Nonequilibrium quench dynamics in quantum quasicrystals

We study the nonequilibrium dynamics of a quasiperiodic quantum Ising chain after a sudden change in the strength of the transverse field at zero temperature. In particular we consider the dynamics of the entanglement entropy and the relaxation of the magnetization. The entanglement entropy increases with time as a power-law, and the magnetization is found to exhibit stretched-exponential relaxation. These behaviors are explained in terms of anomalously diffusing quasiparticles, which are studied in a wave packet approach. The nonequilibrium magnetization is shown to have a dynamical phase transition.Comment: 17 pages, 15 figures; revised version; to appear in New Journal of Physic

Front dynamics in the Harper model

The front dynamics in the Harper (or Aubry-Andr\'e) model (which has a localization transition) is investigated using two different settings, particle number front where the system is at zero temperature, and initially, the particle numbers differ on the two sides, and temperature front where the two sides have different temperature initially. The two differently prepared half systems are connected suddenly, and the following dynamics is investigated. In the extended phase, the dynamics is ballistic, similar to the dynamics of a pure system. At the critical point, one finds a power-law time dependence of the particle number and the entanglement entropy of the zero temperature setting. In the localized phases, the observables oscillate around an average value, which is independent of the system size. The particle number front shapes have been investigated at zero temperature setting, in the extended phase they scale together exactly as in the homogeneous XX chain, however at the critical point the scaling relation contains a power ($t^{0.55}$) of the time. The mutual information between neighboring intervals at the front has been calculated, and it is promotional with the logarithm of the interval length and also with the logarithm of the time in the extended phase and at the critical point. The prefactors of the time and size dependence are equal for the zero temperature process, however differ for the finite temperature front

A Matter of Perception

This pilot study explores the possibility of cognitive training software Neurotracker (NT), to have potential beneficial effects for Traumatic Brain Injury patients with Sensory Processing Disorder. Five subjects with TBI and SPD trained for 5 weeks/21 sessions with Neurotracker. Pre-post training cognitive tests (WAIS TMTA, TMTB, LNS) and surveys were conducted to measure possible cognitive differences with no statistical significant results. However, significant improvement in Neurotracker scores were found. (α=.05, P=.043) between T1 (M=1.79, SD=0.44) and T2 (M =2.73, SD = 0.55) and positive changes associated with attention attention span, divided attention, (multiple) object tracking and motion sickness

The Universal Multizone Crystallizator (UMC) Furnace: An International Cooperative Agreement

The Universal Multizone Crystallizator (UMC) is a special apparatus for crystal growth under terrestrial and microgravity conditions. The use of twenty-five zones allows the UMC to be used for several normal freezing growth techniques. The thermal profile is electronically translated along the stationary sample by systematically reducing the power to the control zones. Elimination of mechanical translation devices increases the systems reliability while simultaneously reducing the size and weight. This paper addresses the UMC furnace design, sample cartridge and typical thermal profiles and corresponding power requirements necessary for the dynamic gradient freeze crystal growth technique. Results from physical vapor transport and traveling heater method crystal growth experiments are also discussed

Structures in grain-refined directionally solidified hypoeutectic Al-Cu alloys: Benchmark experiments under microgravity on-board the International Space Station

