Direct observation of liquid crystals using cryo-TEM: Specimen preparation and low-dose imaging

Liquid crystals (LCs) represent a challenging group of materials for direct transmission electron microscopy (TEM) studies due to the complications in specimen preparation and the severe radiation damage. In this paper, we summarize a series of specimen preparation methods, including thin film and cryo-sectioning approaches, as a comprehensive toolset enabling high-resolution direct cryo-TEM observation of a broad range of LCs. We also present comparative analysis using cryo-TEM and replica freeze-fracture TEM on both thermotropic and lyotropic LCs. In addition to the revisits of previous practices, some new concepts are introduced, e.g., suspended thermotropic LC thin films, combined high-pressure freezing and cryo-sectioning of lyotropic LCs, and the complementary applications of direct TEM and indirect replica TEM techniques. The significance of subnanometer resolution cryo-TEM observation is demonstrated in a few important issues in LC studies, including providing direct evidences for the existence of nanoscale smectic domains in nematic bent-core thermotropic LCs, comprehensive understanding of the twist-bend nematic phase, and probing the packing of columnar aggregates in lyotropic chromonic LCs. Direct TEM observation opens ways to a variety of TEM techniques, suggesting that TEM (replica, cryo, and in situ techniques), in general, may be a promising part of the solution to the lack of effective structural probe at the molecular scale in LC studies. Microsc. Res. Tech. 77:754-772, 2014. © 2014 Wiley Periodicals, Inc.

Assessing distractors and teamwork during surgery: developing an event-based method for direct observation

OBJECTIVE: To develop a behavioural observation method to simultaneously assess distractors and communication/teamwork during surgical procedures through direct, on-site observations; to establish the reliability of the method for long (>3 h) procedures. METHODS: Observational categories for an event-based coding system were developed based on expert interviews, observations and a literature review. Using Cohen's κ and the intraclass correlation coefficient, interobserver agreement was assessed for 29 procedures. Agreement was calculated for the entire surgery, and for the 1st hour. In addition, interobserver agreement was assessed between two tired observers and between a tired and a non-tired observer after 3 h of surgery. RESULTS: The observational system has five codes for distractors (door openings, noise distractors, technical distractors, side conversations and interruptions), eight codes for communication/teamwork (case-relevant communication, teaching, leadership, problem solving, case-irrelevant communication, laughter, tension and communication with external visitors) and five contextual codes (incision, last stitch, personnel changes in the sterile team, location changes around the table and incidents). Based on 5-min intervals, Cohen's κ was good to excellent for distractors (0.74-0.98) and for communication/teamwork (0.70-1). Based on frequency counts, intraclass correlation coefficient was excellent for distractors (0.86-0.99) and good to excellent for communication/teamwork (0.45-0.99). After 3 h of surgery, Cohen's κ was 0.78-0.93 for distractors, and 0.79-1 for communication/teamwork. DISCUSSION: The observational method developed allows a single observer to simultaneously assess distractors and communication/teamwork. Even for long procedures, high interobserver agreement can be achieved. Data collected with this method allow for investigating separate or combined effects of distractions and communication/teamwork on surgical performance and patient outcomes.

First direct observation of sputtered lunar oxygen

We present the first direct measurement of neutral oxygen in the lunar exosphere, detected by the Chandrayaan-1 Energetic Neutral Analyzer (CENA). With the lunar surface consisting of about 60% of oxygen in number, the neutral oxygen detected in CENA's energy range (11 eV−3.3 keV) is attributed to have originated from the lunar surface, where it was released through solar wind ion sputtering. Fitting of CENA's mass spectra with calibration spectra from ground and in-flight data resulted in the detection of a robust oxygen signal, with a flux of 0.2 to 0.4 times the flux of backscattered hydrogen, depending on the solar wind helium content and particle velocity. For the two solar wind types observed, we derive subsolar surface oxygen atom densities of N0= (1.1 ± 0.3) · 107m−3 and (1.4 ± 0.4) · 107m−3, respectively, which agree well with earlier model predictions and measured upper limits. From these surface densities, we derive column densities of NC= (1.5 ± 0.5) · 1013 m−2and (1.6 ± 0.5) · 1013 m−2. In addition, we identified for the first time a helium component. This helium is attributed to backscattering of solar wind helium (alpha particles) from the lunar surface as neutral energetic helium atoms, which has also been observed for the first time. This identification is supported by the characteristic energy of the measured helium atoms, which is roughly 4 times the energy of reflected solar wind hydrogen, and the correlation with solar wind helium content.

