In vitro assessment of cytotoxicity of giomer on human gingival fibroblasts

Root coverage on restored root surfaces has been considered as a challenging issue. The evaluation of cytotoxic effects of restorative materials is a fundamental requirement for sustaining the cell attachment and the clinical success of root coverage. The aim of the present study was to compare the human gingival fibroblast cytotoxicity of the recently introduced giomer composite (GC) with resin ionomer (RI) restorative material. Discs (6x2 mm) of GC and RI restorative materials were prepared using sterile Teflon mold. Extracts from the materials were incubated to cell culture medium for 24, 48 and 72 h. Human gingival fibroblasts (HGF) were exposed to the extracts of the materials while the un-incubated media served as the control group. The cytotoxicity of the materials were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In order to compare the mean values of the measured parameters a Kruskal-Walis test was carried out. MTT assay indicated that human gingival fibroblasts proliferated well in the presence of GC extract. The proliferation rate was higher in cells incubated with GC compared to RI extracts but the differences were not statistically significant (p= 0.09). This in vitro study indicated that GC is a non-toxic material for HGF. However, further studies are needed to assess the other biologic and clinical behavior of this material prior to it being considered as a potentially suitable restorative material to restore the carious root lesions candidated to root coverage procedures

Human Umbilical Cord Blood Stem Cells Differentiate into Keratinocytes under In Vitro Conditions and Culturing Differentiated Cells on Bacterial Cellulose Film

Mesenchymal stem cells (MSC) are capable of self renewing and differentiating into other cell types. Human umbilical cord blood (HUCB) has been investigated as an alternative source to bone marrow. The aim of our examinations was to investigate MSC of HUCB could differentiate into keratinocytes under in vitro conditions. In this study, we examined the differentiation with chemical compounds, then to identify the stem cells are differentiated or not, PCR by using the expression of gene cytokeratin 18 was performed and to examine the proliferation characteristic of differentiated keratinocyte from HUCBMSCs, cultured them on cellulose film. Analysis of PCR confirmed the expression of cytokeratin 18 in keratinocytes; results of our study show that cellulose film isn’t a compatible substrate for differentiated keratinocytes. And growth factor, BMP4, with hydrocortisone and ascorbic acid with specific amounts is an appropriate induction factor for inducing of differentiation into keratinocytes

In vitro assessment of cytotoxicity of giomer on human gingival fibroblasts

Root coverage on restored root surfaces has been considered as a challenging issue. The evaluation of cytotoxic effects of restorative materials is a fundamental requirement for sustaining the cellattachment and the clinical success of root coverage. The aim of the present study was to compare the human gingival fibroblast cytotoxicity of the recently introduced giomer composite (GC) with resinionomer (RI) restorative material. Discs (6×2 mm) of GC and RI restorative materials were prepared using sterile Teflon mold. Extracts from the materials were incubated to cell culture medium for 24, 48and 72 h. Human gingival fibroblasts (HGF) were exposed to the extracts of the materials while the unincubated media served as the control group. The cytotoxicity of the materials were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. In order to compare the mean values of the measured parameters a Kruskal-Walis test was carried out. MTT assay indicated that human gingival fibroblasts proliferated well in the presence of GC extract. The proliferation rate washigher in cells incubated with GC compared to RI extracts but the differences were not statistically significant (p= 0.09). This in vitro study indicated that GC is a non-toxic material for HGF. However, further studies are needed to assess the other biologic and clinical behavior of this material prior to it being considered as a potentially suitable restorative material to restore the carious root lesions candidated to root coverage procedures

Phase Stability, Microstructure, and Mechanical Properties of Spark Plasma Sintered Nanocrystalline Boron-Doped AlCoFeMnNi High-Entropy Alloy

The microstructure and mechanical properties of mechanically alloyed and spark plasma sintered AlCoFeMnNi₋ₓB (x = 0, 0.5, 1, and 5 at. %) high-entropy alloys (HEAs) have been investigated. Boron-doped HEAs were synthesized using mechanical alloying up to 50 h of milling. Synthesized powders were then consolidated at 850, 900, and 950 °C for 10 min under a uniaxial pressure of 40 MPa using spark plasma sintering (SPS). A scanning electron microscope, which was equipped with energy dispersive spectroscopy (EDS), together with an optical microscope (OM) were used to analyze the microstructural evolution. X-ray diffraction analysis was used to differentiate the phases formed in the solution. The mechanical properties of the sintered specimens were analyzed using the shear-punch test (SPT). The fracture surface of the SPT samples was studied using SEM. Thermodynamic calculations revealed that by employing this process, it is possible to produce solid solution HEAs with a duplex FCC + BCC structure. It was shown that boron-doped AlCoFeMnNi high-entropy alloys contain some unique attributes. SPS at 900 °C for a sample with boron up to 0.5 at. % leads to the formation of an alloy with the highest shear strength. A further increase in the boron content in the boron-doped HEAs exhibited a decrease in the maximum shear strength. Finally, the correlations between the microstructural and mechanical characteristics of the sintered boron-containing high-entropy alloys are discussed