Benchmark solidification experiments were successfully performed under microgravity conditions on-board the International Space Station (ISS) within the ESAprogramme CETSOL (Columnar-to-Equiaxed Transition in SOLidification Processing). Cylindrical samples of grain-refined Al-4wt.%Cu, Al-10wt.%Cu and Al-20wt.%Cu alloys were directionally solidified in a gradient furnace to investigate columnar and equiaxed dendritic growth structures as well as the columnar to equiaxed transition under diffusive conditions. The determination of temperature gradients; interface velocities; and cooling rates at liquidus, solidus, and eutectic front positions provides well-defined thermal experimental characterization. The evaluation of the flight samples demonstrates that no significant macrosegregation along the sample axis occurred and no radial effects were observed. Therefore, purely diffusive solidification behaviour without any residual melt convection can be assumed for these microgravity experiments. The analyses of the microstructure in longitudinal cross-sections show dendritic structures without any pore formation and the averaged eutectic fraction is largely constant along the sample. The samples of refined Al-4wt.%Cu alloy show a sharp CET from columnar dendrites to a fine equiaxed steady-state grain structure whereas in the samples of refined Al-10wt.%Cu and Al-20wt.%Cu alloy, only equiaxed dendritic grain growth is observed. A quantitative analysis of the equiaxed grain morphology shows, that the shapes of the equiaxed dendrites depend on the applied temperature gradient, but the grain sizes in radial and longitudinal directions are identical. Therefore, a fully equiaxed dendritic growth structure without dendrite elongation was obtained. Compared to experiments in microgravity with non-refined Al-Cu alloys the average equiaxed grain size is about three times smaller

Investigating the potential barrier function of nanostructured materials formed in engineered barrier systems (EBS) designed for nuclear waste isolation

"This is the peer reviewed version of the following article: Jaime Cuevas Ana Isabel Ruiz Raúl Fernández, "Investigating the Potential Barrier Function of Nanostructured Materials Formed in Engineered Barrier Systems (EBS) Designed for Nuclear Waste Isolation, The Chemical Record 18 (2018): 1065-1075 , which has been published in final form at http://doi.org/10.1002/tcr.201700094. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions."Clay and cement are known nano-colloids originating from natural processes or traditional materials technology. Currently, they are used together as part of the engineered barrier system (EBS) to isolate high-level nuclear waste (HLW) metallic containers in deep geological repositories (DGR). The EBS should prevent radionuclide (RN) migration into the biosphere until the canisters fail, which is not expected for approximately 103 years. The interactions of cementitious materials with bentonite swelling clay have been the scope of our research team at the Autonomous University of Madrid (UAM) with participation in several European Union (EU) projects from 1998 up to now. Here, we describe the mineral and chemical nature and microstructure of the alteration rim generated by the contact between concrete and bentonite. Its ability to buffer the surrounding chemical environment may have potential for further protection against RN migratio

Optimization of the MgO-SiO₂ binding system for fiber-cement production with cellulosic reinforcing elements

A range of MgO and SiO2 blends mixed with water are analyzed to develop clinker-free fiber-cement products reinforced with cellulosic fibers. The target is the development of a binder which is not chemically aggressive to the fibers, but which develops high mechanical strength Mechanical performance of the materials developed is not only influenced by magnesium silicate hydrate (M-S-H) gel content, but is more related to the void content within the paste due to unreacted water, meaning that the gel-space ratio concept is valuable in describing the compressive strengths of these materials. A higher MgO content in the mix formulation leads to M-S-H gels with increased Mg/Si ratio. The Mg/Si ratio also increases over time for each mix, indicated by changes in the gel structure as reaction is not yet complete after 28 days. SEM shows a heterogeneous microstructure which also has regions of high Si content. The 60 wt%MgO-40 wt%SiO2 system is chosen as the optimal formulation since it is the least alkaline binder with high mechanical strength. Bending tests on pastes reinforced with cellulosic pulps prove the efficiency of this binder, which preserves the reinforcing capacity of the fibers much better than Portland cement pastes after 200 cycles of accelerated ageing

Thermal stability of C-S-H phases and applicability of Richardson and Groves’ and Richardson C-(A)-S-H(I) models to synthetic C-S-H

