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A Hanke

Publications and source records attributed to A Hanke.

15 recordsLinked to original sources
PubMed2001

Probing the strong boundary shape dependence of the Casimir force.

We study the geometry dependence of the Casimir energy for deformed metal plates by a path integral quantization of the electromagnetic field. For the first time, we give a complete analytical result for the deformation induced change in Casimir energy delta E in an experimentally testable, nontrivial geometry, consisting of a flat and a corrugated plate. Our results show an interesting crossover for delta E as a function of the ratio of the mean plate distance H, to the corrugation length lambda: For lambda< >H.

Journal Article↗
PubMed2001

Modified critical correlations close to modulated and rough surfaces.

Correlation functions are sensitive to the presence of a boundary. Surface modulations give rise to modified near surface correlations, which can be measured by scattering probes. To determine these correlations, we develop a perturbative calculation in deformations in height from a flat surface. The results, combined with a renormalization group around four dimensions, are also used to predict critical behavior near a self-affine rough surface. We find that a large enough roughness exponent can modify surface critical behavior.

Journal Article↗
PubMed2001

Polymer depletion interaction between two parallel repulsive walls.

The depletion interaction between two parallel repulsive walls confining a dilute solution of long and flexible polymer chains is studied by field-theoretic methods. Special attention is paid to self-avoidance between chain monomers relevant for polymers in a good solvent. Our direct approach avoids the mapping of the actual polymer chains on effective hard or soft spheres. We compare our results with recent Monte Carlo simulations [A. Milchev and K. Binder, Eur. Phys. J. B 3, 477 (1998)] and with experimental results for the depletion interaction between a spherical colloidal particle and a planar wall in a dilute solution of nonionic polymers [D. Rudhardt, C. Bechinger, and P. Leiderer, Phys. Rev. Lett. 81, 1330 (1998)].

Journal Article↗
PubMed2001

Quality of life influenced by primary surgical treatment for stage I-III breast cancer-long-term follow-up of a matched-pair analysis.

BACKGROUND: Breast-conserving therapy has been demonstrated to be just as safe and a less disruptive experience compared with mastectomy for surgically manageable breast cancer. There is, however, no agreement in the literature about the impact of these procedures on several important aspects of quality of life (QOL). The purpose of the present study is to compare the long-term impact of these two surgical approaches on QOL in patients with identical tumor stages and to suggest possible shortcomings of the standard QOL questionnaires. METHOD: Between August 1999 and May 2000, QOL questionnaires were answered by 152 pair-matched patients at the I. Frauenklinik, Ludwig-Maximilians University Munich, as part of routine follow-up examinations. The pairs of patients, each consisting of one patient after mastectomy and one after breast conservation, were selected according to the highest degree of equivalence in tumor stage. All patients had been initially treated for stage I-III breast cancer without evidence of distant metastases. The QOL was evaluated by using the QLQ-C30 questionnaire version 2.0 of the EORTC Study Group on Quality of Life. We formulated seven additional questions about the patients' satisfaction with the primary surgical treatment modality as viewed from their current perspective. The QOL questionnaires were answered after a median interval of 46 months following primary treatment. RESULTS: Tumor stage, prognostic factors, and adjuvant systemic treatment were well balanced between the two groups. No differences between the two groups were observed in terms of all QOL items measured by the QLQ-C30. Our additional questions, however, revealed that patients in the mastectomy group were less satisfied with the cosmetic result of their primary operation (P < .0001), were more likely to feel basic changes in their appearance (P < .0001), and were more likely to be emotionally stressed by these facts (P < .0001). From their perspective at the time of completing the questionnaires, 11 patients in the mastectomy group (15%) would decide differently about the surgical treatment modality, compared with only 3 patients (4%) in the breast conservation group (P = .025). CONCLUSION: While the primary surgical treatment modality seems to have no long-term impact on general QOL, certain body-image-related problems may be caused by mastectomy. Standard measuring instruments for QOL may fail to detect differences in satisfaction and adaptation with the primary surgical treatment modality.

Breast Neoplasms↗
PubMed2001

The Tasmanian children's project: the needs of children with a parent/carer with a mental illness.