Survival analysis in gastric cancer: A multi-center study among Iranian patients

Background: Gastric cancer (GC) has been considered as the 5th most common type of cancer and the third leading cause of cancer-associated death worldwide. The aim of this historical cohort study was to evaluate the survival predictors for all patients with GC using the Cox proportional hazards, extended Cox, and gamma-frailty models. Methods: This historical cohort study was performed according to documents of 1695 individuals having GC referred to three medical centers in Iran from 2001 to 2018. First, most significant prognostic risk factors on survival were selected, Cox proportional hazards, extended Cox, gamma-frailty models were applied to evaluate the effects of the risk factors, and then these models were compared with the Akaike information criterion. Results: The age of patients, body mass index (BMI), tumor size, type of treatment and grade of the tumor increased the hazard rate (HR) of GC patients in both the Cox and frailty models (P < 0.05). Also, the size of the tumor and BMI were considered as time-varying variables in the extended Cox model. Moreover, the frailty model showed that there is at least an unknown factor, genetic or environmental factors, in the model that is not measured (P < 0.05). Conclusions: Some prognostic factors, including age, tumor size, the grade of the tumor, type of treatment and BMI, were regarded as indispensable predictors in patients of GC. Frailty model revealed that there are unknown or latent factors, genetic and environmental factors, resulting in the biased estimates of the regression coefficients. © 2020 The Author(s)

The role of rock joint frictional strength in the containment of fracture propagation

The fracturing phenomenon within the reservoir environment is a complex process that is controlled by several factors and may occur either naturally or by artificial drivers. Even when deliberately induced, the fracturing behaviour is greatly influenced by the subsurface architecture and existing features. The presence of discontinuities such as joints, artificial and naturally occurring faults and interfaces between rock layers and microfractures plays an important role in the fracturing process and has been known to significantly alter the course of fracture growth. In this paper, an important property (joint friction) that governs the shear behaviour of discontinuities is considered. The applied numerical procedure entails the implementation of the discrete element method to enable a more dynamic monitoring of the fracturing process, where the joint frictional property is considered in isolation. Whereas fracture propagation is constrained by joints of low frictional resistance, in non-frictional joints, the unrestricted sliding of the joint plane increases the tendency for reinitiation and proliferation of fractures at other locations. The ability of a frictional joint to suppress fracture growth decreases as the frictional resistance increases; however, this phenomenon exacerbates the influence of other factors including in situ stresses and overburden conditions. The effect of the joint frictional property is not limited to the strength of rock formations; it also impacts on fracturing processes, which could be particularly evident in jointed rock masses or formations with prominent faults and/or discontinuities

Determination of nutritional status and is effective factors among the elderly

Nutritional status is effective in individuals' health and ability. In fact, inappropriate food intake during old ages results in nutritional shortcomings, incidence of many special disorders, and consumption of many health services. This Cross sectional study was conducted to assessment nutritional status and assess impact of some medical and life style factor on nutritional status in Iranian Community-Dwelling Older Adults. Study was conducted on 240 individuals over 60 years of age Nutritional status was assessed using the short form of Mini Nutrition Assessment (MNA) questionnaire. Data were analyzed using chi-square test, ANOVA, and regression model. According to the results, 140(58.3) of the samples were female, with the mean age of 66.98 +/- 6.23 years. Besides, 39(16.2) of the participants had malnutrition, 162 (67.5) were exposed to malnutrition, and 39(16.2) had normal nutritional status. The results showed a significant relationship between nutritional status and some anthropometric measures, such as weight (P=0.050), calf circumference (P=0.040), and arm circumference (P=0.000). Also, a significant relationship was found between the total score of the questionnaire and the subjects' sex (P=0.001) and age (P=0.001). This study indicated the necessity for the health system to pay more attention to the elderly's nutritional screening. In addition, nutritional status screening should be performed more carefully in geriatrics care programs

EFFECT OF ANNEALING ON MICROSTRUCTURE AND CORROSION PERFORMANCE OF ADB AND ALB ALLOYS

Microstructure and corrosion performance of admiralty brass (ADB) and aluminum brass (ALB) alloys after passing different annealing heat treatments were investigated using optical and scanning electron microscope, energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), DC polarization measurements and electrochemical impedance spectroscopy (EIS). The results showed that heat treating of ALB caused gradient in aluminum concentration across the grains whose increased with increasing of annealing temperature. On the other hand, corrosion current density (i corr) of ADB in 3.5%NaCl media decreased with increasing of recrystallization, while ALB showed corrosion behavior inconsistent with ADB. The impedance measurements showed that corrosion rate of ADB decreased with increasing of exposure time from 0 to 15 days which could be related to the formation of SnO 2 surface film and the Sn-rich phases. While polarization resistance of ALB decreased by passing days in the corrosive media which could be associated to establishing of differential aluminum concentration cells

A novel trapezoidal profile of optimized diffraction grating for light trapping in thin silicon solar cells

In this paper, we propose a new design and comprehensive optimization process for improving the diffraction gratings used as the back reflector of silicon solar cells. For this process, the optimum refractive index and its corresponding available material which can be used as the grating material has been chosen as 1.57 and SiO2, respectively. Also, all of geometric parameters which affect the performance of the grating, such as periodicity, height and depth of grating profiles have been studied and the appropriate values for each of them have been proposed. In order to optimize the profile of grating, a transition from triangular to rectangular structure has been considered and finally a specific trapezoidal profile has been chosen as the optimized grating back reflector which enhances the cell efficiency up to 6%. Simulation results show that the different grating profiles have the same duty cycle and therefore use the same amounts of materials