Effective Interaction Model Research Articles

Polyvinylpyrrolidone Behavior in Water/Ethanol Mixed Solvents: Comparison of Modeling Predictions with Experimental Results

The objective of this work is to study the behavior of a neutral polymer, polyvinylpyrrolidone (PVP), in a mixture of water and ethanol. A comparison of the experimental results with a theoretical model of effective solvent interaction with polymer (ESIP) was made. To do so, dynamic light scattering experiments were used to measure the hydrodynamic radius of PVP (M w = 3.6 × 105 g·mol−1) as a function of the ethanol fraction, x A, in the medium at 25 °C. We show that the polymer adopts an ideal chain–globule–coil conformation transition as the ethanol molar fraction varies. This transition is attributed to the change of the solvent quality which results from water and ethanol complex formation. On the other hand, the ternary PVP/water/ethanol system was described by the ESIP model. From the polymer–effective solvent interaction, the second virial coefficient of the polymer/effective solvent and the preferential adsorption parameter were calculated. The obtained results are in agreement with the reported experiments.

The Effects of Cooperative Design Learning Program based on Peer Interaction on Young Children"s Self- Concept

Background : The research aimed to find out the effects of cooperative design learning program on young childrens self-concept, sought to develop an effective design learning program and interactive teaching model between children and their teacher. The research hypothesis was set up so that there are statistical differences in relation to six sub factors of SCI(Self- Concept Inventory): self-concept of physical ability, general self-concept, self-concept of friendship, self-concept of relationship with parents, self-concept of language, and self-concept of mathematics, between a control group and an experimental group who participated in the cooperative the design learning program. Methods : In order to verify the hypothesis, this study conducted design learning program for 12 weeks with 51 young children aged 5 (average months : 67.65) attending kindergarten. To measure young childrens self-concept, this study used the Self-Concept Inventory (SCI) developed by Kyung-hwa Lee and Jin-Young Goh(2006) with the pre- and post-test repeated measure with control group design. The children were divided into an experimental group and a control group. Three design activities: postcard design, pop-up card design, and mobile design were performed thrice a week for 12 weeks. In the case of the experimental group, a pair of children worked out the design process (Discovering -> Brainstorming -> Making decision -> Sketching ->Modeling -> Evaluating) based on cooperative activities. In comparison, the control group conducted selflearning and self-assessment which had been excluded from collaboration. Result : The data analysis results showed statistically significant differences between the experimental group and the control group. Especially, the factor which had remarkable effects on children’s self-concept are general self-concept, self-concept of friendship and self-concept of language. Conclusions : Cooperative design learning positively affects children’s development. The research found out the effects of a cooperative design learning program involving students and their teacher on young childrens self-concept. This data will offer design educators effective foundation resources as well as an interactive teaching model between children and their teacher.

Early establishment response of different Pinus nigra ssp. salzmanii seed sources on contrasting environments: Implications for future reforestation programs and assisted population migration

Forest restoration constitutes an important issue within adaptive environmental management for climate change at global scale. However, effective implementation of these programs can only be achieved by revising current seed transfer guidelines, as they lack inherent spatial and temporal dynamics associated with climate change. In this sense, provenance trials may provide key information on the relative performance of different populations and/or genotypes under changing ecological conditions. This study addresses a methodological approach to evaluate early plantation performance and the consequent phenotypic plasticity and the pattern of the adaptation of different seed sources in contrasting environments. To this end, six seed sources of Salzmann pine were tested at three contrasting trial sites testing a hypothetical assisted population migration. Adaptation at each site was assessed through Joint Regression and Additive Main effect and Multiplication Interaction (AMMI) models. Most of the observed variation was attributed to the environment (above 90% for all traits), even so genotype and genotype by environment interaction (GxE) were significant. Seedlings out-planted under better site conditions did not differ in survival but in height growth. However, on sites with higher constraints, survival differed among seed sources and diameter growth was high. The adaptation analyses (AMMI) indicated that the cold-continental seed source ‘Soria’ performed as a generalist seed source, whereas ‘Cordilleras Béticas’, the southernmost seed source, was more adapted to harsh environments (frost and drought) in terms of survival. The results supported partially the hypothesis that assisted migration of seed sources makes sense within limited transfer distances, and this was reinforced by the GxE results. The present study could be valuable to address adaptive transfer of seedings in ecological restoration and to determine the suitable seed sources for reforestation programs and assisted population migration under climatic changes. The reported results are based on 3 years' data and need to be considered in this context.

