677 research outputs found
Speed of complex network synchronization
No full textSynchrony is one of the most common dynamical states emerging on networks. The speed of convergence towards synchrony provides a fundamental collective time scale for synchronizing systems. Here we study the asymptotic synchronization times for directed networks with topologies ranging from completely ordered, grid-like, to completely disordered, random, including intermediate, partially disordered topologies. We extend the approach of master stability functions to quantify synchronization times. We find that the synchronization times strongly and systematically depend on the network topology. In particular, at fixed in-degree, stronger topological randomness induces faster synchronization, whereas at fixed path length, synchronization is slowest for intermediate randomness in the small-world regime. Randomly rewiring real-world neural, social and transport networks confirms this picture
Do small worlds synchronize fastest?
No full textSmall-world networks interpolate between fully regular and fully random topologies and simultaneously exhibit large local clustering as well as short average path length. Small-world topology has therefore been suggested to support network synchronization. Here we study the asymptotic speed of synchronization of coupled oscillators in dependence on the degree of randomness of their interaction topology in generalized Watts-Strogatz ensembles. We find that networks with fixed in-degree synchronize faster the more random they are, with small worlds just appearing as an intermediate case. For any generic network ensemble, if synchronization speed is at all extremal at intermediate randomness, it is slowest in the small-world regime. This phenomenon occurs for various types of oscillators, intrinsic dynamics and coupling schemes. Copyright (c) EPLA, 201
FTMW/CVI: FOURIER TRANSFORM MICROWAVE / COHERENCE SPECTROSCOPY WITH VIRTUAL INSTRUMENTS
No full textJ. Ekkers and W. H. Flygare, Rev. Sci. Instrum. 47, 448(1976). G. Bestmann and H. Dreizler, Z. Naturforsch. 37a, 615(1982). H. Dreizler, E. Fliege, H. M\""ader, and W. Stahl, Z. Naturforsch. 37a, 1266(1982). D. A. Andrews and J. G. Baker, J. Phys. B20, 5705(1987). T. J. Balle and W. H. Flygare, Rev. Sci. Instrum. 52, 33(1981). L. H. Coudert, F. J. Lovas, R. D. Suenram, and J. T. Hougen, J. Chem. Phys. 87, 6290(1987). L. Martinache, S. Jans-B\""urli, B. Vogelsanger, W. Kresa, and A. Bauder, Chem. Phys. Lett. 149, 424(1988). R. D. Suenram, F. J. Lovas, and K. Matsumura, Ap. J. Lett. 342, L103(1989). J.-U. Grabow, N. Heineking, and W. Stahl, Z. Naturforsch. 46a, 914(1991). U. Andresen, H. Dreizler, J.-U. Grabow and W. Stahl, Rev. Sci. Instrum. 61, 3694(1990). J.-U. Grabow and W. Stahl, Z. Naturforsch. 45a, 1043(1990)Author Institution: Institut f\""ur Physikalische Chemie und ElektrochemieModern Fourier transform microwave (FTMW) spectroscopy, first implemented as an impulse excitation technique in a steady gas-waveguide , started only a quarter of a century ago. Soon after, the method was supplemented for special applications, e.g. Stark-, double , and spectroscopy. The subsequent implementation of the technique in a supersonic jet-resonator was followed by similar developments, i.e. Stark-, double , laser , and . along with the ``coaxially oriented beam-resonator (COBRA) has greatly increased efficiency, resolution, and sensitivity of current FTMW spectrometers. We present the implementation of a complete COBRA-FTMW spectrometer featuring the capabilities given above. The entire experiment is operated, either interactivle or automatically, by a graphical user interface (GUI)-based program which is capable of waveguide and resonator applications. Developed in the C programming language, while following the concept of virtual instruments (VI), the software can co-operate with a wide variety of PCI and IEEE hardware components to build the instrument. Only one application specific logic circuit, which will also be presented, is needed
Accurate rest frequencies for propargylamine in the ground and low-lying vibrational states
No full textContext. To date, several complex organic molecules have been detected in the interstellar medium, and they have been suggested as precursors of biologically important species. Propargylamine (HC ≡ C-CH2-NH2) is structurally similar to a number of other organic molecules which have already been identified by radioastronomy, making it a good candidate for astrophysical detection. Aims. This work provides accurate rest frequencies of propargylamine, from the centimeter-wave to the submillimeter-wave region, useful to facilitate the detection of this molecule in the interstellar medium. Methods. An extensive laboratory study of the rotational spectrum of propargylamine has been performed using a pulsed-jet Fourier Transform Microwave (FTMW) spectrometer (7-19 GHz frequency range) and a frequency modulation microwave spectrometer (75-560 GHz). Several hundred rotational transitions of propargylamine were recorded in the ground and three lowest excited vibrational states. The experiments were supported by high-level ab initio computations, mainly employed to characterize the vibrational state structure and to predict spectroscopic parameters unknown prior to this study. Results. The measured transition frequencies yielded accurate rotational constants and the complete sets of quartic and sextic centrifugal distortion constants for propargylamine in its vibrational ground state. 14N-nuclear quadrupole coupling constants were also determined. Rotational and quartic centrifugal distortion constants were also obtained for the low-lying excited states v13 = 1 (A′), v20 = 1 (A′′), and v21 = 1 (A′′). The a-type Coriolis resonance which couples the v13 = 1 and v21 = 1 levels was analyzed. Conclusions. The determined spectroscopic constants allowed for the compilation of a dataset of highly accurate rest frequencies for astrophysical purposes in the millimeter and submillimeter regions with 1σ uncertainties that are smaller than 0.050 MHz, corresponding to 0.03 km s-1 at 500 GHz in radial equivalent velocity
