Time Refraction of Spin Waves

We present an experimental study of time refraction of spin waves (SWs) propagating in microscopic waveguides under the influence of time-varying magnetic fields. Using space- and time-resolved Brillouin light scattering microscopy, we demonstrate that the broken translational symmetry along the time coordinate results in a loss of energy conservation for SWs and thus allows for a broadband and controllable shift of the SW frequency. With an integrated design of SW waveguide and microscopic current line for the generation of strong, nanosecond-long, magnetic field pulses, a conversion efficiency up to 39% of the carrier SW frequency is achieved, significantly larger compared to photonic systems. Given the strength of the magnetic field pulses and its strong impact on the SW dispersion relation, the effect of time refraction can be quantified on a length scale comparable to the SW wavelength. Furthermore, we utilize time refraction to excite SW bursts with pulse durations in the nanosecond range and a frequency shift depending on the pulse polarity.

Nonlocal Stimulation of Three-Magnon Splitting in a Magnetic Vortex

We present a combined numerical, theoretical, and experimental study on stimulated three-magnon splitting in a magnetic disk in the vortex state. Our micromagnetic simulations and Brillouin-light-scattering results confirm that three-magnon splitting can be triggered even below threshold by exciting one of the secondary modes by magnons propagating in a waveguide next to the disk. The experiments show that stimulation is possible over an extended range of excitation powers and a wide range of frequencies around the eigenfrequencies of the secondary modes. Rate-equation calculations predict an instantaneous response to stimulation and the possibility to prematurely trigger three-magnon splitting even above threshold in a sustainable manner. These predictions are confirmed experimentally using time-resolved Brillouin-light-scattering measurements and are in a good qualitative agreement with the theoretical results. We believe that the controllable mechanism of stimulated three-magnon splitting could provide a possibility to utilize magnon-based nonlinear networks as hardware for neuromorphic computing.

Domain Wall Based Spin-Hall Nano-Oscillators

In the last decade, two revolutionary concepts in nanomagnetism emerged from research for storage technologies and advanced information processing. The first suggests the use of magnetic domain walls in ferromagnetic nanowires to permanently store information in domain-wall racetrack memories. The second proposes a hardware realization of neuromorphic computing in nanomagnets using nonlinear magnetic oscillations in the gigahertz range. Both ideas originate from the transfer of angular momentum from conduction electrons to localized spins in ferromagnets, either to push data encoded in domain walls along nanowires or to sustain magnetic oscillations in artificial neurones. Even though both concepts share a common ground, they live on very different timescales which rendered them incompatible so far. Here, we bridge both ideas by demonstrating the excitation of magnetic auto-oscillations inside nanoscale domain walls using pure spin currents. This Letter will shed light on the current characteristic and spatial distribution of the excited auto-oscillations.

Excitation of Whispering Gallery Magnons in a Magnetic Vortex

We present the generation of whispering gallery magnons with unprecedented high wave vectors via nonlinear 3-magnon scattering in a μm-sized magnetic Ni_{81}Fe_{19} disc which is in the vortex state. These modes exhibit a strong localization at the perimeter of the disc and practically zero amplitude in an extended area around the vortex core. They originate from the splitting of the fundamental radial magnon modes, which can be resonantly excited in a vortex texture by an out-of-plane microwave field. We shed light on the basics of this nonlinear scattering mechanism from an experimental and theoretical point of view. Using Brillouin light scattering microscopy, we investigated the frequency and power dependence of the 3-magnon splitting. The spatially resolved mode profiles give evidence for the localization at the boundaries of the disc and allow for a direct determination of the modes wave number.

