The Acridine Orange test: a clinically relevant screening method for sperm quality during infertility investigation?

To determine the clinical usefulness of Acridine Orange (AO) staining of spermatozoa as a screening test for the evaluation of semen quality during basic infertility investigation, semen smears from 103 randomly chosen males of subfertile couples were examined. The median duration of infertility was 4.5 years (range 1-15) and the median age was 33 years (range 21-43). The outcome of AO staining ranged from 5 to 81%, with a median of 24%, green fluorescent spermatozoa. Results were not significantly related to the parameters of semen analysis (sperm count, motility, standard morphology, viability, pH and volume, as well as fructose concentration and number of found cells) or to local sperm antibody testing and semen cultures. Fluorescence after AO staining was also not related to sperm functional capacity (evaluated using sperm-mucus interaction tests in vitro and in vivo), or the medical history of the patient. No significant differences in the AO test outcome were seen in patients with explained and unexplained infertility, or with regard to subsequent fertility [with a median value of 21% (range 5-46) green fluorescence in the fertile group, compared with a median value of 28% (range 9-81) green fluorescence in the other men]. The results of this prospective study indicate that under the usual conditions of conception, the AO test is not clinically useful as a screening procedure to determine semen quality during basic infertility investigation.     

Removal of E. coli and helminth eggs in UASB: Polishing pond systems in Brazil.

Ponds following anaerobic reactors, such as Upflow Anaerobic Sludge Blanket (UASB) reactors, have been termed polishing ponds in the literature. The present paper analyses the removal of E. coli and helminth eggs in five UASB-polishing pond systems in Brazil. Since there were ponds in series, the total number of ponds was 10. The ponds had average retention times varying from 2 to 21 days, and depths ranging from 0.40 to 2.00 m. The shallow ponds in series, even with low retention times, were able to produce effluents complying with the coliform WHO guidelines for unrestricted irrigation (< or = 1000 MPN/100 ml). An equation for the coliform decay coefficient was proposed: Kb (dispersed flow) = 0.710H(-0955) (20 degrees C). The equation highlights the inverse relationship between the pond depth and the decay coefficient. All polishing pond systems were able to produce effluents with helminth eggs concentrations predominantly equal to zero, and satisfying the WHO guidelines for unrestricted and restricted irrigation (< or = 1 egg/L, arithmetic mean). The approximate range of helminth eggs removal efficiency was predicted satisfactorily.     

The Aleph data acquisition system

Aleph is one of the four large high-energy physics experiments being completed for the LEP (Large Electron Positron) accelerator at CERN. Several hundred thousand detector elements deliver some 500 Mbytes of raw data per second. The author briefly describes the accelerator and the Aleph detector. He then discusses the design and implementation of the multilevel real-time data reduction and acquisition system, covering the requirements, the readout architecture, its implementation, data reduction, aspects of the detector-specific front-end electronics, and Aleph's present status and performance     

A method to study the history of a double oxide film defect in liquid aluminum alloys

Entrained double oxide films have been held responsible for reductions in mechanical properties in aluminum casting alloys. However, their behavior in the liquid metal, once formed, has not been studied directly. It has been proposed that the atmosphere entrapped in the double oxide film defect will continue to react with the liquid metal surrounding it, perhaps leading to its elimination as a significant defect. A silicon-nitride rod with a hole in one end was plunged into liquid aluminum to hold a known volume of air in contact with the liquid metal at a constant temperature. The change in the air volume with time was recorded by real-time X-ray radiography to determine the reaction rates of the trapped atmosphere with the liquid aluminum, creating a model for the behavior of an entrained double oxide film defect. The results from this experiment showed that first oxygen, and then nitrogen, was consumed by the aluminum alloy, to form aluminum oxide and aluminum nitride, respectively. The effect of adding different elements to the liquid aluminum and the effect of different hydrogen contents were also studied. This article is based on a presentation made in the John Campbell Symposium on Shape Casting, held during the TMS Annual Meeting, February 13–17, 2005, in San Francisco, CA.     

Small thermophotovoltaic prototype systems

In an earlier paper we reported on a small grid-connected thermophotovoltaic (TPV) system consisting of an ytterbia mantle emitter and silicon solar cells with 16% efficiency (under solar irradiance in standard test conditions, STCs). The emitter was heated up using a butane burner with a rated thermal power of 1.35 kW (referring to the lower heating value). This system produced an electrical output of 15 W, which corresponds to a thermal to electric (direct current) conversion efficiency of 1.1%. In the interim, further progress has been made, and significantly higher efficiencies have been achieved. The most important development steps are: (1) the infrared radiation-absorbing water filter between emitter and silicon cells (to protect the cells against overheating and against contact with flue gasses) has been replaced by a suitable glass tube. By doing this, it has been possible to prevent losses of convertible radiation in water. (2) Cell cooling has been significantly improved, in order to reduce cell temperature, and therefore increase conversion efficiency. (3) The shape of the emitter has been changed from spherical to a quasi-cylindrical geometry, in order to obtain a more homogeneous irradiation of the cells. (4) The metallic burner tube, on which the ytterbia emitter was fixed in the initial prototypes, has been replaced by a heat-resistant metallic rod, carrying ceramic discs as emitter holders. This has prevented the oxidation and clogging of the perforated burner tube. (5) Larger reflectors have been used to reduce losses in useful infrared radiation. (6) Smaller cells have been used, to reduce electrical series resistance losses. Applying all these improvements to the basic 1.35 kW prototype, we attained a system efficiency of 1.5%. By using preheated air for combustion (at approximately 370 °C), 1.8% was achieved. In a subsequent step, a photocell generator was constructed, consisting of high-efficiency silicon cells (21% STC efficiency). In this generator, the spaces between the cells were minimized, in order to achieve as high an active cell area as possible, while simultaneously reducing radiation losses. This new system has produced an electrical output of 48 W, corresponding to a system efficiency of 2.4%. This is the highest-ever-reported value in a silicon-cell-based TPV system using ytterbia mantle emitters. An efficiency of 2.8% was achieved by using preheated air (at approximately 500 °C). An electronic control unit (fabricated of components with low power consumption, and including a battery store) was developed, in order to make the TPV system self-powered. This unit controls the magnetic gas supply valve between gas supply cylinder and burner as well as the high-voltage ignition electrodes. Both the control unit’s own power consumption and the battery-charging power are supplied directly by the TPV generator. A small commercial inverter is used to transfer excess power to the 230 V grid.     

Viscous and Aeroelastic Effects on Wind Turbine Blades. The VISCEL project. Part I: 3D Navier–Stokes Rotor simulations

Aerodynamic modelling of HAWT rotors by means of “engineering methods” has reached a saddle point, where no further development can be expected without a breakthrough in understanding the physics of unsteady, rotating three‐dimensional flows. However, such a breakthrough becomes ever more necessary, as the size of the wind turbines increases. With the experimental work in that direction being mostly limited to observing the phenomena and interpreting the associated mechanisms, and its increased cost, alternatives are being sought. The use of CFD techniques and state‐of‐the‐art Navier–Stokes solvers is considered a very serious contender, a belief shared by the members of the present consortium, which has worked on the VISCEL JOR3‐CT98‐0208 Joule III project. This project's goal was to determine the aerodynamic characteristics as well as the aeroelastic behaviour of wind turbine blades across their broad range of operational conditions, from attached to highly separated flow regimes. The work programme included specific tasks for the validation and assessment of existing 3D solvers, for the parametric study of 3D flow around realistic blades and for the investigation of aeroelastic stability, at the blade section level. Copyright © 2003 John Wiley & Sons, Ltd.