Vertical Relaxation Research Articles

INFLUENCE OF THE MENSTRUAL CYCLE ON THE PHYSICAL PERFORMANCE OF YOUNG FEMALE STUDENTS AT THE INSTITUT NATIONAL SUPERIEUR DE L EDUCATION POPULAIRE ET DU SPORT (INSEPS) IN DAKAR

Objective:Toevaluatetheinfluenceofthemenstrualcycleonthephysicalqualitiesofsome INSEPS students. Method: 15 female students participated in our study. Each subject performed the verticalrelaxation, reaction speed, abdominal endurance and back endurance tests on the third day ofmenstruationand the third oneaftercessation of bleeding. Results: On average, the subjects had better vertical expansion after menstruation (45.13cm) than during menstruation (43.33 cm), with no significant difference (p=0.57). In terms ofreactionspeed,thegirlsperformedbetteronaverageduringmenstruationthanafter(111versus147), with no significant difference (p=0.06). The best average performance in abdominalendurance was achieved during menstruation (390.6 repetitions versus 367.73 repetitions) butthis difference was statistically insignificant (p=0.56). In back endurance, the best averageperformanceforgirlswasachievedaftermenstruation(342.67repetitionsversus337.53repetitions).Thedifferencewas statisticallyinsignificant (p=0.92). Conclusion:Thisstudy showsthatthe menstrualcycle doesnothave a significantinfluence on the vertical relaxation, reaction speed, abdominal endurance and back enduranceofthe INSEPS students inour sample.

A complete comprehension of InGaAs capping layer deposition on InAs quantum dots by comparison of simulations, luminescence and X-ray diffraction

The mechanism of incorporation of InGaAs capping layer on InAs Quantum dots (QDs) are unclear in most of the literature studies. Various studies suggest vertical strain relaxation to be the cause of the longer wavelength emission of the dots. On the other hand, some suggest preferential In segregation on the periphery of QDs to be the reason for the enhancement of the dot size. In this study, the strain profile, electronic bands, and eigenstates of InAs QDs, with various InGaAs capping layer thickness, have been simulated using nextnano3 software. Further, the structures are grown by a molecular beam epitaxy (MBE) system. Comparison of ground-state emission energy obtained from PL and simulations, proves that strain relaxation alone is not sufficient to explain the shift in the emission wavelength, and indicate presence of a growth mechanism which alters the size of the QDs. From the in-plane and out-plane High-Resolution X-Ray Diffraction (HR-XRD) results, we have explained the complete dynamics involved in the InGaAs capping deposition, which was unclear in the literature up-to-date. Advantages of incorporation of InGaAs capping on the dots, like decrease in strain and defects, preservation of In, and increased activation energy are also observed in the study.

Interaction of a conical carbon scaffold with the thio-substituted model of fluorouracil towards approaching the drug delivery purposes

A representative FeN4-doped conical carbon (C) scaffold was investigated for participating in interactions with the thio-substituted fluorouracil (SFU) anticancer drug by performing density functional theory (DFT) calculations. In this regard, all possible relaxation configurations of SFU at the doped tip of C scaffold were examined, in which three models were obtained including one horizontal relaxation configuration (FC1) and two vertical relaxation configurations (FC2 and FC3). The results indicate the highest stability and strength for FC1 model. Examining formations and strengths of interactions showed two medium strength interactions in each of FC1, FC2, and FC3 models. Moreover, the evaluated electronic molecular orbitals features indicated availability of sensor function for the proposed C scaffold towards the interacting SFU substance. As a consequence, the models were determined to work in dual functions of sensor and carrier towards drug delivery purpose of SFU anticancer drug.

