Science and Technology Directory

Kuncoro Memuat tulisan tentang fisika, sains dan teknologi telekomunikasi.

Luboš Motl: The Reference Frame Theoretical physics blog by a Czech conservative string theorist Luboš Motl, focusing on high-energy physics and the climate change

Not Even Wrong Physics and mathematics discussion from the author at the front line of the string theory controversy.

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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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Electric dipoles at ultralow temperatures. (arXiv:0901.0276v1 [physics.atom-ph]) - We briefly introduce the formalism for describing dipolar molecules in an ultracold gaseous environment. This treatment includes the quantum mechanical states of the dipoles, the electric fields they produce, and their interactions with one another. ...
Feed Source: arxiv.org

Reflow Soldering of Surface Mount Electronic Components in a Laboratory. (arXiv:0901.0136v1 [physics.ins-det]) - We present a basic tutorial for implementing surface mount technology in lab-built scientific instruments. We discuss the advantages and disadvantages of using surface mount chips. We also describe methods for the development and prototyping of surface mount circuitry in home-built electronics. The method of soldering surface mount components in a common toaster oven is described. We provide advice from our own experience in developing this technology, and argue that surface mount technology is often preferable to using leaded components when building large circuits, and is essential if the desired component characteristics are only available in surface mount packages. ...
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Rigorous treatment of electrostatics for spatially varying dielectrics based on energy minimization. (arXiv:0901.0129v1 [physics.class-ph]) - A novel energy minimization formulation of electrostatics that allows computation of the electrostatic energy and forces to any desired accuracy in a system with arbitrary dielectric properties is presented. An integral equation for the scalar charge density is derived from an energy functional of the polarization vector field. This energy functional represents the true energy of the system even in non-equilibrium states. Arbitrary accuracy is achieved by solving the integral equation for the charge density via a series expansion in terms of the equation's kernel, which depends only on the geometry of the dielectrics. The streamlined formalism operates with volume charge distributions only, not resorting to introducing surface charges by hand. Therefore, it can be applied to any spatial variation of the dielectric susceptibility, which is of particular importance in applications to biomolecular systems. The simplicity of application of the formalism to real problems is shown with an...
Feed Source: arxiv.org

Perpendicular electron collisions in drift and acoustic wave instabilities. (arXiv:0901.0107v1 [physics.plasm-ph]) - Perpendicular electron dynamics and the associated collisions are discussed in relation to the collisional drift wave instability. In addition, the limit of small parallel wave numbers of this instability is studied and it is shown to yield a reduced wave frequency. It is also shown that in this case the growth rate in fact {\em decreases} for smaller parallel wave numbers, instead of growing proportional to $1/k_z^2$. As a result, the growth rate appears to be angle dependent and to reach a maximum for some specific direction of propagation. The explanation for this strange behavior is given. A similar analysis is performed for acoustic perturbations in plasmas with unmagnetized ions and magnetized electrons, in the presence of a density gradient. ...
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Synthesis of DNA Templated Tri-functional Electrically Conducting, Optical and Magnetic nanochain of Nicore-Aushell for Bio-device. (arXiv:0901.0087v1 [cond-mat.mtrl-sci]) - Synthesis of tri functional electrically conducting, optical and magnetic nano-chain of Nicore-Aushell has been discussed here. Our Investigation indicates that such material attached with biomolecule DNA in chain form will have great potentiality in medical instrument and bio computer device. ...
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Birefringence lens effects of atom ensemble enhanced by electromagnetically induced transparency. (arXiv:0901.0078v1 [physics.optics]) - We study the optic control for birefringence of a polarized light by an atomic ensemble with a tripod configuration, which is mediated by the electromagnetically induced transparency with a spatially inhomogeneous laser. The atom ensemble splits the linearly polarized light ray into two orthogonally-polarized components, whose polarizations depend on quantum superposition of the initial states of the atom ensemble. Accompanied with this splitting, the atom ensemble behaves as a birefringent lens, which allows one polarized light ray passing through straightly while focus another orthogonal to this polarization with finite aberration of focus. ...
