Condensed Matter Physics

"PDF file: http://dml.riken.jp/pub/nori/pdf/J_Phys_C_C_113_21218_2009.pdf .


We theoretically examine the light-to-electricity energy conversion in a molecular triad coupled to conducting leads. This coupling allows us to drive a current through the system. We derive the equations of motion for the electron density operators and determine the dependence of the current, quantum yield, and thermodynamic efficiency on temperature, the electrochemical potentials of the leads, as well as on the light intensity and frequency of the external electromagnetic field. For the molecular triad consisting of ferrocene, porphyrin, and fullerene molecules, we find that, in the case of relatively strong coupling to the leads, the power-conversion efficiency can exceed 40% and the quantum yield can be more than 90%, instead of the 25% quantum yield observed in experiments. Thus, this system is highly attractive for solar cell applications. The large predicted increase in the efficiency of this system is due to the stronger coupling to the contacts, which allows the triad to move more electrons through it, absorbing more photons per unit time, and doing more work."

Pre-earthquake signals have been widely reported, including perturbations in the ionosphere. These precursory signals, though highly diverse, may be caused by just one underlying physical process: activation of highly mobile electronic charge carriers in rocks that are subjected to ever increasing levels of stress. The charge carriers are defect electrons associated with O− in a matrix of O2−. Known as positive holes or pholes h, they flow out of the stressed rock into the unstressed rock volume, traveling meters in the laboratory, probably kilometers in the field. At the rock–air interface they cause: (i) positive surface potential, (ii) field-ionization of air molecules, (iii) corona discharges. The rate of formation of airborne ions can exceed 109 cm−2 s−1. Massive air ionization prior to major earthquakes increases the electrical conductivity in the air column and may cause ionospheric perturbations, earthquake lights, and unusual animal behavior as well as infrared emission.

We show that invariance properties of the Lagrangian of an incommensurate system, as described by the
Frenkel-Kontorova model, imply the existence of a generalized angular momentum that is an integral of
motion if the system remains floating. The behavior of this quantity can therefore monitor the character of the
system as floating ~when it is conserved! or locked ~when it is not!. We find that, during the dynamics, the
nonlinear couplings of our model cause parametric phonon excitations that lead to the appearance of Umklapp
terms and to a sudden deviation of the generalized momentum from a constant value, signaling a dynamical
transition from a floating to a pinned state. We point out that this transition is related but does not coincide with
the onset of sliding friction, which can take place when the system is still floating.

We provide combinatorial as well as probabilistic interpretations for the q-analogue of the Pochhammer k-symbol introduced by Diaz and Teruel. We introduce q-analogues of the Mellin transform in order to study the q-analogue of the k-gamma distribution.

http://pre.aps.org/abstract/PRE/v71/i4/e041107 .

We analyze the problem of directed quantum transport induced by external exponentially correlated telegraphic noise. In addition to quantum nature of the heat bath, nonlinearity of the periodic system potential brings in quantum contribution. We observe that quantization, in general, enhances classical current at low temperature, while the differences become insignificant at higher temperature. Interplay of quantum diffusion and quantum correction to system potential is analyzed for various ranges of temperature, correlation time and strength of external noise and asymmetry parameters. A possible experimental realization of the observed quantum effects in a superionic conductor placed in a random asymmetric dichotomous electric field has been suggested.

This must be one of the very few peer reviewed and reputably published technical papers to have been written entirely in rhyming verse. The subject matter concerns the physics of a macroscopic quantum system.

No case is known of a mass flow exhibiting diffraction. A fluid flowing through a grid shows no interference effects. Atoms or light passing through a grid do show interference. Because of its macroscopic quantum nature the possibility of just such an interference effect could exist for superfluid helium flow. The experiment was an attempt to see diffraction in liquid helium.  The paper explains, entirely in rhyme, the theory behind the expectation and all the technical details of the experiment. Unfortunately, no diffraction was observed.

ABSTRACT
Electro-ceramics have been extensively investigated over the last few decades due to their applications in telecommunication industry. Ceramists are still working hard to further improve the properties and reduce the size of the electro-ceramics components and cost of production via intelligent composition designing and processing. X-ray diffraction of as-mix-milled PbO and ZrO2, revealed the presence of PbO and ZrO2. Only PbZrO3 was identified by XRD in samples calcined at 800ºC. After sintering at 1150ºC, the major phase present on the surface of the sample was ZrO2 with trace amounts of PbZrO3, however, the bulk of the sample comprised of PbZrO3 only. About 2μm irregular-shaped grains were observed in the secondary electron scanning electron microscope images from the surface of the sample. The necking of these grains into one another revealed that the sintering temperature was higher than the optimum.

