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Biomedical subjects

D Armbruster

Publications and source records attributed to D Armbruster.

13 recordsLinked to original sources
PubMed2001

Perturbed on-off intermittency.

A basic requirement for on-off intermittency to occur is that the system possesses an invariant subspace. We address how on-off intermittency manifests itself when a perturbation destroys the invariant subspace. In particular, we distinguish between situations where the threshold for measuring the on-off intermittency in numerical or physical experiments is much larger than or is comparable to the size of the perturbation. Our principal result is that, as the perturbation parameter increases from zero, a metamorphosis in on-off intermittency occurs in the sense that scaling laws associated with physically measurable quantities change abruptly. A geometric analysis, a random-walk model, and numerical computations support the result.

Journal Article↗
PubMed2000

Intermittency in chaotic rotations

We examine the rotational dynamics associated with bounded chaotic flows, such as those on chaotic attractors, and find that the dynamics typically exhibits on-off intermittency. In particular, a properly defined chaotic rotation tends to follow, approximately, the phase-space rotation of a harmonic oscillator with occasional bursts away from this nearly uniform rotation. The intermittent behavior is identified in several well studied chaotic systems, and an argument is provided for the generality of this behavior.

Journal Article↗
PubMed1997

Marijuana-positive urine test results from consumption of hemp seeds in food products.

Commercially available snack bars and other foodstuffs prepared from pressed hemp seeds were ingested by volunteers. Urine specimens were collected for 24 h after ingestion of the foodstuffs containing hemp seeds and tested for marijuana using an EMIT immunoassay and gas chromatography-mass spectrometry (GC-MS). Specimens from individuals who ate one hemp seed bar demonstrated little marijuana immunoreactivity, and only one specimen screened positive at a 20-ng/mL cutoff. Specimens from individuals who ate two hemp seed bars showed increased immunoreactivity, and five specimens screened positive at a 20-ng/mL cutoff. A single specimen yielded a quantitative GC-MS value (0.6 ng/mL), but it failed to meet reporting criteria. Several specimens from individuals who ate three cookies made from hemp seed flour and butter screened positive at both 50- and 20-ng/mL cutoffs. Two specimens produced quantitative GC-MS values (0.7 and 3.1 ng/mL), but they failed to meet reporting criteria. Several specimens also tested positive with an FDA-approved on-site marijuana-screening device. Hemp seeds similar to those used in the foodstuffs did not demonstrate the presence of marijuana when tested by GC-MS. In this study, ingestion of hemp seed food products resulted in urine specimens that screened positive for marijuana. No specimens gave a GC-MS quantitative value above the limit of detection for marijuana.

Adult↗
PubMed1991

An academic department of health informatics: a vision for the 21st century.

The purpose of this article is to share the vision of an academic health science center in creating a centralized academic and service Department of Health Informatics. To do this, we will present background on the institution, a brief discussion of informatics (including medical and health informatics), and then look in-depth at the Department of Health Informatics, including its mission, goals, organizational structure and operations.

Computer User Training↗
PubMed1987

[Cells in the normal human periodontal ligament. An ultrastructural, histo-enzymological and immunocytochemical study on in vitro cultures].

Four cellular cultures from explants of human periodontal ligament were studied. In these cultures, cells were fusiform or stellate with a high percentage (5 to 10%) of round mitotic cells. The scanning electron microscope confirmed the simultaneous presence of flat cells in interphase and cells in prophase with microvilli and long filipodes and of round mitotic cells with microvilli and blebs. Histoenzymology disclosed in these cells high activities in oxidative enzymes and leucine aminopeptidase. Furthermore some cells showed an alkaline phosphatase activity. Immunocytochemistry detected in most of these cells intermediate vimentin filaments and the presence of type I and III collagen irregularly distributed among these cells. In transmission electron microscopy the elongated cells presented a clear nucleus, numerous endocytosic vesicles, ribosomes and longitudinal filaments. Variations were noted, especially in the quantity and quality of cell secretions, the fibroblasts secreting either the two type I and III collagen or only type I. The rare cells assuming alkaline phosphatase activity were atypical in possibly being provided with osteogenic potential.

Adult↗
PubMed1987

[Periodontal diseases in adults. Immunohistochemical study of inflammatory cells and of collagen].

