Development of a hand-gesture recognition system for human-computer interaction

The aim of this Master Thesis is the analysis, design and development of a robust and reliable Human-Computer Interaction interface, based on visual hand-gesture recognition. The implementation of the required functions is oriented to the simulation of a classical hardware interaction device: the mouse, by recognizing a specific hand-gesture vocabulary in color video sequences. For this purpose, a prototype of a hand-gesture recognition system has been designed and implemented, which is composed of three stages: detection, tracking and recognition. This system is based on machine learning methods and pattern recognition techniques, which have been integrated together with other image processing approaches to get a high recognition accuracy and a low computational cost. Regarding pattern recongition techniques, several algorithms and strategies have been designed and implemented, which are applicable to color images and video sequences. The design of these algorithms has the purpose of extracting spatial and spatio-temporal features from static and dynamic hand gestures, in order to identify them in a robust and reliable way. Finally, a visual database containing the necessary vocabulary of gestures for interacting with the computer has been created.

Expression of the Hox gene complex in the indirect development of a sea urchin

Hox complex genes control spatial patterning mechanisms in the development of arthropod and vertebrate body plans. Hox genes are all expressed during embryogenesis in these groups, which are all directly developing organisms in that embryogenesis leads at once to formation of major elements of the respective adult body plans. In the maximally indirect development of a large variety of invertebrates, the process of embryogenesis leads only to a free-living, bilaterally organized feeding larva. Maximal indirect development is exemplified in sea urchins. The 5-fold radially symmetric adult body plan of the sea urchin is generated long after embryogenesis is complete, by a separate process occurring within imaginal tissues set aside in the larva. The single Hox gene complex of Strongylocentrotus purpuratus contains 10 genes, and expression of eight of these genes was measured by quantitative methods during both embryonic and larval developmental stages and also in adult tissues. Only two of these genes are used significantly during the entire process of embryogenesis per se, although all are copiously expressed during the stages when the adult body plan is forming in the imaginal rudiment. They are also all expressed in various combinations in adult tissues. Thus, development of a microscopic, free-living organism of bilaterian grade, the larva, does not appear to require expression of the Hox gene cluster as such, whereas development of the adult body plan does. These observations reflect on mechanisms by which bilaterian metazoans might have arisen in Precambrian evolution.

Complex Patterns of Alternative Splicing Mediate the Spatial and Temporal Distribution of Perlecan/UNC-52 in Caenorhabditis elegans

The unc-52 gene encodes the nematode homologue of mammalian perlecan, the major heparan sulfate proteoglycan of the extracellular matrix. This is a large complex protein with regions similar to low-density lipoprotein receptors, laminin, and neural cell adhesion molecules (NCAMs). In this study, we extend our earlier work and demonstrate that a number of complex isoforms of this protein are expressed through alternative splicing. We identified three major classes of perlecan isoforms: a short form lacking the NCAM region and the C-terminal agrin-like region; a medium form containing the NCAM region, but still lacking the agrin-like region; and a newly identified long form that contains all five domains present in mammalian perlecan.  Using region-specific antibodies and unc-52 mutants, we reveal a complex spatial and temporal expression pattern for these UNC-52 isoforms. As well, using a series of mutations affecting different regions and thus different isoforms of UNC-52, we demonstrate that the medium NCAM-containing isoforms are sufficient for myofilament lattice assembly in developing nematode body-wall muscle. Neither short isoforms nor isoforms containing the C-terminal agrin-like region are essential for sarcomere assembly or muscle cell attachment, and their role in development remains unclear.

Nuclear Accumulation of S-Adenosylhomocysteine Hydrolase in Transcriptionally Active Cells during Development of Xenopus laevis

The oocyte nuclear antigen of the monoclonal antibody 32-5B6 of Xenopus laevis is subject to regulated nuclear translocation during embryogenesis. It is distributed in the cytoplasm during oocyte maturation, where it remains during cleavage and blastula stages, before it gradually reaccumulates in the nuclei during gastrulation. We have now identified this antigen to be the enzyme S-adenosylhomocysteine hydrolase (SAHH). SAHH is the only enzyme that cleaves S-adenosylhomocysteine, a reaction product and an inhibitor of all S-adenosylmethionine-dependent methylation reactions. We have compared the spatial and temporal patterns of nuclear localization of SAHH and of nuclear methyltransferase activities during embryogenesis and in tissue culture cells. Nuclear localization of Xenopus SAHH did not temporally correlate with DNA methylation. However, we found that SAHH nuclear localization coincides with high rates of mRNA synthesis, a subpopulation colocalizes with RNA polymerase II, and inhibitors of SAHH reduce both methylation and synthesis of poly(A)+ RNA. We therefore propose that accumulation of SAHH in the nucleus may be required for efficient cap methylation in transcriptionally active cells. Mutation analysis revealed that the C terminus and the N terminus are both required for efficient nuclear translocation in tissue culture cells, indicating that more than one interacting domain contributes to nuclear accumulation of Xenopus SAHH.

