The effect of temperature, time of curing and Na2O/SiO2 molar ratio on mechanical and chemical properties of geopolymer cement

The geopolymer cement is a suitable alternative material for Portland cement due to their environmental compatibility, low curing temperature, and high strength. In this research, Kaolin was used as a raw material for the construction of a geopolymer cement, while sodium hydroxide was an alkali hydroxide. Kaolin is calcined at 750 °C to obtain meta-kaolin. Geopolymer samples were prepared at various curing temperatures (25, 50, and 75 °C), different curing times (3, 7, 21, 28, and 60 days) and with different activator ratios (0.6-0.9). The thermal analysis of kaolin was done via DTA/TGA. Investigation on the geopolymer cement structure and phases were performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and magic angle spinning nuclear magnetic resonance (MAS-NMR). Also, the effects of temperature and time of curing and Na2O/SiO2 molar ratio were studied. The results showed that the maximum compressive strength was 115MPa, which obtained at a molar ratio of Na2O/SiO2=0.9, a curing time of 60 days, and a curing temperature of 75 °C. The microstructure of cement was studied using scanning electron microscopy (SEM)

Synthesis of Cu-CNTs nanocomposites via double pressing double sintering method

In this research, copper (Cu)-carbon nanotubes (CNTs) nanocomposites were synthesized with different weight percentages of CNTs by double pressing double sintering (DPDS) method as well as conventional sintering method. A planetary ball mill was used to disperse CNTs in Cu matrix. The milled powders were first cold pressed to 450 MPa in a uniaxial stainless-steel die with cylindrical compacts (diameter: 12 mm and height: 5 mm). The effect of CNTs content and the DPDS method on the properties of the nanocomposites were investigated. The microstructure and phase analysis of Cu-CNTs nanocomposite samples were studied by FESEM and X-Ray Diffraction. The electrical conductivity of nanocomposites was measured and compared to both sintering methods. Mechanical properties of Cu-CNTs nanocomposites were characterized using bending strength and micro-hardness measurements. Enhancements of about 32% in bending strength, 31.6% in hardness and 19.5% in electrical conductivity of Cu-1 wt.% CNTs nanocomposite synthesized by DPDS method were observed as compared to Cu-1 wt.% CNTs nanocomposites fabricated under the similar condition by a conventional sintering process

Electrical and mechanical properties of Cu-CNT nanocomposites sintered by microwave technique

In this research, multiwall carbon nanotubes were dispersed in a copper matrix using a planetary ball mill. The mixed powders were compacted using a uniaxial hydraulic presser. A novel method of microwave sintering was applied to consolidate Cu-CNT nanocomposites Conventional sintering method was also used to sinter samples to investigate the effects of applied methods on the properties of the sample. Sintering time was reduced to 20 min using microwave sintering method. The morphology and phase analysis of nanocomposites were studied by FESEM and XRD. The physical and mechanical properties of Cu-CNT nanocomposites were characterized using electrical conductivity, bending strength, and micro-hardness. The results show that the mechanical properties of Cu-CNT nanocomposites are improved significantly by microwave route. The optimum hardness and bending strength were obtained for 4 vol. % CNT as an optimum amount of reinforcement

Prevalence survey and assessment of risk factors of musculoskeletal disorders among municipality workers in Isfahan city

زمینه و هدف: اختلالات اسکلتی- عضلانی (Musculoskeletal disorders= MSDs) از مهمترین عوامل ناتوانی شغلی در جهان هستند. این موضوع باعث شده که امروزه در دنیا تحقیقات زیادی در زمینه ارزیابی و کنترل این اختلالات انجام شود. مطالعه حاضر با هدف تعیین میزان شیوع و ارزیابی ریسک ابتلا به اختلالات اسکلتی- عضلانی در کارگران مشاغل فضای سبز در شهر اصفهان انجام شد. روش بررسی: در این مطالعه مقطعی، وظایف مختلف کارگر در فیلد فضای سبز مطالعه شدند. در هر عنوان وظیفه 12 کارگر و در مجموع 108 نفر انتخاب و به مطالعه راه یافتند. میزان شیوع درد ناشی از اختلالات اسکلتی- عضلانی با استفاده از پرسشنامه نوردیک و برای ارزیابی خطر ابتلا به اختلالات اسکلتی- عضلانی از روش QEC (Quick exposure check) استفاده شد. یافته ها: بر اساس نتایج حاصل از پرسشنامه نوردیک، 4/82 درصد از افراد این مطالعه در دستگاه اسکلتی- عضلانی دچار درد و ناراحتی بودند که بیشترین شیوع این اختلالات در ناحیه زانو (3/59 درصد) و کمر (8/52 درصد) گزارش شد. در جامعه مورد مطالعه بین سطح ریسک ارگونومیک کار و شیوع علایم اختلالات اسکلتی- عضلانی، ارتباط معنی داری وجود داشت (001/0>P). نتیجه گیری: از آنجایی که در 2/47 درصد از گروه های کاری مطالعه شده، سطح ریسک بالا و بسیار بالاست لازم است اقدامات اصلاحی و کنترلی هرچه زودتر شروع گردد. بر اساس ، عمده ترین مشکل ارگونومیکی در مشاغل فضای سبز پوسچر (Posture) نامطلوب، کارهای توأم با حرکات تکراری، خمش و پیچش کمر می باشد

