A robust binary supramolecular organic framework (SOF) with high CO2 adsorption and selectivity

A robust binary hydrogen-bonded supramolecular organic framework (SOF-7) has been synthesized by solvothermal reaction of 1,4-bis-(4-(3,5-dicyano-2,6 dipyridyl)dihydropyridyl)benzene (1) and 5,5’-bis-(azanediyl)-oxalyl-diisophthalic acid (2). Single crystal X-ray diffraction analysis shows that SOF-7 comprises 2 and 1,4-bis-(4-(3,5-dicyano-2,6-dipyridyl)pyridyl)benzene (3), the latter formed in situ from the oxidative dehydrogenation of 1. SOF-7 shows a three-dimensional four-fold interpenetrat-ed structure with complementary O−H···N hydrogen bonds to form channels that are decorated with cyano- and amide-groups. SOF-7 exhibits excellent thermal stability and sol-vent and moisture durability, as well as permanent porosity. The activated desolvated material SOF-7a shows high CO2 sorption capacity and selectivity compared with other po-rous organic materials assembled solely through hydrogen bonding

Diagnostic assistance system to detect progression of diabetic retinopathy (DR) in fundus images of follow up examinations of patients with diabetes

Abstract Purpose: An important step in detecting and monitoring DR is regular screening by fundus images. The aim is to identify patients with sight-threatening DR timely to be able to initiate adequate treatment and thus to prevent loss of vision (blindness). We developed an algorithm to detect progression between follow up examinations in order to minimize the time consuming diagnostic of the images by an ophthalmologist. Methods: Digital fundus images of 12 patients (4 female, 8 male) with diabetes (10 type 1, 2 type 2) were retrospectively selected from the records of the Department of Ophthalmology of the Oulu University Hospital. Red-free fundus images of each eye were clinically graded for DR, and eyes with progression were included. A 5-step classification was used: no DR, mild DR, moderate DR, severe non-proliferative DR or proliferative DR. There were at least 5 cases presenting every transition, e.g. from no DR to mild DR. A total of 158 grayscale fundus images of 24 eyes were included. The mean age at time of the first examination was 34 ± 15 years, and 43 ± 13 years at the latest examination. The number of examinations varied between 4 and 9 per eye. For each eye, the progression map of all possible combinations of two individual fundus images were calculated. First, the two images were roughly registered with help of a similarity transformation. A finer registration was implemented patchwise together with the adjustment of the contrast between them as a second step. The next step consisted of the calculation of the difference map between the two images. The remaining noise from the background was filtered as a last step by considering the local noise level from the two source images. Results: The transition between the different grades of DR was correctly detected (true positive) in 91% of the instances, and the absence of transition (true negative) in 94%. In 6% of the cases the algorithm signaled progression without clinically detectable change of DR grade (false positive), and in 9% (false negative) the algorithm was not able to detect clinically detected progression. Conclusions: The results demonstrate that the algorithm developed for the detection of progression of DR in fundus images does reliably highlight changes between the images, and has the potential to reduce the time needed for evaluation of images by an ophthalmologist

Calcium isotope fractionation in calcite and aragonite

Calcium isotope fractionation was measured on skeletal aragonite and calcite from different marine biota and on inorganic calcite. Precipitation temperatures ranged from 0 to 28°C. Calcium isotope fractionation shows a temperature dependence in accordance with previous observations: 1000 · ln(αcc) = −1.4 + 0.021 · T (°C) for calcite and 1000 · ln(αar) = −1.9 + 0.017 · T (°C) for aragonite. Within uncertainty the temperature slopes are identical for the two polymorphs. However, at all temperatures calcium isotopes are more fractionated in aragonite than in calcite. The offset in δ44/40Ca is about 0.6‰. The underlying mechanism for this offset may be related to the different coordination numbers and bond strengths of the calcium ions in calcite and aragonite crystals, or to different Ca reaction behavior at the solid-liquid interface. Recently, the observed temperature dependence of the Ca isotope fractionation was explained quantitatively by the temperature control on precipitation rates of calcium carbonates in an experimental setting (Lemarchand et al., 2004). We show that this mechanism can in principle also be applied to CaCO3 precipitation in natural environments in normal marine settings. Following this model, Ca isotope fractionation in marine Ca carbonates is primarily controlled by precipitation rates. On the other hand the larger Ca isotope fractionation of aragonite compared to calcite can not be explained by different precipitation rates. The rate control model of Ca isotope fractionation predicts a strong dependence of the Ca isotopic composition of carbonates on ambient CO32− concentration. While this model is in general accordance with our observations in marine carbonates, cultured specimens of the planktic foraminifer Orbulina universa show no dependence of Ca-isotope fractionation on the ambient CO32− concentration. The latter observation implies that the carbonate chemistry in the calcifying vesicles of the foraminifer is independent from the ambient carbonate ion concentration of the surrounding water