Mixed waste ferrite as a novel sorbent for carbon dioxide derived from flue gases

Ferrite is a potential sorbent for flue gases such as CO₂, H₂S and SO₂. This paper discusses the adsorption and decomposition of CO₂ into carbon by hydrogen-activated waste ferrites prepared from Berkeley Pit acid mine water (Butte, MT). The decomposition effectiveness of these waste ferrites was studied at 300 °C and compared with the synthetic magnetite obtained from ferrous sulfate solution in our laboratory. The decomposition was measured by two methods: indirectly by measuring the adsorption rate of CO₂ and directly by analysing the carbon deposited on the samples. The results indicated that the mixed waste ferrite had good affinity for the adsorption and decomposition. The CO₂ decomposition data of both sorbents fitted the first-order reaction kinetics. Even though the surface area of the magnetite was higher than that of waste ferrite, the CO₂ decomposition rate of the waste ferrite was estimated to be 2.5 times higher than that of magnetite under identical conditions. The carbon analysis deposited on the sample indicated that the CO₂ was 100% decomposed into carbon and other carbon/hydrogen compounds by the waste ferrite, whereas the conversion was 43% by the magnetite. In terms of specific adsorption of carbon, ferrite was three to five times more efficient than magnetite.     

Vessel wall detection and blood noise reduction in intravascularultrasound imaging

Scattering from blood limits the contrast between the vessel wall and the lumen in intravascular ultrasound imaging. This makes it difficult to localize the vessel wall, especially on still images. This paper presents a method for automatic detection of vessel walls and reduction of blood noise based on correlation of the RF-signal between adjacent frames. The ultrasound RF-signal is quadrature demodulated, digitized, stored in memory, and transferred to a computer for processing and analysis. The absolute value of the cross-correlation coefficient between two adjacent frames is used to differentiate between stationary and fluctuating signals. Models and numerical calculations presented in this work indicate that the cross-correlation coefficient obtained from a radially dilating vessel wall will be larger than 0.8 under standard 20 MHz imaging conditions. The corresponding value from blood is less than 0.2 for blood velocities exceeding 0.5 cm s^-1 . The blood-noise filter is based on detecting this difference in correlation and displays vessel wall regions with no modifications, while regions detected as blood are rejected. A simplified vessel-wall detector that is suitable for real-time implementation is proposed. The performance of this detector and the blood noise filter are demonstrated by in vitro experiments     

A dislocation shielding prediction of the toughness transition during cleavage of semibrittle crystals

An interconnected set of observations assesses current equilibrium models of the ductile-brittle-transition temperature (DBTT). This involvesin situ transmission electron microscopy (TEM) studies of crack-tip dislocations in single and polycrystals and bulk fracture toughness tests at various temperatures. Beyond K_I values of 8 MPa · m^1/2 in both iron-base single and polycrystals, large numbers of redundant dislocations are created, as postulated recently by Weertman. [38] Still, the necessary shielding dislocations, as required by equilibrium, can be detected at values as high as 20 and 40 MPa · m^1/2 byex situ TEM and electron channeling, respectively. In addition, the close approach of dislocations to the crack tip in some of the studies, as opposed to others, suggests that large dislocation free zones (DFZ) are a thin-film artifact. However, a failure criterion based partly on the Rice-Thomson model’21 is both consistent with the absence of a large DFZ and observed fracture toughness variations with test temperature. It is emphasized that this toughness transition is entirely in the semibrittle regime where cleavage is the failure mode. Nevertheless,K _lc values increase from 3 to 60 MPa·m^1/2 with an increase in test temperature. This article is based on a presentation made in the symposium “Quasi-Brittle Fracture” presented during the TMS fall meeting, Cincinnati, OH, October 21–24, 1991, under the auspices of the TMS Mechanical Metallurgy Committee and the ASM/MSD Flow and Fracture Committee.     

Laminar flame theory. Part II

The laminar flame theory under the condition of minimum entropy production is presented. The equation of the temperature boundary layer is obtained for Le=0, and its general solution is found. It is shown that the mechanism of laminar flame propagation can be treated from the viewpoint of stationary thermal explosion in a cylindrical vessel of radius 2 as the critical regime in which the burnup is taken into account in an unusual form. Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 22–30, September–October, 1993     

Superconductivity and magnetism in niobium doped YBa2Cu3O7 Related high Tc ceramics

Magnetic characterization has been performed on the members of the cuprateniobate RBa₂Cu₂NbO₈ (R = Pr, Nd, and La) series and R_1.5Ce_0.5Sr₂Cu₂NbO₁₀ (R = Pr, Eu, Nd, and Sm) series. The PrBCNO samples show a signature in the magnetization of a magnetic ordering at 12K. The PrCSCNO sample is nonsuperconducting and shows two distinct orderings at 17K and 53K. No such magnetic phase transition is observed down to 2K in the Nd and La based RBCNO materials or the Nd, Sm, and Eu based RCSCNO materials. Measurements of the lower critical field curve, dc irreversibility line, and critical curent densities are reported for each of the superconducting NdCSCNO, SmCSCNO, and EuCSCNO compounds.     

