Philippe Bloch: Reducing distance between experiments and CERN
2009-01-01
With its unique combination of several hundred staff members and thousands of users from around the world sharing offices and physics data and profiting from mutually beneficial exchanges of know-how and expertise, the PH Department is a good example of a successful worldwide collaboration, set up as it was to construct and run the Laboratory’s physics experiments. The PH Depart-ment has always played host to thousands of users that contribute to CERN experiments and work on them, and whose numbers are set to grow in the years to come. With his long-standing experience as a user and then as the head of the CERN group within the CMS collaboration, Philippe Bloch, the new PH Department Head, is in favour of closer links between the Department and the experiments. "I think that the PH management should have a direct link to the experiments, and to do so we are holding regular management team meetings comprising members of the Department’s management and the e...
Quantum distance and the Euler number index of the Bloch band in a one-dimensional spin model.
Ma, Yu-Quan
2014-10-01
We study the Riemannian metric and the Euler characteristic number of the Bloch band in a one-dimensional spin model with multisite spins exchange interactions. The Euler number of the Bloch band originates from the Gauss-Bonnet theorem on the topological characterization of the closed Bloch states manifold in the first Brillouin zone. We study this approach analytically in a transverse field XY spin chain with three-site spin coupled interactions. We define a class of cyclic quantum distance on the Bloch band and on the ground state, respectively, as a local characterization for quantum phase transitions. Specifically, we give a general formula for the Euler number by means of the Berry curvature in the case of two-band models, which reveals its essential relation to the first Chern number of the band insulators. Finally, we show that the ferromagnetic-paramagnetic phase transition in zero temperature can be distinguished by the Euler number of the Bloch band.
Circularly polarized few-cycle optical rogue waves: rotating reduced Maxwell-Bloch equations.
Xu, Shuwei; Porsezian, K; He, Jingsong; Cheng, Yi
2013-12-01
The rotating reduced Maxwell-Bloch (RMB) equations, which describe the propagation of few-cycle optical pulses in a transparent media with two isotropic polarized electronic field components, are derived from a system of complete Maxwell-Bloch equations without using the slowly varying envelope approximations. Two hierarchies of the obtained rational solutions, including rogue waves, which are also called few-cycle optical rogue waves, of the rotating RMB equations are constructed explicitly through degenerate Darboux transformation. In addition to the above, the dynamical evolution of the first-, second-, and third-order few-cycle optical rogue waves are constructed with different patterns. For an electric field E in the three lower-order rogue waves, we find that rogue waves correspond to localized large amplitude oscillations of the polarized electric fields. Further a complementary relationship of two electric field components of rogue waves is discussed in terms of analytical formulas as well as numerical figures.
Reducing the distance in distance-caregiving by technology innovation
Directory of Open Access Journals (Sweden)
Lazelle E Benefield
2007-07-01
Full Text Available Lazelle E Benefield1, Cornelia Beck21College of Nursing, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA; 2Pat & Willard Walker Family Memory Research Center, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USAAbstract: Family caregivers are responsible for the home care of over 34 million older adults in the United States. For many, the elder family member lives more than an hour’s distance away. Distance caregiving is a growing alternative to more familiar models where: 1 the elder and the family caregiver(s may reside in the same household; or 2 the family caregiver may live nearby but not in the same household as the elder. The distance caregiving model involves elders and their family caregivers who live at some distance, defined as more than a 60-minute commute, from one another. Evidence suggests that distance caregiving is a distinct phenomenon, differs substantially from on-site family caregiving, and requires additional assistance to support the physical, social, and contextual dimensions of the caregiving process. Technology-based assists could virtually connect the caregiver and elder and provide strong support that addresses the elder’s physical, social, cognitive, and/or sensory impairments. Therefore, in today’s era of high technology, it is surprising that so few affordable innovations are being marketed for distance caregiving. This article addresses distance caregiving, proposes the use of technology innovation to support caregiving, and suggests a research agenda to better inform policy decisions related to the unique needs of this situation.Keywords: caregiving, family, distance, technology, elders
Tsukamoto, Shigeru; Hirose, Kikuji; Blügel, Stefan
2014-07-01
Generalized Bloch wave functions of bulk structures, which are composed of not only propagating waves but also decaying and growing evanescent waves, are known to be essential for defining the open boundary conditions in the calculations of the electronic surface states and scattering wave functions of surface and junction structures. Electronic complex band structures being derived from the generalized Bloch wave functions are also essential for studying bound states of the surface and junction structures, which do not appear in conventional band structures. We present a novel calculation method to obtain the generalized Bloch wave functions of periodic bulk structures by solving a generalized eigenvalue problem, whose dimension is drastically reduced in comparison with the conventional generalized eigenvalue problem derived by Fujimoto and Hirose [Phys. Rev. B 67, 195315 (2003)]. The generalized eigenvalue problem derived in this work is even mathematically equivalent to the conventional one, and, thus, we reduce computational cost for solving the eigenvalue problem considerably without any approximation and losing the strictness of the formulations. To exhibit the performance of the present method, we demonstrate practical calculations of electronic complex band structures and electron transport properties of Al and Cu nanoscale systems. Moreover, employing atom-structured electrodes and jellium-approximated ones for both of the Al and Si monatomic chains, we investigate how much the electron transport properties are unphysically affected by the jellium parts.
Kartashov, Yaroslav V; Vysloukh, Victor A; Torner, Lluis
2014-07-01
We introduce Bloch-wave beatings in arrays of multimode periodically bent waveguides with a transverse refractive index gradient. The new phenomenon manifests itself in the periodic drastic increase of the amplitude of the Bloch oscillations that accompanies resonant conversion of modes guided by the individual waveguides. The Bloch-wave beatings are found to be most pronounced when the length of the resonant mode conversion substantially exceeds the longitudinal period of the Bloch oscillations. The beating frequency decreases when the amplitude of waveguide bending decreases, while the beating amplitude is restricted by the amplitude of the Bloch oscillations that emerge from the second allowed band of the Floquet-Bloch lattice spectrum.
Kartashov, Yaroslav V; Torner, Lluis
2014-01-01
We introduce Bloch-wave beatings in arrays of multimode periodically bent waveguides with a transverse refractive index gradient. The new phenomenon manifests itself in the periodic drastic increase of the amplitude of the Bloch oscillations that accompanies resonant conversion of modes guided by the individual waveguides. The Bloch-wave beatings are found to be most pronounced when the length of the resonant mode conversion substantially exceeds the longitudinal period of the Bloch oscillations. The beating frequency decreases when the amplitude of waveguide bending decreases, while the beating amplitude is restricted by the amplitude of the Bloch oscillations that emerge from the second allowed band of the Floquet-Bloch lattice spectrum.
Bloch-wave engineering of quantum dot-micropillars for cavity quantum electrodynamics experiments
DEFF Research Database (Denmark)
Lermer, Matthias; Gregersen, Niels; Dunzer, Florian;
2012-01-01
We have employed Bloch-wave engineering to realize submicron diameter ultra-high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced ...
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
A new characterization of univalent Bloch functions is given by investigating the growth order of an essentially increasing function. Our contribution can be considered as a slight improvement of the well-known Pommerenke's result and its all generalizations, and the proof presented in this paper is independently developed.
Quantum state transfer via Bloch oscillations.
Tamascelli, Dario; Olivares, Stefano; Rossotti, Stefano; Osellame, Roberto; Paris, Matteo G A
2016-05-18
The realization of reliable quantum channels, able to transfer a quantum state with high fidelity, is a fundamental step in the construction of scalable quantum devices. In this paper we describe a transmission scheme based on the genuinely quantum effect known as Bloch oscillations. The proposed protocol makes it possible to carry a quantum state over different distances with a minimal engineering of the transmission medium and can be implemented and verified on current quantum technology hardware.
Reducing the distance: equity issues in distance learning in public education
Campbell, Patricia B.; Storo, Jennifer
1996-12-01
Distance learning and educational equity both began with an emphasis on access, on providing underserved students with an increased access to education. Today definitions of equity have gone beyond simple access to include equal or equivalent treatment and outcomes while definitions of underserved students have expanded to include girls, children of color, children with limited English proficiency and children with disabilities. At the same time the definition of distance learning has expanded to include new technologies, new audiences and new roles. Based on these new definitions and roles, the article raises a number of equity challenges for distance learning educators centering around who is taught, what is taught and how the teaching is done. To answer these challenges, a series of recommendations are suggested that educators can implement to make distance learning a leader in increasing educational equity for all students. The time to act is now.
Polychromatic optical Bloch oscillations.
Longhi, Stefano
2009-07-15
Bloch oscillations (BOs) of polychromatic beams in circularly curved optical waveguide arrays are smeared out owing to the dependence of the BO spatial period on the wavelength. Here it is shown that restoring of the self-imaging property of the array and approximate BOs over relatively broad spectral ranges can be achieved by the insertion of suitable lumped phase slips uniformly applied across the array.
Reduced Inverse Distance Weighting Interpolation for Painterly Rendering
Papari, Giuseppe; Petkov, Nicolai; Jiang,; Petkov, N
2009-01-01
The interpolation problem of irregularly distributed data, in a multidimensional domain is considered. A modification of the inverse distance weighting interpolation formula. is proposed; making computation time independent of the number of data, points. Only the first K neighbors of a given point a
Entangled Bloch Spheres: Bloch Matrix And Two Qubit State Space
Gamel, Omar
2016-01-01
We represent a two qubit density matrix in the basis of Pauli matrix tensor products, with the coefficients constituting a Bloch matrix, analogous to the single qubit Bloch vector. We find the quantum state positivity requirements on the Bloch matrix components, leading to three important inequalities, allowing us to parameterize and visualize the two qubit state space. Applying the singular value decomposition naturally separates the degrees of freedom to local and nonlocal, and simplifies the positivity inequalities. It also allows us to geometrically represent a state as two entangled Bloch spheres with superimposed correlation axes. It is shown that unitary transformations, local or nonlocal, have simple interpretations as axis rotations or mixing of certain degrees of freedom. The nonlocal unitary invariants of the state are then derived in terms of local unitary invariants. The positive partial transpose criterion for entanglement is generalized, and interpreted as a reflection, or a change of a single ...
Polarization controlled directional propagation of Bloch surface wave.
Kovalevich, Tatiana; Boyer, Philippe; Suarez, Miguel; Salut, Roland; Kim, Myun-Sik; Herzig, Hans Peter; Bernal, Maria-Pilar; Grosjean, Thierry
2017-03-06
Bloch surface waves (BSWs) are recently developing alternative to surface plasmon polaritons (SPPs). Due to dramatically enhanced propagation distance and strong field confinement these surface states can be successfully used in on-chip all-optical integrated devices of increased complexity. In this work we propose a highly miniaturized grating based BSW coupler which is gathering launching and directional switching functionalities in a single element. This device allows to control with polarization the propagation direction of Bloch surface waves at subwavelength scale, thus impacting a large panel of domains such as optical circuitry, function design, quantum optics, etc.
Local gravity measurement with the combination of atom interferometry and Bloch oscillations
Charrière, Renée; Zahzam, Nassim; Bidel, Yannick; Bresson, Alexandre
2011-01-01
We present a local measurement of gravity combining Bloch oscillations and atom interferometry. With a falling distance of 0.8 mm, we achieve a sensitivity of 2x10-7 g with an integration time of 300 s. No bias associated with the Bloch oscillations has been measured. A contrast decay with Bloch oscillations has been observed and attributed to the spatial quality of the laser beams. A simple experimental configuration has been adopted where a single retro-reflected laser beam is performing atoms launch, stimulated Raman transitions and Bloch oscillations. The combination of Bloch oscillations and atom interferometry can thus be realized with an apparatus no more complex than a standard atomic gravimeter.
DEFF Research Database (Denmark)
Larsen, Gunvor Riber; Guiver, Jo W
2013-01-01
from links tourists make between physical distance and reaching cultural dissimilarity. Sometimes travel itself was integral with the holiday experience. While cost and time savings were important, the total holiday price was more important than the journey price. Measures are suggested for reducing...... the distances travelled and changing the modes used, and so reducing environmental impacts, including changing leave allowances, better marketing of nearby destinations with cultural differences, and promoting slow travel....
A theory of generalized Bloch oscillations.
Duggen, Lars; Lew Yan Voon, L C; Lassen, Benny; Willatzen, Morten
2016-04-20
Bloch oscillations of electrons are shown to occur for cases when the energy spectrum does not consist of the traditional evenly-spaced ladders and the potential gradient does not result from an external electric field. A theory of such generalized Bloch oscillations is presented and an exact calculation is given to confirm this phenomenon. Our results allow for a greater freedom of design for experimentally observing Bloch oscillations. For strongly coupled oscillator systems displaying Bloch oscillations, it is further demonstrated that reordering of oscillators leads to destruction of Bloch oscillations. We stipulate that the presented theory of generalized Bloch oscillations can be extended to other systems such as acoustics and photonics.
Jones, Charlotte; Hine, Donald W; Marks, Anthony D G
2017-02-01
Many people perceive climate change as psychologically distant-a set of uncertain events that might occur far in the future, impacting distant places and affecting people dissimilar to themselves. In this study, we employed construal level theory to investigate whether a climate change communication intervention could increase public engagement by reducing the psychological distance of climate change. Australian residents (N = 333) were randomly assigned to one of two treatment conditions: one framed to increase psychological distance to climate change (distal frame), and the other framed to reduce psychological distance (proximal frame). Participants then completed measures of psychological distance of climate change impacts, climate change concern, and intentions to engage in mitigation behavior. Principal components analysis indicated that psychological distance to climate change was best conceptualized as a multidimensional construct consisting of four components: geographic, temporal, social, and uncertainty. Path analysis revealed the effect of the treatment frame on climate change concern and intentions was fully mediated by psychological distance dimensions related to uncertainty and social distance. Our results suggest that climate communications framed to reduce psychological distance represent a promising strategy for increasing public engagement with climate change.
A theory of generalized Bloch oscillations
DEFF Research Database (Denmark)
Duggen, Lars; Lew Yan Voon, L. C.; Lassen, Benny;
2016-01-01
Bloch oscillations of electrons are shown to occur for cases when the energy spectrum does not consist of the traditional evenly-spaced ladders and the potential gradient does not result from an external electric field. A theory of such generalized Bloch oscillations is presented and an exact cal...... oscillations. We stipulate that the presented theory of generalized Bloch oscillations can be extended to other systems such as acoustics and photonics.......Bloch oscillations of electrons are shown to occur for cases when the energy spectrum does not consist of the traditional evenly-spaced ladders and the potential gradient does not result from an external electric field. A theory of such generalized Bloch oscillations is presented and an exact...... calculation is given to confirm this phenomenon. Our results allow for a greater freedom of design for experimentally observing Bloch oscillations. For strongly coupled oscillator systems displaying Bloch oscillations, it is further demonstrated that reordering of oscillators leads to destruction of Bloch...
Observation of anharmonic Bloch oscillations.
Dreisow, Felix; Wang, Gang; Heinrich, Matthias; Keil, Robert; Tünnermann, Andreas; Nolte, Stefan; Szameit, Alexander
2011-10-15
We report on the experimental observation of Bloch oscillations of an optical wave packet in a lattice with second-order coupling. To this end, we employ zigzag waveguide arrays, in which the second-order coupling can be precisely tuned.
Bloch constant of holomorphic mappings on the unit polydisk of C~n
Institute of Scientific and Technical Information of China (English)
2008-01-01
In this paper,we give a definition of Bloch mappings defined in the unit polydisk Dn, which generalizes the concept of Bloch functions defined in the unit disk D.It is known that Bloch theorem fails unless we have some restrictive assumption on holomorphic mappings in several complex variables.We shall establish the corresponding distortion theorems for subfamiliesβ（K）andβloc（K） of Bloch mappings defined in the polydisk Dn,which extend the distortion theorems of Liu and Minda to higher dimensions.As an application,we obtain lower and upper bounds of Bloch constants for various subfamilies of Bloeh mappings defined in Dn.In particular,our results reduce to the classical results of Ahlfors and Landau when n=1.
Bloch oscillations in carbon nanotubes.
Jódar, Esther; Pérez-Garrido, Antonio; Rojas, Fernando
2009-05-27
Bloch oscillations arise when electrons are in a one-dimensional linear chain of atoms under a constant electric field. In this paper we show numerically that electrons in different types of carbon nanotubes show oscillations with a Bloch frequency proportional to the constant electric field applied along the nanotube axis. We show these oscillations, calculating the quadratic displacement as a function of the electric field. Because of the double periodicity of the nanotubes' geometry (the lattice constant and the lines of atoms) two frequencies appear, one twice the value of the other. These frequencies coincide perfectly with those predicted for a linear chain of atoms, taking into account the periodicity considered in each case.
Bloch oscillations in carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Jodar, Esther; Perez-Garrido, Antonio [Departamento Fisica Aplicada, Antiguo Hospital de Marina Campus Muralla del Mar, UPCT, Cartagena 30202 Murcia (Spain); Rojas, Fernando [Centro de Nanociencias y Nanotecnologia-UNAM, Apartado Postal 356, Ensenada, Baja California 22800 (Mexico)], E-mail: ejodar@upct.es
2009-05-27
Bloch oscillations arise when electrons are in a one-dimensional linear chain of atoms under a constant electric field. In this paper we show numerically that electrons in different types of carbon nanotubes show oscillations with a Bloch frequency proportional to the constant electric field applied along the nanotube axis. We show these oscillations, calculating the quadratic displacement as a function of the electric field. Because of the double periodicity of the nanotubes' geometry (the lattice constant and the lines of atoms) two frequencies appear, one twice the value of the other. These frequencies coincide perfectly with those predicted for a linear chain of atoms, taking into account the periodicity considered in each case. (fast track communication)
Hybrid Bloch-Anderson localization of light
Stutzer, Simon; Vysloukh, Victor A; Konotop, Vladimir V; Nolte, Stefan; Torner, Lluis; Szameit, Alexander
2013-01-01
We investigate the interplay of Bloch oscillations and Anderson localization in optics. Gradual washing out of Bloch oscillations and the formation of nearly stationary averaged intensity distributions, which are symmetric for narrow and strongly asymmetric for broad input excitations, are observed experimentally in laser-written waveguide arrays. At large disorder levels Bloch oscillations are completely destroyed and both narrow and wide excitations lead to symmetric stationary averaged intensity distributions with exponentially decaying tails.
Optical analogue of electronic Bloch oscillations.
Sapienza, Riccardo; Costantino, Paola; Wiersma, Diederik; Ghulinyan, Mher; Oton, Claudio J; Pavesi, Lorenzo
2003-12-31
We report on the observation of Bloch oscillations in light transport through periodic dielectric systems. By introducing a linear refractive index gradient along the propagation direction the optical equivalent of a Wannier-Stark ladder was obtained. Bloch oscillations were observed as time-resolved oscillations in transmission, in direct analogy to electronic Bloch oscillations in conducting crystals where the Wannier-Stark ladder is obtained via an external electric field. The observed oscillatory behavior is in excellent agreement with transfer matrix calculations.
Hybrid Bloch-Anderson localization of light.
Stützer, Simon; Kartashov, Yaroslav V; Vysloukh, Victor A; Konotop, Vladimir V; Nolte, Stefan; Torner, Lluis; Szameit, Alexander
2013-05-01
We investigate the interplay of Bloch oscillations and Anderson localization in optics. Gradual washing out of Bloch oscillations and the formation of nearly stationary averaged intensity distributions, which are symmetric for narrow and strongly asymmetric for broad input excitations, are observed experimentally in laser-written waveguide arrays. At large disorder levels Bloch oscillations are completely destroyed and both narrow and wide excitations lead to symmetric stationary averaged intensity distributions with exponentially decaying tails.
Hybrid Bloch-Anderson localization of light
Stutzer, Simon; Yaroslav V. Kartashov; Vysloukh, Victor A.; Konotop, Vladimir V.; Nolte, Stefan; Torner, Lluis; Szameit, Alexander
2013-01-01
We investigate the interplay of Bloch oscillations and Anderson localization in optics. Gradual washing out of Bloch oscillations and the formation of nearly stationary averaged intensity distributions, which are symmetric for narrow and strongly asymmetric for broad input excitations, are observed experimentally in laser-written waveguide arrays. At large disorder levels Bloch oscillations are completely destroyed and both narrow and wide excitations lead to symmetric stationary averaged int...
Large momentum beam splitter using Bloch oscillations.
Cladé, Pierre; Guellati-Khélifa, Saïda; Nez, François; Biraben, François
2009-06-19
The sensitivity of an inertial sensor based on an atomic interferometer is proportional to the velocity separation of atoms in the two arms of the interferometer. In this Letter we describe how Bloch oscillations can be used to increase this separation and to create a large momentum transfer (LMT) beam splitter. We experimentally demonstrate a separation of 10 recoil velocities. Light shifts during the acceleration introduce phase fluctuations which can reduce the fringes contrast. We precisely calculate this effect and demonstrate that it can be significantly reduced by using a suitable combination of LMT pulses. We finally show that this method seems to be very promising to realize a LMT beam splitter with several tens of recoils and a very good efficiency.
Bloch-wave engineering of quantum dot-micropillars for cavity quantum electrodynamics experiments
Lermer, Matthias; Dunzer, Florian; Reitzenstein, Stephan; Höfling, Sven; Mørk, Jesper; Worschech, Lukas; Kamp, Martin; Forchel, Alfred
2011-01-01
We have employed Bloch-wave engineering to realize submicron diameter ultra-high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced scattering loss leads to record-high visibility of the strong coupling in MPs with modest oscillator strength quantum dots. A quality factor of 13,600 and a Rabi splitting of 85 \\mueV with an estimated visibility v of 0.38 are observed for a small mode volume MP with a diameter dc of 850 nm.
Directory of Open Access Journals (Sweden)
Janakiraman Kamal
2011-06-01
Full Text Available Abstract Background Shock absorbing insoles are effective in reducing the magnitude and rate of loading of peak impact forces generated at foot strike during running, whereas the foot impact force during running has been considered to be an important cause of intravascular hemolysis in long distance runners. Objective of this study was to evaluate the intravascular hemolysis during running and compare the effect of two different types of insoles (Soft and Firm on hemolysis. Methods Twenty male long and middle distance runners volunteered to participate in this study. We selected two insoles (Soft and Firm according to their hardness level (SHORE 'A' scale. Participants were randomly assigned to the soft insole (group 1 and firm insole (group 2 group with ten athletes in each group. Each athlete completed one hour of running at the calculated target heart rate (60-70%. Venous blood samples were collected before and immediately after running. We measured unconjucated bilirubin (mg/dl, lactate dehydrogenase (μ/ml, hemoglobin (g/l and serum ferritin (ng/ml as indicators of hemolysis. Results Our study revealed a significant increase in the mean values of unconjucated bilirubin (P Conclusion Our results indicate that intravascular hemolysis occurs in athletes during long distance running and we conclude that addition of firm insoles effectively reduces the amount of hemolysis in runners compared to soft insoles.
REDUCING THE COGNITIVE LOAD ON ANALYSTS THROUGH HAMMING DISTANCE BASED ALERT AGGREGATION
Directory of Open Access Journals (Sweden)
Peter Mell
2014-07-01
Full Text Available Previous work introduced the idea of grouping alert s at a Hamming distance of 1 to achieve lossless al ert aggregation; such aggregated meta-alerts were shown to increase alert interpretability. However, a mea n of 84023 daily Snort alerts were reduced to a still formidable 14099 meta-alerts. In this work, we add ress this limitation by investigating several approaches that all contribute towards reducing the burden on the analyst and providing timely analysis. We explore m inimizing the number of both alerts and data elemen ts by aggregating at Hamming distances greater than 1. We show how increasing bin sizes can improve aggregation rates. And we provide a new aggregation algorithm that operates up to an order of magnitud e faster at Hamming distance 1. Lastly, we demonstrat e the broad applicability of this approach through empirical analysis of Windows security alerts, Snor t alerts, netflow records, and DNS logs. The result is a reduction in the cognitive load on analysts by mini mizing the overall number of alerts and the number of data elements that need to be reviewed in order for an analyst to evaluate the set of original alerts.
Bloch oscillations in atom interferometry
Cladé, Pierre
2014-01-01
In Paris, we are using an atom interferometer to precisely measure the recoil velocity of an atom that absorbs a photon. In order to reach a high sensitivity, many recoils are transferred to atoms using the Bloch oscillations technique. In this lecture, I will present in details this technique and its application to high precision measurement. I will especially describe in details how this method allows us to perform an atom recoil measurement at the level of $1.3 \\times 10^{-9}$. This measurement is used in the most precise determination of the fine structure constant that is independent of quantum electrodynamics.
Electric dipoles on the Bloch sphere
Vutha, Amar C
2014-01-01
The time evolution of a two-level quantum mechanical system can be geometrically described using the Bloch sphere. By mapping the Bloch sphere evolution onto the dynamics of oscillating electric dipoles, we provide a physically intuitive link between classical electromagnetism and the electric dipole transitions of atomic & molecular physics.
Bloch-Zener oscillations in binary superlattices.
Dreisow, F; Szameit, A; Heinrich, M; Pertsch, T; Nolte, S; Tünnermann, A; Longhi, S
2009-02-20
Bloch-Zener oscillations, i.e., the coherent superposition of Bloch oscillations and Zener tunneling between minibands of a binary lattice, are experimentally demonstrated for light waves in curved femtosecond laser-written waveguide arrays. Visualization of double-periodicity breathing and oscillation modes is reported, and synchronous tunneling leading to wave reconstruction is demonstrated.
Barefoot Running Reduces the Submaximal Oxygen Cost in Female Distance Runners.
Berrones, Adam J; Kurti, Stephanie P; Kilsdonk, Korey M; Cortez, Delonyx J; Melo, Flavia F; Whitehurst, Michael
2016-08-01
Berrones, AJ, Kurti, SP, Kilsdonk, KM, Cortez, DJ, Melo, FF, and Whitehurst, M. Barefoot running reduces the submaximal oxygen cost in female distance runners. J Strength Cond Res 30(8): 2348-2353, 2016-Being a competitive distance runner is, in part, attributable to a high V[Combining Dot Above]O2max. However, running economy (RE) is a more robust indicator of distance running performance among endurance athletes of similar V[Combining Dot Above]O2max levels. The purpose of this study was to examine the influence of unshod (barefoot) vs. shod (wearing shoes) running on RE (expressed as ml·kg·min) during three 5-minute submaximal running trials representing 65, 75, and 85% of V[Combining Dot Above]O2max. Other physiologic and perceptual variables such as respiratory exchange ratio, lactate, heart rate, and ratings of perceived exertion were also chosen as dependent variables. We measured V[Combining Dot Above]O2max in 14 recreationally active trained distance female runners (age = 27.6 ± 1.6 years; height = 163.3 ± 1.7 cm; weight = 57.8 ± 1.9 kg) who were completely inexperienced with unshod running. After initial testing, each subject was randomized to either unshod or shod for days 2 and 3. We analyzed the data with a 2-way (condition by intensity) repeated-measures analysis of variance. Submaximal oxygen consumption was significantly reduced at 85% of V[Combining Dot Above]O2max (p = 0.018), indicating an improvement in RE, but not during the 65% or 75% trials (p > 0.05, both). No other dependent measure was different between unshod and shod conditions. Our results indicate that the immediate improvement to RE while barefoot occurs at a relatively high fraction of maximal oxygen consumption. For the recreational or competitive distance runner, training or competing while barefoot may be a useful strategy to improve endurance performance.
``Bloch wave'' modification of stimulated Raman by stimulated Brillouin scattering
Dodd, E. S.; Vu, H. X.; DuBois, D. F.; Bezzerides, B.
2013-03-01
Using the reduced-description particle-in-cell (RPIC) method, we study the coupling of backward stimulated Raman scattering (BSRS) and backward stimulated Brillouin scattering (BSBS) in regimes where the reflectivity involves the nonlinear behavior of particles trapped in the daughter plasma waves. The temporal envelope of a Langmuir wave (LW) obeys a Schrödinger equation where the potential is the periodic electron density fluctuation resulting from an ion-acoustic wave (IAW). The BSRS-driven LWs in this case have a Bloch wave structure and a modified dispersion due to the BSBS-driven spatially periodic IAW, which includes frequency band gaps at kLW˜kIAW/2˜k0 (kLW, kIAW, and k0 are the wave number of the LW, IAW, and incident pump electromagnetic wave, respectively). This band structure and the associated Bloch wave harmonic components are distinctly observed in RPIC calculations of the electron density fluctuation spectra and this structure may be observable in Thomson scatter. Bloch wave components grow up in the LW spectrum, and are not the result of isolated BSRS. Self-Thomson scattered light from these Bloch wave components can have forward scattering components. The distortion of the LW dispersion curve implies that the usual relationship connecting the frequency shift of the BSRS-scattered light and the density of origin of this light may become inaccurate. The modified LW frequency results in a time-dependent frequency shift that increases as the IAW grows, detunes the BSRS frequency matching condition, and reduces BSRS growth. A dependence of the BSRS reflectivity on the IAW Landau damping results because this damping determines the levels of IAWs. The time-dependent reflectivity in our simulations is characterized by bursts of sub-picosecond pulses of BSRS alternating with multi-ps pulses of BSBS, and BSRS is observed to decline precipitously as soon as SBS begins to grow from low levels. In strong BSBS regimes, the Bloch wave effects in BSRS are
Magnetic Bloch oscillations in nanowire superlattice rings.
Citrin, D S
2004-05-14
The recent growth of semiconductor nanowire superlattices encourages hope that Bloch-like oscillations in such structures formed into rings may soon be observed in the presence of a time-dependent magnetic flux threading the ring. These magnetic Bloch oscillations are a consequence of Faraday's law; the time-dependent flux produces an electromotive force around the ring, thus leading to the Bloch-like oscillations. In the spectroscopic domain, generalized Wannier-Stark states are found that are manifestations of the emf-induced localization of the states.
Quasi-BLOCH oscillations in curved coupled optical waveguides.
Joushaghani, Arash; Iyer, Rajiv; Poon, Joyce K S; Aitchison, J Stewart; de Sterke, C Martijn; Wan, Jun; Dignam, Marc M
2009-10-01
We report the observation of quasi-Bloch oscillations, a recently proposed, new type of dynamic localization in the spatial evolution of light in a curved coupled optical waveguide array. By spatially resolving the optical intensity at various propagation distances, we show the delocalization and final relocalization of the beam in the waveguide array. Through comparisons with other structures, we show that this dynamic localization is robust beyond the nearest-neighbor tight-binding approximation and exhibits a wavelength dependence different from conventional dynamic localization.
REDUCING THE EFFECTS OF ISOLATION AND PROMOTING INCLUSIVITY FOR DISTANCE LEARNERS THROUGH PODCASTING
Directory of Open Access Journals (Sweden)
Anthony CHAN
2007-01-01
Full Text Available This article reports on an initiative to explore the potential of using supplementary audio podcast material to reduce the anxiety caused by isolation and to promote a sense of inclusivity amongst both undergraduate and postgraduate students studying an information technology subject in external mode with Australia’s largest provider of distance education. The podcasts were structured as a series of short, 3 to 5 minute talkback radio-style segments, with senior students holding discussions on pertinent issues related to the subject and its content in a relaxed and informal style. Both quantitative and qualitative data was obtained through a web-based survey conducted at the end of semester to gain insight into the views, experiences and perceived learning value of the podcasts from the perspective of the student listeners. Findings suggest that the approach was largely successful in achieving its aforementioned aims. In addition, the student listeners saw the podcasts as being especially effective in clarifying and enhancing their understanding of the subject; providing backup/reinforcement of what they had learnt; as well as supplying guidance on the direction in which to channel their study efforts. Overall, the authors believe podcasting has tremendous potential to assist in acculturating distance learners and aiding them in moving towards complete social and academic integration into institutional life, despite the presence of physical separation. The authors’ future research plans are also briefly outlined.
Reduced K-best sphere decoding algorithm based on minimum route distance and noise variance
Institute of Scientific and Technical Information of China (English)
Xinyu Mao; Jianjun Wu; Haige Xiang
2014-01-01
This paper focuses on reducing the complexity of K-best sphere decoding (SD) algorithm for the detection of uncoded multi-ple input multiple output (MIMO) systems. The proposed algorithm utilizes the threshold-pruning method to cut nodes with partial Euclidean distances (PEDs) larger than the threshold. Both the known noise value and the unknown noise value are considered to generate the threshold, which is the sum of the two values. The known noise value is the smal est PED of signals in the detected layers. The unknown noise value is generated by the noise power, the quality of service (QoS) and the signal-to-noise ratio (SNR) bound. Simulation results show that by considering both two noise values, the proposed algorithm makes an efficient reduction while the performance drops little.
Wave impedance retrieving via Bloch modes analysis
DEFF Research Database (Denmark)
Andryieuski, Andrei; Ha, S.; Sukhorukov, A.;
2011-01-01
of the Bloch mode, respectively. Case studies prove that our ap-proach can determine material and wave effective parameters of lossy and lossless metamaterials. In some examples when the passivity is violated we made further analysis and showed that this is due to the failure of concept of impedance retrieving......-ciples violation, like antiresonance behaviour with Im(ε) mode analysis of periodic metamaterials to extract the dominating (fundamental) Bloch mode. Then it is possible to determine the Bloch and wave impedances by the surface and volume aver-aging of the electromagnetic field......The main bottleneck in the restoration of electromagnetic effective parameters is connected to the impedance retrieving. The S-parameters method gives the input (Bloch) impedance, which, being then used for permittivity and permeability determination, causes some fundamental physics prin...
Bloch oscillations in optical dissipative lattices.
Efremidis, Nikolaos K; Christodoulides, Demetrios N
2004-11-01
We show that Bloch oscillations are possible in dissipative optical waveguide lattices with a linearly varying propagation constant. These oscillations occur in spite of the fact that the Bloch wave packet experiences coupling gain and (or) loss. Experimentally, this process can be observed in different settings, such as in laser arrays and lattices of semiconductor optical amplifiers. In addition, we demonstrate that these systems can suppress instabilities arising from preferential mode noise growth.
Experimental observation of spectral Bloch oscillations.
Bersch, Christoph; Onishchukov, Georgy; Peschel, Ulf
2009-08-01
We report on the first, to our knowledge, experimental observation of spectral Bloch oscillations in an optical fiber employing the interaction between a probe signal and a traveling-wave periodic potential. The spectrum of weak probe pulses is shown to oscillate on account of their group-velocity mismatch to the periodic field. The behavior of a cw probe spectrum reveals the actual discrete nature of the effect. Recurrences of the spectrum after one and two Bloch periods are demonstrated.
Resonant delocalization and Bloch oscillations in modulated lattices.
El-Ganainy, R; Christodoulides, D N; Rüter, C E; Kip, D
2011-04-15
We study the propagation of light in Bloch waveguide arrays exhibiting periodic coupling interactions. Intriguing wave packet revival patterns as well as beating Bloch oscillations are demonstrated. A new resonant delocalization phase transition is also predicted.
Fractional Bloch oscillations in photonic lattices.
Corrielli, Giacomo; Crespi, Andrea; Della Valle, Giuseppe; Longhi, Stefano; Osellame, Roberto
2013-01-01
Bloch oscillations, the oscillatory motion of a quantum particle in a periodic potential, are one of the most fascinating effects of coherent quantum transport. Originally studied in the context of electrons in crystals, Bloch oscillations manifest the wave nature of matter and are found in a wide variety of different physical systems. Here we report on the first experimental observation of fractional Bloch oscillations, using a photonic lattice as a model system of a two-particle extended Bose-Hubbard Hamiltonian. In our photonic simulator, the dynamics of two correlated particles hopping on a one-dimensional lattice is mapped into the motion of a single particle in a two-dimensional lattice with engineered defects and mimicked by light transport in a square waveguide lattice with a bent axis.
Fractional Bloch oscillations in photonic lattices
Corrielli, Giacomo; Della Valle, Giuseppe; Longhi, Stefano; Osellame, Roberto; 10.1038/ncomms2578
2013-01-01
Bloch oscillations, the oscillatory motion of a quantum particle in a periodic potential, are one of the most fascinating effects of coherent quantum transport. Originally studied in the context of electrons in crystals, Bloch oscillations manifest the wave nature of matter and are found in a wide variety of different physical systems. Here we report on the first experimental observation of fractional Bloch oscillations, using a photonic lattice as a model system of a two-particle extended Bose-Hubbard Hamiltonian. In our photonic simulator, the dynamics of two correlated particles hopping on a one-dimensional lattice is mapped into the motion of a single particle in a two-dimensional lattice with engineered defects and mimicked by light transport in a square waveguide lattice with a bent axis.
Observation of Bloch oscillations in molecular rotation
Floß, Johannes; Averbukh, Ilya Sh; Bucksbaum, Philip H
2015-01-01
The periodically kicked quantum rotor is known for non-classical effects such as quantum localisation in angular momentum space or quantum resonances in rotational excitation. These phenomena have been studied in diverse systems mimicking the kicked rotor, such as cold atoms in optical lattices, or coupled photonic structures. Recently, it was predicted that several solid state quantum localisation phenomena - Anderson localisation, Bloch oscillations, and Tamm-Shockley surface states - may manifest themselves in the rotational dynamics of laser-kicked molecules. Here, we report the first observation of rotational Bloch oscillations in a gas of nitrogen molecules kicked by a periodic train of femtosecond laser pulses. A controllable detuning from the quantum resonance creates an effective accelerating potential in angular momentum space, inducing Bloch-like oscillations of the rotational excitation. These oscillations are measured via the temporal modulation of the refractive index of the gas. Our results int...
Bloch oscillations in complex crystals with PT symmetry.
Longhi, S
2009-09-18
Bloch oscillations in complex lattices with PT symmetry are theoretically investigated with specific reference to optical Bloch oscillations in photonic lattices with gain or loss regions. Novel dynamical phenomena with no counterpart in ordinary lattices, such as nonreciprocal Bloch oscillations related to violation of the Friedel's law of Bragg scattering in complex potentials, are highlighted.
Terahertz Bloch oscillator with a modulated bias.
Hyart, Timo; Alexeeva, Natalia V; Mattas, Jussi; Alekseev, Kirill N
2009-04-10
Electrons performing Bloch oscillations in an energy band of a dc-biased superlattice in the presence of weak dissipation can potentially generate THz fields at room temperature. The realization of such a Bloch oscillator is a long-standing problem due to the instability of a homogeneous electric field in conditions of negative differential conductivity. We establish the theoretical feasibility of stable THz gain in a long superlattice device in which the bias is quasistatically modulated by microwave fields. The modulation waveforms must have at least two harmonics in their spectra.
Observation of Bloch Oscillations in Molecular Rotation.
Floß, Johannes; Kamalov, Andrei; Averbukh, Ilya Sh; Bucksbaum, Philip H
2015-11-13
We report the observation of rotational Bloch oscillations in a gas of nitrogen molecules kicked by a periodic train of femtosecond laser pulses. A controllable detuning from the quantum resonance creates an effective accelerating potential in angular momentum space, inducing Bloch-like oscillations of the rotational excitation. These oscillations are measured via the temporal modulation of the refractive index of the gas. Our results introduce room-temperature laser-kicked molecules as a new laboratory for studies of localization phenomena in quantum transport.
On the origin of the Bloch correction in stopping
Khodyrev, V. A.
2000-11-01
The energy loss in the collision of a moving charged projectile with a free electron is described in a rigorous approach. The collision is treated as stationary scattering of an electron in the projectile Coulomb field. In the laboratory frame, the picture can be represented as a spatial distribution of energy losses to the electron. It has been shown that the local rate of the energy gain can be presented as a product of the induced electron current and the projectile electric field. The analytical results and numerical calculations reveal a principal disagreement with the generally recognized condition for the classical description, η = Z1e2/ℎv≳1 (Z1e and v are, respectively, the charge and velocity of the projectile): for any value of η, the quantum effects appear to be significant in the close vicinity of the projectile trajectory (small impact parameters) restricted by the distance ~λ = ℎ/mv. Essentially, the problem has been cleared in the qualitative analysis of collisions with electron wavepackets. The main results of the Bloch theory are reproduced in a simpler way. The clearer basis permits us to eliminate the ambiguity in the interpretation of the origin of the Bloch correction, which reflects in fact the evolution of the classical features in the quantum mechanical picture.
Directory of Open Access Journals (Sweden)
Amy Woods
Full Text Available To determine the effect of intravenous iron supplementation on performance, fatigue and overall mood in runners without clinical iron deficiency.Fourteen distance runners with serum ferritin 30-100 µg · L(-1 were randomly assigned to receive three blinded injections of intravenous ferric-carboxymaltose (2 ml, 100 mg, IRON or normal saline (PLACEBO over four weeks (weeks 0, 2, 4. Athletes performed a 3,000 m time trial and 10 × 400 m monitored training session on consecutive days at week 0 and again following each injection. Hemoglobin mass (Hbmass was assessed via carbon monoxide rebreathing at weeks 0 and 6. Fatigue and mood were determined bi-weekly until week 6 via Total Fatigue Score (TFS and Total Mood Disturbance (TMD using the Brief Fatigue Inventory and Brunel Mood Scale. Data were analyzed using magnitude-based inferences, based on the unequal variances t-statistic and Cohen's Effect sizes (ES.Serum ferritin increased in IRON only (Week 0: 62.8 ± 21.9, Week 4: 128.1 ± 46.6 µg · L(-1; p = 0.002 and remained elevated two weeks after the final injection (127.0 ± 66.3 µg · L(-1, p = 0.01, without significant changes in Hbmass. Supplementation had a moderate effect on TMD of IRON (ES -0.77 with scores at week 6 lower than PLACEBO (ES -1.58, p = 0.02. Similarly, at week 6, TFS was significantly improved in IRON vs. PLACEBO (ES -1.54, p = 0.05. There were no significant improvements in 3,000 m time in either group (Week 0 vs. Week 4; Iron: 625.6 ± 55.5 s vs. 625.4 ± 52.7 s; PLACEBO: 624.8 ± 47.2 s vs. 639.1 ± 59.7 s; but IRON reduced their average time for the 10 × 400 m training session at week 2 (Week 0: 78.0 ± 6.6 s, Week 2: 77.2 ± 6.3; ES-0.20, p = 0.004.During 6 weeks of training, intravenous iron supplementation improved perceived fatigue and mood of trained athletes with no clinical iron deficiency, without concurrent improvements in oxygen transport capacity or performance.
Bloch-wave engineering of quantum dot micropillars for cavity quantum electrodynamics experiments.
Lermer, M; Gregersen, N; Dunzer, F; Reitzenstein, S; Höfling, S; Mørk, J; Worschech, L; Kamp, M; Forchel, A
2012-02-01
We have employed Bloch-wave engineering to realize submicron diameter high quality factor GaAs/AlAs micropillars (MPs). The design features a tapered cavity in which the fundamental Bloch mode is subject to an adiabatic transition to match the Bragg mirror Bloch mode. The resulting reduced scattering loss leads to record-high vacuum Rabi splitting of the strong coupling in MPs with modest oscillator strength quantum dots. A quality factor of 13, 600 and a splitting of 85 μeV with an estimated visibility v of 0.41 are observed for a small mode volume MP with a diameter d{c} of 850 nm.
Mechanical Properties of Laminate Materials: From Surface Waves to Bloch Oscillations
DEFF Research Database (Denmark)
Liang, Z.; Willatzen, Morten; Christensen, Johan
2015-01-01
for designing Bloch oscillations in classical plate structures and show how mechanical Bloch oscillations can be generated in arrays of solid plates when the modal wavelength is gradually reduced. The design recipe describes how Bloch oscillations in classical structures of arbitrary dimensions can be generated......We propose hitherto unexplored and fully analytical insights into laminate elastic materials in a true condensed-matter-physics spirit. Pure mechanical surface waves that decay as evanescent waves from the interface are discussed, and we demonstrate how these designer Scholte waves are controlled......, and we demonstrate this numerically for structures with millimeter and centimeter dimensions in the kilohertz to megahertz range. Analytical predictions agree entirely with full wave simulations showing how elastodynamics can mimic quantum-mechanical condensed-matter phenomena....
Electronic Bloch oscillation in bilayer graphene gradient superlattices
Energy Technology Data Exchange (ETDEWEB)
Cheng, Hemeng; Li, Changan; Song, Yun [Department of Physics, Beijing Normal University, Beijing 100875 (China); Ma, Tianxing, E-mail: txma@bnu.edu.cn [Department of Physics, Beijing Normal University, Beijing 100875 (China); Beijing Computational Science Research Center, Beijing 100084 (China); Wang, Li-Gang, E-mail: sxwlg@yahoo.com [Department of Physics, Zhejiang University, Hangzhou 310027 (China); Lin, Hai-Qing [Beijing Computational Science Research Center, Beijing 100084 (China)
2014-08-18
We investigate the electronic Bloch oscillation in bilayer graphene gradient superlattices using transfer matrix method. By introducing two kinds of gradient potentials of square barriers along electrons propagation direction, we find that Bloch oscillations up to terahertz can occur. Wannier-Stark ladders, as the counterpart of Bloch oscillation, are obtained as a series of equidistant transmission peaks, and the localization of the electronic wave function is also signature of Bloch oscillation. Furthermore, the period of Bloch oscillation decreases linearly with increasing gradient of barrier potentials.
Fractional Bloch Oscillations in photonic lattices
Directory of Open Access Journals (Sweden)
Corrielli G.
2013-11-01
Full Text Available We present the photonic analogy of the Fractional Bloch Oscillations [1]: the oscillatory motion of interacting particles moving in a periodic potential, under the presence of a static force. The analogy is implemented with the propagation of classical light in a specially engineered photonic waveguides lattice, fabricated in fused silica substrate via femtosecond laser micromachining.
Pogrebnyak, Victor A.; Furlani, Edward P.
2016-05-01
We study wave propagation in uniform materials with periodic boundary profiles and introduce for the first time Bloch resonances and Bloch gaps. Bloch resonances are due to transverse phase matching, i.e., the coupling of two transverse standing waves corresponding to different harmonics. These are distinct from well-known Bragg resonances that result from longitudinal phase matching. We show that Bloch gaps can be engineered over the entire first Brillouin zone up to an infinite wavelength, i.e., kx=0 , where kx is the wave number in the direction of propagation. This is in contrast to Bragg gaps that open at a fixed wavelength, twice the period of the structure. Bloch resonances and gaps can be tuned by reconfiguring the boundary profile and we derive analytical expressions that predict these phenomena when the amplitude of the profile is small. The theory is fundamental as it broadly applies to wave phenomena that span the quantum to continuum scale with applications that range from condensed matter to acoustics. We validate the theory experimentally for the electromagnetic field at GHz frequencies. We also discuss potential photonic and electronic applications of the theory such as a white-light distributed feedback laser and a two-dimensional electron gas transistor.
Bloch oscillations in plasmonic waveguide arrays.
Block, A; Etrich, C; Limboeck, T; Bleckmann, F; Soergel, E; Rockstuhl, C; Linden, S
2014-05-12
The combination of modern nanofabrication techniques and advanced computational tools has opened unprecedented opportunities to mold the flow of light. In particular, discrete photonic structures can be designed such that the resulting light dynamics mimics quantum mechanical condensed matter phenomena. By mapping the time-dependent probability distribution of an electronic wave packet to the spatial light intensity distribution in the corresponding photonic structure, the quantum mechanical evolution can be visualized directly in a coherent, yet classical wave environment. On the basis of this approach, several groups have recently observed discrete diffraction, Bloch oscillations and Zener tunnelling in different dielectric structures. Here we report the experimental observation of discrete diffraction and Bloch oscillations of surface plasmon polaritons in evanescently coupled plasmonic waveguide arrays. The effective external potential is tailored by introducing an appropriate transverse index gradient during nanofabrication of the arrays. Our experimental results are in excellent agreement with numerical calculations.
Resummations in the Bloch-Nordsieck model
Jakovac, A
2011-01-01
We studied different levels of resummations of the exactly solvable Bloch-Nordsieck model in order to be able to compare the approximations with an exact result. We studied one-loop perturbation theory, 2PI resummation and Schwinger-Dyson equations truncated in a way to maintain Ward-identities. At all levels we carefully performed renormalization. We found that although the 2PI resummation does not exhibit infrared sensitivity at the mass shell (the one-loop perturbation theory does), but it is still far from the exact solution. The method of truncated Schwinger-Dyson equations, however, is exact in this model, so it provides a new way of solving the Bloch-Nordsieck model. This method can also be generalized to other, more complicated theories.