Roles for genomic imprinting and the zygotic genome in placental development

The placenta contains several types of feto-maternal interfaces where zygote-derived cells interact with maternal cells or maternal blood for the promotion of fetal growth and viability. The genetic factors regulating the interactions between different cell types within feto-maternal interfaces and the relative contributions of the maternal and zygotic genomes are poorly understood. Genomic imprinting, the epigenetic process responsible for parental origin-dependent functional differences between homologous chromosomes, has been proposed to contribute to these events. Previous studies showed that mouse conceptuses with an absence of imprinted differences between the two copies of chromosome 12 (upon paternal inheritance of both copies) die late in gestation and have a variety of defects, including placentomegaly. Here we examined the role of chromosome 12 imprinting in these placentae in more detail. We show that the spatial interactions between different cell types within feto-maternal interfaces are defective and identify abnormal behaviors in both zygote-derived and maternal cells that are attributed to the genome of the zygote but not the mother. These include compromised invasion of the maternal decidualized endometrium and the central maternal artery situated within it by zygote-derived trophoblast, abnormalities in the wall of the central maternal artery, and defects within the zygote-derived cellular layer of the labyrinth, which is in direct contact with maternal blood. These findings demonstrate multiple roles for chromosome 12 imprinting in the placenta that have not previously been associated with imprinting effects. They provide insights into the function of imprinting in placental development and have evolutionary and clinical implications.

The neural development and organization of letter recognition: Evidence from functional neuroimaging, computational modeling, and behavioral studies

Although much of the brain’s functional organization is genetically predetermined, it appears that some noninnate functions can come to depend on dedicated and segregated neural tissue. In this paper, we describe a series of experiments that have investigated the neural development and organization of one such noninnate function: letter recognition. Functional neuroimaging demonstrates that letter and digit recognition depend on different neural substrates in some literate adults. How could the processing of two stimulus categories that are distinguished solely by cultural conventions become segregated in the brain? One possibility is that correlation-based learning in the brain leads to a spatial organization in cortex that reflects the temporal and spatial clustering of letters with letters in the environment. Simulations confirm that environmental co-occurrence does indeed lead to spatial localization in a neural network that uses correlation-based learning. Furthermore, behavioral studies confirm one critical prediction of this co-occurrence hypothesis, namely, that subjects exposed to a visual environment in which letters and digits occur together rather than separately (postal workers who process letters and digits together in Canadian postal codes) do indeed show less behavioral evidence for segregated letter and digit processing.

The copper transporter CTR1 provides an essential function in mammalian embryonic development

Copper serves as an essential cofactor for a variety of proteins in all living organisms. Previously, we described a human gene (CTR1;SLC31A1) that encodes a high-affinity copper-uptake protein and hypothesized that this protein is required for copper delivery to mammalian cells. Here, we test this hypothesis by inactivating the Ctr1 gene in mice by targeted mutagenesis. We observe early embryonic lethality in homozygous mutant embryos and a deficiency in copper uptake in the brains of heterozygous animals. Ctr1−/− embryos can be recovered at E8.5 but are severely developmentally retarded and morphologically abnormal. Histological analysis reveals discontinuities and variable thickness in the basement membrane of the embryonic region and an imperfect Reichert's membrane, features that are likely due to lack of activity in the collagen cross-linking cupro-enzyme lysyl oxidase. A collapsed embryonic cavity, the absence of an allantois, retarded mesodermal migration, and increased cell death are also apparent. In the brains of heterozygous adult mice, which at 16 months are phenotypically normal, copper is reduced to approximately half compared with control littermates, implicating CTR1 as the required port for copper entry into at least this organ. A study of the spatial and temporal expression pattern of Ctr1 during mouse development and adulthood further shows that CTR1 is ubiquitously transcribed with highest expression observed in the specialized epithelia of the choroid plexus and renal tubules and in connective tissues of the eye, ovary, and testes. We conclude that CTR1 is the primary avenue for copper uptake in mammalian cells.

