Mechanical and durability properties of cement mortar with Algerian natural pozzolana

This paper presents a study of the properties and behaviour of cement mortar with natural pozzolana from Algeria. The effect of level of addition of natural pozzolana (0, 10, 20, 30, and 40%) on the mechanical properties of mortars at different ages as well as the effect of curing environment and the period of initial curing on the mechanical properties were investigated. The performance of natural pozzolana cement exposed to three aggressive solutions (acids, sulphate, and chloride) is also analysed. The results indicate that the strength of pozzolanic cement is lower than that of plain Portland cement at early ages, but can reach the same order of strength at longer curing periods. The enhancement of the resistance to acid and sulphate attack as well as to chloride ion penetration of natural pozzolanic cement is also demonstrated.     

Reliability evaluation of electrical power systems including multi-state considerations

A new approach is introduced for calculating the electrical network reliability indices, such as multi-state stationary availability, expected multi-state capacity, expected unsupplied demand, loss of load probability and total failed system probability. The universal moment generating function approach (UMGF) is used to evaluate the different reliability indices of the power system. In this paper we present a survey of recent work which treats the more sophisticated and realistic models in which components and systems may comprise many states ranging from perfect-working to complete failure. Such systems are multi-state (MSS) as they can have different levels of output performance. The objective is to determine the power structure which minimizes costs and satisfies reliability levels. A computer program has been developed to implement the UMGF technique, and an illustrative example is presented.     

Identification and antibiotic resistance of Lactobacilli isolated from raw cow’s milk of Oujda City (Morocco)

In this study, a Lactobacillus strain was isolated from raw cow milk. It was tentatively identified at the species level according to its carbohydrate fermentation profile and phenotype characteristics as Lactobacillus paracasei KSNM. The susceptibility of the identified Lactobacillus to 23 antibiotics was performed using the disc diffusion testing method. Inhibition zone diameters were measured and expressed in terms of sensitive, intermediate or resistant. KSNM strain was sensitive toward; amoxicillin, ampicillin, amoxyclav (amoxicillin + clavulanic acid), tetracycline, macrolides, sulfamides/trimethoprim, and rifampicin. But, it expressed intermediate sensitivity toward; cefamandole, cefaclor, and cephalothin. However, it was resistant to penicillin G, aminoglycosides, quinolones, ciprofloxacin, lincomycin, nitroxolin, and a large number of cephalosporins, which included cefoxitin, cefotaxime, and ceftriaxone.     

Kinetics and Thermodynamics of Oil Extraction from Olive Cake

The kinetics of oil extraction from olive cake by using ethanol 96% was studied for different solvent-to-solids ratios and temperatures. The thermodynamic aspect of the extraction process was also examined. In the kinetic study, the results produced by the model of So and Macdonald (a model involving two main mechanisms of oil extraction: a washing process and a diffusion process with two stages) were found to be in good agreement with the experimental data. The yield of oil in the extract increased with increasing contact time, solvent-to-solids ratio and extraction temperature. The calculated values of the mass transfer coefficients of various stages of the extraction were found to increase linearly with solvent-to-solids ratio and temperature. In all cases, the predominant mechanism in the extraction was the washing of the oil occurring on the particle surface. The values of the activation energy were 8.56 kJ mol⁻¹ for the washing stage, 9.88 kJ mol⁻¹ for the first stage of diffusion and 17.55 kJ mol⁻¹ for the second stage of diffusion by changing temperature from 20 to 50 °C. Further, the results obtained from thermodynamic study of extraction process gave positive values of enthalpy and entropy changes and negative values of change in free energy. Under the equilibrium conditions, the temperature coefficient was found to be 1.02.     

