102,673 research outputs found
The canonical Kravchuk basis for discrete quantum mechanics
No full textThe well known Kravchuk formalism of the harmonic oscillator obtained from the direct discretization method is shown to be a new way of formulating discrete quantum phase space. It is shown that the Kravchuk oscillator Hamiltonian has a well defined unitary canonical partner which we identify with the quantum phase of the Kravchuk oscillator. The generalized discrete Wigner function formalism based on the action and angle variables is applied to the Kravchuk oscillator and its continuous limit is examined
Ethylene Decomposition at Undercoordinated Sites on Cu(410)
No full textControlling hydrocarbon chemistry on metal surfaces is important
for both heterogeneous catalysis and nanotechnology. Formation
of C-C bonds and C-H scission is central to carbon nanotube
synthesis whereas the inhibition of carbon growth (C-C breaking)
is important for preventing the poisoning of industrial catalysts.
Although the importance of special surface active sites for catalysis has been known for many years, only a few investigations deal with the influence of undercoordinated sites on reaction selectivity.
In this communication we demonstrate the bond breaking selectivity for molecular ethylene adsorbed on Cu(410). While on terraces ethylene is reversibly π-bonded, the step sites induce not only unexpected di-σ-bonding but also complete dehydrogenation at rather low crystal temperatures, T. The resulting carbon decorates the step edges
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Digital Electronics Equipment for the RIPEN Apparatus
No full textThe RIPEN apparatus is a neutron detector array composed of BC501 liquid scintillators specifically suited for neutron detection and time of flight measurement. It was installed at Legnaro National Laboratory in early `90s, while the last measurement campaign was performed in 2007. At present the apparatus is undergoing a process of complete substitution of readout/acquisition electronics. The capabilities of digital electronics have been tested using CAEN V1720 VME digitizers (12 bit, 250MS/s). Analogue RC/CR emulation filters have been developed to perform neutron/ discrimination: zero crossing technique as well as gate integrated method have been implemented. Signal interpolation routines allowed to obtain also 1 ns timing performances. During June 2011 a subset of 8 detectors was successfully used to perform an in-beam experiment to measure neutron production cross sections. This required the use of 2 VME synchronized acquisition boards and the development of a specific on-line analysis software. We will present a short description of the RIPEN apparatus at LNL and the digital electronic setup. Specifically developed pulse shape algorithms will also be illustrated, as well as the results obtained in calibration and in-beam measurements
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Ethene adsorption and decomposition on the Cu(410) surface
No full textThe influence of open steps on the surface properties is shown by investigating the interaction of molecular ethene with Cu(410). We find a surprisingly low-temperature, site-selective chemistry at the strongly under-coordinated step sites. Ethene bonds either in a pi-bonded or in a di-sigma-bonded state or undergoes complete dehydrogenation. All pathways involve the low-coordination sites at the step, since the first species is partially stabilized with respect to low-Miller-index Surfaces, while the other two are observed only on Cu(410). When annealing the surface, dehydrogenation and transformation into the di-sigma-bonded moiety proceed, both processes being favored by faster heating rates. The so-generated carbon (presumably C(2) admolecules) decorates the step edges, thereby blocking the active sites for subsequent dissociation and permitting only pi-bonding of ethene. The dip de loss of carbon disappears ill high-resolution electron energy loss spectroscopy when annealing to room temperature, indicating that carbon moves to more coplanar or even to subsurface sites where it still influences the sin-face chemistry. The surface reactivity is recovered when heating the crystal to 900 K since C dissolves then deep enough into the bulk
Pelevin’s Trinity in the novel “t”: author – protagonist – reader
No full textThe article attempts to interpret Pelevin's artistic strategy in the novel "T" by exploring its subject organization and addressing the key problems of the author, the protagonist, and the reader as they are seen by the researcher. The article analyzes the peculiarities of constructing the narrative reality in the novel "T", and goes on to discuss Pelevin's philosophic models of the development of the humankind, and the emergence of his new anthropology
(<i>S</i>)-Glutamic Acid on Ag(100): Self-Assembly in the Nonzwitterionic Form
No full textThe fundamental understanding of adsorption and self-organization of biological molecules at surfaces is of greatest importance for a huge variety of possible applications, ranging from molecular electronics to the study of biocompatible materials; hygiene, and biofouling. In spite of that, the characterization of the interactions of organic molecules of biological interest with surfaces is far from being complete. In the present paper we report on a combined microscopic (scanning tunneling microscopy (STM)) and spectroscopic (X-ray photoemission spectroscopy and high resolution electron energy loss spectroscopy) study of glutamic acid (Glu) adsorption and self-assembly on Ag(100) at different temperature. STM allows one to determine the structures of the Glu layers, for which empirical models are proposed, while photoemission spectra exclude adsorption in the zwitterionic form, which is the most common especially for weakly interacting substrates
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