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Articles 1 - 30 of 278
Full-Text Articles in Physics
Determining Magnetic Nanoparticle Size Distributions From Thermomagnetic Measurements., R. S. Dipietro, H. G. Johnson, S. P. Bennett, T. J. Nummy, L. H. Lewis, D. Heiman
Determining Magnetic Nanoparticle Size Distributions From Thermomagnetic Measurements., R. S. Dipietro, H. G. Johnson, S. P. Bennett, T. J. Nummy, L. H. Lewis, D. Heiman
Laura H. Lewis
Thermomagnetic measurements are used to obtain the size distribution and anisotropy of magnetic nanoparticles. An analytical transformation method is described which utilizes temperature-dependent zero-field cooling magnetization data to provide a quantitative measurement of the average diameter and relative abundance of superparamagnetic nanoparticles. Applying this method to self-assembled MnAs nanoparticles in MnAs–GaAs composite films reveals a log-normal size distribution and reduced anisotropy for nanoparticles compared to bulk materials. This analytical technique holds promise for rapid assessment of the size distribution of an ensemble of superparamagnetic nanoparticles.
Universal Properties Of Linear Magnetoresistance In Strongly Disordered Mnas-Gaas Composite Semiconductors, H. G. Johnson, S. P. Bennett, R. Barua, L. H. Lewis, D. Heiman
Universal Properties Of Linear Magnetoresistance In Strongly Disordered Mnas-Gaas Composite Semiconductors, H. G. Johnson, S. P. Bennett, R. Barua, L. H. Lewis, D. Heiman
Laura H. Lewis
Linear magnetoresistance (LMR) occurs in semiconductors as a consequence of strong electrical disorder and is characterized by nonsaturating magnetoresistance that is proportional to the applied magnetic field. By investigating a disordered MnAs-GaAs composite material, it is found that the magnitude of the LMR is numerically equal to the carrier mobility over a wide range and is independent of carrier density. This behavior is complementary to the Hall effect that is independent of the mobility and dependent on the carrier density. Moreover, the LMR appears to be insensitive to the details of the disorder and points to a universal explanation of …
Determining Magnetic Nanoparticle Size Distributions From Thermomagnetic Measurements., R. S. Dipietro, H. G. Johnson, S. P. Bennett, T. J. Nummy, L. H. Lewis, D. Heiman
Determining Magnetic Nanoparticle Size Distributions From Thermomagnetic Measurements., R. S. Dipietro, H. G. Johnson, S. P. Bennett, T. J. Nummy, L. H. Lewis, D. Heiman
Donald Heiman
Thermomagnetic measurements are used to obtain the size distribution and anisotropy of magnetic nanoparticles. An analytical transformation method is described which utilizes temperature-dependent zero-field cooling magnetization data to provide a quantitative measurement of the average diameter and relative abundance of superparamagnetic nanoparticles. Applying this method to self-assembled MnAs nanoparticles in MnAs–GaAs composite films reveals a log-normal size distribution and reduced anisotropy for nanoparticles compared to bulk materials. This analytical technique holds promise for rapid assessment of the size distribution of an ensemble of superparamagnetic nanoparticles.
Magnetotransport Properties Of Mn-Si-C Based Nanostructures, Sungmu Kang, Greg A. Brewer, Battogtokh Jugdersuren, Robert Dipietro, Don Heiman, Andrew C. Buechele, David A. Mckeown, Ian L. Pegg, John Philip
Magnetotransport Properties Of Mn-Si-C Based Nanostructures, Sungmu Kang, Greg A. Brewer, Battogtokh Jugdersuren, Robert Dipietro, Don Heiman, Andrew C. Buechele, David A. Mckeown, Ian L. Pegg, John Philip
Donald Heiman
Boron-incorporated Mn5SiC nanowires were grown using chemical vapor deposition method. The nanowire cluster exhibits magnetic hysteresis loops at room temperature and the strength of the magnetic behavior depends on the concentration of the boron incorporation. Mn5SiC nanowire-based devices exhibit spin dependent transport properties which shows significant changes with boron content. Large magnetoresistance is observed in lightly boron-incorporated nanowire devices and it decreases with increase in boron content.
