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Physicists offer foundation for uprooting a hallowed principle of physics - Physicists at Indiana University have developed a promising new way to identify a possible abnormality in a fundamental building block of Einstein's theory of relativity known as "Lorentz invariance." If confirmed, the abnormality would disprove the basic tenet that the laws of physics remain the same for any two objects traveling at a constant speed or rotated relative to one another....
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Zeroing in on Hubble's constant - (PhysOrg.com) -- In the early part of the 20th Century, Carnegie astronomer Edwin Hubble discovered that the universe is expanding. The rate of expansion is known as the Hubble constant. Its precise value has been hotly debated for all of the 80 intervening years. The value of the Hubble constant is a key ingredient in determining the age and size of the universe. ...
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Scientists determine Viking trade routes by the metal in their swords - Scientists at the National Physical Laboratory (NPL) in Teddington have worked with the Wallace Collection to analyse the contents of Viking swords - and the results shed new light on trade routes in the middle ages....
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Physicists are first to 'squeeze' light to quantum limit - (PhysOrg.com) -- A team of University of Toronto physicists have demonstrated a new technique to squeeze light to the fundamental quantum limit, a finding that has potential applications for high-precision measurement, next-generation atomic clocks, novel quantum computing and our most fundamental understanding of the universe....
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Scientists Extend the Lifetime of Quantum Memory - (PhysOrg.com) -- Storing and sending information using quantum phenomena is one of the hottest areas of research today; scientists across the globe are investigating how to make quantum communication possible for real-life applications. In a key step, a group of researchers was recently able to greatly improve the lifetime of a form of quantum memory....
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Electromagnetic Phantom Exorcises Specters of Metal Detector Tests - In the comics, the Phantom is a masked crimefighter who protected the innocent from pirates, hijackers and other evildoers. While not as dashing or exciting as its costumed namesake, this electromagnetic phantom -- a carbon and polymer mixture that simulates the human body -- is being readied by the National Institute of Standards and Technology for its upcoming role as a different kind of protector. The NIST phantom serves as a mannequin in a standardized performance test for walk-through metal detectors or WTMDs such as those used at airports....
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Efficient organic LEDs a step toward better lights - (PhysOrg.com) -- For those who love "green" compact fluorescent bulbs but hate their cold light, here's some good news: Researchers are closer to flipping the switch on cheaper, richer LED-type room lighting....
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Fock states could hold clues to quantum memory components - (PhysOrg.com) -- “Fock states will play a role in the future of quantum computing,” Andrew Cleland tells PhysOrg.com. “We have completed the first experimental measurement of the time decay of Fock states in a superconducting quantum circuit, and we believe this will provide useful information as we work toward developing a quantum computer.” Cleland is a professor at the University of California, Santa Barbara, and works with a group headed by John Martinis....
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PS3s help astrophysicists solve mystery of black hole vibrations - (PhysOrg.com) -- Using only the computing power of 16 Sony Playstation 3 gaming consoles, scientists at The University of Alabama in Huntsville and the University of Massachusetts, Dartmouth, have solved a mystery about the speed at which vibrating black holes stop vibrating....
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What Can Swiss Cheese Teach us About Dark Energy? - (PhysOrg.com) -- About 10 years ago, scientists reached the astonishing conclusion that our universe is accelerating apart at ever-increasing speeds, stretching space and time itself like melted cheese. The force that's pushing the universe apart is still a mystery, which is precisely why it was dubbed "dark energy." ...
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Math professor discovers chaos on a 'fluid trampoline' - (PhysOrg.com) -- A water drop placed on a soap film that vibrates up and down may bounce as if on a trampoline -- but it's much more than that, according to MIT mathematicians who say the "fluid trampoline" is the simplest fluid example of chaos theory ever explored....
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Researchers discover new type of laser - A Princeton-led team of researchers has discovered an entirely new mechanism for making common electronic materials emit laser beams. The finding could lead to lasers that operate more efficiently and at higher temperatures than existing devices, and find applications in environmental monitoring and medical diagnostics....
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Solving the mysteries of metallic glass - (PhysOrg.com) -- Researchers at MIT and the National University of Singapore have made significant progress in understanding a class of materials that has resisted analysis for decades. Their findings could lead to the rapid discovery of a variety of useful new kinds of glass made of metallic alloys with potentially significant mechanical, chemical and magnetic applications....
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Scientists create titanium-based structural metallic-glass composites - Scientists from the California Institute of Technology have created a range of structural metallic-glass composites, based in titanium, that are lighter and less expensive than any the group had previously created, while still maintaining their toughness and ductility--the ability to be deformed without breaking....