Feed Source: arxiv.org

Accurate calculations of spectroscopic constants for the Yb dimer. (arXiv:0901.0077v1 [physics.chem-ph]) - The dissociation energy, equilibrium distance, and vibrational constant for the ground state of the Yb_2 molecule are calculated. The relativistic effects are introduced through generalized relativistic effective core potentials with very high precision. The scalar relativistic coupled cluster method particularly well suited for closed-shell van-der-Waals systems is used for the correlation treatment. Extensive generalized correlation basis sets were constructed and employed. The corrections for high-order cluster amplitudes and spin-orbit interactions are taken into account. ...
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Quantum mechanical observer and superstring/M theory. (arXiv:0901.0060v1 [physics.gen-ph]) - Terms are suggested for inclusion in a Lagrangian density as seen by an observer O2, to represent the dynamics of a quantum mechanical observer O1 that is an initial stage in an observation process. This paper extends an earlier paper which suggested that the centre-of-mass kinetic energy of O1 could correspond to, and possibly underlie, the Lagrangian density for bosonic string theory, where the worldsheet coordinates are the coordinates which O1 can observe. The present paper considers a fermion internal to O1, in addition to O1's centre of mass. It is suggested that quantum mechanical uncertainties in the transformation between O1's and O2's reference systems might require O2 to use $d$ spinor fields for this fermion, where $d$ is the number of spacetime dimensions. If this is the case, and if the symmetry/observability arguments in arXiv:hep-th/0601104 apply, the resulting Lagrangian density for the dynamics of O1 might resemble, or even underli...
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Microscopic Approach to Analyze Solar-Sail Space-Environment Effects. (arXiv:0901.0047v1 [physics.space-ph]) - Near-sun space-environment effects on metallic thin films solar sails as well as hollow-body sails with inflation fill gas are considered. Analysis of interaction of the solar radiation with the solar sail materials is presented. This analysis evaluates worst-case solar radiation effects during solar-radiation-pressure acceleration. The dependence of the thickness of solar sail on temperature and on wavelength of the electromagnetic spectrum of solar radiation is investigated. Physical processes of the interaction of photons, electrons, protons and helium nuclei with sail material atoms and nuclei, and inflation fill gas molecules are analyzed. Calculations utilized conservative assumptions with the highest values for the available cross sections for interactions of solar photons, electrons and protons with atoms, nuclei and hydrogen molecules. It is shown that for high-energy photons, electrons and protons the beryllium sail is mostly transparent. Sail material will be partially io...
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Non-specular Reflective Optics. (arXiv:0901.0140v1 [physics.optics]) - Geometrically decorated two-dimensional (2D) discrete surfaces can be more effective than conventional smooth reflectors in managing wave radiation. Constructive non-specular wave scattering permits the scattering angle to be other than twice that of incidence and can result in gross violations of the law of reflection. Hence significant fraction of the phase space becomes accessible. A wide range of novel reflective behaviors ensues; including the phenomenon of negative reflection were energy transport remains on the same side of the normal. Also, at a critical incidence coherent superposition can force both the transmitted and reflected waves to graze the scattering surface thus synergistically reinforcing the diffractive process in a behavior reminiscent of critical internal reflection of ray optics. We experimentally demonstrate the concept with measurements on a one-dimensionally periodic system (grating) where the scattering angle is shown to be an inverse circular function of...
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Concentration Invariance of Cyclic Species. (arXiv:0901.0152v1 [physics.chem-ph]) - We examine the concentration invariance of cyclic species for the irreversible polymerization. The simulation results show that the invariance holds in good approximation in the irreversible process also. The validity of the simulation equations employed was confirmed through comparison with the recent experimental observations by the Nagoya university group carried out independently of the present work. ...
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A comprehensive numerical model of wind-blown sand. (arXiv:0901.0270v1 [physics.flu-dyn]) - Wind-blown sand, or "saltation", ejects dust aerosols into the atmosphere, creates sand dunes, and erodes geological features. We present a comprehensive numerical model of steady-state saltation that, in contrast to most previous studies, can simulate saltation over mixed soils. Our model simulates the motion of saltating particles due to gravity, fluid drag, particle spin, fluid shear, and turbulence. Moreover, the model explicitly accounts for the retardation of the wind due to drag from saltating particles. We also developed a physically-based parameterization of the ejection of surface particles by impacting saltating particles which matches experimental results. Our numerical model is the first to reproduce measurements of the wind shear velocity at the impact threshold (i.e., the lowest shear velocity for which saltation is possible) and of the aerodynamic roughness length in saltation. It also correctly predicts a wide range of other saltation processes, including profiles o...