Magnetic Signature Of Symmetry Reduction In Epitaxial La₀.₆₇Sr₀.₃₃Mno₃ Films, Radhika Barua, L. H. Lewis, D. Heiman
Magnetic Signature Of Symmetry Reduction In Epitaxial La₀.₆₇Sr₀.₃₃Mno₃ Films, Radhika Barua, L. H. Lewis, D. Heiman
Donald Heiman
The magnetic properties of epitaxially grown La0.67Sr0.33MnO3 perovskite thin films were investigated to elucidate an unexpected broken symmetry between orthogonal [100] and [010] inplane directions, resulting from the magnetostructural coupling between the film and the cubic SrTiO3 (001) substrate. The films were synthesized by molecular beam epitaxy with either complete or zero A-site cation disorder. Magnetization measured in [100] and [010] directions shows differences that signal a reduction of the in-plane cubic symmetry only for T < 290 K. The magnetization asymmetry is more robust in the film with complete A-site disorder. These results are attributed to a dominant Mn3+ character …
Large Low Field Magnetoresistance In La₀.₆₇Sr₀.₃₃Mno₃ Nanowire Devices, Battogtokh Jugdersuren, Sungmu Kang, Robert S. Dipietro, Don Heiman, David Mckeown, Ian L. Pegg, John Philip
Large Low Field Magnetoresistance In La₀.₆₇Sr₀.₃₃Mno₃ Nanowire Devices, Battogtokh Jugdersuren, Sungmu Kang, Robert S. Dipietro, Don Heiman, David Mckeown, Ian L. Pegg, John Philip
Donald Heiman
Large low field magnetoresistance (LFMR) of about 28% is observed in La0.67Sr0.33MnO3 nanowires with 80 nm in diameter at T = 300 K. A gradual decrease in the LFMR has been found with increase in wire diameter. The LFMR drops to zero for wires above 280 nm in diameter. The nanowires are grown by means of electrospinning process and exhibit distorted orthorhombic crystal structure. The large LFMR is considered as a grain boundary effect as observed in several perovskite systems. The large LFMR observed in these manganites with reduced dimensions may be useful for room temperature device applications.
Large Coercivity In Nanostructured Rare-Earth-Free Mnxga Films, Don Heiman, Tom Nummy, Steve Bennett, Tom Cardinal
Large Coercivity In Nanostructured Rare-Earth-Free Mnxga Films, Don Heiman, Tom Nummy, Steve Bennett, Tom Cardinal
Donald Heiman
The magnetic hysteresis of MnxGa films exhibit remarkably large coercive fields as high as HC=2.5 T when fabricated with nanoscale particles of a suitable size and orientation. This coercivity is an order of magnitude larger than in well-ordered epitaxial film counterparts and bulk materials. The enhanced coercivity is attributed to the combination of large magnetocrystalline anisotropy and ~50-100 nm size nanoparticles. The large coercivity is also replicated in the electrical properties through the anomalous Hall effect. The magnitude of the coercivity approaches that found in rare-earth magnets, making them attractive for rare-earth-free magnet applications.
Ordering Of Glass Rods In Nematic And Cholesteric Liquid Crystals, A. T. Juhl, Deng-Ke Yang, V. P. Tondiglia, L. V. Natarajan, Timothy J. White, Timothy J. Bunning
Ordering Of Glass Rods In Nematic And Cholesteric Liquid Crystals, A. T. Juhl, Deng-Ke Yang, V. P. Tondiglia, L. V. Natarajan, Timothy J. White, Timothy J. Bunning
Deng-Ke Yang
The orientational assembly of glass rods (3 x similar to 15 mu m) in nematic, twisted nematic, and cholesteric liquid crystal cells was observed and quantified with optical microscopy. At this size, the rods were affected strongly by gravity and sedimented to the bottom of the cells. Temporal visualization of the sedimentation process (induced by flipping the cell over) shed insight into the effect the liquid crystal order had on the glass rod orientation. For nematic and twisted nematic geometries, the glass rods were aligned parallel to the local director orientation. Control experiments indicate that the rod alignment is not …
Wiki Leaks Revelations In Global Context—The War Between ‘Right To Publish’ And ‘Ethical Code Of Conduct, Ratnesh Dwivedi Mr
Wiki Leaks Revelations In Global Context—The War Between ‘Right To Publish’ And ‘Ethical Code Of Conduct, Ratnesh Dwivedi Mr
Ratnesh Dwivedi
WikiLeaks is an international non-profit organisation that publishes submissions of private, secret, and classified media from anonymous news sources, news leaks, and whistleblowers. Its website, launched in 2006 under The Sunshine Press organisation claimed a database of more than 1.2 million documents within a year of its launch. WikiLeaks describes its founders as a mix of Chinese dissidents, journalists, mathematicians, and start-up company technologists from the United States, Taiwan, Europe, Australia, and South Africa. Julian Assange, an Australian Internet activist, is generally described as its director. The site was originally launched as a user-editable wiki, but has progressively moved towards …
