Search PubMed⌕ Search

Biomedical subjects

B J Powell

Publications and source records attributed to B J Powell.

At least 19 recordsLinked to original sources
PubMed2005

Half-filled layered organic superconductors and the resonating-valence-bond theory of the hubbard-heisenberg model.

We present a resonating-valence-bond theory of superconductivity for the Hubbard-Heisenberg model on an anisotropic triangular lattice. Our calculations are consistent with the observed phase diagram of the half-filled layered organic superconductors, such as the beta, beta', kappa, and lambda phases of (BEDT-TTF)2X [bis(ethylenedithio)tetrathiafulvalene] and (BETS)2X [bis(ethylenedithio)tetraselenafulvalene]. We find a first order transition from a Mott insulator to a dx2-y2 superconductor with a small superfluid stiffness and a pseudogap with dx2-y2 symmetry.

Journal Article↗
PubMed2004

A first-principles density-functional calculation of the electronic and vibrational structure of the key melanin monomers.

We report first-principles density-functional calculations for hydroquinone (HQ), indolequinone (IQ), and semiquinone (SQ). These molecules are believed to be the basic building blocks of the eumelanins, a class of biomacromolecules with important biological functions (including photoprotection) and with the potential for certain bioengineering applications. We have used the difference of self-consistent fields method to study the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, Delta(HL). We show that Delta(HL) is similar in IQ and SQ, but approximately twice as large in HQ. This may have important implications for our understanding of the observed broadband optical absorption of the eumelanins. The possibility of using this difference in Delta(HL) to molecularly engineer the electronic properties of eumelanins is discussed. We calculate the infrared and Raman spectra of the three redox forms from first principles. Each of the molecules have significantly different infrared and Raman signatures, and so these spectra could be used in situ to nondestructively identify the monomeric content of macromolecules. It is hoped that this may be a helpful analytical tool in determining the structure of eumelanin macromolecules and hence in helping to determine the structure-property-function relationships that control the behavior of the eumelanins.

Benzoquinones↗
PubMed2000

Mortality in male alcoholics after ten to fourteen years.

OBJECTIVE: Alcoholics frequently die prematurely. The purpose of this study was to determine: (1) whether subjects in a sample of 360 male alcoholics, followed over a period of 10-14 years, died prematurely: (2) if so, from what causes; and (3) whether such deaths are predictable from characteristics present at initial assessment. METHOD: Subjects were male veterans (N = 360) with a diagnosis of alcoholism admitted to an inpatient substance abuse treatment program at the Kansas City Veterans Affairs (VA) Medical Center during 1980-1984 who consented to participate in intake evaluations and subsequent follow-ups at 1 year and 10-14 years later. Of the 357 (99.2%) men located at the 10-14 year follow-up, 96 (26.6%) were confirmed as deceased, 255 survivors agreed to be reassessed and 6 subjects refused reassessment. Information regarding cause of death was obtained from death certificates, VA records and other sources. RESULTS: At intake, the subsequently deceased men were older, had less education, lower psychosocial functioning, more medical problems and greater psychiatric severity. Their overall death rate was 2.5 times greater than that of a reference group of men. Men in the 35-44 year age group were 5.5 times as likely to die. A statistical model utilizing measures of alcohol dependence to predict mortality from intake to 10-14 year follow-up indicated that alcoholics who limited drinking were half as likely to die whereas those who engaged in morning drinking were 2.5 times more likely to die. CONCLUSIONS: Alcoholic men, especially those in the group aged 35 to 44 years, have a significantly higher risk of premature death than a reference group of men. Men who engaged in morning drinking and could not limit drinking appeared to be at higher risk of mortality 10 years later.

Adult↗
PubMed1999

The comparative validity of eleven alcoholism typologies.

