Extremal basic frequency of non-homogeneous plates

In this paper we propose two numerical algorithms to derive the extremal principal eigenvalue of the bi-Laplacian operator under Navier boundary conditions or Dirichlet boundary conditions. Consider a non-homogeneous hinged or clamped plate $\Omega$, the algorithms converge to the density functions on $\Omega$ which they yield the maximum or minimum basic frequency of the plate

A Development Model for Identifying the Uncertainty Sources and Their Impacts on Bridge Construction Projects

Bridge construction projects are rife with uncertainty because of their unique features, from execution of the work, time estimation, inspection and assessment to fund allocation. Therefore, a critical step is recognise and categorise the uncertainties associated in bridge building in order to meet project objectives in terms of quality, cost, schedule, environmental, safety, and technical indicators. Various models, however, have been created to detect and prioritise the uncertainty. One of the most commonly used approaches for dealing with uncertainty is the spherical fuzzy set. To formulate an issue, this technique uses a mathematical procedure. The analytic hierarchy process (AHP), on the other hand, is a computer technique that solves a complicated problem by breaking it down into numerous basic problems. A hybrid model based on spherical fuzzy sets and AHP (SAHP) can benefit from both approaches. This study proposes a SAHP based on group decision making (GSAHP) to prioritise the sources of uncertainty in bridge construction projects. Likewise, a modified algorithm is proposed for checking the consistency of the spherical fuzzy matrices. To show the model potential, a real case study is illustrated and evaluated. The model demonstrates its capabilities in modelling uncertainty under an environment with a number of unknown components. The findings reveal that the “delays” factor is of the highest, and the “project team conflicts” parameter is of the least importance. The research findings could be used by decision makers and managers to develop preventive measures

Epidemiology of substance and opium use among adult residents of Tehran; a comprehensive report from Tehran cohort study (TeCS)

Background: The prevalence and burden of substance and opium use have increased worldwide over the past decades. In light of rapid population changes in Tehran, we aimed to evaluate the prevalence of opium and other substance use among adult residents in Tehran, Iran. Method: From March 2016 to March 2019, we utilized data from 8 296 participants in the Tehran Cohort Study recruitment phase (TeCS). We calculated the age-sex-weighted prevalence of substance use and the geographic distribution of substance use in Tehran. We also used logistic regression analysis to determine possible determinants of opium use. Result: We analyzed data from 8 259 eligible participants with complete substance use data and the average age of participants was 53.7 ± 12.75 years. The prevalence of substance use was 5.6% (95% confidence interval [CI]: 4.6- 7.1%). Substance use was more common in males than females (Prevalence: 10.5% [95% CI: 8.6- 12.6%] vs. 0.5% [95% CI: 0.2- 1.2%], respectively). The age-sex weighted prevalence of substance use was 5.4% (95% CI: 4.6-7.1%). Moreover, opium was the most frequently used substance by 95.8% of substance users. Additionally, we found that male gender (Odds ratio [OR]: 12.1, P < 0.001), alcohol intake (OR: 1.3, P = 0.016), and smoking (OR: 8.5, P < 0.001) were independently associated with opium use. Conclusions: We found that the prevalence of substance use in Tehran was 5.6%, and opium was the most frequently used substance. In addition, male gender, lower levels of education, alcohol, and tobacco consumption are the main risk factors for substance use in Tehran. Healthcare providers and policymakers can utilize our results to implement preventive strategies to minimize substance use in Tehran

HYSSOP and POLIUM could help to prevent COVID-19 in high-risk population: The results of a parallel randomized placebo-controlled field trial

243-253This study was conducted to evaluate the effect of HYSSOP (composed of Hyssopus officinalis L., Echium amoenum Fisch & C. A. Mey and Glycyrrhiza glabra L.) and POLIUM (contained Teucrium polium L., Cuscuta epithymum Murr and Cichorium intybus L.) combined distilled herbal medicines compared to placebo in the prevention of COVID-19. This is a double-blind parallel placebo-controlled field trial conducted on 751 asymptomatic individuals whose one of the family members recently had a positive RT-PCR test for COVID-19. They were divided into three groups including POLIUM, HYSSOP and placebo using random blocks with a 1:1:1 allocation ratio. Participants received daily 5 cc (under 12 years) or 10 cc (over 12 years) of allocated oral medications for 20 days. The primary outcome was the frequency of positive RT-PCR test among participants who became symptomatic. The mean age of participants was 36.6. Nineteen participants get infected by COVID-19 during the intervention; fifteen of them belonged to the placebo and four to the POLIUM group. Fisher's exact test indicated significant differences between HYSSOP and placebo (p<0.001) as well as POLIUM and placebo (p=0.009) groups in terms of COVID-19 confirmed by PCR tests. Cox regression model adjusted for confounders illustrated that the hazard of getting infection by COVID-19 in POLIUM and HYSSOP groups decreased by 66% (OR (95% CI): 0.34 (0.12 to 0.94); p=0.038) and 93% (OR (95% CI): 0.07 (0.01to 0.56); p=0.012) respectively, compared to placebo .Oral administration of HYSSOP and POLIUM with the other supportive health care could decrease the risk of getting COVID-19