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Comment on "Interplanetary coronal mass ejections that are undetected by solar coronagraphs" by T. A. Howard and G. M. Simnett. (arXiv:0901.0258v1 [physics.space-ph]) - Howard and Simnett (HS) employed a new technique for associating LASCO CMEs to SMEI ICMEs. In order to extrapolate the SMEI data back to the LASCO field of view they used nonlinear trajectories, dependent on a speed and direction, what is more realistic than the linear extrapolation with only one parameter (a speed). However, there are two errors and one mistake in their procedure: (1) HS used two free parameters of the direction, whereas only one can be freely selected, because the second is provided by SMEI data. As a result, the directions determined by HS are incorrect. (2) HS overlooked that, since the trajectory depends on more than one parameter, there is a broad set of trajectories, for various speeds and directions, matching the event, and thus a broad range of the onset times. HS select only one trajectory for each SMEI event. Therefore the associations made by them are incomplete, and they should be reexamined. As long as it is not done any conclusion about CMEs undetecte...
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Friction factor for turbulent flow in rough pipes from Heisenberg's closure hypothesis. (arXiv:0901.0255v1 [physics.flu-dyn]) - We show that the main results of the analysis of the friction factor for turbulent pipe flow reported in G. Gioia and P. Chakraborty (GC), Phys. Rev. Lett. 96, 044502 (1996) can be recovered by assuming the Heisenberg closure hypothesis for the turbulent spectrum. This highlights the structural features of the turbulent spectrum underlying GC's analysis. ...
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Unification of Gravitational and Electromagnetic Fields in Riemanian geometry. (arXiv:0901.0201v1 [physics.gen-ph]) - The gravitational field and the source-free electromagnetic field can be unified preliminarily by the equations in the Riemanian geometry, both are contractions of im and ik, respectively. So it will be equivalent to the Yang gravitational equations. From this we can obtain the Lorentz equations of motion, the first system and second source-free system of Maxwell field equations. This unification can be included in the gauge theory, and the unified gauge group is GL(2,C), which is just the same as the gauge group of the Riemanian manifold. ...
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The covariant formulation of Maxwell's equations expressed in a form independent of specific units. (arXiv:0901.0194v1 [physics.class-ph]) - The covariant formulation of Maxwell's equations can be expressed in a form independent of the usual systems of units by introducing the constants alpha, beta and gamma into these equations. Maxwell's equations involving these constants are then specialized to the most commonly used systems of units: Gaussian, SI and Heaviside-Lorentz by giving the constants alpha, beta and gamma the values appropriate to each system. ...
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Macroscopic Maxwell's equations and negative index materials. (arXiv:0901.0187v1 [physics.optics]) - We study the linear phenomenological Maxwell's equations in the presence of a polarizable and magnetizable medium (magnetodielectric). In case the medium is dispersive, non-absorptive, and the electric and magnetic permeabilities are equal, then they can assume the value -1 (+1 is their vacuum value) for a discrete set of frequencies, i.e., for these frequencies the medium behaves as a negative index material (NIM). We show that such systems have a well-defined time evolution. In particular the fields remain square integrable (and the electromagnetic energy finite) if this is the case at some initial time. Next we turn to the Green's function (a tensor), associated with the electric Helmholtz operator, for a set of parallel layers filled with a material. We express it in terms of two scalar ones. For the case that a half space is filled with the material and with a single dispersive Lorentz form for both electric and magnetic permeabilities we obtain an explicit form for the Green's...
