Establishing neuronal identity in vertebrate neurogenic placodes

The trigeminal and epibranchial placodes of vertebrate embryos form different types of sensory neurons. The trigeminal placodes form cutaneous sensory neurons that innervate the face and jaws, while the epibranchial placodes (geniculate, petrosal and nodose) form visceral sensory neurons that innervate taste buds and visceral organs. In the chick embryo, the ophthalmic trigeminal (opV) placode expresses the paired homeodomain transcription factor Pax3 from very early stages, while the epibranchial placodes express Pax2. Here, we show that Pax3 expression in explanted opV placode ectoderm correlates at the single cell level with neuronal specification and with commitment to an opV fate. When opV (trigeminal) ectoderm is grafted in place of the nodose (epibranchial) placode, Pax3-expressing cells form Pax3-positive neurons on the same schedule as in the opV placode. In contrast, Pax3-negative cells in the grafted ectoderm are induced to express the epibranchial placode marker Pax2 and form neurons in the nodose ganglion that express the epibranchial neuron marker Phox2a on the same schedule as host nodose neurons. They also project neurites along central and peripheral nodose neurite pathways and survive until well after the main period of cell death in the nodose ganglion. The older the opV ectoderm is at the time of grafting, the more Pax3-positive cells it contains and the more committed it is to an opV fate. Our results suggest that, within the neurogenic placodes, there does not appear to be a two-step induction of 'generic' neurons followed by specification of the neuron to a particular fate. Instead, there seems to be a one-step induction in which neuronal subtype identity is coupled to neuronal differentiation

Defining Technology for Learning: Cognitive and Physical Tools of Inquiry

This essay explores definitions of technology and educational technology. The authors argue the following points: 1. Educational stakeholders, and the public at large, use the term technology as though it has a universally agreed upon definition. It does not, and how technology is defined matters. 2. For technology in schools to support student learning, it must to be defined in a way that describes technology as a tool for problem-solving. 3. Integration of technology, particularly when paired with teacher-centered practices, has the potential of reinforcing and heightening the negative consequences of a conception of learning that positions students as recipients of knowledge instead constructors of knowledge. Essay concludes with a call for leaders in the field of educational technology to provide guidance by adopting a definition that encapsulates the third point above

Validating Network Value of Influencers by means of Explanations

Recently, there has been significant interest in social influence analysis. One of the central problems in this area is the problem of identifying influencers, such that by convincing these users to perform a certain action (like buying a new product), a large number of other users get influenced to follow the action. The client of such an application is a marketer who would target these influencers for marketing a given new product, say by providing free samples or discounts. It is natural that before committing resources for targeting an influencer the marketer would be interested in validating the influence (or network value) of influencers returned. This requires digging deeper into such analytical questions as: who are their followers, on what actions (or products) they are influential, etc. However, the current approaches to identifying influencers largely work as a black box in this respect. The goal of this paper is to open up the black box, address these questions and provide informative and crisp explanations for validating the network value of influencers. We formulate the problem of providing explanations (called PROXI) as a discrete optimization problem of feature selection. We show that PROXI is not only NP-hard to solve exactly, it is NP-hard to approximate within any reasonable factor. Nevertheless, we show interesting properties of the objective function and develop an intuitive greedy heuristic. We perform detailed experimental analysis on two real world datasets - Twitter and Flixster, and show that our approach is useful in generating concise and insightful explanations of the influence distribution of users and that our greedy algorithm is effective and efficient with respect to several baselines

To nourish or destroy?

