2,120 research outputs found
Replication Code for: "Digital Payments and Consumption: Evidence from the 2016 Demonetization in India"
No full textReplication code for
"Digital Payments and Consumption: Evidence from the 2016 Demonetization in India" (RFS)
Authors: Sumit Agarwal, Pulak Ghosh, Jing Li, and Tianyue Rua
Performance analysis of the WiNC2R platform:
No full textA Cognitive Radio (CR) is an intelligent transceiver device, able to support multiple technologies, dynamic re-configurability, ease of programming and collaboration with other CR devices to improve the communication efficiency. The two key requirements for an efficient CR implementation are flexibility in operation/programming and speed.
WiNC2R (Winlab Network Centric Cognitive Radio) achieves high speed of operation using its hardware platform and flexibility using its software-configurable architecture. The current WiNC2R architecture implements an 802.11a-like OFDM flow. We evaluate the WiNC2R hardware architecture to see the modularity in the architecture, separation of data and control flow and the performance in terms of latency and throughput. To test the system, the Xilinx Bus Functional Model environment, which is designed to test the IBM standard bus-architecture-based hardware systems, is used. We use a simple ALOHA protocol in the MAC layer to communicate between two WiNC2R nodes and evaluate the performance under the best-case scenario, where the performance is only hindered by the architecture itself rather than external conditions like channel state.
The results of our basic experiments showed that for a single OFDM 802.11a-like flow, the Unit Control Modules (UCM) were idle for almost 80% of the total processing time.
We then tested the WiNC2R system to study the effects of changing the frame size. It was seen that the latencies in the WiNC2R transmitter are frame-size dependent while those in the receiver mainly depend on the size of the data in the last chunk rather than the size of the whole frame. We suggest that chunk size should be 2 OFDM symbols, and chunking be moved to MAC layer for better performance. We give analytical estimates of resulting performance improvement. In the next experiment, we describe virtualization in the WiNC2R by adding more flows. We describe the steps to implement the additional flows and estimate maximum number of concurrent flows possible.
In the last analysis, we show the effect of operating clock frequency on the performance. We prove that at 250 MHz operating frequency and 2 OFDM symbols per chunk, the current WiNC2R implementation will be able to satisfy the SIFS criterion.M.S.Includes bibliographical references (p. 72-73)by Sumit Satarka
Electronic Structure of Cobalt-Corrole-Pyridine Complexes:Noninnocent Five-Coordinate Co(II) Corrole-Radical States
No full textTwo sets of complexes of Co-triarylcorrole-bispyridine complexes, Co[TpXPC](py)2 and Co[Br8TpXPC](py)2 have been synthesized, where TpXPC refers to a meso-tris(para-X-phenyl)corrole ligand with X = CF3, H, Me, and OMe and Br8TpXPC to the corresponding β-octabrominated ligand. The axial pyridines in these complexes were found to be labile and, in dilute solutions in dichloromethane, the complexes dissociate almost completely to the five-coordinate monopyridine complexes. Upon addition of a small quantity of pyridine, the complexes revert back to the six-coordinate forms. These transformations are accompanied by dramatic changes in color and optical spectra. 1H NMR spectroscopy and X-ray crystallography have confirmed that the bispyridine complexes are authentic low-spin Co(III) species. Strong substituent effects on the Soret maxima and broken-symmetry DFT calculations, however, indicate a CoII-corrole2- formulation for the five-coordinate Co[TpXPC](py) series. The calculations implicate a Co(dz2)-corrole("a2u") orbital interaction as responsible for the metal-ligand antiferromagnetic coupling that leads to the open-shell singlet ground state of these species. Furthermore, the calculations predict two low-energy S = 1 intermediate-spin Co(III) states, a scenario that we have been able to experimentally corroborate with temperature-dependent EPR studies. Our findings add to the growing body of evidence for noninnocent electronic structures among first-row transition metal corrole derivatives.</p
Electronic Structure of Manganese Corroles Revisited: X‑ray Structures, Optical and X‑ray Absorption Spectroscopies, and Electrochemistry as Probes of Ligand Noninnocence
No full textPresented
herein is a detailed multitechnique investigation of ligand noninnocence
in S = 3/2 manganese corrole
derivatives at the formal MnIV oxidation state. The Soret
maxima of Mn[TpXPC]Cl (TpXPC = meso-tris(p-X-phenyl)corrole, where X =
CF3, H, Me, and OMe) were found to red-shift over a range
of 37 nm with increasing electron-donating character of X. For Mn[TpXPC]Ph, in contrast, the complex Soret envelopes were found
to be largely independent of X. These observations suggested a noninnocent
corrole•2–-like ligand for the MnCl complexes
and an innocent corrole3– ligand for the MnPh complexes.
