393 research outputs found

    The Fermiac or Fermi’s Trolley

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    The Fermiac, known also as Fermi’s trolley or Monte Carlo trolley, is an analog computer used to determine the change in time of the neutron population in a nuclear device, via the Monte Carlo method. It was invented by Enrico Fermi and constructed by Percy King at Los Alamos in 1947, and used for about two years. A replica of the Fermiac was built at INFN mechanical workshops of Bologna in 2015, on behalf of the Museo Storico della Fisica e Centro Studi e Ricerche “Enrico Fermi”, thanks to the original drawings made available by Los Alamos National Laboratory (LANL). This reproduction of the Fermiac was put in use, and a simulation was developed

    Roughness and Finite Size Effect in the NYSE Stock-Price Fluctuations

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    We consider the roughness properties of NYSE (New York Stock Exchange) stock-price fluctuations. The statistical properties of the data are relatively homogeneous within the same day but the large jumps between different days prevent the extension of the analysis to large times. This leads to intrinsic finite size effects which alter the apparent Hurst (H) exponent. We show, by analytical methods, that finite size effects always lead to an enhancement of H. We then consider the effect of fat tails on the analysis of the roughness and show that the finite size effects are strongly enhanced by the fat tails. The non stationarity of the stock price dynamics also enhances the finite size effects which, in principle, can become important even in the asymptotic regime. We then compute the Hurst exponent for a set of stocks of the NYSE and argue that the interpretation of the value of H is highly ambiguous in view of the above results. Finally we propose an alternative determination of the roughness in terms of the fluctuations from moving averages with variable characteristic times. This permits to eliminate most of the previous problems and to characterize the roughness in useful way. In particular this approach corresponds to the automatic elimination of trends at any scale.Comment: 13 pages, 11 fugure

    Synthesis and biological evaluation of new 3-amino-2-azetidinone derivatives as anticolorectal cancer agents

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    Several synthetic combretastatin A4 (CA-4) derivatives were recently prepared to increase the drug efficacy and stability of the natural product isolated from the South African tree Combretum caffrum. A group of ten 3-amino-2-azetidinone derivatives, as combretastatin A4 analogues, was selected through docking experiments, synthesized and tested for their anti-proliferative activity against the colon cancer SW48 cell line. These molecules, through the formation of amide bonds in position 3, allow the synthesis of various derivatives that can modulate the activity with great resistance to hydrolytic conditions. The cyclization to obtain the 3-aminoazetidinone ring is highly diastereoselective and provides a trans biologically active isomer under mild reaction conditions with better yields than the 3-hydroxy-2-azetidinone synthesis. All compounds showed IC50 values ranging between 14.0 and 564.2 nM, and the most active compound showed inhibitory activity against tubulin polymerization in vitro, being a potential therapeutic agent against colon cancer

    Exact Results for the Roughness of a Finite Size Random Walk

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    We consider the role of finite size effects on the value of the effective Hurst exponent H. This problem is motivated by the properties of the high frequency daily stock-prices. For a finite size random walk we derive some exact results based on Spitzer's identity. The conclusion is that finite size effects strongly enhance the value of H and the convergency to the asymptotic value (H=1/2) is rather slow. This result has a series of conceptual and practical implication which we discuss.Comment: 5 pages, 3 figure

    Extending ballistic graphene FET lumped element models to diffusive devices

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    In this work, a modified, lumped element graphene field effect device model is presented. The model is based on the "Top-of-the-barrier" approach which is usually valid only for ballistic graphene nanotransistors. Proper modifications are introduced to extend the model's validity so that it accurately describes both ballistic and diffusive graphene devices. The model is compared to data already presented in the literature. It is shown that a good agreement is obtained for both nano-sized and large area graphene based channels. Accurate prediction of drain current and transconductance for both cases is obtained

    Insulin and serine metabolism as sex-specific hallmarks of Alzheimer's disease in the human hippocampus