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Solving the mysteries of metallic glass - (PhysOrg.com) -- Researchers at MIT have made significant progress in understanding a class of materials that has resisted analysis for decades. Their findings could lead to the rapid discovery of a variety of useful new kinds of glass made of metallic alloys with potentially significant mechanical, chemical and magnetic applications....
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Flexible Polymer Transistors 'Printed' Using Ultraviolet Light - (PhysOrg.com) -- Computer and television displays made using flexible, bendable polymer materials are technologies of the future, promising roll-up computer monitors and other innovations. Scientists are making progress toward bringing these technologies into our homes and offices....
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Earth not center of the universe, surrounded by 'dark energy': cosmologists report - Earth's location in the Universe is utterly unremarkable, despite recent theories that propose toppling a foundation of modern cosmology, according to a team of University of British Columbia researchers....
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BaBar Collaboration Completes Data Reprocessing - (PhysOrg.com) -- One might think that processing the records of 22 billion electron and positron collisions once would be enough. But not so for the BaBar collaboration, which this week announced the completion of reprocessing for 99.99 percent of its huge coffers of Upsilon(4S) raw data....
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Researchers advance knowledge of little 'nano-machines' in our body - A discovery by Canada-U.S. biophysicists will improve the understanding of ion channels, akin to little 'nano-machines' or 'nano-valves' in our body, which when they malfunction can cause genetic illnesses that attack muscles, the central nervous system and the heart....
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Researchers lay out vision for lighting 'revolution' - A "revolution" in the way we illuminate our world is imminent, according to a paper published this week by two professors at Rensselaer Polytechnic Institute....
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PICO and SALVE: Understanding the subatomic world better - Two new high-resolution transmission electron microscopes, co-financed by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), are set to open up new opportunities for research in physics and materials science. The new research microscopes at RWTH Aachen University and the University of Ulm will enable exceptional, state-of-the-art developments in the field of electron optics in Germany and be available to a broad group of users....
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Scientists Demonstrate Microscale System to Study Frustration in Buckled Monolayers of Microspheres - (PhysOrg.com) -- A team of University of Pennsylvania physicists has demonstrated a simple system based on micron-sized spheres in water to study and control geometric frustration. Their research, published today in the journal Nature, elucidates open questions about frustration and frustration relief and provides a new tool for scientists grappling with these issues in a variety of fields from magnetism to basic statistical mechanics....
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'Seeing' the quantum world - Quantum physics is both mysterious and difficult to grasp. Barry Sanders, director of the University of Calgary's Institute for Quantum Information Science, is hoping to change that....
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The Green (and blue, red, and white) lights of the future - A revolution in energy-efficient, environmentally-sound, and powerfully-flexible lighting is coming to businesses and homes, according to a paper in latest special energy issue of Optics Express, the Optical Society's open-access journal....
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Semiconductor Lasers Generate Better Random Numbers - (PhysOrg.com) -- Random numbers -- numbers without any pattern -- are vital to many applications, such as computer simulations, statistics, and cryptography. There are many ways to generate them using unpredictable physical processes, including electric-signal noise and radioactive decay, but these methods cannot produce the quantities of numbers needed to keep up with the high data-processing rates of today's computers....
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Christmas delayed for physicists waiting for Large Hadron Collider - (PhysOrg.com) -- A University of Alberta researcher has learned that the Large Hadron Collider's experiments to duplicate the Big Bang and the origins of the universe will get going again in late July....
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Dark Energy Found Stifling Growth in Universe - (PhysOrg.com) -- For the first time, astronomers have clearly seen the effects of "dark energy" on the most massive collapsed objects in the universe using NASA's Chandra X-ray Observatory. By tracking how dark energy has stifled the growth of galaxy clusters and combining this with previous studies, scientists have obtained the best clues yet about what dark energy is and what the destiny of the universe could be....
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Researchers interpret asymmetry in early universe - (PhysOrg.com) -- The Big Bang is widely considered to have obliterated any trace of what came before. Now, astrophysicists at the California Institute of Technology (Caltech) think that their new theoretical interpretation of an imprint from the earliest stages of the universe may also shed light on what came before....
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Solving a 300 year old geology problem using kitchen materials - (PhysOrg.com) -- Physicists at the University of Toronto have cracked the mystery behind the strange and uncannily well-ordered hexagonal columns found at such popular tourist sites as Northern Ireland's Giant's Causeway and California's Devil's Postpile, using water, corn starch, and a heat lamp....
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ALICE particle accelerator achieves energy recovery - (PhysOrg.com) -- UK scientists have successfully demonstrated energy recovery on the ALICE advanced particle accelerator design, potentially paving the way for new accelerators using a fraction of the energy required under conventional methods....