Symmetric States on the Octonionic Bloch Ball
Graydon, Matthew
2012-02-01
Finite-dimensional homogeneous self-dual cones arise as natural candidates for convex sets of states and effects in a variety of approaches towards understanding the foundations of quantum theory in terms of information-theoretic concepts. The positive cone of the ten-dimensional Jordan-algebraic spin factor is one particular instantiation of such a convex set in generalized frameworks for quantum theory. We consider a projection of the regular 9-simplex onto the octonionic projective line to form a highly symmetric structure of ten octonionic quantum states on the surface of the octonionic Bloch ball. A uniform subnormalization of these ten symmetric states yields a symmetric informationally complete octonionic quantum measurement. We discuss a Quantum Bayesian reformulation of octonionic quantum formalism for the description of two-dimensional physical systems. We also describe a canonical embedding of the octonionic Bloch ball into an ambient space for states in usual complex quantum theory.
Generalized Bloch-Wangsness-Redfield Kinetic Equations
Fatkullin, Nail
2011-01-01
We present a compact and general derivation of the generalized Bloch-Wangsness-Redfield kinetic equations for systems with the static spin Hamiltonian utilizing the concept of the Liouville space. We show that the assumptions of short correlation times and large heat capacity of the lattice are sufficient to derive the kinetic equations without the use of perturbation theory for the spin-lattice interaction operator. The perturbation theory is only applied for calculation of the kinetic coeff...
Bloch oscillations of path-entangled photons.
Bromberg, Yaron; Lahini, Yoav; Silberberg, Yaron
2010-12-31
We show that when photons in N-particle path-entangled |N,0)+|0,N) or N00N states undergo Bloch oscillations, they exhibit a periodic transition between spatially bunched and antibunched states. The period of the bunching-antibunching oscillation is N times faster than the period of the oscillation of the photon density, manifesting the unique coherence properties of N00N states. The transition occurs even when the photons are well separated in space.
Photonic Bloch oscillations of correlated particles.
Longhi, Stefano
2011-08-15
A photonic realization of Bloch oscillations (BOs) of two correlated electrons that move on a one-dimensional periodic lattice, based on spatial light transport in a square waveguide array with a defect line, is theoretically proposed. The signature of correlated BOs, such as frequency doubling of the oscillation frequency induced by particle interaction, can be simply visualized by monitoring the spatial path followed by an optical beam that excites the array near the defect line.
Compact composition operators on the Bloch space in polydiscs
Institute of Scientific and Technical Information of China (English)
ZHOU; Zehua
2001-01-01
［1］Timoney, R., Bloch function in several complex variables, I, Bull. London Math. Soc., 1980, 12(37): 241.［2］Shi, J. H., Luo, L., Composition operators on the Bloch space of several complex variables, Acta Math. Sinica, 2000, 16(1): 85.［3］Madigan, K., Matheson, A., Compact composition operators on the Bloch space, Trans. Amer. Math. Soc., 1995, 347(7): 2679.
Bloch oscillations in the presence of plasmons and phonons
Ghosh; Jonsson; Wilkins
2000-07-31
The coupling between Bloch oscillating electrons and longitudinal optical phonons in a superlattice leads to resonant phonon excitation but no gap in the Bloch-phonon spectrum. In addition, we predict a sharp transition from plasma to Bloch oscillations at nu(B) = 2nu(P). From a microscopic description with phenomenological dampings, we numerically map out the behavior of coupled Bloch-plasmon-phonon modes for a wide range of parameters, and mimic experimental conditions. Our results are in good agreement with recent experiments by Dekorsy et al. [Phys. Rev. Lett. 85, 1080 (2000)].
Meinert, F; Mark, M J; Kirilov, E; Lauber, K; Weinmann, P; Gröbner, M; Nägerl, H-C
2014-05-16
We study atomic Bloch oscillations in an ensemble of one-dimensional tilted superfluids in the Bose-Hubbard regime. For large values of the tilt, we observe interaction-induced coherent decay and matter-wave quantum phase revivals of the Bloch oscillating ensemble. We analyze the revival period dependence on interactions by means of a Feshbach resonance. When reducing the value of the tilt, we observe the disappearance of the quasiperiodic phase revival signature towards an irreversible decay of Bloch oscillations, indicating the transition from regular to quantum chaotic dynamics.
Long-distance translocations to create a second millerbird population and reduce extinction risk
Holly Freifeld,; Sheldon Plentovich,; Chris Farmer,; Charles Kohley,; Peter Luscomb,; Work, Thierry M.; Daniel Tsukayama,; George Wallace,; Mark MacDonald,; Sheila Conant,
2016-01-01
Translocation is a conservation tool used with increasing frequency to create additional populations of threatened species. In addition to following established general guidelines for translocations, detailed planning to account for unique circumstances and intensive post-release monitoring to document outcomes and guide management are essential components of these projects. Recent translocation of the critically endangered Nihoa millerbird (Acrocephalus familiaris kingi) provides an example of this planning and monitoring. The Nihoa millerbird is a passerine bird endemic to Nihoa Island in the remote Northwestern Hawaiian Islands. The closely related, ecologically similar Laysan millerbird (Acrocephalus familiaris familiaris) went extinct on Laysan Island in the early 20th century when the island was denuded by introduced rabbits. To reduce extinction risk, we translocated 50 adult Nihoa millerbirds more than 1000 km by sea to Laysan, which has recovered substantially in the past century and has ample habitat and a rich prey-base for millerbirds. Following five years of intensive background research and planning, including development of husbandry techniques, fundraising, and regulatory compliance, translocations occurred in 2011 and 2012. Of 11 females in each cohort, 8 (2011 cohort) and 11 (2012 cohort) produced at least one brood of fledglings during their first year on Laysan. At the conclusion of monitoring in September 2014, 37 of the translocated birds were known to survive, and the population was estimated at 164 birds. The reintroduction of millerbirds to Laysan represents a milestone in the island's ongoing restoration.
Entangled Bloch spheres: Bloch matrix and two-qubit state space
Gamel, Omar
2016-06-01
We represent a two-qubit density matrix in the basis of Pauli matrix tensor products, with the coefficients constituting a Bloch matrix, analogous to the single qubit Bloch vector. We find the quantum state positivity requirements on the Bloch matrix components, leading to three important inequalities, allowing us to parametrize and visualize the two-qubit state space. Applying the singular value decomposition naturally separates the degrees of freedom to local and nonlocal, and simplifies the positivity inequalities. It also allows us to geometrically represent a state as two entangled Bloch spheres with superimposed correlation axes. It is shown that unitary transformations, local or nonlocal, have simple interpretations as axis rotations or mixing of certain degrees of freedom. The nonlocal unitary invariants of the state are then derived in terms of local unitary invariants. The positive partial transpose criterion for entanglement is generalized, and interpreted as a reflection, or a change of a single sign. The formalism is used to characterize maximally entangled states, and generalize two qubit isotropic and Werner states.
Bloch spaces on bounded symmetric domains in complex Banach spaces
Institute of Scientific and Technical Information of China (English)
DENG; Fangwen
2006-01-01
We give a definition of Bloch space on bounded symmetric domains in arbitrary complex Banach space and prove such function space is a Banach space. The properties such as boundedness, compactness and closed range of composition operators on such Bloch space are studied.
Synchronization of Bloch oscillations by a ring cavity.
Samoylova, M; Piovella, N; Robb, G R M; Bachelard, R; Courteille, Ph W
2015-06-01
We consider Bloch oscillations of ultracold atoms stored in a one-dimensional vertical optical lattice and simultaneously interacting with a unidirectionally pumped optical ring cavity whose vertical arm is collinear with the optical lattice. We find that the feedback provided by the cavity field on the atomic motion synchronizes Bloch oscillations via a mode-locking mechanism, steering the atoms to the lowest Bloch band. It also stabilizes Bloch oscillations against noise, and even suppresses dephasing due to atom-atom interactions. Furthermore, it generates periodic bursts of light emitted into the counter-propagating cavity mode, providing a non-destructive monitor of the atomic dynamics. All these features may be crucial for future improvements of the design of atomic gravimeters based on recording Bloch oscillations.
Bloch-Like Oscillations in Finite Quantum Structures
DEFF Research Database (Denmark)
Duggen, Lars; Willatzen, Morten; Lassen, Benny;
Inspired by several attempts to generate Bloch-like oscillations in different fields of physics [1,2], we examine a multitude of oscillator systems and interactions that lead to Bloch oscillations in finite quantum structures. A general requirement is the existence of a common period in the time...... of individual quantum wells and changing the coupling strength as a function of position. It is, furthermore, demonstrated that the application of a magnetic field to a structure of quantum wells may lead to the observation of Bloch oscillations (similar to Bloch oscillations stemming from the Stark effect......) and derive rather general mathematical relations between quantum systems that allow the existence of Bloch oscillations. References: [1]: G. Corrielli, A. Crespi, G. Della Valle, S. Longhi, and R. Osellame, Nature Communications 4, 1555 (2013) [2]: H. Sanchis-Alepuz, Y. A. Kosevich, and J. Sanchez...
Experimental observation of N00N state Bloch oscillations.
Lebugle, Maxime; Gräfe, Markus; Heilmann, René; Perez-Leija, Armando; Nolte, Stefan; Szameit, Alexander
2015-09-22
Bloch oscillations of quantum particles manifest themselves as periodic spreading and relocalization of the associated wave functions when traversing lattice potentials subject to external gradient forces. Albeit this phenomenon is deeply rooted into the very foundations of quantum mechanics, all experimental observations so far have only contemplated dynamics of one and two particles initially prepared in separable local states. Evidently, a more general description of genuinely quantum Bloch oscillations will be achieved on excitation of a Bloch oscillator by nonlocal states. Here we report the observation of Bloch oscillations of two-particle N00N states, and discuss the nonlocality on the ground of Bell-like inequalities. The time evolution of two-photon N00N states in Bloch oscillators, whether symmetric, antisymmetric or partially symmetric, reveals transitions from particle antibunching to bunching. Consequently, the initial states can be tailored to produce spatial correlations akin to those of bosons, fermions and anyons, presenting potential applications in photonic quantum simulation.
On unorthodox solutions of the Bloch equations
Moroz, Alexander
2012-01-01
A systematic, rigorous, and complete investigation of the Bloch equations in time-harmonic driving classical field is performed. Our treatment is unique in that it takes full advantage of the partial fraction decomposition over real number field, which makes it possible to find and classify all analytic solutions. Torrey's analytic solution in the form of exponentially damped harmonic oscillations [Phys. Rev. {\\bf 76}, 1059 (1949)] is found to dominate the parameter space, which justifies its use at numerous occasions in magnetic resonance and in quantum optics of atoms, molecules, and quantum dots. The unorthodox solutions of the Bloch equations, which do not have the form of exponentially damped harmonic oscillations, are confined to rather small detunings $\\delta^2\\lesssim (\\gamma-\\gamma_t)^2/27$ and small field strengths $\\Omega^2\\lesssim 8 (\\gamma-\\gamma_t)^2/27$, where $\\gamma$ and $\\gamma_t$ describe decay rates of the excited state (the total population relaxation rate) and of the coherence, respectiv...
Energy Technology Data Exchange (ETDEWEB)
Friedberg, Richard [Department of Physics, Columbia University, New York, NY 10027 (United States); Manassah, Jamal T. [HMS Consultants, Inc., PO Box 592, New York, NY 10028 (United States)], E-mail: jmanassah@gmail.com
2008-07-28
The superradiance from a slab of inverted two-level atoms is theoretically analyzed in the linear regime from both the perspective of the expansion in eigenfunctions of the integral equation with the Lienard-Wiechert potential as kernel, and that of linearizing the Maxwell-Bloch equations. We show the equivalence of both approaches. We show that the so-called Reduced Maxwell-Bloch equations do not yield even approximately the correct solution when applied in the obvious way, but that they can be made to give the correct solution by adding a fictitious input field.
Bloch oscillations in chirped layered structures with metamaterials.
Davoyan, Arthur R; Shadrivov, Ilya V; Sukhorukov, Andrey A; Kivshar, Yuri S
2008-03-01
We analyze the Bloch oscillations of electromagnetic waves in chirped layered structures with alternating layers of negative-index metamaterial and conventional dielectric under the condition of the zero average refractive index. We consider the case when the chirp is introduced by varying the thickness of the layers linearly across the structure. We demonstrate that such structures can support three different types of the Bloch oscillations for electromagnetic waves associated with either propagating or evanescent guided modes. In particular, we predict a novel type of the Bloch oscillations associated with coupling between surface waves excited at the interfaces separating the layers of negative-index metamaterial and the layers of the conventional dielectric.
Bloch oscillations of THz acoustic phonons in coupled nanocavity structures.
Lanzillotti-Kimura, N D; Fainstein, A; Perrin, B; Jusserand, B; Mauguin, O; Largeau, L; Lemaître, A
2010-05-14
Nanophononic Bloch oscillations and Wannier-Stark ladders have been recently predicted to exist in specifically tailored structures formed by coupled nanocavities. Using pump-probe coherent phonon generation techniques we demonstrate that Bloch oscillations of terahertz acoustic phonons can be directly generated and probed in these complex nanostructures. In addition, by Fourier transforming the time traces we had access to the proper eigenmodes in the frequency domain, thus evidencing the related Wannier-Stark ladder. The observed Bloch oscillation dynamics are compared with simulations based on a model description of the coherent phonon generation and photoelastic detection processes.
Bloch oscillations in a one-dimensional spinor gas.
Gangardt, D M; Kamenev, A
2009-02-20
A force applied to a spin-flipped particle in a one-dimensional spinor gas may lead to Bloch oscillations of the particle's position and velocity. The existence of Bloch oscillations crucially depends on the viscous friction force exerted by the rest of the gas on the spin excitation. We evaluate the friction in terms of the quantum fluid parameters. In particular, we show that the friction is absent for integrable cases, such as an SU(2) symmetric gas of bosons or fermions. For small deviations from the exact integrability the friction is very weak, opening the possibility to observe Bloch oscillations.
Bloch inductance in small-capacitance Josephson junctions.
Zorin, A B
2006-04-28
We show that the electrical impedance of a small-capacitance Josephson junction also includes, in addition to the capacitive term -i/(omega)CB, an inductive term i(omega)LB. Similar to the known Bloch capacitance CB(q), the Bloch inductance LB(q) also depends periodically on the quasicharge, q, and its maximum value achieved at q=e(mod 2e) always exceeds the value of the Josephson inductance of this junction LJ(phi) at fixed phi=0. The effect of the Bloch inductance on the dynamics of a single junction and a one-dimensional array is described.
A Bloch-Wigner complex for SL_2
Hutchinson, Kevin
2011-01-01
We introduce a refinement of the Bloch-Wigner complex of a field F. This is a complex of modules over the multiplicative group of the field. Instead of computing K_2 and indecomposable K_3 - as the classical Bloch-Wigner complex does - it calculates the second and third integral homology of SL_2 of the field. On passing to coinvariants for the action of the multiplicative group we recover the classical Bloch-Wigner complex. The case of finite fields is included throughout the article.
Spin wave vortex from the scattering on Bloch point solitons
Energy Technology Data Exchange (ETDEWEB)
Carvalho-Santos, V.L., E-mail: vagson.carvalho@usach.cl [Instituto Federal de Educação, Ciência e Tecnologia Baiano - Campus Senhor do Bonfim, Km 04 Estrada da Igara, 48970-000 Senhor do Bonfim, Bahia (Brazil); Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Elías, R.G., E-mail: gabriel.elias@usach.cl [Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Nunez, A.S., E-mail: alnunez@dfi.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago (Chile)
2015-12-15
The interaction of a spin wave with a stationary Bloch point is studied. The topological non-trivial structure of the Bloch point manifests in the propagation of spin waves endowing them with a gauge potential that resembles the one associated with the interaction of a magnetic monopole and an electron. By pursuing this analogy, we are led to the conclusion that the scattering of spin waves and Bloch points is accompanied by the creation of a magnon vortex. Interference between such a vortex and a plane wave leads to dislocations in the interference pattern that can be measurable by means of magnon holography.
An approximation formula for the Bloch-Siegert shift of the Rabi model
Rapedius, K
2015-01-01
So far the Bloch-Siegert shift of the Rabi model has only been calculated numerically or by means of perturbation theory valid in either the weak or strong driving regime only. Recently Yan, L\\"u, and Zheng [Phys.~Rev.~A {\\bf 91}, 053834 (2015)] showed how to reduce the problem to solving a system of three nonlinear equations. Here, we pursue an alternative approach based on a perturbation expansion extrapolation technique. We are thus able to derive an explicit analytical approximation formula for the Bloch-Siegert shift of the Rabi model which is valid for all parameter regimes from weak to strong driving. Comparison with numerically exact results reveals an excellent agreement over the entire driving-strength range.
Bloch state tomography using Wilson lines
Li, Tracy; Duca, Lucia; Reitter, Martin; Grusdt, Fabian; Demler, Eugene; Endres, Manuel; Schleier-Smith, Monika; Bloch, Immanuel; Schneider, Ulrich
2016-05-01
Topology and geometry are essential to our understanding of modern physics, underlying many foundational concepts from high-energy theories, quantum information, and condensed-matter physics. In condensed-matter systems, a wide range of phenomena stem from the geometry of the band eigenstates, which is encoded in the matrix-valued Wilson line for general multiband systems. Using an ultracold gas of rubidium atoms loaded in a honeycomb optical lattice, we realize strong-force dynamics in Bloch bands that are described by Wilson lines and observe an evolution in the band populations that directly reveals the band geometry. Our technique enables a full determination of band eigenstates, Berry curvature, and topological invariants, including single- and multiband Chern and Z2 numbers.
Bloch vector, disclination and exotic quantum holonomy
Energy Technology Data Exchange (ETDEWEB)
Tanaka, Atushi, E-mail: tanaka-atushi@tmu.ac.jp [Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan); Cheon, Taksu [Laboratory of Physics, Kochi University of Technology, Tosa Yamada, Kochi 782-8502 (Japan)
2015-09-04
A topological formulation of the eigenspace anholonomy, where eigenspaces are interchanged by adiabatic cycles, is introduced. The anholonomy in two-level systems is identified with a disclination of the director (headless vector) of a Bloch vector, which characterizes eigenprojectors. The covering map structure behind the exotic quantum holonomy and the role of the homotopy classification of adiabatic cycles are elucidated. The extensions of this formulation to nonadiabatic cycles and N-level systems are outlined. - Highlights: • A topological formulation of the eigenspace anholonomy is proposed. • The covering map structure behind the anholonomy is identified. • The role of homotopy classification of adiabatic cycles is explained. • The anholonomy in two-level systems is associated with disclinations. • The present formulation offers an extension to nonadiabatic cycles.
Reexamination of Bloch-Messiah reduction
Cariolaro, Gianfranco; Pierobon, Gianfranco
2016-06-01
The Bloch-Messiah (BM) reduction allows the decomposition of an arbitrarily complicated Gaussian unitary into a very simple scheme in which linear optical components are separated from nonlinear ones. It is based on the combined application of the eigendecomposition (EID) and singular value decomposition (SVD) of the two matrices associated to the Bogoliubov transformation of the given Gaussian unitary, with the constraint that the unitary matrices appearing in the SVDs must verify a stringent condition, called in the paper "rotation condition". Thus, for a correct evaluation of the BM reduction, one has to choose, among the possible SVD pairs, the pair that meets this condition. The paper develops an approach to this problem, which is based on the introduction of a balancing matrix in the SVDs to fulfill the rotation condition. The theory is illustrated with a few application examples.
Coupled bloch-phonon oscillations in semiconductor superlattices
Dekorsy; Bartels; Kurz; Kohler; Hey; Ploog
2000-07-31
We investigate coherent Bloch oscillations in GaAs/AlxGa1-xAs superlattices with electronic miniband widths larger than the optical phonon energy. In these superlattices the Bloch frequency can be tuned into resonance with the optical phonon. Close to resonance a direct coupling of Bloch oscillations to LO phonons is observed which gives rise to the coherent excitation of LO phonons. The density necessary for driving coherent LO phonons via Bloch oscillations is about 2 orders of magnitude smaller than the density necessary to drive coherent LO phonons in bulk GaAs. The experimental observations are confirmed by the theoretical description of this phenomenon [A.W. Ghosh et al., Phys. Rev. Lett. 85, 1084 (2000)].
Estimates on Bloch constants for planar harmonic mappings
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
The Bloch constants for quasiregular harmonic mappings and open planar harmonic mappings are considered. Better estimates are obtained. The results, presented in this paper, improve the one made by Chen et al. and Grigoryan.
Composition Operators on Dirichlet Spaces and Bloch Space
Institute of Scientific and Technical Information of China (English)
Yuan CHENG; Sanjay KUMAR; Ze Hua ZHOU
2014-01-01
In this paper we give a Carleson measure characterization for the compact composition operators between Dirichlet type spaces. We use this characterization to show that every compact composition operator on Dirichlet type spaces is compact on the Bloch space.
Calculation of the relativistic Bloch correction to stopping power
Ahlen, S. P.
1982-01-01
Bloch's technique of joining the nonrelativistic Bethe and Bohr stopping-power expressions by taking into account wave-packet effects for close collisions is extended to the relativistic case. It is found that Bloch's nonrelativistic correction term must be modified and that charge asymmetric terms appear. Excellent agreement is observed by comparing the results of these calculations to recent data on the stopping power of relativistic heavy ions.
Bloch-mode analysis for retrieving effective parameters of metamaterials
DEFF Research Database (Denmark)
Andryieuski, Andrei; Ha, Sangwoo; Sukhorukov, Andrey A.;
2012-01-01
by our method with a high accuracy. We employ both surface and volume averaging of the electromagnetic fields of the dominating (fundamental) Bloch modes to determine the Bloch and wave impedances, respectively. We discuss how this method works for several characteristic examples, and demonstrate...... that this approach can be useful for retrieval of both material and wave effective parameters of a broad range of metamaterials....
Uriarte, María; Anciães, Marina; da Silva, Mariana T B; Rubim, Paulo; Johnson, Erik; Bruna, Emilio M
2011-04-01
Seed dispersal is a crucial component of plant population dynamics. Human landscape modifications, such as habitat destruction and fragmentation, can alter the abundance of fruiting plants and animal dispersers, foraging rates, vector movement, and the composition of the disperser community, all of which can singly or in concert affect seed dispersal. Here, we quantify and tease apart the effects of landscape configuration, namely, fragmentation of primary forest and the composition of the surrounding forest matrix, on individual components of seed dispersal of Heliconia acuminata, an Amazonian understory herb. First we identified the effects of landscape configuration on the abundance of fruiting plants and six bird disperser species. Although highly variable in space and time, densities of fruiting plants were similar in continuous forest and fragments. However, the two largest-bodied avian dispersers were less common or absent in small fragments. Second, we determined whether fragmentation affected foraging rates. Fruit removal rates were similar and very high across the landscape, suggesting that Heliconia fruits are a key resource for small frugivores in this landscape. Third, we used radiotelemetry and statistical models to quantify how landscape configuration influences vector movement patterns. Bird dispersers flew farther and faster, and perched longer in primary relative to secondary forests. One species also altered its movement direction in response to habitat boundaries between primary and secondary forests. Finally, we parameterized a simulation model linking data on fruit density and disperser abundance and behavior with empirical estimates of seed retention times to generate seed dispersal patterns in two hypothetical landscapes. Despite clear changes in bird movement in response to landscape configuration, our simulations demonstrate that these differences had negligible effects on dispersal distances. However, small fragments had reduced densities
Supercurrent enhancement in Bloch domain walls.
Robinson, J W A; Chiodi, F; Egilmez, M; Halász, Gábor B; Blamire, M G
2012-01-01
Conventional spin-singlet Cooper pairs convert into spin-triplet pairs in ferromagnetic Josephson junctions in which the superconductor/ferromagnet interfaces (S/F) are magnetically inhomogeneous. Although much of the theoretical work describing this triplet proximity effect has considered ideal junctions with magnetic domain walls (DW) at the interfaces, in practice it is not easily possible to isolate a DW and propagate a supercurrent through it. The rare-earth magnet Gd can form a field-tuneable in-plane Bloch DW if grown between non-co-linearly aligned ferromagnets. Here we report supercurrents through magnetic Ni-Gd-Ni nanopillars: by field annealing at room temperature, we are able to modify the low temperature DW-state in Gd and this result has a striking effect on the junction supercurrent at 4.2 K. We argue that this result can only be explained in terms of the interconversion of triplet and singlet pairs, the efficiency of which depends on the magnetic helicity of the structure.
Representing distance, consuming distance
DEFF Research Database (Denmark)
Larsen, Gunvor Riber
to mobility and its social context. Such an understanding can be approached through representations, as distance is being represented in various ways, most noticeably in maps and through the notions of space and Otherness. The question this talk subsequently asks is whether these representations of distance...... are being consumed in the contemporary society, in the same way as places, media, cultures and status are being consumed (Urry 1995, Featherstone 2007). An exploration of distance and its representations through contemporary consumption theory could expose what role distance plays in forming...... are present in theoretical and empirical elaborations on mobility, but these remain largely implicit and unchallenged (Bauman 1998). This talk will endeavour to unmask distance as a theoretical entity by exploring ways in which distance can be understood and by discussing distance through its representations...
Landau-Zener Bloch Oscillations with Perturbed Flat Bands.
Khomeriki, Ramaz; Flach, Sergej
2016-06-17
Sinusoidal Bloch oscillations appear in band structures exposed to external fields. Landau-Zener (LZ) tunneling between different bands is usually a counteracting effect limiting Bloch oscillations. Here we consider a flat band network with two dispersive and one flat band, e.g., for ultracold atoms and optical waveguide networks. Using external synthetic gauge and gravitational fields we obtain a perturbed yet gapless band structure with almost flat parts. The resulting Bloch oscillations consist of two parts-a fast scan through the nonflat part of the dispersion structure, and an almost complete halt for substantial time when the atomic or photonic wave packet is trapped in the original flat band part of the unperturbed spectrum, made possible due to LZ tunneling.
Bloch Oscillations of Einstein-Podolsky-Rosen States
Lebugle, Maxime; Heilmann, René; Perez-Leija, Armando; Nolte, Stefan; Szameit, Alexander
2015-01-01
Bloch Oscillations (BOs) of quantum particles manifest themselves as periodic spreading and re-localization of the associated wave functions when traversing lattice potentials subject to external gradient forces. Albeit BOs are deeply rooted into the very foundations of quantum mechanics, all experimental observations of this phenomenon so far have only contemplated dynamics of one or two particles initially prepared in separable local states, which is well described by classical wave physics. Evidently, a more general description of genuinely quantum BOs will be achieved upon excitation of a Bloch-oscillator lattice system by nonlocal states, that is, containing correlations in contradiction with local realism. Here we report the first experimental observation of BOs of two-particle Einstein-Podolsky-Rosen states (EPR), whose associated N-particle wave functions are nonlocal by nature. The time evolution of two-photon EPR states in Bloch-oscillators, whether symmetric, antisymmetric or partially symmetric, r...
Weighted Composition Operators from Hardy Spaces into Logarithmic Bloch Spaces
Directory of Open Access Journals (Sweden)
Flavia Colonna
2012-01-01
Full Text Available The logarithmic Bloch space Blog is the Banach space of analytic functions on the open unit disk 𝔻 whose elements f satisfy the condition ∥f∥=supz∈𝔻(1-|z|2log (2/(1-|z|2|f'(z|<∞. In this work we characterize the bounded and the compact weighted composition operators from the Hardy space Hp (with 1≤p≤∞ into the logarithmic Bloch space. We also provide boundedness and compactness criteria for the weighted composition operator mapping Hp into the little logarithmic Bloch space defined as the subspace of Blog consisting of the functions f such that lim|z|→1(1-|z|2log (2/(1-|z|2|f'(z|=0.
Surface optical Bloch oscillations in semi-infinite waveguide arrays.
Chremmos, I D; Efremidis, N K
2012-06-01
We predict that surface optical Bloch oscillations can exist in semi-infinite waveguide arrays with a linear index variation, if the array parameters close to the boundary are appropriately perturbed. The perturbation is such that the surface states obtain the Wannier-Stark ladder eigenvalues of the unperturbed infinite array. The number of waveguides, whose parameters need to be controlled, decreases with increasing ratio of index gradient over coupling. The configuration can find applications as a "matched" termination of waveguide arrays to eliminate the distortion of Bloch oscillations due to reflection on the boundaries.
Control of interaction-induced dephasing of Bloch oscillations.
Gustavsson, M; Haller, E; Mark, M J; Danzl, J G; Rojas-Kopeinig, G; Nägerl, H-C
2008-02-29
We report on the control of interaction-induced dephasing of Bloch oscillations for an atomic Bose-Einstein condensate in an optical lattice. We quantify the dephasing in terms of the width of the quasimomentum distribution and measure its dependence on time for different interaction strengths which we control by means of a Feshbach resonance. For minimal interaction, the dephasing time is increased from a few to more than 20 thousand Bloch oscillation periods, allowing us to realize a BEC-based atom interferometer in the noninteracting limit.
Optical BLOCH oscillations and Zener tunneling with nonclassical light.
Longhi, Stefano
2008-11-01
A quantum theory of optical Bloch oscillations and Zener tunneling (ZT) in arrays of coupled waveguides is theoretically presented, and the particlelike behavior of photons undergoing ZT is highlighted. In singly-periodic arrays excited by a photon-number-state input beam, each photon behaves as a classical particle which independently undergoes a coin-toss ZT event with a probability described by classical Zener theory. In binary arrays, excitation with two tilted beams enables us to observe the Hong-Ou-Mandel interference for two photons undergoing Bloch-Zener oscillations.
Unidirectional optical Bloch oscillations in asymmetric waveguide arrays.
Kumar, Pradeep; Levy, Miguel
2011-11-15
We present an analytical proof of the existence of unidirectional optical Bloch oscillations in a waveguide array system. It is shown that the presence of nonreciprocity in the system allows for a complete normal-mode dephasing in one of the propagation directions, resulting in a unidirectional breakdown in Bloch oscillations. A model system consisting of an array of transversely magnetized asymmetric Si/SiO2 waveguides with a magneto-optic cover layer is presented. Large index contrasts between film and cover are critical for practical realizations.
Superfluidity versus Bloch oscillations in confined atomic gases.
Büchler, H P; Geshkenbein, V B; Blatter, G
2001-09-01
We study the superfluid properties of (quasi) one-dimensional bosonic atom gases/liquids in traps with finite geometries in the presence of strong quantum fluctuations. Driving the condensate with a moving defect we find the nucleation rate for phase slips using instanton techniques. While phase slips are quenched in a ring resulting in a superfluid response, they proliferate in a tube geometry where we find Bloch oscillations in the chemical potential. These Bloch oscillations describe the individual tunneling of atoms through the defect and thus are a consequence of particle quantization.
Fundamentals and applications of the Landau–Lifshitz–Bloch equation
Atxitia, U.; Hinzke, D.; Nowak, U.
2017-01-01
The influence of thermal excitations on magnetic materials is a topic of increasing relevance in the theory of magnetism. The Landau–Lifshitz–Bloch equation describes magnetisation dynamics at finite temperatures. It can be considered as an extension of already established micromagnetic methods with a comparable numerical effort. This review is a brief summary of this new field of research, with a focus on the fundamentals of the Landau–Lifshitz–Bloch equation, its connection with the stochastic Landau–Lifshitz equation, and its applications in modern magnetism.
Generation of 1D interference patterns of Bloch surface waves
Kadomina, E. A.; Bezus, E. A.; Doskolovich, L. L.
2016-09-01
Interference patterns of Bloch surface waves with a period that is significantly less than the wavelength of incident radiation are formed using dielectric diffraction gratings located on the surface of photonic crystal. The simulation based on electromagnetic diffraction theory is used to demonstrate the possibility of high-quality interference patterns due to resonant enhancement of higher evanescent diffraction orders related to the excitation of the Bloch surface waves. The contrast of the interference patterns is close to unity, and the period is less than the period of the diffraction structure by an order of magnitude.
COMPOSITION OPERATORS ON THE LITTLE BLOCH SPACE IN POLYDISCS
Institute of Scientific and Technical Information of China (English)
Zhou Zehua; Zhu Min; Shi Jihuai
2005-01-01
Let Un be the unit polydisc of Cn and φ = (φ1,…,φn) a holomorphic self map of Un. This paper shows that the composition operator Cφ induced by φ is bounded on the little Bloch space β0*(Un) if and only if φ∈β0*(Un) for every l=1,2,…,n, and also gives a sufficient and necessary condition for the composition operator Cφ to be compact on the little Bloch spaceβ0* (Un).
Energy Technology Data Exchange (ETDEWEB)
Kozlowski, K.K.
2010-12-15
Starting from the form factor expansion in finite volume, we derive the multidimensional generalization of the so-called Natte series for the zero-temperature, time and distance dependent reduced density matrix in the non-linear Schroedinger model. This representation allows one to read-off straightforwardly the long-time/large-distance asymptotic behavior of this correlator. Our method of analysis reduces the complexity of the computation of the asymptotic behavior of correlation functions in the so-called interacting integrable models, to the one appearing in free fermion equivalent models. We compute explicitly the first few terms appearing in the asymptotic expansion. Part of these terms stems from excitations lying away from the Fermi boundary, and hence go beyond what can be obtained by using the CFT/Luttinger liquid based predictions. (orig.)
Topological optical Bloch oscillations in a deformed slab waveguide.
Longhi, Stefano
2007-09-15
Spatial Bloch oscillations of light waves of purely topological origin are theoretically shown to exist in weakly deformed slab waveguides. As the optical rays trapped in the deformed waveguide can roll freely, wave diffraction is strongly affected by the topology of the deformed surface, which can be tailored to simulate the effect of a tilted periodic refractive index.
Interaction-induced decoherence of atomic BLOCH oscillations.
Buchleitner, Andreas; Kolovsky, Andrey R
2003-12-19
We show that the energy spectrum of the Bose-Hubbard model amended by a static field exhibits Wigner-Dyson level statistics. In itself a characteristic signature of quantum chaos, this induces the irreversible decay of Bloch oscillations of cold, interacting atoms loaded into an optical lattice, and provides a Hamiltonian model for interaction-induced decoherence.
The Bloch-Kato Conjecture and Galois Theory
Karagueuzian, Dikran; Miná\\vc, Ján
2010-01-01
We investigate the relations in Galois groups of maximal p-extensions of fields, the structure of their natural filtrations, and their relationship with the Bloch-Kato conjecture proved by Rost and Voevodsky with Weibel's patch. Our main focus is on the third degree, but we provide examples for all degrees.
Compact composition operators on the Bloch space in polydiscs
Institute of Scientific and Technical Information of China (English)
无
2001-01-01
Let Un be the unit polydisc of Cn and =(1,…n) a holomorphicself-map of Un. As the main result of the paper, it shows that the composition operator Cφ is compact on the Bloch space β(Un) if and only if for every ε>0, there exists a δ>0, such thatwhenever dist((z),Un)<δ.
Lines crossing a tetrahedron and the Bloch group
Hutchinson, Kevin
2011-01-01
We consider a simple modification of the Chow group CH^2(Spec(k),3) using only linear subvarieties in affine spaces and show that it maps surjectively to the Bloch group B(k) for any infinite field k. We also describe the kernel of this map.
Angermeyer, Angus; Crosby, Sarah C; Huber, Julie A
2016-01-01
In many habitats, microorganisms exhibit significant distance-decay patterns as determined by analysis of the 16S rRNA gene and various other genetic elements. However, there have been few studies that examine how the similarities of both taxonomic and functional genes co-vary over geographic distance within a group of ecologically related microbes. Here, we determined the biogeographic patterns of the functional dissimilatory sulfite reductase gene (dsrA) and the 16S rRNA gene in sulfate-reducing bacterial communities of US East Coast salt marsh sediments. Distance-decay, ordination and statistical analyses revealed that the distribution of 16S rRNA genes is strongly influenced by geographic distance and environmental factors, whereas the dsrA gene is not. Together, our results indicate that 16S rRNA genes are likely dispersal limited and under environmental selection, whereas dsrA genes appear randomly distributed and not selected for by any expected environmental variables. Selection, drift, dispersal and mutation are all factors that may help explain the decoupled biogeographic patterns for the two genes. These data suggest that both the taxonomic and functional elements of microbial communities should be considered in future studies of microbial biogeography to aid in our understanding of the diversity, distribution and function of microorganisms in the environment.
Anderson wall and Bloch oscillations in molecular rotation
Floß, Johannes
2014-01-01
We describe a universal behavior of linear molecules excited by a periodic train of short laser pulses under quantum resonance conditions. In a rigid rotor the resonance causes an unlimited ballistic growth of the angular momentum. We show that the centrifugal distortion of rotating molecules eventually halts the growth, by causing Anderson localization beyond a critical value of the angular momentum -- the Anderson wall. Its position solely depends on the molecular rotational constants and lies in the range of a few tens of hbar. Below the wall, rotational excitation oscillates with the number of pulses due to a mechanism similar to Bloch oscillations in crystalline solids. We suggest optical experiments capable of observing the rotational Anderson wall and Bloch oscillations at ambient conditions with the help of existing laser technology.
Anderson wall and BLOCH oscillations in molecular rotation.
Floß, Johannes; Averbukh, Ilya Sh
2014-07-25
We describe a universal behavior of linear molecules excited by a periodic train of short laser pulses under quantum resonance conditions. In a rigid rotor, the resonance causes an unlimited ballistic growth of the angular momentum. We show that the centrifugal distortion of rotating molecules eventually halts the growth, by causing Anderson localization beyond a critical value of the angular momentum--the Anderson wall. Its position solely depends on the molecular rotational constants and lies in the range of a few tens of ℏ. Below the wall, rotational excitation oscillates with the number of pulses due to a mechanism similar to Bloch oscillations in crystalline solids. We suggest optical experiments capable of observing the rotational Anderson wall and Bloch oscillations at near-ambient conditions with the help of existing laser technology.
Bloch-Redfield equations for modeling light-harvesting complexes
Jeske, Jan; Plenio, Martin B; Huelga, Susana F; Cole, Jared H
2014-01-01
We challenge the commonly held view that Bloch-Redfield equations are a less powerful tool than phenomenological Lindblad equations for modeling exciton transport in photosynthetic complexes. This view predominantly originates from the misuse of the secular approximation. We provide a detailed description of how to model both coherent oscillations and several types of noise, giving explicit examples. All issues with non-positivity are overcome by a consistent straightforward physical noise model. Herein also lies the strength of the Bloch-Redfield approach because it facilitates the analysis of noise-effects by linking them back to physical parameters of the noise environment. This includes temporal and spatial correlations and the strength and type of interaction between the noise and the system of interest. Finally we analyze a prototypical dimer system as well as a 7-site Fenna-Matthews-Olson (FMO) complex in regards to spatial correlation length of the noise, noise strength, temperature and their connecti...
Bloch-mode analysis for effective parameters restoration
DEFF Research Database (Denmark)
Lavrinenko, Andrei; Andryieuski, Andrei; Ha, Sangwoo;
2012-01-01
We utilize the Bloch-mode analysis of periodic composite structures to introduce an approach for retrieving effective parameters of homogenized metamaterials. In the case of single-mode propagation we can restore a complex effective refractive index with a high accuracy. By further employing surf...... on the nature of microfields returned by Maxwell's solvers, showing that ignoring of difference between magnetic strength and induction lead to incorrect determination of the Poynting vector....
Nonreciprocal Bloch oscillations in magneto-optic waveguide arrays.
Levy, Miguel; Kumar, Pradeep
2010-09-15
We show that nonreciprocal optical Bloch-like oscillations can emerge in transversely magnetized waveguide arrays in the presence of an effective index step between the waveguides. Normal modes of the system are shown to acquire different wavenumbers in opposite propagation directions. Significant differences in phase coherence and decoherence between these normal modes are presented and discussed. Nonreciprocity is established by imposing unequal vertical refractive index gradients at the substrate/core and core/cover interfaces in the presence of transverse magnetization.
Acoustic Bloch oscillations in a two-dimensional phononic crystal.
He, Zhaojian; Peng, Shasha; Cai, Feiyan; Ke, Manzhu; Liu, Zhengyou
2007-11-01
We report the observation of acoustic Bloch oscillations at megahertz frequency in a two-dimensional phononic crystal. By creating periodically arrayed cavities with a decreasing gradient in width along one direction in the phononic crystal, acoustic Wannier-Stark ladders are created in the frequency domain. The oscillatory motion of an incident Gaussian pulse inside the sample is demonstrated by both simulation and experiment.
Super Bloch Oscillation in a PT symmetric system
Turker, Z
2016-01-01
Wannier-Stark ladder in a PT symmetric system is generally complex that leads to amplified/damped Bloch oscillation. We show that a non-amplified wave packet oscillation with very large amplitude can be realized in a non-Hermitian tight binding lattice if certain conditions are satisfied. We show that pseudo PT symmetry guarantees the reality of the quasi energy spectrum in our system.
Bloch oscillations of Bose-Einstein condensates: breakdown and revival.
Witthaut, D; Werder, M; Mossmann, S; Korsch, H J
2005-03-01
We investigate the dynamics of Bose-Einstein condensates in a tilted one-dimensional periodic lattice within the mean-field (Gross-Pitaevskii) description. Unlike in the linear case the Bloch oscillations decay because of nonlinear dephasing. Pronounced revival phenomena are observed. These are analyzed in detail in terms of a simple integrable model constructed by an expansion in Wannier-Stark resonance states. We also briefly discuss the pulsed output of such systems for stronger static fields.
Damping of Bloch oscillations in the Hubbard model.
Eckstein, Martin; Werner, Philipp
2011-10-28
Using nonequilibrium dynamical mean-field theory, we study the isolated Hubbard model in a static electric field in the limit of weak interactions. Linear response behavior is established at long times, but only if the interaction exceeds a critical value, below which the system exhibits an ac-type response with Bloch oscillations. The transition from ac to dc response is defined in terms of the universal long-time behavior of the system, which does not depend on the initial condition.
Weak solutions of the Landau-Lifshitz-Bloch equation
Le, Kim Ngan
2016-12-01
The Landau-Lifshitz-Bloch (LLB) equation is a formulation of dynamic micromagnetics valid at all temperatures, treating both the transverse and longitudinal relaxation components important for high-temperature applications. We study LLB equation in case the temperature raised higher than the Curie temperature. The existence of weak solution is showed and its regularity properties are also discussed. In this way, we lay foundations for the rigorous theory of LLB equation that is currently not available.
Continuity, the Bloch-Torrey equation, and Diffusion MRI
Hall, Matt G
2016-01-01
The Bloch equation describes the evolution of classical particles tagged with a magnetisation vector in a strong magnetic field and is fundamental to many NMR and MRI contrast methods. The equation can be generalised to include the effects of spin motion by including a spin flux, which typically contains a Fickian diffusive term and/or a coherent velocity term. This form is known as the Bloch-Torrey equation, and is fundamental to MR modalities which are sensitive to spin dynamics such as diffusion MRI. Such modalities have received a great deal of interest in the research literature over the last few years, resulting in a huge range of models and methods. In this work we make make use of a more general Bloch-Torrey equation with a generalised flux term. We show that many commonly employed approaches in Diffusion MRI may be viewed as different choices for the flux terms in this equation. This viewpoint, although obvious theoretically, is not usually emphasised in the diffusion MR literature and points to inte...
Directory of Open Access Journals (Sweden)
Bernhard Streck
2012-10-01
Full Text Available The essay wants to deconstruct the genre of utopias so popular in the 20th century political writings. Human history shows manifold respect to stories about non-existent worlds which mix reality and non-reality, but outside the area of Abrahamitic beliefs there was rarely hope for a future. The secular version of such eschatological teachings begins with Karl Marx in the 19th century and culminates in the prophetic as well as revolutionary writings of Ernst Bloch around the terrible wars of the 20th century. This philosopher succeeded in both parts of post-war Germany and is still venerated inside and outside the academias. Compared with the so-called dystopias of Max Weber, Aldous Huxley or George Orwell the political visions of Bloch lack any sense of reality and seem to be quite useless to the understanding of present tendencies in world politics.
Effect of noise on trace distance of remote state preparation
Institute of Scientific and Technical Information of China (English)
Chen Ai-Xi; Li Jia-Hua
2005-01-01
The influence of noise on the remote preparation of a qubit by an entangled pair is investigated. In Bloch sphere representation, we use the trace distance to describe how close the final state is to the original state to be prepared.Our studies include two cases. Firstly, we consider the sender and the receiver sharing a mixture of two Bell states as quantum channel in remote state preparation (RSP), and calculate the trace distance as a function of mixture ratio and angle of a state to be prepared. Secondly, the system-environment interaction is taken into account by including stochastic fluctuating terms in the system Hamiltonian. Solving the Bloch equations, we obtain the evolution density matrix of the system. We then apply this stochastic model to study the effect of noise on the trace distance of RSP.
A refined Bloch group and the third homology of SL_2 of a field
Hutchinson, Kevin
2011-01-01
We introduce a variation of the Bloch group of a field F, which we call the refined Bloch group of F, and which bears essentially the same relationship to the third integral homology of SL_2 of the field as the classical Bloch group has to the indecomposable K_3 of the field. We use the properties of the refined Bloch group to prove that H_3 of SL_2 of a global field is never finitely generated, and to calculate - up to some 2- and 3-torsion - H_3 of SL_2 of local fields with finite residue field of odd characteristic.
Duality and Distance Formulas in Spaces Defined by Means of Oscillation
Perfekt, Karl-Mikael
2011-01-01
For the classical space of functions with bounded mean oscillation, it is well known that VMO** = BMO and there are many characterizations of the distance from a function f in BMO to VMO. When considering the Bloch space, results in the same vein are available with respect to the little Bloch space. In this paper such duality results and distance formulas are obtained by pure functional analysis. Applications include general M\\"obius invariant spaces such as Q_K-spaces, Lipschitz-H\\"older spaces and rectangular BMO of several variables.
The Bloch wave operator: generalizations and applications: Part I. The time-independent case
Energy Technology Data Exchange (ETDEWEB)
Killingbeck, John P [Mathematics Department, University of Hull, Hull HU6 7RX (United Kingdom); Jolicard, Georges [Observatoire de Besancon (UMR-CNRS 6091), Universite de Franche-Comte, 41 bis, Avenue de l' Observatoire, 25000 Besancon (France)
2003-05-23
This is part 1 of a two-part review on wave operator theory and methods. The basic theory of the time-independent wave operator is presented in terms of partitioned matrix theory for the benefit of general readers, with a discussion of the links between the matrix and projection operator approaches. The matrix approach is shown to lead to simple derivations of the wave operators and effective Hamiltonians of Loewdin, Bloch, Des Cloizeaux and Kato as well as to some associated variational forms. The principal approach used throughout stresses the solution of the nonlinear equation for the reduced wave operator, leading to the construction of the effective Hamiltonians of Bloch and of Des Cloizeaux. Several mathematical techniques which are useful in implementing this approach are explained, some of them being relatively little known in the area of wave operator calculations. The theoretical discussion is accompanied by several specimen numerical calculations which apply the described techniques to a selection of test matrices taken from the previous literature on wave operator methods. The main emphasis throughout is on the use of numerical methods which use iterative or perturbation algorithms, with simple Pade approximant methods being found sufficient to deal with most of the cases of divergence which are encountered. The use of damping factors and relaxation parameters is found to be effective in stabilizing calculations which use the energy-dependent effective Hamiltonian of Loewdin. In general the computations suggest that the numerical applications of the nonlinear equation for the reduced wave operator are best carried out with the equation split into a pair of equations in which the Bloch effective Hamiltonian appears as a separate entity. The presentation of the theoretical and computational details throughout is accompanied by references to and discussion of many works which have used wave operator methods in physics, chemistry and engineering. Some of
Traffic restrictions on Routes Bloch, Maxwell and Bohr
TS Department
2008-01-01
Excavation and pipework is being carried out in the framework of the transfer of the waste water treatment plant for the effluents from the surface treatment workshops from Building 254 to Building 676, currently under construction. This work may encroach onto Routes Bloch, Maxwell and Bohr and disrupt the flow of traffic. Users are requested to comply with the road signs that will be erected. The work is expected to last until the beginning of December 2008. Thank you for your understanding. TS/CE and TS/FM Groups Tel.7 4188 or 16 4314
Tunable photonic Bloch oscillations in electrically modulated photonic crystals.