This paper presents some of the key findings and recommendations of the report The Tasmanian Children's Project (TCP): The Needs of Children with a Parent/Carer with a Mental Illness, October, 1999. The TCP, a collaborative venture between the University of Tasmania's School of Nursing and the Mental Health Services - South, Tasmania (Department of Health and Human Services), is the first study in Tasmania to formally examine the needs of children where the parent/carer has a mental illness. The study is a modified replication and extension of the 1993/94 Victorian Children's Project. Extension aspects of the TCP included interviews with children (in addition to parents and service providers), the inclusion of data on both maternal and paternal mental illness and a broad definition of mental illness (beyond psychotic illness and major affective disorder). The report highlights the need to provide a range of programs that encourage the development of personal competency among children, parents, and other family members and those that emphasize interagency collaboration. Implications of this research for mental health nursing education and practice are also addressed.

Adolescent↗
PubMed2001

[Dynamic imaging of the nasal cavity and the paranasal sinuses with polarized 3helium MRI].

PURPOSE: Reduced or blocked ventilation of the paranasal sinuses is probably the most important factor in the development of sinusitis. Recently, the use of optically polarized noble gas isotopes has attracted increasing interest for use in a variety of promising MR applications. The aim of this study was to test the feasibility of imaging and visualization ventilation of the nasal cavity and paranasal sinus in MR by inhalation of hyperpolarized (3)helium. The goal was to evaluate ventilation defects of the paranasal sinuses. VOLUNTEERS AND METHODS: Three volunteers were enrolled in the study. (3)Helium was polarized to 40 - 50 % by direct optical pumping. 300 ml of 100 % (3)helium were administered in the left nasal vestibule through a glass tube. With a closed contralateral nasal vestibule, the Valsalva maneuver was performed twice. Using a dedicated application unit, which is also used in MR imaging of the lung, an exact amount of (3)helium gas was administered at the beginning of inspiration. Measurements were carried out on a clinical 1.5 T scanner. Coronal images of the nasal cavity and paranasal sinuses were acquired using ultrafast gradient-echo pulse sequence (TR = 2 ms, TE = 0.7 ms, FA < 2 degrees, 75 x 128, FOV = 500) with an image aquisition time of 130 ms. RESULTS: The oral cavity and nasal cavities display a very high signal intensity after inhalation of polarized (3)helium gas. The signal intensity in the left maxillary sinus was higher compared to the right one. The mean signal intensity on the left side was 526 +/- 86 and on the right side 336 +/- 102. The left and right frontal sinus and ethmoid sinus only show signal of hyperpolarized (3)helium after two Valsalva maneuvers. Because of the low signal intensity of the frontal and ethmoid cells their visualization was incomplete. The signal to noise ratio was 14.1 for the left maxillary sinus, 8.9 for the right side, 6.3 for the left ethmoid sinus, 5.8 for the right side and 6.6 for the left frontal sinus and 7.8 for the right side. CONCLUSION: (3)Helium MR allows imaging of the nasal cavity and the paranasal sinuses. Perhaps this method could be a new tool to visualize the ventilation of the maxillary sinus without ionizing radiation. Interpretations about the ventilation of the frontal and ethmoid cells remain speculative.

Administration, Inhalation↗
PubMed2000

Critical adsorption on defects in ising magnets and binary alloys

Long-range correlations in a magnet close to its critical point or in a binary alloy close to a continuous order-disorder transition can substantially enhance the effect of local perturbations. It is demonstrated using a position-space renormalization procedure that quasi-one-dimensional defects which break the symmetry of the order parameter have pronounced effects: They cause long-range critical adsorption profiles and give rise to new universal critical exponents, which are identified and calculated using field-theoretical methods.

Journal Article↗
PubMed1999

Effect of synthetic matrix-metalloproteinase inhibitors on invasive capacity and proliferation of human malignant gliomas in vitro.

