Analysis of breakage and coalescence models for bubble columns

This work was aimed at evaluating the performance of bubble breakage and coalescence models in bubble column simulations. A total of five different models were considered (two for breakage and three for coalescence). These selected models had their parameters estimated using experimental data of bubble size distributions for the air–water system in an isothermal bubble column. Bubble sizes were measured with a photographic technique for two gas superficial velocities at three bubbling heights. Model parameters were estimated using the maximum likelihood technique applied to a one-dimensional population balance model, which was solved by the method of classes. The results allowed to conclude, within the experimental uncertainty, that it was necessary to adjust the parameters of some of the models according to the operational conditions. For other models, the same parameter values could be used to represent different operational conditions.     

Fish liver and seagull eggs,vitamin D‐rich foods with a shadow: Results from the Norwegian Fish and Game Study

Scope Fish liver, fish liver oil, oily fish and seagull eggs have been major sources of vitamin D for the coastal population of Norway. They also provide dioxin and polychlorinated dioxin‐like compounds (dl‐compounds), which may interfere with vitamin D homeostasis. We investigated whether serum 25‐hydroxyvitamin D (25(OH)D) might be compromised by concomitant intake of dl‐compounds. Methods and results We studied 182 adults participating in the Norwegian Fish and Game Study. Participants who consumed fish liver and/or seagull eggs had higher dl‐compound intake and blood concentrations than non‐consumers (p < 0.001). Vitamin D intake was higher (p < 0.001), whereas serum 25(OH)D was lower (p = 0.029) in consumers than in non‐consumers. Among non‐consumers, vitamin D intake was associated with serum 25(OH)D (β=1.06; 95% CI: 0.48, 1.63). This association was weaker among consumers (β = 0.52; 95% CI: ?0.05, 1.08), but strengthened when adjusted for retinol intake (β = 0.66; 95% CI: 0.12, 1.21). The association between vitamin D intake and serum 25(OH)D did not seem to be compromised by intake of dl‐compounds. Conclusion To secure adequate vitamin D status while keeping the intake of dioxins and dl‐polychlorinated biphenyls low, a healthy diet should include both supplemental vitamin D and oily fish. Despite high nutrient content, dietary fish liver and seagull eggs should be restricted, due to dl‐compounds and possible vitamin A‐D antagonism.     

Protein-induced changes during the maturation process of human dendritic cells: A 2-D DIGE approach

Dendritic cells (DCs) are unique antigen presenting cells, which upon maturation change from a specialized antigen‐capturing cell towards a professional antigen presenting cells. In this study, a 2‐D DIGE analysis of immature and mature DCs was performed, to identify proteins changing in expression upon maturation. The protein expression profile of immature and mature DCs, derived from CD14⁺ peripheral blood monocytes was investigated using two pH ranges (pH 4–7 and 6–9) (n = 4). Ninety one differentially expressed spots (p<0.01) were detected, from which we identified 74 spots (81.32%) corresponding to 41 different proteins. The proteins identified play a role in diverse processes, such as antigen processing/presentation, vesicle transport and cytoskeleton remodeling. In addition, a protein interaction network contained 29 (out of 41) proteins, suggesting that, although they functionally originate from distinct classes, these proteins are acting as a protein‐interactome. In conclusion, the proteins shown here to be altered in expression upon maturation are in line with the morphological and functional changes observed during the maturation process, providing a better understanding of the processes involved. This will open new avenues for investigating treatment regimens for immune‐associated disorders.     

Infiltration and dimensional scaling of inkjet droplets on thick isotropic porous materials

We study the imbibition of picoliter (pL)-sized inkjet droplets on controlled pore glass membranes (CPG), as a suitable model for isotropic three-dimensional porous materials. We do so using a variety of liquids, i.e., water, formamide and diiodomethane, and measure the evolution of the imbibition process using high-speed digital imaging. Here, experiments were conducted on 2–280 nm CPG membranes with drops with initial volumes ranging from 100 to 600 pL. We derive scaling laws for imbibition through dimensional analysis and advance the argument that the rate of absorption is related to two-dimensionless groups \(V = v(t) \epsilon /v_{\text{tot}} ;\,T = tkp_{\text{c}} /\mu \,\left( { \epsilon /v_{\text{tot}} } \right)^{2/3} ,\) where v(t) is the imbibed volume, as determined from experiments, t is the time, v _tot the total liquid volume, \( \epsilon \) the porosity, μ the liquid viscosity, k the permeability, and p _c the Laplace capillary pressure. We show this scaling to well describe the system at intermediate T values and report that \(V \propto T^{0.8} .\)      

A Physical Model Study of Swirl Phenomena in a Top Blown Bath

The present study is focused on swirl motion in a top blown water model, where a deep water swirl motion is observed. During the experiments, the top lance, with cylindrical nozzles, was placed above the water surface and thereby produced an external force on the bath. The effect on how different parameters, such as nozzle diameter and the distance between the bath surface and nozzle exit, i.e. the lance height, affect the swirl motion were studied. More specifically, the amplitude and period of the swirl as well as the starting and damping time of the swirl were determined. The amplitude was found to increase with an increased nozzle diameter and gas flow, while the period had a constant value of about 0.5 s for all nozzle diameters, gas flows and lance heights. The starting time for the swirl motion was found to decrease with an increased gas flow, while the damping time was found to be independent of gas flow rate, nozzle diameter, lance height and ratio of depth to diameter.     