A Critical Study Of Organizational Communication And Organizational Communication Theories- A Historical Perspective, Ratnesh Dwivedi Mr
A Critical Study Of Organizational Communication And Organizational Communication Theories- A Historical Perspective, Ratnesh Dwivedi Mr
Ratnesh Dwivedi
Organizational Communication is the study that looks at human communication within and outside the organization. Conrad and Poole (1998) break the definition of organizational communication in parts, by first defining communication and then analyses the organization. These researchers define communication as “a process through which people, acting together, create, sustain, and manage meanings through the use of verbal and nonverbal signs and symbols within a particular context” (Conrad and Poole, 1998, p. 5). In the context of this book, Kenyans and their leaders are communicating their views and final decision through the ballot box to elect their third president, during …
Public Accountability And Media : Its Success And Failure In Performing The Role As A Force For Public Accountability, Ratnesh Dwivedi Mr
Public Accountability And Media : Its Success And Failure In Performing The Role As A Force For Public Accountability, Ratnesh Dwivedi Mr
Ratnesh Dwivedi
Media accountability is a phrase that refers to the general (especially western) belief that mass media has to be accountable in the public’s interest - that is, they are expected to behave in certain ways that contribute to the public good. The concept is not clearly defined, and often collides with commercial interests of media owners; legal issues, such as the constitutional right to the freedom of the press in the U.S.; and governmental concerns about public security and order. Several international organizations, like International Freedom of Expression Exchange, Freedom House, International Press Institute, World Press Freedom Committee and the …
Application Of Asymptotic Expansions For Maximum Likelihood Estimators' Errors To Gravitational Waves From Inspiraling Binary Systems: The Network Case, Salvatore Vitale, Michele Zanolin
Application Of Asymptotic Expansions For Maximum Likelihood Estimators' Errors To Gravitational Waves From Inspiraling Binary Systems: The Network Case, Salvatore Vitale, Michele Zanolin
Michele Zanolin
Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou
Transport And Magnetic Critical Current In Superconducting Mgb2 Wires, J. Horvat, W. K. Yeoh, J. H. Kim, S. X. Dou
Shi Xue Dou
Direct comparison of the magnetic and transport critical current density (Jc) for the same pieces of copper-sheathed MgB2 wires shows a large discrepancy in magnitude and field dependence of the two. The value of magnetic Jc can differ from the value of transport Jc by a factor of 10 or more. This discrepancy does not occur merely because of the difference in the voltage at which the magnetic and transport Jc are measured, but mainly because of the specific microstructure of MgB2. Such microstructure results in superconducting screening on at least two different length-scales, despite the absence of weak links …
Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis
Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis
Roger A. Lewis
An unusual concept for a simple and inexpensive terahertz source is presented: unpeeling adhesive tape. The observed spectrum of this terahertz radiation exhibits a peak at 2 THz and a broader peak at 18 THz. The radiation is not polarized. The mechanism of terahertz radiation is tribocharging of the adhesive tape and subsequent discharge, possibly bremsstrahlung with absorption or energy density focusing during the dielectric breakdown of a gas. The accompanying optical emission is also a consequence of tribocharging.
Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis
Peeling Adhesive Tape Emits Electromagnetic Radiation At Terahertz Frequencies, J. Horvat, R. A. Lewis
Josip Horvat
An unusual concept for a simple and inexpensive terahertz source is presented: unpeeling adhesive tape. The observed spectrum of this terahertz radiation exhibits a peak at 2 THz and a broader peak at 18 THz. The radiation is not polarized. The mechanism of terahertz radiation is tribocharging of the adhesive tape and subsequent discharge, possibly bremsstrahlung with absorption or energy density focusing during the dielectric breakdown of a gas. The accompanying optical emission is also a consequence of tribocharging.
