101 research outputs found
Boundary-layer-flow instability in a rapidly rotating and strong precessing sphere
No full textThe linear stability analysis of the steady flow is performed in a rapidly rotating sphere with strong precession. It is shown that the localized mode destabilizing the boundary-layer flow determines the stability boundary, giving the asymptote, , which is consistent with the results obtained by direct numerical simulation
Marginal sea overflows and the upper ocean interaction
No full textAuthor Posting. © American Meteorological Society, 2009. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 39 (2009): 387-403, doi:10.1175/2008JPO3934.1.Marginal sea overflows and the overlying upper ocean are coupled in the vertical by two distinct mechanisms—by an interfacial mass flux from the upper ocean to the overflow layer that accompanies entrainment and by a divergent eddy flux associated with baroclinic instability. Because both mechanisms tend to be localized in space, the resulting upper ocean circulation can be characterized as a β plume for which the relevant background potential vorticity is set by the slope of the topography, that is, a topographic β plume.
The entrainment-driven topographic β plume consists of a single gyre that is aligned along isobaths. The circulation is cyclonic within the upper ocean (water columns are stretched). The transport within one branch of the topographic β plume may exceed the entrainment flux by a factor of 2 or more.
Overflows are likely to be baroclinically unstable, especially near the strait. This creates eddy variability in both the upper ocean and overflow layers and a flux of momentum and energy in the vertical. In the time mean, the eddies accompanying baroclinic instability set up a double-gyre circulation in the upper ocean, an eddy-driven topographic β plume. In regions where baroclinic instability is growing, the momentum flux from the overflow into the upper ocean acts as a drag on the overflow and causes the overflow to descend the slope at a steeper angle than what would arise from bottom friction alone.
Numerical model experiments suggest that the Faroe Bank Channel overflow should be the most prominent example of an eddy-driven topographic β plume and that the resulting upper-layer transport should be comparable to that of the overflow. The overflow-layer eddies that accompany baroclinic instability are analogous to those observed in moored array data. In contrast, the upper layer of the Mediterranean overflow is likely to be dominated more by an entrainment-driven topographic β plume. The difference arises because entrainment occurs at a much shallower location for the Mediterranean case and the background potential vorticity gradient of the upper ocean is much larger.SK’s support during the time of his Ph.D.
research in the MIT/WHOI Joint Program was provided
by the National Science Foundation through
Grant OCE04-24741. JP and JY have also received
support from the Climate Process Team on Gravity
Current Entrainment, NSF Grant OCE-0611530. JY has
also been supported by NSF Grant OCE-0351055
Racemization of chiral sulfoxide using an immobilized oxovanadium catalyst
No full textThis is a pre-copyedited, author-produced version of an article accepted for publication in Bulletin of the Chemical Society of Japan following peer review. The version of record Nishio Tomoya, Shigemitsu Hajime, Kida Toshiyuki, et al. Racemization of chiral sulfoxide using an immobilized oxovanadium catalyst. Bulletin of the Chemical Society of Japan 98, 3651 (2024) is available online at: https://doi.org/10.1093/bulcsj/uoae144.Racemization of optically active compounds is an essential process in asymmetric transformations such as dynamic kinetic resolution and deracemization. In this study, the racemization of chiral sulfoxides under mild thermal conditions was realized using a novel silica-gel-supported oxovanadium catalyst. Specifically, we screened reaction conditions, analyzed the substrate scope, and conducted mechanistic studies of the silica-gel-supported oxovanadium-catalyzed racemization of sulfoxides. The racemization reaction has a wide substrate scope, including alkyl aryl sulfoxides and diaryl sulfoxides. The catalyst could be reused by exploiting its heterogeneous nature. Mechanistic studies suggested that racemization proceeds via the formation of a radical cation intermediate mediated by the oxovanadium(V)/(IV) redox cycle
Automated Radiographic Measurements of Knee Osteoarthritis
No full textObjective: Herewith, we report the development of Orthopedic Digital Image Analysis (ODIA) software that is developed to obtain quantitative measurements of knee osteoarthritis (OA) radiographs automatically. Manual segmentation and measurement of OA parameters currently hamper large-cohort analyses, and therefore, automated and reproducible methods are a valuable addition in OA research. This study aims to test the automated ODIA measurements and compare them with available manual Knee Imaging Digital Analysis (KIDA) measurements as comparison. Design: This study included data from the CHECK (Cohort Hip and Cohort Knee) initiative, a prospective multicentre cohort study in the Netherlands with 1,002 participants. Knee radiographs obtained at baseline of the CHECK cohort were included and mean medial/lateral joint space width (JSW), minimal JSW, joint line convergence angle (JLCA), eminence heights, and subchondral bone intensities were compared between ODIA and KIDA. Results: Of the potential 2,004 radiographs, 1,743 were included for analyses. Poor intraclass correlation coefficients (ICCs) were reported for the JLCA (0.422) and minimal JSW (0.299). The mean medial and lateral JSW, eminence height, and subchondral bone intensities reported a moderate to good ICC (0.7 or higher). Discrepancies in JLCA and minimal JSW between the 2 methods were mostly a problem in the lateral tibia plateau. Conclusions: The current ODIA tool provides important measurements of OA parameters in an automated manner from standard radiographs of the knee. Given the automated and computerized methodology that has very high reproducibility, ODIA is suitable for large epidemiological cohorts with various follow-up time points to investigate structural progression, such as CHECK or the Osteoarthritis Initiative (OAI).Biomaterials & Tissue Biomechanic
