Characterization of bubbles in a bubble column by image analysis

Fundação para a Ciência e a Tecnologia (FCT); EC

Characterizing the automatic radon flux transfer standard system Autoflux: laboratory calibration and field experiments

High-quality, long-term measurements of terrestrial trace gas emissions are important for investigations of atmospheric, geophysical and biological processes to help mitigate climate change and protect the environment and the health of citizens. High-frequency terrestrial fluxes of the radioactive noble gas 222Rn, in particular, are useful for validating radon flux maps and used to evaluate the performance of regional atmospheric models, to improve greenhouse gas emission inventories (by the radon tracer method) and to determine radon priority areas for radiation protection goals. A new automatic radon flux system (Autoflux) was developed as a transfer standard (TS) to assist with establishing a traceability chain for field-based radon flux measurements. The operational characteristics and features of the system were optimized based on a literature review of existing flux measurement systems. To characterize and calibrate Autoflux, a bespoke radon exhalation bed (EB) facility was also constructed with the intended purpose of providing a constant radon exhalation under a specific set of controlled laboratory conditions. The calibrated Autoflux was then used to transfer the derived calibration to a second continuous radon flux system under laboratory conditions; both instruments were then tested in the field and compared with modeled fluxes. This paper presents (i) a literature review of state-of-the-art radon flux systems and EB facilities; (ii) the design, characterization and calibration of a reference radon EB facility; (iii) the design, characterization and calibration of the Autoflux system; (iv) the calibration of a second radon flux system (INTE_Flux) using the EB and Autoflux, with a total uncertainty of 9 % (k = 1) for an average radon flux of ∼ 1800 mBq m−2 s−1 under controlled laboratory conditions; and (v)​​​​​​​ an example application of the calibrated TS and INTE_Flux systems for in situ radon flux measurements, which are then compared with simulated radon fluxes. Calibration of the TS under different environmental conditions and at lower reference fluxes will be the subject of a separate future investigation.</p

Chemiluminescence response induced by mesenteric ischaemia/reperfusion: effect of antioxidative compounds ex vivo

Ischaemia and reperfusion (I/R) play an important role in human pathophysiology as they occur in many clinical conditions and are associated with high morbidity and mortality. Interruption of blood supply rapidly damages metabolically active tissues. Restoration of blood flow after a period of ischaemia may further worsen cell injury due to an increased formation of free radicals. The aim of our work was to assess macroscopically the extent of intestinal pathological changes caused by mesenteric I/R, and to study free radical production by luminol enhanced chemiluminescence (CL) of ileal samples. In further experiments, the antioxidative activity of the drugs tested was evaluated spectrophotometrically by the use of the DPPH radical. We studied the potential protective ex vivo effect of the plant origin compound arbutin as well as of the pyridoindole stobadine and its derivative SMe1EC2. I/R induced pronounced haemorrhagic intestinal injury accompanied by increase of myeloperoxidase (MPO) and N-acetyl-β-D-glucosaminidase (NAGA) activity. Compared to sham operated (control) rats, there was only a slight increase of CL response after I/R, probably in association with neutrophil increase, indicated by enhanced MPO activity. All compounds significantly reduced the peak values of CL responses of the ileal samples ex vivo, thus reducing the I/R induced increase of free radical production. The antioxidants studied showed a similar inhibitory effect on the CL response influenced by mesenteric I/R. If proved in vivo, these compounds would represent potentially useful therapeutic antioxidants

Antibodies Against Oxidized LDL -Theory and Clinical Use

Summary Modification of low density lipoprotein (LDL) particles due to oxidation, glycation and binding of advanced glycation end-products (AGEs) or malondialdehyde (MDA, a final product of lipid peroxidation) is considered most important in the process of atherogenesis. Oxidatively modified LDL are distinguished by another receptor type, which was discovered on the surface of macrophages and was called the scavenger receptor. Uncontrolled intake of LDL converts macrophages to foam cells; their accumulation under the vascular endothelium is considered as the first stage of atherosclerosis. Oxidation of LDL is a complex process taking place in both the extra-and intracellular space. At the end of this oxidative process, modified LDL particles show chemotactic, cytotoxic and immunogenic properties. Oxidized LDL express a large number of epitopes and cause production of polyclonal autoantibodies against these products, especially against apoB 100 modified by MDA and 4-hydroxynonenal. IgoxLDL (antibodies against oxidized LDL) can be demonstrated either directly in intimal lesions or as a component of circulating immune complexes. IgoxLDL do not form a homogeneous group but a varied mixture of antibodies-isoantibodies caused by HDL and LDL polymorphism, antibodies against the lipid phase of LDL and antibodies against modified apoB 100 of the immunoglobulin class IgA or IgG. Antibodies against oxLDL were found in many diseases other than atherosclerosis such as diabetes mellitus, renovascular syndrome, uremia, rheumatic fever, morbus Bechtjerev or lupus erythematodes. Newborns have practically the same levels of IgoxLDL as their mothers; however, these values did not differ from those in the healthy population of non-pregnant women of the same age. The decrease in IgoxLDL titer was very slow and lasted many months; that is why this parameter cannot be considered suitable for describing the rapid changes during oxidative stress of the organism. Positive correlation of IgoxLDL with antiphospholipids and other antibodies was repeatedly demonstrated; their determination can thus be used as a marker for the description of total production of autoantibodies in various diseases. The changes and correlations of IgoxLDL, anti-β-2-glycoprotein I IgG and antiphospholipid antibodies support the immunological link between thrombotic and atherosclerotic processes in the human body

The Effect of Surface Treatment on Composite Repair Bond Strength Longevity

Introduction: Composite restorations undergo degradation in the oral cavity, which may compromise their aesthetic and functional properties, cause failure of marginal integrity, increased abrasion or even partial fracture of the filling. Instead of complete removal of such restorations, they can be repaired. Aim: To study the bond strength of a new composite resin to an aged composite substrate after a 4-month storage in distilled water or sodium laurylsulphate solution (SLS). Two various surface treatments and two different adhesive systems were tested. Materials and methods: Light cured specimens of a micro-hybrid composite (Filtek Z250, shade A2) were aged in distilled water (37 °C) for 5 months. Composite surface was prepared either by grinding (SiC paper P320, mean grain size 46 µm, equivalent to red diamond bur) or by air abrasion (Rondoflex; Al2O3 50 µm; 3.2 bar; 60 s). Composite build-ups were made from the same composite material using two adhesive systems (Optibond FL, Gluma Comfort Bond). The microtensile bond strength (n = 13-16) was measured after a 4-month storage of specimens at 37 °C in distilled water or in a solution of sodium lauryl sulfate (1.5 wt. %). Control specimens were stored in distilled water for 24 hours (37 °C). Results: A decrease of the bond strength compared to the control group on the ground surface after the 4-month storage in distilled water or SLS was found to be adhesive system- dependant. The bond strength for Optibond FL decreased by 52% in SLS only (p &lt; 0.001), but for Gluma Comfort Bond it decreased by 45% in distilled water (p &lt; 0.001) and by 61% in SLS (p &lt; 0,001). On the air-abraded surface the bond strength decreased only for Optibond FL in SLS (p &lt; 0.01), by 31%. Conclusion: Long-term durability of composite repair can be maintained by preparing the original composite surface using air abrasion. The effect of the adhesive system on the bond strength was not significant