Proportioning cement based composites with burnt coal cinder

This paper presents an experimental investigation to advance a stepwise procedure to proportion plain and slag concrete mixes with burnt coal cinder waste as coarse aggregate. When typical strength of coarse aggregate in concrete is lower than the concrete strength required, conventional methods such as British Method, ACI and country’s standard code cannot be used directly since failure of concrete is predominantly by aggregate crushing. To analyze the data, concrete, for simplicity, is regarded as two phase composite of cement mortar matrix and coarse aggregate. With the concrete and constituent cement mortar matrix strengths and their respective volume fractions as input parameters, the typical strength of coarse aggregate in concrete is determined from linear law of mixtures. Using again the same law, the cement mortar matrix strength required for higher or at par to that of the typical aggregate strength is calculated. To arrive at water–cement ratio for matrix strength, the Generalized Abrams’ law is employed.     

Impact of traffic localization on communication rates in ad-hoc networks

The effect of traffic distribution on communication rates and receiver complexity in ad-hoc networks is addressed, considering a network with constant density of users and a certain traffic model. Information theoretic upper bounds on communication rates are derived under an assumption that transmitting nodes as well as receiving nodes cooperate. It is shown that for the case of large signal attenuation the bounds hold even when the cooperation among users is limited to a certain region of the network domain. Furthermore, achievability bounds on communication rates are derived. The bounds rely on two proposed local cooperation strategies. A comparison shows that the upper bounds are tight and closely follow the achievability results. Finally, the impact of traffic localization on the receiver complexity is addressed.     

Synthetic peptides corresponding to the beta-hairpin loop of rabbit defensin NP-2 show antimicrobial activity

Mammalian defensins, a class of antibacterial peptides, are composed of 29-35 amino acids with six cysteines which form three disulfide bonds. Structural studies indicate a triple stranded beta-sheet structure with a well defined beta-hairpin loop at the C-terminal region. It is demonstrated in this report that 18 and 26 residue synthetic peptides corresponding to the beta-hairpin region, constrained by a single disulfide bond, have potent antimicrobial activity without hemolytic activity. Circular dichroism spectroscopy indicates that the single S-S bridge appears to constrain the peptides to a beta-structure. Peptides corresponding to the beta-hairpin region of defensins could thus be attractive candidates as therapeutic agents as well as good model compounds for investigation of the various physiological actions of defensins.     

Stability and Mobility of Sand-Bed Channels Affected by Seepage

Seepage effects on the stability, mobility, and incipient motion of sand-bed particles are experimentally investigated. Seepage through a sand bed in a downward direction (suction) reduces the stability of particles, and it can even initiate their movement. The bed erosion is increased with the increased rates of suction. Whereas the seepage in an upward direction (injection) increases the stability of bed particles, it does not aid initiating their movement. The rate of bed erosion is reduced or even stopped by the increased injection rates. Hydrodynamic conditions leading to the so-called “pseudoincipient motion” with suction (for the initiation of particles movement that are otherwise at rest under no-seepage conditions), and with injection (for only arresting the particles movement that are otherwise moving initially) are evaluated. The conventional Shields curve cannot be used to predict such pseudoincipient motion conditions with seepage. The concepts thus developed are useful for a better understanding of the sediment transport mechanics and in the design of stable alluvial channels affected by seepage.     

Direct surface temperature measurement by infrared radiation in elastohydrodynamic contacts and the correlation with the blok flash temperature theory

An infrared microdetector was employed to measure surface temperatures in elastohydrodynamic contacts with Hertz pressures up to 2 GPa, sliding velocities up to 6.0 m s^?1 and rolling velocities up to 1.25 m s^?1 with slide/roll ratios from ?2 to +2. Different surface roughnesses were also employed. The lambda ratio (mean film thickness to composite surface roughness) was varied from 20 to considerably less than 1. The surfaces employed were AISI 52100 steel against Al₂O₃ and the lubricant was a typical naphthenic hydrocarbon. High maximum surface temperatures have been observed (to 300 °C). Analysis of the data shows very good correlation with the Blok flash temperature theory for simple sliding (∑ = ± 2). An extension of this theory to include two moving surfaces at unequal temperatures predicts the ball surface temperature quite accurately.     

AUTOMATED MEASUREMENT OF AGGREGATE INDICES OF SHAPE

Aggregate angularity is a significant factor in determining pavement resistance to rutting. Determination of aggregate angularity by direct means allows a more meaningful study of the mechanisms of pavement deformation. However, direct techniques have not been developed sufficiently to allow a more advanced study of angularity effects on pavement. Utilizing modern digital imaging hardware and image analysis techniques, we report here the development of an automated system for measuring aggregate angularity. Combining high resolution video, image capture hardware, sample transport, and computerized analysis, an instrument was constructed and used to compare various aggregate samples. Differentiation of known good quality aggregate from poorer grades was possible. Shape indices were developed from basic linear measurements, and the Hough Transform technique. These indices appear to have value in quantifying aggregate shape, and in studying the mechanisms of pavement deformation, and possibly the prediction of pavement longevity.     

strawberry notch encodes a conserved nuclear protein that functions downstream of Notch and regulates gene expression along the developing wing margin of Drosophila

Although many individuals with traumatic brain injury (TBI) perform well on standard neuropsychological tests, they often exhibit marked functional difficulties. The functions which are impaired seem to be analogous to the role of the central executive system (CES) in Baddeley's [Working Memory, 1986, Oxford University Press, New York] widely accepted model of working memory. The purpose of this study was to investigate CES function in individuals with TBI with a dual-task paradigm. We studied 25 non-demented persons who were at various stages in their recovery from severe TBI and compared their performance on a dual-task paradigm to a group of age-matched controls. Our dual-task paradigm measured performance on a simple visual reaction time task both alone (baseline) and during concurrent tasks of articulation or digit span. Subjects were also assessed with other neuropsychological tests of executive function. TBI patients had slower reaction times on the primary task when performed alone (P < 0.05) and greater decrements in performance during dual-task conditions (P < 0.01). They also exhibited significantly greater deficits than control subjects on other measures of executive function. Although correlations between dual-task performance and other executive measures were quite low, principle components analysis suggested that a common factor does exist between these measures. These findings support the conclusion that TBI patients have a working memory impairment that is due to dysfunction of the CES and which may be related to executive function deficits as measured by standard neuropsychological testing.