Photolithographic Surface Micromachining Of Polydimethylsiloxane (Pdms), Weiqiang Chen, Raymond H. W. Lam, Jianping Fu
Photolithographic Surface Micromachining Of Polydimethylsiloxane (Pdms), Weiqiang Chen, Raymond H. W. Lam, Jianping Fu
Weiqiang Chen
A major technical hurdle in microfluidics is the difficulty in achieving high fidelity lithographic patterning on polydimethylsiloxane (PDMS). Here, we report a simple yet highly precise and repeatable PDMS surface micromachining method using direct photolithography followed by reactive ion etching (RIE). Our method to achieve surface patterning of PDMS applied an O2 plasma treatment to PDMS to activate its surface to overcome the challenge of poor photoresist adhesion on PDMS for photolithography. Our photolithographic PDMS surface micromachining technique is compatible with conventional soft lithography techniques and other silicon-based surface and bulk micromachining methods. To illustrate the general application of our …
Physics Of Quasi-Monoenergetic Laser-Plasma Acceleration Of Electrons In The Blowout Regime, Serguei Y. Kalmykov, Bradley A. Shadwick, Arnaud Beck, Erik Lefebvre
Physics Of Quasi-Monoenergetic Laser-Plasma Acceleration Of Electrons In The Blowout Regime, Serguei Y. Kalmykov, Bradley A. Shadwick, Arnaud Beck, Erik Lefebvre
Serge Youri Kalmykov
No abstract provided.
Risk-Based Critical Infrastructure Priorities For Emp And Solar Storms, George H. Baker Iii
Risk-Based Critical Infrastructure Priorities For Emp And Solar Storms, George H. Baker Iii
George H Baker
Two electromagnetic phenomena have the potential to create continental-scale disasters. The first, nuclear electromagnetic pulse (EMP), results from a nuclear detonation high above the tropopause. The second, a major solar storm, or "solar tsunami" occurs naturally when an intense wave of charged particles from the sun perturbs the earth's magnetic field. Both phenomena can debilitate electrical and electronic systems necessary for the operation of infrastructure systems and services. One reason why a U.S. protection program has yet to be initiated is that policy makers continue to wrestle with the question of where to begin, given the Department of Homeland Security’s …
Carbon Nanotube Growth Via Spray Pyrolysis, Robert Welch Call
Carbon Nanotube Growth Via Spray Pyrolysis, Robert Welch Call
Robert W Call
Spray pyrolysis is a promising method to create carbon nanotube forests (CNFs) on various surfaces. By injecting metallocene-hydrocarbon solutions into a heated quartz reactor, catalyst particles and carbon nanotubes can be formed simultaneously. Factors that affect CNF growth include the precursor concentration, injection rate and duration, carrier gas flow rate, substrate surface, growth temperature, and the composition of gases inside the reactor. The CNF morphologies affected by these factors will be presented and, hopefully, an optimum condition will be found.
Boundary Effects In Large-Aspect-Ratio Lasers, G.K. Harkness, W.J. Firth, John B. Geddes, J.V Moloney, E.M. Wright
Boundary Effects In Large-Aspect-Ratio Lasers, G.K. Harkness, W.J. Firth, John B. Geddes, J.V Moloney, E.M. Wright
John B. Geddes
We study theoretically the effect of transverse boundary conditions on the traveling waves foundin infinitely extended and positively detuned laser systems. We find that for large-aspect-ratiosystems, well above threshold and away from the boundaries, the traveling waves persist. Sourceand sink defects are observed on the boundaries, and in very-large-aspect-ratio systems these defectscan also exist away from the boundaries. The transverse size of the sink defect, relative to the sizeof the transverse domain, is important in determining the final pattern observed, and so, close tothreshold, standing waves are always observed.
