Surface spin waves in superconducting and insulating ferromagnets

Surface magnetization waves are studied on a semi-infinite magnetic medium in the perpendicular geometry. Both superconducting and insulating ferromagnets are considered. Exchange and dipole energies are taken into account, as well as retardation effects. At large wave vectors, the spectrum for a superconductor and insulator is the same, though for the former the branch is terminated much earlier than for the latter due to excitation of plasmons. At small wave vectors, the surface wave is more robust in the superconductor since it is separated from the bulk continuum by a finite gap.Comment: 4 pages, 2 figure

Fully developed triplet proximity effect

We present a model for fully developed triplet proximity effect in superconductor-ferromagnet heterostructures. Within the circuit-theory approximation, we evaluate the Green's functions, the density of states, and the Josephson current that depend essentially on the magnetization configuration.Comment: 4 pages, 4 figure

Microwave Response and Spin Waves in Superconducting Ferromagnets

Excitation of spin waves is considered in a superconducting ferromagnetic slab with the equilibrium magnetization both perpendicular and parallel to the surface. The surface impedance is calculated and its behavior near propagation thresholds is analyzed. Influence of non-zero magnetic induction at the surface is considered in various cases. The results provide a basis for investigation of materials with coexisting superconductivity and magnetism by microwave response measurements.Comment: 10 pages, 7 figure

Excitation of Spin Waves in Superconducting Ferromagnets

This Letter presents a theoretical analysis of propagation of spin waves in a superconducting ferromagnet. The surface impedance was calculated for the case when the magnetization is normal to the sample surface. We found the frequencies at which the impedance and the power absorption have singularities related to the spin wave propagation, and determined the form of these singularities. With a suitable choice of parameters, there is a frequency interval in which two propagating spin waves of the same circular polarization are generated, one of them having a negative group velocity.Comment: 4 pages, 2 figures, submitted to PR

Prevention of Pyelonephritis Due to Escherichia coli in Rats with Gentamicin Stored in Kidney Tissue

Although gentamicin is known to accumulate and persist in the kidneys after systemic administration, its antibacterial activity at this site has not been determined. In the present study the accumulation of gentamicin in rat kidneys before infection prevented obstructive pyelonephritis due to Escherichia coli despite heavy urinary tract infection in the obstructed pelvis; thus the kidneys were protected against infection in the absence of effective levels of gentamicin in the urine. Stored gentamicin also protected pyelonephritic rats from relapse after complete obstruction of the kidneys. The level of antimicrobial activity of gentamicin in whole kidney tissue was 95% less than that anticipated on the basis of levels measured after dilution of kidney tissue homogenates; this low level of activity apparently was due in part to high concentrations of solutes. In view of these results in rats, the possibility must be considered that despite reduced activity, gentamicin storage might be useful in the prophylaxis of kidney infection in patients with abnormalities of the urinary tract. In the treatment of established kidney infection, the dose of gentamicin could be reduced and the interval of its administration increased for minimal toxicit

Synergism of Ampicillin and Gentamicin against Obstructive Pyelonephritis Due to Escherichia coli in Rats

Rats with obstructive pyelonephritis due to Escherichia coli were treated for different intervals with ampicillin and gentamicin either alone or in combination. The combination of ampicillin and gentamicin was synergistic in vitro and significantly more effective in vivo than was either drug alone. After treatment for 10 days, the combination of ampicillin and gentamicin was the only regimen that sterilized all of the pyelonephritic kidneys. The importance of achieving sterility was illustrated by the observation that severe infection and acute pyelonephritis recurred after religation of the ureter in 12 (71%) of 17 ampicillin-treated animals that had harbored as few as 46 organisms per kidney before ligation. A synergistic combination of antibiotics rapidly sterilizes obstructed pyelonephritic kidneys. In view of the particular risk of renal infection in the presence of urinary obstruction in humans, synergistic antibiotic combinations may be useful in the treatment of obstructive pyelonephritis in human