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Nonlinear Dimensionality Reduction Methods in Climate Data Analysis. (arXiv:0901.0537v1 [physics.ao-ph]) - Linear dimensionality reduction techniques, notably principal component analysis, are widely used in climate data analysis as a means to aid in the interpretation of datasets of high dimensionality. These linear methods may not be appropriate for the analysis of data arising from nonlinear processes occurring in the climate system. Numerous techniques for nonlinear dimensionality reduction have been developed recently that may provide a potentially useful tool for the identification of low-dimensional manifolds in climate data sets arising from nonlinear dynamics. In this thesis I apply three such techniques to the study of El Nino/Southern Oscillation variability in tropical Pacific sea surface temperatures and thermocline depth, comparing observational data with simulations from coupled atmosphere-ocean general circulation models from the CMIP3 multi-model ensemble. The three methods used here are a nonlinear principal component analysis (NLPCA) approach based on neural ne...
Feed Source: arxiv.org

Finite-difference time-domain formulation of stochastic noise in macroscopic atomic systems. (arXiv:0901.0430v1 [physics.optics]) - A numerical model based on the finite-difference time-domain method is developed to simulate fluctuations which accompany the dephasing of atomic polarization and the decay of excited state's population. This model is based on the Maxwell-Bloch equations with c-number stochastic noise terms. We successfully apply our method to a numerical simulation of the atomic superfluorescence process. This method opens the door to further studies of the effects of stochastic noise on light-matter interaction and transient processes in complex systems without prior knowledge of modes. ...
Feed Source: arxiv.org

Proposal for measuring the quantum states of neutrons in the gravitational field with a CCD-based pixel sensor. (arXiv:0901.0418v1 [physics.ins-det]) - An experimental setup is proposed for the precise measurement of the quantum states of ultracold neutrons bound in the earth's gravitational field. The experiment utilizes a CCD-based pixel sensor and magnification system to observe the fine structure of the neutron distribution. In this work, we analyzed the sensor's deposited energy measurement capability and found that its spatial resolution was 5.3 um. A magnifying power of two orders of magnitude was realized by using a cylindrical rod as a convex mirror. ...
Feed Source: arxiv.org

Visible Fluorescence Emission from Self-assembled Porphyrin Nanotubes. (arXiv:0901.0378v1 [physics.atom-ph]) - Porphyrin nanotubes (PNTs) are prepared by self-assembly using meso-tetrakis (4-sulfonatophenyl) porphyrin and Fe(III) meso-Tetra (N-Methyl-4-Pyridyl) porphyrin in water as starting materials. Long tubes of about one micron diameter are formed with bunches of smaller tubes attached to it, as judged from the analysis of HRTEM images. The PNTs formed by this method are found to exhibit good visible emission at 669 nm on excitation at 432 nm whereas both parent porphyrin monomers do not exhibit any fluorescence. This result highlights the scope of PNTs as functional components in the design of biofriendly devices in medical as well as nanophotonics applications. ...
Feed Source: arxiv.org

Coupling between a dark and a bright eigenmode in a terahertz metamaterial. (arXiv:0901.0365v1 [physics.optics]) - Terahertz time domain spectroscopy and rigorous simulations are used to probe the coupling between a dark and a bright plasmonic eigenmode in a metamaterial with broken symmetry. The metamaterial consists of two closely spaced split ring resonators that have their gaps in non-identical positions within the ring. For normal incidence and a fixed polarization both lowest order eigenmodes of the split ring resonators can be excited; although one of them has to be regarded as dark since coupling is prohibited because of symmetry constraints. Emphasis in this work is put on a systematic evaluation of the coupling effects depending on a spectral tuning of both resonances. ...
Feed Source: arxiv.org

Evolve Networks Towards Better Performance: a Compromise between Mutation and Selection. (arXiv:0901.0357v1 [cond-mat.stat-mech]) - The interaction between natural selection and random mutation is frequently debated in recent years. Does similar dilemma also exist in the evolution of real networks such as biological networks? In this paper, we try to discuss this issue by a simple model system, in which the topological structure of networks is repeatedly modified and selected in order to make them have better performance in dynamical processes. Interestingly, when the networks with optimal performance deviate from the steady state networks under pure mutations, we find the evolution behaves as a balance between mutation and selection. Furthermore, when the timescales of mutations and dynamical processes are comparable with each other, the steady state of evolution is mainly determined by mutation. On the opposite side, when the timescale of mutations is much longer than that of dynamical processes, selection dominates the evolution and the steady-state networks turn to have much improved performance and highly h...
