Nanostructuring and macroscopic behavior of type V deep eutectic solvents based on monoterpenoids.

Type V natural deep eutectic solvents based on monoterpenoids (cineole, carvone, menthol, and thymol) are studied using a combined experimental and molecular modeling approach. The reported physicochemical properties showed low viscous fluids whose properties were characterized as a function of temperature. The theoretical study combining quantum chemistry and classical molecular dynamics simulations provided a nanoscopic characterization of the fluids, particularly for the hydrogen bonding network and its relationship with the macroscopic properties. The considered fluids constitute a suitable type of solvents considering their properties, cost, origin, and sustainability in different technological applications and sow the possibility of developing type V NADES from different types of molecules, especially in the terpenoid family of compounds.

Insights into Glycol Ether-Alkanol Mixtures from a Combined Experimental and Theoretical Approach.

The binary liquid mixtures of glycol ethers (glymes) + 1-alkanol were characterized from the microscopic and macroscopic viewpoints through a combined experimental and theoretical study. Structuring, dynamics, and intermolecular forces were determined using density functional theory and classical molecular dynamics methods. The macroscopic behavior was studied though the measurement of relevant physicochemical properties and Raman IR studies. The changes in intermolecular forces with mixture composition, temperature, and the effects from the types of glymes as well as 1-alkanols were considered. Hydrogen bonding in the mixed fluids, its changes upon mixing, and mixture composition showed a large effect on fluids' structure and determined most of the fluids' properties together with the presence of hydrophobic domains from long 1-alkanols.

Physicochemical Insights on Alkylcarbonate-Alkanol Solutions.

Macroscopic properties and structuring at the molecular level of dialkylcarbonate + 1-alkanol mixed fluids have been studied as a function of alkyl chain lengths in 1-alkanol and dialkylcarbonate, mixture composition, and temperature. A combined experimental and computational approach was considered for studying the relationships between the nanoscopic structure of the mixed fluids; nature, extension, and organization of hydrogen bonding; and physicochemical properties. Thermodynamics characterization, using excess and mixing properties, are related with the strength and characteristics of intermolecular forces. Classic molecular dynamics simulations and quantum chemistry calculations provide a detailed picture of the mixed fluids' structuring and dynamic behavior.

Rotational Distraction for the Treatment of Severe Mandibular Retrognathia.

BACKGROUNDS: The main problem with intraoral distraction of the mandible is the inability to achieve the three-dimensional mandibular correction as planned preoperatively. We developed a technique that allows spontaneous changes in the direction of mandibular elongation using an intraoral distractor. METHODS: After mandibular osteotomy, the distractor is fixed to the distal segment of the mandible using a single bicortical screw, allowing anterior-posterior, vertical and limited lateromedial changes in the vector of distraction. Mandibular lengthening is performed while keeping the maxilla and mandible in class I occlusion with intermaxillary fixation. RESULTS: As the distraction device is activated allowing mandibular elongation, the proximal segment, guided by the surrounding soft tissues, moves and rotates posterosuperiorly. Mandibular lengthening is continued until the condylar head reaches an adequate position in the mandibular fossa as confirmed clinically and radiographically. CONCLUSION: Thirty-three patients with mandibular retrognathia received this treatment and good results were obtained.

Characterization of amide-alkanediol intermolecular interactions.

The properties of formamide + 1,2-alkanediol binary liquid systems were studied both at the macro- and microscopic levels using a combined experimental and computational methodology. Physicochemical properties, infrared spectroscopy, and solvatochromic studies together with classic molecular dynamics and quantum chemistry calculations allowed the main characteristics of these binary fluids to be inferred with regard to the variations of hydrogen bonding with formamide and 1,2-alkanediol molecular structures, mixture composition, and temperature. The complexity of these liquid systems arising from the presence of three different functional groups, which may act as hydrogen bond donors and acceptors, is analyzed, allowing a detailed picture to be inferred of the studied systems which is of relevance both for basic liquid state theory and for industrial purposes.