Dynamic High Contrast Reflective Coloration From Responsive Polymer/Cholesteric Liquid Crystal Architectures, Michael E. Mcconney, Timothy J. White, Vincent P. Tondiglia, Lalgudi V. Natarajan, Deng-Ke Yang, Timothy J. Bunning
Dynamic High Contrast Reflective Coloration From Responsive Polymer/Cholesteric Liquid Crystal Architectures, Michael E. Mcconney, Timothy J. White, Vincent P. Tondiglia, Lalgudi V. Natarajan, Deng-Ke Yang, Timothy J. Bunning
Deng-Ke Yang
We report on high reflectivity CLC structures (R > 50%) whose wavelength can be thermally tuned reversibly by a de-swelling/re-swelling transition unique to ordered solvent-gel systems. The system contains no chiral dopant and the coloration is completely induced by a responsive chiral structured gel. The de-swelling transition, leading to blue tuning, occurs at the nematic-isotropic transition of the liquid crystal, which is a result of a mismatch in the orientational energy of the isotropic liquid crystal and the anisotropic gel. The re-swelling transition subsequently occurs at the nematic-isotropic transition of gel, due to the miscibility of the isotropic liquid crystal and …
Extraction Of Signals From Chaotic Laser Data, John B. Geddes, Kevin Short, Kelly Black
Extraction Of Signals From Chaotic Laser Data, John B. Geddes, Kevin Short, Kelly Black
John B. Geddes
Several experimental groups have demonstrated communication with chaotic lasers. We analyzedata collected from a message-modulated erbium-doped fiber-ring laser (provided by VanWiggerenand Roy). We show that the transmitted signal is dominated by convolution of the message with theresponse function of the laser. A simple model based on the topology of the laser allows us to recovera hidden message. While prior estimates indicate that the laser dynamics are high dimensional, weshow that only four parameters are required, each of which can be recovered from the transmittedsignal alone.
Violence On The Brain: A Critique Of Neuroscience In Criminal Law, Amanda C. Pustilnik
Violence On The Brain: A Critique Of Neuroscience In Criminal Law, Amanda C. Pustilnik
Amanda C Pustilnik
Is there such a thing as a criminally "violent brain"? Does it make sense to speak of "the neurobiology of violence" or the "psychopathology of crime"? Is it possible to answer on a physiological level what makes one person engage in criminal violence and another not, under similar circumstances? This Article first demonstrates parallels between certain current claims about the neurobiology of criminal violence and past movements that were concerned with the law and neuroscience of violence: phrenology, Lombrosian biological criminology, and lobotomy. It then engages in a substantive review and critique of several current claims about the neurological bases …
Holographic Renormalization Of Asymptotically Lifshitz Spacetimes, Robert Mcnees, Robert Mann
Holographic Renormalization Of Asymptotically Lifshitz Spacetimes, Robert Mcnees, Robert Mann
Robert A McNees IV
A variational formulation is given for a theory of gravity coupled to a massive vector in four dimensions, with Asymptotically Lifshitz boundary conditions on the fields. For theories with critical exponent z = 2 we obtain a well-defined variational principle by explicitly constructing two actions with local boundary counterterms. As part of our analysis we obtain solutions of these theories on a neighborhood of spatial infinity, study the asymptotic symmetries, and consider different definitions of the boundary stress tensor and associated charges. A constraint on the boundary data for the fields figures prominently in one of our formulations, and in …
Spin And Exchange Coupling For Ti Embedded In A Surface Dipolar Network, Pushpa Raghani, Jesus Cruz, Barbara Jones
Spin And Exchange Coupling For Ti Embedded In A Surface Dipolar Network, Pushpa Raghani, Jesus Cruz, Barbara Jones
Pushpa Raghani
We have studied the spin and exchange coupling of Ti atoms deposited on a Cu2N/Cu(100) surface using density functional theory with generalized gradient approximation +U. In agreement with experiments, we find that Ti has the highest binding on top of Cu atoms. We also find that the spin of individual Ti atoms deposited on the Cu2N/Cu(100) surface increases as Ti coverage on the surface is decreased. For U=0, the spin of a Ti atom starts at S=0 at high coverages and increases to S=1/2 as the coverage is decreased, which agrees very well with results obtained from STM experiments. At …
X-Ray Scattering Study Of The Incommensurate Phase In Mg-Doped Cugeo3, Rebecca J. Christianson, Y. J. Wang, S.C. Lamarra, R. J. Birgeneau, V. Kiryukhin, T. Masuda, I. Tsukada, K. Uchinokura, B. Keimer
X-Ray Scattering Study Of The Incommensurate Phase In Mg-Doped Cugeo3, Rebecca J. Christianson, Y. J. Wang, S.C. Lamarra, R. J. Birgeneau, V. Kiryukhin, T. Masuda, I. Tsukada, K. Uchinokura, B. Keimer
Rebecca J. Christianson
We present results of a systematic x-ray scattering study of the effects of Mg doping on the high-fieldincommensurate phase of CuGeO3. Lorentzian-squared line shapes, the changing of the first-order transition tosecond order, and the destruction of long-range order with infinitesimal doping are observed, consistent withrandom-field effects in a three-dimensional XY system. Values for the soliton width in pure and lightly dopedCuGeO3 are deduced. We find that even a very small doping has a drastic effect on the shape of the latticemodulation.
