1,721,041 research outputs found
Bipartite modular structure of intrinsic, RNA hairpin-independent termination signal for phage RNA polymerases
No full textThe phage SP6 RNA and T7 RNA polymerases, which are closely related to each other, intrinsically stop at two signals in the Escherichia coli rrnB terminator t1 through different mechanisms. The downstream signal functioned without an RNA secondary structure formation, in which the signal was still active when separated from the upstream, hairpin-forming signal, and IMP incorporation enhanced its efficiency. The sequence from -15 to -1 was essential for the downstream, hairpin-independent termination (at -1), The results of SP6 transcription with heteroduplex templates and ribonucleotide analogs suggested that the downstream signal consists of two functionally different modules. The effects of iodo-CMP or IMP incorporation into RNA on termination efficiency mere not sensitive to incorporation at -9 and upstream, but they were reactive to incorporation at -6 and -2, as reflected by strong iodo-rC:dG and weak rI:dC base pairing. Thus, the downstream module (from -8 similar to -6 to -1) appears to facilitate the release of RNA. Mismatches in the templates at -6 to +1 allowed for efficient termination, unlike those upstream of the sequence. The upstream module (from -15 to;-8 similar to -7) functions as a duplex. Pausing of the SP6 elongation complex at the termination site was detected when RNA release was suppressed by the incorporation of 5-bromo-UMP, and it was dependent on the upstream module, Results of single-round SP6 transcriptions using 3'-deoxynucleotides and immobilized templates indicated that RNA was not released from the elongation complexes halted at the termination site on the template variants carrying mutations in the upstream or downstream module, whereas such complexes on the wild type template were dissociated. Thus, halting or simple pausing was not sufficient for termination even when the downstream module was intact. The upstream module appears to mediate such conformation change necessary for termination
Performance-driven event-based synchronization for multi-FPGA simulation accelerator with event time-multiplexing bus
No full textSimulation is the most viable solution for the functional verification of system-on-chip (SoC). The acceleration of simulation with multi-field programmable gate array (multi-FPGA) emulator is a promising method to comply with the increasing complexity and large gate capacity of SoC. Time multiplexing of interconnection wires is the inevitable solution to solve the pin limitation problem that limits the gate utilization of FPGAs and speed of multi-FPGA simulation accelerators. The most time-consuming factor of multi-FPGA simulation acceleration is the synchronization time between a software simulator and a multi-FPGA system and the inter-FPGA synchronization time. This paper proposes a performance-driven signal synchronization mechanism for a simulation accelerator with multiple FPGAs using time-multiplexed interconnection. The event-based signal synchronization optimizes the synchronization time between a software simulator and the multi-FPGA system as well as the synchronization time among FPGAs. The synchronization time among FPGAs is optimized by circuit partitioning considering the signal probability, net dependency reduction, and efficient net clustering to reduce addressing overhead. The synchronization time between the software simulator and the multi-FPGA system is also optimized by exploiting the event probability of primary nets. Experiments show that the synchronization time is reduced to 6.2-9.8% of traditional mechanisms
Scheduling driven circuit partitioning algorithm for multiple FPGAs using time-multiplexed, off-chip, multi-casting interconnection architecture
No full textThe gate utilization of FPGAs and speed of emulation in multi-FPGA system are limited by the interconnection architecture and the number of pins. The time-multiplexing of interconnection wires is required for multi-FPGA systems incorporating several state-of-the-art FPGAs. This article proposes a circuit partitioning algorithm called SCheduling driven Algorithm for TOMi (SCATOMi) for multi-FPGA systems with interconnection architecture called Time-multiplexed, Off chip, Multi-casting interconnection (TOMi). SCATOMi improves the performance of the TOMi architecture by limiting the number of inter-FPGA signal transfers on the critical path and considering the scheduling of inter-FPGA signal transfers. The performance of the partitioning result of SCATOMi is 5.5 times faster than traditional partitioning algorithms. Experiments on architecture comparison show that, by adopting the proposed TOMi interconnection architecture along with SCATOMi, the pin count is reduced to 15.2-81.3% while the critical path delay is reduced to 46.1-67.6% compared to traditional architectures. (C) 2004 Elsevier B.V. All rights reserved
Bursting Force Distribution of the Post-Tensioning Achorage Zone according to the Shape of Anchorage
No full textHybrid neural network models for bankruptcy predictions
