Rheology, Properties and Microstructure Development of Polymer/Carbon Nanotube Composites in Microinjection Molding Process

RÉSUMÉ Dans le cadre de cette thèse des concepts nouveaux pour l'alignement des nanotubes de carbone multi-couche (MWCNT) induit par le cisaillement, la caractérisation de MWCNT / polymères nanocomposites et la fabrication par microinjection de pièces à base de nanocomposites optimisés sont présentés. Les effets des microstructures et des morphologies développées dans diverses conditions, de mise en oeuvre par le procédé de micromoulage sur les propriétés rhéologiques, électriques et mécaniques de nanocomposites à base de CNT sont étudiés. Le développement dans la technologie des microsystèmes et la demande constante de dispositifs fonctionnels à des échelles de longueur de plus en plus petites a imposé l'application du procédé de moulage par microinjection comme une technologie clé dans ce domaine. Le moulage par microinjection est un procédé relativement nouveau avec un grand potentiel de production en série de microdispositifs comprenant des détails d’un niveau de complexité élevé qu’il n’est pas possible de fabriquer par les techniques de moulage par injection classique. Il s'agit d'un nouveau domaine de recherche et on s'attend à une croissance continue au cours des dix prochaines années, étant donné la tendance croissante à la miniaturisation des composants et l'augmentation de la demande de microdispositifs. Les nanotubes de carbone sont des matériaux de grande utilité dans ce contexte avec des conductivités électrique et thermique supérieures et des propriétés mécaniques extrêmement importantes, essentiellement dues à leur structure et à leur facteur de forme élevé. Par conséquent, les nanocomposites à base de CNT dans une matrice de polymère sont des matériaux prometteurs pour la fabrication de micropièces multifonctionnelles ayant des propriétés uniques pour une large gamme d'applications. L’étude des propriétés rhéologiques des matériaux composites, notamment leur comportement viscoélastique a non seulement une importance pratique, liée à leur mise en oeuvre, mais a aussi un intérêt scientifique, car elle peut être utilisée comme une sonde de la microstructure des composites investigués. Par conséquent, une recherche fondamentale est nécessaire pour établir la relation entre le comportement rhéologique, les conditions de mise en oeuvre et les propriétés finales des pièces en composites à base de nanotubes de carbone / polymère par le procédé de microinjection.----------Carbon nanotubes (CNTs) are great materials with superior electrical and thermal conductivity, mechanical properties and high aspect ratio. Consequently, CNT/polymer nanocomposites are promising materials for making multifunctional microscale components with unique properties and a wide range of applications. If considerable research has been conducted regarding the physical properties of carbon nanotube filled nanocomposites, including mechanical properties, electrical conductivity and rheological properties, only a few investigations have focused on the practical applications of nanocomposites in various industrial fields. In this dissertation, we intended to create a predictive understanding of the coupling of microinjection molding process to the development of the performance properties of carbon nanotube/polymer composites, focusing on the rheology, microstructure and properties of microparts. To explore the CNTs feature and to enable their processing, the nanocomposite preparation was optimized through a set of rheological measurements and microstructure characterization. We first examined the rheological behavior of polycarbonate (PC)/ MWCNT nanocomposites in light of interactions between CNTs and polymer chains or between CNTs themselves. To understand the percolated structure, the nanocomposites were characterized via a set of rheological, electrical and thermal conductivity measurements. The rheological measurements revealed that the structure and properties were temperature dependent; the percolation threshold was significantly lower at higher temperature suggesting stronger nanotube interactions. However, when the measurement temperature was high enough the percolation threshold tend to reach a plateau (0.3 wt%) The nanotube networks were also sensitive to the steady shear deformation particularly at high temperature. Following preshearing, the elastic modulus decreased markedly indicating that the nanotubes were aligned in the flow direction. Consequently, they interconnected minimally leading to a remarkable increase in the percolation threshold. The effect is more pronounced at higher temperature suggesting that nanotubes became more rigid. As expected, it was found that the rheological threshold (0.3-0.8 wt%) was smaller than the thermal (1-2 wt%) and electrical threshold (2-3 wt%)

Effects of various disinfectants on surface roughness and color stability of thermoset and 3D-printed acrylic resin