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Epigenetic Landscape of Interacting Cells: A Model Simulation for Developmental Process. (arXiv:0901.0180v1 [q-bio.CB]) - We propose a physical model for developmental process at cellular level to discuss the mechanism of epigenetic landscape. In our simplified model, a minimal model, the network of the interaction among cells generates the landscape epigenetically and the differentiation in developmental process is understood as a self-organization. The effect of the regulation by gene expression which is a key ingredient in development is renormalized into the interaction and the environment. At earlier stage of the development the energy landscape of the model is rugged with small amplitude. The state of cells in such a landscape is susceptible to fluctuations and not uniquely determined. These cells are regarded as stem cells. At later stage of the development the landscape has a funnel-like structure corresponding to the canalization in differentiation. The rewinding or stability of the differentiation is also demonstrated by substituting test cells into the time sequence of the model development....
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Numerical Performance of Compact Fourth Order Formulation of the Navier-Stokes Equations. (arXiv:0901.0172v1 [physics.flu-dyn]) - 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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Pedestrian Traffic: on the Quickest Path. (arXiv:0901.0170v1 [physics.soc-ph]) - When a large group of pedestrians moves around a corner, most pedestrians do not follow the shortest path, which is to stay as close as possible to the inner wall, but try to minimize the travel time. For this they accept to move on a longer path with some distance to the corner, to avoid large densities and by this succeed in maintaining a comparatively high speed. In many models of pedestrian dynamics the basic rule of motion is often either "move as far as possible toward the destination" or - reformulated - "of all coordinates accessible in this time step move to the one with the smallest distance to the destination". Atop of this rule modifications are placed to make the motion more realistic. These modifications usually focus on local behavior and neglect long-ranged effects. Compared to real pedestrians this leads to agents in a simulation valuing the shortest path a lot better than the quickest. So, in a situation as the movement of a large crowd around a corner, one needs a...
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Scientific Computing in the Cloud. (arXiv:0901.0029v1 [cond-mat.mtrl-sci]) - We investigate the feasibility of high performance scientific computation using cloud computers as an alternative to traditional computational tools. The availability of these large, virtualized pools of compute resources raises the possibility of a new compute paradigm for scientific research with many advantages. For research groups, cloud computing provides convenient access to reliable, high performance clusters and storage, without the need to purchase and maintain sophisticated hardware. For developers, virtualization allows scientific codes to be optimized and pre-installed on machine images, facilitating control over the computational environment. Preliminary tests are presented for serial and parallelized versions of the widely used x-ray spectroscopy and electronic structure code FEFF on the Amazon Elastic Compute Cloud, including CPU and network performance. ...
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Positive and negative entropy production in thermodynamic systems. (arXiv:0901.0023v1 [physics.gen-ph]) - This article presents a heuristic combination of the local and global formulations of the second law of thermodynamics that suggests the possibility of theoretical existence of thermodynamic processes with positive and negative entropy production.Such processes may exhibit entropy couplings that reveal an unusual behavior from the point of view of conventional thermodynamics. ...
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{\Large $\gamma$} induced multiparticle emissions of medium mass nuclei at intermediate energies. (arXiv:0811.4097v3 [nucl-th] UPDATED) - A comprehensive analysis of multiparticle emissions following photon induced reactions at intermediate energies is provided. Photon induced reaction is described in the energy range of $\sim 30-140$ MeV with an approach based on the quasideuteron nuclear photoabsorption model followed by the process of competition between light particle evaporation and fission for the excited nucleus. The evaporation-fission process of the compound nucleus is simulated in a Monte-Carlo framework. The study shows almost no fission events for the medium mass nuclei and reproduces satisfactorily well the available experimental data of photonuclear reaction cross sections at energies $\sim 30-140$ MeV. ...
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Optical Pumping : Experiment and Theory Revisited. (arXiv:0810.2579v2 [physics.gen-ph] UPDATED) - The objective of this paper is to share our enthusiasm for optical pumping experiments and to encourage their use in researches on practical physics. The experimental technique has been well developed and the apparatus sophisticated, but, by paying attention to a few details, reliable operation can be repeated. Some theoretical principles for optical pumping are also introduced and they can be demonstrated experimentally. ...
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Optimal geometry for efficient loading of an optical dipole trap. (arXiv:0809.1999v2 [physics.atom-ph] UPDATED) - One important factor which determines efficiency of loading cold atoms into an optical dipole trap from a magneto-optical trap is the distance between the trap centers. By studying this efficiency for various optical trap depths (2--110 mK) we find that for optimum dipole trap loading, longitudinal displacements up to 15 mm are necessary. An explanation for this observation is presented and compared with other work and a simple analytical formula is derived for the optimum distance between the trap centers. ...
