Liquid-gas phase transition in Bose-Einstein condensates with time evolution

We study the effects of a repulsive three-body interaction on a system of trapped ultracold atoms in a Bose-Einstein condensed state. The stationary solutions of the corresponding s-wave nonlinear Schrödinger equation suggest a scenario of first-order liquid-gas phase transition in the condensed state up to a critical strength of the effective three-body force. The time evolution of the condensate with feeding process and three-body recombination losses has a different characteristic pattern. Also, the decay time of the dense (liquid) phase is longer than expected due to strong oscillations of the mean-squared radius.

Chaos in collapsing Bose-condensed gas

We reinvestigate the dynamics of the grow and collapse of Bose-Einstein condensates in a system of trapped ultracold atoms with negative scattering lengths, and found a new behavior in the long time scale evolution: the number of atoms can go far beyond the static stability limit. The condensed state is described by the solution of the time-dependent nonlinear Schrödinger equation, in a model that includes atomic feeding and three-body dissipation. Our results for the model show that, by changing the feeding parameter and when a substantial depletion of the ground-state exists, a chaotic behavior is found. We consider a criterion proposed by Deissler and Kaneko [Phys. Lett. A 119, 397 (1987)] to diagnose spatiotemporal chaos. ©2000 The American Physical Society.

Filmes evaporados de ftalocianina de cobalto: arquitetura molecular e aplicação sensorial

Pós-graduação em Ciência e Tecnologia de Materiais - FC

iCONVERT: an integrated device for the UV-assisted determination of H2S via mid-infrared gas sensors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

An introductory informatics theoretical framework, based on an integrable lattice model using quantized function algebras, for studying DNA-ionized gas interaction system

Usually we observe that Bio-physical systems or Bio-chemical systems are many a time based on nanoscale phenomenon in different host environments, which involve many particles can often not be solved explicitly. Instead a physicist, biologist or a chemist has to rely either on approximate or numerical methods. For a certain type of systems, called integrable in nature, there exist particular mathematical structures and symmetries which facilitate the exact and explicit description. Most integrable systems, we come across are low-dimensional, for instance, a one-dimensional chain of coupled atoms in DNA molecular system with a particular direction or exist as a vector in the environment. This theoretical research paper aims at bringing one of the pioneering ‘Reaction-Diffusion’ aspects of the DNA-plasma material system based on an integrable lattice model approach utilizing quantized functional algebras, to disseminate the new developments, initiate novel computational and design paradigms.

Obtenção e caracterização molecular e fisiológica de plantas de soja contendo o gene AtGolS2 sob déficit hídrico

Pós-graduação em Agronomia (Genética e Melhoramento de Plantas) - FCAV

Graphene modification with gold nanoparticles using the gas aggregation technique

Gold nanoparticles (Au-NPs) were deposited on single layer graphene (SLG) and few layers graphene (FLG) by applying the gas aggregation technique, previously adapted to a 4-gun commercial magnetron sputtering system. The samples were supported on SiO2 (280 nm)/Si substrates, and the influence of the applied DC power and deposition times on the nanoparticle-graphene system was investigated by Confocal Raman Microscopy. Analysis of the G and 2D bands of the Raman spectra shows that the integrated intensity ratio (I-2D/I-G) was higher for SLG than for FLG. For the samples produced using a sputtering power of 30W, the intensity (peak height) of the G and 2D bands increased with the deposition time, whereas for those produced applying 60W the peak heights of the G and 2D bands decreased with the deposition time. This behaviour was ascribed to the formation of larger Au-NPs aggregates in the last case. A significant increase of the Full Width Half Maximum (FWHM) of the G band for SLG and FLG was also observed as a function of the DC power and deposition time. Surprisingly, the fine details of the Raman spectra revealed an unintentional doping of SLG and FLG accompanying the increase of size and aggregation of the Au-NPs. (C) 2011 Elsevier B.V. All rights reserved.

Gas-phase reactivity of protonated 2-oxazoline derivatives: mass spectrometry and computational studies

RATIONALE: Oxazolines have attracted the attention of researchers worldwide due to their versatility as carboxylic acid protecting groups, chiral auxiliaries, and ligands for asymmetric catalysis. Electrospray ionization tandem mass spectrometric (ESI-MS/MS) analysis of five 2-oxazoline derivatives has been conducted, in order to understand the influence of the side chain on the gas-phase dissociation of these protonated compounds under collision-induced dissociation (CID) conditions. METHODS: Mass spectrometric analyses were conducted in a quadrupole time-of-flight (Q-TOF) spectrometer fitted with electrospray ionization source. Protonation sites have been proposed on the basis of the gas-phase basicity, proton affinity, atomic charges, and a molecular electrostatic potential map obtained on the basis of the quantum chemistry calculations at the B3LYP/6-31 + G(d, p) and G2(MP2) levels. RESULTS: Analysis of the atomic charges, gas-phase basicity and proton affinities values indicates that the nitrogen atom is a possible proton acceptor site. On the basis of these results, two main fragmentation processes have been suggested: one taking place via neutral elimination of the oxazoline moiety (99 u) and another occurring by sequential elimination of neutral fragments with 72 u and 27 u. These processes should lead to formation of R+. CONCLUSIONS: The ESI-MS/MS experiments have shown that the side chain could affect the dissociation mechanism of protonated 2-oxazoline derivatives. For the compound that exhibits a hydroxyl at the lateral chain, water loss has been suggested to happen through an E2-type elimination, in an exothermic step. Copyright (C) 2012 John Wiley & Sons, Ltd.

