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Search Results: 1 - 10 of 603 matches for " Gergely Szekely "
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A Geometrical Characterization of the Twin Paradox and its Variants
Gergely Szekely
Mathematics , 2008, DOI: 10.1007/s11225-010-9253-7
Abstract: The aim of this paper is to provide a logic-based conceptual analysis of the twin paradox (TwP) theorem within a first-order logic framework. A geometrical characterization of TwP and its variants is given. It is shown that TwP is not logically equivalent to the assumption of the slowing down of moving clocks, and the lack of TwP is not logically equivalent to the Newtonian assumption of absolute time. The logical connection between TwP and a symmetry axiom of special relativity is also studied.
First-Order Logic Foundation of Relativity Theories
Judit X. Madarasz,Istvan Nemeti,Gergely Szekely
Mathematics , 2006,
Abstract: Motivation and perspective for an exciting new research direction interconnecting logic, spacetime theory, relativity--including such revolutionary areas as black hole physics, relativistic computers, new cosmology--are presented in this paper. We would like to invite the logician reader to take part in this grand enterprise of the new century. Besides general perspective and motivation, we present initial results in this direction.
A Logical Analysis of the Time-Warp Effect of General Relativity
Judit X. Madarasz,Istvan Nemeti,Gergely Szekely
Mathematics , 2007,
Abstract: Several versions of the Gravitational Time Dilation effect of General Relativity are formulated by the use of Einstein's Equivalence Principle. It is shown that all of them are logical consequence of a first-order axiom system of Special Relativity extended to accelerated observers.
Twin Paradox and the logical foundation of relativity theory
Judit X. Madarasz,Istvan Nemeti,Gergely Szekely
Mathematics , 2005, DOI: 10.1007/s10701-005-9041-9
Abstract: We study the foundation of space-time theory in the framework of first-order logic (FOL). Since the foundation of mathematics has been successfully carried through (via set theory) in FOL, it is not entirely impossible to do the same for space-time theory (or relativity). First we recall a simple and streamlined FOL-axiomatization SpecRel of special relativity from the literature. SpecRel is complete with respect to questions about inertial motion. Then we ask ourselves whether we can prove usual relativistic properties of accelerated motion (e.g., clocks in acceleration) in SpecRel. As it turns out, this is practically equivalent to asking whether SpecRel is strong enough to "handle" (or treat) accelerated observers. We show that there is a mathematical principle called induction (IND) coming from real analysis which needs to be added to SpecRel in order to handle situations involving relativistic acceleration. We present an extended version AccRel of SpecRel which is strong enough to handle accelerated motion, in particular, accelerated observers. Among others, we show that the Twin Paradox becomes provable in AccRel, but it is not provable without IND.
Glial Cell Line-Derived Neurotrophic Factor (GDNF) as a Novel Candidate Gene of Anxiety
Eszter Kotyuk, Gergely Keszler, Nora Nemeth, Zsolt Ronai, Maria Sasvari-Szekely, Anna Szekely
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080613
Abstract: Glial cell line-derived neurotrophic factor (GDNF) is a neurotrophic factor for dopaminergic neurons with promising therapeutic potential in Parkinson's disease. A few association analyses between GDNF gene polymorphisms and psychiatric disorders such as schizophrenia, attention deficit hyperactivity disorder and drug abuse have also been published but little is known about any effects of these polymorphisms on mood characteristics such as anxiety and depression. Here we present an association study between eight (rs1981844, rs3812047, rs3096140, rs2973041, rs2910702, rs1549250, rs2973050 and rs11111) GDNF single nucleotide polymorphisms (SNPs) and anxiety and depression scores measured by the Hospital Anxiety and Depression Scale (HADS) on 708 Caucasian young adults with no psychiatric history. Results of the allele-wise single marker association analyses provided significant effects of two single nucleotide polymorphisms on anxiety scores following the Bonferroni correction for multiple testing (p = 0.00070 and p = 0.00138 for rs3812047 and rs3096140, respectively), while no such result was obtained on depression scores. Haplotype analysis confirmed the role of these SNPs; mean anxiety scores raised according to the number of risk alleles present in the haplotypes (p = 0.00029). A significant sex-gene interaction was also observed since the effect of the rs3812047 A allele as a risk factor of anxiety was more pronounced in males. In conclusion, this is the first demonstration of a significant association between the GDNF gene and mood characteristics demonstrated by the association of two SNPs of the GDNF gene (rs3812047 and rs3096140) and individual variability of anxiety using self-report data from a non-clinical sample.
