Quantum Dynamical Effects as a Singular Perturbation for Observables in Open Quasi-Classical Nonlinear Mesoscopic Systems

We review our results on a mathematical dynamical theory for observables for open many-body quantum nonlinear bosonic systems for a very general class of Hamiltonians. We show that non-quadratic (nonlinear) terms in a Hamiltonian provide a singular "quantum" perturbation for observables in some "mesoscopic" region of parameters. In particular, quantum effects result in secular terms in the dynamical evolution, that grow in time. We argue that even for open quantum nonlinear systems in the deep quasi-classical region, these quantum effects can survive after decoherence and relaxation processes take place. We demonstrate that these quantum effects in open quantum systems can be observed, for example, in the frequency Fourier spectrum of the dynamical observables, or in the corresponding spectral density of noise. Estimates are presented for Bose-Einstein condensates, low temperature mechanical resonators, and nonlinear optical systems prepared in large amplitude coherent states. In particular, we show that for Bose-Einstein condensate systems the characteristic time of deviation of quantum dynamics for observables from the corresponding classical dynamics coincides with the characteristic time-scale of the well-known quantum nonlinear effect of phase diffusion.Comment: changed content

Individuals behavior regarding open WI-FI networks

As WI-FI became commercially available and accepted by consumers into their homes and businesses the concept of Internet access was quickly associated to this technology. The mentioned occurred due to how the technology was primordially advertised, as a convenient accessory that enables users to have a cable free experience when dealing with their home network (primary created to distribute Internet access). This perception about the technology drives unwary and low tech individuals to believe that all open WIFI networks correspond to Internet access and so they do not hesitate in order to connect to these networks. The actions of these individuals in most cases could result in disappointment because they end up not getting Internet access and in other cases some networks could be deployed in order to take advantage of the individuals by making them subjects to attacks or some kind of harm. In order to understand the actions of these individuals this project presents a methodology which aims to capture the thoughts and perception of these individuals when facing open WI-FI networks. The methodology involved the creation of an open WI-FI network scenario with which the individuals interacted, and through this interaction information regarding their behavior was obtained by using a survey questionnaire. From analyzing the gathered information it was discovered that individuals are conscious about WI-FI technology in a vague manner, they really do not care about the details as long as it works for them, they assume security responsibility which tends to be clouded by too much trust

The Raman spectra of serine and 3,3-dideutero-serine in aqueous solution

The Raman spectra of serine [[alpha]-amino-[beta]-hydroxypropionic acid; HOCH2CH(NH3)+COO-] and 3,3-dideutero-serine [HOCD2CH(NH3)+COO-] in aqueous solution were studied in the range 4000-300 cm-1. The data obtained for the deuterated compound are novel and provide compelling evidence that previously reported assignments for the undeuterated amino acid should be revised.http://www.sciencedirect.com/science/article/B6THW-4KNMB16-1/1/19da7b30f32b5efeacb053228a66c4a

Infrared spectroscopic studies of novel hydroxybisphosphonates and molecular modelling of their interaction with hydroxyapatite

Bisphosphonates (BPs) are a class of drugs widely used in the treatment of several metabolic bone disorders associated with increased bone resorption, including osteoporosis, Paget’s disease and metastic bone disease [1]. Although BPs can directly inhibit the cellular activity of osteoclasts, their ability to adsorb to bone mineral is also an important factor in determining their potency and duration of action [2]. In this study, we performed a molecular modelling analysis, by molecular mechanics, of the molecular structures of hydroxy(1H-indazol-3-yl)methylenediphosphonic acid (BP1; Figure 1a) and hydroxy(1-methyl-1H-indazol-3-yl)methylenediphosphonic acid (BP2; Figure 1b) and examined their interactions with hydroxyapatite (HA) by energy-minimising 50 different orientations for judiciously selected low energy conformers of each ligand at 10 Å from the mineral surface. We also calculated the vibrational spectra for each BP with semiempirical methods and compared then with FTIR spectra obtained experimentaly. The calculated interaction energies of the studied BPs with HA suggests that BP2 interacts stronger with hydroxyapatite than BP1. These results are in agreement with in vitro and in vivo studies of the 153Sm-BPs complexes. Complex 153Sm-BP2 showed, in vitro, higher HA binding than complex 153Sm-BP1. In vivo studies showed different farmacokinetics parameters with complex 153Sm-BP2 presenting initial higher levels of bone uptake than complex 153Sm-BP1, which concentration is increasing during the 24 h period studied

Quantum theory of transient transport in semiconductors: A Monte Carlo approach

A new Monte Carlo method is presented for the evaluation of the density matrix from the solution of the Liouville–von Neumann equation for an ensemble of noninteracting electrons in a semiconductor crystal. The method is applied to the study of the electron transient response to a high external electric field in Si and to the relaxation of photoexcited electrons in GaAs in absence of external electric fields. The phonon population is always assumed at equilibrium, but no assumptions are made about the strength of the electron-phonon interaction. Results show that typical quantum features such as energy-nonconserving transitions, intracollisional field effect, and multiple collisions change the very first transient of the system with respect to a semiclassical description

