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Biomedical subjects

H E Zimmerman

Publications and source records attributed to H E Zimmerman.

13 recordsLinked to original sources
PubMed2001

Energy distribution and redistribution and chemical reactivity. The generalized delta overlap-density method for ground state and electron transfer reactions: a new quantitative counterpart of electron-pushing.

A new approach to prediction of organic reactions and understanding of the electron flow involved in the reaction mechanisms is presented. The method developed permits comparison of electronic structures of species different in multiplicity, charge, and geometry based on use of spin- and charge-independent entities-"overlap corrected density matrices". The method utilizes the basis orbitals of one molecule A (e.g. reactant) in the computation of a second molecule, B, derived from the first by an approach to product. This then provides two Overlap-Density Matrices with a common set of basis (e.g. hybrid) orbitals. Subtraction of Overlap-Density Matrix B from Matrix A affords the Delta Overlap-Density Matrix. Each element of the Delta Overlap-Density matrix gives the change in electron population of a bond or of a single hybrid orbital. Molecule B may differ from A by the addition or loss of an electron, by stretching of a bond, by electronic excitation, or by some other perturbation. The Delta Overlap-Density matrices afford a detailed description of the reaction process and provide predictions of overall reactions including such subtleties as regiochemistry.

Journal Article↗
PubMed2001

Excited- and ground-state versions of the tri-pi-methane rearrangement: mechanistic and exploratory organic photochemistry.

The di-pi-methane rearrangement with two pi-groups bonded to a single carbon leading to pi-substituted cyclopropanes is now well established. The present research had as its goal the exploration of molecular systems having three pi-moieties attached to an sp(3)-hybridized atom in a search for a tri-pi-methane rearrangement. Indeed, it was found that such systems do rearrange photochemically to afford cyclopentenes. However, it was also established that vinylcyclopropanes ring-expand to cyclopentenes on direct irradiation. Since both three-ring and five-ring photoproducts often are found to be produced, it was important to establish that the observed photochemistry was really the result of a true single-step tri-pi-methane rearrangement and not the consequence of two sequential rearrangements, first to form a vinyl cyclopropane which subsequently ring expanded to the cyclopentene. The general situation has three species-A, B, and C-corresponding to tri-pi-methane reactant A, vinylcyclopropane photoproduct B, and cyclopentene photoproduct C. Three rate constants are involved, k(1) for A --> B, k(2) for A --> C, and k(3) for B --> C. The kinetics were applied to two examples with provision to avoid differential light absorption; this utilized singlet sensitization. It was determined that direct formation of the cyclopentene photoproduct proceeds more rapidly than the ring-expansion route. In contrast to the di-pi-methane rearrangement, the tri-pi-methane reaction was found to be preferred by the singlet, while in these sterically congested systems, the triplet led to di-pi-methane reactivity. Finally, a ground-state counterpart of the reaction was obtained.

Crystallography, X-Ray↗
PubMed2000

The need to know: experiences of critically ill patients.

BACKGROUND: Critically ill patients vary in their memories of their experience in the intensive care unit. Some have little recall and need to learn about their critical illness. Others have more vivid memories of their experiences, some of which were extremely unpleasant. Patients' not knowing what was happening may have exacerbated the unpleasant experiences. OBJECTIVES: To elicit the experience of knowing for critically ill patients and to explore the differences in perceptions between patients who were intubated and those who were not intubated during the illness. METHODS: Grounded theory was used to explore the meaning of knowing and not knowing and the process by which knowing occurs. Unstructured interviews were done with 14 patients. RESULTS: Knowing had 2 phases: the need to know (1) during and (2) after the critical illness. The first phase had 3 facets: needing information, needing to be oriented, and having confusing perceptions. The second phase had 2 facets: needing information about what had happened and piecing together events. Many experiences with knowing during and after a critical illness were similar for both intubated and nonintubated patients. The main difference was the intensity of the experience in some categories. CONCLUSIONS: Critically ill patients have a strong need to know throughout and after their time in the intensive care unit. Nurses must address this need for constant reorientation to the past and present in these patients. In addition, adequate nursing staff must be available for these patients.

Adult↗
PubMed1998

Do autopsies of critically ill patients reveal important findings that were clinically undetected?

OBJECTIVE: To determine if autopsies performed on patients who die in the medical intensive care unit (ICU) provide clinically important new information. DESIGN: Retrospective review. SETTING: A 16-bed medical-coronary ICU. PATIENTS: Patients who underwent autopsy during a 1-yr period. INTERVENTIONS: Pre mortem diagnoses were determined from the medical record. Autopsy results were obtained from the final pathology report. A panel of three physicians with certification of added qualifications in critical care medicine reviewed the findings. MEASUREMENTS AND MAIN RESULTS: These questions were asked: a) Is the primary clinical diagnosis confirmed? b) Are the clinical and pathologic causes of death the same? c) Are new active diagnoses revealed? and d) If the new findings had been known before death, would the clinical management have differed? Forty-one autopsies (31% of deaths) were done that showed: a) the same primary clinical diagnosis and post mortem diagnosis in 34 (83%) patients; b) the same clinical and pathologic cause of death in 27 (66%) patients; c) new active diagnoses in 37 (90%) patients; and d) findings that would have changed medical ICU therapy had the findings been known in 11 (27%) patients. CONCLUSIONS: Although the primary clinical diagnosis was accurate in most cases before death, the cause of death was frequently unknown. Almost all autopsies demonstrated new diagnoses, and knowledge of these new findings would have changed medical ICU therapy in many cases. In the critical care setting, autopsies continue to provide information that could be important for education and quality patient care.

Adolescent↗
PubMed1990

Framework for the Rhode Island response to the injury problem.

Injuries are the fourth leading cause of death in Rhode Island as well as the US and are responsible for the greatest amount of premature death. Recent years have brought more national attention to the role of public health in injury prevention. The Rhode Island Department of Health has been involved in a variety of injury control research, programs and legislation. In 1989, the Injury Prevention Program was funded through a grant from the Centers for Disease Control to coordinate and implement injury control programs in the Department. Injury prevention priorities are set on the basis of mortality and morbidity data. An analysis of Rhode Island death certificate data from 1979 to 1988 reveals that motor vehicle crashes, suicides, falls, and homicides are the leading causes of injury deaths. Age patterns vary for each cause, but males predominate in all categories of injury deaths. Activities to reduce injuries are underway or planned. Physicians will play key roles in this effort.

Adolescent↗