High Temperature Behavior of Nano-Structured Ceramic Composites Studied by Mechanical Spectroscopy

Silicon nitride based ceramics (SiAlONs); tetragonal polycrystalline zirconia (3Y‐TZP); alumina and their composites reinforced with different amount of multi‐ walled carbon‐nanotubes (CNTs) have been processed by Spark Plasma Sintering (SPS). High temperature mechanical spectroscopy measurements were performed in each material between room temperature and 1600 K. In each of these materials, anelastic and viscoplastic relaxation phenomena were investigated and responsible mechanisms were explained. In particular, grain boundary (GB) sliding, which is responsible for high temperature plasticity in fine grained ceramics, gives rise to a peak or an exponential increase in the high temperature mechanical loss. Peak and exponential background depend on two forces, which control the GB sliding: a friction force due to the GB viscosity and a restoring force due to the elasticity of the surrounding grains. In the present thesis, ceramics and composites have been processed, which allow one to study the role played by these forces on the thermo‐ mechanical behavior of these refractory materials. SiAlON ceramics were chosen for studying the viscous force due to the inter‐granular glassy phase. In zirconia and alumina, it is shown how the CNT reinforcements may improve the restoring force and consequently the creep resistance. Different grades of SiAlON ceramics, processed with different sintering aids (Ca2+, Y3+, Yb3+), with oxygen rich (CaO, Y2O3 and Yb2O3) and nitrogen rich (CaH2, YN and YbN) compounds, have been studied. Mechanical spectroscopy has been used to analyze the behavior of the residual glassy phase, present after sintering, either as grain‐boundary glassy (GB) films or glass pockets located in GB triple junctions. The mechanical loss spectra show a relaxation peak, which is due to a relaxation phenomenon (the so called “α‐relaxation”) associated with the glass transition in the amorphous phase. The peak position depends on the glass viscosity and the peak height is mainly affected by the glassy phase amount and the SiAlON bimodal microstructure, namely equiaxed versus elongated grains. Moreover the peak height depends on the restoring force provided by the neighboring grains, which limit the GB sliding process. As a matter of fact, a good correlation between the mechanical loss peak and plastic deformation in a compression test has been observed. It is concluded that the elongated grains in the bimodal microstructure provide a higher restoring force, which limits the GB sliding of smaller equiaxed grains. In the case of equiaxed fine grained oxide ceramics, such as zirconia and alumina, the restoring force has been increased by CNT additions, which can reinforce the GBs. 3Y‐TZPcomposites with a homogenous distributions of CNTs, ranging within 0.5 – 5 wt%, were processed by SPS. A significant improvement in room temperature fracture toughness and shear modulus as well as creep performance at high temperature were obtained, and interpreted as due to the GB reinforcing role of the CNTs. To support this interpretation, high‐resolution electron microscopy and Raman spectroscopy have been carried out. Moreover, a remarkable enhancement of the electrical conductivity up to ten orders of magnitude due to CNT additions has been obtained with respect to the pure ceramics. The isothermal spectrum of the 3Y‐TZP composites (measured at 1600 K) is composed of a mechanical loss peak at a frequency of about 0.1 Hz, which is superimposed on an exponential increase at lower frequency. This is interpreted as primarily due to GB sliding. The absence of a well‐marked peak in monolithic 3Y‐ TZP is justified by considering that the restoring force decreases at low frequencies or high temperatures. Therefore, GB sliding is no more restricted and the mechanical loss increases exponentially, which is correlated to macroscopic creep. With CNT additions the mechanical loss decreases and the relaxation peak is better resolved with respect to the background. This is interpreted by the pinning effect of CNTs on GBs, providing addition source of restoring force, which can hinder GB sliding at high temperature, resulting in a creep resistance improvement. Similarly to 3Y‐TZP based composites, alumina specimens (3 different types of alumina powders) reinforced with different amount of CNTs were sintered by SPS. It is shown how the initial particle size of the powders may affect the dispersion of CNTs. Measurement of different properties, such as hardness, fracture toughness and mechanical loss at high temperature, have evidenced the crucial role of the CNT dispersion in the obtained mechanical properties

Sensitivity Analysis of Transient Storage Parameters in Mathematical Modeling of Pollution Transport in Rivers Containing Storage Zone

