Lumbar puncture has, for many years, been the responsibility of the internal medicine physician or the neurologist. As more patients have undergone spine surgery and with the current increase in body ...mass index of the general population, the radiologist has been consulted with increasing frequency to perform lumbar puncture with fluoroscopic guidance. Radiology, in fact, is now the dominant overall provider of lumbar puncture procedures. The procedure is more difficult when the needle length increases, and if fluoroscopy is used, landmarks are more difficult to visualize with increasing subcutaneous fat. Our goal with this review was to describe our techniques for lumbar puncture in the difficult patient, with emphasis on using fluoroscopy in the obese patient and to suggest maneuvers that might make the procedure easier. Combining our experience from performing these procedures on an obese population, we would like to share our tips, especially with trainees early in their career.
Annually averaged solar radiation in the McMurdo Dry Valleys, Antarctica has varied by over 20 W m
during the past three decades; however, the drivers of this variability are unknown. Because small ...differences in radiation are important to water availability and ecosystem functioning in polar deserts, determining the causes are important to predictions of future desert processes. We examine the potential drivers of solar variability and systematically eliminate all but stratospheric sulfur dioxide. We argue that increases in stratospheric sulfur dioxide increase stratospheric aerosol optical depth and decrease solar intensity. Because of the polar location of the McMurdo Dry Valleys (77-78°S) and relatively long solar ray path through the stratosphere, terrestrial solar intensity is sensitive to small differences in stratospheric transmissivity. Important sources of sulfur dioxide include natural (wildfires and volcanic eruptions) and anthropogenic emission.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Cryoconite holes host active microbial communities despite their extreme physical conditions. In the McMurdo Dry Valleys of Antarctica, these perennially cold, mini-ecosystems form ice lids that can ...persist for many years thereby isolating the cryoconite from nutrient and carbon inputs. Despite much recent work on cryoconite holes in Antarctica, little is known about nutrient dynamics and limitations in these ice-enclosed ecosystems. We used multiple biogeochemical approaches, including stable isotope signatures (δ
15
N and δ
13
C), nutrients concentrations (C, N, P), and enzyme activities, to evaluate what nutrients are likely limiting to biological activity in cryoconite hole sediments on Taylor, Canada, and Commonwealth glaciers in Taylor Valley, one of the McMurdo Dry Valleys. Nutrient concentrations (C, N, and P) varied in accordance with previous studies showing that the most inland of the three glaciers (Taylor Glacier) is the most oligotrophic. C-to-N ratios of Canada and Commonwealth cryoconite-hole sediments were close to the global mean for biologically-active sediments and soils, whereas Taylor Glacier cryoconite deviated from the global mean and were similar to the high C:N ratios seen in Taylor Valley soils. C and N stable isotope signatures on Commonwealth and Canada glaciers are congruent with values for efficient C and N fixation by nostocalean cyanobacteria, combined with higher levels of denitrification on Canada Glacier. In contrast, stable isotope signatures on the more oligotrophic Taylor Glacier are reflective of atmospheric deposition of N and C, or N inputs from nearby soils. Enzyme stoichiometric approaches further support extreme nutrient limitation on Taylor Glacier and indicate that P is the ultimate limiting nutrient across all three glaciers. Extremely high DIN-to-phosphate ratios also indicate P limitation across all three glaciers with Commonwealth Glacier being less severely P-limited than the other two glaciers. At a broader scale, this work provides a comprehensive framework for understanding how biogeochemical cycling of C, N and P vary across nutrient and climatic gradients in the cryobiosphere, and point towards the need for experimental work to test the relative controls of climate, microbes, and nutrients on biogeochemistry of cryoconite holes and other ecosystems of the cryosphere.
