Parallel efficiency of the C.R.F. method on an IBM RS/6000 cluster platform

A new numerical method for kinetic equations in several dimensions has been recently presented by Motta and Wick (1991). The method has been then applied to simple models to test its applicability to realistic physical situations. In the present paper we discuss the parallel performance of the method on a distributed memory platform based on a cluster of IBM RS/6000 superscalar workstations.     

Role of Bioflocculation on Chemical Oxygen Demand Removal in Solids Contact Chamber of Trickling Filter/Solids Contact Process

The trickling filter/solids contact (TF/SC) process was developed in the late 1970s to improve the quality of the final effluent from existing trickling filter plants, to be able to meet stricter Environmental Protection Agency effluent requirements. Although this process has successfully achieved this objective, it is still not completely understood, there is limited information regarding the flocculation phenomena occurring in the solids contact chamber (SCC), and no information could be found on the relationship between flocculation and organic matter removal kinetics. To better understand the kinetics of biological flocculation in a continuous flow SCC, a long-term experimental program was conducted using a TF/SC pilot plant constructed at the Marrero, La., wastewater treatment plant. This program started in January 1998 and has continued through date. The present article will focus on two major areas: (1) the kinetics of bioflocculation in the SCC; and (2) effect of bioflocculation on chemical oxygen demand (COD) removal. Analysis of the wastewater composition revealed that, on the average, only 18.7% of the total COD in the SCC influent is truly dissolved. Therefore, most of the total COD removal observed in the SCC must be due to a physical process, such as flocculation. The experimental data confirmed that flocculation of the particulate COD contained in the trickling filter effluent explains the high total COD removal observed at the SCC. Both total and colloidal COD removals are well explained by the first-order flocculation model.     

Preparation of Cu-Ni alloys through a new chemical route

A copper-nickel alloy has been prepared from an aqueous solution of the nitrates of copper and nickel, through co-formation of their ultrafine mixed oxides, by heating around 650 K followed by reduction with hydrogen at a very low temperature (below 623 K). The effect of temperature (473 to 623 K) on the kinetics of the hydrogen reduction of the co-formed oxides of Ni and Cu has been studied. The activation energy of the reduction reaction has been calculated and found to be 35.8 kJ/mole. A mechanism for the kinetics of the process has been suggested. It has been possible to get high-purity Cu-Ni alloy powder (50 at. pct each) free of any detectable oxygen, from their co-formed oxides, by hydrogen reduction at 623 K in less than 20 minutes. Although the X-ray analysis of the co-formed oxides has shown separate peaks for CuO and NiO, the alloy powder has exhibited a single peak with a d spacing lying in between those of Cu and Ni. It is suggested that the alloying of the two metals has taken place during the H₂ reduction of nanosized oxide particles of copper and nickel, prepared by the aforementioned chemical route. The alloy powder has been sintered at 1273 K. The density and hardness of the consolidated alloy have been measured and found to be close to the theoretical values. The alloy has also been subjected to cold reduction and annealing, in addition to metallograph examination and characterization by a scanning electron microscope (SEM), to confirm the homogeneity of the alloy.     

High-voltage management in single-supply CHE NOR-type flash memories

In a flash memory, a number of voltage levels different from V/sub DD/ are needed to perform the required operations (read, program, and erase) on the array cells. In the case of single-supply memory devices, voltages higher than V/sub DD/ as well as negative voltages, which are referred to as high voltages (HVs), must be produced on-chip. This paper aims at giving the reader an overview of how HVs are generated and managed in single-supply NOR-type flash memories programmed by channel hot-electron injection. Both schemes used for conventional (i.e., bilevel) memory devices and schemes designed to meet multilevel memory requirements are addressed.     

Configuring online problem-solving resources with the Internet Reasoning Service

The paper discusses the Internet Reasoning Service, a Web-based front end that lets developers prototype knowledge-based applications quickly out of reusable problem-solving resources in distributed libraries.     