Hydrologists studying rivers must determine the relative importance of in-river processes to understand the fate of pollutants. Storage processes are one of the most of this. Currently, the most reliable method for determining the importance of storage processes in the solute transfer is to estimate the stream-storage exchange coefficient (α) and the cross-sectional area ratio (AS/A) in the transient storage model (TSM) with tracer experiment data (Wallis and Manson, 2019). Calibrating the parameters depends on the reciprocal coverage between parameter effects on BTCs and the model's sensitivity to each parameter (Zaramella et al., 2016). Previous studies have quantified the sensitivity of the TSM in inverse modeling (Kelleher et al., 2013; Wlostowski et al., 2013). Due to tracer test data for these studies, their results cannot provide a comprehensive picture of the model behavior. In this study, using Monte Carlo-based methods, an attempt has been made to investigate the effect of different pollutant transfer circumstances in the river by defining a framework with Peclet and Damkohler numbers and pollutant injection time series on storage parameters sensitivity

Practical In Situ Implementation of a Multicamera Multisystem Calibration

Consumer-grade cameras are generally low-cost and available off-the-shelf, so having multicamera photogrammetric systems for 3D reconstruction is both financially feasible and practical. Such systems can be deployed in many different types of applications: infrastructure health monitoring, cultural heritage documentation, bio-medicine, as-built surveys, and indoor or outdoor mobile mapping for example. A geometric system calibration is usually necessary before a data acquisition mission in order for the results to have optimal accuracy. A typical system calibration must address the estimation of both the interior and the exterior, or relative, orientation parameters for each camera in the system. This article reviews different ways of performing a calibration of a photogrammetric system consisting of multiple cameras. It then proposes a methodology for the simultaneous estimation of both the interior and the relative orientation parameters which can work in several different types of scenarios including a multicamera multisystem calibration. A rigorous in situ system calibration was successfully implemented and tested. The same algorithm is able to handle the equivalent to a traditional-style bundle adjustment, that is, a network solution without constraints, for a single or multicamera calibrations, and the proposed bundle adjustment with built-in relative orientation constraints for the calibration of a system or multiple systems of cameras

Effects of phosalone plant pesticide on sperm parameters and sexual hormone levels in Wistar rats: An experimental study

Background: Phosalone is an organophosphate insecticide, applied to control of plant pests. This compound has various side effects because it acts as an acetyl cholinesterase enzyme inhibitor. Objective: To investigate the effects of phosalone on the sperm parameters of and levels of sex hormones in adult male rats. Materials and Methods: In this experimental study, 16 adult (8-12 wk) male Wister rates (weighing 220-280 gr) were randomly assigned into 4 groups (n = 4/each). Group 1 (control) received only routine adequate water and food; Group 2, 3, and 4 received different low doses of phosalone (60, 90, and 120 mg/kg respectively). The rats were weighed and anesthetized after 48 days. Sperm parameters including number, motility, and viability as well as sex hormones (such as Luteinizing Hormone, Follicle Stimulating Hormone, and testosterone) were evaluated and compared after removing the epididymis tail. Results: Our results showed that phosalone decreased sperm motility, viability, and number in a dose-dependent manner. The level of FSH and LH was increased, and testosterone was decreased. Also, depending on the dose, phosalone decrease sperm motility and viability (p ≤ 0.001), while the level of FSH and LH was increased and testosterone was decreased (p = 0.861). Conclusion: Phosalone has negative effects on reproductive indices in male rats and can cause serious damage and decrease the number and sperms motility. It can also cause infertility due to changing the concentration of hormones. Key words: Organophosphate, Pesticides, Phosalone, Sperm, Sex hormones

The development and validation of teaching- learning process instrument in smart schools in educational system of the Islamic Republic of Iran

Background and Objectives:The purpose of the present descriptive-survey study is development and validation of teaching - learning process instrument in smart schools in educational system of the Islamic Republic of Iran. Methods: The research tool i.e. the researcher-made questionnaire was designed and implemented based on research background. First, the theoretical foundations and research background in this field were studied And three dimensions of indicators, components and tools were extracted and designed in the form of scale items. In the next step, to evaluate the validity of this scale, item analysis method was used and all items had the required validity more than 0.4. In addition, the reliability of the scale was determined and confirmed by Cronbach's alpha. then The designed questionnaire was provide after validation to statistical sample of 216 teachers of smart schools in Gorgan randomly selected based on the sample size formula in the academic year of 1395-1396. who were. Finally, The results were analyzed using descriptive and inferential statistical methods. Friedman test and one-sample t-test statistical techniques were used to analyze statistical data. Findings The results of this study show that the teaching and learning indicators in smart schools have the greatest impact on creating a dynamic and attractive environment for students' creativity and the least amount is related to the promotion of the assessment of high levels of thinking, knowledge and skills. In terms of teaching and learning components of intelligent schools, the highest level of influences is on teachers' familiarity with IT skills and the least amount on the promotion of critical thinking and students’ self-directedness. Also, regarding teaching and learning tools, smart schools have had the greatest impact on hybrid technology (film, image, etc.), and the least amount of influence on the production of blogs and educational sites. Conclusion: Smart schools are one of the most important achievements in the development of information technology in order to fundamentally change the educational system. Technology can be used as a powerful tool to improve the quality and efficiency of education, but it should be noted that the combination of information and communication technology with education and learning system is a multifaceted and complex process. According to the findings of the present study, in examining the infrastructure of smart schools, quantitative and qualitative aspects of indicators, components and effective tools of smartening up process should be considered. Undoubtedly, development of smart schools in the country will not be successful regardless of the attitude of the authorities, parents, students and most importantly teachers to this technology. In other words, to succeed in this, determining the factors affecting a positive attitude to technology-based learning is of particular importance because a positive attitude increases motivation and better acceptance of technology as well as active participation in the related activities. Moreover, With a scientific and technological view of the current situation of the country's educational system and producing various electronic content and empowering teachers in the field of information technology it is possible with a long term planning to provide a dynamic ground and bring about structural developments in all dimensions for the educational environment and the teaching-learning process in smart schools. In knowledge-based societies, the development of smart schools is welcomed as a way to train creative and entrepreneurial force and is considered as a way of sustainable development. According to this principle, the entry of our country into this field can provide the ground for increasing and sustainable development.   ===================================================================================== COPYRIGHTS  ©2020 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

