Influence of MWCNT/surfactant dispersions on the mechanical properties of Portland cement pastes

This work studies the reinforcing effect of Multi Walled Carbon Nanotubes (MWCNT) on cement pastes. A 0.35% solid concentration of MWCNT in powder was dispersed in deionized water with sodium dodecyl sulfate (cationic surfactant), cetylpyridinium chloride (anionic surfactant) and triton X-100 (amphoteric surfactant) using an ultrasonic tip processor. Three concentrations of each surfactant (1mM, 10mM and 100mM) were tested, and all samples were sonicated until an adequate dispersion degree was obtained. Cement pastes with additions of carbon nanotubes of 0.15% by mass of cement were produced in two steps; first the dispersions of MWCNT were combined with the mixing water using an ultrasonic tip processor to guarantee homogeneity, and then cement was added and mixed until a homogeneous paste was obtained. Direct tensile strength, apparent density and open porosity of the pastes were measured after 7 days of curing. It was found that the MWCNT/surfactants dispersions decrease the mechanical properties of the cement based matrix due to an increased porosity caused by the presence of surfactants. © Published under licence by IOP Publishing Ltd

Exclusive W + photon production in proton-antiproton collisions I: general formalism

We present a detailed computation of the fully exclusive cross section of p + antip --> W + photon + X with X = 0 and 1 jet in the framework of the factorization theorem and dimensional regularization. Order alpha-strong and photon bremsstrahlung contributions are discussed in the MS-bar mass factorization scheme. The resulting expressions are ready to be implemented numerically using Monte Carlo techniques to compute single and double differential cross sections and correlations between outgoing pairs of particles.Comment: ITP-SB-93-72, 40 pages, LateX. 3*4 figures in separate file. ([email protected]) ([email protected]

Auslander-Buchweitz approximation theory for triangulated categories

We introduce and develop an analogous of the Auslander-Buchweitz approximation theory (see \cite{AB}) in the context of triangulated categories, by using a version of relative homology in this setting. We also prove several results concerning relative homological algebra in a triangulated category \T, which are based on the behavior of certain subcategories under finiteness of resolutions and vanishing of Hom-spaces. For example: we establish the existence of preenvelopes (and precovers) in certain triangulated subcategories of \T. The results resemble various constructions and results of Auslander and Buchweitz, and are concentrated in exploring the structure of a triangulated category \T equipped with a pair (\X,\omega), where \X is closed under extensions and $\omega$ is a weak-cogenerator in \X, usually under additional conditions. This reduces, among other things, to the existence of distinguished triangles enjoying special properties, and the behavior of (suitably defined) (co)resolutions, projective or injective dimension of objects of \T and the formation of orthogonal subcategories. Finally, some relationships with the Rouquier's dimension in triangulated categories is discussed.Comment: To appear at: Appl. Categor. Struct. (2011); 22 page

How good are the Garvey-Kelson predictions of nuclear masses?

The Garvey-Kelson relations are used in an iterative process to predict nuclear masses in the neighborhood of nuclei with measured masses. Average errors in the predicted masses for the first three iteration shells are smaller than those obtained with the best nuclear mass models. Their quality is comparable with the Audi-Wapstra extrapolations, offering a simple and reproducible procedure for short range mass predictions. A systematic study of the way the error grows as a function of the iteration and the distance to the known masses region, shows that a correlation exists between the error and the residual neutron-proton interaction, produced mainly by the implicit assumption that $V_{np}$ varies smoothly along the nuclear landscape.Comment: 10 pages, 18 figure

A study on males' experiences with intimate partner violence

The purpose of this study is to examine the experiences and characteristics of men as\ud victims of intimate partner violence (IPV). This secondary analysis was conducted on\ud preexisting quantitative data collected by Pennell and Burke (2002). Using the\ud descriptive design, this quantitative study focused on data collected by the San Diego\ud Association of Governments (SANDAG) and supported by the National Institute of\ud Justice (NIJ). There were a total of 385 victims of IVP in the sample, of which 73\ud were male victims. The main instrument used to gather data for the study was from\ud computerized databases, telephone interviews, and self-enumerated questionnaires,\ud including several Likert-type scales items. A major finding was that white, middle\ud aged (n = 34.82) males had the highest percent of being a victim of IPV by their\ud spouses. Over a quarter of the male victims were abused by a significant other. Most\ud suspects used physical abuse against the male victims by using their hands to hit,\ud push or shove the men. Male victims of IPV were reluctant to seek medical attention,\ud although nearly a third of the men sustained injuries from the abuse. Another major\ud finding was that male victims of IPV still do not have the resources readily available\ud to them such as counseling in comparison to female victims of IPV. Most male\ud victims of IPV had a history of IPV. Finally, male victims reported that their children\ud were present over half of the time when the abuse occurred. There is a real need for\ud more awareness about male victims of IPV. Professionals who engage with male\ud victims of IPV firsthand need to be educated about the barriers that men endure and realize that women can be the perpetrator. Further research needs to be conducted to\ud gain a better understanding of male victims??? experiences with intimate partner\ud violence