Feed Source: arxiv.org

Properties of tug-of-war model for cargo transport by molecular motors. (arXiv:0901.0350v1 [physics.bio-ph]) - Molecular motors are essential components for the biophysical functions of the cell. Our current quantitative understanding of how multiple motors move along a single track is not complete; even though models and theories for single motor chemomechanics abound. Recently, M.J.I. M$\ddot{\rm u}$ller {\em et al.} have developed a tug-of-war model to describe the bidirectional movement of the cargo (PNAS(2008) 105(12) P4609-4614). Through Monte Carlo simulations, they discovered that the tug-of-war model exhibits several qualitative different motility regimes, which depend on the precise value of single motor parameters, and they suggested the sensitivity can be used by a cell to regulate its cargo traffic. In the present paper, we carry out a thorough analysis of the tug-of-war model. All the stable, i.e., biophysically observable, steady states are obtained. Depending on several parameters, the system exhibits either uni-, bi- or tristability. Based on the separating boundary of the d...
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Thomson scattering from high-temperature high-density plasmas revisited. (arXiv:0901.0346v1 [physics.plasm-ph]) - The theory of Thomson scattering from high-temperature high-density plasmas is revisited from the view point of plasma fluctuation theory. Three subtle effects are addressed with a unified theory. The first is the correction of the first order of $v/c$, where $v$ is the particle velocity and $c$ is the light speed, the second is the plasma dielectric effect, and the third is the finite scattering volume effect. When the plasma density is high, the first effect is very significant in inferring plasma parameters from the scattering spectra off electron plasma waves. The second is also be notable but less significant. When the size of the scattering volume is much larger than the probe wavelength, the third is negligible. ...
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Efficient all-optical switching using slow light within a hollow fiber. (arXiv:0901.0336v1 [quant-ph]) - We demonstrate a fiber-optical switch that is activated at tiny energies corresponding to few hundred optical photons per pulse. This is achieved by simultaneously confining both photons and a small laser-cooled ensemble of atoms inside the microscopic hollow core of a single-mode photonic-crystal fiber and using quantum optical techniques for generating slow light propagation and large nonlinear interaction between light beams. ...
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Overview of the structural unification of quantum mechanics and relativity using the algebra of quantions. (arXiv:0901.0332v1 [physics.gen-ph]) - The purpose of this contribution is to provide an introduction for a general physics audience to the recent results of Emile Grgin that unifies quantum mechanics and relativity into the same mathematical structure. This structure is the algebra of quantions, a non-division algebra that is the natural framework for electroweak theory on curved space-time. Similar with quaternions, quantions preserve the core features of associativity and complex conjugation while giving up the unnecessarily historically biased property of division. Lack of division makes possible structural unification with relativity (one cannot upgrade the linear Minkowski space to a division algebra due to null light-cone vectors) and demands an adjustment from Born's standard interpretation of the wave function in terms of probability currents. This paper is an overview to the theory of quantions, followed by discussions and conjectures. ...
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Some Subtle Concepts in Fundamental Physics. (arXiv:0901.0309v1 [physics.gen-ph]) - In this paper, we discuss some subtle concepts, such as coordinate, measurement, simultaneity, Lorentz-FitzGerald contraction, singularity in fundamental physics. The explanations of these concepts in textbooks are usually incomplete and lead to puzzles. Some long-standing paradoxes such as the Ehrenfest one are caused by misinterpretation of these concepts. The analysis shows these concepts all have simple and naive meanings, and can be well understood along suitable logical procedure. The discussion may shed lights on some famous paradoxes, and provide some new insights into the structure and feature of a promising unified field theory. ...
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Laser Cooled High-Power Fiber Amplifier. (arXiv:0901.0299v1 [physics.optics]) - A theoretical model for laser cooled continuous-wave fiber amplifier is presented. The amplification process takes place in the Tm3+-doped core of the fluoride ZBLAN (ZrF4-BaF2-LaF3-AlF3-NaF) glass fiber. The cooling process takes place in the Yb3+:ZBLAN fiber cladding. It is shown that for each value of the pump power and the amplified signal there is a distribution of the concentration of the Tm3+ along the length of the fiber amplifier, which provides its athermal operation. The influence of a small deviation in the value of the amplified signal on the temperature of the fiber with the fixed distribution of the Tm3+ions in the fiber cladding is investigated. ...
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Whispering gallery mode enhanced optical force with resonant tunneling excitation in the Kretschmann geometry. (arXiv:0901.0454v1 [physics.optics]) - The boundary element method is applied to investigate the optical forces when whispering gallery modes (WGMs) are excited by a total internally reflected wave. Such evanescent wave is particularly effective in exciting the high-$Q$ WGM, while the low angular or high radial order modes are suppressed relatively. This results in a large contrast between the forces on and off resonance, and thus allows for high size-selectivity. We fully incorporate the prism-particle interaction and found that the optical force behaves differently at different separations. Optimal separation is found which corresponds to a compromise between intensity and $Q$ factor. ...
