WERank: Towards Rank Degradation Prevention for Self-Supervised Learning Using Weight Regularization

A common phenomena confining the representation quality in Self-Supervised Learning (SSL) is dimensional collapse (also known as rank degeneration), where the learned representations are mapped to a low dimensional subspace of the representation space. The State-of-the-Art SSL methods have shown to suffer from dimensional collapse and fall behind maintaining full rank. Recent approaches to prevent this problem have proposed using contrastive losses, regularization techniques, or architectural tricks. We propose WERank, a new regularizer on the weight parameters of the network to prevent rank degeneration at different layers of the network. We provide empirical evidence and mathematical justification to demonstrate the effectiveness of the proposed regularization method in preventing dimensional collapse. We verify the impact of WERank on graph SSL where dimensional collapse is more pronounced due to the lack of proper data augmentation. We empirically demonstrate that WERank is effective in helping BYOL to achieve higher rank during SSL pre-training and consequently downstream accuracy during evaluation probing. Ablation studies and experimental analysis shed lights on the underlying factors behind the performance gains of the proposed approach

Investigating the Causes of Visual Impairment and Legal Blindness among Patients Coming to a Referral Hospital in Tehran, Iran

Purpose: To examine the causes of vision impairment and blindnessin a referral medical center in Tehran, Iran.Patients and Methods:  The present cross-sectional study was conducted on visually impaired and legally blind patients in optometricclinic of Rasoul-e-Akram hospital, Tehran, Iran, in 2015. We used the WHO criteria to evaluate visual impairment. The visual acuity of patients was recorded in a mono-eye fashion (right eye first then the left eye) using a 6-meter Snellen chart. The refractive error was evaluated and the best corrected visual acuity (BCVA) was recorded. Patients were then referred to ophthalmology department to diagnose the main cause of reduced vision.Results:  This study included 77 legally blind or visually impaired patients. After examining the underlying causes of visual impairment, we found that 41.17 % of visual impairment among patients was caused by cataracts and 29.41 % was caused by retinal diseases. Corneal pathology, glaucoma and other diseases were the rarer causes of low vision among subjects. The causes of legal blindness were different; retinal diseases were the main causes of legal blindness (46.51 %) followed by cataract (30.23 %) and corneal pathology (13.95 %).Conclusion:  Our results from a referral hospital in Tehran indicates that retinal pathology was the most common cause of legal blindness among our patients, while the most common cause of visual impairment was cataract. Due to the natural differences of epidemiologic findings gathered from a referral center and the community, multicenter studies are recommended to better evaluate the causes of visual impairment in our community.Keywords: Visual; Impairment; Legal; Blindness; Iran.

Scalable Graph Self-Supervised Learning

In regularization Self-Supervised Learning (SSL) methods for graphs, computational complexity increases with the number of nodes in graphs and embedding dimensions. To mitigate the scalability of non-contrastive graph SSL, we propose a novel approach to reduce the cost of computing the covariance matrix for the pre-training loss function with volume-maximization terms. Our work focuses on reducing the cost associated with the loss computation via graph node or dimension sampling. We provide theoretical insight into why dimension sampling would result in accurate loss computations and support it with mathematical derivation of the novel approach. We develop our experimental setup on the node-level graph prediction tasks, where SSL pre-training has shown to be difficult due to the large size of real world graphs. Our experiments demonstrate that the cost associated with the loss computation can be reduced via node or dimension sampling without lowering the downstream performance. Our results demonstrate that sampling mostly results in improved downstream performance. Ablation studies and experimental analysis are provided to untangle the role of the different factors in the experimental setup

The Prevalence of Accommodative Insufficiency among Students of an Iranian Medical School

Purpose: To evaluate the prevalence of accommodative insufficiency in a student population from Iran.Patients and Methods: This cross-sectional study was performed on 596 eyes from 298 participants (157 males, 141 females) in age range of 18 to 29 years among students from Iran University of Medical Sciences, Tehran, Iran, between 2014 and 2015. The amplitude of accommodation among volunteers in this study was evaluated using the Donder's push up method. Then, the minimum normal amplitude of accommodation for a given age was estimated by Hofstetter formula (15 - 0.25 * age in years), and then the prevalence of accommodative insufficiency among the study population was determined according to this calculations. Results: We found the prevalence of accommodative insufficiency to be 7.2% in the study population. The prevalence of accommodative insufficiency was 4.1% and 7.25% among males and females respectively (P < 0.001). Conclusion: The prevalence of accommodative insufficiency in our study population was less than previous studies among children, which might be explained by the role of natural selection (people with accommodative disorders might have less chance of excelling in education and entering higher education institutes than patients without this disorder). We also found a statistically significant higher prevalence of accommodative insufficiency among female college aged students compared to male students.Keywords: Accommodation, insufficiency, prevalence, eye, Iran

The Effects of Orthodontic Tooth Movement on Clinical Attachment Level Changes in Treated Periodontitis Adult Patients with Malocclusion: A Systematic Review and Meta-analysis

Objective: To investigate the effects of orthodontic tooth movement on clinical attachment level (CAL) changes in treated periodontitis in adult patients with malocclusion. Material and Methods: Present study is based on PRISMA guidelines; all articles published in international databases such as PubMed, Scopus, Science Direct, and Embase between 2012 to May 2022 are included. 95% confidence interval (CI) for mean difference with fixed effect modal and inverse-variance were calculated. Data analysis was performed using STATA.V16 software. Results: In the initial review, duplicate studies were eliminated, abstracts of 175 studies were reviewed, two authors reviewed the full text of 21 studies, and finally, eleven studies were selected. The mean of CAL gain was 2.29 mm (MD, 95% CI -2.47 mm, -2.12 mm; p=0.00) (I2=91.81%; p=0.00; high heterogeneity). The mean difference of PPD changes was –1.93 mm (MD, 95% CI -2.07 mm, -1.80 mm; p=0.00) (I2=98.52%; p=0.00; high heterogeneity). Conclusion: Due to the limitations of the study and based on the meta-analysis, it is observed that orthodontic treatment is performed with higher success after reconstructive surgery with periodontal improvement

