Size Depending Separation of HAP:Eu Nanoparticles in Dispersed Sol

The panicle size has a strong impact on the interactions between nanoparticles and cells. However, the synthesis process of nanoparticles limits the range of achievable average panicle sizes. When biocompatible hydroxyapatite nanoparticles （HAP） are doped with the luminescent rare earth elemeat Europium （Eu）, the panicle size becomes larger compared to pure HAP. Hence, a panicle size reduction is necessary to achieve similar experimental conditions when stbstituting pure HAP with luminescent HAP ： Eu nanoparticles to investigate particlecell-interactions in cell culture experiments. While the sedimentation process of particles in liquids and gels has been well described in literature, the separation of particles in dispersed colloids has not been studied, yet. In this study, the size depending separation and particle size redaction of a homogeneous dispersed nanoparticle sol by gravity and centrifugation were investigated. As the results showed, shorter time of centrifugation at higher speed can reduce the average particle size compared to the decline of the panicle concentation in the upper sol layer most efficiently. This ceatrifugation method has some similarity to the overspeeding technique which is commonly used to lower the transient time to reach the equilibrium of sedimentation.

Nonlinear free vibrations of porous composite microplates incorporating various microstructural-dependent strain gradient tensors

The main objective of the present numerical analysis is to predict the nonlinear frequency ratios associated with the nonlinear free vibration response of porous composite plates at microscale in the presence of different microstructural gradient tensors.To achieve this end,by taking cubic-type elements into account,isogeometric models of porous composite microplates are obtained with and without a central cutout and relevant to various porosity patterns of distribution along the plate thickness.The established unconventional models have the capability to capture the effects of various unconventional gradient tensors continuity on the basis of a refined shear deformable plate formulation.For the simply supported microsized uniform porous functionally graded material(UPFGM)plate having the oscillation amplitude equal to the plate thickness,it is revealed that the rotation gradient tensor causes to reduce the frequency ratio about 0.73%,the dilatation gradient tensor causes to reduce it about 1.93%,and the deviatoric stretch gradient tensor leads to a decrease of it about 5.19%.On the other hand,for the clamped microsized U-PFGM plate having the oscillation amplitude equal to the plate thickness,these percentages are equal to 0.62%,1.64%,and 4.40%,respectively.Accordingly,it is found that by changing the boundary conditions from clamped to simply supported,the effect of microsize on the reduction of frequency ratio decreases a bit.

Size Dependence of First-order Hyperpolarizability of CdS Nanoparticles Studied by Hyper-Rayleigh Scattering

The second-order optical nonlinearity of CdS nanoparticles with different diameters of 28.0, 30.0, 31.5, 50.0, and 91.0 A was studied by hyper-Rayleigh scattering technique. Results show that the first-order hyperpolarizability P value per CdS partiele decreases as size is reduced to diameter of 31.5 A; however, as CdS size further decreases, this trend is reversed and (J value increases. Substantially, the normalized P value per CdS formula unit, β0, exhibits systematic enhancement with decreasing size. This phenomenon is interpreted in terms of a so-called surfaee contribution mechanism.

GLOBAL DYNAMICS OF AN SEIR EPIDEMIC MODEL WITH IMMIGRATION OF DIFFERENT COMPARTMENTS

The SEIR epidemic model studied here includes constant inflows of new susceptibles, exposeds, infectives, and recovereds. This model also incorporates a population size dependent contact rate and a disease-related death. As the infected fraction cannot be eliminated from the population, this kind of model has only the unique endemic equilibrium that is globally asymptotically stable. Under the special case where the new members of immigration are all susceptible, the model considered here shows a threshold phenomenon and a sharp threshold has been obtained. In order to prove the global asymptotical stability of the endemic equilibrium, the authors introduce the change of variable, which can reduce our four-dimensional system to a three-dimensional asymptotical autonomous system with limit equation.

Static and Dynamic Pull-In Instability of Nano-Beams Resting on Elastic Foundation Based on the Nonlocal Elasticity Theory

This paper provides the static and dynamic pullin behavior of nano-beams resting on the elastic foundation based on the nonlocal theory which is able to capture the size effects for structures in micron and sub-micron scales. For this purpose, the governing equation of motion and the boundary conditions are driven using a variational approach. This formulation includes the influences of fringing field and intermolecular forces such as Casimir and van der Waals forces. The differential quadrature （DQ） method is employed as a high-order approximation to discretize the governing nonlinear differential equation, yielding more accurate results with a Considerably smaller number of grid points. In addition, a powerful analytical method called parameter expansion method （PEM） is utilized to compute the dynamic solution and frequency-amplitude relationship. It is illustrated that the first two terms in series expansions are sufficient to produce an acceptable solution of the mentioned structure. Finally, the effects of basic parameters on static and dynamic pull-in insta- bility and natural frequency are studied.

