PubMed Health⌕ Search

Biomedical subjects

M Schoen

Publications and source records attributed to M Schoen.

16 recordsLinked to original sources
PubMed2003

Collective dynamics near a phase transition in confined fluids.

We performed molecular dynamics simulations in the microcanonical ensemble (MEMD) for a "simple" fluid confined between two solid substrates. From the calculation of the intermediate scattering function F(k( parallel ),t) and through the memory function formalism, we extract material ( i.e. transport and thermodynamics) coefficients in the vicinity of the liquid-gas phase transition. Our results show that approaching the limit of stability ( i.e. the spinodal), the dynamics of the system changes markedly.

Journal Article↗
PubMed2001

Role of nanoscopic liquid bridges in static friction.

Interpretations of recent experiments on the effects of humidity on friction hypothesize that liquid-water bridges can span nanoscopic gaps at the interface between the sliding surfaces. By means of a lattice-gas model the mechanisms by which such bridges may engender static friction at a single ideal nanoscopic contact were studied. The model contact consists of a simple (spherically symmetric) fluid constrained between two plane-parallel substrates decorated with weakly and strongly attractive stripes that alternate periodically in one transverse direction. In analogy with the experiments the shear yield stress (yield strength) tau(s) of the contact was computed as a function of the chemical potential mu of the fluid (the analog of humidity). The influence of other thermodynamic state variables, such as temperature and distance between the substrates, and of the relative strength of the stripes on the yield-strength curves (i.e., tau(s) versus mu) was explored. Some intriguing correlations between experiment and theory are observed.

Journal Article↗
PubMed2000

Correlation of stress and structure in a simple fluid confined to a pore with furrowed walls

A Lennard-Jones (12,6) film confined between two furrowed walls was simulated by the grand canonical ensemble Monte Carlo method. The walls are constructed by gouging triangular grooves in planar substrates that are structureless on the molecular scale. The furrows are infinitely long in one transverse direction (y) and of nanoscopic width (s(x)) and depth (D). The furrows in the two walls are maintained parallel and in register. The diagonal components of the stress tensor (T(alphaalpha), alpha=x,y,z) are computed as functions of D and the separation between the substrates (s(z)) at fixed temperature, chemical potential, and s(x). The T(alphaalpha) for the film between the furrowed walls are strongly shifted from their counterparts for the film between flat (i.e., planar) walls. The shifts are rationalized in terms of the structure of the film, which becomes more ordered as the furrows deepen and the packing of film molecules becomes more restricted in the two dimensions normal to the y direction. The results demonstrate the profound impact of the coupling between molecular and nanoscopic scales on the properties of geometrically constrained fluids.

Journal Article↗
PubMed1999

Socially inhibited individuals show heightened DTH response during intense social engagement.

To determine whether altered cellular immune response might mediate the increased health risks associated with social inhibition, we examined delayed type hypersensitivity (DTH) responses in 36 adults under conditions of low and high intensity social engagement. Participants come from a study of psychological factors in functional bowel disease and fibromyalgia. Under high engagement conditions, socially inhibited individuals showed significantly increased induration in response to intradermal tetanus toxoid. Under low engagement conditions, these individuals showed less pronounced DTH responses that did not differ in magnitude from those of uninhibited individuals. This pattern of results was found using two different measures of social inhibition and was independent of social inhibition's definition as a continuously distributed trait vs a discrete category. These data are consistent with the general hypothesis that social inhibition represents a predisposition to physiologic hyperresponsiveness that requires an exogenous social trigger for expression.

Adult↗
PubMed1999

Absence of simulation evidence for critical depletion in slit pores.

Recent Monte Carlo simulation studies of a Lennard-Jones fluid confined to a mesoscopic slit pore have reported evidence of "critical depletion" in the pore local number density near the liquid-vapor critical point. In this Brief Report we demonstrate that the observed depletion effect is in fact a simulation artifact arising from small systematic errors associated with the use of long range corrections for the potential truncation. Owing to the large near-critical compressibility, these errors lead to significant changes in the pore local number density. We suggest ways of avoiding similar problems in future studies of confined fluids.

Journal Article↗
PubMed1993

Resistance to health: when the mind interferes with the desire to become well.

Secondary gain has long been viewed as a variable that can significantly affect a patient's recovery from such conditions as chronic pain disorders, factitious and somatoform disorders, and other psychological disorders. Secondary gain has not been evaluated in terms of its impact on major illnesses such as cancer or autoimmune disorders. In this paper I discuss how secondary gain can be present in such illnesses and how it results in a resistance to health. This resistance to health can lead not only to medical noncompliance, but can also ultimately affect the progression and recovery from the illness. I describe how hypnosis can be used to ferret out this resistance to health and how patients in a hypnotic state will indicate or express their resistance to becoming healthy. The advantage of this approach is that it enables the clinician to deal directly with the patient's unconscious resistance to health.

Adult↗
PubMed1989

Richter's transformation of lymphoma complicating Gaucher's disease.

A case of lymphoma in a middle-aged woman with Gaucher's disease, a mu-kappa monoclonal gammopathy, peripheral lymphocytosis, and massive splenomegaly is described. There was no evidence of Gaucher's disease in the splenectomy specimen. Instead, the splenic architecture was effaced by a small lymphocytic lymphoma (SLL), with a few foci of large cell lymphoma (LCL). Immunoperoxidase studies showed that both lymphomatous components had a mu-kappa immunophenotype. Flow cytometric analysis of peripheral blood and spleen lymphocyte surface markers confirmed monoclonality. The intensity of surface immunoglobulin expression and the results of other cell marker studies in the SLL component were consistent with a stage of differentiation beyond that typical of chronic lymphocytic leukemia (CLL). The presence of abundant cytoplasmic immunoglobulin in the SLL and the association with monoclonal gammopathy were more consistent with Waldenström's macroglobulinemia or plasmacytoid lymphocytic lymphoma. The immunohistochemical and flow cytometric findings suggest that the SLL component evolved clonally or underwent Richter's transformation to LCL. Although Gaucher's disease has been associated with a variety of B-cell disorders, the subsequent transformation to a high-grade lymphoma has not been previously reported.

B-Lymphocytes↗
PubMed1988

Acardiac fetus in a triplet pregnancy.

The acardiac monster represents one of the most severe but rare congenital anomalies. It occurs only in multiple gestations associated with vascular anastomoses between the affected fetus and its co-twin. The prenatal diagnosis of an acardiac fetus must be suspected in any multiple gestation in which cardiac activity cannot be documented sonographically in a growing fetus. We report an acardiac fetus occurring in a spontaneously conceived triplet pregnancy. A review of the literature, including pathogenetic theories and sonographic reports, is discussed.

Abnormalities, Severe Teratoid↗
PubMed1985

A conceptual framework and treatment strategy for the alcoholic urge to drink utilizing hypnosis.

The present paper proposes a theoretical framework and a treatment strategy for dealing with the urges to drink that alcoholics experience during recovery. Two models are proposed: the Defense Model and the Conditioning Model. Each model covers a specific period of time during recovery in which the urges to drink occur. The Defense Model describes the urges that result in the initial recovery period, while the Conditioning Model is invoked to explain urges that materialize in the later phases of recovery. Next, a treatment strategy is delineated that incorporates these models and employs the use of hypnosis. The treatment strategy is divided into three phases, with the first and second phases dealing with the alcoholic's unconscious and the third phase being directed at the alcoholic's conscious.

Alcoholism↗