“Good celebrations foster and nourish faith. Poor celebrations may weaken and destroy it” – this statement from Music in Catholic Worship, sums up well the instinct that many people have about the relationship between liturgy and faith. Those charged with the responsibility of planning and leading liturgical celebrations hold a sacred trust – to do everything in their power to ensure that the celebrations they plan and lead are in fact ‘good’ celebrations from the perspective of the worshipping assembly whose faith can be either nourished or destroyed by those celebrations, and from the perspective of the Church which has outlined with increasing specificity in recent times, its official vision of what constitutes ‘good’ liturgical celebrations

Transcending text: Liturgy as medium of evangelisation 50 years after Vatican II

Dr. Clare V. Johnson is Senior Lecturer in Liturgical Studies and Sacramental Theology at Australian Catholic University (Strathfield, NSW). Her research is published in Studia Liturgica, Worship, Liturgy, Australian Journal of Liturgy, Pastoral Liturgy, and other journals. She is editor of Ars Liturgiae: Worship, Aesthetics and Praxis (Chicago: LTP, 2003) and contributing co-editor of Vatican II: Reception and Implementation in the Australian Church (Mulgrave: Garrett, 2012). She serves as assistant editor of Studia Liturgica and is a member of the National Liturgical Council advising the Australian Bishops’ Commission on the Liturgy. The article is her public address during the Hobart Conference of the Academy

Competence, specification and induction of Pax-3 in the trigeminal placode

Placodes are discrete regions of thickened ectoderm that contribute extensively to the peripheral nervous system in the vertebrate head. The paired-domain transcription factor Pax-3 is an early molecular marker for the avian ophthalmic trigeminal (opV) placode, which forms sensory neurons in the ophthalmic lobe of the trigeminal ganglion. Here, we use collagen gel cultures and heterotopic quail-chick grafts to examine the competence, specification and induction of Pax-3 in the opV placode. At the 3-somite stage, the whole head ectoderm rostral to the first somite is competent to express Pax-3 when grafted to the opV placode region, though competence is rapidly lost thereafter in otic-level ectoderm. Pax-3 specification in presumptive opV placode ectoderm occurs by the 8-somite stage, concomitant with robust Pax-3 expression. From the 8-somite stage onwards, significant numbers of cells are committed to express Pax-3. The entire length of the neural tube has the ability to induce Pax-3 expression in competent head ectoderm and the inductive interaction is direct. We propose a detailed model for Pax-3 induction in the opV placode

Feminisation of the Veterinary Profession: Opportunity or Threat?

Feminisation is a term used in the social sciences to describe a profound shift in the gender balance from male to female within a population. The veterinary profession has experienced such a shift over the past 30 years. Research has shown that feminisation can have paradoxical effects on gender equality and status for a profession. However, Clare Allen suggests that, by understanding the processes behind feminisation, and responding appropriately, there is reason to be optimistic for the future of the veterinary profession.This is the author accepted manuscript. The final version is available from BMJ Group via http://dx.doi.org/10.1136/vr.i214

Convicts and coolies : rethinking indentured labour in the nineteenth century

This article seeks to shift the frame of analysis within which discussions of Indian indentured migration take place. It argues that colonial discourses and practices of indenture are best understood not with regard to the common historiographical framework of whether it was 'a new system of slavery', but in the context of colonial innovations in incarceration and confinement. The article shows how Indian experiences of and knowledge about transportation overseas to penal settlements informed in important ways both their own understandings and representations of migration and the colonial practices associated with the recruitment of indentured labour. In detailing the connections between two supposedly different labour regimes, it thus brings a further layer of complexity to debates around their supposed distinctions

