Sustainable Concrete for the 21st Century Concept of Strength through Durability

The world is passing through difficult and troubled times, and we live in a rapidly changing world. The construction industry is facing many challenges – global warming, climate change forces, and the capability to achieve sustainable development and economic progress without damaging our environment. The concrete industry in particular faces further challenges. There is extensive evidence to show that concrete materials and concrete structures all over the world are deteriorating at a rapid rate, and that we are unable to ensure their long-term durable service life performance. To confound this situation, we are also faced with an urgent need to regenerate our infrastructure systems if we are to eradicate poverty and provide a decent Quality of Life for all the peoples of the world. This paper shows that the current emphasis on high strength and very high strength, and the design philosophy of Durability through Strength for concrete materials and concrete structures is fundamentally flawed. It is this misleading concept and vision that is primarily responsible for the lack of durable performance of concrete in real life environments. To change this scenario, this paper advocates that concrete materials must be manufactured for durability and not for strength. It is shown that this concept of Strength through Durability can be achieved through careful design of the cement matrix and its microstructure. If concrete is to be an eco-friendly, and sustainable driving force and construction material for social change, the need is to produce durable concrete with strengths of 30 to 60 to 80 MPa rather than very high strength concrete without an assured durable performance

On Neutrino Masses and Family Replication

The old issue of why there are more than one family of quarks and leptons is reinvestigated with an eye towards the use of anomaly as a tool for constraining the number of families. It is found that, by assuming the existence of right-handed neutrinos (which would imply that neutrinos will have a mass) and a new chiral SU(2) gauge theory, strong constraints on the number of families can be obtained. In addition, a model, based on that extra SU(2), is constructed where it is natural to have one "very heavy" fourth neutrino and three almost degenerate light neutrinos whose masses are all of the Dirac type.Comment: RevTex, 12 pages with 1 figure, minor changes to the text and added acknowledgment

Long-Time Fluctuations in a Dynamical Model of Stock Market Indices

Financial time series typically exhibit strong fluctuations that cannot be described by a Gaussian distribution. In recent empirical studies of stock market indices it was examined whether the distribution P(r) of returns r(tau) after some time tau can be described by a (truncated) Levy-stable distribution L_{alpha}(r) with some index 0 < alpha <= 2. While the Levy distribution cannot be expressed in a closed form, one can identify its parameters by testing the dependence of the central peak height on tau as well as the power-law decay of the tails. In an earlier study [Mantegna and Stanley, Nature 376, 46 (1995)] it was found that the behavior of the central peak of P(r) for the Standard & Poor 500 index is consistent with the Levy distribution with alpha=1.4. In a more recent study [Gopikrishnan et al., Phys. Rev. E 60, 5305 (1999)] it was found that the tails of P(r) exhibit a power-law decay with an exponent alpha ~= 3, thus deviating from the Levy distribution. In this paper we study the distribution of returns in a generic model that describes the dynamics of stock market indices. For the distributions P(r) generated by this model, we observe that the scaling of the central peak is consistent with a Levy distribution while the tails exhibit a power-law distribution with an exponent alpha > 2, namely beyond the range of Levy-stable distributions. Our results are in agreement with both empirical studies and reconcile the apparent disagreement between their results

A new mechanism for a naturally small Dirac neutrino mass

A mechanism is proposed in which a right-handed neutrino zero mode and a right-handed charged lepton zero mode can be localized at the same place along an extra compact dimension while having markedly different spreads in their wave functions: a relatively narrow one for the neutrino and a rather broad one for the charged lepton. In their overlaps with the wave function for the left-handed zero modes, this mechanism could produce a natural large hierarchy in the effective Yukawa couplings in four dimensions, and hence a large disparity in masses.Comment: 6 pages (2 with figures), twocolumn forma

Naming Racism: A Conceptual Look at Internalized Racism in US Schools

Internalized racism describes the conscious and unconscious acceptance of a racial hierarchy where whites are consistently ranked above People of Color. Although scholars across multiple disciplines have discussed this concept, the role of schools in instilling and perpetuating internalized racism within Students of Color has very rarely been examined. This paper is a conceptual piece that utilizes a Critical Race Theory framework to acknowledge the racialized experiences within classroom pedagogy, curriculum, and unequal school resources. We examine how these factors can negatively affect racial group-identity and contribute to internalized racism for Students of Color. Because internalized racism works to sustain educational and social inequity, this paper also explores ways that schools can function to break this cycle

Cruise Report: CD149 – RRS Charles Darwin 18th July to 6th August, 2003. Spreading-ridge geometry, hydrothermal activity, and the influence of modern and ancient hotspots on the Carlsberg Ridge - northwestern Indian Ocean

Cruise CD149 on board the RRS Charles Darwin aimed to explore the Carlsberg Ridge, Northern Indian Ocean. The cruise recovered multibeam swath bathymetry (EM12), dredge samples from 20 stations, water column profiles from 16 stations and water samples from one station, between 57 and 61.5°E. The initial results were: a discovery of a hydrothermal super plume – a plume signal rising 1200m above the seafloor and extending 30km along the ridge crest (named by the ship’s company as the iGass Plume); recovery of an extinct hydrothermal site with oxidised sulphide chimney fragments; imagery of a megamullion site with recovery of dolerite, flazer gabbro and moderately fresh peridotite from a core complex of lower crust and upper mantle; and fresh basaltic glass samples from 95% of the sites sampled.Until this cruise, the western Carlsberg Ridge was almost unknown, with only two or three poorly located rock samples, no continuous bathymetry, only a few single-track geophysics lines and no exploration for hydrothermal activity. However, the ridge is important since it probably includes the unradiogenic end-member of the Indian Ocean mantle source (at its eastern end), is likely to have a distal influence from the Afar hotspot (at its western end), and has a history of recent changes in spreading geometry reflected in an unusual segmentation pattern. It also represents a distal portion of the midocean ridge system that is connected through its eastern end only, thus having significant implications for the dispersal and colonisation of hydrothermal ecosystems