Relative Core Size Research Articles

Assessing Plasmonic Nanoprobes in Electromagnetic Field Enhancement for SERS Detection of Biomarkers.

The exploration of the plasmonic field enhancement of nanoprobes consisting of gold and magnetic core@gold shell nanoparticles has found increasing application for the development of surface-enhanced Raman spectroscopy (SERS)-based biosensors. The understanding of factors controlling the electromagnetic field enhancement, as a result of the plasmonic field enhancement of the nanoprobes in SERS biosensing applications, is critical for the design and preparation of the optimal nanoprobes. This report describes findings from theoretical calculations of the electromagnetic field intensity of dimer models of gold and magnetic core@gold shell nanoparticles in immunoassay SERS detection of biomarkers. The electromagnetic field intensities for a series of dimeric nanoprobes with antibody–antigen–antibody binding defined interparticle distances were examined in terms of nanoparticle sizes, core–shell sizes, and interparticle spacing. The results reveal that the electromagnetic field enhancement not only depended on the nanoparticle size and the relative core size and shell thicknesses of the magnetic core@shell nanoparticles but also strongly on the interparticle spacing. Some of the dependencies are also compared with experimental data from SERS detection of selected cancer biomarkers, showing good agreement. The findings have implications for the design and optimization of functional nanoprobes for SERS-based biosensors.

Linear general rate model of chromatography for core–shell particles: Analytical solutions and moment analysis

Due to their proven performance and improved availability, core–shell particles are increasingly applied for chromatographic separations. This paper presents semi-analytical solutions and a moment analysis of a detailed mathematical model for fixed-beds packed with core–shell particles. The model considers axial dispersion, interfacial mass transfer, intraparticle diffusion, linear adsorption, and the injection of rectangular pulses. The Laplace transformation is used as a basic tool to derive semi-analytical solutions. In addition the first three statistical temporal moments are derived from solutions in the Laplace domain. The numerical Laplace inversion is applied for back transformation of the solution in the actual time domain. In order to demonstrate their potential, different scenarios are considered to quantify the effects of the relative core size, axial dispersion, film mass transfer resistance and intraparticle diffusion resistance in the porous layer on the elution profiles. An important new result is the derivation of a plate height equation for fully porous and core–shell particles respecting the Danckwerts boundary conditions.

Universal distribution of mutational effects on protein stability, uncoupling of protein robustness from sequence evolution and distinct evolutionary modes of prokaryotic and eukaryotic proteins

Robustness to destabilizing effects of mutations is thought of as a key factor of protein evolution. The connections between two measures of robustness, the relative core size and the computationally estimated effect of mutations on protein stability (ΔΔG), protein abundance and the selection pressure on protein-coding genes (dN/dS) were analyzed for the organisms with a large number of available protein structures including four eukaryotes, two bacteria and one archaeon. The distribution of the effects of mutations in the core on protein stability is universal and indistinguishable in eukaryotes and bacteria, centered at slightly destabilizing amino acid replacements, and with a heavy tail of more strongly destabilizing replacements. The distribution of mutational effects in the hyperthermophilic archaeon Thermococcus gammatolerans is significantly shifted toward strongly destabilizing replacements which is indicative of stronger constraints that are imposed on proteins in hyperthermophiles. The median effect of mutations is strongly, positively correlated with the relative core size, in evidence of the congruence between the two measures of protein robustness. However, both measures show only limited correlations to the expression level and selection pressure on protein-coding genes. Thus, the degree of robustness reflected in the universal distribution of mutational effects appears to be a fundamental, ancient feature of globular protein folds whereas the observed variations are largely neutral and uncoupled from short term protein evolution. A weak anticorrelation between protein core size and selection pressure is observed only for surface residues in prokaryotes but a stronger anticorrelation is observed for all residues in eukaryotic proteins. This substantial difference between proteins of prokaryotes and eukaryotes is likely to stem from the demonstrable higher compactness of prokaryotic proteins.

Features of drawing axially symmetric composite wares with a filament core made of nonferrous metals and alloys

The mechanism of plastic deformation of axisymmetric composite wares with dissimilar components during drawing is more complex than with a similar treatment of a monometal. By virtue of the specifics of the deformation mode, the constant nonuniformity of deformation is inherent to axisymmetric drawing; it depends on the reduction in the passage, the die cone angle, the relative length of the calibrating die rib, the friction ratio between the wire and die in the deformation region, the coefficient of connection strength of the core and sleeve interfaces, the relative core size, and the ratio of stresses of the plastic flow of the sleeve and the core. The features of drawing the composite wares with a monofilament and a multifilament core and implementation conditions of the uniform proportional flow of both components without the formation of fractures of the core continuity, the surface sleeve fracture, and the fracture of the ware itself are established by experimental investigations.

Voltammetric detection of metal nanoparticles separated by liquid chromatography.

Fast-scan cyclic voltammetric (FSCV) detection of the separation of small (< 2-nm core diameter) organothiolate monolayer-protected gold clusters (MPCs) by high-performance liquid chromatography (HPLC) is demonstrated in this paper. Cyclic voltammograms taken at 1-s intervals (scan rate 150 V/s) display distinctive current-potential patterns for different MPCs, aiding in their identification. Previous amperometric detection of MPC separations required multiple HPLC runs at different electrode potentials to construct hydrodynamic current-potential voltammograms. Theory for ratiometric response of photodiode array absorbance and constant potential amperometry detectors was further tested on the fast-scan voltammetric detector and gave reasonable relative core size results for a mixture of Au140 and Au38 MPCs. In the first analysis of mixed MPC monolayer composition that is not simply an overall average result, preliminary HPLC experiments on MPCs with mixed hexanethiolate and ferrocenyl-octanethiolate monolayers resolved peaks that are shown to correspond to different average numbers of ferrocene-labeled ligands per MPC.