Spatial and temporal control of RNA stability

Maternally encoded RNAs and proteins program the early development of all animals. A subset of the maternal transcripts is eliminated from the embryo before the midblastula transition. In certain cases, transcripts are protected from degradation in a subregion of the embryonic cytoplasm, thus resulting in transcript localization. Maternal factors are sufficient for both the degradation and protection components of transcript localization. Cis-acting elements in the RNAs convert transcripts progressively (i) from inherently stable to unstable and (ii) from uniformly degraded to locally protected. Similar mechanisms are likely to act later in development to restrict certain classes of transcripts to particular cell types within somatic cell lineages. Functions of transcript degradation and protection are discussed.

Distribution of parthenogenetic cells in the mouse brain and their influence on brain development and behavior.

A systematic analysis of parthenogenetic (PG) cell fate within the central nervous system (CNS) was made throughout fetal development and neonatal and adult life. Chimeras were made between PG embryos carrying a ubiquitously expressed lacZ transgene and normal fertilized embryos. After detailed histological analysis, we find that the developmental potential of PG cells is spatially restricted to certain parts of the brain. PG cells are prevalent in telencephalic structures and are largely excluded from diencephalic structures, especially the hypothalamus. These spatial restrictions are established early in development. Behavioral studies with chimeras identified an increase in male aggression when the proportion of PG cells in the brain was high. These studies demonstrate that imprinted genes play key roles in development of the CNS and may be involved in behavior.

Expression of pax-6 during urodele eye development and lens regeneration.

Regeneration of eye tissues, such as lens, seen in some urodeles involves dedifferentiation of the dorsal pigmented epithelium and subsequent differentiation to lens cells. Such spatial regulation implies possible action of genes known to be specific for particular cell lineages and/or axis. Hox genes have been the best examples of genes for such actions. We have, therefore, investigated the possibility that such genes are expressed during lens regeneration in the newt. The pax-6 gene (a gene that contains a homeobox and a paired box) has been implicated in the development of the eye and lens determination in various species ranging from Drosophila to human and, because of these properties, could be instrumental in the regeneration of the urodele eye tissues as well. We present data showing that pax-6 transcripts are present in the developing and the regenerating eye tissues. Furthermore, expression in eye tissues, such as in retina, declines when a urodele not capable of lens regeneration (axolotl) surpasses the embryonic stages. Such a decline is not seen in adult newts capable of lens regeneration. This might indicate a vital role of pax-6 in newt lens regeneration.

Prenatal monocular enucleation induces a selective loss of low-spatial-frequency cortical responses to the remaining eye.

During early development, interactions between the two eyes are critical in the formation of eye-specific domains within the lateral geniculate nucleus and the visual cortex. When monocular enucleation is done early in prenatal life, it induces remarkable anatomical and functional reorganizations of the visual pathways. Behavioral data have shown a loss in sensitivity to low-spatial-frequency gratings in cats. To correlate the behavioral observations with a possible change in the analysis of contrast at the level of primary visual areas we recorded visual evoked potentials at the 17/18 border in two cats enucleated prenatally (gestational age at enucleation, 39-42 days), three neonatal, two control animals, and one animal with a surgical removal of Y-ganglion fibers. Our results show a strong attenuation in the amplitude of response at all contrast values for gratings of low spatial frequency in prenatally enucleated cats, whereas neonatally enucleated and control animals present responses of comparable amplitude. We conclude that the behavioral results reflect the reduced sensitivity for low frequencies of visual cortical neurons. In addition, we define a critical period for the development of the contrast-sensitivity function that seems to be limited to the prenatal gestation period. We suggest that the prenatal interruption of binocular interactions leads to a functional elimination of the Y-ganglion system.

Spatial organization of retinal information about the direction of image motion.

