Unsupervised bubble calorimetry analysis: Surface tension from isothermal titration calorimetry.

HYPOTHESIS: The injection of air into the sample cell of an isothermal titration calorimeter containing a liquid provides a rich-in-information signal, with a periodic contribution arising from the creation, growing and release of bubbles. The identification and analysis of such contributions allow the accurate determination of the surface tension of the target liquid. EXPERIMENTS: Air is introduced at a constant rate into the sample cell of the calorimeter containing either a pure liquid or a solution. The resulting calorimetric signal is analyzed by a new algorithm, which is implemented into a computational code. FINDINGS: The thermal power generated by our experiments is often noisy, thus hiding the periodic signal arising from the bubbles' formation and release. The new algorithm was tested with a range of different types of calorimetric raw data, some of them apparently being just noise. In all cases, the contribution of the bubbles to the signal was isolated and the corresponding period was successfully determined in an automated way. It is also shown that two reference measurements suffice to calibrate the instrument at a given temperature, regardless the injection rate, allowing the direct determination of surface tension values for the liquid contained in the sample cell.

A New Type of Supramolecular Fluid Based on H2 O-Alkylammonium/Phosphonium Solutions.

Here we show that by adjusting the concentration of tetrabutyl ammonium and phosphonium salts in water (≈1.5-2.0 m), hydrophobic solvation triggers the formation of a unique, highly incompressible supramolecular liquid, with a dynamic structure similar to clathrates, involving essentially all H2 O molecules of the solvent. Despite the increasing local order, the thermal diffusivity, and compressibility of these supramolecular liquids is strongly decreased with respect to bulk water due to slower relaxation dynamics. The results presented in this paper open an avenue to design a new family of supramolecular fluids, stable under atmospheric conditions, which can find important technological applications in energy storage and conversion.

Hydrophobic solvation increases thermal conductivity of water.

The interaction of water with small alcohols can be used as a model for understanding hydrophobic solvation of larger and more complex amphiphilic molecules. Despite its apparent simplicity, water/ethanol mixtures show important anomalies in several of their properties, like specific heat or partial molar volume, whose precise origin are still a matter of debate. Here we report high-resolution thermal conductivity, compressibility, and IR-spectroscopy data for water/ethanol solutions showing three distinct regions of solvation, related to changes in the H-bond network. Notably, the thermal conductivity shows a surprising increase of ≈3.1% with respect to pure water at dilute concentrations of ethanol (x = 0.025), which suggests a strengthening of H-bond network of water. Our results prove that the rate of energy transfer in water can be increased by hydrophobic solvation, due to the cooperative nature of the H-bond network.

Late-onset refractive shift after small-aperture corneal inlay implantation.

We present a series of 5 consecutive cases in which a small-aperture corneal inlay (Kamra ACI7000PDT) was uneventfully implanted in a corneal pocket created at a depth between 200 µm and 250 µm. Three months after surgery, all patients had good visual results, normal corneal surfaces, and adequate stromal healing. Between 6 months and 19 months after surgery, visually significant refractive changes appeared in the form of a hyperopic shift in 4 cases and a myopic shift in 1 case. Topical steroids were ineffective. In 2 cases, the inlay was explanted. Among the adverse events reported in the 2015 approval of the small-aperture corneal inlay was a low incidence of late refractive changes. Recently, we have encountered a relatively higher frequency of these adverse events. Thus, we evaluated the hypothesis that a relationship between these late refractive changes and the decreased diffusivity of nutritional fluid to the anterior stroma accentuated by a lower depth of implantation is the cause.

Refractive Changes Induced by Spherical Aberration in Laser Correction Procedures: An Adaptive Optics Study.

