Hyperbranched quasi-1D nanostructures for solid-state dye-sensitized solar cells.

In this work we demonstrate hyperbranched nanostructures, grown by pulsed laser deposition, composed of one-dimensional anatase single crystals assembled in arrays of high aspect ratio hierarchical mesostructures. The proposed growth mechanism relies on a two-step process: self-assembly from the gas phase of amorphous TiO2 clusters in a forest of tree-shaped hierarchical mesostructures with high aspect ratio; oriented crystallization of the branches upon thermal treatment. Structural and morphological characteristics can be optimized to achieve both high specific surface area for optimal dye uptake and broadband light scattering thanks to the microscopic feature size. Solid-state dye sensitized solar cells fabricated with arrays of hyperbranched TiO2 nanostructures on FTO-glass sensitized with D102 dye showed a significant 66% increase in efficiency with respect to a reference mesoporous photoanode and reached a maximum efficiency of 3.96% (among the highest reported for this system). This result was achieved mainly thanks to an increase in photogenerated current directly resulting from improved light harvesting efficiency of the hierarchical photoanode. The proposed photoanode overcomes typical limitations of 1D TiO2 nanostructures applied to ss-DSC and emerges as a promising foundation for next-generation high-efficiency solid-state devices comprosed of dyes, polymers, or quantum dots as sensitizers.

Prevalence, clinical features, and CPAP adherence in REM-related sleep-disordered breathing: a cross-sectional analysis of a large clinical population.

PURPOSE: Due to inconsistent definitions used in the literature, the prevalence of rapid eye movement (REM)-related sleep-disordered breathing (SDB) has been quite variable and its clinical significance remains unclear. This study aimed to compare the prevalence of and clinical characteristics between various criteria for defining REM-related SDB. We also investigated how frequently CPAP therapy was recommended in patients with REM-related SDB and if they had lower CPAP adherence compared to non-stage-specific SDB. METHODS: In this cross-sectional study, we evaluated 1,019 consecutive adults referred for a polysomnogram for suspicion of SDB. The prevalence of REM-related SDB was calculated based on "traditional criteria" commonly reported in the literature and a "strict criteria" that minimized the contribution of SDB during non-REM sleep. RESULTS: The prevalence of REM-related SDB ranged from 13.5% to 36.7%. There were no clinically significant differences between the strict definition and the traditional definition of REM-related SDB. REM-related SDB was more prevalent in women, younger individuals and African Americans. Compared to non-stage-specific obstructive sleep apnea (OSA), patients with REM-related SDB were equally symptomatic and hypersomnolent. CPAP titration was recommended in 88% of patients with REM-related SDB vs. 94% of patients with non-stage-specific OSA (p < 0.001). There was no significant difference in CPAP adherence between the two groups. CONCLUSIONS: Regardless of how REM-related SDB is defined, it was highly prevalent in our large clinical cohort. Compared to non-stage-specific OSA, these patients were equally hypersomnolent and adherent to CPAP therapy despite having overall significantly milder OSA. Further research is needed to better establish whether these patients will derive any benefit from long-term CPAP therapy.

The impact of sleep consultation prior to a diagnostic polysomnogram on continuous positive airway pressure adherence.

BACKGROUND: Polysomnograms (PSGs) are routinely ordered by nonsleep specialists. However, it is unknown whether a sleep specialist consultation prior to a diagnostic PSG influences adherence to continuous positive airway pressure (CPAP) therapy. METHODS: This study was done at the University of Chicago Sleep Disorders Center and included 403 patients with obstructive sleep apnea who had CPAP adherence data available. CPAP was set up at home, and objective adherence was remotely monitored during the first 30 days of therapy. Physicians who ordered PSGs were divided into two groups: sleep specialists and nonsleep specialists. RESULTS: Patients were aged 52.5 ± 14 years, 47% were men, and 54% were African American. Mean daily CPAP use was greater in patients who were referred by sleep specialists (n = 105, 279 ± 179 min/d) than in patients referred by nonsleep specialists (n = 298, 219 ± 152 min/d, P = .005). In the linear regression model adjusting for several covariates, only two predictors were significantly associated with CPAP adherence. A sleep specialist consultation prior to the diagnostic PSG was associated with 58.2 min more per day (P = .002), and African American race was associated with 56.0 min less per day (P = .002) of CPAP use. CONCLUSIONS: In this cohort study, CPAP adherence was significantly higher with a sleep specialist consultation prior to the diagnostic PSG. In addition, African American race was associated with worse adherence to therapy. A better understanding of predictors of CPAP adherence may be useful in identifying patients who may benefit from a sleep specialist consultation prior to ordering a diagnostic PSG.