An immunohistochemical study was performed on 9 gingival biopsy specimens from patients suffering of a periodontal disease comparatively to 7 control specimens from patients with inflammatory gingival hyperplasia of various causes and from healthy gums. We used mono or polyclonal antibodies as markers of the different types of inflammatory cells (T-1 lymphocytes and their subsets, B-lymphocytes, macrophages, plasma cells). In patients with periodontal disease, the high percentage of transformed T-lymphocytes with a majority of helpers was obvious. In controls, the inflammatory cells were principally B-lymphocytes, macrophages and plasma cells. The characterization of different types of collagen produced by periodontal fibroblasts was performed by specific antibodies (anti I, III, V collagen sera). The respective ratio and the topographic distribution of those collagen substances were different in patients with periodontal disease and controls. In the first eventuality, one could find quite exclusively type I collagen. In the other group, type I collagen was associated with type III sub epithelial and type IV perivasor ar collagen. By means of these findings, the pathogenesis of the periodontal disease was discussed and its immune mechanism was suggested.

Biopsy↗
PubMed1976

[Influence of fatty-acid and glucose content of the perfusate on the energy metabolism of the preserved canine kidney].

Thirty-seven canine kidneys were preserved by hypothermic low flow perfusion for 24-120 h with solution I containing albumin, free fatty acids, and glucose, or with solution II containing Haemaccel without free fatty acids or glucose. Following 48 h preservation the renal ATP and SAN content was identical in both groups, irrespective of the availability of substrates from the perfusate.

Animals↗
PubMed1975

[Effect of pO2 in perfusate on metabolism of preserved dog kidneys].

In 48 canine kidneys submitted to an ischemia of 2 min duration normal cortical ATP values with a nearly unchanged content of total adenine nucleotides (SAN) were resumed by a five minute gravity perfusion. During the following 24 hours of low flow perfusion at 6 degrees C the extent of preservation of ATP and SAN correlated with the arterial oxygen pressure of the perfusate.

Adenine Nucleotides↗
PubMed1975

[Controlled hypothermia of ischemic extremities for the prevention of tourniquet shock].

The tourniquet-shock in dogs was produced after recirculation of ischemically stressed bilateral hind limbs. 4 of 7 dogs died within 5 hours after release of the tourniquets. The cause of heart failure could be defined by hypercaliaemia, metabolic acidosis and hemoconcentration. The development of tourniquet-shock could be suppressed by hypothermic preservation of the ischemic extremities.

Acidosis↗
PubMedDate not supplied

Obstetric first aid in the community--partners in safe motherhood. A strategy for reducing maternal mortality.

The unacceptably high levels of maternal mortality that are prevalent throughout the developing world are a product of many factors; most notably, these include nonexistent, inaccessible or inadequate facility-based emergency care, poorly developed referral linkages, predominance of home-based care by attendants and family members who are poorly equipped to respond to emergencies, and the complexities of problem recognition and decision making during emergencies leading to inappropriate or delayed action. This paper describes an innovative community-oriented strategy that has been designed to reduce maternal mortality and that targets women, families, and traditional birth attendants (TBAs) using two complimentary training interventions. The strategy reflects the authors' conviction that the training of professional and paraprofessional health workers in emergency care is essential, but that it must be complemented by the education and mobilization of families, communities, and TBAs who must, in turn, come to common perceptions on the need for and means of intervening to prevent a maternal death. Collaborating with partners in the US Agency for International Development-funded Primary Providers Training and Education in Reproductive Health Project. Special Project staff of the American College of Nurse-Midwives will lead development and testing of the strategy through operations research activities in selected countries.

Community Health Services↗
PubMedDate not supplied

Home based life saving skills: promoting safe motherhood through innovative community-based interventions.

In much of the developing world, home birth with unskilled attendants is the norm, and maternal and neonatal mortality rates are high. A comprehensive approach to address this problem needs to upgrade referral facilities and strengthen the skills of trained health care providers. To improve pregnancy outcomes, a program must also provide education, motivation, and mobilization of pregnant women, families, and communities (whose members must come to a common understanding of the need for and the means to prevent death of a woman or neonate). Consequently, the American College of Nurse Midwives (ACNM) has expanded the Life Savings Skills Series to include Home Based Life Saving Skills (HBLSS). HBLSS is a community and competency-based program that aims to reduce maternal and neonatal mortality by increasing access to basic life saving measures within the home and community and by decreasing delays in reaching referral facilities where life-threatening problems can be managed.

Community Health Services↗