Memory-enhancing effects of secreted forms of the beta-amyloid precursor protein in normal and amnestic mice

When administered intracerebroventricularly to mice performing various learning tasks involving either short-term or long-term memory, secreted forms of the beta-amyloid precursor protein (APPs751 and APPs695) have potent memory-enhancing effects and block learning deficits induced by scopolamine. The memory-enhancing effects of APPs were observed over a wide range of extremely low doses (0.05-5,000 pg intracerebroventricularly), blocked by anti-APPs antisera, and observed when APPs was administered either after the first training session in a visual discrimination or a lever-press learning task or before the acquisition trial in an object recognition task. APPs had no effect on motor performance or exploratory activity. APPs695 and APPs751 were equally effective in the object recognition task, suggesting that the memory-enhancing effect of APPs does not require the Kunitz protease inhibitor domain. These data suggest an important role for APPss on memory processes.     

Chest radiographic data acquisition and quality assurance in multicenter studies

Dorsal fusion with the internal fixator has become the standard treatment of instabilities and deformities of the thoracolumbar spine. With our new device, the modular spine fixator (MSF), which has been specially designed for short-distance instrumentations, we have increasingly been treating unstable injuries of the thoracolumbar spine by one-level stabilization. Prerequisite is an accurate evaluation of the indication, including CT and MRI to assess the involvement of the intervertebral disc and the ligamental structures. The operative technique differs in some details from the procedure in more-multi-level instrumentations, especially concerning the application of the pedicle screws. The instrumentation is always combined with posterior allogenic bone grafting. Since the beginning of 1993 we also perform anterior autogenic transpedicular bone grafting. Between January 1991 and July 1995, 57 one-level stabilizations with the MSF were performed. Of the 57 patients operated on 39, 27 men and 12 women, with an average age of 41 years, have had a clinical and radiographic follow-up examination so far, on average, 27 months after the accident. Seventeen patients were completely free of pain and 17 patients (were only) sensitive to weather changes or had minor pain during great physical stress. Five patients had pain even during slight physical stress or at rest. The preoperatively measured Cobb angle was 15.1 degrees on average, after the operation 5.2 degrees, and at the time of the follow-up examination amounted to 8.1 degrees. The patients' range of motion was normal. Only five minor complications have been seen. No implant fatigue failure has been noted in this series. We derive from these results that, for correct indications, one-level stabilization can be performed successfully and should be firmly established in the operative treatment of unstable fractures of the thoracolumbar spine.     

Instabilities generated by friction in a pad–disc system during the braking process

This paper presents a numerical and experimental study of a pad–disc tribometer. The explicit dynamic finite element software PLAST 3 in 3-D is used to simulate the behaviour of the two bodies involved. Coulomb's friction law is used at the contact surface with a constant coefficient. For this application, temporal simulations show that separation occurs between surfaces, proof of instabilities. This unstable state is characterized by a stick–slip–separation wave. We show that instabilities describe a periodic shock phenomenon at the contact interface. Consequently, the acceleration spectrum recorded on the surface of the pad reveals periodicity in the frequency domain. It shows also that, in this case, the vibrations responsible for the instability are localized in the pad. The mode responsible for squealing can be obtained by a modal analysis of the pad–disc system by assuming that the interface is stuck. We highlight the importance of the pad Poisson's ratio in the occurrence of this unstable state. A numerical/experimental comparison has been performed and the fundamental frequency of squeal obtained experimentally and its magnitude agree with those calculated numerically with PLAST 3.     

Hydatid cyst of the psoas muscle. Apropos of a case

The authors report a rare case of hydatid cyst of the psoas muscle in a 28-year-old woman, operated for vertebrospinal hydatid cyst. The patient presented with a left iliac fossa mass. Ultrasonography and computed tomography contributed to the preoperative diagnosis, despite negative hydatid serology. A retroperitoneal approach by left lumbotomy with partial pericystectomy was performed. In the light of this case, the authors discuss the diagnostic and therapeutic problems raised by hydatid cyst of the psoas muscle.     

Microwave spectra in external-cavity semiconductor lasers:theoretical modeling of multipass resonances

We show theoretically that the behavior of an external-cavity semiconductor laser depends on the microscopic intensity distribution of the feedback light. Adapted rate equations are developed based on the traveling-wave model. This model successfully predicts the double-peaked structure of the external-cavity resonance (centered around c/2L) and multiple-pass resonances when the system is misaligned