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Notes: Polymer solution dynamics may be inferred from light scattering spectra of dissolved optical probe particles. We compare a variety of probes in solutions of several polymers. In the "overlapping'' concentration/molecular weight regime, the Stokes–Einstein equation fails by up to a factor of 2, while the probe diffusion coefficient D follows a scaling law D/D0=exp(−aMγcνRδ) (c, M, and R are the polymer concentration, molecular weight, and the probe radius, respectively). Experimentally, γ=0.8±0.1, ν=0.6–1.0, and δ=−0.1 to 0, contrary to the theoretical predictions γ=0 and δ=1. With very high molecular-weight polymers, we observe a further "entangled'' regime, characterized by huge (104) failures of the Stokes–Einstein equation and the appearance of "fast'' modes in the scattering spectrum.

Notes: Previous studies have shown that nanoparticle chain aggregates (NCA) of titania are elastic [S. K. Friedlander, H. D. Jang and K. H. Ryu, Appl. Phys. Lett. 72, 1 (1998)]. The NCA were a few tenths of a micron long and composed of (approximately) 7 nm primary particles. They were produced by thermal decomposition of titanium tetraisopropoxide vapor in nitrogen. The goal of this study was to see whether the elastic behavior depends on (a) the material properties, (b) primary particle size, and (c) method of NCA formation. For this purpose, titania, alumina, and iron oxide NCA were generated by laser ablation. Rotating metal foil targets were mounted in a small cylindrical chamber and exposed to an excimer laser beam. The resulting aerosol was swept out by an oxygen stream. The generator was operated to produce NCA with similar mobility diameter and primary particle size. The NCA were deposited on the carbon or formvar films of an electron micrograph grid. Under the electron beam a hole develops in the carbon film in the neighborhood of the deposited NCA. The NCA then stretch and contract as described in our earlier study [S. K. Friedlander, H. D. Jang and K. H. Ryu, Appl. Phys. Lett. 72, 1 (1998)]. The titania, alumina, and iron oxide NCA generated by laser ablation all showed elastic behavior for primary particles smaller than about 10 nm. However, titania NCA composed of 36 nm primary particles did not exhibit elastic behavior indicating that very small primary nanoparticles are needed for this phenomenon to occur. The small scale stretching and contraction of chain segments were studied by measuring changes in the bond angles between adjoining particles and in the lengths of the segments studied. The elastic behavior is probably associated with local folding of chain segments due to van der Waals forces. Under tension, folded chains straighten but when the tension is relaxed, folds tend to reform but not reversibly. Rotation and sliding probably occur at the boundaries between particles during stretching. We hypothesize that elastic behavior is a general property of NCA composed of transition metal oxides with primary particles smaller than 10–15 nm; the phenomenon has now been observed for NCA produced in two ways, thermal decomposition and laser ablation. These phenomena may play a role in the action of nanoparticle additives such as fumed silica and carbon black used to improve the properties of rubber. NCA elasticity may also contribute to the ductile properties of nanoparticle compacts. © 2000 American Institute of Physics.

Notes: The injection of an additional strong focused electron beam from a special designed electron gun into a magnetic electron cyclotron resonance (ECR) confinement field is studied. The electron gun uses a cathode with a long lifetime and resistiveness providing high emission current densities with electron currents up to 50 mA and voltages up to 4 keV. A sequence of aluminum foils is used to investigate the trajectories of the electrons in the magnetic field without plasma. The high density electron beam passes through the foils, welds them, and prints its image into the foils. Details of this technique are described in Ref. 1. Using this technique we see that before the electrons enter the sextupole region the beam moves along the magnetic straight lines preserving its structure. Only a central beam passes through the sextupole region, thereby changing its form due to the interaction with radial components of the magnetic field. A new operation method at our 14.5 GHz ECR ion source is based on so-called reflection mode electrons (RMEs) analogous to a known electron beam ion source operation regime.2 The basic idea is that electrons, which traveling from the cathode in a strong axial field, meet an anticathode potential, are reflected from it, move back to the cathode, and will be reflected again and so on. It can be supposed that the electrons will make reflections up to the moment when the anode aperture of the gun is fulfilled and the electrons will be collected on the anode electrode. Investigations are performed extracting nitrogen ions using the RME beam. As a result we got a clear increase in the beam current of the extracted ions (e.g., at 10 mA electron injection an increase of the current of N5+ ions up to 400%) and a shift of the measured ion charge state distribution to higher mean ionization stages. Measured x-ray spectra from a neon loaded plasma show for the case of RME operation increasing energy shifts to the high energy side of the spectra, i.e., the mean ionization degree of the ions in the plasma increases. They also increase the intensity of the neon K x rays (more than 100% increase for RME injection of Ee=4 keV and Ie=10 mA) indicating that for the same operation parameters the mean density of energetic electrons rises at RME injection, i.e., there are more electrons with energies high enough to ionize K-shell electrons in neon. © 2000 American Institute of Physics.

Notes: A compact electron beam ion trap (WEBIT) working at room temperature without any cryogenic components is described and experimentally investigated. The trap design is based on permanent magnet technology. For the formation of the electron beam a Pierce electron gun equipped with a cathode of high emissivity is used. The ion trap is created by a compressed electron beam passing through a drift tube system consisting of three sections with corresponding electrical trap potentials. X-ray spectra measured with a Si(Li) semiconductor detector indicate the production of Kr34+, Xe44+, Ce48+, Ir64+, and Hg66+ ions. © 2000 American Institute of Physics.

Notes: Abstract  Background: Approximately 1% of patients require temporary circulatory support due to refractory cardiogenic shock following cardiac surgery. Such patients are at very high risk for subsequent morbidity and mortality. We evaluated the results of temporary extracorporeal membrane oxygenation (ECMO) support in patients with postcardiotomy cardiogenic shock. Methods: From November 1997 to February 2000, 7900 patients underwent cardiac surgery in our institution. Ninety-five patients (1.2%) (CABG, n = 63; AVR, n = 16; CABG and AVR, n = 8; other procedures, n = 8) required temporary postoperative ECMO support. ECMO implantation was performed via the femoral vessels or via the right atrium and ascending aorta. Intraaortic balloon counterpulsation was employed in all patients. Results: Mean duration of ECMO support was 2.8 ± 2.1 days. Forty-five patients (47%) were successfully weaned from ECMO. Of these, 28 patients were discharged from hospital 35.8 ± 20.8 days post-ECMO support. Overall hospital mortality for all ECMO patients was considerable at 71%. Mortality rate in the combined CABG and AVR group was 100% (P 〈 0.05 versus the other surgical groups). ECMO support was complicated by renal failure in 64% of patients, bleeding requiring mediastinal reexploration in 62%, ischemia of the lower limbs in 16%, cerebral edema in 6%, and cerebral hemorrhage in 3%. Conclusions: ECMO is a suitable technique for short-term treatment of refractory postoperative low cardiac output. Mortality rates are comparable to other cardiac assist devices, with approximately 30% of patients able to be discharged from hospital. (J Card Surg 2003;18:512-518)