bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of coarse aggregate on the mode of failure of concrete in compression and flexure
Authors: Jones R. , Kaplan M. F. 
Published: July 2012

Summary Experiments have been made to determine the flexural and compressive strengths of concretes containing thirteen different coarse aggregates. In the compression tests, observations were made by an ultrasonic pulse technique to detect the onset of cracking prior to failure. The main results were as follows. Concretes containing smooth gravels began to crack at lower compressive stresses than did concretes containing coarser-textured aggregate. The compressive strengths did not show such appreciable differences. Concretes which best resisted pre-cracking in compression also gave highest flexural strengths. The relation between the flexural strength of the concrete and the stress at which cracks first occurred in compression was independent of the type of coarse aggregate; no such unique relation existed between flexural strength and ultimate compressive strength. Tentative conclusions are drawn on the mode of failure of the concrete as follows. Pre-cracking in a cube when tested in compression probably arises from local breakdown in the adhesion between the coarse aggregate and the cement. The average compressive stress at which the first cracks occur is determined by those properties of the aggregate which influence the aggregate-cement bond. Pre-cracking in compression does not lead to the immediate fracture of the concrete specimen. A contribution to the ultimate strength is provided by the mechanical interlocking of the coarse aggregate after pre-cracking has occurred. Thus the compressive strength of concrete is usually greater than the compressive strength of its comparable mortar. In flexure, pre-cracking causes fracture of the concrete specimen and the only properties of the coarse aggregate which influence the flexural strength are those which appear to determine the aggregate-cement bond. In general the flexural strength of concrete is lower than the flexural strength of the corresponding mortar.
Some experiments on the applicability of the principle of superposition to the strains of concrete subjected to changes of stress, with particular reference to prestressed concrete
Authors: Davies R. D. 
Published: July 2012

Summary The paper describes experiments to test the validity of McHenry's hypothesis that the principle of superposition can be applied to the strains, including the creep strains, of concrete subjected to changes of stress. It is concluded that, although the hypothesis is by no means strictly correct, it is nearer the truth than the assumption that change of strain is proportional to change of stress. The application of the hypothesis to prestressed beams under sustained loads is considered with reference to the distribution of stress on a cross-section and to bending.
The relation between standard deviation and mean strength of concrete test cubes
Authors: Neville A. M. 
Published: July 2012

Summary Tests on laboratory-made concrete of various mix proportions, types of cement, and ages at test indicate that, for a constant degree of control, the standard deviation within a batch is directly proportional to the mean strength of the concrete. A similar relation applies to the standard deviation between batches. These relations do not hold good for very low strengths—below about 1,500 lb/in2. An examination of field data, carefully separated according to the degree of control exercised, suggests that for site-made concrete also the standard deviation increases with the increase in the mean strength. Thus the present practice of designing mixes on the basis of a constant coefficient of variation, as recommended by Road Note No. 4, is believed to be satisfactory.
The relation between ultrasonic pulse velocity and the compressive strength of concretes having the same workability but different mix proportions
Authors: Kaplan M. F. 
Published: July 2012

Summary Experiments have been made to investigate whether, for concrete of a given workability, the relation hetween ultrasonic pulse velocity and compressive strength is independent of variations in age and in mix proportions (i.e. aggregate/cement and water/cement ratios). It is concluded that, for concrete made of the same type of material, curves relating pulse velocity to compressive strength may be drawn for concrete of the same workability but different mix proportions, provided that the tests are done at the same age. When tests are done at different ages the relation is dependent on both mix proportions and age. This dependence is, however, not so apparent at low compressive strengths.
An examination of the stresses in the anchorage zone of a post-tensioned prestressed concrete beam
Authors: Douglas D. J. , Trahair N. S. 
Published: July 2012