Effect of hydrogen bond formation on the elastic molecular scattering: a case study with methanol

Rayleigh optical activities of small hydrogen-bonded methanol clusters containing two to five molecules are reported. For the methanol trimer, tetramer, and pentamer both cyclic and linear structures are considered. After the geometry optimizations, the dipole moments and the dipole polarizabilities (mean, interaction, and anisotropic components) are calculated using HF, MP2 and DFT (B3LYP, B3P86 and BH&HLYP) with aug-cc-pVDZ extended basis set. The polarizabilities are used to analyse the depolarization ratios and the Rayleigh scattering activities. The variations in the activity and in the depolarization for Rayleigh scattered radiation with the increase in the cluster size for both cyclic and linear structures are analysed.

Structure and electronic properties of hydrated mesityl oxide: a sequential quantum mechanics/molecular mechanics approach

The hydration of mesityl oxide (MOx) was investigated through a sequential quantum mechanics/molecular mechanics approach. Emphasis was placed on the analysis of the role played by water in the MOx syn-anti equilibrium and the electronic absorption spectrum. Results for the structure of the MOx-water solution, free energy of solvation and polarization effects are also reported. Our main conclusion was that in gas-phase and in low-polarity solvents, the MOx exists dominantly in syn-form and in aqueous solution in anti-form. This conclusion was supported by Gibbs free energy calculations in gas phase and in-water by quantum mechanical calculations with polarizable continuum model and thermodynamic perturbation theory in Monte Carlo simulations using a polarized MOx model. The consideration of the in-water polarization of the MOx is very important to correctly describe the solute-solvent electrostatic interaction. Our best estimate for the shift of the pi-pi* transition energy of MOx, when it changes from gas-phase to water solvent, shows a red-shift of -2,520 +/- 90 cm(-1), which is only 110 cm(-1) (0.014 eV) below the experimental extrapolation of -2,410 +/- 90 cm(-1). This red-shift of around -2,500 cm(-1) can be divided in two distinct and opposite contributions. One contribution is related to the syn -> anti conformational change leading to a blue-shift of similar to 1,700 cm(-1). Other contribution is the solvent effect on the electronic structure of the MOx leading to a red-shift of around -4,200 cm(-1). Additionally, this red-shift caused by the solvent effect on the electronic structure can by composed by approximately 60 % due to the electrostatic bulk effect, 10 % due to the explicit inclusion of the hydrogen-bonded water molecules and 30 % due to the explicit inclusion of the nearest water molecules.

Structure and anomalous solubility for hard spheres in an associating lattice gas model

In this paper we investigate the solubility of a hard-sphere gas in a solvent modeled as an associating lattice gas. The solution phase diagram for solute at 5% is compared with the phase diagram of the original solute free model. Model properties are investigated both through Monte Carlo simulations and a cluster approximation. The model solubility is computed via simulations and is shown to exhibit a minimum as a function of temperature. The line of minimum solubility (TmS) coincides with the line of maximum density (TMD) for different solvent chemical potentials, in accordance with the literature on continuous realistic models and on the "cavity" picture. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4743635]

Selectivity and Mechanisms Driven by Reaction Dynamics: The Case of the Gas-Phase OH-+CH3ONO2 Reaction

Well-established statistical approaches such as transition-state theory based on high-level calculated potential energy profiles are unable to account for the selectivity observed in the gas-phase OH- + CH3ONO2 reaction. This reaction can undergo bimolecular nucleophilic displacement at either the carbon center (S(N)2@C) or the nitrogen center (S(N)2@N) as well as a proton abstraction followed by dissociation (E(CO)2) pathway. Direct dynamics simulations yield an S(N)2:E(CO)2 product ratio in close agreement with experiment and show that the lack of reactivity at the nitrogen atom is due to the highly negative electrostatic potential generated by the oxygen atoms in the ONO2 group that scatters the incoming OH-. In addition to these dynamical effects, the nonstatistical behavior of these reactions is attributed to the absence of equilibrated reactant complexes and to the large number of recrossings, which might be present in several ion-molecule gas-phase reactions.