Tracking individual membrane proteins and their biochemistry: The power of direct observation

The advent of single molecule fluorescence microscopy has allowed experimental molecular biophysics and biochemistry to transcend traditional ensemble measurements, where the behavior of individual proteins could not be precisely sampled. The recent explosion in popularity of new super-resolution and super-localization techniques coupled with technical advances in optical designs and fast highly sensitive cameras with single photon sensitivity and millisecond time resolution have made it possible to track key motions, reactions, and interactions of individual proteins with high temporal resolution and spatial resolution well beyond the diffraction limit. Within the purview of membrane proteins and ligand gated ion channels (LGICs), these outstanding advances in single molecule microscopy allow for the direct observation of discrete biochemical states and their fluctuation dynamics. Such observations are fundamentally important for understanding molecular-level mechanisms governing these systems. Examples reviewed here include the effects of allostery on the stoichiometry of ligand binding in the presence of fluorescent ligands; the observation of subdomain partitioning of membrane proteins due to microenvironment effects; and the use of single particle tracking experiments to elucidate characteristics of membrane protein diffusion and the direct measurement of thermodynamic properties, which govern the free energy landscape of protein dimerization. The review of such characteristic topics represents a snapshot of efforts to push the boundaries of fluorescence microscopy of membrane proteins to the absolute limit.

Direct observation of molecular arrays in the organized smooth endoplasmic reticulum.

BACKGROUND Tubules and sheets of endoplasmic reticulum perform different functions and undergo inter-conversion during different stages of the cell cycle. Tubules are stabilized by curvature inducing resident proteins, but little is known about the mechanisms of endoplasmic reticulum sheet stabilization. Tethering of endoplasmic reticulum membranes to the cytoskeleton or to each other has been proposed as a plausible way of sheet stabilization. RESULTS Here, using fluorescence microscopy we show that the previously proposed mechanisms, such as membrane tethering via GFP-dimerization or coiled coil protein aggregation do not explain the formation of the calnexin-induced organized smooth endoplasmic reticulum membrane stacks. We also show that the LINC complex proteins known to serve a tethering function in the nuclear envelope are excluded from endoplasmic reticulum stacks. Finally, using cryo-electron microscopy of vitreous sections methodology that preserves cellular architecture in a hydrated, native-like state, we show that the sheet stacks are highly regular and may contain ordered arrays of macromolecular complexes. Some of these complexes decorate the cytosolic surface of the membranes, whereas others appear to span the width of the cytosolic or luminal space between the stacked sheets. CONCLUSION Our results provide evidence in favour of the hypothesis of endoplasmic reticulum sheet stabilization by intermembrane tethering.

El ordenamiento territorial en zonas de montaña

El proyecto de investigación para el Ordenamiento Territorial del Valle de Lerma (Salta, Argentina), incluye tanto zonas de valle propiamente dicho como sectores altos (hasta la divisoria de cuencas – aproximadamente de 2000 msnm hacia E y 4500 msnm hacia O). Se plantea la necesidad de un diagnóstico socio-económico. El objetivo es una aproximación real al sistema, mediante la observación directa y la interacción con los pobladores locales. Interesa elaborar un modelo cognocitivo del escenario actual considerando las problemáticas y potencialidades asociadas a la calidad de vida, el uso del suelo y de los recursos naturales, las perspectivas de los pobladores locales y las tendencia de las actividades productivas. El fin último es llegar a elaborar propuestas que permitan la mejora de la calidad de vida y el desarrollo productivo, en un contexto de creatividad y respeto, si se pretende signar las bases para la “conservación" e impulso de estas áreas. La información secundaria disponible sobre las zonas altas es prácticamente inexistente, por lo cual se pretende efectuar salidas de campo a los sectores altos para la georeferenciación de recorridos, sitios de valor cultural y natural, accidentes geográficos, infraestructuras y comunidades dispersas, como así la observación y registro de problemáticas y potencialidades asociadas al uso de los recursos, visita a pobladores locales, entrevistas abiertas y participación en actividades cotidianas.