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Phase Transitions and Chaos in Long-Range Models of Coupled Oscillators. (arXiv:0807.1870v4 [cond-mat.stat-mech] UPDATED) - We study the chaotic behavior of the synchronization phase transition in the Kuramoto model. We discuss the relationship with analogous features found in the Hamiltonian Mean Field (HMF) model. Our numerical results support the connection between the two models, which can be considered as limiting cases (dissipative and conservative, respectively) of a more general dynamical system of damped-driven coupled pendula. We also show that, in the Kuramoto model, the shape of the phase transition and the largest Lyapunov exponent behavior are strongly dependent on the distribution of the natural frequencies. ...
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The scintillation and ionization yield of liquid xenon for nuclear recoils. (arXiv:0807.0459v2 [astro-ph] UPDATED) - XENON10 is an experiment designed to directly detect particle dark matter. It is a dual phase (liquid/gas) xenon time-projection chamber with 3D position imaging. Particle interactions generate a primary scintillation signal (S1) and ionization signal (S2), which are both functions of the deposited recoil energy and the incident particle type. We present a new precision measurement of the relative scintillation yield \leff and the absolute ionization yield Q_y, for nuclear recoils in xenon. A dark matter particle is expected to deposit energy by scattering from a xenon nucleus. Knowledge of \leff is therefore crucial for establishing the energy threshold of the experiment; this in turn determines the sensitivity to particle dark matter. Our \leff measurement is in agreement with recent theoretical predictions above 15 keV nuclear recoil energy, and the energy threshold of the measurement is 4 keV. A knowledge of the ionization yield \Qy is necessary to establish the trigger threshol...
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Unitary gauge considered harmful. (arXiv:0804.2284v4 [physics.gen-ph] UPDATED) - I informally review the Higgs mechanism, focusing on fundamental aspects which should be common knowledge but apparently are not, explain why your understanding of gauge symmetry breaking is a decreasing function of your reliance on the unitary gauge, and discuss some implications for cosmology (domains, dark energy, CMB cold spot). ...
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Comment on "Using Three-Body Recombination to Extract Electron Temperatures of Ultracold Plasmas". (arXiv:0803.2382v2 [physics.space-ph] UPDATED) - In the recent work Fletcher et al. [Phys. Rev. Lett., v.99, p.145001 (2007)] reported on the novel experimental technique, enabling to measure the temperature of the expanding ultracold plasmas over a considerable time interval (up to 60-70 {\mu}s). It was unexpectedly found that the electron temperature dropped with time as T_e(t) ~ t^{-\alpha} with \alpha = 1.2 +/- 0.1 \approx 1 instead of \alpha = 2, which would be expected for the adiabatic cooling of electrons in the cloud expanding linearly in time. The above-cited authors supposed that 'the difference is likely due to the significant heating effects from 3-body recombination' (i.e. the inelastic processes), but they did not provide sufficient quantitative estimates supporting such a conclusion. The aim of the present comment is to mention that the experimentally revealed t^{-1}-dependence can be explained under quite general assumptions by the purely elastic processes in the ultracold plasma, as it was done a few years ago in...
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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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Thermodynamic Description of Elastic Solids. (arXiv:0705.1484v3 [physics.chem-ph] UPDATED) - The original postulate of Joule regarding the mechanical equivalency of heat, known as the first law of thermodynamics, is revisited in solid phase. It is demonstrated that this postulate does not holds for elastic solids. It is suggested that the thermal energy is stored by the vibrational energy and the mechanical energy by the elastic deformation. These two energies do not completely interchangeable and they should not be summed. The first law of thermodynamics should be specified by stating that the mechanical equivalency of heat is valid only if the thermal and mechanical energies are conserved by the same physical process. If this condition is not satisfied like in solid phase then the mechanical equivalency of heat is valid. The consequence of the separation of thermal end elastic energies is that the mechanical work performed by thermal expansion must be included in the thermal energy. Thus the sum of the vibrational energy and the thermal work should be constant at any give...