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DOBA, EMUNI, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We assessed the feasibility of the Molecular Transducers of Physical Activity Consortium (MoTrPAC) human adult clinical exercise protocols, while also documenting select cardiovascular, metabolic, ...and molecular responses to these protocols. After phenotyping and familiarization sessions, 20 subjects (25 ± 2 yr, 12 M, 8 W) completed an endurance exercise bout (
= 8, 40 min cycling at 70% V̇o
), a resistance exercise bout (
= 6, ∼45 min, 3 sets of ∼10 repetition maximum, 8 exercises), or a resting control period (
= 6, 40 min rest). Blood samples were taken before, during, and after (10 min, 2 h, and 3.5 h) exercise or rest for levels of catecholamines, cortisol, glucagon, insulin, glucose, free fatty acids, and lactate. Heart rate was recorded throughout exercise (or rest). Skeletal muscle (vastus lateralis) and adipose (periumbilical) biopsies were taken before and ∼4 h following exercise or rest for mRNA levels of genes related to energy metabolism, growth, angiogenesis, and circadian processes. Coordination of the timing of procedural components (e.g., local anesthetic delivery, biopsy incisions, tumescent delivery, intravenous line flushes, sample collection and processing, exercise transitions, and team dynamics) was reasonable to orchestrate while considering subject burden and scientific objectives. The cardiovascular and metabolic alterations reflected a dynamic and unique response to endurance and resistance exercise, whereas skeletal muscle was transcriptionally more responsive than adipose 4 h postexercise. In summary, the current report provides the first evidence of protocol execution and feasibility of key components of the MoTrPAC human adult clinical exercise protocols. Scientists should consider designing exercise studies in various populations to interface with the MoTrPAC protocols and DataHub.
This study highlights the feasibility of key aspects of the MoTrPAC adult human clinical protocols. This initial preview of what can be expected from acute exercise trial data from MoTrPAC provides an impetus for scientists to design exercise studies to interlace with the rich phenotypic and -omics data that will populate the MoTrPAC DataHub at the completion of the parent protocol.
The weather of the McMurdo Dry Valleys, Antarctica, the largest ice‐free region of the Antarctica, has been continuously monitored since 1985 with currently 14 operational meteorological stations ...distributed throughout the valleys. Because climate is based on a 30‐year record of weather, this is the first study to truly define the contemporary climate of the McMurdo Dry Valleys. Mean air temperature and solar radiation based on all stations were −20°C and 102 W m−2, respectively. Depending on the site location, the mean annual air temperatures on the valleys floors ranged between −15°C and −30°C, and mean annual solar radiation varied between 72 and 122 W m−2. Surface air temperature decreased by 0.7°C per decade from 1986 to 2006 at Lake Hoare station (longest continuous record), after which the record is highly variable with no trend. All stations with sufficiently long records showed similar trend shifts in 2005 ±1 year. Summer is defined as November through February, using a physically based process: up‐valley warming from the coast associated with a change in atmospheric stability.
