Stimulated Amplification of Propagating Spin Waves

Spin-wave amplification techniques are key to the realization of magnon-based computing concepts. We introduce a novel mechanism to amplify spin waves in magnonic nanostructures. Using the technique of rapid cooling, we create a nonequilibrium state in excess of high-energy magnons and demonstrate the stimulated amplification of an externally seeded, propagating spin wave. Using an extended kinetic model, we qualitatively show that the amplification is mediated by an effective energy flux of high energy magnons into the low energy propagating mode, driven by a nonequilibrium magnon distribution.

Controlling the Nonlinear Relaxation of Quantized Propagating Magnons in Nanodevices

Relaxation of linear magnetization dynamics is well described by the viscous Gilbert damping processes. However, for strong excitations, nonlinear damping processes such as the decay via magnon-magnon interactions emerge and trigger additional relaxation channels. Here, we use space- and time-resolved microfocused Brillouin light scattering spectroscopy and micromagnetic simulations to investigate the nonlinear relaxation of strongly driven propagating spin waves in yttrium iron garnet nanoconduits. We show that the nonlinear magnon relaxation in this highly quantized system possesses intermodal features, i.e., magnons scatter to higher-order quantized modes through a cascade of scattering events. We further show how to control such intermodal dissipation processes by quantization of the magnon band in single-mode devices, where this phenomenon approaches its fundamental limit. Our study extends the knowledge about nonlinear propagating spin waves in nanostructures which is essential for the construction of advanced spin-wave elements as well as the realization of Bose-Einstein condensates in scaled systems.

Spin Pinning and Spin-Wave Dispersion in Nanoscopic Ferromagnetic Waveguides

Spin waves are investigated in yttrium iron garnet waveguides with a thickness of 39 nm and widths ranging down to 50 nm, i.e., with an aspect ratio thickness over width approaching unity, using Brillouin light scattering spectroscopy. The experimental results are verified by a semianalytical theory and micromagnetic simulations. A critical width is found, below which the exchange interaction suppresses the dipolar pinning phenomenon. This changes the quantization criterion for the spin-wave eigenmodes and results in a pronounced modification of the spin-wave characteristics. The presented semianalytical theory allows for the calculation of spin-wave mode profiles and dispersion relations in nanostructures.

Phase-to-intensity conversion of magnonic spin currents and application to the design of a majority gate

Magnonic spin currents in the form of spin waves and their quanta, magnons, are a promising candidate for a new generation of wave-based logic devices beyond CMOS, where information is encoded in the phase of travelling spin-wave packets. The direct readout of this phase on a chip is of vital importance to couple magnonic circuits to conventional CMOS electronics. Here, we present the conversion of the spin-wave phase into a spin-wave intensity by local non-adiabatic parallel pumping in a microstructure. This conversion takes place within the spin-wave system itself and the resulting spin-wave intensity can be conveniently transformed into a DC voltage. We also demonstrate how the phase-to-intensity conversion can be used to extract the majority information from an all-magnonic majority gate. This conversion method promises a convenient readout of the magnon phase in future magnon-based devices.

29Si-Kernresonanzuntersuchungen an N-Trimethylsilyl-substituierten Aminen und Amiden / 29Si Nuclear Magnetic Resonance Studies on N-Trimethylsilyl Derivatives of Amines and Amides

The 29Si chemical shifts of several trimethyl silyl derivatives of amines and amides are measured and compared to other chemical and theoretical properties such as the basicities or the electronic charge on the nitrogen or the hydrogen of the N-H group of the amine or the amide. Whereas the 29Si chemical shift of saturated amines can be rationalized in terms of substituent effects, the shifts of aromatic amines show some dependency on the basic character of the amine. There seems to be little correlation between 29Si chemical shifts and electronic charge, but there is a similarity of 29Si with 1H chemical shifts of the NH group, which is interpreted as depending on anisotropy effects.

On the unusual fluorescence properties of xanthone in water

Photo-excited xanthone is known to undergo ultrafast intersystem crossing (ISC) in the 1 ps time domain. Correspondingly, its fluorescence quantum yield in most solvents is very small ( approximately 10(-4)). Surprisingly, the quantum yield in water is 100 times larger, while ISC is still rapid ( approximately 1 ps), as seen by ultrafast pump probe absorption spectroscopy. Temperature dependent steady state and time resolved fluorescence experiments point to a delayed fluorescence mechanism, where the triplet (3)npi* state primarily accessed by ISC is nearly isoenergetic with the photo-excited (1)pipi* state. The delayed fluorescence of xanthone in water decays with a time constant of 700 ps, apparently by internal conversion between the (3)npi* state and the lowest lying triplet state (3)pipi*.