Statistical design of experiments was used to investigate the effect the process parameters on electrophoretic deposition (EPD) of alumina onto steel substrates from its suspension in iso-propanol. The process parameters considered were (i) concentration of particles in the suspension (solid loading), (ii) electrode separation, (iii) applied potential, and (iv) deposition time on the quantity of ceramic particles electrophoretically deposited. A 2^4 full factorial matrix, with four repetitions of the center point, was used to develop the predictive regression equation for deposition of alumina per unit area of the electrode in the design space. The results show that particle concentration has the most dominant effect with more than 50% contribution to the deposited amount. A good correlation was obtained between predicted and experimental values suggesting that the model can predict data accurately in the experimental matrix.

The structure of a new class of boron nanostructures barrelenes and tubulenes - based on a boron atomic lattice
constructed by the alternating B-atomic polygons with central atoms and without them has been proposed and their properties have been described. Ab initio density functional calculations have been performed for the energy and electronic 7 on the lowest energy fullerene B80. It has been shown that the energy and band gap of a barrelene are lower than the respective quantities of the corresponding fullerene and tend to the respective values for nanotubes in the infinite limit. It has been shown that there are isomers of nanotubes of the same type that are significantly different in symmetry and electronic properties: a semiconductor (C5v symmetry) and a metal (D5h symmetry).

Techniques for producing needle-shaped specimens suitable for atom probe analysis from a bulk material via electropolishing and ion beam milling were investigated. A 7020 Aluminium alloy of composition Al-4.8%Zn-1.3%Mg (%wt, as cast), an Aluminium alloy of composition Al-1.1%Cu-0.5%Mg (%wt, as cast), and a spinodal Fe-Ni-Mn-Al alloy of composition 30%Fe-20%Ni-25%Mn-25%Al (%wt, as cast and treated for 1 hour at 1005˚C then air cooled) were explored. Procedures were characterised in detail using a CCD camera and SEM microscopy and parameters for the most efficient preparation methods were deduced. Extensive atom probe data was obtained from the 7020 specimen.

The effect of metallurgical parameters on the Brinell hardness of heat-treated 319 type alloys was investigated, to quantify the effects of alloying elements (Mg, Fe, Mn, Sr) and aging parameters on the hardness of heat-treated 319 alloys containing alpha-Fe or beta-Fe intermetallics. The corresponding alloy melts (at 750°C +/- 5°C) were cast into preheated graphite-coated metallic molds to prepare samples for hardness measurements. These samples were heat treated (solution treatment: 8h@495°C; quenching in warm water (65°C); aging at 155°, 180°, 200° and 220°C for 4h). Different aging times (2, 4, 6 and 8h) were also studied for the 180° and 220°C aging temperatures. Hardness measurements were made using a Brinell hardness tester (10 mm diameter ball and 500 kgf). Experimental correlations between the metallurgical and heat treatment parameters and the hardness values obtained were analyzed using factorial analysis (2k factorial design). For this, two levels of Mg (0.1 and 0.28 wt%), Fe-intermetallics (2% and 5%), Sr (0 and 200 ppm - non-modified and modified conditions), and two aging temperatures (180° and 220°C) and times (2h and 8h) were selected. The results obtained are in agreement with the experimental findings for these aging times and temperatures. It is found that the hardness increases with increasing Mg content and volume fraction of -Fe intermetallics, but decreases with Sr modification and with increasing aging temperature and time.

Three inorganic–organic layered perovskite-type hybrids of the general formula [(CnH2n + 1NH3)2PbI4], n = 4, 5 and 6, display a number of reversible first-order phase transitions in the temperature range from 256 to 393 K. [(C4H9NH3)2PbI4] has a single phase transition, [(C5H11NH3)2PbI4] has two phase transitions and [(C6H13NH3)2PbI4] has three phase transitions. In all three cases, the lowest-temperature phase transition is thermochromic and the crystals change colour from yellow in their lowest-temperature phase to orange in their higher-temperature phase for [(C4H9NH3)2PbI4] and [(C6H13NH3)2PbI4], and from orange to red for [(C5H11NH3)2PbI4]. The structural details associated with this phase transition have been investigated via single-crystal X-Ray diffraction, SC-XRD, for all three compounds.

The title compound, [NH3C6H4NH3][ZnI4] . 2H2O, crystallizes as an organic-inorganic hybrid. The ionic layer consists of isolated ZnI4 tetrahedra. The hydrocarbon layer has two symmetry independant para-phenylenediammonium cations that link to the ionic layer via hydrogen bonding. Two waters of hydration lie between the ZnI4 and the two cations.