El DOI en las revistas científicas del portal SciELO

Se presenta una descripción del portal de revistas científicas SciELO y del identificador DOI a través de su alcance, año de creación, historia, administración, normativa, estructura, ISBN-A y fuentes de consulta. Se brinda información acerca de la aplicación del DOI en las citas bibliográficas: en los estilos APA y Vancouver y en las normas ISO 690 (ISO, 2010) y ABNT 6023 (ABNT, 2002). El trabajo se propuso explorar el grado de implementación del DOI en las revistas científicas disponibles en SciELO, identificar el lugar de visualización del DOI, conocer la cantidad de editores según el prefijo DOI, determinar la cantidad de títulos de revistas que incluyen en el sufijo el código ISSN e identificar grado de aplicación del DOI en los estilos y en las normas de citas bibliográficas disponibles dentro de SciELO. Se aplicó una metodología descriptiva donde los datos fueron recolectados a través de la observación directa de las páginas web de las 898 revistas vigentes disponibles entre los meses de diciembre de 2012 y enero de 2013 en el portal SciELO. Se concluye que: menos del 50 de los países que conforman SciELO en la actualidad están empleando el DOI en sus publicaciones; el código se visualiza fundamentalmente en los archivos HTML; sólo 30 de los 929 editores lo implementaron y que en la mayoría de los casos se incluye el ISSN dentro del sufijo del identificador y que, si bien SciELO utiliza el DOI en la totalidad de las citas de sus artículos, no lo hace en forma estricta tal como lo establecen las normas y los estilos

Approche empirique des difficultés de compréhension en traduction, mises en évidence par la méthode d'observation du raisonnement á voix haute (Protocole Verbal - PV)

Fil: Daule, Gabriela. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

El DOI en las revistas científicas del portal SciELO

Se presenta una descripción del portal de revistas científicas SciELO y del identificador DOI a través de su alcance, año de creación, historia, administración, normativa, estructura, ISBN-A y fuentes de consulta. Se brinda información acerca de la aplicación del DOI en las citas bibliográficas: en los estilos APA y Vancouver y en las normas ISO 690 (ISO, 2010) y ABNT 6023 (ABNT, 2002). El trabajo se propuso explorar el grado de implementación del DOI en las revistas científicas disponibles en SciELO, identificar el lugar de visualización del DOI, conocer la cantidad de editores según el prefijo DOI, determinar la cantidad de títulos de revistas que incluyen en el sufijo el código ISSN e identificar grado de aplicación del DOI en los estilos y en las normas de citas bibliográficas disponibles dentro de SciELO. Se aplicó una metodología descriptiva donde los datos fueron recolectados a través de la observación directa de las páginas web de las 898 revistas vigentes disponibles entre los meses de diciembre de 2012 y enero de 2013 en el portal SciELO. Se concluye que: menos del 50 de los países que conforman SciELO en la actualidad están empleando el DOI en sus publicaciones; el código se visualiza fundamentalmente en los archivos HTML; sólo 30 de los 929 editores lo implementaron y que en la mayoría de los casos se incluye el ISSN dentro del sufijo del identificador y que, si bien SciELO utiliza el DOI en la totalidad de las citas de sus artículos, no lo hace en forma estricta tal como lo establecen las normas y los estilos

Approche empirique des difficultés de compréhension en traduction, mises en évidence par la méthode d'observation du raisonnement á voix haute (Protocole Verbal - PV)

Fil: Daule, Gabriela. Universidad Nacional de La Plata. Facultad de Humanidades y Ciencias de la Educación; Argentina.