Denture cleansers are extensively utilized to inhibit the colonization of various Candida species. Currently, additive technology in denture fabrication has become more prevalent. This study aims to assess the impact of disinfectants on the surface roughness and color stability of distinct denture bases. Disc-shaped samples (N=66) were exposed to three different disinfectants: 0.5% sodium hypochlorite, 1% hydrogen peroxide, and 2% chlorhexidine. The samples underwent evaluation via spectrophotometry and profilometry, respectively. Data analysis was conducted utilizing analysis of variance (ANOVA) (p < 0.05). Within the heat-cured group, sodium hypochlorite resulted in the most notable change in surface roughness (0.2 μm), while chlorhexidine exhibited the least impact (0.001 μm), showing a significant difference (p <0.008). The color change (ΔE) for 3D-printed samples immersed in all disinfectants was higher compared to heat-cured samples. Among the heat-cured samples, chlorhexidine induced the highest ΔE (2.76), while sodium hypochlorite resulted in the lowest (ΔE = 1.44), and this difference was statistically significant (p <0.008). Chlorhexidine caused the most significant color alteration among the solutions, while sodium hypochlorite induced the most considerable changes in surface roughness

Medical image registration using unsupervised deep neural network: A scoping literature review

In medicine, image registration is vital in image-guided interventions and other clinical applications. However, it is a difficult subject to be addressed which by the advent of machine learning, there have been considerable progress in algorithmic performance has recently been achieved for medical image registration in this area. The implementation of deep neural networks provides an opportunity for some medical applications such as conducting image registration in less time with high accuracy, playing a key role in countering tumors during the operation. The current study presents a comprehensive scoping review on the state-of-the-art literature of medical image registration studies based on unsupervised deep neural networks is conducted, encompassing all the related studies published in this field to this date. Here, we have tried to summarize the latest developments and applications of unsupervised deep learning-based registration methods in the medical field. Fundamental and main concepts, techniques, statistical analysis from different viewpoints, novelties, and future directions are elaborately discussed and conveyed in the current comprehensive scoping review. Besides, this review hopes to help those active readers, who are riveted by this field, achieve deep insight into this exciting field

The Relationship between the Results of Coagulation Profile and Severity of Pulmonary Involvement in COVID-19 Patients

Introduction: COVID-19 is currently a global pandemic, and coagulation-related mortality has been widely reported in patients suffering from it.&nbsp;Objective: this article aimed to investigate the coagulation profile of COVID-19 patients.&nbsp;Methods: This was a cross-sectional study conducted using a retrospective research design. We recruited patients with COVID-19 admitted to a hospital from June 15th to July 7th, 2020. Upon patients' entering a blood sample was drawn from each patient for assessing patient’s coagulation profile (PT, PTT, INR, Platelet count); and a chest high-resolution computed tomography (HRCT) scan was performed for each patient. The study patients were divided in to sever group (CO-RADS score 5) and non-sever group (CO-RADS score &lt;5).&nbsp;Results: Thirty-six patients (20 males and 16 females) with a mean age of 54.7±17.5 years were studied. Of them, 11 cases (30.56%) had severe pulmonary involvement. Also, the coagulation profiles were longer in the severe group than non-sever group. As well, the means of platelet count that were 232.440 per microliter in the non-severe group and 289.180 per microliter in the severe and non-sever groups, respectively; but still not statistically significant (p&gt;0.05). The Area under the ROC Curve (AUC) for PT and INR was 0.615 and 0.611, respectively. The AUC for platelet count was 0.680 (95% CI: 0.501 to 0.859) and had an acceptable discriminating power.&nbsp;Conclusions: In this study, we did not find any statistically significant relationship between the results of coagulation tests and the severity of pulmonary involvement according to HRCT scan findings in COVID-19 patients. But further analyses suggest that, except PTT, the other coagulation tests (PT, INR, and platelet count) may discriminate severe COVID-19 patients

Preparation and quality control of 177 Lu-chitosan for radiosynovectomy

ABSTRACT Introduction: Rheumatoid arthritis (RA) is the most common autoimmune disease, leading to the destruction of the joints and causing pain, disability, and immobility in the patients. Radiosynovectomy (RSV) has been applied as an effective treatment for the patients with resistant synovitis after failure of long-term pharmacotherapy and intra-articular steroid injection for more than 50 years. Several radiopharmaceuticals have been developed for RSV so far, but still development of new radiophamaceuticals is of crucial interest. In this research, the 177 Lu-chitosan complex ( 177 Lu-CHITO) was introduced as a new agent for RSV. Methods: 177 Lu was produced by irradiation of a natural Lu 2 O 3 target at a thermal neutron flux of approximately 4 × 1

