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Chapman University

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2007

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Articles 1 - 19 of 19

Full-Text Articles in Physical Sciences and Mathematics

Slow-Light Fourier Transform Interferometer, Zhimin Shi, Robert W. Boyd, Ryan M. Camacho, Praveen K. Vudyasetu, John C. Howell Dec 2007

Slow-Light Fourier Transform Interferometer, Zhimin Shi, Robert W. Boyd, Ryan M. Camacho, Praveen K. Vudyasetu, John C. Howell

Mathematics, Physics, and Computer Science Faculty Articles and Research

We describe a new type of Fourier transform (FT) interferometer in which the tunable optical delay between the two arms is realized by using a continuously variable slow-light medium instead of a moving arm as in a conventional setup. The spectral resolution of such a FT interferometer exceeds that of a conventional setup of comparable size by a factor equal to the maximum group index of the slow-light medium. The scheme is experimentally demonstrated by using a rubidium atomic vapor cell as the tunable slow-light medium, and the spectral resolution is enhanced by a factor of approximately 100.

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Transients Of The Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity, John C. Howell, M. V. Pack, R. M. Camacho Sep 2007

Transients Of The Electromagnetically-Induced-Transparency-Enhanced Refractive Kerr Nonlinearity, John C. Howell, M. V. Pack, R. M. Camacho

Mathematics, Physics, and Computer Science Faculty Articles and Research

We report observations of the dynamics of electromagnetically induced transparency (EIT) in a Λ system when the ground states are Stark shifted. Interactions of this type exhibit large optical nonlinearities called Kerr nonlinearities, and have numerous applications. The EIT Kerr nonlinearity is relatively slow, which is a limiting factor that may make many potential applications impossible. Using rubidium atoms, we observe the dynamics of the EIT Kerr nonlinearity using a Mach-Zehnder interferometer to measure phase modulation of the EIT fields resulting from a pulsed signal beam Stark shifting the ground state energy levels. The rise times and transients agree well …

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Electromagnetically Induced Transparency Line Shapes For Large Probe Fields And Optically Thick Media, M. V. Pack, R. M. Camacho, John C. Howell Jul 2007

Electromagnetically Induced Transparency Line Shapes For Large Probe Fields And Optically Thick Media, M. V. Pack, R. M. Camacho, John C. Howell

Mathematics, Physics, and Computer Science Faculty Articles and Research

We calculate the line shape and linewidths for electromagnetically induced transparency (EIT) in optically thick, Doppler broadened media (buffer gasses are also considered). In generalizing the definition of the EIT linewidth to optically thick media, we find two different linewidth definitions apply depending on whether the experiment is pulsed or continuous wave (cw). Using the cw definition for the EIT line shape we derive analytic expressions describing the linewidth as a function of optical depth. We also review the EIT line shapes in optically thin media and provide physical arguments for how the line shapes change as a function of …

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Wide-Bandwidth, Tunable, Multiple-Pulse-Width Optical Delays Using Slow Light In Cesium Vapor, Ryan M. Camacho, Michael V. Pack, John C. Howell, Aaron Schweinsberg, Robert W. Boyd Apr 2007

Wide-Bandwidth, Tunable, Multiple-Pulse-Width Optical Delays Using Slow Light In Cesium Vapor, Ryan M. Camacho, Michael V. Pack, John C. Howell, Aaron Schweinsberg, Robert W. Boyd

Mathematics, Physics, and Computer Science Faculty Articles and Research

We demonstrate an all-optical delay line in hot cesium vapor that tunably delays 275 ps input pulses up to 6.8 ns and 740 input ps pulses up to 59 ns (group index of approximately 200) with little pulse distortion. The delay is made tunable with a fast reconfiguration time (hundreds of ns) by optically pumping out of the atomic ground states.