Structure of alkylcarbonate + n-alkane mixed fluids.

The properties of dialkylcarbonate + n-alkane mixed fluids were studied both from macroscopic and from microscopic viewpoints using thermophysical measurements combined with classic molecular dynamics simulations and DFT quantum chemistry studies. The objective of this study is a whole range characterization of dialkylcarbonate-containing systems as fuel oxygenated additives. The reported results allowed analyzing the structure, dynamics, and intermolecular forces in these systems as a function of composition and temperature, paying attention to the mechanism of carbonate-n-alkane interaction for understanding the role of dialkylcarbonates in fuel properties.

Insights from quantum chemistry into piperazine-based ionic liquids and their behavior with regard to CO2.

The short-range properties of alkylpiperazine ionic liquids paired with propionate and lactate anions were analyzed and their affinity for CO2 molecules studied using density functional theory. Anion-cation interactions led to the development of strong intermolecular hydrogen bonding through the cation amine position, as confirmed through variations in structural and vibrational properties upon pair formation. Topological analysis via the atoms-in-molecules approach revealed the development of intense bond and ring critical points in the intermolecular regions, which is in agreement with charge transfer from lone pairs in anion oxygen atoms of carboxylate groups through antibonding orbitals in cation amine groups. Such anion-cation interactions are weakly dependent on cation alkyl chain length but are remarkably affected by the presence of an anion hydroxyl group. Interactions with CO2 molecules are stronger for anions than for cations, especially for propionate anions, and are also affected strongly by the anion hydroxyl group.

Study on hydroxylammonium-based ionic liquids. I. Characterization.

Two selected ammonium-based ionic liquids, 2-hydroxyethyltrimethylammonium L-(+)-lactate and tris(2-hydroxyethyl)methylammonium methylsulfate, were fully characterized. The most relevant thermophysical properties of pure fluids were measured and analyzed as a function of temperature. Structural features were inferred from solvatochromic and Fourier transform infrared (FTIR) studies. Moisture absorption ability was also studied by gravimetric, spectroscopic, and Karl Fischer methods. Likewise, the water effect on fluids properties was analyzed. Polarity was studied by approaches based on solvatochromic measurements and on the water effect on FTIR spectra. Moreover, as computational work, quantum chemistry and molecular dynamics simulation methods were used to analyze the main molecular-level structural features in these fluids. The work is divided into two parts; in this first paper, the main objective is fully characterizing these ionic liquids in the pure state, and in the second paper CO(2) absorption will be analyzed, therefore leading to a deep knowledge of factors controlling structuring, properties, and CO(2) absorption for this family of ionic liquids in comparison with available information for other relevant types of ionic liquids.

On the viscosity of pyridinium based ionic liquids: an experimental and computational study.

A study on the viscosity of eight pyridinium based ionic liquids is reported for wide pressure and temperature ranges. Measurements were performed using an electromagnetic moving piston viscometer. Experimental data were fitted to a Tait-like equation demonstrating good correlations, which was used to calculate pressure/viscosity and temperature/viscosity coefficients. The effect of the involved anions and cation on the ionic liquid viscosity was analyzed from a molecular viewpoint using hole theory, quantum chemistry calculations using density functional theory, and classical molecular dynamics simulations. The analysis of the experimental and computational results shows the complex effects controlling viscosity of studied fluids, including strength of ionic pairs, molecular sizes, and mobility and effects rising from the availability and cavity sizes distributions in pyridinium-based ionic liquids.

Study on hydroxylammonium-based ionic liquids. II. Computational analysis of CO2 absorption.

