In this work, we report the discovery with Fermi/LAT of γ-ray emission from three radio-loud narrow-line Seyfert 1 galaxies: PKS 1502+036 (z = 0.409), 1H 0323+342 (z = 0.061), and PKS 2004 – 447 (z = ...0.24). In addition to PMN J0948+0022 (z = 0.585), the first source of this type to be detected in γ rays, they may form an emerging new class of γ-ray active galactic nuclei (AGNs). Lastly, these findings can have strong implications on our knowledge about relativistic jets and the unified model of the AGN.
A three-stage 21-26-GHz medium-power amplifier fabricated in f/sub T/=120 GHz 0.2 /spl mu/m SiGe HBT technology has 19 dB small-signal gain and 15 dB gain at maximum output power. It delivers 23 dBm, ...19.75% PAE at 22 GHz, and 21 dBm, 13% PAE at 24 GHz. The differential common-base topology extends the supply to BV/sub CEO/ of the transistors (1.8 V). New on-chip components, such as onchip interconnects with floating differential shields, and self-shielding four-way power combining/dividing baluns provide inter-stage coupling and single-ended I/O interfaces at the input and output. The 2.45/spl times/2.45 mm/sup 2/ MMIC was mounted as a flipchip and tested without a heatsink.
We developed a generalized technique to characterize polymer–nanopore interactions via single channel ionic current measurements. Physical interactions between analytes, such as DNA, proteins, or ...synthetic polymers, and a nanopore cause multiple discrete states in the current. We modeled the transitions of the current to individual states with an equivalent electrical circuit, which allowed us to describe the system response. This enabled the estimation of short-lived states that are presently not characterized by existing analysis techniques. Our approach considerably improves the range and resolution of single-molecule characterization with nanopores. For example, we characterized the residence times of synthetic polymers that are three times shorter than those estimated with existing algorithms. Because the molecule’s residence time follows an exponential distribution, we recover nearly 20-fold more events per unit time that can be used for analysis. Furthermore, the measurement range was extended from 11 monomers to as few as 8. Finally, we applied this technique to recover a known sequence of single-stranded DNA from previously published ion channel recordings, identifying discrete current states with subpicoampere resolution.
Railway signaling facilitates two main functions, namely, train detection and train control, in order to maintain safe separations among the trains. Track circuits are the most commonly used train ...detection means with the simple open/close circuit principles; and subsequent adoption of axle counters further allows the detection of trains under adverse track conditions. However, with electrification and power electronics traction drive systems, aggravated by the electromagnetic interference in the vicinity of the signaling system, railway engineers often find unstable or even faulty operations of track circuits and axle counting systems, which inevitably jeopardizes the safe operation of trains. A new means of train detection, which is completely free from electromagnetic interference, is therefore required for the modern railway signaling system. This paper presents a novel optical fiber sensor signaling system. The sensor operation, field setup, axle detection solution set, and test results of an installation in a trial system on a busy suburban railway line are given.
Zero mode waveguides (ZMWs), subwavelength optical nanostructures with dimensions ranging from 50 to 200
nm, have been used to study systems involving ligand-receptor interactions. We show that under ...proper conditions, lipid membranes will invaginate into the nanostructures, which confine optical excitation to subattoliter volumes. Fluorescence correlation spectroscopy (FCS) was used to characterize the diffusion of fluorescently tagged lipids in liquid-disordered phase 1-palmitoyl-2-oleoyl-
sn-glycero-3-phosphocholine (POPC) and gel phase 1,2-distearoyl-
sn-glycero-3-phosphocholine (DSPC) membranes incubated on the nanostructured surface. In contrast to the POPC, DSPC membranes did not appear to enter the structures, suggesting that invagination is dependent on membrane rigidity. Although correlation curves obtained from POPC membranes conformed to previously derived models for diffusion in the evanescent field within the nanostructure, the diffusion constants obtained were systematically lower than expected. The validity of the one-dimensional diffusion model for membrane diffusion is discussed and it is concluded that the erroneous diffusion constants are a result of nontrivial membrane conformation within the ZMWs. Additionally, FCS was used to characterize the fraction of fluorescently labeled tetanus toxin C fragment bound to a ganglioside-populated POPC membrane within the ZMWs. This allowed the determination of the toxin's equilibrium binding constant at a concentration of 500
nM; higher than possible with diffraction-limited FCS. To our knowledge, the results presented here are the first reported for supported lipid bilayers in nanostructured devices. Furthermore, they open the possibility of studying membrane imbedded receptors and proteins at physiological concentrations with single-molecule resolution.
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