Feed Source: arxiv.org

Solar activity and the mean global temperature. (arXiv:0901.0515v1 [physics.geo-ph]) - The variation with time from 1956-2002 of the globally averaged rate of ionization produced by cosmic rays in the atmosphere is deduced and shown to have a cyclic component of period roughly twice the 11 year solar cycle period. Long term variations in the global average surface temperature as a function of time since 1956 are found to have a similar cyclic component. The cyclic variations are also observed in the solar irradiance and in the mean daily sun spot number. The cyclic variation in the cosmic ray rate is observed to be delayed by 2-4 years relative to the temperature, the solar irradiance and daily sun spot variations suggesting that the origin of the correlation is more likely to be direct solar activity than cosmic rays. Assuming that the correlation is caused by such solar activity, we deduce that the maximum recent increase in the mean surface temperature of the Earth which can be ascribed to this activity is $\lesssim14%$ of the observed global warming. ...
Feed Source: arxiv.org

Low-energy quantum gravity: new challenges for an experiment and observation. (arXiv:0901.0510v1 [physics.gen-ph]) - Some new challenges for an experiment and observation, which are consequences of the model of low-energy quantum gravity by the author, are considered here. In particular, the property of asymptotic freedom of this model leads to the unexpected consequence: if a black hole arises due to a collapse of a matter with some characteristic mass of particles, its full mass should be restricted from the bottom. For usual baryonic matter, this limit of mass is of the order $10^{7}M_{\odot}$. ...
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Scaling factors for ab initio vibrational frequencies: comparison of uncertainty models for quantified prediction. (arXiv:0901.0489v1 [physics.data-an]) - Bayesian Model Calibration is used to revisit the problem of scaling factor calibration for semi-empirical correction of ab initio calculations. A particular attention is devoted to uncertainty evaluation for scaling factors, and to their effect on prediction of observables involving scaled properties. We argue that linear models used for calibration of scaling factors are generally not statistically valid, in the sense that they are not able to fit calibration data within their uncertainty limits. Uncertainty evaluation and uncertainty propagation by statistical methods from such invalid models are doomed to failure. To relieve this problem, a stochastic function is included in the model to account for model inadequacy, according to the Bayesian Model Calibration approach. In this framework, we demonstrate that standard calibration summary statistics, as optimal scaling factor and root mean square, can be safely used for uncertainty propagation only when large calibration sets of p...
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On the Statistical Properties of the 3D Incompressible Navier-Stokes-Voigt Model. (arXiv:0901.0474v1 [physics.flu-dyn]) - The Navier-Stokes-Voigt (NSV) model of viscoelastic incompressible fluid has been recently proposed as a regularization of the 3D Navier-Stokes equations for the purpose of direct numerical simulations. In this work we investigate its statistical properties by employing phenomenological heuristic arguments, in combination with Sabra shell model simulations of the analogue of the NSV model. For large values of the regularizing parameter, compared to the Kolmogorov length scale, simulations exhibit multiscaling inertial range, and the dissipation range displaying low intermittency. These facts provide evidence that the NSV regularization may reduce the stiffness of direct numerical simulations of turbulent flows, with a small impact on the energy containing scales. ...
Feed Source: arxiv.org

Preseismic oscillating electric field "strange attractor" like precursor, of T=14 days, triggered by M1 tidal wave. Application on large (Ms > 6.0R) EQs in Greece (March 18th, 2006 - November 17th, 2008). (arXiv:0901.0467v1 [physics.geo-ph]) - The "strange attractor like" precursor, calculated from the Earth's oscillating electric field registered at PYR and HIO monitoring sites located in Greece, is studied in the domain of T = 14 days. It is assumed that the generating precursory signals focal mechanism is triggered by the corresponding M1 (moon declination) tidal wave. The obtained results from the analysis of eight (8) cases of large (Ms>6.0R) EQs that occurred from March 18th, 2006 to November 17th, 2008 suggest the validity of the method. Moreover, it is found that the specific methodology applied for T = 14 days behaves very closely to the same one when applied for T = 1 day even though there is a resolution decrease in the calculated predictive time window for the occurrence of the oncoming large EQ. It is speculated that this type of precursor, once it is present in one distinct oscillating component of the seismic precursory generated electric field, then, most probably, it is present in most of its other osc...
