in which these results relate to sexual selection theory are discussed

Ultrastructure of the coeloms of auricularia larval (\u3cem\u3eHolothuroidea Echinodermata\u3c/em\u3e): evidence for the presence of an axocoel

A hallmark feature of echinoderm larvae is the development of the left anterior coelom. This coelom, called the axohydrocoel, consists of the morphologically distinct, but undivided, left axocel and hydrocel. The axocoelic portion forms a duct that opens to the exterior via a pore on the dorsal surface of the animal. Holothuroid larvae are thought to lack an axocoel, but develop an anterior coelom, duct, and pore that are regarded as parts of the hydrocoel. New ultrastructural data, however, show that holothuroid auricularia larvae possess an axocel and hydrocel united together into an axohydrocoel. During development the anterior coelom consists of an interconnected left somatocoel, hydrocoel, and axocoel. The left somatocoel separates from the axohydrocoel and subdivides into left and right somatocoels. The somatocoels and hydrocoel region of the axohydrocoel are lined by a monociliated mesothelium having characteristics of transporting epithelia. The axocoel epithelium, like that of asteroid larvae, is composed of mesothelial podocytes. A duct connects the axocoel directly to the open dorsal pore and is lined with a columnar transporting epithelium. The occurrence of a specialized podocyte-lined cavity between the surface pore and the hydrocoel in echinoderm larvae is indicative of an axocoel. That similar structures occur in auricularia larvae supports the identification of an axocoel in holothuroids

Academic Supports Preferred by Academically Struggling African American Students at a Predominantly White University

Academic supports offered by Predominately White Institutions (PWIs) meet the needs of individuals who achieve standards such as high grade point averages and high standardized test scores, and who can negotiate traditional college institutions. Evidence indicates that retention and graduation rates for underrepresented minority students may be lower in comparison to White peers at the same institutions. Observations indicated that academic supports offered by a Midwestern PWI, may not provide the services preferred by African American students who struggle academically in two colleges, the College of Education and the College of Nursing. A mixed-methods design was used to determine what academic supports were known and being used by academically struggling African American students at a PWI. Survey questions and interviews focused on gaining understandings of student preferences for academic supports in a population of academically struggling African American students. These results may be used to design academic supports for struggling African American students and may be generalized to PWIs of similar demographics and socio-cultural settings. Application of the results to academic support design may improve retention and graduation rates for this student group. Students requested increased interaction with faculty, late night or 24-hour tutoring services, assistance with time management, more social media to assist with reminders about assignments and class projects, and assistance with technology and online classes. Some differences were noted between what was recorded in the literature and the results of this study in the areas of study groups, same ethnicity faculty, group membership and mentoring

Elastic Convection in Vibrated Viscoplastic Fluids

We observe a new type of behavior in a shear thinning yield stress fluid: freestanding convection rolls driven by vertical oscillation. The convection occurs without the constraint of container boundaries yet the diameter of the rolls is spontaneously selected for a wide range of parameters. The transition to the convecting state occurs without hysteresis when the amplitude of the plate acceleration exceeds a critical value. We find that a non-dimensional stress, the stress due to the inertia of the fluid normalized by the yield stress, governs the onset of the convective motion.Comment: 4 pages, 6 figure

Modeling And Control Of A Three-phase Isolated Grid-connected Converter For Photovoltaic Applications

