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Search Results: 1 - 10 of 851 matches for " Zoltan Ferjentsik "
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The chick somitogenesis oscillator is arrested before all paraxial mesoderm is segmented into somites
Gennady Tenin, David Wright, Zoltan Ferjentsik, Robert Bone, Michael J McGrew, Miguel Maroto
BMC Developmental Biology , 2010, DOI: 10.1186/1471-213x-10-24
Abstract: Here we show that during development there is an imbalance between the speed of somite formation and growth of the presomitic mesoderm (PSM)/tail bud. This decrease in the PSM size of the chick embryo is not due to an acceleration of the speed of somite formation because it remains constant until the last stages of somitogenesis, when it slows down. When the chick embryo reaches its final number of somites at stage HH 24-25 there is still some remaining unsegmented PSM in which expression of components of the somitogenesis oscillator is no longer dynamic. Finally, we identify a change in expression of retinoic acid regulating factors in the tail bud at late stages of somitogenesis, such that in the chick embryo there is a pronounced onset of Raldh2 expression while in the mouse embryo the expression of the RA inhibitor Cyp26A1 is downregulated.Our results show that the chick somitogenesis oscillator is arrested before all paraxial mesoderm is segmented into somites. In addition, endogenous retinoic acid is probably also involved in the termination of the process of segmentation, and in tail growth in general.Somitogenesis is the earliest sign of segmentation in the developing vertebrate embryo [1-3]. During this process vertebrate embryos generate transitory structures called somites that later in development give rise to the vertebral column, most of the skeletal musculature and much of the dermis [4]. This process starts very early soon after gastrulation has initiated and proceeds in an anterior-to-posterior direction during body axis elongation. The elongation of the body axis of the vertebrate embryo has been traditionally divided into two phases termed primary and secondary body formation [5,6]. During the first phase the somites and other types of mesoderm are derived from cells that have traversed the primitive streak (in amniotes) or its equivalent (in anamniote vertebrates). Fate mapping analyses have shown that the primitive streak contains distinct stem
Notch Is a Critical Component of the Mouse Somitogenesis Oscillator and Is Essential for the Formation of the Somites
Zoltan Ferjentsik,Shinichi Hayashi equal contributor,J. Kim Dale equal contributor,Yasumasa Bessho,An Herreman,Bart De Strooper,Gonzalo del Monte,Jose Luis de la Pompa,Miguel Maroto
PLOS Genetics , 2009, DOI: 10.1371/journal.pgen.1000662
Abstract: Segmentation of the vertebrate body axis is initiated through somitogenesis, whereby epithelial somites bud off in pairs periodically from the rostral end of the unsegmented presomitic mesoderm (PSM). The periodicity of somitogenesis is governed by a molecular oscillator that drives periodic waves of clock gene expression caudo-rostrally through the PSM with a periodicity that matches somite formation. To date the clock genes comprise components of the Notch, Wnt, and FGF pathways. The literature contains controversial reports as to the absolute role(s) of Notch signalling during the process of somite formation. Recent data in the zebrafish have suggested that the only role of Notch signalling is to synchronise clock gene oscillations across the PSM and that somite formation can continue in the absence of Notch activity. However, it is not clear in the mouse if an FGF/Wnt-based oscillator is sufficient to generate segmented structures, such as the somites, in the absence of all Notch activity. We have investigated the requirement for Notch signalling in the mouse somitogenesis clock by analysing embryos carrying a mutation in different components of the Notch pathway, such as Lunatic fringe (Lfng), Hes7, Rbpj, and presenilin1/presenilin2 (Psen1/Psen2), and by pharmacological blocking of the Notch pathway. In contrast to the fish studies, we show that mouse embryos lacking all Notch activity do not show oscillatory activity, as evidenced by the absence of waves of clock gene expression across the PSM, and they do not develop somites. We propose that, at least in the mouse embryo, Notch activity is absolutely essential for the formation of a segmented body axis.
Entanglement entropy in quantum spin chains with broken reflection symmetry
Zoltan Kadar,Zoltan Zimboras
Physics , 2010, DOI: 10.1103/PhysRevA.82.032334
Abstract: We investigate the entanglement entropy of a block of L sites in quasifree translation-invariant spin chains concentrating on the effect of reflection symmetry breaking. The majorana two-point functions corresponding to the Jordan-Wigner transformed fermionic modes are determined in the most general case; from these it follows that reflection symmetry in the ground state can only be broken if the model is quantum critical. The large L asymptotics of the entropy is calculated analytically for general gauge-invariant models, which has, until now, been done only for the reflection symmetric sector. Analytical results are also derived for certain non-gauge-invariant models, e.g., for the Ising model with Dzyaloshinskii-Moriya interaction. We also study numerically finite chains of length N with a non-reflection-symmetric Hamiltonian and report that the reflection symmetry of the entropy of the first L spins is violated but the reflection-symmetric Calabrese-Cardy formula is recovered asymptotically. Furthermore, for non-critical reflection-symmetry-breaking Hamiltonians, we find an anomaly in the behavior of the "saturation entropy" as we approach the critical line. The paper also provides a concise but extensive review of the block entropy asymptotics in translation invariant quasifree spin chains with an analysis of the nearest neighbor case and the enumeration of the yet unsolved parts of the quasifree landscape.
Four-jet production in $e^+e^-$ annihilation at next-to-leading order
Zoltan Nagy,Zoltan Trocsanyi
Physics , 1997, DOI: 10.1016/S0920-5632(97)01037-2
Abstract: We present a partonic Monte Carlo event generator that can be used for calculating the group independent kinematical functions of any infrared safe four-jet observable at NLO accuracy. As an example, we calculate the differential distribution of the $\Pi_1$ and $\Pi_4$ Fox-Wolfram moments. We find large K factors (K $>$ 2). The effect of the radiative correction is to increase the overall normalization, but not to reduce the renormalization scale dependence significantly.
