An Extended Nebulosity Of Highly Ionized-Gas In The Sbo Seyfert-Galaxy NGC-3516 - Detection And Study Of The Physical Conditions Of The Gas

NSF AST 73-05312Astronom

TMS over V5 disrupts motion prediction

Given the vast amount of sensory information the brain has to deal with, predicting some of this information based on the current context is a resource-efficient strategy. The framework of predictive coding states that higher-level brain areas generate a predictive model to be communicated via feedback connections to early sensory areas. Here, we directly tested the necessity of a higher-level visual area, V5, in this predictive processing in the context of an apparent motion paradigm. We flashed targets on the apparent motion trace in-time or out-of-time with the predicted illusory motion token. As in previous studies, we found that predictable in-time targets were better detected than unpredictable out-of-time targets. However, when we applied functional magnetic resonance imaging-guided, double-pulse transcranial magnetic stimulation (TMS) over left V5 at 13–53 ms before target onset, the detection advantage of in-time targets was eliminated; this was not the case when TMS was applied over the vertex. Our results are causal evidence that V5 is necessary for a prediction effect, which has been shown to modulate V1 activity (Alink et al. 2010). Thus, our findings suggest that information processing between V5 and V1 is crucial for visual motion prediction, providing experimental support for the predictive coding framework

Proteins that interact with the sodium-dependent glutamate transporters

Glutamate transporters play a crucial role in the central nervous system, helping to terminate synaptic excitatory transmission by lowering the extracellular glutamate concentration, keeping the extracellular glutamate concentration below neurotoxic levels, and being involved in the pathology of ischaemia. Little is known about the proteins that target and anchor these transporters to the plasma membrane or modulate their activity. Using electrophysiological, molecular, biochemical and cell biological techniques, I have studied the role of such interacting proteins. I dialysed into retinal Muller cells peptides homologous to the amino- or carboxy- terminals of the GLAST glutamate transporter to competitively disrupt interactions of the terminals with endogenous proteins. By studying their effects on the membrane current generated by the transporter, using whole-cell patch-clamping, I have shown that protein interactions at the carboxy-terminal of GLAST modulate the apparent glutamate affinity of the transporter. Using the yeast two-hybrid system, I identified two proteins, the I1 imidazoline receptor candidate protein and the ajuba protein, that interact with the amino-terminal of the glutamate transporter GLT-1. To further characterise the interaction between GLT-1 and ajuba, I generated polyclonal antibodies to ajuba. Ajuba and GLT-1 interact directly in biochemical assays, and they co-localise and interact in a heterologous mammalian system. Furthermore, they are both expressed in brain and retina and they may interact and co-localise in retinal bipolar cells and cerebellar structures in vivo. Electrophysiological studies suggest that ajuba does not modulate the apparent affinity of GLT-1 for glutamate. Previous work has shown that ajuba activates MAP kinase and c-jun kinase, that it shuttles between the nucleus and the cell membrane and that it is likely to interact with the cytoskeleton. I demonstrate here that ajuba is a component of adherens junctions and binds to the epithelial-cadherin complex in biochemical assays, implying that ajuba might also have a role in the formation or regulation of adherens junctions

Fuel versus Food

Many countries are actively encouraging the supply of biofuels as a low carbon alternative to the use of fossil fuels for transportation. To what extent do these trends imply a reallocation of scarce land away from food to fuel production? This paper critically reviews the small but growing literature in this area. We find that an increase in biofuel production may have a significant effect on food prices and in certain parts of the world, in speeding up deforestation through land conversion. However, more work needs to be done to examine the effect of newer generation biofuel technologies that are less land-intensive as well as the effect of environmental regulation and trade policies on land allocation between fuel and food.agricultural production; biofuel economics; climate policy; environmental regulation; land allocation

Cross-diffusion systems with excluded volume effects and asymptotic gradient flows

In this paper we discuss the analysis of a cross-diffusion PDE system for a mixture of hard spheres, which was derived by Bruna and Chapman from a stochastic system of interacting Brownian particles using the method of matched asymptotic expansions. The resulting cross-diffusion system is valid in the limit of small volume fraction of particles. While the system has a gradient flow structure in the symmetric case of all particles having the same size and diffusivity, this is not valid in general. We discuss local stability and global existence for the symmetric case using the gradient flow structure and entropy variable techniques. For the general case, we introduce the concept of an asymptotic gradient flow structure and show how it can be used to study the behavior close to equilibrium. Finally we illustrate the behavior of the model with various numerical simulations

Lane formation by side-stepping

In this paper we study a system of nonlinear partial differential equations, which describes the evolution of two pedestrian groups moving in opposite direction. The pedestrian dynamics are driven by aversion and cohesion, i.e. the tendency to follow individuals from the own group and step aside in the case of contraflow. We start with a 2D lattice based approach, in which the transition rates reflect the described dynamics, and derive the corresponding PDE system by formally passing to the limit in the spatial and temporal discretization. We discuss the existence of special stationary solutions, which correspond to the formation of directional lanes and prove existence of global in time bounded weak solutions. The proof is based on an approximation argument and entropy inequalities. Furthermore we illustrate the behavior of the system with numerical simulations

The Steep Spectrum Quasar PG1404+226 with ASCA, HST and ROSAT

(abridged) We present and discuss our observations of the NL quasar PG1404+226 with ASCA and HST, and a re-analysis of our earlier observations with ROSAT. The soft X-ray spectrum is very steep and displays an absorption feature (edge or line at ~1.1 keV). We have applied a variety of models to the ASCA and ROSAT spectra without finding a completely satisfactory fit, and the identification of the edge remains uncertain. A satisfactory fit of the ASCA spectrum assuming that the edge is produced by highly ionized iron (using the code absori in XSPEC) is obtained with an overabundance of iron by a factor > 25 compared to solar, a suggestion supported by the extremely high equivalent width of the Fe K_alpha line at 6.4 keV. A warm absorber model fitting the absorption feature with NeVII-NeX edges and assuming a peculiar oxygen/neon abundance ratio is consistent with the ROSAT data but not the ASCA data. Finally, it is also possible that the observed edge is caused by a OVIII or OVII edge or line, blueshifted by z_abs=0.2 to 0.5 depending on the specific identification, as has been suggested previously for 2 other NL quasars, but there are no other features in the UV and X-ray spectra in support of this suggestion. Two systems of UV absorption lines, one nearly at rest in the source frame, the other blueshifted by ~1900 km/s are identified in the HST/FOS spectra. Photoionization models indicate that the UV absorption and the ~1 keV absorption are probably caused by absorbers with different physical conditions. PG1404+226 is one more case of AGN where both UV and X-ray absorption features are detected, thereby increasing further the significance of the previously noted statistical association of the two types of absorbers.Comment: 11 pages, A&A in pres

The taste of the mango. A Jaina-Buddhist controversy on evidence

In the classical framework of Indian philosophy, the different schools of thought agree on the fact that the correctness of an inference relies on a special universal relation standing between the probans, or evidence-property, and the probandum, or target-property. In this framework, there is a controversy between Buddhist and Jain philosophers concerning the characteristics of this universal relation. This article presents this controversy as developed in the Pariksamukham, the Introduction to Philosophical Investigation, an epistemological treatise written by the Digambara monk Manikyanandi (9th c.)