Disentangling Thermal from Electronic Contributions in the Spectral Response of Photoexcited Perovskite Materials.

Disentangling electronic and thermal effects in photoexcited perovskite materials is crucial for photovoltaic and optoelectronic applications but remains a challenge due to their intertwined nature in both the time and energy domains. In this study, we employed temperature-dependent variable-angle spectroscopic ellipsometry, density functional theory calculations, and broadband transient absorption spectroscopy spanning the visible to mid-to-deep-ultraviolet (UV) ranges on MAPbBr3 thin films. The use of deep-UV detection opens a new spectral window that enables the exploration of high-energy excitations at various symmetry points within the Brillouin zone, facilitating an understanding of the ultrafast responses of the UV bands and the underlying mechanisms governing them. Our investigation reveals that the photoinduced spectral features remarkably resemble those generated by pure lattice heating, and we disentangle the relative thermal and electronic contributions and their evolutions at different delay times using combinations of decay-associated spectra and temperature-induced differential absorption. The results demonstrate that the photoinduced transients possess a significant thermal origin and cannot be attributed solely to electronic effects. Following photoexcitation, as carriers (electrons and holes) transfer their energy to the lattice, the thermal contribution increases from ∼15% at 1 ps to ∼55% at 500 ps and subsequently decreases to ∼35-50% at 1 ns. These findings elucidate the intricate energy exchange between charge carriers and the lattice in photoexcited perovskite materials and provide insights into the limited utilization efficiency of photogenerated charge carriers.

Band Gap Renormalization at Different Symmetry Points in Perovskites.

Using ultrafast broad-band transient absorption (TA) spectroscopy of photoexcited MAPbBr3 thin films with probe continua in the visible and the mid- to deep-ultraviolet (UV) ranges, we capture the ultrafast renormalization at the fundamental gap at the R symmetry point of the Brillouin zone (BZ) and a higher energy gap at the M symmetry point. Advanced global lifetime analysis and lifetime density distribution analysis are applied to extract quantitative information. Our work confirms the similarity of the response at both high-symmetry points, which indicates a band edge renormalization that rises within the instrument response function (IRF, ∼250 fs) and decays in ca. 400-600 fs, undergoing an energy red shift of 90-150 meV. The reported time scale corresponds to the decay of free carriers into neutral excitons. The ability to monitor different high-symmetry points in photoexcited perovskites opens exciting prospects for the characterization of a large class of materials and for photonic applications.

ApoE4 allele is associated with late-life depression: a population-based study.

OBJECTIVE: This study aimed to clarify the relationship between the epsilon4 allele and late-life depression, taking into account lipid profile, vascular diseases, and sociodemographics. METHODS: Using a multilevel stratified random sampling strategy, a total of 500 subjects aged 65 to 74 years were recruited for this cross-sectional study from the official household records of an entire county in southern Taiwan. Depressive symptoms were assessed by the Taiwanese Depression Questionnaire (TDQ). Cognitive function was assessed by the Short Portable Mental Status Questionnaire. Blood samples were collected for the determination of the apolipoprotein E (ApoE) polymorphism and the lipid profile. RESULTS: A total of 283 subjects (58.7% male, with a mean age of 69.2 +/- 2.7 years) completed all questionnaires and collection of blood samples. Using the chi(2) test, the overall difference for frequency of the presence of the epsilon4 allele was significant among the severe group (TDQ score >18), moderate group (TDQ score 9-18), and mild group (TDQ score <9). The proportion of history of heart disease was significantly higher in the severe group than in the mild or moderate group. Kruskal-Wallis statistics revealed that the mean total and low-density lipoprotein cholesterol levels were significantly higher in the severe group than in the moderate or mild group. With our two-level four-class latent class regression model, the presence of the epsilon4 allele was significantly associated with the severely depressed group as compared to the nondepressed group, adjusting for vascular diseases and lipid profile. CONCLUSION: The ApoE epsilon4 allele may be correlated with severe depression in the elderly through ways other than the "vascular depression" hypothesis.

The development and application of the telemedicine system in psychiatric counseling.