The isomorphous structures of 2-methyl-4-nitroanilinium bromide, C7H9N2O2+·Br-, and 2-methyl-4-nitroanilinium iodide, C7H9N2O2+·I-, exhibit ionic layers separated by hydrocarbon layers. The hydrocarbon layer stacks head-to-head, while in the ionic layer, the ammonium groups and halide anions interact via hydrogen bonds to form infinite chains.

Divalent ions dissolved in the aqueous subphase of fatty acid Langmuir monolayers have two types of effects on the structure of the organic film. The first and more familiar effect is to induce a structure similar to the high-pressure "S" phase on pure water, even at low pressures; ions of the first type include Ni 2+ (aq), Ba 2+ -(aq), Co 2+ (aq), and Cu 2+ (aq). The presence of ions of the second type results in the appearance of superlattice structures: we see a 1 × 2 superlattice with Mn 2+ (aq) and a 2 × 2 superlattice with Mg 2+ (aq), and it is known that Cd 2+ (aq) and Pb 2+ (aq) also cause the formation of superlattices. Out-of-plane (Bragg rod) scans indicate that Mn 2+ (aq) and Mg 2+ (aq) interact with the headgroups so strongly that the organic film buckles, with a periodic out-of-plane density modulation (amplitude ∼2.5 Å). In addition, a thin (∼4 Å) ordered inorganic layer forms in the subphase under the Langmuir film.

The properties of amphiphilic organic monolayers ("Langmuir films") at the air-water interface are strongly affected by metal ions in the aqueous subphase, and such monolayers can be used as templates to grow oriented crystals from dissolved salts. Our synchrotron X-ray studies of fatty acid monolayers spread on a dilute aqueous solution of lead ions indicate that a ∼5 Å thick ordered layer is formed in the subphase. The lattice is commensurate with the organic lattice and has 14 times the unit cell area. It is unlikely that lead ions alone would form such a large repeat unit; indeed, using anomalous X-ray scattering, we detect no evidence of lead within the ordered layer. Thus, the interfacial superlattice is not simply an array of lead ions but may consist of lead hydrolysis products and water molecules.

We report the direct observation of internal layering in thin (ϳ45 90 Å) liquid films of nearly spherical, nonpolar molecules, tetrakis(2-ethylhexoxy)silane, using synchrotron x-ray reflectivity. The Patterson functions have secondary maxima indicating layer formation, and model-independent fitting to the reflectivity data shows that there are three electron density oscillations near the solid-liquid interface, with a period of ϳ10 Å (consistent with the molecular dimensions). The oscillation amplitude has a strong inverse dependence on the substrate surface roughness. [S0031-9007(99)08677-9]

This paper presents a nouvelle and non-destructiveBroadbandcharacterizationmethodwhichusesacoplanarlineforthemeasurementofthecomplexpermittivityoflineardielectricmaterialsandprecisely,thatofferroelectricthinfilms.Themethodusesthetransmissioncoefficientandthequasi-TEManalysistofindtheeffectivepermittivityofthemultilayersystem,andthenthecoplanarconformalmappingtechniqueisemployedtoextracttherelativepermittivityofthethinlayer.Comparingourresultstothoseofcavityresonatormethodat12GHzshowsagoodagreement.Themeasurementisdoneinthemicrowavefrequencyband(45MHz–20GHz).

We are building up a light scattering setup at the Instituto de Astrofísica de Andalucía (IAA), Granada, Spain. The design of this new setup is based on the well known apparatus currently located at the Astronomical Institute "Anton Pannekoek", University of Amsterdam, The Neteherlands [1],[2]. By using a polarization modulation technique, all scattering matrix elements as function of the scattering angle are obtained from 8 separate measurement runs. In this new setup we use an Argon-Kripton laser (483 nm, 488 nm, 514 nm, 568 nm, and 647 nm) as light source. The detectors are mounted on dove tails that allow their movement backward and forward. In addition, the detectors have been designed to minimize blockage of the laser beam at positions close to the forward and backward directions. In this way we intend to do measurements covering an angle range from 3 to 177 degrees. The alignment of the optics is automatically done and controlled from the computer reducing the measurement time.

The renormalization group (RG) method is applied to the study of discrete dynamical systems. As a particular example, the Hénon map is considered as being applied to describe the transverse betatron oscillations in a cyclic accelerator or storage ring possessing a FODO-cell structure with a single thin sextupole. A powerful RG method is developed that is valid correct to fourth order in the perturbation amplitude, and a technique for resolving the resonance structure of the Hénon map is also presented. This calculation represents an application of the RG method to the study of discrete dynamical systems in a unified manner capable of reducing the dynamics of the system both far from and close to resonances, thus preserving the symplectic symmetry of the original map.

