Real-Time Visualization and Dynamics of Boron Nitride Nanotubes Undergoing Brownian Motion.

We report the first real-time imaging of individualized boron nitride nanotubes (BNNTs) via stabilization with a rhodamine surfactant and fluorescence microscopy. We study the rotational and translational diffusion and find them to agree with predictions based on a confined, high-aspect-ratio rigid rod undergoing Brownian motion. We find that the behavior of BNNTs parallels that of individualized carbon nanotubes (CNTs), indicating that BNNTs could also be used as model rigid rods to study soft matter systems, while avoiding the experimental disadvantages of CNTs due to their strong light absorption. The use and further development of our technique and findings will accelerate the application of BNNTs from material engineering to biological studies.

Adverse Effect of PTFE Stir Bars on the Covalent Functionalization of Carbon and Boron Nitride Nanotubes Using Billups-Birch Reduction Conditions.

The functionalization of nanomaterials has long been studied as a way to manipulate and tailor their properties to a desired application. Of the various methods available, the Billups-Birch reduction has become an important and widely used reaction for the functionalization of carbon nanotubes (CNTs) and, more recently, boron nitride nanotubes. However, an easily overlooked source of error when using highly reductive conditions is the utilization of poly(tetrafluoroethylene) (PTFE) stir bars. In this work, we studied the effects of using this kind of stir bar versus using a glass stir bar by measuring the resulting degree of functionalization with 1-bromododecane. Thermogravimetric analysis studies alone could deceive one into thinking that reactions stirred with PTFE stir bars are highly functionalized; however, the utilization of spectroscopic techniques, such as Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, tells otherwise. Furthermore, in the case of CNTs, we determined that using Raman spectroscopy alone for analysis is not sufficient to demonstrate successful chemical modification.

Surfactant-assisted individualization and dispersion of boron nitride nanotubes.

Boron nitride nanotubes (BNNTs) belong to a novel class of material with useful thermal, electronic and optical properties. However, the study and the development of applications of this material requires the formation of stable dispersions of individual BNNTs in water. Here we address the dispersion of BNNT material in water using surfactants with varying properties. The surfactants were compared based on the quantity of BNNTs dispersed and the quality of the dispersions, as visualized by AFM and cryo-TEM. All surfactants produce dispersions of individualized or small bundles of BNNTs. Of the surfactants tested, high molecular weight, nonionic surfactants suspend the most BNNTs, while ionic surfactants remove the most h-BN impurities. The surfactant dispersions were further characterized by ensemble measurements, such as UV absorption and photoluminescence, dynamic light scattering (DLS), and zeta potential to investigate dispersion stability and quality. These techniques provide a facile strategy for testing future BNNT dispersions. The results of this study reveal that BNNT dispersions in aqueous solution can be tuned to fit a specific application through surfactant selection.

An Insight into the Phase Transformation of WS2 upon Fluorination.

The transformation from semiconducting to metallic phase, accompanied by a structural transition in 2D transition metal dichalcogenides has attracted the attention of the researchers worldwide. The unconventional structural transformation of fluorinated WS2 (FWS2 ) into the 1T phase is described. The energy difference between the two phases debugs this transition, as fluorination enhances the stability of 1T FWS2 and makes it energetically favorable at higher F concentration. Investigation of the electronic and optical nature of FWS2 is supplemented by possible band structures and bandgap calculations. Magnetic centers in the 1T phase appear in FWS2 possibly due to the introduction of defect sites. A direct consequence of the phase transition and associated increase in interlayer spacing is a change in friction behavior. Friction force microscopy is used to determine this effect of functionalization accompanied phase transformation.

Fluorinated h-BN as a magnetic semiconductor.

We report the fluorination of electrically insulating hexagonal boron nitride (h-BN) and the subsequent modification of its electronic band structure to a wide bandgap semiconductor via introduction of defect levels. The electrophilic nature of fluorine causes changes in the charge distribution around neighboring nitrogen atoms in h-BN, leading to room temperature weak ferromagnetism. The observations are further supported by theoretical calculations considering various possible configurations of fluorinated h-BN structure and their energy states. This unconventional magnetic semiconductor material could spur studies of stable two-dimensional magnetic semiconductors. Although the high thermal and chemical stability of h-BN have found a variety of uses, this chemical functionalization approach expands its functionality to electronic and magnetic devices.

Increased solubility and fiber spinning of graphenide dispersions aided by crown-ethers.

Graphenide solutions in NMP have been prepared by dispersing potassium intercalated graphite with the assistance of 18-crown-6. The highest graphenide solubility achieved is 1.5 mg mL-1. Graphenide solutions have been applied to spin graphene/SWCNT hybrid fibers.

Stabilization of amorphous paracetamol based systems using traditional and novel strategies.

There is a special interest in having pharmaceutical active ingredients in the amorphous state due to their increased solubility and therefore, higher bioavailability. Nevertheless, not all of them present stable amorphous phases. In particular, paracetamol is an active ingredient widely known for its instability when prepared in the amorphous state. In the present work thermally stable amorphous binary paracetamol based systems were obtained showing stability on a wide range of temperatures: below its glass transition temperature (Tg) as amorphous solids in the glassy state and above their glass transition temperature, where these materials exist as stable supercooled liquids. To achieve stabilization of the binary paracetamol based system several strategies were applied and optimized, being the selection of the container material a key and novel approach to control the mechanical stress during cooling, eliminating cracks which act as nucleation centers leading to crystallization.