No full textThe objective of this paper is to develop the hybrid neural network models for bankruptcy prediction. The proposed hybrid neural network models are (1) a MDA-assisted neural network, (2) an ID3-assisted neural network, and (3) a SOFM(self organizing feature map)-assisted neural network. Both the MDA-assisted neural network and the ID3-assisted neural network are the neural network models operating with the input variables selected by the MDA method and IDS respectively. The SOFM-assisted neural network combines a backpropagation model (supervised learning) with a SOFM model (unsupervised learning). The performance of the hybrid neural network model is evaluated using MDA and IDS as a benchmark. Empirical results using Korean bankruptcy data show that hybrid neural network models are very promising neural network models for bankruptcy prediction in terms of predictive accuracy and adaptability
A novel active inductor and its application to inductance-controlled oscillator
No full textThis paper describes a novel active inductor using a common-source cascode FET with an inductive feedback. A compact lossy active inductor, which consists of a common-source FET and a feedback resistor, was used as the feedback inductor to achieve high Q-factor and tunability, as well as reduce the chip size. The fabricated active inductor achieved more than 100 Q-factors with the maximum value of 3400 over the frequency range of 200 MHz, in the vicinity of 1.7 GHz. Inductance was tuned from 9.6 to 56 nH at 1.7 GHz by the variation of the feedback resistance of the lossy active inductor. Using this active inductor (as a frequency-selective element in the resonator), a monolithic inductance-controlled FET oscillator was fabricated, which demonstrated an 18% frequency-tuning range from 1.73 to 2.07 GHz, with an output power range from -9.3 to -6.3 dBm
Noise parameter extraction of a GaAs MESFET with Monte-Carlo simulation
No full textAll of the noise parameters of a GaAs metal-semiconductor field-fffect transistor (MESFET) are extracted using 2-dimensional Monte-Carlo simulation for the first time. The general procedure for extracting the noise parameters is presented. The spectrums and correlations of the input-equivalent noise-voltage and noise-current sources are calculated. The y parameters of a GaAs MESFET are also extracted to obtain noise parameters and to analyze device characteristics for the first time
Viability of E-coli cells containing phage RNA polymerase and promoter: interference of plasmid replication by transcription
No full textStrong transcription of phage promoters often renders the host E. coli cells containing the phage RNA polymerase inviable. When expression of the phage SP6 RNA polymerase gene in one plasmid was induced in the E. coli JM109 cells, cells that bear an active SP6 promoter were inviable. When it was not induced (the polymerase was still produced in low level), viability of the host cells and stability of the promoter-bearing plasmids depended on the orientation of the promoter with respect to that of the replication origin and on the sequence of the origin. A group of SP6 promoter-bearing plasmids (group I plasmids) that had the promoter directed towards the ColE1 replication origin, rendered the polymerase-containing host cells inviable in selective media. When the sequence of the origin was different (group II plasmids), this adverse effect was not observed. When the promoter direction was same as the replication origin and the ampicillin-resistant gene (group III plasmids), many satellites formed around the colonies on ampicillin-containing agar plates. These effects were caused by strong transcription of the phage SP6 promoter by its RNA polymerase, since they were reduced or eliminated by inserting an active terminator just downstream of the promoter. The viability of host cells and copy number of the promoter/terminator-bearing plasmids appear to be quantitatively related with efficiency of initiation and termination of the phage transcription. These systems may be useful for in vivo screening for mutant variants of the phage promoter, polymerase and terminator that are affected in their efficiency. (C) 1998 Elsevier Science B.V. All rights reserved
A NEW GAAS FIELD-EFFECT TRANSISTOR (FET) WITH DIPOLE BARRIER (DIB)
No full textA new GaAs field effect transistor (FET) with dipole-barrier (DIBFET) employing a delta-n (delta(n)) layer and a delta-p (delta(p)) layer is proposed and fabricated. Electrons are confined in the upper undoped-GaAs layer (the channel layer) rather than around the delta(n) layer by the influence of the transverse electric field resulting from the dipole-barrier formation. This leads to the high electron concentration of 1.5x10(18)cm(-3) with the electron drift mobility of 3600 cm(2)/V.s in the undoped GaAs channel at room temperature. The fabricated GaAs DIBFET with 0.8 mu m gate length shows the maximum value of extrinsic transconductance of 366 mS/mm. The drain current density is larger than 800 mA/mm. The current gain cutoff frequency f(T) of 16.7 GHz and the maximum oscillation frequency f(max) of 67 GHz are obtained. One-dimensional calculation of device characteristics is performed for the purpose of evaluating the device performance
Theoretical comparison of (111) and (100) GaAs/AlGaAs p-type quantum well infrared photodetectors
No full textIntersubband absorptions in p-type GaAs/Al0.3Ga0.7As quantum wells (QWs) grown on (111) substrates are theoretically investigated using the multiband effective mass model. Because of the stronger band mixing of (100) QW, the peak absorption coefficient of the (100) QW is about twice as large as that of (111) QW. Nevertheless, the detectivity of (111) Quantum Well Infrared Photodetector (QWIP) is found to be similar to 30% larger than that of (100) QWIP because of the smaller dark current of (111) QWIP. This is due to the smaller heavy-hole confinement energy in (111) QW
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