Inclusion Growth and Removal in Gas‐Stirred Ladles

A static modelling approach was used to study the growth and removal of inclusions during gas stirring in a ladle. A mathematical model of a gas‐stirred ladle was used to predict the data necessary to calculate growth and removal of inclusions. Results indicated that inclusion growth resulting from laminar shear collisions is negligible in comparison with growth from turbulent and Stokes collisions. Furthermore, the need for a model describing inclusion flotation by spherical‐cap bubbles was identified. Since the existing models presented in the literature are only valid for spherical bubbles, a model for the removal of inclusions by spherical‐cap bubbles was developed. Inclusion removal to the slag, refractory and by bubble flotation was compared. The mechanism determined to be responsible for the removal of the majority of inclusions larger than 25 μm was Stokes flotation and for the majority of the smaller inclusions, bubble flotation by spherical‐cap bubbles (assuming plane contact between the inclusion and the bubble).     

The effect of fluid consumption on the forest workers' performance strategy

The heart rate development and time consumption of four Zimbabwean forest workers engaged in manual harvesting were studied to assess their performance strategy and whether this strategy was affected by differences in fluid consumption. Each worker was studied during 8 consecutive working days and produced 2.4 m3 pulpwood/day. They consumed either 0.17 l or 0.6 l of water each 1/2 hour with one fluid scheme assigned to each day according to a randomised block (person) design with four replicates (days). All workers were found to harvest large trees at the start of the working day and small trees at the end. All workers took longer to complete their task when on the low fluid scheme, however, the effect on the heart rate development varied for the individual workers as the strategies adopted to accommodate the stress inflicted by the low fluid scheme, varied for the individual workers. It is recommended that sufficient fluid supply during work be accompanied by training of the workers to convey the need and benefits of sufficient fluid consumption.     

Decreased drug accumulation in a mitoxantrone-resistant gastric carcinoma cell line in the absence of P-glycoprotein

The developmental commitment to a T helper 1 (Th1)- or Th2-type response can significantly influence host immunity to pathogens. Extinction of the IL-12 signaling pathway during early Th2 development provides a mechanism that allows stable phenotype commitment. In this report we demonstrate that extinction of IL-12 signaling in early Th2 cells results from a selective loss of IL-12 receptor (IL-12R) beta 2 subunit expression. To determine the basis for this selective loss, we examined IL-12R beta 2 subunit expression during Th cell development in response to T cell treatment with different cytokines. IL-12R beta 2 is not expressed by naive resting CD4+ T cells, but is induced upon antigen activation through the T cell receptor. Importantly, IL-4 and IFN-gamma were found to significantly modify IL-12 receptor beta 2 expression after T cell activation. IL-4 inhibited IL-12R beta 2 expression leading to the loss of IL-12 signaling, providing an important point of regulation to promote commitment to the Th2 pathway. IFN-gamma treatment of early developing Th2 cells maintained IL-12R beta 2 expression and restored the ability of these cells to functionally respond to IL-12, but did not directly inhibit IL-4 or induce IFN-gamma production. Thus, IFN-gamma may prevent early Th cells from premature commitment to the Th2 pathway. Controlling the expression of the IL-12R beta 2 subunit could be an important therapeutic target for the redirection of ongoing Th cell responses.     

Gender differences in both spontaneous and stimulated leptin secretion by human omental adipose tissue in vitro: dexamethasone and estradiol stimulate leptin release in women, but not in men

Leptin is a hormone secreted by the adipocytes to serve as a signal to the central nervous system to regulate energy homeostasis. Circulating leptin mainly reflects both total fat mass and the size of constituent adipocytes, although other ancillary hormonal factors may contribute to its blood concentration. Relevant gender differences in leptin concentrations have been reported, but it is not clear whether the elevated leptin levels in women are an intrinsic property of their adipocytes or merely reflect a greater amount of fat reserves. To clarify these points, a systematic study with organ culture from human omental adipose tissue either stimulated or not with steroid hormones was undertaken in samples obtained at surgery from 67 nonobese donors (33 women and 34 men). The assay was standardized in periods of 24 h ending at 96 h, with no apparent tissue damage. Each adipose tissue sample from a single donor was incubated in triplicate, and leptin results are expressed as the mean +/- SEM of the integrated secretion to the medium (area under the curve; nanograms of leptin per g tissue/48 h). Control nonstimulated samples showed a steady leptin secretion along the 96 h studied, with the peak of secretory activity reached at 48 h; afterward, the in vitro secretion reached a plateau state. Spontaneous leptin secretion in samples from 33 women (3904 +/- 347) was significantly higher (P < 0.05) than that in samples from 34 men (2940 +/- 323). Coincubation of adipose tissue with 1 mumol/L dexamethasone induced a clear-cut leptin increase (P < 0.05) in samples from women (5848 +/- 624; n = 12), but did not change the spontaneous release of leptin in samples from men (3353 +/- 741; n = 6). Similarly, coincubation of adipose tissue with 1 mumol/L estradiol induced a notable leptin increase (P < 0.05) in samples from women (5698 +/- 688; n = 9), whereas it did not alter the secretion in the male samples (3373 +/- 444; n = 6). In samples from both sexes, coincubation with 1 mumol/L estrone or progesterone had no effect, whereas 1 mumol/L forskolin significantly (P < 0.05) reduced leptin release. In conclusion, leptin secretion from omental adipose tissue in vitro 1) is significantly higher in samples from women than in samples from men, 2) is stimulated by dexamethasone and estradiol in women but not in men, 3) is not modified by progesterone or estrone in both sexes, and 4) is inhibited by forskolin in both genders. This different response to the stimulation of adipose tissue may be the biological basis for the gender differences observed in circulating levels of human leptin.