Wang, Gang; Huang, Ji Ping; Yu, Kin Wah
2008-10-01
We exploit theoretically the occurrence and tunability of photonic Bloch oscillations (PBOs) in one-dimensional photonic crystals (PCs) containing nonlinear composites. Because of the enhanced third-order nonlinearity (Kerr-type nonlinearity) of composites, photons undergo oscillations inside tilted photonic bands, which are achieved by the application of graded external-pump electric fields on such PCs, varying along the direction perpendicular to the surface of layers. The tunability of PBOs (including amplitude and period) is readily achieved by changing the field gradient. With an appropriate graded pump ac or dc electric field, terahertz PBOs can appear and cover a terahertz band in an electromagnetic spectrum.
Localization without recurrence and pseudo-Bloch oscillations in optics.
Longhi, Stefano
2015-10-15
Dynamical localization, i.e., the absence of secular spreading of a quantum or classical wave packet, is usually associated with Hamiltonians by the pure point spectrum, i.e., with a normalizable and complete set of eigenstates. Such systems always show quasi-periodic dynamics (recurrence). Here, we show, rather counter-intuitively, that dynamical localization can be observed in Hamiltonians with an absolutely continuous spectrum, where recurrence effects are forbidden. An optical realization of such a Hamiltonian is proposed based on beam propagation in a self-imaging optical resonator with a phase grating. Localization without recurrence in this system is explained in terms of pseudo-Bloch optical oscillations.
Plasmonic Bloch oscillations in cylindrical metal-dielectric waveguide arrays.
Shiu, Ruei-Cheng; Lan, Yung-Chiang; Chen, Chin-Min
2010-12-01
This study investigates plasmonic Bloch oscillations (PBOs) in cylindrical metal-dielectric waveguide arrays (MDWAs) by performing numerical simulations and theoretical analyses. Optical conformal mapping is used to transform cylindrical MDWAs into equivalent chirped structures with permittivity and permeability gradients across the waveguide arrays, which is caused by the curvature of the cylindrical waveguide. The PBOs are attributed to the transformed structure. The period of oscillation increases with the wavelength of the incident Gaussian beam. However, the amplitude of oscillation is almost independent of wavelength.
Localization without recurrence and pseudo-Bloch oscillations in optics
Longhi, Stefano
2015-01-01
Dynamical localization, i.e. the absence of secular spreading of a quantum or classical wave packet, is usually associated to Hamiltonians with purely point spectrum, i.e. with a normalizable and complete set of eigenstates, which show quasi-periodic dynamics (recurrence). Here we show rather counter-intuitively that dynamical localization can be observed in Hamiltonians with absolutely continuous spectrum, where recurrence effects are forbidden. An optical realization of such an Hamiltonian is proposed based on beam propagation in a self-imaging optical resonator with a phase grating. Localization without recurrence in this system is explained in terms of pseudo-Bloch optical oscillations.
Photon BLOCH oscillations in porous silicon optical superlattices.
Agarwal, V; del Río, J A; Malpuech, G; Zamfirescu, M; Kavokin, A; Coquillat, D; Scalbert, D; Vladimirova, M; Gil, B
2004-03-01
We report the first observation of oscillations of the electromagnetic field in an optical superlattice based on porous silicon. These oscillations are an optical equivalent of well-known electronic Bloch oscillations in crystals. Elementary cells of our structure are composed by microcavities whose coupling gives rise to the extended collective modes forming optical minigaps and minibands. By varying thicknesses of the cavities along the structure axis, we have created an effective electric field for photons. A very high quality factor of the confined optical state of the Wannier-Stark ladder may allow lasing in porous silicon-based superlattices.
Plasmonic Bloch oscillations in monolayer graphene sheet arrays.
Fan, Yang; Wang, Bing; Huang, He; Wang, Kai; Long, Hua; Lu, Peixiang
2014-12-15
We investigate the spatial plasmonic Bloch oscillations (BOs) in the monolayer graphene sheet arrays (MGSAs) as the surface plasmon polaritons (SPPs) between graphene in the arrays experience weak coupling. In order to realize BOs, linear gradient of the potential is introduced by changing the chemical potentials of individual graphene sheets or the interlayer space between graphene. Numerical simulations show that the complete plasmonic BOs can be observed in the former MGSAs. However, only harmonic oscillations occur in the latter of varying interlayer space. Theoretical analysis based on the coupled-mode theory agrees well with the numerical simulations.
Tunable photonic Bloch oscillations in electrically modulated photonic crystals
Wang, Gang; Yu, Kin Wah
2008-01-01
We exploit theoretically the occurrence and tunability of photonic Bloch oscillations (PBOs) in one-dimensional photonic crystals (PCs) containing nonlinear composites. Because of the enhanced third-order nonlinearity (Kerr type nonlinearity) of composites, photons undergo oscillations inside tilted photonic bands, which are achieved by the application of graded external pump electric fields on such PCs, varying along the direction perpendicular to the surface of layers. The tunability of PBOs (including amplitude and period) is readily achieved by changing the field gradient. With an appropriate graded pump AC or DC electric field, terahertz PBOs can appear and cover a terahertz band in electromagnetic spectrum.
From Bloch to random lasing in ZnO self-assembled nanostructures
DEFF Research Database (Denmark)
Garcia-Fernandez, Pedro David; Cefe, López
2013-01-01
In this paper, we present measurements on UV lasing in ZnO ordered and disordered nanostructures. Bloch lasing is achieved in the ordered structures by exploiting very low group-velocity Bloch modes in ZnO photonic crystals. In the second case, random lasing is observed in ZnO photonic glasses. W...
Bloch oscillations and mean-field effects of Bose-Einstein condensates in 1D optical lattices.
Morsch, O; Müller, J H; Cristiani, M; Ciampini, D; Arimondo, E
2001-10-01
We have loaded Bose-Einstein condensates into one-dimensional, off-resonant optical lattices and accelerated them by chirping the frequency difference between the two lattice beams. For small values of the lattice well depth, Bloch oscillations were observed. Reducing the potential depth further, Landau-Zener tunneling out of the lowest lattice band, leading to a breakdown of the oscillations, was also studied and used as a probe for the effective potential resulting from mean-field interactions as predicted by Choi and Niu [Phys. Rev. Lett. 82, 2022 (1999)]. The effective potential was measured for various condensate densities and trap geometries, yielding good qualitative agreement with theoretical calculations.
Bloch-Zener oscillations in a tunable optical honeycomb lattice
Energy Technology Data Exchange (ETDEWEB)
Uehlinger, Thomas; Greif, Daniel; Jotzu, Gregor; Esslinger, Tilman [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich (Switzerland); Tarruell, Leticia [Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland and LP2N, Universite Bordeaux 1, IOGS, CNRS, 351 cours de la Liberation, 33405 Talence (France)
2013-12-04
Ultracold gases in optical lattices have proved to be a flexible tool to simulate many different phenomena of solid state physics [1, 2]. Recently, optical lattices with complex geometries have been realized [3, 4, 5, 6, 7], paving the way to simulating more realistic systems. The honeycomb structure has recently become accessible in an optical lattice composed of mutually perpendicular laser beams. This lattice structure exhibits topological features in its band structure – the Dirac points. At these points, two energy bands intersect linearly and the particles behave as relativistic Dirac fermions. In optical lattices, Bloch oscillations [8] resolved both in time and in quasi-momentum space can be directly observed. We make use of such Bloch-Zener oscillations to probe the vanishing energy gap at the Dirac points as well as their position in the band structure. In small band gap regions, we observe Landau-Zener tunneling [7, 9] to the second band and the regions of maximum transfer can be identified with the position of the Dirac points.
Bloch-Redfield equations for modeling light-harvesting complexes.
Jeske, Jan; Ing, David J; Plenio, Martin B; Huelga, Susana F; Cole, Jared H
2015-02-14
We challenge the misconception that Bloch-Redfield equations are a less powerful tool than phenomenological Lindblad equations for modeling exciton transport in photosynthetic complexes. This view predominantly originates from an indiscriminate use of the secular approximation. We provide a detailed description of how to model both coherent oscillations and several types of noise, giving explicit examples. All issues with non-positivity are overcome by a consistent straightforward physical noise model. Herein also lies the strength of the Bloch-Redfield approach because it facilitates the analysis of noise-effects by linking them back to physical parameters of the noise environment. This includes temporal and spatial correlations and the strength and type of interaction between the noise and the system of interest. Finally, we analyze a prototypical dimer system as well as a 7-site Fenna-Matthews-Olson complex in regards to spatial correlation length of the noise, noise strength, temperature, and their connection to the transfer time and transfer probability.
Ley-Chavez, Adriana; Hmar-Lagroun, Tatiana; Douglas-Ntagha, Pamela; Cumbo, Charlotte L
2016-01-01
Inefficient facility layouts have been found to be a challenge in health care, with excessive walking adding to the demands of staff and creating delays, which can impact the quality of care. Minimizing unnecessary transportation during care delivery improves efficiency, reduces delays, and frees up resources for use on value-added activities. This article presents a methodology and application of facility design to improve responsiveness and efficiency at a large hospital. The approach described provides the opportunity to improve existing layouts in facilities in which the floor plan is already defined, but there is some flexibility to relocate key areas. The existing physical constraints and work flows are studied and taken into consideration, and the volume of traffic flow throughout the facility guides the decision of where to relocate areas for maximum efficiency. Details on the steps followed and general recommendations to perform the necessary process and data analyses are provided. We achieved a 34.8% reduction in distance walked (4740 miles saved per year) and a 30% reduction in floors traveled in elevators (344 931 floors, which translate to 842 hours spent using elevators) by relocating 4 areas in which frequently used resources are housed.
Directory of Open Access Journals (Sweden)
Bin Liu
Full Text Available Playing crucial roles in various cellular processes, such as recognition of specific nucleotide sequences, regulation of transcription, and regulation of gene expression, DNA-binding proteins are essential ingredients for both eukaryotic and prokaryotic proteomes. With the avalanche of protein sequences generated in the postgenomic age, it is a critical challenge to develop automated methods for accurate and rapidly identifying DNA-binding proteins based on their sequence information alone. Here, a novel predictor, called "iDNA-Prot|dis", was established by incorporating the amino acid distance-pair coupling information and the amino acid reduced alphabet profile into the general pseudo amino acid composition (PseAAC vector. The former can capture the characteristics of DNA-binding proteins so as to enhance its prediction quality, while the latter can reduce the dimension of PseAAC vector so as to speed up its prediction process. It was observed by the rigorous jackknife and independent dataset tests that the new predictor outperformed the existing predictors for the same purpose. As a user-friendly web-server, iDNA-Prot|dis is accessible to the public at http://bioinformatics.hitsz.edu.cn/iDNA-Prot_dis/. Moreover, for the convenience of the vast majority of experimental scientists, a step-by-step protocol guide is provided on how to use the web-server to get their desired results without the need to follow the complicated mathematic equations that are presented in this paper just for the integrity of its developing process. It is anticipated that the iDNA-Prot|dis predictor may become a useful high throughput tool for large-scale analysis of DNA-binding proteins, or at the very least, play a complementary role to the existing predictors in this regard.
Sanchis-Alepuz, Helios; Kosevich, Yuriy A; Sánchez-Dehesa, José
2007-03-30
We demonstrate the existence of Bloch oscillations of acoustic fields in sound propagation through a superlattice of water cavities and layers of methyl methacrylate. To obtain the acoustic equivalent of a Wannier-Stark ladder, we employ a set of cavities with different thicknesses. Bloch oscillations are observed as time-resolved oscillations of transmission in a direct analogy to electronic Bloch oscillations in biased semiconductor superlattices. Moreover, for a particular gradient of cavity thicknesses, an overlap of two acoustic minibands occurs, which results in resonant Zener-like transmission enhancement.
Inducing transport in a dissipation-free lattice with super Bloch oscillations.
Haller, Elmar; Hart, Russell; Mark, Manfred J; Danzl, Johann G; Reichsöllner, Lukas; Nägerl, Hanns-Christoph
2010-05-21
Particles in a perfect lattice potential perform Bloch oscillations when subject to a constant force, leading to localization and preventing conductivity. For a weakly interacting Bose-Einstein condensate of Cs atoms, we observe giant center-of-mass oscillations in position space with a displacement across hundreds of lattice sites when we add a periodic modulation to the force near the Bloch frequency. We study the dependence of these "super" Bloch oscillations on lattice depth, modulation amplitude, and modulation frequency and show that they provide a means to induce linear transport in a dissipation-free lattice.
Bender, N; Ellis, F M; Kottos, T
2015-01-01
We propose a family of {\\it local} $\\cal{PT}$-symmetric photonic lattices with transverse index gradient $\\omega$, where the emergence of {\\it stable} Bloch-Zener oscillations are controlled by the degree of non-Hermiticity $\\gamma$ of the lattice. In the exact $\\cal{PT}$-symmetric phase we identify a condition between $\\omega$ and $\\gamma$ for which a wavepacket self -imaging together with a cascade of splittings and giant recombinations occurs at various propagation distances. The giant wavepacket recombination is further enhanced by introducing local impurities.
Coulomb blockade and BLOCH oscillations in superconducting Ti nanowires.
Lehtinen, J S; Zakharov, K; Arutyunov, K Yu
2012-11-01
Quantum fluctuations in quasi-one-dimensional superconducting channels leading to spontaneous changes of the phase of the order parameter by 2π, alternatively called quantum phase slips (QPS), manifest themselves as the finite resistance well below the critical temperature of thin superconducting nanowires and the suppression of persistent currents in tiny superconducting nanorings. Here we report the experimental evidence that in a current-biased superconducting nanowire the same QPS process is responsible for the insulating state--the Coulomb blockade. When exposed to rf radiation, the internal Bloch oscillations can be synchronized with the external rf drive leading to formation of quantized current steps on the I-V characteristic. The effects originate from the fundamental quantum duality of a Josephson junction and a superconducting nanowire governed by QPS--the QPS junction.
Landau-Lifhsitz-Bloch equation for exchange coupled grains
Vogler, Christoph; Bruckner, Florian; Suess, Dieter
2014-01-01
Heat assisted recording is a promising technique to further increase the storage density in hard disks. Multilayer recording grains with graded Curie temperature is discussed to further assist the write process. Describing the correct magnetization dynamics of these grains, from room temperature to far above the Curie point, during a write process is required for the calculation of bit error rates. We present a coarse grained approach based on the Landau-Lifshitz-Bloch (LLB) equation to model exchange coupled grains with low computational effort. The required temperature dependent material properties such as the zero-field equilibrium magnetization as well as the parallel and normal susceptibilities are obtained by atomistic Landau-Lifshitz-Gilbert (LLB) simulations. Each grain is described with one magnetization vector. In order to mimic the atomistic exchange interaction between the grains a special treatment of the exchange field in the coarse grained approach is presented.
Bloch-Messiah reduction of Gaussian unitaries by Takagi factorization
Cariolaro, Gianfranco; Pierobon, Gianfranco
2016-12-01
The Bloch-Messiah (BM) reduction allows the decomposition of an arbitrarily complicated Gaussian unitary into a very simple scheme in which linear optical components are separated from nonlinear ones. The nonlinear part is due to the squeezing possibly present in the Gaussian unitary. The reduction is usually obtained by exploiting the singular value decomposition (SVD) of the matrices appearing in the Bogoliubov transformation of the given Gaussian unitary. This paper discusses a different approach, where the BM reduction is obtained in a straightforward way. It is based on the Takagi factorization of the (complex and symmetric) squeeze matrix and has the advantage of avoiding several matrix operations of the previous approach (polar decomposition, eigendecomposition, SVD, and Takagi factorization). The theory is illustrated with an application example in which the previous and present approaches are compared.
Entanglement and the three-dimensionality of the Bloch ball
Energy Technology Data Exchange (ETDEWEB)
Masanes, Ll., E-mail: ll.masanes@gmail.com [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Müller, M. P. [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany); Pérez-García, D. [Departamento de Analisis Matematico and IMI, Universidad Complutense de Madrid, 28040 Madrid (Spain); Augusiak, R. [ICFO-Institut de Ciencies Fotoniques, 08860 Castelldefels, Barcelona (Spain)
2014-12-15
We consider a very natural generalization of quantum theory by letting the dimension of the Bloch ball be not necessarily three. We analyze bipartite state spaces where each of the components has a d-dimensional Euclidean ball as state space. In addition to this, we impose two very natural assumptions: the continuity and reversibility of dynamics and the possibility of characterizing bipartite states by local measurements. We classify all these bipartite state spaces and prove that, except for the quantum two-qubit state space, none of them contains entangled states. Equivalently, in any of these non-quantum theories, interacting dynamics is impossible. This result reveals that “existence of entanglement” is the requirement with minimal logical content which singles out quantum theory from our family of theories.
Bloch-Nordsieck Estimates of High-Temperature QED
Fried, H M; Sheu, Y -M
2008-01-01
In anticipation of a subsequent application to QCD, we consider the case of QED at high temperature. We introduce a Fradkin representation into the exact, Schwingerian, functional expression of a fermion propagator, as well as a new and relevant version of the Bloch-Nordsieck (BN) model, which extracts the soft contributions of every perturbative graph, in contradistinction to the assumed separation of energy scales of previous semi-perturbative treatments. Our results are applicable to the absorption of a fast particle which enters a heat bath, as well as to the propagation of a symmetric pulse within the thermal medium due to the appearance of an instantaneous, shock-wave-like source acting in the medium. An exponentially-decreasing time dependence of the incident particle's initial momentum combines with a stronger decrease in the particle's energy, estimated by a sum over all Matsubara frequencies, to model an initial "fireball", which subsequently decays in a Gaussian fashion. When extended to QCD, quali...
Stable BLOCH oscillations of cold atoms with time-dependent interaction.
Gaul, C; Lima, R P A; Díaz, E; Müller, C A; Domínguez-Adame, F
2009-06-26
We investigate Bloch oscillations of interacting cold atoms in a mean-field framework. In general, atom-atom interaction causes dephasing and destroys Bloch oscillations. Here we show that Bloch oscillations are persistent if the interaction is modulated harmonically with suitable frequency and phase. For other modulations, Bloch oscillations are rapidly damped. We explain this behavior in terms of collective coordinates whose Hamiltonian dynamics permits one to predict a whole family of stable solutions. In order to describe also the unstable cases, we carry out a stability analysis for Bogoliubov excitations. Using Floquet theory, we are able to predict the unstable modes as well as their growth rate, found to be in excellent agreement with numerical simulations.
Bloch Oscillations of Two-Component Bose-Einstein Condensates in Optical Lattices
Institute of Scientific and Technical Information of China (English)
GU Huai-Qiang; WANG Zhi-Cheng; JIN Kang; TAN Lei
2006-01-01
@@ We study the Bloch oscillations of two-component Bose-Einstein condensates trapped in spin-dependent optical lattices. The influence of the intercomponent atom interaction on the system is discussed in detail Accelerated breakdown of the Bloch oscillations and revival phenomena are found respectively for the repulsive and attractive case. For both the cases, the system will finally be set in a quantum self-trapping state due to dynamical instability.
Imaging of Bloch oscillations in erbium-doped curved waveguide arrays.
Chiodo, N; Della Valle, G; Osellame, R; Longhi, S; Cerullo, G; Ramponi, R; Laporta, P; Morgner, U
2006-06-01
We report a direct observation of Bloch-like dynamics of light in curved waveguide arrays manufactured in Er:Yb-doped phosphate glass by femtosecond laser writing. The green upconversion fluorescence emitted by excited erbium ions is exploited to image the flow of the guided pump light at approximately 980 nm along the array. Direct and clear evidence of periodic light breathing for single-waveguide excitation, closely related to Bloch oscillations, is reported.
Photonic Bloch oscillations and Wannier-Stark ladders in exponentially chirped Bragg gratings.
Wilkinson, P B
2002-05-01
The formation of photonic Bloch oscillations and Wannier-Stark ladders is demonstrated in an exponentially chirped one-dimensional Bragg grating. The photonic Bloch oscillations are investigated using Hamiltonian optics, and direct analogies are made with electron dynamics in periodic potentials. The results of transfer matrix calculations are presented, which show the existence of a photonic Wannier-Stark ladder that should be detectable in experiments.
Band structure and Bloch states in birefringent 1D magnetophotonic crystals: An analytical approach
Lévy, M; Levy, Miguel; Jalali, Amir A
2007-01-01
An analytical formulation for the band structure and Bloch modes in elliptically birefringent magnetophotonic crystals is presented. The model incorporates both the effects of gyrotropy and linear birefringence generally present in magneto-optic thin film devices. Full analytical expressions are obtained for the dispersion relation and Bloch modes in a layered stack photonic crystal and their properties are analyzed. It is shown that other models recently discussed in the literature are contained as special limiting cases of the formulation presented herein.
Weighted Composition Operators from Bergman-Type Spaces into Bloch Spaces
Indian Academy of Sciences (India)
Songxiao Li; Stevo Stević
2007-08-01
Let be an analytic self-map and be a fixed analytic function on the open unit disk in the complex plane $\\mathbb{C}$. The weighted composition operator is defined by $$u C_\\varphi f=u\\cdot p (f\\circ\\varphi), f\\in H(D).$$ Weighted composition operators from Bergman-type spaces into Bloch spaces and little Bloch spaces are characterized by function theoretic properties of their inducing maps.
A dorsal fold in Gymnura micrura (Bloch and Scheneider, 1801 (Chondrichthyes: Gymnuridae
Directory of Open Access Journals (Sweden)
Jorge Luiz Silva Nunes
2009-04-01
Full Text Available This paper reports a dorsal fold which is a membranous structure located on the tail of two juvenile butterfly rays, Gymnura micrura (Bloch & Scheneider, 1801, caught through artisanal fishery in the shallow waters of Maranhão State (Brazil.Neste manuscrito registra-se uma nadadeira dorsal em dois espécimes juvenis de Gymnura micrura (Bloch and Scheneider, 1801 capturadas pela pesca artesanal em águas rasas do estado do Maranhão (Brasil.
2014-01-01
In this article we propose to discuss the concept of hope and daydream from the writings of Ernst Bloch and Paulo Freire. Based on the production of Ernst Bloch explored the philosophy of hope, as an expression of affection expectant positive, from the imperative to understand how the act related to a political commitment by the constitution from seeking concrete utopias. The problematization of the term from Paulo Freire, in turn, enters the discussion about the importance of Pedagogy of Hop...
Rodriguez, Gilberto A.; Lonai, John D.; Mernaugh, Raymond L.; Weiss, Sharon M.
2014-08-01
A porous silicon (PSi) Bloch surface wave (BSW) and Bloch sub-surface wave (BSSW) composite biosensor is designed and used for the size-selective detection of both small and large molecules. The BSW/BSSW structure consists of a periodic stack of high and low refractive index PSi layers and a reduced optical thickness surface layer that gives rise to a BSW with an evanescent tail that extends above the surface to enable the detection of large surface-bound molecules. Small molecules were detected in the sensor by the BSSW, which is a large electric field intensity spatially localized to a desired region of the Bragg mirror and is generated by the implementation of a step or gradient refractive index profile within the Bragg mirror. The step and gradient BSW/BSSW sensors are designed to maximize both resonance reflectance intensity and sensitivity to large molecules. Size-selective detection of large molecules including latex nanospheres and the M13KO7 bacteriophage as well as small chemical linker molecules is reported.
Bennett, Charles H; Li, Ming; Vitanyi, Paul M B; Zurek, Wojciech H
2010-01-01
While Kolmogorov complexity is the accepted absolute measure of information content in an individual finite object, a similarly absolute notion is needed for the information distance between two individual objects, for example, two pictures. We give several natural definitions of a universal information metric, based on length of shortest programs for either ordinary computations or reversible (dissipationless) computations. It turns out that these definitions are equivalent up to an additive logarithmic term. We show that the information distance is a universal cognitive similarity distance. We investigate the maximal correlation of the shortest programs involved, the maximal uncorrelation of programs (a generalization of the Slepian-Wolf theorem of classical information theory), and the density properties of the discrete metric spaces induced by the information distances. A related distance measures the amount of nonreversibility of a computation. Using the physical theory of reversible computation, we give...
Saini, Tarun Deep; Sahni, Varun
2010-01-01
By observing mergers of compact objects, future gravity wave experiments would measure the luminosity distance to a large number of sources to a high precision but not their redshifts. Given the directional sensitivity of an experiment, a fraction of such sources (gold plated -- GP) can be identified optically as single objects in the direction of the source. We show that if an approximate distance-redshift relation is known then it is possible to statistically resolve those sources that have multiple galaxies in the beam. We study the feasibility of using gold plated sources to iteratively resolve the unresolved sources, obtain the self-calibrated best possible distance-redshift relation and provide an analytical expression for the accuracy achievable. We derive lower limit on the total number of sources that is needed to achieve this accuracy through self-calibration. We show that this limit depends exponentially on the beam width and give estimates for various experimental parameters representative of futu...
Geometry of the generalized Bloch sphere for qutrit
Goyal, Sandeep K; Singh, Rajeev; Simon, Sudhavathani
2011-01-01
The geometry of the generalized Bloch sphere $\\Omega_3$, the state space of a qutrit is studied. Closed form expressions for $\\Omega_3$, its boundary $\\partial \\Omega_3$, and the set of extremals $\\Omega_3^{\\rm ext}$ are obtained by use of an elementary observation. These expressions and analytic methods are used to classify the 28 two-sections and the 56 three-sections of $\\Omega_3$ into unitary equivalence classes, completing the works of earlier authors. It is shown, in particular, that there are families of two-sections and of three-sections which are equivalent geometrically but not unitarily, a feature that does not appear to have been appreciated earlier. A family of three-sections of obese-tetrahedral shape whose symmetry corresponds to the 24-element tetrahedral point group $T_d$ is examined in detail. This symmetry is traced to the reduction of the adjoint representation of SU(3), the symmetry underlying $\\Omega_3$, into direct sum of the two-dimensional and the two (inequivalent) three-dimensional ...
Bloch wave approach to the optics of crystals.
Ponti, S; Oldano, C; Becchi, M
2001-08-01
The Bloch wave method is used to find the effective permittivity tensor epsilon of periodic liquid crystals and artificial structures whose period p is short with respect to the light wavelength lambda and whose optical properties are defined by a permittivity field epsilon(r). The main role of the multiple scattering within the periodic medium is evidenced, and very general expressions of epsilon, based on expansions in ascending powers of the ratio p/lambda and of the light wave vector k, are found. Such expansions allow to discuss the general properties of epsilon, to clarify the role of the spatial dispersions, i.e., to separate the part of epsilon explicitly depending on k from its k-independent part, and to find some interesting properties of crystals that are (i) periodic in only one direction, or (ii) locally isotropic. Finally, the limits of validity of the macroscopic model are discussed. Within these limits only a few terms of the power expansions are required, and their expressions are explicitly given. The obtained results are also useful to better understand the macroscopic optical properties of solid crystals.
Polarization controlled directional excitation of Bloch surface waves (Conference Presentation)
Kovalevich, Tatiana; Boyer, Philippe; Bernal, Maria-Pilar; Kim, Myun-Sik; Herzig, Hans Peter; Grosjean, Thierry
2016-09-01
Bloch surface waves (BSWs) are electromagnetic surface waves which can be excited at the interface between periodic dielectric multilayer and a surrounding medium. In comparison with surface plasmon polaritons these surface states perform high quality factor due to low loss characteristics of dielectric materials and can be exited both by TE and TM polarized light. A platform consisting of periodic stacks of alternative SiO2 and Si3N4 layers is designed and fabricated to work at the wavelength of 1.55 µm. The platform has an application in sensing and in integrated optics domain. A standard way of BSW excitation is coupling via Kretschmann configuration, but in this work we investigate a grating coupling of BSWs. Grating parameters are analytically and numerically optimized by RCWA and FDTD methods in order to obtain the best coupling conditions. The light is launched orthogonally to the surface of the photonic crystal and the grating. Due to a special grating configuration we demonstrate directionality of the BSW propagation depending on polarization of the incident light. The structure was experimentally realized on the surface of the photonic crystal by FIB milling. Experimental results are in a good agreement with a theory. The investigated configuration can be successfully used as a BSW launcher in on-chip all-optical integrated systems and work as a surface wave switch or modulator.
Geometry of the generalized Bloch sphere for qutrits
Goyal, Sandeep K.; Neethi Simon, B.; Singh, Rajeev; Simon, Sudhavathani
2016-04-01
The geometry of the generalized Bloch sphere Ω3, the state space of a qutrit, is studied. Closed form expressions for Ω3, its boundary ∂Ω3, and the set of extremals {{{Ω }}}3{{ext}} are obtained by use of an elementary observation. These expressions and analytic methods are used to classify the 28 two-sections and the 56 three-sections of Ω3 into unitary equivalence classes, completing the works of earlier authors. It is shown, in particular, that there are families of two-sections and of three-sections which are equivalent geometrically but not unitarily, a feature that does not appear to have been appreciated earlier. A family of three-sections of obese-tetrahedral shape whose symmetry corresponds to the 24-element tetrahedral point group T d is examined in detail. This symmetry is traced to the natural reduction of the adjoint representation of SU(3), the symmetry underlying Ω3, into direct sum of the two-dimensional and the two (inequivalent) three-dimensional irreducible representations of T d .
Directory of Open Access Journals (Sweden)
Mohammad Razaz
2015-03-01
Full Text Available This paper provides an algorithm of fault resistance compensation for digital ground distance relay considering the voltage and current transformer effects. Performance of the conventional ground distance relaying manner is adversely affected by different ground faults and also typical type, called a simultaneous open conductor and ground fault. The proposed scheme by using local-end data only, has shown satisfactory performances under wide variations in fault location, with different values of fault resistance and having positive and negative of power transfer angle. The presented method which has been carried out on the IEEE 14 bus benchmark is executed in PSCAD/EMTDC and MATLAB software, and the results show the accurate performance of mentioned configuration.
Energy Technology Data Exchange (ETDEWEB)
Lazcano, Z.; Arriaga, J., E-mail: arriaga@ifuap.buap.mx [Instituto de Física, Benemérita Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110-A, Ciudad Universitaria, 72570 Puebla (Mexico); Aliev, G. N. [Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)
2014-04-21
We report the theoretical calculations and the experimental demonstration of acoustic Bloch oscillations and Wannier-Stark ladders in linear tilted multilayer structures based on porous silicon. The considered structures consist of layers with constant porosity alternated by layers with a linear gradient in the parameter η=1/v{sub L}{sup 2} along the growth direction in order to tilt the acoustic band gap. The purpose of this gradient is to mimic the tilted electronic miniband structure of a superlattice semiconductor under an external electric field. In this way, acoustic Wannier-Stark ladders of equidistant modes are formed and they were experimentally confirmed in the transmission spectrum around 1.2 GHz. Their frequency separation defines the period of the acoustic Bloch oscillations. We fabricated three different structures with the same thicknesses but different values in the η parameter to observe the effect on the period of the Bloch oscillations. We measured the acoustic transmission spectra in the frequency domain, and by using the Fourier transform, we obtained the transmission in the time domain. The transmission spectra of the fabricated samples show acoustic Bloch oscillations with periods of 27, 24, and 19 ns. The experimental results are in good agreement with the transfer matrix calculations. The observed phenomenon is the acoustic counterpart of the well known electronic Bloch oscillations.
Bloch Oscillation in a One-Dimensional Array of Small Josephson Junctions
Shimada, Hiroshi; Katori, Shunsuke; Gandrothula, Srinivas; Deguchi, Tomoaki; Mizugaki, Yoshinao
2016-07-01
A distinct Bloch nose was demonstrated in the current-voltage characteristics of a one-dimensional array of 20 small Josephson junctions. Arrays of direct-current superconducting quantum interference device (dc-SQUID) structures were used as leads to the array of junctions, and the environmental impedance was tuned with a magnetic field. The observed Bloch nose had a negative differential resistance of its magnitude of as large as 14.3 MΩ, a blockade voltage of 0.36 mV, and a decrease in voltage of 0.21 mV due to the Bloch oscillation, all of which are larger than those obtained in a single junction by more than one order. The observed Bloch oscillation was quantitatively described on the basis of the Bloch oscillation of each single junction in combination with the charge soliton model in a long array. Unexpected constant-current spikes, whose origin lay in the dc-SQUID in the leads, were also observed to be superposed on the current-voltage characteristics when the Coulomb blockade appeared.
Non-destructive monitoring of Bloch oscillations in an optical cavity
Keßler, H; Venkatesh, B P; Georges, Ch; Hemmerich, A
2016-01-01
Bloch oscillations are a hallmark of coherent wave dynamics in periodic potentials. They occur as the response of quantum mechanical particles in a lattice if a weak force is applied. In optical lattices with their perfect periodic structure they can be readily observed and employed as a quantum mechanical force sensor, for example, for precise measurements of the gravitational acceleration. However, the destructive character of the measurement process in previous experimental implementations poses serious limitations for the precision of such measurements. In this article we show that the use of an optical cavity operating in the regime of strong cooperative coupling allows one to directly monitor Bloch oscillations of a cloud of cold atoms in the light leaking out of the cavity. Hence, with a single atomic sample the Bloch oscillation dynamics can be mapped out, while in previous experiments, each data point required the preparation of a new atom cloud. The use of a cavity-based monitor should greatly impro...
Observation of Bloch oscillations in complex PT-symmetric photonic lattices
Wimmer, Martin; Christodoulides, Demetrios; Peschel, Ulf
2016-01-01
Light propagation in periodic environments is often associated with a number of interesting and potentially useful processes. If a crystalline optical potential is also linearly ramped, light can undergo periodic Bloch oscillations, a direct outcome of localized Wannier-Stark states and their equidistant eigenvalue spectrum. Even though these effects have been extensively explored in conservative settings, this is by no means the case in non-Hermitian photonic lattices encompassing both amplification and attenuation. Quite recently, Bloch oscillations have been predicted in parity-time-symmetric structures involving gain and loss in a balanced fashion. While in a complex bulk medium, one intuitively expects that light will typically follow the path of highest amplification, in a periodic system this behavior can be substantially altered by the underlying band structure. Here, we report the first experimental observation of Bloch oscillations in parity-time-symmetric mesh lattices. We show that these revivals ...
Bloch bound states in the radiation continuum in a periodic array of dielectric rods
Bulgakov, Evgeny N
2014-01-01
We consider an infinite periodic array of dielectric rods in vacuum with the aim to demonstrate three types of a Bloch bound states in the continuum (BSC), symmetry protected with a zero Bloch vector, embedded into one diffraction channel with nonzero Bloch vector, and embedded into two and three diffraction channels. The first and second types of the BSC exist in a wide range of material parameters of the rods, while the third occurs only at a specific value of the radius of the rods. We show that the second type supports the power flux along the array. In order to find BSC we put forward an approach based on the expansion over the Hankel functions. We show how the BSC reveals itself in the scattering function when the singular BSC point is approached along a specific path in the parametric space.
Bloch wave deafness and modal conversion at a phononic crystal boundary
Directory of Open Access Journals (Sweden)
Vincent Laude
2011-12-01
Full Text Available We investigate modal conversion at the boundary between a homogeneous incident medium and a phononic crystal, with consideration of the impact of symmetry on the excitation of Bloch waves. We give a quantitative criterion for the appearance of deaf Bloch waves, which are antisymmetric with respect to a symmetry axis of the phononic crystal, in the frame of generalized Fresnel formulas for reflection and transmission at the phononic crystal boundary. This criterion is used to index Bloch waves in the complex band structure of the phononic crystal, for directions of incidence along a symmetry axis. We argue that within deaf frequency ranges transmission is multi-exponential, as it is within frequency band gaps.
Experimental realization of Bloch oscillations in a parity-time synthetic silicon photonic lattice.
Xu, Ye-Long; Fegadolli, William S; Gan, Lin; Lu, Ming-Hui; Liu, Xiao-Ping; Li, Zhi-Yuan; Scherer, Axel; Chen, Yan-Feng
2016-04-20
As an important electron transportation phenomenon, Bloch oscillations have been extensively studied in condensed matter. Due to the similarity in wave properties between electrons and other quantum particles, Bloch oscillations have been observed in atom lattices, photonic lattices, and so on. One of the many distinct advantages for choosing these systems over the regular electronic systems is the versatility in engineering artificial potentials. Here by utilizing dissipative elements in a CMOS-compatible photonic platform to create a periodic complex potential and by exploiting the emerging concept of parity-time synthetic photonics, we experimentally realize spatial Bloch oscillations in a non-Hermitian photonic system on a chip level. Our demonstration may have significant impact in the field of quantum simulation by following the recent trend of moving complicated table-top quantum optics experiments onto the fully integrated CMOS-compatible silicon platform.
Integral type operators from normal weighted Bloch spaces to QT,S spaces
Directory of Open Access Journals (Sweden)
Yongyi GU
2016-08-01
Full Text Available Operator theory is an important research content of the analytic function space theory. The discussion of simultaneous operator and function space is an effective way to study operator and function space. Assuming that is an analytic self map on the unit disk Δ, and the normal weighted bloch space μ-B is a Banach space on the unit disk Δ, defining a composition operator C∶C(f=f on μ-B for all f∈μ-B, integral type operator JhC and CJh are generalized by integral operator and composition operator. The boundeness and compactness of the integral type operator JhC acting from normal weighted Bloch spaces to QT,S spaces are discussed, as well as the boundeness of the integral type operators CJh acting from normal weighted Bloch spaces to QT,S spaces. The related sufficient and necessary conditions are given.
Bloch wave deafness and modal conversion at a phononic crystal boundary
Laude, Vincent; Moiseyenko, Rayisa P.; Benchabane, Sarah; Declercq, Nico F.
2011-12-01
We investigate modal conversion at the boundary between a homogeneous incident medium and a phononic crystal, with consideration of the impact of symmetry on the excitation of Bloch waves. We give a quantitative criterion for the appearance of deaf Bloch waves, which are antisymmetric with respect to a symmetry axis of the phononic crystal, in the frame of generalized Fresnel formulas for reflection and transmission at the phononic crystal boundary. This criterion is used to index Bloch waves in the complex band structure of the phononic crystal, for directions of incidence along a symmetry axis. We argue that within deaf frequency ranges transmission is multi-exponential, as it is within frequency band gaps.
Observation of fractional Bloch band quantum Hall states in graphene/h-BN superlattices
Wang, Lei; Gao, Yuanda; Wen, Bo; Hone, James; Dean, Cory
The Hofstadter energy spectrum provides a uniquely tunable system to study emergent topological order in the regime of strong interactions. Previous experiments, however, have been limited to low Bloch band fillings where only the Landau level index plays a role. Here we report measurements of high mobility graphene superlattices where the complete unit cell of the Hofstadter spectrum is accessible. We observe coexistence of conventional fractional quantum Hall effect (QHE) states together with the integer QHE states associated with the fractal Hofstadter spectrum. At large magnetic field, we observe signatures of another series of states, which appears at fractional Bloch filling index. These fractional Bloch band QHE states are not anticipated by existing theoretical pictures and point towards a distinct type of many-body state.
Experimental realization of Bloch oscillations in a parity-time synthetic silicon photonic lattice
Xu, Ye-Long; Fegadolli, William S.; Gan, Lin; Lu, Ming-Hui; Liu, Xiao-Ping; Li, Zhi-Yuan; Scherer, Axel; Chen, Yan-Feng
2016-04-01
As an important electron transportation phenomenon, Bloch oscillations have been extensively studied in condensed matter. Due to the similarity in wave properties between electrons and other quantum particles, Bloch oscillations have been observed in atom lattices, photonic lattices, and so on. One of the many distinct advantages for choosing these systems over the regular electronic systems is the versatility in engineering artificial potentials. Here by utilizing dissipative elements in a CMOS-compatible photonic platform to create a periodic complex potential and by exploiting the emerging concept of parity-time synthetic photonics, we experimentally realize spatial Bloch oscillations in a non-Hermitian photonic system on a chip level. Our demonstration may have significant impact in the field of quantum simulation by following the recent trend of moving complicated table-top quantum optics experiments onto the fully integrated CMOS-compatible silicon platform.
The Bloch-vector space for N-level systems -- the spherical-coordinate point of view --
Kimura, G
2003-01-01
The Bloch-vector spaces for $N$-level systems are investigated from the spherical-coordinate point of view. We find that the maximum radius in each direction, which is due to the construction of the Bloch-vector space, is determined by the minimum eigenvalue of the corresponding observable (generator of SU(N)). As one of the applications of this, we reveal the dual properties of the structure of the Bloch-vector space; if one of the direction of the Bloch vector reaches the large ball (pure state), the opposite direction can only reach the small ball, and vice versa. This also leads us to the new representation of quantum states which generalize the Bloch vector.
Atomic Bloch-Zener oscillations and Stückelberg interferometry in optical lattices.
Kling, Sebastian; Salger, Tobias; Grossert, Christopher; Weitz, Martin
2010-11-19
We report on experiments investigating quantum transport and band interferometry of an atomic Bose-Einstein condensate in an optical lattice with a two-band miniband structure, realized with a Fourier-synthesized optical lattice potential. Bloch-Zener oscillations, the coherent superposition of Bloch oscillations and Landau-Zener tunneling between the two bands, are observed. When the relative phase between paths in different bands is varied, an interference signal is observed, demonstrating the coherence of the dynamics in the miniband system. Measured fringe patterns of this Stückelberg interferometer allow us to interferometrically map out the band structure of the optical lattice over the full Brillouin zone.
Sankin, Vladimir; Andrianov, Alexandr; Petrov, Alexey; Zakhar'in, Alexey; Lepneva, Ala; Shkrebiy, Pavel
2012-10-09
: We report on efficient terahertz (THz) emission from high-electric-field-biased SiC structures with a natural superlattice at liquid helium temperatures. The emission spectrum demonstrates a single line, the maximum of which shifts linearly with increases in bias field. We attribute this emission to steady-state Bloch oscillations of electrons in the SiC natural superlattice. The properties of the THz emission agree fairly with the parameters of the Bloch oscillator regime, which have been proven by high-field electron transport studies of SiC structures with natural superlattices.
Bloch-Zener oscillations across a merging transition of Dirac points.
Lim, Lih-King; Fuchs, Jean-Noël; Montambaux, Gilles
2012-04-27
Bloch oscillations are a powerful tool to investigate spectra with Dirac points. By varying band parameters, Dirac points can be manipulated and merged at a topological transition toward a gapped phase. Under a constant force, a Fermi sea initially in the lower band performs Bloch oscillations and may Zener tunnel to the upper band mostly at the location of the Dirac points. The tunneling probability is computed from the low-energy universal Hamiltonian describing the vicinity of the merging. The agreement with a recent experiment on cold atoms in an optical lattice is very good.
Schrodinger cat states prepared by Bloch oscillation in a spin-dependent optical lattice
Wu, B J
2011-01-01
We propose to use Bloch oscillation of ultra-cold atoms in a spin-dependent optical lattice to prepare schrodinger cat states. Depending on its internal state, an atom feels different periodic potentials and thus has different energy band structures for its center-of-mass motion. Consequently, under the same gravity force, the wave packets associated with different internal states perform Bloch oscillation of different amplitudes in space and in particular they can be macroscopically displaced with respect to each other. In this way, a cat state can be prepared.
Nearly three orders of magnitude enhancement of Goos-Hanchen shift by exciting Bloch surface wave.
Wan, Yuhang; Zheng, Zheng; Kong, Weijing; Zhao, Xin; Liu, Ya; Bian, Yusheng; Liu, Jiansheng
2012-04-09
Goos-Hanchen effect is experimentally studied when the Bloch surface wave is excited in the forbidden band of a one-dimensional photonic band-gap structure. By tuning the refractive index of the cladding covering the truncated photonic crystal structure, either a guided or a surface mode can be excited. In the latter case, strong enhancement of the Goos-Hanchen shift induced by the Bloch-surface-wave results in sub-millimeter shifts of the reflected beam position. Such giant Goos-Hanchen shift, ~750 times of the wavelength, could enable many intriguing applications that had been less than feasible to implement before.
Generation of Entangled Bloch States for Two Atomic Samples Trapped in Separated Cavities
Institute of Scientific and Technical Information of China (English)
ZHENG Shi-Biao
2007-01-01
A scheme is presented for the generation of entangled states for two atomic ensembles trapped in two distant cavities.In the scheme,each atomic sample is initially in a Bloch state and the cavity mode is initially in a coherent state with a small amplitude.The dispersive atom-cavity interaction leads to a photon-number dependent phase shift on the atomic system.The detection of a photon leaking from the cavities makes the two atomic samples collapse to an entangled Bloch state.
McQuinn, Kristen B W; Dolphin, Andrew E; Berg, Danielle; Kennicutt, Robert
2016-01-01
Great investments of observing time have been dedicated to the study of nearby spiral galaxies with diverse goals ranging from understanding the star formation process to characterizing their dark matter distributions. Accurate distances are fundamental to interpreting observations of these galaxies, yet many of the best studied nearby galaxies have distances based on methods with relatively large uncertainties. We have started a program to derive accurate distances to these galaxies. Here we measure the distance to M51 - the Whirlpool galaxy - from newly obtained Hubble Space Telescope optical imaging using the tip of the red giant branch method. We measure the distance modulus to be 8.58+/-0.10 Mpc (statistical), corresponding to a distance modulus of 29.67+/-0.02 mag. Our distance is an improvement over previous results as we use a well-calibrated, stable distance indicator, precision photometry in a optimally selected field of view, and a Bayesian Maximum Likelihood technique that reduces measurement unce...
DEFF Research Database (Denmark)
Zhukovsky, Sergei; Lavrinenko, Andrei
2012-01-01
We propose proof-of-concept designs of Bragg reflectors and Fabry-Pe´rot resonators for large wave vector waves (Bloch bulk plasmon polaritons) in multilayer metal-dielectric hyperbolic metamaterials. The designs are based on hybrid multilayers having both subwavelength and wavelength...
Floquet-Bloch waves and suppression of vibrations in multi-scale fluid-solid systems
Carta, Giorgio; Movchan, Alexander B
2016-01-01
The paper presents a mathematical model for an industry inspired problem of vibration isolation applied to a cluster of elastic fluid-filled containers. We develop a systematic approach employing full fluid-solid interaction and Floquet-Bloch waves in periodic multi-scale systems. The analytical findings are accompanied by numerical simulations, including frequency response analyses and computations in the transient regime.
Dynamic localization and Bloch oscillations in the spectrum of a frequency mode-locked laser.
Longhi, Stefano
2005-04-01
It is shown that a frequency mode-locked laser with a sinusoidal sweep of modulation frequency around a mode-locking condition represents an ideal optical system for observing in the spectral domain the phenomena of dynamic localization and Bloch oscillations of electrons in an ideal solid placed in an external ac electric field.
Institute of Scientific and Technical Information of China (English)
OUYANG BiYao; ZHAO XianGeng; CHEN ShiGang; LIU Jie
2001-01-01
In this paper, we study the dynamic behavior and quasi-energy spectrum of multiband superlattice Bloch electrons in quantum kicked potential. We show analytically and numerically the avoided crossing and band suppression about the quasi-energy spectrum, the dynamic nonlocalization, and the electron oscillation behavior between two bands.
Beam splitter and combiner based on Bloch oscillations in spatially modulated waveguide arrays
Zhang, Yiqi; Zhong, Weiping; Wen, Feng; Guo, Yang; Guo, Yao; Lu, Keqing; Zhang, Yanpeng
2014-01-01
We numerically investigate the light beam propagation in periodic waveguide arrays which are elaborately modulated with certain structures. We find that the light beam may split, coalesce, deflect, and be localized during propagation in these spatially modulated waveguide arrays. All the phenomena originate from Bloch oscillations, and supply possible method for fabricating on-chip beam splitters and beam combiners.