Excited-state dynamics of bacteriorhodopsin probed by broadband femtosecond fluorescence spectroscopy

The impact of varying excitation densities (approximately 0.3 to approximately 40 photons per molecule) on the ultrafast fluorescence dynamics of bacteriorhodopsin has been studied in a wide spectral range (630-900 nm). For low excitation densities, the fluorescence dynamics can be approximated biexponentially with time constants of <0.15 and approximately 0.45 ps. The spectrum associated with the fastest time constant peaks at 650 nm, while the 0.45 ps component is most prominent at 750 nm. Superimposed on these kinetics is a shift of the fluorescence maximum with time (dynamic Stokes shift). Higher excitation densities alter the time constants and their amplitudes. These changes are assigned to multi-photon absorptions.

Strychninvergiftung

HISTORY AND ADMISSION FINDINGS

A 46-year-old man presented two hours after ingestion of about 250 mg strychnine with severe violent, generalized convulsions, triggered by external stimuli. During the convulsion-free periods there were no abnormal signs in the physical examination.

INVESTIGATION

The presence of strychnine was confirmed by urine analysis with gas chromatography-mass spectrometry.

TREATMENT AND COURSE

Because diazepam as anticonvulsant of choice was not effective in abating the convulsions the patient was intubated. A combination with midazolam, fentanyl and pancuronium was effective in controlling the convulsions. The patient was discharged from ICU on day three.

CONCLUSION

Fatal outcome of strychnine poisoning demands an aggressive management with early intubation, control of muscle tremors and prevention of rhabdomyolisis and renal failure.

Atomic force microscopy and scanning near-field optical microscopy studies on the characterization of human metaphase chromosomes

A better knowledge of biochemical and structural properties of human chromosomes is important for cytogenetic investigations and diagnostics. Fluorescence in situ hybridization (FISH) is a commonly used technique for the visualization of chromosomal details. Localizing specific gene probes by FISH combined with conventional fluorescence microscopy has reached its limit. Also, microdissecting DNA from G-banded human metaphase chromosomes by either a glass tip or by laser capture needs further improvement. By both atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM), local information from G-bands and chromosomal probes can be obtained. The final resolution allows a more precise localization compared to standard techniques, and the extraction of very small amounts of chromosomal DNA by the scanning probe is possible. Besides new strategies towards a better G-band and fluorescent probe detection, this study is focused on the combination of biochemical and nanomanipulation techniques which enable both nanodissection and nanoextraction of chromosomal DNA.

Evaluation of a new bioabsorbable barrier for recession therapy: a feasibility study

BACKGROUND

The objective of this study was to evaluate the feasibility of a new polylactic acid bioabsorbable barrier in the treatment of gingival recession.

METHODS

Twenty patients with buccal recession defects (Miller class I, II, and III; mean recession: 4.0 +/- 1.2 mm; range: 2.0 to 6.8 mm) participated. After thorough scaling and root surface conditioning with 10% tetracycline-HCl, a trapezoidal mucoperiosteal flap was prepared. A customized barrier was applied to cover the defect. Barriers adhered directly to tooth and bone and no sutures were used. The barrier was subsequently covered by a coronally positioned flap. Assessments of probing depths were performed by means of a controlled-force electronic probe, and recession was determined on stone models with a digital caliper at baseline and 12 months following therapy.

RESULTS

Eight barriers showed limited exposure (1 to 2 mm) with minimal signs of gingival inflammation between 2 and 6 weeks following surgery. Comparing baseline measurements with outcomes at 12 months, significant root coverage and probing attachment gain were observed (P <0.0001, paired t test). Mean gingival recession was reduced to 0.4 +/- 0.5 mm, corresponding to a mean root coverage of 91.9%, and overall attachment gains amounted to 4.2 mm. A significant gain of keratinized tissue was found (2.9 +/- 0.7 mm), and mean probing depths were slightly reduced from 2.2 to 1.7 mm.

CONCLUSIONS

The results of this study indicate favorable outcomes after using a new bioabsorbable barrier material for root coverage in recession-type defects.

A dynamic and direct visualization model for the study of nasal airflow

OBJECTIVE

To evaluate nasal airflow characteristics during physiologic breathing in normal and pathologic conditions.