Summary The work described is the result of investigations carried out in the Department of Civil Engineering of the University of Sydney in an attempt to determine the effect of high concentrations of stress in the anchorage zone of a prestressed concrete beam. The problem was idealized as that of the stress distribution due to the application ofa circular concentrated load acting at one end of a concrete cylinder, the theoretical analysis and experimental procedure being in this way simplified. A mathematical analysis of a three-dimensional case to determine the stresses throughout the anchorage zone is described and the results are compared with those of other writers. In a series of tests designed to verify the theoretical analysis, the loads required to cause failure were much greater than those predicted on the basis of current theories of failure and on the assumption of elastic behaviour. Further experimental work involving measurement by electrical resistance strain gauges of the surface strains showed good agreement with strains predicted theoretically. Attention is called to the fact that the tensile strains measured corresponded to stresses of approximately four times the ultimate tensile stress of the concrete as determined by the Brazilian method of testing.
Hydrothermal reactions between lime and aggregate fines
Authors: Midgley H. G. , Chopra S. K. 
Published: July 2012

Summary Hydrothermal reactions between lime and aggregate such as pulverized fuel ash, expanded colliery shale, ground quartz, granulated and foamed blastfurnace slag have been studied. The compressive strength and mineralogy have been determined for various mixtures of lime and aggregate fines autoclaved at 160 lb/in2 for 2,6,16 and 48 hours. The cementitious minerals identified were: tobermorite (calcium silicate hydrate) and a hydrogarnet when the aggregate was pulverized fuel ash or shale; tobermorite and zonotlite when it was quartz; and poorly crystalline tobermorite (tobermorite gel), dicalcium silicate alpha-hydrate and a hydrogarnet when the aggregate was slag glass. When dicalcium silicate alpha-hydrate was the predominant phase, the strength of the blocks was lower than when tobermorite was the main phase.
Hydration of tricalcium aluminate with lignosulphonate additives
Authors: Young J. F. 
Published: July 2012

Summary Lignosulphonates modify the hydration of tricalcium aluminate: acicular crystals form instead of the usual hexagonal plates, and by X-ray diffraction, DTA* and optical data it has been shown that these can represent more than one hydration product. The differences in reaction products are attributed to small changes in hydration conditions. In pastes of tricalcium aluminate, C2AH8† and C4AH13 crystallize with a new crystal habit, rather than forming a new hydrate. Current theories explaining the effect of lignosulphonates on the mechanical strengths of concrete are discussed.
Effect of calcium chloride on the durability of pre-tensioned wire in prestressed concrete
Authors: Roberts M. H. 
Published: July 2012

Summary This paper gives in the first place an account of investigations which were made to determine the extent to which calcium chloride may be present in the free state in concrete at various temperatures, since this will have a bearing on the extent of corrosion of embedded steel. It has been concluded that while there is a tendency for a large proportion of the added calcium chloride to react with the hydrating cement at normal temperatures, the residual small amount of free chloride always retained in solution will give an appreciable chloride concentration in solution and will cause a certain amount of corrosion of embedded steel. The amount of free chloride in solution is influenced by the composition of the cement, and will increase with an increase in the amount of calcium chloride added and with increasing temperature. These conclusions offer a reasonable interpretation of some of the findings of the second part of the paper which covers a direct study of corrosion of high-tensile steel embedded in different concretes containing calcium chloride. The present results indicate that with good concrete practice in mix design, depth of cover, and specification of materials, the additional corrosion induced by the use of flake calcium chloride up to about 2 % by weight of the cement in dense normally cured ordinary Portland cement concrete will have no structural significance. However, corrosion is greater under other conditions, and it appears that the degree of corrosion obtained in the presence of calcium chloride will depend on a number of factors, such as the quality of the concrete and adequacy of the casting procedures, the composition of the cement, the amount of calcium chloride added, the conditions of curing and storage of the concrete, and the diameter and initial surface condition of the steel wires.
The influence of support conditions on the behaviour of square concrete tanks
Authors: Davies J. D. 
Published: July 2012