Testing the importance of collective correlations in neutrinolessββdecay

We investigate the extent to which theories of collective motion can capture the physics that determines the nuclear matrix elements governing neutrinoless double-beta decay. To that end we calculate the matrix elements for a series of isotopes in the full $pf$ shell, omitting no spin-orbit partners. With the inclusion of isoscalar pairing, a separable collective Hamiltonian that is derived from the shell model effective interaction reproduces the full shell-model matrix elements with good accuracy. A version of the generator coordinate method that includes the isoscalar pairing amplitude as a coordinate also reproduces the shell model results well, an encouraging result for theories of collective motion, which can include more single-particle orbitals than the shell model. We briefly examine heavier nuclei relevant for experimental double-beta decay searches, in which shell-model calculations with all spin-orbit partners are not feasible; our estimates suggest that isoscalar pairing also plays a significant role in these nuclei, though one we are less able to quantify precisely.

The scattering cross sections for6,7Li +nreactions

We investigate the continuum-discretized coupled-channel analysis to the integrated elastic and inelastic scattering cross sections for 6,7 Li + n reactions. We used the Jeukenne- Lejeune-Mahaux effective nucleon-nucleon interaction and optical model potential at incident neutron energies below and above 10 MeV, respectively. The calculated elastic and inelastic scattering cross sections with observed incident energies are almost in good agreement with experimental and evaluated data. cross sections for 6,7 Li at incident neutron energies below 10 MeV by using optical model potential (OMP) (7,8) and above 10 MeV by using JLM. We adjust the normalization constants for the OMP, because the agreement of the calculated cross sections with the data in very low incident energies of the neutron is insufficient without any adjustments. The energy dependent normalization constants, real part λv and imaginary part λw, of the OMP and JLM are determined explicitly from the integrated elastic cross section data, respectively. Comparing the results of calculations with experimental data, we discuss that the present CDCC calculations, which reproduce the experimental data observed in incident energies higher than 10 MeV with the single folding potential of the JLM and in lower energies with introducing the normalization factors for the cluster folding potential of the OMP.

A new parameter-free soft-core potential for silica and its application to simulation of silica anomalies.

A core-softening of the effective interaction between oxygen atoms in water and silica systems and its role in developing anomalous thermodynamic, transport, and structural properties have been extensively debated. For silica, the progress with addressing these issues has been hampered by a lack of effective interaction models with explicit core-softening. In this work, we present an extension of a two-body soft-core interatomic force field for silica recently reported by us [S. Izvekov and B. M. Rice, J. Chem. Phys. 136(13), 134508 (2012)] to include three-body forces. Similar to two-body interaction terms, the three-body terms are derived using parameter-free force-matching of the interactions from ab initio MD simulations of liquid silica. The derived shape of the O-Si-O three-body potential term affirms the existence of repulsion softening between oxygen atoms at short separations. The new model shows a good performance in simulating liquid, amorphous, and crystalline silica. By comparing the soft-core model and a similar model with the soft-core suppressed, we demonstrate that the topology reorganization within the local tetrahedral network and the O-O core-softening are two competitive mechanisms responsible for anomalous thermodynamic and kinetic behaviors observed in liquid and amorphous silica. The studied anomalies include the temperature of density maximum locus and anomalous diffusivity in liquid silica, and irreversible densification of amorphous silica. We show that the O-O core-softened interaction enhances the observed anomalies primarily through two mechanisms: facilitating the defect driven structural rearrangements of the silica tetrahedral network and modifying the tetrahedral ordering induced interactions toward multiple characteristic scales, the feature which underlies the thermodynamic anomalies.

