326 research outputs found
Dynamic fluctuations coincide with periods of high and low modularity in resting-state functional brain networks
We investigate the relationship of resting-state fMRI functional connectivity
estimated over long periods of time with time-varying functional connectivity
estimated over shorter time intervals. We show that using Pearson's correlation
to estimate functional connectivity implies that the range of fluctuations of
functional connections over short time scales is subject to statistical
constraints imposed by their connectivity strength over longer scales. We
present a method for estimating time-varying functional connectivity that is
designed to mitigate this issue and allows us to identify episodes where
functional connections are unexpectedly strong or weak. We apply this method to
data recorded from participants, and show that the number of
unexpectedly strong/weak connections fluctuates over time, and that these
variations coincide with intermittent periods of high and low modularity in
time-varying functional connectivity. We also find that during periods of
relative quiescence regions associated with default mode network tend to join
communities with attentional, control, and primary sensory systems. In
contrast, during periods where many connections are unexpectedly strong/weak,
default mode regions dissociate and form distinct modules. Finally, we go on to
show that, while all functional connections can at times manifest stronger
(more positively correlated) or weaker (more negatively correlated) than
expected, a small number of connections, mostly within the visual and
somatomotor networks, do so a disproportional number of times. Our statistical
approach allows the detection of functional connections that fluctuate more or
less than expected based on their long-time averages and may be of use in
future studies characterizing the spatio-temporal patterns of time-varying
functional connectivityComment: 47 Pages, 8 Figures, 4 Supplementary Figure
Numerical investigation on sand erosion phenomenon of coated and uncoated vanes in low-pressure gas turbine
For energy saving and less environmental impact, efficient energy utilization is of importance. In a gas-turbine engine, its performance increases as increasing temperature of the turbine inlet flow. However, turbine components are required to be protected from the high temperature flows. Recently, ceramic matrix composite (referred as CMC, hereafter) is expected to be utilized as protecting the gas-turbine components due to the excellent properties of CMC in high temperature conditions: low density, high strength and high rigidity. Therefore, the CMC allows us to increase the inlet temperature and leads to high performance of gas-turbine engines. On the other hand, sand erosion phenomenon is one of serious problems in gas-turbine engines. Sand particles ingested from the engine inlet impinge and erode the wall surfaces, which can cause engine failure. In order to prevent the sand erosion phenomenon, anti-erosion coatings have been developed and adopted for gas-turbines, although the anti-erosion characteristics of the CMC coating have not completely been clarified. The objective of the present paper is to perform numerical simulations of sand erosion phenomenon on the coated and the uncoated T106 CMC vanes in a low-pressure gas turbine. We investigate the flow field, particle trajectories and the eroded shape of the CMC turbine vanes. The results show that the erosion occurs near the leading edge and at the 90 percent axial chord on the pressure surface in both of the coated and uncoated cases. In the uncoated case, the severe erosion phenomenon is observed especially. Accordingly, we have concluded that the coating obviously played an important role in protecting the CMC vanes from sand erosion
Fluctuations between high- and low-modularity topology in time-resolved functional connectivity
Modularity is an important topological attribute for functional brain
networks. Recent studies have reported that modularity of functional networks
varies not only across individuals being related to demographics and cognitive
performance, but also within individuals co-occurring with fluctuations in
network properties of functional connectivity, estimated over short time
intervals. However, characteristics of these time-resolved functional networks
during periods of high and low modularity have remained largely unexplored. In
this study we investigate spatiotemporal properties of time-resolved networks
in the high and low modularity periods during rest, with a particular focus on
their spatial connectivity patterns, temporal homogeneity and test-retest
reliability. We show that spatial connectivity patterns of time-resolved
networks in the high and low modularity periods are represented by increased
and decreased dissociation of the default mode network module from
task-positive network modules, respectively. We also find that the instances of
time-resolved functional connectivity sampled from within the high (low)
modularity period are relatively homogeneous (heterogeneous) over time,
indicating that during the low modularity period the default mode network
interacts with other networks in a variable manner. We confirmed that the
occurrence of the high and low modularity periods varies across individuals
with moderate inter-session test-retest reliability and that it is correlated
with previously-reported individual differences in the modularity of functional
connectivity estimated over longer timescales. Our findings illustrate how
time-resolved functional networks are spatiotemporally organized during periods
of high and low modularity, allowing one to trace individual differences in
long-timescale modularity to the variable occurrence of network configurations
at shorter timescales.Comment: Reorganized the paper; to appear in NeuroImage; arXiv abstract
shortened to fit within character limit
Polarization-resolved second-harmonic-generation imaging of dermal collagen fiber in prewrinkled and wrinkled skins of ultraviolet-B-exposed mouse