In vitro reconstitution of Artemia satellite chromatin

We report the characterization of an in vitro chromatin assembly system derived from Artemia embryos and its application to the study of AluI-113 satellite DNA organization in nucleosomes. The system efficiently reconstitutes chromatin templates by associating DNA, core histones, and H1. The polynucleosomal complexes show physiological spacing of repeat length 190 +/- 5 base pairs, and the internucleosomal distances are modulated by energy-using activities that contribute to the dynamics of chromatin conformation. The assembly extract was used to reconstitute tandemly repeated AluI-113 sequences. The establishment of preferred histone octamer/satellite DNA interactions was observed. In vitro, AluI-113 elements dictated the same nucleosome translational localizations as found in vivo. Specific rotational constraints seem to be the central structural requirement for nucleosome association. Satellite dinucleosomes showed decreased translational mobility compared with mononucleosomes. This could be the consequence of interactions between rotationally positioned nucleosomes separated by linker DNA of uniform length. AluI-113 DNA led to weak cooperativity of nucleosome association in the proximal flanking regions, which decreased with distance. Moreover, the structural properties of satellite chromatin can spread, thus leading to a specific organization of adjacent nucleosomes.     

Multielectrode microprobes for deep-brain stimulation fabricated with a customizable 3-D electroplating process

Although deep-brain stimulation (DBS) can be used to improve some of the severe symptoms of Parkinson's disease (e.g., Bradykinesia, rigidity, and tremors), the mechanisms by which the symptoms are eliminated are not well understood. Moreover, DBS does not prevent neurodegeneration that leads to dementia or death. In order to fully investigate DBS and to optimize its use, a comprehensive long-term stimulation study in an animal model is needed. However, since the brain region that must be stimulated, known as the subthalamic nucleus (STN), is extremely small (500 microm x 500 microm x 1 mm) and deep within the rat brain (10 mm), the stimulating probe must have geometric and mechanical properties that allow accurate positioning in the brain, while minimizing tissue damage. We have designed, fabricated, and tested a novel micromachined probe that is able to accurately stimulate the STN. The probe is designed to minimize damage to the surrounding tissue. The probe shank is coated with gold and the electrode interconnects are insulated with silicon nitride for biocompatibility. The probe has four platinum electrodes to provide a variety of spatially distributed stimuli, and is formed in a novel 3-D plating process that results in a microwire like geometry (i.e., smoothly tapering diameter) with a corresponding mechanically stable shank.     

The 5alpha-reductase in the central nervous system: expression and modes of control

The present paper will summarize two important aspects of the interactions between steroids and the brain, which have recently been studied in the authors' laboratory. In particular the paper will consider data on: (1) the significance of the two isoforms of the 5alpha-R during brain ontogenesis and development, and (2) the cross-talk between glial and neuronal elements, particularly in relation to the metabolism of sex hormones. (1) The data obtained have shown that the 5alpha-R type 1 enzyme is constitutively expressed in the rat CNS at all stages of brain development. Moreover, the expression of the 5alpha-R type 1 is similar in males and in females, and does not appear to be controlled by androgens. The gene expression of the 5alpha-R type 2 is totally different. This isoform appears to be expressed in the rat brain almost exclusively in the late fetal/early post-natal life and is controlled by testosterone. (2) The present data show that two cell lines derived respectively from a rat glioma (C6 cell line) and from a human astrocytoma (1321N1 cell line) are able to convert testosterone and progesterone into their corresponding 5alpha-reduced metabolites dihydrotestosterone and dihydroprogesterone. The possibility that secretory products of normal and tumoral brain cells might be able to influence steroid metabolism occurring in the two glial cell lines previously mentioned has been considered.     

Optically transparent monopole antenna with high radiation efficiency manufactured with silver grid layer (AgGL)

A technology based on a meshed silver/titanium bilayer printed on glass substrate is briefly presented. A sheet resistance equal to 0.054 /sq with 81.3 of optical transparency is obtained. The performances of a monopole antenna made from such a material have been investigated. The measured S₁₁ and gain of the transparent antenna are compared with those of an antenna fabricated from a reflective silver/titanium film, and stand for reference. The transparent antenna provides radiation efficiency better than 85%.