Variance and stability analyses of growth characters in half-sib Betula platyphylla families at three different sites in China

Growth characteristics have a complex inheritance pattern, and gene–environment interactions make predicting tree responses to environmental change difficult. In this study, we planted 44 Betula platyphylla families at three different sites (Mao er shan forestry center in Shangzhi, Jilin experiment forestry center in Jilin, Lang xiang forestry center in Langxiang) in northeastern China. Variation and stability of genotype–environment interactions of different families were analyzed using additive main effect and multiplicative interaction models. Variation analysis indicated significant differences between site × family interaction mean values for height, diameter at breast height, volume, and stem straight degree, suggesting that most genotypes responded differently according to location. The phenotypic coefficients of variation of different traits ranged from 12.84 % (stem straight degree in Langxiang) to 53.34 % (volume in Langxiang) and heritabilities of the different traits varied from 0.485 (diameter at breast height in Mao er shan) to 0.781 (height in Jilin). Correlation analysis showed a significantly positive association between tree height, diameter at breast height, and volume at the same and different sites, but stem straight degree showing a weaker correlation with other traits. Stability analysis indicated that some families had high tree heights but were sensitive to environmental conditions, whereas others had average tree heights but were resistant to environmental conditions. These results suggest that families should be bred in various habitats to assess growth under favorable and unfavorable environments. Under a selection ratio of 10 %, four families (family 1–7, 4–7, 3–12 and 4–13) were rated as superior families. The average height, diameter at breast height, volume, and stem straight degree of these four families were higher than average of all the families by 12.24, 16.82, 32.28 and 6.28 % in the four test sites, respectively.

Revisiting the monopole components of effective interactions for the shell model

In this paper, we revisit the monopole components of effective interactions for the shell model. Without going through specific nuclei or shell gaps, universal roles of central, tensor, and spin–orbit forces can be proved, reflecting the intrinsic features of shell model effective interactions. For monopole matrix elements, even and odd channels of central force often have a canceling effect. However, for the contributions to the shell evolution, its even and odd channels could have both positive or negative contributions, enhancing the role of central force on the shell structure. Tensor force is generally weaker than central force. However, for the effect on shell evolutions, tensor force can dominate or play a competitive role. A different systematics has been discovered between T = 1 and 0 channels. For example, tensor force, well established in the T = 0 channel, becomes uncertain in the T = 1 channel. We calculate the properties of neutron-rich oxygen and calcium isotopes in order to study T = 1 channel interactions further. It is learned that the main improvements of empirical interactions are traced to the central force. For non-central forces, antisymmetric spin–orbit (ALS) force, originated from many-body perturbations or three-body force, could also play an explicit role. T = 1 tensor forces are less constrained so their effect can differ in different empirical interactions. The influence of tensor force may sometimes be canceled by many-body effects. For T = 0 channels of effective interactions, which is the main source of neutron–proton correlations, central and tensor forces are the leading components. For T = 1 channels, which can act between like-particles, the request for many-body correlations could be more demanding, so that the monopole anomaly of the T = 1 channel might be more serious.

The effect of genotype by environment interaction, phenotypic plasticity and adaptation on Pinus halepensis reforestation establishment under expected climate drifts

