Effect of compositional variation of dental MTA cements on setting time

2021 ◽  
Vol 48 (2) ◽  
pp. 99-118
Author(s):  
Yun-Jeong Park ◽  
Ju-Hee Kang ◽  
Hyeon Seo ◽  
Ho-Jun Song ◽  
Yeong-Joon Park
2014 ◽  
Vol 2 (1) ◽  
pp. 1-6
Author(s):  
Surbhi Sharma ◽  
◽  
Amit Sarin ◽  
Navjeet Sharma ◽  
◽  
...  

2017 ◽  
pp. 80-85
Author(s):  
V. P. Ovchinnikov ◽  
O. V. Rozhkova ◽  
N. A. Aksenova ◽  
P. V. Ovchinnikov

In the article studies of oil-filled compositions with the addition of blast-furnace slag for strength at elevated temperatures are presented. The rheological parameters of the slag cement slag cement mortar, as well as the setting time, were studied. Conclusions are drawn about the prospects of further study of slag cementcontaining compositions.


Author(s):  
Х.М. Хетагуров

Кленовники Северного Кавказа – особый тип лесных формаций. Особенность проявляется не только в структуре фитоценозов, но и в способах самовозобновления. Объект исследования – чистые и смешанные кленовники в нескольких урочищах РСО-Алания. Объекты расположены в различных условиях горного рельефа и на разной высоте над уровнем моря, от 1100 до 1900 м. Целью исследования является установление особенностей семенного возобновления кленовников, произрастающих в верхнем поясе распространения лесов на Северном Кавказе. Для достижения поставленной цели устанавливали время цветения и созревания семян по вертикальным поясам распространения кленовников. Обилие цветения и средний балл плодоношения устанавливали по В.Г. Капперу. Биометрические характеристики семян определяли по урочищам в трех повторностях. Учет подроста проводили на круговых учетных площадках по 10 м2, в соответствии с методикой А.В. Грязькина. Установлено, что цветение клена Траутфеттера начинается 10–14 мая и заканчивается в третьей декаде мая. Семена начинают созревать к концу августа – к началу сентября. Сроки опадения семян растянуты. Часть семян попадает на почву до начала листопада, поэтому они оказываются погребенными под опадом. Такие семена быстро теряют всхожесть, выпревают. Другая часть опадает вместе с листьями. Третья категория семян (самые легкие) держатся на деревьях до декабря и даже до весны. Естественное возобновление клена семенами под пологом материнского древостоя сильно затруднено из-за мощного травяного покрова. В древостое с сомкнутым пологом доля цветущих и плодоносящих деревьев составляет 2–3%, а средний балл плодоношения составляет 1,3. Освещенность на поверхности почвы не превышает 100 люкс, т. е. составляет 0,2–0,3% от освещенности на открытом месте; на высоте 1,3 м (над травостоем) освещенность несколько выше – от 1,2 до 1,6 тыс. люкс. Под пологом древостоя преобладает подрост вегетативного происхождения. У верхней границы кленового леса подрост семенного происхождения встречается в окнах, прогалинах и на открытых местах в количестве 430–630 экз./га. По высоте преобладает крупный подрост 50–60%, доля мелкого – 10–20%. The maple stands of the North Caucasus – a special type of forest formations. The peculiarity is manifested not only in the structure of phytocoenoses, but also in the ways of self-renewing. Object of research – pure and mixed maple stands in some areas of North Ossetia-Alania. The properties are located in various mountainous terrain and at different heights above sea level from 1100 to 1900 m. The aim of the study is to establish the characteristics of the seed the resumption of the maple stands growing in the upper belt of forests spread in the Northern Caucasus. To achieve this goal setting time of flowering and ripening of seeds on vertical zones distribution dominated. The abundance of flowering and the average score of fruiting was established by V.G. Capper. Biometric characteristics of the seeds was determined by the tracts in three replicates. Accounting for the undergrowth was carried out on a circular experimental plots at 10 m2, in accordance with the method of A.V. Grashkin. It is established that the flowering maple Trautvetter begins may 10–14 and ends in the third week of may. Seeds begin to ripen by late August – early September. The timing of subsidence of the stretched seed. Some of the seeds falls to the ground before the leaves, so they are trapped under the litter. These seeds quickly lose their germination, vypivaet. The other part falls along with the leaves. The third category of seeds (the light) stay on the trees until December and even till spring. Natural regeneration of maple seeds under the canopy of parent stand is very difficult due to the strong grass cover. In forest stands with dense canopy, proportion of flowering and fruit-bearing trees is 2–3%, and the average score of fruiting is 1.3. The illumination on the surface of the soil does not exceed 100 Lux, i. e. 0.2–0.3% of the light in the open, at a height of 1.3 m (on grass) the lighting is slightly higher, from 1.2 to 1.6 thousand Suite. Under the canopy of the forest the undergrowth is dominated by vegetative origin. At the upper boundary of the maple forest, saplings of seed origin occurs in Windows, clearings and open places in the number 430–630 ind./ha. In height dominated by large undergrowth of 50–60%, the share of small – 10–20%.


Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 382 ◽  
Author(s):  
Danying Gao ◽  
Zhenqing Zhang ◽  
Yang Meng ◽  
Jiyu Tang ◽  
Lin Yang

This work aims to investigate the effect of additional flue gas desulfurization gypsum (FGDG) on the properties of calcium sulfoaluminate cement (CSAC) blended with ground granulated blast furnace slag (GGBFS). The hydration rate, setting time, mechanical strength, pore structure and hydration products of the CSAC-GGBFS mixture containing FGDG were investigated systematically. The results show that the addition of FGDG promotes the hydration of the CSAC-GGBFS mixture and improves its mechanical strength; however, the FGDG content should not exceed 6%.


2021 ◽  
pp. 100175
Author(s):  
Cyriaque Rodrigue Kaze ◽  
Adeyemi Adesina ◽  
Gisèle Laure Lecomte-Nana ◽  
Thamer Alomayri ◽  
Elie Kamseu ◽  
...  

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Travis T. Sims ◽  
Molly B. El Alam ◽  
Tatiana V. Karpinets ◽  
Stephanie Dorta-Estremera ◽  
Venkatesh L. Hegde ◽  
...  

AbstractDiversity of the gut microbiome is associated with higher response rates for cancer patients receiving immunotherapy but has not been investigated in patients receiving radiation therapy. Additionally, current studies investigating the gut microbiome and outcomes in cancer patients may not have adjusted for established risk factors. Here, we sought to determine if diversity and composition of the gut microbiome was independently associated with survival in cervical cancer patients receiving chemoradiation. Our study demonstrates that the diversity of gut microbiota is associated with a favorable response to chemoradiation. Additionally, compositional variation among patients correlated with short term and long-term survival. Short term survivor fecal samples were significantly enriched in Porphyromonas, Porphyromonadaceae, and Dialister, whereas long term survivor samples were significantly enriched in Escherichia Shigella, Enterobacteriaceae, and Enterobacteriales. Moreover, analysis of immune cells from cervical tumor brush samples by flow cytometry revealed that patients with a high microbiome diversity had increased tumor infiltration of CD4+ lymphocytes as well as activated subsets of CD4 cells expressing ki67+ and CD69+ over the course of radiation therapy. Modulation of the gut microbiota before chemoradiation might provide an alternative way to enhance treatment efficacy and improve treatment outcomes in cervical cancer patients.


Genetics ◽  
2002 ◽  
Vol 162 (4) ◽  
pp. 1805-1810 ◽  
Author(s):  
Martin J Lercher ◽  
Nick G C Smith ◽  
Adam Eyre-Walker ◽  
Laurence D Hurst

AbstractThe large-scale systematic variation in nucleotide composition along mammalian and avian genomes has been a focus of the debate between neutralist and selectionist views of molecular evolution. Here we test whether the compositional variation is due to mutation bias using two new tests, which do not assume compositional equilibrium. In the first test we assume a standard population genetics model, but in the second we make no assumptions about the underlying population genetics. We apply the tests to single-nucleotide polymorphism data from noncoding regions of the human genome. Both models of neutral mutation bias fit the frequency distributions of SNPs segregating in low- and medium-GC-content regions of the genome adequately, although both suggest compositional nonequilibrium. However, neither model fits the frequency distribution of SNPs from the high-GC-content regions. In contrast, a simple population genetics model that incorporates selection or biased gene conversion cannot be rejected. The results suggest that mutation biases are not solely responsible for the compositional biases found in noncoding regions.


Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 731
Author(s):  
Chunlong Huang ◽  
Zirui Cheng ◽  
Jihui Zhao ◽  
Yiren Wang ◽  
Jie Pang

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.


2021 ◽  
Vol 2 (3) ◽  
pp. 501-515
Author(s):  
Rajib Kumar Biswas ◽  
Farabi Bin Ahmed ◽  
Md. Ehsanul Haque ◽  
Afra Anam Provasha ◽  
Zahid Hasan ◽  
...  

Steel fibers and their aspect ratios are important parameters that have significant influence on the mechanical properties of ultrahigh-performance fiber-reinforced concrete (UHPFRC). Steel fiber dosage also significantly contributes to the initial manufacturing cost of UHPFRC. This study presents a comprehensive literature review of the effects of steel fiber percentages and aspect ratios on the setting time, workability, and mechanical properties of UHPFRC. It was evident that (1) an increase in steel fiber dosage and aspect ratio negatively impacted workability, owing to the interlocking between fibers; (2) compressive strength was positively influenced by the steel fiber dosage and aspect ratio; and (3) a faster loading rate significantly improved the mechanical properties. There were also some shortcomings in the measurement method for setting time. Lastly, this research highlights current issues for future research. The findings of the study are useful for practicing engineers to understand the distinctive characteristics of UHPFRC.


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