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Digital Support For Abductive Learning In Introductory Computing Courses, Atanas Radenski Mar 2007

Digital Support For Abductive Learning In Introductory Computing Courses, Atanas Radenski

Mathematics, Physics, and Computer Science Faculty Articles and Research

Students who grew up browsing the Web are skilled in what is usually referred to as abduction, a reasoning process that starts with a set of specific observations and then generates the best possible explanation of those observations. In order to exploit the abduction skills of contemporary students, we have developed digital CS1/2 study packs that promote and support active learning through abduction, i.e., abductive learning. The study packs integrate a variety of digital resources: online self-guided labs, e-texts, tutorial links, sample programs, quizzes, and slides. These online packs stimulate students to learn abductively by browsing, searching, and performing self-guided …

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Large-Alphabet Quantum Key Distribution Using Energy-Time Entangled Bipartite States, Irfan Ali-Khan, Curtis J. Broadbent, John C. Howell Feb 2007

Large-Alphabet Quantum Key Distribution Using Energy-Time Entangled Bipartite States, Irfan Ali-Khan, Curtis J. Broadbent, John C. Howell

Mathematics, Physics, and Computer Science Faculty Articles and Research

We present a protocol for large-alphabet quantum key distribution (QKD) using energy-time entangled biphotons. Binned, high-resolution timing measurements are used to generate a large-alphabet key with over 10 bits of information per photon pair, albeit with large noise. QKD with 5% bit error rate is demonstrated with 4 bits of information per photon pair, where the security of the quantum channel is determined by the visibility of Franson interference fringes. The protocol is easily generalizable to even larger alphabets, and utilizes energy-time entanglement which is robust to transmission over large distances in fiber.

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All-Optical Delay Of Images Using Slow Light, Ryan M. Camacho, Curtis J. Broadbent, Irfan Ali-Khan, John C. Howell Jan 2007

All-Optical Delay Of Images Using Slow Light, Ryan M. Camacho, Curtis J. Broadbent, Irfan Ali-Khan, John C. Howell

Mathematics, Physics, and Computer Science Faculty Articles and Research

Two-dimensional images carried by optical pulses (2 ns) are delayed by up to 10 ns in a 10 cm cesium vapor cell. By interfering the delayed images with a local oscillator, the transverse phase and amplitude profiles of the images are shown to be preserved. It is further shown that delayed images can be well preserved even at very low light levels, where each pulse contains on average less than one photon.

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Eddy Correlation Measurements Of The Air/Sea Flux Of Dimethylsulfide Over The North Pacific Ocean, Christa A. Marandino, Warren J. De Bruyn, Scott D. Miller, Eric S. Saltzman Jan 2007

Eddy Correlation Measurements Of The Air/Sea Flux Of Dimethylsulfide Over The North Pacific Ocean, Christa A. Marandino, Warren J. De Bruyn, Scott D. Miller, Eric S. Saltzman

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Shipboard measurements of air/sea fluxes and sea surface concentrations of dimethylsulfide (DMS) were made over the tropical and midlatitude North Pacific Ocean. Atmospheric pressure chemical ionization mass spectrometry was used to measure DMS levels in ambient air and in air equilibrated with surface seawater drawn from a depth of 5 m. Air/sea fluxes were obtained using eddy covariance. Corrections and uncertainties involved in the calculation of fluxes from shipboard data are discussed. The surface ocean DMS concentrations measured during this study ranged from 1 to 10 nM, and atmospheric mixing ratios ranged from 20 to 1000 ppt. Air/sea fluxes ranged …

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Coupling Coherence Distinguishes Structure Sensitivity In Protein Electron Transfer, Tatiana Prytkova, Igor V. Kurnikov, David Beratan Jan 2007

Coupling Coherence Distinguishes Structure Sensitivity In Protein Electron Transfer, Tatiana Prytkova, Igor V. Kurnikov, David Beratan

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Quantum mechanical analysis of electron tunneling in nine thermally fluctuating cytochrome b562 derivatives reveals two distinct protein-mediated coupling limits. A structure-insensitive regime arises for redox partners coupled through dynamically averaged multiple-coupling pathways (in seven of the nine derivatives) where heme-edge coupling leads to the multiple-pathway regime. A structure-dependent limit governs redox partners coupled through a dominant pathway (in two of the nine derivatives) where axial-ligand coupling generates the single-pathway limit and slower rates. This two-regime paradigm provides a unified description of electron transfer rates in 26 ruthenium-modified heme and blue-copper proteins, as well as in numerous photosynthetic proteins.