Summary The paper describes a theoretical and experimental investigation of the structural behaviour of a tank in the shape of a cube under six different support conditions which include point, line and distributed reaction patterns. It is demonstrated that the method of supporting the tank has a significant effect upon the magnitude and distribution of the bending moments, particularly those values used in the design of the sections of the wall panels and floor slabs of tanks. The accuracy of the analytical predictions is checked by deflexion and curvature measurements taken on a Perspex model tank with appropriately simulated support conditions. Generally, there is a good correlation between the theoretical and experimental results.
An investigation of the unit weight of concrete
Authors: Popovics Sándor 
Published: July 2012

Summary Experimental results are presented which show the effects of cement content, air content, slump, aggregate grading and specific gravities on the unit weight of fresh and hardened concrete. With a knowledge of these effects an intelligent and resolute selection of the different proportions for a specified concrete density can be made. Formulae are presented which show the relations between the concrete composition and the unit weight of the fresh and hardened concrete. These formulae are applicable even when the mineral aggregate is a mixture of two or more materials of different specific gravities. The form of the equations presented is relatively simple considering the large number of variables involved. Values computed from the formulae show good agreement with experimental results. These formulae thus provide a new and easy method for selecting the most economical concrete composition for a given unit weight of concrete.
The creep of concrete under uniaxial tension
Authors: Illston J. M. 
Published: July 2012

Summary Tests are reported on the strain of concrete under sustained uniaxial tensile stress. The effects on this strain of the level of stress, the time under load, the age of loading and the humidity of storage are examined and compared with the behaviour under compressive stress. In general, the influence of the factors was much the same for both senses of stress but differences were found in the rates of creep, in the magnitudes of the strains under saturated conditions of storage and in the shape of the recovery curve after removal of load. Finally, two further tests are reported which indicate that the strains under a cycle of tension or compression are unaffected by a previous cycle under a stress of opposite sense.
Effect of the arrangement of reinforcement on the behaviour of reinforced concrete slabs
Authors: Taylor R. , Maher D. R. H. , Hayes B. 
Published: July 2012

Summary Tests on 10 two-way spanning, simply supported, reinforced concrete slabs are reported. The slabs were designed to have similar ultimate loads, but different arrangements of the reinforcement were adopted. The span/depth ratio was also varied. All slabs sustained loads higher than the theoretical collapse load given by the yield-line theory. The increased carrying capacity, due partly to tensile membrane action, ranged from 26 to 80 % depending on the arrangement of the reinforcement.
Further evidence relating to the ‘new hypothesis of sulphate expansion’
Authors: Chatterji S. , Jeffery J. W. 
Published: July 2012

Summary A recently proposed mechanism of sulphate expansion of cements has been subjected to further tests. According to the proposed mechanism, an addition of CaCO3 to Portland cement should result in a better performance in sulphate solution. To test this, a single batch of Portland cement was used neat and in two 9:1 ‘cement’ mixtures madefrom cement and CaCO3 and cement and quartz respectively. A series of 1:4 ‘cement’ :sand mortar prisms was made with the neat cement and with each of the two ‘cement’ mixtures. After water curing, these prisms were exposed to sulphate solutions, and their expansion was measured. The results showed that the mixture of CaCO3 and Portland cement performed better than both the neat Portland cement and the mixture of quartz and Portland cement, thereby corroborating the proposed mechanism of sulphate expansion. The significance of these results for other properties of Portland cement is also discussed.
Prognostic Value of Resting Heart Rate on Cardiovascular and Renal Outcomes in Type 2 Diabetic Patients
Authors: Miot Aurelie , Ragot Stéphanie , Hammi Wala , Saulnier Pierre-Jean , Sosner Philippe , Piguel Xavier , Torremocha Florence , Marechaud Richard , Hadjadj Samy 
Published: July 2012

OBJECTIVE
Epidemiological studies and randomized clinical trials have demonstrated in various populations that resting heart rate (RHR) was an independent predictor of cardiovascular (CV) risk and all-cause mortality. However, few data specifically evaluated the relationship between RHR and long-term CV and renal complications in a large population of type 2 diabetic (T2D) patients.