Single-crystal X-ray structures of three Mn[TpXPC]Cl
complexes revealed skeletal bond-length alternations indicative of
a noninnocent corrole, while no such alternation was observed for
Mn[TpOMePC]Ph. B3LYP density functional theory (DFT)
calculations on Mn[TPC]Cl yielded strong spatial separation of the
α and β spin densities, consistent with an antiferromagnetically
coupled MnIII-corrole•2– description.
By comparison, relatively little spatial separation of the α
and β spin densities was found for Mn[TPC]Ph, consistent with
an essentially MnIV-corrole3– description.
X-ray absorption of near-edge spectroscopy (XANES) revealed a moderate
blue shift of 0.6 eV for the Mn K-pre-edge of Mn[TpCF3PC]Ph and a striking enhancement of the pre-edge intensity,
relative to Mn[TpCF3PC]Cl, consistent
with a more oxidized, i.e., MnIV, center in Mn[TpCF3PC]Ph. Time-dependent DFT calculations indicated
that the enhanced intensity of the Mn K-pre-edge of Mn[TpCF3PC]Ph results from the extra 3dz2 hole, which mixes strongly with the Mn 4pz orbital. Combined with similar results on
Fe[TPC]Cl and Fe[TPC]Ph, the present study underscores the considerable
potential of metal K-edge XANES in probing ligand noninnocence in
first-row transition-metal corroles. Cyclic voltammetry measurements
revealed highly negative first reduction potentials for the Mn[TpXPC]Ph series (∼−0.95 V) as well as large
electrochemical HOMO-LUMO gaps of ∼1.7 V. The first reductions,
however, are irreversible, suggesting cleavage of the Mn–Ph
bond
TIME-DEPENDENT SYSTEMS AND CHAOS IN STRING THEORY
No full textOne of the phenomenal results emerging from string theory is the AdS/CFT correspondence or gauge-gravity duality: In certain cases a theory of gravity is equivalent to a dual gauge theory, very similar to the one describing non-gravitational interactions of fundamental subatomic particles. A difficult problem on one side can be mapped to a simpler and solvable problem on the other side using this correspondence. Thus one of the theories can be understood better using the other.
The mapping between theories of gravity and gauge theories has led to new approaches to building models of particle physics from string theory. One of the important features to model is the phenomenon of confinement present in strong interaction of particle physics. This feature is not present in the gauge theory arising in the simplest of the examples of the duality. However this N = 4 supersymmetric Yang-Mills gauge theory enjoys the property of being integrable, i.e. it can be exactly solved in terms of conserved charges. It is expected that if a more realistic theory turns out to be integrable, solvability of the theory would lead to simple analytical expressions for quantities like masses of the hadrons in the theory. In this thesis we show that the existing models of confinement are all nonintegrable--such simple analytic expressions cannot be obtained.