Movement of NH3 through the human urea transporter B: a new gas channel

Aquaporins and Rh proteins can function as gas (CO2 and NH3) channels. The present study explores the urea, H2O, CO2, and NH3 permeability of the human urea transporter B (UT-B) (SLC14A1), expressed in Xenopus oocytes. We monitored urea uptake using [14C]urea and measured osmotic water permeability (Pf) using video microscopy. To obtain a semiquantitative measure of gas permeability, we used microelectrodes to record the maximum transient change in surface pH (∆pHS) caused by exposing oocytes to 5% CO2/33 mM HCO3- (pHS increase) or 0.5 mM NH3/NH4+ (pHS decrease). UT-B expression increased oocyte permeability to urea by >20-fold, and Pf by 8-fold vs. H2O-injected control oocytes. UT-B expression had no effect on the CO2-induced ∆pHS but doubled the NH3-induced ∆pHS. Phloretin reduced UT-B-dependent urea uptake (Jurea * ) by 45%, Pf * by 50%, and (- ∆pHS * )NH3 by 70%. p-Chloromercuribenzene sulfonate reduced Jurea * by 25%, Pf * by 30%, and (∆pHS * )NH3 by 100%. Molecular dynamics (MD) simulations of membrane-embedded models of UT-B identified the monomeric UT-B pores as the main conduction pathway for both H2O and NH3 and characterized the energetics associated with permeation of these species through the channel. Mutating each of two conserved threonines lining the monomeric urea pores reduced H2O and NH3 permeability. Our data confirm that UT-B has significant H2O permeability and for the first time demonstrate significant NH3 permeability. Thus the UTs become the third family of gas channels. Inhibitor and mutagenesis studies and results of MD simulations suggest that NH3 and H2O pass through the three monomeric urea channels in UT-B.

Polymorphs solvates and co-crystals of molecular materials

The scope of my research project is to produce and characterize new crystalline forms of organic compounds, focusing the attention on co-crystals and then transferring these notions on APIs to produce co-crystals of potential interest in the pharmaceutical field. In the first part of this work co-crystallization experiments were performed using as building blocks the family of aliphatic dicarboxylic acids HOOC-(CH2)n-COOH, with n= 2-8. This class of compounds has always been an object of study because it is characterized by an interesting phenomenon of alternation of melting points: the acids with an even number of carbon atoms show a melting point higher than those with an odd one. The acids were co-crystallized with four dipyridyl molecules (formed by two pyridine rings with a different number of bridging carbon atoms) through the formation of intermolecular interactions N•••(H)O. The bases used were: 4,4’-bipyridine (BPY), 1,2-bis(4-pyridyl)ethane (BPA), 1,2-(di-4-pyridyl)ethylene (BPE) and 1,2-bis(4-pyridyl)propane (BPP). The co-crystals obtained by solution synthesis were characterized by different solid-state techniques to determine the structure and to see how the melting points in co-crystals change. In the second part of this study we tried to obtain new crystal forms of compounds of pharmaceutical interest. The APIs studied are: O-desmethylvenlafaxine, Lidocaine, Nalidixic Acid and Sulfadiazine. Each API was subjected to Polymorph Screening and Salt/Co-crystal Screening experiments to identify new crystal forms characterized by different properties. In a typical Salt/Co-crystal Screening the sample was made to react with a co-former (solid or liquid) through different methods: crystallization by solution, grinding, kneading and solid-gas reactions. The new crystal forms obtained were characterized by different solid state techniques (X-ray single crystal diffraction, X-ray powder diffraction, Differential Scanning Calorimetry, Thermogravimetric Analysis, Evolved gas analysis, FT-IR – ATR, Solid State N.M.R).

Understanding The Physiological, Biochemical, and Molecular Mechanisms of Salinity Tolerance in Strawberry Cultivars and in HvTPK1-Overexpressed Barley

The research was carried out to investigate of main elements of salt stress response in two strawberry cultivars, Elsanta and Elsinore. Plants were grown under 0, 10, 20 and 40 mM NaCl for 80 days. Salinity dramatically affected growth in both cultivars, although Elsinore appeared to be more impaired than Elsanta. Moreover a significant reduction of leaf photosynthesis, evaporation, and stomatal conductance was recorded 24 hrs after the stress was applied in both cultivars, whereas physiological functions were differentially restored after acclimation. However, cv. Elsanta had more efficient leaf gas exchange and water status than cv. Elsinore. In general, Fruit yield reduced upon salinization, wheares fruit quality concerning fruit taste, aroma, appearance, total soluble solids and titratable acidity, did not change but rather was enhanced under moderate salinity. On the other hand fruit quality was impaired at severe salt stress. Fruit antioxidant content and antioxidant capacity were enhanced significantly by increasing salt concentration in both cultivars. The oxidative effects of the stress were defined by the measures of some enzymatic activities and lipid peroxidation. Consistently, an increase in superoxide dismutase (SOD), catalase (CAT), peroxide dismutase (POD) enzymes and higher content of proline and soluble proteins were observed in cv. Elsinore than in cv. Elsanta. The increase coincided with a decrease in lipid peroxidation. The research confirmed that although strawberry cultivars were sensitive to salinity, difference between cultivars exist; The experiment revealed that cv. Elsanta could stand severe salt stress, which was lethal to cv. Elsinore. The parameters measured in the previous experiment were proposed as early screening tools for the salt stress response in nine strawberry genotypes. The results showed that, wheares Elsanta and Elsinore cultivars had a lower dry weight reduction at 40 mM NaCl among cultivars, Naiad, Kamila, and Camarosa were the least salt-sensitive cultivars among the screened.