Microplastic accumulation in riverbed sediment via hyporheic exchange from headwaters to mainstems

Bidirectional flow between surface water and sediment leads to high accumulation of small and lightweight microplastics in rivers.

V2G Pilot Projects

Electric vehicles (EVs) are not only a viable energy efficient mode of transport, but they have considerable capacity of providing flexible and quick responding storage alternative based on vehicle-to-grid (V2G) scheme. V2G technology facilitates bidirectional flow of energy to and from the vehicle by a power converter. However, there is skepticism regarding the economic profitability of the V2G scheme. Despite the aforementioned challenges, the V2G technology is explored in matured markets. A number of V2G pilot projects across the world have investigated different aspects of V2G integration such as technological readiness, economic feasibility, social benefits, and challenges of V2G. This work aims to review the existing pilot projects on V2G functionality.

An SDN-Based Solution for Horizontal Auto-Scaling and Load Balancing of Transparent VNF Clusters

This paper studies the problem of the dynamic scaling and load balancing of transparent virtualized network functions (VNFs). It analyzes different particularities of this problem, such as loop avoidance when performing scaling-out actions, and bidirectional flow affinity. To address this problem, a software-defined networking (SDN)-based solution is implemented consisting of two SDN controllers and two OpenFlow switches (OFSs). In this approach, the SDN controllers run the solution logic (i.e., monitoring, scaling, and load-balancing modules). According to the SDN controllers instructions, the OFSs are responsible for redirecting traffic to and from the VNF clusters (i.e., load-balancing strategy). Several experiments were conducted to validate the feasibility of this proposed solution on a real testbed. Through connectivity tests, not only could end-to-end (E2E) traffic be successfully achieved through the VNF cluster, but the bidirectional flow affinity strategy was also found to perform well because it could simultaneously create flow rules in both switches. Moreover, the selected CPU-based load-balancing method guaranteed an average imbalance below 10% while ensuring that new incoming traffic was redirected to the least loaded instance without requiring packet modification. Additionally, the designed monitoring function was able to detect failures in the set of active members in near real-time and active new instances in less than a minute. Likewise, the proposed auto-scaling module had a quick response to traffic changes. Our solution showed that the use of SDN controllers along with OFS provides great flexibility to implement different load-balancing, scaling, and monitoring strategies.

Bidirectional flow of action potentials in axons drives activity dynamics in neuronal cultures

Objective: Recent technological advances are revealing the complex physiology of the axon and challenging long-standing assumptions. Namely, while most action potential (AP) initiation occurs at the axon initial segment in central nervous system neurons, initiation in distal parts of the axon has been reported to occur in both physiological and pathological conditions. The functional role of these ectopic APs, if exists, is still not clear, nor its impact on network activity dynamics. Approach: Using an electrophysiology platform specifically designed for assessing axonal conduction we show here for the first time regular and effective bidirectional axonal conduction in hippocampal and dorsal root ganglia cultures. We investigate and characterize this bidirectional propagation both in physiological conditions and after distal axotomy. Main results: A significant fraction of APs are not coming from the canonical synapse-dendrite-soma signal flow, but instead from signals originating at the distal axon. Importantly, antidromic APs may carry information and can have a functional impact on the neuron, as they consistently depolarize the soma. Thus, plasticity or gene transduction mechanisms triggered by soma depolarization can also be affected by these antidromic APs. Conduction velocity is asymmetrical, with antidromic conduction being slower than orthodromic. Significance: Altogether these findings have important implications for the study of neuronal function in vitro, reshaping our understanding on how information flows in neuronal cultures.

Selective extraction of biomolecules using a bidirectional flow filter

We present a microfluidic device for selective separation and extraction of molecules based on their diffusivity. The separation relies on electroosmotically-driven bidirectional flows in which high diffusivity species experience a net-zero velocity, and lower diffusivity species are advected to a collection reservoir. The device can operate continuously and is suitable for processing low sample volumes. Using several model systems, we showed that the extraction efficiency of the system is maintained at more than 90% over tens of minutes, with a purity of more than 99%. We demonstrate the applicability of the device to the extraction of genomic DNA from short DNA fragments.

Proposal of a Mask and Its Performance Analysis with CFD for an Enhanced Aerodynamic Geometry That Facilitates Filtering and Breathing against COVID-19

As a result of the recent events associated with the SARS-CoV-2 around the world, there has been a need for research to strengthen health care. The use of masks or respirators has been an effective measure, reducing the risk of contagion caused by the spread of the virus in public places. Currently, there are masks that retain up to 99% of particles >0.3 microns; however, they lack an airtight seal with the face, leading to discomfort and poor protection in conditions without social distancing and areas without ventilation. The device proposed in this study includes a geometric design of static valves with convergent spirals and interior baffles that promotes enhanced aerodynamics with bidirectional flow. According to the analysis and CFD simulation of the proposed reusable, washable, and economic mask and valve system for breathing, coughing, and sneezing events, enhanced air exchange could be maintained, facilitating a higher inhalation flow through the side of the mask (62%) and a higher exhalation through the front of the mask (74%), thereby avoiding the recirculation of the flow to the interior of the mask. The inclusion of filters with KN95 characteristics in the inlets and outlets maintains velocities below 10 cm/s, reducing the probability of infection.

CFD Model of the Density-Driven Bidirectional Flows through the West Crack Breach in the Great Salt Lake Causeway

Stratified flows and the resulting density-driven currents occur in the natural environment and commonly in saline lakes. In the Great Salt Lake, Utah, USA, the northern and southern portions of the lake are divided by an east-to-west railroad causeway that disrupts natural lake currents and significantly increases salt concentrations in the northern section. To support management efforts focused on addressing rising environmental and economic concerns associated with varied saltwater densities throughout the lake, the causeway was recently modified to include a new breach. The purpose of this new breach is to enhance salt exchange between the northern and southern sections of the lake. Since construction, it typically exhibits a strong density-driven bidirectional flow pattern, but estimating flows and salt exchange has proven to be difficult. To obtain much needed insights into the ability of this hydraulic structure to exchange water and salt between the two sections of the lake, a field campaign coupled with CFD modeling was undertaken. Results from this study indicate that the vertical velocity profile in the breach is sensitive to density differences between flow layers along with breach geometry and water surface elevations. The CFD model was able to accurately represent the bidirectional flows through the breach and provides for improved estimates of water and salt exchanges between the north and south sections of the lake.