Enamel Surface Roughness after Orthodontic Bracket Debonding and Composite Resin Removal by Two Types of Burs

Objective: Increased enamel surface roughness following orthodontic bracket debonding leads to increased plaque accumulation and enamel decalcification. Therefore, different methods are employed to achieve smoother enamel surfaces after bracket debonding. This study  compared enamel surface roughness following orthodontic bracket debonding and composite resin removal using white stone and tungsten carbide burs.Methods: In this in-vitro, experimental study, 20 first and second premolars of 10-20 year-olds were collected and their crowns were mounted in acrylic blocks. Roughness of the buccal surfaces of teeth was determined by atomic force microscopy (AFM) and the brackets were bonded to the teeth. After bracket debonding, composite remnants were removed using white stone and tungsten carbide burs. Parameters of enamel surface roughness were determined by AFM and time required for composite removal was also calculated. Repeated measures ANOVA was used to assess the changes in parameters based on the time of measurement, type of bur and their interaction effect. Time required for composite resin removal by bur was analyzed using one-way ANOVA and Tukey’s multiple comparisons.Results: Resin removal increased enamel surface roughness compared to the baseline values in all groups. However, no significant differences were noted between the two types of burs regarding arithmetic average of the roughness profile (Ra), the root mean square roughness (Rq) and the maximum peak-to-valley height in the sampling length (Rt) after resin removal. Time required for resin removal with tungsten carbide bur (34.2 seconds) was significantly shorter than with white stone bur (56.6 seconds)(both ps<0.0001).Conclusion: Considering the similar enamel surface roughness values achieved by the two burs, tungsten carbide burs are recommended for resin removal following orthodontic bracket debonding

Relationship between Dairy Product Consumption and Oligospermia; a Case-Control Study

Introduction: Infertility affects an estimated 15% of couples globally and in Iran, a quarter of Introduction: One of the current debates regarding men’s reproductive health is the declining sperm count and the role of nutritional and environmental factors. This study aims to investigate the association between dairy product consumption and oligozoospermia, sperm count of 5 to 15 million per milliliter of semen, in adult men.Materials and Methods: This age-matched case-control study was conducted on 102 oligozoospermia and 306 healthy men (control group). Both groups were recruited from an infertility clinic in Tehran, the Royan Institute. Dietary intake of subjects was collected using a valid and reliable 168-item food frequency questionnaire. Odds ratios (OR), ex-tracted from conditional logistic regression, were used to compare the occurrence of oligozoospermia by tertiles of dairy intake. Results: After adjusting for potential confounding variables, the high intake of low-fat dairy products was inversely associated with the risk of oligozoospermia (OR: 0.48; 95%CI: 0.24 – 0.95), (P =0.046). The higher intake of high–fat dairy products [(OR: 2.44; 95%CI: 1.26 – 4.73), (P =0.008)], high–fat milk [(OR: 2.16; 95%CI: 1.09 – 4.30), (P =0.043)], and ice creams [(OR: 2.37; 95%CI: 1.25 – 4.50), (P =0.008)] were also positively associated with oligozo-ospermia.Conclusion: The high intake of low–fat dairy foods seems to have a protective effect on oligozoospermia. Higher intake of high – fat dairy products, high– fat milk, and ice creams were associated with an increased risk of oligozo-ospermia.

Intraspecific Crossability in Andrographis paniculata Nees: A Barrier against Breeding of the Species

