Unbiased evaluation of keypoint detectors with respect to rotation invariance

The authors present the results of a comparative performance study of algorithms for detecting keypoints in digital images. The Harris, good features to track (GFTT), SIFT, SURF, FAST, ORB, BRISK, and the MSER keypoint detectors were tested using two types of images: POV‐Ray simulated images and photographs from the Caltech 256 image dataset. They tested the repeatability of detection of the image keypoints for the evaluated detectors for a series of images with one degree rotations from 0 to 180° (3982 images in total). In the evaluation scenario they adopted an original approach in which they did not hold back a single image to be the reference image. They conclude that the most computationally complex detector, i.e. the SIFT performs best under rotation transformation of images. However, the FAST and ORB detectors, while being less computationally demanding, perform almost equally well. Hence, they can be viable choices in image processing tasks for mobile applications

Closed Head Injury in a Mouse Model Results in Molecular Changes Indicating Inflammatory Responses

Cerebral gene expression changes in response to traumatic brain injury will provide useful information in the search for future trauma treatment. In order to characterize the outcome of mild brain injury, we studied C57BL/6J mice in a weight-drop, closed head injury model. At various times post-injury, mRNA was isolated from neocortex and hippocampus and transcriptional alterations were studied using quantitative reverse transcriptase PCR and gene array analysis. At three days post-injury, the results showed unilateral injury responses, both in neocortex and hippocampus, with the main effect seen on the side of the skull hit by the dropping weight. Upregulated transcripts encoded products characterizing reactive astrocytes, phagocytes, microglia, and immune-reactive cells. Markers for oligodendrocytes and T-cells were not altered. Notably, strong differences in the responses among individual mice were seen (e.g., for the Gfap transcript expressed by reactive astrocytes and the chemokine Ccl3 transcript expressed by activated microglial cells). In conclusion, mild TBI chiefly activates transcripts leading to tissue signaling, inflammatory processes, and chemokine signaling, as in focal brain injury, suggesting putative targets for drug development

Body size at birth and blood pressure among children in developing countries

Background: studies in developed countries have shown that reduced fetal growth is related to raised blood pressure in childhood and adult life. Little is known about this association in developing countries, where fetal growth retardation is common.Methods: in 1994–1995, we measured blood pressure in 1570 3–6-year-old children living in China, Guatemala, Chile, Nigeria and Sweden. We related their blood pressure to patterns of fetal growth, as measured by body proportions at birth. The children were all born after 37 weeks gestation and weighed more than 2.5 kg at birth.Results: in each country, blood pressure was positively related to the child's current weight. After adjusting for this and gender, systolic pressure was inversely related to size at birth in all countries except Nigeria. In Chile, China and Guatemala, children who were proportionately small at birth had raised systolic pressure. For example, in Chile, systolic pressure adjusted for current weight increased by 4.9 mmHg (95% CI : 2.1, 7.7) for every kilogram decrease in birthweight, by 1 mmHg (95% CI : 0.4, 1.6) for every centimetre decrease in birth length, and by 1.3 mmHg (95% CI : 0.4, 2.2) for every centimetre decrease in head circumference at birth. In Sweden, systolic pressure was higher in children who were disproportionately small, that is thin, at birth. Systolic pressure increased by 0.3 mmHg (95% CI : 0.0, 0.6) for every unit (kg/m3) decrease in ponderal index at birth. These associations were independent of the duration of gestation.Conclusions: raised blood pressure among children in three samples from China, Central and South America is related to proportionate reduction in body size at birth, which results from reduced growth throughout gestation. The relation between fetal growth and blood pressure may be different in African populations. Proportionately reduced fetal growth is the prevalent pattern of fetal growth retardation in developing countries, and is associated with chronic undernutrition among women. Improvement in the nutrition and health of girls and young women may be important in preventing cardiovascular disease in developing countries

Titanium dioxide nanoparticles prepared by laser pyrolysis : synthesis and photocatalytic properties

TiO2 nanoparticles were synthesized via the laser pyrolysis of titanium tetrachloride-based gas-phase mixtures. In the obtained nanopowders, a mixture of anatase and rutile phases with mean particle size of about 14 nm was identified. Using the thermal heated laser nanopowders, mechanically stable films were produced by immobilizing titania nanopowders on glass substrates (the doctor blading method followed by compression). The photocatalytic activity of the prepared films was tested by the degradation of 4-chlorophenol in an aqueous solution under UV-illumination. By referring to known commercial samples (Degussa P25) similarly prepared, higher photocatalytic efficiency was found for the laser-prepared samples

Scanning electrochemical cell microscopy platform for ultrasensitive photoelectrochemical imaging

The development of techniques for nanoscale structure–activity correlations is of major importance for the fundamental understanding and rational design of (photo)electrocatalysts. However, the low conversion efficiency of characteristic materials generates tiny photoelectrochemical currents at the submicrometer to nanoscale, in the fA range, which are challenging to detect and measure accurately. Here, we report the coupling of scanning electrochemical cell microscopy (SECCM) with photoillumination, to create a submicrometer spatial resolution cell that opens up high resolution structure–(photo)activity measurements. We demonstrate the capabilities of the technique as a tool for: (i) high spatial resolution (photo)activity mapping using an ionic liquid electrolyte at a thin film of TiO2 aggregates, commonly used as a photoanode in dye sensitized solar cells (DSSCs) and (ii) in situ (photo)activity measurements of an electropolymerized conjugated polymer on a transparent Au substrate in a controlled atmospheric environment. Quantitative data, including localized (photo)electrochemical transients and external quantum efficiency (EQE), are extracted, and prospects for further technique development and enhancement are outlined