Rheological investigation of colloidal systems

Ceramic processing such as cementation and casting are among the most widely used methods for production of commercial products with different size and properties to date. Highly loaded and stable aqueous suspensions whose rheological behavior can be controlled by low content of organic additives are highly desired. To have control over the viscosity and improve fluidity/solid loading of ceramic suspensions, different series of polycarboxylate ether-based copolymers (PCEs) that include acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, vinylphosphonic acid, and polyethylene glycol-1000 were synthesized. The effect of monomer feed ratio and molecular weight of copolymer on dispersing ability of the copolymers, fluidity of the pastes, and rheological behavior of suspensions were characterized and performance of these copolymers as rheology modifiers was reported. For the first time in literature, dedicated superplasticizers for i) calcium aluminate cement (CAC) and ii) ordinary portland cement-calcined clay-calcium carbonate ternary blends were synthesized such that they caters to the characteristic properties of these systems; i) high rate of surface development and surface charge in CAC and ii) layered structure of calcined clay and high concentration of sulfate ions in ternary blended cement. The effect of PCEs on i) rheological behavior of alumina suspensions and ii) fabrication of highly loaded alumina suspensions and machining of solid cast green bodies were also investigated. While 20 vol. % pure alumina suspensions showed severe particle jamming, 35 vol. % alumina suspensions with more than 1 wt. % copolymers displayed Newtonian behavior. These suspensions found to be suitable for fabrication of solid cast green bodies and provided ability of significant removal of material in machining process

Extensional rheology and stability behavior of alumina suspensions in the presence of AMPS-modified polycarboxylate ether-based copolymers

A series of polycarboxylate ether-based copolymers that include acrylic acid, 2-acrylamido-2-methylpropane sulfonic acid, and polyethylene glycol-1000 was synthesized, and the performance of these copolymers as rheology modifiers in aqueous alumina suspensions was characterized. We discussed the effect of monomer feed ratio and molecular weight on dispersing ability of these copolymers and on extensional behavior of alumina suspensions. Results of zeta potential analysis determined that using the copolymers even at 0.5 wt.% results in all-negative zeta potentials for the entire pH range (2-12). These copolymers immensely affect the extensional rheological behavior of alumina suspensions-while 20 vol.% pure alumina suspension showed severe strain hardening behavior, suspensions with 1 wt.% copolymers and 35 vol.% alumina particles displayed no strain hardening. In this series, the copolymer with lowest molecular weight decreased the extensional viscosity of suspensions at the rupture of thread with three orders of magnitude as well

3D direct-write printing of water soluble micromoulds for high-resolution rapid prototyping

Direct-write printing has contributed tremendously to additive manufacturing; in particular extrusion based printing where it has extended the range of materials for 3D printing and thus enabled use across many more sectors. The printing inks for direct-write printing however, need careful synthesis and invariably undergo extensive preparation before being able to print. Hence, new ink synthesis efforts are required every time a new material is to be printed; this is particularly challenging for low storage modulus (G’) materials like silicones, especially at higher resolutions (under 10 µm). Here we report the development of a precise (< 10 µm) 3D printable polymer, with which we 3D print micromoulds which are filled with standard silicones like polydimethylsiloxane (PDMS) and left to cure at room temperature. The proof of concept is demonstrated using a simple water soluble polymer as the mould material. The approach enables micrometre scale silicone structures to be prototyped with ease, away from the cleanroom

Poly(carboxylate ether)-based superplasticizer achieves workability retention in calcium aluminate cement

Calcium aluminate cement (CAC) suffers from loss of workability in less than an hour (~15 minutes) after first touch of water. Current superplasticizers that are utilized to modify the viscosity of cement admixtures are designed to target ordinary Portland cement (OPC). The high affinity between these superplasticizers and cement particles were found to be detrimental in CAC systems. Utilization of a monomer that, instead, facilitates gradual adsorption of a superplasticizer provides workability retention. For the first time in literature, we report a superplasticizer that caters to the properties of CAC such as high rate of surface development and surface charge. While neat CAC was almost unworkable after 1 hour, with the addition of only 0.4% of the optimized superplasticizer, 90% fluidity retention was achieved

Cytochrome P450 2C19 Polymorphism in Iranian Patients with Coronary Artery Disease

<p><strong>BACKGROUND:</strong> The polymorphisms of cytochrome P450 2C19 (CYP2C19) gene are major prognostic factors for the response to clopidogrel therapy in patients with coronary artery diseases (CAD). The CYP2C19*2 is the most important allele responsible for resistance to clopidogrel therapy. This study examined CYP2C19 gene polymorphism (CYP2C19*1 and *2) in Iranian patients.</p> <p>&nbsp;</p> <p><strong>METHODS:</strong> This cross-sectional study was performed on 43 Iranian patients with CAD who underwent percutaneous coronary intervention (PCI) and received drug-eluted stents (DES). CYP2C19 polymorphisms were assessed using real time PCR and frequency of CYP2C19*1 and CYP2C19*2 were determined, and then homo- or heterozygous state of genes was detected by Melt Curve Analysis method.</p> <p>&nbsp;</p> <p><strong>RESULTS:</strong> Forty three patients (mean age = 58.8 &plusmn; 10.0 years, 79.1% male) participated in this study. CYP2C19*1/CYP2C19*1 genotype was observed in 31 (72.1%) of participates, CYP2C19*1/CYP2C19*2 genotype in 10 (23.3%), and CYP2C19*2/CYP2C19*2 genotype in 2 patients (4.7%). The frequency of CYP2C19*2 allele in the sample was 27.9%.</p> <p>&nbsp;</p> <p><strong>CONCLUSION:</strong> This study demonstrated a high prevalence of CYP2C19*2 gene polymorphism in Iranian patients. Further studies with larger samples or longitudinal are required to determine the effects of this polymorphism on the prognosis of CAD patients in our population.</p> <p>&nbsp;</p> <p><strong>Keywords:</strong> CYP2C19, Polymorphism, Clopidogrel, Coronary Artery Disease, Iran.</p> <p>&nbsp;</p

A PCE-based rheology modifier allows machining of solid cast green bodies of alumina

The performance of a poly(carboxylate ether) (PCE)-based superplasticizer to enable the machining of green bodies that are solid cast from suspensions of alumina was investigated. An alumina loading of 35 vol% in the presence of 1.25 wt% superplasticizer was established to be suitable for lathing and removal of significant amount of material through drilling. A reduction of 77% in the diameter of green bodies that corresponds to a 59% reduction in volume was achieved. The lathed green bodies exhibited smooth terraces without visible cracks. All of the green bodies were sintered without a polymer burnout step

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

A Survey of Sophisticated Capital Budgeting Techniques, Risk and Inflation Analysis in Long Term Projects

This study is investigating the extent of using and effectiveness of sophisticated techniques and risk and inflation analyzing in evaluation of long term projects in Tehran Stock Exchange in 2006. To collect data for this research we designed a reliable and valid questionnaire. The result indicate that the managers of the companies in Tehran Stock Exchange are using the following techniques: net present value, profitability index, internal rate of return, and accounting rate of return in order to evaluate the long term projects. Also the results showed that in view of the above managers techniques based on inflation such as the method based on real value of cash flow have the most effectiveness in decision making for investment. Other results showed that the most important obstacles of using sophisticated capital budgeting techniques are not employing scientific and practical word force; and insufficient indexes and variants in the country to implement required calculations