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Flavin Charge Transfer Transitions Assist Dna Photolyase Electron Transfer, Spiros S. Skourtis, Tatiana Prytkova, David Beratan Jan 2007

Flavin Charge Transfer Transitions Assist Dna Photolyase Electron Transfer, Spiros S. Skourtis, Tatiana Prytkova, David Beratan

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

This contribution describes molecular dynamics, semi-empirical and ab-initio studies of the primary photo-induced electron transfer reaction in DNA photolyase. DNA photolyases are FADH−-containing proteins that repair UV-damaged DNA by photo-induced electron transfer. A DNA photolyase recognizes and binds to cyclobutatne pyrimidine dimer lesions of DNA. The protein repairs a bound lesion by transferring an electron to the lesion from FADH−, upon photo-excitation of FADH− with 350–450 nm light. We compute the lowest singlet excited states of FADH− in DNA photolyase using INDO/S configuration interaction, time-dependent density-functional, and time-dependent Hartree-Fock methods. The calculations identify the lowest singlet excited state of FADH− …

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Pi-Calculus In Logical Form, Marcello M. Bonsangue, Alexander Kurz Jan 2007

Pi-Calculus In Logical Form, Marcello M. Bonsangue, Alexander Kurz

Engineering Faculty Articles and Research

Abramsky’s logical formulation of domain theory is extended to encompass the domain theoretic model for picalculus processes of Stark and of Fiore, Moggi and Sangiorgi. This is done by defining a logical counterpart of categorical constructions including dynamic name allocation and name exponentiation, and showing that they are dual to standard constructs in functor categories. We show that initial algebras of functors defined in terms of these constructs give rise to a logic that is sound, complete, and characterises bisimilarity. The approach is modular, and we apply it to derive a logical formulation of pi-calculus. The resulting logic is a …

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Improved Associated Conditions In Rapid Intensifications Of Tropical Cyclones, Ruixin Yang, J. Tang, Menas Kafatos Jan 2007

Improved Associated Conditions In Rapid Intensifications Of Tropical Cyclones, Ruixin Yang, J. Tang, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

Rapid intensification (RI) of tropical cyclones (TC) is a major error source in TC intensity forecasting. In order to improve the estimates of RI probability, association rules are used to facilitate the process of mining for candidate sets of conditions. Compared to the relation analysis method, the technique of association rules can simply explore associations among multiple conditions. Our mining results identified a reduced predictor set with fewer factors identified in previous studies but improved RI probabilities. That is, the RI probability with three conditions satisfied: low vertical shear, high humidity, and the TC being in an intensification phase is …

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Influences Of Winter Haze On Fog/Low Cloud Over The Indo-Gangetic Plains, Ritesh Gautam, N. C. Hsu, Menas Kafatos Jan 2007

Influences Of Winter Haze On Fog/Low Cloud Over The Indo-Gangetic Plains, Ritesh Gautam, N. C. Hsu, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

The aerosol loading in south Asia has increased considerably because of the growing population, urbanization, and industrialization in recent years. To understand the effects of aerosols on cloud properties in this region, we have analyzed an extensive collection of aerosol and cloud properties, obtained from the Moderate resolution Imaging Spectroradiometer (MODIS) data, over the Indian subcontinent during winter 2000–2006. During these winter months, the Indo-Gangetic (IG) plains, in the northern part of India, are subjected to dense haze and fog on the basis of MODIS climatology of aerosol optical depth and cloud properties (cloud effective radius, cloud top pressure, and …

