Localization of the components of the cardiac conduction system (CCS) is essential for many therapeutic procedures in cardiac surgery and interventional cardiology. While histological studies provided fundamental insights into CCS localization, this information is incomplete and difficult to translate to aid in intraprocedural localization. To advance our understanding of CCS localization, we set out to establish a framework for quantifying nodal region morphology. Using this framework, we quantitatively analyzed the sinoatrial node (SAN) and atrioventricular node (AVN) in ovine with menstrual age ranging from 4.4 to 58.3 months. In particular, we studied the SAN and AVN in relation to the epicardial and endocardial surfaces, respectively. Using anatomical landmarks, we excised the nodes and adjacent tissues, sectioned those at a thickness of 4 µm at 100 µm intervals, and applied Masson’s trichrome stain to the sections. These sections were then imaged, segmented to identify nodal tissue, and analyzed to quantify nodal depth and superficial tissue composition. The minimal SAN depth ranged between 20 and 926 µm. AVN minimal depth ranged between 59 and 1192 µm in the AVN extension region, 49 and 980 µm for the compact node, and 148 and 888 µm for the transition to His Bundle region. Using a logarithmic regression model, we found that minimal depth increased logarithmically with age for the AVN (R2=0.818, P=0.002). Also, the myocardial overlay of the AVN was heterogeneous within different regions and decreased with increasing age. Age associated alterations of SAN minimal depth were insignificant. Our study presents examples of characteristic tissue patterns superficial to the AVN and within the SAN. We suggest that the presented framework provides quantitative information for CCS localization. Our studies indicate that procedural methods and localization approaches in regions near the AVN should account for the age of patients in cardiac surgery and interventional cardiology.
: Forests play a major role in the global carbon cycle. Previous studies on the capacity of forests to sequester atmospheric CO2 have mostly focused on carbon uptake, but the roles of carbon turnover time and its spatiotemporal changes remain poorly understood. Here, we used long-term inventory data (1955-2018) from 695 mature forest plots to quantify temporal trends in living vegetation carbon turnover time across tropical, temperate, and cold climate zones, and compared plot data to eight Earth system models (ESMs). Long-term plots consistently showed decreases in living vegetation carbon turnover time, likely driven by increased tree mortality across all major climate zones. Changes in living vegetation carbon turnover time were negatively correlated with CO2 enrichment in both forest plot data and ESM simulations. However, plot-based correlations between living vegetation carbon turnover time and climate drivers such as precipitation and temperature diverged from those of ESM simulations. Our analyses suggest that forest carbon sinks are likely to be constrained by a decrease in living vegetation carbon turnover time, and accurate projections of forest carbon sink dynamics will require an improved representation of tree mortality processes and their sensitivity to climate in ESMs.
Future projections suggest an increase in drought globally with climate change. Current vegetation models typically regulate the plant photosynthetic response to soil moisture stress through an empirical function, rather than a mechanistic response where plant water potentials respond to changes in soil water. This representation of soil moisture stress may introduce significant uncertainty into projections for the terrestrial carbon cycle. We examined the use of the soil moisture limitation function in historical and future emissions scenarios in nine Earth system models. We found that soil moisture-limited productivity across models represented a large and uncertain component of the simulated carbon cycle, comparable to 3-286% of current global productivity. Approximately 40-80% of the intermodel variability was due to the functional form of the limitation equation alone. Our results highlight the importance of implementing mechanistic water limitation schemes in models and illuminate several avenues for improving projections of the land carbon sink.
