Deep Collaborative Filtering Approaches for Context-Aware Venue Recommendation

In recent years, vast amounts of user-generated data have being created on Location-Based Social Networks (LBSNs) such as Yelp and Foursquare. Making effective personalised venue suggestions to users based on their preferences and surrounding context is a challenging task. Context-Aware Venue Recommendation (CAVR) is an emerging topic that has gained a lot of attention from researchers, where context can be the user's current location for example. Matrix Factorisation (MF) is one of the most popular collaborative filtering-based techniques, which can be used to predict a user's rating on venues by exploiting explicit feedback (e.g. users' ratings on venues). However, such explicit feedback may not be available, particularly for inactive users, while implicit feedback is easier to obtain from LBSNs as it does not require the users to explicitly express their satisfaction with the venues. In addition, the MF-based approaches usually suffer from the sparsity problem where users/venues have very few rating, hindering the prediction accuracy. Although previous works on user-venue rating prediction have proposed to alleviate the sparsity problem by leveraging user-generated data such as social information from LBSNs, research that investigates the usefulness of Deep Neural Network algorithms (DNN) in alleviating the sparsity problem for CAVR remains untouched or partially studied

Objective Determination of Optimal Number of Spectral-Domain Optical Coherence Tomographic Images of Retina to Average

<div><p>Purpose</p><p>To determine by objective methods the minimum number of spectral-domain optical coherence tomographic (SD-OCT) images to average to obtain the clearest retinal image.</p><p>Methods</p><p>SD-OCT Images were obtained from 9 healthy eyes and also from a phantom eye model. The SD-OCT images were obtained by averaging 1, 5, 20, 60, and 100 B-scan images. The reflectivity (mean gray value) of the different retinal layers was evaluated in these images. The image quality was evaluated by the size of the standard deviations (SDs) and the contrast-to-noise ratios (CNRs). A phantom eye model made by TiO₂ silicone plates was also examined.</p><p>Results</p><p>The SDs decreased significantly when the number of images averaged increased from 1 to 5 and also from 5 to 20 (<i>P</i><0.05, post hoc Tukey's honestly significant difference tests). The SD of the automatic real time averaging of 1 (ART = 1) and ART = 5 were significantly larger than the SD of ART = 100 (<i>P</i><0.05). The SDs of all other averaged numbers were not significantly larger than that of ART = 100. The CNR increased with an increase in the number of images averaged, and there was a significant increase between ART = 1 to 5 and between ART = 5 to 20 (<i>P</i><0.05). No significant differences in the CNR was observed between ART = 5, ART = 20 and ART = 60. Similar results were obtained with the phantom eye model.</p><p>Conclusions</p><p>Although the image quality of the SD-OCT images of the retina improved with an increase in the number of images averaged, it does not improve significantly by averaging more than 20 images.</p></div

Region of interest (ROI) in each layer of a normal human retina.

<p>The region of interest is indicated by the arrows. A, original OCT image; B, vitreous was selected as ROI (white line); C. and D. IPL was selected as ROI (black lines); E. ONL was selected as ROI (white line); and F. ELM was selected as ROI (black line).</p

Gray values of SD-OCT reflectivity of each retinal layer of normal human eyes.

<p>The mean gray values of retina were significantly lower in the single scan image than in image averaged 100 times (mean gray value; **; <i>P</i><0.01; post hoc Dunnett's multiple comparison test). ROI, region of interest; vit, vitreous body; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, photoreceptor inner segment/outer segment junction; COST, cone outer segment tip; RPE, retinal pigment epithelium. ART indicates automatic real time averaging.</p

Representative SD-OCT images of fovea without (A) and with (B, C) automatic real time (ART) averaging.

<p>A: ART averaging  = 1; B: ART averaging  = 20; C: ART averaging  = 100. ART.</p

Intra- and inter-rater agreement of the reflectivity of SD-OCT images of a human eye.

<p>ROI, region of interest; vit, vitreous body; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, photoreceptor inner segment/outer segment junction; COST, cone outer segment tips; RPE, retinal pigment epithelium.</p>†<p>:intra-class correlation coefficients (ICC) using one-way model,</p>‡<p>; ICC using a two-way model for absolute agreement. All <i>P</i> values are <0.001</p><p>Intra- and inter-rater agreement of the reflectivity of SD-OCT images of a human eye.</p

Standard deviations (SDs) after averaging in normal human eyes.

<p>The SD of the gray value of the OCT images decreases as the number of images averaged increases. ROI, region of interest; vit, vitreous body; IPL, inner plexiform layer; INL, inner nuclear layer; ONL, outer nuclear layer; ELM, external limiting membrane; IS/OS, photoreceptor inner segment/outer segment junction; COST, cone outer segment tip; RPE, retinal pigment epithelium. ART indicates automatic real time (ART) averaging. **; <i>P</i><0.01, *:<i>P</i><0.05, post hoc Tukey's HSD tests.</p

Different Effects of Thrombin on VEGF Secretion, Proliferation, and Permeability in Polarized and Non-polarized Retinal Pigment Epithelial Cells

<div><p></p><p>We investigated the effect of thrombin on the secretion of vascular endothelial growth factor (VEGF), on cellular proliferation, and on the integrity of the barrier function of polarized retinal pigment epithelial (RPE) cells. In addition, we compared the responses of polarized to that of non-polarized RPE cells. Porcine polarized RPE cells were established using Transwell membranes. The polarization of the RPE cells was determined by their high transepithelial electrical resistance (TER > 200 Ω cm²) and by their differential secretion of VEGF (basal direction >apical direction by 2.5×). RPE cells were incubated with thrombin (5–20 U/ml) for 24 h. The concentration of VEGF in the culture medium was measured by enzyme-linked immunosorbent assay, and the TER was measured. Cellular proliferation was assessed by Ki-67 immunostaining. The area of laser-induced choroidal naovascularization (CNV) was measured in rat eyes and compare to that of controls with or without thrombin. Our results showed that thrombin significantly increased VEGF secretion both in polarized and non-polarized RPE cells in a dose-dependent way. Thrombin did not significantly affect the TER or the expression of tight-junctional proteins in polarized RPE cells, but decreased it in non-polarized RPE cells by inducing intercellular gaps. Ki-67-positive cells were observed in non-polarized RPE cells but not in polarized RPE cells as controls. After thrombin exposure, the number of Ki-67-positive cells increased significantly in non-polarized RPE cells but not in polarized RPE cells. The area of CNV was larger in thrombin-injected eye than control eyes. Although thrombin increased VEGF secretion regardless of cell polarity, its effects on proliferation and barrier integrity were dependent upon cell polarity. Cell polarization is an important factor for determining the response of RPE cells to thrombin, and the different responsive patterns to thrombin upon cell polarity might explain the complicated pathology of such diseases as age-related macular degeneration.</p></div

Choroidal area on EDI-OCT images.

<p>Choroidal area on EDI-OCT images.</p

Indocyanine green angiographic findings and choroidal area.

<p>Indocyanine green angiographic findings and choroidal area.</p