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Biomedical subjects

J Hage

Publications and source records attributed to J Hage.

16 recordsLinked to original sources
PubMed1989

Chemical evolution of interstellar dust, comets and the origins of life.

It now appears that the chemical evolution of the pre-solar system interstellar dust ensures that a major fraction of comets is in the form of complex organic molecules at least partially of a prebiotic nature and that the submicron interstellar dust preserves its chemical integrity as result of forming a very tenuous low density comet structure whose solid matter occupies approximately 1/5 of the total volume. This low density micro structure further provides a physical basis for comets bringing a significant fraction of the original interstellar organic molecules to the earth unmodified by the impact event. Finally, the evidence for a large number of comet collisions with the early earth ensured that the major organic molecular budget on the earth's surface was "continuously" supplied along with water well before 3.8 billion years ago which is the earliest date for life. The chemistry and morphological structure of a comet nucleus as an aggregate of interstellar dust is used to provide comparisons with a variety of comet Halley results: the density of the nucleus and of the dust; the dust cloud model and its consequences on the production of C+ and CN in the coma by small organic grains; the surface albedo and the low nucleus heat conductivity and high surface temperature; the appearance of 10(-14) g and 10(-17) g dust particles along with higher masses; the mass spectra of dust and infrared spectroscopy as evidence for complex organic grain mantles and of very small (approximately 0.01 micrometer) carbonaceous and silicate grains; the appearance of small grains resulting from breakup of larger grains. The cosmic ray dosage of a comet nucleus during its 4.5 billion years in the Oort cloud appears to be many orders of magnitude less than the dosage of the preaggregated interstellar dust by ultraviolet photons except perhaps in the outer few meters of the nucleus of a new comet. The heat conductivity calculated for aggregated dust is certainly less than 10(-4) that of crystalline ice. This, in combination with the interstellar dust microstructure, provide a basis for showing that solar heating of the interior of a nucleus is lower than previously estimated.

Carbon↗
PubMed1978

Size, technology, complexity, and structural differentiation: toward a theoretical synthesis.

This paper proposes a theoretical synthesis of the concepts of organizational size, technology, complexity, and structural differentiation. It suggests and finds that the most important determinant of differentiation in the division of labor is the scope of an organization's task, a technological dimension, and not organizational size. Neither horizontal nor vertical differentiation is thought to be determined by size while the scope of the task is proposed as a determinant of horizontal differentiation. The findings, however, support only the inference of a moderate causal connection between either size or task scope and either form of differentiation. Throughout the analysis and discussion the contrast between causal inference based on associations of levels and change rates is discussed. When dealing with the organizational processes addressed in this paper, both associations must be examined to adequately portray the complexity of the causal processes inferred.

Models, Theoretical↗
PubMed1977

Endocrine-like cells of the pulmonary epithelium of the human adult lung.

The morphological and histochemical characteristics of endocrine-like cells of the pulmonary epithelium of the right lower lobe of 12 human adult lungs were studied. Few cells were reactive to the argyrophil silver method of Grimelius and of Sevier and Munger and cells with a similar morphology and distribution emitted a green or yellow fluorescence after treatment of the lung epithelium with the amine presursors L-DOPA or L-HTP, respectively. A greater number of cells seems to be demonstrated by electron microscopy. The cells were characterized by small, round secretory granules showing a central dense core and a very thin clear halo between the core and the surrounding membrane. The cells are thought to be related to the endocrine-like cells of the pulmonary epithelium of the human foetal lung and to cells of carcinoids of larger bronchi.

Adult↗
PubMed1977

Malignant acanthosis nigricans--a para-endocrine syndrome?

A case is reported of acanthosis nigricans associated with a gastric carcinoma. The gastric cancer was of the diffuse, infiltrating type. Many tumour cells were identified by means of histochemistry and electron microscopy as neoplastic enterochromaffin-like cells. It is suggested that cancers associated with acanthosis nigricans might constitute a certain group of carcinomas in which parts of the tumour cells arise from the APUD-series of endocrine cells.

Acanthosis Nigricans↗
PubMedDate not supplied

Femur fractures in chest-injured patients: is reaming contraindicated?

OBJECTIVE: To determine if reamed femoral intramedullary nailing increases the pulmonary complications seen in chest-injured patients. DESIGN: Retrospective review of prospectively collected trauma database data from January 1991 to October 1994. SETTING: Methodist Hospital, Indianapolis, Indiana, Level I Trauma Center. PATIENTS: Group I: Chest-injured patients [chest Abbreviated Injury Score (AIS) > or = 2] without femur or tibia fractures. Group II: Chest-injured patients (chest AIS > or = 2) with femoral reamed intramedullary fixation. Group III: Chest-injured patients (chest AIS > or = 2) with femoral shaft fixation using nonreamed fixation (rush rods, plating, or external fixation). Group IV: Non-chest-injured patients (chest AIS < 2) with femoral reamed intramedullary fixation. MAIN OUTCOME MEASUREMENT/HYPOTHESIS: Reamed femoral intramedullary nailing does not alter pulmonary outcomes, even in chest-injured patients. RESULTS: Groups I and II had a very similar incidence of adult respiratory distress syndrome (ARDS), pneumonia, and number of ventilator days. Group III had a significantly higher incidence of ARDS and number of ventilator days than did Group I or II. Group III did not have a chest AIS score significantly different than Groups I and II. Group II had significantly higher ARDS and more ventilator days than did Group IV when only analyzing raw data. When injury severity was adjusted, there were no significant differences in pulmonary outcomes. CONCLUSION: Reamed intramedullary femoral fixation did not increase pulmonary morbidity in chest-injured patients.

Adult↗