Crack damage evolution in coal at elevated temperatures

This work studies the behaviour of coal samples at various thermal environments from sub-zero temperatures of -100 to 300 °C by monitoring their fracture speed, ultimate strength, and crack damage evolution mode. High-speed recordings captured at 140,000 frames per second identified three different fracture evolution modes as a function of the applied ambient temperature. As the temperature increases, the fracture behaviour was observed to be through intact rock bridges resulting in reduced crack speeds and smaller fragments. Interestingly, at sub-zero temperatures, a different failure pattern was observed through the formation of a single fracture plane resulting in larger fragments with sharper edges

EFFECTS OF DEXAMETHASONE IN PRIMARY INTRACEREBRAL HEMORRHAGE IN THE SOUTH WEST OF IRAN

ABSTRACT Objective: Previous study revealed the value of dexamethasone in the treatment of vasogenic edema associated with brain tumor and abscess. However there are poor documented studies about its usefulness in primary intracerebral hemorrhage. In this study we evaluated dexamethasone effects in primary intracerebral hemorrhage. Methodology: In a double blind randomized placebo-controlled clinical trial we evaluated 200 intracerebral hemorrhage cases between 40 to 80 years old whom were admitted at Golestan Hospital (Ahwaz, IR) between March 2002 And March 2003. They were divided in two groups; dexamethasone (N=100) and placebo (N=100). Then mortality, GI bleeding, fever, electrolytes disturbances, hypertension and hyperglycemic status were analyzed in two groups. Ethical considerations were employed and subjects were followed by appropriate statistical methods for 21 days to assess the major outcomes. Results: Mortality was much higher in the dexamethasone group; Dexamethasone group (49.3%) and placebo (23.4%) and also fever was higher seen in the dexamethasone group; dexamethasone group (40.2%) and placebo group (24.7%) but there was not any significant statistical difference between two groups as regards other complications. Conclusion: Dexamethasone is widely used for cerebral edema associated conditions but in this study we saw that it's complications in intracerebral hemorrhage such as increasing fever and mortality are significantly higher. Hence it use for treatment of primary intracerebral hemorrhage should be reconsidered

Effects of different levels of vitamin premix in finisher diets on performance, immuno - competence and meat lipid oxidation of chickens fed on corn - soybean meal

The present study was carried out to examine the effects of a vitamin premix (VP)reduction or withdrawal from finisher diet (29-43 days) on performance,immuno-competence,and characteristicsof leg bones and meat lipid oxidation of chickens fed oncorn-soybeanmeal based diet. A total of 900 male broiler chickens (Ross 308) were allocatedtofivetreatment groups(0, 33%, 66%, 100% and 133% VP), withninereplicates per treatmentgroup. At 29 and 36 days of ages, four birds from each replicate were injected with sheepredblood cells (SRBC). The cell-mediated immunity was determined via phytohemagglutinin(PHA) and 1-chloro 2-4-dinitrobenzen (DNCB)at 34 and 42 days of ages.At 33, 38 and 43days of age, 42 days of ages, and two birds of each replicate were slaughteredand boneparameters measured. The oxidative stability was evaluated by thiobarbituric acid reactivesubstances (TBARS) on the thigh samples that were stored for 90 day at-80 ̊C. The resultsshowed that reduction or withdrawal of VP from diets at different time points of the finisherperiod did not affect performance, immunocompetence and characteristics of leg bones.Results of TBARS showed thatlipid peroxidation of the treatment without VP wassignificantly higher than of the other treatments when slaughtered at 43 days of age. Finally,the results of this study demonstrated that it is not possible to reduce the VP in finisherbroilers’ diets without negative effects on meat quality during the time of freezing

The Effect of Mesenchymal Stem Cells on the Expression of IDOand Qa2 Molecules in Dendritic Cells

Purpose: Mesenchymal stem cells (MSCs) have been shown to reduce the activity of immunecells, including dendritic cells (DCs). But the exact mechanism of mesenchymal inhibitionof DCs is still unknown. In this study, the effect of mesenchymal cells on the expression ofindoleamine dioxygenase (IDO) and Qa2 molecules in DCs was evaluated.Methods: MSCs and DCs were respectively isolated from the bone marrow and spleen of BALB/cmice. Then DCs were co-cultured with MSCs in the present and absence of lipopolysaccharides(LPS). Then the expression of mRNA and protein of IDO and Qa2 molecules were investigatedin DCs that were treated with MSCs.Results: The expression of IDO and Qa2 mRNA in DCs that were treated with MSCs did notsignificantly differ from the control group. The expression of IDO protein in DCs that were coculturedwith MSCs (in 1:10 and 1:50 ratios) in absence of LPS was increased, although theywere not statistically significant (P values: 0.24 and 0.18, respectively). The expression of Qa2protein in DCs that were co-cultured with MSCs (in 1:10 and 1:50 ratios) in presence of LPS wasincreased, although they were not statistically significant (P-values: 0.09 and 0.33, respectively).Conclusion: Our results denied the possibility that MSCs led to the induction of tolerogenic DCsby increasing the expression of the IDO and Qa2 immunomodulatory molecules