PURPOSE: To study the effect on vision of induced negative and positive spherical aberration within the range of laser vision correction procedures. METHODS: In 10 eyes (mean age: 35.8 years) under cyclopegic conditions, spherical aberration values from -0.75 to +0.75 µm in 0.25-µm steps were induced by an adaptive optics system. Astigmatism and spherical refraction were corrected, whereas the other natural aberrations remained untouched. Visual acuity, depth of focus defined as the interval of vision for which the target was still perceived acceptable, contrast sensitivity, and change in spherical refraction associated with the variation in pupil diameter from 6 to 2.5 mm were measured. RESULTS: A refractive change of 1.60 D/µm of induced spherical aberration was obtained. Emmetropic eyes became myopic when positive spherical aberration was induced and hyperopic when negative spherical aberration was induced (R2 = 81%). There were weak correlations between spherical aberration and visual acuity or depth of focus (R2 = 2% and 3%, respectively). Contrast sensitivity worsened with the increment of spherical aberration (R2 = 59%). When pupil size decreased, emmetropic eyes became hyperopic when preexisting spherical aberration was positive and myopic when spherical aberration was negative, with an average refractive change of 0.60 D/µm of spherical aberration (R2 = 54%). CONCLUSIONS: An inverse linear correlation exists between the refractive state of the eye and spherical aberration induced within the range of laser vision correction. Small values of spherical aberration do not worsen visual acuity or depth of focus, but positive spherical aberration may induce night myopia. In addition, the changes in spherical refraction when the pupil constricts may worsen near vision when positive spherical aberration is induced or improve it when spherical aberration is negative. [J Refract Surg. 2017;33(7):470-474.].

Is the Capsular Bag Perimeter Round or Elliptical?

PURPOSE: To report findings that could suggest an elliptical shape of the capsular bag. METHODS: Five eyes of three patients with axial length greater than 24 mm underwent phacoemulsification cataract surgery with plate-haptic multifocal toric intraocular lens (IOL) implantation oriented in the vertical meridian. RESULTS: In all cases, correct orientation of the IOLs was verified 30 minutes after surgery. After 24 hours, all eyes demonstrated unwanted rotation of the IOLs ranging from 15 to 45 degrees. The IOLs remained stable in the new position in all cases until adhesion of the capsular bag took place. CONCLUSION: These observations could suggest that the perimeter of the capsular bag has an elliptical shape. Therefore, the IOL tends to become fixated in a meridian of the capsular bag that best fits the diagonal diameter of the IOL.

STAND: Surface Tension for Aggregation Number Determination.

Taking advantage of the extremely high dependence of surface tension on the concentration of amphiphilic molecules in aqueous solution, a new model based on the double equilibrium between free and aggregated molecules in the liquid phase and between free molecules in the liquid phase and those adsorbed at the air/liquid interface is presented and validated using literature data and fluorescence measurements. A key point of the model is the use of both the Langmuir isotherm and the Gibbs adsorption equation in terms of free molecules instead of the nominal concentration of the solute. The application of the model should be limited to non ionic compounds since it does not consider the presence of counterions. It requires several coupled nonlinear fittings for which we developed a software that is publicly available in our server as a web application. Using this tool, it is straightforward to get the average aggregation number of an amphiphile, the micellization free energy, the adsorption constant, the maximum surface excess (and so the minimum area per molecule), the distribution of solute in the liquid phase between free and aggregate species, and the surface coverage in only a couple of seconds, just by uploading a text file with surface tension vs concentration data and the corresponding uncertainties.

Control of Induced Spherical Aberration in Moderate Hyperopic LASIK by Customizing Corneal Asphericity.

