The selection of wanted from unwanted messages requires discriminatory mechanisms of as great a complexity as those in normal perception, as is indicated by behavioral evidence. The results of neurophysiology experiments on selective attention are compatible with this supposition. This presents a difficulty for Filter theory. Another mechanism is proposed, which assumes the existence of a shifting reference standard, which takes up the level of the most important arriving signal. The way such importance is determined in the system is further (...) described. Neurophysiological evidence relative to this postulation is discussed. (shrink)

In the past several years, observational entropy has been developed as both a quantum generalization of Boltzmann entropy, and as a rather general framework to encompass classical and quantum equilibrium and non-equilibrium coarse-grained entropy. In this paper we review the construction, interpretation, most important properties, and some applications of this framework. The treatment is self-contained and relatively pedagogical, aimed at a broad class of researchers.

In many bilaterian phyla, appendages are morphological traits that characterise the identity of the various body parts. In pterygote insects, wings are dorsal appendages on the thorax. The famous “bithorax” fly created by Ed Lewis is the emblematic example of the role of Hox genes.1 Now, Tomoyasu et al.,2 using classical genetics, transgenesis and RNAi, have examined the function of thoracic Hox genes in the beetle Tribolium castaneum. Beetles have rigid elytra in place of the first pair of wings. Instead (...) of the expected transformation of the elytron into a wing, loss of Hox genes' function leads to the homeotic transformation of the second pair of dorsal appendages, the wings, into elytra. This has important consequences for the way that we see the role of Hox genes in development and evolution. BioEssays 27:673–675, 2005. © 2005 Wiley Periodicals, Inc. (shrink)

Cosmological boundary conditions for particles and fields are often discussed as a Cauchy problem, in which configurations and conjugate momenta are specified on an “initial” time slice. But this is not the only way to specify boundary conditions, and indeed in action-principle formulations we often specify configurations at two times and consider trajectories joining them. Here, we consider a classical system of particles interacting with short range two body interactions, with boundary conditions on the particles’ positions for an initial and (...) a final time. For a large number of particles that are randomly arranged into a dilute gas, we find that a typical system trajectory will spontaneously collapse into a small region of space, close to the maximum density that is obtainable, before expanding out again. If generalizeable, this has important implications for the cosmological arrow of time, potentially allowing a scenario in which both boundary conditions are generic and also a low-entropy state “initial” state of the universe naturally occurs. (shrink)

The Crustacea present a variety of body plans not encountered in any other class or phylum of the Metazoa. Here we review our current knowledge on the complement and expression of the Hox genes in Crustacea, addressing questions related to the evolution of body architecture. Specifically, we discuss the molecular mechanisms underlying the homeotic transformation of legs into feeding appendages, which occurred in parallel in several branches of the crustacean evolutionary tree. A second issue that can be approached by the (...) comparative study of Hox genes and their expression in the Crustacea bears on the homology of the abdomen. We discuss whether the so‐called “abdominal” tagma of the crustaceans is homologous to the abdomen of insects. In addition, the homology of the abdomen between malacostracan and non‐malacostracan crustaceans has also been questioned. We also address the question of the molecular developmental basis of the apparent lack of an abdomen in barnacles. We discuss these issues in relation to the problem of constraint versus adaptation in evolution. BioEssays 25:878–887, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

This chapter explores how the end of slavery is remembered in Tanzania. While the subject of ‘The end of slavery in Africa’ has attracted a substantial number of outstanding scholars, few researchers have conducted oral interviews, especially in East Africa. The author undertook field research, collecting contemporary memories of the end of slavery over a period of three months in the mid-1990s in various parts of Tanzania. The interviews were meant to complement archival research. The chapter shows that the memory (...) of the end of slavery and the archival record fail to correspond with each other, and offers an explanation of why this is the case. (shrink)

I review how both the parasegmental and segmental frames are used in constructing the body plan of the arthropods. The parasegment is the primary genetic unit, as shown by Hox gene expression, and the parasegmental design is maintained in the nerve cord. It is, however, not maintained in the epidermis, where the cuticle grooves are segmental, and in the musculature, which is segmental in organisation. This frame shift is reflected in the sensory and motor nerve connections between the ganglia and (...) the periphery. I suggest that the need for movement in an organism equipped with a hard exoskeleton was the functional constraint that shaped this apparently complex mode of development. BioEssays 26:1117–1125, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

Jessica Deutsch is a New York based artist. She earned her BFA in illustration at Parsons, & has also studied at Midreshet Harova & Bezalel Academy. She loves sharing her passion for Jewish spirituality through creative practices. Deutsch has worked with the New Shul, and was an artist in residence at the Brandeis Collegiate Institute.