Realistic clocks, universal decoherence, and the black hole information paradox

Ordinary quantum mechanics is formulated on the basis of the existence of an ideal classical clock external to the system under study. This is clearly an idealization. As emphasized originally by Salecker and Wigner and more recently by others, there exist limits in nature to how "classical" even the best possible clock can be. With realistic clocks, quantum mechanics ceases to be unitary and a fundamental mechanism of decoherence of quantum states arises. We estimate the rate of the universal loss of unitarity using optimal realistic clocks. In particular, we observe that the rate is rapid enough to eliminate the black hole information puzzle: all information is lost through the fundamental decoherence before the black hole can evaporate. This improves on a previous calculation we presented with a suboptimal clock in which only part of the information was lost by the time of evaporation.     

Study of the distribution of trace elements in six species of marine organisms of the Ligurian Sea (north-western Mediterranean)--comparison with previous findings

This paper presents the results of the determination of several trace elements (total and organic mercury, selenium, cadmium, lead, copper, manganese and zinc) in six species of marine organisms (Nephrops norvegicus, Engraulis encrasicolus, Mullus barbatus, Mullus surmuletus, Merluccius merluccius, and Sarda sarda), sampled in the Ligurian Sea (North-West Mediterranean) during a three-year period, from 1998 to 2000. The species analysed (388 samples) are the same studied in previous investigations in the same area (260 samples), so that a comparison with previous data measured in 1977-1986 was possible, in order to evaluate the variation of the marine environment in that area with respect to that period. Biological parameters of the specimens (length and weight of the individuals, and also sex for N. norvegicus) were taken into account in order to make possible the comparison between old and new data. No appreciable variation occurred in the levels of the trace elements analysed during the period 1998-2000, while the comparison with the data collected about 25 years ago showed a decrease of all the elements except for selenium.     

Many-body perturbation theory using the density-functional concept: beyond the GW approximation

We propose an alternative formulation of many-body perturbation theory that uses the density-functional concept. Instead of the usual four-point integral equation for the polarizability, we obtain a two-point one, which leads to excellent optical absorption and energy-loss spectra. The corresponding three-point vertex function and self-energy are then simply calculated via an integration, for any level of approximation. Moreover, we show the direct impact of this formulation on the time-dependent density-functional theory. Numerical results for the band gap of bulk silicon and solid argon illustrate corrections beyond the GW approximation for the self-energy.     

Self-organized ordering of nanostructures produced by ion-beam sputtering

We study the self-organized ordering of nanostructures produced by ion-beam sputtering of targets amorphizing under irradiation. By introducing a model akin to models of pattern formation in aeolian sand dunes, we extend consistently the current continuum theory of erosion by IBS. We obtain new nonlinear effects responsible for the in-plane ordering of the structures, whose strength correlates with the degree of ordering found in experiments. Our results highlight the importance of redeposition and surface viscous flow to this nanopattern formation process.     

Dihydropyridines in MCRs. Tandem processes leading to modular tetrahydroquinoline systems with up to 6 diversity elements

An efficient, modular method for the synthesis of highly substituted tetrahydroquinoline systems is described. The Lewis acid catalyzed interaction of dihydropyridines with glyoxalate and anilines affords the heterocyclic parent systems in good yields. Tandem one-pot processes allow the incorporation of additional components: a preliminary nucleophilic attack on pyridinium salts generates the reactive dihydropyridine in situ, and subsequent electrophilic reactions on the secondary amine complete the assembly of the final targets, which have up to 6 diversity points.     

Asymptotic Analysis of Reacting Materials with Saturated Explosion. I. Low-Frequency Waves

We derive and study asymptotic equations describing the behavior of low-frequency disturbances in a chemically reacting gas, whose amplitude is inversely proportional to the large activation energy of the reaction. We make an assumption of small heat release, so that fuel depletion is included in the model at leading order. For homogeneous combustion, introducing this assumption removes the thermal-runaway singularity which always forms in models previously used. We demonstrate that for spatially varying solutions, wave-propagation effects permit a singularity still to form, if the initial data has a step discontinuity with amplitude larger than a critical value. We suggest that appearance of this singularity in the model always signifies the birth of a detonation wave, and we describe the evolution of the wave beyond the singularity time.     

The occurrence of sequence patterns in ergodic Markov chains

The occupation measure identity is used to derive the expected waiting time for the first occurrence of a fixed finite pattern in a sequence of observations generated by an ergodic Markov chain.     

Carbon nanotube–polybithiophene photovoltaic devices with high open‐circuit voltage

We report the preparation of photovoltaic devices using modified single wall carbon nanotubes, SWNTs. Devices are produced stacking on top of fluorine‐doped tin‐oxide, an electrochemically deposited polybithiophene layer, a layer of SWNT blended with poly(3‐octylthiophene) and an evaporated top metal contact, Ca/Al or Al. Ca/Al‐top‐electrode devices achieve open‐circuit voltages of 1.81 V and average power conversion efficiency of 1.48% at irradiance of 15.5 W m^–2, spectrally distributed following AM1.5. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Application of a catalyst-free Domino Mannich/Friedel-Crafts alkylation reaction for the synthesis of novel tetrahydroquinolines of potential antitumor activity

A useful and efficient method to construct diversely substituted 1,2,3,4-tetrahydroquinolines in good to excellent yields has been developed through a catalyst-free Domino Mannich and intramolecular Friedel-Crafts alkylation reactions of N-arylamines with paraformaldehyde and electron-rich olefins via the formation of N-aryl-N-alkylmethyleneiminium ions as the key intermediates to afford the target products. Nine of the new compounds were evaluated in the US National Cancer Institute (NCI), where compound 5f (R1?=?6-MeO, R2?=?p-ClC6H4 and X?=?pyrrolidin-2-onyl) presented a remarkable activity against 57 cancer cell lines, with the most important GI50 values ranging from 1.46 to 8.28?μM from in vitro assays. Further studies performed over the active compound 5f on HCT116 colon cancer cells indicated that its effect on cell death is exerted through a cell cycle arrest (S phase) in a dose dependent manner, as well as suppression on the cell proliferation process.