Transport properties of oxygen-deficient YBa2Cu3O7−x thin films

We report on measurements of the in-plane resistivityρ and Hall coefficientR _H (B∥c) of various oxygen-deficient epitaxial films of YBa₂Cu₃O_7?x in the normal state. The superconducting transition temperaturesT _c of the samples vary from 14 to 90 K. Both the resistivity and the Hall coefficient exhibit a strong dependence on the oxygen content and the temperature. Asx increases,T _c decreases continuously, whileρ andR _H gradually increase in magnitude. Furthermore, also the characteristic linear dependences ofραT andR _Hα T ^?1 of the highly doped compounds changes to a nonlinear behavior for the samples withT _c lower than 60 K. The unusual doping and temperature dependence ofR _H will be compared to the predictions of our calculations, based on a two-dimensional tight-binding model using the relaxation-time approximation. The model considers also the next-nearest-neighbor hopping, which strongly influences the predicted Hall coefficient. Additionally, the cotangent of the Hall angle cot(Θ _H ) is discussed in the framework of the two-dimensional Luttinger liquid theory.     

Structural determination of N-2''-hydroxyoctadecenoyl-1-O-beta-D-glucopyranosyl-9-methyl-4, 8-sphingadienine from species of Aspergillus

The barrier function, surface biochemistry, and morphology of confluent monolayers of endothelial cells isolated from different segments of the bovine lung vasculature [microvessels (BLMVEC), vein (BPVEC) and artery (BPAEC)] were grown in culture and compared. A number of common cell surface proteins were identified along with two proteins of 46 and 48 kDa found exclusively on BPVEC. Lectin affinity chromatography revealed multiple glycosylation differences. The lectins, Arachis hypogaea (AHA) and Lycopersicum esculentum (LEA) agglutinins, interacted with several glycoproteins of BLMVEC but not of BPAEC. Bandeiraea simplicifolia (BS-1) and Caragana arborescens (CAA) agglutinins recognized several glycoproteins of BPVEC and BPAEC but not BLMVEC. Permeabilities were much lower for BLMVEC than BPAEC or BPVEC monolayers, with a range of about 16-fold less for sucrose to 2-fold less for albumin. Electron microscopy revealed that BLMVEC have a greater surface density of plasmalemmal vesicles (approximately 4-fold) and more extensively developed intercellular junctions with more focal membrane adhesion sites per junction (approximately 9-fold) than the other cells. We conclude that: i) BLMVEC monolayers form a much more restrictive barrier to molecular transport as a result of the tighter junctional formation; and ii) endothelial surface glycoproteins may be differentially glycosylated depending on their segmental location within the vasculature.     

Inhalation toxicity of 1,6-hexanediamine dihydrochloride in F344/N rats and B6C3F1 mice

1,6-Hexanediamine (HDA) is a high production volume chemical which is used as an intermediate in the synthesis of paints, resins, inks, and textiles and as a corrosion inhibitor in lubricants. Two- and 13-week studies of the toxicity of the dihydrochloride salt of HDA (HDDC) were conducted in male and female Fischer 344/N rats and B6C3F1 mice using whole-body inhalation exposure. Both species were evaluated for histopathologic and reproductive effects, and rats were examined for clinical chemistry and hematologic changes. In the 2-week inhalation studies, animals were exposed to 10-800 mg HDDC/m3, 6 hr per day. All rats, all female mice, and two of five male mice in the high-exposure group died before the end of the study. Surviving mice in this group had a dose-dependent depression in body weight gain. Clinical signs were primarily related to upper respiratory tract irritation and included dyspnea and nasal discharge in both species. Treatment-related histopathologic lesions included inflammation and necrosis of the laryngeal epithelium of both species and the tracheal epithelium of mice, as well as focal inflammation and ulceration of the respiratory and olfactory nasal mucosa. In the 13-week inhalation studies, animals were exposed to HDDC at concentrations of 1.6-160 mg/m3 for 6 hr per day, 5 days per week. In addition to the base study groups, a supplemental group of rats at each exposure level was included to assess the effect of HDDC on reproduction. No treatment-related changes in organ weights or organ-to-body-weight ratios occurred in rats, and no treatment-related clinical signs or gross lesions were seen in either species. Chemical-related microscopic lesions were limited to the upper respiratory tract (larynx and nasal passages) in the two highest exposure groups and were similar in both species. These lesions included minimal to mild focal erosion, ulceration, inflammation, and hyperplasia of the laryngeal epithelium, in addition to degeneration of the olfactory and respiratory nasal epithelium. HDDC caused no significant changes in sperm morphology or vaginal cytology and no significant adverse effects on reproduction in rats or mice. Hematologic and clinical chemistry changes in rats were minor and sporadic and were not accompanied by related histologic findings. HDDC did not increase the frequency of micronucleated erythrocytes in mice.(ABSTRACT TRUNCATED AT 400 WORDS)