Response to comments on upgrading of middle distillate fractions of a syncrude from Athabasca oil sands

In response to an interpretation made by Moore and Akgerman of data taken from a recent publication, previously unexplainable phenomena are accounted for, based on new experimental results. These relate to a thermodynamic equilibrium reaction involving saturation of aromatic hydrocarbons in synthetic crude middle distillates.     

Magnetic permeability measurements in bioanalysis and biosensors

A new transducer concept in bioanalysis and biosensors, utilizing measurements of magnetic permeability, is reported. A model system based on dextran ferrofluid, concanavalin A immobilized to a carrier (Sepharose), and glucose was used to demonstrate the feasibility of this approach. Direct ferromagnetic detection of the dextran ferrofluid was achieved by using a measuring coil (transducer) in a Maxwell bridge. A sensitivity of 21 μV/(μg Fe/mL) and a rsd value of 3.8% were obtained (n = 5). It was also demonstrated that a small, non-ferromagnetic metabolite (glucose) could be detected using a competitive approach. With an increasing concentration of glucose (20-40 mM), we observed a decrease in the response (0.59-0.11 mV). Reference measurements performed on Sepharose without the biorecognition element, concanavalin A, showed no significant response (0.01 mV). Some potential advantages and drawbacks of this novel type of magnetic transducer are discussed. The advantages include very low interference from the sample matrix, as the transducer is only sensitive to ferromagnetic substances, which rarely are present in samples. In addition, it is suggested that these transducers should be free from fouling. The new transducers are proposed to provide the basis for a new group of affinity biosensors suitable for in vivo and in vitro use.     

PRODUCTION OF HIGH QUALITY CETANE ENHANCER FROM DEPITCHED TALL OIL*

Abstract

Tall oil (anglicized Swedish term for pine oil) is a co-product in the Kraft pulping of resinous softwood trees such as spruce and pine. A technology to convert tall oil into high quality diesel additive has been developed and licensed to Arbokem of Vancouver to market the process worldwide. Laboratory and pilot-scale studies were carried out to characterize the product properties and to determine the fundamental and engineering parameters for process scale-up. The tall oil was supplied by BC Chemicals of Prince George, B.C. Pilot plant runs were also carried out to generate volumes of the diesel cut for blending with a base diesel provided by Petro-Canada Products. The blend (PineDiesel) was used for road tests by Canada Post Corporation and for emission tests by Environment Canada.

This paper describes the tall oil conversion at pilot-plant scale. A lumped parameter kinetics model used to guide the process is also presented.     

HYDROPROCESSING OF COAL-DERIVED MIDDLE DISTILLATE

Coal-derived middle distillate, boiling range 437 to 623^°K, was hydrotreated in a fixed bed reactor with a commercial N_iO-M_o0₃/ Al₂O₃ catalyst. The feedstock contained predominantly highly-substituted aromatics. The product heteroatom content and aromaticity decreased with increased process temperature or pressure. Aromaticity was proportional to liquid space velocity. Heteroatonms could be effectively reduced at hydroprocessing conditions of 653^°K, 10 MPa, and 2 WHSV. Experimentally-derived cetane number was found to be proportional to product aromaticity. Severe hydroprocessing conditions were required to produce diesel fuel of acceptable cetane number.     

Basic fibroblast growth factor augments podocyte injury and induces glomerulosclerosis in rats with experimental membranous nephropathy

Podocyte injury is believed to contribute to glomerulosclerosis in membranous nephropathy. To identify the factors involved, we investigated the effects of basic fibroblast growth factor (bFGF), a cytokine produced by podocytes, on rats with membranous nephropathy (passive Heymann nephritis [PHN]). All rats received a daily i.v. bolus of 10 microg bFGF or vehicle from days 3-8 after PHN induction. In proteinuric PHN rats on day 8, bFGF injections further increased proteinuria. Podocytes of bFGF-injected PHN rats showed dramatic increases in mitoses, pseudocyst formation, foot process retraction, focal detachment from the glomerular basement membrane, and desmin expression. bFGF injections in PHN rats did not alter antibody or complement deposition or glomerular leukocyte influx. bFGF-injected PHN rats developed increased glomerulosclerosis when compared with control PHN rats. Also, bFGF induced proteinuria and podocyte damage in rats injected with 10% of the regular PHN-serum dose. None of these changes occurred in bFGF-injected normal rats, complement-depleted PHN rats or rats injected with 5% of the regular PHN serum dose. These divergent bFGF effects were explained in part by upregulated glomerular bFGF receptor expression, induced by PHN serum. Thus, bFGF can augment podocyte damage, resulting in increased glomerular protein permeability and accelerated glomerulosclerosis. This bFGF action is confined to previously injured podocytes. Release of bFGF from glomerular sources (including podocytes themselves) during injury may represent an important mechanism by which podocyte damage is enhanced or becomes self sustained.     