The visual stimuli that elicit neural activity differ for different retinal ganglion cells and these cells have been categorized by the visual information that they transmit. If specific visual information is conveyed exclusively or primarily by a particular set of ganglion cells, one might expect the cells to be organized spatially so that their sampling of information from the visual field is complete but not redundant. In other words, the laterally spreading dendrites of the ganglion cells should completely cover the retinal plane without gaps or significant overlap. The first evidence for this sort of arrangement, which has been called a tiling or tessellation, was for the two types of "alpha" ganglion cells in cat retina. Other reports of tiling by ganglion cells have been made subsequently. We have found evidence of a particularly rigorous tiling for the four types of ganglion cells in rabbit retina that convey information about the direction of retinal image motion (the ON-OFF direction-selective cells). Although individual cells in the four groups are morphologically indistinguishable, they are organized as four overlaid tilings, each tiling consisting of like-type cells that respond preferentially to a particular direction of retinal image motion. These observations lend support to the hypothesis that tiling is a general feature of the organization of information outflow from the retina and clearly implicate mechanisms for recognition of like-type cells and establishment of mutually acceptable territories during retinal development.

Complejos turísticos residenciales: análisis del crecimiento del turismo residencial en el Mediterráneo español y en el Litoral Nordestino (Brasil) y su impacto socio-ambiental

Entre las diversas formas de turismo que aparecen a partir de la segunda mitad del siglo pasado, el turismo residencial surge como uno de los principales fenómenos en los escenarios brasileño e internacional. El crecimiento de esta actividad ha sido un factor importante para la generación de empleo e ingresos en los municipios del litoral sudeste de Brasil y de la costa española mediterránea. Pero recientemente, se observa un crecimiento acelerado de esta modalidad de turismo en la costa del Nordeste de Brasil. Este proceso ha generado beneficios económicos para la región al igual que impactos socioambientales. El primer objetivo de este artículo fue realizar un enfoque exploratorio, identificando el escenario de la oferta y la demanda de la construcción de complejos turísticos residenciales en el Nordeste brasileño por medio del relevamiento de sites y entrevistas a las inmobiliarias, constructoras, incorporadoras, operadoras hoteleras y organismos públicos. Los resultados de la investigación muestran el gran interés del capital internacional en construir mega proyectos de segunda residencia en el nordeste, adaptados a la demanda internacional, principalmente europea. El segundo objetivo fue comparar y analizar la evolución, las etapas y las características del turismo residencial en la costa española mediterránea, como ejemplo de modelo consolidado, con la actividad en el Nordeste brasileño, como modelo en expansión. Se verificó que ambas regiones turísticas fueron afectadas por la crisis económica y por deficiencias estructurales de sus respectivos modelos, las cuales potencian impactos económicos y socioambientales.

Grouping genetic operators for the delineation of functional areas based on spatial interaction

The delineation of functional economic areas, or market areas, is a problem of high practical relevance, since the delineation of functional sets such as economic areas in the US, Travel-to-Work Areas in the United Kingdom, and their counterparts in other OECD countries are the basis of many statistical operations and policy making decisions at local level. This is a combinatorial optimisation problem defined as the partition of a given set of indivisible spatial units (covering a territory) into regions characterised by being (a) self-contained and (b) cohesive, in terms of spatial interaction data (flows, relationships). Usually, each region must reach a minimum size and self-containment level, and must be continuous. Although these optimisation problems have been typically solved through greedy methods, a recent strand of the literature in this field has been concerned with the use of evolutionary algorithms with ad hoc operators. Although these algorithms have proved to be successful in improving the results of some of the more widely applied official procedures, they are so time consuming that cannot be applied directly to solve real-world problems. In this paper we propose a new set of group-based mutation operators, featuring general operations over disjoint groups, tailored to ensure that all the constraints are respected during the operation to improve efficiency. A comparative analysis of our results with those from previous approaches shows that the proposed algorithm systematically improves them in terms of both quality and processing time, something of crucial relevance since it allows dealing with most large, real-world problems in reasonable time.

The episcopal complex of Eio-El Tolmo de Minateda (Hellín, Albacete, Spain). Architecture and spatial organization. 7th to 8th centuries AD

The episcopal complex of Eio, located in El Tolmo de Minateda, was built between the end of the 6th century and the beginning of the 7th century, possibly as a political decision taken by the ecclesiastical authority in the capital of the Visigothic kingdom (Toletum). With the comprehensive study of the whole complex presented below (construction cycles, furniture, decoration and location of spaces), we can interpret the function of each space in the basilica and the domus episcopi, the liturgical and general movement routes, the existence of some hierarchical environments, and specify the chronological development of the buildings. After the Arab-Berber conquest of Hispania in the early 8th century, the whole complex will experience a series of transformations that will convert the religious and monumental public area into a private, residential and industrial Islamic quarter.