An Introduction to the Source Concept for Antennas

Antenna parameters particularly relevant to electrically small antenna design are reviewed in this paper. Source current definitions are accentuated leading to the introduction of the source concept which advantageously utilize only spatially bounded quantities. The framework of the source concept incorporates powerful techniques such as structural and modal decomposition, operator’s inversion and current optimization, thus opening new, challenging possibilities for antenna design, analysis and synthesis

Excitation of a Conducting Cylinder Using the Theory of Characteristic Modes

This paper describes the application of the theory of characteristic modes to excite a conducting cylinder representing the chassis of a rocket. Mode excitation is achieved by cutting H-shaped slots on the cylinder at specific locations where the maximum of modal current distribution occurs. The L-matching network is designed to match the impedance of the slots to the input coaxial cable. Finally, the proposed concept is verified during manufacturing and measurement. It is shown that the measured results are in excellent agreement with the simulation

Optically induced coherent intra-band dynamics in disordered semiconductors

On the basis of a tight-binding model for a strongly disordered semiconductor with correlated conduction- and valence band disorder a new coherent dynamical intra-band effect is analyzed. For systems that are excited by two, specially designed ultrashort light-pulse sequences delayed by tau relatively to each other echo-like phenomena are predicted to occur. In addition to the inter-band photon echo which shows up at exactly t=2*tau relative to the first pulse, the system responds with two spontaneous intra-band current pulses preceding and following the appearance of the photon echo. The temporal splitting depends on the electron-hole mass ratio. Calculating the population relaxation rate due to Coulomb scattering, it is concluded that the predicted new dynamical effect should be experimentally observable in an interacting and strongly disordered system, such as the Quantum-Coulomb-Glass.Comment: to be published in Physical Review B15 February 200

Phonon-induced dephasing of localized optical excitations

The dynamics of strongly localized optical excitations in semiconductors is studied including electron-phonon interaction. The coupled microscopic equations of motion for the interband polarization and the carrier distribution functions contain coherent and incoherent contributions. While the coherent part is solved through direct numerical integration, the incoherent one is treated by means of a generalized Monte Carlo simulation. The approach is illustrated for a simple model system. The temperature and excitation energy dependence of the optical dephasing rate is analyzed and the results are compared to those of alternative approaches

The influence of composition on the swelling of kraft black liquor during pyrolysis

"May, 1986.

Magnetization dynamics and frustration in the multiferroic double perovskite Lu2MnCoO6

We investigate the magnetic ordering and the magnetization dynamics (from kHz to THz time scales) of the double perovskite Lu2MnCoO6 using elastic neutron diffraction, muon spin relaxation, and micro-Hall magnetization measurements. This compound is known to be a type II multiferroic with the interesting feature that a ferromagneticlike magnetization hysteresis loop couples to an equally hysteretic electric polarization in the bulk of the material despite a zero-field magnetic ordering of the type ↑↑↓↓ along Co-Mn spin chains. Here we explore the unusual dynamics of this compound and find extremely strong fluctuations, consistent with the axial next-nearest-neighbor Ising (ANNNI) model for frustrated spin chains. We identify three temperature scales in Lu2MnCoO6 corresponding to the onset of highly fluctuating long-range order below TN=50±3 K identified from neutron scattering, the onset of magnetic and electric hysteresis, with change in kHz magnetic and electric dynamics below a 30 K temperature scale, and partial freezing of ∼MHz spin fluctuations in the muon spin relaxation data below 12±3 K. Our results provide a framework for understanding the multiferroic behavior of this compound and its hysteresis and dynamics

Indications and results of sternal allograft transplantation: learning from a worldwide experience

