A regulatory code for neurogenic gene expression in the Drosophila embryo

Bioinformatics methods have identified enhancers that mediate restricted expression in the Drosophila embryo. However, only a small fraction of the predicted enhancers actually work when tested in vivo. In the present study, co-regulated neurogenic enhancers that are activated by intermediate levels of the Dorsal regulatory gradient are shown to contain several shared sequence motifs. These motifs permitted the identification of new neurogenic enhancers with high precision: five out of seven predicted enhancers direct restricted expression within ventral regions of the neurogenic ectoderm. Mutations in some of the shared motifs disrupt enhancer function, and evidence is presented that the Twist and Su(H) regulatory proteins are essential for the specification of the ventral neurogenic ectoderm prior to gastrulation. The regulatory model of neurogenic gene expression defined in this study permitted the identification of a neurogenic enhancer in the distant Anopheles genome. We discuss the prospects for deciphering regulatory codes that link primary DNA sequence information with predicted patterns of gene expression

The New IEEE-754 Standard for Floating Point Arithmetic

The current IEEE-754 floating point standard was adopted 23 years ago. IEEE chartered a committee to revise the standard to include new common practice in floating point arithmetic, to incorporate decimal floating point into the standard, and to address the issue of reproducible results. This talk will visit these issues, based on the current work of the IEEE-754 revisions committee, which expects that a new standard will be adopted sometime in 2008

Enter the movement: Generating stimulus from sceneography and proposing \u27De-sign\u27 as a tool for choreographic invention

The purpose of this study was to provide the notion of ‘de-sign’ as a proposed aid for movement composition and is the core framework of my research, which is aimed at empowering the dancer/choreographer with a multi-disciplinary aesthetic and a focus for dialectic discussion and experimentation with all material enclosed within the scenographic. De-sign is a method for decoding scenography (as a deconstruction tool to extract the components of composition classified as elements and principles). The play on words is a deliberate acknowledgement of the ‘design’ in the scenographic environment which, in this study, takes into account that all forms of designed theatrical components can be ‘de-constructed’ and re-designed with and for the choreography. The overall aim of the research is to examine the application of scenography for extending dance-making practice through the catalyst of de-sign. To this end, I created three inter-disciplinary installations/performances/scenographies as a way to analyse the ‘space’ and everything within it for movement composition (See Figures: 7., 8. and 9.). The creation of the spaces was a way of compressing the choreographic experiment by supplying a prepared environment as an example space for creative encounters. It is worth noting that it was never the focus of the research to investigate the relationship between the dancer/choreographers with the sound, lighting and stage designers. In any performance environment there is a dialogue between these people but the point of this study was how I might facilitate the relationship between the scenographic material and the dancers for the making of choreography. The dancer/choreographer operates in a ‘de-sign’ paradigm and uses a relatively simple list of structured principles to analyse the environment and employ these principles as triggers for invention to develop choreographic ideas. In de-signing of the given installation’s scenography, the dancers were asked to extend their ideas from the details as well as from the more prominent information and signs into which they would normally probe. in order to find unity, in their engagement with the whole. My research practice consisted of setting up scenographic environments as practical incubators for the immersive experience of the dancer/choreographer and thereby testing de-sign’s capacity for creative compositional movement growth

James G. Blaine\u27s Grade Patrol March

https://digitalcommons.library.umaine.edu/mmb-me/1110/thumbnail.jp

On-Shell Description of Unsteady Flames

The problem of non-perturbative description of unsteady premixed flames with arbitrary gas expansion is solved in the two-dimensional case. Considering the flame as a surface of discontinuity with arbitrary local burning rate and gas velocity jumps given on it, we show that the front dynamics can be determined without having to solve the flow equations in the bulk. On the basis of the Thomson circulation theorem, an implicit integral representation of the gas velocity downstream is constructed. It is then simplified by a successive stripping of the potential contributions to obtain an explicit expression for the vortex component near the flame front. We prove that the unknown potential component is left bounded and divergence-free by this procedure, and hence can be eliminated using the dispersion relation for its on-shell value (i.e., the value along the flame front). The resulting system of integro-differential equations relates the on-shell fuel velocity and the front position. As limiting cases, these equations contain all theoretical results on flame dynamics established so far, including the linear equation describing the Darrieus-Landau instability of planar flames, and the nonlinear Sivashinsky-Clavin equation for flames with weak gas expansion.Comment: 21 pages, 3 figures; extended discussion of causality, new references adde

Study of combustion experiments in space

The physical bases and scientific merits were examined of combustion experimentation in a space environment. For a very broad range of fundamental combustion problems, extensive and systematic experimentation at reduced gravitational levels (0 g 1) are viewed as essential to the development of needed observations and related theoretical understanding

Interaction of acoustic waves with flame front propagation

International audienceThe mechanisms of laminar premixed flame propagation have been intensively studied over the last century. Numerous authors have highlighted intrinsic phenomena in flame propagation such as Darrieus-Landau instability and Rayleigh-Taylor instability. Rayleigh-Taylor instability is often linked to the interaction between the flame front and an acoustic wave. To better characterize the interaction between a flame and aerodynamic conditions, we designed a special vertical closed tube apparatus. Our analysis focused on the behavior of a flame that propagates in a uniform stoichiometric mixture of H2 and O2 diluted with nitrogen. The experimental investigation revealed that acoustic waves emitted as the flame formed near the ignition point could increase the flame front surface by a factor of 10. An acoustic node with an amplitude of 1.3 m was identified and seemed to be responsible for the disappearance of one of the acoustic modes and for a reduction in the average flame surface. This could explain why the flame trajectory had two distinct parts: one corresponding to propagation at a high speed in the lower part of the tube, and the other with a slower speed in the upper part of the tube. The flame surface seemed to depend primarily on the frequencies of vibration and marginally on the nature of the reactive components. Propagation velocities, obtained by multiplying these flame surfaces by the fundamental burning velocity, strongly depended on the mixture reactivity

On the pulsating instability of two-dimensional flames

We consider a well-known thermo-diffusive model for the propagation of a premixed, adiabatic flame front in the large-activation-energy limit. That model depends only on one nondimensional parameter β, the reduced Lewis number. Near the pulsating instability limit, as β↓β0= 32/3, we obtain an asymptotic model for the evolution of a quasi-planar flame front, via a multi-scale analysis. The asymptotic model consists of two complex Ginzburg–Landau equations and a real Burgers equation, coupled by non-local terms. The model is used to analyse the nonlinear stability of the flame front