In the previous work of this series, we reported a wide experimental and computational analysis of the properties of hydroxylammonium-based ionic liquids. This family of ionic liquids shows very favorable economical, technological, and environmental properties in comparison with other ionic liquid types. We report in this work a computational study, using quantum chemistry and molecular dynamics methods, to analyze the absorption of carbon dioxide by hydroxylammonium ionic liquids. The selected compounds were 2-hydroxyethyl-trimethylammonium L-(+)-lactate and tris(2-hydroxyethyl)methylammonium methylsulfate. The main objective of this work is to study and analyze CO(2) absorption from the molecular point of view, therefore contributing to the knowledge and advancement on the absorption ability of ionic liquids. The computational study would lead to a deeper knowledge of factors controlling CO(2) absorption for this ionic liquid family in comparison with available information for other relevant types. The results were analyzed considering the effects of absorbed gas on the ionic liquid structuring from a molecular level viewpoint, interionic interactions, diffusion of the involved compounds, and interaction of CO(2) with anions and cations. The reported results show a strong effect of the presence of hydroxyl groups in the involved cations and anions through the interaction with CO(2) molecules, along with the effects rising from the size of cations on the fluid structure.

Study of dimethoxyethane/ethanol solutions.

The unusual properties of poly(ethyleneoxide) + alcohol mixtures were analyzed using a poly(ethylene oxide) monomer (1,2-dimethoxyethane) in ethanol solutions as a model. A collection of thermophysical measurements and computational studies, using density functional theory and classical molecular dynamics approaches, provide valuable information about the molecular-level structure of this mixture and on the interaction between 1,2-dimethoxyethane and ethanol molecules. Thermophysical measurements show remarkable deviations from ideality, which are related to the development of intermolecular hydrogen bonding between both molecules upon mixing and to the balance of homo- and heteroassociations. Density functional theory allows better characterization from energetic and structural viewpoints. In this work, the characteristics for the different 1,2-dimethoxyethane/ethanol hydrogen-bonding complexes are analyzed via atoms in a molecule and natural bond orbital methods. Classical molecular dynamics simulations are carried out for pure 1,2-dimethoxyethane and for mixtures in the whole composition range. Force field validation is done by comparison of predicted thermophysical properties with measured ones and through the analysis of 1,2-dimethoxyethane conformers. Structural features are inferred from the analysis of radial and distribution functions and their evolution with composition, together with the study of molecular distribution in the mixed fluids (microheterogeneities). Dynamic aspects of the mixtures' behavior are inferred from the calculated self-diffusion constants and mean square displacements. The whole study points to a highly structured fluid, whose structure is determined by the balance of the 1,2-dimethoxyethane disrupting effect on the ethanol hydrogen-bonding network and the appearance of microheterogeneities.

Experimental and computational study on the properties of pure and water mixed 1-ethyl-3-methylimidazolium L-(+)-lactate ionic liquid.

Ionic liquids have attracted great attention, from both industry and academe, as alternative fluids for a large collection of applications. Although the term green is used frequently to describe ionic liquids in general, it is obvious that it cannot be applied to the huge quantity of possible ionic liquids, and thus, those with adequate environmental and technological profiles must be selected for further and deeper studies, from both basic science and applied approaches. In this work, 1-ethyl-3-methylimidazolium L-(+)-lactate ionic liquid is studied, because of its remarkable properties, through a wide-ranging approach considering thermophysical, spectroscopic, and computational tools, to gain a deeper insight into its complex liquid structure, both pure and mixed with water, thus implying the main factors that would control the technological applications that could be designed using this fluid. The reported results shows a strongly structured pure ionic liquid, in which hydrogen bonding, because of the hydroxyl group of the lactate anion, develops a remarkable role, together with Coulombic forces to determine the fluid's behavior. Upon mixing with water, the ionic liquid retains its structure up to very high dilution levels, with the effect of the ionic liquid on the water structure being very large, even for very low ionic liquid mole fractions. Thus, in water solution, the studied ionic liquid evolves from noninteracting ions solvated by water molecules toward large interacting structures with increasing ionic liquid content.

Characterization of two lactones in liquid phase: an experimental and computational approach.

