Search results for " Multiple"
showing 10 items of 903 documents
Cytotoxic Compounds from the Fruits of Uapaca togoensis towards Multifactorial Drug-Resistant Cancer Cells
2014
Cancer cells may rapidly acquire multidrug resistance, mainly due to the presence of adenosine triphosphate-binding cassette transporters, epidermal growth factor receptor, or mutations in the p53 tumor suppressor gene. This work was designed to assess the cytotoxicity of the methanol crude extracts and compounds from the fruits of Uapaca togoensis, namely, β-amyryl acetate (1), 11-oxo-α-amyryl acetate (2), lupeol (3), pomolic acid (4), futokadsurin B (5), arborinin (6), and 3-O-β-D-glucopyranosyl sitosterol (7) against nine drug sensitive and multidrug-resistant cancer cell lines. The resazurin reduction assay was used to evaluate the cytotoxicity of the fruits of U. togoensis and compound…
Development and Partial Characterization of a Human T-Lymphoblastic Leukemic (CCRF-CEM) Cell Line Resistant to Etoposide. Analysis of Possible Circum…
1996
We have selected an etoposide-resistant variant (CCRF-CEM/VP-16) of the human T-lymphoblastic CCRF-CEM leukemia for study. Resistance to the topoisomerase II (topo II) inhibitor was about 11-fold and stable. Other data revealed that the new cell line had acquired an atypical, non-P-glycoprotein overexpressing multidrug resistant (MDR) phenotype with cross-resistance to other topo II inhibitors (amsacrine, doxorubicin, and mitoxantrone) and to glucocorticoids, but not to novobiocin, ICRF-187, vincristine or cisplatin. In a first instance, we assumed that altered drug-topo II interactions, based on quantitative and/or qualitative modifications of the enzyme, are a cause of resistance in the c…
Duty-ratio control of Nonlinear phase noise in dispersion-managed WDM transmissions using RZ-DPSK modulation at 10 Gb/s
2006
International audience; The authors compare analytical and numerical estimates, showing that the nonlinear phase noise of short optical pulses associated with the coupling between amplified spontaneous emission noise and fiber nonlinearity may be controlled by adjusting the duty cycle of the return-to-zero (RZ) signal modulation format. The impact of this effect in the optimization of the performance of 10-Gb/s dispersion-managed wavelength division multiplexed (WDM) systems using RZ-differential phase-shift keying (DPSK) modulation is discussed. By extensive numerical simulations, it is shown that the transmission quality of ultradense WDM systems using the RZ-DPSK modulation format may be…
Angular Momentum Coupling
2007
In nuclear physics, as also in atomic and molecular physics, the entities to be described consist of sub-entities with some orbital angular momentum and spin. The angular momentum of the entity is built, then, of the angular momenta of the sub-entities. This building process leads to quantum-mechanical angular momentum coupling. This chapter presents the basic machinery for treating angular momentum and its coupling. Clebsch-Gordan coefficients and 3j symbols are introduced. It is shown that Clebsch-Gordan coefficients and 3j symbols relate to the coupling of two angular momenta. Increasing the number of angular momenta to be coupled leads to more complicated coupling patterns. Transformati…
Transfer of optical orbital angular momentum to a bound electron
2016
Photons can carry angular momentum, not only due to their spin, but also due to their spatial structure. This extra twist has been used, for example, to drive circular motion of microscopic particles in optical tweezers as well as to create vortices in quantum gases. Here we excite an atomic transition with a vortex laser beam and demonstrate the transfer of optical orbital angular momentum to the valence electron of a single trapped ion. We observe strongly modified selection rules showing that an atom can absorb two quanta of angular momentum from a single photon: one from the spin and another from the spatial structure of the beam. Furthermore, we show that parasitic ac-Stark shifts from…
The UWB-OFDM Channel Analysis in Frequency
2009
In this paper, the ultra-wideband channel with orthogonal frequency division multiplexing (UWB-OFDM) is analyzed in the frequency domain. For UWB-OFDM channels with log-normal fading in the time domain, we show that the amplitude of each subcarrier can be approximated by a Nakagami-m random variable, where the fading parameter, the mean power and the correlation coefficient are expressed in terms of the following parameters: time arrival of the clusters, inter-arrival time of rays inside clusters, and power decay constants of rays and clusters.
Optical demultiplexing of millimeter-wave subcarriers for wireless channel distribution employing dual wavelength FBGs
2007
An optical mm-wave demultiplexer is presented. Double sideband modulation with suppressed optical carrier and filtering properties of dual overwritten fiber Bragg gratings are the fundamentals for optical demultiplexing of mm-wave radio-on-fiber signals: using a single optical carrier, Millimeter-wave signals of 20 and 40 GHz frequencies carrying independent data are created, transmitted over fiber, demultiplexed and wireless distributed to be detected and data recovered in a mobile unit. Double sideband modulation with suppressed optical carrier yields no power penalty due to chromatic dispersion, while the filtering properties of the dual overwritten fiber Bragg gratings allow less than −…
1 Tb/s·km WDM transmission over multimode fibre link
2008
We demonstrate 1 Tb/smiddotkm WDM error-free transmission (highest reported value to our knowledge) over a MMF link by a combination of low-linewidth lasers and central launch.
Limits of ultra-high bit rate RZ data transmissions in terrestrial optical fiber systems
2006
We numerically study the limits of the terrestrial optical fiber systems as a function of the bit rate. In particular, we compare for 160-, 320- and 640-Gbit/s the limits of single channel and WDM configurations.
Optimization of wavelength division multiplexing in N×160Gbit/s terrestrial transmission systems
2005
Abstract We analyze, from an engineering viewpoint, the prospects of an exploitable upgrade of terrestrial fiber systems based on standard monomode fiber and dispersion compensating units, for future N × 160 Gbit/s transmission systems. We show that dispersion swing, average dispersion and input pulse power are the key parameters that govern the system performances. We show that whenever the dispersion swing is arranged in a symmetrical setup and the compensation ratio is optimized accordingly, one may obtain a significant improvement of the transmission performances.