Skin wrinkling is a typical symptom of cutaneous photoaging; however, the skin wrinkling depends on not only the actual age but also exposure history to ultraviolet B (UVB) rays in individuals. Therefore, there is considerable need for its assessment technique in vivo in skin cosmetics and antiaging dermatology. Wrinkles always appear as linear grooves in the skin, and dermal collagen fibers play an important role to determine the morphology and mechanical properties of the skin. Therefore, an optical probe sensitive to dermal collagen fiber and its orientation will be useful. Polarization-resolved second-harmonic-generation (SHG) microscopy is a promising approach for in vivo evaluation of collagen fiber orientation because the efficiency of SHG light is sensitive to collagen fiber orientation when the incident light is linearly polarized. We investigate orientation change of dermal collagen fiber in prewrinkled and wrinkled skins of the UVB-exposed mouse model using polarization-resolved SHG microscopy. A polarization anisotropic image of the SHG light indicates that the change of collagen fiber orientation starts in the prewrinkled skin of UVB-exposed mice, then the wrinkle appears. Furthermore, the dominant direction of collagen fiber orientation in the prewrinkled skin is significantly parallel to the wrinkle direction in the wrinkled skin. This result implies that the change of collagen fiber orientation is a trigger of wrinkling in cutaneous photoaging
Japanese Translation and Validation of Genomic Knowledge Measure in the International Genetics Literacy and Attitudes Survey (iGLAS-GK)
Knowledge of genetics is essential for understanding the results of genetic testing and its implications. Recent advances in genomic research have allowed us to predict the risk of onset of common diseases based on individual genomic information. It is anticipated that more people will receive such estimates of risks based on their genomic data. However, currently, there is no measure for genetic knowledge that includes post-genome sequencing advancements in Japan. In this study, we translated the genomic knowledge measure in the International Genetics Literacy and Attitudes Survey (iGLAS-GK) into Japanese and validated it in a general Japanese adult population (n = 463). The mean score was 8.41 (SD 2.56, range 3–17). The skewness and kurtosis were 0.534 and 0.088, respectively, and the distribution showed a slightly positive skewness. Exploratory factor analysis proposed a six-factor model. Results for 16 of the 20 items of the Japanese version of the iGLAS-GK were comparable to those from previous studies in other populations. These results indicate that the Japanese version is reliable and can be used to measure the genomic knowledge of adults in the general population, and this version of the knowledge measure maintains the multidimensional structure for assessing genomic knowledge
Heat transfer enhancement and torque reduction by traveling wave-like blowing and suction in turbulent Taylor-Couette flow
Direct numerical simulations of turbulent Taylor-Couette flows are performed to investigate the effect of a traveling wave control on torque and heat transfer. In the Taylor-Couette flow, inner and outer cylinders are rotating and immobile, respectively, and the temperature difference between cylinder walls is maintained as constant. The ratio between the inner and outer cylinder is 0.882, and the Reynolds number is set as 84,000. A traveling wave-like blowing and suction is imposed on an inner cylinder wall. A parametric study shows the effect of control parameters on torque and heat transfer. We focused on three characteristic parameter sets: heat transfer enhancement, relaminarization phenomenon, and simultaneous achievement of torque reduction and heat transfer enhancement. We employed identity equations by using three-component decomposition to clarify contributions from advection, turbulence, and diffusion on torque and Stanton number. The results indicated that the traveling wave control affects the turbulence and advection contributions
Intraoperative ultrasonographic localization of pulmonary ground-glass opacities
ObjectivesGround-glass opacities are typically difficult to inspect and to palpate during video-assisted thoracic surgery. We therefore examined whether ultrasonographic assessments could localize ground-glass opacities and help to achieve adequate resection margins.MethodsAn intraoperative ultrasonographic procedure was prospectively performed on 44 patients harboring ground-glass opacities of less than 20 mm in diameter to localize these lesions and to achieve adequate margins. We also examined whether there were any complications resulting from the intraoperative ultrasonogram, such as lung injury, heart injury, or arrhythmia. We excluded patients with both asthma and chronic obstructive pulmonary disease from this study inasmuch as the intraoperative ultrasonographic procedure is more difficult to interpret when residual air is present in the lung.ResultsA total of 53 ground-glass opacities were successfully identified by intraoperative ultrasonography without any complications. Of the 20 mixed ground-glass opacities that we examined, 15 were found on palpation. However, only 4 (12.1%) of the 33 pure ground-glass opacities could be palpated. In all instances in which complete collapse of the lung was achieved (30/53 of these cases), high-quality echo images were obtained. Additionally, a strong correlation was found between the resection margins measured by ultrasonogram and the margins determined by histologic examination in the resected lung specimens (r2 = 0.954, P < .001).ConclusionsIntraoperative ultrasonography can both safely and effectively localize pulmonary ground-glass opacities in a completely deflated lung. This procedure is also useful for the evaluation of surgical margins in a resected lung. Hence, ultrasonography may assist surgeons to perform minimally invasive lung resections with clear surgical margins during the treatment of solitary lung ground-glass opacity
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