In this work, an experimental and computational study on the properties and molecular-level liquid structure of gamma-butyrolactone and gamma-valerolactone is reported. These fluids are selected because of their possible use as alternative green solvents considering their favorable environmental and toxicological profiles. The experimental study was carried out measuring a selected collection of relevant thermophysical properties, at ambient pressure as a function of temperature, together with a detailed spectroscopic study. The reported set of experimental thermophysical properties is valuable for process design purposes and because of their relationships with microscopic fluids' structure. Spectroscopic studies were carried out using attenuated total reflection infrared spectroscopy (ATR-FTIR), solvatochromic studies and microwave dielectric relaxation spectroscopy (DRS) measurements; all the spectroscopic studies were performed as a function of temperature. Moreover, density functional theory (DFT) and classical molecular dynamics simulations (MD) were used to obtain a detailed picture of the intermolecular interactions within the fluid, at short and long ranges, and of other relevant features leading to the liquid structure of the studied fluids. The whole study points to a fluids' picture in which, in spite of the absence of specific interactions such as hydrogen bonding, a remarkable ordering appears rising from the dipolar interactions and from the shapes of the involved molecules.

Insights into the ethyl lactate + water mixed solvent.

The mixed green solvent ethyl lactate + water is studied from macro- and microscopic viewpoints using a wide collection of experimental and computational tools. High-pressure thermophysical data, density, and dynamic viscosity provide valuable information on the macroscopic behavior of the mixed fluid, which is of remarkable importance for industrial purposes, and through the analysis of the derived excess and mixing properties lead to relationships with molecular level properties. Large deviations from ideality are obtained, which are related to the development of strong intermolecular hydrogen bonding between both molecules upon mixing. Computational studies, using the density functional theory, both in gas phase and water solution, allow to characterize, from energetic and structural viewpoints, the different ethyl lactate/water association complexes. The use of atoms in a molecule and natural bond orbital methods sheds light into the properties of ethyl lactate/water hydrogen bonding. Classical molecular dynamics simulations are carried out for the whole composition range, and as a function of pressure and temperature. Force field validation is done by comparison of predicted thermophysical properties with measured ones. Structural features are inferred from the analysis of radial distribution functions and their evolution with composition, pressure, and temperature, and dynamic aspects are inferred from the calculated self-diffusion constants and mean square displacements. The whole study points to a highly structured fluid, in which hydrogen bonding is developed both for water-rich and ethyl-lactate-rich solvents, showing a remarkable effect in the fluid structure upon the addition of the second component for both pure compounds, even more important for the effect of ethyl lactate on water hydrogen bonding network.

High-pressure study of the methylsulfate and tosylate imidazolium ionic liquids.

The considerable interest aroused in recent years by the unique properties and industrial applications of ionic liquids has given rise to the need for a detailed statement of the linkage between their molecular features and the observed macroscopic behavior. A combined experimental/computational approach to the study of ionic liquids is submitted here and applied to the relevant, nonhalogenated ionic liquids 1,3-dimethylimidazolium methylsulfate and 1-ethyl-3-methylimidazolium tosylate. To establish a reliable equation of state pertinent to these fluids, density data over wide pressure (0.1-60 MPa) and temperature (318.15-428.15 K) ranges, along with high pressure (1-70 MPa) viscosities and other selected ambient pressure properties were measured to assemble sufficient experimental information for the seek of predictive models for process design. A computational method based on ab initio and classical molecular dynamics yielded a deal of structural information, borne out by the experimental readings. Likewise, the predictive ability of the force field applied in molecular dynamics simulations was faced with the measured properties. The pictorial description of the selected ionic liquids reached this way may become widespread to other relevant examples in order to infer valuable structure/property relationships.