Root Canal Therapy: Understanding the Foundations of Endodontic Diagnosis and Treatment
No full textabstract: My thesis consisted of both a self-directed study and a creative project. I worked with Dr. Michael Grabow, an endodontist of 20 years, to understand the scientific and technical aspects of root canal therapy. The first phase of the thesis was a review of dental biology, tooth development, morphology, physiology, radiology, and endodontics. The second phase was the creative project in which I learned the technical process of performing a root canal. In this phase, I observed Dr. Grabow execute root canal therapy on live patients and extracted teeth (obtained from an oral surgeon). I then completed root canals of my own on extracted teeth, under the instruction and oversight of Dr. Grabow
Rate Data for "Water Gas Shift and Methane Steam Reforming Kinetics on Pt+PdAl2O3 Monolith"
No full textRate data for manuscript "Water Gas Shift and Methane Steam Reforming Kinetics on Pt+Pd/Al2O3 Monolit
Tunneling motions of argon on chlorofluoromethane
No full textThe rotational supersonic jet Fourier transform microwave spectra of the 35Cl and 37Cl species of the molecular complex chlorofluoromethane-argon show that, in its equilibrium conformation, the argon atom is located out of the ClCF plane, interacting with the F and Cl atoms.
All rotational transitions are split in several quadrupole components, each of them further split into two lines, due to the tunneling motion of the Ar atom between two equivalent positions, below and above the ClCF plane. The feasible low energy pathway between the structurally degenerate conformations is described, in a first approximation, by a circular motion around the C-Cl bond, with barriers estimated to be about 61 and 100 cm-1
Chloromethane-water adduct: Rotational spectrum, weak hydrogen bonds, and internal dynamics
No full textThe rotational spectra of four isotopologues of the 1:1 complex between chloromethane and water revealed the presence of only one rotamer in a pulsed jet expansion. The two subunits are linked through two weak hydrogen bonds, O-H⋅⋅⋅Cl (R(H⋅⋅⋅Cl) =2.638(2) Å) and C-H⋅⋅⋅O (R(H⋅⋅⋅O) =2.501(2) Å), forming a five-membered ring. All transitions display the hyperfine structure due to the (35)Cl (or (37)Cl) nuclear quadrupole effects. Dynamical features in the spectrum are caused by two large-amplitude motions. Each component line appears as an asymmetric doublet with a relative intensity ratio of 1:3. The splittings led to the determination of barrier to internal rotation of water around its symmetry axis, V(2) =320(10) cm(-1). Finally, an unexpected small value of the inertial defect (-0.96 uÅ(2) rather than -3.22 uÅ(2)) allowed the estimation of the barrier to the internal rotation of the CH(3) group, V(3) ≈8 cm(-1)
On the Cl⋯C halogen bond: a rotational study of CF3Cl–CO
No full textThe rotational spectra of two isotopologues (CF335Cl-CO and CF337Cl-CO) of the CF3Cl-CO adduct have been investigated and analyzed using supersonic-jet Fourier transform microwave spectroscopy, and found to have the features of a symmetric top. Rotational, centrifugal distortion, and nuclear quadrupole (35Cl and 37Cl) coupling constants have been precisely obtained from high-resolution measurements. The two subunits of the complex are held together via a Cl⋯C halogen bond interaction. Information on the internal dynamics and the dissociation energy of the complex is provided
Passive NOx Adsorption - Pd/ZSM-5
No full textVehicles are the source of a large portion of worldwide NOx (NO and NO2) emissions that have far-reaching ramifications on climate, ecological balance and human health. Although vehicles are presently equipped with catalytic converters that significantly reduce NOx at high temperatures (> 200°C) before emission, the majority of the NOx escapes during the cold-start period of an engine – the time taken by the converter to reach its required operating temperature (> 200°C). Passive NOx Adsorbers (PNA) have shown potential to prevent cold-start NOx emissions. Specifically, Pd/ZSM-5 - medium pore ion-exchanged zeolite - can act as a PNA by trapping NOx at lower temperatures ( 200°C) for catalytic reduction. Density Functional Theory (DFT) simulations of passive NOx adsorption to Pd/ZSM-5 were performed to identify active sites in ZPd and calculate the binding free energies (BFE) of adsorbates – NO, NO2, O2 and CO - at different temperatures. BFE data revealed that adsorbate binding becomes weaker with increasing temperature. Comparison of BFE data for Pd/ZSM-5 with corresponding data for Pd/SSZ-13 (small pore zeolite PNA) showed that the former is a stronger adsorbent.Chemical and Biomolecular Engineering, William A. Brookshire Department ofHonors Colleg
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