Influence of an elevated nutrition risk score in patients suffering from esophageal cancer following tumor resection

Background: Patients who suffer from malignant tumors of the esophagus and esophagogastric junction have 5-year survival rates of up to 83%, something that is documented in the early stages of cancer. Too often, weight loss is an underestimated sign for patients suffering from cancer on the upper gastrointestinal tract. Weight loss is associated with different adverse outcomes. Even after tumor resection, malnutrition remains a severe problem that still affects long-term disease free survivors.Material and methods: This study included the clinical courses of 205 patients suffering from cancer of the esophagus or the esophagogastric junction who were operated on between July 2007 and December 2009. On admission, the nutrition risk score was evaluated. Follow-up data were collected routinely. The aim of the underlying study was to show the prevalence of an elevated nutrition risk score (NRS) and to demonstrate its influence on perioperative mortality and morbidity. Furthermore, the relevance of an elevated nutrition risk score on the postoperative survival was analyzed.Results: More than a third (35.8%) of the patients included in this study had a nutrition risk score of at least three. A preoperative elevated nutrition risk score did not have a significant influence on perioperative morbidity or on 30-days mortality rate. In patients with early tumor stage UICC stage I a/b, an elevated risk score of 3 or more had a significant influence on postoperative survival. In contrast, in advanced tumor stages an increased NRS did not have a significant negative influence on survival within both UICC II a/b and UICC IIII a/b. Conclusions: Further studies are required to demonstrate whether a nutritional intervention can improve the survival rates of patients suffering from malignant tumors within the esophagus and in whom an operation has to be performed.Keywords: Weight loss, esophageal cancer, NRS

Magnetic domain walls as reconfigurable spin-wave nanochannels

In the research field of magnonics, it is envisaged that spin waves will be used as information carriers, promoting operation based on their wave properties. However, the field still faces major challenges. To become fully competitive, novel schemes for energy-efficient control of spin-wave propagation in two dimensions have to be realized on much smaller length scales than used before. In this Letter, we address these challenges with the experimental realization of a novel approach to guide spin waves in reconfigurable, nano-sized magnonic waveguides. For this purpose, we make use of two inherent characteristics of magnetism: the non-volatility of magnetic remanence states and the nanometre dimensions of domain walls formed within these magnetic configurations. We present the experimental observation and micromagnetic simulations of spin-wave propagation inside nano-sized domain walls and realize a first step towards a reconfigurable domain-wall-based magnonic nanocircuitry.

Optimizing phase contrast in transmission electron microscopy with an electrostatic (Boersch) phase plate

Imaging of weak amplitude and phase objects, such as unstained vitrified biological samples, by conventional transmission electron microscopy (TEM) suffers from poor object contrast since the amplitude and phase of the scattered electron wave change only very little. In phase contrast light microscopy the imaging of weak phase objects is greatly enhanced by the use of a quarter-wave phase plate, which produces high signal contrast by shifting the phase of the scattered light. An analogous quarter-wave plate for the electron microscope, designed as an electrostatic einzel lens, was proposed by Boersch in 1947 but the small dimensions of the device have impeded its realization up to now. We here present the first fabrication and application of a miniaturized electrostatic einzel lens driven as TEM quarter-wave phase plate. Phase modulation is generated by the electrostatic field confined to the inside of a microstructured ring electrode. This field affects the phase velocity of the unscattered part of the electron wave. By varying its strength the phase shift of the primary beam can be adjusted to pi/2, producing strong phase contrast independent of spatial frequency. The phase plate proves to be mechanically stable and does not impair image quality, in particular it does not reduce the high-resolution signal. The expected residual lens effect of the einzel lens is minimal. Our microlens is supported by conducting rods arranged in a threefold symmetry. This particular geometry provides optimized single-sideband signal transfer for spatial frequencies otherwise obstructed by the supporting rods.

Effects of creatine on synthesis and release of gamma-[3H]aminobutyric acid

Creatine has been used previously to alter the energy balance of neurons in brain slices. In the present experiments, it was found to reduce the accumulation of gamma-[3H]aminobutyric acid ([3H]GABA) as synthesized from [3H]glutamine or [3H]glutamic acid in slices of rat neostriatum. The lowest effective concentration was 5 mM. Creatine (25 mM) was also effective when the degrading enzyme of GABA, i.e., GABA-alpha-oxoglutarate transaminase, was blocked by gabaculine. Creatine (25 mM) did not inhibit the uptake and subsequent accumulation of [3H]GABA. Thus, indirect evidence was obtained that creatine decreased the activity of the synthesizing enzyme of GABA, i.e., glutamate decarboxylase. When the direct effect of creatine (25 mM) on glutamate decarboxylase was studied in vitro, the agent indeed decreased the activity of the enzyme. Creatine (25 mM) also diminished the release of [3H]GABA (expressed as dpm/mg wet weight) from rat neostriatal slices, probably by reducing its synthesis and thus its readily releasable pool. These data are of importance for studies with creatine in complex neuronal systems, because they show that the agent changes not only neuronal energy balance, but also synthesis and release of the ubiquitous transmitter GABA.