Time-Dependent Strength Of Colloidal Gels, S. Manley, Benny Davidovitch, Neil R. Davies, L. Cipelletti, A. E. Bailey, Rebecca J. Christianson, U. Gasser, V. Prasad, P. N. Segre, M. P. Doherty, S. Sankaran, A. L. Jankovsky, B. Shiley, J. Bowen, J. Eggers, C. Kurta, T. Lorik, D. A. Weitz
Time-Dependent Strength Of Colloidal Gels, S. Manley, Benny Davidovitch, Neil R. Davies, L. Cipelletti, A. E. Bailey, Rebecca J. Christianson, U. Gasser, V. Prasad, P. N. Segre, M. P. Doherty, S. Sankaran, A. L. Jankovsky, B. Shiley, J. Bowen, J. Eggers, C. Kurta, T. Lorik, D. A. Weitz
Rebecca J. Christianson
Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.
Spinodal Decomposition In A Model Colloid-Polymer Mixture In Microgravity, A. E. Bailey, W. C. K. Poon, Rebecca J. Christianson, A. B. Schofield, U. Gasser, V. Prasad, S. Manley, P. N. Segre, L. Cipelletti, W. V. Meyer, M. P. Doherty, S. Sankaran, A. L. Jankovsky, W. L. Shiley, J. P. Bowen, J. C. Eggers, C. Kurta, T., Jr. Lorik, P. N. Pusey, D. A. Weitz
Spinodal Decomposition In A Model Colloid-Polymer Mixture In Microgravity, A. E. Bailey, W. C. K. Poon, Rebecca J. Christianson, A. B. Schofield, U. Gasser, V. Prasad, S. Manley, P. N. Segre, L. Cipelletti, W. V. Meyer, M. P. Doherty, S. Sankaran, A. L. Jankovsky, W. L. Shiley, J. P. Bowen, J. C. Eggers, C. Kurta, T., Jr. Lorik, P. N. Pusey, D. A. Weitz
Rebecca J. Christianson
We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.
X-Ray Scattering Studies Of Two Length Scales In The Critical Fluctuations Of Cugeo3, Y. J. Wang, Y. J. Kim, Rebecca J. Christianson, S. C. Lamarra, F. C. Chou, R. J. Birgeneau
X-Ray Scattering Studies Of Two Length Scales In The Critical Fluctuations Of Cugeo3, Y. J. Wang, Y. J. Kim, Rebecca J. Christianson, S. C. Lamarra, F. C. Chou, R. J. Birgeneau
Rebecca J. Christianson
The critical fluctuations of CuGeO3 have been measured by synchrotron x-ray scattering, and two length scales are clearly observed. The ratio between the two length scales is found to be significantly different along the a axis, with the a axis along the surface normal direction. We believe that such a directional preference is a clear sign that random surface strains, especially those caused by dislocations, are the origin of the long length scale fluctuations.
Discrete Beam Acceleration In Uniform Waveguide Arrays, Ramy El-Ganainy, Konstantinos G. Makris, Mohammad-Ali Miri, Demetrios N. Christodoulides, Zhigang Chen
Discrete Beam Acceleration In Uniform Waveguide Arrays, Ramy El-Ganainy, Konstantinos G. Makris, Mohammad-Ali Miri, Demetrios N. Christodoulides, Zhigang Chen
Ramy El-Ganainy
Within the framework of the tight-binding model we demonstrate that Wannier-Stark states can freely accelerate in uniform optical lattices. As opposed to accelerating Airy wave packets in free space, our analysis reveals that in this case the beam main intensity features self-bend along two opposite hyperbolic trajectories. Two-dimensional geometries are also considered and an asymptotic connection between these Wannier-Stark ladders and Airy profiles is presented.