An expert aid to fault diagnosis and trouble-shooting in satellitecommunications

Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal     

Gastrointestinal problems in diabetes

Gastrointestinal symptoms are often encountered in patients with diabetes mellitus. Symptoms may arise in any region of the alimentary tract; common symptoms are heartburn, nausea, vomiting, diarrhea, constipation, fecal incontinence, and abdominal pain. This article reviews practical approaches to the identification of the pathophysiologic mechanisms involved in diabetic enteropathies and their complications and briefly outlines strategies to treat these symptoms. Particular emphasis is placed on applied physiologic tests and the choice of pharmacotherapy (e.g., cisapride, erythromycin, or octeotide). The current role of pancreatic transplantations also is briefly reviewed.     

On the Possibility of Observing Third Sound on 3He

This paper focuses on the hydrodynamics of third sound on a superfluid ³ He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range.     

Molecular cloning of human Frizzled-6

The Frizzled genes encode receptors for WNTs, secreted glycoproteins implicated in development as well as in carcinogenesis. In this paper, we report molecular cloning of Hfz6, the human homologue of Mfz6. Nucleotide sequence analysis showed that the Hfz6 gene encodes the 706 amino-acid protein with seven transmembrane domains, a cystein-rich domain in the N-terminal extracellular region, two N-linked glycosylation sites, and two cystein residues in the second and third extracellular loops. Hfz6 mRNA 4.4-kb in size was detected in various normal adult and fetal tissues, and a larger amount of Hfz6 mRNA was detected in both fetal lung and fetal kidney. The Hfz6 gene has been mapped to human chromosome 8q22.3-q23.1. In conclusion, we have cloned Hfz6, which encodes a seven-transmembrane receptor with the cystein-rich domain in the N-terminal extracellular region, but without the Ser/Thr-X-Val motif in the C-terminus.     

Lactococcus lactis and stress

It is now generally recognized that cell growth conditions in nature are often suboptimal compared to controlled conditions provided in the laboratory. Natural stresses like starvation and acidity are generated by cell growth itself. Other stresses like temperature or osmotic shock, or oxygen, are imposed by the environment. It is now clear that defense mechanisms to withstand different stresses must be present in all organisms. The exploration of stress responses in lactic acid bacteria has just begun. Several stress response genes have been revealed through homologies with known genes in other organisms. While stress response genes appear to be highly conserved, however, their regulation may not be. Thus, search of the regulation of stress response in lactic acid bacteria may reveal new regulatory circuits. The first part of this report addresses the available information on stress response in Lactococcus lactis. Acid stress response may be particularly important in lactic acid bacteria, whose growth and transition to stationary phase is accompanied by the production of lactic acid, which results in acidification of the media, arrest of cell multiplication, and possible cell death. The second part of this report will focus on progress made in acid stress response, particularly in L. lactis and on factors which may affect its regulation. Acid tolerance is presently under study in L. lactis. Our results with strain MG1363 show that it survives a lethal challenge at pH 4.0 if adapted briefly (5 to 15 minutes) at a pH between 4.5 and 6.5. Adaptation requires protein synthesis, indicating that acid conditions induce expression of newly synthesized genes. These results show that L. lactis possesses an inducible response to acid stress in exponential phase. To identify possible regulatory genes involved in acid stress response, we determined low pH conditions in which MG1363 is unable to grow, and selected at 37 degrees C for transposition insertional mutants which were able to survive. About thirty mutants resistant to low pH conditions were characterized. The interrupted genes were identified by sequence homology with known genes. One insertion interrupts ahrC, the putative regulator of arginine metabolism; possibly, increased arginine catabolism in the mutant produces metabolites which increase the pH. Several other mutations putatively map at some step in the pathway of (p)ppGpp synthesis. Our results suggest that the stringent response pathway, which is involved in starvation and stationary phase survival, may also be implicated in acid pH tolerance.     

Value analysis of intermittent generation sources from the systemoperations perspective

The objective of this study is to determine the economic and operational impact on energy cost of incorporating large photovoltaic (PV) and wind energy conversion systems (WECS) into the electric utility generation mix. In most cases, PV and WECS power outputs are subtracted from the utility load with the expectation that conventional generation would meet the residual load. This approach is valid for small penetration levels and/or for PV and WECS facilities connected near load centers, However, several constraints such as thermal generation characteristics, fuel supply and delivery, spinning reserve requirements, and hydro availability are not adequately represented in this process. To determine the optimal value of large-scale PV and WECS applications, a new methodology that would take into account the aforementioned constraints as well as a more global penetration is developed. Results indicate that while high hydro availability increases PV penetration levels, high ramping rates can also significantly increase penetration levels     

Synthesis of heterocyclic metal complexes and their evaluation as marine antifoulants

4-Amino-3-thio-1,24-triazolidine (L₁) and 4-amino-5-thio-1,3,4-thiadiazole (L_II) as well as their metal complexes of the general formulae ML_I·2H₂O and ML_IICl (M; Pb(II), Cd(II) and Zn(II)) were prepared. With Sn(II), we obtained Sn(L_I)₂·2H₂O and SnL_IICl, respectively. The structures of the compounds were identified through elemental analysis, and IR and UV spectra measurements, in addition to thermal analysis in case of the metal complexes. The antifouling properties of the compounds were tested by their incorporation into paint formulations which were applied to PVC substrates and tested in water from Alexandria western harbour. When the compounds were added at 17·5% by volume, the coated panels were fouled after 3 months of immersion. The addition of 6·7% by volume of tributyltin oxide to 15·8% of the prepared compounds in one formulation elevated the paint efficiency and prevented fouling for 11 months. Paint containing solely tributyltin oxide at the same concentration was inactive against algae.