The ambiguity of crossability in Andrographis paniculata (AP) was pointed out in the present research. Accordingly, the effects of different style length and crossing time on intraspecific crossability of seven AP accessions in 21 possible combinations were investigated. The best results came out between 08:00 to 11:00 h for manual out-crossing of AP, while the time from 12:00 to 18:00 h showed a decreasing trend. Moreover, 12 mm style length was found as the most proper phenological stage in terms of stigmatic receptivity to perform out-crossing in this plant. All in all, AP behaved unlikely in each combination, and a significant difference was observed in crossability of AP accessions (P < 0.01). The lowest and highest crossability rate was found in hybrids 21 (11261NS × 11344K) and 27 (11322PA × 11350T) with 0.25% and 13.33%, respectively. Furthermore, a significant negative relationship between style length and crossibility (r2 = 0.762∗∗) was recorded in this research. As a final conclusion, crossing time and proper style length can improve the intraspecific crossability in the species, considerably. Despite all the mentioned contrivances, we still believe that a genetic incongruity should be involved as an additional obstacle in crossability of those combinations that failed or responded deficiently to outcrossing

An innovative method to assess clinical reasoning skills: Clinical reasoning tests in the second national medical science Olympiad in Iran

BACKGROUND: Clinical reasoning plays a major role in the ability of doctors to make a diagnosis and reach treatment decisions. This paper describes the use of four clinical reasoning tests in the second National Medical Science Olympiad in Iran: key features (KF), script concordance (SCT), clinical reasoning problems (CRP) and comprehensive integrative puzzles (CIP). The purpose of the study was to design a multi instrument for multiple roles approach in clinical reasoning field based on the theoretical framework, KF was used to measure data gathering, CRP was used to measure hypothesis formation, SCT and CIP were used to measure hypothesis evaluation and investigating the combined use of these tests in the Olympiad. A bank of clinical reasoning test items was developed for emergency medicine by a scientific expert committee representing all the medical schools in the country. These items were pretested by a reference group and the results were analyzed to select items that could be omitted. Then 135 top-ranked medical students from 45 medical universities in Iran participated in the clinical domain of the Olympiad. The reliability of each test was calculated by Cronbach's alpha. Item difficulty and the correlation between each item and the total score were measured. The correlation between the students' final grade and each of the clinical reasoning tests was calculated, as was the correlation between final grades and another measure of knowledge, i.e., the students' grade point average. RESULTS: The combined reliability for all four clinical reasoning tests was 0.91. Of the four clinical reasoning tests we compared, reliability was highest for CIP (0.91). The reliability was 0.83 for KF, 0.78 for SCT and 0.71 for CRP. Most of the tests had an acceptable item difficulty level between 0.2 and 0.8. The correlation between the score for each item and the total test score for each of the four tests was positive. The correlations between scores for each test and total score were highest for KF and CIP. The correlation between scores for each test and grade point average was low to intermediate for all four of the tests. CONCLUSION: The combination of these four clinical reasoning tests is a reliable evaluation tool that can be implemented to assess clinical reasoning skills in talented undergraduate medical students, however these data may not generalizable to whole medical students population. The CIP and KF tests showed the greatest potential to measure clinical reasoning skills. Grade point averages did not necessarily predict performance in the clinical domain of the national competitive examination for medical school students

From Beale Number to Pole Placement Design of a Free Piston Stirling Engine

In this paper, pole placement-based design and analysis of a free piston Stirling engine (FPSE) is presented and compared to the well-defined Beale number design technique. First, dynamic and thermodynamic equations governing the engine system are extracted. Then, linear dynamics of the free piston Stirling engine are studied using dynamic systems theory tools such as root locus. Accordingly, the effects of variations of design parameters such as mass of pistons, stiffness of springs, and frictional damping on the locations of dominant closed-loop poles are investigated. The design procedure is thus conducted to place the dominant poles of the dynamic system at desired locations on the s-plane so that the unstable dynamics, which is the required criterion for energy generation, is achieved. Next, the closed-loop poles are selected based on a desired frequency so that a periodical system is found. Consequently, the design parameters, including mass and spring stiffness for both power and displacer pistons, are obtained. Finally, the engine power is calculated through the proposed control-based analysis and the result is compared to those of the experimental work and the Beale number approach. The outcomes of this work clearly reveal the effectiveness of the control-based design technique of FPSEs compared to the well-known approaches such as Beale number