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The self-interaction force on an arbitrarily moving point-charge and its energy-momentum radiation rate: A mathematically rigorous derivation of the Lorentz-Dirac equation of motion. (arXiv:0812.3493v2 [physics.class-ph] UPDATED) - The classical theory of radiating point-charges is revisited: the retarded potentials, fields, and currents are defined as nonlinear generalized functions and all calculations are made in a Colombeau algebra. The total rate of energy-momentum radiated by an arbitrarily moving relativistic point-charge under the effect of its own field is shown to be rigorously equal to minus the self-interaction force due to that field. This solves, without changing anything in Maxwell's theory, numerous long-standing problems going back to more than a century. As an immediate application an unambiguous derivation of the Lorentz-Dirac equation of motion is given, and the origin of the problem with the Schott term is explained: it was due to the fact that the correct self-energy of a point charge is not the Coulomb self-energy, but an integral over a delta-squared function which yields a finite contribution to the Schott term that is either absent or incorrect in the customary formulations. ...
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Simultaneous inference of Jefimenko's and Maxwell's equations from retardation. (arXiv:0812.4647v2 [physics.class-ph] UPDATED) - Assuming the idea of retardation as an underlying axiom, we investigate how Jefimenko's and Maxwell's equations can be inferred. In the inference, we begin with the retarded versions of Coulomb's and Biot-Savart's field expression as an incomplete, starting ansatz. By calculating and comparing their divergences, curls, and time derivatives, we improve the ansatz. Thus improved ansatz is further improved through the same procedure and the final ansatz fields are identified with Jefimenko's fields. Our inference of Maxwell's equations is in much the same spirit as the derivation of static differential equations (divergences and curls) from the Coulomb's and Biot-Savart's fields known experimentally without knowing their governing laws of the divergence and curl equations. ...
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Derivation of the potential, field, and locally-conserved charge-current density of an arbitrarily moving point-charge. (arXiv:physics/0612232v5 [physics.class-ph] UPDATED) - The complete charge-current density and field strength of an arbitrarily accelerated relativistic point-charge are explicitly calculated. The current density includes, apart from the well-established three-dimensional delta-function which is sufficient for its global conservation, additional delta-contributions depending on the second and third proper-time derivatives of the position, which are necessary for its local conservation as required by the internal consistency of classical electrodynamics which implies that local charge-conservation is an {identity}. Similarly, the field strength includes an additional delta-contribution which is necessary for obtaining this result. The Lienard-Wiechert field and charge-current density must therefore be interpreted as nonlinear generalized functions, i.e., not just as distributions, even though only linear operations are necessary to verify charge-current conservation. The four-potential from which this field and the conserved charge-curre...
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The locally-conserved current density of the Lienard-Wiechert field. (arXiv:physics/0612090v8 [physics.class-ph] UPDATED) - The complete charge-current density and field strength of an arbitrarily accelerated relativistic point-charge are explicitly calculated. That current includes, apart from the well-established delta-function term which is sufficient for its global conservation, additional contributions depending on the second and third proper-time derivatives of the position. These extra contributions are necessary for the local conservation of that current, whose divergence must vanish {identically} even if it is a distribution, as is the case here. Similarly, the field strength includes an additional delta-like contribution which is necessary for obtaining this result. Altogether, the Lienard-Wiechert field and charge-current density must therefore be interpreted as nonlinear generalized functions, i.e., not just as distributions, even though only linear operations are needed to verify local charge-current conservation. ...
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Large amplitude of the internal motion of DNA immersed in bio-fluid. (arXiv:physics/0512206v2 [physics.flu-dyn] UPDATED) - The interaction between large internal motion of DNA surrounded by bio-fluid is investigated. The phenomenon is modelled using the relativistic Navier-Stokes lagrangian describing the bio-fluid coupled to the standard Klein-Gordon lagrangian describing the DNA. It is shown that the equation of motion at non-relativistic limit, v << c, reproduces the well-known Sine-Gordon equation. The effect of the interaction in a single soliton solution is also given and discussed. ...
