Monitoring of liquid flow through microtubes using a micropressure sensor

The pressure-driven liquid flow through microtubes was studied in a range of very low Reynolds numbers (<0.15) by monitoring the pressure change in situ. Cylindrical microtubes with diameters ranging from 50 ?m to 500 ?m were examined and two types of tube material, namely PEEK polymer and fused silica were compared. A good linear relation for the pressure drop versus flow rate was obtained. Apparent deviations between the measured slopes with those calculated using conventional theory were attributed to uncertainties in the calculated values which are dominated by the uncertainties in the microtube diameters. It was found that a period of stabilisation time was required for reaching a steady flow after the syringe pump was switched on/off or to a different flow rate. The stabilisation time was likely due to the compressibility of the fluid. Insignificant difference between PEEK polymer and fused silica microtubes in terms of flow resistance was observed. The in-situ measurement of pressure drops provides a convenient approach for monitoring fluid flow through microtubes and detecting dimensional changes within microchannels in Lab-on-a-Chip and microreactor systems

Investigating the flow dynamics in the obstructed and stented ureter by means of a biomimetic artificial model.

Double-J stenting is the most common clinical method employed to restore the upper urinary tract drainage, in the presence of a ureteric obstruction. After implant, stents provide an immediate pain relief by decreasing the pressure in the renal pelvis (P). However, their long-term usage can cause infections and encrustations, due to bacterial colonization and crystal deposition on the stent surface, respectively. The performance of double-J stents - and in general of all ureteric stents - is thought to depend significantly on urine flow field within the stented ureter. However very little fundamental research about the role played by fluid dynamic parameters on stent functionality has been conducted so far. These parameters are often difficult to assess in-vivo, requiring the implementation of laborious and expensive experimental protocols. The aim of the present work was therefore to develop an artificial model of the ureter (i.e. ureter model, UM) to mimic the fluid dynamic environment in a stented ureter. The UM was designed to reflect the geometry of pig ureters, and to investigate the values of fluid dynamic viscosity (?), volumetric flow rate (Q) and severity of ureteric obstruction (OB%) which may cause critical pressures in the renal pelvis. The distributed obstruction derived by the sole stent insertion was also quantified. In addition, flow visualisation experiments and computational simulations were performed in order to further characterise the flow field in the UM. Unique characteristics of the flow dynamics in the obstructed and stented ureter have been revealed with using the developed UM

Oscillation dynamics of embolic microspheres in flows with red blood cell suspensions

Dynamic nature of particle motion in blood flow is an important determinant of embolization based cancer therapy. Yet, the manner in which the presence of high volume fraction of red blood cells influences the particle dynamics remains unknown. Here, by investigating the motions of embolic microspheres in pressure-driven flows of red blood cell suspensions through capillaries, we illustrate unique oscillatory trends in particle trajectories, which are not observable in Newtonian fluid flows. Our investigation reveals that such oscillatory behavior essentially manifests when three simultaneous conditions, namely, the Reynolds number beyond a threshold limit, degree of confinement beyond a critical limit, and high hematocrit level, are fulfilled simultaneously. Given that these conditions are extremely relevant to fluid dynamics of blood or polymer flow, the observations reported here bear significant implications on embolization based cancer treatment as well as for complex multiphase fluidics involving particle

Eucommia ulmoides extract attenuates angiotensin II-induced cardiac microvascular endothelial cell dysfunction by inactivating p53

Angiotensin II (AngII) causes endothelial dysfunction. Eucommia ulmoides extract (EUE) is documented to manipulate AngII, but its impact on cardiac microvascular endothelial cell (CMVEC) function remains unknown. This study determines the effects of EUE on AngII-treated CMVECs. CMVECs were treated with different concentrations of AngII or EUE alone and/or the p53 protein activator, WR-1065, before AngII treatment, followed by examinations of the apoptotic, migratory, proliferative, and angiogenic capacities and nitric oxide (NO), p53, von Willebrand factor (vWF), endothelin (ET)-1, endothelial NO synthase (eNOS), manganese superoxide dismutase (MnSOD), hypoxia-inducible factor (HIF)-1α, and vascular endothelial growth factor (VEGF) levels. AngII induced CMVEC dysfunction in a concentration-dependent manner. EUE enhanced the proliferative, migratory, and angiogenic capacities and NO, MnSOD, and eNOS levels but repressed apoptosis and vWF and ET-1 levels in AngII-induced dysfunctional CMVECs. Moreover, AngII increased p53 mRNA levels, p-p53 levels in the nucleus, and p53 protein levels in the cytoplasm and diminishes HIF-1α and VEGF levels in CMVECs; however, these effects were counteracted by EUE treatment. Moreover, WR-1065 abrogated the mitigating effects of EUE on AngII-induced CMVEC dysfunction by activating p53 and decreasing HIF-1α and VEGF expression. In conclusion, EUE attenuates AngII-induced CMVEC dysfunction by upregulating HIF-1α and VEGF levels via p53 inactivation