Hypoxia-induced transcription of dopamine D3 and D4 receptors in human neuroblastoma and astrocytoma cells
Melinda Bence, Eva Kereszturi, Viktor Mozes, Maria Sasvari-Szekely, Gergely Keszler
BMC Neuroscience , 2009, DOI: 10.1186/1471-2202-10-92
Abstract: Quantitative RT-PCR assays revealed that the transcription of both type D3 and D4 postsynaptic dopamine receptors (DRD3 and DRD4) was induced several fold upon 2-day hypoxia in a cell-specific manner, while the vascular endothelial growth factor gene was activated after 3-hr incubation in hypoxia. On the other hand, mRNA levels of type 2 dopamine receptor, dopamine transporter, monoamino oxidase and catechol-O-methyltransferase were unaltered, while those of the dopamine receptor regulating factor (DRRF) were decreased by hypoxia. Notably, 2-day hypoxia did not result in elevation of protein levels of DRD3 and DRD4.In light of the relatively delayed transcriptional activation of the DRD3 and DRD4 genes, we propose that slow-reacting hypoxia sensitive transcription factors might be involved in the transactivation of DRD3 and DRD4 promoters in hypoxia.The brain is considered a fully aerobic organ as it requires about 20% of total oxygen consumption in humans [1]. Interruption of steady oxygen supply results in focal necrosis and causes severe dysfunction in the ischemic penumbra [2]. Numerous studies underlined the seminal role of hypoxia inducible factor-1α (HIF-1α) in governing the hypoxic response in both neurons and glial cells [3,4]. The neuroprotective role of HIF-1α has been demonstrated in the ischemic penumbra through erythropoietin induction [5] as well as in mediating a neuroprotective response to amyloid-β peptide [6]. However, the regulation of central neurotransmission systems has not been thoroughly investigated under hypoxic conditions, although their inadequate adaptation might contribute to the development of cerebral palsy and abnormal behavioural patterns in patients affected by pre- or postnatal cerebral hypoxia, respectively [7-9].Apart from its well-known functions in the nigro-striatal pathway, dopamine plays a very important role in the regulation of mood, affections, impulsivity and cognitive functions in the limbic system [10]. Dopaminergic
Altered gene expression profiles in the hippocampus and prefrontal cortex of type 2 diabetic rats
Omar Abdul-Rahman, Maria Sasvari-Szekely, Agota Ver, Klara Rosta, Bernadett K Szasz, Eva Kereszturi, Gergely Keszler
BMC Genomics , 2012, DOI: 10.1186/1471-2164-13-81
Abstract: Following pathway analysis and validation of gene lists by real-time polymerase chain reaction, 30 genes from the hippocampus, such as the inhibitory neuropeptide galanin, synuclein gamma and uncoupling protein 2, and 22 genes from the prefrontal cortex, e.g. galanin receptor 2, protein kinase C gamma and epsilon, ABCA1 (ATP-Binding Cassette A1), CD47 (Cluster of Differentiation 47) and the RET (Rearranged During Transfection) protooncogene, were found to exhibit altered expression levels in type 2 diabetic model animals in comparison to non-diabetic control animals. These gene lists proved to be partly overlapping and encompassed genes related to neurotransmission, lipid metabolism, neuronal development, insulin secretion, oxidative damage and DNA repair. On the other hand, no significant alterations were found in the transcriptomes of the corpus striatum in the same animals. Changes in the cerebral gene expression profiles seemed to be specific for the type 2 diabetic model, as no such alterations were found in streptozotocin-treated animals.According to our knowledge this is the first characterization of the whole-genome expression changes of specific brain regions in a diabetic model. Our findings shed light on the complex role of insulin signaling in fine-tuning brain functions, and provide further experimental evidence in support of the recently elaborated theory of type 3 diabetes.Diabetes mellitus is a chronic and heterogenous metabolic disorder affecting millions of patients worldwide. Type 1 diabetes is characterized by absolute insulin deficiency due to viral or autoimmune destruction of pancreatic beta cells, while the major feature of the more common type 2 variant is obesity-linked impairment of intracellular insulin signaling [1-3]. Apart from its well-known effect on blood sugar levels, insulin is known to regulate the growth, differentiation and metabolism of its target cells at multiple levels [1]. Insulin signaling pathways have been shown to conv