Fabrication of functionally graded Ni-Al2O3 nanocomposite coating and evaluation of its properties

In this study, functionally graded Ni-Al2O3 composite coating (FGN-A) has been produced from nickel Watt’s bath containing different concentrations of Al2O3 particles. For this, different composite coatings were electroplated in the same bath with different particles concentration to find the optimum concentration of particles in which the maximum content with uniform distribution of Al2O3 particles in the coating can be achieved. So, Al2O3 concentration was continuously increased in the electroplating bath. The composite coatings were characterized by SEM and EDS. Structure and phase composition were identified by XRD analysis. Microhardness of the coatings was evaluated employing Vickers Instrument. Three-point bend test was carried out to compare the adhesion strength of the coatings and dry sliding wear tests were performed using a pin-on-disk wear apparatus. Study on the resulting sample shows that FGN-A by Al2O3 gradient distribution in cross-section is coated successfully. By increasing Al2O3 particles content in Ni matrix, microhardness grows from interface toward the surface of the coating. The result of bending test show that the functionally graded composite coating shows excellent adhesion to substrate compared with the uniformly distributed Ni-Al2O3 (UN-A) on the same substrate. This has been attributed to lower mechanical mismatch between coating and substrate in functionally graded composite coating compared with uniformly distributed one. The results of wear resistance measurements test revealed that wear resistances of functionally graded Ni-Al2O3 is higher than that of ordinary distributed composite coating

Characteristics of Astigmatism after MyoRing Implantation

Considering the rising number of MyoRing implantation procedures in keratoconic corneas and the refractive outcomes associated with this treatment modality, this study aimed to evaluate and compare the magnitude and axis orientation of total and corneal astigmatism between before and after MyoRing implantation in 34 eyes of 28 patients with keratoconus (KCN) (mean age: 29.41 ± 7.0 years). The inclusion criterion was a reliable diagnosis of clinical KCN based on corneal biomicroscopic and tomographic findings. The mean total astigmatism of ocular refraction decreased significantly from -4.27 ± 3.15 D (before MyoRing implantation) to -2.18 ± 1.63 D (after MyoRing implantation) (P < 0.001). The mean astigmatism in the anterior and posterior surface of the cornea decreased significantly by 1.16 D (P = 0.001) and 0.24 D (P = 0.009), respectively, after MyoRing implantation. Before MyoRing implantation, the axis orientation of total ocular astigmatism for with-the-rule, oblique, and against-the-rule astigmatism was 21%, 42%, and 37%, respectively; at 6 months after MyoRing implantation, it was 18%, 24%, and 58%, respectively. Before MyoRing implantation, the axis orientation for with-the-rule, against-the-rule, and oblique astigmatism of the anterior surface of the cornea was 59%, 24%, and 17%, respectively; at 6 months after MyoRing implantation, it was 52%, 24%, and 24%, respectively. Before MyoRing implantation, the axis orientation of with-the-rule, oblique, and against-the-rule astigmatism of the posterior surface of the cornea was 68%, 29%, and 3%, respectively; at 6 months after MyoRing implantation, it was 67%, 12%, and 12%, respectively. MyoRing implantation significantly decreased the amount of total, anterior, and posterior corneal astigmatism

Novel compound heterozygous variants in XYLT1 gene caused Desbuquois dysplasia type 2 in an aborted fetus: a case report

Background Desbuquois dysplasia type 2 (DBQD2) is an infrequent dysplasia with a wide range of symptoms, including facial deformities, growth retardation and short long bones. It is an autosomal recessive disorder caused by mutations in the XYLT1 gene that encodes xylosyltransferase-1. Case presentation We studied an aborted fetus from Iranian non-consanguineous parents who was therapeutically aborted at 19 weeks of gestation. Ultrasound examinations at 18 weeks of gestation revealed growth retardation in her long bones and some facial problems. Whole-exome sequencing was performed on the aborted fetus which revealed compound heterozygous XYLT1 mutations: c.742G>A; p.(Glu248Lys) and c.1537 C>A; p.(Leu513Met). Sanger sequencing and segregation analysis confirmed the compound heterozygosity of these variants in XYLT1. Conclusion The c.1537 C>A; p.(Leu513Met) variant has not been reported in any databases so far and therefore is novel. This is the third compound heterozygote report in XYLT1 and further supports the high heterogeneity of this disease

Corneal topography and higher-order aberrations in patients with type 2 diabetes mellitus

