Papers by Daniel Hernandez
Chromosoma, 1980
EM investigation of Ag-AS-NOR staining after short glutaraldehyde prefixation followed by Carnoy ... more EM investigation of Ag-AS-NOR staining after short glutaraldehyde prefixation followed by Carnoy fixation maintained good ultrastructural preservation and reactive selectivity. This enables exact localization of silver deposits both in the fibrillar centers of typical or segregated nucleoli during interphase, and in chromosome NORs during mitosis. These results argue in favour of the possibility that fibrillar centers are the interphasic counterpart of chromosome NORs. Special structures such as nucleolar blobs and remnants usually considered to be of nucleolar origin, were also stained. — These findings seem to indicate a relationship between the distribution of the silver-stained proteins, the arrangement of the nucleolar structures and the degree of nucleolar activity resulting from the experimental conditions. These results are of interest at the time when the concept of the nucleolar matrix is gradually emerging.
Chromosoma, 1982
Application of NOR silver staining to Pleurodeles oocyte nuclei showed selective silver deposits ... more Application of NOR silver staining to Pleurodeles oocyte nuclei showed selective silver deposits on the fibrillar part of the nucleoli in situ. This staining was adapted to nucleoli spread on grids, by a procedure which allowed the spreading of transcription units from both nucleoli and lampbrush chromosomes on the same grids. This permitted localization of the predominant nucleolar Ag-stained proteins on the nucleolar transcriptional units and not on the lampbrush chromosomes. These proteins were found exclusively on the transcribed part of the nucleolar genes and were not seen in apparently untranscribed spacer regions. The proteins seemed preferentially located on the DNP axis rather than on the RNP fibrils.
RELATIVE REPRESENTATION OF SPATIAL KNOWLEDGE: THE 2-D CASE DANIEL HERNANDEZ Institut fir Informat... more RELATIVE REPRESENTATION OF SPATIAL KNOWLEDGE: THE 2-D CASE DANIEL HERNANDEZ Institut fir Informatik Technische Univenitit Minchen Arcisstrafie 21 8000 Munchtn S Germany ABSTRACT. There have been some straightforward efforts to extend Allen's ...
New England Journal of Medicine, 2003
Severe pulmonary hypertension constitutes a group of diseases characterized by complex, lumen-occ... more Severe pulmonary hypertension constitutes a group of diseases characterized by complex, lumen-occluding vascular lesions that develop in genetically susceptible persons. The only viral infection associated with severe pulmonary hypertension has been that due to human immunodeficiency virus type 1, but neither the viral genome nor viral antigens have been demonstrated in pathologic lesions. We examined lung-tissue samples from 16 patients with sporadic primary pulmonary hypertension and 14 patients with secondary pulmonary hypertension for evidence of infection with human herpesvirus 8 (HHV-8). HHV-8 infection was ascertained immunohistochemically with use of an antibody directed against latency-associated nuclear antigen 1 (LANA-1), and a polymerase-chain-reaction (PCR) assay was performed on lung DNA to detect the viral cyclin gene of HHV-8. Sequence analysis was also performed. In lung tissue from 10 of 16 patients with primary pulmonary hypertension (62 percent), cells within the plexiform lesions as well as cells outside the lesions were positive for LANA-1 on immunohistochemical analysis. Tissue from the same 10 patients contained viral cyclin on PCR analysis. No LANA-1 was detected in lung tissue from patients with secondary pulmonary hypertension, although one such patient had PCR evidence of viral cyclin. Plexiform lesions from patients with primary pulmonary hypertension had a histologic and immunohistochemical resemblance to cutaneous Kaposi's sarcoma lesions. The spectrum of trigger factors and molecular mechanisms leading to severe pulmonary hypertension and the formation of plexiform lesions is apparently wide, including both genetic and epigenetic factors. Our data suggest that infection with the vasculotropic virus HHV-8 may have a pathogenetic role in primary pulmonary hypertension.
