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

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

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

Wider Retinal Artery Trajectories in Eyes with Macular Hole Than in Fellow Eyes of Patients with Unilateral Idiopathic Macular Hole

<div><p>Purpose</p><p>To determine whether the width of the retinal artery (RA) trajectory was associated with the presence of a macular hole (MH).</p><p>Methods</p><p>A retrospective cross sectional case-control study was performed. The fundus photographs were rotated 90 degrees, and the coordinates of the best fit curve of the RA trajectory were determined automatically based on these plots using the ImageJ program. The converted coordinates were fit to a second degree polynomial (ax²/100 + bx + c) equation. The width and steepness of the RA trajectory, “a”, of the eyes with a MH eye were compared to that of the fellow eyes.</p><p>Results</p><p>One hundred and ten eyes of 55 consecutive patients (30 women) with a unilateral MH and healthy fellow eyes were analyzed. The mean age was 64.9 years (range 47-81 years). The constant ‘a’ was significantly smaller in eyes with a MH than that of the fellow eyes (0.379 ± 0.094 vs 0.416 ± 0.121, <i>P</i> = 0.001, paired <i>t</i> test), indicating that the RA trajectory was wider in the MH eyes than in the fellow eyes. There was a significant correlation between the axial length and ‘a’ of the RA trajectory in the MH eyes (R = 0.273, <i>P</i> = 0.044) and in the fellow eyes (R = 0.356, <i>P</i> = 0.008; Spearman’s rank correlation coefficient).</p><p>Conclusions</p><p>Because eyes with a MH have a significantly wider and flatter RA trajectory, there may be greater traction on the fovea which is located between the RA arches. The causative role of this finding is still unclear.</p></div

Axial length of macular hole eye and fellow eye (paired-eyes).

<p>There was no significant difference in the axial lengths between the MH eyes and fellow eyes (<i>P</i> = 0.462).</p

Retinal artery (RA) trajectory and posterior vitreous detachment in fellow eyes.

<p>The status of the posterior vitreous interface was classified according to Uchino et al [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0122876#pone.0122876.ref023" target="_blank">23</a>]. There was no significant difference in the ‘a’ of the RA trajectory between any two of classifications including S0 and S4 (<i>P</i> = 0.370, Mann-Whitney U test).</p