Effect of organoclay platelets on the mechanical properties of wood Á plastic composites formulated with virgin and recycled polypropylene

Abstract This study investigated the effects of organoclay platelet contents (0, 3 and 5 wt%) and polypropylene type (virgin and recycled) on the mechanical properties of polypropylene/wood flour composites. Composite samples were made by melt compounding and consequent injection moulding. The tensile, flexural and impact properties of resultant composites were determined. X-ray diffraction (XRD) analysis of composites with 3 and 5% nanoclay content was also conducted. The results indicated that tensile and flexural properties of the composites increased with the addition of nanoclay particles up to 3 wt% and decreased thereafter. The impact strength of the composites, however, decreased with the incorporation of nanoclay. The mechanical properties of the recycled polypropylene-based nanocomposites were statistically comparable with those based on virgin polypropylene. XRD analysis revealed that the degree of intercalation in the nanocomposites containing 3% nanoclay was higher than in those containing 5%. Based on these results, it can be concluded that recycled polypropylene could be used instead of virgin polypropylene in the production of value-added products with no significant adverse effects on the mechanical properties

Numerical Radius Inequalities for Finite Sums of Operators

In this paper, we obtain some sharp inequalities for numerical radius of finite sums of operators. Moreover, we give some applications of our result in estimation of spectral radius. We also compare our results with some known results

The relationship between perceived stress and pregnancy distress with self‐care of pregnant women: The mediating role of social support—A cross‐sectional study

Abstract Background and Aims Pregnancy is a stressful experience, which can affect different aspects of a woman's life. Yet, women with a supportive network of friends and family may experience lower stress and improved self‐care behavior. The study aimed to investigate the relationship between perceived stress and pregnancy distress with the self‐care of pregnant women, as well as the mediating role of social support. Methods This cross‐sectional study was conducted from February to May 2022 in Babol, Iran. A total of 157 pregnant women participated in the study. The participants completed five questionnaires, including a demographic and obstetric questionnaire, a Self‐care questionnaire, Perceived Social support (PSS), Perceived Stress Inventory (PSI), and Pregnancy Specific Distress. Structural equation modeling was used to test the hypothesis relationships among the variables. Results We found that Perceived stress (β = −0.221, p = 0.012β) and pregnancy distress (β = −0.203, p = 0.002β) had a negative and significant effect on the self‐care of pregnant women. Also, perceived stress (β = −0.429, p < 0.001β) and pregnancy distress (β = −0.381, p < 0.001β) had a negative and significant effect on the social support of pregnant women. The results exhibited a significant specific indirect effect between pregnancy distress, perceived stress, and pregnancy self‐care, with social support as the mediator: standardized indirect effect = −0.068, −0.076, respectively. Conclusion According to the findings, social support plays a direct and mediating role in improving self‐care behaviors among pregnant women. Therefore, providing strategies and measures to improve perceived social support by maternal health professionals may be expected to reduce the impact of stress on pregnant women's self‐care. The implementation of policies and social interventions to improve the social support of pregnant women can be one of the applications of the findings

The lack of association between different LDL‐C levels and oxidized LDL in patients with type 2 diabetes

Abstract Background High concentrations of low‐density lipoprotein cholesterol (LDL‐C) have been a known risk factor for cardiovascular diseases. Also, the role of oxidized LDL (ox‐LDL) in forming atherosclerosis plaque has been proven. However, it has not yet been proven that atherogenic LDL‐C by‐products like ox‐LDL will decrease by keeping the LDL levels at the desired level. This study aimed to examine the relationship between LDL‐C and ox‐LDL in different LDL‐C values in patients with type 2 diabetes (T2D). Methods In this cross‐sectional study, 347 patients with T2D who received statins were enrolled. LDL‐C values were defined into four groups as LDL‐C 100 mg/dL in patients with T2D. However, the revealed association of ox‐LDL with TG level and TG/HDL ratio may be considered in the clinic