Transparent monolithic zirconia gels: effects of acetylacetone content on gelation

Transparent yttria-stabilized zirconia monolithic gels were synthesized under controlled conditions for hydrolysis and chemical polymerization. The influence of acetylacetone on the previous chemical reactions was explored, and a plausible explanation was proposed concerning the outstanding role of this additive during the gelation process. Small-angle X-ray scattering was used to estimate the size of the polymeric species and to investigate the influence of acetylacetone on the structure of the gels prepared.     

A simple one-cycle power supply for approach to saturation studiesin soft magnetic polycrystalline toroidal samples

The ring shape is a good solution to the study of the magnetization processes of magnetic materials because demagnetizing fields are easily avoided. However, when small samples are investigated, the magnitude of the field applied is necessarily limited by the low number of primary winding turns, and by the cross section of the wire itself. The use of sequential-type techniques for high current supply allows this problem to be avoided. One-cycle power production from the 50 Hz AC-line voltage is a simple example of such techniques. An electronic device designed around a commercial integrated circuit is described. A full period of current of 20-ms duration is applied to the load with a magnitude ranging from 0 to 100 A. Magnetization parameters of soft polycrystalline ring ceramics approaching the saturation region are studied as an application. The fitness to measure such characteristic parameters as saturation magnetization and magnetic hardness is shown     

On the stationary distribution of speed and location of random waypoint

In "Stationary distributions for the random waypoint mobility model" (TMC, Vol. 3, No, 1), Navidi and Camp find the stationary distribution of the random waypoint model, with or without pause on a rectangular area. In this short note, we show that, under the stationary regime, speed and location are independent.     

An integrated system to remote monitor and control anaerobic wastewater treatment plants through the internet.

The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem.     

Making polyurethane foams from microemulsions

A remarkable correlation exists between the degree of expansion of polyurethane foams and the structure of the reacting premixes. Polyurethane foams obtained from reacting premixes containing microemulsions are highly expanded. The expansion rate is proportional to the volume fraction of microemulsion in the premix. The stability of premixes with and without microemulsion is completely different suggesting distinct creaming mechanisms. We apply this idea to synthesize polyurethane foams from microemulsions successfully. This approach can be used to rationalize the design of polyurethane formulations leading to highly expanded foams.     

Synthesis, characterization and devitrification behaviour of an yttrium containing boroaluminate glass

The glass forming region in the B₂O₃-Al₂O₃-Y₂O₃ composition diagram has been determined by a melting and quenching procedure at temperatures up to 1800°C. Different physical characteristics (density, coefficient of thermal expansion, glass transition and crystallization peak temperatures) have been determined for a 35B₂O₃-40Al₂O₃-25Y₂O₃ glass composition (in mol.%). By using a predictive model and some NMR structural data, different elastic moduli (Young's modulus, bulk modulus, shear modulus and Poisson's ratio) have been calculated. The devitrification behaviour has also been studied. Internal crystallization is the dominant mechanism and a new (Y, Al)BO₃ ternary phase has been characterized by X-ray powder diffraction. The temperature and time nucleation dependence have been determined from DTA experiments as well as the crystallization kinetics (i.e. the Avrami exponent and the activation energy for crystal growth).     

Bench-Scale Testing of Nanofiltration for Seawater Desalination

A dual-staged nanofiltration process is being evaluated as an alternative to reverse osmosis for seawater desalination. The primary goal of this system is to reduce energy consumption while producing potable water at an acceptable recovery rate. Investigation of this system at the bench-scale level focused on membrane surface characterization, ion rejection (including boron, bromide, and iodide rejection), and flux decline. Results from this study showed that two commercially available nanofiltration membranes can effectively desalinate seawater. Although fouling was apparent—and resulted in approximately 20% flux decline over 3 days—a critical flux was not identifiable. Operation of the system at different cross-flow velocities revealed the significance of hydrodynamic conditions on the polarization modulus, and hence on membrane performance.     

Mechanism of human immunodeficiency virus type 1 localization in CD4-negative thymocytes: differentiation from a CD4-positive precursor allows productive infection

Human immunodeficiency virus (HIV) infection of the thymus could have profound effects on development of the immune response, particularly in children. We and others have established that in addition to infecting and depleting CD4-bearing thymocytes, functional HIV proviruses are found in thymocytes lacking surface CD4 expression. Using in vitro thymocyte cultures, we show that neither HIV-mediated down regulation of CD4 nor CD4-independent infection contributes to the localization of HIV in cells lacking the primary virus receptor. Rather, infection of a CD4-positive precursor cell (CD4 positive/CD8 positive) with subsequent differentiation into a mature CD4-negative phenotype results in productively infected CD4-negative cells. This novel mechanism may contribute to pathogenesis by distributing viral sequences into functional subsets of T cells typically refractory to HIV infection and could account for the presence of viral DNA in CD8-positive lymphocytes recently observed in patients.     

Autoimmune hemolytic anemia and posthepatitis-C liver cirrhosis

Here we are presenting the case of a 70-years-old woman who has hepatic cirrhosis anti-HCV and insulin-dependent diabetes mellitus, without relevant epidemiologic ascendants or previous transfusions and HBV, HIV negatives. On admission to our hospital she showed signs of autoimmune hemolytic anaemia (AHA) which was confirmed by positive direct Coombs test and an improvement in blood test after corticoid treatment. Having discarded other possible causes such as drugs infectious diseases or essential mixed cryoglobulinemia (CME), we put forward the possible association between AHA and infection by HCV, where AHA was an extrahepatic immunological manifestation of HCV. This fact has never been brought to light in previous medical literature.