Dynamics of an oscillating microbubble in a blood-like Carreau fluid.

A numerical model for cavitation in blood is developed based on the Keller-Miksis equation for spherical bubble dynamics with the Carreau model to represent the non-Newtonian behavior of blood. Three different pressure waveforms driving the bubble oscillations are considered: a single-cycle Gaussian waveform causing free growth and collapse, a sinusoidal waveform continuously driving the bubble, and a multi-cycle pulse relevant to contrast-enhanced ultrasound. Parameters in the Carreau model are fit to experimental measurements of blood viscosity. In the Carreau model, the relaxation time constant is 5-6 orders of magnitude larger than the Rayleigh collapse time. As a result, non-Newtonian effects do not significantly modify the bubble dynamics but do give rise to variations in the near-field stresses as non-Newtonian behavior is observed at distances 10-100 initial bubble radii away from the bubble wall. For sinusoidal forcing, a scaling relation is found for the maximum non-Newtonian length, as well as for the shear stress, which is 3 orders of magnitude larger than the maximum bubble radius.

Characterizing viscoelastic materials via ensemble-based data assimilation of bubble collapse observations.

Viscoelastic material properties at high strain rates are needed to model many biological and medical systems. Bubble cavitation can induce such strain rates, and the resulting bubble dynamics are sensitive to the material properties. Thus, in principle, these properties can be inferred via measurements of the bubble dynamics. Estrada et al. (2018) demonstrated such bubble-dynamic high-strain-rate rheometry by using least-squares shooting to minimize the difference between simulated and experimental bubble radius histories. We generalize their technique to account for additional uncertainties in the model, initial conditions, and material properties needed to uniquely simulate the bubble dynamics. Ensemble-based data assimilation minimizes the computational expense associated with the bubble cavitation model, providing a more efficient and scalable numerical framework for bubble-collapse rheometry. We test an ensemble Kalman filter (EnKF), an iterative ensemble Kalman smoother (IEnKS), and a hybrid ensemble-based 4D-Var method (En4D-Var) on synthetic data, assessing their estimations of the viscosity and shear modulus of a Kelvin-Voigt material. Results show that En4D-Var and IEnKS provide better moduli estimates than EnKF. Applying these methods to the experimental data of Estrada et al. (2018) yields similar material property estimates to those they obtained, but provides additional information about uncertainties. In particular, the En4D-Var yields lower viscosity estimates for some experiments, and the dynamic estimators reveal a potential mechanism that is unaccounted for in the model, whereby the apparent viscosity is reduced in some cases due to inelastic behavior, possibly in the form of material damage occurring at bubble collapse.

Acoustic Measurements of Nucleus Size Distribution at the Cavitation Threshold.

An understanding of the acoustic cavitation threshold is essential for minimizing cavitation bio-effects in diagnostic ultrasound and for controlling cavitation-mediated tissue ablation in focused ultrasound procedures. The homogeneous cavitation threshold is an intrinsic material property of recognized importance to biomedical ultrasound as well as a variety of other applications requiring cavitation control. However, measurements of the acoustic cavitation threshold in water differ from those predicted by classic nucleation theories. This persistent discrepancy is explained by combining recently developed methods for acoustically nucleating single bubbles at threshold with numerical modeling to obtain a nucleus size distribution consistent with first-principles estimates for ion-stabilized nuclei. We identify acoustic cavitation at threshold as a reproducible subtype of heterogeneous cavitation with a characteristic nucleus size distribution. Knowledge of the nucleus size distribution could inspire new approaches to achieving cavitation control in water, tissue and a variety of other media.

Single-bubble dynamics in histotripsy and high-amplitude ultrasound: Modeling and validation.

