Task failure from inspiratory resistive loaded breathing: a role for inspiratory muscle fatigue?

The use of non-invasive resistive breathing to task failure to assess inspiratory muscle performance remains a matter of debate. CO2 retention rather than diaphragmatic fatigue was suggested to limit endurance during inspiratory resistive breathing. Cervical magnetic stimulation (CMS) allows discrimination between diaphragmatic and rib cage muscle fatigue. We tested a new protocol with respect to the extent and the partitioning of inspiratory muscle fatigue at task failure. Nine healthy subjects performed two runs of inspiratory resistive breathing at 67 (12)% of their maximal inspiratory mouth pressure, respiratory rate ( f R), paced at 18min-1, with a 15-min pause between runs. Diaphragm and rib cage muscle contractility were assessed from CMS-induced esophageal (P es,tw), gastric (P ga,tw), and transdiaphragmatic (P di,tw) twitch pressures. Average endurance times of the first and second runs were similar [9.1 (6.7)and 8.4 (3.5)min]. P di,tw significantly decreased from 33.1 to 25.9cmH2O in the first run, partially recovered (27.6cmH2O), and decreased further in the second run (23.4cmH2O). P es,tw also decreased significantly (-5.1 and -2.4cmH2O), while P ga,tw did not change significantly (-2.0 and -1.9cmH2O), indicating more pronounced rib cage rather than diaphragmatic fatigue. End-tidal partial pressure of CO2 (P ETCO2) rose from 37.2 to 44.0 and 45.3mmHg, and arterial oxygen saturation (S aO2) decreased in both runs from 98% to 94%. Thus, task failure in mouth-pressure-targeted, inspiratory resistive breathing is associated with both diaphragmatic and rib cage muscle fatigue. Similar endurance times despite different degrees of muscle fatigue at the start of the runs indicate that other factors, e.g. increases in P ETCO2, and/or decreases in S aO2, probably contributed to task-failur

Arctic warming, moisture increase and circulation changes observed in the Ny-Ålesund homogenized radiosonde record

Radiosonde measurements obtained at the Arctic site Ny-Ålesund (78.9°N, 11.9°E), Svalbard, from 1993 to 2014 have been homogenized accounting for instrumentation discontinuities by correcting known errors in the manufacturer provided profiles. The resulting homogenized radiosonde record is provided as supplementary material at http://doi.pangaea.de/10.1594/PANGAEA.845373. From the homogenized data record, the first Ny-Ålesund upper-air climatology of wind, temperature and humidity is presented, forming the background for the analysis of changes during the 22-year period. Particularly during the winter season, a strong increase in atmospheric temperature and humidity is observed, with a significant warming of the free troposphere in January and February up to 3 K per decade. This winter warming is even more pronounced in the boundary layer below 1 km, presumably amplified by mesoscale processes including e.g. orographic effects or the boundary layer capping inversion. Though the largest contribution to the increasing atmospheric water vapour column in winter originates from the lowermost 2 km, no increase in the contribution by specific humidity inversions is detected. Instead, we find an increase in the humidity content of the large-scale background humidity profiles. At the same time, the tropospheric flow in winter is found to occur less frequent from northerly directions and to the same amount more frequent from the South. We conclude that changes in the atmospheric circulation lead to an enhanced advection of warm and moist air from lower latitudes to the Svalbard region in the winter season, causing the warming and moistening of the atmospheric column above Ny-Ålesund, and link the observations to changes in the Arctic Oscillation

Methods and apparatus for additive manufacturing of glass

In illustrative implementations of this invention, a crucible kiln heats glass such that the glass becomes or remains molten. A nozzle extrudes the molten glass while one or more actuators actuate movements of the nozzle, a build platform or both. A computer controls these movements such that the extruded molten glass is selectively deposited to form a 3D glass object. The selective deposition of molten glass occurs inside an annealing kiln. The annealing kiln anneals the glass after it is extruded. In some cases, the actuators actuate the crucible kiln and nozzle to move in horizontal x, y directions and actuate the build platform to move in a z-direction. In some cases, fluid flows through a cavity or tubes adjacent to the nozzle tip, in order to cool the nozzle tip and thereby reduce the amount of glass that sticks to the nozzle tip