Prevalência de estenose da artéria subclávia em pacientes candidatos a cirurgia de revascularização do miocárdio: registro multicêntrico / Prevalence of stenosis of the left subclavia artery in CABG candidates: a multicenter registry

Introdução: Aproximadamente 90 por cento dos pacientes submetidos a cirurgia de revascularização do miocárdio (CRM) recebem enxerto de artéria torácica interna esquerda. A ocorrência de estenose da artéria subclávia esquerda pode resultar em falência do enxerto por limitação de fluxo coronário. A prevalência de estenose da artéia subclávia esquerda em pacientes com aterosclerose coronária grave, considerados candidatos a CRM, não é conhecida. Objetivo: Determinar a prevalência e a eficácia da avaliação clínica para diagnóstico a estenose da artéria subclávia esquerda em candidatos a CRM. Método: Em um registro multicêntrico, realizou-se angiografia seletiva da artéria subclávia esquerda em pacientes com indicação de CRM na ocasião da cinecoronariografia. Estenoses maiores ou iguais a 50 por cento antes da origem da artéria torácica interna foram considerdas significativas. Resultados: Dos 205 pacientes estudados, 16 (7,8 por cento) apresentavam estenose significativa da artéria subclávia esquerda. A medida da pressão arterial não-invasiva diferencial entre...

Background: Approximately 90% of the patients submitted to coronary artery bypass graft surgery (CABG) receive a left internal thoracic artery (LITA) graft. Stenosis of the left subclavian artery can result in graft failure due to restricted coronary flow. The prevalence of stenosis of the left subclavian artery in patients with severe coronary atherosclerosis, deemed candidates to CABG, is not known. Objective: To assess the prevalence of stenosis of left subclavian artery in CABG candidates, as well as the diagnostic effectiveness of clinical evaluation. Methods: In a multicenter registry, selective angiography of the left subclavian artery was carried out in patients considered candidates to CABG during coronary cineangiography. Stenoses ≥ 50% proximal to the origin of the LITA were considered significant. Results: A total of 205 patients were included. Significant stenosis of the left subclavian artery was observed in 16 (7.8%) patients. Noninvasive differential arterial blood pressure measurement ≥ 10 mmHg between both arms showed low sensitivity (37.5%) and low positive predictive value (13.3%) for stenosis identification. No clinical predictors of significant stenosis were identified by univariate analysis. Conclusion: Stenosis of the left subclavian artery is not uncommon in CABG candidates. Noninvasive blood pressure gradient between both arms has low diagnostic accuracy. Therefore, in patients candidates to CABG, selective angiography of the left subclavian artery should be considered, because of the risk of reduced flow and coronary-subclavian steal syndrome in patients with non-diagnosed stenosis of the subclavian artery who receive a LITA graft.

Measurements and predictive models for the N-methyl-2-pyrrolidone/water/methanol system.

This work reports on the properties and structure of N-methyl-2-pyrrolidone in binary and ternary liquid mixtures with water and/or methanol. A comprehensive set of thermophysical properties have been measured at 298.15 K and 0.1 MPa over the whole composition range. On the basis of the derived excess and mixing properties, the fluid structure was analyzed by looking into the forces and geometry factors that effectively control the mixture behavior. Application of the inverted Kirkwood-Buff theory provides a reasonable link between the macroscopic properties and the microscopic features. A density functional theory computation was carried out to analyze the structure and energy features of the hydrogen bonded complexes formed between the components. Use of semiempirical models in the framework of molecular-based equations of state according to the PC-SAFT approach led to unsatisfactory predicted thermophysical properties. The conclusions arrived at give away the existence of strong heteroassociations and hydrogen bonding self-associations that determine the complex nature of the fluid structure.

On the properties of methylbenzoate/n-hexane mixed solvents: a theoretical and experimental study.

This paper reports on an experimental and theoretical study of methylbenzoate/n-hexane mixed solvents as a function of pressure and temperature in the whole composition range. We have measured the pressure-volume-temperature (PVT) behavior of these fluids over wide temperature and pressure ranges; from the experimental data, relevant derived coefficients required for the fluid's characterization were calculated. The structure of mixed fluids was analyzed from macroscopic data according to excess and mixing properties. The statistical associating fluid theory (SAFT) and perturbed chain (PC)-SAFT molecularly based equations of state were used to predict the PVT behavior with model parameters for pure fluids fitted from correlation of available saturation literature data. The results provided by the PC-SAFT equation of state were clearly superior. Using the fitted PC-SAFT parameters, the global phase behavior of the mixture was predicted, and a type I pattern was inferred according to the van Konynenburg systematic. The molecular level structure was studied through classical molecular dynamics simulations in the NPT ensemble using the optimized potential for liquid simulations (all atom version) (OPLS-AA) force field. Molecular dynamics provides, on one hand, theoretical values of thermophysical properties, which are compared with the experimental ones to check the quality of simulations, and, on the other hand, valuable molecular level structural and dynamic information. Based on both macroscopic and microscopic studies, fluid structure was inferred.

