Experimental studies of strong dipolar interparticle interaction in monodisperse Fe3O4 nanoparticles

Interparticle interaction of monodisperse Fe3 O4 nanoparticles has been experimentally investigated by dispersing the nanoparticles in solvents. With increasing the interparticle distances to larger than 100 nm in a controlled manner, the authors found that the blocking temperature (TB) of the nanoparticles drops continuously and eventually gets saturated with a total drop in TB of 7-17 K observed for 3, 5, and 7 nm samples, compared with their respective nanopowder samples. By carefully studying the dependence of TB on the interparticle distance, the authors could demonstrate that the experimental dependence of TB follows the theoretical curve of the dipole-dipole interaction. © 2007 American Institute of Physics.open313

Bell inequality test with entanglement between an atom and a coherent state in a cavity

We study Bell inequality tests with entanglement between a coherent-state field in a cavity and a two-level atom. In order to detect the cavity field for such a test, photon on/off measurements and photon number parity measurements, respectively, are investigated. When photon on/off measurements are used, at least 50% of detec- tion efficiency is required to demonstrate violation of the Bell inequality. Photon number parity measurements for the cavity field can be effectively performed using ancillary atoms and an atomic detector, which leads to large degrees of Bell violations up to Cirel'son's bound. We also analyze decoherence effects in both field and atomic modes and discuss conditions required to perform a Bell inequality test free from the locality loophole.Comment: 13 pages, 9 figure

Single-Molecule Three-Color FRET with Both Negligible Spectral Overlap and Long Observation Time

Full understanding of complex biological interactions frequently requires multi-color detection capability in doing single-molecule fluorescence resonance energy transfer (FRET) experiments. Existing single-molecule three-color FRET techniques, however, suffer from severe photobleaching of Alexa 488, or its alternative dyes, and have been limitedly used for kinetics studies. In this work, we developed a single-molecule three-color FRET technique based on the Cy3-Cy5-Cy7 dye trio, thus providing enhanced observation time and improved data quality. Because the absorption spectra of three fluorophores are well separated, real-time monitoring of three FRET efficiencies was possible by incorporating the alternating laser excitation (ALEX) technique both in confocal microscopy and in total-internal-reflection fluorescence (TIRF) microscopy

Estimation of beam prestress by deflection and strain measurements

textLaboratory test of reinforced and prestressed concrete structures have been used widely to explore the behavior of reinforced and prestressed concrete components and structures; Such tests are often time-consuming and costly. However, numerical models have been shown to compare favorably with experiments. Thus, computations are viewed nowadays as efficient alternatives to tests, time-wise and cost-wise. In the research reported in this thesis, finite-element model were used in a study of pretressed structural components in order to correlate levels of pretension with deflection and strain measurements. The two main objectives were to develop a suitable finite element model of prestressed concrete beams and to forecast beam prestension on the basis of deformations resulting from specified simple load, e.g., a uniformly distributed transverse load. A commercial finite-element analysis package (ANSYS 12) was used to set up, use and evaluate the computational model. Furthermore, a finite-difference model was employed in order to ascertain the validity of ANSYS results by comparison with engineering beam theory taking into account the applied pretension. This study demonstrates the potential usefulness of deflection and strain measurements as indicators of the pretension applied or remaining in prestressed concrete beams.Civil, Architectural, and Environmental Engineerin

Leaching Behavior Of Concrete Containing Municipal Solid Waste Incineration Bottom Ash

The object of this study was to investigate the impacts of municipal solid waste incineration (MSWI) bottom ash (BA) regarding cement hydration and leaching when used cement-based materials. As a mean of cement hydration assessment, energy dispersive X-ray (EDS) and X-ray diffraction (XRD) analysis were conducted on MSWI BA \u27as is\u27, hydrated BA, and BA-combined cement paste. The results show that MSWI BA led to small amount of cement hydration. In addition, the leaching characteristics of major alkaline and trace elements from concrete containing varied amounts (10%-50%) of BA were investigated by synthetic precipitation leaching procedure (SPLP) batch testing. The results reveal that the release of highly alkaline elements increases with increasing the BA content. However, the release of selected alkaline and trace heavy metals is reduced when mixed with PCC properly due to the binding effect in cement mixtures and consuming from cement hydration. Results show that crushed PCC mixed with the MSWI BA demonstrated significant reduction of Al and Si. Moreover, Mg ranged from 475.9 μg/L for the 100% BA to 181.3 μg/L for the PCC with 50% BA and Cu ranged from 45.5 μg/L to 15.1 μg/L

Numerical Analysis of Reflective Cracking in an Asphalt Concrete Overlay over a Flexible Pavement