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Gauge invariant fluid lagrangian and its application to cosmology. (arXiv:physics/0508086v3 [physics.flu-dyn] UPDATED) - A lagrangian for relativistic fluid systems with matters inside is developed using gauge principle. In the model, the gauge boson represents the fluid field in a form $A_\mu \equiv \epsilon_\mu \phi$, where $\epsilon_\mu$ contains the fluid kinematics and $\phi$ is an auxiliary field representing the fluid distribution. This leads to a new relativistic equation of motion for fluid, but which further coincides to the classical Euler equation at non-relativistic limit. The lagrangian is applied to model homogeneous universe as a bulk pure fluid system. Taking the simplest case of fluid with radial velocity and uniform distribution, the free energy density is calculated and its behaviour around Hubble distance is discussed. ...
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Kronecker Graphs: an approach to modeling networks. (arXiv:0812.4905v1 [stat.ML] CROSS LISTED) - How can we model networks with a mathematically tractable model that allows for rigorous analysis of network properties? Networks exhibit a long list of surprising properties: heavy tails for the degree distribution; small diameters; and densification and shrinking diameters over time. Most present network models either fail to match several of the above properties, are complicated to analyze mathematically, or both. In this paper we propose a generative model for networks that is both mathematically tractable and can generate networks that have the above mentioned properties. Our main idea is to use the Kronecker product to generate graphs that we refer to as "Kronecker graphs". First, we prove that Kronecker graphs naturally obey common network properties. We also provide empirical evidence showing that Kronecker graphs can effectively model the structure of real networks. We then present KronFit, a fast and scalable algorithm for fitting the Kronecker graph generation model to la...
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Evaporation and fluid dynamics of a sessile drop of capillary size. (arXiv:0812.4758v1 [physics.flu-dyn] CROSS LISTED) - Theoretical description and numerical simulation of an evaporating sessile drop are developed. We jointly take into account the hydrodynamics of an evaporating sessile drop, effects of the thermal conduction in the drop and the diffusion of vapor in air. A shape of the rotationally symmetric drop is determined within the quasistationary approximation. Nonstationary effects in the diffusion of the vapor are also taken into account. Simulation results agree well with the data of evaporation rate measurements for the toluene drop. Marangoni forces associated with the temperature dependence of the surface tension, generate fluid convection in the sessile drop. Our results demonstrate several dynamical stages of the convection characterized by different number of vortices in the drop. During the early stage the street of vortices arises near a surface of the drop and induces a non-monotonic spatial distribution of the temperature over the drop surface. The initial number of near-surface ...
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Intermittency and Thermalization in Turbulence. (arXiv:0812.2495v2 [nlin.CD] CROSS LISTED) - A dissipation rate in Fourier space, which grows faster than any power of the wave number, may be scaled to lead a hydrodynamic system {\it actually} or {\it potentially} converge to its Galerkin truncation. The former case means convergence to the truncation at a finite wavenumber $k_G$, as the hyperviscosity scaling in [U. Frisch et al., Phys. Rev. Lett. {\bf 101}, 144501 (2008)]; the latter realizes as the wavenumber grows to infinity. The dissipation rate model $\mu [\cosh(k/k_c)-1]$, which reduces to the Newtonian viscosity dissipation rate $\nu k^2$ for small $k/k_c$, is used for a typical case study. Thermalization physics of Navier-Stokes turbulence, such as intermittency reduction and destruction of the self-organization of the flow, are investigated numerically with this dissipation model. ...
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Improved radiative corrections for (e,e'p) experiments - A novel approach to multi-photon bremsstrahlung. (arXiv:0805.1535v2 [nucl-th] CROSS LISTED) - Radiative processes lead to important corrections to (e,e'p) experiments. While radiative corrections can be calculated exactly in QED and to a good accuracy also including hadronic corrections, these corrections cannot be included into data analyses to arbitrary orders exactly. Nevertheless consideration of multi-photon bremsstrahlung above the low-energy cut-off is important for many (e,e'p) experiments. To date, higher-order bremsstrahlung effects concerning electron scattering experiments have been implemented approximately by employing the soft-photon approximation (SPA). In this paper we propose a novel approach to multi-photon emission which partially removes the SPA from (e,e'p) experiments. In this combined approach one hard photon is treated exactly; and additional softer bremsstrahlung photons are taken into account resorting to the soft-photon approximation. This partial removal of the soft-photon approximation is shown to be relevant for the missing-energy distribution ...
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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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