Flow-based and sieving matrix-free DNA differentiation by a miniaturized field flow fractionation device

DNA separation is typically done by gel electrophoresis based on its charge property. In our previous work, we reported that dielectrophoresis could be used to manipulate polystyrene nanoparticles' motion by using a miniaturized electrical field flow fractionation device (micro-EFFF) with a segmented electrode operated under a pulsed voltage (PV). In this work, we report the manipulation and separation of DNA molecules using the micro-EFFF. DNA motion was in situ visualized inside the device. Results revealed that dielectrophoresis governed DNA motion, which was strongly correlated with the pulse frequency but not the duty cycle of a PV. A longer retention time of DNA molecules was measured under a PV. The retention time increased with the length of DNA molecules. As the micro-EFFF is flow-based and sieving-matrix-free, it has a potential to be applied to sample preparation in a micrototal analysis system or when fractionated molecules are needed for downstream analysis.     

Measurement of pressure-gradient-driven currents in tokamak edge plasmas

Localized currents driven by pressure gradients play a pivotal role in the magnetohydrodynamic stability of toroidal plasma confinement devices. We have measured the currents generated in the edge of L- (low) and H- (high confinement) mode discharges on the DIII-D tokamak, utilizing the Zeeman effect in an injected lithium beam to obtain high resolution profiles of the poloidal magnetic field. We find current densities in excess of 1 MA/m2 in a 1 to 2 cm region near the peak of the edge pressure gradient. These values are sufficient to challenge edge stability theories based on specific current formation models.     

液相外延GaAs_（1-x）_P_x_混晶的光学声子，等离子体激元和LO声子-等离子激元耦合模

在40--7 0 0 (1/cm)波数和4.2--300 K 温度范围内研究了不同组份液相外延n 型GaAs_（1-x）_P_x__样品的红外反射谱. 对反射谱进行了鹰谐振子拟合与K-K 关系计算.从而获得了有关描述GaAs_（1-x）_P_x__样品的光学声子模、等离子体激元、LO 声子-等离子体激元藕合模的重要物理参量及红外光学常数信息. 基于这些计算结果, 提出了双导带谷并计及与x 能谷相联系的施主能级模型, 用它解释等离子体激元频率和实验观察的三支主要的祸合模的温度变化规律。 关键词：     

刻蚀改变InGaN/AlGaN应变多量子阱发光特性

为了分析干法刻蚀对应变多量子阱(SMQWs)发光特性的影响,采用感应耦合等离子体(ICP)刻蚀技术对金属有机物化学气相沉积(MOCVD)生长的InGaN/AIGaN应变多量子阱覆盖层表面刻蚀了约95 nm。通过光致发光(PL)特性表征发现,干法刻蚀后量子阱光致发光强度较未刻蚀量子阱光致发光强度提高了近3倍。干法刻蚀后,量子阱表面呈现高低起伏状形貌,粗糙度提高,出射光在起伏状粗糙形貌表面反复散射,从而逃逸概率增大,有助于光致发光强度增强。理论计算结果得出表面形貌变化引起的量子阱光致发光强度增强因子约为1．3倍。另外,由于所采用的感应耦合等离子体功率较小,刻蚀损伤深度几乎不会达到量子阱阱层,然而干法刻蚀过程中Ar离子隧穿到量子阱阱层内部可能形成新的发光中心,从而使量子阱的发光强度得到提高。     

Toward Scalable Nanofluidic Osmotic Power Generation from Hypersaline Water Sources with a Metal–Organic Framework Membrane

Nanofluidic membranes have shown great promise in harvesting osmotic energy but its scalablity remains challenging since most studies only tested with a membrane area of ≈10⁻² mm² or smaller. We demonstrate that metal-organic-framework membranes with subnanometer pores can be used for scalable osmotic power generation from hypersaline water sources. Our membrane can be scaled up to a few mm², and the power density can be stabilized at 1.7 W m⁻². We reveal that the key is to improve the out-of-membrane conductance while keeping the membrane's charge selectivity, contradicting the previous conception that the ionic conductivity of the membrane plays the dominating role. We highlight that subnanometer pores are essential to ensure the charge selectivity in hypersaline water sources. Our results suggest the importance to engineer the interplay between the in-membrane and out-of-membrane ion transport properties for scalable osmotic power generation.     

