A simple analytical method is developed to compare the combinations of stator and rotor pole numbers in flux-switching permanent magnet (PM) machines in terms of back electromotive force (EMF) and ...electromagnetic torque. The winding connections and winding factors of machines having all poles and alternate poles wound, and different numbers of phases, from two to six, are determined by the coil-EMF vectors. Their differences from analyzing the conventional fractional-slot PM machines with concentrated nonoverlapping windings are highlighted. The general conditions are established for balanced symmetrical back-EMF waveform. It shows that the optimized rotor pole number should be close to the number of stator poles, whereas larger torque can be obtained by the machine with relatively higher rotor pole number. The analysis is validated by finite-element analyses and experiment.
This paper overviews the recent development and new topologies of flux-switching (FS) machines, with particularly emphasis on the permanent magnet (PM) type. Specific design issues, including winding ...configurations, combinations of stator and rotor pole numbers, rotor pole width, split ratio, etc., are investigated, while the torque capability of selected FSPM machines is also compared.
The molecular mechanism underlying gastric cancer (GC) invasion and metastasis is still poorly understood. In this study, we tried to investigate the roles of CXCR4 and CXCR2 signalings in gastric ...cancer metastasis. A highly invasive gastric cancer cell model was established. Chemokines receptors were profiled to search for the accountable ones. Then the underlying molecular mechanism was investigated using both in vitro and in vivo techniques, and the clinical relevance of CXCR4 and CXCR2 expression was studied in gastric cancer samples. CXCR4 and CXCR2 were highly expressed in a high invasive gastric cancer cell model and in gastric cancer tissues. Overexpression of CXCR4 and CXCR2 was associated with more advanced tumor stage and poorer survival for GC patients. CXCR4 and CXCR2 expression strongly correlated with each other in the way that CXCR2 expression changed accordingly with the activity of CXCR4 signaling and CXCR4 expression also changed in agreement with CXCR2 activity. Further studies demonstrated CXCR4 and CXCR2 can both activated NF-κB and STAT3 signaling, while NF-κBp65 can then transcriptionally activate CXCR4 and STAT3 can activate CXCR2 expression. This crosstalk between CXCR4 and CXCR2 contributed to EMT, migration and invasion of gastric cancer. Finally, Co-inhibition of CXCR4 and CXCR2 is more effective in reducing gastric cancer metastasis. Our results demonstrated that CXCR4 and CXCR2 cross-activate each other to promote the metastasis of gastric cancer.
ABSTRACT
Observations in the local universe show a tight correlation between the masses of supermassive black holes (SMBHs; MBH) and host-galaxy bulges (Mbulge), suggesting a strong connection ...between SMBH and bulge growth. However, direct evidence for such a connection in the distant universe remains elusive. We have studied sample-averaged SMBH accretion rate ($\overline{\rm BHAR}$) for bulge-dominated galaxies at z = 0.5–3. While previous observations found $\overline{\rm BHAR}$ is strongly related to host-galaxy stellar mass (M⋆) for the overall galaxy population, our analyses show that, for the bulge-dominated population, $\overline{\rm BHAR}$ is mainly related to SFR rather than M⋆. This ${\overline{\rm BHAR}}$–SFR relation is highly significant, e.g. 9.0σ (Pearson statistic) at z = 0.5–1.5. Such a $\overline{\rm BHAR}$–SFR connection does not exist among our comparison sample of galaxies that are not bulge dominated, for which M⋆ appears to be the main determinant of SMBH accretion. This difference between the bulge-dominated and comparison samples indicates that SMBHs only coevolve with bulges rather than the entire galaxies, explaining the tightness of the local MBH−Mbulge correlation. Our best-fitting ${\overline{\rm BHAR}}$–SFR relation for the bulge-dominated sample is ${\log \overline{\rm BHAR}= \log \mathrm{SFR} - (2.48\pm 0.05)}$ (solar units). The best-fitting $\overline{\rm BHAR}/\mathrm{SFR}$ ratio (10−2.48) for bulge-dominated galaxies is similar to the observed MBH/Mbulge values in the local universe. Our results reveal that SMBH and bulge growth are in lockstep, and thus non-causal scenarios of merger averaging are unlikely the origin of the MBH−Mbulge correlation. This lockstep growth also predicts that the MBH−Mbulge relation should not have strong redshift dependence.
Bright quasars, powered by accretion onto billion-solar-mass black holes, already existed at the epoch of reionization, when the Universe was 0.5-1 billion years old
. How these black holes formed in ...such a short time is the subject of debate, particularly as they lie above the correlation between black-hole mass and galaxy dynamical mass
in the local Universe. What slowed down black-hole growth, leading towards the symbiotic growth observed in the local Universe, and when this process started, has hitherto not been known, although black-hole feedback is a likely driver
. Here we report optical and near-infrared observations of a sample of quasars at redshifts 5.8 ≲ z ≲ 6.6. About half of the quasar spectra reveal broad, blueshifted absorption line troughs, tracing black-hole-driven winds with extreme outflow velocities, up to 17% of the speed of light. The fraction of quasars with such outflow winds at z ≳ 5.8 is ≈2.4 times higher than at z ≈ 2-4. We infer that outflows at z ≳ 5.8 inject large amounts of energy into the interstellar medium and suppress nuclear gas accretion, slowing down black-hole growth. The outflow phase may then mark the beginning of substantial black-hole feedback. The red optical colours of outflow quasars at z ≳ 5.8 indeed suggest that these systems are dusty and may be caught during an initial quenching phase of obscured accretion
.
Permanent-magnet vernier machine (PMVM) is a relatively new type of PM machines. An analytical subdomain model accounting for tooth-tips and flux modulation poles is developed to accurately predict ...on-load field distributions in PMVMs. Based on two-dimensional (2-D) polar coordinate and magnetic vector potential, this method solves the Maxwell's equations in slot, air-gap, flux modulation pole slot (FMPS), and PM regions. Consequently, the electromagnetic performance such as cogging torque, back-electromotive force (EMF), electromagnetic torque, power factor, and magnet loss are calculated. In addition, the model can also be used for the evaluation of demagnetization withstand capability. The finite-element analysis (FEA) and experimental results validate the accuracy of the developed analytical model.
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