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Process of relaxation of Lennard-Jones cluster with an intrinsic pore was investigated by molecular dynamics method for different phase states of an initial cluster. Strong dependence of pore relaxation character on the initial cluster phase state was demonstrated. It was shown that, for the initially solid cluster, the system can reach metastable state where pore radius is fixed at one of the discrete set of values. These values do not depend on initial cluster temperature and size. Thus, it was demonstrated that, in a wide range of cluster sizes, inside solid clusters "magic" pores can stabilize forming a metastable state., Comment: 13 pages/ 4 figures

The diffusive evolution has been studied of gas-filled pore has in a bounded particle in gas media. The nonlinear equation set, describing the behaviour of gas-filled pore on bounded particle is obtained. Asymptotic modes are considered for evolution of small and large pores. Analytical solutions are obtained in asymptotic modes. The comparison is conducted of these solutions with results of numerical solution of complete equation set. The characteristic regularities of gas-filled pore behavior are found at arbitrary pore position relative to matrix particle center., Comment: 30 pages, 6 figures. arXiv admin note: text overlap with arXiv:1810.10319

In the present work, evolution of gas-filled pore inside spherical nanoshells is considered. On the supposition that diffusion fluxes are quasistationary, the nonlinear equation system is obtained analytically, that describes completely the behaviour of gas-filled pore and matrix shell. Two limiting cases are considered: the case when the pore is small as compared to the matrix shell and the case of the pore close to the matrix shell boundary. The characteristic regularities of pore behaviour are established., Comment: 26 pages, 9 figures. arXiv admin note: substantial text overlap with arXiv:1809.06565

In the present work, the behavior of vacancy pore inside of spherical particle is investigated. On the assumption of quasistationarity of diffusion fluxes, the nonlinear equation set was obtained analytically, that describes completely pore behavior inside of spherical particle. Limiting cases of small and large pores are considered. The comparison of numerical results with asymptotic behavior of considered limiting cases of small and large pores is discussed., Comment: 25 pages, 10 figures

We review the radio very long baseline interferometry (VLBI) observations of the guide star, IM Peg, and three compact extragalactic reference sources, 3C 454.3, B2250+194, and B2252+172, made in support of the NASA/Stanford gyroscope relativity mission, GP-B. The main goal of the observations was the determination of the proper motion of IM Peg relative to the distant universe. VLBI observations made between 1997 and 2005 yield a proper motion of IM Peg of -20.83 $\pm$ 0.09 mas yr$^{-1}$ in RA and -27.27 $\pm$ 0.09 mas yr$^{-1}$ in dec, in a celestial reference frame of extragalactic radio galaxies and quasars virtually identical to the International Celestial Reference Frame 2 (ICRF2). They also yield a parallax for IM Peg of 10.37 $\pm$ 0.07 mas, corresponding to a distance of 96.4 $\pm$ 0.7 pc. The uncertainties are standard errors with statistical and estimated systematic contributions added in quadrature. These results met the pre-launch requirements of the GP-B mission to not discernibly degrade the estimates of the geodetic and frame-dragging effects. The paper also reports on a 1$\sigma$ upper limit on the magnitude of the components of the proper motion of the 'core' of 3C 454.3 relative to the ICRF2 of 46 and 56 $\mu$as yr$^{-1}$ in RA and dec, respectively, and presents densely sampled ellipses of the parallax and the orbit of the giant of the binary system. It further gives a sequence of images of the flickering radio emission relative to the disk of the giant. For a 'movie of a star,' see http://www.yorku.ca/bartel/impeg.mpg ., Comment: Invited review accepted for publication in a Special Issue of Classical and Quantum Gravity, 27 pages, 9 figures, 3 tables

This work is devoted to molecular dynamics modeling of collision of nanoparticle having a small number of degrees of freedom with a structureless plain. The new regularities are established that determine properties of such particles. Generalized collision law is obtained where particle properties are determined by two coefficient, on of which corresponds to restitution coefficient. The discovered regularity predicts the existence of anomalous mode of particle reflection from a massive plain. In this mode, velocity of nanoparticle after reflection from a plain can exceed the initial one. The criterion of realization of such mode is obtained. Anomalous collision mode was observed during numerical modeling. Physical mechanism are discussed of phenomena that are observed during numerical experiments., Comment: 6 pages, 4 figures

