Metaphoric coherence: Distinguishing verbal metaphor from `anomaly\u27

Theories and computational models of metaphor comprehension generally circumvent the question of metaphor versus “anomaly” in favor of a treatment of metaphor versus literal language. Making the distinction between metaphoric and “anomalous” expressions is subject to wide variation in judgment, yet humans agree that some potentially metaphoric expressions are much more comprehensible than others. In the context of a program which interprets simple isolated sentences that are potential instances of cross‐modal and other verbal metaphor, I consider some possible coherence criteria which must be satisfied for an expression to be “conceivable” metaphorically. Metaphoric constraints on object nominals are represented as abstracted or extended along with the invariant structural components of the verb meaning in a metaphor. This approach distinguishes what is preserved in metaphoric extension from that which is “violated”, thus referring to both “similarity” and “dissimilarity” views of metaphor. The role and potential limits of represented abstracted properties and constraints is discussed as they relate to the recognition of incoherent semantic combinations and the rejection or adjustment of metaphoric interpretations

Interaction of quasilocal harmonic modes and boson peak in glasses

The direct proportionality relation between the boson peak maximum in glasses, $\omega_b$, and the Ioffe-Regel crossover frequency for phonons, $\omega_d$, is established. For several investigated materials $\omega_b = (1.5\pm 0.1)\omega_d$. At the frequency $\omega_d$ the mean free path of the phonons $l$ becomes equal to their wavelength because of strong resonant scattering on quasilocal harmonic oscillators. Above this frequency phonons cease to exist. We prove that the established correlation between $\omega_b$ and $\omega_d$ holds in the general case and is a direct consequence of bilinear coupling of quasilocal oscillators with the strain field.Comment: RevTex, 4 pages, 1 figur

Detection and localization of continuous gravitational waves with pulsar timing arrays: The role of pulsar terms

A pulsar timing array is a Galactic-scale detector of nanohertz gravitational waves (GWs). Its target signals contain two components: the \u27Earth term\u27 and the \u27pulsar term\u27 corresponding to GWs incident on the Earth and pulsar, respectively. In this work we present a Frequentist method for the detection and localization of continuous waves that takes into account the pulsar term and is significantly faster than existing methods. We investigate the role of pulsar terms by comparing a full-signal search with an Earth-term-only search for non-evolving black hole binaries. By applying the method to synthetic data sets, we find that (i) a full-signal search can slightly improve the detection probability (by about five per cent); (ii) sky localization is biased if only Earth terms are searched for and the inclusion of pulsar terms is critical to remove such a bias; (iii) in the case of strong detections (with signal-to-noise ratio ≳30), it may be possible to improve pulsar distance estimation through GW measurements

Abrupt grain boundary melting in ice

The effect of impurities on the grain boundary melting of ice is investigated through an extension of Derjaguin-Landau-Verwey-Overbeek theory, in which we include retarded potential effects in a calculation of the full frequency dependent van der Waals and Coulombic interactions within a grain boundary. At high dopant concentrations the classical solutal effect dominates the melting behavior. However, depending on the amount of impurity and the surface charge density, as temperature decreases, the attractive tail of the dispersion force interaction begins to compete effectively with the repulsive screened Coulomb interaction. This leads to a film-thickness/temperature curve that changes depending on the relative strengths of these interactions and exhibits a decrease in the film thickness with increasing impurity level. More striking is the fact that at very large film thicknesses, the repulsive Coulomb interaction can be effectively screened leading to an abrupt reduction to zero film thickness.Comment: 8 pages, 1 figur

The two emission states of PSR B1534+12

We have observed PSR~B1534+12 (J1537+1155), a pulsar with a neutron star companion, using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We found that this pulsar shows two distinct emission states: a weak state with a wide pulse profile and a burst state with a narrow pulse profile. The weak state is always present. We cannot, with our current data, determine whether the pulse energy of the weak state follows a normal or a log-normal distribution. The burst state energy distribution follows a power-law. The amplitude of the single pulse emission in the burst state varies significantly; the peak flux intensity of the brightest pulse is 334 times stronger than that of the average pulse. We also examined the timing precision achievable using only bright pulses, which showed no demonstrable improvement because of pulse jitter and therefore quantified the jitter noise level for this pulsar.Comment: 6 pages, 6 figures, accepted for publication in The Astrophysical Journal Letter

Axiomatic approach to radiation reaction of scalar point particles in curved spacetime

Several different methods have recently been proposed for calculating the motion of a point particle coupled to a linearized gravitational field on a curved background. These proposals are motivated by the hope that the point particle system will accurately model certain astrophysical systems which are promising candidates for observation by the new generation of gravitational wave detectors. Because of its mathematical simplicity, the analogous system consisting of a point particle coupled to a scalar field provides a useful context in which to investigate these proposed methods. In this paper, we generalize the axiomatic approach of Quinn and Wald in order to produce a general expression for the self force on a point particle coupled to a scalar field following an arbitrary trajectory on a curved background. Our equation includes the leading order effects of the particle's own fields, commonly referred to as ``self force'' or ``radiation reaction'' effects. We then explore the equations of motion which follow from this expression in the absence of non-scalar forces.Comment: 17 pages, 1 figur

