Xwnt-5A: a maternal Wnt that affects morphogenetic movements after overexpression in embryos of Xenopus laevis

To contribute to an understanding of the roles and mechanisms of action of Wnts in early vertebrate development, we have characterized the normal expression of Xenopus laevis Wnt-5A, and investigated the consequences of misexpression of this putative signalling factor. Xwnt-5A transcripts are expressed throughout development, and are enriched in both the anterior and posterior regions of embryos at late stages of development, where they are found primarily in ectoderm, with lower levels of expression in mesoderm. Overexpression of Xwnt-5A in Xenopus embryos leads to complex malformations distinct from those achieved by ectopic expression of Xwnts −1, −3A, or −8. This phenotype is unlikely to result from Xwnt-5A acting as an inducing agent, as overexpression of Xwnt-5A does not rescue dorsal structures in UV-irradiated embryos, does not induce mesoderm in blastula caps, and Xwnt-5A does not alter the endogenous patterns of expression of goosecoid, Xbra, or Xwnt-8. To pursue whether Xwnt-5A has the capacity to affect morphogenetic movements, we investigated whether overexpression of Xwnt-5A alters the normal elongation of blastula cap explants induced by activin. Intriguingly, Xwnt-5A blocks the elongation of blastula caps in response to activin, without blocking the differentiation of either dorsal or ventral mesoderm within these explants. The data are consistent with Xwnt-5A having the potential activity of modifying the morphogenetic movements of tissues

The Bulk RS KK-gluon at the LHC

We study the possibility of discovering and measuring the properties of the lightest Kaluza-Klein excitation of the gluon in a Randall-Sundrum scenario where the Standard Model matter and gauge fields propagate in the bulk. The KK-gluon decays primarily into top quarks. We discuss how to use the $t \bar{t}$ final states to discover and probe the properties of the KK-gluon. Identification of highly energetic tops is crucial for this analysis. We show that conventional identification methods relying on well separated decay products will not work for heavy resonances but suggest alternative methods for top identification for energetic tops. We find, conservatively, that resonances with masses less than 5 TeV can be discovered if the algorithm to identify high $p_T$ tops can reject the QCD background by a factor of 10. We also find that for similar or lighter masses the spin can be determined and for lighter masses the chirality of the coupling to $t\bar t$ can be measured. Since the energetic top pair final state is a generic signature for a large class of new physics as the top quark presumably couples most strongly to the electroweak symmetry breaking sector, the methods we have outlined to study the properties of the KK-gluon should also be important in other scenarios.Comment: 21 pages, 13 figure

Semantic properties and the computational model of mind.

Much of the contemporary research in cognitive psychology presupposes an information processing or computational model of human cognitive processes. On this view cognitive states are characterized as relations to internally inscribed representations. Jerry Fodor and Zenon Pylyshyn have argued that those representations have a combinatorial syntax and a compositional semantics, and Fodor has argued that the individuation of representations according to semantic type corresponds, roughly, to individuation according to syntactic type. I investigate whether this computational model requires us to appeal, directly or indirectly, to the semantic properties of representations when we explain cognitive behavior. I first discuss the requirements of scientific explanation in general, and the constraints of materialism and physicalism in particular. Then I outline how it is possible for semantic entities to be involved in cognitive explanations, and how Fodor and Pylyshyn think they are involved in explanations on the computational model. I consider whether, given the computational model, references to representations are necessary to explain cognitive processes or whether references to representations can be eliminated in favor or references to uninterpreted formulae. Finally I criticize the argument, suggested by both Fodor and Pylyshyn, that it is our ability to respond to nonnomic or nonprojectable properties of stimuli that requires explanation in terms of the semantic properties of representations

Academic Success and the Transfer of Community College Credits in the Principles of Economics

A growing number of today’s college students attend local 2-year community colleges. Many of these students will ultimately transfer to major universities in pursuit of the traditional Bachelors degree. The question of whether such transfer credits adequately prepare students for future academic endeavors is important for educators interested in preparing successful students and maintaining the quality of their institution. In this paper, we examine whether students who transfer credits earned for the traditional Principles of Economics course sequence achieve the same levels of academic success, measured in terms of GPA, as students taking the sequence at a major state university. The model indicates that community college transfer students perform poorly relative to native students in terms of cumulative GPA. This result is driven by a self-selection process whereby the more academically challenged students are those who choose to transfer credit from 2-year schools. The results of our model are used to develop a grade equivalency measure between the university and 2-year schools. Using this measure we are able to reject the hypothesis that grades are equivalent between 2- and 4-year institutions. Finally, we find that grades in the Principles of Economics sequence are strong predictors of overall academic success

Preparation of pigments for space-stable thermal control coatings Interim summary report, 1 Jun. 1968 - 30 Apr. 1969

Control of vapor phase reaction kinetics to produce pigments by homogeneous nucleatio

d-dimensional Oscillating Scalar Field Lumps and the Dimensionality of Space

Extremely long-lived, time-dependent, spatially-bound scalar field configurations are shown to exist in $d$ spatial dimensions for a wide class of polynomial interactions parameterized as $V(\phi) = \sum_{n=1}^h\frac{g_n}{n!}\phi^n$. Assuming spherical symmetry and if $V''<0$ for a range of values of $\phi(t,r)$, such configurations exist if: i) spatial dimensionality is below an upper-critical dimension $d_c$; ii) their radii are above a certain value $R_{\rm min}$. Both $d_c$ and $R_{\rm min}$ are uniquely determined by $V(\phi)$. For example, symmetric double-well potentials only sustain such configurations if $d\leq 6$ and $R^2\geq d[3(2^{3/2}/3)^d-2]^{-1/2}$. Asymmetries may modify the value of $d_c$. All main analytical results are confirmed numerically. Such objects may offer novel ways to probe the dimensionality of space.Comment: In press, Physics Letters B. 6 pages, 2 Postscript figures, uses revtex4.st

Gravitational conformal invariance and coupling constants in Kaluza-Klein theory

We introduce a generalized gravitational conformal invariance in the context of non-compactified 5D Kaluza-Klein theory. It is done by assuming the 4D metric to be dependent on the extra non-compactified dimension. It is then shown that the conformal invariance in 5D is broken by taking an absolute cosmological scale $R_0$ over which the 4D metric is assumed to be dependent weakly on the 5th dimension. This is equivalent to Deser's model for the breakdown of the conformal invariance in 4D by taking a constant cosmological mass term $\mu^2\sim R_0^{-2}$ in the theory. We set the scalar field to its background cosmological value leading to Einstein equation with the gravitational constant $G_N$ and a small cosmological constant. A dual Einstein equation is also introduced in which the matter is coupled to the higher dimensional geometry by the coupling $G_N^{-1}$. Relevant interpretations of the results are also discussed.Comment: 10 pages, LaTeX, some cghanges in the tex