69 research outputs found
Halogen ligth thermogravimetric technique for determining the retained water in fine aggregates used for concrete mixing design
[EN] Measuring the rate of water retention of the aggregates used in mortars and concrete is required to achieve a good mix design. The water retention, specifically absorption, is used to keep constant the water/cement ratio. This paper focuses on the study of a new technique for measuring retained water in fine aggregates. In order to obtain results, the procedure described in the existing standards takes more than 24 h. Additionally, it involves high consumption of heat energy due to the use of drying ovens. Furthermore, the results obtained remain highly variable and therefore discussed by the scientific community.In this research, a novel technique based on a halogen moisture analyzer was implemented. The technique was assessed using an experiment design with a surface response model. The most important factors and levels were identified together with the interactions between them. Finally, the model was validated and the results
obtained with this technique were compared with those obtained by conventional techniques in order to verify that they were equivalent.Arias Jaramillo, Y.; Paya Bernabeu, JJ.; Ochoa Botero, JC. (2015). Halogen ligth thermogravimetric technique for determining the retained water in fine aggregates used for concrete mixing design. Journal of Thermal Analysis and Calorimetry: an international forum for thermal studies. 123:127-134. doi:10.1007/s10973-015-4902-8S127134123Djerbi Tegguer A. Determining the water absorption of recycled aggregates utilizing hydrostatic weighing approach. Constr Build Mater. 2012;27:112–6.Kasemchaisiri R, Tangtermsirikul S. A method to determine water retainability of porous fine aggregate for design and quality control of fresh concrete. Constr Build Mater. 2007;21:1322–34.Gonilho Pereira C, Castro-Gomes J, Pereira de Oliveira L. Influence of natural coarse aggregate size, mineralogy and water content on the permeability of structural concrete. Constr Build Mater. 2009;23:602–8.Cortas R, Roiziére E, Staquet S, Hamami A, Delplancke-Ogletree M. Effect of the water saturation of aggregates on the shrinkage induced cracking risk of concrete at early age. Cem Concr Compos. 2014;50:1–9.Black R. The determination of specific gravity using Siphon-Can method. Cem Concr Aggreg. 1986;8:46–50.Saxer E. A direct method of determining absorption and specific gravity of aggregates. 1956;2.Hughes B, Famili H., Part 1—Absorption of concrete aggregates, Part 2—saturated air techniques for determining the absorption of aggregates. In: Absorptions of concrete aggregates. Birmingham University; 1971.Tam VWY, Gao XF, Tam CM, Chan CH. New approach in measuring water absorption of recycled aggregates. Constr Build Mater. 2008;22:364–9.Balcedowiak W. Phase analysis of high-calcium line by TG. J Therm Anal Calorim. 2000;60:70–7.Mendoza O, Tobón JI. An alternative thermal method for identification of pozzolanic activity in Ca(OH)2/pozzolan pastes. J Therm Anal Calorim. 2013;114:589–96.Kosmatka SH, Kerkhoff B, Panarese W, MacLeod NF, McGrath RJ, Design and control of concrete mixtures. 7rd ed. Cement association of Canada. 2002. pp. 88.Cárdenas JI, Restrepo C. Patrimonio geológico y patrimonio minero de la cuenca carbonÃfera del suroeste antioqueño, Colombia. BoletÃn de ciencias de la tierra. 2006;18:91–102 ISSN 0120-3630 .Klein NS, Aguado A, Tollares-Carbonari BM, Real LV. Prediction of the water absorption by aggregates over time: modelling through the use of value function and experimental validation. Constr Build Mater. 2014;69:213–20
Fermi-liquid instabilities at magnetic quantum phase transitions
This review discusses instabilities of the Fermi-liquid state of conduction
electrons in metals with particular emphasis on magnetic quantum critical
points. Both the existing theoretical concepts and experimental data on
selected materials are presented; with the aim of assessing the validity of
presently available theory. After briefly recalling the fundamentals of
Fermi-liquid theory, the local Fermi-liquid state in quantum impurity models
and their lattice versions is described. Next, the scaling concepts applicable
to quantum phase transitions are presented. The Hertz-Millis-Moriya theory of
quantum phase transitions is described in detail. The breakdown of the latter
is analyzed in several examples. In the final part experimental data on
heavy-fermion materials and transition-metal alloys are reviewed and confronted
with existing theory.Comment: 62 pages, 29 figs, review article for Rev. Mod. Phys; (v2) discussion
extended, refs added; (v3) shortened; final version as publishe
Large Anomalous Hall effect in a silicon-based magnetic semiconductor
Magnetic semiconductors are attracting high interest because of their
potential use for spintronics, a new technology which merges electronics and
manipulation of conduction electron spins. (GaMn)As and (GaMn)N have recently
emerged as the most popular materials for this new technology. While Curie
temperatures are rising towards room temperature, these materials can only be
fabricated in thin film form, are heavily defective, and are not obviously
compatible with Si. We show here that it is productive to consider transition
metal monosilicides as potential alternatives. In particular, we report the
discovery that the bulk metallic magnets derived from doping the narrow gap
insulator FeSi with Co share the very high anomalous Hall conductance of
(GaMn)As, while displaying Curie temperatures as high as 53 K. Our work opens
up a new arena for spintronics, involving a bulk material based only on
transition metals and Si, and which we have proven to display a variety of
large magnetic field effects on easily measured electrical properties.Comment: 19 pages with 5 figure
Committing curriculum time to science literacy: The benefits from science based media resources
Kaposi sarcoma-associated herpesvirus (KSHV) is linked with the development of Kaposi sarcoma and the B lymphocyte disorders primary effusion lymphoma (PEL) and multi-centric Castleman disease. T cell immunity limits KSHV infection and disease, however the virus employs multiple mechanisms to inhibit efficient control by these effectors. Thus KSHV-specific CD4+ T cells poorly recognize most PEL cells and even where they can, they are unable to kill them. To make KSHV-infected cells more sensitive to T cell control we treated PEL cells with the thymidine analogue azidothymidine (AZT), which sensitizes PEL lines to Fas-ligand and TRAIL challenge; effector mechanisms which T cells use. PELs co-cultured with KSHV-specific CD4+ T cells in the absence of AZT showed no control of PEL outgrowth. However in the presence of AZT PEL outgrowth was controlled in an MHC-restricted manner. To investigate how AZT sensitizes PELs to immune control we first examined BJAB cells transduced with individual KSHV-latent genes for their ability to resist apoptosis mediated by stimuli delivered through Fas and TRAIL receptors. This showed that in addition to the previously described vFLIP protein, expression of vIRF3 also inhibited apoptosis delivered by these stimuli. Importantly vIRF3 mediated protection from these apoptotic stimuli was inhibited in the presence of AZT as was a second vIRF3 associated phenotype, the downregulation of surface MHC class II. Although both vFLIP and vIRF3 are expressed in PELs, we propose that inhibiting vIRF3 function with AZT may be sufficient to restore T cell control of these tumor cells
Calispe: A Program for the Calibration of Energy Dispersive XAS Spectra
We present a computer program for the calibration of energy dispersive XAS spectra. It was developed for the ESRF bearnline
ID24 and is implemented on a Unix workstation. Glitches due to multiple beam diffraction of the monochromator which are always
present in the raw data are used as energy normals. The program features a TCUTK graphical interface
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