bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNA Repair Pathway Choice Is Influenced by the Health of Drosophila melanogaster
Authors: Wang Alethea D , Agrawal Aneil F 
Published: July 2012

Abstract
In nature, individuals vary tremendously in condition and this may be an important source of variation in mutation rate. Condition is likely to affect cell state and thereby impact the amount of DNA damage sustained and/or the way it is repaired. Here, we focus on DNA repair. If low-condition individuals are less capable of devoting the same level of resources to accurate repair, they may suffer higher mutation rates. However, repair decisions are also governed by various aspects of cell physiology, which may render the prediction that “higher-condition individuals use better repair mechanisms” too simplistic. We use a larval diet manipulation in Drosophila melanogaster to create high- and low-condition individuals and then contrast their relative usage of three repair pathways [homologous recombination (HR), single-strand annealing (SSA), and nonhomologous end joining (NHEJ)] that differ in their mechanistic requirements and their mutational consequences. We find that low-condition flies are more likely than high-condition flies to use the most conservative of these three repair pathways, suggesting that physiological constraints on repair pathway usage may be more important than energetic costs. We also show that the repair differences between high- and low-condition flies resemble those between young and old flies, suggesting the underlying mechanisms may be similar. Finally, we observe that the effect of larval diet on adult repair increases as flies age, indicating that developmental differences early in life can have long-lasting consequences.
Apparatus and methods employed in the X-ray examination of cement compounds at Birkbeck College Research Laboratories
Authors: Jeffery J. W. 
Published: July 2012

Summary: The scope of the work being undertaken in the Cement Section of Birkbeck College Research Laboratories is outlined. A brief account of the phenomena of X-ray reflection from crystals is followed by a description of: (a) X-ray tubes, H. T. gear and general layout of the laboratory: (b) powder cameras and accessories, and powder photographs; (c) single crystal cameras and photographs; (d) a special camera for long range work; (e) photographs taken of hydration products using a mica cell; (f) auxiliary apparatus. The article ends with an appeal for co-operation from users and manufacturers of cement to provide the crystal specimens necessary to carryon the work.
The strength of reinforced concrete beams in shear
Authors: Wilby C. B. 
Published: July 2012

Summary This paper deals mainly with the effect of the following factors upon the ultimate shearing strengths of beams:— (i) The percentage and spacing of the web reinforcement for stirrups inclined at 45° to the horizontal. (ii) The ratio of span under shear to the eflective depth for beams with plain webs and for two series of beams with different web ratios. (iii) The percentages of longitudinal compression and tension reinforcement for beams with plain webs and for two series of beams with different web ratios. In the beams with reinforced webs the stirrups were inclined at 45° to the horizontal, and a total of 79 shear failures was investigated from a study of asymmetrically reinforced beams and eccentrically loaded beams. The basic assumptions of the various theories in existence were investigated by numerous measurements of concrete and steel strains, defiexions, and widths of cracks. The results are discussed with regard to existing theories and past research work. It is shown that even small percentages of web reinforcement, below the percentage permitted by the British Code of Practice, were effective in increasing the ultimate shearing failing load. The yield stress of the stirrup was never exceeded and the internal and external shearing forces can only be balanced by assuming that the beam behaves like an open-frame girder. The many theories are compared with the actual failing loads in shear and it is seen that the present British Code of Practice greatly unde~estimates the shearing strength of beams.
Vibrated concrete and mortar cubes: distribution of compressive strength
Authors: Williams T. E. H. 
Published: July 2012

Summary: This paper studies the variation in compressive strength of vibrated mortar cubes and vibrated concrete cubes. Within each of the four series of tests (two mortar and two concrete) the water-cement ratio was constant, but varied from series to series. The effect on compressive strength of varying the grading of the fine aggregate in concrete was observed. The mixes (including water-cement ratio) in the two mortar series were identical, but in one series (M.1) the mortar was vibrated to complete compaction by an electro-magnetic vibrator and in the other mortar series (M.2) a vibrator of the type described in BS 12(1947) was used for the specified time of 2 minutes for each cube. The coefficient of variation of concrete strength was found to be less than 4 per cent and that of mortar strength to be more than 5 per cent. It was determined that wide variations in fine aggregate grading had no effect on the dispersion of the values of the compressive strength of concrete. The two methods of compaction used for mortar cubes resulted in widely different mean compressive strengths but the coefficients of variation obtained/or the two series were similar.
An experiment on the theory of voids in granular materials
Authors: Worthington P. M. 
Published: July 2012