Development of the family needs assessment tool for caregivers of individuals with neurological conditions in Latin America / Desarrollo del instrumento de evaluación de las necesidades familiares para cuidadores de personas con alteraciones neurológicas en Latinoamérica

This study developed and examined the psychometric proprieties of the Spanish Family Needs Assessment Tool (FNAT) for caregivers of individuals with neurological conditions in Latin America. Twentyseven items from previously published caregiver family needs scales were combined to represent nine types of needs. These items were administered to 308 caregivers of individuals with neurological conditions in Latin America. An exploratory factor analysis suggested the retention 14 items and five factors: Household Needs, Informational Needs, Financial Needs, Health Needs, and Social Support Needs. A confirmatory factor analysis then examined the fit of the five-factor solution and suggested adequate model fit. Cronbach's alphas for the overall scale and subscales suggested acceptable internal consistency. The FNAT holds promise to help researchers and clinicians assess the family needs of caregivers in Latin America.

El objetivo de este estudio fue evaluar las propiedades psicométricas del instrumento de evaluación de necesidades familiares (FNAT) en un grupo de 308 cuidadores de personas con alteraciones neurológicas en Latinoamérica. El FNAT consta de 27 ítems que miden algunas de las principales necesidades que experimentan los cuidadores de estas personas. Con el objetivo de determinar la estructura factorial del instrumento se realizó un análisis factorial exploratorio. Los resultados muestran que de los 27 ítems iniciales del instrumento se obtuvieron 5 factores (Necesidades de ayuda en tareas domésticas, necesidades de recibir información, necesidades apoyo financiero, necesidades de ayuda para mejorar la salud y necesidades de apoyo social) que estarían conformados por 14 ítems. Mediante un análisis factorial confirmatorio, se evaluó el nivel de ajuste de estos cinco factores cuyo resultado final muestra un ajuste adecuado del modelo y un nivel aceptable de consistencia interna tanto para la escala completa como para las subescalas. En conclusión, esta nueva versión del FNAT de 14 ítems posee buenas características psicométricas que lo hacen ser un instrumento confiable en la evaluación de las necesidades de cuidadores de personas con alteraciones neurológicas tanto en contextos clínicos como de investigación.

The ties that bind: the relationship between caregiver burden and the neuropsychological functioning of TBI survivors.

Advances in medical and assistive technology have increased the likelihood of survival following a traumatic brain injury (TBI). Consequently, families frequently must provide care to individuals with TBI. Because they are rarely prepared for the associated demanding medical needs and financial burden, family caregivers are at risk for physical and emotional problems, which can negatively influence their individual and family functioning. Whereas scholars have examined the influence of survivor functioning on caregiver burden, few have explicitly recognized that caregiver burden also influences survivor functioning. Results of a multivariate linear regression suggest that, in a sample of 51 pairs of TBI survivors and their caregivers living in Colombia, survivors receiving care from a family member who reported a higher level of burden had poorer objective neuropsychological functioning than those receiving care from a family member who reported a lower level of burden, after controlling for survivor education and history of occupational therapy. Therefore, a family-focused approach might maximize intervention effectiveness, especially for Latin American and Hispanic families, which tend to be characterized by a strong sense of familism. The emphasis on family can create problems in a healthcare system that views the individual as the primary unit.

Memoria de trabajo y rendimiento académico en estudiantes de primer semestre de una universidad de la ciudad de barranquilla / Working memory and academic achievement in freshmen students of a university in barranquilla

La memoria de trabajo puede ser un componente de gran influencia en el rendimiento académico, aunque no es el único que lo determina. Este artículo muestra los resultados de una investigación en la que se intentó determinar la correlación que existe entre la memoria de trabajo y el rendimiento académico en estudiantes de primer semestre de diferentes programas de una universidad de Barranquilla. No se encontró correlación entre ninguna de las medidas de memoria de trabajo utilizadas y el rendimiento académico de los participantes. Estos resultados pueden ser explicados por los efectos que otras variables tienen en el rendimiento académico, como la cognición, la motivación, el afecto y el contexto.

Working memory can influence academic achievement, eventhough is not the only component. This article shows research findings that tried to determine the correlation between working memory and academic achievement in freshmen students of a university in Barranquilla. There was not correlation between any of the working memory measures used and academic achievement. These results can be explained throughout many variables that can affect academic achievement such as, cognition, motivation, emotion and context.

Efectos musculares de las pistas directas planas en pacientes de 3 a 5 años con mordida profunda / Muscular effects of Planas Direct Tracks in patients from 3 to 5 years with deep bite

Se realizó un estudio piloto con el propósito de evaluar los cambios electromiográficos producidos por la adaptación de Pistas Directas de Planas (PDP) en una muestra de 7 niños entre los 3 y los 5 años de edad en quienes se había diagnosticado mordida profunda. Para el efecto antes de colocar las Pistas de Planas se efectuó un primer registro electromiográfico de los músculos temporal anterior y masetero derechos mientras el paciente masticaba una goma de mascar sin edulcorantes. Luego de 1 mes de la adaptación de las PDP se llevo a cabo un segundo registro del funcionamiento de los mismos haces musculares con las mismas condiciones y a continuación se realizaron las comparaciones de los dos registros obtenidos. Aunque se presentó una tendencia a la disminución de la actividad electromiográfica, los cambios no fueron estadísticamente significativos.

A pilot study in a sample of 7 children with deep bite and between 3 and 5 years old was carried out to evaluate the electromyographic changes after Planas Direct Tracks (PDT) adaptation. An initial electromyographic register of the masseter and anterior temporal right muscles was made while the children chewed gum. A month after the PDT adaptation, a second electromyographic register was taken and comparisons were made. Although an electromyographic activity decrease tendency was presented, the changes were not statistically significant.