Symptoms of Arctic Amplification observed in Ny-Ålesund

Over the recent decades, temperature increase in the Arctic has been almost twice as large as the global average. This amplification of global warming is attributed to various feedback mechanisms present in the Arctic environment. Some processes are locally confined to the diminishing sea ice cover of the Arctic ocean, particularly the sea ice – albedo effect during polar day. Other amplifying processes related to the increasing open water surface of the Arctic ocean include e.g. the increasing heat flux from the ocean to the atmosphere. The resulting latent heat flux and augmenting evaporation contribute to an increasing atmospheric moisture content, which affects the longwave downward radiation directly or via changing cloud microphysics. Furthermore, atmospheric moisture and heat are more frequently advected from lower latitudes into the Arctic in relation to changes in the atmospheric circulation. During the dark period of polar night, the Arctic warming trend is not homogenously distributed over the polar cap, but occurs strongest at the surface in the Barents / Kara Seas and in the free troposphere of the Arctic North Atlantic sector. Thus, Svalbard is located in a key region of climate change. Observations from Ny-Ålesund at the west coast of the Svalbard archipelago show an annual temperature increase of 1.4 K per decade since the 1990s, with an average temperature that by now exceeds those observed during the early Arctic warming period in the 1920 to 1940s. The recent winter warming is even twice as high, and is accompanied by an increase in atmospheric moisture. Surface radiation observations in winter further indicate a change in cloudiness along with an increase in net longwave radiation. Although the winter warming is bottom-amplified, radiosonde observations show that the increasing temperature signal occurs over the entire troposphere. Indeed, part of the Svalbard winter warming is associated with enhanced warm and moist air advection in the free troposphere caused by increased cyclonic activity related to changes in atmospheric circulation patterns. The various processes contributing to Arctic amplification of climate warming link the local observations from Ny-Ålesund with processes occurring both in the Arctic and in the northern hemispheric mid-latitudes

Vertical thermodynamic structure of the troposphere during the Norwegian young sea ICE expedition

The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and boundary layer characteristics. We provide statistics of temperature inversion characteristics, static stability, and boundary layer extent. During winter, when radiative cooling is most effective, we find the strongest impact of synoptic cyclones. Changes to thermodynamic characteristics of the boundary layer are associated with transitions between the radiatively “clear” and “opaque” atmospheric states. In spring, radiative fluxes warm the surface leading to lifted temperature inversions and a statically unstable boundary layer. Further, we compare the N-ICE2015 static stability distributions to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Ålesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. For Ny-Ålesund, we observe similar characteristics above 1000 m, while the topography and ice-free fjord surrounding Ny-Ålesund generate great differences below. The long-term radiosonde record (1993–2014) from Ny-Ålesund indicates that during the N-ICE2015 spring period, temperatures were close to the climatological mean, while the lowest 3000 m were 1–3∘C warmer than the climatology during winter

Additive Manufacturing of Optically Transparent Glass

We present a fully functional material extrusion printer for optically transparent glass. The printer is composed of scalable modular elements able to operate at the high temperatures required to process glass from a molten state to an annealed product. We demonstrate a process enabling the construction of 3D parts as described by computer-aided design models. Processing parameters such as temperature, which control glass viscosity, and flow rate, layer height, and feed rate can thus be adjusted to tailor printing to the desired component, its shape, and its properties. We explored, defined, and hard-coded geometric constraints and coiling patterns as well as the integration of various colors into the current controllable process, contributing to a new design and manufacturing space. We report on performed characterization of the printed materials executed to determine their morphological, mechanical, and optical properties. Printed parts demonstrated strong adhesion between layers and satisfying optical clarity. This molten glass 3D printer demonstrates the production of parts that are highly repeatable, enable light transmission, and resemble the visual and mechanical performance of glass constructs that are conventionally obtained. Utilizing the optical nature of glass, complex caustic patterns were created by projecting light through the printed objects. The 3D-printed glass objects described here can thus be extended to implementations across scales and functional domains including product and architectural design. This research lies at the intersection of design, engineering, science, and art, representing a highly interdisciplinary approach.Massachusetts Institute of Technology. Department of Mechanical EngineeringGlass Art Society (Technology Advancing Glass Grant