Efficient operation of a high-power X-band gyroklystron

Experimental studies of amplification in a two-cavity X-band gyroklystron are reported. The system utilizes a thermionic magnetron injection gun at voltages up to 440 kV and currents up to 190 A in 1-μs pulses. Optimum performance is achieved by tapering the magnetic-field profile. Peak powers of 20 MW in the TE01 mode at 9.87 GHz are measured with calibrated crystals and with methanol calorimetry. Resultant efficiencies are in excess of 31% and large-signal gains surpass 26 dB. The experimental results are in good agreement with simulated results from a partially self-consistent, nonlinear, steady-state code

Applications of remote sensing in hydrology

OWRT Project no. B-160-COLO

Beam-plasma interaction in Astron

The beam-plasma interactions in the Astron device are examined utilizing a model which consists of a homogeneous, cold, relativistic electron beam (E-layer particles) streaming through a Maxwellian plasma normal to a uniform external magnetic field. Using linear stability analysis the model shows that the strongest interactions occur at beam harmonics in the vicinity of the plasma normal modes which are near the upper hybrid frequency, and above each subsequent multiple of the plasma electron cyclotron frequency. The possible stabilizing effects of collisions between plasma electrons and background neutral particles, as well as the energy spread for beam particles are also examined. It is shown that collisional effects are especially strong at collision frequencies of the order of the beam cyclotron frequency and that the combined effects of collisions and energy spread may lead to quenching of the unstable modes. Comparison of the analytical results with experimental observations is presented and discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48946/2/ppv15i8p729.pd

High-Density Peptide Arrays with Combinatorial Laser Fusing

Combinatorial laser fusing is a new method to produce high-density peptide arrays with feature sizes as small as 10 mu m. It combines the high spot densities achieved by lithographic methods with the cost-efficiency of biofunctional xerography. The method is also adapted for other small molecules compatible with solid phase synthesis

Solid-material-based Coupling Efficiency Analyzed with Time-of-Flight Secondary Ion Mass Spectrometry

The coupling behavior of a microparticle embedded amino acid active-ester into a Poly(ethylene glycol)methacrylate-film, synthesized onto a silicon wafer by a grafting from approach, is characterized using dynamic time-of-flight secondary ion mass spectrometry (ToF-SIMS) to analyze the 3d distribution of the amino acids in the polymer film. Besides standard solid phase peptide synthesis, employing solubilized amino acids in a solvent, we used solid polymer microparticles, incorporating the amino acids. These microparticles were especially designed for a new technique to produce high-density combinatorial peptide microarrays: upon heating, the particles become viscous, which releases the embedded amino acids to diffuse and couple to the surface. In the scope of the development of this new particle-based application, ToF-SIMS is used to analyze a complex chemically modified polymer surface layer. Due to depth profile measurements, it is possible to investigate the particle-based coupling reaction not only on the surface, but also into the depth of the PEGMA film

Trace elements in glucometabolic disorders: an update

Many trace elements, among which metals, are indispensable for proper functioning of a myriad of biochemical reactions, more particularly as enzyme cofactors. This is particularly true for the vast set of processes involved in regulation of glucose homeostasis, being it in glucose metabolism itself or in hormonal control, especially insulin. The role and importance of trace elements such as chromium, zinc, selenium, lithium and vanadium are much less evident and subjected to chronic debate. This review updates our actual knowledge concerning these five trace elements. A careful survey of the literature shows that while theoretical postulates from some key roles of these elements had led to real hopes for therapy of insulin resistance and diabetes, the limited experience based on available data indicates that beneficial effects and use of most of them are subjected to caution, given the narrow window between safe and unsafe doses. Clear therapeutic benefit in these pathologies is presently doubtful but some data indicate that these metals may have a clinical interest in patients presenting deficiencies in individual metal levels. The same holds true for an association of some trace elements such as chromium or zinc with oral antidiabetics. However, this area is essentially unexplored in adequate clinical trials, which are worth being performed

Different expectations: a comparative history of structure, experience, and strategic alliances in the U.S. and U.K. poultry sectors, 1920-1990

This comparative historical analysis demonstrates how memory and reflexive interpretations of the past can shape entrepreneurial willingness to collaborate with larger firms in an industry. Emphasizing the importance of spatial metaphors and periodization for developing historical knowledge, the paper focuses on how the historical space of experience explains how entrepreneurs make strategic choices regarding collaboration under conditions of complexity and uncertainty. Comparing the U.S. and U.K. emerging poultry sectors offers a methodologically novel analysis of an important but little‐studied agribusiness sector, offering a dual reading that compares two versions of historical reasoning both theoretically and empirically

Flute‐Like Instabilities in Plasma with Cylindrical Relativistic Electron Beam

The linearized, relativistic Vlasov equations are analyzed for the stability of flute‐like modes in an infinite, collisionless plasma with a cold background and a relativistic annular electron beam situated in a uniform external magnetic field. Neglecting self‐fields, a dispersion equation is obtained for small thickness beams. It is found that oscillations with frequency near harmonics of the gyrofrequency of the relativistic electrons are unstable. The most unstable oscillations are shown to be those with long wavelengths relative to the thickness of the beam. Growth rates and conditions for instability are given for systems where the beam particles are charge neutralized by cold background ions, and when the beam particles are dilute compared with the background species. For rarefied beams, an instability occurs at the hybrid frequency of the background species where the growth rate depends on the beam thickness. As the background density increases, a critical value can be reached where the long‐wavelength oscillations are stabilized; and short‐wavelength oscillations become most unstable. For these modes growth rates are maximized with respect to the harmonic number ℓℓ, and beam velocity β  =  υ/cβ=υ∕c.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71355/2/PFLDAS-13-7-1851-1.pd

A very-thin walled sample holder for liquids

A sample holder for liquids is described which was developed for use in neutron scattering measurements. The design is very simple and inexpensive to fabricate, yet the walls of the container are very thin, 0.002" aluminum, reducing this contribution to the background to a minimum.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32215/1/0000274.pd