Synthetic C-S-H samples prepared with bulk C/S ratios from 0.75 to 1.5 were analyzed by coupled TG/DSC/FTIR and in-situ XRD while heating, in order to correlate observed weight loss curves with the kinetics of evolved gases, and to investigate the transformations C-S-H→β-wollastonite→α-wollastonite. The temperature of the transformation to β-wollastonite increased with increasing C/S. The temperature for the transformation from β- to α-wollastonite meanwhile decreased with increasing C/S; indicating that excess CaO stabilized the α-polymorph. The transformation C-S-H→β-wollastonite was accompanied by the formation of α`LC2S for C/S > 1. In the case of C-S-H with C/S = 1.5, both β-C2S and rankinite were formed and then decomposed before the transformation to β-wollastonite and α`LC2S. C-S-H with low C/S was found to be more stable upon heating. The chemical structural models of Richardson and Groves’ and Richardson C-A-S-H(I) were used to obtain the structural-chemical formulae

A glucose biosensor based on novel Lutetium bis-phthalocyanine incorporated silica-polyaniline conducting nanobeads

The facile preparation of highly sensitive electrochemical bioprobe based on lutetium 13 phthalocyanine incorporated silica nanoparticles (SiO2(LuPc2)) grafted with Poly(vinyl 14 alcohol-vinyl acetate) itaconic acid (PANI(PVIA)) doped polyaniline conducting nanobeads 15 (SiO2(LuPc2)PANI(PVIA)-CNB) is reported. The preparation of CNB involves two stages (i) 16 pristine synthesis of LuPc2 incorporated SiO2 and PANI(PVIA); (ii) covalent grafting of 17 PANI(PVIA) onto the surface of SiO2(LuPc2). The morphology and other physico-chemical 18 characteristics of CNB were investigated. The scanning electron microscopy images show 19 that the average particle size of SiO2(LuPc2)PANI(PVIA)-CNB was between 180-220 nm. 20 The amperometric measurements showed that the fabricated SiO2(LuPc2)PANI(PVIA)-21 CNB/GOx biosensor exhibited wide linear range (1-16 mM) detection of glucose with a low 22 detection limit of 0.1 mM. SiO2(LuPc2)PANI(PVIA)-CNB/GOx biosensor exhibited high 23 sensitivity (38.53 μA mM−1 cm−2) towards the detection of glucose under optimized 24 conditions. Besides, the real (juice and serum) sample analysis based on a standard addition 25 method and direct detection method showed high precision for measuring glucose at 26 SiO2(LuPc2)PANI(PVIA)-CNB/GOx biosensor. The SiO2(LuPc2)PANI(PVIA)-CNB/GOx 27 biosensor stored under refrigerated condition over a period of 45 days retains ~ 96.4 % 28 glucose response current

Columnar and Equiaxed Solidification of Al-7 wt.% Si Alloys in Reduced Gravity in the Framework of the CETSOL Project

International audienceDuring casting, often a dendritic microstructure is formed, resulting in a columnar or an equiaxed grain structure, or leading to a transition from columnar to equiaxed growth (CET). The detailed knowledge of the critical parameters for the CET is important because the microstructure affects materials properties. To provide unique data for testing of fundamental theories of grain and microstructure formation, solidification experiments in microgravity environment were performed within the European Space Agency Microgravity Application Promotion (ESA MAP) project Columnar-to-Equiaxed Transition in SOLidification Processing (CETSOL). Reduced gravity allows for purely diffusive solidification conditions, i.e., suppressing melt flow and sedimentation and floatation effects. On-board the International Space Station, Al-7 wt.% Si alloys with and without grain refiners were solidified in different temperature gradients and with different cooling conditions. Detailed analysis of the microstructure and the grain structure showed purely columnar growth for nonrefined alloys. The CET was detected only for refined alloys, either as a sharp CET in the case of a sudden increase in the solidification velocity or as a progressive CET in the case of a continuous decrease of the temperature gradient. The present experimental data were used for numerical modeling of the CET with three different approaches: (1) a front tracking model using an equiaxed growth model, (2) a three-dimensional (3D) cellular automaton–finite element model, and (3) a 3D dendrite needle network method. Each model allows for predicting the columnar dendrite tip undercooling and the growth rate with respect to time. Furthermore, the positions of CET and the spatial extent of the CET, being sharp or progressive, are in reasonably good quantitative agreement with experimental measurements