Genotype by environment interaction (GEI) is becoming an important issue within the proactive adaptive silviculture oriented to global changes. However, there is a considerable lack of information on how GEI and phenotypic plasticity may affect early establishment (survival and early growth) performance in many non-commercial forest species, such as Aleppo pine, a key species in semiarid forest restoration programs. The objectives of this study were to (1) evaluate the phenotypic plasticity and adaptation in the broad context of GEI of eleven Aleppo pine seed sources regarding survival, height and diameter growth after outplanting in contrasting core and marginal habitats representing core-to-dry and cold-to-core drifts and to (2) compare the efficiency of joint regression and Additive Main effect and Multiplication Interaction (AMMI) models in elucidating the pattern of the adaptation of the eleven seed sources regarding these traits. Even though phenotypic plasticity was low, more plasticity was observed in the core drift than the dry drift. Specific adaptation to extreme environments was coupled with lower phenotypic plasticity. Among traits, plasticity was lower for survival and height than for diameter in the dry drift and the opposite for the core drift. There were also significant environment, genotype and GEI effects. AMMI models revealed higher capabilities than joint regression in determining seed sources adaptation across environments. Specifically, seed sources with higher plasticity performed better on the core habitat conditions. Southern seed sources of ‘Bética Septentrional’ and ‘La Mancha’ suited more to the dry environment. However, ‘Maestrazgo Los Serranos’ seed source grew better under the cooler local conditions. ‘Levante Interior’ seed source performed as a generalist genotype adapted to both drifts. These results make a significant contribution towards reforestation programs with practical implications for abiotic stress tolerance and assisted population migration in response to climate change.

Evidence for Increased neutron and proton excitations between 51 − 63Mn

The hyperfine structures of the odd-even 51−63Mn atoms (N=26−38) were measured using bunched beam collinear laser spectroscopy at ISOLDE, CERN. The extracted spins and magnetic dipole moments have been compared to large-scale shell-model calculations using different model spaces and effective interactions. In the case of 61,63Mn, the results show the increasing importance of neutron excitations across the N=40 subshell closure, and of proton excitations across the Z=28 shell gap. These measurements provide the first direct proof that proton and neutron excitations across shell gaps are playing an important role in the ground state wave functions of the neutron-rich Mn isotopes.

Elastic scattering of low energy electrons in partially ionized dense semiclassical plasma

Elastic scattering of electrons by hydrogen atoms in a dense semiclassical hydrogen plasma for low impact energies has been studied. Differential scattering cross sections were calculated within the effective model of electron-atom interaction taking into account the effect of screening as well as the quantum mechanical effect of diffraction. The calculations were carried out on the basis of the phase-function method. The influence of the diffraction effect on the Ramsauer–Townsend effect was studied on the basis of a comparison with results made within the effective polarization model of the Buckingham type.

Self-ordering and collective dynamics of transversely illuminated point-scatterers in a 1D trap

We study point-like polarizable particles confined in a 1D very elongated trap within the evanescent field of an optical nano-fiber or nano-structure. When illuminated transversely by coherent light, collective light scattering into propagating fiber modes induces long-range interactions and eventually crystallization of the particles into regular order. We develop a simple and intuitive scattering-matrix based approach to study these long-range interactions by collective scattering and the resulting light-induced self-ordering. For few particles we derive explicit conditions for self-consistent stable ordering. In the purely dispersive limit with negligible back-scattering, we recover the prediction of an equidistant lattice as previously found for effective dipole-dipole interaction models. We generalize our model to experimentally more realistic configurations including backscattering, absorption and a directional scattering asymmetry. For larger particle ensembles the resulting self-consistent particle-field equations can be numerically solved to study the formation of long-range order and stability limits.

Effective protein-protein interaction from structure factor data of a lysozyme solution

We report the determination of an effective protein-protein central potential for a lysozyme solution, obtained from the direct inversion of the total structure factor of the system, as extracted from small angle neutron scattering. The inversion scheme rests on a hypernetted-chain relationship between the effective potential and the structural functions, and is preliminarily tested for the case of a Lennard-Jones interaction. The characteristics of our potential are discussed in comparison with current models of effective interactions in complex fluids. The phase behavior predictions are also investigated.

