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Biomedical subjects

R Berndt

Publications and source records attributed to R Berndt.

At least 19 recordsLinked to original sources
PubMed2003

Surface-state Stark shift in a scanning tunneling microscope.

We report a quantitative low-temperature scanning tunneling spectroscopy (STS) study on the Ag(111) surface state over an unprecedented range of currents (50 pA to 6 microA) through which we can tune the electric field in the tunnel junction of the microscope. We show that in STS a sizable Stark effect causes a shift of the surface-state binding energy E0. Data taken are reproduced by a one-dimensional potential model calculation, and are found to yield a Stark-free energy E0 in agreement with recent state-of-the-art photoemission spectroscopy measurements.

Journal Article↗
PubMed2003

[Histopathological diagnosis of Barrett's mucosa and associated neoplasias. Results of a consensus conference of the Working Group for "Gastroenterological Pathology of the German Society for Pathology" on 22 September 2001].

There are a number of difficulties regarding the diagnosis of Barrett's mucosa and the varying grades of neoplasia that may be associated with it. It was therefore the aim of a consensus conference of the "Working Group for Gastroenterological Pathology within the German Society of Pathology" to achieve standardization regarding the following issues: definition and diagnostic criteria for Barrett's mucosa and its discrimination from intestinal metaplasia of the cardia, diagnostic criteria for intraepithelial neoplasia, number of biopsies necessary to establish the diagnosis, significance of additional immunohistochemical and/or molecular biological methods as well as importance of a second opinion in the diagnosis of intraepithelial neoplasia.

Barrett Esophagus↗
PubMed2002

Electromagnetic coupling on an atomic scale.

Light emission from a scanning tunneling microscope is used to investigate the electromagnetic coupling (EMC) of a metal tip and a metal sample. Subatomic scale modifications of the tip-sample region cause spectral shifts of the fluorescence as demonstrated for a monatomic step and by variation of the tip-sample distance. For sharp tips the EMC is confined to a lateral range of a few nm. The results are consistent with model calculations of the electromagnetic response of an appropriate tip-sample geometry.

Journal Article↗
PubMed2001

Sharper images by focusing soft X-rays with photon sieves.

Fresnel zone plates consisting of alternating transmissive and opaque circular rings can be used to focus X-rays. The spatial resolution that can be achieved with these devices is of the order of the width of the outermost zone and is therefore limited by the smallest structure (20-40 nm) that can be fabricated by lithography today. Here we show that a large number of pinholes distributed appropriately over the Fresnel zones make it possible to focus soft X-rays to spot sizes smaller than the diameter of the smallest pinhole. In addition, higher orders of diffraction and secondary maxima can be suppressed by several orders of magnitude. In combination with the next generation of synchrotron light sources (free-electron lasers) these 'photon sieves' offer new opportunities for high-resolution X-ray microscopy and spectroscopy in physical and life sciences.

Journal Article↗
PubMed2001

Luminescence from metallic quantum wells in a scanning tunneling microscope.

The tunneling current of a scanning tunneling microscope is reported to cause light emission from the metallic quantum well system Na on Cu(111). Optical spectra along with tunneling spectroscopy show that one component of the emission is due to interband transitions between quantum well states of the Na layer. The other component is similar to plasmon-mediated emission observed previously from noble metals. The emission is a unique local probe of the electronic structure of this quantum well system.

Journal Article↗
PubMed2000

Controlled modification of individual adsorbate electronic structure

Modification of the electronic structure of a single Mn adsorbate placed within a geometrical array of adatoms on Ag(111) is observed using local spectroscopy with the scanning tunneling microscope. The changes result from coupling between the adsorbate level and surface electronic states of the substrate. These surface states are scattered coherently within the adatom array, mediating the presence and shape of the array to the adsorbate within. The dimension and geometry of the adatom array thus provide a degree of control over the induced changes.

Journal Article↗
PubMed2000

Dimensionality effects in the lifetime of surface states

A long-standing discrepancy between experimental and theoretical values for the lifetimes of holes in the surface-state electron bands on noble metal surfaces is resolved; previous determinations of both are found to have been in error. The ability of the scanning tunneling microscope to verify surface quality before taking spectroscopic measurements is used to remove the effects of defect scattering on experimental lifetimes, found to have been a significant contribution to prior determinations. A theoretical treatment of inelastic electron-electron scattering is developed that explicitly includes intraband transitions within the surface state band. In our model, two-dimensional decay channels dominate the electron-electron interactions that contribute to the hole decay and are screened by the electron states of the underlying three-dimensional electron system.

Journal Article↗
PubMed1998

[Diagnosis of pulmonary diseases with transthoracic ultrasound].

The indications or ultrasound in the evaluation of pulmonary disorders are described. Clinical applications are several lung diseases in adults and especially in children. In specific, well-defined applications, the feasibilities of ultrasound are promising. Sonography provides important additional information to chest X-ray and is even superior to CT under special circumstances. Pulmonary sonography is a useful link between conventional X-ray and more expensive cross-sectional imaging. In the evaluation of pulmonary diseases at present the potential of ultrasound is not optimally used.

Adult↗
PubMed1995

Endometrioid adenoma (polypoid endometriosis) of the omentum maius.

Endometrioid adenoma (polypoid endometriosis) of the omentum maius in an 89-year old female is reported. The tumor measured 1 cm in diameter and consisted of resting or weakly proliferating, partially macrocystic endometrial glands, encapsulated by delicate fibrous connective tissue. Immunohistochemically, glandular and stromal cells expressed estrogen receptor strongly, progesterone receptor weakly and CA 125 only weakly in a few glands. This is another, but rare example of the capacity of the omentum maius to develop tumors of the Müllerian variety.

Abdominal Neoplasms↗
PubMed1994

[Comparison of computerized tomography and B-image ultrasound in imaging diagnosis of the mediastinum].

40 patients with suspected mediastinal tumors were independently examined with computed tomography (CT) and sonography. The findings were confirmed by bronchoscopy, mediastinoscopy or surgery. In the assessment of the upper and middle mediastinum, sonography reaches a high sensitivity. On the contrary, in the evaluation of the anterior and posterior mediastinum, sonography is clearly inferior to CT. 90% of the tumors demonstrated by CT could be assessed with sonography. The most frequent tumors can be diagnosed with ultrasound. The evaluation of tumors in the paravertebral and retrosternal space is limited. Sonography of the mediastinum is a noninvasive, well-reproducible and cost-effective imaging modality that provides important information in cases of unclear X-ray and CT findings. The preliminary results encourage to a more frequent use of mediastinal sonography.

Adult↗