Effects of somatostatin-14 on the in vitro release of [3H]GABA from slices of rat caudatoputamen

Slices (300 microns) of rat caudatoputamen were incubated in Krebs-Henseleit medium and loaded with [3H]glutamine, part of which was converted to [3H]GABA. This conversion takes place only in GABA-neurons most of which probably contribute to the striatonigral pathway. After a 24 min equilibration period, release of radioactivity was stimulated with veratridine (3.1-4 mumol/l) or K+ (15-25 mmol/l) in the absence or presence of somatostatin-14. From the radioactivity released [3H]GABA was separated by cationic exchange chromatography and measured. Somatostatin-14 affected the release of [3H]GABA in a manner which depended on its concentration as well as on the extent of stimulus-evoked release. Somatostatin-14 (1 nmol/l) enhanced the moderate release (2-4% of tissue content) elicited by veratridine (3.1 mumol/l) or K+ (20 mmol/l), but had no effect on the more pronounced release (5-8% of tissue content) elicited by veratridine (4 mumol/l) or K+ (25 mmol/l). Somatostatin-14 (10 nmol/l) had no effect on the moderate release of [3H]GABA, but diminished the pronounced one. Further experiments provided evidence that the somatostatin-14-induced enhancement was not brought about by a direct action on GABA-neurons but was probably indirect, i.e. mediated by other striatal neurons. In contrast, the diminution of the release of [3H]GABA caused by somatostatin-14 may be due to its direct action on releasing neurons. Two antisera against somatostatin lowered the pronounced release indicating that endogenous somatostatin may also enhance the release of [3H]GABA. In addition, endogenous somatostatin seems also to be able to diminish the release under certain experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Antifilarial activities of benzazole derivatives. 2. Microfilaricidal effects against Litomosoides carinii, Acanthocheilonema. vitae, Brugia malayi and B. pahangi in Mastomys natalensis

The spectrum of antimicrofilarial activities of eighteen 2-tertbutylbenzazole derivatives was evaluated comparatively in Mastomys natalensis infected with Litomosoides carinii, Acanthocheilonema viteae, Brugia malayi or B. pahangi. The minimal effective dose (DEM) against microfilariae (greater than 95% reduction of microfilariae counts in the peripheral blood) was determined on day 3 (DEM-3), on day 7, 14, 21, 28 and 42 (DEM-7, DEM-14, DEM-21, DEM-28 and DEM-42) after the first treatment. All compounds were effective against the microfilariae of all 4 species. The benzoxazole derivatives were invariably less potent than the corresponding benzothiazole analogues. Upon repeated oral treatment (once daily [o.d.] for five days) the DEM-7 of the benzoxazoles varied depending on the species and on the chemical structure between 25 mg/kg o.d. x 5 and greater than 100mg/kg o.d. x 5 days. Within the benzothiazole series the DEM-7 varied between 6.25 mg/kg o.d. x 5 and 100 mg/kg x 5. In all but 5 of the 40 parasite-compound combinations of the benzothiazoles the 5-methoxy-derivates were more effective than the 5-methyl analogues. Similar differences were found with the eight benz-oxazoles tested. The lowest DEM-7 was observed with compound CGP 20308 which is 2-tert-butyl-5-methoxy-6-isothio-cyanatobenzothiazole and with compound CGP 20376 which is 3-(2-tert-butyl-5-methoxy-benzothiazol-6-yl] amino-thiocabo-nylthio) propionic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Bilateral ablation of frontal cortex reduces concentration of cholecystokinin-like immunoreactivity in rat dorsolateral striatum