DEFF Research Database (Denmark)
Zhukovsky, Sergei; Babicheva, Viktoriia; Orlov, A. A.;
2014-01-01
Optics of hyperbolic metamaterials is revisited in terms of large-wavevector waves, evanescent in isotropic media but propagating in presence of extreme anisotropy. Identifying the physical nature of these waves as Bloch volume plasmon polaritons, we derive their existence conditions and outline ...
Proof of an entropy conjecture for Bloch coherent spin states and its generalizations
DEFF Research Database (Denmark)
H. Lieb, Elliott; Solovej, Jan Philip
2014-01-01
in 1978 who also extended the conjecture to Bloch SU(2) spin-coherent states for every angular momentum $J$. This conjecture is proved here. We also recall our 1991 extension of the Wehrl map to a quantum channel from $J$ to $K=J+1/2, J+1, ...$, with $K=\\infty$ corresponding to the Wehrl map to classical...
Floquet-Bloch vs. Nicolson-Ross-Weir Extraction for Magneto-Dielectric Bragg Stacks
DEFF Research Database (Denmark)
Clausen, Niels Christian Jerichau; Arslanagic, Samel; Breinbjerg, Olav
2014-01-01
We extract and compare the permittivity and permeability from a dielectric and a magnetodielectric Bragg stack with the Floquet-Bloch (FB) method for the infinite stack and the Nicolson-Ross- Weir (NRW) method for the finite stack. While the extracted propagation constants are identical, the wave...
Generation of Superpositions of Two Bloch States in an Ion Trap
Institute of Scientific and Technical Information of China (English)
ZHENG Shi-Biao
2003-01-01
We propose a scheme for the generation of superpositions of two Bloch states for a collection of ions. Inthe scheme the ions are trapped in a linear potential and interact with laser beams. Our scheme does not put anyrequirement on the Lamb-Dicke parameters.
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Volkov, V.S.; Søndergaard, Thomas;
2002-01-01
the interference between a quasihomogeneous background field and Bloch harmonics of the PCW mode, we account for spatial frequency spectra of the intensity variations and determine the propagation constant of the PCW mode at 1520 nm. The possibilities and limitations of SNOM imaging for the characterization...
DEFF Research Database (Denmark)
Gaididei, Yu. B.; Christiansen, Peter Leth
2008-01-01
We study a parametrically driven Ginzburg-Landau equation model with nonlinear management. The system is made of laterally coupled long active waveguides placed along a circumference. Stationary solutions of three kinds are found: periodic Ising states and two types of Bloch states, staggered...... and unstaggered. The stability of these states is investigated analytically and numerically. The nonlinear dynamics of the Bloch states are described by a complex Ginzburg-Landau equation with linear and nonlinear parametric driving. The switching between the staggered and unstaggered Bloch states under...
Institute of Scientific and Technical Information of China (English)
LIU Jing; LI Chunsheng; NING Ping
2013-01-01
Pampus cinereus (Bloch,1795) (Stromateidae),a species believed to be widely distributed throughout the Indo-Western Pacific region,was redescribed and a neotype was designated.The designation of a neotype was necessary because of ambiguous data in Bloch's original description and the loss of the original type specimen.Morphological data indicated that 10 recently-collected specimens from the coasts of southern China agreed well with Bloch's original description and figure ofP.cinereus.A neotype for this species was selected from among the 10 specimens,and a detailed description is presented in this paper.
DEFF Research Database (Denmark)
Mann, Nishan; Combrié, Sylvian; Colman, Pierre
2013-01-01
We present theory and measurements ofdisorder-induced losses for low loss 1.5 mmlong slow light photonic crystal waveguides. A recent class of dispersion engineered waveguides increases the bandwidth of slow light and shows lower propagation losses for the same group index. Our theory and experim...
The Extended Edit Distance Metric
Fuad, Muhammad Marwan Muhammad
2007-01-01
Similarity search is an important problem in information retrieval. This similarity is based on a distance. Symbolic representation of time series has attracted many researchers recently, since it reduces the dimensionality of these high dimensional data objects. We propose a new distance metric that is applied to symbolic data objects and we test it on time series data bases in a classification task. We compare it to other distances that are well known in the literature for symbolic data objects. We also prove, mathematically, that our distance is metric.
Tilted resonators in a triangular elastic lattice: chirality, Bloch waves and negative refraction
Tallarico, Domenico; Movchan, Alexander B; Colquitt, Daniel J
2016-01-01
We consider a vibrating triangular mass-truss lattice whose unit cell contains a resonator of a triangular shape. The resonators are connected to the triangular lattice by trusses. Each resonator is tilted, i.e. it is rotated with respect to the triangular lattice's unit cell through an angle $\\vartheta_0$. This geometrical parameter is responsible for the emergence of a resonant mode in the Bloch spectrum for elastic waves and strongly affects the dispersive properties of the lattice. Additionally, the tilting angle $\\vartheta_0$ triggers the opening of a band gap at a Dirac-like point. We provide a physical interpretation of these phenomena and discuss the dynamical implications on elastic Bloch waves. The dispersion properties are used to design a structured interface containing tilted resonators which exhibit negative refraction and focussing, as in a "flat elastic lens".
Suppression of space broadening of exciton polariton beams by Bloch oscillation effects
Duan, Xudong; Zhang, Yongyou
2015-01-01
We theoretically study the transport of exciton polaritons under different applied photon potentials. The relation between the photon potentials and the thickness of the cavity layer is calculated by the finite element simulation. The theoretical analysis and numerical calculation indicate that the cavity photon potential is proportional to the thickness of the cavity layer with the coefficient being about $1.8$ meV/nm. Further, the periodic and linear photon potentials are considered to control the transport of the exciton polaritons in weak- and strong-field pump situations. In both situations the periodic potential cannot by itself effectively suppress the scatterings of the disorder potentials of the cavity photons and excitons and the nonlinear exciton-exciton interaction. When the linear potential is added to the cavity photons, the polariton transport exhibits the Bloch oscillation behavior. Importantly, the polariton Bloch oscillation can strongly suppress the space broadening due to the disorder pote...
Floß, Johannes; Averbukh, Ilya Sh
2016-05-19
We describe a universal behavior of linear molecules excited by a periodic train of short laser pulses under conditions close to the quantum resonance. The quantum resonance effect causes an unlimited ballistic growth of the angular momentum. We show that a disturbance of the quantum resonance, either by the centrifugal distortion of the rotating molecules or a controlled detuning of the pulse train period from the so-called rotational revival time, eventually halts the growth by causing Anderson localization beyond a critical value of the angular momentum, the Anderson wall. Below the wall, the rotational excitation oscillates with the number of pulses due to a mechanism similar to Bloch oscillations in crystalline solids. We suggest optical experiments capable of observing the rotational Anderson wall and Bloch oscillations at near-ambient conditions with the help of existing laser technology.
Phase transition to spatial Bloch-like oscillation in squeezed photonic lattices
Nezhad, M Khazaei; Golshani, M; Mahdavi, S M; Langari, A
2013-01-01
We propose an exactly solvable waveguide lattice incorporating inhomogeneous coupling coefficient. This structure provides a classical analogue to the squeezed number and squeezed coherent intensity distribution in quantum optics where the propagation length plays the role of squeezed amplitude. The intensity pattern is obtained in a closed form for an arbitrary distribution of the initial beam profile. We have also investigated the phase transition to the spatial Bloch-like oscillations by adding a linear gradient to the propagation constant of each waveguides ($ \\alpha $). Our analytical results show that the Bloch-like oscillations appear above a critical value for the linear gradient of propagation constant ($ \\alpha > \\alpha_{c} $). The phase transition (in the propagation properties of the waveguide) is a result of competition between discrete and Bragg diffraction. Moreover, the light intensity decay algebraically along each waveguide at the critical point while it falls off exponentially below the cri...
Tarallo, M G; Poli, N; Chiofalo, M L; Wang, F -Y; Tino, G M
2012-01-01
In this paper we describe and compare different methods used for accurate determination of forces acting on matter-wave packets in optical lattices. The quantum interference nature responsible for the production of both Bloch oscillations and coherent delocalization is investigated in detail. We study conditions for optimal detection of Bloch oscillation for a thermal ensemble of cold atoms with a large velocity spread. We report on the experimental observation of resonant tunneling in an amplitude-modulated (AM) optical lattice up to the sixth harmonic with Fourier-limited linewidth. We then explore the fundamental and technical phenomena which limit both the sensitivity and the final accuracy of the atomic force sensor at 10^{-7} precision level [1], with an analysis of the coherence time of the system and addressing few simple setup changes to go beyond the current accuracy.
Magneto-optical switching of Bloch surface waves in magnetophotonic crystals
Romodina, M. N.; Soboleva, I. V.; Fedyanin, A. A.
2016-10-01
Bloch-surface-wave (BSW) excitation controlled by Faraday rotation in one-dimensional magnetophotonic crystals is presented. Dispersion curves of the Bloch surface wave and waveguide modes of magnetophotonic crystals consisting of silicon dioxide and bismuth-substituted yttrium-iron-garnet (Bi:YIG) quarter-wavelength-thick layers are calculated using Berreman's 4×4 transfer matrix method. Enhanced Faraday rotation observed in the magnetophotonic crystals in the spectral vicinity of the BSW resonance enables the magneto-optical switching of BSWs. The excitation of the BSWs at the magnetophotonic crystal surface for p-polarized incident light is induced by magneto-optical activity in the Bi:YIG layers.
A Refresher of the Original Bloch’s Law Paper (Bloch, July 1885)
2015-01-01
In 1885, Adolphe-Moïse Bloch asked the following simple question “Is there a law describing the relationship between the duration of a light and its perceived intensity?” Based on a series of experiments using a Foucault regulator and a candle, Bloch concluded that “when the lighting duration varies from 0.00173 to 0.0518 seconds (…) the [visible] light is markedly in inverse proportion to its duration”—his famous law. As this law pertains to the more general and hotly debated question of accumulation of sensory information over time, it is timely to offer the public a full translation of Bloch’s original paper (from French) and to present it within the context of contemporary research. PMID:27433317
A Refresher of the Original Bloch’s Law Paper (Bloch, July 1885
Directory of Open Access Journals (Sweden)
Andrei Gorea
2015-08-01
Full Text Available In 1885, Adolphe-Moïse Bloch asked the following simple question “Is there a law describing the relationship between the duration of a light and its perceived intensity?” Based on a series of experiments using a Foucault regulator and a candle, Bloch concluded that “when the lighting duration varies from 0.00173 to 0.0518 seconds (… the [visible] light is markedly in inverse proportion to its duration”—his famous law. As this law pertains to the more general and hotly debated question of accumulation of sensory information over time, it is timely to offer the public a full translation of Bloch’s original paper (from French and to present it within the context of contemporary research.
Nanoscale switch for vortex polarization mediated by Bloch core formation in magnetic hybrid systems
Wohlhüter, Phillip; Bryan, Matthew Thomas; Warnicke, Peter; Gliga, Sebastian; Stevenson, Stephanie Elizabeth; Heldt, Georg; Saharan, Lalita; Suszka, Anna Kinga; Moutafis, Christoforos; Chopdekar, Rajesh Vilas; Raabe, Jörg; Thomson, Thomas; Hrkac, Gino; Heyderman, Laura Jane
2015-08-01
Vortices are fundamental magnetic topological structures characterized by a curling magnetization around a highly stable nanometric core. The control of the polarization of this core and its gyration is key to the utilization of vortices in technological applications. So far polarization control has been achieved in single-material structures using magnetic fields, spin-polarized currents or spin waves. Here we demonstrate local control of the vortex core orientation in hybrid structures where the vortex in an in-plane Permalloy film coexists with out-of-plane maze domains in a Co/Pd multilayer. The vortex core reverses its polarization on crossing a maze domain boundary. This reversal is mediated by a pair of magnetic singularities, known as Bloch points, and leads to the transient formation of a three-dimensional magnetization structure: a Bloch core. The interaction between vortex and domain wall thus acts as a nanoscale switch for the vortex core polarization.
Bloch oscillations as generators of polarons in a 1D crystal
Energy Technology Data Exchange (ETDEWEB)
Nazareno, H.N. [International Center for Condensed Matter Physics, Universidade de Brasília, P.O. Box 04513, 70910-900 Brasília, DF (Brazil); Brito, P.E. de, E-mail: pedebrito@unb.br [Universidade de Brasília, PPG-CIMA, Campus Planaltina, 73345-010 Brasília, DF (Brazil)
2016-08-01
The main purpose of this work is to characterize the kind of propagation/localization of carriers in a one-dimensional crystalline structure along the tight-binding model while the electron–phonon interaction is taken into account through a deformation potential and the system is under the action of a dc electric field. The lattice was treated in the classical formalism of harmonic vibrations. A remarkable effect is obtained due to the presence of the electric field. On one side the particle performs Bloch oscillations and at the same time it interacts with the lattice and as a result at each turning point of its trajectory phonons are generated that carry with them a fraction of the electronic wave packet, it is the polaron formation. This way the Bloch oscillations pump polarons into the system. We explain why the polaron is formed at returning points of the oscillations.
Quantum Theory of Conducting Matter Newtonian Equations of Motion for a Bloch Electron
Fujita, Shigeji
2007-01-01
Quantum Theory of Conducting Matter: Newtonian Equations of Motion for a Bloch Electron targets scientists, researchers and graduate-level students focused on experimentation in the fields of physics, chemistry, electrical engineering, and material sciences. It is important that the reader have an understanding of dynamics, quantum mechanics, thermodynamics, statistical mechanics, electromagnetism and solid-state physics. Many worked-out problems are included in the book to aid the reader's comprehension of the subject. The Bloch electron (wave packet) moves by following the Newtonian equation of motion. Under an applied magnetic field B the electron circulates around the field B counterclockwise or clockwise depending on the curvature of the Fermi surface. The signs of the Hall coefficient and the Seebeck coefficient are known to give the sign of the major carrier charge. For alkali metals, both are negative, indicating that the carriers are "electrons." These features arise from the Fermi surface difference...
Comment on "On the analytical solution of the optical Bloch equations"
Noh, Heung-Ryoul; Jhe, Wonho
2012-02-01
In a recent paper [P.J. Colmenares and J.L. Paz, Opt. Commun. 284 (2011) 5171], analytical solutions of the optical Bloch equations are presented. This paper follows the same procedures as presented in the paper by the authors [H.R. Noh and W. Jhe, Opt. Commun. 283 (2010) 2353] but concludes that their results are substantially different from the results of the authors. We find that the discrepancy results from the wrong initial conditions employed by those authors for one of the Bloch vector components ( w), whose initial value must be 1 not 0. We also find that if proper initial conditions are used, there are no discrepancies between the two results.
Raman fingerprints on the Bloch sphere of a spinor Bose-Einstein condensate
Schultz, Justin T.; Hansen, Azure; Murphree, Joseph D.; Jayaseelan, Maitreyi; Bigelow, Nicholas P.
2016-10-01
We explore the geometric interpretation of a diabatic, two-photon Raman process as a rotation on the Bloch sphere for a pseudo-spin-? system. The spin state of a spin-? quantum system can be described by a point on the surface of the Bloch sphere, and its evolution during a Raman pulse is a trajectory on the sphere determined by properties of the optical beams: the pulse area, the relative intensities and phases and the relative frequencies. We experimentally demonstrate key features of this model with a ?Rb spinor Bose-Einstein condensate, which allows us to examine spatially dependent signatures of the Raman beams. The two-photon detuning allows us to precisely control the spin density and imprinted relative phase profiles, as we show with a coreless vortex. With this comprehensive understanding and intuitive geometric interpretation, we use the Raman process to create and tailor as well as study and characterize exotic topological spin textures in spinor BECs.
EXTENDED CES(A)RO OPERATORS ON THE BLOCH SPACE IN THE UNIT BALL OF Cn
Institute of Scientific and Technical Information of China (English)
胡璋剑
2003-01-01
The paper defines an extended Cesàro operator Tg with holomorphic symbolg in the unit ball B of Cn asWhere g(z)= ∑j=1∑n zj g/ zj is the radial derivative of g. In this paper, the author characterizes g for which Tg is bounded (or compact) on the Bloch spaceB and the little Blochspace B0.
The generalized Hodge and Bloch conjectures are equivalent for general complete intersections
Voisin, Claire
2011-01-01
Let $X$ be a smooth complex projective variety with trivial Chow groups. (By trivial, we mean that the cycle class is injective.) We show (assuming the Lefschetz standard conjecture) that if the vanishing cohomology of a general complete intersection $Y$ of ample hypersurfaces in $X$ has geometric coniveau $\\geq c$, then the Chow groups of cycles of dimension $\\leq c-1$ of $Y$ are trivial. The generalized Bloch conjecture for $Y$ is this statement with "geometric coniveau" replaced by "Hodge coniveau".
Anti-Newtonian dynamics and self-induced Bloch oscillations of correlated particles
Longhi, Stefano
2014-01-01
We predict that two correlated particles hopping on a one-dimensional Hubbard lattice can show transient self-acceleration and self-induced Bloch oscillations as a result of anti-Newtonian dynamics. Self-propulsion occurs for two particles with opposite effective mass on the lattice and requires long-range particle interaction. A photonic simulator of the two-particle Hubbard model with controllable long-range interaction, where self-propulsion can be observed, is discussed.
Sensitive measurement of forces at the micron scale using Bloch oscillations of ultracold atoms.
Carusotto, I; Pitaevskii, L; Stringari, S; Modugno, G; Inguscio, M
2005-08-26
We show that Bloch oscillations of ultracold fermionic atoms in the periodic potential of an optical lattice can be used for a sensitive measurement of forces at the micrometer length scale, e.g., in the vicinity of a dielectric surface. In particular, the proposed approach allows us to perform a local and direct measurement of the Casimir-Polder force which is, for realistic experimental parameters, as large as 10(-4) gravity.
Freezing of nonlinear Bloch oscillations in the generalized discrete nonlinear Schrödinger equation.
Cao, F J
2004-09-01
The dynamics in a nonlinear Schrödinger chain in a homogeneous electric field is studied. We show that discrete translational invariant integrability-breaking terms can freeze the Bloch nonlinear oscillations and introduce new faster frequencies in their dynamics. These phenomena are studied by direct numerical integration and through an adiabatic approximation. The adiabatic approximation allows a description in terms of an effective potential that greatly clarifies the phenomena.
Bloch oscillations and Zener tunneling in two-dimensional photonic lattices.
Trompeter, Henrike; Krolikowski, Wieslaw; Neshev, Dragomir N; Desyatnikov, Anton S; Sukhorukov, Andrey A; Kivshar, Yuri S; Pertsch, Thomas; Peschel, Ulf; Lederer, Falk
2006-02-10
We report on the first experimental observation of photonic Bloch oscillations and Zener tunneling in two-dimensional periodic systems. We study the propagation of an optical beam in a square lattice superimposed on a refractive index ramp. We observe oscillations of the beam inside the first Brilloin zone and tunneling of light from the first to the higher-order bands of the lattice band gap spectrum.
San agustín y la utopía según ernst bloch
2011-01-01
Nuestro propósito en este breve trabajo es presentar la lectura que Emst Bloch hace del pensamiento de San Agustín sobre la utopía de la Ciudad de Dios en su libro Principio Esperanza y hacer un análisis esquemático de dicha lectura con algunos comentarios críticos a varías de sus afirmaciones.
Maxwell-Bloch Equations Modeling of Ultrashort Optical Pulse Propagation in Semiconductor Materials
Goorjian, Peter M.; Agrawal, Govind, P.
1997-01-01
An algorithm has been developed that solves the semiconductor Maxwell-Bloch equations, without making the standard slowly-varying envelope (SVEA) and rotating-wave (RWA) approximations. It is applied to study the propagation of ultrashort pulses in semiconductor materials. The results include many-body effects due to the Coulomb interaction among the charge carriers as well as the nonlinear effects resulting from spectral hole-burning.
Dynamic scattering of electron vortex beams – A Bloch wave analysis
Energy Technology Data Exchange (ETDEWEB)
Mendis, B.G., E-mail: b.g.mendis@durham.ac.uk
2015-02-15
Two important applications of electron vortex beams are in electron magnetic chiral dichroism (EMCD) measurements and nanoparticle manipulation. In both cases orbital angular momentum (
Pusch, Andreas; Wuestner, Sebastian; Hamm, Joachim M; Tsakmakidis, Kosmas L; Hess, Ortwin
2012-03-27
Nanoplasmonic metamaterials are an exciting new class of engineered media that promise a range of important applications, such as subwavelength focusing, cloaking, and slowing/stopping of light. At optical frequencies, using gain to overcome potentially not insignificant losses has recently emerged as a viable solution to ultra-low-loss operation that may lead to next-generation active metamaterials. Maxwell-Bloch models for active nanoplasmonic metamaterials are able to describe the coherent spatiotemporal and nonlinear gain-plasmon dynamics. Here, we extend the Maxwell-Bloch theory to a Maxwell-Bloch Langevin approach-a spatially resolved model that describes the light field and noise dynamics in gain-enhanced nanoplasmonic structures. Using the example of an optically pumped nanofishnet metamaterial with an embedded laser dye (four-level) medium exhibiting a negative refractive index, we demonstrate the transition from loss-compensation to amplification and to nanolasing. We observe ultrafast relaxation oscillations of the bright negative-index mode with frequencies just below the THz regime. The influence of noise on mode competition and the onset and magnitude of the relaxation oscillations is elucidated, and the dynamics and spectra of the emitted light indicate that coherent amplification and lasing are maintained even in the presence of noise and amplified spontaneous emission.
Observation of Bloch oscillations in complex PT-symmetric photonic lattices.
Wimmer, Martin; Miri, Mohammed-Ali; Christodoulides, Demetrios; Peschel, Ulf
2015-12-07
Light propagation in periodic environments is often associated with a number of interesting and potentially useful processes. If a crystalline optical potential is also linearly ramped, light can undergo periodic Bloch oscillations, a direct outcome of localized Wannier-Stark states and their equidistant eigenvalue spectrum. Even though these effects have been extensively explored in conservative settings, this is by no means the case in non-Hermitian photonic lattices encompassing both amplification and attenuation. Quite recently, Bloch oscillations have been predicted in parity-time-symmetric structures involving gain and loss in a balanced fashion. While in a complex bulk medium, one intuitively expects that light will typically follow the path of highest amplification, in a periodic system this behavior can be substantially altered by the underlying band structure. Here, we report the first experimental observation of Bloch oscillations in parity-time-symmetric mesh lattices. We show that these revivals exhibit unusual properties like secondary emissions and resonant restoration of PT symmetry. In addition, we present a versatile method for reconstructing the real and imaginary components of the band structure by directly monitoring the light evolution during a cycle of these oscillations.
Adele Bloch-Bauer (1881-1925): Possible diagnoses for Gustav Klimt's Lady in Gold.
da Mota, Licia Maria H; Neubarth, Fernando; de Carvalho, Jozélio F; Diniz, Leonardo R; Aires, Rodrigo B; Dos Santos-Neto, Leopoldo L
2016-08-01
One of the most famous works by the Austrian symbolist painter Gustav Klimt and one of the most widely reproduced works of art worldwide, Adele Bloch-Bauer I which portrays the beautiful wife of Austrian magnate Ferdinand Bloch-Bauer. Adele was the only woman painted by Klimt on more than one occasion. Apart from the beauty and value of the painting, the daring sea of gold that surrounds Adele and the gentle intimacy with which her fragile figure is portrayed have shrouded the history of this painting in mystery. Beyond speculation as to a special bond between artist and model, observation of the painting with a keener, clinical gaze yields evidence of potential illness in the model: facial erythema which, if not produced artificially by makeup, could represent a malar rash; pallor or cyanosis of the hands; and her draped fingers, which seemingly attempt to hide a deformity. This paper seeks to provide a biographical review both of the painter, Gustav Klimt, and of the subject, Adele Bloch-Bauer; to analyse Klimt's two portrayals of her in a search for evidence of a potential intimate relationship between artist and muse and, finally, to compile clinical evidence of possible diagnoses for the Lady in Gold.
Tanifuji, T.
2016-03-01
Time-resolved multi-distance measurements are studied to retrieve absorption and reduced scattering coefficients of adult heads, which have enough depth sensitivity to determine the optical parameters in superficial tissues and brain separately. Measurements were performed by putting the injection and collection fibers on the left semi-sphere of the forehead, with the injection fiber placed toward the temporal region, and by moving the collection fiber between 10 and 60 mm from the central sulcus. It became clear that optical parameters of the forehead at all collection fibers were reasonably determined by selecting the appropriate visibility length of the geometrical head models, which is related to head surface curvature at each position.
Bingi, Jayachandra; Nair, Radhika V.; Vijayan, C.
2017-02-01
Light propagation and localization in a random structure with a periodic background is an upcoming paradigm for novel photonic applications. This paper demonstrates the phenomenon of time dependent transmittance of evanescent Bloch modes (EBM) in ZnS random photonic crystal (RPC) which forms the basis for photonic delay switching. The RPC is fabricated by colloidal self-assembly with ZnS nanospheres of size 215 nm. An anomalous reciprocity and time dependent transmission at EBM (mid band gap wavelength) are observed in coherent back scattering and transmission studies respectively. These are explained on the basis of restricted propagation of EBMs through random channels in the periodic background and enhanced field storage inside RPC. The channelized propagation of EBMs is evident from decreasing time delay of transmittance at reduced thicknesses. The proportionality between transmission time delay and incident power confirms photon (field) storage within the RPC. The results indicate that structures with systematically engineered EBM channels can work as wavelength selective delay switch and further provide a short time photon storage system under non-absorbing conditions.
Energy Technology Data Exchange (ETDEWEB)
Clade, P
2005-10-15
From a measurement of the recoil velocity of an atom absorbing a photon, it is possible to deduce a determination of the ratio h/m between the Planck constant and the mass of the atoms and then to deduce a value of the fine structure constant alpha. To do this measurement, we use the technique of Bloch oscillations, which allows us to transfer a large number of recoils to atoms. A velocity sensor, based on velocity selective Raman transition, enables us to measure the momentum transferred to the atoms. A measurement with a statistical uncertainty of 4.4 10{sup -9}, in conjunction with a careful study of systematic effects (5 10{sup -9}), has led us to a determination of alpha with an uncertainty of 6.7 10{sup -9}: {alpha}{sup -1}(Rb) = 137.03599878 (91). This uncertainty is similar to the uncertainty of the best determinations of alpha based on atom interferometry. (author)
McQuinn, Kristen. B. W.; Skillman, Evan D.; Dolphin, Andrew E.; Berg, Danielle; Kennicutt, Robert
2016-11-01
M104 (NGC 4594; the Sombrero galaxy) is a nearby, well-studied elliptical galaxy included in scores of surveys focused on understanding the details of galaxy evolution. Despite the importance of observations of M104, a consensus distance has not yet been established. Here, we use newly obtained Hubble Space Telescope optical imaging to measure the distance to M104 based on the tip of the red giant branch (TRGB) method. Our measurement yields the distance to M104 to be 9.55 ± 0.13 ± 0.31 Mpc equivalent to a distance modulus of 29.90 ± 0.03 ± 0.07 mag. Our distance is an improvement over previous results as we use a well-calibrated, stable distance indicator, precision photometry in a optimally selected field of view, and a Bayesian maximum likelihood technique that reduces measurement uncertainties. The most discrepant previous results are due to Tully-Fisher method distances, which are likely inappropriate for M104 given its peculiar morphology and structure. Our results are part of a larger program to measure accurate distances to a sample of well-known spiral galaxies (including M51, M74, and M63) using the TRGB method. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
McQuinn, Kristen. B. W.; Skillman, Evan D.; Dolphin, Andrew E.; Berg, Danielle; Kennicutt, Robert
2016-07-01
Great investments of observing time have been dedicated to the study of nearby spiral galaxies with diverse goals ranging from understanding the star formation process to characterizing their dark matter distributions. Accurate distances are fundamental to interpreting observations of these galaxies, yet many of the best studied nearby galaxies have distances based on methods with relatively large uncertainties. We have started a program to derive accurate distances to these galaxies. Here we measure the distance to M51—the Whirlpool galaxy—from newly obtained Hubble Space Telescope optical imaging using the tip of the red giant branch method. We measure the distance modulus to be 8.58 ± 0.10 Mpc (statistical), corresponding to a distance modulus of 29.67 ± 0.02 mag. Our distance is an improvement over previous results as we use a well-calibrated, stable distance indicator, precision photometry in a optimally selected field of view, and a Bayesian Maximum Likelihood technique that reduces measurement uncertainties. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Energy Technology Data Exchange (ETDEWEB)
Saenphet, S.; Thaworn, W.; Saenphet, K. [Chiang Mai University, Chiang Mai (Thailand). Faculty of Science
2009-09-15
The acidity of mine water generally makes it toxic to most organisms. The gills, kidneys and livers of Anabas testudineus Bloch fish inhabiting the acidic water (pH 2-4) of an unused lignite mine in Li District, Lamphun Province, Thailand were examined and compared to those of farmed fish. Tissue abnormalities were found in all investigated organs. Deterioration and telangiectasia of gill filaments were found. Liver tissue revealed hemorrhages, blood congestion and necrotic cells with mononuclear cell infiltration. In addition, hypertrophy of the epithelial cells of the renal tubules with reduced lumens, aneurisms of the renal tubules, and contractions of the glomeruli in the Bowman's capsule were observed. These histopathological findings suggest the acidic water in this habitat causes severe damage to the internal organs of fish and consequently alter their physiological status. Since the water in this pond is utilized by local people, these findings highlight the need for adequate water treatment.
Rabi Oscillations in Realistic Superlattice with Finite Bloch Bands
Institute of Scientific and Technical Information of China (English)
FAN Wen-Bin; ZHANG Ping; LUO Ying; ZHAO Xian-Geng
2001-01-01
We investigate the dynamical processes taking place in nanodevices by high-frequency dc-ac fields. We found that Rabi oscillations between minibands are clearly identified under theoretical resonant conditions derived by an ideal two-band superlattice model, the resonant conditions have broadened, and the amount of broadening is about four times of the Rabi oscillation frequency. We also want to elucidate the role of different mechanisms that could lead to loss of quantum coherence. Our results show how the dephasing effects of disorder of interface roughness and doping fluctuation that after some periods destroy coherent oscillations, such as Rabi oscillations,can be reduced dramatically if we apply a bias static electric field to the superlattice system. The doping fluctuation dephasing effect is much stronger than that of interface roughness in the coherent process of realistic superlattices.
Kosevich, Yuriy A; Gann, Vladimir V
2013-06-19
We study the localization of magnon states in finite defect-free Heisenberg spin-1/2 ferromagnetic chains placed in an inhomogeneous magnetic field with a constant spatial gradient. Continuous transformation from the extended magnon states to the localized Wannier-Zeeman states in a finite spin chain placed in an inhomogeneous field is described both analytically and numerically. We describe for the first time the non-monotonic dependence of the energy levels of magnons, both long and short wavelength, on the magnetic field gradient, which is a consequence of magnon localization in a finite spin chain. We show that, in contrast to the destruction of the magnon band and the establishment of the Wannier-Stark ladder in a vanishingly small field gradient in an infinite chain, the localization of magnon states at the chain ends preserves the memory of the magnon band. Essentially, the localization at the lower- or higher-field chain end resembles the localization of the positive- or negative-effective-mass band quasiparticles. We also show how the beat dynamics of coherent superposition of extended spin waves in a finite chain in a homogeneous or weakly inhomogeneous field transforms into magnon Bloch oscillations of the superposition of localized Wannier-Zeeman states in a strongly inhomogeneous field. We provide a semiclassical description of the magnon Bloch oscillations and show that the correspondence between the quantum and semiclassical descriptions is most accurate for Bloch oscillations of the magnon coherent states, which are built from a coherent superposition of a large number of the nearest-neighbour Wannier-Zeeman states.
DERIVATIVES OF HARMONIC MIXED NORM AND BLOCH-TYPE SPACES IN THE UNIT BALL OF Rn
Institute of Scientific and Technical Information of China (English)
Tang Xiaomin; Hu Zhangjian; Lu Xiaofen
2011-01-01
Let H(B) be the set of all harmonic functions f on the unit ball B of Rn.For 0 ＜ p,q ≤ ∞ and a normal weight φ, the mixed norm space Hp,q,φ(B) consists of all functions f in H(B) for which the mixed norm ||·||p,q,φ ＜ ∞. In this article, we obtain some characterizations in terms of radial, tangential, and partial derivative norms in Hp,q,φ(B).The parallel results for the Bloch-type space are also obtained. As an application, the analogous problems for polyharmonic functions are discussed.
Estey, Brian; Müller, Holger; Kuan, Pei-Chen; Lan, Shau-Yu
2014-01-01
We describe a new scheme for atom interferometry based on both large-momentum transfer Bragg beam splitters and Bloch oscillations. Combining the advantages of previous approaches to recoil-sensitive interferometers, we increase the signal and suppress a systematic phase shift caused by Bragg diffraction at least 60-fold, matching experiment to theory; the systematic shift can be eliminated from Mach-Zehnder interferometers. We demonstrate high contrast, interference with up to 4.4 million radians of phase difference between freely evolving matter waves, and a resolution of $\\delta \\alpha/\\alpha=0.33\\,$ppb$\\sqrt{\\rm 6h}$ available to measurements of the fine structure constant.
Nontrivial Bloch oscillations in waveguide arrays with second-order coupling.
Wang, Gang; Huang, Ji Ping; Yu, Kin Wah
2010-06-01
Under the influence of the next-nearest-neighbor interaction, we theoretically investigate the occurrence of Bloch oscillations in zigzag waveguide arrays. Because of the special topological configuration of the lattice itself, the second-order coupling (SOC) can be enhanced significantly and leads to the band alteration beyond the nearest-neighbor model, i.e., the offset of minimum value from the band edge. Contrary to the behavior in the vanishing SOC, the oscillation patterns exhibit new features, namely, a double turning-back occurs when the beam approaches the band edge. Our results can be applied to some ordered-lattice systems.
Bloch Oscillations of Cold Atoms in a Cavity: Effects of Quantum Noise
Venkatesh, B Prasanna
2013-01-01
In this communication we extend our theory of Bloch oscillations of cold atoms inside an optical cavity [Venkatesh et al., Phys. Rev. A 80, 063834 (2009)] to include the effects of quantum noise. By solving the coupled dynamics of linearized fluctuations about the atomic and optical meanfields, we are able to include the effects of quantum measurement backaction upon the atoms and ultimately examine how this influences the signal-to-noise ratio of a measurement of external forces using this system. One of the hurdles we overcome along the way is the proper treatment of fluctuations about time-dependent meanfields in the cold atom cavity-QED context.
On-chip optical isolation via unidirectional Bloch oscillations in a waveguide array.
Kumar, Pradeep; Levy, Miguel
2012-09-15
We propose to use the unidirectionality of the optical Bloch oscillation phenomenon achievable in a magneto-optic asymmetric waveguide array to achieve optical isolation. At the 1.55 μm telecommunication wavelength, our isolator design exhibits an isolation ratio of 36 dB between forward- and backward-propagating waves. The proposed design consists of a waveguide array made in a silicon-on-insulator substrate with a magnetic garnet cover layer. A key role is played by the transverse-magnetic mode nonreciprocal phase shift effect.
Bloch oscillations of quasispin polaritons in a magneto-optically controlled atomic ensemble
Jiang, Chang; Zhou, Lan
2012-01-01
We consider the propagation of a quantized polarized light in a magneto-optically manipulated atomic ensemble with a tripod configuration. Polariton formalism is applied when the medium is subjected to a washboard magnetic field under electromagnetically induced transparency. The dark-state polariton with multiple components is achieved. We analyze quantum dynamics of the dark-state polariton by some experiment data from rubidium D1-line. It is found that one component propagates freely, however the wavepacket trajectory of the other component performs Bloch oscillations.
Stopping and time reversal of light in dynamic photonic structures via Bloch oscillations.
Longhi, Stefano
2007-02-01
It is theoretically shown that storage and time reversal of light pulses can be achieved in a coupled-resonator optical waveguide by dynamic tuning of the cavity resonances without maintaining the translational invariance of the system. The control exploits the Bloch oscillation motion of a light pulse in the presence of a refractive index ramp, and it is therefore rather different from the mechanism of adiabatic band compression and reversal proposed by Yanik and Fan in recent works [Phys. Rev. Lett., 92, 083901 (2004); 93, 173903 (2004)].
Long-living BLOCH oscillations of matter waves in periodic potentials.
Salerno, M; Konotop, V V; Bludov, Yu V
2008-07-18
The dynamics of matter waves in linear and nonlinear optical lattices subject to a spatially uniform linear force is studied both analytically and numerically. It is shown that by properly designing the spatial dependence of the scattering length it is possible to induce long-living Bloch oscillations of gap-soliton matter waves in optical lattices. This occurs when the effective nonlinearity and the effective mass of the soliton have opposite signs for all values of the crystal momentum in the Brillouin zone. The results apply to all systems modeled by the periodic nonlinear Schrödinger equation, including propagation of light in photonic and photorefractive crystals with tilted band structures.
Micromagnetic structure of the domain wall with Bloch lines in an electric field
Borich, M. A.; Tankeev, A. P.; Smagin, V. V.
2016-07-01
The micromagnetic structure of the domain wall (DW) with periodically distributed horizontal Bloch lines in a ferromagnetic film in an external electric field has been studied. The effect of the electric field on the internal DW micromagnetic structure is caused by inhomogeneous magnetoelectric coupling. Possible scenarios of the DW internal structure transformations implemented with varying the electric fields strength have been analyzed in detail. For each scenario, static characteristics of the system, such as the energy, DW profile, DW effective thickness, and electric polarization have been calculated.
Bloch oscillating transistor as the readout element for hot electron bolometers
Hassel, Juha; Seppä, Heikki; Lindell, Rene; Hakonen, Pertti
2004-10-01
In this paper we analyse the properties of the Bloch oscillating transistor as a preamplifier in cryogenic devices. We consider here especially the readout of hot electron bolometers (HEBs) based on Normal-Superconductor-Insulator tunnel junctions, but the results also apply more generally. We show that one can get an equivalent noise voltage below 1 nV/√Hz with a single BOT. By using N BOTs in a parallel array configuration, a further reduction by factor √N may be achieved.
Identification of Bloch-modes in hollow-core Photonic Crystal Fiber cladding
DEFF Research Database (Denmark)
Couny, F.; Benabid, F.; Roberts, John;
2007-01-01
length of fiber. A detailed study of the modes near the edges of the band gap shows that it is formed by the influence of three types of resonator: the glass interstitial apex, the silica strut which joins the neighboring apexes, and the air hole. The cladding electromagnetic field which survives......We report on the experimental visualization of the cladding Bloch-modes of a hollow-core photonic crystal fiber. Both spectral and spatial field information is extracted using the approach, which is based on measurement of the near-field and Fresnel-zone that results after propagation over a short...
Energy Technology Data Exchange (ETDEWEB)
Lyo, Sungkwun Kenneth; Pan, Wei; Reno, John Louis; Wendt, Joel Robert; Barton, Daniel Lee
2008-09-01
We have investigated the physics of Bloch oscillations (BO) of electrons, engineered in high mobility quantum wells patterned into lateral periodic arrays of nanostructures, i.e. two-dimensional (2D) quantum dot superlattices (QDSLs). A BO occurs when an electron moves out of the Brillouin zone (BZ) in response to a DC electric field, passing back into the BZ on the opposite side. This results in quantum oscillations of the electron--i.e., a high frequency AC current in response to a DC voltage. Thus, engineering a BO will yield continuously electrically tunable high-frequency sources (and detectors) for sensor applications, and be a physics tour-de-force. More than a decade ago, Bloch oscillation (BO) was observed in a quantum well superlattice (QWSL) in short-pulse optical experiments. However, its potential as electrically biased high frequency source and detector so far has not been realized. This is partially due to fast damping of BO in QWSLs. In this project, we have investigated the possibility of improving the stability of BO by fabricating lateral superlattices of periodic coupled nanostructures, such as metal grid, quantum (anti)dots arrays, in high quality GaAs/Al{sub x}Ga{sub 1-x}As heterostructures. In these nanostructures, the lateral quantum confinement has been shown theoretically to suppress the optical-phonon scattering, believed to be the main mechanism for fast damping of BO in QWSLs. Over the last three years, we have made great progress toward demonstrating Bloch oscillations in QDSLs. In the first two years of this project, we studied the negative differential conductance and the Bloch radiation induced edge-magnetoplasmon resonance. Recently, in collaboration with Prof. Kono's group at Rice University, we investigated the time-domain THz magneto-spectroscopy measurements in QDSLs and two-dimensional electron systems. A surprising DC electrical field induced THz phase flip was observed. More measurements are planned to investigate this
Measurement of group-velocity dispersion of Bloch modes in photonic-crystal-fiber rocking filters.
Wong, G K L; Zang, L; Kang, M S; Russell, P St J
2010-12-01
We use low-coherence interferometry to measure the group-velocity dispersion (GVD) of the fast and slow Bloch modes of structural rocking filters, produced by twisting a highly birefringent photonic crystal fiber to and fro while scanning a focused CO(2) laser beam along it. The GVD curves in the vicinity of the resonant wavelength differ dramatically from those of the unperturbed fiber, suggesting that rocking filters could be used in the optimization of, e.g., four-wave mixing and supercontinuum generation. Excellent agreement is obtained between theory and experiment.
Toxicity studies of butachlor to the freshwater fish Channa punctata (Bloch).
Tilak, K S; Veeraiah, K; Bhaskara Thathaji, P; Butchiram, M S
2007-04-01
The toxicity studies were conducted on the fish Channa punctata (Bloch) by employing static and continuous flow through systems, for the toxicant butachlor (technical grade+) and its commercial formulation+ (machete 50% EC). The LC50 values are 297.89 ppb and 247.46 ppb for 24 hr and 48 hr in static for technical and 636.45 and 546.09 for machete. In continuous flow through the values are 270.05, 233.52 to the technical and 567.85 and 481.49 respectively for machete. The tissues show qualitative accumulation and were quantitatively analysed by gas liquid chromatography (GLC).
Sturmberg, Björn C. P.; Dossou, Kokou B.; Lawrence, Felix J.; Poulton, Christopher G.; McPhedran, Ross C.; Martijn de Sterke, C.; Botten, Lindsay C.
2016-05-01
We describe EMUstack, an open-source implementation of the Scattering Matrix Method (SMM) for solving field problems in layered media. The fields inside nanostructured layers are described in terms of Bloch modes that are found using the Finite Element Method (FEM). Direct access to these modes allows the physical intuition of thin film optics to be extended to complex structures. The combination of the SMM and the FEM makes EMUstack ideally suited for studying lossy, high-index contrast structures, which challenge conventional SMMs.
Derivation of the Landau-Lifshitz-Bloch equation from continuum thermodynamics
Berti, Alessia; Giorgi, Claudio
2016-11-01
Within the continuum thermodynamic framework, we derive the evolution equation for the magnetization vector in a ferromagnetic body. This procedure leads to an evolution equation that generalizes the well-known Landau-Lifshitz model for magnetically saturated bodies and looks very similar to the Landau-Lifshitz-Bloch equation which was obtained by Garanin in 1997 from statistical mechanics. As a byproduct, we also obtain a generalization of the Gilbert equation when the magnetic field is far from saturation. By virtue of a suitable choice of the Gibbs free energy, this phenomenological model is able to describe the phase transition occurring from the paramagnetic to the ferromagnetic regime in anisotropic ferromagnets.
Experimental reconstruction of the Berry curvature in a topological Bloch band
Weitenberg, Christof; Flaeschner, Nick; Rem, Benno; Tarnowski, Matthias; Vogel, Dominik; Luehmann, Dirk-Soeren; Sengstock, Klaus
2016-05-01
Topological properties lie at the heart of many fascinating phenomena in solid state systems such as quantum Hall systems or Chern insulators. The topology can be captured by the distribution of Berry curvature, which describes the geometry of the eigenstates across the Brillouin zone. Employing fermionic ultracold atoms in a hexagonal optical lattice, we engineer the Berry curvature of the Bloch bands using resonant driving and measure it with full momentum resolution. Our results pave the way to explore intriguing phases of matter with interactions in topological band structures.
Experimental reconstruction of the Berry curvature in a Floquet Bloch band
Fläschner, N.; Rem, B. S.; Tarnowski, M.; Vogel, D.; Lühmann, D.-S.; Sengstock, K.; Weitenberg, C.
2016-05-01
Topological properties lie at the heart of many fascinating phenomena in solid-state systems such as quantum Hall systems or Chern insulators. The topology of the bands can be captured by the distribution of Berry curvature, which describes the geometry of the eigenstates across the Brillouin zone. Using fermionic ultracold atoms in a hexagonal optical lattice, we engineered the Berry curvature of the Bloch bands using resonant driving and show a full momentum-resolved measurement of the ensuing Berry curvature. Our results pave the way to explore intriguing phases of matter with interactions in topological band structures.
Nonlinear waves of the Hirota and the Maxwell-Bloch equations in nonlinear optics
Institute of Scientific and Technical Information of China (English)
Li Chuan-Zhong; He Jing-Song; K.Porseizan
2013-01-01
In this paper,considering the Hirota and the Maxwell-Bloch (H-MB) equations which are governed by femtosecond pulse propagation through a two-level doped fiber system,we construct the Darboux transformation of this system through a linear eigenvalue problem.Using this Daurboux transformation,we generate multi-soliton,positon,and breather solutions (both bright and dark breathers) of the H-MB equations.Finally,we also construct the rogue wave solutions of the above system.
Deza, Michel Marie
2016-01-01
This 4th edition of the leading reference volume on distance metrics is characterized by updated and rewritten sections on some items suggested by experts and readers, as well a general streamlining of content and the addition of essential new topics. Though the structure remains unchanged, the new edition also explores recent advances in the use of distances and metrics for e.g. generalized distances, probability theory, graph theory, coding theory, data analysis. New topics in the purely mathematical sections include e.g. the Vitanyi multiset-metric, algebraic point-conic distance, triangular ratio metric, Rossi-Hamming metric, Taneja distance, spectral semimetric between graphs, channel metrization, and Maryland bridge distance. The multidisciplinary sections have also been supplemented with new topics, including: dynamic time wrapping distance, memory distance, allometry, atmospheric depth, elliptic orbit distance, VLBI distance measurements, the astronomical system of units, and walkability distance. Lea...
Wieser, R.
2016-10-01
The derivation of the time dependent Schrödinger equation with transversal and longitudinal relaxation, as the quantum mechanical analog of the classical Landau-Lifshitz-Bloch equation, has been described. Starting from the classical Landau-Lifshitz-Bloch equation the transition to quantum mechanics has been performed and the corresponding von-Neumann equation deduced. In a second step the time Schrödinger equation has been derived. Analytical proofs and computer simulations show the correctness and applicability of the derived Schrödinger equation.
Bloch-like surface waves in Fibonacci quasi-crystals and Thue-Morse aperiodic dielectric multilayers
Koju, Vijay; Robertson, William M.
2016-09-01
Bloch surface waves (BSWs) in periodic dielectric multilayer structures with surface defect have been extensively studied. However, it has recently been recognized that quasi-crystals and aperiodic dielectric multilayers also support Bloch-like surface waves (BLSWs). In this work, we numerically show the existence of BLSWs in Fibonacci quasi-crystals and Thue-Morse aperiodic dielectric multilayers using the prism coupling technique. We compare the surface field enhancement and penetration depth of BLSWs in these structures with that of BSWs in their periodic counterparts.
Wieser, R
2016-10-05
The derivation of the time dependent Schrödinger equation with transversal and longitudinal relaxation, as the quantum mechanical analog of the classical Landau-Lifshitz-Bloch equation, has been described. Starting from the classical Landau-Lifshitz-Bloch equation the transition to quantum mechanics has been performed and the corresponding von-Neumann equation deduced. In a second step the time Schrödinger equation has been derived. Analytical proofs and computer simulations show the correctness and applicability of the derived Schrödinger equation.
de Lima, M M; Kosevich, Yu A; Santos, P V; Cantarero, A
2010-04-23
We present the experimental observation of Bloch oscillations, the Wannier-Stark ladder, and Landau-Zener tunneling of surface acoustic waves in perturbed grating structures on a solid substrate. A model providing a quantitative description of our experimental observations, including multiple Landau-Zener transitions of the anticrossed surface acoustic Wannier-Stark states, is developed. The use of a planar geometry for the realization of the Bloch oscillations and Landau-Zener tunneling allows a direct access to the elastic field distribution. The vertical surface displacement has been measured by interferometry.
