Squaring the Circle: The Cultural Relativity of 'Good' Shape

The Gestalt theorists of the early twentieth century proposed a psychological primacy for circles, squares and triangles over other shapes. They described them as 'good' shapes and the Gestalt premise has been widely accepted. Rosch (1973), for example, suggested that shape categories formed around these 'natural' prototypes irrespective of the paucity of shape terms in a language. Rosch found that speakers of a language lacking terms for any geometric shape nevertheless learnt paired-associates to these 'good' shapes more easily than to asymmetric variants. We question these empirical data in the light of the accumulation of recent evidence in other perceptual domains that language affects categorization. A cross-cultural investigation sought to replicate Rosch's findings with the Himba of Northern Namibia who also have no terms in their language for the supposedly basic shapes of circle, square and triangle. A replication of Rosch (1973) found no advantage for these 'good' shapes in the organization of categories. It was concluded that there is no necessary salience for circles, squares and triangles. Indeed, we argue for the opposite because these shapes are rare in nature. The general absence of straight lines and symmetry in the perceptual environment should rather make circles, squares and triangles unusual and, therefore, less likely to be used as prototypes in categorization tasks. We place shape as one of the types of perceptual input (in philosophical terms, 'vague') that is readily susceptible to effects of language variation

Network synchronization: Optimal and Pessimal Scale-Free Topologies

By employing a recently introduced optimization algorithm we explicitely design optimally synchronizable (unweighted) networks for any given scale-free degree distribution. We explore how the optimization process affects degree-degree correlations and observe a generic tendency towards disassortativity. Still, we show that there is not a one-to-one correspondence between synchronizability and disassortativity. On the other hand, we study the nature of optimally un-synchronizable networks, that is, networks whose topology minimizes the range of stability of the synchronous state. The resulting ``pessimal networks'' turn out to have a highly assortative string-like structure. We also derive a rigorous lower bound for the Laplacian eigenvalue ratio controlling synchronizability, which helps understanding the impact of degree correlations on network synchronizability.Comment: 11 pages, 4 figs, submitted to J. Phys. A (proceedings of Complex Networks 2007

Entangled networks, synchronization, and optimal network topology

A new family of graphs, {\it entangled networks}, with optimal properties in many respects, is introduced. By definition, their topology is such that optimizes synchronizability for many dynamical processes. These networks are shown to have an extremely homogeneous structure: degree, node-distance, betweenness, and loop distributions are all very narrow. Also, they are characterized by a very interwoven (entangled) structure with short average distances, large loops, and no well-defined community-structure. This family of nets exhibits an excellent performance with respect to other flow properties such as robustness against errors and attacks, minimal first-passage time of random walks, efficient communication, etc. These remarkable features convert entangled networks in a useful concept, optimal or almost-optimal in many senses, and with plenty of potential applications computer science or neuroscience.Comment: Slightly modified version, as accepted in Phys. Rev. Let

A novel neurotrophic therapeutic strategy for experimental stroke.

Human chorionic gonadotropin (hCG) promotes proliferation of endogenous neural stem cells, and erythropoietin (EPO) promotes differentiation of these cells into neural stem cells. The current study examined effects of sequential administration of these two compounds, initiated 24 h after stroke. At that time, rats were randomized into four treatment groups: hCG+EPO (3 IM doses hCG over 5 days, followed by 3 IV doses EPO over 3 days), hCG+Saline using the same schedule, Saline+EPO using the same schedule, or neither drug (Saline+Saline). The primary endpoint was the composite neurological score, measured 11 times, from 1 h until 12 weeks post-insult. The neurological score was different across treatment groups (p<0.03). Pairwise testing of groups found that the hCG+EPO group had significantly better behavior at 6/10 post-stroke time points as compared to Saline+Saline. The differences observed when comparing the two-drug group with placebo were less apparent when comparing either of the one-drug groups with placebo. The two one-drug treatment arms did not significantly differ at any time point. Treatment with hCG+EPO significantly reduced total lesion volume by 82-89% compared to the other three treatment groups. The current therapeutic strategy improved behavioral outcome and reduced lesion volume with a time window of 24 h after the onset of stroke. The results from these experiments provide new insight into the effects of these two growth factors on stroke in rats, and could suggest a potential for translation into human stroke studies

Comment on the Definition of Eligible Organization for Purposes of Coverage of Certain Preventive Services Under the Affordable Care Act

