Dual-Mode Conversion of Photodetector and Neuromorphic Vision Sensor via Bias Voltage Regulation on a Single Device.

Simultaneous implementation of photodetector and neuromorphic vision sensor (NVS) on a single device faces a great challenge, due to the inherent speed discrepancy in their photoresponse characteristics. In this work, a trench-bridged GaN/Ga2 O3 /GaN back-to-back double heterojunction array device is fabricated to enable the advanced functionalities of both devices on a single device. Interestingly, the device shows fast photoresponse and persistent photoconductivity behavior at low and high voltages, respectively, through the modulation of oxygen vacancy ionization and de-ionization processes in Ga2 O3 . Consequently, the role of the optoelectronic device can be altered between the photodetector and NVS by simply adjusting the magnitude of bias voltage. As a photodetector, the device is able to realize fast optical imaging and optical communication functions. On the other hand, the device exhibits outstanding image sensing, image memory, and neuromorphic visual pre-processing as an NVS. The utilization of NVS for image pre-processing leads to a noticeable enhancement in both recognition accuracy and efficiency. The results presented in this work not only offer a new avenue to obtain complex functionality on a single optoelectronic device but also provide opportunities to implement advanced robotic vision systems and neuromorphic computing.

The SUSTech-SYSU dataset for automatically segmenting and classifying corneal ulcers.

Corneal ulcer is a common ophthalmic symptom. Segmentation algorithms are needed to identify and quantify corneal ulcers from ocular staining images. Developments of such algorithms have been obstructed by a lack of high quality datasets (the ocular staining images and the corresponding gold-standard ulcer segmentation labels), especially for supervised learning based segmentation algorithms. In such context, we prepare a dataset containing 712 ocular staining images and the associated segmentation labels of flaky corneal ulcers. In addition to segmentation labels for flaky corneal ulcers, we also provide each image with three-fold class labels: firstly, each image has a label in terms of its general ulcer pattern; secondly, each image has a label in terms of its specific ulcer pattern; thirdly, each image has a label indicating its ulcer severity degree. This dataset not only provides an excellent opportunity for investigating the accuracy and reliability of different segmentation and classification algorithms for corneal ulcers, but also advances the development of new supervised learning based algorithms especially those in the deep learning framework.

[Inner- and inter-species differences of mercury concentration in common fishes from the Yellow Sea].

Mercury concentration in marine fishes and its influencing factors are the key problems in the study of mercury biomagnification in marine ecosystems. In order to understand the inner- and inter-species differences of mercury concentration in fishes from the Yellow Sea, a total of 164 marine wild fishes covering nine different species were collected from the area from August to October, 2012. Mercury (total mercury) concentration in fish muscle tissue was measured by a direct mercury analyzer. Body length and wet weight of each sample were also determined. Moreover, feeding habit and trophic level of different species were examined. Hg concentrations (dry weight) in the muscle tissues of the 164 individuals ranged from 0.025 micro x g(-1) to 0.526 microg x g(-1), with an average of (0.124 +/- 0.096) microg x g(-1). By an inner-species analysis, log10 Hg concentration was significantly correlated to their body length and wet weight. Predator fishes with trophic level > 2.8 were more readily to be contaminated by Hg than the filter feeder with trophic level < 2.8. Furthermore, species with higher increasing rate of weight had lower Hg concentration in the muscle due to growth dilution. The results suggest that length and weight are the main factors affecting the inner- species difference of mercury concentration in common fishes from the Yellow Sea, while dietary preference, trophic level and increasing rate of weight are the main factors affecting the inter-species difference from the Yellow Sea.

[Separation of isomeric compounds by high speed countercurrent chromatography].

High speed countercurrent chromatography (HSCCC) was successfully used for the separation and preparation of isomeric compounds. The influence of various two-phase solvent systems on the resolution of the natural catechin isomers of (-) -epigallocatechin gallate (EGCG) and (-) -gallocatechin gallate (GCG) from green tea polyphenols and the synthetic isomeric compounds of para-, ortho-, meta-bromoanilline was investigated. The results indicated that the catechin isomers of (-) -EGCG and (-) -GCG can be isolated through two runs of preparative HSCCC with two-phase solvent system composed of n-hexane-ethyl acetate-water (1: 10: 10 in volume ratio). The upper organic phase was used as stationary phase and the lower aqueous phase as mobile phase, while the mobile phase was operated at a flow rate of 3.5 mL/min, and the apparatus rotated at 800 r/min. High performance liquid chromatographic analysis of (-) -EGCG and (-) -GCG revealed that the purity was all over 98%. The isomeric compounds of para-, ortho-, meta-bromoaniline can also be effectively isolated through a single run of preparative HSCCC with the mobile phase flow rate of 3.0 mL/min and the apparatus rotation speed of 800 r/min by using tetrachloromethane-chloroform-methanol-water (7: 3: 7: 3 in volume ratio) as two-phase solvent system, while the lower phase was selected as stationary phase and the upper phase as mobile phase.