Diffusivity in water and fluorescence properties of?organic nanoparticles produced in?flames

Rotational and translational diffusion properties in water of nano organic carbon (NOC) particles collected from premixed laminar ethylene/air flames have been investigated using both time resolved fluorescence polarisation anisotropy (TRFPA) and fluorescence correlation spectroscopy (FCS). Insight into the NOC sizes, structures and rigidity has been gained through diffusion properties exploiting their fluorescence in different spectral ranges. The TRFPA measurements revealed the presence of two classes of particles. The first composed of particles with a mean size of 1.5?nm which absorb and fluoresce in the UV, and a second class composed of slightly larger particles, about 2.2?nm, which absorb and fluoresce in the visible and were also detected by FCS. From FCS measurements particle concentration and fluorescence quantum yield have been evaluated.     

Randomness in Classical Mechanics and?Quantum Mechanics

The Copenhagen interpretation of quantum mechanics assumes the existence of the classical deterministic Newtonian world. We argue that in fact the Newton determinism in classical world does not hold and in the classical mechanics there is fundamental and irreducible randomness. The classical Newtonian trajectory does not have a direct physical meaning since arbitrary real numbers are not observable. There are classical uncertainty relations: Δq>0 and Δp>0, i.e. the uncertainty (errors of observation) in the determination of coordinate and momentum is always positive (non zero).     

Primordial perturbations and non-gaussianities in Ho?ava-Lifshitz gravity

We investigate primordial perturbations and non-gaussianities in the Ho?ava-Lifshitz theory of gravitation. In the UV limit, the scalar perturbation in the Ho?ava theory is naturally scale-invariant, ignoring the details of the expansion of the Universe. One may thus relax the exponential inflation and the slow-roll conditions for the inflaton field. As a result, it is possible that the primordial non-gaussianities, which are " slow-roll suppressed” in the standard scenarios, become large. We calculate the non-gaussianities from the bispectrum of the perturbation and find that the equilateral-type non-gaussianity is of the order of unity, while the local-type non-gaussianity remains small, as in the usual single-field slow-roll inflation model in general relativity. Our result is a new constraint on Ho?ava-Lifshitz gravity.     

Unreasonable and “Unreasonable” in Quantum Mechanics?

The particles of quantum mechanics (QM) are discrete undulatory entities which are described in terms of the complex state vectors of the theory in full agreement with experiment. The wave-particle paradox stems from the fact that undulation and discreteness are inconsistent within the classical theory which was historically the point of departure for the canonical foundation. The author describes his prolonged efforts of anchoring the state vector of QM in experiment rather in obsolete theory.     

Is there icosahedral ordering in liquid and undercooled metals?

The local structure of simple liquids is significantly different from that of corresponding crystalline systems. Signatures of fivefold local ordering have been previously found, but current knowledge is limited to pair distribution, leaving considerable uncertainty in the determination of the geometrical structure. New x-ray absorption experimental results on liquid and undercooled liquid copper, interpreted using an advanced data-analysis method based on multiple-scattering simulations, are shown to contain direct information on triplet correlations making feasible a reliable determination of the bond-angle distribution and fraction of nearly icosahedral configurations in liquids.     

Spectral structure of 510.6 and 578.2 nm lines in?a?CuBr?vapor?laser

Considering the hyperfine structure and the isotopic splitting of copper active atomic levels, the temporal behavior of the spectral structure of amplified spontaneous emission at 510.6 nm line was calculated. The spectral line shapes of 510.6 and 578.2 nm laser lines were measured and compared with the calculated results at different experimental configurations, i.e., without cavity mirrors, with the back mirror, and with cavity mirrors. The results of the 578.2 nm line revealed that the mode competition was involved in the formation of laser oscillation.     

Causality and Bell-CHSH Inequalities Violations in?Entanglement Swapping Schemes

An ample amount of evidence supporting the violation of locality has been presented in quantum theory. If such an instantaneous influencing is possible, it is worth considering the possibility of a causality violation in quantum theory, i.e., a future event influencing the past. Motivated by the delayed-choice gedanken experiment, we provide two protocols of entanglement swapping that are subtle in involving causality conditions. In particular, we present protocols in which locality constraints are identical to causality conditions and closely examine Bell-inequalities violation based on these protocols. These protocols will provide a clear picture of how quantum theory still preserves causality while locality is violated. We also discuss a potential threat to the entanglement-based key distribution schemes.     

Detection of combined changes in interaural time and intensity differences: Segregated mechanisms in cue type and in operating frequency range?