Chromosoma, 1982
The relative distribution of NOR proteins and chromatin fibers in the nucleoli was visualized in ... more The relative distribution of NOR proteins and chromatin fibers in the nucleoli was visualized in human cell line. The chromatin was revealed by a Feulgen-like procedure using osmium-ammine as DNA tracer. This selective staining was combined with NOR-silver staining. We provide morphological evidence for constant overlapping of the silver deposit sites with dispersed intranucleolar chromatin fibers. Silver stained proteins were sometimes observed in contact with the chromatin fibers, suggesting that at least some of the Ag-NOR proteins might be closely connected with the dispersed nucleolar DNA.
A framework for the representation of qualitative distances is developed inspired by previous wor... more A framework for the representation of qualitative distances is developed inspired by previous work on qualitative orientation. It is based on the concept of “distance systems” consisting of a list of distance relations and a set of structure relations that describe how the distance relations in turn relate to each other. The framework is characterized by making the role of the “frame of reference” explicit, which captures contextual information essential for the representation of distances. The composition of distance relations as main inference mechanism to reason about distances within a given frame of reference is explained, in particular under “homogeneous structural restrictions”. Finally, we introduce articulation rules as a way to mediate between different frames of reference.
Discrete time, 25 KTPI track-following servos were designed for magnetic hard disk drive dual sta... more Discrete time, 25 KTPI track-following servos were designed for magnetic hard disk drive dual stage actuators using the μ-synthesis methodology. The design methodology was tested on two microactuator models. The first is a model of a piezoelectrically actuated suspension, under development by Hutchinson Technology Incorporated. The second is a model of an electrostatically actuated MEMS microactuator, under development by the IBM Almaden Research Center. Low order controllers were successfully designed for both models, which achieved the prescribed robustness and performance requirements
Artificial Intelligence, 1997
A framework for the qualitative representation of positional information in a two-dimensional spa... more A framework for the qualitative representation of positional information in a two-dimensional space is presented. Qualitative representations use discrete quantity spaces, where a particular distinction is introduced only if it is relevant to the context being modeled. This allows us to build a flexible framework that accommodates various levels of granularity and scales of reasoning. Knowledge about position in large-scale space is commonly represented by a combination of orientation and distance relations, which we express in a particular frame of reference between a primary object and a reference object. While the representation of orientation comes out to be more straightforward, the model for distances requires that qualitative distance symbols be mapped to geometric intervals in order to be compared; this is done by defining structure relations that are able to handle, among others, order of magnitude relations; the frame of reference with its three components (distance system, scale, and type) captures the inherent context dependency of qualitative distances. The principal aim of the qualitative representation is to perform spatial reasoning: as a basic inference technique, algorithms for the composition of positional relations are developed with respect to same and different frames of reference. The model presented in this paper has potential applications in areas as diverse as Geographical Information Systems (GIS), Computer Aided Design (CAD), and Document Recognition.
Various relation-based systems, concerned with the qualitative representation and processing of s... more Various relation-based systems, concerned with the qualitative representation and processing of spatial knowledge, have been developed in numerous application domains. In this article, we identify the common concepts underlying qualitative spatial knowledge representation, we compare the representational properties of the different systems, and we outline the computational tasks involved in relation-based spatial information processing. We also describe symbolic spatial indexes, relation-based structures that combine several ideas in spatial knowledge representation. A symbolic spatial index is an array that preserves only a set of spatial relations among distinct objects in an image, called the modeling space; the index array discards information, such as shape and size of objects, and irrelevant spatial relations. The construction of a symbolic spatial index from an input image can be thought of as a transformation that keeps only a set of representative points needed to define the relations of the modeling space. By keeping the relative arrangements of the representative points in symbolic spatial indexes and discarding all other points, we maintain enough information to answer queries regarding the spatial relations of the modeling space without the need to access the initial image or an object database. Symbolic spatial indexes can be used to solve problems involving route planning, composition of spatial relations, and update operations.
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Papers by Daniel Hernandez