skip to main content


This content will become publicly available on June 16, 2024

Title: Ventricular Helix Angle Trends and Long-Range Connectivity
Porcine hearts (N = 14) underwent ex vivo diffusion tensor imaging (DTI) at 3T. DTI analysis showed regional differences in helix angle (HA) range. The HA range in the posterior free wall was significantly greater than that of the anterior free wall (p = 0.02), the lateral free wall (p < 0.001) and the septum (p = 0.008). The best-fit transmural HA function also varied by region, with eight regions best described by an arctan function, seven by an arcsine function, and a single region by a linear function. Tractography analysis was performed, and the length that the tracts spanned within the epicardial, midwall, and endocardial segments was measured. A high number of tracts span the epicardial and mid-wall thirds, with fewer tracts spanning the mid-wall and endocardial thirds. Connectivity analysis of the number of tracts connecting different ventricular regions showed a high prevalence of oblique tracts that may be critical for long-range connectivity.  more » « less
Award ID(s):
2205043
NSF-PAR ID:
10433204
Author(s) / Creator(s):
; ; ;
Editor(s):
Bernard, Olivier; Clarysse, Patrick; Duchateau, Nicolas; Ohayon, Jacques; Viallon, Magalie
Date Published:
Journal Name:
Lecture notes in computer science
Volume:
13958
ISSN:
0302-9743
Page Range / eLocation ID:
64 - 73
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Bernard, Olivier ; Clarysse, Patrick ; Duchateau, Nicolas ; Ohayon, Jacques ; Viallon, Magalie (Ed.)
    Porcine hearts (N = 14) underwent ex vivo diffusion tensor imaging (DTI) at 3T. DTI analysis showed regional differences in helix angle (HA) range. The HA range in the posterior free wall was significantly greater than that of the anterior free wall (p = 0.02), the lateral free wall (p < 0.001) and the septum (p = 0.008). The best-fit transmural HA function also varied by region, with eight regions best described by an arctan function, seven by an arcsine function, and a single region by a linear function. Tractography analysis was performed, and the length that the tracts spanned within the epicardial, midwall, and endocardial segments was measured. A high number of tracts span the epicardial and mid-wall thirds, with fewer tracts spanning the mid-wall and endocardial thirds. Connectivity analysis of the number of tracts connecting different ventricular regions showed a high prevalence of oblique tracts that may be critical for long-range connectivity. 
    more » « less
  2. Abstract

    This study examines the relationship between water depth and diatom assemblages from lake-sediment-surface samples at Kelly Lake, California. A total of 40 surface-sediment samples (integrated upper 5 cm) were taken at various depths within the small (~ 3.74 ha) 5.7 m-deep lake. Secchi depths, water temperature, pH, salinity, conductivity, and total dissolved solids were also measured. Some diatom species showed distinct association with depth (e.g.,Fragilaria crotonensis, Nitzschia semirobusta). The relationship between the complete diatom assemblages and water depth was analyzed and assessed by depth-cluster analysis, a one-way analysis of similarity, principal components analysis and canonical correspondence analysis. Statistically significant differences were found between the assemblages associated with shallow depth (0–1.25 m), mid-depth (1.25–3.75 m), and deep-water (3.75–5.2 m) locations. The relationship between diatom assemblages and lake depth allowed two transfer models to be developed using the Modern Analogue Technique and Weighted Averaging Partial Least Squares. These models were compared and assessed by residual scatter plots. The results indicate that diatom-inferred transfer models based on surface-sediment samples from a single, relatively small and shallow lake can be a useful tool for studying past hydroclimatic variability (e.g., lake depth) from similar lakes in California and other regions where the large number of lakes required for traditional transfer-function development may not exist.

     
    more » « less
  3. null (Ed.)
    In order to better understand how our visual system processes information, we must understand the underlying brain connectivity architecture, and how it can get reorganized under visual deprivation. The full extent to which visual development and visual loss affect connectivity is not well known. To investigate the effect of the onset of blindness on structural connectivity both at the whole-brain voxel-wise level and at the level of all major whitematter tracts, we applied two complementary Diffusion-Tension Imaging (DTI) methods, TBSS and AFQ. Diffusion-weighted brain images were collected from three groups of participants: congenitally blind (CB), acquired blind (AB), and fully sighted controls. The differences between these groups were evaluated on a voxel-wise scale with Tract-Based Spatial Statistics (TBSS) method, and on larger-scale with Automated Fiber Quantification (AFQ), a method that allows for between-group comparisons at the level of the major fiber tracts. TBSS revealed that both blind groups tended to have higher FA than sighted controls in the central structures of the brain. AFQ revealed that, where the three groups differed, congenitally blind participants tended to be more similar to sighted controls than to those participants who had acquired blindness later in life. These differences were specifically manifested in the left uncinated fasciculus, the right corticospinal fasciculus, and the left superior longitudinal fasciculus, areas broadly associated with a range of higher-level cognitive systems. 
    more » « less
  4. Abstract