PURPOSE: To compare differences in induced aberrations and visual acuity after wavefront-optimized LASIK and aspheric-customized LASIK for the treatment of hyperopia. METHODS: Forty consecutive eyes underwent uneventful LASIK for treatment of moderate hyperopia (+3.82 ± 0.63 diopters [D] [+2.75; +5.125]). A standard procedure was performed in the wavefront-optimized LASIK group (n = 24), whereas a postoperative Q-factor equal to zero was scheduled in the aspheric-customized LASIK group (n = 16). RESULTS: At 6 months, mean spherical aberration for a 6-mm pupil diameter was -0.39 ± 0.23 µm (range: -0.76 to 0.01 µm) and Q-factor was -0.52 ± 0.22 (range: -1.00 to -0.12 µm) in the wavefront-optimized group and 0.04 ± 0.18 µm (range: -0.34 to 0.29 µm) and -0.04 ± 0.25 (range: -0.64 to 0.40 µm) in the aspheric-customized LASIK group (P ≤ .05). All remaining outcomes showed no significant differences between groups. UDVA was 20/18.69 ± 0.15 (range: 0.80 to 1.20) in the wavefront-optimized LASIK group and 20/20 ± 0.17 (range: 0.50 to 1.20) in the aspheric-customized LASIK group. One patient in the wavefront-optimized LASIK group lost two or more lines of CDVA and no lines were lost in the aspheric-customized LASIK group. CONCLUSIONS: The results in this small cases series suggest that using an aspheric-customized ablation profile with a target Q-factor equal to 0 in moderate hyperopic LASIK is statistically compatible with a diminishing induced spherical aberration without altering procedural safety when the WaveLight Allegretto 400-Hz excimer laser platform (Alcon Laboratories, Inc., Fort Worth, TX) is used.

Influence on Visual Quality of Intraoperative Orientation of Asymmetric Intraocular Lenses.

PURPOSE: To evaluate visual quality when changing the intraocular orientation of the Lentis Mplus LS-312MF nonrotational symmetric +3.00 diopters aspheric multifocal intraocular lens ([IOL] Oculentis GmbH, Berlin, Germany) in normal eyes. METHODS: An artificial eye was used to measure the in vitro wavefront of the IOL. The corneal topography of 20 healthy patients was obtained. For each eye, a computational analysis simulated the implantation of the IOL. The modulation transfer function (MTF) and an image quality parameter (visually modulated transfer function [VSMTF] metric) were calculated for a 5.0-mm pupil and for three conditions: distance, intermediate, and near vision. The procedure was repeated for each eye after a rotation of the IOL with respect to the cornea from 0° to 360° in 1° steps. RESULTS: Statistical analysis showed significant differences in mean VSMTF values between orientations for distance vision. Optimal orientation of the IOL (different for each eye) showed a mean improvement of 58% ± 19% (range: 20% to 121%) in VSMTF values with respect to the worst possible orientation. For these orientations, intermediate and near vision quality were statistically indistinguishable. The MTFs were different between orientations, showing a mean difference of approximately 5 cycles per degree in the maximum spatial frequencies that can be transferred between the best and the worst orientations for distance vision. CONCLUSIONS: The results suggest that implantation of this nonrotational symmetric IOL should improve visual outcomes if it is oriented to coincide with a customized meridian. A simple, practical method is proposed to find an approximation to the angle that an Mplus IOL should be inserted.

Recommendations for post-adaption care of an ocular prosthesis: A review.

An ocular prosthesis must be maintained in a suitable state of cleanliness, fit and preservation. Otherwise its functioning may be compromised, leading to a variety of diseases. However, there is a lack of consensus on the care of such prostheses. This review assembles and attempts to update existing knowledge in this area and discusses the most appropriate care regimes.

Rotationally asymmetric multifocal IOL implantation in acquired nystagmus with spectacle and contact lens intolerance.

PURPOSE: To describe a case of refractive lens exchange with multifocal intraocular lens implantation in a 52-year-old woman with emmetropic presbyopia who had near glasses and contact lens intolerance after acquired nystagmus. METHODS: Preoperative corrected distance visual acuity was 20/25 in the right eye, 20/20 in the left eye, and 20/20 binocularly. Corrected near visual acuity was 20/30 in the right eye and 20/20 in the left eye, reaching 20/20 binocularly but showing unsatisfactory binocular vision with asthenopia and intolerance to prolonged reading. The surgical plan entailed bilateral implantation of multifocal intraocular lens. RESULTS: Three months postoperatively, uncorrected distance visual acuity was 20/20 in the right eye and 20/20 in the left eye, reaching 20/20 binocularly. Monocular and binocular uncorrected near visual acuity of 20/20 was achieved without symptoms of asthenopia in prolonged reading. There were no changes in nystagmus characteristics after surgery. CONCLUSIONS: Multifocal intraocular lens implantation to manage a case of clinically significant acquired nystagmus may be a safe alternative, especially if others options have failed.