Rat striatum (caudatoputamen, CP) contains high concentrations of cholecystokinin-like immunoreactivity (CCK-LI) which is not synthesized in the CP itself, but is brought to it by afferent projections. Some of these have been reported to originate in the sensori-motor cortex. The source of the major part of the CCK-LI in the CP is not known. In the present study, it was investigated whether neurons in the frontal cortex send CCK-LI-containing fibers to the CP. Ablation of the frontal pole of one hemisphere did not decrease but significantly enhanced the CCK-LI in the dorsal CP. Unilateral ablation of the frontal pole combined with the ipsilateral severance of corpus callosum fibers reduced ipsilaterally the concentration of CCK-LI in the dorsolateral CP by approximately 60%. Also ablation of the frontal poles of both sides bilaterally reduced the concentration of CCK-LI in the dorsolateral CP by approximately 40%. It is concluded that the neuronal elements in the dorsolateral CP of one side, which contain CCK-LI, are in some way connected with neurons in the frontal poles of both hemispheres. This connection may be just functional or may be due to CCK-containing fibers, which originate in the frontal pole.

Antifilarial activities of benzazole derivatives. 1. Macrofilaricidal effects against Litomosoides carinii, Dipetalonema viteae, Brugia malayi, and B. pahangi in Mastomys natalensis

Eighteen 2-tert-butyl-benzazole derivatives were evaluated comparatively as macrofilaricidal agents against L. carinii (L.c.), D. viteae (D.v.), B. malayi (B.m.) and B. pahangi (B.p.). Upon repeated treatment (once daily) for five consecutive days the eight benzoxazole derivatives were invariably less potent than the corresponding benzothiazole derivatives. The minimal curative dose (DCM) of the benzoxazoles varied depending on the species and on the chemical structure between 25 and 100 mg/kg p.o. once daily for five days. In the benzothiazole series the lowest DCMs were observed with compound CGP 20376 which is the 5-methoxy-6-dithiocarbamic-S-(2-carboxy-ethyl)ester derivative. This compound eliminated all macrofilariae of L.c., B.m. and Bp. at 6.25 mg/kg p.o. once a day for five days, whereas 12.5 mg/kg x 5 days were needed against D.v. For all other benzothiazole derivatives the DCMs varied between 6.25 mg/kg p.o. x 5 to 100 mg/kg x 5. Six of the most potent benzothiazoles were tested by single oral treatment. In general doses had to be increased 2-4 times to reach minimum curative effects. CGP 20376 was fully effective against B.m. and B.p. at 12.5 mg/kg p.o., against L.c. at 25 mg/kg p.o. and against D.v. at 50 mg/kg p.o.. This compound has been selected from this series of novel benzazoles as a first candidate for trials against human bancroftian filariasis.

Effect of cyclosporin A and some derivatives in Litomosoides carinii-infected Mastomys natalensis

Litomosoides carinii-infected Mastomys natalensis were treated 85 days post infection with cyclosporin A (CyA) or 8 derivatives with different immunosuppressive capacities. CyA (oral doses of 5 X 25 mg/kg, 5 X 50 mg/kg, 5 X 80 mg/kg on consecutive days) reduced parasitaemia levels in a dose dependent way, beginning 3 weeks after first drug administration. Using 5 X 50 and 5 X 80 mg/kg animals were free from circulating microfilariae on the day of necropsy (day 56). Derivatives were administered in 5 daily oral doses of 50 mg/kg. Compounds B-5-49 and G-7-53 had similar effects as CyA. Compounds A-4-16 and E-6-44 caused mean microfilaraemia reductions of about 80% until day 56. Compounds C-5-34, D-6-45, F-7-62 and H-7-94 were only marginally effective (10-40%). None of the drugs affected the number or the motility of adult worms. However, in the case of efficacious compounds the number of intrauterine microfilariae was considerably reduced and most of the intrauterine stages were pathologically altered. The efficacy of the various derivatives was independent of their immunosuppressive activity in vivo and in vitro, their anti-inflammatory activity and their activity against Plasmodium berghei. Effects on intrauterine stages were first detectable 7 days after treatment with 5 X 80 mg CyA/kg when the number of intrauterine microfilariae had decreased and the proportion of pathologically altered stages had increased. Alterations increased with time after treatment. Additionally, the uteri contained relatively large amounts of highly active microfilariae which were still included in an ovoid sheath.(ABSTRACT TRUNCATED AT 250 WORDS)