Although physiological studies have revealed segregated binaural pathways, namely the medial and lateral superior olives, it is unclear whether the human auditory system has separate mechanisms for different cue types (interaural time and intensity differences; ITD and IID, respectively) and for operating frequency ranges. This study hypothesized "channels" for ITD and IID processing, and examined channel interaction at low and high frequencies based on the signal detection theory. The stimuli were a 125- or 500-Hz tone and a 4-kHz tone amplitude-modulated with a half-wave-rectified 125-Hz sinusoid, presented dichotically with various baseline ITDs and IIDs. The detectability indices, d('), for ITD and IID changes, imposed individually or simultaneously in the same direction, were derived from the results of a forced-choice task. The degree of channel interaction was estimated by comparing d(') for combined cues with those for individual cues. The estimated interaction showed little effect of baseline ITD or IID. The results generally exhibited nonzero interaction, indicating that the cue processes are not completely independent. The interaction was stronger for high frequencies than for low frequencies. The results can be interpreted as indicating the involvement of different binaural mechanisms for different frequency regions.     

Are particle and photon tunneling and filling in barriers local or non-local phenomena?

It is shown that particle and photon tunneling exhibits a non-local behaviour. This is also true for the wave filling in a semiclosed barrier with a dead stopper. In this connection, we discuss and define for the first time the penetration time of such a barrier in the wave-packet approach.     

Magnetic behavior in UFe?Zn?? and URu?Zn?? single crystals

The magnetic, electrical transport and thermodynamic properties of the compounds UFe?Zn?? and URu?Zn?? were studied on single-crystalline specimens over wide ranges of temperature and magnetic field. The results indicate that the two ternaries are paramagnetic moderately enhanced heavy fermion systems. Their physical behavior is governed predominantly by the hybridization of uranium 5f orbitals with electronic states of ligands, which brings about considerable delocalization of the 5f states.     

Who is whistling? Localizing and identifying phonating dolphins in captivity

Acoustic communication through whistles is well developed in dolphins. However, little is known on how dolphins are using whistles because localizing the sound source is not an easy task. In the present study, the hyperbola method was used to localize the sound source using a two-hydrophone array. A combined visual and acoustic method was used to determine the identity of the whistling dolphin. In an aquarium in Mexico City where two adult bottlenose dolphins were housed we recorded 946 whistles during 22 days. We found that a dolphin was located along the calculated hyperbola for 72.9% of the whistles, but only for 60.3% of the whistles could we determine the identity of the whistling dolphin. However, sometimes it was possible to use other cues to identify the whistling dolphin. It could be the animal that performed a behavior named “observation” at the time whistling occurred or, when a whistle was only recorded on one channel, the whistling dolphin could be the animal located closest to the hydrophone that captured the whistle. Using these cues, 15.4% of the whistles were further ascribed to either dolphin to obtain an overall identification efficiency of 75.7%. Our results show that a very simple and inexpensive acoustic setup can lead to a reasonable number of identifications of the captive whistling dolphin: this is the first study to report such a high rate of whistles identified to the free swimming, captive dolphin that produced them. Therefore, we have a data set with which we can investigate how dolphins are using whistles. This method can be applied in other aquaria where a small number of dolphins is housed; though, the actual efficiency of this method will depend on how often dolphins spend time next to each other and on the reverberation conditions of the pool.     

Partial Traces in Decoherence and in Interpretation: What Do Reduced States Refer to?

The interpretation of the concept of reduced state is a subtle issue that has relevant consequences when the task is the interpretation of quantum mechanics itself. The aim of this paper is to argue that reduced states are not the quantum states of subsystems in the same sense as quantum states are states of the whole composite system. After clearly stating the problem, our argument is developed in three stages. First, we consider the phenomenon of environment-induced decoherence as an example of the case in which the subsystems interact with each other; we show that decoherence does not solve the measurement problem precisely because the reduced state of the measuring apparatus is not its quantum state. Second, the non-interacting case is illustrated in the context of no-collapse interpretations, in which we show that certain well-known experimental results cannot be accounted for due to the fact that the reduced states of the measured system and the measuring apparatus are conceived as their quantum states. Finally, we prove that reduced states are a kind of coarse-grained states, and for this reason they cancel the correlations of the subsystem with other subsystems with which it interacts or is entangled.     

Modeling of ultrashort pulsed laser ablation in water and?biological tissues in cylindrical coordinates

A numerical model combining the ultrafast radiative transfer and the ablation rate equation is proposed to investigate the transient process of plasma formation during laser plasma-mediated ablation of absorbing-scattering media. The focus beam propagation governed by the transient equation of radiative transfer is solved by the transient discrete ordinates method to account for scattering effect. The temporal evolution of the free-electron density governed by the ablation rate equation is calculated using a fourth-order Runge–Kutta method to examine various effects such as the multiphoton, chromophore, and cascade ionizations. The threshold of optical breakdown, the shape and maximum length of plasma growth for ablation in water are predicted by the present model and compared with the existing experimental and numerical data. Good agreements have been found. The dynamic process of plasma formation for ablation in the model skin tissue is simulated. A parametric study with regard to the influences of the ionization energy and the critical free-electron density on the ablation threshold of the tissue is conducted.     