Simulated effect of corneal asphericity increase (Q-factor) as a refractive therapy for presbyopia.

PURPOSE: To determine the theoretical effect of an increase in the negative Q-factor (hyperprolateness) on the refractive state and its effect on presbyopia treatment. METHODS: Ray tracing software was used to simulate the Navarro eye model. To simulate refractive therapy, corneal Q-factor ranged from 0 to -1.50. Refractive state of the model eye was defined as the target vergence required to maximize retinal image quality according to several image quality metrics. The change of refractive state produced by pupil constriction from 6 to 2 mm was estimated. RESULTS: For 0 ≥ Q ≥ -0.6, spherical aberration of the model eye is positive, therefore, pupil miosis causes a hypermetropic shift in refractive state. Over the range -0.6 ≥ Q ≥ -1.5, spherical aberration becomes negative and pupil constriction causes the eye's far point to approach the eye, inducing a myopic shift. A maximum 0.60-diopter myopic shift in refractive state due to pupil constriction occurred for Q=-1.25. CONCLUSIONS: Optical modeling predicts that surgically induced negative corneal Q-value will produce a change in the refractive state of the eye after pupillary miosis.

Talla, peso, somatotipo y composición corporal en gimnastas de elite españoles desde la infancia hasta la edad adulta / Height, weight, somatotype and body composition in elite Spanish gymnasts from childhood to adulthood

Introducción y objetivos: El objeto del presente estudio fue caracterizar, a lo largo de la edad, el comportamiento de la talla y el peso (7-25 años), el somatotipo y la composición corporal (12-18 años), en gimnastas masculinos de élite. Métodos: Basándose en un diseño mixto-longitudinal se analizó de cada una de las variables: a) evolución a lo largo de la edad, y b) diferencias en relación con una muestra de referencia. El somatotipo se analizó mediante el método Heath-Carter, la masa grasa mediante la fórmula de Slaughter y la masa muscular mediante la fórmula de Poort-mans. Resultados: Los gimnastas son significativamente más bajos y ligeros que la muestra de referencia. Además, los mejores gimnastas lo son aún más que el resto de compañeros de entrenamiento, salvo los especialistas en suelo y salto, donde el tren inferior es protagonista. El pico de crecimiento de la talla se produce a la edad de 14 años, a la misma edad que en la muestra de referencia. El 90% de los gimnastas se clasifica en un perfil ecto-mesomórfico. Poseen un porcentaje de masa grasa significativamente inferior al de la muestra de referencia. El somatotipo, la masa libre de grasa y el porcentaje de masa muscular no describen incrementos significativos a lo largo de la edad. Conclusiones: Los gimnastas españoles muestran un patrón de crecimiento, en las variables de estudio analizadas (talla, peso, somatotipo y composición corporal), que responde a la normalidad. Las principales diferencias entre éstos y la muestra de referencia se producen desde las primeras edades analizadas. Todos estos factores sugieren la implicación de un proceso de selección, tanto previo como el que el propio proceso de entrenamiento realiza a lo largo de los años, antes de alcanzar la elite deportiva(AU)

Introduction and aims: The aim of the present study was to characterize the evolution of height and weight (from 7 to 25 years old) and somatotype and body composition (from 12 to 18 years old) in elite male gymnasts. Method: For each of the variables, a mixed-longitudinal design was used to analyze: a) its evolution with age and b) its differences with respect to a reference population. Somatotype was analyzed with the Heath-Carter method, fat free mass with the Slaughter formula and muscle mass with the Poortman formula. Results: Male gymnasts were significantly shorter and lighter than the reference population. The best gymnasts were even more so with respect to their fellow gymnasts, except for specialists in vault and floor where the lower limbs are especially important. The peak height velocity occured at the age of 14, at the same age as in the reference population. The somatotype was ecto-mesomorphic in 90% of the gymnasts. Fat mass percentage was significantly lower than in the reference population. Somatotype, fat free mass and muscle mass showed no significant increases with age. Conclusions: Gymnasts showed a growth pattern considered as normal in the variables analyzed in the present study. The main differences between the gymnasts and the reference group were observed from the beginning of the follow-up. These findings suggest the effects of a selection process, both before and during the training process, before the elite level is reached(AU)