A variety of approaches have been used to model the dynamics of a single, isolated bubble nucleated by a microsecond length high-amplitude ultrasound pulse (e.g. a histotripsy pulse). Until recently, the lack of single-bubble experimental radius vs. time data for bubble dynamics under a well-characterized driving pressure has limited model validation efforts. This study uses radius vs. time measurements of single, spherical histotripsy-nucleated bubbles in water to quantitatively compare and validate a variety of bubble dynamics modeling approaches, including compressible and incompressible models as well as different thermal models. A strategy for inferring an analytic representation of histotripsy waveforms directly from experimental radius vs. time and cavitation threshold data is presented. We compare distributions of a calculated validation metric obtained for each model applied to 88 experimental data sets. There is minimal distinction (<1%) among the modeling approaches for compressibility and thermal effects considered in this study. These results suggest that our proposed strategy to infer the waveform, combined with simple models minimizing parametric uncertainty and computational resource demands accurately represent single-bubble dynamics in histotripsy, including at and near the maximum bubble radius. Remaining sources of parametric and model-based uncertainty are discussed.

Modeling tissue-selective cavitation damage.

The destructive growth and collapse of cavitation bubbles are used for therapeutic purposes in focused ultrasound procedures and can contribute to tissue damage in traumatic injuries. Histotripsy is a focused ultrasound procedure that relies on controlled cavitation to homogenize soft tissue. Experimental studies of histotripsy cavitation have shown that the extent of ablation in different tissues depends on tissue mechanical properties and waveform parameters. Variable tissue susceptibility to the large stresses, strains, and strain rates developed by cavitation bubbles has been suggested as a basis for localized liver tumor treatments that spare large vessels and bile ducts. However, field quantities developed within microns of cavitation bubbles are too localized and transient to measure in experiments. Previous numerical studies have attempted to circumvent this challenge but made limited use of realistic tissue property data. In this study, numerical simulations are used to calculate stress, strain, and strain rate fields produced by bubble oscillation under histotripsy forcing in a variety of tissues with literature-sourced viscoelastic and acoustic properties. Strain field calculations are then used to predict a theoretical damage radius using tissue ultimate strain data. Simulation results support the hypothesis that differential tissue responses could be used to design tissue-selective treatments. Results agree with studies correlating tissue ultimate fractional strain with resistance to histotripsy ablation and are also consistent with experiments demonstrating smaller lesion size under exposure to higher frequency waveforms. Methods presented in this study provide an approach for modeling tissue-selective cavitation damage in general.

Comparative study of the dynamics of laser and acoustically generated bubbles in viscoelastic media.

Experimental observations of the growth and collapse of acoustically and laser-nucleated single bubbles in water and agarose gels of varying stiffness are presented. The maximum radii of generated bubbles decreased as the stiffness of the media increased for both nucleation modalities, but the maximum radii of laser-nucleated bubbles decreased more rapidly than acoustically nucleated bubbles as the gel stiffness increased. For water and low stiffness gels, the collapse times were well predicted by a Rayleigh cavity, but bubbles collapsed faster than predicted in the higher stiffness gels. The growth and collapse phases occurred symmetrically (in time) about the maximum radius in water but not in gels, where the duration of the growth phase decreased more than the collapse phase as gel stiffness increased. Numerical simulations of the bubble dynamics in viscoelastic media showed varying degrees of success in accurately predicting the observations.

Determinantes del mantenimiento del consumo de tabaco: extensión de la Teoría de la Conducta Planificada / Determinants of maintenance snuff consumption: extension of the Theory of Planned Behavior

El objetivo fundamental de este trabajo es explorar la importancia de las emociones positivas y negativas, la norma moral y la conducta pasada en la intención de mantener el consumo del tabaco más allá de la explicación dada por la Teoría de la Conducta Planificada. Se utilizó una muestra final de 202 estudiantes fumadores de la Universidad de Santiago de Compostela, con edades comprendidas entre 18 y 25 años. Los resultados muestran que las variables añadidas aumentan de forma significativa la capacidad explicativa del modelo (ΔR² = 20 %). Esto, junto con la relación que presentan estas variables con la intención conductual [emociones positivas (β = .23); norma moral (β = -.14); conducta pasada (β= .72)], es lo que hace que estas variables adquieran relevancia explicativa en el modelo y nos dote de herramientas necesarias para intervenir y ayudar a mejorar la salud de nuestros jóvenes.

