Detecting hierarchical and overlapping community structures in networks

2014-2015 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe

Decentralized adaptive pinning control for cluster synchronization of complex dynamical networks

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Dirac Leptogenesis with a Non-anomalous U(1)′U(1)^{\prime} Family Symmetry

We propose a model for Dirac leptogenesis based on a non-anomalous $U(1)^{\prime}$ gauged family symmetry. The anomaly cancellation conditions are satisfied with no new chiral fermions other than the three right-handed neutrinos, giving rise to stringent constraints among the charges. Realistic masses and mixing angles are obtained for all fermions. The model predicts neutrinos of the Dirac type with naturally suppressed masses. Dirac leptogenesis is achieved through the decay of the flavon fields. The cascade decays of the vector-like heavy fermions in the Froggatt-Nielsen mechanism play a crucial role in the separation of the primodial lepton numbers. We find that a large region of parameter space of the model gives rise to a sufficient cosmological baryon number asymmetry through Dirac leptogenesis.Comment: 8 pages, 8 figures, version to appear in JHE

Mitigation of low-frequency current ripple in fuel-cell inverter systems through waveform control

published_or_final_versio

Removal of NOx and NOy in Asian outflow plumes: Aircraft measurements over the western Pacific in Januray 2002

The Pacific Exploration of Asian Continental Emission Phase A (PEACE-A) aircraft measurement campaign was conducted over the western Pacific in January 2002. Correlations of carbon monoxide (CO) with carbon dioxide (CO2) and back trajectories are used to identify plumes strongly affected by Asian continental emissions. ΔCO/ΔCO2 ratios (i.e., linear regression slopes of CO-CO2) in the plumes generally fall within the variability range of the CO/CO2 emission ratios estimated from an emission inventory for east Asia, demonstrating the consistency between the aircraft measurements and the emission characterization. Removal rates of reactive nitrogen (NOx and NOy) for the study region (altitude <4 km, 124°-140°E, 25°-45°N) are estimated using the correlation with CO2, the photochemical age of the plumes, and the NOx/ CO2 emission ratio derived from the emission inventory. The plume age is estimated from the rates of hydrocarbon decay and hydroxyl radical (OH) concentration calculated using a constrained photochemical box model. The average lifetime of NOx is estimated to be 1.2 ± 0.4 days. Possible processes controlling the NOx lifetime are discussed in conjunction with results from earlier studies. The average lifetime of NOy is estimated to be 1.7 ± 0.5 days, which is comparable to the NOy lifetime of 1.7-1.8 days that has been previously reported for outflow from the United States. This similarity suggests the importance of chemical processing near the source regions in determining the NOy abundance. Copyright 2004 by the American Geophysical Union

Multiple Ca2+ signaling pathways regulate intracellular Ca 2+ activity in human cardiac fibroblasts

Ca2+ signaling pathways are well studied in cardiac myocytes, but not in cardiac fibroblasts. The aim of the present study is to characterize Ca2+ signaling pathways in cultured human cardiac fibroblasts using confocal scanning microscope and RT-PCR techniques. It was found that spontaneous intracellular Ca2+ (Cai 2+) oscillations were present in about 29% of human cardiac fibroblasts, and the number of cells with Cai 2+ oscillations was increased to 57.3% by application of 3% fetal bovine serum. Cai 2+ oscillations were dependent on Ca2+ entry. Cai2+ oscillations were abolished by the store-operated Ca2+ (SOC) entry channel blocker La3+, the phospholipase C inhibitor U-73122, and the inositol trisphosphate receptors (IP3Rs) inhibitor 2-aminoethoxydiphenyl borate, but not by ryanodine. The IP3R agonist thimerosal enhanced Ca2+ i oscillations. Inhibition of plasma membrane Ca2+ pump (PMCA) and Na+-Ca2+ exchanger (NCX) also suppressed Ca i 2+ oscillations. In addition, the frequency of Ca i 2+ oscillations was reduced by nifedipine, and increased by Bay K8644 in cells with spontaneous Cai 2+ oscillations. RT-PCR revealed that mRNAs for IP3R1-3, SERCA1-3, CaV1.2, NCX3, PMCA1,3,4, TRPC1,3,4,6, STIM1, and Orai1-3, were readily detectable, but not RyRs. Our results demonstrate for the first time that spontaneous Cai 2+ oscillations are present in cultured human cardiac fibroblasts and are regulated by multiple Ca2+ pathways, which are not identical to those of the well-studied contractile cardiomyocytes. This study provides a base for future investigations into how Ca2+ signals regulate biological activity in human cardiac fibroblasts and cardiac remodeling under pathological conditions. © 2009 Wiley-Liss, Inc.postprin

Phase retrieval by coherent modulation imaging

Phase retrieval is a long-standing problem in imaging when only the intensity of the wavefield can be recorded. Coherent diffraction imaging is a lensless technique that uses iterative algorithms to recover amplitude and phase contrast images from diffraction intensity data. For general samples, phase retrieval from a single-diffraction pattern has been an algorithmic and experimental challenge. Here we report a method of phase retrieval that uses a known modulation of the sample exit wave. This coherent modulation imaging method removes inherent ambiguities of coherent diffraction imaging and uses a reliable, rapidly converging iterative algorithm involving three planes. It works for extended samples, does not require tight support for convergence and relaxes dynamic range requirements on the detector. Coherent modulation imaging provides a robust method for imaging in materials and biological science, while its single-shot capability will benefit the investigation of dynamical processes with pulsed sources, such as X-ray free-electron lasers

Automated adaptive analysis of tagged magnetic resonance images of the mouse heart

The full potential of tagged MRI of the mouse heart for non-invasive evaluation of cardiac mechanics in transgenic animals has not been realized due to excessive user involvement with available image processing algorithms. Therefore, we developed an automated, rapid, high-resolution analysis technique, called High Density Mapping (HDM), that uses spectral correlation to efficiently quantify regional wall deformation, does not entail tracking of individual tags, and involves minimal user interaction. HDM analysis distinguishes regional mechanics in healthy and infarcted mice within 2 minutes. This new method may help promote the practical use of tagged MRI in mice and other species.published_or_final_versio

A note on Makeev's conjectures

A counterexample is given for the Knaster-like conjecture of Makeev for functions on $S^2$. Some particular cases of another conjecture of Makeev, on inscribing a quadrangle into a smooth simple closed curve, are solved positively

Demonstration of astrocytes in cultured amniotic fluid cells of three cases with neural-tube defect

We have investigated the origin of rapidly adhering (RA) cells in three cases of neural tube defects (two anencephali, one encephalocele). We were able to demonstrate the presence of glial fibrillary acidic (GFA) protein in variable percentages (4–80%) of RA cells cultured for 4–6 days by use of indirect immunofluorescence with GFA antiserum. Cells cultured from amniotic fluids of normal pregnancies and fetal fibroblasts were completely GFA protein negative. GFA protein is well established as a highly specific marker for astrocytes. Demonstration of astrocytes may prove to be a criterion of high diagnostic value for neural tube defects. The percentage of astrocytes decreased with increasing culture time, while the percentage of fibronectin positive cells increased both in amniotic fluid cell cultures from neural tube defects and normal pregnancies