Evidence of a C60 /Co interface reconstruction and its influence on magnetic properties

By using grazing incidence x-ray diffraction and scanning tunneling microscopy experiments, we determine the interface structure of a ${\mathrm{C}}_{60}$ layer deposited on a Co(0001) surface. The room temperature deposition gives rise to a ($4\ifmmode\times\else\texttimes\fi{}4$) molecular structure with a 10% vertical relaxation of the underneath Co atoms. When annealed around 550 K, the interface undergoes a structural change with most of the buckyballs sitting in a seven Co vacancies nanohole. Ab initio calculations show that this interface reconstruction is stabilized by a strong C-Co hybridization and has a significant impact both on the interfacial magnetic anisotropy that is decreased and on the molecular spin polarization that it increased.

Notch-based speed trajectory optimisation for high-speed railway automatic train operation

Automatic train operation (ATO) systems are fast becoming one of the key components of the intelligent high-speed railway (HSR). Designing an effective optimal speed trajectory for ATO is critical to guide the high-speed train (HST) to operate with high service quality in a more energy-efficient way. In many advanced HSR systems, the traction/braking systems would provide multiple notches to satisfy the traction/braking demands. This paper modelled the applied force as a controlled variable based on the selection of notch to realise a notch-based train speed trajectory optimisation model to be solved by mixed integer linear programming (MILP). A notch selection model with flexible vertical relaxation was proposed to allow the traction/braking efforts to change dynamically along with the selected notch by introducing a series of binary variables. Two case studies were proposed in this paper where Case study 1 was conducted to investigate the impact of the dynamic notch selection on train operations, and the optimal result indicates that the applied force can be flexibly adjusted corresponding to different notches following a similar operation sequence determined by optimal train control theory. Moreover, in addition to the maximum traction/braking notches and coasting, medium notches with appropriate vertical relaxation would be applied in accordance with the specific traction/braking demands to make the model feasible. In Case study 2, a comprehensive numerical example with the parameters of CRH380AL HST demonstrates the robustness of the model to deal with the varying speed limit and gradient in a real-world scenario. The notch-based model is able to obtain a more realistic optimal strategy containing dynamic notch selection and speed trajectory with an increase (1.622%) in energy consumption by comparing the results of the proposed model and the non-notch model.

Effects of the surface wettability of nanoparticles on the impact dynamics of droplets

Herein, we report an experimental investigation on droplet impact dynamics with a particular interest in the effects of hydrophilicity and hydrophobicity of particles on the impact dynamics. Remarkable contact line pinning and receding breakup were observed when hydrophobic particles were present in the droplets, while hydrophilic particles showed little effect on the dynamics. Furthermore, the maximum retraction height and vertical oscillatory relaxation time for the droplet were restrained by hydrophobic particles. Scanning electron microscopy and rheological analyses revealed that these phenomena may be related to the adsorption and deposition of hydrophobic particles near the three-phase contact line, which leads to an increase in local viscosity and friction near the edge of the drop. In addition, the contact line pinning is positively associated with the Weber number and particle concentration. Our work provides a novel approach for droplet impact dynamics control, particularly for suppressing the oscillation and contraction of droplets.

A combined experimental and theoretical investigation of the excited-state dynamics of 2,4,6-trinitrotoluene (TNT) in DMSO solvent.

In the present contribution we carried out a TDDFT and femtosecond transient absorption study of the excited state dynamics of TNT in DMSO solvent. Vertical excitation and excited state relaxation were calculated at the SMD/M06-2X/TZVP level of theory. The electron absorption spectrum for the DMSO solvated TNT was calculated and compared with the experimental results. The results of the electronic excitation energies and the spin-orbital constants imply an intersystem crossing for the S1-T2 transition. The femtosecond time-resolved transient absorption measurements of the TNT in DMSO show the presence of two absorption signals around 650 nm and 540 nm, which are assigned to the population in the lowest singlet and triplet excited states, S1 and T1, respectively. The fast decay of the S1 state population is assigned to an efficient S1-T2 intersystem crossing, which soon internally converts to the T1 state. The slow decay of the T1 population is attributed to the nonradiative transition to the S0 state. The combined theoretical and experimental results present a mechanistic view of the photophysical dynamics of TNT in DMSO solution.