An ASCA Study of the Heavy Element Distribution in Clusters of Galaxies

We perform a spatially resolved X-ray spectroscopic study of a set of 11 relaxed clusters of galaxies observed by the ROSAT/PSPC and ASCA/SIS. Using a method which corrects for the energy dependent effects of the ASCA PSF based on ROSAT images, we constrain the spatial distribution of Ne, Si, S and Fe in each cluster. Theoretical prescriptions for the chemical yields of Type Ia and II supernovae, then allow determination of the Fe enrichment from both types of supernovae as a function of radius within each cluster. Using optical measurements from the literature, we also determine the iron mass-to-light ratio (IMLR) separately for Fe synthesized in both types of supernovae. For clusters with the best photon statistics, we find that the total Fe abundance decreases significantly with radius, while the Si abundance is either flat or decreases less rapidly, resulting in an increasing Si/Fe ratio with radius. This result indicates a greater predominance of Type II SNe enrichment at large radii in clusters. We suggest that the high Si/Fe ratios in the outskirts of rich clusters may arise from enrichment by Type II SNe released to ICM via galactic star burst driven winds. Abridged.Comment: 17 pages, ApJ in press (Nov. 2000), a study of systematics is adde

Timing analysis for 20 millisecond pulsars in the Parkes Pulsar Timing Array

We present timing models for 20 millisecond pulsars in the Parkes Pulsar Timing Array. The precision of the parameter measurements in these models has been improved over earlier results by using longer data sets and modelling the non-stationary noise. We describe a new noise modelling procedure and demonstrate its effectiveness using simulated data. Our methodology includes the addition of annual dispersion measure (DM) variations to the timing models of some pulsars. We present the first significant parallax measurements for PSRs J1024-0719, J1045-4509, J1600-3053, J1603-7202, and J1730-2304, as well as the first significant measurements of some post-Keplerian orbital parameters in six binary pulsars, caused by kinematic effects. Improved Shapiro delay measurements have resulted in much improved pulsar mass measurements, particularly for PSRs J0437-4715 and J1909-3744 with $M_p=1.44\pm0.07$ $M_\odot$ and $M_p=1.47\pm0.03$ $M_\odot$ respectively. The improved orbital period-derivative measurement for PSR J0437-4715 results in a derived distance measurement at the 0.16% level of precision, $D=156.79\pm0.25$ pc, one of the most fractionally precise distance measurements of any star to date.Comment: 21 pages, 5 figures, 7 tables. Accepted for publication in MNRA

Supernova Remnants in the Magellanic Clouds. V. The Complex Interior Structure of the N206 SNR

The N206 supernova remnant (SNR) in the Large Magellanic Cloud (LMC) has long been considered a prototypical "mixed morphology" SNR. Recent observations, however, have added a new twist to this familiar plot: an elongated, radially-oriented radio feature seen in projection against the SNR face. Utilizing the high resolution and sensitivity available with the Hubble Space Telescope, Chandra, and XMM-Newton, we have obtained optical emission-line images and spatially resolved X-ray spectral maps for this intriguing SNR. Our findings present the SNR itself as a remnant in the mid to late stages of its evolution. X-ray emission associated with the radio "linear feature" strongly suggests it to be a pulsar-wind nebula (PWN). A small X-ray knot is discovered at the outer tip of this feature. The feature's elongated morphology and the surrounding wedge-shaped X-ray enhancement strongly suggest a bow-shock PWN structure.Comment: 41 pages including 7 figures, accepted for publication by the Astrophysical Journa

Pulse Jitter and Single-pulse Variability in Millisecond Pulsars

Understanding the jitter noise resulting from single-pulse phase and shape variations is important for the detection of gravitational waves using pulsar timing array. We presented measurements of jitter noise and single-pulse variability of 12 millisecond pulsars that are part of the International Pulsar Timing Array sample using the Five-hundred-meter Aperture Spherical radio Telescope (FAST). We found that the levels of jitter noise can vary dramatically among pulsars. A moderate correlation with a correlation coefficient of 0.57 between jitter noise and pulse width is detected. To mitigate jitter noise, we performed matrix template matching using all four Stokes parameters. Our results revealed a reduction in jitter noise ranging from 6.7\% to 39.6\%. By performing longitude-resolved fluctuation spectrum analysis, we identified periodic intensity modulations in 10 pulsars. In PSR J0030+0451, we detected single-pulses with energies more than 10 times the average pulse energy, suggesting the presence of giant pulses. We also observed a periodic mode-changing phenomenon in PSR J0030+0451. We examined the achievable timing precision by selecting a sub-set of pulses with a specific range of peak intensity, but no significant improvement in timing precision is achievable.Comment: 14 pages, 9 figures, Accepted for publication in Ap