Does gravity cause load-bearing bridges in colloidal and granular systems?

We study structures which can bear loads, "bridges", in particulate packings. To investigate the relationship between bridges and gravity, we experimentally determine bridge statistics in colloidal packings. We vary the effective magnitude and direction of gravity, volume fraction, and interactions, and find that the bridge size distributions depend only on the mean number of neighbors. We identify a universal distribution, in agreement with simulation results for granulars, suggesting that applied loads merely exploit preexisting bridges, which are inherent in dense packings.     

Can MBPT and QED be merged in a systematic way?

The possiblities of merging QED with the standard many-body perturbation theory (MBPT) for atomic systems in a rigorous and systematic way are analysed. Time-dependent MBPT, based on the time-evolution operator, a technique well developed particularly in nuclear theory, is used and somewhat reformulated to be consistent with the covariant QED formalism. An effective QED Hamiltonian, free from singularities, is constructed. The procedure can be applied to degenerate and quasi-degenerate systems (extended model space), which is not possible with the standard QED technique based upon the S-matrix formulation. To include in the model space closely lying energy levels, such as fine-structure levels, can have a dramatic effect on the convergence rate. The electron-electron interaction is investigated in detail, and it is shown that it can be separated into irreducible multi-photon interactions, which in principle can be iterated as in standard MBPT. Singularities do not appear, and a simple procedure for evaluating residual finite contributions is described. Comparison is made with the closely related Green's function technique. The procedure is presently being tested on the fine-structure levels of He-like ions.     

Nonholonomic Ricci Flows, Exact Solutions in Gravity, and?Symmetric and Nonsymmetric Metrics

We provide a proof that nonholonomically constrained Ricci flows of (pseudo) Riemannian metrics positively result into nonsymmetric metrics (as explicit examples, we consider flows of some physically valuable exact solutions in general relativity). There are constructed and analyzed three classes of solutions of Ricci flow evolution equations defining nonholonomic deformations of Taub NUT, Schwarzschild, solitonic and pp-wave symmetric metrics into nonsymmetric ones.     

The Dynamical Behaviour of Test Particles in?a?Quasi-spherical Spacetime and the?Physical Meaning?of?Superenergy

We calculate the instantaneous proper radial acceleration of test particles (as measured by a locally defined Lorentzian observer) in a Weyl spacetime, close to the horizon. As expected from the Israel theorem, there appear some bifurcations with respect to the spherically symmetric case (Schwarzschild) which are explained in terms of the behaviour of the superenergy, bringing out the physical relevance of this quantity in the study of general relativistic systems.     

Why are large cities faster? Universal scaling and self-similarity in urban organization and dynamics

Cities have existed since the beginning of civilization and have always been intimately connected with humanity's cultural and technological development. Much about the human and social dynamics that takes place is cities is intuitively recognizable across time, space and culture; yet we still do not have a clear cut answer as to why cities exist or to what factors are critical to make them thrive or collapse. Here, we construct an extensive quantitative characterization of the variation of many urban indicators with city size, using large data sets for American, European and Chinese cities. We show that social and economic quantities, characterizing the creation of wealth and new ideas, show increasing returns to population scale, which appear quantitatively as a power law of city size with an exponent β≃ 1.15 > 1. Concurrently, quantities characterizing material infrastructure typically show economies of scale, namely β≃ 0.8 < 1. The existence of pervasive scaling relations across city size suggests a universal social dynamics common to all cities within an urban system. We sketch some of their general ingredients, which include the acceleration of social life and a restructuring of individual social networks as cities grow larger. We also build simple dynamical models to show that increasing returns in wealth and innovation can fuel faster than exponential growth, which inexorably lead to crises of urban organization. To avoid them we show that growth may proceed in cycles, separated by major urban adaptations, with the unintended consequence that the duration of such cycles decreases with larger urban population size and is now estimated to be shorter than a human lifetime.     

A New Kind of Bipartite Coherent-Entangled State and?Its?Applications in Quantum Optics

A new kind of bipartite coherent-entangled state (CES) is introduced in the two-mode Fock space which exhibits the properties of both coherent state and entangled state. The set of CESs make up a complete and partly nonorthogonal representation. A simple experimental scheme to produce the CES is proposed by using a beam splitter. Some applications of the CES are also presented in quantum optics.