Downstream environmental effects of dam operations: Changes in habitat quality for native fish species

Hydropeaking dam operation and water extractions for irrigation have been broadly stated as alterations to natural flow regimes, which have also been noticed in the Biobío Watershed, in Central Chile, since 1996. In the Biobío River, most of native fish species are endemic and very little is known about them. Their ecological and social values have never been estimated, and there is lack of information about their habitat preferences. Furthermore, changes on fish habitat availability due to natural and/or man‐made causes have not been evaluated. In this study, eight native fish species, in a representative reach of the Biobío River, were studied and their preferred habitats were surveyed and characterized. A hydrodynamic model was built and linked to the fish habitat simulation model CASiMiR. Fuzzy rules and fuzzy sets were developed for describing habitat preference of the native fish species. CASiMiR was then used to simulate how physical habitat conditions vary due to flow control (i.e. upstream dams). Results show how overall habitat quality, expressed as weighted usable area (WUA) and hydraulic habitat suitability (HHS), changes and fluctuates due to the dam operation and how the daily hydropeaking is influencing quantity, quality and location of different habitats. The study suggests that the analysed fish are highly susceptible to flow control, as dams are currently operated, and fish habitat improvement suggestions are proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

Functionality of egg white proteins as affected by high intensity ultrasound

The goal of this contribution was to determine the impact of HIUS on the thermal aggregation, gelation, foaming and emulsifying properties of egg white (EW) proteins.     

Exhaust emissions and electric energy generation in a stationary engine using blends of diesel and soybean biodiesel

The present work describes an experimental investigation concerning the electric energy generation using blends of diesel and soybean biodiesel. The soybean biodiesel was produced by a transesterification process of the soybean oil using methanol in the presence of a catalyst (KOH). The properties (density, flash point, viscosity, pour point, cetane index, copper strip corrosion, conradson carbon residue and ash content) of the diesel and soybean biodiesel were determined. The exhaust emissions of gases (CO, CO₂,C_xH_y,O₂, NO, NO_x and SO₂) were also measured. The results show that for all the mixtures tested, the electric energy generation was assured without problems. It has also been observed that the emissions of CO, C_xH_y and SO₂ decrease in the case of diesel–soybean biodiesel blends. The temperatures of the exhaust gases and the emissions of NO and NO_x are similar to or less than those of diesel.     

A theoretical study of the electronic structure and bonding of the monoclinic phase of

The electronic properties of the Mg₂NiH₄ monoclinic phase are calculated using a density functional approach calculation. The crystalline parameters and interatomic distances calculated are close to the experimental values within a 3% error. We also evaluate the density of states (DOS) and character of the chemical bonding for the hydrogen's located in their equilibrium positions. While the Ni–Mg interaction is dominant in the pure alloy, in the hydride the hydrogen atoms present a bonding much more developed with Ni than with Mg. The principal bonding interaction is Ni sp–H s. Moreover, a small bonding between Ni d_eg and H 1s is observed. Up the Fermi level, the Ni–H interaction is slightly antibonding. The Mg–Ni bonding interactions are weaker in the hydride phase when compared with the pure Mg₂Ni alloy. The present study is potentially useful because the alloys Mg–Ni are good materials for hydrogen storage.     

Stigma and barriers to care in soldiers postcombat.

The present study examined the effects of leadership and unit cohesion on mental health stigma and perceived barriers to care. A sample of 680 soldiers from combat support units were surveyed 3 months after their return from combat operations in Iraq. The survey included scales on psychological symptoms and perceptions of leader behaviors and unit cohesion, as well as items assessing stigma and barriers to care. The sample was used to test the independent and interactive effects of leadership and unit cohesion on soldiers’ perceptions of stigma and barriers to care. Analyses yielded significant interaction effects between leadership and cohesion in predicting stigma and barriers to care, while controlling for the effects of mental health symptoms. Soldiers who rated their leaders more highly and who reported higher unit cohesion also reported lower scores on both stigma and perceived barriers to care. Thus, positive leadership and unit cohesion can reduce perceptions of stigma and barriers to care, even after accounting for the relationship between mental health symptoms and these outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flexible joints control: A minimum-time feed-forward technique

The paper proposes a linear programming approach to the feed-forward minimum-time control of flexible joints. Taking into account both input and output constraints, the optimal bang–bang control is computed by discretizing a continuous-time joint model and by solving a sequence of linear programming feasibility problems. The resulting joint motion is a smooth rest-to-rest motion without oscillations. Theoretical analysis is presented and proof of convergence is given. Experimental results illustrate the proposed open-loop technique. Comparisons are made with inversion-based techniques.     

Bernoulli Theorem, Minimum Specific Energy, and Water Wave Celerity in Open-Channel Flow

One basic principle of fluid mechanics used to resolve practical problems in hydraulic engineering is the Bernoulli theorem along a streamline, deduced from the work-energy form of the Euler equation along a streamline. Some confusion exists about the applicability of the Bernoulli theorem and its generalization to open-channel hydraulics. In the present work, a detailed analysis of the Bernoulli theorem and its extension to flow in open channels are developed. The generalized depth-averaged Bernoulli theorem is proposed and it has been proved that the depth-averaged specific energy reaches a minimum in converging accelerating free surface flow over weirs and flumes. Further, in general, a channel control with minimum specific energy in curvilinear flow is not isolated from water waves, as customary state in open-channel hydraulics.     

Calibration of subnanometer motion with picometer accuracy

We have developed a method for calibrating subnanometer movements of a piezoelectric actuator with picometer accuracy and for a wide range of frequencies. This range make this calibration useful for scanning probe microscopes, particularly for an apertureless scanning near-field optical microscope in which the tip is dithered to modulate the optical signal. The setup consists of a Michelson interferometer that has a mobile arm capable of moving more than one fringe. The piezoelectric actuator to be calibrated vibrates at the desired frequency in the other arm. Net displacement can be calculated by simultaneous measurement of an interferometric signal and its derivative. Hysteresis of the system can be also measured. It will be shown that the actuator response is linear only for the low-frequency region (in our case as much as approximately 10 kHz). Above that frequency range, higher harmonics appear and cannot be neglected to obtain real displacement. Finally, it will be shown that the use of higher harmonics in calibration or detection schemes (that rely on the linearity of the response) must be validated, and this technique has proved adequate for that purpose.