Summary The purpose of this experiment was to study the way in which the voids ratio of a granular material depends upon the grading, and in particular to find the grading curve which gives the minimum voids ratio. The theoretical approach is discussed, but as it is not amenable to a complete study of the problem a carefully controlled experiment was carried out. The applications are not discussed in this paper but the most useful application is in the design of concrete mixes.
The design of prestressed continuous beams of uniform section
Authors: Robertson R. G. 
Published: July 2012

Summary The economy of continuous prestressed beams is investigated, with particular reference to three-span beams. Maximum moment envelopes and maximum moment coefficients for three-span beams of several span ratios are given, and compared to those for simply supported spans. At the critical section prestressing may be arranged to neutralize the mean moment, so that the maximum stresses are equalized in top and bottom fibres; this results in an equation giving the beam dimensions in terms of the range of moment. At other sections the stresses are smaller, and the position of the cable may be adjusted so as to eliminate secondary moments; the required cable profile depends on the span ratios and the loading, and a method of determining a suitable profile is described. Precast beams erected as simple spans and subsequently made continuous are shown to be less economical in material than cast in situ continuous beams when the preliminary cables required for the erection of the precast spans are left in place; haunched beams are shown to be less economical than beams of uniform section when live load predominates. Three examples illustrate the calculations for the three types of construction.
The effect of grading and shape on the bulk density of concrete aggregates
Authors: Moncrieff D. S. 
Published: July 2012

Summary Laboratory tests have shown that variation of grading within the limits permitted by the British Standard 882:1944 for concrete aggregates results in differences of as much as 12 lb/cu.ft. in the compacted bulk density of coarse aggregates, and 13 lb/cu.ft. in Class A and 31 lb/cu.ft. in Class B fine aggregates. It was also found that the bulk densities of different gradings of a rounded aggregate were between 5 and 10 per cent higher than those of the corresponding gradings of an angular aggregate with the same specific gravity.
Foundations for concrete roads: their preparation and protection
Authors: Maclean D. J. 
Published: July 2012

Summary This paper describes the practical measures that should be adopted by road engineers in the initial preparation and for the subsequent protection of the foundations of concrete roads. The provision of a stable foundation for a concrete road consists of: (1) the selection of suitable soils for embankments and materials for the road bases; (2) the compaction of these soils and materials; (3) the control of the moisture conditions in these soils and materials. Each of these aspects is dealt with in turn, and the paper concludes with a selection of photographs of concrete roads which illustrate a number of cases in which defects might have been avoided if more attention had been given in the first place to the provision of a stable foundation.
Effect on reinforcement in concrete of calcium chloride used as an admixture
Authors: Muller P. P. 
Published: July 2012

Summary This paper gives a brief account of some long-term tests which were undertaken to determine the possible adverse effects of the use of calcium chloride as an admixture upon the reinforcement of concrete. It was found that, even after more than six years, there was no sign of corrosion attributable to the use of calcium chloride.
The distribution of a load in a box-section bridge from tests on a Xylonite model
Authors: Little G. 
Published: July 2012

Summary A small model of a box beam bridge was tested for its load distribution properties. The distribution was determined experimentally by deflexion and strain readings. The material used in the construction of the model was Xylonite, a cellulose-base material of Young's modulus 33·33 × 104 lb/sq.in. and modulus of rigidity 11·7 × 104 lb/sq.in. The experimental distribution of deflexions and longitudinal bending moments proved to be in close agreement with the distribution given by a theoretical treatment involving distribUlion factors. The distribution patterns were found to be virtually unaffected by changes in the longitudinal position of the load. On the other hand, there were large discrepancies between the experimental and theoretical transverse bending moments. The discrepancies were almost certainly due in part to the small absolute values of the bending moments, which were only about 40 per cent of the corresponding longitudinal moments, and to their high rate of variation across the transverse section both in magnitude and sense. Nevertheless, it was confirmed that the maximum transverse moment occurs at the centre of the bridge when the load is at its position of minimum eccentricity. Further investigation into the distribution of transverse moments will be made on suitably designed models.
An experimental investigation of the influence of the formation of a plastic hinge on the shear strength of a singly reinforced concrete beam
Authors: Khan N. M. , Mattock A. H. 
Published: July 2012

Summary A series of rectangular reinforced concrete beams was tested in such a way as to simulate the conditions at a plastic hinge over a support of a continuous beam approaching failure. With the plastic hinge moment constant, the shear force on the section was increased until failure occurred in shear. Similar sections were tested in shear in an uncracked state. The results indicate that the presence of a plastic hinge does not reduce the ultimate shear strength of a reinforced concrete section.
A method for the calculation of the specific gravities of calcium silicates from their refractive indices
Authors: Howison J. W. , Taylor H. F. W. 
Published: July 2012

