Science at Oxford

Faraday demonstrated electromagnetic induction in 1831 using an iron ring wound with two wire coils; on interrupting battery current in one coil, momentary currents arose in the other. Between Faraday's ring and the induction coil, coiled instruments developed via meandering paths. This paper explores the opening phase of that work in the late 1830s, as the iron core, primary wire coil, and secondary wire coil were researched and differentiated. ‘Working knowledge’ (defined by Baird) gained with materials and phenomena was crucial to innovations. To understand these material-based interactions, I experimented with hand-wound coils, along with examining historical texts, drawings, and artefacts. My experience recovered the historical dead-end of two-wire coils and ensuing work with long-coiled single conductors initiated by Faraday and Henry. The shock and spark heightened in these coils provided feedback to the many instrumental configurations tested by Page, Callan, Sturgeon, Bachhoffner, and others. The continuous conductor differentiated into two segments soldered together: a thick short wire carrying battery current and a long thin wire for elevating shocks (voltage). The joined wires eventually separated, yet their transitional connection documents belief that the induced effects depend on continuity. These coiled instruments, with their intertwined histories, show experimental work and understandings in the process of developing. Seeing the nonlinear paths by which these instruments developed deepens our understanding of historical experiences, and of how people learn.     

The sub-energetic gamma-ray burst GRB 031203 as a cosmic analogue to the nearby GRB 980425

Over the six years since the discovery of the gamma-ray burst GRB 980425, which was associated with the nearby (distance approximately 40 Mpc) supernova 1998bw, astronomers have debated fiercely the nature of this event. Relative to bursts located at cosmological distance (redshift z approximately 1), GRB 980425 was under-luminous in gamma-rays by three orders of magnitude. Radio calorimetry showed that the explosion was sub-energetic by a factor of 10. Here we report observations of the radio and X-ray afterglow of the recent GRB 031203 (refs 5-7), which has a redshift of z = 0.105. We demonstrate that it too is sub-energetic which, when taken together with the low gamma-ray luminosity, suggests that GRB 031203 is the first cosmic analogue to GRB 980425. We find no evidence that this event was a highly collimated explosion viewed off-axis. Like GRB 980425, GRB 031203 appears to be an intrinsically sub-energetic gamma-ray burst. Such sub-energetic events have faint afterglows. We expect intensive follow-up of faint bursts with smooth gamma-ray light curves (common to both GRB 031203 and 980425) to reveal a large population of such events.     

Situated learning theory versus traditional cognitive learning theory: Why management education should not ignore management learning

This paper describes the differences between situated learning theory (SLT) and traditional cognitive theory (TCT). SLT is distinctive because it perceives learning to be a socially relational rather than a mentalist process. SLT places research attention upon knowledge productionin situ and in the course of work practices rather than upon learning transmission in the classroom. This paper argues that SLT's emphasis on the social context of learning is problematic and ambiguous. SLT sees context as pregiven, which is consistent with modernist thought, but also sees it as emergent, which is more consistent with postmodern thought. The implications of this are discussed and the SLT-TCT debate is used to shed light on management education from the perspective of management learning.     

Birth of a relativistic outflow in the unusual γ-ray transient Swift J164449.3+573451

Active galactic nuclei, which are powered by long-term accretion onto central supermassive black holes, produce relativistic jets with lifetimes of at least one million years, and the observation of the birth of such a jet is therefore unlikely. Transient accretion onto a supermassive black hole, for example through the tidal disruption of a stray star, thus offers a rare opportunity to study the birth of a relativistic jet. On 25 March 2011, an unusual transient source (Swift J164449.3+573451) was found, potentially representing such an accretion event. Here we report observations spanning centimetre to millimetre wavelengths and covering the first month of evolution of a luminous radio transient associated with Swift J164449.3+573451. The radio transient coincides with the nucleus of an inactive galaxy. We conclude that we are seeing a newly formed relativistic outflow, launched by transient accretion onto a million-solar-mass black hole. A relativistic outflow is not predicted in this situation, but we show that the tidal disruption of a star naturally explains the observed high-energy properties and radio luminosity and the inferred rate of such events. The weaker beaming in the radio-frequency spectrum relative to γ-rays or X-rays suggests that radio searches may uncover similar events out to redshifts of z?≈?6.     

Structural and serological evidence for a novel mechanism of antigenic variation in foot-and-mouth disease virus.

Changes resulting in altered antigenic properties of viruses nearly always occur on their surface and have been attributed to the substitution of residues directly involved in binding antibody. To investigate the mechanism of antigenic variation in foot-and-mouth disease virus (FMDV), variants that escape neutralization by a monoclonal antibody have been compared crystallographically and serologically with parental virus. FMDVs form one of the four genera of the Picornaviridae. The unenveloped icosahedral shell comprises 60 copies each of four structural proteins VP1-4. Representatives from each of the genera have similar overall structure, but differences in the external features. For example, human rhinovirus has a pronounced 'canyon' that is proposed to contain the cell attachment site, whereas elements of the attachment site for FMDV, which involves the G-H loop (residues 134-160) and C-terminus (200-213) of VP1, are exposed on the surface. Moreover, this G-H loop, which is a major antigenic site of FMDV, forms a prominent, highly accessible protrusion, a feature not seen in other picornaviruses. It is this loop that is perturbed in the variant viruses that we have studied. The amino acid mutations characterizing the variants are not at positions directly involved in antibody binding, but result in far-reaching perturbations of the surface structure of the virus. Thus, this virus seems to use a novel escape mechanism whereby an induced conformational change in a major antigenic loop destroys the integrity of the epitope.     

sRNA methylase activity of embryonic liver

Résumé Utilisant SAM-¹⁴CH₃ il a été démontré que le foie foetal a plus d'activité de sRNA methylase que le foie adulte.

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This investigation was supported in part by an allocation from a Public Health Service General Research Support Grant No. SO 1 FR-05545-03, and an American Cancer Society Grant No. IN 19F to The Jackson Laboratory, Bar Harbor, Maine, and by Public Health Service Research Grants No. HD-01496 from the National Institute of Child Health and Human Development and No. FR-00251 from the Division of Research Facilities and Resources.     

On the role of carbonic anhydrase in the anticonvulsant effects of triethyltin (TET)

Summary Triethyltin (TET) and acetazolamide (ACTZ) both produce marked anticonvulsant effects as evaluated by the maximal electroshock seizure test. However, the mechanism responsible for the anticonvulsant effect of TET and ACTZ is probably not the same since TET does not inhibit the activity of carbonic anhydrase isozyme C in vitro.This study was supported by NIEHS Toxicology Training grant No. ES07 090, NIOSH grant No. OH07085 and a University of Texas Biomedical Research grant. We wish to thank Rebecca Crenshaw for her excellent technical assistance.