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Numerical simulation of Faraday waves. (arXiv:0901.0464v1 [physics.flu-dyn]) - We simulate numerically the full dynamics of Faraday waves in three dimensions for two incompressible and immiscible viscous fluids. The Navier-Stokes equations are solved using a finite-difference projection method coupled with a front-tracking method for the interface between the two fluids. The domain of calculation is periodic in the horizontal directions and bounded in the vertical direction by two rigid horizontal plates. The critical accelerations and wavenumbers, as well as the temporal behaviour at onset are compared with the results of the linear Floquet analysis of Kumar and Tuckerman [J. Fluid Mech. 279, 49-68 (1994)]. The finite amplitude results are compared with the experiments of Kityk et al. [Phys. Rev. E 72, 036209 (2005)]. In particular we reproduce the detailed spatiotemporal spectrum of both square and hexagonal patterns within experimental uncertainty. ...
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Ensemble Kalman filter with the unscented transform. (arXiv:0901.0461v1 [physics.ao-ph]) - A modification scheme to the ensemble Kalman filter (EnKF) is introduced based on the concept of the unscented transform (Julier et al., 2000; Julier and Uhlmann, 2004), which therefore will be called the ensemble unscented Kalman filter (EnUKF) in this work. When the error distribution of the analysis is symmetric (not necessarily Gaussian), it can be shown that, compared to the ordinary EnKF, the EnUKF has more accurate estimations of the ensemble mean and covariance of the background by examining the multidimensional Taylor series expansion term by term. This implies that, the EnUKF may have better performance in state estimation than the ordinary EnKF in the sense that the deviations from the true states are smaller. For verification, some numerical experiments are conducted on a 40-dimensional system due to Lorenz and Emanuel (Lorenz and Emanuel, 1998). Simulation results support our argument. ...
Feed Source: arxiv.org

Experience versus Talent Shapes the Structure of the Web. (arXiv:0901.0296v1 [cs.CY]) - We use sequential large-scale crawl data to empirically investigate and validate the dynamics that underlie the evolution of the structure of the web. We find that the overall structure of the web is defined by an intricate interplay between experience or entitlement of the pages (as measured by the number of inbound hyperlinks a page already has), inherent talent or fitness of the pages (as measured by the likelihood that someone visiting the page would give a hyperlink to it), and the continual high rates of birth and death of pages on the web. We find that the web is conservative in judging talent and the overall fitness distribution is exponential, showing low variability. The small variance in talent, however, is enough to lead to experience distributions with high variance: The preferential attachment mechanism amplifies these small biases and leads to heavy-tailed power-law (PL) inbound degree distributions over all pages, as well as over pages that are of the same age. The b...
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Degenerate Perturbation Theory Describing the Mixing of Orbital Angular Momentum Modes in Fabry-P\'erot Cavity Resonators. (arXiv:0901.0289v1 [physics.optics]) - We present an analytic perturbation theory which extends the paraxial approximation for a common cylindrically symmetric stable optical resonator and incorporates the differential, polarization-dependent reflectivity of a Bragg mirror. The degeneracy of Laguerre-Gauss modes with distinct orbital angular momentum (OAM) and polarization, but identical transverse order N, will become observably lifted at sufficiently small size and high finesse. The resulting paraxial eigenmodes possess two distinct OAM components, the fractional composition subtly depending on mirror structure. ...
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Rotationally induced vortices in optical cavity modes. (arXiv:0811.4265v2 [physics.optics] UPDATED) - We show that vortices appear in the modes of an astigmatic optical cavity when it is put into rotation about its optical axis. We study the properties of these vortices and discuss numerical results for a specific realization of such a set-up. Our method is exact up to first order in the time-dependent paraxial approximation and involves bosonic ladder operators in the spirit of the quantum-mechanical harmonic oscillator. ...
Feed Source: arxiv.org

The IceCube Data Acquisition System: Signal Capture, Digitization, and Timestamping. (arXiv:0810.4930v2 [physics.ins-det] UPDATED) - IceCube is a km-scale neutrino observatory under construction at the South Pole with sensors both in the deep ice (InIce) and on the surface (IceTop). The sensors, called Digital Optical Modules (DOMs), detect, digitize and timestamp the signals from optical Cherenkov-radiation photons. The DOM Main Board (MB) data acquisition subsystem is connected to the central DAQ in the IceCube Laboratory (ICL) by a single twisted copper wire-pair and transmits packetized data on demand. Time calibration is maintained throughout the array by regular transmission to the DOMs of precisely timed analog signals, synchronized to a central GPS-disciplined clock. The design goals and consequent features, functional capabilities, and initial performance of the DOM MB, and the operation of a combined array of DOMs as a system, are described here. Experience with the first InIce strings and the IceTop stations indicates that the system design and performance goals have been achieved. ...
Feed Source: arxiv.org

Rotational stabilization and destabilization of an optical cavity. (arXiv:0809.0221v2 [physics.optics] UPDATED) - We investigate the effects of rotation about the axis of an astigmatic two-mirror cavity on its optical properties. This simple geometry is the first example of an optical system that can be destabilized and, more surprisingly, stabilized by rotation. As such, it has some similarity with both the Paul trap and the gyroscope. We illustrate the effects of rotational (de)stabilization of a cavity in terms of the spatial structure and orbital angular momentum of its modes. ...