Estevez, J Octavio; Arriaga, Jesús; Mendez-Blas, Antonio; Reyes-Ayona, Edgar; Escorcia, José; Agarwal, Vivechana
2012-07-23
: Theoretical demonstration and experimental evidence of photon Bloch oscillations and Wannier-Stark ladders (WSLs) in dual-periodical (DP) multilayers, based on porous silicon, are presented. An introduction of the linear gradient in refractive indices in DP structure, which is composed by stacking two different periodic substructures N times, resulted in the appearance of WSLs. Theoretical time-resolved reflection spectrum shows the photon Bloch oscillations with a period of 130 fs. Depending on the values of the structural parameters, one can observe the WSLs in the near infrared or visible region which may allow the generation of terahertz radiation with a potential applications in several fields like imaging.
Cadoret, Malo; de Mirandes, Estefania; Cladé, Pierre; Guellati-Khélifa, Saïda; Schwob, Catherine; Nez, François; Julien, Lucile; Biraben, François
2008-12-01
We report a new experimental scheme which combines atom interferometry with Bloch oscillations to provide a new measurement of the ratio h/mRb. By using Bloch oscillations, we impart to the atoms up to 1600 recoil momenta and thus we improve the accuracy on the recoil velocity measurement. The deduced value of h/mRb leads to a new determination of the fine structure constant alpha(-1) =137.03599945 (62) with a relative uncertainty of 4.6 x 10(-9). The comparison of this result with the value deduced from the measurement of the electron anomaly provides the most stringent test of QED.
McQuinn, Kristen B W; Dolphin, Andrew E; Berg, Danielle; Kennicutt, Robert
2016-01-01
M104 (NGC 4594; the Sombrero galaxy) is a nearby, well-studied elliptical galaxy included in scores of surveys focused on understanding the details of galaxy evolution. Despite the importance of observations of M104, a consensus distance has not yet been established. Here, we use newly obtained Hubble Space Telescope optical imaging to measure the distance to M104 based on the tip of the red giant branch method. Our measurement yields the distance to M104 to be 9.55 +/- 0.13 +/- 0.31 Mpc equivalent to a distance modulus of 29.90 +/- 0.03 +/- 0.07 mag. Our distance is an improvement over previous results as we use a well-calibrated, stable distance indicator, precision photometry in a optimally selected field of view, and a Bayesian Maximum Likelihood technique that reduces measurement uncertainties. The most discrepant previous results are due to Tully-Fisher method distances, which are likely inappropriate for M104 given its peculiar morphology and structure. Our results are part of a larger program to measu...
Indira Gandhi National Open University, New Delhi (India). Distance Education Council.
Since its inception in India in 1962, distance education has grown in popularity. The Distance Education Council (DEC) directs distance learning within India's higher education system. The DEC's promotion, coordination, and maintenance of standards for distance education are its three major roles. Its initiatives include grants, support for…
Training for Distance Teaching through Distance Learning.
Cadorath, Jill; Harris, Simon; Encinas, Fatima
2002-01-01
Describes a mixed-mode bachelor degree course in English language teaching at the Universidad Autonoma de Puebla (Mexico) that was designed to help practicing teachers write appropriate distance education materials by giving them the experience of being distance students. Includes a course outline and results of a course evaluation. (Author/LRW)
Creating full-Bloch Bose-Einstein condensates with Raman q-plates
Schultz, Justin T.; Hansen, Azure; Murphree, Joseph D.; Jayaseelan, Maitreyi; Bigelow, Nicholas P.
2016-06-01
A coherent two-photon optical Raman interaction in a pseudo-spin-1/2 Bose-Einstein condensate (BEC) serves as a q-plate for atoms, converting spin to orbital angular momentum. This Raman q-plate has a singular pattern in its polarization distribution in analogy to the singular birefringent q-plates used in singular optics. The vortex winding direction and magnitude as well as the final spin state of the BEC depend on the initial spin state and the topology of the optical Raman q-plate beams. Drawing on the mathematical and geometric foundations of singular optics, we derive the equivalent Jones matrix for this Raman q-plate and use it to create and characterize atomic spin singularities in the BEC that are analogous to optical C-point singularities in polarization. By tuning the optical Raman parameters, we can generate a coreless vortex spin texture which contains every possible superposition in a two-state system. We identify this spin texture as a full-Bloch BEC since every point on the Bloch sphere is represented at some point in the cross section of the atomic cloud. This spin-orbit interaction and the spin textures it generates may allow for the observation of interesting geometric phases in matter waves and lead to schemes for topological quantum computation with spinor BECs.
Raman fingerprints on the Bloch sphere of a spinor Bose-Einstein condensate
Schultz, Justin T; Murphree, Joseph D; Jayaseelan, Maitreyi; Bigelow, Nicholas P
2016-01-01
We explore the geometric interpretation of a diabatic, two-photon Raman process as a rotation on the Bloch sphere for a pseudo-spin-1/2 system. The spin state of a spin-1/2 quantum system can be described by a point on the surface of the Bloch sphere, and its evolution during a Raman pulse is a trajectory on the sphere determined by properties of the optical beams: the pulse area, the relative intensities and phases, and the relative frequencies. We experimentally demonstrate key features of this model with a $^{87}$Rb spinor Bose-Einstein condensate, which allows us to examine spatially dependent signatures of the Raman beams. The two-photon detuning allows us to precisely control the spin density and imprinted relative phase profiles, as we show with a coreless vortex. With this comprehensive understanding and intuitive geometric interpretation, we use the Raman process to create and tailor as well as study and characterize exotic topological spin textures in spinor BECs.
Wannier-Bloch approach to localization in high harmonics generation in solids
Osika, Edyta N; Ortmann, Lisa; Suárez, Noslen; Pérez-Hernández, Jose Antonio; Szafran, Bartłomiej; Ciappina, Marcelo F; Sols, Fernando; Landsman, Alexandra S; Lewenstein, Maciej
2016-01-01
Emission of high-order harmonics from solids provides a new avenue in attosecond science. On one hand, it allows to investigate fundamental processes of the non-linear response of electrons driven by a strong laser pulse in a periodic crystal lattice. On the other hand, it opens new paths toward efficient attosecond pulse generation, novel imaging of electronic wave functions, and enhancement of high-order harmonic generation (HHG) intensity. A key feature of HHG in a solid (as compared to the well-understood phenomena of HHG in an atomic gas) is the delocalization of the process, whereby an electron ionized from one site in the periodic lattice may recombine with any other. Here, we develop an analytic model, based on the localized Wannier wave functions in the valence band and delocalized Bloch functions in the conduction band. This Wannier-Bloch approach assesses the contributions of individual lattice sites to the HHG process, and hence addresses precisely the question of localization of harmonic emission...
Dynamic scattering of electron vortex beams--a Bloch wave analysis.
Mendis, B G
2015-02-01
Two important applications of electron vortex beams are in electron magnetic chiral dichroism (EMCD) measurements and nanoparticle manipulation. In both cases orbital angular momentum (〈Lz〉) transfer between the vortex beam and the specimen due to dynamic scattering is critical. In general the 〈Lz〉 pendellösung consists of short and long wavelength oscillations. The former is due to interference between the tightly bound 1s and more dispersive non-1s Bloch states, while the latter is due to interference between the non-1s states. For EMCD experiments with ±ħ angular momentum beams, momentum transfer can be minimised by selecting the appropriate aperture size, so that the probe wavefunction approximately matches that of the 2p-type Bloch states. For manipulating nanoparticles with large angular momentum beams small apertures are required to excite the 1s state and thereby enhance the short wavelength oscillations in 〈Lz〉. This enables efficient momentum transfer to the specimen, provided the nanoparticle dimension corresponds to a minimum in the 〈Lz〉 pendellösung.
Dai, Jin; Niemi, Antti J.; He, Jianfeng; Sieradzan, Adam; Ilieva, Nevena
2016-03-01
We inquire how structure emerges during the process of protein folding. For this we scrutinize collective many-atom motions during all-atom molecular dynamics simulations. We introduce, develop, and employ various topological techniques, in combination with analytic tools that we deduce from the concept of integrable models and structure of discrete nonlinear Schrödinger equation. The example we consider is an α -helical subunit of the HIV envelope glycoprotein gp41. The helical structure is stable when the subunit is part of the biological oligomer. But in isolation, the helix becomes unstable, and the monomer starts deforming. We follow the process computationally. We interpret the evolving structure both in terms of a backbone based Heisenberg spin chain and in terms of a side chain based XY spin chain. We find that in both cases the formation of protein supersecondary structure is akin the formation of a topological Bloch domain wall along a spin chain. During the process we identify three individual Bloch walls and we show that each of them can be modelled with a precision of tenths to several angstroms in terms of a soliton solution to a discrete nonlinear Schrödinger equation.
Dynamics of Bloch State Positronium Emission from MOF Targets Studied via Rydberg TOF Spectroscopy
Piñeiro Escalera, Alina; Jones, Adric; Mills, Allen
2016-05-01
Recent advances in the efficient production and detection of Rydberg positronium (Ps) have made it possible to perform energy- and angle- resolved time-of-flight (TOF) spectroscopy with Ps. We report here TOF measurements of Ps emission from the metal-oxide framework (MOF) targets, MOF-5 and ZIF-8. MOFs are a recently synthesized class of chemical structures, characterized by high long-range order and large surface area to volume ratios (i.e., they are highly porous and uniform, crystalline materials). Ps is found to be emitted predominantly in a series of monoenergetic peaks, providing clear evidence of Ps Bloch states. Measuring the relative populations of the monoenergetic peaks, as a function of implantation energy and target temperature, provides insight into the target-dependent dynamics of Bloch state Ps. Work supported by the U.S. National Science Foundation Grants No. PHY 1206100 and No. PHY 1040590 and the National Science Foundation Graduate Research Fellowship Progam (NSF-GRFP). DOE BES DE-FG02-13ER46972 (MOF-5 synthesis and characterization).
Tscherbul, Timur V; Brumer, Paul
2015-03-14
We present an efficient theoretical method for calculating the time evolution of the density matrix of a multilevel quantum system weakly interacting with incoherent light. The method combines the Bloch-Redfield theory with a partial secular approximation for one-photon coherences, resulting in a master equation that explicitly exposes the reliance on transition rates and the angles between transition dipole moments in the energy basis. The partial secular Bloch-Redfield master equation allows an unambiguous distinction between the regimes of quantum coherent vs. incoherent energy transfer under incoherent light illumination. The fully incoherent regime is characterized by orthogonal transition dipole moments in the energy basis, leading to a dynamical evolution governed by a coherence-free Pauli-type master equation. The coherent regime requires non-orthogonal transition dipole moments in the energy basis and leads to the generation of noise-induced quantum coherences and population-to-coherence couplings. As a first application, we consider the dynamics of excited state coherences arising under incoherent light excitation from a single ground state and observe population-to-coherence transfer and the formation of non-equilibrium quasisteady states in the regime of small excited state splitting. Analytical expressions derived earlier for the V-type system [T. V. Tscherbul and P. Brumer, Phys. Rev. Lett. 113, 113601 (2014)] are found to provide a nearly quantitative description of multilevel excited-state populations and coherences in both the small- and large-molecule limits.
Deza, Michel Marie
2014-01-01
This updated and revised third edition of the leading reference volume on distance metrics includes new items from very active research areas in the use of distances and metrics such as geometry, graph theory, probability theory and analysis. Among the new topics included are, for example, polyhedral metric space, nearness matrix problems, distances between belief assignments, distance-related animal settings, diamond-cutting distances, natural units of length, Heidegger’s de-severance distance, and brain distances. The publication of this volume coincides with intensifying research efforts into metric spaces and especially distance design for applications. Accurate metrics have become a crucial goal in computational biology, image analysis, speech recognition and information retrieval. Leaving aside the practical questions that arise during the selection of a ‘good’ distance function, this work focuses on providing the research community with an invaluable comprehensive listing of the main available di...
Hardware Euclidean Distance Transform Implementation
Institute of Scientific and Technical Information of China (English)
XIE Ying-hua; ZENG Pei-feng; TANG Li-ping
2004-01-01
Based on an efficient algorithm of Euclidean distance transform for binary images, a circuit of O(N2) size is proposed. With in-place calculation, both the intermediate data storing and the result output use the same memory with the input data. This reduces the amount of memory largely. By replacing multipliers with counters, comparators, and adders, the circuit size is further reduced and its calculation speed is improved also.
Kadantsev, Eugene S.; Klooster, Rob; De Boeij, Paul L.; Ziegler, Tom
2007-01-01
Analytic energy gradients with respect to atomic coordinates for systems with translational invariance are formulated within the framework of Kohn-Sham Density Functional Theory. The energy gradients are implemented in the BAND program for periodic DFT calculations which directly employs a Bloch bas
Magnetic Bloch oscillations in the near-Ising antiferromagnet CoCl2#center dot#2D2O
DEFF Research Database (Denmark)
Christensen, N.B.; Lefmann, K.; Johannsen, I.;
2000-01-01
We have investigated the possible occurrence of magnetic Bloch oscillations in CoCl2 . 2D(2)O. We were unable to observe these oscillations at 20.0 K, just above T-N. In an attempt to explain this result, we studied spin waves in the a*-c* plane in order to estimate the effect of the interchain...
Energy Technology Data Exchange (ETDEWEB)
Sokolov, V. N. [Department of Theoretical Physics, Institute for Semiconductor Physics, NASU, Pr. Nauki 41, Kiev 03028 (Ukraine); Iafrate, G. J. [Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, North Carolina 27695-8617 (United States)
2014-02-07
A theory for the spontaneous emission (SE) of terahertz radiation for a Bloch electron traversing a single energy miniband of a superlattice (SL) in a cavity, while undergoing elastic scattering is presented. The Bloch electron is accelerated under the influence of a superimposed external constant electric field and an internal inhomogeneous electric field, while radiating into a microcavity. The analysis of the SE accounts for both the spectral structure of nonharmonic miniband components and the Bloch oscillation degradation effects arising from elastic scattering due to SL interface roughness. The interface roughness effects are decomposed into contributions arising from independent planar and cross-correlated neighboring planar interfaces; parametric numerical estimates show that the cross-correlated contribution to the SE relaxation rate is relatively small, representing less than roughly 10% of the total relaxation rate. It is shown that the degradation effects from SL interface roughness can be more than compensated for by the enhancements derived from microcavity-based tuning of the emission frequency to the cavity density of states peak. The theoretical approach developed herein has general applicability beyond its use for elastic scattering due to interface roughness. As well, the results obtained in this analysis can be useful in the development of SL-based Bloch-oscillator terahertz devices.
DEFF Research Database (Denmark)
de Lasson, Jakob Rosenkrantz; Rigal, B.; Kapon, E.;
We design slow and fast light photonic crystal waveguides for single-photon emission using a Bloch mode expansion and scattering matrix technique. We propose slow light designs that increase the group index-waveguide mode volume ratio for larger Purcell enhancement, and address efficient slow...
Valset, K; Tafto, J
2011-06-01
We classify the point symmetries at the different points in the Brillouin zone for the 17 two-dimensional space groups and the symmetries of the Bloch waves for the 10 two-dimensional crystallographic point groups. Simple examples involving breakdown of Friedels law, Gjonnes-Moodie lines, and reflection and refraction at interfaces are presented.
Categorical perception of tactile distance.
Knight, Frances Le Cornu; Longo, Matthew R; Bremner, Andrew J
2014-05-01
The tactile surface forms a continuous sheet covering the body. And yet, the perceived distance between two touches varies across stimulation sites. Perceived tactile distance is larger when stimuli cross over the wrist, compared to when both fall on either the hand or the forearm. This effect could reflect a categorical distortion of tactile space across body-part boundaries (in which stimuli crossing the wrist boundary are perceptually elongated) or may simply reflect a localised increased in acuity surrounding anatomical landmarks (in which stimuli near the wrist are perceptually elongated). We tested these two interpretations across two experiments, by comparing a well-documented bias to perceive mediolateral tactile distances across the forearm/hand as larger than proximodistal ones along the forearm/hand at three different sites (hand, wrist, and forearm). According to the 'categorical' interpretation, tactile distances should be elongated selectively in the proximodistal axis thus reducing the anisotropy. According to the 'localised acuity' interpretation, distances will be perceptually elongated in the vicinity of the wrist regardless of orientation, leading to increased overall size without affecting anisotropy. Consistent with the categorical account, we found a reduction in the magnitude of anisotropy at the wrist, with no evidence of a corresponding localised increase in precision. These findings demonstrate that we reference touch to a representation of the body that is categorically segmented into discrete parts, which consequently influences the perception of tactile distance.
Distances from Planetary Nebulae
Ciardullo, R
2003-01-01
The [O III] 5007 planetary nebula luminosity function (PNLF) occupies an important place on the extragalactic distance ladder. Since it is the only method that is applicable to all the large galaxies of the Local Supercluster, it is uniquely useful for cross-checking results and linking the Population I and Population II distance scales. We review the physics underlying the method, demonstrate its precision, and illustrate its value by comparing its distances to distances obtained from Cepheids and the Surface Brightness Fluctuation (SBF) method. We use the Cepheid and PNLF distances to 13 galaxies to show that the metallicity dependence of the PNLF cutoff is in excellent agreement with that predicted from theory, and that no additional systematic corrections are needed for either method. However, when we compare the Cepheid-calibrated PNLF distance scale with the Cepheid-calibrated SBF distance scale, we find a significant offset: although the relative distances of both methods are in excellent agreement, th...
A generalized evidence distance
Institute of Scientific and Technical Information of China (English)
Hongming Mo; Xi Lu; Yong Deng
2016-01-01
How to efficiently measure the distance between two basic probability assignments (BPAs) is an open issue. In this paper, a new method to measure the distance between two BPAs is proposed, based on two existing measures of evidence distance. The new proposed method is comprehen-sive and generalized. Numerical examples are used to ilus-trate the effectiveness of the proposed method.
On the relationship between Bloch modes and phase-related refractive index of photonic crystals.
Sun, Guilin; Kirk, Andrew G
2007-10-01
It has previously been shown that the phase-related refractive index is positive in photonic crystals that display negative refraction at higher bands. We hypothesize that the phase velocity is governed by a wave that can be related to the dominant Bloch mode. This dominant wave can be identified from an approximate solution of Maxwell Equations using a homogeneously averaged dielectric constant and the dominant wavevector is related to the fundamental wavevector and the reciprocal lattice vectors. We validate this hypothesis by numerical Fourier decomposition of the field in the entire simulation domain. It confirms that for negative refraction at higher bands, the phase-related refractive index is indeed positive and differs significantly from the negative value of effective refractive index calculated from the band structure.
Bloch-Redfield-Wangsness theory engine implementation using symbolic processing software.
Kuprov, Ilya; Wagner-Rundell, Nicola; Hore, P J
2007-02-01
We describe a general method for the automated symbolic processing of Bloch-Redfield-Wangsness relaxation theory equations for liquid-phase spin dynamics in the algebraically challenging case of rotationally modulated interactions. The processing typically takes no more than a few seconds (on a contemporary single-processor workstation) and yields relaxation rate expressions that are completely general with respect to the spectral density functions, relative orientations, and magnitudes of the interaction tensors, with all cross-correlations accounted for. The algorithm easily deals with fully rhombic interaction tensors, and is able, with little if any modification, to treat a large variety of the relaxation mechanisms encountered in NMR, EPR, and spin dynamics in general.
Sub-cycle control of terahertz high-harmonic generation by dynamical Bloch oscillations
Schubert, O; Langer, F; Urbanek, B; Lange, C; Huttner, U; Golde, D; Meier, T; Kira, M; Koch, S W; Huber, R
2016-01-01
Ultrafast charge transport in strongly biased semiconductors is at the heart of highspeed electronics, electro-optics, and fundamental solid-state physics. Intense light pulses in the terahertz (THz) spectral range have opened fascinating vistas: Since THz photon energies are far below typical electronic interband resonances, a stable electromagnetic waveform may serve as a precisely adjustable bias. Novel quantum phenomena have been anticipated for THz amplitudes reaching atomic field strengths. We exploit controlled THz waveforms with peak fields of 72 MV/cm to drive coherent interband polarization combined with dynamical Bloch oscillations in semiconducting gallium selenide. These dynamics entail the emission of phase-stable high-harmonic transients, covering the entire THz-to-visible spectral domain between 0.1 and 675 THz. Quantum interference of different ionization paths of accelerated charge carriers is controlled via the waveform of the driving field and explained by a quantum theory of inter- and in...
Chirped dual periodic structures for photonic Bloch oscillations and Zener tunneling.
Estevez, J O; Arriaga, J; Reyes-Ayona, E; Agarwal, V
2015-06-29
Experimental evidence of photon Wannier-stark ladders (WSLs) and Zener tunneling (ZT) in one dimensional dual-periodical (DP) optical superlattices based on Porous Silicon (PSi), is presented. An introduction of linear gradient in physical thickness of the layers, composed of five stacks of two different periodic substructures, resulted in the appearance of four WSLs resonances and resonant Zener tunneling of nearest resonances of two consecutive WSLs. Theoretical analysis of time-resolved reflection spectra as a function of gradient reveals the presence of photonic Bloch oscillations (BOs) and an eventual tunneling at a specific value of linear gradient (20%), has been demonstrated through scattering maps. Measured reflection from different DP photonic structures confirm the presence of minibands, WSLs and ZT in the near infrared region.
Bloch oscillations of ultracold atoms: a tool for a metrological determination of h/m Rb.
Battesti, Rémy; Cladé, Pierre; Guellati-Khélifa, Saïda; Schwob, Catherine; Grémaud, Benoît; Nez, François; Julien, Lucile; Biraben, François
2004-06-25
We use Bloch oscillations in a horizontal moving standing wave to transfer a large number of photon recoils to atoms with a high efficiency (99.5% per cycle). By measuring the photon recoil of 87Rb, using velocity-selective Raman transitions to select a subrecoil velocity class and to measure the final accelerated velocity class, we have determined h/m(Rb) with a relative precision of 0.4 ppm. To exploit the high momentum transfer efficiency of our method, we are developing a vertical standing wave setup. This will allow us to measure h/m(Rb) better than 10(-8) and hence the fine structure constant alpha with an uncertainty close to the most accurate value coming from the (g-2) determination.
Backaction-driven transport of Bloch oscillating atoms in ring cavities.
Goldwin, J; Venkatesh, B Prasanna; O'Dell, D H J
2014-08-15
We predict that an atomic Bose-Einstein condensate strongly coupled to an intracavity optical lattice can undergo resonant tunneling and directed transport when a constant and uniform bias force is applied. The bias force induces Bloch oscillations, causing amplitude and phase modulation of the lattice which resonantly modifies the site-to-site tunneling. For the right choice of parameters a net atomic current is generated. The transport velocity can be oriented oppositely to the bias force, with its amplitude and direction controlled by the detuning between the pump laser and the cavity. The transport can also be enhanced through imbalanced pumping of the two counterpropagating running wave cavity modes. Our results add to the cold atoms quantum simulation toolbox, with implications for quantum sensing and metrology.
Zheng, Ming Jie; Wang, Gang; Yu, Kin Wah
2010-12-01
We have studied the optical oscillation and tunneling of light waves in optical waveguide ladders (OWLs) formed by two coupled planar optical waveguide arrays. For the band structure, a midzone gap is formed owing to band hybridization, and its wavenumber position can be tuned throughout the whole Brillouin zone, which is different from the Bragg gap. By imposing a gradient in the propagation constant in each array, Bloch-Zener oscillation (BZO) is realized with Zener tunneling between the bands occurring at the midzone, which is contrary to the common BZO with tunneling at the center or edge of the Brillouin zone. The occurrence of BZO is demonstrated by using the field-evolution analysis. The tunable hybridization at the midzone enhances the tunability of BZO in the OWLs. This Letter may offer new insights into the coherent phenomena in optical lattices.
Optical Bloch oscillations and Zener tunneling of Airy beams in ionic-type photonic lattices.
Xiao, Fajun; Zhu, Weiren; Shang, Wuyun; Wang, Meirong; Zhang, Peng; Liu, Sheng; Premaratne, Malin; Zhao, Jianlin
2016-08-01
We report on the existence of optical Bloch oscillations (OBOs) and Zener tunneling (ZT) of Airy beams in ionic-type photonic lattices with a refractive index ramp. Different from their counterparts in uniform lattices, Airy beams undergoing OBOs show an alternatively switched concave and convex trajectory as well as a periodical revival of input beam profiles. Moreover, the ionic-type photonic lattice established in photorefractive crystal exhibits a reconfigurable lattice structure, which provides a flexible way to tune the amplitude and period of the OBOs. Remarkably, it is demonstrated that the band gap of the lattice can be readily controlled by rotating the lattice inducing beam, which forces the ZT rate to follow two significant different decay curves amidst decreasing index gradient. Our results open up new possibilities for all-optical switching, routing and manipulation of Airy beams.
Quasiclassical analysis of Bloch oscillations in non-Hermitian tight-binding lattices
Graefe, E M; Rush, A
2016-01-01
Many features of Bloch oscillations in one-dimensional quantum lattices with a static force can be described by quasiclassical considerations for example by means of the acceleration theorem, at least for Hermitian systems. Here the quasiclassical approach is extended to non-Hermitian lattices, which are of increasing interest. The analysis is based on a generalised non-Hermitian phase space dynamics developed recently. Applications to a single-band tight-binding system demonstrate that many features of the quantum dynamics can be understood from this classical description qualitatively and even quantitatively. Two non-Hermitian and $PT$-symmetric examples are studied, a Hatano-Nelson lattice with real coupling constants and a system with purely imaginary couplings, both for initially localised states in space or in momentum. It is shown that the time-evolution of the norm of the wave packet and the expectation values of position and momentum can be described in a classical picture.
High tip angle approximation based on a modified Bloch-Riccati equation.
Boulant, Nicolas; Hoult, David I
2012-02-01
When designing a radio-frequency pulse to produce a desired dependence of magnetization on frequency or position, the small flip angle approximation is often used as a first step, and a Fourier relation between pulse and transverse magnetization is then invoked. However, common intuition often leads to linear scaling of the resulting pulse so as to produce a larger flip angle than the approximation warrants--with surprisingly good results. Starting from a modified version of the Bloch-Riccati equation, a differential equation in the flip angle itself, rather than in magnetization, is derived. As this equation has a substantial linear component that is an instance of Fourier's equation, the intuitive approach is seen to be justified. Examples of the accuracy of this higher tip angle approximation are given for both constant- and variable-phase pulses.
Electroweak corrections and Bloch-Nordsieck violations in 2-to-2 processes at the LHC
Stirling, W J
2013-01-01
We consider the effect of next-to-leading order (NLO) electroweak corrections to Standard Model 2-to-2 processes, taking into account the potentially large double logarithms originating from both real and virtual corrections. A study of the leading Sudakov logarithms is presented and Bloch-Nordsieck (BN) violations are discussed for processes at the CERN Large Hadron Collider. In particular, we focus on the processes Z/photon+jet and also the ratio of Z to photon production. This ratio is known to be insensitive to NLO QCD corrections but this is not expected to be the case for the electroweak corrections. We also comment on the effect of electroweak corrections and the presence of BN violation for QCD processes, in particular dijet production, and also for purely electroweak processes such as W + H and W + Z associated production.
Design of guided Bloch surface wave resonance bio-sensors with high sensitivity
Kang, Xiu-Bao; Wen, Li-Wei; Wang, Zhi-Guo
2017-01-01
The sensing performance of bio-sensors based on guided Bloch surface wave (BSW) resonance (GBR) is studied. GBR is realized by coupling the propagating electromagnetic wave with BSW on one side of a one-dimensional photonic crystal slab via the grating on the other side. The sensitivity of the designed bio-sensors is proportional to the grating constant when the wavelength spectrum is analyzed, and inversely proportional to the normal wave vector of the incident electromagnetic wave when the angular spectrum is resolved. For a GBR bio-sensor designed to operate near 70° angle of incidence from air, the angular sensitivity is very high, reaching 128 deg RIU-1. The sensitivity can be substantially increased by designing bio-sensors for operating at larger angles of incidence.
Modified-Bloch-equation description of EPR transient nutations and free induction decay in solids
Energy Technology Data Exchange (ETDEWEB)
Asadullina, N.Ya.; Asadullin, Ya.Ya. [Kazan State Technical University, Department of General Physics, Kazan (Russian Federation); Asadullin, T.Ya. [Kazan State Technical University, Department of General Physics, Kazan (Russian Federation). E-mail: atimur@physics.ktsu-kai.ru
2001-04-09
Based on the experimental work by Boscaino et al on the EPR transient nutations (TNs) and free induction decay (FID) in solids, we propose the modified Bloch equations (MBEs). In addition to the Tomita expression for power-dependent parameter T{sub 2u}, we give an original phenomenological expression for power-dependent parameter T{sub 2v} and tuning {delta}. Both analytical (in the form of a Torrey solution with these parameters) and numerical solutions of MBE are obtained for TN and for different FID regimes with very good agreement between theory and experiment. We also discuss the meaning and role of the instantaneous diffusion mechanism in the transient pulse experiments. (author)
Sub-nanometer linewidth perfect absorption in visible band induced by Bloch surface wave
Cong, Jiawei; Liu, Wenxing; Zhou, Zhiqiang; Ren, Naifei; Ding, Guilin; Chen, Mingyang; Yao, Hongbing
2016-12-01
We demonstrate the unity absorption of visible light with an ultra-narrow 0.1 nm linewidth. It arises from the Bloch surface wave resonance in alternating TiO2/SiO2 multilayers. The total absorption and narrow linewidth are explained from the radiative and absorptive damping, which are quantitatively determined by the temporal coupled mode theory. When a silver film with proper thickness is added to the absorber, the perfect absorption is achieved with only 3 structural bilayers, in contrast with 8 bilayers required without Ag. Furthermore, significant field enhancement and an ultrahigh 2600/RIU sensing figure-of-merit are simultaneously obtained at resonance, which might facilitate applications in nonlinear optical devices and high resolution refractive index sensing.
Bloch waves in an arbitrary two-dimensional lattice of subwavelength Dirichlet scatterers
Schnitzer, Ory
2016-01-01
We study waves governed by the planar Helmholtz equation, propagating in an infinite lattice of subwavelength Dirichlet scatterers, the periodicity being comparable to the wavelength. Applying the method of matched asymptotic expansions, the scatterers are effectively replaced by asymptotic point constraints. The resulting coarse-grained Bloch-wave dispersion problem is solved by a generalised Fourier series, whose singular asymptotics in the vicinities of scatterers yield the dispersion relation governing modes that are strongly perturbed from plane-wave solutions existing in the absence of the scatterers; there are also empty-lattice waves that are only weakly perturbed. Characterising the latter is useful in interpreting and potentially designing the dispersion diagrams of such lattices. The method presented, that simplifies and expands on Krynkin & McIver [Waves Random Complex, 19 347 2009], could be applied in the future to study more sophisticated designs entailing resonant subwavelength elements di...
Coexisting localized and extended optical Bloch states in a periodic deep wire array microcavity
Löchner, Franz J. F.; Mischok, Andreas; Brückner, Robert; Lyssenko, Vadim G.; Zakhidov, Alexander A.; Fröb, Hartmut; Leo, K.
2015-09-01
We embed periodic SiO2 wires in an organic microcavity, producing a rectangular potential by the different optical thicknesses of the active layer due to the additional SiO2 layer. By μ -photoluminescence spectroscopy, we observe the energy dispersion of the photons and obtain discrete localized below and extended Bloch states above the potential barrier, respectively, showing that electro-magnetic waves can behave like massive particles, such as electrons, in crystal lattices. We investigate the dependencies on wire width and period and use the Kronig-Penney model to describe the photon energy dispersion, including an "effective mass" of a photon propagating through a microcavity implying polarization splitting. We obtain excellent agreement between experiment, simulation and analytical calculation.
Huang, Zhongyi; Markowich, Peter; Sparber, Christof
2012-01-01
We present a new numerical method for accurate computations of solutions to (linear) one dimensional Schr\\"odinger equations with periodic potentials. This is a prominent model in solid state physics where we also allow for perturbations by non-periodic potentials describing external electric fields. Our approach is based on the classical Bloch decomposition method which allows to diagonalize the periodic part of the Hamiltonian operator. Hence, the dominant effects from dispersion and periodic lattice potential are computed together, while the non-periodic potential acts only as a perturbation. Because the split-step communicator error between the periodic and non-periodic parts is relatively small, the step size can be chosen substantially larger than for the traditional splitting of the dispersion and potential operators. Indeed it is shown by the given examples, that our method is unconditionally stable and more efficient than the traditional split-step pseudo spectral schemes. To this end a particular fo...
Identification of Bloch-modes in hollow-core photonic crystal fiber cladding.
Couny, F; Benabid, F; Roberts, P J; Burnett, M T; Maier, S A
2007-01-22
We report on the experimental visualization of the cladding Bloch-modes of a hollow-core photonic crystal fiber. Both spectral and spatial field nformation is extracted using the approach, which is based on measurement of the near-field and Fresnel-zone that results after propagation over a short length of fiber. A detailed study of the modes near the edges of the band gap shows that it is formed by the influence of three types of resonator: the glass interstitial apex, the silica strut which joins the neighboring apexes, and the air hole. The cladding electromagnetic field which survives the propagation is found to be spatially coherent and to contain contributions from just a few types of cladding mode.
DEFF Research Database (Denmark)
Bozhevolnyi, Sergey I.; Volkov, V.S.; Søndergaard, Thomas;
2002-01-01
We employ a collection scanning near-field optical microscope (SNOM) to image the propagation of light at telecommunication wavelengths along straight and bent regions of silicon-on-insulator photonic crystal waveguides (PCWs) formed by removing a single row of holes in the triangular 410-nm......-period lattice along the GammaM direction of the irreducible Brillouin zone. We obtain high quality SNOM images of PCWs excited in the wavelength range of 1520-1570 nm, which indicate good PCW mode confinement and low propagation loss. Using averaged cross sections of the intensity distributions before and after...... the interference between a quasihomogeneous background field and Bloch harmonics of the PCW mode, we account for spatial frequency spectra of the intensity variations and determine the propagation constant of the PCW mode at 1520 nm. The possibilities and limitations of SNOM imaging for the characterization...
Deformed Harmonic Oscillators for Metal Clusters and Balian-Bloch Theory
Bonatsos, D; Raychev, P P; Terziev, P A; Bonatsos, Dennis
2003-01-01
The predictions for the shell structure of metal clusters of the three-dimensional q-deformed harmonic oscillator (3D q-HO), utilizing techniques of quantum groups and having the symmetry Uq(3)$\\supset$SOq(3), are compared to the restrictions imposed by the periodic orbit theory of Balian and Bloch, of electrons moving in a spherical cavity. It is shown that agreement between the predictions of the two models is established through the introduction of an additional term to the Hamiltonian of the 3D q-HO, which does not influence the predictions for supershells. This term preserves the Uq(3)$\\supset$SOq(3) symmetry, while in addition it can be derived through a variational procedure, analogous to the one leading from the usual harmonic oscillator to the Morse oscillator by introducing the concept of the Variable Frequency Oscillator (VFO).
Wu, Zhizhang; Huang, Zhongyi
2016-07-01
In this paper, we consider the numerical solution of the one-dimensional Schrödinger equation with a periodic lattice potential and a random external potential. This is an important model in solid state physics where the randomness results from complicated phenomena that are not exactly known. Here we generalize the Bloch decomposition-based time-splitting pseudospectral method to the stochastic setting using the generalized polynomial chaos with a Galerkin procedure so that the main effects of dispersion and periodic potential are still computed together. We prove that our method is unconditionally stable and numerical examples show that it has other nice properties and is more efficient than the traditional method. Finally, we give some numerical evidence for the well-known phenomenon of Anderson localization.
A Bloch-Torrey Equation for Diffusion in a Deforming Media
Energy Technology Data Exchange (ETDEWEB)
Rohmer, Damien; Gullberg, Grant T.
2006-12-29
Diffusion Tensor Magnetic Resonance Imaging (DTMRI)technique enables the measurement of diffusion parameters and therefore,informs on the structure of the biological tissue. This technique isapplied with success to the static organs such as brain. However, thediffusion measurement on the dynamically deformable organs such as thein-vivo heart is a complex problem that has however a great potential inthe measurement of cardiac health. In order to understand the behavior ofthe Magnetic Resonance (MR)signal in a deforming media, the Bloch-Torreyequation that leads the MR behavior is expressed in general curvilinearcoordinates. These coordinates enable to follow the heart geometry anddeformations through time. The equation is finally discretized andpresented in a numerical formulation using implicit methods, in order toget a stable scheme that can be applied to any smooth deformations.Diffusion process enables the link between the macroscopic behavior ofmolecules and themicroscopic structure in which they evolve. Themeasurement of diffusion in biological tissues is therefore of majorimportance in understanding the complex underlying structure that cannotbe studied directly. The Diffusion Tensor Magnetic ResonanceImaging(DTMRI) technique enables the measurement of diffusion parametersand therefore provides information on the structure of the biologicaltissue. This technique has been applied with success to static organssuch as the brain. However, diffusion measurement of dynamicallydeformable organs such as the in-vivo heart remains a complex problem,which holds great potential in determining cardiac health. In order tounderstand the behavior of the magnetic resonance (MR) signal in adeforming media, the Bloch-Torrey equation that defines the MR behavioris expressed in general curvilinear coordinates. These coordinates enableus to follow the heart geometry and deformations through time. Theequation is finally discretized and presented in a numerical formulationusing
Directory of Open Access Journals (Sweden)
Claudiu Alexandru Baciu
2015-12-01
Full Text Available In our researches we have determined the variation of certain physiological indexes, such as the oxygen consume, the breathing rhythm, the glycaemia and the number of red blood cells under the action of Coragen insecticide on Carassius auratus gibelio Bloch. Under the action of Coragen, we have registered significant changes in the oxygen consume, the breathing rhythm, the number of red blood cells and glycemia at the Carassius auratus gibelio Bloch items, considered as answers to the stress provoked by emissions. The highest variations of the physiological indexes, from the perspective of the percentage, were noticed at the glycemia, which at the mark was 28 mg/dl, and in the treated sample, with 0.1 ml/l Coragen is 42 mg/dl, representing a 50% growth and at the breathing rhythm in 24 hours, where values significantly decreased with 41.18% at the concentration of 0.07 ml/l and with 39.33% at the concentrations of 0.05 and 0.1 ml/l Coragen. The slightest variations of the physiological indexes, from the perspective of percentage, were noticed at the oxygen consumption, which, at the mark is of 55.302 ml oxygen/kg/hour, and for the treated sample, with 0.1 ml/l Coragen is 34.81 ml oxygen/kg/hour, representing a decrease of 37.06% in 24 hours and the number of red blood cells, where the values have significantly decrease with 9.58%, 13.48%, respectively 18.44% for the concentrations of 0.05, 0.07 and 0.1 ml/l Coragen.
DEFF Research Database (Denmark)
Larsen, Gunvor Riber
The environmental impact of tourism mobility is linked to the distances travelled in order to reach a holiday destination, and with tourists travelling more and further than previously, an understanding of how the tourists view the distance they travel across becomes relevant. Based on interviews...... contribute to an understanding of how it is possible to change tourism travel behaviour towards becoming more sustainable. How tourists 'consume distance' is discussed, from the practical level of actually driving the car or sitting in the air plane, to the symbolic consumption of distance that occurs when...... travelling on holiday becomes part of a lifestyle and a social positioning game. Further, different types of tourist distance consumers are identified, ranging from the reluctant to the deliberate and nonchalant distance consumers, who display very differing attitudes towards the distance they all travel...
Ristad, E S; Ristad, Eric Sven; Yianilos, Peter N.
1996-01-01
In many applications, it is necessary to determine the similarity of two strings. A widely-used notion of string similarity is the edit distance: the minimum number of insertions, deletions, and substitutions required to transform one string into the other. In this report, we provide a stochastic model for string edit distance. Our stochastic model allows us to learn a string edit distance function from a corpus of examples. We illustrate the utility of our approach by applying it to the difficult problem of learning the pronunciation of words in conversational speech. In this application, we learn a string edit distance with one fourth the error rate of the untrained Levenshtein distance. Our approach is applicable to any string classification problem that may be solved using a similarity function against a database of labeled prototypes. Keywords: string edit distance, Levenshtein distance, stochastic transduction, syntactic pattern recognition, prototype dictionary, spelling correction, string correction, ...
Interface Simulation Distances
Directory of Open Access Journals (Sweden)
Pavol Černý
2012-10-01
Full Text Available The classical (boolean notion of refinement for behavioral interfaces of system components is the alternating refinement preorder. In this paper, we define a distance for interfaces, called interface simulation distance. It makes the alternating refinement preorder quantitative by, intuitively, tolerating errors (while counting them in the alternating simulation game. We show that the interface simulation distance satisfies the triangle inequality, that the distance between two interfaces does not increase under parallel composition with a third interface, and that the distance between two interfaces can be bounded from above and below by distances between abstractions of the two interfaces. We illustrate the framework, and the properties of the distances under composition of interfaces, with two case studies.
Distance Education for People with Visual Impairments
Liakou, Maria; Manousou, Evaggelia
2015-01-01
This paper studies the standards of higher Distance Education, focusing on the Hellenic Open University, for people who have visual impairments, so that it becomes fully accessible and thus helps reduce social exclusion. Specifically, it aims to study the operational context of Distance Education, the possibilities that modern technology provides…
Ziegler, Gerhard
2011-01-01
Distance protection provides the basis for network protection in transmission systems and meshed distribution systems. This book covers the fundamentals of distance protection and the special features of numerical technology. The emphasis is placed on the application of numerical distance relays in distribution and transmission systems.This book is aimed at students and engineers who wish to familiarise themselves with the subject of power system protection, as well as the experienced user, entering the area of numerical distance protection. Furthermore it serves as a reference guide for s
Directory of Open Access Journals (Sweden)
B. Prasanna Venkatesh
2015-12-01
Full Text Available In this paper we give a new description, in terms of optomechanics, of previous work on the problem of an atomic Bose–Einstein condensate interacting with the optical lattice inside a laser-pumped optical cavity and subject to a bias force, such as gravity. An atomic wave packet in a tilted lattice undergoes Bloch oscillations; in a high-finesse optical cavity the backaction of the atoms on the light leads to a time-dependent modulation of the intracavity lattice depth at the Bloch frequency which can in turn transport the atoms up or down the lattice. In the optomechanical picture, the transport dynamics can be interpreted as a manifestation of dynamical backaction-induced sideband damping/amplification of the Bloch oscillator. Depending on the sign of the pump-cavity detuning, atoms are transported either with or against the bias force accompanied by an up- or down-conversion of the frequency of the pump laser light. We also evaluate the prospects for using the optomechanical Bloch oscillator to make continuous measurements of forces by reading out the Bloch frequency. In this context, we establish the significant result that the optical spring effect is absent and the Bloch frequency is not modified by the backaction.
Institute of Scientific and Technical Information of China (English)
Zhang Bing-Zhi; Cui Hu; Li Xiang-Heng; She Wei-Long
2009-01-01
We theoretically study the beam dynamical hehaviour in a modulated optical lattice with a quadratic potential in a photovoltaic photorefractive crystal. We find that two different Bloch oscillation patterns appear for the excitation of both broad and narrow light beams. One kind of optical Landau-Zener tunnelling also appears upon the Bloch oscillation and can be controlled by adjusting the parameter of the optical lattice. Unlike the case of linear potential, the energy radiation due to Landau-Zener tunnelling can be confined in modulated lattices of this kind. For high input intensity levels, the Landau-Zener tunnelling is suppressed by the photovoltaic photorefractive nonlinearity and a symmetry breaking of beam propagation from the modulational instability appears.
Liu, Yangyang; Zeng, Xiaoge; Popovic, Milos A
2013-01-01
We experimentally demonstrate broadband waveguide crossing arrays showing ultra low loss down to $0.04\\,$dB/crossing ($0.9\\%$), matching theory, and crosstalk suppression over $35\\,$dB, in a CMOS-compatible geometry. The principle of operation is the tailored excitation of a low-loss spatial Bloch wave formed by matching the periodicity of the crossing array to the difference in propagation constants of the 1$^\\text{st}$- and 3$^\\text{rd}$-order TE-like modes of a multimode silicon waveguide. Radiative scattering at the crossing points acts like a periodic imaginary-permittivity perturbation that couples two supermodes, which results in imaginary (radiative) propagation-constant splitting and gives rise to a low-loss, unidirectional breathing Bloch wave. This type of crossing array provides a robust implementation of a key component enabling dense photonic integration.
Biomechanics of Distance Running.
Cavanagh, Peter R., Ed.
Contributions from researchers in the field of running mechanics are included in the 13 chapters of this book. The following topics are covered: (1) "The Mechanics of Distance Running: A Historical Perspective" (Peter Cavanagh); (2) "Stride Length in Distance Running: Velocity, Body Dimensions, and Added Mass Effects" (Peter Cavanagh, Rodger…
ORDERED WEIGHTED DISTANCE MEASURE
Institute of Scientific and Technical Information of China (English)
Zeshui XU; Jian CHEN
2008-01-01
The aim of this paper is to develop an ordered weighted distance (OWD) measure, which is thegeneralization of some widely used distance measures, including the normalized Hamming distance, the normalized Euclidean distance, the normalized geometric distance, the max distance, the median distance and the min distance, etc. Moreover, the ordered weighted averaging operator, the generalized ordered weighted aggregation operator, the ordered weighted geometric operator, the averaging operator, the geometric mean operator, the ordered weighted square root operator, the square root operator, the max operator, the median operator and the min operator axe also the special cases of the OWD measure. Some methods depending on the input arguments are given to determine the weights associated with the OWD measure. The prominent characteristic of the OWD measure is that it can relieve (or intensify) the influence of unduly large or unduly small deviations on the aggregation results by assigning them low (or high) weights. This desirable characteristic makes the OWD measure very suitable to be used in many actual fields, including group decision making, medical diagnosis, data mining, and pattern recognition, etc. Finally, based on the OWD measure, we develop a group decision making approach, and illustrate it with a numerical example.
Normalized information distance
Vitányi, P.M.B.; Balbach, F.J.; Cilibrasi, R.L.; Li, M.; Emmert-Streib, F.; Dehmer, M.
2009-01-01
The normalized information distance is a universal distance measure for objects of all kinds. It is based on Kolmogorov complexity and thus uncomputable, but there are ways to utilize it. First, compression algorithms can be used to approximate the Kolmogorov complexity if the objects have a string
Normalized information distance
Vitányi, P.M.B.; Balbach, F.J.; Cilibrasi, R.L.; Li, M.
2008-01-01
The normalized information distance is a universal distance measure for objects of all kinds. It is based on Kolmogorov complexity and thus uncomputable, but there are ways to utilize it. First, compression algorithms can be used to approximate the Kolmogorov complexity if the objects have a string
Simulação de sinais de RMN através das equações de Bloch
Directory of Open Access Journals (Sweden)
Tiago Bueno Moraes
2014-01-01
Full Text Available The aim of this paper was to present a simple and fast way of simulating Nuclear Magnetic Resonance signals using the Bloch equations. These phenomenological equations describe the classical behavior of macroscopic magnetization and are easily simulated using rotation matrices. Many NMR pulse sequences can be simulated with this formalism, allowing a quantitative description of the influence of many experimental parameters. Finally, the paper presents simulations of conventional sequences such as Single Pulse, Inversion Recovery, Spin Echo and CPMG.
Normalized Information Distance
Vitanyi, Paul M B; Cilibrasi, Rudi L; Li, Ming
2008-01-01
The normalized information distance is a universal distance measure for objects of all kinds. It is based on Kolmogorov complexity and thus uncomputable, but there are ways to utilize it. First, compression algorithms can be used to approximate the Kolmogorov complexity if the objects have a string representation. Second, for names and abstract concepts, page count statistics from the World Wide Web can be used. These practical realizations of the normalized information distance can then be applied to machine learning tasks, expecially clustering, to perform feature-free and parameter-free data mining. This chapter discusses the theoretical foundations of the normalized information distance and both practical realizations. It presents numerous examples of successful real-world applications based on these distance measures, ranging from bioinformatics to music clustering to machine translation.