A small molecular size system giving unexpected surface effects: alpha-Cyclodextrin + sodium dodecyl sulfate in water.

Maximum drop volumes (MDV) and the resultant surface tension values (sigma) of alpha-cyclodextrin (alpha-CD) + sodium dodecyl sulfate (SDS) aqueous mixtures have been determined over a broad concentration range of both solutes at 283.15, 293.15, 303.15, 313.15, and 323.15 K. Drops significantly larger than those of pure water (up to approximately 25% larger) were observed at low temperatures for solutions with [alpha-CD]/[SDS] concentration ratios, approximately > 2, producing unexpectedly high surface tension values. Our results indicate that at certain solute concentration ratios and temperatures, the drop volume method provides wrong values for equilibrium surface tensions. This is due to the high viscoelasticity of the surface film whose effect is important even though the injection rate of the drops was slow and the solutes molecular sizes are small.

Valoración nutricional de los hábitos alimentarios en jóvenes esgrimistas de competición / No disponible

Introducción y objetivos: Si bien las necesidades nutricionalesy el perfil somático del esgrimista de élite han sidodescritos, no sucede así en jóvenes esgrimistas. El objetivodel presente estudio fue doble: describir el perfil cineantropométricode un grupo de jóvenes esgrimistas de competicióny valorar sus hábitos alimentarios.Métodos: El presente estudio, de carácter observacional ydescriptivo, agrupa las variables analizadas en dos valoraciones:a) valoración nutricional (registro de 24 h): energíatotal, hidratos de carbono, proteínas, lípidos, fibra, colesterol,contenido en agua de la dieta, vitaminas y minerales; b)valoración cineantropométrica: talla, peso, somatotipo ycomposición corporal.Resultados: El 26,3% del grupo se situó por encima de losvalores recomendados de ingesta energética, mientras queel 57,9% lo hizo por debajo. El consumo de hidratos de carbonofue inferior a los valores recomendados, mientras quela ingesta de proteínas y lípidos fue superior. El 89,5 y el63,2% del grupo se situó por debajo de las recomendacionesde grasas monoinsaturadas y poliinsaturadas, respectivamente.El 89,5% registró valores de grasas saturadas porencima de la ingesta recomendada. El consumo de fibra fuedeficitario en el 52,6% de los casos. El consumo de colesterolfue en cambio superior (73,7%). Se registraron valoresde vitaminas acordes con las recomendaciones, no siendoasí en el caso de algunos minerales. Ambos sexos conformangrupos notablemente heterogéneos a nivel somático.Conclusiones: La mayoría de los jóvenes esgrimistas analizadosposeen hábitos alimentarios no adecuados para mantenerun estado de vida saludable ni para la práctica deportiva.Resulta necesario corregir dichos hábitos basándose enuna correcta educación y seguimiento nutricional. Más aún silo que se pretende es optimizar su rendimiento deportivo.La valoración cineantropométrica ratifica estos resultados