Gender Differences in COVID-19 Deceased Cases in Jahrom City, South of Iran

Objective: To evaluate the clinical and epidemiological features of deceased patients and comparing the discrepancies between male and female patients based on high prevalence of coronavirus disease 2019 (COVID-19), its irreversible effects and the rising mortality rate in Jahrom city. Methods: This is a descriptive-analytical retrospective study that was conducted from the beginning of March 2020 to the end of November 2020. The study population were included all patients with COVID-19 who admitted to Peymaniyeh Hospital in Jahrom and died of COVID-19. Clinical and demographic data were collected from medical records and analyzed by SPSS software. Results: In this study, 61 patients (57.54%) were men and 45 patients (42.36%) were women. The mean age was 68.7±18.33 in men and 68.82±14.24 in women. The mean hospitalization length was 9.69±7.75 days in men and 9.69±7.75 days in women patients. There was no statistically significant difference between men and women patients (p>0.05). The results showed that 17 (27.87%) men and 28 (45.9%) of women patients had hypertension and the prevalence of this disease was significantly higher in women than men (p=0.01). In this study, 7 (11.48%) men and 13 (21.31%) women had hyperlipidemia. The frequency of hyperlipidemia in women caseswas significantly higher than in men patients (p=0.024). Men cases’ diastolic blood pressure (mean=77.53) was significantly higher than women’s diastolic blood pressure at the same time with a mean of 71.42 (p <0.05). Conclusion: The findings of the study represented the mortality rate in men which is higher than women patients. The prevalence of underlying diseases such as hypertension and hyperlipidemia were higher in women than men. Despite higher mortality among women, symptoms such as fever and dyspnea were less common in women than men

Global, regional, and national burden of stroke and its risk factors, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background Regularly updated data on stroke and its pathological types, including data on their incidence, prevalence, mortality, disability, risk factors, and epidemiological trends, are important for evidence-based stroke care planning and resource allocation. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) aims to provide a standardised and comprehensive measurement of these metrics at global, regional, and national levels. Methods We applied GBD 2019 analytical tools to calculate stroke incidence, prevalence, mortality, disability-adjusted life-years (DALYs), and the population attributable fraction (PAF) of DALYs (with corresponding 95% uncertainty intervals [UIs]) associated with 19 risk factors, for 204 countries and territories from 1990 to 2019. These estimates were provided for ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage, and all strokes combined, and stratified by sex, age group, and World Bank country income level. Findings In 2019, there were 12·2 million (95% UI 11·0–13·6) incident cases of stroke, 101 million (93·2–111) prevalent cases of stroke, 143 million (133–153) DALYs due to stroke, and 6·55 million (6·00–7·02) deaths from stroke. Globally, stroke remained the second-leading cause of death (11·6% [10·8–12·2] of total deaths) and the third-leading cause of death and disability combined (5·7% [5·1–6·2] of total DALYs) in 2019. From 1990 to 2019, the absolute number of incident strokes increased by 70·0% (67·0–73·0), prevalent strokes increased by 85·0% (83·0–88·0), deaths from stroke increased by 43·0% (31·0–55·0), and DALYs due to stroke increased by 32·0% (22·0–42·0). During the same period, age-standardised rates of stroke incidence decreased by 17·0% (15·0–18·0), mortality decreased by 36·0% (31·0–42·0), prevalence decreased by 6·0% (5·0–7·0), and DALYs decreased by 36·0% (31·0–42·0). However, among people younger than 70 years, prevalence rates increased by 22·0% (21·0–24·0) and incidence rates increased by 15·0% (12·0–18·0). In 2019, the age-standardised stroke-related mortality rate was 3·6 (3·5–3·8) times higher in the World Bank low-income group than in the World Bank high-income group, and the age-standardised stroke-related DALY rate was 3·7 (3·5–3·9) times higher in the low-income group than the high-income group. Ischaemic stroke constituted 62·4% of all incident strokes in 2019 (7·63 million [6·57–8·96]), while intracerebral haemorrhage constituted 27·9% (3·41 million [2·97–3·91]) and subarachnoid haemorrhage constituted 9·7% (1·18 million [1·01–1·39]). In 2019, the five leading risk factors for stroke were high systolic blood pressure (contributing to 79·6 million [67·7–90·8] DALYs or 55·5% [48·2–62·0] of total stroke DALYs), high body-mass index (34·9 million [22·3–48·6] DALYs or 24·3% [15·7–33·2]), high fasting plasma glucose (28·9 million [19·8–41·5] DALYs or 20·2% [13·8–29·1]), ambient particulate matter pollution (28·7 million [23·4–33·4] DALYs or 20·1% [16·6–23·0]), and smoking (25·3 million [22·6–28·2] DALYs or 17·6% [16·4–19·0]). Interpretation The annual number of strokes and deaths due to stroke increased substantially from 1990 to 2019, despite substantial reductions in age-standardised rates, particularly among people older than 70 years. The highest age-standardised stroke-related mortality and DALY rates were in the World Bank low-income group. The fastest-growing risk factor for stroke between 1990 and 2019 was high body-mass index. Without urgent implementation of effective primary prevention strategies, the stroke burden will probably continue to grow across the world, particularly in low-income countries.publishedVersio

Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: In an era of shifting global agendas and expanded emphasis on non-communicable diseases and injuries along with communicable diseases, sound evidence on trends by cause at the national level is essential. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides a systematic scientific assessment of published, publicly available, and contributed data on incidence, prevalence, and mortality for a mutually exclusive and collectively exhaustive list of diseases and injuries. Methods: GBD estimates incidence, prevalence, mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life-years (DALYs) due to 369 diseases and injuries, for two sexes, and for 204 countries and territories. Input data were extracted from censuses, household surveys, civil registration and vital statistics, disease registries, health service use, air pollution monitors, satellite imaging, disease notifications, and other sources. Cause-specific death rates and cause fractions were calculated using the Cause of Death Ensemble model and spatiotemporal Gaussian process regression. Cause-specific deaths were adjusted to match the total all-cause deaths calculated as part of the GBD population, fertility, and mortality estimates. Deaths were multiplied by standard life expectancy at each age to calculate YLLs. A Bayesian meta-regression modelling tool, DisMod-MR 2.1, was used to ensure consistency between incidence, prevalence, remission, excess mortality, and cause-specific mortality for most causes. Prevalence estimates were multiplied by disability weights for mutually exclusive sequelae of diseases and injuries to calculate YLDs. We considered results in the context of the Socio-demographic Index (SDI), a composite indicator of income per capita, years of schooling, and fertility rate in females younger than 25 years. Uncertainty intervals (UIs) were generated for every metric using the 25th and 975th ordered 1000 draw values of the posterior distribution. Findings: Global health has steadily improved over the past 30 years as measured by age-standardised DALY rates. After taking into account population growth and ageing, the absolute number of DALYs has remained stable. Since 2010, the pace of decline in global age-standardised DALY rates has accelerated in age groups younger than 50 years compared with the 1990–2010 time period, with the greatest annualised rate of decline occurring in the 0–9-year age group. Six infectious diseases were among the top ten causes of DALYs in children younger than 10 years in 2019: lower respiratory infections (ranked second), diarrhoeal diseases (third), malaria (fifth), meningitis (sixth), whooping cough (ninth), and sexually transmitted infections (which, in this age group, is fully accounted for by congenital syphilis; ranked tenth). In adolescents aged 10–24 years, three injury causes were among the top causes of DALYs: road injuries (ranked first), self-harm (third), and interpersonal violence (fifth). Five of the causes that were in the top ten for ages 10–24 years were also in the top ten in the 25–49-year age group: road injuries (ranked first), HIV/AIDS (second), low back pain (fourth), headache disorders (fifth), and depressive disorders (sixth). In 2019, ischaemic heart disease and stroke were the top-ranked causes of DALYs in both the 50–74-year and 75-years-and-older age groups. Since 1990, there has been a marked shift towards a greater proportion of burden due to YLDs from non-communicable diseases and injuries. In 2019, there were 11 countries where non-communicable disease and injury YLDs constituted more than half of all disease burden. Decreases in age-standardised DALY rates have accelerated over the past decade in countries at the lower end of the SDI range, while improvements have started to stagnate or even reverse in countries with higher SDI. Interpretation: As disability becomes an increasingly large component of disease burden and a larger component of health expenditure, greater research and developm nt investment is needed to identify new, more effective intervention strategies. With a rapidly ageing global population, the demands on health services to deal with disabling outcomes, which increase with age, will require policy makers to anticipate these changes. The mix of universal and more geographically specific influences on health reinforces the need for regular reporting on population health in detail and by underlying cause to help decision makers to identify success stories of disease control to emulate, as well as opportunities to improve. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens