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Biomedical subjects

A Schiller

Publications and source records attributed to A Schiller.

At least 19 recordsLinked to original sources
PubMed2002

Photon propagator, monopoles, and the thermal phase transition in three dimensional compact QED.

We investigate the gauge boson propagator in the three dimensional compact Abelian gauge model in the Landau gauge at finite temperature. The presence of the monopole plasma in the confinement phase leads to the appearance of an anomalous dimension in the momentum dependence of the propagator. The anomalous dimension as well as an appropriate ratio of photon wave function renormalization constants with and without monopoles is observed to be an order parameter for the deconfinement phase transition. We discuss the relation between our results and the confining properties of the gluon propagator in non-Abelian gauge theories.

Journal Article↗
PubMed2002

Broken unitarity and phase measurements in Aharonov-Bohm interferometers.

Aharonov-Bohm mesoscopic solid-state interferometers yield a conductance which contains a term cos(phi+beta), where phi relates to the magnetic flux. Experiments with a quantum dot on one of the interfering paths aim to relate beta to the dot's intrinsic Friedel transmission phase alpha(1). For closed systems, which conserve the electron current (unitarity), the Onsager relation requires that beta = 0 or pi. For open systems, we show that in general beta depends on the details of the broken unitarity. Although it gives information on the resonances of the dot, beta is generally not equal to alpha(1). A direct relation between beta and alpha(1) requires specific ways of opening the system, which are discussed.

Journal Article↗
PubMed2001

Projecting the Kondo effect: theory of the quantum mirage.

A microscopic theory is developed for the projection (quantum mirage) of the Kondo resonance from one focus of an elliptic quantum corral to the other focus. The quantum mirage is shown to be independent of the size and the shape of the ellipse, and experiences lambdaF/4 oscillations ( lambdaF is the surface-band Fermi wavelength) with an increasing semimajor axis length. We predict an oscillatory behavior of the mirage as a function of a weak magnetic field applied perpendicular to the sample.

Journal Article↗
PubMed2001

Androgen deficiency in women with hypopituitarism.

Androgen deficiency in men is associated with severe osteopenia, alterations in body composition including an increase in fat mass, and decreased libido. Little is known about the pathophysiology, metabolic consequences, or gender-specific effects of androgen deficiency in women. Acquired hypopituitarism in women is characterized by central hypogonadism and/or hypoadrenalism and therefore may affect critical sources of androgen production in women. We hypothesized that serum androgen levels would be decreased in women with hypopituitarism. We therefore determined serum androgen levels in 55 women with hypopituitarism and 92 controls. This included 4 subsets of hypopituitary women: 1) women less than 50 yr old not receiving estrogen, 2) women less than 50 yr old receiving estrogen, 3) women more than 50 yr old not receiving estrogen, and 4) women more than 50 yr old receiving estrogen. Premenopausal controls with regular menstrual cycles were studied in the early follicular phase, midcycle, and luteal phase during one cycle. All other subjects were studied 3 times during the month at comparable intervals to mimic these 3 time points of the normal menstrual cycle. Serum testosterone, free testosterone, androstenedione, and dehydroepiandrosterone sulfate levels were markedly reduced in all 4 groups of women with hypopituitarism compared with controls (P < 0.0001). Moreover, serum testosterone, free testosterone, and androstenedione levels were lower in women with central hypoadrenalism and hypogonadism than in subjects with hypoadrenalism or hypogonadism alone (P < 0.025). Mean DHEAS levels were decreased in hypopituitary women with both hypogonadism and hypoadrenalism compared with those in women with hypogonadism alone (P < 0.0001). These data demonstrate hypoandrogenemia in women with hypopituitarism. The physiological consequences of low androgen levels in this population remain to be determined.

Adenoma↗
PubMed2001

[Consenting and declining patients for an intervention group after breast cancer surgery differ in terms of quality of life, coping and immunological functional assays].

OBJECTIVE: Psychosocial intervention during the course of cancer is still being controversially disputed in psychosomatic studies. Immunological and endocrinological parameters can serve as links in observing the influence of the interactive processes involved. MATERIAL AND METHODS: The approach to determine whether psychotherapeutic intervention can lead to an improved quality of life on the one hand, and to a change in immune defenses in breast cancer patients as well, employed using the EORTC QLQ-C30 and optimistic self-efficacy (OKE) as well as evaluating lymphocyte subpopulations, lymphocyte proliferation and NK cell activity. Fifty-three breast cancer patients were offered the chance to participate in a psychosocial intervention group. Twenty-three accepted the offer. Randomized sampling of the group participants was determined twice by using the 30 EORTC QLQ-C30 parameters. In addition, immune function was measured before beginning (T1) and after completing the group intervention sessions (T2). This data was compared with that of the declining group. RESULTS: The analysis of the individual EORTC parameters in the pre- and post-comparison showed a decrease in "emotional strain" and an increase in "all-around quality of life" at the T2 test period. NK cell activity was increased at T2 as well in the participating group and was higher than that of the declining group both at T1 and T2 testing times. CONCLUSION: Participation in the psychosocial intervention group resulted in a marked decrease in the emotional strain and an increase in the quality of life. The increased NK-cell activity with lowered T-cell activation in comparison to the decliners hints at a coherence between coping behaviour and changes of the immunological cell function. The results of this study will be investigated further in a greater sample.

Adaptation, Psychological↗
PubMed1997

Flow cytometrical and genotypic analysis of primary non-Hodgkin's lymphoma of bone.

Primary malignant lymphoma of bone presents both diagnostic and therapeutic problems. No previous study has addressed the use of flow cytometry in the immunophenotypic evaluations of bone lymphomas. A 41-year-old Japanese female presented with a large lytic lesion in the right femur. Biopsies from the lesion were examined by light microscopy, immunohistochemistry, 3-color flow cytometry and Southern blotting. Microscopic examination showed a diffuse, noncleaved large cell lymphoma. The lymphoid cells were positive for mature B cell antigens and the phenotype was: CD5-, CD10-, CD19+, 20+, CD22+, IgG+, IgA-, IgM-, kappa-, lambda+, CD1-, CD2-, CD3-, CD4-, CD7-, CD8-. Southern blot analysis revealed rearranged bands on both heavy- and lambda light-chain genes, in contrast to germline configuration on T cell antigen receptor (beta, gamma and delta) genes. Flow cytometry, in conjunction with morphologic and other molecular techniques, can provide a rapid and accurate means of diagnosing primary lymphoma of bone. In addition, the capabilities of flow cytometry to assess cell properties/constituents can be utilized in detailed analysis of adhesion molecules and activation antigen which may lead to better prediction of the prognosis of this group of lymphomas, and may provide further important data for the therapeutic decision making process.

Adult↗
PubMed1995

[Coping with illness/quality of life and immunologic parameters of patients with breast carcinoma and benign tumors].

OBJECTIVE: Maladaptive coping of the cancer illness leads to considerable psychosocial burden which can-as a chronic stress factor-impair various immune functions, e.g. cellular immunity. PATIENTS AND METHODS: In a collective of 118 patients suffering from mammary carcinoma and 48 patients suffering from benign mammary tumors Coping was measured with the EORTC-MAC-scale and Quality of life with three questionnaires. Out of the immunologic variables the lymphocyte subpopulations were determined with flow cytometry. Immunglobulines, neopterin, C-reactive protein, and herpes serology were determined using standard methods. RESULTS: At follow up a slight increase of the mean vales of sum-scores is observed for the adverse coping mechanisms, like helplessness/despair and fear. On the other hand, the values for the coping styles fatalism and denial decrease. Significant correlations are seen between anxious attitude and number of natural killer cells (CD16 and CD56). It must be pointed out that area of social contact show an inverse correlation in patients with mammary cancers: a strong improvement correlates with diminished natural killer cells as well as reduced activated killer cells. CONCLUSIONS: The aim of this study is to determine whether a high risk group can be defined using these parameters and if these parameter can be influenced by psychotherapeutic interventions such as establishing "Coping-support-groups".

Adaptation, Psychological↗