Black Enclaves of Violence: Race and Homicide in Great Plains Cities, 1890-1920

These killings, occurring three years apart in Coffeyville, Kansas, offer bookend images of interracial homicides in the Great Plains. In the first shooting, Charles Vann, a black man and the victim, had been drinking at Walnut and Eleventh Streets in the tenderloin district, a black neighborhood in Coffeyville. This region, near the railroad yards, provided entertainment for black customers and occasionally whites in saloons, brothels, and gambling parlors. William Rodecker, a white male horse trader, had just arrived from Missouri and started drinking heavily in this area. About 8 P.M. Rodecker accosted Vann at the corner of Twelfth and Walnut Streets and began to rag him. Apparently, Vann took offense and allegedly put his hand on his hip pocket. Rodecker quickly pulled a .38 revolver and fired four shots in quick succession, mortally wounding Vann.1 In the second example, on 5 February 1907 Rodecker, just released from prison, became involved in an argument in the exact same area. Al Jesse (one of Vann\u27s friends) pulled a revolver and shot Rodecker three times.2 Not surprisingly, the killing of Rodecker occurred less than one block from the previous shooting. These shootings typified violent behavior in Coffeyville at the beginning of the twentieth century. Since many men carried handguns, it is not surprising that violent confrontations often ended in death. Both homicides are especially significant because of the interracial factor. In the first case Rodecker, the white defendant, appeared before a justice of the peace and was quickly released on a five-hundred-dollar bond, and at a preliminary hearing the Montgomery County district attorney charged Rodecker with murder. Months later a jury found him guilty of manslaughter and a judge sentenced Rodecker from one to five years in prison.3 In the second killing, despite the defendant pleading self-defense (both men had drawn their handguns), an all-white jury found Al Jesse guilty of second-degree murder; he received a twenty-year sentence.4 These dramatic shootings provide historians with a window of opportunity to ask the question: how common were black homicides in Coffeyville, Topeka, and other eastern Kansas cities? MEASURING BLACK VIOLENCE LEVELS There is considerable literature on the black experience in Kansas. For example, Nell Painter and others have examined the black migration of the Exodusters who arrived to make a new life in rural Kansas after the Civil War. However, most of these studies deal with rural agricultural communities such as Nicodemus, Hodgeman, Morton City, and Parsons, which developed when blacks fled the South to escape mob violence, lynching, and discrimination.5 Arriving in large numbers, blacks soon discovered that discrimination also existed in Kansas and Nebraska

Black Enclaves of Violence: Race and Homicide in Great Plains Cities, 1890-1920

These killings, occurring three years apart in Coffeyville, Kansas, offer bookend images of interracial homicides in the Great Plains. In the first shooting, Charles Vann, a black man and the victim, had been drinking at Walnut and Eleventh Streets in the tenderloin district, a black neighborhood in Coffeyville. This region, near the railroad yards, provided entertainment for black customers and occasionally whites in saloons, brothels, and gambling parlors. William Rodecker, a white male horse trader, had just arrived from Missouri and started drinking heavily in this area. About 8 P.M. Rodecker accosted Vann at the corner of Twelfth and Walnut Streets and began to rag him. Apparently, Vann took offense and allegedly put his hand on his hip pocket. Rodecker quickly pulled a .38 revolver and fired four shots in quick succession, mortally wounding Vann.1 In the second example, on 5 February 1907 Rodecker, just released from prison, became involved in an argument in the exact same area. Al Jesse (one of Vann\u27s friends) pulled a revolver and shot Rodecker three times.2 Not surprisingly, the killing of Rodecker occurred less than one block from the previous shooting. These shootings typified violent behavior in Coffeyville at the beginning of the twentieth century. Since many men carried handguns, it is not surprising that violent confrontations often ended in death. Both homicides are especially significant because of the interracial factor. In the first case Rodecker, the white defendant, appeared before a justice of the peace and was quickly released on a five-hundred-dollar bond, and at a preliminary hearing the Montgomery County district attorney charged Rodecker with murder. Months later a jury found him guilty of manslaughter and a judge sentenced Rodecker from one to five years in prison.3 In the second killing, despite the defendant pleading self-defense (both men had drawn their handguns), an all-white jury found Al Jesse guilty of second-degree murder; he received a twenty-year sentence.4 These dramatic shootings provide historians with a window of opportunity to ask the question: how common were black homicides in Coffeyville, Topeka, and other eastern Kansas cities? MEASURING BLACK VIOLENCE LEVELS There is considerable literature on the black experience in Kansas. For example, Nell Painter and others have examined the black migration of the Exodusters who arrived to make a new life in rural Kansas after the Civil War. However, most of these studies deal with rural agricultural communities such as Nicodemus, Hodgeman, Morton City, and Parsons, which developed when blacks fled the South to escape mob violence, lynching, and discrimination.5 Arriving in large numbers, blacks soon discovered that discrimination also existed in Kansas and Nebraska