Corrosion of yttria-fully stabilized zirconias in molten fluorides

Yttria-fully stabilized zirconia ceramics were manufactured from home-made and commercially available powders and were sintered under different conditions. The ceramics were immersed in the corrosive environment of molten LiF, NaF, KF (FLINAK) eutectic for up to 360 h from 700–900 °C. The changes caused in the crystal structure were probed with laser Raman spectroscopy and X-ray diffraction. The degree of corrosion (phase transformation) depends on immersion period, FLINAK temperature, and ceramics microstructure. From the tested ceramics, ZrO₂-8 mol % Y₂O₃ with a grain size larger than 8 μm and having zero open porosity, exhibits the best resistance to the corrosive influence of FLINAK.     

Private employment through public labor marketing offices: A proposal for a more constructive public welfare program

The paper proposes a new program that may reduce dependency on direct cash grants by channeling welfare-sector labor to the private sector of the economy. This program requires establishing a new institution- the local public labor marketing office-whose main function will be to aggressively market the types of labor that the disadvantaged, many of whom are chronically unemployed, can offer. The paper provides a broad view of this and other supporting functions of the local labor marketing offices, the activities in which they should direct their efforts and the advantages of the program over alternative arrangements.Opinions expressed in this paper are those of the author and do not represent the views of The Urban Institute or its sponsors. The paper was written before the author's involvement in related work for the Federal Government.     

DeTRACT: a decentralized,transparent, immutable and open PKI certificate framework

International Journal of Information Security - Public key infrastructure (PKI) is widely used over the Internet to secure and to encrypt communication among parties. PKI involves digital...     

On the properties of spam-advertised URL addresses

The main purpose of most spam e-mail messages distributed on Internet today is to entice recipients into visiting World Wide Web pages that are advertised through spam. In essence, e-mail spamming is a campaign that advertises URL addresses at a massive scale and at minimum cost for the advertisers and those advertised. Nevertheless, the characteristics of URL addresses and of web sites advertised through spam have not been studied extensively. In this paper, we investigate the properties of URL-dissemination through spam e-mail, and the characteristics of URL addresses disseminated through spam. We conclude that spammers advertise URL addresses non-repetitively and that spam-advertised URLs are short-lived, elusive, and therefore hard to detect and filter. We also observe that reputable URL addresses are sometimes used as decoys against e-mail users and spam filters. These observations can be valuable for the configuration of spam filters and in order to drive the development of new techniques to fight spam.     

Speciation of new tri- and tetra-glucoconjugated tetrapyrrolic macrocycles (porphyrins and chlorins): an electronic molecular spectroscopy study

In this work, we study the physicochemical properties of some newly developed glycoconjugated photosensitizers that can be used in photodynamic therapy (PDT) of cancers: meso-tri- and tetra-(meta-O-beta-D-glucosyloxyphenyl)porphyrins and meso-, tri-, and tetra-(meta-O-beta-D-glucosyloxyphenyl)chlorins. Their properties are compared to the non-glycosylated hydroxylated parent compounds meso-tetra-(meta-hydroxyphenyl) porphyrin and meso-tetra-(meta-hydroxyphenyl)chlorin. It was found that at the ground state, all porphyrins present, independent of the substitution, have the same mean ionization constant (pKa = 2.7), corresponding to two indistiguishable steps of protonation of tetrapyrrolic nitrogens. On the other hand, in the case of chlorins, one proton process can be observed and the corresponding nitrogen exhibits a slightly superior basicity (pKa = 3.0) with respect to porphyrins. Hydroxylated compounds present a second transition at high pH corresponding to the ionization of phenol groups (pKa = 10.5). Consequently, all photosensitizers are not charged at physiological pH (approximately 7.4), and so the ionization process does not influence their activity in biological media. Ionization induces very important variations in photosensitizer absorption and emission spectra. For example, absorption in the red region (band V), one of the most important characteristics of a good photosensitizer, is only important for diprotonated porphyrins and neutral chlorins. As far as fluorescence emission is concerned, neutral chlorins are almost six times more fluorescent than the corresponding neutral porphyrins (phi(chlorin)/phi(porphyrin) approximately = 6). It should be emphasized that the spectra modifications induced by pH variations can find interesting applications in the optimization of visible and fluorescence detection in high-performance liquid chromatography (HPLC) as well as in the development of direct, rapid fluorimetric analytical methods.     

The effect of processing parameters on the properties of γ-alumina washcoats deposited on ceramic honeycombs

The coating of cordierite honeycomb specimens with -alumina slurries for the preparation of washcoats for automotive applications was investigated. The dependence of slurry viscosity on factors such as the solids content, the pH and the particle size distribution of the powder used, was determined. Slurry viscosity was correlated to the loading percentage achieved, as well as to the quality of the washcoat in terms of homogeneity and reproducibility. It was found than an adequate solids content in the slurry is necessary for the achievement of satisfactory loading per impregnation. When, though, the particle size of the powder employed is of colloidal dimensions, high solids content leads to extremely high viscosity values. Adjustment of the slurry viscosity is therefore necessary and this was achieved with the use of either HCl or ammonium poly-methacrylate, an organic polyelectrolyte. Optimum loading conditions were achieved when the slurry viscosity lied between 50–150 mPa·s. For a specific solids content, the organic polyelectrolyte led to lower viscosity slurries and resulted in better reproducibility of the loading percentage. With the use of ammonium poly-methacrylate, slurries of fine particles, up to 40 wt% solids content could be handled, resulting in reproducible loading percentages of the order of 15 wt%