A Simple ab Initio Model for the Solvated Electron in Methanol.

The solvation structure of a solvated electron in methanol is investigated with ab initio calculations of small anion methanol clusters in a polarized dielectric continuum. We find that the lowest-energy structure in best agreement with experiment, calculated with CCSD, MP2, and B3LYP methods with aug-cc-pvdz basis set, is a tetrahedral arrangement of four methanol molecules with OH bonds oriented toward the center. The optimum distance from the tetrahedron center to the hydroxyl protons is ∼1.8 Å, significantly smaller than previous estimates. We are able to reproduce experimental radius of gyration Rg (deduced from optical absorption), vertical detachment energy, and resonance Raman frequencies. The electron paramagnetic resonance g-factor shift is qualitatively reproduced using density functional theory.

Isotope Dependence and Quantum Effects on Atomic Hydrogen Diffusion in Liquid Water.

Relative diffusion coefficients were determined in water for the D, H, and Mu isotopes of atomic hydrogen by measuring their diffusion-limited spin-exchange rate constants with Ni(2+) as a function of temperature. H and D atoms were generated by pulse radiolysis of water and measured by time-resolved pulsed EPR. Mu atoms are detected by muonium spin resonance. To isolate the atomic mass effect from solvent isotope effect, we measured all three spin-exchange rates in 90% D2O. The diffusion depends on the atomic mass, demonstrating breakdown of Stokes-Einstein behavior. The diffusion can be understood using a combination of water "cavity diffusion" and "hopping" mechanisms, as has been proposed in the literature. The H/D isotope effect agrees with previous modeling using ring polymer molecular dynamics. The "quantum swelling" effect on muonium due to its larger de Broglie wavelength does not seem to slow its "hopping" diffusion as much as predicted in previous work. Quantum effects of both the atom mass and the water librations have been modeled using RPMD and a qTIP4P/f quantized flexible water model. These results suggest that the muonium diffusion is very sensitive to the Mu versus water potential used.

Ethical and professional challenges posed by patients with genetic concerns: a report of focus group discussions with genetic counselors, physicians, and nurses.

Ninety-seven physicians, nurses, and genetic counselors from four regions within the United States participated in focus groups to identify the types of ethical and professional challenges that arise when their patients have genetic concerns. Responses were taped and transcribed and then analyzed using the Hill et al. (1997, Counsel Psychol 25:517-522) Consensual Qualitative Research method of analysis. Sixteen major ethical and professional domains and 63 subcategories were identified. Major domains are informed consent; withholding information; facing uncertainty; resource allocation; value conflicts, directiveness/nondirectiveness; determining the primary patient; professional identity issues; emotional responses; diversity issues; confidentiality; attaining/maintaining proficiency; professional misconduct; discrimination; colleague error; and documentation. Implications for practitioners who deal with genetic issues and recommendations for additional research are given.

Nondirectiveness in genetic counseling: a survey of practitioners.

The literature defines nondirectiveness as a genetic counseling strategy that supports autonomous decision-making by clients [Fine, 1993]. This study surveyed 781 full members of the National Society of Genetic Counselors (NSGC) between April and June, 1993, to assess how they define nondirectiveness, its importance to their practice, and how and why they are ever directive. Almost 96% of 383 respondents reported viewing nondirectiveness as very important, but 72% stated they are sometimes directive. The most common reasons for directiveness include: difficulties ensuring that verbal and nonverbal cues remain nondirective; to recommend testing; client is unable to understand; a better choice is clear; to recommend medical care or counseling; or when a client has difficulty making a decision. Nonsignificant Chi-square analyses indicated that counselor responses were independent of counselor demographics. While these findings suggest that nondirectiveness is a goal in genetic counseling, it is not the only goal. Recognition of the delicate balance between directing the process and defining the outcome of genetic counseling can enhance clinicians' ability to discern the circumstances under which directiveness is and is not appropriate.

Increased duration and altered topography of EEG microstates during cognitive tasks in chronic schizophrenia.

The surface EEGs of 32 medicated chronic schizophrenic patients, 12 unmedicated chronic schizophrenics and 35 matched healthy controls were analyzed by adaptive segmentation of continuous EEG during a rest condition, a mental arithmetic task, and a CNV paradigm. Results indicate increased duration of brain microstates in both unmedicated and medicated schizophrenics as well as reduced topographic variability. These findings did not vary across the different tasks. Comparing different cognitive tasks, schizophrenics and controls alike showed task-related changes of electric field topography, of EEG microstate duration and of the number of very short microstates (single-peak segments). However, the topography of the microstates during the tasks differed significantly in both medicated and unmedicated schizophenics from that of controls. Age, sex and educational levels did not influence these findings. Neuroleptic medication correlated negatively with microstate duration in a dose-dependent way. There was an inverse relationship between topographic variability and negative symptoms as well as BPRS scores. It is concluded that the temporo-spatial characteristics of brain electric activity indicate an impoverished array of functional modes and enhanced stability of brain electrical microstates in schizophrenia.

Process of forgoing life-sustaining treatment in a university hospital: an empirical study.

OBJECTIVES: The difficult decision to forgo (withhold or withdraw) life-sustaining treatment has received extensive commentary. Little attention has been paid to how physicians do, and should, care for dying patients once this decision is made. This study describes the characteristics of patients who forgo treatment, determines the range and sequential process of forgoing treatment, and suggests ethical and public policy implications. DESIGN: The charts of all patients who died at the University of Minnesota Hospital during a 2-month period were reviewed. The patient information that was collected included age and sex, diagnoses, mental status, location in the hospital length of hospital stay, method of payment, the timing of the first decision to forgo treatment, and the range and sequence of interventions forgone. SETTING: All ICUs and general wards in a 586-bed tertiary care university hospital. PATIENTS: All patients who died at the University of Minnesota Hospital during May and June 1989. MAIN RESULTS: A total of 52 (74%) of 70 patients who died had some intervention withheld or withdrawn before death. Those patients in whom treatment was forgone were more likely to have an underlying malignancy or impaired mental status and longer hospital stays. Thirty-two (62%) of 52 patients who declined some treatment were in an ICU; 26 (50%) of 52 patients required mechanical ventilation. On average, 5.4 separate interventions were forgone per patient. Resuscitation and/or endotracheal intubation were generally the first measures withheld; once a patient required a ventilator, withdrawing the ventilator was a late decision. Precise methods of ventilatory and vasopressor withdrawal varied considerably among patients. CONCLUSIONS: Forgoing life-sustaining treatment is not a single decision but it often occurs in a sequential manner over several days. A strict analysis of the benefits and burdens of various interventions may be inadequate in deciding what interventions are appropriate in the care of the dying patient.