Surface-effects-dominated thermal and mechanical responses of zinc oxide nanobelts

t Molecular dynamics （MD） simulations are carried out to characterize the mechanical and thermal responses of [011^-1]-oriented ZnO nanobelts with lateral dimensions of 21.22A × 18.95 A, 31.02A× 29.42 A, and40.81A ×39.89A over the temperature range of 300-1000 K. The Young＇s modulus and thermal conductivity of the nanobelts are evaluated. Significant surface effects on properties due to the highsurface-to-volume ratios of the nanobelts are observed. For the mechanical response, surface-stress-induced internal stress plays an important role. For the thermal response, surface scattering of phonons dominates. Calculations show that the Young＇s modulus is higher than the corresponding value for bulk ZnO and decreases by -33% as the lateral dimensions increase from 21.22 A × 18.95A to 40.81 A × 39.89A. The thermal conductivity is one order of magnitude lower than the corresponding value for bulk ZnO single crystal and decreases with wire size. Specifically, the conductivity of the 21.22 A × 18.95 A belt is approximately （31-18）% lower than that of the 40.81 A × 39.89 A belt over the temperature range analyzed. A significant dependence of properties on temperature is also observed, with the Young＇s modulus decreasing on average by 12% and the conductivity decreasing by 50% as temperature increases from 300 K to 1000 K.

Size and time dependent internalization of label-free nano-graphene oxide in human macrophages

Graphene oxide shows great promise as a material for biomedical applications, e.g., as a multi-drug delivery platform. With this in view, reports of studies on the interaction between nanosized graphene oxide flakes and biological cells are beginning to emerge. However, the number of studies remains limited, and most used labeled graphene oxide samples to track the material upon endocytosis. Unfortunately, the labeling process alters the surface functionality of the graphene oxide, and this additional funcfionalization has been shown to alter the cellular response. Hence, in this work we used label-free graphene oxide. We carefully tracked the uptake of three different nanoscale graphene oxide flake size distributions using scanning/transmission electron microscopy. Uptake was investigated in undifferentiated human monocyte cells （THP-1） and differentiated macrophage cells. The data show clear size dependence for uptake, such that larger graphene oxide flakes （and clusters） are more easily taken up by the cells compared to smaller flakes. Moreover, uptake is shown to occur very rapidly, within two min of incubation with THP-1 cells. The data highlights a crucial need for cellular incubation studies with nanoparticles, to be conducted for short incubation periods as certain dependencies （e.g., size and concentration） are lost with longer incubation periods.

Couple stress-based nonlinear primary resonant dynamics of FGM composite truncated conical microshells integrated with magnetostrictive layers

The size-dependent geometrically nonlinear harmonically soft excited oscillation of composite truncated conical microshells(CTCMs)made of functionally graded materials(FGMs)integrated with magnetostrictive layers is analyzed.It is supposed that the FGM CTCMs are subjected to mechanical soft excitations together with external magnetic fields.An analytical framework is created by a microstructuredependent shell model having the 3rd-order distribution of shear deformation based on the modified couple stress(MCS)continuum elasticity.With the aid of the discretized form of differential operators developed via the generalized differential quadrature technique,a numerical solution methodology is introduced for obtaining the couple stress-based amplitude and frequency responses related to the primary resonant dynamics of the FGM CTCMs.Jump phenomena due to the loss of the first stability branch and falling down to the lower stable branch can be seen in the nonlinear primary resonance of the FGM CTCMs.It is demonstrated that the hardening type of nonlinearity results in bending the frequency response to the right side,and the MCS type of size effect weakens this pattern.Moreover,for higher material gradient indexes,the hardening type of nonlinearity is enhanced,and the MCS-based frequency response bends more considerably to the right side.

Structural and Spectroscopic Properties of Linear Carbon Chains NC_(2n)N and HC_(2n+_1)N(n=1～10)

Using density functional theory, geometries and vibrational frequencies of linear chains NC2nN and HC2n＋1N （n = 1 - 10） have been investigated. Time-dependent density functional theory （TD-DFF） has been used to calculate the vertical transition energies and oscillator strengths for the x^1∑g^＋→I^1∑u^＋ transition in NC2,N （n = 1 -10） and X^1∑ → I^1∑^＋ transition in HC2n＋1N （n =1 -7）. On the basis of present calculations, the explicit expressions for the size dependence of the excitation energy and the first adiabatic ionization energy in both carbon chains have been suggested.