Amphiphilic diblock copolymer gels: the relationship between structure and rheology

Block copolymers dissolved in a selective solvent form micelles that can be regarded as model colloidal dispersions because by tailoring the copolymer composition, the relative size of core and corona can be controlled. This enables the interaction potential to be varied, such that either hard or soft sphere ordering can be observed above the liquid–solid (sol–gel) transition. Here we review recent work on the structure and rheology of micellar phases formed by block copolymers in solution. First, the structure of solid and liquid micellar phases is considered, and its relationship to flow properties of gels and sols is discussed. Then the ordering of hard versus soft spheres is considered in the context of experimental phase diagrams for poly(styrene)–poly(isoprene) in decane and poly(oxyethylene)–poly(oxybutylene) diblock copolymers in water. The use of experiments in the linear viscoelastic regime to locate the gelation (liquid–solid) transition is then reviewed, and the application of measurements in the linear viscoelastic regime to study relaxation phenomena is also outlined. The nonlinear flow behaviour of micellar block copolymer solutions is then considered. In particular the focus is on the development of a yield stress in the solid phase, creep and stress relaxation measurements which throw light on flow mechanisms, and Fourier transform rheology which provides a quantitative measure of nonlinear viscoelasticity under oscillatory shear. Finally, an overview is provided of recent small–angle scattering experiments that have probed the mechanisms of macroscopic alignment of body–centred and face–centred cubic micellar phases subjected to large–amplitude oscillatory shear or steady shear in a Couette cell.

Morphology and strength of elastic films of structured latices

Thermoplastic elastomers (TPEs) are conventionally made of block copolymers or partly cross-linked polymer blends. Alternatively, TPEs can be prepared from structured latices, too. Hard-soft latex particles with a thermoplastic core and an elastomeric shell yield highly extendable elastic films, the strength of which depends sensitively on the relative core size and the particle architecture. Core-shell particles were prepared, by two-step emulsion polymerization, with the thermoplastic polystyrene (PS) in the core and the elastomer polyethylacrylate (PEA) in the shell. PEA particles were synthesized first. The PS cores were then incorporated in them in the second step. This method permits the design of monocore. as well as multicore, particles. These PS-PEA particles were not cross-linked in the core or in the shell. They can be classified as microblends. Compression-molded films of them exhibited, therefore, a coarsened microphase morphology that was, however, still much finer than that of simple melt-mixed blends PS/PEA. The film morphologies of monocore and multicore particles were different as far as the former yielded spherical PS domains, while the latter yielded extended PS clusters. This was strongly reflected by the stress-strain behavior: Films from multicore particles responded in a viscoelastic, rubbery manner, while films from monocore particles behaved like viscous liquids.

Formation, history and energetics of cores in the terrestrial planets

The cores of the terrestrial planets Earth, Moon, Mercury, Venus and Mars differ substantially in size and in history. Though no planet other than the Earth has a conclusively demonstrated core, the probable cores in Mercury and Mars and Earth's core show a decrease in relative core size with solar distance. The Moon does not fit this sequence and Venus may not. Core formation must have been early (prior to ∼4 · 10 9 yr. ago) in the Earth, by virtue of the existence of ancient rock units and ancient paleomagnetism and from UPb partitioning arguments, and in Mercury, because the consequences of core infall would have included extensional tectonic features which are not observed even on Mercury's oldest terrain. If a small core exists in the Moon, still an open question, completion of core formation may be placed several hundred million years after the end of heavy bombardment on tectonic and thermal grounds. Core formation time on Mars is loosely constrained, but may have been substantially later than for the other terrestrial planets. The magnitude and extent of early heating to drive global differentiation appear to have decreased with distance from the sun for at least the smaller bodies Mercury, Moon and Mars. Energy sources to maintain a molten state and to fuel convection and magnetic dynamos in the cores of the terrestrial planets include principally gravitational energy, heat of fusion, and long-lived radioactivity. The gravitational energy of core infall is quantifiable and substantial for all bodies but the Moon, but was likely spent too early in the history of most planets to prove a significant residual heat source to drive a present dynamo. The energy from inner core freezing in the Earth and in Mercury is at best marginally able to match even the conductive heat loss along an outer core adiabat. Radioactive decay in the core offers an attractive but unproven energy source to maintain core convection.

Some investigations of the effects of core size and steel and concrete quality in short reinforced concrete columns

Summary: The work described is a continuation of earlier work on short concrete columns, which had as its object the determination of the effect of lateral reinforcement on column strength. It was clear from this earlier work that relative core size would be likely to have a significant effect on strength, and the present investigations were initiated primarily to examine this. On the assumption that the currently accepted formula for helically bound columns had some justification for taking as one of its terms “"core area by concrete strength,” it was believed that high quality concrete would demonstrate the effect of core size better than a more ordinary concrete and a series of tests (Group I) was carried out in this way. As the tests failed to indicate any marked effect, columns (Group II) were made with normal concrete and high quality steel. To round off the work a third group was made of normal quality steel and concrete. In the main, binders were of a normal square type and of a materially constant strength, but a few were of modified shapes. As a result of the tests it has been possible to formulate general conclusions concerning the effect of core size, cover thickness, concrete and main steel strength, and core shape, to confirm the general conclusions of earlier work that binder contribution to strength was proportional to 1/pitch2 and to indicate that there is material advantage in using high quality steel as main reinforcement. Actual test loads are compared in the tables with loads calculated by a formula derived from the earlier tests, where core area was a constant proportion of the column area (51 per cent.), where concrete strength was sensibly constant, and where main steel consisted of various sizes of normal black bar. The significance of the various changes is thus revealed more clearly.