Charge-Induced Structural Changes in a Single Molecule Investigated by Atomic Force Microscopy

Intramolecular structural relaxations occurring upon electron transfer are crucial in determining the rate of redox reactions. Here, we demonstrate that subangstrom structural changes occurring upon single-electron charging can be quantified by means of atomically resolved atomic force microscopy (AFM) for the case of single copper(II)phthalocyanine (CuPc) molecules deposited on an ultrathin NaCl film. Imaging the molecule in distinct charge states (neutral and anionic) reveals characteristic differences in the AFM contrast. In comparison to density functional theory simulations these changes in contrast can be directly related to relaxations of the molecule's geometric structure upon charging. The dominant contribution arises from a nonhomogeneous vertical relaxation of the molecule, caused by a change in the electrostatic interaction with the surface.

Emission of electromagnetic waves from walls of esophagus under domination of wall slip effect

Abstract On explanation of biomedical applications and its complexity, the contraction and relaxation of Eyring-Powell fluid in esophagus has turned out to be notable amongst the challenging research fields of fluid mechanics. Therefore, the main idea of this paper is to classify the simultaneous significances of compliant walls and emission of electromagnetic waves from walls of electrically conducting Eyring-Powell fluid. Conductivity of the fluid is increased by adding the Brownian motion and thermophoresis effects. Moreover, the velocity of the channel and the fluid particles near the surfaces are assumed to be different. Due to vertical contraction and relaxation, the body forces are taken in the form of mixed convection. The dimensionless variables are utilized to convert the required partial differential equations including mass, momentum and energy into dimensionless form. The solutions of the reduced partial differential equations subject to the given boundary conditions are calculated by using Mathematica. Moreover, the various solutions for dimensionless fluid concentration, velocity, and temperature distributions are captured for different values of embedded parameters. The different dimensionless parameters governing the flow, heat and mass transfer characteristics are the Schmidt number, radiation parameter, Hartmann number, local temperature Grashof number, slip parameters, local nanoparticles Grashof number, thermophoresis parameter, Brownian motion parameter, fluid parameters and Prandtl number. Maximum velocity is noted an increasing function of velocity slip parameter. Further maximum temperature enhances by increasing Brownian motion and thermophoresis parameters. More specifically the effects of slip parameters, Brownian motion and thermophoresis parameters on the flow stream have been examined. The velocity profile shows enhance behavior for large values of velocity parameter and mixed convection, whereas, reverse impact is noticed for magnetic field. Increasing concentration slip parameter causes reduction in nanoparticle volume fraction, while temperature of the fluid rises by increasing thermal slip parameter.

Mapping the Conditions for Hydrodynamic Instability on Steady-State Accretion Models of Protoplanetary Disks

Abstract Hydrodynamic instabilities in disks around young stars depend on the thermodynamic stratification of the disk and on the local rate of thermal relaxation. Here, we map the spatial extent of unstable regions for the Vertical Shear Instability (VSI), the Convective Overstability (COS), and the amplification of vortices via the Subcritical Baroclinic Instability (SBI). We use steady-state accretion disk models, including stellar irradiation, accretion heating, and radiative transfer. We determine the local radial and vertical stratification and thermal relaxation rate in the disk, which depends on the stellar mass, disk mass, and mass accretion rate. We find that passive regions of disks—that is, the midplane temperature dominated by irradiation—are COS unstable about one pressure scale height above the midplane and VSI unstable at radii >10 au. Vortex amplification via SBI should operate in most parts of active and passive disks. For active parts of disks (midplane temperature determined by accretion power), COS can become active down to the midplane. The same is true for the VSI because of the vertically adiabatic stratification of an internally heated disk. If hydrodynamic instabilities or other nonideal MHD processes are able to create α-stresses (>10−5) and released accretion energy leads to internal heating of the disk, hydrodynamic instabilities are likely to operate in significant parts of the planet-forming zones in disks around young stars, driving gas accretion and flow structure formation. Thus, hydrodynamic instabilities are viable candidates to explain the rings and vortices observed with the Atacama Large Millimeter/submillimeter Array and Very Large Telescope.

