269 research outputs found
Achieving high titer in a non-platform CHO cell culture process when converting to an internal medium platform
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Improvement of the noise figure of the CEBAF switched electrode electronics BPM system
The Continuous Electron Beam Accelerator Facility (CEBAF) is a high-intensity continuous wave electron accelerator for nuclear physics located at Thomas Jefferson National Accelerator Facility. A beam energy of 4 GeV is achieved by recirculating the electron beam five times through two anti-parallel 400 MeV linacs. In the linacs, where there is recirculated beam, the BPM specifications must be met for beam intensities between 1 and 1,000 {micro}A. To avoid a complete redesign of existing electronics, they investigated ways to improve the noise figure of the linac BPM switched electrode electronics (SEE) so that they could be used in the transport lines. This paper will focus on the source of the excessive out-of-band noise and how it was reduced. The development, commissioning and operational results of this low-noise variant of the linac style SEE BPMs as well as techniques for determining the noise figure of the RF chain will also be presented
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Effects of Intensity and Position Modulation On Switched Electrode Electronics Beam Position Monitor Systems at Jefferson Lab
Two types of switched electrode electronics beam position monitors are in use at Jefferson Lab. Together they provide accurate beam position to the control system for beam intensities between 50 nA and 2 mA. One version, called the linac style, has a switching frequency of 125 kHz. The other, called the transport type, has a switching frequency of 7 kHz. The basic system provides information to the control system at a 1 Hz update rate. The systems are regularly used to measure the AC component of beam position and energy as well as suppress this motion as part of a fast feedback system. Position data produced by the system are also acquired on an event by event basis as part of the nuclear physics program in two of the experimental halls. This paper will focus on the AC characteristics of the system. These characteristics are affected by analog filter frequencies and a time delay between the measurement of the positive electrode signal and the negative electrode signal. The errors introduced by position and intensity modulation on the measured beam characteristics will also be discussed
Magician simulator — A realistic simulator for heterogeneous teams of autonomous robots
We report on the development of a new simulation environment for use in Multi-Robot Learning, Swarm Robotics, Robot Teaming, Human Factors and Operator Training. The simulator provides a realistic environment for examining methods for localization and navigation, sensor analysis, object identification and tracking, as well as strategy development, interface refinement and operator training (based on various degrees of heterogeneity, robot teaming, and connectivity). The simulation additionally incorporates real-time human-robot interaction and allows hybrid operation with a mix of simulated and real robots and sensor inputs
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The Nature Press, Vol. 3
Nature News was a newsletter publication about activities at the Cheadle Center for Biodiveristy and Ecological Restoration
DNA barcoding evidence for the North American presence of alfalfa cyst nematode, Heterodera medicaginis
Specimens of Heterodera have been collected from alfalfa fields in Kearny County, Kansas and Carbon County, Montana. DNA barcoding with the COI mitochondrial gene indicate that the species is not Heterodera glycines, soybean cyst nematode, H. schachtii, sugar beet cyst nematode, or H. trifolii, clover cyst nematode. Maximum likelihood phylogenetic trees show that the alfalfa specimens form a sister clade most closely related to H. glycines, with a 4.7% mean pairwise sequence divergence across the 862 nucleotides of the COI marker. Morphological analyses of juveniles and cysts conform to the measurements of H. medicaginis, the alfalfa cyst nematode originally described from the USSR in 1971. Initial host testing demonstrated that the nematode reproduced on alfalfa, but not on soybeans, tomato, or corn. Collectively, the evidence suggests that this finding represents the first record of H. medicaginis in North America. Definitive confirmation of this diagnosis would require COI sequence of eastern European isolates of this species
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