Evaluation of the enthalpy of formation, proton affinity, and gas-phase basicity of gamma-butyrolactone and 2-pyrrolidinone by isodesmic reactions

The knowledge of thermochemical parameters such as the enthalpy of formation, gas-phase basicity, and proton affinity may be the key to understanding molecular reactivity. The obtention of these thermochemical parameters by theoretical chemical models may be advantageous when experimental measurements are difficult to accomplish. The development of ab initio composite models represents a major advance in the obtention of these thermochemical parameters,. but these methods do not always lead to accurate values. Aiming at achieving a comparison between the ab initio models and the hybrid models based on the density functional theory (DFT), we have studied gamma-butyrolactone and 2-pyrrolidinone with a goal of obtaining high-quality thermochemical parameters using the composite chemical models G2, G2MP2, MP2, G3, CBS-Q, CBS-4, and CBS-QB3; the DFT methods B3LYP, B3P86, PW91PW91, mPW1PW, and B98; and the basis sets 6-31G(d), 6-31+G(d), 6-31G(d,p), 6-31+G(d,p), 6-31++G(d,p), 6-311G(d), 6-311+G(d), 6-311G(d,p), 6-311+G(d,p), 6-311++G(d,p), aug-cc-pVDZ, and aug-cc-pVTZ. Values obtained for the enthalpies of formation, proton affinity, and gas-phase basicity of the two target molecules were compared to the experimental data reported in the literature. The best results were achieved with the use of DFT models, and the B3LYP method led to the most accurate data.

Gas-phase dissociation of 1,4-naphthoquinone derivative anions by electrospray ionization tandem mass spectrometry

Gas-phase dissociation pathways of deprotonated 1,4-naphthoquinone (NQ) derivatives have been investigated by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The major decomposition routes have been elucidated on the basis of quantum chemical calculations at the B3LYP/6-31+G(d,p) level. Deprotonation sites have been indicated by analysis of natural charges and gas-phase acidity. NQ anions underwent an interesting reaction under collision-induced dissociation conditions, which resulted in the radical elimination of the lateral chain, in contrast with the even-electron rule. Possible pathways have been suggested, and their mechanisms have been elucidated on the basis of Gibbs energy and enthalpy values for the anions previously described at each pathway. Copyright (C) 2009 John Wiley & Sons, Ltd.

Finite-temperature correlations and density profiles of an inhomogeneous interacting one-dimensional Bose gas

We calculate the density profiles and density correlation functions of the one-dimensional Bose gas in a harmonic trap, using the exact finite-temperature solutions for the uniform case, and applying a local density approximation. The results are valid for a trapping potential that is slowly varying relative to a correlation length. They allow a direct experimental test of the transition from the weak-coupling Gross-Pitaevskii regime to the strong-coupling, fermionic Tonks-Girardeau regime. We also calculate the average two-particle correlation which characterizes the bulk properties of the sample, and find that it can be well approximated by the value of the local pair correlation in the trap center.

Gas-surface interactions in the thermal and sub-thermal regime: A molecular dynamics study

Molecular dynamics simulations are used to study the interaction of low-energy Ar atoms with the Ni(001) surface, Angular scattering distributions, in and out of the plane of incidence, are investigated as a function of incident energy, angles of incidence, crystallographic orientation of the incident beam and surface temperature. The results show a clear transition to the structure scattering regime at around 2 eV. However, at lower energies, two sub-regimes are revealed by the simulations, Far energies up to 250 meV, scattering is mainly diffuse, and significant trapping on the surface is observed, At energies above this level, lobular patterns start to form and trapping decreases with the increase in energy, Generally, there is a weak temperature dependence, but variations in the angle of incidence and/or changes in the crystallographic direction, generate significant changes in the scattering patterns.