DESIGN

The choana of an anatomical human model was connected to a pump that simulated physiological pressure changes in the upper airway system. Normal ambient air was used as medium. The airstream was marked with aerosolized water particles, and was observed through an exact but translucent replica of the original nasal septum.

RESULTS

In physiologic conditions the airflow is mixed. Turbulence is clearly visible even with low flow velocities. There is less turbulence with lower flow rates. The nasal airflow follows a triphasic pattern of acceleration, near-steady state, and deceleration. Turbulence is prominent in the first and third phases. The main flow stream passes through the middle meatus at all rates. Hypertrophic mucosal membranes and turbinates increase the proportion of air passing the middle meatus. With decongested turbinates, flow distribution is more even. After turbinectomy there is a significant amount of airflow passing along the floor of the nose. The olfactory region is aerated only toward the end of inspiration and during the entire expiration phase.

CONCLUSIONS

This model allows the investigation of airflow distribution and turbulence under physiologic conditions and the examination of the influence of pathologic conditions on these parameters. Overzealous trimming of turbinates results in an unphysiologic distribution of airflow.

Treatment of gingival recession with titanium reinforced barrier membranes versus connective tissue grafts

It was the aim of this study to compare barrier membrane therapy with connective tissue grafts in the treatment of recession defects. Fifteen patients with 2 paired vestibular recession defects participated in the study. After thorough scaling and root surface conditioning with tetracycline-HCl, defects were randomly assigned to 1 of 2 treatment modalities. In one of the defects, a trapezoidal mucoperiosteal flap was prepared, and a titanium reinforced expanded polytetrafluoroethylene membrane was adapted to the defect and secured by a sling suture. The membrane was subsequently covered by a coronally positioned flap secured with crown attached sutures. The other defect was treated with a connective tissue graft employing the "envelope technique." Twelve months after therapy, both treatment modalities showed significant root coverage and probing attachment gain. Gingival recession decreased from 3.6+/-0.7 mm to 0.5+/-0.5 mm for membrane treated defects and from 3.6+/-1.0 mm to 0.5+/-0.5 mm following use of grafts, corresponding to mean root coverages of 87.1% and 86.9%, respectively. Mean gains of keratinized tissue of 1.5 mm (membrane) and 2.5 mm (graft) could be observed. Thus, the results of this study demonstrate that both titanium reinforced barrier membranes and connective tissue grafts can be successfully used to treat periodontal recession defects.

[Epistaxis strategy--experiences with the last 360 hospitalizations]

BACKGROUND

The purpose of this study was to analyze the therapy concept used in the management of severe epistaxis in order to optimize the quality of our treatment and to arrive at an optimal therapeutic concept.

MATERIAL AND METHODS

The study was performed as a retrospective analysis of the charts of all 335 patients treated as inpatients for epistaxis over a period of 6 years.

RESULTS

An increased rate of complications was found in the following three situations: 1. Age > 65 years, 2. chronic obstructive pulmonary disease, 3. several systemic illnesses. Recurrence was increased with septal perforations and Osler's disease.

CONCLUSIONS

Localization of the site of bleeding is the first priority and allows treatment of bleeding with bipolar electrocautery. If the bleeding vessel is not found, insertion of a Merocel pack is recommended. Patients with persistent or recurrent bleeding are treated in the operating theater under general anesthesia if they are at an elevated risk for complications or have a septal deviation which is clinically significant. The nose is systematically visualized with the endoscope, bleeding vessels are coagulated under endoscopic control, and, where appropriate, a septoplasty is performed. In the remaining cases an epipharynx balloon is inserted, combined with an anterior pack. Angiography with superselective embolization, external ligation of the ethmoidal arteries, and endonasal obliteration of the sphenopalatine artery is reserved for cases where the measures discussed above have failed.

