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Biomedical subjects

H Stoll

Publications and source records attributed to H Stoll.

At least 19 recordsLinked to original sources
PubMed2006

Magnetic vortex core reversal by excitation with short bursts of an alternating field.

The vortex state, characterized by a curling magnetization, is one of the equilibrium configurations of soft magnetic materials and occurs in thin ferromagnetic square and disk-shaped elements of micrometre size and below. The interplay between the magnetostatic and the exchange energy favours an in-plane, closed flux domain structure. This curling magnetization turns out of the plane at the centre of the vortex structure, in an area with a radius of about 10 nanometres--the vortex core. The vortex state has a specific excitation mode: the in-plane gyration of the vortex structure about its equilibrium position. The sense of gyration is determined by the vortex core polarization. Here we report on the controlled manipulation of the vortex core polarization by excitation with small bursts of an alternating magnetic field. The vortex motion was imaged by time-resolved scanning transmission X-ray microscopy. We demonstrate that the sense of gyration of the vortex structure can be reversed by applying short bursts of the sinusoidal excitation field with amplitude of about 1.5 mT. This reversal unambiguously indicates a switching of the out-of-plane core polarization. The observed switching mechanism, which can be understood in the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application in data storage.

Journal Article↗
PubMed2004

Somatic mutations of KIT in familial testicular germ cell tumours.

Somatic mutations of the KIT gene have been reported in mast cell diseases and gastrointestinal stromal tumours. Recently, they have also been found in mediastinal and testicular germ cell tumours (TGCTs), particularly in cases with bilateral disease. We screened the KIT coding sequence (except exon 1) for germline mutations in 240 pedigrees with two or more cases of TGCT. No germline mutations were found. Exons 10, 11 and 17 of KIT were examined for somatic mutations in 123 TGCT from 93 multiple-case testicular cancer families. Five somatic mutations were identified; four were missense amino-acid substitutions in exon 17 and one was a 12 bp in-frame deletion in exon 11. Two of seven TGCT from cases with bilateral disease carried KIT mutations compared with three out of 116 unilateral cases (P=0.026). The results indicate that somatic KIT mutations are implicated in the development of a minority of familial as well as sporadic TGCT. They also lend support to the hypothesis that KIT mutations primarily take place during embryogenesis such that primordial germ cells with KIT mutations are distributed to both testes.

DNA Mutational Analysis↗
PubMed2001

Ab initio calculations on bismuth cluster polycations.

Ab initio calculations on bismuth polycationic species of the types Bi(n(n-2))+, Bi(n(n-4))+, and Bi(n(n-6))+ (n = 3 - 12) were performed at the Hartree-Fock and density functional theory levels in order to investigate their general properties and the applicability of Wade's rules on bismuth polycations. Some exceptions to Wade's rules were encountered, and, moreover, several predicted and calculated minima show only meta-stable behavior. The bonding in bismuth polycations is characterized by a high degree of electron delocalization and "three-dimensional aromaticity".

Journal Article↗
PubMed2001

Theoretical investigations of proton-bound cluster ions.

Several proton-bound cluster ions have been studied by means of coupled cluster calculations with large basis sets. Among these are complexes of a krypton or xenon atom with the cations HCO+, HN2+ and HNCH+. Various spectroscopic properties have been calculated in all cases. Effects of vibrational anharmonicity are particularly pronounced for the intramolecular stretching vibrations of Kr...HN2+ and Xe...HN2+. The proton stretching vibration of (N2)H+(N2) is predicted around 800 cm-1, with a large transition dipole moment of 1.15 D. Both (N2)H+(N2) and (HCN)H+(NCH) have linear centrosymmetric equilibrium structures. Those of (OC)H+(CO) and (HCC-)H+(CCH-) are asymmetric with barrier heights to the centrosymmetric saddle points of 382 and 2323 cm-1, respectively. The dissociation energy of the anionic complex Cl-...HCCH is calculated to be Do = 3665 cm-1, 650 cm-1 larger than the corresponding value for Br-...HCCH. The complex between a fluoride ion and acetylene is more strongly bound and shows strongly anharmonic behaviour, similar to the bihalides FHF- or ClHCl-. Strong Fermi resonance interaction is predicted between nu 3 (approximately proton stretch) and 2 nu 4 (first overtone of intermolecular stretch).

Journal Article↗
PubMed1999

Protein kinase C mu is negatively regulated by 14-3-3 signal transduction proteins.

Recent studies have documented direct interaction between 14-3-3 proteins and key molecules in signal transduction pathways like Ras, Cbl, and protein kinases. In T cells, the 14-3-3tau isoform has been shown to associate with protein kinase C theta and to negatively regulate interleukin-2 secretion. Here we present data that 14-3-3tau interacts with protein kinase C mu (PKCmu), a subtype that differs from other PKC members in structure and activation mechanisms. Specific interaction of PKCmu and 14-3-3tau can be shown in the T cell line Jurkat by immunocoprecipitiation and by pulldown assays of either endogenous or overexpressed proteins using PKCmu-specific antibodies and GST-14-3-3 fusion proteins, respectively. Using PKCmu deletion mutants, the 14-3-3tau binding region is mapped within the regulatory C1 domain. Binding of 14-3-3tau to PKCmu is significantly enhanced upon phorbol ester stimulation of PKCmu kinase activity in Jurkat cells and occurs via a Cbl-like serine containing consensus motif. However, 14-3-3tau is not a substrate of PKCmu. In contrast 14-3-3tau strongly down-regulates PKCmu kinase activity in vitro. Moreover, overexpression of 14-3-3tau significantly reduced phorbol ester induced activation of PKCmu kinase activity in intact cells. We therefore conclude that 14-3-3tau is a negative regulator of PKCmu in T cells.

14-3-3 Proteins↗
PubMed1998

Oncology Home Care Service.

The Oncology Home Care Service in Basel provides nursing support to let cancer sufferers choose where they receive palliative care. Most of the cost is borne by the patient's health insurance.

Adolescent↗
PubMed1992

Photodynamic therapy for the treatment of basal cell carcinoma.

BACKGROUND: Photodynamic therapy is an investigational method for the treatment of a variety of solid tumors. The purpose of this study was to determine the optimum factors and illustrate the effectiveness of photodynamic therapy in the treatment of basal cell carcinomas. This was a prospective study in which patients presenting with primary or recurrent basal cell tumors, particularly but not exclusively widespread tumors or large single tumors, were offered the option of photodynamic therapy in their treatment regimen. RESULTS: Patients were administered 1 mg/kg of a photosensitizer (Photofrin II). Light doses (630 nm) ranged from 72 to 288 J/cm2. A total of 37 patients with 151 sites were treated in this study. A complete response rate of 88% was achieved with one application. Morbidity was low; the most significant side effects were moderate pain and edema. CONCLUSIONS: Photodynamic therapy is a modality that offers localized treatment of primary or recurrent nonmelanoma skin cancer. By applying reciprocal doses of photosensitizer and light, the efficacy of photodynamic therapy in the treatment of skin lesions is demonstrated achieving significant light penetration into tissue with a high complete response rate of the lesions and acceptable normal tissue response.

Basal Cell Carcinoma↗