Glioma invasion into the surrounding brain tissue is still a major obstacle for any therapeutical approach. As in other solid tumors, matrix-metalloproteases (MMPs) have been suggested as being involved. The aim of this study was to evaluate whether the use of MMP inhibitors to target the protease-mediated invasion process could be a feasible approach. Two human cell lines (U251 and GaMG) and surgical specimens of 6 patients with malignant gliomas were grown as monolayers and spheroid cultures respectively. MMP- and u-PA-mRNA expression was investigated by semi-quantitative RT-PCR. Invasion was studied in Matrigel-coated Boyden chamber transwell assays for monolayers and in confrontation cultures of tumor spheroids with fetal rat brain aggregates in the presence of the synthetic MMP inhibitors batimastat (BB-94) and marimastat (BB-2516). Cytotoxicity/cytostatic effects of high concentrations of both compounds were assessed by growth curves, MTT assays and flow cytometry in human glioma cell lines. Batimastat and marimastat revealed a cytostatic effect at high concentrations (above 1 microM) without cytotoxicity. Both MMP inhibitors effectively reduced glioma invasion in Boyden-chamber assays at low concentrations of 0.3 microM. In confrontation cultures, concentrations of 10 microM and above were necessary to reduce invasion. This effect was observable with inter-individual heterogeneity in the patient's tumor material. MMP inhibitors effectively reduce glioma invasion, although high concentrations were required in 3-dimensional culture systems. At these concentrations, both compounds revealed a cytostatic, but no cytotoxic effect. Thus, high local concentrations of MMP inhibitors could offer a new therapeutic strategy for the treatment of gliomas.

Animals↗
PubMed1999

Critical adsorption on curved objects.

A systematic field-theoretical description of critical adsorption on curved objects such as spherical or rodlike colloidal particles immersed in a fluid near criticality is presented. The temperature dependence of the corresponding order parameter profiles and of the excess adsorption are calculated explicitly. Critical adsorption on elongated rods is substantially more pronounced than on spherical particles. It turns out that, within the context of critical phenomena in confined geometries, critical adsorption on a microscopically thin "needle" represents a distinct universality class of its own. Under favorable conditions the results are relevant for the flocculation of colloidal particles.

Journal Article↗
PubMed1999

Polymer depletion effects near mesoscopic particles.

The behavior of mesoscopic particles dissolved in a dilute solution of long, flexible, and nonadsorbing polymer chains is studied by field-theoretic methods. For spherical and cylindrical particles the solvation free energy for immersing a single particle in the solution is calculated explicitly. Important features are qualitatively different for self-avoiding polymer chains as compared with ideal chains. The results corroborate the validity of the Helfrich-type curvature expansion for general particle shapes and allow for quantitative experimental tests. For the effective interactions between a small sphere and a wall, between a thin rod and a wall, and between two small spheres, quantitative results are presented. A systematic approach for studying effective many-body interactions is provided. The common Asakura-Oosawa approximation modeling the polymer coils as hard spheres turns out to fail completely for small particles and still fails by about 10% for large particles.

Journal Article↗
PubMed1999

Critical adsorption near edges.

Symmetry breaking surface fields give rise to nontrivial and long-ranged order parameter profiles for critical systems such as fluids, alloys, or magnets confined to wedges. We discuss the properties of the corresponding universal scaling functions of the order parameter profile and the two-point correlation function, and determine the critical exponents eta(parallel) and eta( perpendicular) for the so-called normal transition.

Journal Article↗
PubMed1998

The cytomorphological spectrum of mantle cell lymphoma is reflected by distinct biological features.

Mantle cell (centrocytic) non-Hodgkin's lymphoma (MCL) is a malignant tumour with unique biological features. The pathogenesis of MCL seems to be strongly associated with aberrant function of the cell cycle. 110 cases of MCL have been analysed for their cytomorphological features, mitotic and proliferation indices, bcl-1 rearrangements, p53 expression patterns and DNA content by both interphase cytogenetic as well as DNA flow cytometric analyses. According to cytomorphology, three subtypes were recognized: a common, a lymphoblastoid and a pleomorphic variant of MCL. Blastic MCL subtypes were characterized by distinctly elevated mitotic and proliferation indices, frequent bcl-1 rearrangements at the MTC locus, and overexpression of p53. The most interesting finding, however, was a striking tendency of blastoid MCL subtypes to harbour chromosome numbers in the tetraploid range, a feature clearly separating these neoplasms from other types of B-cell NHL and possibly being related to its unphysiological expression of cyclin D1. Although characterised by a uniform immunophenotype and common biological background, MCL shows a broad spectrum of morphological features ranging from small cell to blastic types, and this spectrum is mirrored by distinct biological features.

Cell Division↗