An Efficient Algorithm for Almost Instantaneous VF Code Using Multiplexed Parse Tree
No full textAlmost Instantaneous VF code proposed by Yamamoto and Yokoo in 2001, which is one of the variable-length-to-fixed-length codes, uses a set of parse trees and achieves a good compression ratio. However, it needs much time and space for both encoding and decoding than an ordinary VF code does. In this paper, we proved that we can multiplex the set of parse trees into a compact single tree and simulate the original encoding and decoding procedures. Our technique reduces the total number of nodes into O(2ℓk - k2), while it is originally O(2ℓk), where ℓ and k are the codeword length and the alphabet size, respectively. The experimental results showed that we could encode and decode over three times faster for natural language texts by using this technique
Influenza B viruses are more susceptible to high temperatures than influenza A viruses
No full textAbstract Seasonal influenza is caused by two subtypes of influenza A virus (A/H1N1 and A/H3N2) and two lineages of influenza B viruses (B/Victoria-lineage and B/Yamagata-lineage). Seasonal influenza viruses replicate efficiently in the human upper respiratory tract, where the temperature is 33 °C. In this study, we investigated the susceptibility of seasonal influenza A and B viruses to different temperatures. We examined the differences in viral replication efficiency inside cultured cells and in infectious titre outside cultured cells at different temperatures (i.e., 33 °C, 37 °C, and 39 °C). We found that there were differences in temperature sensitivity between influenza A and B viruses, with influenza B viruses being more temperature sensitive. In addition, we found that cells cultured at 39 °C and infected with influenza B virus showed decreased expression of HA protein with receptor-binding activity on the cell surface. Our findings contribute to our understanding of the properties of seasonal influenza viruses
Enhancement of applicability of high-efficiency random sampling method using control variates method and sensitivity coefficients
No full textThe CV-S method is a high-efficiency random sampling method to estimate statistical moments of random variables, and it uses an approximated target parameter which are linearly dependent on input as a mockup parameter. In order to enhance the applicability of the CV-S method, we propose to use a mockup parameter which is different from but similar to a target parameter and whose sensitivity coefficients are available. In the present work, nuclear fuel burnup problems are concerned, and standard deviation of k infinity and nuclide number densities at certain fuel burnup are estimated by the CV-S method. Through numerical tests, it is clearly demonstrated that even if sensitivity coefficients of non burnup-related parameters in a simple system like a fuel pin-cell are used as the mockup, the CV-S method has a potential to efficiently estimate statistical moments of burnup-related parameters in a complicated system like a fuel assembly
Stimulus frequency dependence of blood oxygenation level-dependent functional magnetic resonance imaging signals in the somatosensory cortex of rats
No full textUnderstanding the mechanism Of Coupling between neuronal events and hemodynamic responses is important in non-invasive functional imaging of the brain. The stimulus frequency dependence of hemodynamic responses has been studied using a rat somatosensory cortex model most results for short stimulus durations reveal peak frequencies at which the hemodynamic response is maximized. However, such peak frequencies have not been observed in studies using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) signals with long stimulus durations. To clarify whether the stimulus frequency dependence of BOLD signals depends on the stimulus duration, we measured BOLD signals at 7 T with short- and long-stimulus durations for stimulating rat forepaw at 1-10 Hz using spin-echo echo-planar imaging to enhance changes in activation focus. For both these durations, BOLD signals were significantly higher at stimulus frequencies of 3 or 5 Hz in agreement with the results of previous studies using optical techniques. Our results show that stimulus duration has little influence on the stimulus frequency dependence of BOLD signals in the rat somatosensory model. The discrepant results of most previous fMRI studies using gradient-echo sequence may be ascribed to the difference of imaging to enhance activation focus or draining vein. (C) 2008 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved
Extensive Accumulation of Influenza Virus NS1 Protein in the Nuclei Causes Effective Viral Growth in Vero Cells
No full textWe previously showed that modified A/Puerto Rico/8/34 (PR8) influenza master strain had improved viral rescue and growth properties in African green monkey kidney (Vero) cell line by introducing NS gene of Vero-adapted A/England/1/53 (vaEng53). In the present study, it was found that the NS1 protein derived from vaEng53 was extensively accumulated in the nuclei than that of PR8. This accumulation was caused by 7 amino acid differences in C-terminal region of NS1 protein. These results suggest that specific accumulation of NS1 protein may contribute to efficient viral replication in Vero cells
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