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    Healthy aging is an ambitious aspiration for humans, but neurodegenerative disorders, such as Alzheimer's disease (AD), strongly affect quality of life. Using an integrated omics approach, we investigate alterations in the molecular composition of postmortem hippocampus samples of healthy persons and individuals with AD. Profound differences are apparent between control and AD male and female cohorts in terms of up- and downregulated metabolic pathways. A decrease in the insulin response is evident in AD when comparing the female with the male group. The serine metabolism (linked to the glycolytic pathway and generating the N-methyl-D-aspartate [NMDA] receptor coagonist D-serine) is also significantly modulated: the D-Ser/total serine ratio represents a way to counteract age-related cognitive decline in healthy men and during AD onset in women. These results show how AD changes and, in certain respects, almost reverses sex-specific proteomic and metabolomic profiles, highlighting how different pathophysiological mechanisms are active in men and women

    New Eco-gas mixtures for the Extreme Energy Events MRPCs: results and plans

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    The Extreme Energy Events observatory is an extended muon telescope array, covering more than 10 degrees both in latitude and longitude. Its 59 muon telescopes are equipped with tracking detectors based on Multigap Resistive Plate Chamber technology with time resolution of the order of a few hundred picoseconds. The recent restrictions on greenhouse gases demand studies for new gas mixtures in compliance with the relative requirements. Tetrafluoropropene is one of the candidates for tetrafluoroethane substitution, since it is characterized by a Global Warming Power around 300 times lower than the gas mixtures used up to now. Several mixtures have been tested, measuring efficiency curves, charge distributions, streamer fractions and time resolutions. Results are presented for the whole set of mixtures and operating conditions, %. A set of tests on a real EEE telescope, with cosmic muons, are being performed at the CERN-01 EEE telescope. The tests are focusing on identifying a mixture with good performance at the low rates typical of an EEE telescope.Comment: 8 pages, 6 figures, proceedings for the "XIV Workshop on Resistive Plate Chambers and Related Detectors" (19-23 February 2018), Puerto Vallarta, Jalisco State, Mexic

    A simulation tool for MRPC telescopes of the EEE project

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    The Extreme Energy Events (EEE) Project is mainly devoted to the study of the secondary cosmic ray radiation by using muon tracker telescopes made of three Multigap Resistive Plate Chambers (MRPC) each. The experiment consists of a telescope network mainly distributed across Italy, hosted in different building structures pertaining to high schools, universities and research centers. Therefore, the possibility to take into account the effects of these structures on collected data is important for the large physics programme of the project. A simulation tool, based on GEANT4 and using GEMC framework, has been implemented to take into account the muon interaction with EEE telescopes and to estimate the effects on data of the structures surrounding the experimental apparata.A dedicated event generator producing realistic muon distributions, detailed geometry and microscopic behavior of MRPCs have been included to produce experimental-like data. The comparison between simulated and experimental data, and the estimation of detector resolutions is here presented and discussed

    The Extreme Energy Events HECR array: status and perspectives

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    The Extreme Energy Events Project is a synchronous sparse array of 52 tracking detectors for studying High Energy Cosmic Rays (HECR) and Cosmic Rays-related phenomena. The observatory is also meant to address Long Distance Correlation (LDC) phenomena: the network is deployed over a broad area covering 10 degrees in latitude and 11 in longitude. An overview of a set of preliminary results is given, extending from the study of local muon flux dependance on solar activity to the investigation of the upward-going component of muon flux traversing the EEE stations; from the search for anisotropies at the sub-TeV scale to the hints for observations of km-scale Extensive Air Shower (EAS).Comment: XXV ECRS 2016 Proceedings - eConf C16-09-04.

    The zero degree detector at BESIII

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    Abstract A small-size calorimeter has been built in the Frascati National Laboratory of INFN for BESIII detector based on the BEPCII storage ring of the Institute of High Energy Physics in Beijing. It has been installed in one of the two small-theta angle regions of BEPCII to measure the energy of photons from Initial State Radiation events and is currently taking data together with BESIII. The detector is a sandwich of Pb and scintillating fibers, the same technique employed for the KLOE calorimeter at the DA Ί NE accelerator, but the readout is actuated by way of bundles of clear plastic fibers. We describe here the fabrication, present results from tests with cosmic rays and at the Frascati Beam Test Facility, the installation in BESIII, and preliminary luminosity measurements
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