Predictors of slow-wave sleep in a clinic-based sample.

Slow-wave sleep has been associated with several physiological phenomena, including glucose metabolism, sympathetic nervous system activity, hormonal secretion and blood pressure regulation. The aim of these analyses was to determine which sociodemographic and medical factors were associated with slow-wave sleep duration in a large clinical sample. We conducted cross-sectional analysis of clinical data from 1019 consecutive adults over a 10-month period who had their first in-laboratory polysomnogram for suspicion of obstructive sleep apnea. Patients either underwent in-laboratory full-night polysomnogram followed by full-night continuous positive airway pressure titration or split-night polysomnogram. Patients also completed questionnaires to assess race, education, marital status and medical co-morbidities. A multiple linear regression model that predicted the natural log of slow-wave sleep in minutes indicated that African Americans had approximately 48% less slow-wave sleep than non-African Americans. Increasing age and male gender were also associated with less slow-wave sleep. Overweight and obese individuals had significantly less slow-wave sleep than those not overweight, even after adjustment for obstructive sleep apnea severity. Finally, those with severe obstructive sleep apnea had significantly less slow-wave sleep than those with less severe obstructive sleep apnea even after adjustment for obesity. Results remained unchanged when patients who had a split-night polysomnogram were excluded. We observed less slow-wave sleep in African Americans, a group at increased risk of diabetes and hypertension compared with Caucasians, and in those who are overweight and obese and those with severe obstructive sleep apnea. Future research needs to explore potential reasons for reduced slow-wave sleep in these individuals.

Depressive symptoms and obesity as predictors of sleepiness and quality of life in patients with REM-related obstructive sleep apnea: cross-sectional analysis of a large clinical population.

BACKGROUND: The clinical significance of rapid eye-movement (REM)-related obstructive sleep apnea (OSA) is unknown. Moreover, it is unclear what the determinants of sleepiness and quality of life (QoL) are among these patients. Our aim was to identify whether the apnea-hypopnea index during REM sleep (AHI(REM)), AHI during NREM sleep (AHI(NREM)), depressive symptoms, or obesity are independent predictors of excessive daytime sleepiness and reduced QoL in patients with REM-related OSA. We also assessed if these characteristics were predictors of sleepiness and QoL in all patients with OSA (AHI ≥ 5) as well as in non-stage specific OSA. METHODS: This was a cross-sectional analysis of a clinic-based population with OSA. In order to minimize the contribution of AHI(NREM), we defined REM-related OSA using the following criteria: an overall AHI ≥ 5, AHI(REM)/AHI(NREM) ≥ 2, AHI(NREM) the lowest quartile of the entire cohort. We examined the predictors of subjective sleepiness using the Epworth Sleepiness Scale (ESS) and QoL using the short-form quality of life questionnaire-12 (SF-12). RESULTS: Of 1019 consecutive adults that were referred for their first in-laboratory polysomnogram for suspicion of OSA over a 10 month period, 931 had OSA. REM-related OSA was present in 126 patients. In adjusted linear regression models, AHI(NREM) was a significant predictor of sleepiness in the entire cohort of patients with OSA as well as non-stage specific OSA, but not in the REM-related OSA group. AHI(REM) was not a significant predictor of ESS or QoL in any of the three groups. However, greater depressive symptoms and body mass index were significant independent predictors of ESS and reduced QoL in the REM-related OSA group. CONCLUSION: Higher depression scores and obesity, rather than the severity of OSA (as measured by AHI(NREM) and AHI(REM)), were predictive of sleepiness and QoL scores in patients with REM-related OSA.