Background Reconstruction of the anterior chest wall defect after sternectomy is a challenge for cardiothoracic surgeons. In 2010 the Padua group published the first case of cadaveric sternum transplantation after sternectomy. This multi-center study reports the clinical indications, early and long-term results of sternal chondral allograft transplantation. Methods This is a retrospective multicentre-study from seven Academic-Centres. Demographic data, surgical indications, technical details, early postoperative results were collected. The complications, long-term stability and tolerance of the allografts were also analysed. Results Between January 2008 and December 2019 58-patients underwent sternectomy followed by reconstruction using cadaveric-cryopreserved sterno-chondral allografts. Thirty-two patients were males, with a median age of 63.5 years(IQR50-72). Indications for sternectomy were secondary sternal tumors(n=13), primary sternal tumors(n=15) and non-neoplastic disease(30). Thirty patients underwent total sternectomy, 16 lower-body sternectomy and 12 upper-body-manubrium resection. The 30-days mortality was 5%. The overall morbidity was 31%. Six early reoperations were necessary because of bleeding(n=1), titanium-plates dislocation(n=1) and re-suture of the skin in the lower part of the incision(n=4). Overall, the 5-year survival was 74%. The surviving patient\u2019s reconstructions are stable and free from mechanical or infective complications. Conclusions The main indications for sternal allograft implantation were complex post sternotomy dehiscence followed by primary or secondary tumor involvement of the sternum. The collected results demonstrate that sterno-chondral allograft transplantation is a safe and effective method in reconstructing the anterior chest wall after sternectomy. Further studies to demonstrate the integration of the bone grafts into the patient\u2019s sternal wall will be made

Status reports to the Pulping Processes Project Advisory Committee

"October 20-21, 1986."Fine structure of wood pulp fibers project 3288 / R. H. Atalla ; Raman microprobe investigation of molecular structure and organization in the native state of woody tissue: project 3521-2 / R. H. Atalla and Umesh P. Agarwal ; Raman spectroscopy and the raman microprobe: valuable new tools for characterizing wood and wood pulp fibers / R. H. Atalla ; Further 13C NMR evidence for the coexistence of two crystalline forms in native celluloses / D. L. VanderHart, R. H. Atalla ; Raman microprobe investigation of molecular structure and organization in the native state of woody tissue / R. H. Atalla ; Raman microprobe evidence for lignin orientation in the cell walls of native woody tissue / Rajai H. Atalla, Umesh P. Agarwal ; In situ Raman microprobe studies of plant cell walls: macromolecular organization and compositional variability in the secondary wall of picea mariana (mill.) B. S. P. / U. P. Agarwal, and R. H. Atalla ; Raman spectra of celluloses / James H. Wiley, and Rajai H. Atalla ; A highly crystalline cellulose from rhizoclonium hieroglyphicum / Rajai H. Atalla and Rebecca E. Whitmore and David L. VanderHart ; Oxygen sensitive background in the Raman spectra of woody tissue / U. P. Agarwal and R. H. Atalla ; Smelt-water explosions: project 3456-2 / T. M. Grace ; Fundamental processes in alkali recovery furnaces: project 3473-1 / T. M. Grace, J. H. Cameron, and D. T. Clay ; Fundamental processes in alkali recovery furnaces fume generation ; Fume generation during oxidation of alkali carbonate/sulfide melts / J. H. Cameron ; A kinetic study of kraft char gasification with CO2 / Kristin A. Goerg, John H. Cameron ; Fundamental processes in alkali recovery furances black liquor burning ; The influence of water on black liquor combustion / B. A. Moreland, D. T. Clay ; Swelling of kraft black liquor during pyrolysis / P. T. Miller and D. T. Clay ; The influence of composition on the swelling of kraft black liquor during pyrolysis / P. T. Miller, D. T. Clay, and W. F. W. Lonsky ; Sulfur release and retention during combustion of kraft black liquor / James G. Cantrell and David T. Clay ; Fundamental processes in alkali recovery furnaces implementation of black liquor combustion knowledge ; Fundamental studies of black liquor combustion: project 3473-6 / D. T. Clay ; Improved process for bleached pulp / T. J. McDonough ; A kinetic study of high yield aq-sulphite pulping of loblolly pine / A.J. Eagle, T.J. McDonough ; Fundamentals of selectivity in pulping and bleaching: project 3475 / D. R. Dimmel ; Development and application of analytical techniques: project 3477 / D. B. Easty ; Development and application of analytical techniques analysis of pulping and bleaching liquors by ion chromatography ; Development and application of analytical techniques pyrolysis gas chromatography ; Fundamentals of brightness stability: project 3524 / W. F. W. Lonsky ; Strong, intact, high-yield fibers: project 3566 / T. J. McDonough, S. Aziz ; Computer model of recovery furnaces: project 3605 / T. M. Grace -- Handouts