This paper describes the modeling and control of a three-phase grid-connected converter fed by a photovoltaic array. The converter is composed of an isolated DC-DC converter and a three-phase DC-AC voltage source inverter The converters are modeled in order to obtain small-signal transfer functions that are used in the design of three closed-loop controllers: for the output voltage of the PV array, the DC link voltage and the output currents. Simulated and experimental results are presented.223215228Barbosa, P.G., Rolim, L.G.B., Watanabe, E.H., Hanitsch, R., Control strategy for grid-connected DC-AC converters with load power factor correction (1998) IEE Proceedings: Generation, Transmission and Distribution, 145 (5), pp. 487-491Buso, S., Mattavelli, P., (2006) Digital Control in Power Electronics, Morgan & Claypool Publishers.De Souza, K.C.A., Coelho, R.F., Martins, D.C., Proposta de um sistema fotovoltaico de dois est́agios conectado ̀a rede eĺetrica comercial, Re-vista Eletr̂onica de Pot̂encia (SOBRAEP) (2007) Brazilian Journal of Power Electronics, 12 (2), pp. 129-136Erickson, R.W., Maksimovic, D., (2001) Fundamentals of Power Electronics, , Kluwer Academic PublishersFranklin, G.F., Powell, J.D., Emami-Naeini, A., (1995) Feedback Control of Dynamic SystemsKubo, M.M., Villalva, M.G., Maraf̃ao, F.P., Rup-Pert, F.E., Ańalise e projeto de PLL de desempenho melhorado baseado em filtro passa-baixas chebyshev inverso (2006) 16th Brazilian Conference on Automatic Control, CBA.KC200GT High Efficiency Multicrystal Photovoltaic Module (Datasheet)., , Kyocera (n.d.)Maraf̃ao, F.P., Deckmann, S.M., Pomilio, J.A., MacHado, R.Q., A software-based PLL model: Analysis and applications (2004) Congresso Brasileiro de Autoḿatica, CBA, Brazilian Conference of Control and AutomationMaraf̃ao, F.P., Deckmann, S.M., Pomilio, J.A., Machado, R.Q., Metodologia de projeto e ańalise de algoritmos de sincronismo PLL, Revista da Sociedade Brasileira de Eletr̂onica de Pot̂encia (SOBRAEP) (2005) Brazilian Journal of Power Electronics, 10, p. 1Middlebrook, R., Small-signal modeling of pulse-width modulated switched-mode power converters (1988) Proceedings of the IEEE, 76 (4), pp. 343-354Middlebrook, R.D., Cuk, S., A general unified approach to modelling switching converter power stage (1976) IEEE Power Electronics Specialists Conference, pp. 18-34Oppenheim, A.V.E., Schafer, R., (1989) Discrete-Time Signal ProcessingVillalva, M.G., Gazoli, J.R., Ruppert, F.E., Comprehensive approach to modeling and simulation of photovoltaic arrays (2009) IEEE Transactions on Power Electronics, 25 (5), pp. 1198-1208Villalva, M.G., Gazoli, J.R., Ruppert, F.E., Modeling and circuit-based simulation of photovoltaic arrays, Revista Eletr̂onica de Pot̂encia (SO-BRAEP) (2009) Brazilian Journal of Power ElectronicsVillalva, M.G., Ruppert, F.E., Buck converter with variable input voltage for photovoltaic applications (2007) Congresso Brasileiro de Eletr̂onica de Pot̂encia (COBEP)Villalva, M.G., Ruppert, F.E., Dynamic analysis of the input-controlled buck converter fed by a photovoltaic array, revista controle & automa̧c̃ao - Sociedade brasileira de autoḿatica (2008) Brazilian Journal of Control and Automation, 19 (4), pp. 463-474Villalva, M.G., Ruppert, F.E., Input-controlled buck converter for photovoltaic applications: Modeling and design (2008) 4th IET Conference on Power Electronics, Machines and Drives. PEMD, pp. 505-50

What does the rho-meson do? In-medium mass shift scenarios versus hadronic model calculations

The NA60 experiment has studied low-mass muon pair production in In-In collisions at $158 {\rm AGeV}$ with unprecedented precision. With these results there is hope that the in-medium modifications of the vector meson spectral function can be constrained more thoroughly than before. We investigate in particular what can be learned about collisional broadening by a hot and dense medium and what constrains the experimental results put on in-medium mass shift scenarios. The data show a clear indication of considerable in-medium broadening effects but disfavor mass shift scenarios where the $\rho$-meson mass scales with the square root of the chiral condensate. Scaling scenarios which predict at finite density a dropping of the $\rho$-meson mass that is stronger than that of the quark condensate are clearly ruled out since they are also accompanied by a sharpening of the spectral function.Comment: Proceeding contribution, Talk given by J. Ruppert at Workshop for Young Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus Collisions (Hot Quarks 2006), Villasimius, Sardinia, Italy, 15-20 May 2006. To appear in EPJ

Hard and soft probe - medium interactions in a 3D hydro+micro approach at RHIC

We utilize a 3D hybrid hydro+micro model for a comprehensive and consistent description of soft and hard particle production in ultra-relativistic heavy-ion collisions at RHIC. In the soft sector we focus on the dynamics of (multi-)strange baryons, where a clear strangeness dependence of their collision rates and freeze-out is observed. In the hard sector we study the radiative energy loss of hard partons in a soft medium in the multiple soft scattering approximation. While the nuclear suppression factor $R_{AA}$ does not reflect the high quality of the medium description (except in a reduced systematic uncertainty in extracting the quenching power of the medium), the hydrodynamical model also allows to study different centralities and in particular the angular variation of $R_{AA}$ with respect to the reaction plane, allowing for a controlled variation of the in-medium path-length.Comment: 5 pages, 4 figures, Quark Matter 2006 proceedings, to appear in Journal of Physics

Probing Color Response - Wakes in a Color Plasma

The wake induced in a hot QCD medium by a high momentum parton (jet precursor) is calculated in the framework of linear response theory. Two different scenarios are discussed: a weakly coupled quark gluon plasma (pQGP) as described by hard-thermal loop (HTL) perturbation theory and a strongly cupled QGP (sQGP) with the properties of a quantum liquid. In the latter case the wake could exhibit a pronounced Mach cone structure. This physical mechanism could be important for the understanding of preliminary data from the PHENIX and STAR experiments at RHIC on the angular distribution of low-pt secondaries stemming from the away-side jet which indicate maxima at $\Delta\phi=\pi \pm 1.1$.Comment: Prepared for: Workshop on Correlations and Fluctuations in Relativistic Nuclear Collisions, MIT, Cambridge, Massachusetts, USA, 21-23 April 200