Propagation and deposition of stony debris flows at channel confluences

The fluid dynamics of stony debris flows generated in two small tributaries adjacent to each other and flowing into a main receiving channel was analyzed experimentally at a laboratory scale. The analysis on the propagation along the tributaries and deposition in the main channel provide information about sediment-water mobility, dangerous damming, and potential hazard. Debris flows were generated by releasing a preset water discharge over an erodible layer of saturated gravels material. As a consequence, the debris flow sediment concentration varied accordingly to the entrainment rate which, in turn, was strongly controlled by the tributary slope. The data collected by acoustic level sensors, pore fluid pressure transducers, and a load cell were used to characterize the evolution of bulk density and solid concentration of the sediment-water mixture. These two parameters were relevant to assess the stony debris flow mobility which contributes to determine the shape of sediment deposits in the main channel. The detailed bed topography surveys carried out in the main channel at the end of each experiment provided information on the morphology of these deposits and on the interplay of adjacent confluences. The influences of conflu- ence angle, tributary slopes, and triggering conditions have been investigated, for a total of 18 different configurations. Within the investigated range of parameters, the slope angle was the parameter that mainly influences the stony debris flow mobility while, for adjacent confluences, the degree of obstruction within the receiving channel was strongly influenced by the triggering scenario

Integrating Outdoor Leadership Education into the Academic Setting

To integrate outdoor leadership education effectively within university academic programs, innovative curricula need to be developed that combine field and classroom work. The goal must be to enable students to understand and assimilate the knowledge base within the classroom and to be able to.apply and show judgment and competence in the field

Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest

Zoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experiment, we evaluated the impact of the invasive phytophagous pest Halyomorpha halys on this plant volatile-mediated tritrophic communication. Results showed that the invasive herbivorous adults do not induce plants to recruit the native egg parasitoid, but they can disrupt the local infochemical network. In fact, T. podisi females are not attracted by volatiles emitted by plants damaged by H. halys feeding alone or combined with oviposition activity, nor are they attracted by plants concurrently infested by P. maculiventris and H. halys, indicating the specificity in the parasitoid response and the ability of the invasive herbivore in interrupting the semiochemical communication between plants and native egg parasitoids. To the best of our knowledge, this is the first study showing that zoophytophagous predator attacks induce indirect plant defences similarly to those defence strategies adopted by plants as a consequence of single or concurrent infestations of herbivorous insects

A comparative assessment of two different debris flow propagation approaches – blind simulations on a real debris flow event

Abstract. A detailed comparison between the performances of two different approaches to debris flow modelling was carried out. In particular, the results of a mono-phase Bingham model (FLO-2D) and that of a two-phase model (TRENT-2D) obtained from a blind test were compared. As a benchmark test the catastrophic event of 1 October 2009 which struck Sicily causing several fatalities and damage was chosen. The predicted temporal evolution of several parameters of the debris flow (such as flow depth and propagation velocity) was analysed in order to investigate the advantages and disadvantages of the two models in reproducing the global dynamics of the event. An analysis between the models' results with survey data have been carried out, not only for the determination of statistical indicators of prediction accuracy, but also for the application of the Receiver Operator Characteristic (ROC) approach. Provided that the proper rheological parameters and boundary conditions are assigned, both models seem capable of reproducing the inundation areas in a reasonably accurate way. However, the main differences in the application rely on the choice of such rheological parameters. Indeed, within the more user-friendly FLO-2D model the tuning of the parameters must be done empirically, with no evidence of the physics of the phenomena. On the other hand, for the TRENT-2D the parameters are physically based and can be estimated from the properties of the solid material, thus reproducing more reliable results. A second important difference between the two models is that in the first method the debris flow is treated as a homogeneous flow, in which the total mass is kept constant from its initiation in the upper part of the basin to the deposition in a debris fan. In contrast, the second approach is suited to reproduce the erosion and deposition processes and the displaced mass can be directly related to the rainfall event. Application of both models in a highly urbanized area reveals the limitation of numerical simulation which is inadequate in describing some disturbances of the flows that occurred during the alluvial event (e.g. the cars, the volume of debris within buildings etc.) which have a crucial influence on the evaluation of the maximum and final flow depths

Moods of 3-Week and 5-Week Outdoor Expedition Participants

The purpose of this research project was to investigate and document the cycle of mood states displayed by outdoor recreation expedition participants. It was hypothesized that an individual\u27s moods pass through a predictable cycle during the beginning, middle, and end phases of a 3-week to 5-week outdoor expedition.This cycle would include fluctuations in mood states such as anger/hostility, confusion/bewilderment, de­pression/dejection, fatigue, tension/anxiety, and vigor. It was anticipated that ten­sion/anxiety would be high in the beginning, medium to high in the middle, and then low at the end. Depression/dejection was ex­pected to be low in the beginning, high in the middle, and medium to low at the end. Anger/hostility was hypothesized to low in the beginning, high in the middle, and low at the end. Vigor/activity was anticipated to be high in the beginning, low in the middle, and high at the end. It was expected that fa­tigue/inertia would be high in the beginning, low in the middle, and then medium to low at the end. Finally, confusion/bewilderment was predicted to be high in the beginning, then I.ow in the middle and end

A nonlinear rotational, quasi-2DH, numerical model for spilling wave propagation

The propagation of spilling waves interacting with complex bathymetries was studied by means of a new two-dimensional weakly dispersive, fully nonlinear Boussinesq-type of model. In particular, the governing equations were derived assuming the flow as rotational, and the effects of vorticity due to breaking were included through the surface roller concept, which was defined and implemented on the basis of a new algorithm developed for the purpose. The propagation of vorticity, due to wave breaking, is estimated under the assumption that the effect of convection is leading order with respect to the effect of vorticity-stretching and that the breaking phenomenon does not show high curvature on the horizontal plane. In particular, the dynamic problem is decoupled in a lateral direction considering a series of separated sections in which vorticity is solved. In this way it is possible to obtain rotational information along the domain to a reasonable computational cost. The numerical model was validated in a simple one-dimensional case and then applied to the study of breaking-generated vorticity due to wave motion over a submerged shoal

Laser pulse annealing of ion-implanted GaAs

GaAs single-crystals wafers are implanted at room temperature with 400-keV Te + ions to a dose of 1×10^15 cm^–2 to form an amorphous surface layer. The recrystallization of this layer is investigated by backscattering spectrometry and transmission electron microscopy after transient annealing by Q-switched ruby laser irradiation. An energy density threshold of about 1.0 J/cm^2 exists above which the layer regrows epitaxially. Below the threshold the layer is polycrystalline; the grain size increases as the energy density approaches threshold. The results are analogous to those reported for the elemental semiconductors, Si and Ge. The threshold value observed is in good agreement with that predicted by the simple model successfully applied previously to Si and Ge