Estimating distances from parallaxes
Astraatmadja, Tri L.; Bailer-Jones, Coryn
2017-01-01
In astrometric surveys such as Gaia and LSST, parallaxes will be measured for about a billion stars, but zero distances will be measured. Distances must be inferred from the parallaxes, and the common inference practice is by inverting the parallax. This, however, is only appropriate when there is no noise present. As noise will always be present and most stars in future surveys will have non-negligible fractional parallax uncertainties, we must treat distance estimation as an inference problem. The usage of prior assumptions become unavoidable. In this talk I will present a method on how to infer distances using Bayesian inference. Three minimalists, isotropic priors are used, as well an anisotropic prior derived from the observability of stars in a Milky Way model. The performance of these priors are investigated using a simulated Gaia-like catalogue. Recent results of distance estimation using the parallaxes of 2 million Gaia DR1 stars will also be discussed.
Savoie, Baptiste
2012-01-01
Starting with a nearest-neighbors tight-binding model, we rigorously investigate the bulk zero-field orbital susceptibility of a non-interacting Bloch electrons gas in graphene-like solids at fixed temperature and density of particles. In the zero-temperature limit and in the semiconducting situation, we derive a complete expression which holds for an arbitrary number of bands with possible degeneracies. In the particular case of a two-bands gapped model, all involved quantities are exactly written down. Besides the formula we obtain have the special feature to be suitable for numerical computations since it only involves the eigenvalues and associated eigenfunctions of the Bloch Hamiltonian, together with the derivatives (up to the second order) w.r.t. the quasi-momentum of the matrix-elements of the Bloch Hamiltonian. Finally we give a simple application for the two-bands gapped model by considering the case of a dispersion law which is linear w.r.t. the quasi-momentum in the gapless limit. Through this ins...
The Bloch wave operator: generalizations and applications: II. The time-dependent case
Energy Technology Data Exchange (ETDEWEB)
Jolicard, Georges [Observatoire de Besancon (UMR-CNRS 6091), Universite de Franche-Comte, 41 bis, Avenue de l' Observatoire, 25000 Besancon (France); Killingbeck, John P [Observatoire de Besancon (UMR-CNRS 6091), Universite de Franche-Comte, 41 bis, Avenue de l' Observatoire, 25000 Besancon (France); Mathematics Department, University of Hull, Hull HU6 7RX (United Kingdom)
2003-10-10
Part II of the review shows how the stationary Bloch wave operator of part I can be suitably modified to give a time-dependent wave operator. This operator makes it possible to use a relatively small active space in order to describe the dynamical processes which occur in quantum mechanical systems which have a time-dependent Hamiltonian. A close study is made of the links between the time-dependent and time-independent wave operators at the adiabatic limit; the analysis clarifies the way in which the wave operator formalism allows the time evolution of a system or a wave packet to be described in terms of a fast evolution inside the active space together with weak transitions out of this space which can be treated by perturbation methods. Two alternative wave operator equations of motion are derived and analysed. The first one is a non-linear differential equation in the usual Hilbert space; the second one is a differential equation in an extended Hilbert space with an extra time variable added and becomes equivalent to the usual Bloch equation when the Floquet Hamiltonian is taken in place of the ordinary Hamiltonian. A study is made of the close relationships between the time-dependent wave operator formalism, the Floquet theory and the (t, t') theory. Some original methods of solution of the two forms of wave operator equation are proposed and lead to new techniques of integration for the time-dependent Schroedinger equation (e.g., the generalized Green equation procedure). Mixed procedures involving both the time-independent and time-dependent wave operators are shown to be applicable to the internal eigenstate problem for large complex matrices. A detailed account is given of the description of inelastic and photoreactive processes by means of the time-dependent wave operator formalism, with particular attention to laser-molecule interactions. The emphasis is on projection operator techniques, with special attention being given to the method of selection
Isolation by distance, web service
Directory of Open Access Journals (Sweden)
Bohonak Andrew J
2005-03-01
Full Text Available Abstract Background The population genetic pattern known as "isolation by distance" results from spatially limited gene flow and is a commonly observed phenomenon in natural populations. However, few software programs exist for estimating the degree of isolation by distance among populations, and they tend not to be user-friendly. Results We have created Isolation by Distance Web Service (IBDWS a user-friendly web interface for determining patterns of isolation by distance. Using this site, population geneticists can perform a variety of powerful statistical tests including Mantel tests, Reduced Major Axis (RMA regression analysis, as well as calculate FST between all pairs of populations and perform basic summary statistics (e.g., heterozygosity. All statistical results, including publication-quality scatter plots in Postscript format, are returned rapidly to the user and can be easily downloaded. Conclusion IBDWS population genetics analysis software is hosted at http://phage.sdsu.edu/~jensen/ and documentation is available at http://www.bio.sdsu.edu/pub/andy/IBD.html. The source code has been made available on Source Forge at http://sourceforge.net/projects/ibdws/.
Estimating distances from parallaxes
Bailer-Jones, C A L
2015-01-01
Astrometric surveys such as Gaia and LSST will measure parallaxes for hundreds of millions of stars. Yet they will not measure a single distance. Rather, a distance must be estimated from a parallax. In this didactic article, I show that doing this is not trivial once the fractional parallax error is larger than about 20%, which will be the case for about 80% of stars in the Gaia catalogue. Estimating distances is an inference problem in which the use of prior assumptions is unavoidable. I investigate the properties and performance of various priors and examine their implications. A supposed uninformative uniform prior in distance is shown to give very poor distance estimates (large bias and variance). Any prior with a sharp cut-off at some distance has similar problems. The choice of prior depends on the information one has available - and is willing to use - concerning, for example, the survey and the Galaxy. I demonstrate that a simple prior which decreases asymptotically to zero at infinite distance has g...
Institute of Scientific and Technical Information of China (English)
杨小平; 何伟; 孙亚琳; 廖俊宇
2012-01-01
As a tool of data analysis and formalizing for knowledge management, Formal Concept Analysis! FCA) can effective mine knowledge interested for people from lager textual data, and which are held in esteem by many researchers. The premise of FCA is that need a pure and well defined formal context. Extracting characteristic word directly from the text and exploiting document with characteristic words to form textual formal context(TFC) , which lead to generating a highly sparse two-dimensional table with a lot of noise. It seriously affects efficiency of building concept lattice and the structure of lattice. Therefore, it is necessary to find an effective method for reducing the textual formal context. Comprehensively considering the nature of textual formal context in this paper, we propose a method named TFC-Reducing for the reduction of textual formal context from the view of semantic distance between attributes and mathematical theory, and give a method for evaluating reduction of textual formal context, named as information losses entropy ILE and semantic coverage SC.%形式概念分析作为数据分析和知识处理的形式化工具,可以有效的从海量文本数据中挖掘出人们感兴趣的知识,受到许多研究人员的推崇.形式概念分析的前提条件是必须有一个纯净、良好定义的形式背景.从文本中直接提取特征词,利用文本-特征词形成的文本型形式背景(Textual Formal Context TFC)是一个高度稀疏的二维表,带有很多的噪音信息,严重影响形式概念分析的建格效率以及概念格的结构.因此找到一种有效的文本型形式背景约简方法很有必要.本文综合考虑文本型形式背景的本质特征,从属性语义距离和数学原理出发,提出了一种文本型形式背景的约简方法TFC-Reducing,并给出文本型形式背景约简的评价方法-信息损失熵和语义覆盖度.
MOTIVATION FOR DISTANCE EDUCATION
Directory of Open Access Journals (Sweden)
R zvan TEF NESCU
2009-10-01
Full Text Available Beginning with the 1980’s the new information, communication and computer based technologies stimulated the development of the distance education. In Romania the universities adapted rapidly to this type of learning that became an important financing source for most of them. In this article we approach the causes of attraction for the distance education. For this purpose we use an investigation we did on a group of students at Distance Education including interviews regarding their reasons for choosing this type of learning.
Directory of Open Access Journals (Sweden)
Debraj Roy
2013-10-01
Full Text Available Histopathology on the olfactory organ of a snakehead fish, Channa punctatus (Bloch, 1793 were assessed after exposing the fish to 2.5 mg/L and 5mg/L of CdCl2 for 15 days, 30 days and 45 days. Cellular organization of the epithelium was affected severely with degeneration of sensory and supporting cells and hyperplasia of basal cells and mucous cells. Mucous cell proliferation indicates the upregulation of mucous secretion to protect the epithelium from toxic effect of cadmium. The olfactory epithelium was endowed with the multipotent basal cells which differentiate into sensory cells, supporting cells and other cell types of the epithelium during normal cells turn over and in the event of cell death. However, due to cadmium exposure proliferating basal cells failed to differentiate into normal cells and the undifferentiated proliferated cell formed lump and intraepithelial lesion altering the composition of the entire epithelium. Present study indicates that in prolonged exposure to cadmium chloride olfactory functions of the fish might be impaired due to loss of all sensory cells.
Grating-Coupling-Based Excitation of Bloch Surface Waves for Lab-on-Fiber Nanoprobes
Scaravilli, Michele; Cusano, Andrea; Galdi, Vincenzo
2016-01-01
In this paper, we investigate for the first time the possibility to excite Bloch surface waves (BSWs) on the tip of single-mode optical fibers. Within this framework, we first demonstrate the possibility to exploit a grating-coupling mechanism for on-tip excitation of BSWs, and highlight the flexibility of the proposed design as well as its intrinsic robustness to unavoidable fabrication tolerances. Subsequently, with a view towards label-free chemical and biological sensing, we present an optimized design to maximize the sensitivity (in terms of wavelength shift) of the arising resonances with respect to changes in the refractive properties of the surrounding environment. Numerical results indicate that the attained sensitivities are in line with those exhibited by state-of-the-art plasmonic nanoprobes, with the key advantage of exhibiting much narrower spectral resonances. This prototype study paves the way for a new class of miniaturized high-performance surface-wave fiber-optic devices for high-resolution...
Pandey, Rakesh K; Singh, Ram N; Singh, Sarika; Singh, Narendra N; Das, Vijai K
2009-05-01
Pesticides are chemicals used for pest control in the agricultural fields. They finally reach the surrounding water bodies through surface runoff affecting the aquatic fauna. Dimethoate is frequently used organophosphate pesticide due to its high effectiveness and rapid breakdown into environmentally safe products. A 96 hr static acute toxicity test was carried out to determine the LC50 value of dimethoate, on the freshwater airbreathing catfish Heteropneustes fossilis (Bloch). The fish were exposed to 7 different concentrations of dimethoate (2.50, 2.75, 3.00, 3.25, 3.50, 3.75 and 4.00 mg l(-1)) for toxicity bioassay. Control (0.00 mg l(-1)) was also carried out. The data were subjected to Finney's Probit analysis and processed with Trimmed Spearman-Karber statistical software. The LC50 values for dimethoate for 24, 48, 72 and 96 hr were 3.38, 3.23, 3.08 and 2.98 mg l(-1), respectively. At higher concentration of dimethoate (3.25 mg l(-1) and above) the fish showed uncoordinated behaviour such as erratic and jerky swimming, attempt to jump out of water, frequent surfacing and gulping of air, decrease in opercular movement and copious secretion of mucus all over the body.
Abner Doubleday, Marc Bloch, and the cultural significance of baseball in rural America.
Vaught, David
2011-01-01
In 1907 baseball's promoters decreed that Civil War hero Abner Doubleday created the game in the village of Cooperstown, New York, in 1839. Baseball thus acquired a distinctly rural American origin and a romantic pastoral appeal. Skeptics have since presented irrefutable evidence that America's pastime was neither born in the United States nor was a product of rural life. But in their zeal to debunk the myth of baseball's rural beginnings, historians have fallen prey to what Annales School founder Marc Bloch famously called the "idol of origins," and all but neglected the very real phenomenon of rural baseball itself. The claim that baseball has always been "a city game for city men" does not stand up to empirical scrutiny anymore than the Doubleday myth itself, as this address demonstrates with three case studies -- Cooperstown in the 1830s, Davisville, California, in the 1880s, and Milroy, Minnesota, in the 1950s. Baseball may have been a source of rural nostalgia for city people, but it was the sport of choice for farmers and a powerful cultural agent.
The analysis of cytochrome b nucleotidic sequence for Carassius gibelio (Bloch, 1782
Directory of Open Access Journals (Sweden)
Lucian D. Gorgan
2009-01-01
Full Text Available The paper is part of a larger scale study for some genes` (Cytb, ND4L and D-loop nucleotidic structure identification by sequencing, to distinguish the structural differences and their exact length inase pairs. Research was carried out on individuals of Carassius gibelio (Bloch, 1782 (Actinopterygii,Cypriniformes from two different populations, Iezăreni and Movileni (Iaşi, from which dorsal musculartissue was sampled. Mitochondrial DNA (mtDNA isolation and purification was carried out automaticallyusing Promega’s Maxwell 16 (SEV module. Cytochrome b (cytb was multiplied by a two stage>polymerase chain reaction (PCR, using two sets of complementary primers (1 set for each fragment.Direct sequencing of PCR products revealed that the cytochrome b has one sequence of 1140bp. Theobtained sequences were subsequently compared with sequences of the same gene from otherindividuals within this species, towards identifying possible differences in the nucleotidic structure.Key Words: Carassius, cytocrhome b, mtDNA.
Differential geometric invariants for time-reversal symmetric Bloch-bundles: The "Real" case
De Nittis, Giuseppe; Gomi, Kiyonori
2016-05-01
Topological quantum systems subjected to an even (resp. odd) time-reversal symmetry can be classified by looking at the related "Real" (resp. "Quaternionic") Bloch-bundles. If from one side the topological classification of these time-reversal vector bundle theories has been completely described in De Nittis and Gomi [J. Geom. Phys. 86, 303-338 (2014)] for the "Real" case and in De Nittis and Gomi [Commun. Math. Phys. 339, 1-55 (2015)] for the "Quaternionic" case, from the other side it seems that a classification in terms of differential geometric invariants is still missing in the literature. With this article and its companion [G. De Nittis and K. Gomi (unpublished)] we want to cover this gap. More precisely, we extend in an equivariant way the theory of connections on principal bundles and vector bundles endowed with a time-reversal symmetry. In the "Real" case we generalize the Chern-Weil theory and we show that the assignment of a "Real" connection, along with the related differential Chern class and its holonomy, suffices for the classification of "Real" vector bundles in low dimensions.
Photonic lattices in organic microcavities: Bloch states and control of lasing
Mischok, Andreas; Brückner, Robert; Fröb, Hartmut; Lyssenko, Vadim G.; Leo, Karl
2015-09-01
Organic microcavities comprising the host:guest emitter system Alq3:DCM offer an interesting playground to experimentally study the dispersion characteristics of laterally patterned microlasers due to the broad emission spectrum and large oscillator strength of the organic dye. By structuring of metallic or dielectric sublayers directly on top of the bottom mirror, we precisely manipulate the mode structure and influence the coherent emission properties of the device. Embedding silver layers into a microcavity leads to an interaction of the optical cavity-state in the organic layer and the neighboring metal which red-shifts the cavity resonance, creating a Tamm-plasmon-polariton state. A patterning of the metal can in turn be exploited to fabricate deep photonic wells of micron-size, efficiently confining light in lateral direction. In periodic arrays of silver wires, we create a Kronig-Penney-like optical potential in the cavity and in turn observe optical Bloch states spanning over several photonic wires. We modify the Kronig-Penney theory to analytically describe the full far-field emission dispersion of our cavities and show the emergence of either zero- , π-, or 2π- phase-locking in the system. By investigating periodic SiO2 patterns, we experimentally observe stimulated emission from the ground and different excited discrete states at room temperature and are able to directly control the laser emission from both extended and confined modes of the photonic wires at room-temperature.
Establishment of a cell line from kidney of seabass, Lates calcarifer (Bloch
Directory of Open Access Journals (Sweden)
Phromkunthong, W.
2003-01-01
Full Text Available Primary cell culture from caudal fin and kidney of seabass (Lates calcarifer Bloch using tissue explant method were cultured in three different medias with various salt concentrations. Only seabass kidney (SK cells grew well in Leibovitze's-15 medium containing 8 g/l of NaCl supplemented with 10 % fetal bovine serum at an optimum temperature of 25 oC. Over a period of 24 months, SK cells were subcultured over than 75 passages and exhibited epithelial-like cells. The chromosome number of SK cells was 42. The cells were found to be free from bacterial, fungal and mycoplasma contamination. Seabass cells can be kept at -80 oC and/or in liquid nitrogen (-196 oC for at least 24 months with a survival rate of 83.20 and 74.50 %, respectively. Nine fish viruses were tested for their infectivity and this SK cells were susceptible to sand goby virus (SGV, chub reovirus (CRV, snake-head rhabdovirus (SHRV, red seabream iridovirus (RSIV, seabass iridovirus (SIV and grouper iridovirus-2 (GIV-2.
Effects of the projectile electronic structure on Bethe-Bloch stopping parameters for Ag
Energy Technology Data Exchange (ETDEWEB)
Moussa, D., E-mail: djamelmoussa@gmail.co [USTHB, Faculte de Physique, B.P. 32, 16111 Bab-Ezzouar, Algiers (Algeria); Damache, S. [Division de Physique, CRNA, 02 Bd. Frantz Fanon, B.P. 399 Alger-gare, Algiers (Algeria); Ouichaoui, S., E-mail: souichaoui@gmail.co [USTHB, Faculte de Physique, B.P. 32, 16111 Bab-Ezzouar, Algiers (Algeria)
2010-06-15
Energy losses of protons and alpha particles in silver have been accurately measured under the same experimental conditions over the velocity range E{sub lab}=(0.192-2.595) MeV/amu using the transmission method. Deduced S(E) stopping powers are compared to most accurate ones from the literature, to values generated by the SRIM-2008 computer code and to ICRU-49 compilation. They were analyzed in the framework of modified Bethe-Bloch theory for extracting Ag target mean excitation and ionization potential, I, and Barkas effect parameter, b. Values of (466{+-}5) eV and 1.20{+-}0.01 for these two parameters were inferred from the proton S(E) data while the alpha particle data yielded values of (438{+-}4) eV and 1.38{+-}0.01, respectively. The (I, b) stopping parameters thus exhibit opposite variations as the projectile charge increases, similarly as we have found previously for nickel . This can be ascribed only to an effect of the projectile electronic structure at low velocities. The obtained results are discussed in comparison to previous ones reported in the literature.
Mass Spectrum of Fermion on Bloch Branes with New Scalar-fermion Coupling
Xie, Qun-Ying; Zhao, Zhen-Hua; Du, Yun-Zhi; Zhang, Yu-Peng
2015-01-01
In order to localize a left- or right-handed fermion zero mode on a thick brane, one usually introduces the Yukawa coupling $\\eta \\bar{\\Psi} F(\\chi) \\Psi$ between a bulk fermion and the background scalar field $\\chi$. However, the Yukawa coupling will do not work if the background scalar is an even function of the extra dimension. Recently, Ref. [Phy. Rev. \\textbf{D} 89 (2014) 086001] has presented a new scalar-fermion coupling form $\\lambda \\bar \\Psi \\Gamma^M \\partial_M F(\\chi) \\gamma^5 \\Psi$ in order to deal with this problem. In this paper, we investigate the localization and mass spectrum of fermion on the Bloch brane by using the new scalar-fermion coupling with $F(\\chi)=\\chi^n$. It is found that the effective potentials have rich structure and may be volcano-like, finite square well-like, and infinite potentials, which depend on the parameter $n$. As a result, there may appear some resonant KK fermions, finite or infinite numbers of bound KK fermions.
Venkatesh, B Prasanna; Goldwin, J
2015-01-01
We analyze the optomechanics of an atomic Bose-Einstein condensate interacting with the optical lattice inside a laser-pumped optical cavity and subject to a uniform bias force such as gravity. An atomic wave packet in a tilted lattice undergoes Bloch oscillations; in a cavity the backaction of the atoms on the light leads to a time-dependent modulation of the intracavity lattice at the Bloch frequency. When the Bloch frequency is on the order of the cavity damping rate we find transport of the atoms either up or down the lattice. The transport dynamics can be interpreted as a manifestation of dynamical backaction-induced sideband damping/amplification of the optomechanical Bloch oscillator. Depending on the sign of the pump-cavity detuning, atoms are transported either with or against the bias force accompanied by an up- or down-conversion of the frequency of the pump laser light. We also evaluate the prospects for using the optomechanical Bloch oscillator to make continuous measurements of forces by reading...
Distance learning for similarity estimation
Yu, J.; Amores, J.; Sebe, N.; Radeva, P.; Tian, Q.
2008-01-01
In this paper, we present a general guideline to find a better distance measure for similarity estimation based on statistical analysis of distribution models and distance functions. A new set of distance measures are derived from the harmonic distance, the geometric distance, and their generalized
Stereoscopic distance perception
Foley, John M.
1989-01-01
Limited cue, open-loop tasks in which a human observer indicates distances or relations among distances are discussed. By open-loop tasks, it is meant tasks in which the observer gets no feedback as to the accuracy of the responses. What happens when cues are added and when the loop is closed are considered. The implications of this research for the effectiveness of visual displays is discussed. Errors in visual distance tasks do not necessarily mean that the percept is in error. The error could arise in transformations that intervene between the percept and the response. It is argued that the percept is in error. It is also argued that there exist post-perceptual transformations that may contribute to the error or be modified by feedback to correct for the error.
Institute of Scientific and Technical Information of China (English)
Palanivel Bharadhirajan; Natarajan Periyasamy; Sambantham Murugan
2014-01-01
Objective: To assess the nutritions in Mene maculata (Bloch & Schneider, 1801) (M. maculata). Methods: Fishes (14-16 cm) were obtained from the landings at Parangipettai for the evaluation of biochemical composition. The present study deals with biochemical composition such as protein, carbohydrate, lipid, amino acids fatty acids, vitamins and minerals which were evaluated in the moonfish.Results:protein was high in the tissue (23.16%), followed by the carbohydrate (1.3%) and lipid (2.62%). Totally 20 essential and nonessential amino acids were present at the rate of 46.72% and 43.91%. In the analysis, the fatty acid profile by gas chromatography revealed the presence of higher amount of saturated fatty acid (palmitic acid 22.17%) than monounsaturated fatty acid (oleic acid 14.51%) and polyunsaturated fatty acid (alpha linolenic acid 16.07%). Vitamins were detected in M. maculata. Among them, vitamin A was found in higher levels (124.5 mg/g), whereas vitamin B6 was noticed as lower levels (0.34 mg/g). In the present study, totally 5 macro minerals and 2 trace minerals were reported. The macro mineral calcium (156.7 mg/g) was found at the highest level and other minerals such as sodium (31.98 mg/g), potassium (21.33 mg/g), copper (1.43 mg/g) and magnesium (0.341 mg/g) were also detected in the moonfish.Conclusions:The results of proximate composition in M. maculata showed that the percentage of The result showed that the moonfish M. maculata tissue is a valuable food recipe for human consumption, due to its high quality protein and well-balanced amino acids.
Sets avoiding integral distances
Kurz, Sascha
2012-01-01
We study open point sets in Euclidean spaces $\\mathbb{R}^d$ without a pair of points an integral distance apart. By a result of Furstenberg, Katznelson, and Weiss such sets must be of Lebesgue upper density zero. We are interested in how large such sets can be in $d$-dimensional volume. We determine the lower and upper bounds for the volumes of the sets in terms of the number of their connected components and dimension, and also give some exact values. Our problem can be viewed as a kind of inverse to known problems on sets with pairwise rational or integral distances.
DEFF Research Database (Denmark)
Hansen, Finn J. S.; Clausen, Christian
2001-01-01
The case study represents an example of a top-down introduction of distance teaching as part of Danish trials with the introduction of multimedia in education. The study is concerned with the background, aim and context of the trial as well as the role and working of the technology and the organi......The case study represents an example of a top-down introduction of distance teaching as part of Danish trials with the introduction of multimedia in education. The study is concerned with the background, aim and context of the trial as well as the role and working of the technology...
Distances to Dark Clouds: Comparing Extinction Distances to Maser Parallax Distances
Foster, Jonathan B; Benjamin, Robert A; Hoare, Melvin G; Jackson, James M
2012-01-01
We test two different methods of using near-infrared extinction to estimate distances to dark clouds in the first quadrant of the Galaxy using large near infrared (2MASS and UKIDSS) surveys. VLBI parallax measurements of masers around massive young stars provide the most direct and bias-free measurement of the distance to these dark clouds. We compare the extinction distance estimates to these maser parallax distances. We also compare these distances to kinematic distances, including recent re-calibrations of the Galactic rotation curve. The extinction distance methods agree with the maser parallax distances (within the errors) between 66% and 100% of the time (depending on method and input survey) and between 85% and 100% of the time outside of the crowded Galactic center. Although the sample size is small, extinction distance methods reproduce maser parallax distances better than kinematic distances; furthermore, extinction distance methods do not suffer from the kinematic distance ambiguity. This validatio...
Distances to star forming regions
Loinard, Laurent
2014-01-01
The determination of accurate distances to star-forming regions are discussed in the broader historical context of astronomical distance measurements. We summarize recent results for regions within 1 kpc and present perspectives for the near and more distance future.
Antes, desde y para el exilio. Herencia de esta época (1935/1962 de Ernst Bloch
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Salmerón Infante, Miguel
2009-10-01
Full Text Available The first edition of Erbschaft dieser Zeit was published in Zurich in 1935, during Ernst Bloch’s five-year period of emigration from Nazi-Germany in various European capitals before his final emigration to America for ten years in 1938. In this book Bloch made a courageous stand in defence of the artistic avant-garde against the dogmatic advocates of socialist realism. His particularly adversary was Georg Lukács. But of course one of the most fascinating aspects of the book is that is also reads as a contemporary observation of the rise of the Nazis. Erbschaft is undoubtedly the major work of Weimar Germany Exile.La primera edición de Erbschaft dieser Zeit fue publicada en 1935 en Zurich, durante la emigración de Ernst Bloch de la Alemania nazi por un período de cinco años en el que residió en varias capitales europeas antes de su marcha definitiva a América en 1938, donde vivió diez años. En este libro Bloch hace una encorajinada defensa de la vanguardia artística contra los abogados del realismo socialista. Su adversario específico era Georg Lukács. Pero sin duda alguna uno de los aspectos más fascinantes de este libro es que puede leerse como una observación contemporánea de la ascensión al poder de los nazis. Erbschaft es indudablemente la obra clave del exilio de la Alemania de Weimar.
Zhang, Wen-Zhuo
2012-01-01
We derive a set of optical Bloch equations (OBEs) directly from the minimal-coupling Hamiltonian density of the bound-state quantum electrodynamics (bound-state QED). Such optical Bloch equations are beyond the former widely-used ones due to that there is no electric dipole approximation (EDA) on the minimal-coupling Hamiltonian density of the bound-state QED. Then our optical Bloch equations can describe a two-level atom interacting with a monochromatic light of arbitrary wavelength, which are suitable to study the spectroscopy and the Rabi oscillations of two-level atoms in X-ray laser beams since that the wavelength of X-ray is close to an atom to make the electric dipole approximation (EDA) invalid.
Tekin-Ozan, Selda; Kir, Ismail
2007-01-01
Concentrations of some heavy metals (Fe, Zn, Cu, Mn and Cr) in liver of pike (Esox lucius L., 1758) and its endoparasite [Raphidascaris acus (Bloch, 1779)] inhabiting Işikli Lake (Turkey) were analyzed using atomic absorption spectrophotometry. Only Fe and Zn were detected in R. acus and liver of fish, while levels of Cu, Mn and Cr were below detection limit (acus were 68.4 and 86.9 times higher than in the liver. Nematodes could provide reliable information about the heavy metal pollution of the lakes.
Ferrari, G; Poli, N; Sorrentino, F; Tino, G M
2006-08-11
We report on the observation of Bloch oscillations on the unprecedented time scale of several seconds. The experiment is carried out with ultracold bosonic 88Sr atoms loaded into a vertical optical standing wave. The negligible atom-atom elastic cross section and zero angular momentum in the ground state makes 88Sr an almost ideal Bose gas, insensitive to typical mechanisms of decoherence due to thermalization and external stray fields. The small size of the system enables precision measurements of forces at micrometer scale. This is a challenge in physics for studies of surfaces, Casimir effects, and searches for deviations from Newtonian gravity predicted by theories beyond the standard model.
Cladé, Pierre; de Mirandes, Estefania; Cadoret, Malo; Guellati-Khélifa, Saïda; Schwob, Catherine; Nez, François; Julien, Lucile; Biraben, François
2006-01-27
We report an accurate measurement of the recoil velocity of 87Rb atoms based on Bloch oscillations in a vertical accelerated optical lattice. We transfer about 900 recoil momenta with an efficiency of 99.97% per recoil. A set of 72 measurements of the recoil velocity, each one with a relative uncertainty of about 33 ppb in 20 min integration time, leads to a determination of the fine structure constant with a statistical relative uncertainty of 4.4 ppb. The detailed analysis of the different systematic errors yields to a relative uncertainty of 6.7 ppb. The deduced value of alpha-1 is 137.035 998 78(91).
Liu, Yangyang; Shainline, Jeffrey M.; Zeng, Xiaoge; Popovic, Milos A.
2013-01-01
We experimentally demonstrate broadband waveguide crossing arrays showing ultra low loss down to $0.04\\,$dB/crossing ($0.9\\%$), matching theory, and crosstalk suppression over $35\\,$dB, in a CMOS-compatible geometry. The principle of operation is the tailored excitation of a low-loss spatial Bloch wave formed by matching the periodicity of the crossing array to the difference in propagation constants of the 1$^\\text{st}$- and 3$^\\text{rd}$-order TE-like modes of a multimode silicon waveguide....
Buschlinger, Robert; Peschel, Ulf
2014-01-01
We present a time-domain model for the simulation of light-matter interaction in semiconductors in arbitrary geometries and across a wide range of excitation conditions. The electromagnetic field is treated classically using the finite-difference time-domain method. The polarization and occupation numbers of the semiconductor material are described using the semiconductor Bloch equations including many-body effects in the screened Hartree-Fock approximation. Spontaneous emission noise is introduced using stochastic driving terms. As an application of the model, we present simulations of the dynamics of a nanowire laser including optical pumping, seeding by spontaneous emission and the selection of lasing modes.
Spatial differentiation of Bloch surface wave beams using an on-chip phase-shifted Bragg grating
Doskolovich, L. L.; Bezus, E. A.; Bykov, D. A.; Soifer, V. A.
2016-11-01
Bloch surface waves (BSWs) supported by the interfaces between a photonic crystal and a homogeneous medium are considered as a prospective information carrier in integrated photonic circuits. In the present work, we study the application of on-chip phase-shifted Bragg gratings for spatial differentiation of BSW beams. The presented simulation results demonstrate a high accuracy of the performed differentiation. It is shown that upon differentiation of a Gaussian BSW beam, a two-dimensional analogue of the Hermite-Gaussian mode is generated in reflection. The obtained results may find application in the design of new planar devices for analog optical information processing.
Institute of Scientific and Technical Information of China (English)
SANG Hong-Yi; LI Zhi-Yuan; GU Ben-Yuan
2005-01-01
@@ Defect modes in one-dimensional photonic crystals (PCs) can be readily detected from the solution of the transmission spectra via the standard transfer-matrix method. We adopt an analytic Bloch-mode approach to examine this problem in terms of eigenmode solutions and investigate the dispersion behaviour of localized defect modes supported by a defect layer sandwiched within two symmetric semi-infinite PCs that are made from multiple constituents. The results show that the number of defect modes grows when the dielectric constant and width of the defect layer increase.
Zuo, J M; Gjonnes, K; Spence, J C
1989-05-01
The FORTRAN source code is given for a computer program that calculates the two-dimensional intensity distribution in convergent-beam transmission electron microdiffraction (CBED) patterns from perfect crystals. The program uses the eigenvalue or Bloch-wave method. It allows three-dimensional dynamical diffraction, and so includes all higher-order Laue zone effects without approximation. No symmetry reduction is included. The program accepts noncentrosymmetric or centrosymmetric crystal structures and allows absorption corrections to be included. It uses the "EISPACK" subroutines for the diagonalisation of a general complex matrix. Up to 100 CBED disks may be included. The code is also available via "Bitnet."
Numerical investigation of the flat band Bloch modes in a 2D photonic crystal with Dirac cones.
Zhang, Peng; Fietz, Chris; Tassin, Philippe; Koschny, Thomas; Soukoulis, Costas M
2015-04-20
A numerical method combining complex-k band calculations and absorbing boundary conditions for Bloch waves is presented. We use this method to study photonic crystals with Dirac cones. We demonstrate that the photonic crystal behaves as a zero-index medium when excited at normal incidence, but that the zero-index behavior is lost at oblique incidence due to excitation of modes on the flat band. We also investigate the formation of monomodal and multimodal cavity resonances inside the photonic crystals, and the physical origins of their different line-shape features.
2007-06-20
probabilities for SE at fundamental Bloch frequency into the waveguide TE10 mode with and without the scattering taking into account analyzing the ratio P rse ...the limit of τ → ∞, with N finite, the expected result P rse → 1. Also, for this limit, the integral (27) becomes a linear function of N , IN(τνB...is shown in Fig. 5 for several values of the parameter τνB. In Fig. 6, we show the dependence of the relative SE probability P rse [Eq.(42
Rahman, Monsurur; Karim, Reza; Byramjee, Framarz
2015-01-01
Many educational institutions in the United States are currently offering programs through distance learning, and that trend is rising. In almost all spheres of education a developing country like Bangladesh needs to make available the expertise of the most qualified faculty to her distant people. But the fundamental question remains as to whether…
DEFF Research Database (Denmark)
Bærenholdt, Jørgen Ole
Coping with distances - Producing Nordic Atlantic Societies Mennesker håndterer afstande og producerer derved samfund. Dette er det grundlæggende synspunkt i en afhandling, hvor samfund ikke tages for givet. Samfund er tværtimod noget som hele tiden må produceres, genproduceres og forandres, og d...
Encyclopedia of Distance Learning
Howard, Caroline, Ed.; Boettecher, Judith, Ed.; Justice, Lorraine, Ed.; Schenk, Karen, Ed.; Rogers, Patricia, Ed.; Berg, Gary, Ed.
2005-01-01
The innovations in computer and communications technologies combined with on-going needs to deliver educational programs to students regardless of their physical locations, have lead to the innovation of distance education programs and technologies. To keep up with recent developments in both areas of technologies and techniques related to…
Murphy, Elizabeth; Rodriguez-Manzanares, Maria A.
2012-01-01
Rapport has been recognized as important in learning in general but little is known about its importance in distance education (DE). The study we report on in this paper provides insights into the importance of rapport in DE as well as challenges to and indicators of rapport-building in DE. The study relied on interviews with 42 Canadian…
Misconceptions of Astronomical Distances
Miller, Brian W.; Brewer, William F.
2010-01-01
Previous empirical studies using multiple-choice procedures have suggested that there are misconceptions about the scale of astronomical distances. The present study provides a quantitative estimate of the nature of this misconception among US university students by asking them, in an open-ended response format, to make estimates of the distances…
Institute of Scientific and Technical Information of China (English)
马速良; 马会萌; 蒋小平; 段国栋; 李娜
2015-01-01
风电功率波动对电网造成不容忽视的影响。风电并网处加入混合储能系统可有效降低风电对电网的影响。首先， 有效地分解风电有功功率，得到混合储能系统需平抑的波动功率；然后，在电池及超级电容器荷电状态、额定功率及充放电时间的允许范围内实现超级电容器优先充放电的协调控制方式；最后，应用映射于Bloch球面的量子遗传算法，确定满足混合储能系统技术要求及工程指标的混合储能系统配置方案，使混合储能系统成本最低。算例分析证明了在监测荷电状态等约束条件下，优先超级电容器充放电控制方式的有效性及 Bloch 球面量子遗传算法配置混合储能系统方法的合理性。%It can not be ignored that active power fluctuations in wind power's influence on the grid. The hybrid energy storage system access to the place in which wind power connected to the power grid can effectively reduce the impact of the intermittency of wind power. Firstly, the fluctuating power of wind power was separated to derive the output power of the hybrid energy storage system Secondly, charging and discharging of the super-capacitor were firstly controlled in the allowable range of the power rating, the states of charge and the durations of charging or discharging of the hybrid energy storage. At last, the Bloch spherical quantum genetic algorithm was applied to decide the combination scheme of hybrid energy storage system to meet the technical requirements of hybrid energy storage system and engineering indicators and make the cost be the lowest. In the example, the validity of the control model based on priority control of super-capacitor charging and discharging and the effectiveness of configuring hybrid energy storage system capacity with the Bloch spherical quantum genetic algorithm was proved.
Fuzzy clustering with Minkowski distance
P.J.F. Groenen (Patrick); U. Kaymak (Uzay); J.M. van Rosmalen (Joost)
2006-01-01
textabstractDistances in the well known fuzzy c-means algorithm of Bezdek (1973) are measured by the squared Euclidean distance. Other distances have been used as well in fuzzy clustering. For example, Jajuga (1991) proposed to use the L_1-distance and Bobrowski and Bezdek (1991) also used the L_inf
Tolman's Luminosity-Distance, Poincare's Light-Distance and Cayley-Klein's Hyperbolic Distance
Pierseaux, Yves
2009-01-01
We deduce Tolman's formula of luminosity-distance in Cosmology from Poincare's definition of light-distance with Lorentz Transformation (LT).In Minkowskian metric, if distance is proper time (as it is often argued) then light-distance must be also the shortest distance, like proper duration (unlike Einstein's longest length within rest system). By introducing Poincare's proper light-distance in Einstein's basic synchronization we deduce a dilated distance between observer and receding mirror (with relativistic Doppler factor). Such a distance corresponds not to an Euclidean distance (Einstein's rigid rod) but to an Hyperbolic distance (Cayley-Klein) with a Lobatchevskian Horizon. From a basic proportionality hyperbolic distance-velocity, we deduce the law of Hubble. By following Penrose's Lobatchevskian representation of LT, we transform Special Relativity (SR) into an Hyperbolic Cosmological Relativity (HCR). by using only the LT but the whole LT. In Hyperbolic Rotation motion (basic active LT or Einstein's ...
Web-based description of the space radiation environment using the Bethe-Bloch model
Cazzola, Emanuele; Calders, Stijn; Lapenta, Giovanni
2016-01-01
Space weather is a rapidly growing area of research not only in scientific and engineering applications but also in physics education and in the interest of the public. We focus especially on space radiation and its impact on space exploration. The topic is highly interdisciplinary, bringing together fundamental concepts of nuclear physics with aspects of radiation protection and space science. We give a new approach to presenting the topic by developing a web-based application that combines some of the fundamental concepts from these two fields into a single tool that can be used in the context of advanced secondary or undergraduate university education. We present DREADCode, an outreach or teaching tool to rapidly assess the current conditions of the radiation field in space. DREADCode uses the available data feeds from a number of ongoing space missions (ACE, GOES-13, GOES-15) to produce a first order approximation of the radiation dose an astronaut would receive during a mission of exploration in deep space (i.e. far from the Earth’s shielding magnetic field and from the radiation belts). DREADCode is based on an easy-to-use GUI interface available online from the European Space Weather Portal (www.spaceweather.eu/dreadcode). The core of the radiation transport computation to produce the radiation dose from the observed fluence of radiation observed by the spacecraft fleet considered is based on a relatively simple approximation: the Bethe-Bloch equation. DREADCode also assumes a simplified geometry and material configuration for the shields used to compute the dose. The approach is approximate and sacrifices some important physics on the altar of rapid execution time, which allows a real-time operation scenario. There is no intention here to produce an operational tool for use in space science and engineering. Rather, we present an educational tool at undergraduate level that uses modern web-based and programming methods to learn some of the most important
Surdutovich, G. I.; Ghiner, A. V.
2000-08-01
A famous model of a two-level atom interacting with the classical electromagnetic field is used to illustrate the fundamental problem of the relationship between the dynamical and relaxation processes under the interaction of radiation with a quantum-mechanical system and, as a result, to derive nonlinear Bloch-like equations. The presented considerations are based on the analysis of the balance of the fluxes of energy between atomic and field subsystems. It is shown that the generally accepted model of the exponential relaxation deduced for an isolated excited atom and inserted customarily into optical Bloch equations (OBE) describing atom in an external field always leads to a very strange result: spontaneous emission of an atom should be accompanied by the radiation of the coherent field into the external field's mode. Making use of only the energetic considerations, we found the relaxation mechanism (in the form of additional terms in the OBE) which, on the one hand, guarantees the fulfillment of the energetic balance and, on the other hand, allows to introduce arbitrary additional collision-like relaxation mechanism without violation of this balance. Note that these additional terms introduced into OBE from the energetic considerations in a remarkable manner exactly correspond to the renormalization of the external field with the allowance of the classical radiation damping (RD) effect. The revisited OBE may be used as the starting point for considering the dynamics of an atom by making allowance for the quantum properties of an external field.
Energy Technology Data Exchange (ETDEWEB)
Sun, H.Y. E-mail: hysun@165e.com; Hu, H.N.; Sun, Y.P.; Nie, X.F
2004-08-01
Influence of rotating in-plane field on vertical Bloch lines in the walls of second kind of dumbbell domains (IIDs) was investigated, and a critical in-plane field range [H{sub ip}{sup 1},H{sub ip}{sup 2}] of which vertical-Bloch lines (VBLs) annihilated in IIDs is found under rotating in-plane field (H{sub ip}{sup 1} is the maximal critical in-plane-field of which hard domains remain stable, H{sub ip}{sup 2} is the minimal critical in-plane-field of which all of the hard domains convert to soft bubbles (SBs, without VBLs)). It shows that the in-plane field range [H{sub ip}{sup 1}, H{sub ip}{sup 2}] changes with the change of the rotating angle {delta}{phi} H{sub ip}{sup 1} maintains stable, while H{sub ip}{sup 2} decreases with the decreasing of rotating angle {delta}{phi}. Comparing it with the spontaneous shrinking experiment of IIDs under both bias field and in-plane field, we presume that under the application of in-plane field there exists a direction along which the VBLs in the domain walls annihilate most easily, and it is in the direction that domain walls are perpendicular to the in-plane field.
Directory of Open Access Journals (Sweden)
Alexander V. Baryshev
2014-12-01
Full Text Available A one-dimensional photonic crystal (PhC with termination by a metal film—a plasmonic photonic-crystal slab—has been theoretically analyzed for its optical response at a variation of the dielectric permittivity of an analyte and at a condition simulating the molecular binding event. Visualization of the Bloch surface wave resonance (SWR was done with the aid of plasmon absorption in a dielectric/metal/dielectric sandwich terminating a PhC. An SWR peak in spectra of such a plasmonic photonic crystal (PPhC slab comprising a noble or base metal layer was shown to be sensitive to a negligible variation of refractive index of a medium adjoining to the slab. As a consequence, the considered PPhC-based optical sensors exhibited an enhanced sensitivity and a good robustness in comparison with the conventional surface-plasmon and Bloch surface wave sensors. The PPhC biosensors can be of practical importance because the metal layer is protected by a capping dielectric layer from contact with analytes and, consequently, from deterioration.
Institute of Scientific and Technical Information of China (English)
陈锦锐
2013-01-01
Due to the large amount of exercise, long persistent time, and huge energy consumption, athletes are prone to fatigue and consume too much nutrition in long distance running. There-fore, reasonable nutritional supplement helps to restore physical fitness and effectively relieve fatigue. This paper preliminarily discusses how higher vocational students' reduce fatigue and supplement nutrition in long distance running, aiming to improve the quality and efficiency of higher vocational students' long dis-tance running.% 在长跑运动中，由于运动量较大，持续性时间较长，能量消耗巨大，容易导致疲劳，营养消耗过多；因此合理地补充营养，有助于恢复体能，可以有效缓解疲劳。文中就高职学生开展长跑运动项目时，如何减缓疲劳以及补充营养等问题进行了初步的探讨，目的在于提高高职院校学生长跑运动训练的质量和效率。
Monge Distance between Quantum States
Zyczkowski, K; Zyczkowski, Karol; Slomczynski, Wojciech
1998-01-01
We define a metric in the space of quantum states taking the Monge distance between corresponding Husimi distributions (Q--functions). This quantity fulfills the axioms of a metric and satisfies the following semiclassical property: the distance between two coherent states is equal to the Euclidean distance between corresponding points in the classical phase space. We compute analytically distances between certain states (coherent, squeezed, Fock and thermal) and discuss a scheme for numerical computation of Monge distance for two arbitrary quantum states.
Jones, Kyle M.; Randtke, Edward A.; Howison, Christine M.; Pagel, Mark D.
2016-03-01
We have developed a MRI method that can measure extracellular pH in tumor tissues, known as acidoCEST MRI. This method relies on the detection of Chemical Exchange Saturation Transfer (CEST) of iopamidol, an FDA-approved CT contrast agent that has two CEST signals. A log10 ratio of the two CEST signals is linearly correlated with pH, but independent of agent concentration, endogenous T1 relaxation time, and B1 inhomogeneity. Therefore, detecting both CEST effects of iopamidol during in vivo studies can be used to accurately measure the extracellular pH in tumor tissues. Past in vivo studies using acidoCEST MRI have suffered from respiration artifacts in orthotopic and lung tumor models that have corrupted pH measurements. In addition, the non-linear fitting method used to analyze results is unreliable as it is subject to over-fitting especially with noisy CEST spectra. To improve the technique, we have recently developed a respiration gated CEST MRI pulse sequence that has greatly reduced motion artifacts, and we have included both a prescan and post scan to remove endogenous CEST effects. In addition, we fit the results by parameterizing the contrast of the exogenous agent with respect to pH via the Bloch equations modified for chemical exchange, which is less subject to over-fitting than the non-linear method. These advances in the acidoCEST MRI technique and analysis methods have made pH measurements more reliable, especially in areas of the body subject to respiratory motion.
Advanced hierarchical distance sampling
Royle, Andy
2016-01-01
In this chapter, we cover a number of important extensions of the basic hierarchical distance-sampling (HDS) framework from Chapter 8. First, we discuss the inclusion of “individual covariates,” such as group size, in the HDS model. This is important in many surveys where animals form natural groups that are the primary observation unit, with the size of the group expected to have some influence on detectability. We also discuss HDS integrated with time-removal and double-observer or capture-recapture sampling. These “combined protocols” can be formulated as HDS models with individual covariates, and thus they have a commonality with HDS models involving group structure (group size being just another individual covariate). We cover several varieties of open-population HDS models that accommodate population dynamics. On one end of the spectrum, we cover models that allow replicate distance sampling surveys within a year, which estimate abundance relative to availability and temporary emigration through time. We consider a robust design version of that model. We then consider models with explicit dynamics based on the Dail and Madsen (2011) model and the work of Sollmann et al. (2015). The final major theme of this chapter is relatively newly developed spatial distance sampling models that accommodate explicit models describing the spatial distribution of individuals known as Point Process models. We provide novel formulations of spatial DS and HDS models in this chapter, including implementations of those models in the unmarked package using a hack of the pcount function for N-mixture models.
Gladders, M D; Burns, C R; Attard, A; Casey, M P; Hamilton, D; Mallén-Ornelas, G; Karr, J L; Poirier, S M; Sawicki, M; Barrientos, F; Barkhouse, W A; Brodwin, M; Clark, J; McNaughton, R; Ruetalo-Pacheco, M; Mochnacki, S W; Gladders, Michael D.; Clarke, Tracy E.; Burns, Christopher R.; Attard, Allen; Casey, Michael P.; Hamilton, Devon; Mallen-Ornelas, Gabriela; Karr, Jennifer L.; Poirier, Sara M.; Sawicki, Marcin; Barrientos, Felipe; Barkhouse, Wayne; Brodwin, Mark; Clark, Jason; Naughton, Rosemary Mc; Ruetalo-Pacheco, Marcelo; Mochnacki, Stefan W.
1998-01-01
We present the first set of distance limits from the David Dunlap Observatory Intermediate Velocity Cloud (DDO IVC) distance project. Such distance measures are crucial to understanding the origins and dynamics of IVCs, as the distances set most of the basic physical parameters for the clouds. Currently there are very few IVCs with reliably known distances. This paper describes in some detail the basic techniques used to measure distances, with particular emphasis on the the analysis of interstellar absorption line data, which forms the basis of our distance determinations. As an example, we provide a detailed description of our distance determination for the Draco Cloud. Preliminary distance limits for a total of eleven clouds are provided.