Infrared and Raman spectroscopic characterization of the hydrogen-bonding network in l-serine crystal

The IR spectra (4000-400 cm-1) of neat and isotopically substituted (ND/OD <= 10% D and [congruent with]30% D) polycrystalline l-serine ([alpha]-amino-[beta]-hydroxypropionic acid; HO-CH2-CH(NH3)+-COO-) were recorded in the temperature range 300-10 K and assigned. The isotopic-doping/low-temperature methodology, which allows for decoupling of individual proton vibrational modes from the crystal bulk vibrations, was used for estimating the lengths and energies of the different H-bonds present in l-serine crystal. To this end, the frequency shifts observed in both the NH/OH stretching and out-of-plane bending spectral regions (relatively to reference values for these vibrations in non-hydrogen-bonded l-serine molecules) were used, together with previously developed empirical correlations between these spectral parameters and the H-bond properties. In addition, the room-temperature Raman spectrum (4000-150 cm-1) of a single crystal of neat l-serine was also recorded and interpreted. A systematic comparison was made between the spectroscopic data obtained currently for l-serine and previously for dl-serine, revealing that the vibrational spectra of the two crystals reflect well the different characteristics of their hydrogen-bond networks, and also correlate accurately with the different susceptibility of the two crystals to pressure-induced strain.http://www.sciencedirect.com/science/article/B6THW-4K4WMR3-2/1/211ac428c09ebc9eb45cf3b81d93fcb

Molecular structure and charge density analysis of p-methoxybenzoic acid (anisic acid)

A concerted X-ray and ab initio SCF-MO study of the structure and charge density of p-methoxybenzoic acid (anisic acid) is reported. An extensive X-ray data set (7401 reflections) was measured on a single crystal using Mo Kα radiation and the structure refined with 2121 unique reflections, leading to a final R(F)-factor of 0.047 calculated for reflections with I>2σ. The molecular geometry of crystalline anisic acid, where the molecules dimerize via a moderately strong CO–H⋯O hydrogen bond, is compared with that of the isolated molecule, resulting from SCF-MO ab initio calculations. A topological analysis of the molecular charge density was performed using Bader's method to gain insight into the dominant intra- and intermolecular interactions in this compound. In particular, the effects of the substituents on the observed distortions of the benzene ring were investigated as well as the internal rotation of the methyl group

Molecular structure of S-ethylthioacrylate Combined vibrational spectroscopic and abinitioSCF-MO study

Ab initio 6-31G* SCF-MO calculations have been carried out on S-ethyl thioacrylate [CH2CHC(O)SCH2CH3]. Fully optimized geometries, relative stabilities, dipole moments and harmonic force fields for several conformers of this molecule have been determined and the results compared with those for similar molecules. Together with FTIR and Raman spectroscopic data, the theoretical results demonstrate that S-ethyl thioacrylate exists in two different conformations about the Cα–C bond (the s-cis and s-trans forms, with CC–CO dihedral angles equal to 0° and 180°, respectively); the s-cis conformation being more stable than the s-trans form by ca. 6 kJ mol-1 for the isolated molecule. Comparison of the experimental and theoretical vibrational spectra confirms that, as concluded from our previous study on the analogous trans-S-ethyl thiocrotonate molecule (R. Fausto, P. J. Tonge and P. R. Carey, J. Chem. Soc., FaradayTrans., 1994, 90, 3491), the presence of the s-trans isomer of an α,β-unsaturated thioester can be successfully monitored by the IR band at ca. 1170 cm-1, ascribed to the Cα–C stretching mode of this form. In addition, we were also able to identify some IR bands sensitive to the conformation of the ethyl group that may be used as spectroscopic probes to study conformational equilibria associated with this internal degree of freedom in more complex S-ethyl thioester

Low-temperature infrared spectra and hydrogen bonding in polycrystalline dl-serine and deuterated derivatives

The FT-IR spectra of polycrystalline dl-serine [[alpha]-amino-[beta]-hydroxypropionic acid; HO-CH2-CH(NH3)+-COO-] and isotopically substituted [ND/ODAlcohol (90% D); CD2 (>98% D)] dl-serine were recorded in the range 4000-500 cm-1 in the temperature range 300-10 K, and fully assigned. The isotopic-doping/low-temperature methodology, which allows for decoupling of individual proton vibrational modes from the crystal bulk vibrations, was used to estimate the energies of the different H-bonds present in dl-serine crystal. To this end, the frequency shifts observed in both the NH/OH stretching and out-of-plane bending spectral regions (relatively to reference values for these vibrations in non-hydrogen-bonded dl-serine molecules) were used, together with previously developed empirical correlations. The results are compared with available structural data on this amino acid.http://www.sciencedirect.com/science/article/B6THW-4J91R39-2/1/f8f35f435466c8a5204879d330cbade