Spiral cracks in drying precipitates

We investigate the formation of spiral crack patterns during the desiccation of thin layers of precipitates in contact with a substrate. This symmetry-breaking fracturing mode is found to arise naturally not from torsion forces, but from a propagating stress front induced by the fold-up of the fragments. We model their formation mechanism using a coarse-grain model for fragmentation and successfully reproduce the spiral cracks. Fittings of experimental and simulation data show that the spirals are logarithmic, corresponding to constant deviation from a circular crack path. Theoretical aspects of the logarithmic spirals are discussed. In particular we show that this occurs generally when the crack speed is proportional to the propagating speed of stress front.Comment: 4 pages, 5 figures, RevTe

Southern Sky Redshift Survey: Clustering of Local Galaxies

We use the two-point correlation function to calculate the clustering properties of the recently completed SSRS2 survey. The redshift space correlation function for the magnitude-limited SSRS2 is given by xi(s)=(s/5.85 h-1 Mpc)^{-1.60} for separations between 2 < s < 11 h-1 Mpc, while our best estimate for the real space correlation function is xi(r) = (r/5.36 h-1 Mpc)^{-1.86}. Both are comparable to previous measurements using surveys of optical galaxies over much larger and independent volumes. By comparing the correlation function calculated in redshift and real space we find that the redshift distortion on intermediate scales is small. This result implies that the observed redshift-space distribution of galaxies is close to that in real space, and that beta = Omega^{0.6}/b < 1, where Omega is the cosmological density parameter and b is the linear biasing factor for optical galaxies. We also use the SSRS2 to study the dependence of xi on the internal properties of galaxies. We confirm earlier results that luminous galaxies (L>L*) are more clustered than sub-L* galaxies and that the luminosity segregation is scale-independent. We find that early types are more clustered than late types, but that in the absence of rich clusters, the relative bias between early and late types in real space, is not as strong as previously estimated. Furthermore, both morphologies present a luminosity-dependent bias, with the early types showing a slightly stronger dependence on luminosity. We also find that red galaxies are significantly more clustered than blue ones, with a mean relative bias stronger than that seen for morphology. Finally, we find that the relative bias between optical and iras galaxies in real space is b_o/b_I $\sim$ 1.4.Comment: 43 pages, uses AASTeX 4.0 macros. Includes 8 tables and 16 Postscript figures, updated reference

Using the filaments in the LCRS to test the LambdaCDM model

It has recently been established that the filaments seen in the Las Campanas Redshift Survey (LCRS) are statistically significant at scales as large as 70 to 80 Mpc/h in the $-3^{\circ}$ slice, and 50 to 70 Mpc/h in the five other LCRS slices. The ability to produce such filamentary features is an important test of any model for structure formation. We have tested the LCDM model with a featureless, scale invariant primordial power spectrum by quantitatively comparing the filamentarity in simulated LCRS slices with the actual data. The filamentarity in an unbiased LCDM model, we find, is less than the LCRS. Introducing a bias b=1.15, the model is in rough consistency with the data, though in two of the slices the filamentarity falls below the data at a low level of statistical significance. The filamentarity is very sensitive to the bias parameter and a high value b=1.5, which enhances filamentarity at small scales and suppresses it at large scales, is ruled out. A bump in the power spectrum at k~0.05 Mpc/h is found to have no noticeable effect on the filamentarity.Comment: 16 pages, 3 figures; Minor Changes, Accepted to Ap

Magnetodielectric detection of magnetic quadrupole order in Ba(TiO)Cu4_4(PO4_4)4_4 with Cu4_4O12_{12} square cupolas

In vortex-like spin arrangements, multiple spins can combine into emergent multipole moments. Such multipole moments have broken space-inversion and time-reversal symmetries, and can therefore exhibit linear magnetoelectric (ME) activity. Three types of such multipole moments are known: toroidal, monopole, and quadrupole moments. So far, however, the ME-activity of these multipole moments has only been established experimentally for the toroidal moment. Here, we propose a magnetic square cupola cluster, in which four corner-sharing square-coordinated metal-ligand fragments form a noncoplanar buckled structure, as a promising structural unit that carries an ME-active multipole moment. We substantiate this idea by observing clear magnetodielectric signals associated with an antiferroic ME-active magnetic quadrupole order in the real material Ba(TiO)Cu$_4$(PO$_4$)$_4$. The present result serves as a useful guide for exploring and designing new ME-active materials based on vortex-like spin arrangements.Comment: 4 figure

Morphological Variation, Karyology, and Systematic Relationships of \u3ci\u3eHeteromys gaumeri\u3c/i\u3e (Rodentia: Heteromyidae)