Constant detection of CD2, CD3, CD4, and CD5 in fixed and paraffin-embedded tissue using the peroxidase-mediated deposition of biotin-tyramide

Immunohistochemical methods are widely used for diagnostic purposes in histopathology. However, the use of most monoclonal anti-leukocyte antibodies is limited to frozen tissues. Initially, it was believed that formalin fixation in particular, which is the gold standard for morphological tissue preservation, destroys most of the antigen binding sites. In recent years, protease digestion and the introduction of microwave techniques have significantly enhanced the sensitivity of immunohistochemical techniques, and a variety of hidden antigen sites in formalin-fixed tissue have been retrieved for initially unreactive antibodies. It therefore became clear that many of the leukocyte antigens are not irreversibly destroyed but are most probably masked during the fixation process. We developed a technique combining optimized pretreatment of formalin-fixed tissue with a dramatic enhancement of the immunohistochemical sensitivity and named it the ImmunoMax method. The ImmunoMax method proves that by optimizing the technique at the following three levels it is possible to detect formalin-sensitive leukocyte antigens: (a) standard fixation of the tissue; (b) sufficient antigen unmasking; and (c) increasing the substrate turnover by multiplication of binding sites with subsequent enhancement of the immunohistochemical reaction. Using this optimized ImmunoMax method, we were able to detect CD2, CD3, CD4, and CD5 with conventional monoclonal antibodies in formalin-fixed, paraffin-embedded tissue specimens of various lymphoid tissues.

Fabrication and strategic significance of a special resin composite splint in advanced periodontitis

The usefulness of splinting of severely loosened teeth in advanced periodontitis has been discussed extensively, both positively and negatively. Retention of patients own teeth through the aid of this simple and inexpensive resin composite splint provides a satisfactory solution for many affected patients. The fabrication and placement techniques for splints for the anterior and posterior regions are described, as are additional indications for such splints, which are fabricated from resin composite and glass fiber bundles. Such splinting can be provided even for severely loosened, periodontally diseased teeth without danger of intraoperative tooth loss. Long-term retention of such teeth can be ensured only through a risk-oriented postoperative program of oral hygiene and regular examination of the splint.

Nuclear accumulation of p53 in response to treatment with DNA-damaging agents

A number of agents which damage DNA also trigger the nuclear accumulation of the tumor suppressor protein p53. Here we show the correlation with different p53 detection methods. As an example we investigated the effects of the cancer therapy drug mitomycin C on different mammalian cell lines. Our findings demonstrate that either the immunofluorescence techniques (indirect immunofluorescence staining or flow cytometric analysis) or ELISA or immunoblot assays are useful methods in detecting p53 accumulation. Simultaneously we measured DNA damage with the terminal deoxynucleotidyl transferase assay. Compatible data were obtained. Thus p53 accumulation may be used as indicator of DNA injury.

[Use of autologous ear cartilage in eyelid surgery]

Autologous ear cartilage is relatively easy to procure in suitable form and sufficient quantity. At the donor site, there are, as a rule, no complications to be expected. Autologous ear cartilage without conjunctival coverage is of good use for replacing and lengthening the inner layer of an eyelid, not only to reconstruct large eyelid-defects, but also to give additional support and length. The cartilage graft will grow on well, provided the wound is well vascularized. This must not be expected with scarring or poor blood perfusion. The brittleness of the cartilage demands an adapted technique. Precautions to protect the cornea and to prevent adhesions in the fornix are to be taken.

The chemical logic of a minimum protocell

Traditional schemes for the origin of cellular life on earth generally suppose that the chance assembly of polymer synthesis systems was the initial event, followed by incorporation into a membrane-enclosed volume to form the earliest cells. Here we discuss an alternative system consisting of replicating membrane vesicles, which we define as minimum protocells. These consist of vesicular bilayer membranes that self-assemble from relatively rare organic amphiphiles present in the prebiotic environment. If some of the amphiphiles are primitive pigment molecules asymmetrically oriented in the bilayer, light energy can be captured in the form of electrochemical ion gradients. This energy could then be used to convert relatively common precursor molecules into membrane amphiphiles, thereby providing an initial photosynthetic growth process, as well as an appropriate microenvironment for incorporation and evolution of polymer synthesis systems.

The formation of chromophores through amino acid thermolysis and their possible role as prebiotic photoreceptors

The thermal polymerization of amino-acid mixtures was studied at various temperatures and reaction times with specific emphasis on the formation of fluorescent chromophores. The reaction conditions appeared to have a pronounced effect on the ratio of synthesized chromophores and biuret-positive material. During thermolysis of equimolar mixtures of lysine, alanine and glycine or lysine, aspartic acid and glycine small amounts of pteridines and flavines are formed, which are often covalently linked to the thermal oligomer. These heterocyclic compounds are likely formed by condensation reactions of the amino acid break-down and conversion products. Reaction schemes that describe the processes are proposed. The significance of these chromoproteinoids is discussed in respect to prebiotic redox reactions and photoinduced processes.