First principles calculation of redox potential for tetravalent actinides in molten LiCl–KCl eutectic based on vertical substitution and relaxation

The pyroprocessing technology of spent fuel is promise because of its advantages compared with the wet-processing technology; however, the development of pyroprocessing technology depends on the availability of basic physical chemistry properties for the relevant molten salt mixtures. In this work, the first principles molecular dynamics (FPMD) simulation is applied to the evaluation of redox potential of tetravalent actinides (Pa4+, U4+, and Np4+) in molten LiCl–KCl (ClLiK) eutectic. The reduction energetics, referenced to Th4+, is analyzed in terms of vertical substitution and relaxation, and satisfactory agreement is reached between our FPMD evaluations and experimental results reported in literatures.

CO2 charged brines changed rock strength and stiffness at Crystal Geyser, Utah: Implications for leaking subsurface CO2 storage reservoirs

CO2 geological storage in saline aquifers results in acidification of resident brine. Chemical reactions between acidified brine and rock minerals lead to dissolution and precipitation of minerals at various time scales. Mineral dissolution and precipitation are often neglected in assessing the mechanical integrity of target storage formations, yet, changes in rock strength and deformational behavior can impact trapping mechanisms. This study shows the impact of exposure to CO2-charged brine on shear strength and stiffness of various outcrop rocks evaluated through triaxial testing. The tested rocks were exposed to CO2-charged brine over geological time at a naturally occurring near-surface seepage along the Little Grand Wash Fault and Salt Wash Grabens, which include the Crystal Geyser site near the town of Green River, Utah. Prior work suggests that this site provides a near-surface structural analog for possible fault-controlled CO2 leakage over time scales that exceed expected injection time scales (10–100 years). Results show mechanical alteration in various aspects: (1) CO2-charged brine alteration at near-surface conditions results in mineral dissolution/precipitation and reduction of shear strength and brittleness of Entrada sandstone and Summerville siltstone samples, and (2) carbonate precipitation in fractured Mancos shale leads to matrix stiffening and fracture mineralization resulting in overall stiffer and likely tighter shale. Additional discrete element simulations coupled with a bonded-particle-model confirm the role of cement bond size alteration as one of the main controls for rock chemo-mechanical alteration in sandstones. The chemo-mechanical alteration path that mimics cement dissolution (under stressed subsurface conditions) results in vertical compaction and lateral stress relaxation. Overall, results show that rock exposure to CO2-charged brine can impart distinct petrophysical and geomechanical changes according to rock lithology and location with respect to major CO2 conduits. While mineral dissolution in the storage rock may result in undesired reservoir strains and changes of stresses, mineral precipitation downstream from a leakage path can help seal potentially induced fractures.

Strain relaxation induced coexistence of ferromagnetism and antiferromagnetism in (110)-oriented LuMnO3 thin films on YAlO3 : A first-principles study

Substrate strain offers an extra dimension in enriching the functionality of perovskite thin films. The recent observation of the coexistence of ferromagnetism (FM) and antiferromagnetism (AFM) in the ${\mathrm{LuMnO}}_{3}$ thin films on (110)-oriented ${\mathrm{YAlO}}_{3}$ substrate illustrated another interesting example [Phys. Rev. Lett. 111, 037201 (2013); Phys. Rev. B 94, 054423 (2016)]. The FM signal arises from a thin atomic layer near the ${\mathrm{YAlO}}_{3}$ substrate. We propose in this paper that vertical strain relaxation may stabilize the FM structure in the most compressively strained region near the substrate, while the AFM structure is stabilized in less compressively strained outer surfaces of thin films. This physical picture was supported by the magnetic phase diagram vs compressive strain derived from comprehensive first-principles calculations. The critical $[1\overline{1}0]$ strain separating E-AFM and FM structures is $\ensuremath{\epsilon}\ensuremath{\approx}\ensuremath{-}0.0425$, which is close to the value $\ensuremath{\epsilon}\ensuremath{\approx}\ensuremath{-}0.047$ dictated by ${\mathrm{YAlO}}_{3}$ substrate. From the half-metal feature of the FM structure and ferroelectric property of E-AFM structure, the greatly reduced ferroelectric polarization and averaged magnetic moment of $0.5\phantom{\rule{0.16em}{0ex}}{\ensuremath{\mu}}_{B}/\mathrm{Mn}$ can be understood.