OBJECTIVE: This study directly compared the clinical validity of 11 empirically defined alcoholism typologies to determine whether some typologies are clinically more valid than others. METHOD: A sample of 360 hospitalized alcoholic men were extensively evaluated at entry into the study and again 1 year later. Twenty-three measures of clinical validity were employed; 15 were postdictive and 8 were predictive. Postdictive retrospective measures obtained at entry into the study included family history, age of onset and lifetime course characteristics associated with alcoholism severity, general psychopathology and psychosocial functioning. Predictive outcome measures drawn from information obtained during the 1-year follow-up included: abstinence, alcoholism severity and clinician ratings of outcome. The measures were subjected to various statistical analyses, including factor analysis. RESULTS: We found that all of the alcoholism typologies met at least 7 of the 23 a priori measures of clinical validity. The correlations between these conceptually and methodologically disparate typologies were often striking. Exploratory factor analysis, which explained 35% of the variance, suggested three possible underlying dimensions to account for the overlap among typologies: (1) age and its correlates, including age-of-alcoholism onset; (2) "pure" alcoholism versus psychiatrically heterogeneous alcoholism that encompassed antisocial personality disorder; and (3) current severity of psychiatric distress, impairment and dysfunction. CONCLUSIONS: No single method of subtyping alcoholics clearly emerged as superior. All demonstrated some degree of predictive and postdictive clinical validity. Most methods of subtyping correlated positively with each other at moderate, but typically significant, levels.

Adult↗
PubMed1999

Clinical practice guidelines for bipolar disorder from the Department of Veterans Affairs.

BACKGROUND: For the last several years, the Department of Veterans Affairs (VA) has been involved in the development of practice guidelines for major medical, surgical, and mental disorders. This article describes the development and content of the VA-Clinical Practice Guidelines for Bipolar Disorder, which are available in their entirety on the Journal Web site (http://www. psychiatrist.com). METHOD: A multidisciplinary work group composed of content experts in the field of bipolar disorder and practitioners in general clinical practice was convened by the VA's Office of Performance and Quality and the Mental Health Strategic Health Group. The work group was instructed in algorithm development and methods of evidence evaluation. Draft guidelines were developed over the course of 6 months of meetings and conference calls, and that draft was then sent to nationally prominent content experts for final critique. RESULTS: The Bipolar Guidelines are part of the family of the VA Clinical Guidelines for Management of Persons with Psychosis and consist of explicit algorithms supplemented by annotations that explain the specific decision points and their basis in the scientific literature. The guidelines are organized into 5 modules: a Core Module for diagnosis and assignment to mood state plus 4 treatment modules (Manic/Hypomanic/Mixed Episode, Bipolar Depressive Episode, Rapid Cycling, and Bipolar Disorder With Psychotic Features). The modules specify particular diagnostic and treatment tasks at each step, including both somatotherapeutic and psychotherapeutic interventions. CONCLUSION: The VA Bipolar Guidelines are designed for easy clinical reference in decision making with individual patients, as well as for use as a scholarly reference tool. They also have utility in training activities and quality improvement programs.

American Heart Association↗
PubMed1998

Prediction of drinking outcomes for male alcoholics after 10 to 14 years.

This study reports on the long-term outcomes of 360 men who were hospitalized for alcoholism during 1980 to 1984 and followed at 12 months and again 10 to 14 years later. At the 10/14-year follow-up, 96 (26.7%) men were confirmed as deceased; 255 (70.8%) men participated in the assessment/interview battery completed during baseline hospitalization. The battery consisted of psychosocial, alcohol-related, and psychiatric measures. Two distinct but highly correlated outcome measures were selected: a clinical rating scale and a factor score. Overall, predictors from baseline and 12-month follow-up included age at intake hospitalization, alcoholism severity, social stability, drinking days, and antisocial personality disorder. Approximately 37% of the assessed survivors were either totally abstinent or drinking nonabusively throughout the 10/14-year follow-up, whereas another 37% continued to drink abusively. Men who abstained or reduced alcohol intake reported better physical health at follow-up than those who continued to drink. Although our findings did not directly link alcoholism to death, they strongly indicate that chronic alcohol abuse may lead to premature death.

Adult↗
PubMed1996

Pharmacological treatment for antisocial personality disorder alcoholics: a preliminary study.

