Investigation of the effects of time periodic pressure and potential gradients on viscoelastic fluid flow in circular narrow confinements

In this paper we present an in-depth analysis and analytical solution for time periodic hydrodynamic flow (driven by a time-dependent pressure gradient and electric field) of viscoelastic fluid through cylindrical micro- and nanochannels. Particularly, we solve the linearized Poisson–Boltzmann equation, together with the incompressible Cauchy momentum equation under no-slip boundary conditions for viscoelastic fluid in the case of a combination of time periodic pressure-driven and electro-osmotic flow. The resulting solutions allow us to predict the electrical current and solution flow rate. As expected from the assumption of linear viscoelasticity, the results satisfy the Onsager reciprocal relation, which is important since it enables an analogy between fluidic networks in this flow configuration and electric circuits. The results especially are of interest for micro- and nanofluidic energy conversion applications. We also found that time periodic electro-osmotic flow in many cases is much stronger enhanced than time periodic pressure-driven flow when comparing the flow profiles of oscillating PDF and EOF in micro- and nanochannels. The findings advance our understanding of time periodic electrokinetic phenomena of viscoelastic fluids and provide insight into flow characteristic as well as assist the design of devices for lab-on-chip applications

Hypertension Is Associated with Marked Alterations in Sphingolipid Biology: A Potential Role for Ceramide

Background Hypertension is, amongst others, characterized by endothelial dysfunction and vascular remodeling. As sphingolipids have been implicated in both the regulation of vascular contractility and growth, we investigated whether sphingolipid biology is altered in hypertension and whether this is reflected in altered vascular function. Methods and Findings In isolated carotid arteries from spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats, shifting the ceramide/S1P ratio towards ceramide dominance by administration of a sphingosine kinase inhibitor (dimethylsphingosine) or exogenous application of sphingomyelinase, induced marked endothelium-dependent contractions in SHR vessels (DMS: 1.4±0.4 and SMase: 2.1±0.1 mN/mm; n = 10), that were virtually absent in WKY vessels (DMS: 0.0±0.0 and SMase: 0.6±0.1 mN/mm; n = 9, p Conclusions Hypertension is associated with marked alterations in vascular sphingolipid biology such as elevated ceramide levels and signaling, that contribute to increased vascular tone

Microfluidic Construction of Hierarchically Composite Superballs for Sensing Applications

Colloidal photonic crystals have attracted much attention of the scientific world due to their unique optical properties and potential applications in sensing, displays, optoelectronics, controlled superwetting and other fields. Here we report the fabrication of spherical colloidal photonic crystals featured with well-ordered nanopatterns from silica nanoparticles (SiO2NPs) and gold nanoparticles (AuNPs) through a droplet-based microfluidic approach. The colloidal crystals show both the photonic band gaps (PBG) and surface plasmonic resonance (SPR) properties. These proposed hierarchically composite ‘superballs’ will have an excellent performance in sensing applications, due to the fast response (the scattering color change) to the dielectric properties of the surrounding medium. A robust and efficient strategy is proposed and demonstrated to fabricate the composite superballs with multifunctional properties, broadening the perspective of their applications by the advantages of precise control over the size of the particles and flexible change of the fluid composition