bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antenatal group B streptococcus detection in pregnant women: culture or PCR?
Authors: Gerolymatos Gerasimos , Karlovasiti Paraskevi , Sianou Argiri , Logothetis Emmanuel , Kaparos George , Grigoriadis Charalampos , Baka Stavroula 
Published: September 2018

Introduction: Group B streptococcus (GBS) is an important cause of neonatal infections. Maternal GBS colonization screening and intrapartum antimicrobial prophylaxis of colonized women can prevent neonatal diseases. The aim of this study was to assess the prevalence of GBS colonization in pregnant and non-pregnant women and to compare the performance of a polymerase chain reaction (PCR) assay with the established as gold standard technique, culture method, used for the detection of this microorganism.
Methodology: Vaginal and rectal samples collected from 857 pregnant and 370 non-pregnant women were examined through cultures, while the samples collected from 452 pregnant women between 35 and 37 weeks of gestation were assayed by culture and PCR method targeting the cfb gene.
Results: GBS colonization was present in both pregnant and non-pregnant women. The colonization rate was similar in non-pregnant and first trimester pregnant women and then increased from first to the third trimester of pregnancy. GBS cultures for vaginal and rectal samples were positive in 13.2% and 14.3% in non-pregnant women, while in pregnant women 13.2% and 13.7% in the first trimester, and 15.0% and 16.5% in the second trimester, respectively. In third trimester pregnant women, compared to culture method, PCR identified a significantly increased number of GBS positive vaginal (18.4% vs 22.6%, p = 0.0006) and rectal (18.1% vs 21.2%, p = 0.01) samples.
Conclusions: GBS colonization rate was higher in the third trimester. PCR proved to be a rapid and useful GBS screening method allowing a shorter detection time, while identifying more colonized women than culture.
Characterization of diarrheagenic Escherichia coli strains associated with diarrhea in children, Khouzestan, Iran
Authors: Mahdavi Broujerdi Sanaz , Roayaei Ardakani Mohammad , Rezatofighi Seyedeh Elham 
Published: September 2018

Introduction: Diarrheagenic Escherichia coli (DEC) is a major etiologic agent among the pathogens that cause diarrhea in children.
Methodology: To investigate the presence and pathotypes of DEC in children under five years of age, living in the province of Khouzestan, Iran. 208 diarrhea stool samples were screened by multiplex-PCR. The isolated DEC isolates were investigated for resistance to various antimicrobials including the production of extended-spectrum beta-lactamases (ESBLs) and phylogenetic groups were determined.
Results: DEC isolates were identified in 54 (26%) diarrhea samples, and 4 (7%) cases contained two DEC pathotypes. DEC isolated included 35 (16.8%) enteroaggregative E. coli (EAEC), ten (4.8%) enteropathogenic E. coli (EPEC), six (2.9%) enteroinvasive E. coli (EIEC), six (2.9%) enterotoxigenic E. coli (ETEC) and one (0.48%) LEE-positive EAEC. Shiga-toxin producing E. coli (STEC) was not identified in any diarrheal samples. The most prevalent resistance was observed with ceftazidime (88%), followed by ceftizoxime (83%) and ceftriaxone (71%). The majority of isolates (> 75%) were sensitive to Imipenem, ciprofloxacin, and amikacin. More than 65% of the pathogenic isolates showed a multidrug-resistant phenotype. ESBL-producing strains was observed in 79.3% of all DEC isolates. Phylogenetic group B2 was the most predominant group with a frequency of 44.8%. A significant association was observed between the B2 phylogenetic group and the DEC isolates (P < 0.05).
Conclusions: Overall, our findings highlight the importance of the role of DEC isolates in the etiology of diarrhea in children in Iran. The progressive increase in antimicrobial resistance among DEC isolates makes it imperative to implement policies to control the spread of resistant bacteria.
Metal‐to‐Semiconductor Transition and Electronic Dimensionality Reduction of Ca2N Electride under Pressure
Authors: Tang Hu , Wan Biao , Gao Bo , Muraba Yoshinori , Qin Qin , Yan Bingmin , Chen Peng , Hu Qingyang , Zhang Dongzhou , Wu Lailei , Wang Mingzhi , Xiao Hong , Gou Huiyang , Gao Faming , Mao Ho‐kwang , Hosono Hideo 
Published: September 2018