As many practitiones know, compressed streams are very sensitive the transmission errors. Even a single error can have devastating effects and compromise all the data downstream . In fact, the non-resilience of adaptive data compression has been a practical drawback of its use in many applications. Joint source-channel coding [4, 1] has emerged as a possible solution to this problem. Usually, joint source-channel coding trades source bits for channel bits or vice versa, and more than often requires some adjustments in source coding and channel coding parts.

Chinese checkers is a game played on a hexagonal grid. This regular hexagonal tesselation is an artifact of Euclidean geometry that provides a fair playing eld only for games of two, three, four or six players. Hyperbolic geometry allows tessallations of the plane by regular polygons with any number of sides. Hyperbolic versions of the chinese checkers board permit fair games with ve, seven and even more players.

A key challenge that will face nanotechnologies will be controlling the uncertainty introduced by stochastic selfassembly. In this paper we explore architectural and manufacturing strategies to cope with this uncertainty when assembling nanoarrays, crossbars composed of two orthogonal sets of coded parallel nanowires. Because the encodings of nanowires that are assembled into a nanoarray cannot be predicted in advance, a discovery process is needed and specialized decoding circuitry must be employed. We have developed a probabilistic method of analysis so that various design strategies can be evaluated.

We examine the fundamental concept of Popper's falsifiability within an economic model in which a tester hires a potential expert to produce a theory. Payments are made contingent on the performance of the theory vis-a-vis future realizations of the data. We show that if experts are strategic, then falsifiability has no power to distinguish legitimate scientific theories from worthless theories. We also show that even if experts are strategic there are alternative criteria that can distinguish legitimate from worthless theories. * We are grateful to Eddie Dekel, Yossi Feinberg, Nabil Al-Najjar, Sandeep Baliga, Roger Myerson, and Rakesh Vohra for comments and conversations. We also thank workshop participants at Brown,

Motivated by the viscous sintering of amorphous materials in the presence of a distribution of rigid platelet inclusions added to increase the strength of the final sintered medium, a simple model for the shrinkage of compressible pores close to a wall in Stokes flow is proposed. The model assumes that the pore remains elliptical/ellipsoidal in shape at all times. The model is expected to be valid provided the pore is not too far from spherical and not too close to the wall. It relies on a separation of the flow into 'inner' and 'outer' problems. The inner problem is to assume that the ellipsoid evolves in a linear ambient flow given by the first two terms in a local expansion of an outer flow produced by the image singularity distribution of a point-sink near a planar no-slip boundary. The focus of the present paper is to test the viability of the model in the planar case. Using a spectral method based on analytic functions and conformal mappings, the results of a full numerical simulation are compared with the predictions of the planar model. The effects of the proximity of the pore to the wall, the anisotropy in the pore shape and its relative orientation to the wall are all examined. It is observed that, as they shrink, pores drift towards the wall becoming elongated in the direction perpendicular to the wall.

A formula for the generalized Schwarz-Christoffel mapping from a bounded multiply connected circular domain to a bounded multiply connected polygonal domain is derived. The theory of classical Schottky groups is employed. The formula for the derivative of the mapping function contains a product of powers of Schottky-Klein prime functions associated with a Schottky group relevant to the circular pre-image domain. The formula generalizes, in a natural way, the known mapping formulae for simply and doubly connected polygonal domains.

Despite limited literature discussing the global implications of molecular manufacturing (MM), the seeds for certain key debates are starting to be sown. They essentially mirror those
presented for current and near-term nanotechnology: 1. for what purposes will the technology be developed and used, by whom will it be created and owned, what is the nature of the risks it will bring, and what kind of impact will it have upon the global economy and developing world?

The realisation of MM’s central goals would undoubtedly lead to the most concentrated technological tsunami ever witnessed. The unpredictable nature of such a revolution makes answering the previous questions all the more difficult.

However, just as biotechnology is commonly used as a yardstick for nanotechnology evaluations (given the continuity of many social concerns and the relationship between existing biotechnology capabilities and the potential to develop nanotechnology), I argue here that the best way to set up the MM debate, in terms of its impact on developing countries, may be to look at developments and trends in nanotechnology. Central to such analysis is addressing the ways in which nanotechnology creates new possibilities for developing countries in terms of access to technology, potential benefits, risks, and shifting views of science and technology, as well as the imposing of new demands in terms of infrastructure and approaches to science.