Renal osmotic stress-induced cotransporter: expression in the newborn, adult and post-ischemic rat kidney

The renal osmotic stress-induced cotransporter (ROSIT), a new putative member of a family of organic solute transporters, is highly expressed in the kidney. Our in situ hybridization data now reveal that large amounts of ROSIT mRNA can be found in the S3 segment of the proximal tubule. In the developing kidney, ROSIT mRNA is expressed after the S-shaped body stage. Because the S3 segment is the major site of damage in the post-ischemic kidney, we evaluated alterations in ROSIT mRNA expression after ischemic acute tubular necrosis. Renal osmotic stress-induced cotransporter mRNA levels were already decreased eight hours post-ischemia. At seven days post-ischemia, ROSIT mRNA reappeared in a mosaic pattern in the regenerating S3 segment, being fully expressed three weeks after the insult except for focal areas. The exact localization of this putative osmolyte transporter in the kidney, together with that of other known osmolyte transporter will contribute to a better understanding of the mechanism of medullary osmolyte accumulation and its vectorial transport.     

Visualizing gradients in composite design and fabrication

Greater access to computer resources has prompted scientists, engineers, and designers in all disciplines to go beyond the “number crunching” paradigm and establish visual tools and methodologies that are discipline-independent. The tools most commonly used in mechanics and material science are visualizations of gradients in scalar properties (zeroth-order tensors) and various stress glyphs (second-order tensors). Inherent to the study of these properties is the eigenvalue problem whose eigenvalues (zeroth-order tensors) and eigenvectors (first-order tensors) can be used to characterize physical properties that are second, fourth, and higher order tensors. For example, when the eigenvalue problem models a stress state (a second order tensor), it is possible to create glyphs that visualize the stress state and scalar gradients that visualize its individual components. In this article, we describe two cases of visualizing scalar gradients to study residual stresses and cure properties in complex three-dimensional composite structures, then we show how the need to study the distribution of these properties in a continuum leads to the development of visual tools that allow researchers to see gradients in three, four, and five dimensions. Elsewhere we review the visualization of second-order tensors applied to mechanics and material science, and also extend these representations to fourth-order tensors. These visual tools provide more information for the kinds of analysis we describe here     

Renal medullary circulation: morphological characteristics of vessels and their organization

The blood vessels of the renal medulla have several particular features. The supplying vessels of the renal medulla are the efferent arterioles of the juxtamedullary glomeruli. Thus, the blood supply is entirely postglomerular. The distribution of the blood within the renal medulla is effected by the descending vasa recta. Descending and ascending vasa recta form the vascular bundles. Descending vasa recta leave the bundles at any level of the medulla to feed the adjacent capillaries; the longest descending vasa recta reach the papillary tip. The capillary plexus are differently developed. A dense capillary plexus is present only in the inner stripe of the outer medulla. In the inner medulla the capillary plexuses are poorly developed. At these sites ascending recta contribute to the capillarisation. The ascending vasa recta originate from capillaries at any level of the medulla and ascend without joining together towards the intrarenal veins at the cortico-medullary border. They are capillary vessels with wide lumina. Within the outer stripe of the outer medulla these vessels are very narrowly associated with the tubules; interstitial spaces are very poorly developed at this site. These relationships are interpreted as a possible weak point of the medullary circulation in pathological situations.     

Variations of a differential system containing discontinuities

The paper deals with differential equations with discontinuous right-hand sides. The variational equations for the partial derivatives of the solution with respect to the initial values are established. Formulae for the jump in the partial derivatives at the points where the right-hand side is discontinuous are derived. An application to a two-point boundary value problem is given. The theory is extended to allow general variations and transformations of variables at the points of discontinuity.