Hydrocarbon condensation modelling to mitigate fluid coker cyclone fouling

FLUID COKING is a continuous process that thermally converts heavy hydrocarbons, such as oil sands bitumen, to lighter and higher‐value products by horizontal spray injection onto a fluidized bed of hot coke particles. The cyclone sections of commercial fluid coker reactors experience fouling during typical operation, which limits unit run lengths. The main objective of this work is to improve fluid coker reliability by proposing cyclone fouling mitigation strategies based on practical operation modifications. This study developed a process simulation in Aspen Plus to establish the combined impact of vapour‐liquid equilibrium, endothermic thermal cracking reactions, pressure changes, and overall fluid dynamics in the selected fluid coker control volumes. The hydrocarbon composition was defined by applying an assay characterization of distillation data for representative hydrocarbon streams. Case studies were performed to determine the sensitivity of the predicted temperatures and hydrocarbon condensate flow rates for: (a) the burner‐to‐fluid coker transfer line temperature; (b) the hot coke flow rate; (c) hot coke entrainment from the freeboard region; and (d) scouring coke flow rate in the horn chamber. The scouring coke flow rate was identified as the most promising process lever to mitigate fluid coker cyclone fouling.     

Sterol and steryl ester regulation of phospholipase A2 from the mosquito parasiteLagenidium giganteum

Lagenidium giganteum, a facultative parasite of mosquito larvae, cannot synthesize sterols, and requires an exogenous source of these lipids in order to enter its reproductive cycle. This parasite grows vegetatively in the absence of sterols, but requires cholesterol or structurally related compounds to produce motile zoospores, which are the only stage capable of infecting mosquitoes. Sterols structurally related to cholesterol and some steryl esters inhibited the activity ofL. giganteum phospholipase A₂ (PLA₂), an enzyme that hydrolyzes fatty acids from thesn-2 position of glycerophospholipids. Sterols that induce reproduction inhibitedL. giganteum PLA₂ activity, while sterols and steroids that do not support sporulation had minimal effect. Most steryl esters had no effect on enzyme activity, but cholesteryl arachidonate (CA) was a potent inhibitor of parasite PLA₂. Not all enzymes partly purified using a DEAE-Sephacel column were affected by these lipids, demonstrating selective inhibition of specific enzymes. Potency was enhanced by up to several orders of magnitude if epoxy fatty acids were esterified to the cholesterol nucleus. The steryl ester pool was dynamic during morphogenesis, and the fatty acid composition of the steryl esters did not mimic total cell or membrane (glycerophospholipid) fatty acid composition asL. giganteum proceeded through its growth cycle. Synthesis of CA and monoepoxy CA by the parasite was confirmed using electrospray mass spectrometry and collision-induced dissociation. Steryl derivatives selectively inhibited PLA₂ enzymes from bovine pancreas, snake venom, and human cytoplasmic 85-kDa PLA₂.     

Effects of sediment addition on macrobenthic invertebrates in a Northern Canadian River

Two channels built into the Harris River, Northwest Territories were used to study responses of invertebrates to sediment addition. Sediment was added to one channel continuously for approximately 5 h. The other channel was used as a control. In August, 28.27 kg of sediment or 1.38 kg m⁻² of channel bottom were added. Values for September were 35.88 kg or 1.53 kg m⁻².As a result of sediment addition, numbers of macrobenthos drifting from the sediment addition channel (S) increased significantly over those drifting in the control (C) in August (= summer) and September (= fall). Total drift from S was > 3 times higher in August and > 2 times higher in September than from C. Significantly higher numbers of macrobenthos drifted in fall than summer. Numbers of macrobenthos drifting during sediment addition were significantly related to time in September but not in August, indicating a seasonal difference in temporal response to sediment addition. Two explanations are proposed for the response of the September community, as indicated by shape of a polynomial regression curve, to sediment addition. No significant difference existed in standing crops of macrobenthos in the substrate in C and S after sediment addition.Sediment addition caused (1) higher numbers of Oligochaeta and Simuliidae to drift in August and September; (2) higher numbers of Plecoptera and Ephemeroptera to drift in September but not in August; and (3) higher numbers of Hydracarina and Chironomidae to drift in August but not September.We suggest that future work try to relate amounts of settled rather than suspended sediments to quantitative responses of stream macrobenthos. We recommend that highway and pipeline construction undertaken in watersheds of Mackenzie Valley streams during the open-water period, resulting in sediment addition to these streams, should be done during summer rather than spring or fall, providing river discharge is adequate to transport the added sediment.     

