Hydration kinetics of high-performance cementitious systems under different curing conditions

Curing plays an essential role in the modern concrete technology, since it has a crucial effect on the development of concrete properties. High-performance cementitious systems are especially sensitive to the applied curing methods because of self-desiccation and high sensitivity to early-age cracking. Thus, it is of particular interest to compare the efficiency of internal curing and traditional curing techniques such as sealing and water ponding. In this study, the efficiency of different types of curing was estimated by means of isothermal calorimetry. Four different water to cement (w/c) ratios in the range of 0.21–0.45 and four types of curing were studied, including sealing, water ponding with different amount of water, internal curing by saturated lightweight aggregate and super-absorbent polymer. The hydration degree was determined using heat of hydration data. Compressive strength of the tested specimens was measured and analyzed. The results indicate that efficiency of different types of curing strongly depends on w/c ratio.     

TRACE qualification via analysis of the EIR gas-loop experiments with smooth rods

Several gas-loop experimental programs were carried out during the 1970–1980s at the Eidgenössisches Institut für Reaktorforschung (EIR, now PSI), Switzerland. In the present work, a wide range of thermal–hydraulics tests for smooth rods, which form part of the experiments conducted at the time, have been reanalyzed with the aim of qualifying the TRACE code. The latter constitutes the thermal–hydraulics module of PSI’s FAST code system, currently being applied to the multi-physics analysis of advanced fast reactor systems, including the Generation IV Gas-Cooled Fast Reactor (GFR). It is shown, from the present analysis, that the built-in TRACE heat transfer and friction correlations are indeed quite suitable for gas cooling under prototypic GFR conditions.     

I2-doped and pyrrole ring-iodinated semi-conducting oligomers of N-vinyl-3-alkyl-2-phenylpyrroles

I₂-doped and pyrrole ring-iodinated semi-conducting oligomers of N-vinyl-3-alkyl-2-phenylpyrroles have been synthesized by free-radical polymerization of the above monomers (AIBN, 2–5 wt%, 60–80 °C) and further exposure of the oligomers obtained to I₂ vapor. The parent oligomers exhibit paramagnetic and fluorescent properties and stable up to 300–370 °C.     

论中国和世界大地构造学说的危机

当今大地构造学的危机在于权威专家不承认地球是旋转的。绝大部分构造学家的学说是建筑在不运动的地球模型上的。就旋转的地球模型和不运动的地球的模型而言,其地球动力学规律存在着本质的区别。由于地球确实在旋转,我们有理由相信研究者迟早会承认旋转的地球模型。但是启用新模型不是一件简单的事,必须克服某些传统,而且,很多构造规律要在“一张白纸上”重新建立。     

Efficiency of naphthalene biodegradation by Pseudomonas putida G7 in soil

The efficiency of naphthalene degradation by Pseudomonas putida G7 in soil was assessed using a mathematical model. The number of microorganisms and the concentration of naphthalene in soil samples were monitored. The feasibility of a spectrofluorometric method for naphthalene assay in soil samples was compared with high pressure liquid chromatography. A proposed mathematical model described the growth of the naphthalene‐degrading strains and the consumption of substrates (naphthalene, naphthalene degradation intermediates and soil organic substances) in soil. To describe the growth kinetics of microorganisms having high affinity to substrates with low solubility, two differential equations with substrate exponent 2/3 were proposed. These equations were used to describe utilization of soil organic matter. The model parameters characterize the growth rates for different substrates and respective yield coefficients, specific bacterial death and adaptation rates, and also the rates of PAHs degradation and evaporation. These characteristics can be used in choosing the bacterial strains for biopreparations and efficient clean‐up biotechnology of polluted soils. Copyright © 2004 Society of Chemical Industry     

Simulation of complex molecules—Computational requirements for the 1980''s

Improving the understanding of complex molecular systems is an important and interesting use of supercomputers. Computer simulation currently plays, and will continue to play, a vital role in research in this area by acting as a guide to site-specific mutagenesis. This study explains simulations of complex molecules.     