An Evaluation of MTA Cements as Coronal Barrier

INTRODUCTION: Coronal leakage seems to play an important role in the failure of endodontic treatment. A double seal over root canal filling has been suggested as a means of improving the coronal seal. Several restorative materials have been used in an attempt to produce a coronal barrier. The purpose of this study was to assess gray-coloured mineral trioxide aggregate (GMTA), white-coloured mineral trioxide aggregate MTA (WMTA), and Principle (a resin-modified glass ionomer) as coronal barriers to bacterial leakage. MATERIALS AND METHODS: Fifty-one human anterior teeth were cleaned and obturated with gutta-percha and sealer. In group 1, teeth received a 3 mm barrier of GMTA. In groups 2 and 3, samples received WMTA and Principle, respectively. Obturated teeth without barrier were used as positive control and obturated teeth covered with epoxy resin were used as negative control. A leakage model utilizing Enterococcus faecalis used for the evaluation. Leakage was recorded when turbidity was observed. RESULTS: All controls behaved as expected. Three samples in group 1, three samples in group 2, and four samples leaked in group 3. There was no statistically significant difference in leakage between GMTA and WMTA or between GMTA and Principle. CONCLUSION: It seems that GMTA, WMTA and Principle can be recommended as a coronal barrier for up to 90 days

Optimal ground state energy of two-phase conductors

We consider the problem of distributing two conducting materials in a ball with fixed proportion in order to minimize the first eigenvalue of a Dirichlet operator. It was conjectured that the optimal distribution consists of putting the material with the highest conductivity in a ball around the center. In this paper, we show that the conjecture is false for all dimensions greater than or equal to two

An Evaluation of the Sealing Ability of MTA and Resilon: A Bacterial Leakage Study

INTRODUCTION: The purpose of this study was to evaluate the sealing ability of gray-colored mineral trioxide aggregate (GMTA), white-colored MTA (WMTA), and Resilon as root filling materials. MATERIALS AND METHODS: Sixty-six human maxillary central incisors were used in the present study. In the group A, 20 teeth were filled with GMTA. In the group B, 20 teeth were filled with WMTA and in the group C, 20 teeth were filled with Resilon/Epiphany. Three teeth were used as positive (obturated using the single gutta-percha cone technique without sealer) and three were used as negative (obturated with gutta-percha and AH-26 sealer, coated with two layers of nail varnish) controls. A bacterial leakage model utilizing Enterococcus faecalis was used for evaluation. Leakage was noted when turbidity was observed. RESULTS: Controls behaved as expected. In the group A (GMTA) three samples, in the group B (WMTA) four samples, and in the group C (Resilon/Epiphany), two samples were leaked. There was no statistically significant difference between GMTA and WMTA or GMTA and Resilon. CONCLUSION: In conclusion, sealing ability of GMTA and WMTA was similar to Resilon as orthograde root filling materials

Quantifying the Extruded Bacteria Following Use of Two Rotary Instrumentation Systems

INTRODUCTION: All instrumentation techniques have been reported to be associated with extrusion of infected debris. The aim of this study was to evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal instrumentation using the two engine-driven techniques utilizing nickel-titanium instruments (Flex Master and Mtwo). MATERIALS AND METHODS: Seventy extracted maxillary central incisor teeth were used. Access cavities were prepared and root canals were then contaminated with a suspension of Enterococcus faecalis and dried. The contaminated roots were divided into two experimental groups of 30 teeth each and one control group of 10 teeth. Group 1, Flex Master; Group2, Mtwo; Group 3, control group: no instrumentation was attempted. Bacteria extruded from the apical foramen during instrumentation were collected into vials. The microbiological samples from the vials were incubated in culture media for 24 h. Colonies of bacteria were counted and the results were given as number of colony-forming units. The obtained data were analyzed using the Kruskal-Wallis one-way analysis of variance and Mann-Whitney U-tests, with α = 0.05 as the level for statistical significance. RESULTS: Findings showed that there was no significant difference as to the number of extruded bacteria between two engine-driven systems (P&gt;0.05). CONCLUSION: Both engine-driven Nickel-Titanium systems extruded bacteria through the apical foramen

An Evaluation of Dentin’s Effect on the Antifungal Activity of MTA Cements

INTRODUCTION: The aim of this study was to evaluate the effect of dentin on the antifungal activity of gray and white-colored MTA (GMTA, WMTA) using a tube-dilution test. MATERIALS AND METHODS: MTA preparations were tested freshly mixed and after 24h on Candida Albicans (CA). The experiment was performed in 24-well culture plates. Fifty wells were used and divided into four experimental groups (freshly-mixed WMTA, freshly-mixed WMTA plus dentin powder, freshly-mixed GMTA, and freshly-mixed GMTA plus dentin powder) of 10 wells each and control groups of five wells each. Plates of Sabouraud dextrose agar mixed with CA served as positive control and Sabouraud dextrose agar without CA served as negative control. Fresh inoculate of CA was prepared by growing an overnight culture from a stock culture. Aliquots of CA were then taken from the stock culture and plated on the agar compound of the experimental and positive control group. All plates were incubated at 37°C for1h, 24h, and 72h. Growth of fungi was monitored daily by the presence of turbidity. Kruskal-Wallis test was used for statistical analysis. RESULTS: Results showed the inhibitory effect of dentin powder on the antifungal effect of MTA cements during 24h and 72h incubation periods, whereas, there was no significant difference between 1h incubation groups. CONCLUSION: The antifungal effect of freshly mixed MTA cements was decreased in the presence of dentin