Characterization of crude oils using fluorescence lifetime data.

The average fluorescence lifetimes of nine North Sea crude oils with API gravities of between 20 and 51 were measured using a modular, filter based, instrument developed in-house. Two pulsed light emitting diode (LED) excitation sources (460 and 510 nm) were used to excite fluorescence, the lifetime of which was measured at a range of emission wavelengths. Fluorescence lifetimes were found to vary from 1.8 to 8.2 ns with confidence intervals of +/- 0.11 ns. The average lifetimes at all emission wavelengths were linearly correlated with API gravity and with aromatic concentration with the best results being obtained with the 460 nm excitation source. Predictive models with an accuracy of +/- 7.6 API degrees were generated using partial least-squares methods from average fluorescence lifetimes measured at an emission wavelength of 500 nm using 460 nm excitation. A better correlation was found between the aromatic concentration of the oils and the ratio of the average fluorescence lifetimes at measured at 550 and 650 nm using 460 nm excitation. This led to a quantitative model with an accuracy of +/- 5.4% for aromatic concentration.

Chronic, low-grade depression in a nonclinical sample: depressive personality or dysthymia?

Depressive personality disorder (DPD) is being considered for inclusion in future editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM). However, there is substantial conceptual and empirical overlap between DPD and dysthymic disorder (Dysthymia) criteria, suggesting that these two constructs may not be distinct. Confirmatory factor analysis of the DPD traits and dysthymia symptoms in a large, nonclinical sample (N = 368) indicated that a two-factor model was a better fit than a one-factor model. However, binary diagnostic analysis revealed that over half of the individuals meeting criteria for DPD also met criteria for dysthymia and that the best-fitting model allowed the psychological symptoms of dysthymia to load on both DPD and dysthymia latent factors. All of the individuals with DPD alone failed to meet criteria for dysthymia because they did not report chronic depressed mood. Our results suggest that although DPD is not synonymous with Dysthymia, it may be a milder subtype.

Personality and the affective disorders: past efforts, current models, and future directions.

The existence of a relation between personality and the affective disorders has long been observed but with little agreement as to how it can best be described. This paper reviews attempts to address this issue, beginning with an examination of subaffective personality types. The personality dimensions of two major predominant theories, the Five Factor Model of Personality and the Seven Factor Dimensional Psychobiological Model of Temperament and Character, and the relation of these dimensions with bipolar disorder and unipolar depression is also examined. Throughout, the state-versus-trait issue is explored, and the last section is a critical reexamination of this continuing controversy. The overall objective is to search for commonalities in past and present models, and to deal with ongoing concerns, in order to point the way for future research in the field.

Is acculturation unidimensional or bidimensional? A head-to-head comparison in the prediction of personality, self-identity, and adjustment.

The unidimensional model of acculturation posits that heritage and mainstream culture identifications have a strong inverse relation, whereas the bidimensional model posits that the 2 identifications are independent. The authors compared these models in 3 samples of ethnic Chinese (ns = 164, 150, and 204), 1 sample of non-Chinese East Asians (n = 70), and one diverse group of acculturating individuals (n = 140). Although the unidimensional measure showed a coherent pattern of external correlates, the bidimensional measure revealed independent dimensions corresponding to heritage and mainstream culture identification. These dimensions displayed patterns of noninverse correlations with personality, self-identity, and psychosocial adjustment. The authors conclude that the bidimensional model is a more valid and useful operationalization of acculturation.

Response style and the revised NEO personality inventory: validity scales and spousal ratings in a Chinese psychiatric sample.

The effects of response style bias on profile scores from the family of NEO scales and the resultant influence of response style on the predictive capacity of these scales continues to be debated. In this study, a large sample of Chinese psychiatric patients were categorized into four response style groups based on their scores from recently developed "validity" scales for the revised NEO Personality Inventory (NEO PI-R). Mean differences and correlations between self-report and spousal ratings of these patients were examined for the NEO PI-R domain and facet scales. Excessive positive self-presentation bias resulted in mean differences between the self-report and spousal ratings for N and E. Correlations between self-report and spousal ratings were reduced in patients engaging in positive self-presentational bias compared to those who were not so categorized on three of the five NEO PI-R scales. However, these results were manifest only in a sub-sample of psychotic patients. Negative self-presentational bias did not affect mean differences or diminish the correlations between the self-report and spousal ratings.

Diagnostic discriminability of dysthymia and depressive personality disorder.

The Depressive Personality Disorder (DPD) is currently being considered for inclusion in future editions of DSM. However, there is little empirical research on DPD as currently defined in DSM-IV, including whether this disorder is sufficiently distinct from Dysthymic Disorder (Dysthymia). The goal of this study was to explore the relationship between DPD and Dysthymia with a sample of depressed outpatients. Scales were developed for the diagnostic criteria for both DPD and Dysthymia. These scales were then analyzed using cluster and factor analysis. Retroactive diagnostic assignment for these two disorders was also made using these scales. It was hypothesized that if DPD is a viable diagnostic category, then the DPD traits and Dysthymia symptoms would fall into different clusters, produce separate factors, and the comorbidity would be small. Two clusters and two factors, each with a close correspondence to DPD and Dysthymia, were statistically extracted from combined symptom and trait scales. However, 95% of those cases identified as meeting diagnostic criteria for DPD also met criteria for Dysthymia. Despite the ability to distinguish statistically DPD traits from Dysthymia symptoms, there was a high degree of comorbidity, compromising the clinical utility of DPD. The results do suggest, however, that DPD might be best conceptualized as a subcategory of Dysthymia.

Diagnostic viability of depressive personality disorder: theoretical and conceptual issues.

Depressive personality disorder (DPD) is being considered for inclusion in future editions of the Diagnostic and Statistical Manual of Mental Disorders (DSM). In this paper, we review the theoretical and empirical literature on DPD, and examine a number of issues concerning its viability as an Axis II disorder. Three criteria were used as necessary preconditions for the inclusion of DPD on Axis II: (a) substantial theoretical distinctiveness from other disorders, (b) established empirical distinctiveness from other disorders, and (c) sufficient deviation from a "normal temperament." We argue that it is improbable that this disorder could be diagnosed independently of dysthymia, and that there is also considerable symptom overlap with several Cluster C disorders. Although there appears to be sufficient deviation from normality among the entire group of individuals with DPD, those persons whose symptoms are not severe enough to cause overlap with dysthymia may not so deviate. We conclude that the current conceptualization of DPD does not have sufficient discriminative validity or clinical utility to warrant inclusion in future editions of the DSM.