Background: Changes in blood sugar levels cause alterations in the anterior segment and retina of the eye. This study was aimed at evaluating corneal topography, aberrometry, and corneal asphericity in patients with treatment-naive type 2 diabetes mellitus (T2DM). Methods: Participants with treatment-naive T2DM were enrolled in this cross-sectional study. The inclusion criteria were glycated hemoglobin A1c (Hb A1c) greater than or equal to 7.5% and absence of other ocular or systemic diseases. Patients who refused to participate or had a history of topical or systemic steroid use, hyperlipidemia, hypertension, anemia, prior ocular disorder or surgery, diabetic retinopathy, glaucoma, cataract, active ocular inflammatory or infectious disease, or contact lens use were excluded. All participants underwent a comprehensive ophthalmic examination. The Pentacam HR Scheimpflug tomography system (Pentacam High Resolution; Oculus, Wetzlar, Germany) was used to measure the anterior-segment parameters. Results: Sixty eyes of 30 patients with a male-to-female ratio of 1:1 were included; the mean (standard deviation [SD]) age and Hb A1c were 51.63 (6.73) years and 8.82% (1.31%), respectively. The mean (SD) values of central corneal thickness, root mean square (RMS) of total aberration, RMS of lower-order aberrations, RMS of higher-order aberrations, spherical aberration, 0° coma, 90° coma, flat anterior keratometry (K), steep anterior K, mean anterior K, anterior topographic astigmatism, flat posterior K, steep posterior K, mean posterior K, posterior topographic astigmatism, anterior corneal asphericity, and posterior corneal asphericity were 540.22 (24.47) µm, 1.72 (0.73) µm, 1.63 (0.73) µm, 0.51 (0.17) µm, + 0.31 (0.09) µm, - 0.06 (0.15) diopters (D), 0.003 (0.21) D, 43.87 (1.49) D, 44.69 (1.50) D, 44.28 (1.44) D, + 0.82 (0.83) D, - 6.25 (0.27) D, - 6.55 (0.31) D, - 6.40 (0.28) D, - 0.30 (0.15) D, - 0.32 (0.12) Q-value, and - 0.47 (0.17) Q-value, respectively. Conclusions: We presented the mean values of Pentacam parameters for aberrometry, keratometry, and corneal asphericity in patients with treatment-naive T2DM. These values could serve as a baseline for prospective monitoring of the ocular health status of this cohort and for comparison with future cohorts of patients with well-controlled T2DM. Further studies are required to assess the presence and applicability of ocular changes following intensive blood glucose control in T2DM and further understand the related pathophysiology

Screening Characteristics of Bedside Ultrasonography in Confirming Endotracheal Tube Placement; a Diagnostic Accuracy Study

Introduction: Confirmation of proper endotracheal tube placement is one of the most important and lifesaving issues of tracheal intubation. The present study was aimed to evaluate the accuracy of tracheal ultrasonography by emergency residents in this regard.  Method: This was a prospective, cross sectional study for evaluating the diagnostic accuracy of ultrasonography in endotracheal tube placement confirmation compared to a combination of 4 clinical confirmation methods of chest and epigastric auscultation, direct laryngoscopy, aspiration of the tube, and pulse oximetry (as reference test).Results: 150 patients with the mean age of 58.52 ± 1.73 years were included (56.6% male). Sensitivity, specificity, positive predictive value, negative predictive value, and positive and negative likelihood ratio of tracheal ultrasonography in endotracheal tube confirmation were 96 (95% CI: 92-99), 88 (95% CI: 62-97), 98 (95% CI: 94-99), 78 (95% CI: 53-93), 64 (95% CI: 16-255), and 0.2 (95% CI: 0.1-0.6), respectively.Conclusion: The present study showed that tracheal ultrasonography by trained emergency medicine residents had excellent sensitivity (>90%) and good specificity (80-90) for confirming endotracheal tube placement. Therefore, it seems that ultrasonography is a proper screening tool in determining endotracheal tube placement

Correlation between Altmetric and Scientometric Indicators

Objective: Despite the increasing attention to altmetric indicators in scientometric research, there is still doubt about the validity of these indicators in evaluating research. The purpose of this study was to investigate the relationship between scientometric and altmetric indices on scientific products. Materials and Methods: In the altmetric indices section, five indicator classes presented in Scopus and 36 sub-indices were examined. The Spearman correlation indicator was used to evaluate the correlation between altmetric and scientometric indices. The SPSS software version 16 was used to analyze data. The significance level was also considered less than 0.05. Results: The correlation between the number of citations to documents and Usage, Citations, and Capture was significant. There was no significant relationship between social media and mention. Also, there is a significant and positive relationship between the citations to documents and sub-indices of Abstract views, Link out, Readers, Export/saves, and Citation indicator. Conclusion: Given the important relationship between citation rates and altmetric indicators, it can be said that web-based platforms like scientific databases or social media that are publicly accessible play a very important role in increasing the visibility and citation rate and thus the effectiveness of research