Search results for "transformation"
showing 10 items of 1634 documents
Some Improvements on Relativistic Positioning Systems
2018
[EN] We make some considerations about Relativistic Positioning Systems (RPS). Four satellites are needed to position a user. First of all we define the main concepts. Errors should be taken into account. Errors depend on the Jacobian transformation matrix. Its Jacobian is proportional to the tetrahedron volume whose vertexes are the four tips of the receiver-satellite unit vectors. If the four satellites are seen by the user on a circumference in the sky, then, the Jacobian and the tetrahedron volume vanish. The users we consider are spacecraft. Spacecraft to be positioned cannot be close to a null Jacobian satellites-user configuration. These regions have to be avoided choosing an appropr…
Irregular motion recovery in fluorescein angiograms
1997
Abstract Fluorescein angiography is a common procedure in ophthalmic practice, mainly to evaluate vascular retinopathies and choroidopathies from sequences of ocular fundus images. In order to compare the images, a reliable overlying is essential. This paper proposes some methods for the recovery of irregular motion in fluorescein angiograms (FA). The overlying is done by a three step procedure: detection of relevant points, matching points from different images and estimation of the assumed linear geometric transformation. A stochastic model (closely related to the general linear model) allows to fuse the second and third steps. Two different estimators of the geometric transformation are …
Eight Simple Guidelines for Improved Understanding of Transformations and Nonlinear Effects
2021
Jyväskylästä kirjoitettiin: Käyn läpi Extra-Vipusessa ristiriitaisiksi luokitettuja yhteisjulkaisuja. Julkaisu " Eight Simple Guidelines for Improved Understanding of Transformations and Nonlinear Effects" on meillä laitettu A2 ja teillä A1. Meillä varmaan päädytty tuohon A2:een kun tiivistelmässä sanotaan "Building on a systematic review of six leading management journals..". Mutta mitä mieltä olette, kumpi olisi parempi? Transforming variables before analysis or applying a transformation as a part of a generalized linear model are common practices in organizational research. Several methodological articles addressing the topic, either directly or indirectly, have been published in the rec…
Role of Gadd45a in Wip1-dependent regulation of intestinal tumorigenesis.
2012
Conversion of intestinal stem cells into tumor-initiating cells is an early step in Apc(Min)-induced polyposis. Wild-type p53-induced phosphatase 1 (Wip1)-dependent activation of a DNA damage response and p53 has a permanent role in suppression of stem cell conversion, and deletion of Wip1 lowers the tumor burden in Apc(Min) mice. Here we show that cyclin-dependent kinase inhibitor 2a, checkpoint kinase 2, and growth arrest and DNA damage gene 45a (Gadd45a) exert critical functions in the tumor-resistant phenotype of Wip1-deficient mice. We further identified Gadd45a as a haploinsufficient gene in the regulation of Wip1-dependent tumor resistance in mice. Gadd45a appears to function through…
Liver-specific overexpression of matrix metalloproteinase 9 (MMP-9) in transgenic mice accelerates development of hepatocellular carcinoma.
2010
Matrix metalloproteinase-9 (MMP-9) plays a central role in tumor invasion and development of metastases. Expression of MMP-9 had been shown in human hepatocellular carcinomas (HCCs). However, it remained unclear whether MMP-9 could influence development of HCC. In order to address this issue, we generated transgenic mice overexpressing MMP-9 in the liver. In order to avoid embryonic lethality a Cre-lox system was utilized for conditional overexpression of MMP-9 under control of an albumin enhancer and promoter. Induction of MMP-9 overexpression in transgenic mice was achieved by i.v. injection of an adenovirus coding for the Cre recombinase. Initiation of liver carcinogenesis was achieved b…
Role of the insulin-like growth factor system in adrenocortical growth control and carcinogenesis.
2004
Clinically silent adrenocortical adenomas are the most frequent abnormalities in the adrenal gland. In contrast, adrenocortical carcinoma is a rare tumor with an extremely poor prognosis. The factors responsible for the frequent occurrence of benign adrenocortical tumors on one hand and the rare malignant transformation on the other are not known. Several genetic alterations such as loss of imprinting or loss of heterozygosity of the 11p15 gene locus causing a strong IGF-II overexpression have been demonstrated in the majority of adrenocortical carcinomas. In addition to IGF-II overexpression, increased levels of the IGF-I-receptor and IGFBP-2 have been found in advanced human adrenocortica…
Cancer stem cells – old concepts, new insights
2008
Cancer has long been viewed as an exclusively genetic disorder. The model of carcinogenesis, postulated by Nowell and Vogelstein, describes the formation of a tumor by the sequential accumulation of mutations in oncogenes and tumor suppressor genes. In this model, tumors are thought to consist of a heterogeneous population of cells that continue to acquire new mutations, resulting in a highly dynamic process, with clones that out compete others due to increased proliferative or survival capacity. However, novel insights in cancer stem cell research suggest another layer of complexity in the process of malignant transformation and preservation. It has been reported that only a small fraction…
Genetic and molecular analysis of six tumor suppressor genes in Drosophila melanogaster
1990
Six Drosophila melanogaster tumor suppressor genes causing malignant or benign tumors in specific cell types are described. The wild-type alleles of these genes are instrumental in the differentiation of particular cell types. In the homozygous state, recessive mutations in the genes interrupt the differentiation of the cells and thus cause their uncontrolled, autonomous, lethal proliferation. The tumors show all major characteristics of malignant and benign neoplastic growth. Genomic sequences of four of the genes have been identified and are currently being characterized. ImagesFIGURE 1.FIGURE 2.FIGURE 2.
Why are the genomes of endosymbiotic bacteria so stable?
2003
The comparative analysis of three strains of the endosymbiotic bacterium Buchnera aphidicola has revealed high genome stability associated with an almost complete absence of chromosomal rearrangements and horizontal gene transfer events during the past 150 million years. The loss of genes involved in DNA uptake and recombination in the initial stages of endosymbiosis probably underlies this stability. Gene loss, which was extensive during the initial steps of Buchnera evolution, has continued in the different Buchnera lineages since their divergence.
Homemade Site Directed Mutagenesis of Whole Plasmids
2009
Site directed mutagenesis of whole plasmids is a simple way to create slightly different variations of an original plasmid. With this method the cloned target gene can be altered by substitution, deletion or insertion of a few bases directly into a plasmid. It works by simply amplifying the whole plasmid, in a non PCR-based thermocycling reaction. During the reaction mutagenic primers, carrying the desired mutation, are integrated into the newly synthesized plasmid. In this video tutorial we demonstrate an easy and cost effective way to introduce base substitutions into a plasmid. The protocol works with standard reagents and is independent from commercial kits, which often are very expensi…