Feed Source: arxiv.org

Single-Photon Molecular Cooling. (arXiv:0808.1383v3 [physics.chem-ph] UPDATED) - We propose a general method to cool the translational motion of molecules. Our method is an extension of single photon atomic cooling which was successfully implemented in our laboratory. Requiring a single event of absorption followed by a spontaneous emission, this method circumvents the need for a cycling transition and can be applied to any paramagnetic or polar molecule. In our approach, trapped molecules would be captured near their classical turning points in an optical dipole or RF-trap following an irreversible transition process. ...
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Perturbation-Assisted Laser-Induced Atomic Fragment Fluorescence Spectroscopy: A Facile Route to Spin-Forbidden States. (arXiv:0806.2750v3 [physics.chem-ph] UPDATED) - This paper has been withdrawn by the authors, because the authors have made abundant revisions and resubmitted the modified new version entitled "Laser-induced atomic fragment fluorescence spectroscopy: A facile technique for molecular spectroscopy of spin-forbidden states" to arXiv:0812.4554. Thanks for your attention. ...
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Accurate estimator of correlations between asynchronous signals. (arXiv:0805.2310v3 [physics.data-an] UPDATED) - The estimation of the correlation between time series is often hampered by the asynchronicity of the signals. Cumulating data within a time window suppresses this source of noise but weakens the statistics. We present a method to estimate correlations without applying long time windows. We decompose the correlations of data cumulated over a long window using decay of lagged correlations as calculated from short window data. This increases the accuracy of the estimated correlation significantly and decreases the necessary efforts of calculations both in real and computer experiments. ...
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Correlations in commodity markets. (arXiv:0803.3884v2 [q-fin.ST] UPDATED) - In this paper we analyzed dependencies in commodity markets investigating correlations of future contracts for commodities over the period 1998.09.01 - 2007.12.14. We constructed a minimal spanning tree based on the correlation matrix. The tree provides evidence for sector clusterization of investigated contracts. We also studied dynamical properties of commodity dependencies. It turned out that the market was constantly getting more correlated within the investigated period, although the increase of correlation was distributed nonuniformly among all contracts, and depended on contracts branches. ...
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Fixation and consensus times on a network: a unified approach. (arXiv:0801.3083v2 [cond-mat.stat-mech] UPDATED) - We investigate a set of stochastic models of biodiversity, population genetics, language evolution and opinion dynamics on a network within a common framework. Each node has a state, 0 < x_i < 1, with interactions specified by strengths m_{ij}. For any set of m_{ij} we derive an approximate expression for the mean time to reach fixation or consensus (all x_i=0 or 1). Remarkably in a case relevant to language change this time is independent of the network structure. ...
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Mathematics underlying the 2008 financial crisis, and a possible remedy. (arXiv:0811.4678v2 [q-fin.GN] UPDATED) - This paper has been withdrawn by the authors, because it has been made obsolete by the detailed expositions in our papers in arXiv:0812.4885 (the mathematics part) and arXiv:0812.4737 (the economics part). ...
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Tailoring the excitation of localized surface plasmon-polariton resonances by focusing radially-polarized beams. (arXiv:0812.2237v2 [physics.optics] UPDATED) - We study the interaction of focused radially-polarized light with metal nanospheres. By expanding the electromagnetic field in terms of multipoles, we gain insight on the excitation of localized surface plasmon-polariton resonances in the nanoparticle. We show that focused radially-polarized beams offer more opportunities than a focused plane wave or a Gaussian beam for tuning the near- and far-field system response. These results find applications in nano-optics, optical tweezers, and optical data storage. ...
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Charged particle display. (arXiv:0812.2940v3 [physics.optics] UPDATED) - An optical shutter based on charged particles is presented. The output light intensity of the proposed device has an intrinsic dependence on the interparticle spacing between charged particles, which can be controlled by varying voltages applied to the control electrodes. The interparticle spacing between charged particles can be varied continuously and this opens up the possibility of particle based displays with continuous grayscale. ...
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A Cohomological Approach to the Consistent Interactions in the D-dimensional Massless Abelian Yang-Mills Theories. (arXiv:0707.4025v5 [physics.gen-ph] UPDATED) - We review the cohomological solutions of consistent interactions among fields with free gauge symmetries in the viewpoint of antifield formalism. We describe the BRST deformations of obtained consistent interactions among fields with a gauge freedom. We survey its applications to the massless abelian Yang-Mills theories in any D> 2 spacetime dimensions by considering the several order deformations to the master equation. The resulting deformations can halt at the exclusively second orders, while obstructing the higher order deformations on consistent local couplings due to non local interactions. It shall provide the complete gauge structure of the interacting theory in the abelian Yang-Mills theories. ...