Mithramycin encapsulated in polymeric micelles by microfluidic technology as novel therapeutic protocol for beta-thalassemia

This report shows that the DNA-binding drug, mithramycin, can be efficiently encapsulated in polymeric micelles (PM-MTH), based on Pluronic® block copolymers, by a new microfluidic approach. The effect of different production parameters has been investigated for their effect on PM-MTH characteristics. The compared analysis of PM-MTH produced by microfluidic and conventional bulk mixing procedures revealed that microfluidics provides a useful platform for the production of PM-MTH with improved controllability, reproducibility, smaller size, and polydispersity. Finally, an investigation of the effects of PM-MTH, produced by microfluidic and conventional bulk mixing procedures, on the erythroid differentiation of both human erythroleukemia and human erythroid precursor cells is reported. It is demonstrated that PM-MTH exhibited a slightly lower toxicity and more pronounced differentiative activity when compared to the free drug. In addition, PM-MTH were able to upregulate preferentially ?-globin messenger ribonucleic acid production and to increase fetal hemoglobin (HbF) accumulation, the percentage of HbF-containing cells, and their HbF content without stimulating ?-globin gene expression, which is responsible for the clinical symptoms of ß-thalassemia. These results represent an important first step toward a potential clinical application, since an increase in HbF could alleviate the symptoms underlying ß-thalassemia and sickle cell anemia. In conclusion, this report suggests that PM-MTH produced by microfluidic approach warrants further evaluation as a potential therapeutic protocol for ß-thalassemia.<br/

Formation and characteristics of laminar vortices in microscale environments within an obstructed and stented ureter: A computational study

Despite the widespread clinical usage of ureteric stents for the drainage of urine in impaired ureters (e.g. caused by ureteric stones, tumors) many complications are still associated with stent's implants. Encrusting and infective events, due to crystals' deposition and bacterial adhesion on the stent surface, usually lead to stent failure. In earlier experimental results we showed the presence of vortices in regions of the stent (e.g. side holes) which are thought to act as initial anchoring sites for encrusting deposits. In the current study we show computationally how the stent's design is a crucial factor for developing the vortices

Apparent equilibrium shifts and hot-spot formation for catalytic reactions induced by microwave dielectric heating

Microwave dielectric heating of the gas phase decomposition of H2S catalysed by metal sulfides on a -Al2O3 support results in significant apparent shifts in the equilibrium constant, which have been attributed to the development of hot-spots in the catalytic beds; X-ray diffraction and electron microscopy measurements have indicated the formation of hot-spots with dimensions of 90–1000 µm and which involve not only the active phase, but also the support

The role of cell membrane strain in sonoporation characterised by microfluidic-based single-cell analysis

In the present study we have investigated the sonoporation dynamics in a single cell using a novel microfluidic-based approach. Our methodology has successfully addressed the biophysical mechanisms underlying US-induced cell membrane sonoporation by performing in situ measurement of localised cell membrane deformation, and simultaneous quantification of both intracellular calcium concentration ([Ca2+]i) and transmembrane transfer of extracellular membrane-impermeable probes. We have highlighted novel aspects of microbubble-cluster dynamics combined with localised cell membrane strain, which could be responsible for membrane permeabilisation and transmembrane pore formation correlated with the transduction of intracellular biochemical signals (i.e. [Ca2+]i influx) as a result of microbubble-cell interaction

An Efficient Bypassing Void Routing Algorithm for Wireless Sensor Network

Since the sensor node’s distribution in a wireless sensor network (WSN) is irregular, geographic routing protocols using the greedy algorithm can cause local minima problem. This problem may fail due to routing voids and lead to failure of data transmission. Based on the virtual coordinate mapping, this paper proposes an efficient bypassing void routing protocol to solve the control packet overhead and transmission delay in routing void of WSN, which is called EBVRPVCM. The basic idea is to transfer the random structure of void edge to a regular one through mapping the coordinates on a virtual circle. In EBVRPVCM, some strategies, executed in different regions, are selected through virtual coordinates to bypass routing void efficiently. The regular edge is established by coordinate mapping that can shorten the average routing path length and decrease the transmission delay. The virtual coordinate mapping is not affected by the real geographic node position, and the control packet overhead can be reduced accordingly. Compared with RGP and GPSR, simulation results demonstrate that EBVRPVCM can successfully find the shortest routing path with higher delivery ratio and less control packet overhead and energy consumption