Telemedicine are the application and development of the telecommunication networks. In this study, we try to develop the telemedicine system and to discuss the network application of this system in psychiatric counseling. The preliminary result of this study is that the telemedicine system is more effective than traditional consultation and it can provide teleconsultation service for clients with depression through the internet.

Suicidal ideation and associated factors among community-dwelling elders in Taiwan.

The purpose of the present study was to explore the suicidal ideation of community-dwelling elderly and the factors associated with their intention to commit suicide. Using a multilevel stratified sampling strategy, 1000 elderly subjects were recruited (aged 65-74 years old) in Taiwan during the year 2001. The degree of depression and its correlates were assessed. Suicidal ideation was measured by asking respondents if they had had any suicidal thoughts in the previous week. In all, 16.7% of respondents reported suicidal ideation within the past week; its occurrence was related to sex, religious belief, employment status, marital status, average family monthly income, physical health status, depressive symptoms, and community activity participation. Further multivariate logistic regression revealed that, aside from depressive symptoms and a lower level of education, no community participation in the past 6 months was significantly associated with the appearance of suicidal ideation. The prevalence of suicidal ideation among the elderly in Taiwan is higher than in Western countries. Participation in social activities is negatively associated with elderly suicidal ideation. The dimension of social participation deserves further exploration and should be considered in community mental health promotion interventions for elderly people.

Cognitive impairment and associated risk factors among aged community members.

OBJECTIVE: The objective of this paper is to investigate the prevalence of and risk factors associated with cognitive impairment in a community-dwelling elderly population. METHODS: 1000 community residents aged 65-74 years were recruited in the cross-sectional survey of associated factors of cognitive impairment in southern Taiwan. We employed a multilevel stratified sampling strategy and conducted this interview survey from April to June 2001. The survey questionnaire included background information and the Short Portable Mental Status Questionnaire. The relationship between cognitive impairment and each individual variable in personal attributes and social participation were explored. RESULTS: Eight hundred and ninety-four (89.4%) subjects completed the interview and questionnaires. The cognitive impairment rate among all subjects was 4.92%. Of those surveyed, 54.98% were male and 45.02% were female, and the average age was 69.37 (SD 2.73) years. Most survey respondents (72.05%) were married, and 68.90% of the subjects did not participate in any social activities in the last 6 months. Females, those who were illiterate or did not attend school, those who had an average family income below US$860 per month, and persons who did not participate in any social activities had a significantly higher rate of cognitive impairment. CONCLUSION: The educational level and participation in social activities were associated with the cognitive impairment among the aged community dwellers.

Religious attendance and depressive symptoms among community dwelling elderly in Taiwan.

BACKGROUND: The purpose of this study was to investigate the unique association between religious attendance and the prevalence of depressive symptoms among community dwelling elderly persons. METHODS: Employing a multilevel stratified sampling strategy, a total of 1000 subjects, aged 65-74 and living in Taiwan, were recruited for this interview survey during the year 2001. Aside from background information, the Taiwanese Depression Questionnaire (TDQ) and the Neighborhood Quality Index were used to assess degree of depression and its correlates. RESULTS: Altogether, 863 subjects (age, M = 69.4, SD = 2.7) had complete data for analysis; 215 (24.8%) had had depressive symptoms in the past week. Among them, those who were female, (OR = 2.17, 95% CI = 1.59-2.97), illiterate(OR = 2.42, 95% CI = 1.76-3.33), unemployed (OR = 1.80, 95% CI = 1.24-2.61), or not married (OR = 1.71, 95% CI = 1.22-2.38), or those who had less family income (OR = 1.84, 95% CI = 1.24-2.73), physical illness (OR = 2.68, 95% CI = 1.86-3.86), or less social capital (OR = 0.91, 95% CI = 0.88-0.94), were at higher risk of being depressed. Moreover, those (95.2% with religious belief ) who had not attended religious activities during the past 6 months were at higher risk of being depressed than those (100% with religious belief ) who had (OR = 2.63, 95% CI = 1.41-4.91). Multivariate logistic regression disclosed that those never attending religious activities were 2.70 times more likely to be depressed when compared to those who had, after taking into consideration sociodemographics and social capital. CONCLUSION: The attending of religious activities is a protective factor for geriatric depression.