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Selected AbstractsA Bayesian Monte Carlo Approach to Global IlluminationCOMPUTER GRAPHICS FORUM, Issue 8 2009Jonathan Brouillat I.3.7 [Computer Graphics]: Three-Dimensional Graphics an Realism Abstract Most Monte Carlo rendering algorithms rely on importance sampling to reduce the variance of estimates. Importance sampling is efficient when the proposal sample distribution is well-suited to the form of the integrand but fails otherwise. The main reason is that the sample location information is not exploited. All sample values are given the same importance regardless of their proximity to one another. Two samples falling in a similar location will have equal importance whereas they are likely to contain redundant information. The Bayesian approach we propose in this paper uses both the location and value of the data to infer an integral value based on a prior probabilistic model of the integrand. The Bayesian estimate depends only on the sample values and locations, and not how these samples have been chosen. We show how this theory can be applied to the final gathering problem and present results that clearly demonstrate the benefits of Bayesian Monte Carlo. [source] LIGHT REGULATION OF PHYCOBILISOME BIOSYNTHESIS AND CONTROL BY A PHYTOCHROME-LIKE PHOTORECEPTORJOURNAL OF PHYCOLOGY, Issue 2000K. Terauchi Ambient light quality changes dramatically affect the composition of light harvesting structures, the phycobilisomes, in many cyanobacterial species. In the cyanobacterium Fremyella diplosiphon, shifts in the ratio of red to green light lead to transcriptional changes and altered synthesis of several phycobilisome components. This process is called complementary chromatic adaptation (CCA). These two colors have opposite effects: red light activates an operon encoding the biliprotein phycocyanin (PC) and inactivates the operon encoding phycoerythrin (PE), whereas green light activates PE synthesis and shuts down PC synthesis. The effects of red and green light on CCA are photoreversible. Thus, CCA is similar to transcriptional processes that are controlled by phytochromes, a family of eukaryotic red/far red photoreversible photoreceptors. We are using molecular genetics to determine the mechanisms by which F. diplosiphon senses changes in the color of light of its environment. Initial mutant generation and complementation lead to the discovery of three CCA regulatory components that are part of a complex two component system. The most interesting of these is RcaE (regulator of chromatic adaptation), a histidine kinase-class protein containing a region in its amino-terminal half with similarity to the chromophore binding domains of phytochromes. Within this region, RcaE contains a cysteine residue in a similar location as that used for covalent attachment of the open-chain tetrapyrrole chromophore in phytochromes. We will present recent data characterizing RcaE, including in vivo analysis of the chromophore that is attached to RcaE, as well as results from our recent isolation of a new CCA regulatory component. [source] Electronic structure and magnetic properties of Fe3C with 3d and 4d impuritiesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 6 2007I. R. Shein Abstract We study the electronic structure, formation energies, and magnetic properties of cementite Fe3C doped by 3d and 4d transition metals (TM) by means of first-principles calculations. All TM elements demonstrate a preference for the substitution of the general iron position in Fe3C. We predict that early elements (Sc, Ti, V, Cr, Zr, and Nb) stabilize the cementite, while the end elements (Ni, Cu, Pd, and Ag) in the TM series sharply destabilize it. The magnetic properties of impurity atoms are found to depend strongly on their atomic numbers and the trends to ferromagnetic or antiferromagnetic coupling of impurities with Fe atoms in Fe3C coincide with the magnetic behavior of these impurities in Fe. The physical reason is a similar location of the Fermi level in the pseudogap of spin-down and almost filled spin-up Fed states in both Fe3C and Fe. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The Relationship Between Cephalic Scales and Bones in Lizards: A Preliminary Microtomographic Survey on Three Lacertid SpeciesTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2010David Costantini Abstract In the last two decades, there has been a great deal of interest in the morphology and anatomy of the lizard skull in an ecological and evolutionary perspective. However, the relationship between variations in many key anatomical features remains largely unknown. Using microtomography and geometric morphometrics, we examined the relationship between bones and scales associated with the parietal foramen in the three lizards species most common in the Italian peninsula: Podarcis muralis, P. sicula, and Lacerta bilineata. The imprints of the scales are clearly recognizable on the outer bone surface, and this may suggest a structural interaction between these elements. The temporal osteoderms are visible in the larger males and in the larger females of L. bilineata, but they are absent in the smaller specimens of L. bilineata and in all Podarcis specimens. Two parallel rows of pterygoid teeth are present in all the specimens of L. bilineata and are absent in the smaller male of L. bilineata and in both Podarcis species. Cheek osteoderms occurred only in the largest specimens of our sample (i.e., large L. bilineata), being possibly related to hyperostotic processes and densitometric thresholds more than to phylogeny. Minor differences may be also associated with the form of the parietal foramen. In absolute terms the parietal foramen tends to be largest in L. bilineata but in relation to skull length the foramen tends to be larger in P. muralis. In this latter species the foramen is also more elongated. In all three species the fronto-parietal suture occupies a similar location relatively to the scale spatial organization. A shared allometric pattern shows that the main vault enlargement can be localised at the areas anterior to the fronto-parietal suture, providing further information on the possible morphogenetic dynamics associated with the interaction between scales and bones around this structure. Anat Rec, 2010. © 2009 Wiley-Liss, Inc. [source] Functional organization of climbing fibre projection to the cerebellar anterior lobe of the ratTHE JOURNAL OF PHYSIOLOGY, Issue 2 2000H. Jörntell 1The input characteristics and distribution of climbing fibre field potentials evoked by electrical stimulation of various parts of the skin were investigated in the cerebellum of barbiturate anaesthetized rats. Climbing fibre responses were recorded in sagittally oriented microelectrode tracks across the mediolateral width of the anterior lobe. 2Climbing fibres with similar response latencies and convergence patterns terminated in sagittal bands with widths of 0.5,1.5 mm. The principal organization of the anterior lobe with respect to input characteristics and locations of sagittal zones was similar to that in the cat and ferret. Hence, the sagittal bands in the rat were tentatively named the a, b, c1, c2 and d1 zones. 3In contrast to the cat and ferret, the a zone of the rat was characterized by short latency ipsilateral climbing fibre input. Furthermore, it was divisible into a medial ,a1, zone with convergent, proximal input and a lateral ,ax' zone with somatotopically organized input. A forelimb area with similar location and input characteristics as the X zone of the cat was found, but it formed an integral part of the ax zone. A somatotopic organization of ipsilateral, short latency climbing fibre input was alsofound in the c1 zone. 4Rostrally in the anterior lobe, climbing fibres activated at short latencies from the ipsilateral side of the body terminated in a somatotopically organized transverse band which extended from the midline to the lateral end of the anterior lobe. 5The absence of the C3 and Y zones may be interpreted as a reflection of differences in the organization of the motor systems in the rat as compared with the cat. Skilled movements, which in the cat are controlled by the C1, C3 and Y zones via the anterior interposed nucleus, may in the rat be partly controlled by the ax zone via the rostrolateral part of the fastigial nucleus. [source] | ||||||||||