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61.
Directed Molecular Collection by E‐Jet Printed Microscale Chemical Potential Wells in Hydrogel Films 下载免费PDF全文
Shiyan Zhang Spencer J. Kieffer Chunjie Zhang Andrew G. Alleyne Paul V. Braun 《Advanced materials (Deerfield Beach, Fla.)》2018,30(38)
A facile approach to locally concentrate analytes of interest will significantly enhance miniaturized, integrated chemical‐analysis systems. Here, the directed analyte transport and concentration using ≈200 µm‐diameter E‐jet printed chemical potential wells in a polyacrylamide hydrogel is demonstrated. Using a cationic well as the model system, anionic analytes are accumulated into a microscale area with a local concentration enhancement of >50‐fold relative to the surrounding area. By downscaling the diameter of the chemical potential well from a few millimeters to 100s of micrometers, it is found, using both fluorescence and Raman microscopy, that the molecular collection capacity of the well is greatly improved. Additionally, it is shown that molecules can be simultaneously transported and concentrated to arrays of microscale regions using an array of microscale chemical potential wells. This approach enhances many‐fold the limit of detection, enables the formation of microscale potential well arrays with a variety of chemical properties, and provides a novel microscale molecular manipulation technique as an alternative to traditional microfluidic‐based systems. 相似文献
62.
Abstract Fullerene Science and Technology, both the field and the journal, have observed considerable progress during the last few years. The field has continued to mature as witnessed by the many new and interesting results published in thousands of journal articles (1-3) and in a multitude of books and conference proceedings. The recognition of fullerene sciences as a self-containing field of research has been culminating in the awarding of the 1996 Chemistry Nobel Prize to Professors Robert S. Curl, Harold W. Kroto, and Richard E. Smailey. 相似文献
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Insu Paek Luc Mongeau James E. Braun 《Journal of Mechanical Science and Technology》2010,24(9):1781-1791
The performance of a working prototype, operated with and without water flow through the heat exchangers, was measured and
found to be in reasonably close agreement to predictions from a simulation code, DELTAE, based on linear thermoacoustic theory.
Further analysis and DELTAE simulations showed that the coefficient of performance may be significantly reduced when the stack
temperature profile becomes non-linear, i.e. when the system is operated for a temperature span smaller than the optimal value
for a given stack length. Guidelines to avoid this condition are provided. 相似文献
66.
Vehicles with electric drive trains are currently the subject of intense discussion by society. The cost trends of the individual components in the electric drive train are a central aspect of the future market success of the different vehicle drive systems. 相似文献
67.
Clint Alex CottrellScott E. Grasman Mathew ThomasKevin Braun Martin John W. Sheffield 《International Journal of Hydrogen Energy》2011,36(13):7969-7975
In the future, hydrogen-based stationary and portable fuel cell systems can help supply some or all of the power demanded with additional advantages of higher reliability, lower emissions, independence from the general grid, and cogeneration capability. In order to understand how to prepare the future for this technology, this paper describes a thorough investigation of past alternative stationary and portable power projects in order for an assessment of the opportunities for stationary and portable fuel cell markets, as well as interactions with transportation hydrogen systems. The lessons learned from the programs are used to establish best practices and recommendations for a hydrogen strategy that addresses opportunities for hydrogen in power generation systems, as well as to make recommendations for market transformation within the hydrogen fuel cell industry. 相似文献
68.
Regenerative converter for PWM AC drives 总被引:1,自引:0,他引:1
Braun D.H. Gilmore T.P. Maslowski W.A. 《Industry Applications, IEEE Transactions on》1994,30(5):1176-1184
Since the PWM induction motor drive has become the industrial drive of choice, applications involving four-quadrant operation for AC drives have become more common. To satisfy such applications, a regenerative AC/DC converter that is robust is needed to allow bidirectional power flow between the load and power distribution system. A robust technology that is well understood is the 6 SCR converter operating in the inverting mode. However, the typical 6 SCR converter will either limit the maximum DC bus voltage or require a step-up transformer. The proposed regenerative converter allows the SCR power structure to operate as a synchronous line commutator, while a two-transistor series/shunt chopper, with a power resistor, controls the regenerative power flow, and offers an emergency braking capability. In addition, SCR commutation is accomplished by the line voltage and diversion of bus current. Both simulation and experimental results are given 相似文献
69.
Pichia sorbitophila grows rapidly in the presence of very high NaCl concentrations. Under these conditions, even when the K(+) concentration is low, P. sorbitophila cells can maintain low Na(+) and high K(+) contents. This remarkable capacity of P. sorbitophila fails when the external pH is not acidic. This indicates that Na(+) efflux is mediated by an electroneutral Na(+)/H(+) antiporter. We have cloned and sequenced two genes designated as PsNHA1 and PsNHA2, which probably encode two antiporters of this type. The genes present high similarity with the corresponding genes from other yeasts. The heterologous expression of PsNHA1 or PsNHA2 in a Saccharomyces cerevisiae mutant lacking the Na(+) efflux systems and sensitive to high concentrations of Na(+) and K(+) rescued the tolerance and the ability to extrude both cations. The Accession Nos of the sequenced DNA fragments are: PsNHA1, AJ496431; PsNHA2, AJ496432. (TC 2.A.36) Copyright 2002 John Wiley & Sons, Ltd. 相似文献
70.
A simplified sample pretreatment method for industrially PAH-contaminated soils applying automated Soxhlet (Soxtherm) with ethyl acetate as extraction solvent is presented. Laborious pretreatment steps such as drying of samples, cleanup of crude extracts, and solvent exchange were allowed to be bypassed without notable performance impact. Moisture of the soil samples did not significantly influence recoveries of PAHs at a wide range of water content for the newly developed method. However, the opposite was true for the standard procedure using the more apolar 1:1 (v/v) n-hexane/acetone solvent mixture including postextraction treatments recommended by the U.S. EPA. Moreover, ethyl acetate crude extracts did not appreciably effect the chromatographic performance (HPLC-(3D)FLD), which was confirmed by a comparison of the purity of PAH spectra from both pretreatment methods. Up to 20% (v/v) in acetonitrile, ethyl acetate proved to be fully compatible with the mobile phase of the HPLC whereas the same concentration of n-hexane/acetone in acetonitrile resulted in significant retention time shifts. The newly developed pretreatment method was applied to three historically contaminated soils from different sources with extraction efficiencies not being significantly different compared to the standard procedure. Finally, the certified reference soil CRM 524 was subjected to the simplified procedure resulting in quantitative recoveries (>92%) for all PAHs analyzed. 相似文献