Herbal therapy for hemorrhoids: An Overview of Medicinal Plants Affecting Hemorrhoids

Hemorrhoids are one of the most common rectal diseases that affect millions of people in the world and cause many medical and socio-economic problems. The resulting pain is very severe and incurs exorbitant costs for the patient and the government. This study aimed to review the medicinal plants that affect hemorrhoids. Complete databases searched for in those articles were Google Scholar, SID, Scopus, PubMed, Science Direct, and WOS search engines. The search was done for articles published that included the search term containing, medicinal plants and hemorrhoids in their title. This study focused on published articles and papers from 1991 to 2022.The results showed medicinal plants Aloe vera, Trigonella foenum-graecum L, Nigella sativa L, Curcuma longa L, Cocos nucifera L, Solanum nigrum L., Alhagi persarum Boiss & Buhse, Plantago lanceolata L, Achillea santolina, Malva neglecta Wallr,  Rubus fruticosus L  have effects like anti-bleeding, analgesic, anti-inflammatory,  and wound-healing, and with hemorrhoid-healing effect. Generally, the investigated traditional Iranian edible plants are rich in different types of chemical compounds and have special benefits in the prevention and treatment of diseases.Keywords: Medicinal plants; Hemorrhoids; Diseases; Remedy Drugs 

Study of VanA, B, C, D, E Genes in Vancomycin Resistant Enterococci Isolated from Retailed Dried Vegetables in Tehran, Iran

Background: Enterococcus spp. are resistant to many antimicrobials including vancomycin. They may be found in foods and water.Objective: In the current study, van genes were investigated in vancomycin resistant enterococci (VRE) isolated from dried vegetables in Tehran, Iran.Materials and Methods: In this study, 140 dried vegetable samples were collected from local retailers in Tehran, Iran, 2015. Bacteria were isolated using culture, biochemistry and molecular methods. Susceptibility of the enterococcal isolates was assessed to six antibiotics of ampicillin, chloramphenicol, erythromycin, gentamicin, tetracycline and vancomycin using Kirby-Bauer method. The prevalence of vanA, B, C, D, E genes was molecularly studied in VRE using polymerase chain reaction (PCR) and sequencing techniques.Results: Of 140 dried vegetable samples, Enterococcus spp. strains were isolated from 84 samples (60%). Totally, 48% of the isolates were resistant to vancomycin. Of 41 vancomycin-resistant enterococcal isolates, vanA was found in 23 (56.1%), vanB in 8 (19.5%) and vanC in 2 (4.9%) isolates. No vanD or vanE was found in the isolates. Results have shown a high rate of contamination with Enterococcus spp., especially VRE, in dried vegetables in Tehran.Conclusion: Therefore, further hygienic regulations such as personal training and food processing, transportation, storage and marketing must be routine in food industries and local retailers

Global age-sex-specific mortality, life expectancy, and population estimates in 204 countries and territories and 811 subnational locations, 1950–2021, and the impact of the COVID-19 pandemic: a comprehensive demographic analysis for the Global Burden of Disease Study 2021