A short time ago, we reported that a subgroup of hospitalized alcoholic men with comorbid antisocial personality disorder (ASP) seemed to benefit significantly from antidepressant medication at the end of a 6-month period in a double-blind, random assignment, placebo-controlled study. In a reanalysis of those data, we divided the ASP alcoholic group (n = 29) into those who did (n = 15) and who did not (n = 14) also satisfy DSM-III-R criteria for an additional current mood and/or anxiety disorder and then compared the 6-month outcomes of these two smaller subgroups. Despite the small ns, the results for most drinking outcome measures indicated: (1) that ASP alcoholics with a current mood/anxiety disorder improved significantly more with pharmacological treatment, relative to placebo; and (2) that ASP alcoholics with no current mood/anxiety disorder failed to respond differentially to pharmacological treatment over the 6-month period. These findings suggest a possibly useful and inexpensive approach to the long-term management of a very difficult-to-treat subgroup of men substance abusers.

Adult↗
PubMed1996

Digital enhancement of radiographs: can it improve caries diagnosis?

Unlike traditional radiographs, digital images are electronically alterable and offer the potential for enhancing diagnostic information. The authors conducted a small-scale study to examine differences in clinicians' diagnoses of caries using traditional radiographs and digitized images vs. microscopic diagnosis. Two general dentists and one oral-maxillofacial radiologist scored the images for caries. This study suggests that digital enhancements may aid some clinicians in caries diagnosis.

Dental Caries↗
PubMed1995

A double-blind, placebo-controlled study of nortriptyline and bromocriptine in male alcoholics subtyped by comorbid psychiatric disorders.

This double-blind, placebo-controlled, 6-month follow-up treatment study investigated the efficacy of bromocriptine and nortriptyline in attenuating drinking behavior and psychiatric symptoms in 216 male alcoholic patients subtyped by comorbid psychiatric disorder(s). Three well-defined subtypes were examined: alcoholism only, alcoholism + affective/anxiety disorder, and alcoholism + antisocial personality disorder. It was hypothesized that both medications would relieve negative affective symptoms associated with alcohol use and would be particularly effective for the affective/anxiety subgroup. Contrary to our predictions, the only significant effects found were with the antisocial personality disorder patients who were receiving nortriptyline. One interpretation of the results was that nortriptyline may have reduced impulsive drinking in the antisocial personality disorder subgroup by actions on serotonergic neurotransmission.

Adult↗
PubMed1995

Validity of the CAGE questionnaire in screening for alcohol dependence in a walk-in (triage) clinic.

OBJECTIVE: This study assessed the value of the CAGE questionnaire in detecting alcohol dependence in the walk-in (triage) clinic of an acute care Veterans Affairs hospital. METHOD: Male veterans (N = 1,667) attending the walk-in clinic were asked several questions relating to whether they were current drinkers, were seeking alcohol treatment, and whether they had been hospitalized for treatment of alcoholism. Those who were current drinkers, were not seeking alcohol treatment and had not been hospitalized for alcohol treatment were given the CAGE questionnaire followed by a diagnostic interview utilizing DSM III-R criteria to determine the presence or absence of a lifetime diagnosis of alcohol dependence. RESULTS: The diagnostic interview revealed a prevalence rate for alcoholism of 22% in this clinic population. The CAGE scale, when used with one or more yes responses indicating a positive response, achieved a sensitivity of 86% and specificity of 93% when using the diagnostic interview as the criterion standard. CONCLUSIONS: This study adds to the evidence that the CAGE questionnaire is an effective, efficient, easily used screening instrument for the detection of alcohol dependence in a clinical setting.

Adult↗
PubMed1994

Longitudinal evaluation of the seal of IRM root end fillings.

IRM has been recommended for root end filling during endodontic surgery. This study evaluated the seal of IRM root end fillings prepared with various powder to liquid ratios (P:L) at extended time intervals using a fluid filtration method. The P:L of IRM evaluated included 2, 3, 4, 5, and 6 g/ml and the P:L which resulted from the manufacturer's recommended scoop and dropper. Ten teeth were evaluated for microleakage for each group at 1, 2, 3, 4, 8, and 12 wk after insertion. There were no significant differences in the microleakage of any of the various P:L groups at weeks 3, 8, and 12. These results suggest that higher P:L of IRM than those previously recommended for temporary restorations and for endodontic access preparations may be acceptable for root end fillings. IRM of higher P:L has other advantages such as ease of placement and decreased setting time, toxicity, and solubility.