Key Points
Thirty years of meteorological observations between 1986 and 2017 from McMurdo Dry Valleys, Antarctica, are summarized
Surface air temperatures decreased from 1986 to 2005 ±1
Summer season is redefined using physically based processes and is applicable to other ice‐free regions around Antarctica
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Numerous small alpine glaciers occupy the high elevation regions of the central and southern Sierra Nevada, California. An inventory based on 1∶24,000 topographic maps revealed 1719 glaciers and ...perennial snowfields for a total area of 39.15 ± 0.13 km2. The number of ‘true’ glaciers, versus non-moving ice, is estimated to be 122 covering 14.89 ± 0.08 km2 or 38% of the ice-covered area. Historic photographs, geologic evidence, and field mapping were used to determine the magnitude of area change over the past century at 14 glaciers. The area change between 1903 and 2004 ranged from −31% to −78%, averaging −55%. Based on these values rough estimates of volume change suggest an ice volume loss from 1903 (1.09 km3) to 2004 (0.43 km3) of 0.66 km3 (0.59 km3 water). Rapid retreat occurred over the first half of the 20th century beginning in the 1920s and continued through the 1960s after which recession ceased by the early 1980s and some glaciers advanced. Since the late 1980s glaciers resumed retreat with a rapid acceleration starting in the early 2000s. The relatively uniform timing of area changes in the study glaciers is a response to regional climate whereas the magnitude of change is influenced by local topographic effects. Area changes correlate significantly with changes in summer and winter air temperatures. Warmer winter temperatures warm the snowpack lengthening the summer melt season. Spring air temperatures and precipitation may also play an important role. The occurrence of spring snowfall can delay the onset of melt due to the increased surface albedo. Examining the influence of topographic variables we only found headwall height at the top of the glacier to show an influence on glacier change. Higher headwalls shadow the glacier from solar radiation reducing melt and enhancing snow accumulation via avalanching. If the glaciers continue to shrink at current (1972–2004) rates, most will disappear in 50–250 years.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
A discrete warming event (December 21, 2001-January 12, 2002) in the McMurdo Dry Valleys, Antarctica, enhanced glacier melt, stream flow, and melting of permafrost. Effects of this warming included a ...rapid rise in lake levels and widespread increases in soil water availability resulting from melting of subsurface ice. These increases in liquid water offset hydrologic responses to a cooling trend experienced over the previous decade and altered ecosystem properties in both aquatic and terrestrial ecosystems. Here, we present hydrological and meteorological data from the McMurdo Dry Valleys Long Term Ecological Research project to examine the influence of a discrete climate event (warming of >2 °C) on terrestrial environments and soil biotic communities. Increases in soil moisture following this event stimulated populations of a subordinate soil invertebrate species (Eudorylaimus antarcticus, Nematoda). The pulse of melt-water had significant influences on Taylor Valley ecosystems that persisted for several years, and illustrates that the importance of discrete climate events, long recognized in hot deserts, are also significant drivers of soil and aquatic ecosystems in polar deserts. Thus, predictions of Antarctic ecosystem responses to climate change which focus on linear temperature trends may miss the potentially significant influence of infrequent climate events on hydrology and linked ecological processes.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Among aquatic and terrestrial landscapes of the McMurdo Dry Valleys, Antarctica, ecosystem stoichiometry ranges from values near the Redfield ratios for C:N:P to nutrient concentrations in ...proportions far above or below ratios necessary to support balanced microbial growth. This polar desert provides an opportunity to evaluate stoichiometric approaches to understand nutrient cycling in an ecosystem where biological diversity and activity are low, and controls over the movement and mass balances of nutrients operate over 10–106 years. The simple organisms (microbial and metazoan) comprising dry valley foodwebs adhere to strict biochemical requirements in the composition of their biomass, and when activated by availability of liquid water, they influence the chemical composition of their environment according to these ratios. Nitrogen and phosphorus varied significantly in terrestrial and aquatic ecosystems occurring on landscape surfaces across a wide range of exposure ages, indicating strong influences of landscape development and geochemistry on nutrient availability. Biota control the elemental ratio of stream waters, while geochemical stoichiometry (e.g., weathering, atmospheric deposition) evidently limits the distribution of soil invertebrates. We present a conceptual model describing transformations across dry valley landscapes facilitated by exchanges of liquid water and biotic processing of dissolved nutrients. We conclude that contemporary ecosystem stoichiometry of Antarctic Dry Valley soils, glaciers, streams, and lakes results from a combination of extant biological processes superimposed on a legacy of landscape processes and previous climates.
Electrical impedance spectroscopy, in conjunction with the metal-organic framework (MOF) UiO-66-NH2, is used to detect trace levels of the explosive simulant 2,6-dinitrotoluene. The combination of ...porosity and functionality of the MOF provides an effective dielectric structure, resulting in changes of impedance magnitude and phase angle. The promising data indicate that MOFs may be used in low-cost, robust explosive detection devices.
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