Background: Estimates of demographic metrics are crucial to assess levels and trends of population health outcomes. The profound impact of the COVID-19 pandemic on populations worldwide has underscored the need for timely estimates to understand this unprecedented event within the context of long-term population health trends. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 provides new demographic estimates for 204 countries and territories and 811 additional subnational locations from 1950 to 2021, with a particular emphasis on changes in mortality and life expectancy that occurred during the 2020–21 COVID-19 pandemic period. Methods: 22 223 data sources from vital registration, sample registration, surveys, censuses, and other sources were used to estimate mortality, with a subset of these sources used exclusively to estimate excess mortality due to the COVID-19 pandemic. 2026 data sources were used for population estimation. Additional sources were used to estimate migration; the effects of the HIV epidemic; and demographic discontinuities due to conflicts, famines, natural disasters, and pandemics, which are used as inputs for estimating mortality and population. Spatiotemporal Gaussian process regression (ST-GPR) was used to generate under-5 mortality rates, which synthesised 30 763 location-years of vital registration and sample registration data, 1365 surveys and censuses, and 80 other sources. ST-GPR was also used to estimate adult mortality (between ages 15 and 59 years) based on information from 31 642 location-years of vital registration and sample registration data, 355 surveys and censuses, and 24 other sources. Estimates of child and adult mortality rates were then used to generate life tables with a relational model life table system. For countries with large HIV epidemics, life tables were adjusted using independent estimates of HIV-specific mortality generated via an epidemiological analysis of HIV prevalence surveys, antenatal clinic serosurveillance, and other data sources. Excess mortality due to the COVID-19 pandemic in 2020 and 2021 was determined by subtracting observed all-cause mortality (adjusted for late registration and mortality anomalies) from the mortality expected in the absence of the pandemic. Expected mortality was calculated based on historical trends using an ensemble of models. In location-years where all-cause mortality data were unavailable, we estimated excess mortality rates using a regression model with covariates pertaining to the pandemic. Population size was computed using a Bayesian hierarchical cohort component model. Life expectancy was calculated using age-specific mortality rates and standard demographic methods. Uncertainty intervals (UIs) were calculated for every metric using the 25th and 975th ordered values from a 1000-draw posterior distribution. Findings: Global all-cause mortality followed two distinct patterns over the study period: age-standardised mortality rates declined between 1950 and 2019 (a 62·8% [95% UI 60·5–65·1] decline), and increased during the COVID-19 pandemic period (2020–21; 5·1% [0·9–9·6] increase). In contrast with the overall reverse in mortality trends during the pandemic period, child mortality continued to decline, with 4·66 million (3·98–5·50) global deaths in children younger than 5 years in 2021 compared with 5·21 million (4·50–6·01) in 2019. An estimated 131 million (126–137) people died globally from all causes in 2020 and 2021 combined, of which 15·9 million (14·7–17·2) were due to the COVID-19 pandemic (measured by excess mortality, which includes deaths directly due to SARS-CoV-2 infection and those indirectly due to other social, economic, or behavioural changes associated with the pandemic). Excess mortality rates exceeded 150 deaths per 100 000 population during at least one year of the pandemic in 80 countries and territories, whereas 20 nations had a negative excess mortality rate in 2020 or 2021, indicating that all-cause mortality in these countries was lower during the pandemic than expected based on historical trends. Between 1950 and 2021, global life expectancy at birth increased by 22·7 years (20·8–24·8), from 49·0 years (46·7–51·3) to 71·7 years (70·9–72·5). Global life expectancy at birth declined by 1·6 years (1·0–2·2) between 2019 and 2021, reversing historical trends. An increase in life expectancy was only observed in 32 (15·7%) of 204 countries and territories between 2019 and 2021. The global population reached 7·89 billion (7·67–8·13) people in 2021, by which time 56 of 204 countries and territories had peaked and subsequently populations have declined. The largest proportion of population growth between 2020 and 2021 was in sub-Saharan Africa (39·5% [28·4–52·7]) and south Asia (26·3% [9·0–44·7]). From 2000 to 2021, the ratio of the population aged 65 years and older to the population aged younger than 15 years increased in 188 (92·2%) of 204 nations. Interpretation: Global adult mortality rates markedly increased during the COVID-19 pandemic in 2020 and 2021, reversing past decreasing trends, while child mortality rates continued to decline, albeit more slowly than in earlier years. Although COVID-19 had a substantial impact on many demographic indicators during the first 2 years of the pandemic, overall global health progress over the 72 years evaluated has been profound, with considerable improvements in mortality and life expectancy. Additionally, we observed a deceleration of global population growth since 2017, despite steady or increasing growth in lower-income countries, combined with a continued global shift of population age structures towards older ages. These demographic changes will likely present future challenges to health systems, economies, and societies. The comprehensive demographic estimates reported here will enable researchers, policy makers, health practitioners, and other key stakeholders to better understand and address the profound changes that have occurred in the global health landscape following the first 2 years of the COVID-19 pandemic, and longer-term trends beyond the pandemic