Measurement on Spot Size Dependence of Dense WDM Dielectric Multilayer Filters

We present the spot size dependence of dielectric multilayer filters for use in dense WDM systems. We found large dependences of filter performances on the spot size and the incident angle of input light, which should be important for miniaturizing multi-channel add/drop filters.

Size Controlling Preparation, Adsorption and Catalytic Properties of Silica Microspheres

The size-controlled silica microspheres were prepared by a facile method and the growth mechanism was simply studied. The as-prepared samples were characterized by scanning electron microscopy and transmission elec- tron microscopy. The CO2 adsorption behaviors and methane catalytic oxidation were also measured. The results show that the as-prepared silica is perfect sphere, and the particle size can be controlled by adding tartaric acid. Spherical silica and sphere/tube（rod）-shaped silica were obtained by adjusting reaction time. Silica microspheres with uniform size exhibit high capacity of CO2 adsorption, while others with wide size-distribution exhibit excellent catalytic performance, suggesting it is an effective method by regulating size to utilize its advantages selectively. Therefore, it will be an ideal strategy to develop the efficient multifunctional materials by a facile route.

Size dependence of twin formation energy of metallic nanowires

Twin formation energy is an intrinsic quantity for bulk crystals.At the nanoscale,the twin formation energy of covalent SiC nanowires goes up with decreasing dimension.In contrast,this article reports that the twin formation energy of metallic nanowires goes down with decreasing dimension.This result is based on classical molecular statics simulations of four representative metals.Cu and Al represent face-centered cubic(FCC)metals of low and high twin formation energies.Ta represents a body-centered cubic(BCC)metal,and Mg represents a hexagonal close-packed(HCP)metal.For all the four metals,the dependence of twin formation energy on size correlates with lower twin formation energy near surfaces,according to atomic-level analysis.Based on this atomic-level insight,the authors propose a core–shell model that reveals the twin formation energy as inversely proportional to the diameter of nanowires.This dependence is in agreement with the results of molecular statics simulations.

Axisymmetric loading on nanoscale multilayered media

Multilayered nanoscale structures are used in several applications.Because the effect of surface energy becomes nontrivial at such a small scale,a modified continuum theory is required to accurately predict their mechanical behaviors.A Gurtin–Murdoch continuum model of surface elasticity is implemented to establish a computational scheme for investigating an elastic multilayered system under axisymmetric loads with the incorporation of surface/interface energy.Each layer stiffness matrix is derived based on the general solutions of stresses and displacements obtained in the form of the Hankel integral transform.Numerical solutions to the global equation,which are formulated based on the continuity conditions of tractions and displacements across interfaces between layers,yield the displacements at each layer interface and on the top surface of the multilayered medium.The numerical solutions indicate that the elastic responses of multilayered structures are affected significantly by the surface material properties of both the top surface and interfaces,and that they become size dependent.In addition,the indentation problem of a multilayered nanoscale elastic medium under a rigid frictionless cylindrical punch is investigated to demonstrate the application of the proposed solution scheme.

Density Effects on Plant Height Growth and Inequality in Sunflower Populations

Comparisons between competing and non-competing sunflower （Helianthus annuus L.） populations demonstrate pronounced effects of density on plant height growth, height-to-crown width ratio, and s popuiaUon＇s height inequality. In the present study, non-destructive measurements of height and the prolected crown area of sunflower plants were taken at seven times from emergence to fruit maturation in even-aged monospeclflc stands with initial densities of 1, 4, 16, and 64 plants/m^2. The mean height of populations Increased and then decreased with increasing population density; the height Inequalities of uncrowded populations decreased during stand growth, whereas the height inequaiiUes of crowded popuisUons decreased first and then increased during stand development. The interindlvidual relationships between the relative height growth rate and height within uncrowded populations became significantly negative during population growth, whereas these relationships were negative first and then became positive during the development of crowded populations. In the uncrowded populations, the static Interindlvldual relationship between height-to-crown width ratio and volume was positive, whereas for the crowded population these relationships became negative with increasing competition for light. The data suggest that the plastic responses of plant height and height-to-crown width ratio to light competition will become more Intense with increasing competition Intensity. The results of the present study argue strongly for the Importance of size-dependent Individual-level plastic responses due to size-asymmetric light competition In generating the variations in population height inequality.