Pressure and temperature dependent elastic, mechanical and thermodynamical properties of nuclear fuel: UO2 and UN2

The high-pressure (temperature) elastic and thermodynamic properties of UO2 and UN2 is presented. For cubic UO2 and UN2, model effective interatomic interaction potential incorporating long range Coulomb, charge transfer interactions, covalency effect, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions is formulated. Both charge transfer interactions and covalency effect apart from long range Coulomb are important in revealing high-pressure induced associated volume collapse, elastic and thermodynamical properties. The elastic constants, Debye temperature, and thermal expansion coefficient obtained are in good agreement with the available experimental data and other theoretical results. The UO2 and UN2 is mechanically stiffened, thermally softened, and ductile (brittle) in nature as inferred from the pressure (temperature) dependent elastic constants behavior. To our knowledge this is the first quantitative theoretical prediction of the pressure and temperature dependence of elastic, thermal and thermodynamical properties of UO2 and UN2 and still awaits experimental confirmation.

Explore development model for strategic emerging industries & Promote nanotech industrialization and application

As a nation with early R&D activities and significant achievements in papers and patents on nanotech, China noticeably lags behind in the industrialization of the field, and has not yet formed a nanotech “industry” consensus. Suzhou is the first city in China taking nanotech industry as its strategic emerging industry to lead the transforming and upgrading of regional economy. This strategy is highly supported by central government, Chinese Academy of Sciences and Jiangsu Province. The development of strategic emerging industry relies on top-level design and systematic planning. With international experiences, national conditions and regional realities in mind, Suzhou proposed to build nanotech industry ecosystem to layout and integrate industry resources and eventually to establish an effective interactive model in accordance with the need of industrial development. This model has been well recognized and accepted by nanotech related academia, industry and government agencies both domestically and internationally.

Elastic, mechanical, and thermodynamical properties of superionic lithium oxide for high pressures

The elastic and thermodynamic properties of Li2O for high pressures are presented. For cubic Li2O, model effective interatomic interaction potential incorporating long-range Coulomb, charge transfer interactions, covalency effect, Hafemeister and Flygare type short-range overlap repulsion extended up to the second neighbor ions and van der Waals interactions is formulated. Both charge transfer interactions and covalency effect apart from long-range Coulomb are important in revealing high-pressure-induced associated volume collapse, elastic, and thermodynamical properties. The elastic constants, Debye temperature, and thermal expansion coefficient obtained are in good agreement with the available experimental data and other theoretical results. The Li2O is mechanically stiffened, thermally softened, and brittle in nature as inferred from the pressure-dependent elastic constants behavior. To our knowledge, this is the first quantitative theoretical prediction of the pressure dependence of elastic, thermal, and thermodynamical properties of Li2O and still awaits experimental confirmation.

Mechanism of densification in silica glass under pressure as revealed by a bottom-up pairwise effective interaction model

A new short-range pairwise numerical potential for silica is presented. The potential is derived from a single ab initio molecular dynamics (AIMD) simulation of molten silica using the force-matching method with the forces being represented numerically by piecewise functions (splines). The AIMD simulation is performed using the Born-Oppenheimer method with the generalized gradient approximation (BLYP) for the XC energy functional. The new effective potential includes a soft-repulsive shoulder to describe the interactions of oxygen ions at short separations. The new potential, despite being short-ranged and derived from single-phase data, exhibits a good transferability to silica crystalline polymorphs and amorphous silica. The importance of the O-O soft-repulsive shoulder interaction on glass densification under cold and shock compressions is assessed from MD simulations of silica glass under room and shock Hugoniot conditions, respectively. Results from these simulations indicate that the appearance of oxygen complexes (primarily pairs) interacting through soft-repulsive shoulder potential occurs at 8-10 GPa, and under cold compression conditions becomes notable at 40 GPa, essentially coinciding with the transition to a Si sixfold coordination state. An analysis of changes in system structure in compressed and shocked states reveals that the O ions interacting through the soft-repulsive shoulder potential in denser states of silica glass may create a mechanical multi-stability under elevated pressures and thus to contribute to the observed anomalous densification.