Micrometer-scale maps of authigenic microstructures in submarine basaltic tuff from a 1979 Surtsey volcano, Iceland, drill core acquired 15 years after eruptions terminated describe the initial alteration of oceanic basalt in a low temperature hydrothermal system. An integrative investigative approach uses synchrotron source X-ray microdiffraction (µXRD), microfluoresence (µXRF), micro-computed tomography (µCT), and scanning transmission electron microscopy (S/TEM) coupled with Raman spectroscopy to create finely resolved spatial frameworks that record a continuum of alteration in glass and olivine. Micro-analytical maps of vesicular and fractured lapilli in specimens from 157.1, 137.9, and 102.6 m depth, and borehole temperatures of 83, 93.9 and 141.3 °C measured in 1980, respectively, describe the production of nanocrystalline clay mineral, zeolites, and Al-tobermorite in diverse microenvironments. Irregular alteration fronts at 157.1 m depth resemble microchannels associated with biological activity in older basalts. By contrast, linear microstructures with little resemblance to previously described alteration features have nanocrystalline clay mineral (nontronite) and zeolite (amicite) texture. The crystallographic preferred orientation rotates around an axis parallel to the linear feature. Raman spectra indicating degraded and poorly-ordered carbonaceous matter of possible biological origin are associated with nanocrystalline clay mineral in a crystallographically-oriented linear microstructure in altered olivine at 102.6 m and with sub-circular nanoscale cavities in altered glass at 137.9 m depth. Although evidence for biotic processes is inconclusive, the integrated analyses describe the complex organization of previously unrecognized mineral texture in very young basalt. They provide a foundational mineralogical reference for longitudinal, time-lapse characterizations of palagonitized basalt in oceanic environments.
-------------------------- METHODOLOGICAL INFORMATION --------------------------
1. Description of methods used for collection/generation of data: The data were generated by computer simulations using the C++ code "Orchestra", a proprietary hybrid code that follows the dynamical evolution of solids and gas orbiting a central object. Algorithms in the code are described in the following papers (author names abbreviated to B for Bromley, K for Kenyon, and L for Jane X Luu along with a year for publication date, AJ = Astronomical Journal, ApJ = Astrophysical Journal, S=Supplement): KL1998, AJ 115:2136; KL1999, AJ 118:1101; KB2001,AJ 121:538; KB2002,AJ 123:1757; KB2004, AJ 127:513; BK2006, AJ 131:2737; KB2006, AJ 131:1837; KB2008, ApJS 179:451; KB2010, ApJS 188:242; BK2011, ApJ 731:101; KB2012, AJ 143:63; KB2014, AJ 147:8. Initial conditions for these simulations described in the published paper.
2. Methods for processing the data: Various C and fortran programs are used to analyze the data for the calculations. Several C programs needed to extract information from the computer generated binary output files are included with the dataset. The C programs include basic summaries of the structure of the data files and the usage to extract data from each binary file.
3. Instrument- or software-specific information needed to interpret the data: Appropriate software is included in directory.
4. Standards and calibration information, if appropriate: none
5. Environmental/experimental conditions: all calculations were run on the NASA discover cluster
6. Describe any quality-assurance procedures performed on the data: Aside from tests summarized in the papers described in item 1, test calculations are summarized in the Appendix of each paper and compared to an appropriate benchmark.
7. People involved with sample collection, processing, analysis and/or submission: Scott Kenyon and Ben Bromley and --------------------- DATA & FILE OVERVIEW ---------------------
Files summarized in items 1-8 are binary output files from n-body simulations as described in Kenyon & Bromley, "A Pluto-Charon Sonata: Dynamical Limits on fate Masses of the Small Satellites" (2019, Astronomical Journal). Files described in item 9 are ascii txt. The C programs in items 10, 11, and 12 provide different ways to access the binary output. Each C program describes the architecture of the binary files.