Summary A method is described for the calculation of the specific gravity of any anhydrous or hydrated calcium silicate from its mean refractive index. The results usually agree to within ±2% with those determined directly by the suspension or pycnometer methods.
Automatic control and recording of load during relaxation tests on prestressing wires
Authors: Bannister J. L. , Butler L. H. 
Published: July 2012

Summary A simple unit has been incorporated in a universal testing machine to compensate automatically for the continuously reducing load during relaxation tests on prestressing wires. In conjunction with a recording camera, it dispenses with the presence of an observer over the long periods required for the tests. In operation it is found that alternate readings taken with automatic and manual control fall sensibly on a single curve.
Load distribution in bridge slabs (with special reference to transverse bending moments determined from tests on three prestressed concrete slabs)
Authors: Rowe R. E. 
Published: July 2012

Summary Tests on three prestressed concrete slabs of varying span/breadth ratios have given data concerning the load distribution properties of such structural forms. The results for the distribution of deflexions and longitudinal and transverse bending moments under one, two and four equal loads are given and compared with results given by the theoretical analysis. The effect of considering Poisson's ratio in the theoretical analysis is discussed. The distribution of the transverse bending moments, both in the transverse and longitudinal directions, is considered in detail. The maximum value of the transverse moment occurring under the Ministry of Transport abnormal load is esdmated and the position of the wheel loads to give the maximum moment is considered. The variation in the transverse moments along the span due to such abnormal loading is also discussed.
Quality control in prestressed concrete production
Authors: Masterman O. J. 
Published: July 2012

Summary This paper outlines a system of quality control applied to prestressed concrete joists in which the control depends upon daily testing of a random. selection of the actual joists. The non-destructive testing includes obtaining the modulus of elasticity of the concrete and the load at the first crack for each joist; corresponding cubes are made for crushing at 1 and 28 days. Results are analysed and the means and standard deviations recorded.
The effect of creep upon redundant reactions in continuous prestressed concrete beams
Authors: Saeed-ud-din K. , Hall A. S. 
Published: July 2012

Summary The redundant reactions induced in a statically indeterminate prestressed structure by the use of a non-concordant tendon diminish as the prestressing force decreases with time. This effect is not investigated. The possibility exists that the redundant reactions may decrease independently of variation in cable force. A theory is advanced in which the variation of the reactions is expressed in terms of the phenomena of creep at constant stress and stress relaxation at constant strain. Using previous data and suggested relations between these phenomena, it is predicted that, for beams constructed in the normal way, these effects cancel one another. Tests on two-span beams support the predicted variation of reaction, and thus tend to confirm the assumed relation between creep and stress relaxation.
An analysis of deformation and failure characteristics of concrete
Authors: Baker A. L. L. 
Published: July 2012

Summary The paper shows that the aggregate grading and compaction required for strong concrete produce an internal structural system which approximates to a series of lattices in two directions at right-angles. The diagonal members of the lattice are stiffer than the cross members, which represent the mortar in the “voids”, bonded to the diagonal members. The idealized system is analysed in terms of the relative stiffness of the lattice members, and equations are derived and curves plotted from which Poisson's ratio is related to stiffness ratios for various values of the ratio of axial compression to transverse tensile strength. The curves give a reasonable explanation of changes in Poisson's ratio and compressive strength due to changes in the secant elastic modulus of mortar due to creep. The paper also introduces a useful model technique by which the internal structural system of concrete can be represented. Ordinary draper's elastic is used to form a lattice having members of appropriate relative stiffness. The elastic is prestressed to prevent buckling. External compression acting on concrete specimens may be studied as external tension on the model, since changes of internal stresses and strains are sufficient to indicate internal distribution. Such models may be used to obtain the distribution of maximum tensile stresses in a concrete specimen under test, and hence the crack pattern and mode of failure for various shapes and external restraints.
The effect of water absorption by aggregates on the water/cement ratio of concrete
Authors: Newman K. 
Published: July 2012

Summary Tests were made on damp and dry aggregates to discover how the definition of “effective water/cement ratio” is affected by aggregate absorption. Analysis of the results indicates that mixes with saturated river gravel aggregates give higher strengths and compacting factors than supposedly similar mixes made with dry aggregates. The coating of cement paste considerably reduces the rate of absorption, which ceases when the paste hardens. The effective water/cement ratio for strength should be based on the free water content available when the paste hardens. This is known more accurately when saturated aggregates are used. For dry aggregates, crushed rock material becomes saturated to the same degree as after immersion in water for 30 min, but for uncrushed river gravels the degree of saturation depends on the amount and consistence of the cement paste. The effective water/cement ratio for workability is more difficult to define. It can be assumed, provisionally, that initially dry aggregates will have achieved, at the time of the workability test, the same degree of saturation as they would have in water. These effects of absorption only apply to high-strength mixes. Rich, uneconomical site mixes can be avoided if laboratory trials are based on the effective water/cement ratio as defined in this paper.
Hydrothermal reactions in the lime-rich part of the system CaO-SiO2-H2O
Authors: Midgley H. G. , Chopra S. K. 
Published: July 2012

