In Vitro Comparative Analysis of Fracture Resistance of Lithium Disilicate Endocrown and Prefabricated Zirconium Crown in Pulpotomized Primary Molars

AIM: This study aimed to evaluate the effect of lithium disilicate endocrowns compared to prefabricated zirconia crown used for restoring pulpotomized primary molars, on their Fracture Resistance and to compare the loads to failure these different ceramic restorations with previously reported posterior occlusal forces. METHODS: Twenty mandibular left second primary molars were randomly distributed into two groups (n = 10 in each group) the zirconia Crown (Nusmile zr.) Group (G1) and the lithium disilicate (IPS e.max Press) Endocrown Group (G2). In all groups pulpotomy procedure was done before preparation then each sample was prepared based on their allocated restoration, both zirconia crown (Nusmile zr.) and endocrown (IPS e.max Press) were cemented by dual-cure resin cement. All samples were loaded to failure using a universal testing machine (Instron, USA), and the compressive force was applied. The data were analysed using one-way (ANOVA) and Tukey’s post hoc significance difference tests. Differences were considered significant at (p< 0.05). RESULTS: Group zirconia crown (G1) showed significantly higher fracture strength than Group (G2) lithium disilicate endocrown (p < 0.05). CONCLUSION: The zirconia crown showed higher fracture resistance than lithium disilicate endocrown. However, both tested zirconia crown and lithium disilicate endocrown withstood the application of axial occlusal forces greater than the reference values for posterior occlusal loads

Internal clearance behaviour in healthy and faulty bearings

Internal clearance is a critical parameter in bearing design and operation because it affects the bearing's performance. It can be considered as a special type of the looseness fault. Several studies indicate that rolling bearings with large internal clearances showed a short predicted fatigue life. However, the time waveform and spectral features of bearing with internal clearances are partially studied and require further studies. To address this gap, the purpose of this paper is to study the effect of internal clearance on the dynamic response of healthy and faculty rolling bearings in both time waveform and spectral representations. Four experiments are designed and performed: (1) rigid bearing with no defect, (2) rigid bearing with bearing defect, (3) bearing with high internal clearance, (4) bearing with high internal clearance and bearing defect. The results indicate an increase in the overall vibration level with high internal clearance is introduced, however, there is an increase in the overall vibration level when high internal clearance and bearing defect are both presented. The internal clearance negatively affects the impact amplitude of the bearing defect, which also affects the spectral pattern at the natural frequency zone.publishedVersio

SARS-CoV-2 susceptibility and COVID-19 disease severity are associated with genetic variants affecting gene expression in a variety of tissues

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types

A first update on mapping the human genetic architecture of COVID-19

peer reviewe

Effect of Sampling Rates Variation during Cylindricity Error Evaluation

Cylindrical parts are critical elements in many engineering equipment. To perform correctly, their dimensions and cylindricity should be within specified tolerances. Cylindrical parts can be checked using several dedicated and general purpose measuring systems. Coordinate Measuring Machines (CMMs) can been used to probe and scan cylindrical surfaces to evaluate dimensions and form errors. For accurate evaluation of cylindricity error using a CMM, several parameters should be taken into consideration such as measurement strategy, sampling rate, and cylindricity evaluation technique. The large measurement points required need an efficient evaluation algorithm, and due to their advantages, the Minimum Zone Cylindricity evaluation technique (MZC) and Particle Swarm Optimization technique (PSO) are used in this work. The proposed algorithm was developed using Matlab software and applied for the evaluation of cylindricity error of test cylinders. This paper investigates the effect of the change in sampling rate on the value of estimated cylindricity error when using two different strategies, namely, circles and helical. A comparison between both strategies is presented. The effect of the number of scanned circles and helix turns on the estimated cylindricity error is also investigated.nbsp The results showed that sampling rate has more significant effect on the value of estimated cylindricity error than the number of measurement circles or helix turns even for the same number of data points

COVID-19 Host Genetics Initiative. A first update on mapping the human genetic architecture of COVID-19

The COVID-19 pandemic continues to pose a major public health threat, especially in countries with low vaccination rates. To better understand the biological underpinnings of SARS-CoV-2 infection and COVID-19 severity, we formed the COVID-19 Host Genetics Initiative1. Here we present a genome-wide association study meta-analysis of up to 125,584 cases and over 2.5 million control individuals across 60 studies from 25 countries, adding 11 genome-wide significant loci compared with those previously identified2. Genes at new loci, including SFTPD, MUC5B and ACE2, reveal compelling insights regarding disease susceptibility and severity.</p