We moreover show that these nonintegrable systems also exhibit features of chaotic dynamical systems, namely, sensitivity to initial conditions and a typical route of transition to chaos. We proceed to study the quantum mechanics of these systems and check whether their properties match those of chaotic quantum systems. Interestingly, the distribution of the spacing of meson excitations measured in the laboratory have been found to match with level-spacing distribution of typical quantum chaotic systems. We find agreement of this distribution with models of confining strong interactions, conforming these as viable models of particle physics arising from string theory
Proposta de um modelo de qualidade de serviço e segurança para a tecnologia de web services
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Ciência da Computação
Cobalt- and rhodium-corrole-triphenylphosphine complexes revisited: the question of a noninnocent corrole
No full textA reinvestigation of cobalt-corrole-triphenylphosphine complexes has yielded an unexpectedly subtle picture of their electronic structures. UV-vis absorption spectroscopy, skeletal bond length alternations observed in X-ray structures, and broken-symmetry DFT (B3LYP) calculations suggest partial CoII-corrole•2- character for these complexes. The same probes applied to the analogous rhodium corroles evince no evidence of a noninnocent corrole. X-ray absorption spectroscopic studies showed that the Co K rising edge of Co[TPC](PPh3) (TPC = triphenylcorrole) is red-shifted by ∼1.8 eV relative to the bona fide Co(III) complexes Co[TPC](py)2 and Co[TPP](py)Cl (TPP = tetraphenylporphyrin, py = pyridine), consistent with a partial CoII-corrole•2- description for Co[TPC](PPh3). Electrochemical measurements have shown that both the Co and Rh complexes undergo two reversible oxidations and one to two irreversible reductions. In particular, the first reduction of the Rh corroles occurs at significantly more negative potentials than that of the Co corroles, reflecting significantly higher stability of the Rh(III) state relative to Co(III). Together, the results presented herein suggest that cobalt-corrole-triphenylphosphine complexes are significantly noninnocent with moderate CoII-corrole•2- character, underscoring - yet again - the ubiquity of ligand noninnocence among first-row transition metal corroles.</p
Relativistic Fermion on a Ring: Energy Spectrum and Persistent Current
No full textThe energy and persistent current spectra for a relativistic fermion on a ring are studied in
detail. The nonlinear nature of persistent current in relativistic regime and its dependence
on particle mass and ring radius are analysed thoroughly. For a particular ring radius, we
find the existence of a critical mass at which the single ring current does not depend on the
flux. In lower mass regime, the total current spectrum shows plateaus at different height
which appears periodically. The susceptibility as well shows periodic nature with amplitude
depending on particle mass. As we move from higher mass to lower mass regime, we find that
the system turns into paramagnetic from diamagnetic. We also show that same behaviour
is observed if one vary the radius of the ring for a fixed particle mass. Hence the larger
ring will be diamagnetic while the smaller one will be paramagnetic. Finally we propose an
experiment to verify our findings
Ligand Noninnocence In Manganese, Iron, and Cobalt Corroles
No full textIn recent years, first-row metallocorroles have provided some of the most instructive examples of noninnocent ligands. This thesis presents a study of some 50 iron, manganese, and cobalt corrole complexes with different axial ligands (including approximately 30 new compounds and 6 new X-ray structures) with emphasis on their noninnocent/innocent character. UV-vis spectroscopy has for some time provided a convenient empirical probe of ligand noninnocence in transition metal meso-tris(para-X-phenyl)corrole (TpXPC) complexes. Redshifts of the Soret maxima with increasing electron-donating character of the para-substituent X have indicated noninnocent systems, while substituent-insensitive Soret maxima have indicated innocent corrole ligands. I have greatly expanded the scope of this optical probe of noninnocence and used it to identify new classes of noninnocent metallocorroles.
The μ-oxo diiron corroles have long been thought of as true Fe(IV) complexes. However, as discussed in Paper A, a study of the optical spectra of {Fe[TpXPC]}2O
derivatives along with DFT calculations have indicated a noninnocent description for these complexes.
Iron-aryl corroles are classic examples of true Fe(IV) species. Several Fe-aryl corroles were synthesized and examined together with other Fe corrole derivatives by means of UV-vis and NMR spectroscopy and electrochemistry in a detailed study for ligand noninnocence in a wide range of Fe corroles (Paper B). Analogous studies of Mn-aryl corroles were also carried out (Chapter 3), but these have not yet been written up as a manuscript. A collaborative study with the Stanford Synchrotron Radiation Lightsource also provided the first X-ray absorption spectroscopic analysis of the question of ligand noninnocence in Fe corrole complexes.
Cobalt-triphenylphosphine (Co-PPh3) corroles have also been thought of as classic low-spin Co(III) complexes until now. An examination of the UV-vis spectra of Co-PPh3 corroles and DFT calculations again indicated a partially noninnocent Co(II) corrole radical description for these complexes (Paper C). In contrast, an innocent description was indicated for Rh-PPh3 corroles.
Finally, as discussed in Paper D, Co corrole pyridine adducts were likewise studied with a variety of spectroscopic techniques and the noninnocent behavior of the monopyridine adducts was elucidated in considerable detail
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