The main objective of this paper is to explore the importance of positive and negative emotions, the moral norm and the past behavior in the intention of keeping the consumption of snuff beyond the explanation given by the Theory of Planned Behavior. A final sample of202 smokers students at the University of Santiago de Compostela, aged between 18 and 25 years was used. The results show that the added variables significantly increase the explanatory power of the model (ΔR² = 20%). This, together with the list presented by these variables with behavioral intention [positive emotions (β = .23); moral norm (β = -.14); past behavior (β = .72)], it is what makes these explanatory variables acquire relevance in the model and we dowry of tools needed to intervene and help improve the health of our young's.

Computational analysis of the fructosyltransferase enzymes in plants, fungi and bacteria.

Fructosyltransferases (FTases) are enzymes produced by plants, fungi, and bacteria, which are responsible for the synthesis of fructooligosaccharides. In this study, we conducted a computational analysis of reported sequences for FTase from a diverse source of organisms, such as plants, fungi, and bacteria. Ninety-one proteins sequences were obtained; all belonging to the glycoside hydrolase 32 (GH32) and 68 (GH68) families. The sequences were grouped in seven clades, five for plants, one for fungi, and one for bacteria. Our findings suggest that FTases from fungi and bacteria likely evolved from dicotyledonous FTases. The analysis of catalytic domains A, D and E, which contain the amino acids involved in the catalytic binding site, allowed the identification of clade-specific conserved characteristics. The analysis of sequence motifs involved in donor/acceptor molecule affinity showed that additional sequences could be responsible for donor/acceptor molecule affinity. The correlation of this large set of FTases allowed to identify additional features that might be used for the identification and classification of new FTases, and to improve the understanding of these valuable enzymes.

Gene cloning and enzyme structure modeling of the Aspergillus oryzae N74 fructosyltransferase.

The fructooligosaccharides (FOS) represent an important source of prebiotic compounds that are widely used as an ingredient in functional foods. Recently, the strain Aspergillus oryzae N74 was reported as a potential microorganism for the industrial production of FOS, due to its high yields of FOS production. In this work, we used a PCR-cloning strategy to clone the A. oryzae N74 ftase gene as a previous step for recombinant enzyme production. Ftase showed a 1630 bp size with a 99% similarity with other A. oryzae strains and between 1 to 68% identities with other Aspergillus strains. This gene encodes for a 525 amino acids protein with 99% similarity with other A. oryzae strains and between 11 to 69% similarities with other Aspergillus strains. Finally, an A. oryzae N74 FTase tertiary structure model was predicted base on its similarity with other glycoside hydrolase 32 family members. The active site was located inside the ß-propeller domain and was formed for non-charged polar and charged amino acids. In summary, these results shows the high level of sequence conservation between A. oryzae strains and represent a first step towards the development of a FOS production industrial process using recombinant microorganism carrying the ftase gene from A. oryzae N74.

Assessing GHG emissions, ecological footprint, and water linkage for different fuels.

Currently, transport is highly dependent on fossil fuels and responsible for about 23% of world energy-related GHG (greenhouse gas) emissions. Ethanol from sugar cane and corn emerges as an alternative for gasoline in order to mitigate GHG emissions. Additionally, deeper offshore drilling projects such as in the Brazilian Pre-Salt reservoirs and mining projects of nonconventional sources like Tar Sands in Canada could be a solution for supplying demand of fossil fuels in the short and midterm. Based on updated literature, this paper presents an assessment of GHG emissions for four different fuels: ethanol from sugar cane and from corn and gasoline from conventional crude oil and from tar sands. An Ecological Footprint analysis is also presented, which shows that ethanol from sugar cane has the lowest GHG emissions and requires the lowest biocapacity per unit of energy produced among these fuels. Finally, an analysis using the Embodied Water concept is made with the introduction of a new concept, the "CO(2)-Water", to illustrate the impacts of releasing carbon from underground to atmosphere and of the water needed to sequestrate it over the life cycle of the assessed fuels. Using this method resulted that gasoline from fossil fuels would indirectly "require" on average as much water as ethanol from sugar cane per unit of fuel energy produced.