Drug sensitivity patterns of HHV8 carrying body cavity lymphoma cell lines
Rita ?tv?s, Henriette Skribek, Lorand L Kis, Annunziata Gloghini, Laszlo Markasz, Emilie Flaberg, Staffan Eksborg, Jozsef Konya, Lajos Gergely, Antonino Carbone, Laszlo Szekely
BMC Cancer , 2011, DOI: 10.1186/1471-2407-11-441
Abstract: We have analyzed 11 cell lines against 27 frequently used cytostatic drugs in short term (3 days) survival assays using automated high throughput confocal microscopy.All cell lines showed a distinct, individual drug sensitivity pattern. Considering the in vitro used and clinically achieved drug concentration, Vinorelbine, Paclitaxel, Epirubicin and Daunorubicin were the most effective drugs.We suggest that inclusion of the above drugs into PEL chemotherapy protocols may be justified. The heterogeneity in the drug response pattern however indicated that assay-guided individualized therapy might be required to optimize therapeutic response.Human herpesvirus 8 (HHV8) or Kaposi sarcoma herpesvirus (KSHV) is the probable causative agent of two distinct lymphoproliferative disorders: primary effusion lymphoma (PEL) and the plasma cell variant of multicentric Castleman disease (MCD) in addition to Kaposi sarcoma (KS) [1].Primary effusion lymphoma (PEL), or alternatively: body cavity lymphoma is a non-Hodgkin's lymphoma (NHL) of B-cell origin that develops predominantly in the serous body cavities [2]. The lymphoma cells, although lacking many conventional B-cell markers, carry immunoglobulin gene rearrangement and express syndecans, suggesting pre-plasma cell origin. At the clinico-pathological level, PEL is characterized by liquid growth in the serous body cavities associated with spreading along the serous membranes without infiltrative or destructive growth patterns [3,4]. Morphologically, PEL bridges immunoblastic and anaplastic features and frequently displays a certain degree of plasmacell differentiation. In all known cases, the monoclonal B-cell population is infected with HHV-8. Half of the lymphomas are dually infected with HHV-8 and Epstein-Barr virus (EBV) [5]. In the context of AIDS, most cases are associated with other KSHV/HHV8-related diseases such as Kaposi's sarcoma (KS) or multicentric Castleman's disease (MCD). As PEL typically lacks a solid component,
Methods of Object Tracking
Annals of Dunarea de Jos , 2009,
Abstract: This paper presents two methods of object detection/tracking in a video. Thefirst method will use the motion tracking technique combined with density detectionwhich will be described. The second one is based on the SURF algorithm.
A More Flexible Realization of The SUNRED Algorithm
L. Pohl,V. Szekely
Physics , 2007,
Abstract: The high dissipation of integrated circuits means serious problems for packaging and for the design of complex electronic systems. Another important area of research and development nowadays is the integration of sensors and micromechanical systems (MEMS) with electronic circuits. The original Successive Node Reduction (SUNRED) algorithm handles well the first area but require revision for electro-thermal or mechanical fields. As a first stage the updated algorithm is able to solve thermal fields as the original, but with the application of flexible boundary connection handling, it can be much faster than the original. By using object-oriented program model the algorithm can handle non-rectangular 3D fields, and SUNRED mesh resolution is arbitrary, not have to be the power of two anymore.
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