AbstractThe discovery of electrides, in particular, inorganic electrides where electrons substitute anions, has inspired striking interests in the systems that exhibit unusual electronic and catalytic properties. So far, however, the experimental studies of such systems are largely restricted to ambient conditions, unable to understand their interactions between electron localizations and geometrical modifications under external stimuli, e.g., pressure. Here, pressure‐induced structural and electronic evolutions of Ca2N by in situ synchrotron X‐ray diffraction and electrical resistance measurements, and density functional theory calculations with particle swarm optimization algorithms are reported. Experiments and computation are combined to reveal that under compression, Ca2N undergoes structural transforms from R
m symmetry to I
2d phase via an intermediate Fd
m phase, and then to Cc phase, accompanied by the reductions of electronic dimensionality from 2D, 1D to 0D. Electrical resistance measurements support a metal‐to‐semiconductor transition in Ca2N because of the reorganizations of confined electrons under pressure, also validated by the calculation. The results demonstrate unexplored experimental evidence for a pressure‐induced metal‐to‐semiconductor switching in Ca2N and offer a possible strategy for producing new electrides under moderate pressure.
Factors affecting the stability of bubble in autoclaved aerated concrete
Authors: Su Yufeng , Wei Bolei , Sun Xuan , Zhang Hui 
Published: September 2018

AbstractDefects in autoclaved aerated concrete (AAC) products are often caused by gassing formation and bubble stability. In order to eliminate these defects and improve product quality, the factors affecting the bubble stability in AAC slurry in the production, such as the viscosity, water‐solid ratios, temperature of the slurry and four kinds of foamstabilizer was studied. The results showed that the viscosity of the slurry decreased by power function with the increase of the water‐solid ratios. The maximal rising volume first increases and then decreases with increase of water‐solid ratios, which means that there is an optimal water‐solid ratios here. The gassing velocity of aluminum is accelerated by temperature increase and the gassing time is shorted, but meanwhile the bubble stability becomes worse. The bubble stability of slurry is increased by increase in the use of foam stabilizer, but the gassing velocity is suppressed severely at the same time. The addition of four foam stabilizers should not exceed 0.1%. The research results have great significance for the improvement of AAC quality and reasonable application of foam stabilizer.
Tests of AAC walls subjected to vertical loads ‐ Part 1. Zone at the opening
Authors: Drobiec Łukasz 
Published: September 2018

AbstractThe paper describes the results of testing autoclaved aerated concert walls on a natural scale. The walls were made of 18 cm wide blocks and thin layer joints. Reinforced and nonreinforced walls were tested. Basalt grids and typical steel reinforcement (truss type) were used as reinforcements. The load was applied by a reinforced concrete rim beam. In the first part of the work, the impact of the opening (window) on stress distribution and the load capacity of the wall was analyzed.
Chemical admixtures for the optimization of the AAC production
Authors: Zeminian Nicoletta , Guarino Gaetano , Xu Qi 
Published: September 2018

AbstractThe use of chemical admixtures for the improvement of the manufacturing process, as well as for the quality enhancement of elements and buildings, is a regular practice in standard high consistency concrete, both in ready‐mix and in precast applications, but is still quite limited in the production of autoclaved aerated concrete (ACC). This is partially due to the difficulty of replicating the manufacturing process in the laboratory, which includes expansion and setting in the precuring stage, followed by the autoclave treatment at elevated temperature and pressure. This work presents a structured approach to the design of specific chemical admixtures for ACC, which started with the identification of suitable laboratory equipment, and test methods for the simulation of the production process of AAC. This was then expanded with the screening and selection of different chemical formulations, to end with the development of chemical admixtures tailored for the ACC. The results show that, by using these specific admixtures, the producers of AAC can accelerate the production process, thereby increasing the output of the plant; alternatively, when the increase in productivity is not an objective, the same admixtures can be employed to achieve a significant optimization in the composition of the mix.
Analysis of AAC precast lintels embedded in walls different construction
Authors: Drobiec Łukasz , Jasiński Radosław , Mazur Wojciech 
Published: September 2018

AbstractThe paper presents experimental results of lintels embedded in walls different construction. Walls and lintels were made of autoclaved aerated concrete (AAC). Lintels act in different statical conditions. Walls were erected in natural scale as a standard masonry wall, bounded walls, and with additional reinforced concrete cores along vertical edges of window openings. Cracks propagation and destruction of lintels were analyzed. The tests were monitored by Digital Image Correlation system Aramis, and results were analyzed by GOM Correlate software. The results were compared with the results of smaller models, which represent the areas of window opening, and also with the result of lintels tested as simply supported beam according to the standard method.
Highly automated versatile volume production of autoclaved aerated panels
Authors: van Boggelen Daan , van Boggelen Koen , Beier Ralf 
Published: September 2018

AbstractThe need for better and quicker building is growing every day. The shortage for craftsmanship with high costs is pushing building activities toward innovative, industrialized prefab elements and even to a complete casing production. New and affordable autoclaved aerated concrete (AAC) building concepts with its related production technology is a serious request from markets worldwide. AAC panels still have a limited or no market share in most of the countries in the construction industry. Exceptions to this case are Japan, Australia, the Netherlands, Denmark, Belgium, and Germany. The reasons are too many to mention. But the fact is that there are only a very few facilities fit for the future to produce predictable, versatile, high volume “quality” panels, lintels, cladding panels, and AAC boards. This paper presents an image collage and figurative views of our studies and 68 years of panel production experience with information about the lessons learned. Highlighted subjects will be the technology, plant automation, rebar and AAC, the smooth cutting, curing regimes, and handling.
Effects of specimen dimensions and shape on compressive strength of specific autoclaved aerated concrete
Authors: Mazur Wojciech , Drobiec Łukasz , Jasiński Radosław 
Published: September 2018