Ivlev, B I
2005-01-01
Quantum tunneling between two potential wells in a magnetic field can be strongly increased when the potential barrier varies in the direction perpendicular to the line connecting the two wells and remains constant along this line. A periodic structure of the wave function is formed in the direction joining the wells. The resulting motion can be coherent like motion in a conventional narrow band periodic structure. A particle penetrates the barrier over a long distance which strongly contrasts to WKB-like tunneling. The whole problem is stationary. The coherent process can be influenced by dissipation.
Bodini, Olivier; Fernique, Thomas
2009-01-01
In this paper, a structural property of the set of lozenge tilings of a 2n-gon is highlighted. We introduce a simple combinatorial value called Hamming-distance, which is a lower bound for the flipdistance (i.e. the number of necessary local transformations involving three lozenges) between two given tilings. It is here proven that, for n5, We show that there is some deficient pairs of tilings for which the flip connection needs more flips than the combinatorial lower bound indicates.
Lassoued, R.; Lecheheb, M.; Bonnet, G.
2012-08-01
This paper describes an analytical method for the wave field induced by a moving load on a periodically supported beam. The Green's function for an Euler beam without support is evaluated by using the direct integration. Afterwards, it introduces the supports into the model established by using the superposition principle which states that the response from all the sleeper points and from the external point force add up linearly to give a total response. The periodicity of the supports is described by Bloch's theorem. The homogeneous system thus obtained represents a linear differential equation which governs rail response. It is initially solved in the homogeneous case, and it admits a no null solution if its determinant is null, this permits the establishment the dispersion equation to Bloch waves and wave bands. The Bloch waves and dispersion curves contain all the physics of the dynamic problem and the wave field induced by a dynamic load applied to the system is finally obtained by decomposition into Bloch waves, similarly to the usual decomposition into dynamic modes on a finite structure. The method is applied to obtain the field induced by a load moving at constant velocity on a thin beam supported by periodic elastic supports.
Tseitlin, Mark; Eaton, Gareth R; Eaton, Sandra S
2013-12-01
Rapid-scan EPR has been shown to improve the signal-to-noise ratio relative to conventional continuous wave spectroscopy. Equations are derived for the steady-state solution to the Bloch equations as a Fourier expansion in the harmonics of the scan frequency. This simulation method is about two orders of magnitude faster than time-domain numerical integration.
Distance effects in electrochemical micromachining
Xu, Lizhong; Pan, Yue; Zhao, Chuanjun
2016-09-01
Considering exponential dependence of currents on double-layer voltage and the feedback effect of the electrolyte resistance, a distance effect in electrochemical micromachining is found, namely that both time constant and double-layer voltage depend on the separation of electrodes. The double-layer voltage is the real voltage used in processing. Under DC voltage, the apparent voltages between two electrodes are constant for different separations, but the real voltages change with the separations. Small separations exert substantial effects on the real voltages. Accordingly, a DC-voltage small-separation electrochemical micromachining technique was proposed. The double-layer voltage drops sharply as the small separation increases. Thus, the electrochemical reactions are confined to electrode regions in very close proximity even under DC voltage. The machining precision can be significantly enhanced by reducing the voltage and separation between electrodes. With this technique, the machining of conducting materials with submicrometre precision was achieved.
Minimal distances between SCFTs
Energy Technology Data Exchange (ETDEWEB)
Buican, Matthew [Department of Physics and Astronomy, Rutgers University,Piscataway, NJ 08854 (United States)
2014-01-28
We study lower bounds on the minimal distance in theory space between four-dimensional superconformal field theories (SCFTs) connected via broad classes of renormalization group (RG) flows preserving various amounts of supersymmetry (SUSY). For N=1 RG flows, the ultraviolet (UV) and infrared (IR) endpoints of the flow can be parametrically close. On the other hand, for RG flows emanating from a maximally supersymmetric SCFT, the distance to the IR theory cannot be arbitrarily small regardless of the amount of (non-trivial) SUSY preserved along the flow. The case of RG flows from N=2 UV SCFTs is more subtle. We argue that for RG flows preserving the full N=2 SUSY, there are various obstructions to finding examples with parametrically close UV and IR endpoints. Under reasonable assumptions, these obstructions include: unitarity, known bounds on the c central charge derived from associativity of the operator product expansion, and the central charge bounds of Hofman and Maldacena. On the other hand, for RG flows that break N=2→N=1, it is possible to find IR fixed points that are parametrically close to the UV ones. In this case, we argue that if the UV SCFT possesses a single stress tensor, then such RG flows excite of order all the degrees of freedom of the UV theory. Furthermore, if the UV theory has some flavor symmetry, we argue that the UV central charges should not be too large relative to certain parameters in the theory.
Tronc, P.; Kitaev, Yu. E.
2001-05-01
We determined the exact symmetries of conduction and valence Bloch states in type-I and type-II [001] (GaAs)m(AlAs)n superlattices at the Γ point and at some other symmetry points of the Brillouin zone of the superlattices and derived optical selection rules. Contrary to a result widely accepted in the envelope-function approximation (EFA), pz atomic orbitals cannot mix with px and py orbitals to build Bloch states. The phonon-assisted transitions involving the Γ point as an initial or final state are allowed both without and with taking into account the spin-orbit interaction whatever are the symmetries of the initial and final states. The electron band structure of the superlattices is discussed. Within the domain of validity of EFA (i.e., for not too small values of m and n), a detailed analysis of the Bloch-state symmetry and selection rules is provided on imposing invariance of the superlattice structure under the change of z to -z (the σz symmetry operation). It is shown that optical transitions between the conduction states arising from the Γ states of GaAs on one hand and the conduction states arising from the X states of AlAs on the other hand can be allowed from spin-orbit coupling only. The correspondence is provided between the symmetry of a Bloch state and the parity with respect to σz of its associated envelope function. The effect of an electric field parallel to the growth axis is discussed. Quantum wells do not differ from superlattices with regard to Bloch-state and envelope-function symmetries or optical selection rules. All the above results are still valid for any pseudomorphic superlattice or quantum well made of two binary compounds with zinc-blend structure and identical cations or anions, such as, for example, in the GaN/AlN system.
González, Pablo J; Barrera, Guillermo I; Rizzi, Alberto C; Moura, José J G; Passeggi, Mario C G; Brondino, Carlos D
2009-10-01
Electron transfer proteins and redox enzymes containing paramagnetic redox centers with different relaxation rates are widespread in nature. Despite both the long distances and chemical paths connecting these centers, they can present weak magnetic couplings produced by spin-spin interactions such as dipolar and isotropic exchange. We present here a theoretical model based on the Bloch-Wangsness-Redfield theory to analyze the dependence with temperature of EPR spectra of interacting pairs of spin 1/2 centers having different relaxation rates, as is the case of the molybdenum-containing enzyme aldehyde oxidoreductase from Desulfovibrio gigas. We analyze the changes of the EPR spectra of the slow relaxing center (Mo(V)) induced by the faster relaxing center (FeS center). At high temperatures, when the relaxation time T(1) of the fast relaxing center is very short, the magnetic coupling between centers is averaged to zero. Conversely, at low temperatures when T(1) is longer, no modulation of the coupling between metal centers can be detected.
Hernán Antonio Sorgentini
1999-01-01
Apología para la historia o el oficio de historiador de Marc Bloch es hoy una obra ineludible para quienes se inician en el estudio de la historia. Una nueva historia que reconoce haber experimentado un amplio proceso de renovación en el siglo XX, en el que "los Annales" fundados por Marc Bloch y Lucien Febvre han cumplido un papel central. El manuscrito interrumpido de Marc Bloch de Massimo Mastrogregori [director de la Revista di Storia della Storiografia Moderna] forma parte de las renovad...
Isolation by distance, web service
Bohonak Andrew J; Jensen Jeffrey L; Kelley Scott T
2005-01-01
Abstract Background The population genetic pattern known as "isolation by distance" results from spatially limited gene flow and is a commonly observed phenomenon in natural populations. However, few software programs exist for estimating the degree of isolation by distance among populations, and they tend not to be user-friendly. Results We have created Isolation by Distance Web Service (IBDWS) a user-friendly web interface for determining patterns of isolation by distance. Using this site, ...
Improved directional-distance filter
Institute of Scientific and Technical Information of China (English)
2008-01-01
This paper proposes a new spatial-distance weighting function.By combining the weighting function and the traditional directional-distance filter (DDF) in a novel way,a new vector filter-the adaptive distance-weighted directional-distance filter (ADWDDF)-is presented.The experimental results show that the proposed solution provides better filtering performance and preserves better image chromaticity and edge or detail information compared with the traditional DDF and some other typical vector filters.
Reconsidering Moore's Transactional Distance Theory
Giossos, Yiannis; Koutsouba, Maria; Lionarakis, Antonis; Skavantzos, Kosmas
2009-01-01
One of the core theories of distance education is Michael Graham Moore's "Theory of Transactional Distance" that provides the broad framework of the pedagogy of distance education and allows the generation of almost infinite number of hypotheses for research. However, the review of the existing studies relating to the theory showed the use of a…
Xiao, Fajun; Li, Baoran; Wang, Meirong; Zhu, Weiren; Zhang, Peng; Liu, Sheng; Premaratne, Malin; Zhao, Jianlin
2014-09-22
We theoretically report the existence of optical Bloch oscillations (BO) of an Airy beam in a one-dimensional optically induced photonic lattice with a linear transverse index gradient. The Airy beam experiencing optical BO shows a more robust non-diffracting feature than its counterparts in free space or in a uniform photonic lattice. Interestingly, a periodical recurrence of Airy shape accompanied with constant alternation of its acceleration direction is also found during the BO. Furthermore, we demonstrate that the period and amplitude of BO of an Airy beam can be readily controlled over a wide range by varying the index gradient and/or the lattice period. Exploiting these features, we propose a scheme to rout an Airy beam to a predefined output channel without losing its characteristics by longitudinally modulating the transverse index gradient.
High-sensitivity label-free optical fiber optrodes based on the excitation of Bloch surface waves
Scaravilli, M.; Castaldi, G.; Cusano, A.; Galdi, V.
2016-05-01
In this study, the possibility to excite Bloch surface waves (BSWs) on the tip of a single-mode optical fiber is explored for the first time. In particular, we first show the possibility to achieve an on-tip excitation of BSWs, with optimized characteristic of the arising resonances, via an "all-fiber" grating-coupled configuration. Furthermore, envisioning novel high-performance fiber tip nanoprobes for label-free biosensing, we introduce an ad hoc design aimed at maximizing the refractive-index sensitivity. Numerical results indicate that the estimated sensitivities are comparable with those exhibited by current plasmonic lab-on-tip bio-probes, but are accompanied by a higher spectral selectivity. Therefore, this preliminary work paves the way to the development of new classes of miniaturized surface-wave optical fiber devices for low-detection-limit label-free chemical and biological sensing.
Directory of Open Access Journals (Sweden)
Maria Alvaro
2013-02-01
Full Text Available A one-dimensional photonic crystal (1DPC based on a planar stack of dielectric layers is used as an optical transducer for biosensing, upon the coupling of TE-polarized Bloch Surface Waves (BSW. The structure is tailored with a polymeric layer providing a chemical functionality facilitating the covalent binding of orienting proteins needed for a subsequent grafting of antibodies in an immunoassay detection scheme. The polymeric layer is impregnated with Cy3 dye, in such a way that the photonic structure can exhibit an emissive behavior. The BSW-coupled fluorescence shift is used as a means for detecting refractive index variations occurring at the 1DPC surface, according to a label-free concept. The proposed working principle is successfully demonstrated in real-time tracking of protein G covalent binding on the 1DPC surface within a fluidic cell.
Short-period intrinsic Stark GaN /AlGaN superlattice as a Bloch oscillator
Litvinov, V. I.; Manasson, A.; Pavlidis, D.
2004-07-01
We discuss the properties of AlGaN /GaN superlattice (SL) related to the feasibility of a terahertz-range oscillator. The distortion of the conduction-band profile by the polarization fields has been taken into account. We have calculated the conduction-band offset between the pseudomorphic AlGaN barrier and the GaN quantum well, the first miniband width and energy dispersion, as functions of Al content in the barrier. As the short-period SL miniband energy dispersion contains contributions from next to nearest neighbors, it causes anharmonic electron oscillations at the multiples of the fundamental Bloch frequency. The Al content and SL period that favor high-frequency oscillations have been determined.
Energy Technology Data Exchange (ETDEWEB)
Fountaine, Katherine T., E-mail: kfountai@caltech.edu [Department of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Whitney, William S. [Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Department of Physics, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Atwater, Harry A. [Joint Center for Artificial Photosynthesis, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States); Department of Applied Physics and Materials Science, California Institute of Technology, 1200 E. California Blvd., Pasadena, California 91125 (United States)
2014-10-21
We present a unified framework for resonant absorption in periodic arrays of high index semiconductor nanowires that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes, as array density transitions from sparse to dense. Full dispersion relations are calculated for each mode at varying illumination angles using the eigenvalue equation for leaky waveguide modes of an infinite dielectric cylinder. The dispersion relations along with symmetry arguments explain the selectivity of mode excitation and spectral red-shifting of absorption for illumination parallel to the nanowire axis in comparison to perpendicular illumination. Analysis of photonic crystal band dispersion for varying array density illustrates that the modes responsible for resonant nanowire absorption emerge from the leaky waveguide modes.
Burke, Kyle; Heubach, Silvia; Huggan, Melissa; Huntemann, Svenja
2016-01-01
We study the computational complexity of distance games, a class of combinatorial games played on graphs. A move consists of colouring an uncoloured vertex subject to it not being at certain distances determined by two sets, D and S. D is the set of forbidden distances for colouring vertices in different colors, while S is the set of forbidden distances for the same colour. The last player to move wins. Well-known examples of distance games are Node-Kayles, Snort, and Col, whose complexities ...
Binney, James; Kordopatis, Georges; McMillan, Paul J; Sharma, Sanjib; Zwitter, Tomaz; Bienayme, Olivier; Bland-Hawthorn, Joss; Steinmetz, Matthias; Gilmore, Gerry; Williams, Mary E K; Navarro, Julio; Grebel, Eva K; Helmi, Amina; Parker, Quentin; Reid, Warren A; Seabroke, George; Watson, Fred; Wyse, Rosie F G
2013-01-01
Probability density functions are determined from new stellar parameters for the distance moduli of stars for which the RAdial Velocity Experiment (RAVE) has obtained spectra with S/N>=10. The expectation value of distance is larger than the distance implied by the expectation of distance modulus; the latter is itself larger than the distance implied by the expectation value of the parallax. Our parallaxes of Hipparcos stars agree well with the values measured by Hipparcos, so the expectation of parallax is the most reliable distance indicator. The latter are improved by taking extinction into account. We provide one- two- or three-Gaussian fits to the distance pdfs. The effective temperature absolute-magnitude diagram of our stars is significantly improved when these pdfs are used to make the diagram. We use the method of kinematic corrections devised by Schoenrich, Binney & Asplund to check for systematic errors in our estimators for ordinary stars and confirm the conclusion reached from the Hipparcos s...
[Panorama of nursing distance education in Brazil].
Rojo, Priscila Tagliaferro; Vieira, Sheila de Souza; Zem-Mascarenhas, Silvia Helena; Sandor, Elisane Regina; Vieira, Carla Roberta Sola de Paula
2011-12-01
The development of distance education is associated with the popularization and democratization of the accessibility to information and communication technologies. Nursing has been using this modality of education in both undergraduate and graduate courses, which has provided knowledge about other technologies, an easier accessibility, flexibility of time and space, and reduced costs. The objective of this study is map the national higher education distance nursing courses. This exploratory, descriptive study was developed by visiting governmental, non-governmental and institutional websites. Two undergraduate and nine graduate courses in nursing were found, which is considered to be a low number, considering that distance education is an appropriate pedagogical tool that permits to prepare a large number of nurses who are geographically dispersed and who do not have access to the conventional educational processes.
The Distinct Affective Consequences of Psychological Distance and Construal Level
2014-01-01
Much of the existing literature on psychological distance has focused on cognitive outcomes, such as changes in construal level, largely framing affective processes out of the discussion. The current research examines the distinct influences of psychological distance and construal level on affect-based evaluation. In a first set of experiments, psychological distance (vs. closeness) reduces the intensity of felt affect, while abstract (vs. concrete) thinking increases the positivity of one's ...
Planning with Reachable Distances
Tang, Xinyu
2009-01-01
Motion planning for spatially constrained robots is difficult due to additional constraints placed on the robot, such as closure constraints for closed chains or requirements on end effector placement for articulated linkages. It is usually computationally too expensive to apply sampling-based planners to these problems since it is difficult to generate valid configurations. We overcome this challenge by redefining the robot\\'s degrees of freedom and constraints into a new set of parameters, called reachable distance space (RD-space), in which all configurations lie in the set of constraint-satisfying subspaces. This enables us to directly sample the constrained subspaces with complexity linear in the robot\\'s number of degrees of freedom. In addition to supporting efficient sampling, we show that the RD-space formulation naturally supports planning, and in particular, we design a local planner suitable for use by sampling-based planners. We demonstrate the effectiveness and efficiency of our approach for several systems including closed chain planning with multiple loops, restricted end effector sampling, and on-line planning for drawing/sculpting. We can sample single-loop closed chain systems with 1000 links in time comparable to open chain sampling, and we can generate samples for 1000-link multi-loop systems of varying topology in less than a second. © 2009 Springer-Verlag.
Game theory of social distancing in response to an epidemic.
Directory of Open Access Journals (Sweden)
Timothy C Reluga
2010-05-01
Full Text Available Social distancing practices are changes in behavior that prevent disease transmission by reducing contact rates between susceptible individuals and infected individuals who may transmit the disease. Social distancing practices can reduce the severity of an epidemic, but the benefits of social distancing depend on the extent to which it is used by individuals. Individuals are sometimes reluctant to pay the costs inherent in social distancing, and this can limit its effectiveness as a control measure. This paper formulates a differential-game to identify how individuals would best use social distancing and related self-protective behaviors during an epidemic. The epidemic is described by a simple, well-mixed ordinary differential equation model. We use the differential game to study potential value of social distancing as a mitigation measure by calculating the equilibrium behaviors under a variety of cost-functions. Numerical methods are used to calculate the total costs of an epidemic under equilibrium behaviors as a function of the time to mass vaccination, following epidemic identification. The key parameters in the analysis are the basic reproduction number and the baseline efficiency of social distancing. The results show that social distancing is most beneficial to individuals for basic reproduction numbers around 2. In the absence of vaccination or other intervention measures, optimal social distancing never recovers more than 30% of the cost of infection. We also show how the window of opportunity for vaccine development lengthens as the efficiency of social distancing and detection improve.
Distance learning for similarity estimation.
Yu, Jie; Amores, Jaume; Sebe, Nicu; Radeva, Petia; Tian, Qi
2008-03-01
In this paper, we present a general guideline to find a better distance measure for similarity estimation based on statistical analysis of distribution models and distance functions. A new set of distance measures are derived from the harmonic distance, the geometric distance, and their generalized variants according to the Maximum Likelihood theory. These measures can provide a more accurate feature model than the classical Euclidean and Manhattan distances. We also find that the feature elements are often from heterogeneous sources that may have different influence on similarity estimation. Therefore, the assumption of single isotropic distribution model is often inappropriate. To alleviate this problem, we use a boosted distance measure framework that finds multiple distance measures which fit the distribution of selected feature elements best for accurate similarity estimation. The new distance measures for similarity estimation are tested on two applications: stereo matching and motion tracking in video sequences. The performance of boosted distance measure is further evaluated on several benchmark data sets from the UCI repository and two image retrieval applications. In all the experiments, robust results are obtained based on the proposed methods.
Are contemporary tourists consuming distance?
DEFF Research Database (Denmark)
Larsen, Gunvor Riber
represented by tourists? (guiding the empirical inquiry) • Does contemporary tourists consume distance? (guiding discussion merging theory and analysis) Together, these questions seeks to guide a theoretical (first question) and an empirical (second question) discussion of distance set in a leisure mobility...... of distance within the theoretical context of leisure mobility (question one) will be explored through the reading and discussion of literature concerned with concepts and theories that are using distance in their premises or as part of their argumentation. This will primarily be literature on mobility, space...... of 'consumption of distance' (question three) will draw on supplementing theoretical reflections, particularly on consumption, to summarise and bring together the theoretical and empirical analysis, and to discuss whether it is possible and indeed reasonable to understand distance as an object for consumption...
Doctoral education from a distance.
Effken, Judith A
2008-12-01
This article describes the environmental factors that have contributed to the recent rapid growth of nursing doctoral education at a distance. Early and recent efforts to deliver distance doctoral education are discussed, using The University of Arizona College of Nursing experience as the key exemplar. The Community of Inquiry model is introduced as an appropriate model for doctoral education and then used as a framework to evaluate the current state of the art in distance doctoral nursing education. Successes and challenges in delivering doctoral education from a distance are described.
Distance spectra and Distance energy of Integral Circulant Graphs
c, Aleksandar Ili\\'
2011-01-01
The distance energy of a graph $G$ is a recently developed energy-type invariant, defined as the sum of absolute values of the eigenvalues of the distance matrix of $G$. There was a vast research for the pairs and families of non-cospectral graphs having equal distance energy, and most of these constructions were based on the join of graphs. A graph is called circulant if it is Cayley graph on the circulant group, i.e. its adjacency matrix is circulant. A graph is called integral if all eigenvalues of its adjacency matrix are integers. Integral circulant graphs play an important role in modeling quantum spin networks supporting the perfect state transfer. In this paper, we characterize the distance spectra of integral circulant graphs and prove that these graphs have integral eigenvalues of distance matrix $D$. Furthermore, we calculate the distance spectra and distance energy of unitary Cayley graphs. In conclusion, we present two families of pairs $(G_1, G_2)$ of integral circulant graphs with equal distanc...
Transactional Distance and Autonomy in a Distance Learning Environment
Vasiloudis, G.; Koutsouba, M.; Giossos, Y.; Mavroidis, I.
2015-01-01
This paper studies the transactional distance between the students and the tutor as well as the autonomy of students in a postgraduate course of the Hellenic Open University (HOU). The aim of the paper is to examine how the relation between autonomy and transactional distance evolves during an academic year and how this relation is affected by…
van As, Liesl L; van As, Jo G
2007-05-01
During surveys of the biodiversity of fish parasites in the Okavango River and Delta, Botswana, specimens of Lamproglena von Nordmann, 1832 were found associated with the African pike Hepsetus odoe (Bloch). This Lamproglena species distinctly differs from all known species based on morphological features, in particular the cephalothorax and the maxilliped; it is described as L. hepseti n. sp. and is specific to its host, the African pike.
Richter, Marten; Renger, Thomas; Knorr, Andreas
2008-01-01
On the basis of the recent progress in the resolution of the structure of the antenna light harvesting complex II (LHC II) of the photosystem II, we propose a microscopically motivated theory to predict excitation intensity-dependent spectra. We show that optical Bloch equations provide the means to include all 2( N ) excited states of an oligomer complex of N coupled two-level systems and analyze the effects of Pauli Blocking and exciton-exciton annihilation on pump-probe spectra. We use LHC Bloch equations for 14 Coulomb coupled two-level systems, which describe the S (0) and S (1) level of every chlorophyll molecule. All parameter introduced into the Hamiltonian are based on microscopic structure and a quantum chemical model. The derived Bloch equations describe not only linear absorption but also the intensity dependence of optical spectra in a regime where the interplay of Pauli Blocking effects as well as exciton-exciton annihilation effects are important. As an example, pump-probe spectra are discussed. The observed saturation of the spectra for high intensities can be viewed as a relaxation channel blockade on short time scales due to Pauli blocking. The theoretical investigation is useful for the interpretation of the experimental data, if the experimental conditions exceed the low intensity pump limit and effects like strong Pauli Blocking and exciton-exciton annihilation need to be considered. These effects become important when multiple excitations are generated by the pump pulse in the complex.
Exploring characteristics and motives of long distance commuter cyclists
DEFF Research Database (Denmark)
Hansen, Karsten Bruun; Sick Nielsen, Thomas
2014-01-01
, commuter cyclists (45 km from home to work) have more mobility options, higher incomes, and a longer education than other commuter cyclists. The main motive for longer distance cycling is physical exercise, followed by reduced costs and time used for traveling. The long distance commuter cyclists surveyed......Longer distance cycling is a commuting mode that contributes to sustainability and public health objectives, but little is known about current long distance cyclist's motives. The paper explores longer distance commuter cyclists, their characteristics, practice and motives. Longer distance...... are very positive about their commute - pointing to positive experiences, better mood, and stress relief as experiences related to their cycle trip to work. Policy support should devote attention to unlocking the potential that may be embedded in individuals combining their exercise and travel time...
Distance labeling schemes for trees
DEFF Research Database (Denmark)
Alstrup, Stephen; Gørtz, Inge Li; Bistrup Halvorsen, Esben;
2016-01-01
variants such as, for example, small distances in trees [Alstrup et al., SODA, 2003]. We improve the known upper and lower bounds of exact distance labeling by showing that 1/4 log2(n) bits are needed and that 1/2 log2(n) bits are sufficient. We also give (1 + ε)-stretch labeling schemes using Theta...
Virtual Bioinformatics Distance Learning Suite
Tolvanen, Martti; Vihinen, Mauno
2004-01-01
Distance learning as a computer-aided concept allows students to take courses from anywhere at any time. In bioinformatics, computers are needed to collect, store, process, and analyze massive amounts of biological and biomedical data. We have applied the concept of distance learning in virtual bioinformatics to provide university course material…
Quality Content in Distance Education
Yildiz, Ezgi Pelin; Isman, Aytekin
2016-01-01
In parallel with technological advances in today's world of education activities can be conducted without the constraints of time and space. One of the most important of these activities is distance education. The success of the distance education is possible with content quality. The proliferation of e-learning environment has brought a need for…
Distance labeling schemes for trees
DEFF Research Database (Denmark)
Alstrup, Stephen; Gørtz, Inge Li; Bistrup Halvorsen, Esben;
2016-01-01
We consider distance labeling schemes for trees: given a tree with n nodes, label the nodes with binary strings such that, given the labels of any two nodes, one can determine, by looking only at the labels, the distance in the tree between the two nodes. A lower bound by Gavoille et al. [Gavoill...
The Psychology of Psychic Distance
DEFF Research Database (Denmark)
Håkanson, Lars; Ambos, Björn; Schuster, Anja
2016-01-01
and their theoretical underpinnings assume psychic distances to be symmetric. Building on insights from psychology and sociology, this paper demonstrates how national factors and cognitive processes interact in the formation of asymmetric distance perceptions. The results suggest that exposure to other countries...
Faculty Attitudes about Distance Education
Smidt, Esther; McDyre, Brian; Bunk, Jennifer; Li, Rui; Gatenby, Tanya
2014-01-01
In recent years, there has been a dramatic increase in distance learning in higher education. Given this, it is extremely important to understand faculty attitudes about distance education, not only because they can vary widely, but also because it is the faculty, through their design and implementation of online courses, that will shape the…
Hierarchical traits distances explain grassland Fabaceae species’ ecological niches distances
Directory of Open Access Journals (Sweden)
Florian eFort
2015-02-01
Full Text Available Fabaceae species play a key role in ecosystem functioning through their capacity to fix atmospheric nitrogen via their symbiosis with Rhizobium bacteria. To increase benefits of using Fabaceae in agricultural systems, it is necessary to find ways to evaluate species or genotypes having potential adaptations to sub-optimal growth conditions. We evaluated the relevance of phylogenetic distance, absolute trait distance and hierarchical trait distance for comparing the adaptation of 13 grassland Fabaceae species to different habitats, i.e. ecological niches. We measured a wide range of functional traits (root traits, leaf traits and whole plant traits in these species. Species phylogenetic and ecological distances were assessed from a species-level phylogenetic tree and species’ ecological indicator values, respectively. We demonstrated that differences in ecological niches between grassland Fabaceae species were related more to their hierarchical trait distances than to their phylogenetic distances. We showed that grassland Fabaceae functional traits tend to converge among species with the same ecological requirements. Species with acquisitive root strategies (thin roots, shallow root systems are competitive species adapted to non-stressful meadows, while conservative ones (coarse roots, deep root systems are able to tolerate stressful continental climates. In contrast, acquisitive species appeared to be able to tolerate low soil-P availability, while conservative ones need high P availability. Finally we highlight that traits converge along the ecological gradient, providing the assumption that species with similar root-trait values are better able to coexist, regardless of their phylogenetic distance.
Rapid propagation of a Bloch wave packet excited by a femtosecond ultraviolet pulse
Krasovskii, E. E.; Friedrich, C.; Schattke, W.; Echenique, P. M.
2016-11-01
Attosecond streaking spectroscopy of solids provides direct observation of the dynamics of electron excitation and transport through the surface. We demonstrate the crucial role of the exciting field in electron propagation and establish that the lattice scattering of the outgoing electron during the optical pumping leads to the wave packet moving faster than with the group velocity and faster than the free electron. We solve the time-dependent Schrödinger equation for a model of laser-assisted photoemission, with inelastic scattering treated as electron absorption and alternatively by means of random collisions. For a weak lattice scattering, the phenomenological result that the photoelectron moves with the group velocity d E /d ℏ k and traverses on average the distance equal to the mean-free path is proved to hold even at very short traveling times. This offers a novel interpretation of the delay time in streaking experiment and sheds new light on tunneling in optoelectronic devices.
A Comparative Analysis of the Academic Performance of Distance and On-campus Learners
MAGAGULA, C. M.; NGWENYA, A. P.
2015-01-01
This study examined (i) the profile of the distance and on-campus learners, (ii) the academic performance of distance and on-campus learners, (iii) the advantages and disadvantages of learning through distance education and on-campus education, and (iv) how the disadvantages of learning through distance education could be reduced. The study found that the majority of distance and on-campus learners were female, single, and unemployed. Most off-campus learners were more than 20 years old, whil...
The Distance Field Model and Distance Constrained MAP Adaptation Algorithm
Institute of Scientific and Technical Information of China (English)
YUPeng; WANGZuoying
2003-01-01
Spatial structure information, i.e., the rel-ative position information of phonetic states in the feature space, is long to be carefully researched yet. In this pa-per, a new model named “Distance Field” is proposed to describe the spatial structure information. Based on this model, a modified MAP adaptation algorithm named dis-tance constrained maximum a poateriori (DCMAP) is in-troduced. The distance field model gives large penalty when the spatial structure is destroyed. As a result the DCMAP reserves the spatial structure information in adaptation process. Experiments show the Distance Field Model improves the performance of MAP adapta-tion. Further results show DCMAP has strong cross-state estimation ability, which is used to train a well-performed speaker-dependent model by data from only part of pho-
Directory of Open Access Journals (Sweden)
Javier Barrera-Chica
2009-12-01
Full Text Available Objetivo. Estudiar los hábitos alimentarios de la Mayupa (Sternopygus macrurus Bloch & Schneider, 1801 en el río Sinú, Colombia. Materiales y métodos. El contenido estomacal se evaluó con el coeficiente de vacuidad, grado de llenado, grado de digestión, frecuencia de ocurrencia, frecuencia numérica, gravimetría, indice de importancia relativa (IIR y la relación longitud intestinal (LI-longitud total (LT. Resultados. Solo pocos estómagos se encontraron vacíos (CV =6.9% y el 60.0% de las presas se encontraron frescas. Se identificaron cuatro ítems alimentarios: peces, crustáceos, material vegetal y otros. Peces fue el ítem más frecuente (76.9%, abundante (48.3%, con mayor composición por peso (81.9% y con mayor importancia relativa (63.2%. Conclusiones. Los resultados obtenidos permiten inferir que la Mayupa es un pez de hábitos alimentarios carnívoros, con preferencia por los peces.
Higher Order Radial Derivatives of Bloch Type Functions%Bloch型函数的高阶径向导数
Institute of Scientific and Technical Information of China (English)
卓文新
2002-01-01
讨论了复超球上全纯函数的高阶导数的增长速度,证明了f∈Bα的充分必要条件是supa∈B(1-|z|2)m+α-1|Rmf(z)|＜∞,或supa∈B∫B(1-|z|2)(m+α-1)|Rmf(z)|pJRφα(z)dv(z)＜∞,或(1-|z|2)p(m+α-1)|Rmf(z)|pdv(z)是Bergman-Carleson测度.%In this paper, higher order radial derivatives of Bloch type functions in the unit ball of Cn is discussed and it is proved that for f∈H(B), f∈Bα if and only if supα∈B(1-|z|2)m+α-1|Rmf(z)|＜∞, if and only if supa∈B∫B(1-|z|2)P(m+α-1)|Rmf(z)|PJRφα(z)dv(z)＜∞, if and only if (1-|z|2)P(m+α-1)|Rmf(z)|Pdv(z) is a Bergman-Carleson measure.
Walker, Christopher M.; Bankson, James A.
2015-03-01
Magnetic resonance imaging (MRI) of hyperpolarized (HP) agents has the potential to probe in-vivo metabolism with sensitivity and specificity that was not previously possible. Biological conversion of HP agents specifically for cancer has been shown to correlate to presence of disease, stage and response to therapy. For such metabolic biomarkers derived from MRI of hyperpolarized agents to be clinically impactful, they need to be validated and well characterized. However, imaging of HP substrates is distinct from conventional MRI, due to the non-renewable nature of transient HP magnetization. Moreover, due to current practical limitations in generation and evolution of hyperpolarized agents, it is not feasible to fully experimentally characterize measurement and processing strategies. In this work we use a custom Bloch-McConnell simulator with pharmacokinetic modeling to characterize the performance of specific magnetic resonance spectroscopy sequences over a range of biological conditions. We performed numerical simulations to evaluate the effect of sequence parameters over a range of chemical conversion rates. Each simulation was analyzed repeatedly with the addition of noise in order to determine the accuracy and reproducibility of measurements. Results indicate that under both closed and perfused conditions, acquisition parameters can affect measurements in a tissue dependent manner, suggesting that great care needs to be taken when designing studies involving hyperpolarized agents. More modeling studies will be needed to determine what effect sequence parameters have on more advanced acquisitions and processing methods.
Cielocha, Joanna J; Jensen, Kirsten
2013-01-01
A new genus and species of lecanicephalidean cestode, Stoibocephalum arafurense n. gen., n. sp., is described from the sharkray, Rhina ancylostoma Bloch & Schneider, off northern Australia. Stoibocephalum arafurense n. gen., n. sp. is apolytic, and possesses a large, muscular, retractable apical organ, 3 pairs of excretory vessels, and testes in several columns and layers. The presence of 3 pairs of excretory vessels distinguishes this new genus from all other valid lecanicephalidean genera, except Hexacanalis Perrenoud, 1931, from which it can be distinguished based on ovary shape and egg morphology. Stoibocephalum n. gen. most closely resembles Tylocephalum Linton, 1890 but differs from that genus in its ability to completely retract its apical organ into the scolex proper. Scolex microthrix pattern and histological sections of scoleces attached in situ suggest S. arafurense n. gen., n. sp. to attach to the host's intestinal mucosa with apical organ and scolex proper surfaces, rather than just the apical organ surface. This is the third lecanicephalidean species described from the sharkray.
Pereira, Tadeu José; Silva, Gilda; Costa, Maria José; Costa, José Lino
2011-07-01
The Lusitanian toadfish, Halobatrachus didactylus (Bloch and Schneider, 1801), is a subtropical sound-producing marine teleost that inhabits estuaries and other brackish water ecosystems in its northern distribution area. The relative isolation of populations within estuaries may cause important modifications in the bio-ecology of this species. The males of this species present two morphotypes which are more accurately distinguishable during the reproductive season. In the Tagus estuary population, the two types of reproductive males were present: type I, the "characteristic" morphotype, and type II, the alternative morphotype. The opportunistic males had more developed testis while type I males had more developed accessory glands. Type I males presented more developed swimbladders and larger body size and live longer than type II males. On the contrary, type II males grew faster and matured earlier. The feeding habits of the two male morphotypes were similar during the reproductive season but differences were found between reproductive specimens and non-reproductive specimens. The diet of reproductive specimens was mainly composed of benthic prey in contrast to predominance of nectobenthic prey in the diet of non-reproductive specimens. The females of H. didactylus generally had an intermediate pattern between the two male morphotypes. The percentage of type II males tended to be higher in denser areas of the estuary. In comparison with populations from different size ecosystems, smaller ecosystems revealed important modifications on the bio-ecology of the species due to the increased competition for nesting sites and mating partners, favouring alternative male tactics.
Delamare-Deboutteville, J; Bowater, R; Condon, K; Reynolds, A; Fisk, A; Aviles, F; Barnes, A C
2015-12-01
Since 2007, 96 wild Queensland groupers, Epinephelus lanceolatus, (Bloch), have been found dead in NE Australia. In some cases, Streptococcus agalactiae (Group B Streptococcus, GBS) was isolated. At present, a GBS isolate from a wild grouper case was employed in experimental challenge trials in hatchery-reared Queensland grouper by different routes of exposure. Injection resulted in rapid development of clinical signs including bilateral exophthalmia, hyperaemic skin or fins and abnormal swimming. Death occurred in, and GBS was re-isolated from, 98% fish injected and was detected by PCR in brain, head kidney and spleen from all fish, regardless of challenge dose. Challenge by immersion resulted in lower morbidity with a clear dose response. Whilst infection was established via oral challenge by admixture with feed, no mortality occurred. Histology showed pathology consistent with GBS infection in organs examined from all injected fish, from fish challenged with medium and high doses by immersion, and from high-dose oral challenge. These experimental challenges demonstrated that GBS isolated from wild Queensland grouper reproduced disease in experimentally challenged fish and resulted in pathology that was consistent with that seen in wild Queensland grouper infected with S. agalactiae.
Buot, Felix A.; Otadoy, Roland E. S.; Rivero, Karla B.
2017-03-01
Wide ranging interest in Dirac Hamiltonian is due to the emergence of novel materials, namely, graphene, topological insulators and superconductors, the newly-discovered Weyl semimetals, and still actively-sought after Majorana fermions in real materials. We give a brief review of the relativistic Dirac quantum mechanics and its impact in the developments of modern physics. The quantum band dynamics of Dirac Hamiltonian is crucial in resolving the giant diamagnetism of bismuth and Bi-Sb alloys. Quantitative agreement of the theory with the experiments on Bi-Sb alloys has been achieved, and physically meaningful contributions to the diamagnetism has been identified. We also treat relativistic Dirac fermion as an interband dynamics in uniform magnetic fields. For the interacting Bloch electrons, the role of translation symmetry for calculating the magnetic susceptibility avoids any approximation to second order in the field. The expressions for magnetic susceptibility of dilute nonmagnetic alloys give a firm theoretical foundation of the empirical formulas used in fitting experimental results. The unified treatment of all the above calculations is based on the lattice Weyl-Wigner formulation of discrete phase-space quantum mechanics. For completeness, the magnetic susceptibility of Kondo alloys is also given since Dirac fermions in conduction band and magnetic impurities exhibit Kondo effect.
Study of speed endurance middle distance runners
Directory of Open Access Journals (Sweden)
Golovaschenko R.V.
2013-12-01
Full Text Available Purpose : To investigate the boost performance speed endurance runners who specialize in middle-distance running . Material and methods : The study involved team members Vinnytsia region in an amount of 44 people, whose average age was 20,2 ± 2,1 years. Classes are held during the 21-day mesocycle, 5 times a week, twice a day. Things were aimed at enhancing the development of indicators of special speed endurance. Results : The dynamics of the running speed of the model segments that characterize speed endurance athletes. Proved that the improved running 400 meter intervals helps reduce travel time competitive distance of 1500 meters. Conclusion : The use of the program contributes to higher speed endurance, which determines the result in the women's 1,500 meters.
KNOWLEDGE DISTANCE IN INFORMATION SYSTEMS
Institute of Scientific and Technical Information of China (English)
Yuhua QIAN; Jiye LIANG; Chuangyin DANG; Feng WANG; Wei XU
2007-01-01
In this paper, we first introduce the concepts of knowledge closeness and knowledge distance for measuring the sameness and the difference among knowledge in an information system, respectively.The relationship between these two concepts is a strictly mutual complement relation. We then investigate some important properties of knowledge distance and perform experimental analyses on two public data sets, which show the presented measure appears to be well suited to characterize the nature of knowledge in an information system. Finally, we establish the relationship between the knowledge distance and knowledge granulation, which shows that two variants of the knowledge distance can also be used to construct the knowledge granulation. These results will be helpful for studying uncertainty in information systems.
ECONOMICS OF DISTANCE EDUCATION RECONSIDERED
Directory of Open Access Journals (Sweden)
Wolfram LAASER
2008-07-01
Full Text Available ABSTRACT According to Gartner a certain hype of e-Learning was followed by a downturn but eLearning will continue to be an important factor in learning scenarios. However the economic viability of e-learning projects will be questioned with more scrutiny than in earlier periods. Therefore it seems to be a good opportunity to see what can be learned from past experience in costing distance learning projects and what aspects are added by current attempts to measure economic efficiency. After reviewing early research about costing distance learning some more recent approaches will be discussed, such as eLearning ROI-calculators and the concept of total cost of ownership. Furthermore some microeconomic effects referring to localization of distance learning courses are outlined. Finally several unsolved issues in costing distance education are summarized.
Distance Education in Technological Age
Directory of Open Access Journals (Sweden)
R .C. SHARMA
2005-04-01
Full Text Available Distance Education in Technological AgeRomesh Verma (Editor, New Delhi: Anmol Publications, 2005, ISBN 81-261-2210-2, pp. 419 Reviewed by R C SHARMARegional DirectorIndira Gandhi National Open University-INDIA The advancements in information and communication technologies have brought significant changes in the way the open and distance learning are provided to the learners. The impact of such changes is quite visible in both developed and developing countries. Switching over to online mode, joining hands with private initiatives and making a presence in foreign waters, are some of the hallmarks of the open and distance education (ODE institutions in developing countries. The compilation of twenty six essays on themes as applicable to ODE has resulted in the book, Distance Education in Technological Age. These essays follow a progressive style of narration, starting from describing conceptual framework of distance education, how the distance education was emerged on the global scene and in India, and then goes on to discuss emergence of online distance education and research aspects in ODE. The initial four chapters provide a detailed account of historical development and growth of distance education in India and State Open University and National Open University Model in India . Student support services are pivot to any distance education and much of its success depends on how well the support services are provided. These are discussed from national and international perspective. The issues of collaborative learning, learning on demand, life long learning, learning-unlearning and re-learning model and strategic alliances have also given due space by the authors. An assortment of technologies like communication technology, domestic technology, information technology, mass media and entertainment technology, media technology and educational technology give an idea of how these technologies are being adopted in the open universities. The study
Distance Learning for Special Populations
Bates, Rodger A.
2012-01-01
Distance education strategies for remotely deployed, highly mobile, or institutionalized populations are reviewed and critiqued. Specifically, asynchronous, offline responses for special military units, Native Americans on remote reservations, prison populations and other geographically, temporally or technologically isolated niche populations are…
Academy Distance Learning Tools (IRIS)
Department of Transportation — IRIS is a suite of front-end web applications utilizing a centralized back-end Oracle database. The system fully supports the FAA Academy's Distance Learning Program...
Graph distance for complex networks
Shimada, Yutaka; Hirata, Yoshito; Ikeguchi, Tohru; Aihara, Kazuyuki
2016-10-01
Networks are widely used as a tool for describing diverse real complex systems and have been successfully applied to many fields. The distance between networks is one of the most fundamental concepts for properly classifying real networks, detecting temporal changes in network structures, and effectively predicting their temporal evolution. However, this distance has rarely been discussed in the theory of complex networks. Here, we propose a graph distance between networks based on a Laplacian matrix that reflects the structural and dynamical properties of networked dynamical systems. Our results indicate that the Laplacian-based graph distance effectively quantifies the structural difference between complex networks. We further show that our approach successfully elucidates the temporal properties underlying temporal networks observed in the context of face-to-face human interactions.
Categorical perception of tactile distance
Knight, F. L. C.; Longo, M. R.; Bremner, A.J.
2014-01-01
The tactile surface forms a continuous sheet covering the body. And yet, the perceived distance between two touches varies across stimulation sites. Perceived tactile distance is larger when stimuli cross over the wrist, compared to when both fall on either the hand or the forearm. This effect could reflect a categorical distortion of tactile space across body-part boundaries (in which stimuli crossing the wrist boundary are perceptually elongated) or may simply reflect a localised increased ...
Center—Distance Continuous Probability Models and the Distance Measure
Institute of Scientific and Technical Information of China (English)
郑方; 吴文虎; 等
1998-01-01
In this paper,a new statistic model named Center-Distance Continuous Probability Model(CDCPM)for speech recognition is described,which is based on Center-Distance Normal(CDN)distribution.In a CDCPM,the probability transition matrix is omitted,and the observation probability density function(PDF)in each state is in the form of embedded multiple-model(EMM)based on the Nearest Neighbour rule.The experimental results on two giant real-world Chinese speech databases and a real-world continuous-manner 2000 phrase system show that this model is a powerful one.Also,a distance measure for CDPMs is proposed which is based on the Bayesian minimum classification error(MCE) discrimination.
Multiobjective Gate Assignment Based on Passenger Walking Distance and Fairness
Directory of Open Access Journals (Sweden)
Yu Jiang
2013-01-01
Full Text Available Passenger walking distance is an important index of the airport service quality. How to shorten the walking distance and balance the airlines' service quality is the focus of much research on airport gate assignment problems. According to the problems of airport passenger service quality, an optimization gate assignment model is established. The gate assignment model is based on minimizing the total walking distance of all passengers and balancing the average walking distance of passengers among different airlines. Lingo is used in the simulation of a large airport gate assignment. Test results show that the optimization model can reduce the average walking distance of passenger effectively, improve the number of flights assigned to gate, balance airline service quality, and enhance the overall service level of airports and airlines. The model provides reference for the airport gate preassignment.
Hierarchical Clustering Given Confidence Intervals of Metric Distances
Huang, Weiyu
2016-01-01
This paper considers metric spaces where distances between a pair of nodes are represented by distance intervals. The goal is to study methods for the determination of hierarchical clusters, i.e., a family of nested partitions indexed by a resolution parameter, induced from the given distance intervals of the metric spaces. Our construction of hierarchical clustering methods is based on defining admissible methods to be those methods that abide to the axioms of value - nodes in a metric space with two nodes are clustered together at the convex combination of the distance bounds between them - and transformation - when both distance bounds are reduced, the output may become more clustered but not less. Two admissible methods are constructed and are shown to provide universal upper and lower bounds in the space of admissible methods. Practical implications are explored by clustering moving points via snapshots and by clustering networks representing brain structural connectivity using the lower and upper bounds...
Computing Distances between Probabilistic Automata
Directory of Open Access Journals (Sweden)
Mathieu Tracol
2011-07-01
Full Text Available We present relaxed notions of simulation and bisimulation on Probabilistic Automata (PA, that allow some error epsilon. When epsilon is zero we retrieve the usual notions of bisimulation and simulation on PAs. We give logical characterisations of these notions by choosing suitable logics which differ from the elementary ones, L with negation and L without negation, by the modal operator. Using flow networks, we show how to compute the relations in PTIME. This allows the definition of an efficiently computable non-discounted distance between the states of a PA. A natural modification of this distance is introduced, to obtain a discounted distance, which weakens the influence of long term transitions. We compare our notions of distance to others previously defined and illustrate our approach on various examples. We also show that our distance is not expansive with respect to process algebra operators. Although L without negation is a suitable logic to characterise epsilon-(bisimulation on deterministic PAs, it is not for general PAs; interestingly, we prove that it does characterise weaker notions, called a priori epsilon-(bisimulation, which we prove to be NP-difficult to decide.