1. pcs2-0mmm-nnn[a-z] files: heavy satellites, mmm = 100 x mass factor for all satellites, nnn = number of Symplectic steps per PC orbit, a-z = version
2. pcs2-1mmm-nnn[a-z] files: light satellites, mmm = 100 x mass factor for all satellites, nnn = number of Symplectic steps per PC orbit, a-z = version
3. pcs2-2mmm-nnn[a-z] files: light satellites with 2x nominal mass of Styx & Kerberos, mmm = 100 x mass factor for all satellites, nnn = number of Symplectic steps per PC orbit, a-z = version
4. pcs2-3mmm: heavy satellites, 40 Symplectic steps per PC orbit, mmm = 100 x mass factor for Nix only
5. pcs2-4mmm: heavy satellites, 40 Symplectic steps per PC orbit, mmm = 100 x mass factor for Kerberos only
6. pcs2-5mmm: heavy satellites, 40 Symplectic steps per PC orbit, mmm = 100 x mass factor for Hydra only
7. pcs2-6mmm light satellites, 40 Symplectic steps per PC orbit, mmm = 100 x mass factor for Nix only
8. pcs2-7mmm: light satellites, 40 Symplectic steps per PC orbit, mmm = 100 x mass factor for Hydra only
9. pcs2-n000.dat: summary of lifetimes for binary files in each archive 10. lifetime.c: summarizes lifetime and mass factor for binary file usage example: "lifetime pcs2-6110"
11. summary.c: generates basic summary of timesteps in a binary file usage example: "summary pcs1-0013d"
12. extrxyz.c: extracts (x,y,z) for N satellites and outputs (x,y,z) usage example: "extr6d pcs1-6110 6" will output (x,y,z) for SNKH 3. Additional related data collected that was not included in the current data package: There are other binary output files not included in this archive. 4. Are there multiple versions of the dataset? no
This project was a NSF-funded collaborative research project entitled: Collaborative Research: Deciphering Eolian Paleoenvironmental and Hydrodynamic records: Lower Jurassic Navajo Sandstone, Colorado Plateau, USA This was a multifaceted interdisciplinary study of the Lower Jurassic Navajo Sandstone (Ss)--a unique and distinctive unit in all of geologic history. This unit represents the largest known ancient desert (erg), and is typically classified as a record of a hyperarid environment. Furthermore, the Navajo Ss was deposited at a time when mammals were undergoing their first major diversification, and dinosaurs began to dominate the landscape in number and diversity. Our goal was to examine sedimentary features of the erg margin that recorded the active paleohydrology of the desert regime, and examine abundant trace- and body-fossil material to more fully document the structure and evolution of the biota in a variably arid landscape through Navajo Ss deposition. Field studies involved sedimentology and paleoecology. Laboratory studies involved isotope geochemistry of carbonate deposits, as well as thin section petrography.
The widely documented phenomenon of nighttime stomatal conductance (gsn) could lead to substantial water loss with no carbon gain, and thus it remains unclear whether nighttime stomatal conductance confers a functional advantage. Given that studies of gsn have focused on controlled environments or small numbers of species in natural environments, a broad phylogenetic and biogeographic context could provide insights into potential adaptive benefits of gsn. • We measured gsn on a diverse suite of species (n = 73) across various functional groups and climates-of-origin in a common garden to study the phylogenetic and biogeographic/climatic controls on gsn and further assessed the degree to which gsn co-varied with leaf functional traits and daytime gas exchange rates. • Closely related species were more similar in gsn than expected by chance. Herbaceous species had higher gsn than woody species. Species that typically grow in climates with lower mean annual precipitation – where the fitness cost of water loss should be the highest – generally had higher gsn. • Our results reveal the highest gsn rates in species from environments where neighboring plants compete most strongly for water, suggesting a possible role for the competitive advantage of gsn.
The mechanisms governing tree drought mortality and recovery remain a subject of inquiry and active debate given their role in the terrestrial carbon cycle and their concomitant impact on climate change. Counter-intuitively, many trees do not die during the drought itself. Indeed, observations globally have documented that trees often grow for several years after drought before mortality. A combination of meta-analysis and tree physiological models demonstrate that optimal carbon allocation after drought explains observed patterns of delayed tree mortality and provides a predictive recovery framework. Specifically, post-drought, trees attempt to repair water transport tissue and achieve positive carbon balance through regrowing drought-damaged xylem. Further, the number of years of xylem regrowth required to recover function increases with tree size, explaining why drought mortality increases with size. These results indicate that tree resilience to drought-kill may increase in the future, provided that CO2 fertilization facilitates more rapid xylem regrowth.