RESEARCH DESIGN AND METHODS
We performed a single-center, prospective analysis in 1,088 T2D patients. RHR was determined at baseline by electrocardiogram. The primary outcome was a composite criterion of CV and renal morbi-mortality (CV death, nonfatal myocardial infarction and/or stroke, hospitalization for heart failure, renal replacement therapy), which was adjusted for death from non-CV cause as a competing event. The secondary outcome was a renal composite criterion (renal replacement therapy or doubling of baseline serum creatinine) adjusted for all-cause death as a competing event.

RESULTS
During median follow-up of 4.2 years, 253 patients (23%) and 62 patients (6%) experienced the primary and secondary outcomes, respectively. In the subgroup of patients with CV disease history at baseline (n = 336), RHR was found to be associated with the incidence of primary outcome (P = 0.0002) but also with renal risk alone, adjusted for all-cause death as a competing event (secondary outcome; P &lt; 0.0001). In patients without history of CV disease, no relation was found between RHR and the incidence of CV and/or renal events.

CONCLUSIONS
In the real-life setting, RHR constitutes an easy and less time-consuming factor that would permit identification of CV disease diabetic patients with an increased risk for long-term CV and renal complications.
Childhood Nutrition in Predicting Metabolic Syndrome in Adults
Authors: Jääskeläinen Paula , Magnussen Costan G. , Pahkala Katja , Mikkilä Vera , Kähönen Mika , Sabin Matthew A. , Fogelholm Mikael , Hutri-Kähönen Nina , Taittonen Leena , Telama Risto , Laitinen Tomi , Jokinen Eero , Lehtimäki Terho , Viikari Jorma S.A. , Raitakari Olli T. , Juonala Markus 
Published: July 2012

OBJECTIVE
Our aim was to study the associations of childhood lifestyle factors (the frequency of consumption of vegetables, fruit, fish, and meat, butter use on bread, and physical activity) with the metabolic syndrome (MetS) in adulthood.

RESEARCH DESIGN AND METHODS
The study cohort consisted of 2,128 individuals, 3–18 years of age at the baseline, with a follow-up time of 27 years. We used the average of lifestyle factor measurements taken in 1980, 1983, and 1986 in the analyses. Childhood dietary factors and physical activity were assessed by self-reported questionnaires, and a harmonized definition of MetS was used as the adult outcome.

RESULTS
Childhood vegetable consumption frequency was inversely associated with adult MetS (odds ratio [OR] 0.86 [95% CI 0.77–0.97], P = 0.02) in a multivariable analysis adjusted with age, sex, childhood metabolic risk factors (lipids, systolic blood pressure, insulin, BMI, and C-reactive protein), family history of type 2 diabetes and hypertension, and socioeconomic status. The association remained even after adjustment for adulthood vegetable consumption. Associations with the other childhood lifestyle factors were not found. Of the individual components of MetS, decreased frequency of childhood vegetable consumption predicted high blood pressure (0.88 [0.80–0.98], P = 0.01) and a high triglyceride value (0.88 [0.79–0.99], P = 0.03) after adjustment for the above-mentioned risk factors.

CONCLUSIONS
Childhood vegetable consumption frequency is inversely associated with MetS in adulthood. Our findings suggest that a higher intake of vegetables in childhood may have a protective effect on MetS in adulthood.
Effect of Pramlintide on Prandial Glycemic Excursions During Closed-Loop Control in Adolescents and Young Adults With Type 1 Diabetes
Authors: Weinzimer Stuart A. , Sherr Jennifer L. , Cengiz Eda , Kim Grace , Ruiz Jessica L. , Carria Lori , Voskanyan Gayane , Roy Anirban , Tamborlane William V. 
Published: July 2012

OBJECTIVE
Even under closed-loop (CL) conditions, meal-related blood glucose (BG) excursions frequently exceed target levels as a result of delays in absorption of insulin from the subcutaneous site of infusion. We hypothesized that delaying gastric emptying with preprandial injections of pramlintide would improve postprandial glycemia by allowing a better match between carbohydrate and insulin absorptions.