Distance sampling methods and applications
Buckland, S T; Marques, T A; Oedekoven, C S
2015-01-01
In this book, the authors cover the basic methods and advances within distance sampling that are most valuable to practitioners and in ecology more broadly. This is the fourth book dedicated to distance sampling. In the decade since the last book published, there have been a number of new developments. The intervening years have also shown which advances are of most use. This self-contained book covers topics from the previous publications, while also including recent developments in method, software and application. Distance sampling refers to a suite of methods, including line and point transect sampling, in which animal density or abundance is estimated from a sample of distances to detected individuals. The book illustrates these methods through case studies; data sets and computer code are supplied to readers through the book’s accompanying website. Some of the case studies use the software Distance, while others use R code. The book is in three parts. The first part addresses basic methods, the ...
Conceptualizing Educational Research in Distance Education.
Watkins, Ryan; Schlosser, Charles
2003-01-01
Suggests a starting place for formal inquiry into distance education. Topics covered include: background on educational research and research on distance education; research paradigms that are applicable to distance education; subsystems of a distance education program; and a matrix for conceptualizing distance education research. (MES)
The anisotropy of perceived distance: The eyes story
Directory of Open Access Journals (Sweden)
Tošković Oliver
2011-01-01
Full Text Available The aim of this study is to determine whether the eye position shift changes perceived distance, that is, whether kinesthetic information from eye muscles affects distance perception. Two experiments were done, in a dark room (reduced-cue situation, with 27 participants, psychology undergraduates. Participants had a task to match distances of three stimuli, on three viewing directions, 0, 30 and 60 deg rees relative to the body. Head and body of participants were fixed, and they changed viewing directions only by moving their eyes. Stimuli were 7cm
The Distance Geometry of Music
Demaine, Erik D; Meijer, Henk; Rappaport, David; Taslakian, Perouz; Toussaint, Godfried T; Winograd, Terry; Wood, David R
2007-01-01
We demonstrate relationships between the classic Euclidean algorithm and many other fields of study, particularly in the context of music and distance geometry. Specifically, we show how the structure of the Euclidean algorithm defines a family of rhythms which encompass over forty timelines (\\emph{ostinatos}) from traditional world music. We prove that these \\emph{Euclidean rhythms} have the mathematical property that their onset patterns are distributed as evenly as possible: they maximize the sum of the Euclidean distances between all pairs of onsets, viewing onsets as points on a circle. Indeed, Euclidean rhythms are the unique rhythms that maximize this notion of \\emph{evenness}. We also show that essentially all Euclidean rhythms are \\emph{deep}: each distinct distance between onsets occurs with a unique multiplicity, and these multiplicies form an interval $1,2,...,k-1$. Finally, we characterize all deep rhythms, showing that they form a subclass of generated rhythms, which in turn proves a useful prop...
Asymmetric distances for binary embeddings.
Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana
2014-01-01
In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques.
Virtual bioinformatics distance learning suite*.
Tolvanen, Martti; Vihinen, Mauno
2004-05-01
Distance learning as a computer-aided concept allows students to take courses from anywhere at any time. In bioinformatics, computers are needed to collect, store, process, and analyze massive amounts of biological and biomedical data. We have applied the concept of distance learning in virtual bioinformatics to provide university course material over the Internet. Currently, we provide two fully computer-based courses, "Introduction to Bioinformatics" and "Bioinformatics in Functional Genomics." Here we will discuss the application of distance learning in bioinformatics training and our experiences gained during the 3 years that we have run the courses, with about 400 students from a number of universities. The courses are available at bioinf.uta.fi.
Ghost imaging with broad distance
Institute of Scientific and Technical Information of China (English)
段德洋; 张路; 杜少将; 夏云杰
2015-01-01
We present a scheme that is able to achieve the ghost imaging with broad distance. The physical nature of our scheme is that the different wavelength beams are separated in free space by an optical media according to the slow light or dispersion principle. Meanwhile, the equality of the optical distance of the two light arms is not violated. The photon correlation is achieved by the rotating ground glass plate (RGGP) and spatial light modulator (SLM), respectively. Our work shows that a monochromic ghost image can be obtained in the case of RGGP. More importantly, the position (or distance) of the object can be ascertained by the color of the image. Thus, the imaging and ranging processes are combined as one process for the first time to the best of our knowledge. In the case of SLM, we can obtain a colored image regardless of where the object is.
方波电场驱动下的Rabi振荡%Rabi Oscillations Between Bloch Bands in a Square-wave Electric Field
Institute of Scientific and Technical Information of China (English)
宫建平; 邵建立; 段素青; 赵宪庚
2006-01-01
We investigate double Bloch bands driven by a square-wave electric field with a tight-binding model. Using Fourier analysis, we analytically obtain resonance conditions of Rabi oscillation and Rabi frequency in the weak-coupling limit. The results are verified by numerical evolution of electrons.%研究了方波电场驱动下的双Bloch带的紧束缚模型.借助Fourier分析,得到了在弱耦合极限下Rabi振荡及Rabi频率的解析解;这些结果均由电子的数值演化所证实.
Nirlei Hirachy Costa Barros; Wallace Silva Nascimento; Andréa Soares Araújo; Arrilton Araujo Souza; Sathyabama Chellappa
2013-01-01
A biologia reprodutiva do peixe hermafrodita mussum, Synbranchus marmoratus (Bloch, 1795) (Osteichthyes: Synbranchidae) foi investigada no açude Marechal Dutra, Acari, Rio Grande do Norte, utilizando os exemplares capturados mensalmente no período de julho de 2010 á janeiro de 2011. Os peixes capturados foram numerados, pesados, medidos, dissecados as e gônadas foram retiradas, pesadas e identificadas quanto ao sexo. A relação peso-comprimento foi determinada para sexos agrupados. O índice go...
La conciencia de la libertad (La filosofía moral como filosofía de la historia en Ernst Bloch)
Gimbernat, José Antonio
1991-01-01
Not available.
A partir del concepto hegeliano de «progreso en la conciencia de la libertad », se puede hacer una lectura de la filosofía moral de Bloch como filosofía de la historia. Ello conduce a una reino reinterpretación libre y materialista de Hegel y a una recuperación de la moral en el marxismo. En diálogo con Kant se hace posible descubrir el potencial utópico del énfasis subjetivo de la moral. El objetivo del reino de la libertad marxiano es la clave de una histor...
Fast Exact Euclidean Distance (FEED) Transformation
Schouten, Theo; Broek, van den Egon; Kittler, J.; Petrou, M.; Nixon, M.
2004-01-01
Fast Exact Euclidean Distance (FEED) transformation is introduced, starting from the inverse of the distance transformation. The prohibitive computational cost of a naive implementation of traditional Euclidean Distance Transformation, is tackled by three operations: restriction of both the number o
Hajnal, Alen; Bunch, David A; Kelty-Stephen, Damian G
2014-05-01
Visually guided distance perception reflects a relationship of geometrical optical variables with the effort required when traversing the distance. We probed how the representations encoding optical variables might define this relationship. Participants visually judged distances on sloped surfaces and reproduced these distances over flat terrain by walking while blindfolded. We examined the responses for the effects of optical variables (i.e., angular declinations from eye height) and tested whether four measures of trial-by-trial effort moderated the use of the represented optical variables. We predicted that observation time and response speed relative to the observed distance would accentuate the effects of encoded optical variables, and that response time and response speed relative to the traversed distance would reduce the effects of those variables. The results confirmed all of the effects except those of observation time. Given the benefits of longer study for strengthening a memory trace, the failure of observation time to predict the use of optical variables raises questions about the representational encoding of visual traces for distance perception. Relationships among optical variables and other effort measures implicate the interaction of processes across multiple time scales, as in cascade dynamics. Cascade dynamics may provide new directions for accounts of visually guided distance perception.
The Perception of Ideological Distance
Granberg, Donald; Brown, Thad A.
1992-01-01
Data from national election studies in Britain, the Netherlands, Sweden, and the U.S. were analyzed to test hypotheses concerning the perception of ideological distance between parties and candidates. The first hypothesis, derived from Sherif's social judgment theory and Heider's balance theory, was
Lessons in Developing Distance Learning.
Gant, Lenora Peters
1996-01-01
Describes the use of video teletraining (VTT) for distance learning in the Department of Defense. Topics include planning and organizing the VTT facility, staff development, site facilitators, the necessity of protocol, instructional design and development strategies, student involvement and interactivity, and evaluation and assessment. (LRW)
Distance, Lending Relationships and Competition
Degryse, H.A.; Ongena, S.
2002-01-01
A recent string of theoretical papers highlights the importance of geographical distance in explaining pricing and availability of loans to small firms.Lenders located in the vicinity of small firms have significantly lower monitoring and transaction costs, and hence considerable market power if com
Distance, Lending Relationships, and Competition
Degryse, H.A.; Ongena, S.
2003-01-01
A recent string of theoretical papers has highlighted the importance of geographical distance in explaining loan rates for small firms.Lenders located in the vicinity of small firms face significantly lower transportation and monitoring costs, and hence wield considerable market power, if competing
Distance Education Instructional Model Applications.
Jackman, Diane H.; Swan, Michael K.
1995-01-01
A survey of graduate students involved in distance education on North Dakota State University's Interactive Video Network included 80 on campus and 13 off. The instructional models rated most effective were role playing, simulation, jurisprudential (Socratic method), memorization, synectics, and inquiry. Direct instruction was rated least…
Favourite distances in high dimensions
Swanepoel, Konrad J
2011-01-01
Let $S$ be a set of $n$ points in $d$-dimensional Euclidean space. Assign to each $x\\in S$ an arbitrary distance $r(x)>0$. Let $e_r(x,S)$ denote the number of points in $S$ at distance $r(x)$ from $x$. Avis, Erd\\"os and Pach (1988) introduced the extremal quantity $f_d(n)=\\max\\sum_{x\\in S}e_r(x,S)$, where the maximum is taken over all $n$-point sets $S$ in $d$-dimensional space and all assignments $r\\colon S\\to(0,\\infty)$ of distances. We give a quick derivation of the asymptotics of the error term of $f_d(n)$ using only the analogous asymptotics of the maximum number of unit distance pairs in a set of $n$ points, which improves on previous results of Avis, Erd\\"os and Pach (1988) and Erd\\"os and Pach (1990). Then we prove a stability result for $d\\geq 4$, asserting that if $(S,r)$ with $|S|=n$ satisfies $e_r(S)=f_d(n)-o(n^2)$, then, up to $o(n)$ points, $S$ is a Lenz construction with $r$ constant. Finally we use stability to show that for $n$ sufficiently large (depending on $d$) the pairs $(S,r)$ that atta...
Alderson, Tim L.; Svenja Huntemann
2013-01-01
Singleton-type upper bounds on the minimum Lee distance of general (not necessarily linear) Lee codes over ℤq are discussed. Two bounds known for linear codes are shown to also hold in the general case, and several new bounds are established. Codes meeting these bounds are investigated and in some cases characterised.
Video Surveillance using Distance Maps
Schouten, Theo E.; Kuppens, Harco C.; Broek, van den Egon L.; Kehtarnavaz, Nasser; Laplante, Phillip A.
2006-01-01
Human vigilance is limited; hence, automatic motion and distance detection is one of the central issues in video surveillance. Hereby, many aspects are of importance, this paper specially addresses: efficiency, achieving real-time performance, accuracy, and robustness against various noise factors.
Distance Learning: Untried and Untrue
Halfond, Jay A.
2010-01-01
G. K. Chesterton famously once said: "Christianity has not been tried and found wanting; it has been found difficult and not tried." This, the author believes, applies to distance learning as well. There is far too much self-congratulatory hyperbole about the growth and pervasiveness of online learning--which exaggerates reality and overlooks the…
Curriculum Control in Distance Education.
Chesterton, Paul
1985-01-01
The nature of distance education is to shift the locus of curriculum control toward the institution and its staff and away from the students. This imposes a responsibility on the institution to examine and evaluate the values and assumptions underlying the decision-making and the implications of the patterns of control that emerge. (Author/MSE)
The Future of Distance Education.
Saba, Farhad
2000-01-01
Examines factors that will influence how distance education is practiced in the first few decades of this new century. Discusses developments in digital technology; the exponential growth of knowledge about the brain, as well as physiology, chemistry, and psychology of learning; the system relationship between individual learners and instructors;…
A Streaming Distance Transform Algorithm for Neighborhood-Sequence Distances
Directory of Open Access Journals (Sweden)
Nicolas Normand
2014-09-01
Full Text Available We describe an algorithm that computes a “translated” 2D Neighborhood-Sequence Distance Transform (DT using a look up table approach. It requires a single raster scan of the input image and produces one line of output for every line of input. The neighborhood sequence is specified either by providing one period of some integer periodic sequence or by providing the rate of appearance of neighborhoods. The full algorithm optionally derives the regular (centered DT from the “translated” DT, providing the result image on-the-ﬂy, with a minimal delay, before the input image is fully processed. Its efficiency can benefit all applications that use neighborhood- sequence distances, particularly when pipelined processing architectures are involved, or when the size of objects in the source image is limited.
Energy Technology Data Exchange (ETDEWEB)
Xu, J.P. [College of Physics, Hebei Normal University, Shijiazhuang 050016 (China); Liu, S.P. [College of Physics, Hebei Normal University, Shijiazhuang 050016 (China); Guo, G.X. [College of Physics, Hebei Normal University, Shijiazhuang 050016 (China); Zhen, C.M. [College of Physics, Hebei Normal University, Shijiazhuang 050016 (China); Tang, G.D. [College of Physics, Hebei Normal University, Shijiazhuang 050016 (China); Sun, H.Y. [College of Physics, Hebei Normal University, Shijiazhuang 050016 (China); Nie, X.F. [College of Physics, Hebei Normal University, Shijiazhuang 050016 (China)]. E-mail: niexf@mail.hebtu.edu.cn
2004-12-01
The stability of vertical Bloch lines (VBLs) in the second kind of dumbbell domain (IIDs) walls in liquid phase epitaxy garnet bubble films subjected to an in-plane field at various temperatures is studied experimentally. It is found that there exists a critical in-plane field range depending on temperature, in which vertical Bloch lines (VBLs) in the second kind of IIDs walls are unstable, i.e., [Hip(1)(T),Hip(2)(T)]. Here, Hip(1)(T) is the initial critical in-plane field at which VBLs in the walls of IIDs annihilate; while Hip(2)(T) is the lowest in-plane field at which all VBLs in the walls of IIDs have annihilated completely. Also, the critical in-plane field range [Hip(1)(T),Hip(2)(T)],Hip(1)(T) and Hip(2)(T) all decrease with the temperature increasing. Hip(1)(T) and Hip(2)(T) reach zero at T0' and T0, respectively.
Moral distance in dictator games
Directory of Open Access Journals (Sweden)
Fernando Aguiar
2008-04-01
Full Text Available We perform an experimental investigation using a dictator game in which individuals must make a moral decision --- to give or not to give an amount of money to poor people in the Third World. A questionnaire in which the subjects are asked about the reasons for their decision shows that, at least in this case, moral motivations carry a heavy weight in the decision: the majority of dictators give the money for reasons of a consequentialist nature. Based on the results presented here and of other analogous experiments, we conclude that dicator behavior can be understood in terms of moral distance rather than social distance and that it systematically deviates from the egoism assumption in economic models and game theory. %extit{JEL}: A13, C72, C91
Theological Librarianship from a Distance
Directory of Open Access Journals (Sweden)
Melody Diehl Detar
2015-08-01
Full Text Available This essay examines distance theological librarianship and the field’s suitability for remote librarians. A brief introduction to the landscape of online programs in theological education is followed by an overview of virtual librarianship and how theological librarians may serve students while working from a distance themselves. The essay then describes a method for initiating a remote librarian position in a theological library context, and then reviews the steps of determining whether remote work is feasible and desirable at an institution, approaching leadership with a plan, setting up a trial remote work period, and assessing its success. Particular emphasis is given to communication expectations, modes of virtual reference and instruction, campus committee service and meaningful ways of remaining part of the campus community.
Determining distances using asteroseismic methods
Aguirre, V Silva; Basu, S; Campante, T L; Chaplin, W J; Huber, D; Miglio, A; Serenelli, A M; WG#1, KASC
2012-01-01
Asteroseismology has been extremely successful in determining the properties of stars in different evolutionary stages with a remarkable level of precision. However, to fully exploit its potential, robust methods for estimating stellar parameters are required and independent verification of the results is needed. In this talk, I present a new technique developed to obtain stellar properties by coupling asteroseismic analysis with the InfraRed Flux Method. Using two global seismic observables and multi-band photometry, the technique determines masses, radii, effective temperatures, bolometric fluxes, and thus distances for field stars in a self-consistent manner. Applying our method to a sample of solar-like oscillators in the {\\it Kepler} field that have accurate {\\it Hipparcos} parallaxes, we find agreement in our distance determinations to better than 5%. Comparison with measurements of spectroscopic effective temperatures and interferometric radii also validate our results, and show that our technique can ...
Managerial Distance and Virtual Ownership
DEFF Research Database (Denmark)
Hansmann, Henry; Thomsen, Steen
Industrial foundations are autonomous nonprofit entities that own and control one or more conventional business firms. These foundations are common in Northern Europe, where they own a number of internationally prominent companies. Previous studies have indicated, surprisingly, that companies con......, but corporate governance and fiduciary behavior more generally....... on differences among the industrial foundations themselves. We work with a rich data set comprising 113 foundation-owned Danish companies over the period 2003-2008. We focus in particular on a composite structural factor that we term “managerial distance.” We propose this as a measure of the extent to which......-seeking outside owners of the company. Consistent with this hypothesis, our empirical analysis shows a positive, significant, and robust association between managerial distance and the economic performance of foundation owned companies. The findings appear to illuminate not just foundation governance...
Distance Education Use in Rural Schools
Hannum, Wallace H.; Irvin, Matthew J.; Banks, Jonathan B.; Farmer, Thomas W.
2009-01-01
A national survey of rural school systems in the United States was conducted to determine the extent to which distance education is being utilized by rural schools, the technologies used, the curriculum areas impacted, the perceived needs for distance education, their satisfaction with distance education, and the barriers to distance education…
History and Heritage in Distance Education
Anderson, Bill; Simpson, Mary
2012-01-01
Distance education's history is a tremendous resource for all involved in distance education. Some aspects of that history provide enduring touchstones for present distance educators, creating a heritage that should not be overlooked as distance education continues to develop and expand. In this article we draw on the concept of generational…
Effective Teaching in Distance Education. ERIC Digest.
Mielke, Dan
Distance education is an alternative method for delivering academic course work to students unable to attend traditional campus-based classes. This Digest presents information on the many forms of distance education and keys to successful teaching with distance education. Distance education is a method of education in which the learner is…
Distance effects in electrochemical micromachining
2016-01-01
Considering exponential dependence of currents on double-layer voltage and the feedback effect of the electrolyte resistance, a distance effect in electrochemical micromachining is found, namely that both time constant and double-layer voltage depend on the separation of electrodes. The double-layer voltage is the real voltage used in processing. Under DC voltage, the apparent voltages between two electrodes are constant for different separations, but the real voltages change with the separat...
Distance Probes of Dark Energy
Kim, A; Aldering, G; Allen, S; Baltay, C; Cahn, R; D'Andrea, C; Dalal, N; Dawson, K; Denney, K; Eisenstein, D; Finley, D; Freedman, W; Ho, S; Holz, D; Kent, A; Kasen, D; Kessler, R; Kuhlmann, S; Linder, E; Martini, P; Nugent, P; Perlmutter, S; Peterson, B; Riess, A; Rubin, D; Sako, M; Suntzeff, N; Suzuki, N; Thomas, R; Wood-Vasey, W M; Woosley, S
2013-01-01
This document presents the results from the Distances subgroup of the Cosmic Frontier Community Planning Study (Snowmass 2013). We summarize the current state of the field as well as future prospects and challenges. In addition to the established probes using Type IA supernovae and baryon acoustic oscillations, we also consider prospective methods based on clusters, active galactic nuclei, gravitational wave sirens and strong lensing time delays.
Students’ Role in Distance Learning
Beers Fägersten, Kristy
2008-01-01
1. IntroductionMuch of the support that students have in a traditional classroom is absent in a distance learning course. In the traditional classroom, the learner is together with his or her classmates and the teacher; learning is socially embedded. Students can talk to each other and may learn from each other as they go through the learning process together. They also witness the teacher’s expression of the knowledge firsthand. The class participants communicate to each other not ...
Coupling-reducing k-points for photonic crystal fibre calculations
DEFF Research Database (Denmark)
Albertsen, Maja; Lægsgaard, Jesper; Barkou Libori, Stig Eigil;
2003-01-01
of the transverse Bloch wave vector, k. We describe a method to derive k-points that minimize the coupling between repeated images of the guided modes in real space. Calculations have been done for a quadratic and a triangular photonic crystal fiber structure. With the new coupling reducing (CR) k......When describing localized electromagnetic modes in dielectric waveguides by the planewave method, a supercell geometry must necessarily be adopted. We demonstrate in the present work that the convergence of the calculations with respect to supercell size depends strongly on the choice...
The Magnetotail at Lunar Distance
Sibeck, D. G.
2015-12-01
This presentation reviews some of the single-point observations of the magnetotail at lunar distances made by ALSEP, Explorer 33, 35, ISEE-3, and Geotail that form the framework for interpreting more recent dual-spacecraft ARTEMIS observations. Earth's distant magnetotail flaps, twists, and flattens in response to variations in the solar wind flow direction and interplanetary magnetic field (IMF) orientation. It may even disappear leaving nothing more than a wake during strongly northward IMF orientations. Standing slow mode expansion fans provide for a gradual transition between magnetotail lobe and magnetosheath plasma and magnetic field parameters. The distant neutral line may at times reside at lunar distances, creating jets of sunward-streaming plasma within the cislunar plasma sheet and layers of streaming energetic particles on its boundaries. Reconnection at near-Earth neutral lines releases antisunward-moving plasmoids that transit lunar distances, briefly expanding the diameter of the plasma sheet and magnetotail. Taken as a whole, the distant magnetotail is a fascinating plasma laboratory and a region of great important to the magnetosphere.
Fingerprinting with Minimum Distance Decoding
Lin, Shih-Chun; Gamal, Hesham El
2007-01-01
This work adopts an information theoretic framework for the design of collusion-resistant coding/decoding schemes for digital fingerprinting. More specifically, the minimum distance decision rule is used to identify 1 out of t pirates. Achievable rates, under this detection rule, are characterized in two distinct scenarios. First, we consider the averaging attack where a random coding argument is used to show that the rate 1/2 is achievable with t=2 pirates. Our study is then extended to the general case of arbitrary $t$ highlighting the underlying complexity-performance tradeoff. Overall, these results establish the significant performance gains offered by minimum distance decoding as compared to other approaches based on orthogonal codes and correlation detectors. In the second scenario, we characterize the achievable rates, with minimum distance decoding, under any collusion attack that satisfies the marking assumption. For t=2 pirates, we show that the rate $1-H(0.25)\\approx 0.188$ is achievable using an ...
Support Services for Distance Education
Directory of Open Access Journals (Sweden)
Sandra Frieden
1999-01-01
Full Text Available The creation and operation of a distance education support infrastructure requires the collaboration of virtually all administrative departments whose activities deal with students and faculty, and all participating academic departments. Implementation can build on where the institution is and design service-oriented strategies that strengthen institutional support and commitment. Issues to address include planning, faculty issues and concerns, policies and guidelines, approval processes, scheduling, training, publicity, information-line operations, informational materials, orientation and registration processes, class coordination and support, testing, evaluations, receive site management, partnerships, budgets, staffing, library and e-mail support, and different delivery modes (microwave, compressed video, radio, satellite, public television/cable, video tape and online. The process is ongoing and increasingly participative as various groups on campus begin to get involved with distance education activities. The distance education unit must continuously examine and revise its processes and procedures to maintain the academic integrity and service excellence of its programs. Its a daunting prospect to revise the way things have been done for many years, but each department has an opportunity to respond to new ways of serving and reaching students.
Comb-referenced laser distance interferometer for industrial nanotechnology
Jang, Yoon-Soo; Wang, Guochao; Hyun, Sangwon; Kang, Hyun Jay; Chun, Byung Jae; Kim, Young-Jin; Kim, Seung-Woo
2016-08-01
A prototype laser distance interferometer is demonstrated by incorporating the frequency comb of a femtosecond laser for mass-production of optoelectronic devices such as flat panel displays and solar cell devices. This comb-referenced interferometer uses four different wavelengths simultaneously to enable absolute distance measurement with the capability of comprehensive evaluation of the measurement stability and uncertainty. The measurement result reveals that the stability reaches 3.4 nm for a 3.8 m distance at 1.0 s averaging, which further reduces to 0.57 nm at 100 s averaging with a fractional stability of 1.5 × 10-10. The uncertainty is estimated to be in a 10-8 level when distance is measured in air due to the inevitable ambiguity in estimating the refractive index, but it can be enhanced to a 10-10 level in vacuum.
The Monge distance between quantum states
Energy Technology Data Exchange (ETDEWEB)
Zyczkowski, Karol [Institute for Plasma Research, University of Maryland, College Park, MD (United States); Slomczynski, Wojciech [Instytut Matematyki, Uniwersytet Jagiellonski, Cracow (Poland)
1998-11-13
We define a metric in the space of quantum states taking the Monge distance between corresponding Husimi distributions (Q-functions). This quantity fulfils the axioms of a metric and satisfies the following semiclassical property: the distance between two coherent states is equal to the Euclidean distance between corresponding points in the classical phase space. We compute analytically distances between certain states (coherent, squeezed, Fock and thermal) and discuss a scheme for numerical computation of Monge distance for two arbitrary quantum states. (author)
Editorial ~ Global Diversity of Distance Education
2001-01-01
In a panel presentation at the recent International Council for Open and Distance Education (ICDE) world conference in Dusseldorf, Germany, I had the opportunity to explain the unique role and mission of International Review of Research in Open and Distance Learning (IRRODL) vis – vis our more established sister journals: Open Praxis, Open Learning, Journal of Distance Education, Distance Education, and American Journal of Distance Education. Although all of these journals share a common comm...
Bazeia, D; Losano, L
2016-01-01
This work reports on models described by two real scalar fields coupled with gravity in the five-dimensional spacetime, with a warped geometry involving one infinite extra dimension. Through a mechanism that smoothly changes a thick brane into a hybrid brane, one investigates the appearance of hybrid branes hosting internal structure, characterized by the splitting on the energy density and the volcano potential, induced by the parameter which controls interactions between the two scalar fields. In particular, we investigate distinct symmetric and asymmetric hybrid brane scenarios.
Mattig's relation and dynamical distance indicators
Teerikorpi, Pekka
2016-01-01
We discuss how the redshift (Mattig) method in Friedmann cosmology relates to dynamical distance indicators based on Newton's gravity (Teerikorpi 2011). It belongs to the class of indicators where the relevant length inside the system is the distance itself (in this case the proper metric distance). As the Friedmann model has Newtonian analogy, its use to infer distances has instructive similarities to classical dynamical distance indicators. In view of the theoretical exact linear distance-velocity law, we emphasize that it is conceptually correct to derive the cosmological distance via the route: redshift (primarily observed) --> space expansion velocity (not directly observed) --> metric distance (physical length in "cm"). Important properties of the proper metric distance are summarized.
Distance Measurement Solves Astrophysical Mysteries
2003-08-01
Location, location, and location. The old real-estate adage about what's really important proved applicable to astrophysics as astronomers used the sharp radio "vision" of the National Science Foundation's Very Long Baseline Array (VLBA) to pinpoint the distance to a pulsar. Their accurate distance measurement then resolved a dispute over the pulsar's birthplace, allowed the astronomers to determine the size of its neutron star and possibly solve a mystery about cosmic rays. "Getting an accurate distance to this pulsar gave us a real bonanza," said Walter Brisken, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. Monogem Ring The Monogem Ring, in X-Ray Image by ROSAT satellite CREDIT: Max-Planck Institute, American Astronomical Society (Click on Image for Larger Version) The pulsar, called PSR B0656+14, is in the constellation Gemini, and appears to be near the center of a circular supernova remnant that straddles Gemini and its neighboring constellation, Monoceros, and is thus called the Monogem Ring. Since pulsars are superdense, spinning neutron stars left over when a massive star explodes as a supernova, it was logical to assume that the Monogem Ring, the shell of debris from a supernova explosion, was the remnant of the blast that created the pulsar. However, astronomers using indirect methods of determining the distance to the pulsar had concluded that it was nearly 2500 light-years from Earth. On the other hand, the supernova remnant was determined to be only about 1000 light-years from Earth. It seemed unlikely that the two were related, but instead appeared nearby in the sky purely by a chance juxtaposition. Brisken and his colleagues used the VLBA to make precise measurements of the sky position of PSR B0656+14 from 2000 to 2002. They were able to detect the slight offset in the object's apparent position when viewed from opposite sides of Earth's orbit around the Sun. This effect, called parallax, provides a direct measurement of
An overview on distance and pseudo distance functions and their applications
Institute of Scientific and Technical Information of China (English)
ZHU Xiangyang; DING Han; ZHONG Binglin; XIONG Youlun
2003-01-01
The fast and accurate collision detection and distance calculation between geometric models is fundamental in robotics, manufacturing and computer-simulated environments. This paper surveys the state of the art in the theory and algorithms of distance and pseudo distance functions between convex sets. An overview on the existing results, including fast algorithms for distance calculation, definitions and properties of various pseudo distance functions (the J-function, the growth distance, and the pseudo minimum translational distance), is presented. The distance and pseudo distance functions are versatile in a wide range of areas. Their applications in robot motion planning, grasp analysis/synthesis, form error evaluation, and engineering optimization is demonstrated.
NEW HAUSDORFF DISTANCE-BASED VEHICLE LOCATION
Institute of Scientific and Technical Information of China (English)
陈莹; 韩崇昭
2004-01-01
Objective To realize accurate localization of moving vehicles from single monocular intensity image. Methods The new modified Hausdorff distance(M2HD) was adopted, which used dominant points instead of edge maps as features for measuring similarity between image and model projection. Modified simulated annealing (MSA) algorithm was used to find optimum localization parameters. Results M2HD reduces the computational complexity, and improves the matching precision. Furthermore, MSA can fast find global optimum instead of getting into partial one because of its high parallel and robust performance. Conclusion Experiments confirm that the combination of MSA and M2HD can effectively localize the vehicles that are changed both in translation and rotation
McClain, John
This dissertation reports on a novel theoretical and computational framework for calculating low-energy electron reflectivities from crystalline surfaces and its application to two layered systems of two-dimensional materials, graphene and molybdenum disulfide. The framework provides a simple and efficient approach through the matching of a small set of Fourier components of Bloch wave solutions to the Schrodinger Equation in a slab-in-supercell geometry to incoming and outgoing plane waves on both sides of the supercell. The implementation of this method is described in detail for the calculation of reflectivities in the lowest energy range, for which only specular reflection is allowed. This implementation includes the calculation of reflectivities from beams with normal or off-normal incidence. Two different algorithms are described in the case of off-normal incidence which differ in their dependence on the existence of a symmetry with a mirror plane parallel to the crystal surface. Applications to model potentials in one, two, and three dimensions display consistent results when using different supercell sizes and convergent results with the density of Fourier grids. The design of the Bloch wave matching also allows for the accurate modeling of crystalline slabs through the use of realistic potentials determined via density functional theory. The application of the method to low-energy electron scattering from free-standing systems of a few layers of graphene, including the use of these realistic potentials, demonstrates this ability of the method to accurately model real systems. It reproduces the layer-dependent oscillations found in experimental, normal incidence reflectivity curves for a few layers of graphene grown on silicon carbide. The normal incidence reflectivity curves calculated for slabs consisting of few-layer graphene on 10 layers of nickel show some qualitative agreement with experiment. General incidence reflectivity spectra for free
Anxiety and Resistance in Distance Learning
Directory of Open Access Journals (Sweden)
Nazime Tuncay
2010-06-01
Full Text Available The purpose of this study was to investigate students' anxiety and resistance towards learning through distance education.Specifically, the study sought answers to the following questions: -What are the reasons of students not choosing distancelearning courses? -Which symptoms of anxiety, if any, do distance learner’s exhibit towards distance learning? Does genderhave any significant relationships with distance learners' perception of factors that affect their anxiety and resistance? A totalof 120 distance education students in Near East University were observed and 96 of them were interviewed. Computer anxiety,language anxiety, social anxiety were observed to be among the reasons of students’ resistance to distance learning.
A note on the path interval distance.
Coons, Jane Ivy; Rusinko, Joseph
2016-06-01
The path interval distance accounts for global congruence between locally incongruent trees. We show that the path interval distance provides a lower bound for the nearest neighbor interchange distance. In contrast to the Robinson-Foulds distance, random pairs of trees are unlikely to be maximally distant from one another under the path interval distance. These features indicate that the path interval distance should play a role in phylogenomics where the comparison of trees on a fixed set of taxa is becoming increasingly important.
Lightweight Distance Bounding Protocol against Relay Attacks
Kim, Jin Seok; Cho, Kookrae; Yum, Dae Hyun; Hong, Sung Je; Lee, Pil Joong
Traditional authentication protocols are based on cryptographic techniques to achieve identity verification. Distance bounding protocols are an enhanced type of authentication protocol built upon both signal traversal time measurement and cryptographic techniques to accomplish distance verification as well as identity verification. A distance bounding protocol is usually designed to defend against the relay attack and the distance fraud attack. As there are applications to which the distance fraud attack is not a serious threat, we propose a streamlined distance bounding protocol that focuses on the relay attack. The proposed protocol is more efficient than previous protocols and has a low false acceptance rate under the relay attack.
Distance between speed humps and pedestrian crossings: does it matter?
Johansson, Charlotta; Rosander, Peter; Leden, Lars
2011-09-01
Speed humps are a common physical measure installed at pedestrian crossings to reduce vehicle speeds therefore improve the safety and mobility of pedestrians at the crossing. The aim of this study was to determine whether variations in distance between speed humps and pedestrian crossings contribute differently to the safety and mobility of pedestrians and cyclists, especially children and the elderly, and if so, how. Three sites in Sweden were studied, where vehicle speed measurements and video filming at the site resulted in manually coded, road user behaviour of 1972 pedestrians and cyclists. Road user behaviour at three test sites and two comparison sites equipped with speed cushion at distances of about 5m and 10 m from the pedestrian crossing, i.e. about one or two car lengths, were studied. As vehicle speeds were somewhat lower at the pedestrian crossing when the distance between the speed cushion to the pedestrian crossing was greater, and there were positive aspects regarding the mobility of the pedestrians and cyclists, a greater distance of about 10 m or two car lengths between the hump and the pedestrian crossing is suggested. The present study only covers speed cushions, but the same distance is also regarded as important when installing other types of physical measures to reduce vehicle speed.
A Cognitively Grounded Measure of Pronunciation Distance
Wieling, M.; Nerbonne, J.; Bloem, J.; Gooskens, C.; Heeringa, W.; Baayen, R.H.
2014-01-01
In this study we develop pronunciation distances based on naive discriminative learning (NDL). Measures of pronunciation distance are used in several subfields of linguistics, including psycholinguistics, dialectology and typology. In contrast to the commonly used Levenshtein algorithm, NDL is groun
Baryshev, A V; Merzlikin, A M
2014-05-10
The Bloch surface wave resonance (SWR) was visualized with the aid of plasmon absorption in a dielectric/metal/dielectric sandwich terminating a one-dimensional photonic crystal (PhC). An SWR peak in calculated spectra of such a plasmonic photonic crystal (PPhC) slab comprising a noble or base metal layer was demonstrated to be sensitive to a negligible variation of refractive index of a medium adjoining to the slab. The considered structure of PPhC slabs can be of practical importance because the metal layer is protected by a capping dielectric layer from contact with analytes and, consequently, from deterioration. We found that, in case of PPhC slabs, gold (the key element of the surface plasmon resonance-based biosensors) can be replaced by other metals. The PPhC-based sensors can be low-cost, reusable, and robust sensors having a sensitivity surpassing that of the known optical sensors.
Patterson, M.; Hughes, S.; Schulz, S.; Beggs, D. M.; White, T. P.; O'Faolain, L.; Krauss, T. F.
2009-11-01
Through a combined theoretical and experimental study of disorder-induced incoherent scattering losses in slow-light photonic crystal slab waveguides, we show the importance of Bloch mode reshaping and multiple scattering. We describe a convenient and fully three-dimensional theoretical treatment of disorder-induced extrinsic scattering, including the calculation of backscatter and out-of-plane losses per unit cell, and the extrapolation of the unit-cell loss to the loss for an entire disordered waveguide. The theoretical predictions, which are also compared with recent measurements on dispersion engineered silicon waveguides, demonstrate the failure of the Beer-Lambert law due to multiple scattering. We also explain why the previously assumed group velocity scalings of disorder-induced loss break down in general.
La conciencia de la libertad (La filosofía moral como filosofía de la historia en Ernst Bloch
Directory of Open Access Journals (Sweden)
Gimbernat, José Antonio
1991-10-01
Full Text Available Not available.
A partir del concepto hegeliano de «progreso en la conciencia de la libertad », se puede hacer una lectura de la filosofía moral de Bloch como filosofía de la historia. Ello conduce a una reino reinterpretación libre y materialista de Hegel y a una recuperación de la moral en el marxismo. En diálogo con Kant se hace posible descubrir el potencial utópico del énfasis subjetivo de la moral. El objetivo del reino de la libertad marxiano es la clave de una historización política de la libertad, heredada en parte de la tradición liberal, lo que exige a su vez una nueva definición del concepto de progreso.
Non-Bloch nature of alloy states in a conventional semiconductor alloy - GaxIn1-xP as an example
Energy Technology Data Exchange (ETDEWEB)
Wang, Lin-Wang; Zhang, Yong; Mascarenhas, Angelo; Wang, Lin-Wang
2008-07-11
Contrary to the conventional wisdom, electronic states in a 'well behaved' semiconductor alloy such as Ga{sub x}In{sub 1-x}P may drastically deviate from a Bloch state, which can be true even for band edge states if they are derived from degenerate critical points. For Ga{sub x}In{sub 1-x}P in the entire composition range, k-space spectral analyses are performed for the important critical points, revealing the significance of the (near) resonant inter-and intra-valley scatterings of the fluctuation potential in the alloy. The non-trivial implications of such scatterings on the transport and strain effect are discussed.
Directory of Open Access Journals (Sweden)
Maria Eugenia Chaves Maldonado
2016-01-01
Full Text Available In his unfinished and posthumously published book Apologie pour l’histoire, Marc Bloch bestowed on future historians a seminal legacy of critical reflections on the concept of time as the object of historical analysis. During the last decades, the concept of time in History has experienced a renewed interest by professional historians, in particular in reference to the category of anachronism. The Italian historian Carlo Ginzburg and the French art historian Georges Didi-Huberman are among those engaged in this debate. This article offers a reading of two works by these historians with the purpose of underlying the fundamental influence that Marc Bloch’s ideas on time had in Ginzburg and Didi-Hubermans’ critical interventions.
Energy Technology Data Exchange (ETDEWEB)
Zeitoun, Ph.; Oliva, E.; Fajardo, M.; Cheriaux, G.; Le, T. T. T.; Li, L.; Pitman, M.; Ros, D.; Sebban, S.; Velarde, P. [Laboratoire d' Optique Appliquee, ENSTA-PariesTech, CNRS, Ecole Poluytehcnique-PariesTech, chemin d ela huniere, Palaiseau (France); Laboratoire d' Optique Appliquee, ENSTA-PariesTech, CNRS, Ecole Poluytehcnique-PariesTech, chemin d ela huniere, Palaiseau (France); GoLP, Instituto de Plasmas e Fusao Nuclear, Laboratorio Associado, Instituto Superior Tecnico, Lisbon (Portugal); Laboratoire d' Optique Appliquee, ENSTA-PariesTech, CNRS, Ecole Poluytehcnique-PariesTech, chemin d ela huniere, Palaiseau (France); CLUPS, EA4127, Bat 106, Universite Paris-Sud, 91405 Orsay (France); Laboratoire d' Optique Appliquee, ENSTA-PariesTech, CNRS, Ecole Poluytehcnique-PariesTech, chemin d ela huniere, Palaiseau (France); Instituto de Fusion Nuclear, Universidad Politecnica de Madrid, Madrid (Spain)
2012-07-09
By seeding amplifying plasmas pumped with the so-called Transient collisionnal excitation scheme, the amplified pulse seems to be limited to an energy of several 10's of {mu}J. Aiming to attain several mJ, we study the seeding of plasma pumped by long laser pulse. Thanks to our time-dependent Maxwell-Bloch code, we demonstrate that direct seeding with femtosecond pulse is inefficient. We also study the amplification of pulse train with the drawback of re-synchronizing the pulses. We proposed and studied the amplification of high harmonic seed stretched by a grating pair, amplified finally compressed. We consider off-axis diffraction on the gratings for maximizing their efficiency. Considering the phase deformation induced by the amplification and the spectral narrowing the final pulse is 230 fs in duration and 5 mJ.
Sreejith, P; Oommen, O V
2006-04-01
The short-term action of thyroid hormone tri-iodothyronine (T3) was studied in vivo and in vitro on antioxidant enzyme activities in a teleost Anabas testudineus (Bloch). T3 injection in vivo (200 ng) in normal fish decreased the lipid peroxidation products and increased superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) activities after 30 min. T3 in vitro (10(-6) M) increased the antioxidant activities of catalase, glutathione reductase (GR), GPx and glutathione level after 15/30 min, except SOD, substantiating in vivo effects in normal fish. The results suggest a rapid regulatory effect of thyroid hormone in vivo and in vitro, in the removal of reactive oxygen species in A testudineus.
Hemanand, Th; Meitei, N Mohilal; Bandyopadhyay, Probir K; Mitra, Amlan K
2008-01-01
A new species of Henneguya parasitizing tissues affected by the ulcerative disease syndrome of a freshwater fish Anabas testudineus (Bloch) from Khiodum and Pumlen lakes of Manipur state is described. Of the fishes examined 75% were found to be infested with this myxozoan parasite. Mature spores of the new species are elongated, biconvex, and oval with bluntly rounded anterior end and gradually tapering posterior end with a caudal prolongation, measuring 12.6-15.4 (14.0+/- 1.1) microm in length. Length of the caudal prolongation is 11.2-12.6 (11.7+/- 0.6) microm. The width of the spores is 5.6-7.0 (6.3+/- 0.5) microm. The length of the polar capsules is 5.6-6.3 (5.5+/- 0.3) microm.
Distance-based classification of keystroke dynamics
Tran Nguyen, Ngoc
2016-07-01
This paper uses the keystroke dynamics in user authentication. The relationship between the distance metrics and the data template, for the first time, was analyzed and new distance based algorithm for keystroke dynamics classification was proposed. The results of the experiments on the CMU keystroke dynamics benchmark dataset1 were evaluated with an equal error rate of 0.0614. The classifiers using the proposed distance metric outperform existing top performing keystroke dynamics classifiers which use traditional distance metrics.
THE INFLUENCE OF WOMEN ON DISTANCE EDUCATION
2014-01-01
The impact of distance education on women has been significant. Distance education has been a viable means for helping women reach their educational ambitions. Over the last 40 years distance education has increased the ease of access and control over study time. With geographical and time barriers removed, women in particular were able to add the role of student to their list of responsibilities. Women have defeated educational barriers through educational opportunities presented by distance...
Time delay and distance measurement
Abshire, James B. (Inventor); Sun, Xiaoli (Inventor)
2011-01-01
A method for measuring time delay and distance may include providing an electromagnetic radiation carrier frequency and modulating one or more of amplitude, phase, frequency, polarization, and pointing angle of the carrier frequency with a return to zero (RZ) pseudo random noise (PN) code. The RZ PN code may have a constant bit period and a pulse duration that is less than the bit period. A receiver may detect the electromagnetic radiation and calculate the scattering profile versus time (or range) by computing a cross correlation function between the recorded received signal and a three-state RZ PN code kernel in the receiver. The method also may be used for pulse delay time (i.e., PPM) communications.
Normalized Compression Distance of Multiples
Cohen, Andrew R
2012-01-01
Normalized compression distance (NCD) is a parameter-free similarity measure based on compression. The NCD between pairs of objects is not sufficient for all applications. We propose an NCD of finite multisets (multiples) of objacts that is metric and is better for many applications. Previously, attempts to obtain such an NCD failed. We use the theoretical notion of Kolmogorov complexity that for practical purposes is approximated from above by the length of the compressed version of the file involved, using a real-world compression program. We applied the new NCD for multiples to retinal progenitor cell questions that were earlier treated with the pairwise NCD. Here we get significantly better results. We also applied the NCD for multiples to synthetic time sequence data. The preliminary results are as good as nearest neighbor Euclidean classifier.
Rough Way for Academics: Distance Education
Gursul, Fatih
2010-01-01
This study aims to compare the academics' perceptions about face to face and distance education, beside finding out the contributions of distance education to them, difficulties they experience in synchronous and asynchronous distance education environments and suggestions for possible solutions of the existing problems. The sample consists of 52…
Global continuation for distance geometry problems
Energy Technology Data Exchange (ETDEWEB)
More, J.J.; Wu, Zhijun
1995-03-01
Distance geometry problems arise in the interpretation of NMR data and in the determination of protein structure. The authors formulate the distance geometry problem as a global minimization problem with special structure, and show the global smoothing techniques and a continuation approach for global optimization can be used to determine solutions of distance geometry problems with a nearly 100% probability of success.
Perspectives of Research on Distance Education.
Holmberg, Borje
The history of research on distance education was studied. Major research done on distance education in such diverse areas as the United States, Venezuela, and Europe was analyzed. It was discovered that the earliest attempts to develop theories of distance education were mainly concerned with identifying its very concept. Like most educational…
Perceptual constancy in judgments of egocentric distance: prevailing binocular information
Directory of Open Access Journals (Sweden)
Matsushima Elton H.
2003-01-01
Full Text Available Binocular cues were considered the prevailing information on specifying depth since the beginning of vision research. In the present study, two perceptual responses, the classical verbal report and a more recent method, open-loop walking, were used to assess the role of binocular information for egocentric distance perception. In two cue conditions environments, full- and reduced-cue, observers judged and walked egocentric distances of stimuli presented at eye-level, under binocular or monocular viewing. Results indicated perceptual constancy for open-loop walking and binocular responses, as well as poor performances under strong degradation on visual information (reduced-cue under monocular viewing, thus presenting evidence to support the fundamental role of binocular information on perception of egocentric distances. Besides that, visually directed actions could be adequate measures of perceived distance, with a better reliability than verbal report, since they were quite free of intrusion of inferential processes and perceptual tendencies. In addition, reduced head movements, side-to-side as well as back and forth deflexion movements, could have contributed to a near perfect coupling between binocular disparity information and open-loop walking responses.
DEFF Research Database (Denmark)
Henningsen, Arne; Fabricius, Ole; Olsen, Jakob Vesterlund
2014-01-01
and by reduced outputs, we estimate hyperbolic distance functions that account for reduced technical efficiency both in terms of increased inputs and reduced outputs. We estimate these hyperbolic distance functions as “efficiency effect frontiers” with the Translog functional form and a dynamic specification...
Continuity Properties of Distances for Markov Processes
DEFF Research Database (Denmark)
Jaeger, Manfred; Mao, Hua; Larsen, Kim Guldstrand
2014-01-01
In this paper we investigate distance functions on finite state Markov processes that measure the behavioural similarity of non-bisimilar processes. We consider both probabilistic bisimilarity metrics, and trace-based distances derived from standard Lp and Kullback-Leibler distances. Two desirable...... continuity properties for such distances are identified. We then establish a number of results that show that these two properties are in conflict, and not simultaneously fulfilled by any of our candidate natural distance functions. An impossibility result is derived that explains to some extent...
Kinematic Distance of Galactic Planetary Nebulae
Yang, A Y; Zhu, H; Leahy, D A; Wu, D
2016-01-01
We construct \\HI~absorption spectra for 18 planetary nebulae (PNe) and their background sources using the data from the International Galactic Plane Survey. We estimate the kinematic distances of these PNe, among which 15 objects' kinematic distances are obtained for the first time. The distance uncertainties of 13 PNe range from 10% to 50%, which is a significant improvement with uncertainties of a factor two or three smaller than most of previous distance measurements. We confirm that PN G030.2-00.1 is not a PN because of its large distance found here.