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The evolution and distribution of species body size. (arXiv:0901.0251v1 [q-bio.PE] CROSS LISTED) - The distribution of species body size within taxonomic groups exhibits a heavy right-tail extending over many orders of magnitude, where most species are significantly larger than the smallest species. We provide a simple model of cladogenetic diffusion over evolutionary time that omits explicit mechanisms for inter-specific competition and other microevolutionary processes yet fully explains the shape of this distribution. We estimate the model's parameters from fossil data and find that it robustly reproduces the distribution of 4002 mammal species from the late Quaternary. The observed fit suggests that the asymmetric distribution arises from a fundamental tradeoff between the short-term selective advantages (Cope's rule) and long-term selective risks of increased species body size, in the presence of a taxon-specific lower limit on body size. ...
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Numerical Performance of Compact Fourth Order Formulation of the Navier-Stokes Equations. (arXiv:0901.0172v1 [physics.flu-dyn] CROSS LISTED) - In this study the numerical performance of the fourth order compact formulation of the steady 2-D incompressible Navier-Stokes equations introduced by Erturk et al. (Int. J. Numer. Methods Fluids, 50, 421-436) will be presented. The benchmark driven cavity flow problem will be solved using the introduced compact fourth order formulation of the Navier-Stokes equations with two different line iterative semi-implicit methods for both second and fourth order spatial accuracy. The extra CPU work needed for increasing the spatial accuracy from second order (O(x2)) to fourth order (O(x4)) formulation will be presented. ...
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Hydrodynamic interaction in confined geometries. (arXiv:0812.4971v1 [cond-mat.soft] CROSS LISTED) - This article gives an overview of recent theoretical and experimental findings concerning the hydrodynamic interaction between liquid-embedded particles in various confined geometries. A simple unifying description emerges, which accounts for the various findings based on the effect of confinement on conserved fields of the embedding liquid. It shows, in particular, that the hydrodynamic interaction under confinement remains long-ranged, decaying algebraically with inter-particle distance, except for the case of confinement in a rigid linear channel. ...
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The quantum theory of space and time - Lecture/Talk: 3 Mar 2009, 21 Albemarle Street, London, United Kingdom. Organized by The Royal Institution....
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SMART SYSTEMS INTEGRATION 2009 - Conference/Exhibition: 10 Mar 2009 - 11 Mar 2009, Brussel, Belgium. Organized by Mesago Messe Frankfurt GmbH....
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LOT and MicroMaterials Open Day - Workshop: 10 Mar 2009, Wrexham, United Kingdom. Organized by LOT - Oriel Ltd....
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DNA-based nanotechnology: Construction, mechanics, and electronics - Workshop: 11 May 2009 - 15 May 2009, Dresden, Germany. Organized by G. Cuniberti (Dresden, Germany), M. Mertig (Dresden, Germany), H. Yan (Tempe, USA)....
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Nanocomposites 2009 - Conference: 18 Mar 2009 - 19 Mar 2009, Brussels, Belgium. Organized by European Plastics News....
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Bloch Oscillations and Landau-Zener Tunneling: From Hot Electrons to Ultracold Atoms - Workshop: 14 Apr 2009 - 8 May 2009, Dresden, Saxony, Germany. Organized by Ennio Arimondo, Yuriy A. Kosevich, Thomas Pertsch....
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BioStruct09 - Workshop: 16 Feb 2009 - 18 Feb 2009, Area CNR di Firenze, Sesto Fiorentino, Firenze., Italy. Organized by Alberto Imparato & Alessandro Torcini....
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LOT and Quantum Design Workshop - Workshop: 17 Mar 2009, NPL, Teddington, Middx, United Kingdom. Organized by LOT - Oriel Ltd....
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SELF-ASSEMBLY OF GUANOSINE DERIVATIVES: FROM BIOLOGICAL SYSTEMS TO NANOTECHNOLOGICAL APPLICATIONS - Conference: 20 Jun 2009 - 25 Jun 2009, Obergurgl, Austria. Organized by European Science Foundation (ESF), in partnership the Fonds zur Förderung der wissenschaftlichen Forschung in Österreich (FWF) and and the Leopold-Franzens-Universität In....
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INTERNATIONAL SCIENTIFIC MEETING ON NUCLEAR PHYSICS. - School: 4 Jul 2009 - 10 Jul 2009, Palos de la Frontera (Huelva), Andalucía, Spain. Organized by J.A. Caballero, C.E. Alonso, M.V. Andrés, F. Pérez-Bernal and J.E. García-Ramos....
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