Introduction and objectives: Although the nutritional requirements and somatic profile of the elite fencer havebeen described, this information is lacking in young fencers.The aim of the present study was two-fold: firstly, to describethe kinanthropometric profile of a group of youngcompetitive fencers and, secondly, to assess their nutritionalhabits.Methodology: The present observational, descriptivestudy classified the variables analyzed into two categories:a) nutritional assessment (24 h recording): total energy,carbohydrates, proteins, lipids, fiber, cholesterol, dietarywater content, vitamins and minerals; b) kinanthropometricassessment: height, weight, somatotype, and body composition.Results: Total energy intake was above recommended levelsin 26.3% of the group and below these levels in 57.9%.Carbohydrate intake was lower than recommended, whereasprotein and lipid intake was higher. Intake of monounsaturatedand polyunsaturated fats was below recommendedlevels in 89.5% and 63.2% of young fencers,respectively. Saturated fat intake was higher than recommendedintake in 89.5% of the fencers. Fiber consumptionwas deficient in 52.6% of the fencers. In contrast, cholesterolintake was higher than recommended consumption in73.7%. Vitamin intake was in line with recommended levelsbut intake of some minerals was deficient. Both sexes wereremarkably heterogeneous in somatic profile.Conclusions: Nutritional habits in most of the young fencersanalyzed were unsuitable both to maintain a state ofhealth and to practice sport. These habits should be correctedthrough proper education and nutritional follow-upwith further interventions to optimize sports performance.The kinanthropometric assessment confirms these results

Cyclodextrin-based self-assembled nanotubes at the water/air interface.

Native alpha-cyclodextrin (alpha-CD) is found to spontaneously form films at aqueous solution/air interfaces. Shape-response measurements to volume perturbations on drops hanging from a capillary indicate that temperature and sodium dodecyl sulfate (SDS) concentration strongly modify the viscoelastic properties of such films. By using isothermal titration calorimetry (ITC), Brewster angle microscopy (BAM), atomic force microscopy (AFM), and molecular dynamics (MD) simulations, it is shown that the films consist of self-assembled nanotubes whose building blocks are cyclodextrin dimers (alpha-CD2) and alpha-CD2-SDS1 complexes.

On the characterization of host-guest complexes: surface tension, calorimetry, and molecular dynamics of cyclodextrins with a non-ionic surfactant.

Three host-guest systems have been characterized using surface tension (sigma), calorimetry, and molecular dynamics simulations (MD). The hosts were three native cyclodextrins (CD) and the guest the non-ionic carbohydrate surfactant octyl-beta-d-glucopyranoside. It is shown that, for any host-guest system, a rough screening of the most probable complex stoichiometries can be obtained in a model free form, using only calorimetric data. The sigma data were analyzed using a model that includes a newly proposed adsorption isotherm. The equilibrium constants for several stoichiometries were simultaneously obtained through fitting the sigma data. For alpha- and beta-CD, the predominant species is 1:1 and to a lesser extent 2:1, disregarding the existence of the 1:2. For gamma-CD, the 1:2 species dominates, the other two being also present. In an attempt to confirm these results, 10 ns MD simulations for each CD were performed using seven different starting conformations. The MD stable conformations agree with the results found from the experimental data. In one case, the spontaneous dissociation-formation of a complex was observed. Analysis of the trajectories indicates that hydrophobic interactions are primarily responsible for the formation and stability of the inclusion complexes. For the 2:1 species, intermolecular H-bonds between CD molecules result in a tight packed structure where their original truncated cone shape is lost in favor of a cylindrical geometry. Together, the results clearly demonstrate that the often used assumption of considering only a 1:1 species is inappropriate.

Surface tension and density of mixtures of 1,3-dioxolane+alkanols at 298.15 K: analysis under the extended Langmuir model.

Surface tensions (sigma) for [1,3-dioxolane+methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and 1-pentanol] and excess molar volumes (v(E)) for [1,3-dioxolane+methanol, ethanol, 1-propanol, 2-propanol, and 2-butanol] at the temperature 298.15 K and normal atmospheric pressure have been determined as a function of mole fractions. The magnitude of these experimental quantities is discussed in terms of the nature and type of intermolecular interactions in binary mixtures. In order to analyze the surface tension behavior, the extended Langmuir (EL) model was used and the results obtained for the systems containing 1,3-dioxolane were compared with those of other formerly published series: [1,4-dioxane+alkanes] and [1,4-dioxane+alcohols].