Naresuan University Journal
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Investigating the discrepancy between wet-suspension and dry-dispersion derived ice nucleation efficiency of mineral particles
No full textCloud chamber investigations into ice nucleation by mineral particles were compared with results from cold-stage droplet freezing experiments. Kaolinite, NX-illite, and K-feldspar were examined, and K-feldspar was revealed to be the most ice-active mineral particle sample, in agreement with recent cold-stage studies. The ice nucleation efficiencies, as quantified using the ice-active surface site density method, were found to be in agreement with previous studies for the lower temperatures; however, at higher temperatures the efficiency was between a factor of 10 and 1000 higher than those inferred from cold-stage experiments. Numerical process modelling of cloud formation during the experiments, using the cold-stage-derived parameterisations to initiate the ice phase, revealed the cold-stage-derived parameterisations to consistently underpredict the number of ice crystals relative to that observed. We suggest the reason for the underestimation of ice in the model is that the slope of the cold-stage-derived ice-active surface site density vs. temperature curves are too steep, which results in an underestimation of the number of ice crystals at higher temperatures during the expansion. These ice crystals suppress further freezing due to the Bergeron-Findeison process. A coagulation model was used to investigate the idea that the mineral particles coagulate in suspension. This model suggests that coagulation during the experiments may be sufficient to significantly remove the particles for the suspension by sedimentation or reduce the total particle surface area available for ice nucleation to take place. Aggregation was confirmed to take place in mineral suspensions using dynamic light-scattering measurements. However, it is not proven that aggregation of the mineral particles is able to reduce the surface area avail-able for ice nucleation. The implication is that the mineral particles may be more important at nucleating ice at high temperatures than previously thought
8th International Conference on Computational Heat and Mass Transfer
No full textA numerical analysis for the fluid flow and heat transport phenomenon through a rotary thermal regenerator is presented by means of employing the porous media concept. An aluminum core formed of multi packed square passages is simulated as a porous medium of an orthotropic porosity in order to allow the counter-flowing streams to flow in a way similar to that inside the regenerator core. The geometricproperties of the core were transformed into the conventional porous media parameters such as the permeability and the inertial coefficient based on empirical equations; so, the core has been dealt with as a porous medium of known features. Local thermal non-equilibrium situation is assumed between both fluid and solid phases, so heat is allowed to be exchanged between them. The results are presented by means of overall temperature effectiveness, pressure drop, and the relative output power. The use of porous media approach has been found to besufficient to solve the current problem. The data obtained reveals an obvious impact of the core geometrical parameters on both the heat restored and the pressure loss; and hence, the overall efficiency of the regenerator system
Insurance as Maladaptation: Resilience and the 'business as usual' paradox
No full textInsurance and compensation are cited as critical elements of resilience to natural and nonnatural hazards alike. As a strategy of risk management, it emphasises peace of mind, financial recompense and the swift restoration of a ‘business as usual’ status for civil, social and commercial life. Yet despite the contribution of insurance to risk management, the synergies with progressive or adaptive articulations of resilience are not sufficiently explicated. This paper explores the fundamental contradictions of insurance as a form of resilience through a study of flood risk management. It demonstrates how insurance regimes serve to structurally embed risky behaviour and inhibit change after detrimental events. As such, transformative interpretations of resilience conflict with the long-standing principles and operational norms of insurance that privilege normality. The paper concludes that, despite its currency within resilience discourses, insurance is maladaptive and that insurance regimes reinforce exposure and vulnerability through underwriting a return to the ‘status-quo’ rather than enabling adaptive behaviour
Material hardship and 529 college savings plan participation: The mitigating effects of Child Development Accounts
No full textExperience of material hardship can adversely affect a family's ability to make long-term investments in children's development. We examine whether material hardship is associated with one indicator of such investments: participation in a tax-advantaged college savings plan (529 plan). Data for this study come from the SEED for Oklahoma Kids (SEED OK) experiment, an intervention that offers Child Development Accounts with financial incentives to encourage the accumulation of college savings for children from the time of their birth. Results show that material hardship is negatively associated with 529-plan participation, and this association varies by treatment status. At all levels of material hardship, treatment-group mothers are more likely to hold accounts than control-group mothers. These findings suggest that CDAs can be a useful policy tool to support families' financial preparation for college
miR-145 suppresses embryo-epithelial juxtacrine communication at implantation by modulating maternal IGF1R