This comment letter was submitted by U.C. Berkeley corporate law professors in response to a request for comment by the Health and Human Services Department on the definition of eligible organization under the Affordable Care Act in light of the Supreme Court\u27s decision in Burwell v. Hobby Lobby. Eligible organizations will be permitted under the Hobby Lobby decision to assert the religious principles of their shareholders to exempt themselves from the Affordable Care Act\u27s contraceptive mandate for employees. In Hobby Lobby, the Supreme Court held that the nexus of identity between several closely-held, for-profit corporations and their shareholders holding “a sincere religious belief that life begins at conception” was sufficiently close to justify granting such corporations an exemption from the Affordable Care Act\u27s contraceptive mandate pursuant to the Religious Freedom Restoration Act of 1993. More specifically, the Court ascertained that the overall interests of the corporations and their natural-person shareholders were sufficiently identical to warrant ascribing the religious commitments of the shareholders to their corporations. Notably, the Court stopped short of articulating a diagnostic test for determining when a sufficient overlap of interests exists; instead, it concluded that well-established principles in state corporate law should provide such guidance. We believe that state corporate law does in fact provide the diagnostic test the Court desires for determining when it is appropriate to disregard the distinct identity of a corporation for the identity of its shareholders. This test is rooted in the long-standing case law that constitutes the alter ego doctrine (commonly referred to as “veil piercing”). To sustain a claim of veil piercing, state corporate law uniformly requires there to be “unity of ownership and interest” between the corporation and its shareholders. If a corporation is operated as the effective alter ego of its shareholders to such an extent that its separate corporate existence ceases to exist as a practical matter, then a veil piercing claim can be established that effectively attributes the corporation’s legal rights and obligations to its shareholders, and vice versa. A veil piercing conclusion effectively holds that there is no practical difference between the corporation and the shareholders themselves. We therefore propose that for purposes of defining an “eligible organization” under Hobby Lobby, the HHS and other federal organizations should follow the corporate law doctrine of veil piercing. Indeed, to make this doctrine administratively feasible, we further suggest that shareholders of a corporation should have to certify that they and the corporation have a unity in identity and interests, and therefore the corporation should be viewed as the shareholders’ alter ego

Quantum graphs where back-scattering is prohibited

We describe a new class of scattering matrices for quantum graphs in which back-scattering is prohibited. We discuss some properties of quantum graphs with these scattering matrices and explain the advantages and interest in their study. We also provide two methods to build the vertex scattering matrices needed for their construction.Comment: 15 page

Optimal network topologies: Expanders, Cages, Ramanujan graphs, Entangled networks and all that

We report on some recent developments in the search for optimal network topologies. First we review some basic concepts on spectral graph theory, including adjacency and Laplacian matrices, and paying special attention to the topological implications of having large spectral gaps. We also introduce related concepts as ``expanders'', Ramanujan, and Cage graphs. Afterwards, we discuss two different dynamical feautures of networks: synchronizability and flow of random walkers and so that they are optimized if the corresponding Laplacian matrix have a large spectral gap. From this, we show, by developing a numerical optimization algorithm that maximum synchronizability and fast random walk spreading are obtained for a particular type of extremely homogeneous regular networks, with long loops and poor modular structure, that we call entangled networks. These turn out to be related to Ramanujan and Cage graphs. We argue also that these graphs are very good finite-size approximations to Bethe lattices, and provide almost or almost optimal solutions to many other problems as, for instance, searchability in the presence of congestion or performance of neural networks. Finally, we study how these results are modified when studying dynamical processes controlled by a normalized (weighted and directed) dynamics; much more heterogeneous graphs are optimal in this case. Finally, a critical discussion of the limitations and possible extensions of this work is presented.Comment: 17 pages. 11 figures. Small corrections and a new reference. Accepted for pub. in JSTA

The adverse impact of racial microaggressions on college students\u27 self-esteem

Racial microaggressions are subtle (often unintentional or unconscious) forms of racial discrimination that negatively affect victims’ mental health. Utilizing an undergraduate student sample (N = 225), the current study examined the relationship between racial microaggressions and self-esteem. Results indicate that racial microaggressions negatively predict a lower selfesteem, and that microaggressions that occur in educational and workplace environments are particularly harmful to self-esteem. Finally, findings reveal that individuals of various racial and ethnic minority groups experience racial microaggressions differently. Implications for student development and recommendations for further research involving racial microaggressions and college students are discussed

The geomagnetic environment in which sea turtle eggs incubate affects subsequent magnetic navigation behaviour of hatchlings

Loggerhead sea turtle hatchlings (Caretta caretta) use regional magnetic fields as open-ocean navigational markers during trans-oceanic migrations. Little is known, however, about the ontogeny of this behaviour. As a first step towards investigating whether the magnetic environment in which hatchlings develop affects subsequent magnetic orientation behaviour, eggs deposited by nesting female loggerheads were permitted to develop in situ either in the natural ambient magnetic field or in a magnetic field distorted by magnets placed around the nest. In orientation experiments, hatchlings that developed in the normal ambient field oriented approximately south when exposed to a field that exists near the northern coast of Portugal, a direction consistent with their migratory route in the northeastern Atlantic. By contrast, hatchlings that developed in a distorted magnetic field had orientation indistinguishable from random when tested in the same north Portugal field. No differences existed between the two groups in orientation assays involving responses to orbital movements of waves or sea-finding, neither of which involves magnetic field perception. These findings, to our knowledge, demonstrate for the first time that the magnetic environment present during early development can influence the magnetic orientation behaviour of a neonatal migratory animal