3 research outputs found
Surface measurement errors using commercial scanning white light interferometers
This paper examines the performance of commercial scanning white light interferometers in a
range of measurement tasks. A step height artefact is used to investigate the response of the
instruments at a discontinuity, while gratings with sinusoidal and rectangular profiles are used
to investigate the effects of surface gradient and spatial frequency. Results are compared with
measurements made with tapping mode atomic force microscopy and discrepancies are
discussed with reference to error mechanisms put forward in the published literature. As
expected it is found that most instruments report errors when used in regions close to a
discontinuity or those with a surface gradient that is large compared to the acceptance angle
of the objective lens. Amongst other findings, however, we report systematic errors that are
observed when the surface gradient is considerably smaller. Although these errors are
typically less than the mean wavelength they are significant compared to the instrument
resolution and indicate that current scanning white light interferometers should be used with
some caution if sub-wavelength accuracy is required
Charge Generation via Relaxed Charge-Transfer States in Organic Photovoltaics by an Energy-Disorder-Driven Entropy Gain
In
organic photovoltaics, efficient charge generation relies on
our ability to convert excitons into free charges. Efficient charge
separation from “energetic excitons” has been understood
to be governed by delocalization effects promoted by molecular aggregation.
A remaining puzzle is, however, the mechanism underlying charge generation
via relaxed interfacial charge-transfer (CT) excitons that also exhibit
an internal quantum efficiency close to unity. Here, we provide evidence
for efficient charge generation via CT state absorption over a temperature
range of 50–300 K, despite an intrinsically strong Coulomb
binding energy of about 400 meV that cannot be modified by fullerene
aggregation. We explain our observation by entropy-driven charge separation,
with a key contribution from energy disorder. The energy disorder
reduces the charge generation barrier by substantially gaining the
entropy as electron–hole distance increases, resulting in efficient
CT exciton dissociation. Our results underline an emerging consideration
of energy disorder in thermodynamic stability of charge pairs and
highlight the energy disorder as a dominant factor for generating
charges via the CT state. A discussion for a trade-off in harvesting
charges from relaxed CT excitons is also provided
Impact of the joint association between sex, age and diabetes on long-term mortality after acute myocardial infarction
BACKGROUND: The role of sex, and its joint effect with age and diabetes mellitus, on mortality subsequent to surviving an acute myocardial infarction (AMI) beyond 30 days are unclear. The high prevalence of diabetes mellitus in an ethnically diverse Asian population motivates this study. METHODS: The study population comprised of a nationwide cohort of Asian patients with AMI, hospitalized between 2000 to 2005, who survived the first 30 days post-admission and were followed prospectively until death or 12 years. RESULTS: Among the 13,389 survivors, there were fewer women (25.5%) who were older than men (median 70 vs. 58 years) and a larger proportion had diabetes mellitus at admission (51.4% vs. 31.4%). During follow-up 4,707 deaths (women 13.2%; men 22.0%) occurred, with women experiencing higher mortality than men with an averaged hazard ratio (HR): 2.08; 95% confidence interval : 1.96-2.20. However the actual adverse outcome, although always greater, reduced over time with an estimated HR: 2.23 (2.04-2.45) at 30 days to HR: 1.75; (1.47-2.09) 12 years later. The difference in mortality also declined with increasing age: HR 1.80 (1.52-2.13) for those aged 22-59, 1.26 (1.11-1.42) for 60-69, 1.06 (0.96-1.17) and 0.96 (0.85-1.09) for those 70-79 and 80-101 years. Significant two-factor interactions were observed between sex, age and diabetes (P < 0.001). Diabetic women <60 years of age had greater mortality than diabetic men of the same age (adjusted HR: 1.44; 1.14-1.84; P = 0.003), while diabetic women and men ≥60 years of age had a less pronounced mortality difference (adjusted HR: 1.12; 0.99-1.26). CONCLUSIONS: One in two women hospitalized for AMI in this Asian cohort had diabetes and the sex disparity in post-MI mortality was most pronounced among these who were <60 years of age. This underscores the need for better secondary prevention in this high-risk group