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Four Novel Co-Precipitation Procedures For The Synthesis Of Lanthanum-Strontium Manganites, Vuk Uskoković, Miha Drofenik Jan 2007

Four Novel Co-Precipitation Procedures For The Synthesis Of Lanthanum-Strontium Manganites, Vuk Uskoković, Miha Drofenik

Pharmacy Faculty Articles and Research

Lanthanum-strontium manganites were synthesized using co-precipitation method with a reverse micellar microemulsion. Either oxalic acid, sodium hydroxide or tetramethylammonium hydroxide was used for the precipitation of precursor cations in a form that was subsequently calcined under various conditions in order to obtain perovskite manganite phase. Correlations between the properties of the synthesized powder and the calcination conditions have been put forth. The properties of the microemulsion-assisted synthesized material were compared with the samples prepared by following the supposedly similar chemical recombinations in bulk solutions, with an aim to challenge the fact that microemulsions in general have only templating effects on …

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Inside The Rainforests Of The Sea: Coral Reefs And Their Endangerment, Roxanne Greitz Miller Jan 2007

Inside The Rainforests Of The Sea: Coral Reefs And Their Endangerment, Roxanne Greitz Miller

Education Faculty Articles and Research

This article focuses on coral reefs and their endangerment.

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Note On The Ndvi-Lst Relationship And The Use Of Temperature-Related Drought Indices Over North America, D. Sun, Menas Kafatos Jan 2007

Note On The Ndvi-Lst Relationship And The Use Of Temperature-Related Drought Indices Over North America, D. Sun, Menas Kafatos

Mathematics, Physics, and Computer Science Faculty Articles and Research

A comprehensive evaluation of the relationship between vegetation and Land Surface Temperature (LST) over the North America is presented. It is found that the correlations between LST and Normalized Difference Vegetation Index (NDVI) depend on the season-of-year and time-of-day. For winter, the correlation between NDVI and LST is positive. The strong negative correlations between LST and NDVI are only found during the warm seasons. Thus temperature-related drought indices may only be used in the warm seasons from May to October, and should be used with caution during cold seasons in North America. The cooling effect of vegetation on LST is …

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Carathéodory Functions In The Banach Space Setting, Daniel Alpay, Olga Timoshenko, Dan Volok Jan 2007

Carathéodory Functions In The Banach Space Setting, Daniel Alpay, Olga Timoshenko, Dan Volok

Mathematics, Physics, and Computer Science Faculty Articles and Research

We prove representation theorems for Carathéodory functions in the setting of Banach spaces.

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Generalized No-Broadcasting Theorem, Howard Barnum, Jonathan Barrett, Matthew S. Leifer, Alex Wilce Jan 2007

Generalized No-Broadcasting Theorem, Howard Barnum, Jonathan Barrett, Matthew S. Leifer, Alex Wilce

Mathematics, Physics, and Computer Science Faculty Articles and Research

We prove a generalized version of the no-broadcasting theorem, applicable to essentially any nonclassical finite-dimensional probabilistic model satisfying a no-signaling criterion, including ones with ‘‘superquantum’’ correlations. A strengthened version of the quantum no-broadcasting theorem follows, and its proof is significantly simpler than existing proofs of the no-broadcasting theorem.

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A Functional Calculus In A Non Commutative Setting, Fabrizio Colombo, Graziano Gentili, Irene Sabadini, Daniele C. Struppa Jan 2007

A Functional Calculus In A Non Commutative Setting, Fabrizio Colombo, Graziano Gentili, Irene Sabadini, Daniele C. Struppa

Mathematics, Physics, and Computer Science Faculty Articles and Research

In this paper we announce the development of a functional calculus for operators defined on quaternionic Banach spaces. The definition is based on a new notion of slice regularity, see [6], and the key tools are a new resolvent operator and a new eigenvalue problem. This approach allows us to deal both with bounded and unbounded operators.

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