RESEARCH DESIGN AND METHODS
Eight subjects (4 female; age, 15–28 years; A1C, 7.5 ± 0.7%) were studied for 48 h on a CL insulin-delivery system with a proportional integral derivative algorithm with insulin feedback: 24 h on CL control alone (CL) and 24 h on CL control plus 30-μg premeal injections of pramlintide (CLP). Target glucose was set at 120 mg/dL; timing and contents of meals were identical on both study days. No premeal manual boluses were given. Differences in reference BG excursions, defined as the incremental glucose rise from premeal to peak, were compared between conditions for each meal.

RESULTS
CLP was associated with overall delayed time to peak BG (2.5 ± 0.9 vs. 1.5 ± 0.5 h; P &lt; 0.0001) and reduced magnitude of glycemic excursion (88 ± 42 vs. 113 ± 32 mg/dL; P = 0.006) compared with CL alone. Pramlintide effects on glycemic excursions were particularly evident at lunch and dinner, in association with higher premeal insulin concentrations at those mealtimes.

CONCLUSIONS
Pramlintide delayed the time to peak postprandial BG and reduced the magnitude of prandial BG excursions. Beneficial effects of pramlintide on CL may in part be related to higher premeal insulin levels at lunch and dinner compared with breakfast.
Pattern recognition methods as supplementary techniques for identification of salicylamide — cyclodextrins inclusion complexes
Authors: Kosecka-Judin Ewa , Wesolowski Marek , Paukszta Dominik 
Published: July 2012

Abstract
The objective of this study was to learn whether or not the pattern recognition methods, such as agglomerative cluster analysis (CA) and principal component analysis (PCA), can be used as supplementary techniques for identification of salicylamide (SAA) inclusion complexes with β-cyclodextrin (β-CD) and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD). To do this, phase-solubility of SAA in the presence of the cyclodextrins was studied by the Higuchi-Connors method, which showed that the cyclodextrins enhanced the solubility of SAA in water as compared to that of the drug. Next, the solid phase complexes of the drug with β-CD and HP-β-CD were prepared by using the coprecipitation, precipitation-evaporation, and kneading methods. Identification of the inclusion complexes was performed by using thermal analysis, infrared spectroscopy, and wide angle X-ray scattering. Two multivariate statistical methods, CA and PCA, were used as the supplementary techniques for identification of the inclusion complexes. The results of the statistical analysis have shown that CA and PCA are helpful for interpretation of the thermoanalytical and spectral data. Moreover, these methods enabled proper classification of the products in all doubtful cases. They can be used as supplementary techniques to verify the conclusions of the above-mentioned standard methods.
Exploring the possibility of high-valent copper in models of copper proteins with a three-histidine copper-binding motif
Authors: Anamaria Imre , Mot Augustin , Silaghi-Dumitrescu Radu 
Published: July 2012

Abstract
An important function of many copper-containing proteins is activation of O2 and subsequent substrate oxidation. The Cu (III) oxidation state is generally considered to be less accessible because of the highly positive Cu (III)/Cu (II) redox potentials with typical amino acid ligands. Here, we employ density functional (DFT) calculations to explore to what extent copper (III) may be accessed in a biologically-relevant coordination environment around a mononuclear copper center, by breaking the oxygen-oxygen bond in a copper-(hydro) peroxide complex. In agreement with previous findings by Solomon and co-workers on copper models with related coordination patterns, the formally high-valent copper complex produced by O-O bond cleavage appears to harbor both oxidizing equivalents on the ligands. The potential energy surface for such a reaction reveals that with the three-histidine binding motif at the copper, O-O bond cleavage is not impossible, but rather disfavored thermodynamically.
Thermodynamic study of binary mixture of citric acid and tartaric acid
Authors: Meltzer Viorica , Pincu Elena 
Published: July 2012

Abstract
The solid — liquid phase equilibria for binary mixture of citric acid with tartaric acid were measured using differential scanning calorimetry. The phase diagram showed the existence a simple eutectic behavior. The thermal properties of this system as heat of mixing, entropy of fusion and excess thermodynamic functions were computed using enthalpy of fusion values. The composition of eutectic was determined using a Tammann diagram.