Thermoelastic Damping of Functionally Graded Material Micro-Beam Resonators Based on the Modified Couple Stress Theory

Thermoelastic damping(TED)is one of the main internal energy dissipation mechanisms in micro/nano-resonators.Accurate evaluation of TED is important in the design of micro-electromechanical systems and nano-electromechanical systems.In this paper,a theoretical analysis on the TED in functionally graded material(FGM)micro-beam resonators is presented.Equations of motion and the heat conduction equation governing the thermodynamic coupling free vibration of non-homogenous micro-beams are established based on the Euler Bernoulli beam theory associated with the modified couple stress theory.Material properties of the FGM micro-beam are assumed to change in the depth direction as power-law functions.The layer-wise homogenization method is used for solving the heat conduction equation.By using the mathematical similarity of eigenvalue problem between the FGM beam and the reference homogeneous one,the complex natural frequency including TED is expressed in terms of the natural frequency of the isothermal homogenous beam.In the presented numerical results,influences of various characteristic parameters,such as beam thickness,material gradient index,structure size,vibration mode and boundary conditions,on TED are examined in detail.It shows that TED decreases with the increases in the values of length scale parameters because the latter lead to the increase in structural stiffness.

Pion emission in α-particle interactions with various targets of nuclear emulsion detector

The behavior of relativistic hadron multiplicity for 4He-nucleus interactions is investigated. The experi- ment is carried out at 2.1 A and 3.7 A GeV （Dubna energy） to search for the incident energy effect on the interactions inside different emulsion target nuclei. Data are presented in terms of the number of emitted relativistic hadrons in both forward and backward angular zones. The dependence on the target size is presented. For this purpose the statistical events are discriminated into groups according to the interactions with H, CNO, Em, and AgBr target nuclei. The separation of events, into the mentioned groups, is executed based on Glauber＇s multiple scattering theory approach. Features suggestive of a decay mechanism seem to be a characteristic of the backward emission of relativistic hadrons. The results strongly support the assumption that the relativistic hadrons may already be emitted during the de-excitation of the excited target nucleus, in a behavior like that of compound-nucleus disintegration. Regarding the limiting fragmentation hypothesis beyond 1 A GeV, the target size is the main parameter affecting the backward production of the relativistic hadron. The incident energy is a principal factor responsible for the forward relativistic hadron production, implying that this system of particle production is a creation system. However, the target size is an effective parameter as well as the projectile size considering the geometrical concept regarded in the nuclear fireball model. The data are analyzed in the framework of the FRITIOF model.

The influence of aspect ratio on the properties of cobalt nanowire-based magnetorheological fluids

The yield stress of magnetorheological(MR)fluids has been shown to depend on particle morphology,but the exact nature of this contribution is still not fully understood.In this study,MR fluids containing 4 vol.%cobalt particles(spherical particles vs.nano-wires)suspended in silicone oil were investigated.The influence of the aspect ratio on the rheological properties of suspensions that contained cobalt nanowires with aspect ratios ranging from 10 to 101 in increments of~6 is described.The cobalt nanowires were fabricated using alumina template-based electrodeposition,produ-cing wires with 305±66 nm diameters.The shear stress was measured as a function of shear rate for increasing applied mag-netic fields.The apparent yield stress and viscosity as a function of changing aspect ratio of the nanowire suspensions were deter-mined.At a saturated magnetic flux density,the yield stress was found to increase linearly up to an aspect ratio of 23(7.1μm long wires)at which time the yield stress reached a plateau of 3.7 kPa even as the aspect ratio was further increased.As a comparison,suspensions containing 4 vol.%1.6μm spherical cobalt particles only reached a maximum yield stress of 1.6 kPa.

Molecular Dynamics Studies of the Kinetics of Phase Changes in Clusters IV:Crystal Nucleation from Molten (NaCl)_(256) and (NaCl)_(500) Clusters

Molecular dynamics computer simulation based on the Born-Mayer-Huggins potential function has been carried out to study the effects of cluster size and temperature on the nucleation rate of sodium chloride clusters in the temperature range of 580 K to 630 K. Clusters with 256 and 500 NaCl molecules have been studied and the results have been compared with those obtained from 108 molecule clusters. The melting point (MP) of the clusters were observed to increase with the size of the clusters and can be well described by a linear equation MP=1107(37)-1229(23)N -1/3 (N is the number of molecules in the cluster). The nucleation rate was found to decrease with increasing the cluster size or temperature. Various nucleation theories have been used to interpret the nucleation rates obtained from this molecular dynamics simulation. It is possible to use a constant diffuse interface thickness to interpret the nucleation rate from the diffuse interface theory in the temperature range of this study. However,the interfacial free energy estimated from classical nucleation theory and diffuse interface theory increases too fast with increasing the temperature while that from Gran-Gunton theory does not change with changing temperatures. The sizes of critical nuclei estimated from all the theories are smaller than those estimated from our simulations.