Recent trends in fructooligosaccharides production.

Prebiotics are food ingredients that promote host health beneficially due to their effect over the growth and activity of probiotic bacterial species. Prebiotic properties have been demonstrated for inulin-type fructans, galactoolicosaccharides and lactulose. Fructooligosaccharides (FOS), considered as inulin-type fructans, represent an important source of prebiotic compounds that are widely used as an ingredient in functional foods. FOS are produced by the action of fructosyltransferase from many plants, fungi and bacteria, and they are mainly composed of 1-kestose, nystose, and 1-beta-fructofuranosyl nystose. Among them, 1-kestose has better therapeutic properties than those with a high polymeric degree (GF(n > 4)). FOS exhibited properties than those with a high polymeric degree (GF(n>4)). FOS exhibited properties such as low caloric values, non-cariogenic properties, decrease levels of lipids and cholesterol, help gut absorption of ions, and stimulate the bifidobacteria growth in the human colon. This review presents a summary of the patents related with FOS production by industrial sucrose biotransformation or the use of recombinant fructosyltransferase enzymes. Also, a brief description of recent FOS applications will be discussed.

[Mood state indicators for adolescent athletes based on POMS multidimensional model]. / Indicadores del estado de ánimo en deportistas adolescentes según el modelo multidimensional del POMS.

In this paper, we offer a short version of the POMS, with only 33 items, designed to apply to young Spanish athletes. One hundred and six male soccer players, aged 14 and 15 years, participated in the study. In order to select the proposed items, we tried to maximize three criteria: (1) items should be understood by subjects, (2) items should be perceived as conceptually similar as possible to the meaning of their respective factors, and (3) every factor should contain at least 4 items. To meet the second criterion, PROXSCAL scaling procedure was used, which allowed retaining the items closest to the meaning of each factor. All goodness-of-fit indexes were satisfactory in all the proximity analyses performed. In the proposed POMS version, the 33 items refer to seven mood factors, as follows: Tension (4 items), Depression (9 items), Anger (4 items), Vigour (4 items), Fatigue (4 items), Confusion (4 items), and Friendliness (4 items).

Obstrucción intestinal en la altura 1977-1986 / Intestinal obstruction during 1977-1986

En el Hospital "Daniel Alcides Carrión" de Huancayo, a 3,249 m.s.n.m., se han hospitalizado en el lapso de 10 años de enero de 1977 a diciembre de 1986, 467 pacientes con diagnóstico de obstrucción intestinal aguda. Para ello, se revisaron 12,213 Historias Clínicas en el Departamento de Cirugía, encontrando seis causas principales de obstrucción intestinal aguda. a.- Vólvulo del intestino grueso (40.04%), b.- Vólvulo de intestino delgado (23.13%), c.- Bridas y adherencias (10.07%), d.- Hernias externas estranguladas (24.83%), e.- Neoplasias externas estranguladas (24.83%), e.- Neoplasias de colon (1.29%), f.- Cuerpos extraños (0.64%). La edad ha fluctuado desde los cinco a los 87 años de edad. El sexo masculino estuvo en ventaja al sexo femenino en una proporción de 2 a 1. Se precticaron a nivel del intestino grueso 193 resecciones primarias (41.33%), por vólvulo y neoplasias. A nivel del intestino delgado, se realizaron 131 resecciones primarias (28.05%, por vólvulo, bridas y adherencias post-operatoria, hernias estranguladas y cuerpo extraño en íleon. La anastomosis con resultados satisfactorios ha sido la término-terminal en dos planos a puntos separados. En resumen, se han realizado 324 (69.38%) resecciones primarias del intestino grueso y delgado y, 143 (30.62%) pacientes recibieron tratamiento quirúrgico conservador. La complicación más frecuente fué la infección de herida operatoria (76.64%). El tiempo promedio de hospitalización fué de 15 días...