No full textSuccessful implantation requires the synchronization of viable embryonic development with endometrial receptivity. The mechanisms allowing for the initiation of crosstalk between the embryo and the endometrium remain elusive, however recent studies have revealed alterations in endometrial microRNAs (miRs) in women suffering repeated implantation failure; one of the altered miRs is miR-145. We assessed the role of miR-145 and its target, IGF1R, in early implantation. miR-145 overexpression and IGF1R knockdown were achieved in Ishikawa endometrial cells. QPCR, western blotting and 3'UTR luciferase reporter assays confirmed that IGF1R is a direct target of miR-145 in the endometrium. Attachment of mouse embryos or IGF-I-coated beads to endometrial epithelial cells was used to study the effects of altered miR-145 and/or IGF1R expression on early implantation events. miR-145 overexpression or specific reduction of IGF1R impaired attachment in both cases. miR-145/IGF1R target protectors prevented miR-145-mediated reduction in IGF1R and reversed the effect of miR-145 overexpression on attachment. The data demonstrate that miR-145 influences embryo attachment by reducing the level of IGF1R in endometrium
Impact of DC Breaker Systems on Multiterminal VSC-HVDC Stability
No full textThe use of VSC-HVDC grids for offshore wind farm integration will require the use of dc breaker systems and they, at present, will require dc reactors to limit the rate of rise of fault current. The introduction of large dc reactors throughout a VSCHVDC system can have significant impact on its stable operation and will require additional control. This paper analyses this problem and proposes a PSS-like control (DCPSS) to aid dc grid stability and cope with this effect. A generalized analytical model for studies on dc voltage control is presented. Key stability and transient performance issues caused by the use of the dc reactors in a multi-terminal system, are investigated by analyzing poles, zeros and frequency responses of both open-loop and closed-loop models. Design and location identification methods for the DCPSS are provided. Excellent damping enhancement is achieved by this controller. The analytical studies and time-domain simulations in this paper are performed based on two VSC-HVDC models
Immune tolerance. Group 3 innate lymphoid cells mediate intestinal selection of commensal bacteria-specific CD4⁺ T cells.
No full textInflammatory CD4(+) T cell responses to self or commensal bacteria underlie the pathogenesis of autoimmunity and inflammatory bowel disease (IBD), respectively. Although selection of self-specific T cells in the thymus limits responses to mammalian tissue antigens, the mechanisms that control selection of commensal bacteria-specific T cells remain poorly understood. Here, we demonstrate that group 3 innate lymphoid cell (ILC3)-intrinsic expression of major histocompatibility complex class II (MHCII) is regulated similarly to thymic epithelial cells and that MHCII(+) ILC3s directly induce cell death of activated commensal bacteria-specific T cells. Further, MHCII on colonic ILC3s was reduced in pediatric IBD patients. Collectively, these results define a selection pathway for commensal bacteria-specific CD4(+) T cells in the intestine and suggest that this process is dysregulated in human IBD
Properties of small cirrus ice crystals from commercial aircraft measurements and implications for flight operations
No full textMeasurements of cloud ice crystal size distributions have been made by a backscatter cloud probe (BCP) mounted on five commercial airliners flying international routes that cross five continents. Bulk cloud parameters were also derived from the size distributions. As of 31 December 2014, a total of 4399 flights had accumulated data from 665 hours in more than 19 000 cirrus clouds larger than 5 km in length. The BCP measures the equivalent optical diameter (EOD) of individual crystals in the 5–90 µm range from which size distributions are derived and recorded every 4 seconds. The cirrus cloud property database, an ongoing development stemming from these measurements, registers the total crystal number and mass concentration, effective and median volume diameters and extinction coefficients derived from the size distribution. This information is accompanied by the environmental temperature, pressure, aircraft position, date and time of each sample. The seasonal variations of the cirrus cloud properties measured from 2012 to 2014 are determined for six geographic regions in the tropics and extratropics. Number concentrations range from a few per litre for thin cirrus to several hundreds of thousands for heavy cirrus. Temperatures range from 205 to 250 K and effective radii from 12 to 20 µm. A comparison of the regional and seasonal number and mass size distributions, and the bulk microphysical properties derived from them, demonstrates that cirrus properties cannot be easily parameterised by temperature or by latitude. The seasonal changes in the size distributions from the extratropical Atlantic and Eurasian air routes are distinctly different, showing shifts from mono-modal to bi-modal spectra out of phase with one another. This phase difference may be linked to the timing of deep convection and cold fronts that lead to the cirrus formation. Likewise, the size spectra of cirrus over the tropical Atlantic and Eastern Brazil differ from each other although they were measured in adjoining regions. The cirrus crystals in the maritime continental tropical region over Malaysia form tri-modal spectra that are not found in any of the other regions measured by the IAGOS aircraft so far, a feature that is possibly linked to biomass burning or dust. Frequent measurements of ice crystal concentrations greater than 1×105 L−1, often accompanied by anomalously warm temperature and erratic airspeed readings, suggest that aircraft often experience conditions that affect their sensors. This new instrument, if used operationally, has the potential of providing real-time and valuable information to assist in flight operations as well as providing real-time information for along-track nowcasting