Shell Model description of the ββ decay of 136Xe

We study in this Letter the double beta decay of 136Xe with emission of two neutrinos which has been recently measured by the EXO-200 Collaboration. We use the same shell model framework, valence space, and effective interaction that we have already employed in our calculation of the nuclear matrix element (NME) of its neutrinoless double beta decay. Using the quenching factor of the Gamow–Teller operator which is needed to reproduce the very recent high resolution 136Xe (3He, t) 136Cs data, we obtain a nuclear matrix element M2ν=0.025 MeV−1 compared with the experimental value M2ν=0.019(2) MeV−1.

Single-nucleon potential decomposition of the nuclear symmetry energy

The nuclear symmetry energy ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ and its density slope $L(\ensuremath{\rho})$ can be decomposed analytically in terms of the single-nucleon potential in isospin asymmetric nuclear matter. Using three popular nuclear effective interaction models which have been extensively used in nuclear structure and reaction studies, namely, the isospin and momentum-dependent MDI interaction model, the Skyrme-Hartree-Fock approach, and the Gogny-Hartree-Fock approach, we analyze the contribution of different terms in the single-nucleon potential to ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ and $L(\ensuremath{\rho})$. Our results show that the observed different density behaviors of ${E}_{\mathrm{sym}}(\ensuremath{\rho})$ for different interactions are essentially due to the variation of the symmetry potential ${U}_{\mathrm{sym},1}(\ensuremath{\rho},k)$. Furthermore, we find that the contribution of the second-order symmetry potential ${U}_{\mathrm{sym},2}(\ensuremath{\rho},k)$ to $L(\ensuremath{\rho})$ generally cannot be neglected. Moreover, our results demonstrate that the magnitude of ${U}_{\mathrm{sym},2}(\ensuremath{\rho},k)$ is generally comparable with that of ${U}_{\mathrm{sym},1}(\ensuremath{\rho},k)$, indicating that the second-order symmetry potential ${U}_{\mathrm{sym},2}(\ensuremath{\rho},k)$ may have significant corrections to the widely used Lane approximation for the single-nucleon potential in extremely neutron rich or proton rich nuclear matter.

Using force-matching to reveal essential differences between density functionals in ab initio molecular dynamics simulations

The exchange-correlation (XC) functional and value of the electronic fictitious mass μ can be two major sources of systematic errors in ab initio Car-Parrinello Molecular Dynamics (CPMD) simulations, and have a significant impact on the structural and dynamic properties of condensed-phase systems. In this work, an attempt is made to identify the origin of differences in liquid water properties generated from CPMD simulations run with the BLYP and HCTH∕120 XC functionals and two different values of μ (representative of "small" and "large" limits) by analyzing the effective pairwise atom-atom interactions. The force-matching (FM) algorithm is used to map CPMD interactions into non-polarizable, empirical potentials defined by bonded interactions, pairwise short-ranged interactions in numerical form, and Coulombic interactions via atomic partial charges. The effective interaction models are derived for the BLYP XC functional with μ=340 a.u. and μ=1100 a.u. (BLYP-340 and BLYP-1100 simulations) and the HCTH∕120 XC functional with μ=340 a.u. (HCTH-340 simulation). The BLYP-340 simulation results in overstructured water with slow dynamics. In contrast, the BLYP-1100 and HCTH-340 simulations both produce radial distribution functions (indicative of structure) that are in reasonably good agreement with experiment. It is shown that the main difference between the BLYP-340 and HCTH-340 effective potentials arises in the short-ranged nonbonded interactions (in hydrogen bonding regions), while the difference between the BLYP-340 and BLYP-1100 interactions is mainly in the long-ranged electrostatic components. Collectively, these results demonstrate how the FM method can be used to further characterize various simulation ensembles (e.g., density-functional theory via CPMD). An analytical representation of each effective interaction water model, which is easy to implement, is presented.