Group independent color decomposition of next-to-leading order matrix elements for e^+ e^- \to four partons
Zoltan Nagy,Zoltan Trocsanyi
Physics , 1997, DOI: 10.1016/S0370-2693(97)01161-1
Abstract: We present the next-to-leading order partonic cross sections involving an electroweak vector boson and four massless partons (quarks, gluons or long living gluinos) in a general gauge theory with a simple Lie Group. The vector boson couples to a massless lepton pair and a quark-antiquark pair. The cross sections are given in terms of group independent kinematical functions multiplying the eigenvalues of the Casimir operators of the Lie group. This kind of color decomposition is required for the calculation of O($\alpha_s^3$) corrections to the group independent kinematical functions in the four-jet production cross sections in electron-positron annihilation. The knowledge of these corrections facilitates the simultaneous precision meaurement of the strong coupling and the color charge factors using the four-jet LEP or SLC data as well as the test whether these data favour or exclude the existence of a light gluino.
Excluding light gluinos using four-jet LEP events: a next-to-leading order result
Zoltan Nagy,Zoltan Trocsanyi
Physics , 1997,
Abstract: Based upon a next-to-leading order perturbative calculation of the four-jet production rate in electron-positron annihilation and assuming 8 % for the theoretical error emerging from hadronization effects in the $0.002\le \ycut \le 0.004$ range for the Durham clustering algorithm, we exclude the existence of the light gluinos at the 95 % confidence level.
Four-jet angular distributions and color charge measurements: leading order versus next-to-leading order
Zoltan Nagy,Zoltan Trocsanyi
Physics , 1997, DOI: 10.1103/PhysRevD.57.5793
Abstract: We present the next-to-leading order perturbative QCD prediction to the four-jet angular distributions used by experimental collaborations at LEP for measuring the QCD color charge factors. We compare our results to ALEPH data corrected to parton level. We perform a leading order ``measurement'' of the QCD color factor ratios by fitting the leading order perturbative predictions to the next-to-leading order result. Our result shows that in an experimental analysis for measuring the color charge factors the use of the O($\alpha_s^3$) QCD predictions instead of the O($\alpha_s^2$) results may shift the center of the fit by a relative factor of $1+2\as$ in the $T_R/C_F$ direction.
Multi-jet cross sections in deep inelastic scattering at next-to-leading order
Zoltan Nagy,Zoltan Trocsanyi
Physics , 2001, DOI: 10.1103/PhysRevLett.87.082001
Abstract: We present the perturbative prediction for three-jet production cross section in DIS at the NLO accuracy. We study the dependence on the renormalization and factorization scales of exclusive three-jet cross section. The perturbative prediction for the three-jet differential distribution as a function of the momentum transfer is compared to the corresponding data obtained by the H1 collaboration at HERA.
Development of Wearable Micro-actuator Array for 3-D Virtual Tactile Displays  [PDF]
Zoltan Szabo, Eniko T. Enikov
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2012, DOI: 10.4236/jemaa.2012.46031
Abstract: A novel 4 by 4 array of electromagnetic micro-actuators operating on the principle of voice-coil actuators is presented. The intended application of the array is dynamic tactile stimulation, where multiple actuators generate an illusion of touching a moving pattern. In comparison to earlier designs [1-3], the device has smaller dimensions of 2.28 mm in diameter and 7 mm in length, which allowed its use in an array capable of hosting up to a 5 by 5 set of actuators with a rectangular shape covering an area of 18 mm by 21 mm. Using finite element analysis of several conceptual designs of actuators [1,4,5], it was established that the voice-coil type device (where the coil is the moving part) has most beneficial characteristics for the envisioned application. These include sufficient force over a relatively large distance, allowing tactile stimulation of surfaces with irregular shape, fast response, and small foot-print that matches the density of the tactile sensory neurons in the human finger. Eexperimental evaluation of the operation of neighboring actuators spaced at 3.3 mm apart, indicates that there is no crosstalk between the actuators. The resulting density exceeds that of previously reported alternative designs based on moveable permanent magnets [4,6]. Static force measurement indicate that each micro-actuator can produce at least 26 mN of repulsive force over a stroke of 2100 μm with a peak force of 34 mN. The driving circuit operates at 13.5V and generates a vibration frequency of up to 265 Hz without significant change of the force-displacement characteristics. In the higher frequency range (above 100 Hz) the actuator provides at least 15 mN of force over a slightly reduced stroke of 2300 μm, and a peak force of 21 mN. All of the above parameters meet the required threshold values of tactile human perception known from [2] and [3].
Sobre o desuso e o ressurgimento da viola pomposa
Paulinyi, Zoltan;
Per Musi , 2012, DOI: 10.1590/S1517-75992012000100009
Abstract: the viola pomposa is a 5-stringed instrument of baroque origin similar to the traditional orchestral viola, with an additional high e string. it has received divergent names since the late eighteenth century, being confounded with "violino pomposo", "violino tenor", "violoncello da spalla" and even "violoncello piccolo". it never got popularity probably because of its expensive string maintenance and bigger efforts to be played, reasons which don't justify anymore its absence from the concert halls. this article describes a brazilian viola pomposa made by carlos martins del picchia in belo horizonte in 2006 after guadagnini's "la parmigiana" (1765) and lists an international repertory for the instrument, where the brazilian production stands out for printed scores and audio/video recordings.
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