Previous studies have typically illustrated the three cracking mechanisms: (1) thermally induced fatigue due to a horizontal movement, (2) traffic induced fatigue due to vertical differential movement, and (3) surface initiated cracking due to the curling/warping of underlying slabs. Although these mechanisms are commonly observable for asphalt concrete overlay over both flexible and rigid pavements, the behavior and response of asphalt concrete (AC) overlay over a flexible pavement may be somewhat different from those over a rigid pavement due to their different characteristics of material and structure. Approximately 94% of 2.27 million miles of paved roads in the United States are overlaid with asphalt concrete. The mechanism of reflective cracking in AC overlays over flexible pavements has not been separately differentiated. Moreover, the bonding condition between AC overlays and flexible pavements is commonly assumed as bonded condition, although the interface condition can vary. This paper investigates the reflective cracking mechanism in an AC overlay over flexible pavements under different loading conditions by using a finite element (FE) analysis with bonded and unbonded conditions. The FE simulations also include partial top-down cracking conditions in the underlying flexible pavement. Deformed crack shapes and the highest stress concentration under traffic loading were investigated so that the initiation and propagation of reflective cracking are clearly understood. © ASCE 2014

Investigation On Impacts Of Municipal Solid Waste Incineration Bottom Ash On Cement Hydration

The goal of this study is to explore beneficial use of municipal solid waste incineration (MSWI) bottom ash in cement-based products for saving waste-disposal cost, conserving natural resources, and saving energy. However, uncertain engineering characterization of this waste product has been always a major concern; thus, particularly in the United States, there has been no recycling of MSWI bottom ash. In this study, efforts were made to characterize MSWI bottom ash and to evaluate the effects of the ash as a partial replacement of cement and fine aggregate in cement paste and concrete, respectively. This paper presents and discusses: 1) physical and chemical properties of MSWI bottom ash; 2) its effect on cement hydration; and 3) physical and mechanical properties of cement paste and concrete specimens containing bottom ash. The main focus of the investigation particularly was on the impact of MSWI bottom ash on cement hydration. It was found that MSWI bottom ash causes both a hydration effect due to existing calcium oxide, calcium sulfate, and silica dioxide, as well as volume expansion due to hydrogen gas evolution

Investigation On The Effect Of Recycled Asphalt Shingle (Ras) In Portland Cement Mortar

Tear-off roofing shingle, referred to as Reclaimed asphalt shingle (RAS), is the byproduct of construction demolition and it is a major solid waste stream in the U.S. Reuse of this byproduct in road construction sector can contribute to the success of materials sustainability as well as landfill conservation. Ground RAS has similar particle distribution as sand and its major component includes aggregate granules, fibers, and asphalt. To promote the beneficial utilization of RAS, this study evaluates the effect of RAS in cement mortar when used as replacement of sand. In addition, the study investigates how cellulose fibers from RAS behave under high alkaline environment during cement hydration process, which may significantly affect mortar\u27s strength performance. The laboratory study includes measurements of physical, mechanical, and durability behaviors of cement mortar containing RAS replacing sand up to 30%. It was found that the optimum mixture proportions are 5% and 10% for compressive strength and toughness, respectively

Accelerated Calcite Precipitation (Acp) Method For Recycled Concrete Aggregate (Rca)

Recycled concrete aggregate (RCA) is often used as a replacement of virgin aggregate in embankments, roadbed, asphalt and concrete pavements. The use of RCA in drainage systems as pipe backfill materials has not received a large attention due to clogging potential. Calcite precipitation is one of major causes of permittivity reduction in filter fabrics. The calcite formation is a long-term process; thus, a means to evaluate the potential of calcite precipitation in an accelerated manner is necessary. In this study, an accelerated calcite precipitation (ACP) procedure of RCA was developed, and its performance was evaluated. Two types of ACP methods were devised: short-term and long-term simulations. The long-term ACP procedure can be used to determine maximum lifetime calcite precipitation while the short-term ACP procedure can be used to evaluate the effect of test variables (e.g. aggregate type, fine content, etc.) on the calcite precipitation

Improvements To The Aashto Subgrade Resilient Modulus (MR) Equation

Evaluation of subgrade soil stiffness provides valuable information about the expected behavior and response of pavements, which can be used to group pavement sections with similar structural capacities and pavement maintenance and rehabilitation to prioritize projects. A deflection test, such as the falling weight deflectometer (FWD), is commonly used to determine subgrade resilient modulus (MR) from its measured deflection data. A correction factor has been applied to the AASHTO MR equation for adjusting the difference between laboratory MR and the in situ measurements (with the FWD). However, large variations on the correction factor result in less accuracy of subgrade MR based on FWD measurements. The objective of this research is to evaluate the accuracy of the AASHTO M R equation and improve its accuracy by adjusting the MR correction factor. This paper consists of subtasks: (a) evaluating the current AASHTO MR correction factor; (b) evaluating the affecting factors (i.e., subgrade soil stiffness, bedrock depth, highway classification, and environmental condition); and (c) developing a framework to determine accurate MR correction factor. © 2014 American Society of Civil Engineers