Municipalities and energy efficiency in countries in transition: Review of factors that determine municipal involvement in the markets for energy services and energy efficient equipment,or how to augment the role of municipalities as market players

It is widely recognized that many cost-efficient opportunities to employ end-use energy efficiency measures exist in countries in transition (CITs) and that municipal authorities have an essential role to play in capturing these opportunities. The aim of this paper is to review the factors that determine the degree of involvement of local authorities in the market for energy services and energy efficient (EE) equipment in three CITs: Bulgaria, Hungary and the Former Yugoslav Republic of Macedonia (hereafter: Macedonia). We achieve this aim by examining the current status of local governments as the most powerful determinant of municipal market involvement. Two broad groups of factors are discussed: statutory obligations and powers of local governments, especially energy-related tasks, and finance. We explain how specific features within these two areas may influence the motivation of local authorities to improve energy efficiency and their capacity to do so. We argue that greater decentralization is the first step in augmenting the role of local authorities in the market for energy services and EE equipment. Based on the analysis we give recommendations on how to encourage municipal authorities to use market mechanisms more extensively to deliver energy efficiency.     

Using new physics and technology to advance electrostimulated rolling of metals and alloys

Electrostimulated deformation of metals and alloys, using groove or smooth rolling, requires that several important conditions are satisfied. (1) The deformation site must geometrically overlap with the flow of electric current passing through a strip between the rolls; (2) The density of direct or alternating electric current supplied to deformation site must be sufficiently high (of an order of 104-106A/cm2 ); (3) An efficient heat removal from the deformation site must be achieved. In general, the temperature of a strip must be within the range of 100-300℃. (4) The electric resistance at the roll-strip interface must be minimized. Our recent studies also indicate that the electrostimulated rolling in the shortcut regime is a further condition for obtaining high quality rolling of metals. In this regime, the rolls are placed in physical contact even in the absence of a strip that ensures an uninterrupted passage of electric current between the rolls.Provided that the aforementioned conditions are met, the plastic rolling deformation of various metals and lloys, including the most refractory and deformation resistant ones such as tungsten, molybdenum,their allows with rhenium, becomes possible. A single pass through the rolls is usually sufficient to deform a strip by about 50%- 70% as is the case for tungsten. Significantly, the temperature in the deformation site does not exceed 150-200℃.In our opinion, excellent results for electrostimulated rolling obtained by us are related to new previously unknown behavior of metals and alloys, being subject to pressure treatment and rolling.     

Diffusion-weighted echo planar MR imaging of the neck at 3 T using integrated shimming: comparison of MR sequence techniques for reducing artifacts caused by magnetic-field inhomogeneities

Objective

Our objective was to compare available techniques reducing artifacts in echo planar imaging (EPI)-based diffusion-weighed magnetic resonance imaging MRI (DWI) of the neck at 3 Tesla caused by B0-field inhomogeneities.

Materials and methods

A cylindrical fat–water phantom was equipped with a Maxwell coil allowing for additional linear B0-field variations in z-direction. The effect of increasing strength of this superimposed gradient on image quality was observed using a standard single-shot EPI-based DWI sequence (sEPI), a zoomed single-shot EPI sequence (zEPI), a readout-segmented EPI sequence (rsEPI), and an sEPI sequence with integrated dynamic shimming (intEPI) on a 3-Tesla system. Additionally, ten volunteers were examined over the neck region using these techniques. Image quality was assessed by two radiologists. Scan durations were recorded.

Results

With increasing strength of the external gradient, marked distortions, signal loss, and failure of fat suppression were observed using sEPI, zEPI, and rsEPI. These artifacts were markedly reduced using intEPI. Significantly better in vivo image quality was also observed using intEPI compared with the other techniques. Scan time of intEPI was similar to sEPI and zEPI and shorter than rsEPI.

Conclusion

The use of integrated 2D shim and frequency adjustment for EPI-based DWI results in a significant improvement in image quality of the head/neck region at 3 Tesla. Combining integrated shimming with rsEPI or zEPI can be expected to provide additional improvements.

     

High‐Affinity Carbohydrate Binding by Trimeric Benzoboroxoles Measured on Carbohydrate Arrays

Carbohydrates are involved in a wide range of biological processes of pharmaceutical relevance. The selective recognition of carbohydrates is therefore of great interest in biology and medicine. In this study we present the synthesis of fluorescent multimeric benzoboroxoles and the analysis of multivalent binding processes to immobilized carbohydrate arrays by fluorescence spectroscopy. We observed high binding affinities of trimeric benzoboroxoles by determination of K_Dsurf values for their interaction with α‐Gal on glass chips. The observed K_Dsurf values were in the mid‐nM range (49 and 104 nM ) and are comparable to the K_Dsurf values for binding of natural lectins, such as that of ConA to immobilized α‐Man (79 nM ). The array technology was found to be an excellent tool for studying the binding processes of multivalent lectin mimetics with respect to profiling and quantitation.