Morphological variation was assessed within and among populations of Heteromys gaumeri using univariate and multivariate statistical analyses of external and cranial measurements. Although patterns and amount of nongeographic variation in H. gaumeri were similar to other heteromyines, geographic variation was relatively conservative. Mean values of most characters were statistically homogeneous among localities and spatially unpatterned. Consequently, no association was found between levels of within- and among-sample variation for individual characters (the Kluge-Kerfoot phenomenon ). Populations of H. gaumeri were chromosomally monomorphic. The lack of morphological and chromosomal variation in H. gaumeri contrasts sharply with patterns in other heteromyines. Heteromys gaumeri is morphologically and chromosomally distinct from the H. desmarestianus species group (to which it is currently assigned) and appears to share some primitive characters with Liomys (the sister group of Heteromys). We recommend that H. gaumeri be removed from the H. desmarestianus group. Spanish abstract: La variación morfológica intra e interpoblacional de Heteromys gaumeri fue evaluada usando análisis estadísticos univariados y multivariados de medidas externas y craneales. A pesar de que los patrones y cantidad de variación intrapoblacional en H. gaumeri fue similar a la de otros heterominos, la variación geográfica fue relativamente conservadora. Los valores promedio de la mayoría de los caracteres fueron estadisticamente homogeneos entre las localidades, sin mostrar ningún patrón de variación espacial. En conservencia, no se encontró asociación alguna entre los niveles de variación intra e interpoblacional para caracteres individuates ( fenómena Kluge-Kerfoot ), Las poblaciones de H. gaumeri fueron monomórficas cromosómicamente. La falta de variacion tanto morfológica como cronosómica en H. gaumeri contrasta marcadamente con los patrones encontrados anteriormente para otros heteróminos. Heteromys gaumeri es morfológica y cromosómicamente distinguible del grupo H. desmarestianus (al cual se asigna actualmente) y aparentemente comparte algunos caracteres primitives con Liomys (el grupo hermano de Heteromys). Nosotros recomendamos que se remueva a H. gaumeri del grupo H. desmarestianus. Portuguese abstract: Avalia-se a variação morfológica intra- e interpopulacional de Heteromys gaumeri, através de análises estatisticas uni- e multivariadas de medidas externas e craniais. Apesar dos padrões, e da quantidade de variação intrapopulacional em H. gaumeri serem similares aos de outros heteromídeos, a variação geográfica é relativamente conservadora. Os valores médios da maior parte dos caráteres examinados são estatìsticamente homogeneos entre as localidades, e não surgiu nenhum padrão de variações locais. Consequentemente, não foram encontradas assoçiacões entre os níveis de varaiações intra- e interpopulacionais para caráteres individuais (o “fenômeno Kluge-Kerfoot”). Populações de H. gaumeri mostraram-se cromossômicamente monomórficas. A falta de variação morfológica ou cromossômica em H. gaumeri é altamente contrastante aos padrões encontrados em outros heteromídeos. Heteromys gaumeri distinguese tanto morfológica quanto cromossômicamente do grupo H. desmarestianus, ao qual está atualmente designado, e aparentemente possue caráteres primitivos em comum com Liomys—grupo irmão de Heteromys. Recomendamos que H. gaumeri seja removido do grupo H. desmarestianus

Morphological Variation, Karyology, and Systematic Relationships of \u3ci\u3eHeteromys gaumeri\u3c/i\u3e (Rodentia: Heteromyidae)

Morphological variation was assessed within and among populations of Heteromys gaumeri using univariate and multivariate statistical analyses of external and cranial measurements. Although patterns and amount of nongeographic variation in H. gaumeri were similar to other heteromyines, geographic variation was relatively conservative. Mean values of most characters were statistically homogeneous among localities and spatially unpatterned. Consequently, no association was found between levels of within- and among-sample variation for individual characters (the Kluge-Kerfoot phenomenon ). Populations of H. gaumeri were chromosomally monomorphic. The lack of morphological and chromosomal variation in H. gaumeri contrasts sharply with patterns in other heteromyines. Heteromys gaumeri is morphologically and chromosomally distinct from the H. desmarestianus species group (to which it is currently assigned) and appears to share some primitive characters with Liomys (the sister group of Heteromys). We recommend that H. gaumeri be removed from the H. desmarestianus group. Spanish abstract: La variación morfológica intra e interpoblacional de Heteromys gaumeri fue evaluada usando análisis estadísticos univariados y multivariados de medidas externas y craneales. A pesar de que los patrones y cantidad de variación intrapoblacional en H. gaumeri fue similar a la de otros heterominos, la variación geográfica fue relativamente conservadora. Los valores promedio de la mayoría de los caracteres fueron estadisticamente homogeneos entre las localidades, sin mostrar ningún patrón de variación espacial. En conservencia, no se encontró asociación alguna entre los niveles de variación intra e interpoblacional para caracteres individuates ( fenómena Kluge-Kerfoot ), Las poblaciones de H. gaumeri fueron monomórficas cromosómicamente. La falta de variacion tanto morfológica como cronosómica en H. gaumeri contrasta marcadamente con los patrones encontrados anteriormente para otros heteróminos. Heteromys gaumeri es morfológica y cromosómicamente distinguible del grupo H. desmarestianus (al cual se asigna actualmente) y aparentemente comparte algunos caracteres primitives con Liomys (el grupo hermano de Heteromys). Nosotros recomendamos que se remueva a H. gaumeri del grupo H. desmarestianus. Portuguese abstract: Avalia-se a variação morfológica intra- e interpopulacional de Heteromys gaumeri, através de análises estatisticas uni- e multivariadas de medidas externas e craniais. Apesar dos padrões, e da quantidade de variação intrapopulacional em H. gaumeri serem similares aos de outros heteromídeos, a variação geográfica é relativamente conservadora. Os valores médios da maior parte dos caráteres examinados são estatìsticamente homogeneos entre as localidades, e não surgiu nenhum padrão de variações locais. Consequentemente, não foram encontradas assoçiacões entre os níveis de varaiações intra- e interpopulacionais para caráteres individuais (o “fenômeno Kluge-Kerfoot”). Populações de H. gaumeri mostraram-se cromossômicamente monomórficas. A falta de variação morfológica ou cromossômica em H. gaumeri é altamente contrastante aos padrões encontrados em outros heteromídeos. Heteromys gaumeri distinguese tanto morfológica quanto cromossômicamente do grupo H. desmarestianus, ao qual está atualmente designado, e aparentemente possue caráteres primitivos em comum com Liomys—grupo irmão de Heteromys. Recomendamos que H. gaumeri seja removido do grupo H. desmarestianus

