Probe Effects on the Local Gas Holdup Conditions in a Fluidized Bed

Fluidized beds are found in the energy production industry, it is important to know their hydrodynamic conditions, such as local gas holdup or volumetric gas fraction, for effective operation. Local measurement probes have been used to measure local gas holdup. Although the probes are typically as small as possible to mitigate their influence on the local conditions, the invasive nature of this measurement technique has the potential to alter the fluidized bed behavior. This study used a noninvasive measurement technique, X-ray computed tomography (CT) imaging, to determine the local time-average gas holdup everywhere within a 10.2 cm diameter fluidized bed filled with 500-600 μm glass beads in which simulated probes were inserted. Three different probe tips (pointed, rounded, and flat) and two different orientations (horizontal and vertical) were investigated at four different bed heights and two different fluidization velocities. The results show increases in local time-average gas holdup when the probes are present, but the scale of the effects was dependent upon the height at which the probes were placed; the lower the probe within the fluidized bed, the larger the local effects. Probe tip geometry showed no differences in the local gas holdup. Probe orientation was an important factor though, with the horizontal orientation showing a sustained increase in gas holdup values farther upstream from the probe. The two different flow rates used in this study (1.5Umf and 3Umf, where Umf is the minimum fluidization velocity) also showed differences in the amount of variation in gas holdup, but the trends were inconsistent

Exploring the Structure and Function of the SNF1 Kinase Gene in the Slime Mold \u3ci\u3eDictyostelium Discoideum\u3c/i\u3e

All organisms must respond to different environmental stresses. For unicellular organisms, the most important source of stress is starvation or nutrient depletion. These microscopic life forms must respond to a constantly changing food supply in which short periods of nutrient availability are interspersed with extended periods of famine. In addition to complete starvation, these organisms are affected by other chemical changes, such as forced switching from a desirable to a less desirable carbon source, and physical changes, such as heat shock. Many microorganisms respond to such stresses by entering a different phase of their life cycle. For example, the budding yeast Saccharomyces cerevisiae responds by forming ascospores (1). Another unicellular organism, the slime mold Dictyostelium discoideum responds to stress by fruiting body formation (2). Although multicellular organisms are relatively less susceptible to drastic changes in nutrient availability, they still must respond to stresses including nutrient deprivation, heat shock, and toxins. Many multicellular organisms, including mammals, respond to stress by altering their lipid metabolism (3, 4)

A Cell Line for Detection of Botulinum Neurotoxin Type B

Botulinum neurotoxins (BoNTs) type A and type B are commonly used as biopharmaceutics for neurological diseases, uniquely allowing months-long paralysis of target muscles. Their exquisite neuronal specificity is conferred by a multistep process of binding, internalization, cytosolic escape and cleavage of the neuron-specific proteins, SNAP-25 and vesicle-associated membrane proteins (VAMPs), ultimately to inhibit secretion of neurotransmitters. Currently the mouse lethality bioassay is the only available method for quality control testing of VAMP-cleaving botulinum products. Refined assays for botulinum product testing are urgently needed. Specifically, in vitro replacement assays which can account for all steps of BoNT intoxication are in high demand. Here, we describe a novel SiMa cell-based approach where re-engineering of the VAMP molecule allows detection of all BoNT/B intoxication steps using a luminescent enzymatic reaction with sensitivity comparable to mouse LD50 bioassay. The presented one-step enzyme-linked immunosorbent assay meets 3Rs (replacement, reduction, and refinement of the use of animals) objectives, is user-friendly and will accelerate development of new botulinum drugs. The sensitive enzymatic reporter cell line could also be adapted for the detection of toxin activity during the manufacture of botulinum and tetanus vaccines

Probe Effects on the Local Gas Holdup Conditions in a Fluidized Bed

Fluidized beds are found in the energy production industry, it is important to know their hydrodynamic conditions, such as local gas holdup or volumetric gas fraction, for effective operation. Local measurement probes have been used to measure local gas holdup. Although the probes are typically as small as possible to mitigate their influence on the local conditions, the invasive nature of this measurement technique has the potential to alter the fluidized bed behavior. This study used a noninvasive measurement technique, X-ray computed tomography (CT) imaging, to determine the local time-average gas holdup everywhere within a 10.2 cm diameter fluidized bed filled with 500-600 μm glass beads in which simulated probes were inserted. Three different probe tips (pointed, rounded, and flat) and two different orientations (horizontal and vertical) were investigated at four different bed heights and two different fluidization velocities. The results show increases in local time-average gas holdup when the probes are present, but the scale of the effects was dependent upon the height at which the probes were placed; the lower the probe within the fluidized bed, the larger the local effects. Probe tip geometry showed no differences in the local gas holdup. Probe orientation was an important factor though, with the horizontal orientation showing a sustained increase in gas holdup values farther upstream from the probe. The two different flow rates used in this study (1.5Umf and 3Umf, where Umf is the minimum fluidization velocity) also showed differences in the amount of variation in gas holdup, but the trends were inconsistent.</p

The Web: A Means of Delivering and Publishing Serials with an Examination of Copyright Issues

Economic forces have created the need for librarians to explore new methods of delivering information. Technological developments have created the means for librarians themselves to move into electronic publishing to increase cost-efficiency. A new consortium model is proposed in which members would both generate scholarly work and access it at a lower cost. Included are overviews of scholarly publishing, copyright issues, technological feasibility, value added features, and the effects of the proposed consortium