Analysis of Variance↗
PubMed1994

Co-morbidity of lifetime psychiatric disorder among male alcoholic patients.

The lifetime co-morbidity of major psychiatric disorders among male alcoholics was examined with the structured Psychiatric Diagnostic Interview (PDI), which was administered to 928 patients undergoing alcoholism treatment at six Veterans Administration Medical Centers. Thirty-eight percent were positive for alcoholism only; 62% fulfilled inclusive lifetime diagnostic criteria for at least one other additional psychiatric syndrome. Thirty percent satisfied criteria for one additional syndrome; 16% for two additional syndromes; 12% for three; and 4% for four or more disorders in addition to alcoholism. Depression and antisocial personality were the most frequently identified co-occurring syndromes (36% and 24%, respectively) followed by drug abuse and mania (17% each). The additional psychiatric syndromes in this sample were clearly not randomly distributed; instead, certain disorders tended to cluster together such as: drug abuse and antisocial personality; mania and depression; depression and anxiety disorder; and schizophrenia and affective disorder. Implications for classification and treatment are discussed.

Adult↗
PubMed1994

Impact of desipramine or carbamazepine on patient retention in outpatient cocaine treatment: preliminary findings.

This is a preliminary report of a double-blind comparison of desipramine or carbamazepine to placebo among subjects participating in an outpatient cocaine treatment program. Sixty-five subjects were randomly assigned to one of the active drugs or placebo and followed until treatment completion or drop-out to determine if either drug enhanced retention in treatment and/or increased cocaine abstinence. There was no significant difference between carbamazepine or desipramine and placebo on either outcome measure in this preliminary analysis. While this is a preliminary report and does not take into account the heterogeneity of the patients in cocaine treatment, the results are consistent with those of other investigators and suggest that use of desipramine or carbamazepine may not offer any advantage in retaining cocaine-dependent patients in treatment.

Ambulatory Care↗
PubMed1993

Utilization of radiographs for a state dental board examination.

A survey of 97 dentists who had recently taken a state dental board examination was completed to document the use of radiographs for the screening and treatment of their patients. The response rate was 53%. Candidates spent on average 14.25 hours screening a mean of 18 patients to identify the dental pathoses necessary to take the examination. Candidates took a mean of 28.9 (+/- 25.8) radiographs for screening purposes and during the examination with a range of 3 radiographs to a maximum of 141 radiographs. Time in practice and specialty status did not affect the total number of radiographic exposures made. The majority of radiographs taken (53%) were unlikely to be used in the direct care of the patient's dental needs. The results of this survey indicated that efforts to minimize administrative radiographs should be increased.

Adult↗
PubMed1993

Digital radiographic image-based bone level measurements: effect of film density.

Previous studies have demonstrated that accurate alveolar bone-level measurements can be made using digitally enhanced bitewing radiographs. In this study, we determined the effect of exposure variations on bone-level measurement accuracy using digital radiographic images of dry skulls. 6 direct bone-level measurements on the mandibular 1st molars of dry skulls were established by consensus of 2 expert observers. 13 bitewing radiographs were taken on each side of 11 skulls, using a specially designed positioning device. Exposure settings of 70 kVp, 10 mA, and 24 impulses were empirically chosen as the baseline. Kilovoltage and impulses times were individually varied (50 to 100 kVp in 10 kV increments and 15 to 48 impulses in 6 steps) to ensure a wide range of clinically relevant optical densities on the test images. The radiographs were digitized and alveolar bone level measurements, corresponding to those for skulls, were made on the images by 2 observers. Pearson product-moment coefficients between radiographs and criteria measurements were calculated. It was found that dry skull and digital bitewing radiographic measurements were highly correlated, within the limits of exposure parameter variations tested. Accurate measurements of alveolar bone level are possible from bitewing radiographs taken within a wide range of exposures, when digital image processing techniques are employed.

Absorptiometry, Photon↗