Ultra-high energy cosmic rays may come from clustered sources

Clustering of cosmic-ray sources affects the flux observed beyond the cutoff imposed by the cosmic microwave background and may be important in interpreting the AGASA, Fly's Eye, and HiRes data. The standard deviation, sigma, in the predicted number, N, of events above 10^{20} eV is sigma/N = 0.9(r_0/10 Mpc)^{0.9}, where r_0 is the unknown scale length of the correlation function (r_0 = 10 Mpc for field galaxies). Future experiments will allow the determination of r_0 through the detection of anisotropies in arrival directions of ~ 10^{20} eV cosmic-rays over angular scales of Theta ~ r_0/30 Mpc.Comment: Accepted for publication in Astrophysical Journa

The Hox Gene egl-5 Acts as a Terminal Selector for VD13 Development via Wnt Signaling

This work is licensed under a Creative Commons Attribution 4.0 International License.Nervous systems are comprised of diverse cell types that differ functionally and morphologically. During development, extrinsic signals, e.g., growth factors, can activate intrinsic programs, usually orchestrated by networks of transcription factors. Within that network, transcription factors that drive the specification of features specific to a limited number of cells are often referred to as terminal selectors. While we still have an incomplete view of how individual neurons within organisms become specified, reporters limited to a subset of neurons in a nervous system can facilitate the discovery of cell specification programs. We have identified a fluorescent reporter that labels VD13, the most posterior of the 19 inhibitory GABA (γ-amino butyric acid)-ergic motorneurons, and two additional neurons, LUAL and LUAR. Loss of function in multiple Wnt signaling genes resulted in an incompletely penetrant loss of the marker, selectively in VD13, but not the LUAs, even though other aspects of GABAergic specification in VD13 were normal. The posterior Hox gene, egl-5, was necessary for expression of our marker in VD13, and ectopic expression of egl-5 in more anterior GABAergic neurons induced expression of the marker. These results suggest egl-5 is a terminal selector of VD13, subsequent to GABAergic specification

Galaxy Clustering and Large-Scale Structure from z = 0.2 to z = 0.5 in Two Norris Redshift Surveys

(abridged) We present a study of the nature and evolution of large-scale structure based on two independent redshift surveys of faint field galaxies conducted with the 176-fiber Norris Spectrograph on the Palomar 200-inch telescope. The two surveys together sparsely cover ~20 sq. degrees and contain 835 r < 21 mag galaxies with redshifts 0.2 < z < 0.5. Both surveys have a median redshift of z = 0.30. In order to obtain a rough estimate of the cosmic variance, we analyze the two surveys independently. We measure the comoving correlation length to be 3.70 +/- 0.13 h^-1 Mpc at z = 0.30 with a power-law slope gamma = 1.77 +/- 0.05. Dividing the sample into low (0.2 < z < 0.3) and high (0.32 < z < 0.5) redshift intervals, we see no evidence for a change in the comoving correlation length over the redshift range 0.2 < z < 0.5. Similar to the well-established results in the local universe, we find that intrinsically bright galaxies are more strongly clustered than intrinsically faint galaxies and that galaxies with little ongoing star formation, as judged from the rest-frame equivalent width of the [OII]3727, are more strongly clustered than galaxies with significant ongoing star formation. The rest-frame pairwise velocity dispersion of the sample is 326^+67_-52 km s^-1, ~25% lower than typical values measured locally. The appearance of the galaxy distribution, particularly in the more densely sampled Abell 104 field, is quite striking. The pattern of sheets and voids which has been observed locally continues at least to z ~ 0.5. A friends-of-friends analysis of the galaxy distribution supports the visual impression that > 90% of all galaxies at z < 0.5 are part of larger structures with overdensities of > 5.Comment: 40 pages including 26 Postscript figures; revised version to match version accepted by Ap