We present measurements of the total radio flux density as well as very-long-baseline interferometry (VLBI) images of the star, IM Pegasi, which was used as the guide star for the NASA/Stanford relativity mission Gravity Probe B. We obtained flux densities and images from 35 sessions of observations at 8.4 GHz (wavelength = 3.6 cm) between 1997 January and 2005 July. The observations were accurately phase-referenced to several extragalactic reference sources, and we present the images in a star-centered frame, aligned by the position of the star as derived from our fits to its orbital motion, parallax, and proper motion. Both the flux density and the morphology of IM Peg are variable. For most sessions, the emission region has a single-peaked structure, but 25% of the time, we observed a two-peaked (and on one occasion perhaps a three-peaked) structure. On average, the emission region is elongated by 1.4 +- 0.4 mas (FWHM), with the average direction of elongation being close to that of the sky projection of the orbit normal. The average length of the emission region is approximately equal to the diameter of the primary star. No significant correlation with the orbital phase is found for either the flux density or the direction of elongation, and no preference for any particular longitude on the star is shown by the emission region., Comment: Accepted for publication in the Astrophysical Journal Supplement Series

We present a physical interpretation for the locations of the sources of radio emission in IM Pegasi (IM Peg, HR 8703), the guide star for the NASA/Stanford relativity mission Gravity Probe B. This emission is seen in each of our 35 epochs of 8.4-GHz VLBI observations taken from 1997 to 2005. We found that the mean position of the radio emission is at or near the projected center of the primary to within about 27% of its radius, identifying this active star as the radio emitter. The positions of the radio brightness peaks are scattered across the disk of the primary and slightly beyond, preferentially along an axis with position angle, p.a. = (-38 +- 8) deg, which is closely aligned with the sky projections of the orbit normal (p.a. = -49.5 +- 8.6 deg) and the expected spin axis of the primary. Comparison with simulations suggests that brightness peaks are 3.6 (+0.4,-0.7) times more likely to occur (per unit surface area) near the pole regions of the primary (|latitude| >= 70 deg) than near the equator (|latitude| <= 20 deg), and to also occur close to the surface with ~2/3 of them at altitudes not higher than 25% of the radius of the primary., Comment: Accepted for publication in the Astrophysical Journal Supplement Series

We used 8.4 GHz VLBI images obtained at up to 35 epochs between 1997 and 2005 to examine the radio structures of the main reference source, 3C 454.3, and two secondary reference sources, B2250+194 and B2252+172, for the guide star for the NASA/Stanford relativity mission Gravity Probe B (GP-B). For one epoch in 2004 May, we also obtained images at 5.0 and 15.4 GHz. The 35 8.4 GHz images for quasar 3C 454.3 confirm a complex, evolving, core-jet structure. We identified at each epoch a component, C1, near the easternmost edge of the core region. Simulations of the core region showed that C1 is located, on average, 0.18 +- 0.06 mas west of the unresolved "core" identified in 43 GHz images. We also identified in 3C 454.3 at 8.4 GHz several additional components which moved away from C1 with proper motions ranging in magnitude between 0.9c and 5c. The detailed motions of the components exhibit two distinct bends in the jet axis located ~3 and ~5.5 mas west of C1. The spectra between 5.0 and 15.4 GHz for the "moving" components are steeper than that for C1. The 8.4 GHz images of B2250+194 and B2252+172, in contrast to those of 3C 454.3, reveal compact structures. The spectrum between 5.0 and 15.4 GHz for B2250+194 is inverted while that for B2252+172 is flat. Based on its position near the easternmost edge of the 8.4 GHz radio structure, close spatial association with the 43 GHz core, and relatively flat spectrum, we believe 3C 454.3 component C1 to be the best choice for the ultimate reference point for the GP-B guide star. The compact structures and inverted to flat spectra of B2250+194 and B2252+172 make these objects valuable secondary reference sources, Comment: Accepted for publication in the Astrophysical Journal Supplement Seris

We present the principal astrometric results of the very-long-baseline interferometry (VLBI) program undertaken in support of the Gravity Probe B (GP-B) relativity mission. VLBI observations of the GP-B guide star, the RS CVn binary IM Pegasi (HR 8703), yielded positions at 35 epochs between 1997 and 2005. We discuss the statistical assumptions behind these results and our methods for estimating the systematic errors. We find the proper motion of IM Peg in an extragalactic reference frame closely related to the International Celestial Reference Frame 2 (ICRF2) to be -20.83 +- 0.03 +- 0.09 mas/yr in right ascension and -27.27 +- 0.03 +- 0.09 mas/yr in declination. For each component the first uncertainty is the statistical standard error and the second is the total standard error (SE) including plausible systematic errors. We also obtain a parallax of 10.37 +- 0.07 mas (distance: 96.4 +- 0.7 pc), for which there is no evidence of any significant contribution of systematic error. Our parameter estimates for the ~25-day-period orbital motion of the stellar radio emission have SEs corresponding to ~0.10 mas on the sky in each coordinate. The total SE of our estimate of IM Peg's proper motion is ~30% smaller than the accuracy goal set by the GP-B project before launch: 0.14 mas/yr for each coordinate of IM Peg's proper motion. Our results ensure that the uncertainty in IM Peg's proper motion makes only a very small contribution to the uncertainty of the GP-B relativity tests., Comment: Accepted for publication in the Astrophysical Journal Supplement Series

