Screening wall effects of a thin fluidized bed by near-infrared imaging

Near-infrared (NIR) imaging was used to observe water vapour flow in a gas-solid fluidized bed reactor. The technique consisted of a broadband light, an optical filter with a bandwidth centred on strong water vapour absorptions, a Vidicon NIR camera, a nozzle from which an optically active mixture of gas and water vapour was trans-illuminated by an NIR beam and collected data of transmittance were normalized to actual optical path. The procedure was applied to a thin fluidized bed reactor with a low aspect ratio of tube to particle diameters (D-1/d(p)) in order to validate the wall effect on flow dynamics and mass transfer during the reduction of ceria-silica by hydrogen. High concentrations of water vapour emerged in the vicinity of the wall when the bed was operated at pseudo-static conditions but disappeared when the bed was run at minimum bubbling conditions. This result shows the capability of optical methods with affordable costs to 2D imaging opaque packed bed by using a spatially resolved probe located at the exit, which is of great benefit for in situ visualization of anisotropic concentrations in packed beds under industrially relevant conditions and thus for elucidation of the underlying reaction mechanism and diffusion interactions. Crown Copyright (c) 2011 Published by Elsevier B.V. All rights reserved.

Capillary microreactors wall-coated with mesoporous titania thin film catalyst supports

A new method for catalyst deposition on the inner walls of capillary microreactors is proposed which allows exact control of the coating thickness, pore size of the support, metal particle size, and metal loading. The wall-coated microreactors have been tested in a selective hydrogenation reaction. Activity and selectivity reach values close to those obtained with a homogeneous Pd catalyst. The catalyst activity was stable for a period of 1000 h time-on-stream.

Concomitant and antecedent deep venous thrombosis and cancer survival in male US veterans

Survival is reportedly worse in patients with cancer concurrently diagnosed with deep venous thrombosis. However, information on specific malignancies is limited. From a cohort study of male US veterans we identified incident cancer cases (n aEuroS== aEuroS412 008) and compared survival patterns among those with versus without a history of deep venous thrombosis. Using Cox proportional hazard models, we estimated hazard ratios (HRs) and 95%% confidence intervals as measures of the relative risk of dying. Individuals with (versus without) a concomitant deep venous thrombosis and cancer diagnosis had a higher risk of dying (HR aEuroS== aEuroS1.38; 1.28--1.49). The most prominent excess mortality (HR aEuroS== aEuroS1.29--2.55) was observed among patients diagnosed with deep venous thrombosis at the time of diagnosis of lung, gastric, prostate, bladder, or kidney cancer. Increased risk of dying was also found among cancer patients diagnosed with deep venous thrombosis 1 year (HR aEuroS== aEuroS1.14; 1.07--1.22), 1--5 years (HR aEuroS== aEuroS1.14; 1.10--1.19), and > 5 years (HR aEuroS== aEuroS1.27; 1.23--1.31) before cancer; this was true for most cancer sites (HR aEuroS== aEuroS1.17--1.64). In summary, antecedent deep venous thrombosis confers a worse prognosis upon cancer patients. Advanced stage at diagnosis, treatment effects, lifestyle factors, and comorbidity could explain differences by cancer site and time frame between a prior deep venous thrombosis diagnosis and cancer outcome.

Diabetic retinopathy: quantitative variation in capillary basement membrane thickening in arterial or venous environments

Diabetes mellitus was induced in male beagles by a single injection of an alloxan and streptozotocin cocktail and fasting blood sugar levels maintained between 15 and 20 mmol/l. Five years after induction of diabetes, three diabetic animals were sacrificed, together with sex and age-matched controls, and the retinas fixed for either transmission electron microscopy (TEM) or trypsin digestion. In TEM specimens, capillaries in close proximity to the major vessels were designated as either AE (arterial environment) or VE (venous environment) and the thickness of their basement membranes (BMs) measured using an image analyser based two dimensional morphometric analysis system. Results show that the BMs of retinal capillaries from the diabetic dogs were significantly thicker than those from control dogs. Furthermore, within the diabetic group the AE capillaries had thicker BMs than VE capillaries (p less than or equal to 0.05). The controls, however, showed no significant difference in BM thickness between AE and VE capillaries. Although many of the capillaries designated as AE or VE would actually have been derived from the opposite side of the circulation, with respect to BM thickness, they conformed to values of their specific group. The conclusion is that diabetic capillaries are more vulnerable to BM thickening in an arterial environment than in a venous environment.

Domain Wall Propagation in Meso and Nanoscale Ferroelectrics

As part of an ongoing programme to evaluate the extent to which external morphology alters domain wall mobility in ferroelectrics, the electrical switching characteristics of single-crystal BaTiO3 nanorods and thin film plates have been measured and compared. It was found that ferroelectric nanorods were more readily switched than thin plates; increasing the shape constraint therefore appears to enhance switchability. This observation is broadly consistent with previous work, in which local notches patterned along the length of nanorods enhanced switching (McMillen et al 2010 Appl. Phys. Lett. 96 042904), while antinotches had the opposite effect (McQuaid et al 2010 Nano Lett. 10 3566). In this prior work, local enhancement and denudation of the electric field was expected at the notch and antinotch sites, respectively, and this was thought to be the reason for the differences in switching behaviour observed. However, for the simple nanorods and plates investigated here, no differences in the electric field distributions are expected. To rationalise the functional measurements, domain development during switching was imaged directly by piezoresponse force microscopy. A two-stage process was identified, in which narrow needle-like reverse domains initially form across the entire interelectrode gap and then subsequently coarsen through domain wall propagation perpendicular to the applied electric field. To be consistent with the electrical switching data, we suggest that the initial formation of needle domains occurs more readily in the nanorods than in the plates.