Summary The mineralogy of autoclaved products from various forms of calcium silicate andfrom lime and silica has been investigated. The results are as follows. With a CaO/SiO2 ratio of 1, the product is always well crystallized tobermorite. With a CaO/SiO2 ratio of 2, the product varies: starting with lime and silica, dicalcium silicate alpha-hydrate is the first product; this eventually changes into dicalcium silicate beta-hydrate, the stable phase; starting with calcium silicate hydrate I and lime, the first product comprises Flint's CSH(A) and dicalcium silicate alpha-hydrate, and it seems likely that the Flint's CSH(A) will eventually convert to dicalcium silicate alpha-hydrate and the dicalcium silicate alpha-hydrate to dicalcium silicate beta-hydrate; if one starts with β-2CaO.SiO2, the product in the first place is dicalcium silicate gamma-hydrate; in the length of processing used in the experiments reported in this paper, no other phase was found, but it is considered that dicalcium silicate gamma-hydrate is only metastable. With a CaO/SiO2 ratio of 3, again the products vary with the starting minerals: with mixes of lime and silica and with mixes of 2CaO.SiO2 and lime, the first product is dicalcium silicate alpha-hydrate which is eventually converted to the beta-hydrate; with mixes of calcium silicate hydrate (1) and lime, the product is always Flint's CSH(A) with or without some dicalcium silicate alpha-hydrate; with 3CaO.SiO2 as the starting material, the product is always 3CaO.SiO2.1½H2O. It is clear from this work that the form of the starting material has a considerable influence on the nature of the metastable phases produced, and also that, in this part of the system CaO-SiO2-H2O, even prolonged processing up to 90 days is insufficient to produce true equilibrium phases.
Some tests on beams prestressed by fibre-glass cords
Authors: Kajfasz Stanislaw 
Published: July 2012

Summary The paper discusses tests on 12 concrete beams prestressed by fibre-glass cords. The values of the forces in the cables are calculated on the basis of the test results. The influence of bond between tendons and concrete on the behaviour of beams is investigated. The low value of modulus of elasticity offibre-glass tendons is discussed. The results obtained on beams with fibre-glass reinforcement are compared with the results obtained on 23 similar beams prestressed with steel wires.
Some shear tests on reinforced concrete beams without shear reinforcement
Authors: Taylor R. 
Published: July 2012

Summary Tests were made on rectangular reinforced concrete beams without shear reinforcement in order to determine the effect on shear strength of: manner and position of loading; amount and type of reinforcement; strength of concrete. The results indicate that: for short shear spans, a beam loaded directly on its top surface can sustain a load greater than that causing the formation of a major inclined crack (the diagonal cracking load), but only with considerable widening of the crack; a beam loaded through transverse beams or nibs will not sustain a load higher than the diagonal cracking load, whatever the shear span; the diagonal cracking load increases slightly with increase in the amount of longitudinal reinforcement, but is apparently little affected by the bond characteristics of the bars; the diagonal cracking load increases with increase in the strength of the concrete, but not at the rate indicated by the British Standard Code of Practice CP 114:1957. In an evaluation of the results of the tests a method is developed for estimating the diagonal cracking load of rectangular beams without shear reinforcement. From a comparison with available test data it is shown that, though the method is simple in its application, it has a fair degree of accuracy. Design recommendations based on it are given.
Concrete under triaxial stress
Authors: Akroyd T. N. W. 
Published: July 2012

Summary This paper describes the results of the first series of experiments carried out to study the effect of pore-water pressure on the ultimate strength of concrete subject to triaxial stresses. These tests have demonstrated that saturated concrete behaves like a material which does not possess the property of internal friction, when tested triaxially under conditions of no change of water content (undrained test).
The effects of thermal incompatibility and shrinkage on the strength of concrete
Authors: Dougill J. W. 
Published: July 2012

Summary The effect of shrinkage of the mortar on the strength of a concrete specimen is demonstrated by means of a lattice analogy for concrete. The strains due to the thermal incomptability of the cement paste and the aggregate in a concrete heated to high temperatures are taken as a particular example and it is shown that the results deduced from the lattice agree closely with those obtained experimentally by other workers. The limitations of the lattice approach are discussed: it is emphasized that the method is qualitative and that any extension to give quantitative results would be most unlikely to be successful.