Studies on Thiol Etching of Gold by Using QCM-D Sensor as the Sacrificial Probe

There is still a lack of deep understanding on the reaction kinetics and mechanism of thiol etching of gold. Herein, by using the sensor of quartz crystal microbalance (QCM) as the sacrificial probe, the etching reaction of gold has been studied by employing cysteamine (CS) as a typical thiol etchant. The etching reaction is verified as diffusion-controlled and shows a half-order reaction kinetics. It is demonstrated that intact thiol and amino on CS are both crucial for its etching ability to gold. Applied potentials can affect the electron transfer and hence can be used to regulate the gold etching. Our results also reveal that only two carbon atoms of the spacer between thiol and amino on CS are very critical to the excellent etching ability. This work exhibits a new route to explore the thiol etching reaction of gold and elucidates the reaction kinetics and mechanism.     

磁场对载流线圈的作用

讨论了磁场对于载流线圈的合作用力、合力矩、磁力作功公式和载流线圈在外磁场中的相互作用能，以及带电粒子在一对励磁线圈之间的往复运动。     

Turning on the Antimicrobial Activity of Gold Nanoclusters Against Multidrug-Resistant Bacteria**

In this work, we show that the addition of thiourea (TU) initiated broad-spectrum antimicrobial activity of otherwise inactive D-maltose-capped gold nanoclusters (AuNC-Mal). For example, AuNC-Mal/TU was effective against multidrug-resistant Pseudomonas aeruginosa with a minimum inhibitory concentration (MIC) of 1 μg mL⁻¹ (2.5 μM [Au]) while having 30–60 times lower in vitro cytotoxicity against mammalian cells. The reaction of AuNC-Mal and TU generated the antimicrobial species of [Au(TU)₂]⁺ and smaller AuNCs. TU increased the accumulation of Au in bacteria and helped maintain the oxidation state as Au^I (vs. Au^III). The modes of action included the inhibition of thioredoxin reductase, interference with the Cu^I regulation and depletion of ATP. Moreover, the antimicrobial activity did not change in the presence of colistin or carbonyl cyanide 3-chlorophenylhydrazone, suggesting that AuNC-Mal/TU was indifferent to the outer membrane barrier and to bacterial efflux pumps.     

87Sr solid-state NMR as a structurally sensitive tool for the investigation of materials: antiosteoporotic pharmaceuticals and bioactive glasses

Strontium is an element of fundamental importance in biomedical science. Indeed, it has been demonstrated that Sr(2+) ions can promote bone growth and inhibit bone resorption. Thus, the oral administration of Sr-containing medications has been used clinically to prevent osteoporosis, and Sr-containing biomaterials have been developed for implant and tissue engineering applications. The bioavailability of strontium metal cations in the body and their kinetics of release from materials will depend on their local environment. It is thus crucial to be able to characterize, in detail, strontium environments in disordered phases such as bioactive glasses, to understand their structure and rationalize their properties. In this paper, we demonstrate that (87)Sr NMR spectroscopy can serve as a valuable tool of investigation. First, the implementation of high-sensitivity (87)Sr solid-state NMR experiments is presented using (87)Sr-labeled strontium malonate (with DFS (double field sweep), QCPMG (quadrupolar Carr-Purcell-Meiboom-Gill), and WURST (wideband, uniform rate, and smooth truncation) excitation). Then, it is shown that GIPAW DFT (gauge including projector augmented wave density functional theory) calculations can accurately compute (87)Sr NMR parameters. Last and most importantly, (87)Sr NMR is used for the study of a (Ca,Sr)-silicate bioactive glass of limited Sr content (only ~9 wt %). The spectrum is interpreted using structural models of the glass, which are generated through molecular dynamics (MD) simulations and relaxed by DFT, before performing GIPAW calculations of (87)Sr NMR parameters. Finally, changes in the (87)Sr NMR spectrum after immersion of the glass in simulated body fluid (SBF) are reported and discussed.