492 research outputs found
The forward kinematics of doubly-planar Gough-Stewart platforms and the position analysis of strips of tetrahedra
The final publication is available at link.springer.comA strip of tetrahedra is a tetrahedron-tetrahedron truss where any tetrahedron has two neighbors except those in the extremes which have only one. The problem of finding all the possible lengths for an edge in the strip compatible with a given distance imposed between the strip end-points has been revealed of relevance due to the large number of possible applications. In this paper, this is applied to solve the forward kinematics of 6-6 Gough-Stewart platforms with planar base and moving platform, a problem which is known to have up to 40 solutions (20 if we do not consider mirror configurations with respect to the base as different solutions).Peer ReviewedPostprint (author's final draft
The Light-Cone Wave Function of the Pion
The light-cone wave function of the pion is calculated within the
Nambu-Jona-Lasinio model. The result is used to derive the pion electromagnetic
form factor, charge radius, structure function, pi-gamma transition form factor
and distribution amplitude.Comment: 6 pages, 1 figure, elsart.sty; talk given at 10th International
Light-Cone Meeting on Nonperturbative QCD and Hadron Phenomenology,
Heidelberg, Germany, June 200
Factorization of Rational Curves in the Study Quadric and Revolute Linkages
Given a generic rational curve in the group of Euclidean displacements we
construct a linkage such that the constrained motion of one of the links is
exactly . Our construction is based on the factorization of polynomials over
dual quaternions. Low degree examples include the Bennett mechanisms and
contain new types of overconstrained 6R-chains as sub-mechanisms.Comment: Changed arxiv abstract, corrected some type
The Theory of Bonds: A New Method for the Analysis of Linkages
In this paper we introduce a new technique, based on dual quaternions, for
the analysis of closed linkages with revolute joints: the theory of bonds. The
bond structure comprises a lot of information on closed revolute chains with a
one-parametric mobility. We demonstrate the usefulness of bond theory by giving
a new and transparent proof for the well-known classification of
overconstrained 5R linkages.Comment: more detailed explanations and additional reference
Engineering thermostability in archaebacterial glyceraldehyde-3-phosphate dehydrogenase Hints for the important role of interdomain contacts in stabilizing protein conformation
AbstractConstruction of hybrid enzymes between the glyceraldehyde-3-phosphate dehydrogenases from the mesophilic Methanobacterium bryantil and the thermophilic Methanothermus fervidus by recombinant DNA techniques revealed that a short C-terminal fragment of the Mt.fervidus enzyme contributes largely to its thermostability. This C-terminal region appears to be homologous to the α6-helix of cubacterial and eukaryotie glyceraldehyde-3-phosphate dehydrogenases which is involved in the contacts between the two domains of the enzyme subunit. Site-directed mutagenesis experiments indicate that hydrophobic interaction play an important role in these contacts
Immunophenotyping and oncogene amplifications in tumors of the papilla of Vater
Carcinomas of the ampulla of Vater are rare and assumed to generally arise from preexisting adenomas (adenoma-carcinoma sequence). Histologically, distinct subtypes can be distinguished that were shown to differ significantly in terms of clinical outcome. Since pathologists usually receive bioptic tissue samples of ampullary tumors obtained during endoscopy, accurate classification of carcinoma subtypes can sometimes be difficult on morphological criteria alone. We therefore performed immunohistochemistry using a panel of established marker proteins (CK7, CK20, p21, p27, ESA, bax, and ephrin-B2) on 175 carcinoma, 111 adenoma, and 152 normal mucosa specimens of the ampulla of Vater and identified distinct immunoprofiles for every carcinoma subtype. Fluorescence in situ hybridization analyses of therapeutic target genes (c-myc, EGFR1, CCND1, HER2) found CCND1 to represent the most frequently amplified gene in our series (7.5%
Expression of growth factor receptors and targeting of EGFR in cholangiocarcinoma cell lines
BACKGROUND: Cholangiocarcinoma (CC) is a malignant neoplasm of the bile ducts or the gallbladder. Targeting of growth factor receptors showed therapeutic potential in palliative settings for many solid tumors. The aim of this study was to determine the expression of seven growth factor receptors in CC cell lines and to assess the effect of blocking the EGFR receptor in vitro.
METHODS: Expression of EGFR (epithelial growth factor receptor), HGFR (hepatocyte growth factor receptor) IGF1R (insulin-like growth factor 1 receptor), IGF2R (insulin-like growth factor 2 receptor) and VEGFR1-3 (vascular endothelial growth factor receptor 1-3) were examined in four human CC cell lines (EGI-1, HuH28, OZ and TFK-1). The effect of the anti-EGFR-antibody cetuximab on cell growth and apoptosis was studied and cell lines were examined for KRAS mutations.
RESULTS: EGFR, HGFR and IGFR1 were present in all four cell lines tested. IGFR2 expression was confirmed in EGI-1 and TFK-1. No growth-inhibitory effect was found in EGI-1 cells after incubation with cetuximab. Cetuximab dose-dependently inhibited growth in TFK-1. Increased apoptosis was only seen in TFK-1 cells at the highest cetuximab dose tested (1 mg/ml), with no dose-response-relationship at lower concentrations. In EGI-1 a heterozygous KRAS mutation was found in codon 12 (c.35G>A; p.G12D). HuH28, OZ and TFK-1 lacked KRAS mutation.
CONCLUSION: CC cell lines express a pattern of different growth receptors in vitro. Growth factor inhibitor treatment could be affected from the KRAS genotype in CC. The expression of EGFR itself does not allow prognoses on growth inhibition by cetuximab
Fermion Condensates and the Trivial Vacuum of Light-Cone Quantum Field Theory
We discuss the definition of condensates within light-cone quantum field
theory. As the vacuum state in this formulation is trivial, we suggest to
abstract vacuum properties from the particle spectrum. The latter can in
principle be calculated by solving the eigenvalue problem of the light-cone
Hamiltonian. We focus on fermionic condensates which are order parameters of
chiral symmetry breaking. As a paradigm identity we use the
Gell-Mann-Oakes-Renner relation between the quark condensate and the observable
pion mass. We examine the analogues of this relation in the `t~Hooft and
Schwinger model, respectively. A brief discussion of the Nambu-Jona-Lasinio
model is added.Comment: 14 pages, no figures, latex2
Digital MDA for enumeration of total nucleic acid contamination
Multiple displacement amplification (MDA) is an isothermal, sequence-independent method for the amplification of high molecular weight DNA that is driven by ϕ29 DNA polymerase (DNAP). Here we report digital MDA (dMDA), an ultrasensitive method for quantifying nucleic acid fragments of unknown sequence. We use the new assay to show that our custom ϕ29 DNAP preparation is free of contamination at the limit of detection of the dMDA assay (1 contaminating molecule per assay microliter). Contamination in commercially available preparations is also investigated. The results of the dMDA assay provide strong evidence that the so-called ‘template-independent’ MDA background can be attributed to high-molecular weight contaminants and is not primer-derived in the commercial kits tested. dMDA is orders of magnitude more sensitive than PCR-based techniques for detection of microbial genomic DNA fragments and opens up new possibilities for the ultrasensitive quantification of DNA fragments in a wide variety of application areas using MDA chemistry and off-the-shelf hardware developed for digital PCR
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