THE FIRST DETECTION OF PHOTOMETRIC VARIABILITY IN A Y DWARF: WISE J140518.39+553421.3

ABSTRACT We present the first detection of the photometric variability in a spectroscopically confirmed Y dwarf. The Infrared Array Camera on board the Spitzer Space Telescope was used to obtain time series photometry of WISE J140518.39+553421.3 at 3.6 and 4.5 μm over a 24-hr period at two different epochs separated by 149 days. Variability is evident at 4.5 μm in the first epoch and at 3.6 and 4.5 μm in the second epoch, which suggests that the underlying cause or causes of this variability change on the timescales of months. The second-epoch [3.6] and [4.5] light curves are nearly sinusoidal in form, in phase, have periods of roughly 8.5 hr, and have semi-amplitudes of 3.5%. We find that a simple geometric spot model with a single bright spot reproduces these observations well. We also compare our measured semi-amplitudes of the second-epoch light curves to predictions of the static, one-dimensional, partly cloudy, and hot spot models of Morley and collaborators, and find that neither set of models can reproduce the observed [3.6] and [4.5] semi-amplitudes simultaneously. Therefore, more advanced two-dimensional or three-dimensional models that include time-dependent phenomena like vertical mixing, cloud formation, and thermal relaxation are sorely needed in order to properly interpret our observations.

A Model for Turbulent Diffusion in a Vertically Inhomogeneous Atmospheric Boundary Layer

An analytical solution of the one-dimensional turbulent diffusion equation considering non-Fickian closure in a vertically inhomogeneous atmospheric boundary layer (ABL) is presented. The presented solution is improved and more physically consistent in the description of dispersion because it includes (for the first time) the explicit gravitational settling ( ) of large particles. Moreover, deposition velocity ( ) as a boundary condition, vertical turbulent velocity ( ), skewness ( ), vertical Lagrangian time ( ) scale and relaxation time ( ) (“finite-velocity” diffusion) are included. Via numerical simulations, we analyzed the influence of the countergradient term, dry deposition to the ground and gravitational settling on the concentration field. Our results demonstrate an example of the usefulness of analytical solutions to the advection-diffusion equation. DOI: 10.5935/1984-6835.20160087

Palladium-platinum core-shell icosahedra with substantially enhanced activity and durability towards oxygen reduction.

Conformal deposition of platinum as ultrathin shells on facet-controlled palladium nanocrystals offers a great opportunity to enhance the catalytic performance while reducing its loading. Here we report such a system based on palladium icosahedra. Owing to lateral confinement imposed by twin boundaries and thus vertical relaxation only, the platinum overlayers evolve into a corrugated structure under compressive strain. For the core-shell nanocrystals with an average of 2.7 platinum overlayers, their specific and platinum mass activities towards oxygen reduction are enhanced by eight- and sevenfold, respectively, relative to a commercial catalyst. Density functional theory calculations indicate that the enhancement can be attributed to the weakened binding of hydroxyl to the compressed platinum surface supported on palladium. After 10,000 testing cycles, the mass activity of the core-shell nanocrystals is still four times higher than the commercial catalyst. These results demonstrate an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.

A theoretical investigation of the (0001) covellite surfaces.