PM(2.5) and PM(10): The influence of sugarcane burning on potential cancer risk

In Brazil, sugarcane fields are often burned to facilitate manual harvesting, and this burning causes environmental pollution from the large amounts of soot released into the atmosphere. This material contains numerous organic compounds such as PAHs. In this study, the concentrations of PAHs in two particulate-matter fractions (PM(2.5) and PM(10)) in the city of Araraquara (SE Brazil, with around 200,000 inhabitants and surrounded by sugarcane plantations) were determined during the sugarcane harvest (HV) and non-harvest (NHV) seasons in 2008 and 2009. The sampling strategy included four campaigns, with 60 samples in the NHV season and 220 samples in the HV season. The PM(2.5) and PM(10) fractions were collected using a dichotomous sampler (10 L min(-1), 24 h) with Teflon (TM) filters. The filter sets were extracted (ultrasonic bath with hexane/acetone (1:1 v/v)) and analyzed by HPLC/Fluorescence. The median concentration for total PAHs (PM(2.5) in 2009) was 0.99 ng m(-3) (NHV) and 3.3 ng m(-3) (HV). In the HV season, the total concentration of carcinogenic PAHs (benz(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, and benzo(a)pyrene) was 5 times higher than in the NHV season. B(a)P median concentrations were 0.017 ng m(-3) and 0.12 ng m(-3) for the NHV and HV seasons, respectively. The potential cancer risk associated with exposure through inhalation of these compounds was estimated based on the benzo[a]pyrene toxic equivalence (BaP(eq)), where the overall toxicity of a PAR mixture is defined by the concentration of each compound multiplied by its relative toxic equivalence factor (TEF). BaP(eq) median (2008 and 2009 years) ranged between 0.65 and 1.0 ng m(-3) and 1.2-1.4 ng m(-3) for the NHV and HV seasons, respectively. Considering that the maximum permissible BaPeq in ambient air is 1 ng m(-3), related to the increased carcinogenic risk, our data suggest that the level of human exposure to PAHs in cities surrounded by sugarcane crops where the burning process is used is cause for concern. (C) 2010 Published by Elsevier Ltd.

Water deficit and ABA application on leaf gas exchange and flavonoid content in marigold (Calendula officinalis L.)

Water deficit and ABA application on leaf gas exchange and flavonoid content in marigold (Calendula officinalis L.).The goal of this study was to evaluate the effects of water deficit and abscisic acid (ABA) application on physiological parameters and flavonoid production in marigold plant. The experiment was performed under nursery conditions with potted plants. It was tested water deficit by withholding water (control - diary irrigation, 3, 6 and 9 days without irrigation) followed by 3 ABA concentrations (0, 10 e 100 mu M) applied in the beginning of blooming. It was evaluated the relative water content and the leaf gas exchange using a portable infrared gas analyzer (A: net photosynthesis, gs: stomatal conductance, E: transpiration, Ci: CO(2) intercellular concentration and EUA: water use efficiency). At the end of 9 days of water deficit there were significant decreases in all the characteristics evaluated, independent of ABA application. This suggests that the main effect of ABA was to cause a reduction on gs which was accompanied of a reduction in A, only when the plants were submitted to the water deficit. There was no significant difference among the levels of water deficit tested in relation to the total flavonoid content in inflorescences. However, ABA restricted the flavonoids biosynthesis both in control plant and stressed plants.

Ex Vivo Lung Perfusion: Early Report of Brazilian Experience

Introduction. Only about 15% of the potential candidates for lung donation are considered suitable for transplantation. A new method for ex vivo lung perfusion (EVLP) can be used to evaluate and recondition ""marginal,"" nonacceptable lungs. We have herein described an initial experience with ex vivo perfusion of 8 donor lungs deemed nonacceptable. Materials and Methods. After harvesting, the lungs were perfused ex vivo with Steen Solution, an extracellular matrix with high colloid osmotic pressure. A membrane oxygenator connected to the circuit received gas from a mixture of nitrogen and carbon dioxide, maintaining a normal mixed venous blood gas level in the perfusate. The lungs were gradually rewarmed, reperfused, and ventilated for evaluation through analyses of oxygenation capacity, pulmonary vascular resistance (PVR), lung compliance (LC), and biopsy. Results. The arterial oxygen pressure (with inspired oxygen fraction of 100%) increased from a mean of 206 mm Hg in the organ donor at the referring hospital to a mean of 498 mm Hg during the ex vivo evaluation. After 1 hour of EVLP, PVR varied from 440-1454 dynes/sec/cm(5); LC was in the range of 26-90 mL/cmH(2)O. There was no histological deterioration after 10 hours of cold ischemia and 1 hour of EVLP. Conclusions. The ex vivo evaluation model can improve oxygenation capacity of ""marginal"" lungs rejected for transplantation. It has great potential to increase lung donor availability and, possibly, reduce time on the waiting list.

Validation of a manual headspace gas chromatography method for determining volatile compounds in biological fluids

Background: We report the validation of a method for the determination of acetaldehyde, acetone, methanol, and ethanol in biological fluids using manual headspace sample introduction and an acetonitrile internal standard. Method: This method uses a capillary column (I = 30 m, I.D. = 0.25 mm, dF = 0.25 mu m) installed in a gas chromatography-flame ionization detector (GC-FID) apparatus with a run time of 7.5 minutes. Results: Analysis of the retention times and the resolution of the analyte peaks demonstrated excellent separation without widening of the peaks. Precision and accuracy were good (interassay precision < 15% and recovery between 85% and 115%) in both blood and urine. Conclusion: The method was linear (r > 0.09) over the analytical measurement range (AMR) of each analyte.

