The cost, time, and restrictions on creative flexibility associated with current fabrication methods present significant challenges in the development and application of microfluidic devices. ...Additive manufacturing, also referred to as three-dimensional (3D) printing, provides many advantages over existing methods. With 3D printing, devices can be made in a cost-effective manner with the ability to rapidly prototype new designs. We have fabricated a micro free-flow electrophoresis (μFFE) device using a low-cost, consumer-grade 3D printer. Test prints were performed to determine the minimum feature sizes that could be reproducibly produced using 3D printing fabrication. Microfluidic ridges could be fabricated with dimensions as small as 20 μm high × 640 μm wide. Minimum valley dimensions were 30 μm wide × 130 μm wide. An acetone vapor bath was used to smooth acrylonitrile–butadiene–styrene (ABS) surfaces and facilitate bonding of fully enclosed channels. The surfaces of the 3D-printed features were profiled and compared to a similar device fabricated in a glass substrate. Stable stream profiles were obtained in a 3D-printed μFFE device. Separations of fluorescent dyes in the 3D-printed device and its glass counterpart were comparable. A μFFE separation of myoglobin and cytochrome c was also demonstrated on a 3D-printed device. Limits of detection for rhodamine 110 were determined to be 2 and 0.3 nM for the 3D-printed and glass devices, respectively.
We have 3D printed and fabricated micro free‐flow electrophoresis (µFFE) devices in acrylonitrile butadiene styrene (ABS) that exhibit minimal surface adsorption without requiring additional surface ...coatings or specialized buffer additives. 2D, nano LC–micro free flow electrophoresis (2D nLC × µFFE) separations were used to assess both spatial and temporal broadening as peaks eluted through the separation channel. Minimal broadening due to wall adsorption was observed in either the spatial or temporal dimensions during separations of rhodamine 110, rhodamine 123, and fluorescein. Surface adsorption was observed in separations of Chromeo P503 labeled myoglobin and cytochrome c but was significantly reduced compared to previously reported glass devices. Peak widths of < 30 s were observed for both proteins. For comparison, Chromeo P503 labeled myoglobin and cytochrome c adsorb strongly to the surface of glass µFFE devices resulting in peak widths >20 min. A 2D nLC × µFFE separation of a Chromeo P503 labeled tryptic digest of BSA was performed to demonstrate the high peak capacity possible due to the low surface adsorption in the 3D printed ABS devices, even in the absence of surface coatings or buffer additives.
A large fraction of engineered nanomaterials in consumer and commercial products will reach natural ecosystems. To date, research on the biological impacts of environmental nanomaterial exposures has ...largely focused on high-concentration exposures in mechanistic lab studies with single strains of model organisms. These results are difficult to extrapolate to ecosystems, where exposures will likely be at low-concentrations and which are inhabited by a diversity of organisms. Here we show adverse responses of plants and microorganisms in a replicated long-term terrestrial mesocosm field experiment following a single low dose of silver nanoparticles (0.14 mg Ag kg(-1) soil) applied via a likely route of exposure, sewage biosolid application. While total aboveground plant biomass did not differ between treatments receiving biosolids, one plant species, Microstegium vimeneum, had 32 % less biomass in the Slurry+AgNP treatment relative to the Slurry only treatment. Microorganisms were also affected by AgNP treatment, which gave a significantly different community composition of bacteria in the Slurry+AgNPs as opposed to the Slurry treatment one day after addition as analyzed by T-RFLP analysis of 16S-rRNA genes. After eight days, N2O flux was 4.5 fold higher in the Slurry+AgNPs treatment than the Slurry treatment. After fifty days, community composition and N2O flux of the Slurry+AgNPs treatment converged with the Slurry. However, the soil microbial extracellular enzymes leucine amino peptidase and phosphatase had 52 and 27% lower activities, respectively, while microbial biomass was 35% lower than the Slurry. We also show that the magnitude of these responses was in all cases as large as or larger than the positive control, AgNO3, added at 4-fold the Ag concentration of the silver nanoparticles.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Micro free-flow electrophoresis (μFFE) is a unique separation technique because of its continuous nature. Analytes are pressure driven through a planar separation channel, and an electric field ...applied laterally to the flow producing a spatial separation. Fabrication methods associated with μFFE devices hinder our ability to address the limitations of μFFE. This work focuses on a novel fabrication method to reduce the overall fabrication cost and time, followed by validating and characterizing the device. A novel μFFE device is fabricated in acrylonitrile butadiene styrene (ABS) by 3D printing two sides of the device and then acetone vapor bonding them while simultaneously inserting electrodes and clarifying the device. Fluorescent dyes are separated, and their limit of detection determined. After validation of the new fabrication method, a new device design is made with the sample inlet modified so that 2D nLC × μFFE separations can be performed. 2D nLC × μFFE separations of fluorescent dyes, proteins, and tryptic BSA digest are demonstrated. These samples allow comparison between the surface properties of glass and 3D printed devices. Peak asymmetries, widths, and the interface were investigated. Minimal surface adsorption is observed for fluorescent dyes, proteins, and peptides, unlike in glass devices. After investigating surface properties, an open edge device for coupling to mass spectrometry is designed and compared to its glass counterpart. A novel ionization method is demonstrated from a hydrophobic membrane and the open edge device is shown to have stable flow.
Plane‐Wave Density Functional Theory Hutchinson, Maxwell; Fleurat‐Lessard, Paul; Anciaux‐Sedrakian, Ani ...
Electronic Structure Calculations on Graphics Processing Units,
03/2016
Book Chapter
This chapter describes how density functional theory (DFT) calculations with plane‐wave (PW) basis sets can be accelerated using graphics processing units (GPUs). It reviews the steps that are ...required to obtain the electronic structure of condensed‐phase systems using a plane‐wave basis set both for standard, explicit density functionals and hybrid functionals with exact exchange.The chapter then discusses the numerical implementation of the different energy components as well as ionic forces and stress tensors with an eye towards GPU and more general coprocessor architectures. It also discusses specific optimizations for GPUs suitable for hybrid multicore and multi‐GPU platforms along with code samples. Benchmarks for typical simulation setups for energy, band structure, ab initio molecular dynamics and structure relaxations demonstrate the performance improvements that can be achieved with GPUs. GPU technology is progressing quickly, offering larger and faster memory, more processors, and increased functionality.
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