    Central Mexico is characterized by a complex topography that is the result of historic and contemporary tectonic and climatic factors. These events have influenced the evolutionary history of numerous freshwater fishes in the region. Nonetheless, recent studies have shown that life‐history traits and ecological characteristics of species may influence dispersal capabilities and the degree of genetic connectivity.Goodea(Cyprinodontiformes: Goodeidae) is one of the most widely distributed and environmentally tolerant genera of goodeids. In this study, the authors analysed variation in the mitochondrial cytochrome b gene to evaluate the phylogeographic relationships, genetic structure, genetic diversity and demographic history ofGoodeafrom across its distribution range. They found low genetic differentiation and identified shared haplotypes among several regions. Geographic segregation was found in samples southwest and northeast of the Lower Lerma region, with some internal isolated groups showing phylogeographic differentiation and unique haplotypes. The AMOVA best explained genetic structure when grouped by haplogroups rather than when grouped by recognized biogeographic regions. Several regions showed null genetic diversity, raising the possibility of dispersal mediated by humans. Finally, Bayesian Skyline Plot analysis showed a population expansion for the Southwest haplogroup, except for the Armería population and sub‐group II of the Northeast haplogroup. All this suggests a recent colonization ofGoodea atripinnisthroughout some of the biogeographic regions currently inhabited by this species.

     
    more » « less
  5. Abstract

    The spatial distribution of population affects disease transmission, especially when shelter in place orders restrict mobility for a large fraction of the population. The spatial network structure of settlements therefore imposes a fundamental constraint on the spatial distribution of the population through which a communicable disease can spread. In this analysis we use the spatial network structure of lighted development as a proxy for the distribution of ambient population to compare the spatiotemporal evolution of COVID-19 confirmed cases in the USA and China. The Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band sensor on the NASA/NOAA Suomi satellite has been imaging night light at ~ 700 m resolution globally since 2012. Comparisons with sub-kilometer resolution census observations in different countries across different levels of development indicate that night light luminance scales with population density over ~ 3 orders of magnitude. However, VIIRS’ constant ~ 700 m resolution can provide a more detailed representation of population distribution in peri-urban and rural areas where aggregated census blocks lack comparable spatial detail. By varying the low luminance threshold of VIIRS-derived night light, we depict spatial networks of lighted development of varying degrees of connectivity within which populations are distributed. The resulting size distributions of spatial network components (connected clusters of nodes) vary with degree of connectivity, but maintain consistent scaling over a wide range (5 × to 10 × in area & number) of network sizes. At continental scales, spatial network rank-size distributions obtained from VIIRS night light brightness are well-described by power laws with exponents near −2 (slopes near −1) for a wide range of low luminance thresholds. The largest components (104to 105km2) represent spatially contiguous agglomerations of urban, suburban and periurban development, while the smallest components represent isolated rural settlements. Projecting county and city-level numbers of confirmed cases of COVID-19 for the USA and China (respectively) onto the corresponding spatial networks of lighted development allows the spatiotemporal evolution of the epidemic (infection and detection) to be quantified as propagation within networks of varying connectivity. Results for China show rapid nucleation and diffusion in January 2020 followed by rapid decreases in new cases in February. While most of the largest cities in China showed new confirmed cases approaching zero before the end of February, most of these cities also showed distinct second waves of cases in March or April. Whereas new cases in Wuhan did not approach zero until mid-March, as of December 2020 it has not yet experienced a second wave of cases. In contrast, the results for the USA show a wide range of trajectories, with an abrupt transition from slow increases in confirmed cases in a small number of network components in January and February, to rapid geographic dispersion to a larger number of components shortly before mobility reductions occurred in March. Results indicate that while most of the upper tail of the network had been exposed by the end of March, the lower tail of the component size distribution has only shown steep increases since mid-June.

     
    more » « less