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.

Effect of a physical phase plate on contrast transfer in an aberration-corrected transmission electron microscope.

In this theoretical study we analyze contrast transfer of weak-phase objects in a transmission electron microscope, which is equipped with an aberration corrector (C(s)-corrector) in the imaging lens system and a physical phase plate in the back focal plane of the objective lens. For a phase shift of pi/2 between scattered and unscattered electrons induced by a physical phase plate, the sine-type phase contrast transfer function is converted into a cosine-type function. Optimal imaging conditions could theoretically be achieved if the phase shifts caused by the objective lens defocus and lens aberrations would be equal to zero. In reality this situation is difficult to realize because of residual aberrations and varying, non-zero local defocus values, which in general result from an uneven sample surface topography. We explore the conditions--i.e. range of C(s)-values and defocus--for most favourable contrast transfer as a function of the information limit, which is only limited by the effect of partial coherence of the electron wave in C(s)-corrected transmission electron microscopes. Under high-resolution operation conditions we find that a physical phase plate improves strongly low- and medium-resolution object contrast, while improving tolerance to defocus and C(s)-variations, compared to a microscope without a phase plate.

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.

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.

[Dermatological diseases of the external male genitalia : Part 2: Infectious and malignant dermatological]. / Hauterkrankungen am äußeren männlichen Genitale : Teil 2: Infektiöse und maligne Hauterkrankungen.

The urological and andrological examination of male patients should include inspection of the genital skin in order to detect malignant neoplasms, such as erythroplasia of Queyrat and infectious diseases, such as genital warts (condylomata acuminata). Independent of the incidental finding of relevant dermatological alterations in the genital area, sexually transmitted diseases such as syphilis must again be considered more often as the incidence has greatly increased in Germany during the last few years. In addition, urologists should be able to adequately advise patients on all aspects of diseases caused by human papillomavirus. As patients are often alarmed by genital skin lesions and worried that the sex life can be impaired, the initiation of adequate therapy is of great importance.

[Dermatological diseases of the external male genitalia : Part 1]. / Hauterkrankungen am äußeren männlichen Genitale : Teil 1.

The urological examination of male patients includes an inspection of the external genitalia whereby a variety of dermatological alterations can be found. Not all dermatological findings are of clinical relevance. Pearly penile papules and heterotopic sebaceous glands are examples of normal physiological variations. Most penile melanotic macules, angiokeratomas, fibromas and angiomas do not have to be treated; however, penile skin lesions may also be symptoms of other diseases, such as circinate balanitis in Reiter's syndrome and multiple angiokeratomas in Fabry's disease. A typical manifestation of reactions to various drugs is the fixed drug eruption of penile skin. The differential diagnosis of various forms of balanoposthitis may be difficult and requires histological investigations (e.g. plasma cell balanitis or Zoon's disease). In contrast, the clinical manifestation of lichen sclerosus et atrophicus is easy to recognize. The clinical relevance of this disease is due to phimosis and problems during sexual intercourse.

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)

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.

Adenocarcinoma of the pancreas with a predominant intraductal component: a special variety of ductal adenocarcinoma.

A special variety of pancreatic cancer is characterized by a predominant intraductal proliferation with a low-grade proliferation rate. Immunohistochemical peculiarities and the lack of lymph node metastases despite an extended tumor, distinguish it from usual ductal pancreatic carcinoma. Adenocarcinoma of the pancreas with a predominant intraductal component is proposed for its classification.

Intracranial plasma cell granuloma and homocystinuria.

A rare case of plasma cell granuloma (PCG) of the brain is reported. An 18-year-old man with a well known homocystinuria and a history of severe oligophrenia, grand-mal-epilepsia, bilateral ectopia lentis requiring extraction of both lens and operatively correlated genu valgum, died suddenly within a few minutes. In 1993 a hypergammaglobulinemia was noticed and a decortication on the left side after purulent pneumonia became necessary. Four months before death, multiple abscesses in the spleen and pancreas led to splenectomy and resection of the pancreatic tail. Autopsy revealed a pulmonary embolism and an isolated intracranial plasma cell granuloma of the left hemisphere.

Sudden death of an 18-year-old man with homocystinuria and intracranial inflammatory pseudotumor (IPT).

An 18-year-old mentally deficient man with well-known homocystinuria died suddenly within a few minutes. He had a history of severe oligophrenia, bilateral ectopia lentis requiring extraction of both lenses and operatively corrected genu valgum on both sides. In 1993 a hypergammaglobulinemia was noticed and a decortication on the left side after purulent pneumonia became necessary. Four months before death multiple abscesses in the spleen and pancreas lead to splenectomy and resection of the pancreatic tail. Furthermore, an isolated inflammatory pseudotumor (IPT) of the brain was found. Autopsy revealed as cause of death a pulmonary embolism. The pathogenesis of the cause of death and concomitant diseases will be discussed.

Sudden cardiac death due to atypical isolated coronary arteritis?

A case of probable isolated primary arteritis of the coronary arteries (coronaritis) in a 68-year-old man who died suddenly and unexpectedly is presented. The histologic presentation of the disorder is discussed, especially the differential diagnosis of arteritis of the coronary arteries versus distinct coronary artery sclerosis with concomitant inflammatory change.

Object-wave reconstruction by carbon film-based Zernike- and Hilbert-phase plate microscopy: a theoretical study not restricted to weak-phase objects.

Transmission electron microscopy phase-contrast images taken by amorphous carbon film-based phase plates are affected by the scattering of electrons within the carbon film causing a modification of the image-wave function. Moreover, image artefacts are produced by non-centrosymmetric phase plate designs such as the Hilbert-phase plate. Various methods are presented to correct phase-contrast images with respect to the scattering of electrons and image artefacts induced by phase plates. The proposed techniques are not restricted to weak-phase objects and linear image formation. Phase-contrast images corrected by the presented methods correspond to those taken by an ideal centrosymmetric, matter-free phase plate and are suitable for object-wave reconstruction.

Object wave reconstruction by phase-plate transmission electron microscopy.

A method is described for the reconstruction of the amplitude and phase of the object exit wave function by phase-plate transmission electron microscopy. The proposed method can be considered as in-line holography and requires three images, taken with different phase shifts between undiffracted and diffracted electrons induced by a suitable phase-shifting device. The proposed method is applicable for arbitrary object exit wave functions and non-linear image formation. Verification of the method is performed for examples of a simulated crystalline object wave function and a wave function acquired with off-axis holography. The impact of noise on the reconstruction of the wave function is investigated.

Sudden death in childhood due to varicella pneumonia: a forensic case report with clinical implications.

Varicella (chickenpox) is one of the most frequent highly infectious diseases in childhood. It is caused by varicella-zoster virus. Lethal complications are rare. Focused on histological findings, we present a case of a sudden unexpected death of an otherwise healthy 18-month-old girl due to varicella-induced pneumonia. The histological and immunohistochemical investigations of the lung tissue revealed typical findings of a varicella pneumonia: haemorrhagic and necrotic nodules, intra-alveolar fibrin, numerous neutrophilic granulocytes, lymphocytes, plasmacells, macrophages, multinucleated giant cells and hyaline membranes. Varicella-related deaths are preventable by vaccine. To prevent complications and lethal outcome of varicella as reported here, the recommendations concerning vaccination against varicella must be taken into account in paediatric practice.