We made VLBI observations at 8.4 GHz between 1997 and 2005 to estimate the coordinates of the "core" component of the superluminal quasar, 3C 454.3, the ultimate reference point in the distant universe for the NASA/Stanford Gyroscope Relativity Mission, Gravity Probe B. These coordinates are determined relative to those of the brightness peaks of two other compact extragalactic sources, B2250+194 and B2252+172, nearby on the sky, and within a celestial reference frame (CRF), defined by a large suite of compact extragalactic radio sources, and nearly identical to the International Celestial Reference Frame 2 (ICRF2). We find that B2250+194 and B2252+172 are stationary relative to each other, and also in the CRF, to within 1-sigma upper limits of 15 and 30 micro-arcsec/yr in RA and decl., respectively. The core of 3C 454.3 appears to jitter in its position along the jet direction over ~0.2 mas, likely due to activity close to the putative supermassive black hole nearby, but on average is stationary in the CRF within 1-sigma upper limits on its proper motion of 39 micro-arcsec/yr (1.0c) and 30 micro-arcsec/yr (0.8c) in RA and decl., respectively, for the period 2002 - 2005. Our corresponding limit over the longer interval, 1998 - 2005, of more importance to GP-B, is 46 and 56 micro-arcsec/yr in RA and decl., respectively. Some of 3C 454.3's jet components show significantly superluminal motion with speeds of up to ~200 micro-arcsec/yr or 5c in the CRF. The core of 3C 454.3 thus provides for Gravity Probe B a sufficiently stable reference in the distant universe., Comment: Accepted for publication in the Astrophysical Journal Supplement Series

We describe the NASA/Stanford gyroscope relativity mission, Gravity Probe B (GP-B), and provide an overview of the following series of six astrometric and astrophysical papers that report on our radio observations and analyses made in support of this mission. The main goal of this 8.5 year program of differential VLBI astrometry was to determine the proper motion of the guide star of the GP-B mission, the RS CVn binary IM Pegasi (IM Peg; HR 8703). This proper motion is determined with respect to compact, extragalactic reference sources. The results are: -20.833 +- 0.090 mas/yr and -27.267 +- 0.095 mas/yr for, respectively, the right ascension and declination, in local Cartesian coordinates, of IM Peg's proper motion, and 10.370 +- 0.074 mas (i.e., 96.43 +- 0.69 pc) for its parallax (and distance). Each quoted uncertainty is meant to represent an ~70% confidence interval that includes the estimated contribution from systematic error. These results are accurate enough not to discernibly degrade the GP-B estimates of its gyroscopes' relativistic precessions: the frame-dragging and geodetic effects., Comment: Accepted for publication in the Astrophysical Journal Supplement Series

When VLBI observations are used to determine the position or motion of a radio source relative to reference sources nearby on the sky, the astrometric information is usually obtained via: (i) phase-referenced maps; or (ii) parametric model fits to measured fringe phases or multiband delays. In this paper we describe a "merged" analysis technique which combines some of the most important advantages of these other two approaches. In particular, our merged technique combines the superior model-correction capabilities of parametric model fits with the ability of phase-referenced maps to yield astrometric measurements of sources that are too weak to be used in parametric model fits. We compare the results from this merged technique with the results from phase-referenced maps and from parametric model fits in the analysis of astrometric VLBI observations of the radio-bright star IM Pegasi (HR 8703) and the radio source B2252+172 nearby on the sky. In these studies we use central-core components of radio sources 3C 454.3 and B2250+194 as our positional references. We obtain astrometric results for IM Peg with our merged technique even when the source is too weak to be used in parametric model fits, and we find that our merged technique yields superior astrometric results to the phase-referenced mapping technique. We used our merged technique to estimate the proper motion and other astrometric parameters of IM Peg in support of the NASA/Stanford Gravity Probe B mission., Comment: Accepted for publication in the Astrophysical Journal Supplement Series

We present VLBI images of the RS CVn binary star HR 5110 (=BH CVn; HD 118216), obtained from observations made at 8.4 GHz on 1994 May 29/30 in support of the NASA/Stanford Gravity Probe B project. Our images show an emission region with a core-halo morphology. The core was 0.39 +/- 0.09 mas (FWHM) in size, or 66% +/- 20% of the 0.6 +/- 0.1 mas diameter of the chromospherically active K subgiant star in the binary system. The halo was 1.95 +/- 0.22 mas (FWHM) in size, or 1.8 +/- 0.2 times the 1.1 +/- 0.1 mas separation of the centers of the K and F stars. The core increased significantly in brightness over the course of the observations and seems to have been the site of flare activity that generated an increase in the total flux density of ~200% in 12 hours. The fractional circular polarization simultaneously decreased from ~10% to 2.5%., Comment: 22 pages, 4 figures