El DOI en las revistas científicas del portal SciELO

Se presenta una descripción del portal de revistas científicas SciELO y del identificador DOI a través de su alcance, año de creación, historia, administración, normativa, estructura, ISBN-A y fuentes de consulta. Se brinda información acerca de la aplicación del DOI en las citas bibliográficas: en los estilos APA y Vancouver y en las normas ISO 690 (ISO, 2010) y ABNT 6023 (ABNT, 2002). El trabajo se propuso explorar el grado de implementación del DOI en las revistas científicas disponibles en SciELO, identificar el lugar de visualización del DOI, conocer la cantidad de editores según el prefijo DOI, determinar la cantidad de títulos de revistas que incluyen en el sufijo el código ISSN e identificar grado de aplicación del DOI en los estilos y en las normas de citas bibliográficas disponibles dentro de SciELO. Se aplicó una metodología descriptiva donde los datos fueron recolectados a través de la observación directa de las páginas web de las 898 revistas vigentes disponibles entre los meses de diciembre de 2012 y enero de 2013 en el portal SciELO. Se concluye que: menos del 50 de los países que conforman SciELO en la actualidad están empleando el DOI en sus publicaciones; el código se visualiza fundamentalmente en los archivos HTML; sólo 30 de los 929 editores lo implementaron y que en la mayoría de los casos se incluye el ISSN dentro del sufijo del identificador y que, si bien SciELO utiliza el DOI en la totalidad de las citas de sus artículos, no lo hace en forma estricta tal como lo establecen las normas y los estilos

Temperature observation of CORK installation during ODP Leg 168

Four boreholes, drilled a few tens of meters into igneous basement on the eastern flank of the Juan de Fuca Ridge during ODP Leg 168, were sealed and instrumented for long-term monitoring to observe the hydrologic state of young sediment-sealed oceanic crust. The thermal regime is dominated by the effects of rapid fluid circulation in uppermost igneous basement driven by very small non-hydrostatic pressure gradients. Upper basement temperatures are uniform laterally between pairs of holes over distances of hundreds of meters to kilometers. In the case of two holes drilled into a sediment-buried basement ridge and adjacent valley, basement temperatures differ by less than 2 K despite the 2.2 km lateral separation of the sites and the 2.5:1 contrast in sediment cover thickness. Under conductive conditions, upper basement temperatures would differ by roughly 50 K. By comparison with modeling results, the observed degree of isothermality suggests a fluid flux of at least 10**-6 m/s (30 m/yr), and an effective permeability in the range of 10**-10 to 10**-9 m**2 in the uppermost igneous crust. The pressure difference available to drive this rapid flux between the ridge and valley, estimated by comparing the observed pressures via the isothermal upper basement hydrostat that is inferred to connect the two sites, is small (~2 kPa) and also suggests high permeability. Relative to the hydrostats defined by the local conductive sediment geotherms, substantial super-hydrostatic pressure (+18 kPa) is present within the buried basement ridge, and sub-hydrostatic pressure is present in the adjacent valley (-26 kPa). Such pressure differentials are the direct consequence of the advection-dominated thermal regime and small pressure losses in high-permeability basement, and are available to drive fluid seepage through sediment sections vertically up above and horizontally away from buried ridges, and down above valleys. No constraints are provided by any of the observations on the depth in the crust to which thermally or chemically significant flow might extend, although just as in the overlying sediments, the pattern of deep flow may be affected by the near-isothermal and near-hydrostatic conditions present in the permeable uppermost crustal section.

Tab. 1: Direct beam solar radiation measurements for selected stations in Polar regions

As part of a larger experiment, atmospheric turbidity measurements were carried out during the austral summer 1985/86 in Adelie Land, Eastern Antarctica at 1560 m elevation. A comparison of our measurements of the solar beam with those of other areas in the Arctic and Antarctic was carried out. Our values were higher than all measurements from the Arctic. For Antarctica, Plateau and Mizuho Stations, both higher in altitude, had somewhat higher values, while the value of the coastal stations were lower. We calculated also turbidity indexes such as Unke's turbidity factor T and Angstrom's turbidity coefficient ß. Mean values of T were around 2.0, which are low values indeed. Beta values were around 0.04, a rather typical value for polar regions. No trend in turbidity could be observed for the time of observation. Further, it could be shown that the decrease in intensity with increasing optical air mass was less pronounced for larger wavelengths than for shorter ones.