We report on the properties of the (0001) covellites surfaces, which we investigate by periodic slab density functional theory calculations. The absolute surface energies have been computed for all bulk terminations, showing that surfaces terminated by the flat CuS layer are associated with the lowest surface energy. Cleavage is predicted to occur across the [0001] interlayer Cu-S bond. The surfaces obtained by lowest energy cleavage are analyzed in terms of the atomic vertical relaxation, workfunction, and surface band structure. Our study predicts the presence of a shallow pz-derived surface state located 0.26 eV below the Fermi level, which is set to play an important role in the surface reactivity of covellite.

Direct numerical simulations of anisotropic diffusion of spherical particles in sedimentation

We investigated the scaling of the hydrodynamic velocity fluctuations and self-diffusion in the sedimentation of monodispersed spherical particles via direct numerical simulations using the smoothed profile method over a moderate range of volume fractions (0.01≤φ≤0.12). Hydrodynamic velocity fluctuations are visible at large Peclet numbers (Pe), and they scale as (φL/a)(1/2) at low volume fractions (φ≤0.04). Their characteristics become independent of volume fraction at moderate volume fractions (0.06≤φ≤0.12). Both vertical and horizontal self-diffusion coefficients scale as (L/a)(3/2)φ(1/2) at low volume fractions. At moderate volume fractions, the vertical diffusion scales as (L/a)(3/2)φ(-1/2); in contrast, the horizontal diffusion is saturated with respect to volume fraction. The diffusion anisotropy increases with increasing Pe and saturates at high Pe values. The saturated value remains unchanged at low volume fractions, whereas further increase in the volume fraction decreases this anisotropy. The reduction of this anisotropy is attributed to the φ(-1/2) scaling of the vertical relaxation time at moderate volume fractions; however, the horizontal relaxation time is independent of the volume fraction at this regime.

Sedimentation of non-Brownian spheres at high volume fractions

We performed direct numerical simulations of non-Brownian sedimenting particles, using a smooth profile method over a wide range of volume fractions from 0.01 to 0.5. We found that hydrodynamic velocity fluctuations scale as ϕ1/2, both parallel and perpendicular to gravity at low volume fractions (ϕ ≤ 0.04) due to anisotropic microstructure and decay with further increase in ϕ because of many body hydrodynamic interactions. Unlike velocity fluctuations, vertical relaxation times scale as ϕ−1/2 for the full range of volume fractions, whereas horizontal relaxation times decrease as ϕ−1/2 at low volume fractions, remain unchanged and then decrease sharply at high volume fractions. Similarly, horizontal and vertical diffusion coefficients increase as ϕ1/2 at low volume fractions. Moreover, vertical diffusion decays with further increase in ϕ, whereas horizontal diffusion remains unchanged and then decreases. The microstructure analysis of the suspension showed that at low volume fractions the anisotropic microstructure determines the transport properties and at ϕ > 0.12 many body interactions govern the system properties, whereas a cross-over exists in between these two regimes.

Giant Alkali-Metal-Induced Lattice Relaxation as the Driving Force of the Insulating Phase of Alkali-Metal/Si(111):B

Ab initio density-functional theory calculations, photoemission spectroscopy (PES), scanning tunneling microscopy, and spectroscopy (STM, STS) have been used to solve the 2sqrt[3]×2sqrt[3]R30 surface reconstruction observed previously by LEED on 0.5 ML K/Si:B. A large K-induced vertical lattice relaxation occurring only for 3/4 of Si adatoms is shown to quantitatively explain both the chemical shift of 1.14 eV and the ratio 1/3 measured on the two distinct B 1s core levels. A gap is observed between valence and conduction surface bands by ARPES and STS which is shown to have mainly a Si-B character. Finally, the calculated STM images agree with our experimental results. This work solves the controversy about the origin of the insulating ground state of alkali-metal/Si(111):B semiconducting interfaces which were believed previously to be related to many-body effects.