Neonatal Clinical Evaluation, Blood Gas and Radiographic Assessment After Normal Birth, Vaginal Dystocia or Caesarean Section in Dogs

This study aimed to standardize signs and diagnostic criteria of respiratory function in newborn puppies delivered normally or after dystocia and caesarean operation. A total of 48 neonates were allocated into groups: eutocia (n = 20), dystocia (n = 8), caesarean (c)-section (n = 20). Neonatal health was assessed using the Apgar score and body temperature was determined at 0, 5 and 60 min after delivery. Venous blood gases (pO(2) and SO(2)) was measured immediately and 60 min after delivery, and a thoracic radiograph was made between 0 and 5 min of life. The c-section group had significantly lower Apgar scores at birth and 5 min. Hypothermia was present at 5 min in the eutocia and c-section groups, and at 60 min in all groups. The eutocia group had an irregular respiratory pattern in 78% of puppies at birth, 27.7% at 5 min and 21% at 60 min compared with 87.5%, 62.5% and 12.5% of the pups in the dystocia group where there was irregular respiratory rhythm, moderate to intense respiratory sounds with agonic episodes. The c-section group had respiratory alterations in 70%, 45% and 16% of puppies at 0, 5 and 60 min, respectively. Radiographic abnormalities were present in 17% of the pups in the eutocia group, 25% of the pups in the dystocia group and 30% of the pups in the c-section group, respectively. The c-section group had significantly lower SO(2) values at 60 min than at birth. All puppies had hypoxaemia, but a significant decrease was observed in the c-section group. Newborn puppies had tissue hypoxia and irregular respiratory pattern at birth. Caesarean-section puppies had lower vitality; however, all developed satisfactory Apgar scores at 5 min of life, regardless of the obstetric condition.

Long-term survivor mixture model with random effects: application to a multi-centre clinical trial of carcinoma

A mixture model incorporating long-term survivors has been adopted in the field of biostatistics where some individuals may never experience the failure event under study. The surviving fractions may be considered as cured. In most applications, the survival times are assumed to be independent. However, when the survival data are obtained from a multi-centre clinical trial, it is conceived that the environ mental conditions and facilities shared within clinic affects the proportion cured as well as the failure risk for the uncured individuals. It necessitates a long-term survivor mixture model with random effects. In this paper, the long-term survivor mixture model is extended for the analysis of multivariate failure time data using the generalized linear mixed model (GLMM) approach. The proposed model is applied to analyse a numerical data set from a multi-centre clinical trial of carcinoma as an illustration. Some simulation experiments are performed to assess the applicability of the model based on the average biases of the estimates formed. Copyright (C) 2001 John Wiley & Sons, Ltd.

Influences of surface and solvent on retention of HEMA/mixture components after evaporation

Objectives: This study examined the retention of solvents within experimental HEMA/solvent primers after two conditions for solvent evaporation: from a free surface or from dentine surface. Methods: Experimental primers were prepared by mixing 35% HEMA with 65% water, methanol, ethanol or acetone (v/v). Aliquots of each primer (50 mu l) were placed on glass wells or they were applied to the surface of acid-etched dentine cubes (2 mm x 2 mm x 2 mm) (n = 5). For both conditions (i.e. from free surface or dentine cubes), change in primers mass due to solvent evaporation was gravimetrically measured for 10 min at 51% RH and 21 degrees C. The rate of solvent evaporation was calculated as a function of loss of primers mass (%) over time. Data were analysed by two-way ANOVA and Student-Newman-Keuls (p < 0.05). Results: There were significant differences between solvent retention(%) and evaporation rate (%/min) depending on the solvent present in the primer and the condition for evaporation (from free surface or dentine cubes) (p < 0.05). For both conditions, the greatest amount of retained solvent was observed for HEMA/water primer. The rate of solvent evaporation for HEMA/acetone primer was almost 2- to 10-times higher than for HEMA/water primer depending whether evaporation occurred, respectively, from a free surface or dentine cubes. The rate of solvent evaporation varied with time, being in general highest at the earliest periods. Conclusions: The rate of solvent evaporation and its retention into HEMA/solvent primers was influenced by the type of the solvent and condition allowed for their evaporation. (C) 2009 Elsevier Ltd. All rights reserved.