A comparison of miniplates and teeth for orthodontic anchorage.

INTRODUCTION: In this study, we investigated orthodontic space closure of premolar extraction sites with miniplate anchorage compared with conventional tooth-borne anchorage in 8 adult beagle dogs. METHODS: A split-mouth design with all 4 quadrants was used. Four premolars were extracted to create adequate space for premolar retraction. Retraction was performed with nickel-titanium coil springs. In the control side, the premolars were retracted against other teeth, and, in the experimental side, the premolars were retracted against miniplates. Each quadrant received 2 additional bone screws as bone markers for cephalometric superimposition. Lateral cephalograms were taken at initial activation, 6 weeks, and 12 weeks. Three parameters were measured and evaluated: linear space closure, angular tipping, and amount of anchorage slippage. RESULTS: Overall, the miniplates had a high success rate of 93.8% (15 of 16) during the 12-week period of orthodontic loading. Similar amounts of space closure were observed in the control and the experimental sites. A statistically significant difference was observed for the amounts of tipping and anchorage slippage of miniplates vs tooth-borne anchorage. In the maxilla, the mean miniplate tipping was 0.1 degrees , whereas mean tipping of the anchor teeth was 9 degrees (P = .01). In the mandible, the miniplates tipped an average of 3.4 degrees , whereas the mean tipping of the anchor teeth was 13.3 degrees (P = .02). In the maxilla, the miniplates had 1% anchorage loss, whereas the tooth anchors had 37.1% anchorage loss (P = .001). In the mandible, the miniplates had a mean anchorage loss of 4.5%, whereas the tooth anchors had a mean anchorage loss of 31.1% (P = .001). CONCLUSIONS: Although the total amount of space closure was similar in both the control and the experimental groups, the mechanism of space closure was different. In the control group, slippage of the anchor teeth accounted for approximately a third of the space closure. In the experimental group, the miniplates had minimal movement, and space closure was achieved almost entirely by movement of the target teeth. These results confirm that miniplates provide virtually absolute anchorage.

Properties and structure of aromatic ester solvents.

This paper reports on an experimental and theoretical study of the aromatic ester solvents family. Several compounds were selected to analyze the different factors that influence their liquid-state properties and structures. The pressure-volume-temperature behavior of these fluids was measured accurately over wide temperature and pressure ranges and correlated successfully with the empirical TRIDEN equation. From the measured data the relevant derived coefficients of isothermal compressibility, isobaric expansibility, and internal pressure were calculated. The statistical associating fluid theory (SAFT) and perturbed chain statistical associating fluid theory (PC-SAFT) molecularly based equations of state were used to predict the PVT behavior with model parameters obtained from the correlation of available saturation literature data; the results provided by PC-SAFT equations of state were clearly superior for all of the studied solvents. The fluid's molecular level structure was studied by quantum computations at the B3LYP/6-311++g** level and classical molecular dynamics simulations in the NPT ensemble with the OPLS-AA forcefield. Molecular parameters, such as torsional barriers or cluster energetics, were analyzed as a function of ester structures. The molecular dynamics study provides, on one hand, theoretical values of thermophysical properties, which are compared with the experimental ones, and, on the other hand, valuable molecular level structural information. On the basis of both macroscopic and microscopic studies complex fluid structures were inferred with important effects arising from the geometries of the studied molecules and from the existence of remarkable intermolecular forces of dominating dipolar nature.