On 18 November 1993, we observed the QSO 1150+812 and the BL Lac object 1803+784, nearly 15\deg apart on the sky, with a VLBI array, simultaneously recording at 8.4 and 2.3 GHz. Using difference astrometry techniques, we determined the coordinates of 1803+784 relative to those of 1150+812 to be \Delta\alpha = 6h 7m 33.18469 arcsec +- 0.00020 arcsec \Delta\delta = -2deg 30' 25''.13557 +- 0''.00075 These standard errors contain estimated contributions from the propagation medium, the effects of source opacity, and the possible misidentification of the reference point in some of the maps. We obtained comparably accurate and consistent relative positions of the radio sources with GPS-based ionosphere corrections, thus demonstrating that dual-frequency observations are not required for state-of-the-art accuracy in VLBI astrometry. These results also demonstrate the feasibility of using single-frequency measurements for sources separated by 15$^\circ$ on the sky, and open the avenue for the application of this technique on a full-sky scale., Comment: 12 pages, 5 figures

We determined the separations of the radio sources in the triangle formed by the BL Lac objects 1803+784 and 2007+777, and the QSO 1928+738 from intercontinental interferometric observations carried out in November 1991 at the frequencies of 2.3 and 8.4 GHz simultaneously. We successfully connected differenced phase delays over 7^o on the sky at 8.4 GHz at an epoch of maximum solar activity. The effects of the ionosphere on these VLBI data were mostly removed by estimates of the total electron content from observations of GPS satellites. The comparison of the estimated separation of QSO 1928+738 and BL 2007+777 with previous such estimates obtained from data at different epochs leads us to a particular alignment of the maps of QSO 1928+738 at different epochs relative to those of BL 2007+777, although with significant uncertainty. For this alignment, the jet components of QSO 1928+738 show a mean proper motion of 0.32+/-0.10 mas/yr and also suggest an identification for the position of the core of this radio source., Comment: 13 pages, 8 figures, accepted for publication in Astronomy & Astrophysics

Future NASA and Air Force missions require reliable and safe sources of energy with high specific energy and energy density that can provide thousands of charge-discharge cycles at more than 40% depth- of-discharge and that can operate at low temperatures. All solid-state batteries have substantial advantages with respect to stability, energy density, storage fife and cyclability. Among all solid-state batteries, those with flexible polymer electrolytes offer substantial advantages in cell dimensionality and commensurability, low temperature operation and thin film design. The above considerations suggest that lithium-polymer electrolyte systems are promising for high energy density batteries and should be the systems of choice for NASA and US Air Force applications. Polyelectrolytes (single ion conductors) are among most promising avenues for achieving a major breakthrough 'in the applicability of polymer- based electrolyte systems. Their major advantages include unit transference number for the cation, reduced cell polarization, minimal salt precipitation, and favorable electrolyte stability at interfaces. Our research is focused on synthesis, modeling and cell testing of single ion carriers, polyelectrolytes. During the first year of this project we attempted the synthesis of two polyelectrolytes. The synthesis of the first one, the poly(ethyleneoxide methoxy acrylateco-lithium 1,1,2-trifluorobutanesulfonate acrylate, was attempted few times and it was unsuccessful. We followed the synthetic route described by Cowie and Spence. The yield was extremely low and the final product could not be separated from the impurities. The synthesis of this polyelectrolyte is not described in this report. The second polyelectrolyte, comb polysiloxane polyelectrolyte containing oligoether and perfluoroether sidechains, was synthesized in sufficient quantity to study the range of properties such as thermal stability, Li- ion- conductivity and stability toward lithium metal. Also, the batteries containing this polyelectrolyte were assembled and tested. The results are detailed below. The synthesis of another polyelectrolyte similar to polysiloxane polyelectrolyte has been started, however, the synthesis was not completed due to termination of the project.

From a series of simultaneous 8.4 and 2.3 GHz VLBI observations of the quasar 4C 39.25 phase referenced to the radio source 0920+390, carried out in 1990-1992, we have measured the proper motion of component b in 4C 39.25: mu(sub alpha) = 90 +/- 43 (mu)as/yr, mu(sub beta) = 7 +/- 68 (mu)as/yr, where the quoted uncertainties account for the contribution of the statistical standard deviation and the errors assumed for the parameters related to the geometry of the interferometric array, the atmosphere, and the source structure. This proper motion is consistent with earlier interpretations of VLBI hybrid mapping results, which showed an internal motion of this component with respect to other structural components. Our differential astrometry analyses show component b to be the one in motion. Our results thus further constrain models of this quasar.