AbstractThis paper present results from testing shape and dimensions of specimens on compressive strength of autoclaved aerated concrete (AAC) concrete with nominal density classes 400, 500, 600, and 700. The tests were conducted on standard cube specimens 100 mm × 100 mm × 100 mm, cylindrical and rectangular specimens made of AAC blocks. DANTEC optical measurement system was used to analyze how specimen shape affected the mechanism of specimen destruction. Obtained results were analyzed and Neville's algorithm was adapted.
Influence of secondary raw materials on synthesis of tobermorite in lime–silicate composite
Authors: Černý Vít , Drochytka Rostislav , Kulísek Karel , Húšt'avová Jana 
Published: September 2018

AbstractCrystalline calcium silicate hydrate (CSH) phases, primarily tobermorite, arise in the microstructure of autoclaved aerated concretes (AACs) during autoclaving, which affects the concrete's important characteristics. Calcium oxide/hydroxide and silicon oxide are the feedstocks for the hydrothermal reactions. When producing AACs, aside from commonly used raw materials, it is also possible to utilize secondary raw materials rich in silicon oxide. The use of such secondary raw materials provides the opportunity for the construction industry to lower its impact on the environment. This work describes the investigation of individual added secondary raw materials’ influence on the microstructure of AAC. The tested materials were as follows: high‐temperature fly ash, FBC ash, slag, ground container glass, and zeolite. The materials were mixed with quicklime at a molar ratio of calcium oxide to silicon oxide of 0.73 and 1.0. Autoclave reactors were used for the synthesis of tobermorite under laboratory conditions. Autoclaving took place at 170 and 190°C with hydrothermal soaking times of 4, 8, and 16 h. The additive with the most significant impact on microstructure was fly ash, while ground container glass showed the greatest influence on mechanical characteristics.
Six sigma in the AAC production
Authors: Haas Martin , Petrov Ivaylo 
Published: September 2018

AbstractThe aim of this paper is to explain the six sigma tools such as control charts, boxplots, and hypothesis test. These tools have been used to detect root causes of production disturbances such as damaged grinding media in a ball mill or a big variation in compressive strength of an aerated autoclaved concrete (AAC) product. Another example shows how the variation of the fineness of grinded sand could be reduced. Hypothesis tests were used to check if fluidizers can reduce rising cracks or if a shortened autoclave cycle has an influence on product properties such as compressive strength or durability.This paper does not explain the whole six sigma project of each example. It only shows the results of the projects and the tools that have been used. This paper underlines that the knowledge about the variation in each subprocess of the AAC production cycle is essential for improving the process and to eliminate disturbances.
Durability of autoclaved aerated concrete based on Polish experience
Authors: Zapotoczna‐Sytek Genowefa 
Published: September 2018

AbstractThe question of durability in the construction industry applies to building materials, components, and structures. In general, building materials, components, and structures are considered durable if their properties remain stable. Durability characteristics depend on a number of complex factors and conditions and may not always be effectively determined using simple standardized methods. Despite ongoing discussions and research, the question of durability and its measuring methods remains elusive. Studies revealed, for example, that shrinkage, phase composition, and durability of autoclaved aerated concrete (AAC) are interrelated. The durability of a building or structure, as discussed in research papers, involves the durability of products and the (designed and anticipated) useful life. Studies on the durability of AAC have been prompted by the increasing production and use of AAC in the construction industry in Poland, specifically in wall constructions. Researches began in early 1960s and focused on AAC materials in industrial production and AAC partitions in experimental conditions and real‐world residential buildings. The studies examined the levels and distribution of moisture in concrete walls; conclusions have been formulated concerning the drying time, the effects of indoor and outdoor conditions, and the partition orientation relative to the points of the compass. Extended research on AAC durability co‐funded by AAC production plants and the Institute of Ceramics and Building Materials (ICiMB, formerly COBRPB CEBET) were resumed in 1999. The studies examined AAC made with fly ash and sand sampled at 5 cm intervals from partitions of 20—35, 40‐year‐old buildings and AAC stored outdoors under extreme conditions for the period of 21 and 40 years (protected with a tarpaper top cover), exposed to snow during winter. The building's technical condition was evaluated when the concrete samples were collected. The following research questions were addressed:

operating moisture levels in partitions made of AAC produced using various production technologies (based on fly ash, sand);
mineral composition and porosity structure of AAC after a long period of use (as compared to the mineral composition of “fresh” AAC produced using the same technologies); and
whether changes in the tested parameters over time may contribute to AAC destruction, resulting in loss or significant reduction of AAC basic qualities, including compressive strength and frost resistance.
The results of these studies will be discussed in this article. An analysis of the results of studies confirms the durability profile of AAC, which should be considered in formulating conclusions about the possible uses of AAC. Further research is needed to determine the limit values of AAC properties in the context of real‐world applications.
Compressive strength of autoclaved aerated concrete: Test methods comparison
Authors: Walczak Paweł 
Published: September 2018