NanoSIMS: Insights into the Organization of the Proteinaceous Scaffold within Hexactinellid Sponge Spicules

The giant basal spicules (GBS) from Monorhaphis chuni (Porifera [sponges], Hexactinellida) represent the largest biosilica structures on Earth and can reach lengths of 300 cm (diameter of 1.1 cm). The amorphous silica of the inorganic matrix is formed enzymatically by silicatein. During this process, the enzyme remains trapped inside the lamellar‐organized spicules. In order to localize the organic silicatein scaffold, the inside of a lamella has been analyzed by nano‐secondary ion mass spectrometry (NanoSIMS). It is shown that the GBSs are composed of around 245 concentrically arranged individual siliceous lamellae. These surround an internal siliceous axial cylinder. The lamellae adjacent to the cylinder are thicker (10–30 μm) than the more peripheral lamellae (2–10 μm). One lamella of a thickness of 18 μm has been selected for further analysis. This lamella itself is composed of three sublamellae with an individual thickness of 2–6 μm each, which are then further organized into three cylindrical slats (thickness: 1.6–1.8 μm). Other than the main lamellae, the sublamellae are not separated from each other by gaps. The element analysis of the sublamellae by NanoSIMS revealed that the siliceous matrix is embedded in an organic matrix that consists of up to 6–10 wt/% of C. The pattern of C distribution reflects a distinct zonation of the organic material within the solid intralamellar biosiliceous material. A growth model for the lamella starting from nanosized silica particles is proposed: During formation of a lamella nanosized silica particles fuse, through biosintering processes, to slats that build the individual sublamellae, which then finally form the lamellae. In turn, those lamellae may form the higher structural entity, the axial cylinder.     

Communication length as an index of communicator attitude: A replication.

Attempted a replication of a study by A. Mehrabian (see 40:2) who extended studies of speech behavior to apply to letters of recommendation. 69 undergraduates were asked to write 2 letters, both positive. For the 1st letter they were asked to assume strong liking for the person they were describing; for the 2nd letter they were to assume strong dislike for the person being described. Mehrabian's Ss wrote significantly more words in the 1st letters. The replication fully confirms his results. These findings suggest that the written channel of communication may be as sensitive a mirror of S's underlying attitudinal state as earlier research had revealed was the case with the spoken channel of communication. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Black Intelligence Test of Cultural Homogeneity and Wechsler Adult Intelligence Scale scores of Black and White police applicants.

Administered the 100-item Black Intelligence Test of Cultural Homogeneity (BITCH) and the full WAIS to 83 Black and White police applicants. Ss' mean age was in the early 20's, and their mean educational level was 21/2 yrs of college. Results reveal considerable overlap in the distributions of individual WAIS Full Scale IQ between the Black and White Ss, but 2 totally nonoverlapping distributions of scores on the BITCH, with no White Ss scoring above Black Ss. BITCH means were as follows: White females, 60.9; White males, 64.1; Black females, 86.7; and Black males, 83.9. The corresponding WAIS Full Scale IQ means were 117.2, 117.8, 110.2, and 101.6, respectively. Correlational analyses between the BITCH and each of the 14 WAIS measures revealed no relation between score on the BITCH and score on the WAIS. It is concluded that the lack of concurrent validity for the present form of the BITCH and its lack of adequate ceiling for Black applicants presents problems for its use in a program of police selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)