AbstractAutoclaved aerated concrete (AAC) is one of the most popular building materials for wall construction. For example, in 2017, Poland produced about 4.9 million cubic meters of AAC, which covers approximately 40% of wall building material market. One of the most important properties of building material used for the construction of wall, except thermal conductivity value, is its compressive strength value. In accordance with EN 771–4:2011+A1:2015 and EN 772‐1:2011+A1:2015, compressive strength of AAC can be determined by two alternative test methods: by drying at temperature not higher than 50°C with moisture content 6% ± 2%, or by drying at temperature 70°C and multiplying the result by 0.8 coefficient. In this work, tested blocks of AAC were manufactured in different plants with different densities. In this work, impact of drying conditions on AAC compressive strength was described.
Durability of autoclaved aerated concrete—if carbonation is really dangerous? Facts and myths
Authors: Walczak Paweł , Małolepszy Jan 
Published: September 2018

AbstractAutoclaved aerated concrete (AAC) is used as one of the most popular building materials for many years. The first production unit using an autoclaving process began in 1927. Since then, millions of cubic meters of this material have been produced around the world. Production technologies have been developed in different countries using the production process and available raw materials such as sand, siliceous fly ash from burning coal with and without biomass, or slag. Over 90 years of experience has proved that AAC is a universal and durable material. A few publications have shown negative influence of carbon dioxide on calcium silicate hydrates stability (C‐S‐H, tobermorite), which are present in most of available building materials, such as construction concrete, silicate, or AAC. The influence of carbon dioxide on durability, phase composition, and properties of AAC is tested in a research area. The influence of CO2 has been tested in natural conditions as in artificial weathering. In this work, density, compressive strength, lambda values, shrinkage, and phase composition were tested.
Simulation of AAC for sustainable design and construction
Authors: Kirby Jason T. , Fouad Fouad H. , Schoch Torsten 
Published: September 2018

AbstractResidential and commercial building sectors of the United States consume nearly 40% (or ∼38 quadrillion BTUs) of the nation's total energy demand. Regrettably, conventional forms of energy production have an adverse impact on natural ecosystems and alternative power generation lags in terms of meeting the required capacity. Faced with rising energy costs, diminishing fuel resources, and emerging environmental concerns, the US building industry has begun to address these challenges by adopting sustainable and/or green building practices. Greater durability, reduced maintenance, and reasonable cost premiums are desirable parameters for emerging materials. While autoclaved aerated concrete is well established in other parts of the globe, the US building industry is unaccustomed with its use and application. Computer simulation models represent one of the most reliable methods to test alternative design considerations in that they are cost/time efficient and can evaluate energy consumption with reasonable accuracy. The research (2009–2011) presented in this paper is a comparative evaluation of three shell construction techniques using computer simulations. Thermal, economic, and environmental characteristics of each wall system are evaluated.
Customized AAC equipment based on various demands
Authors: Xu Shunwu , Chen Xinjiang , Qi Guoliang 
Published: September 2018

AbstractIn order to meet various clients’ demands, KEDA SUREMAKER puts forward the concept of customized design. With this concept, the management team, technical experts, and process experts visit clients’ site to get feedback from their practical production experience and analyze the common characteristics of various demands to provide customized solutions.
Autoclaving of ultra‐high performance concrete (UHPC)
Authors: von Werder Julia , Simon Sebastian , Lehmann Christian , Selleng Christian , Fontana Patrick , Meng Birgit 
Published: September 2018

AbstractBy the combination of an optimized granulometry, a reduced water–cement ratio and the use of superplasticizers ultra‐high performance concrete achieves a compressive strength of over 150 N/mm2 and a high resistance regarding acids and water‐soluble salts. In different research projects the effect of an autoclavation on the mechanical strength and the phase composition was analyzed. In systematic studies, the concrete mix and the process parameters were varied. The results show that autoclavation leads to an improved pozzolanic and hydraulic reaction and significantly improves the mechanical strength compared to a conventional thermal treatment. If a minimum time‐span for hydration is ensured, the achievable strength level is not dependent on the prestorage time. However, the duration of the autoclaving is significant. After the maximum strength is reached there is only a very slight decrease, even if unrealistically long autoclaving times are applied.