The ground state hyperfine splitting of positronium ΔHFS is sensitive to high order corrections of quantum electrodynamics (QED) in bound state. The theoretical prediction and the averaged ...experimental value for ΔHFS have a discrepancy of 15 ppm, which is equivalent to 3.9 standard deviations (s.d.). A new precision measurement which reduces the systematic uncertainty from the positronium thermalization effect was performed, in which the non-thermalization effect was measured to be as large as 10±2 ppm in a timing window we used. When this effect is taken into account, our new result becomes ΔHFS=203.3942±0.0016(stat.,8.0 ppm)±0.0013(sys.,6.4 ppm) GHz, which favors the QED prediction within 1.2 s.d. and disfavors the previous experimental average by 2.6 s.d.
Pancreatic cancer is one of the most difficult malignancies to treat owing to the rapid acquisition of resistance to chemotherapy. Gemcitabine, a first-line treatment for pancreatic cancer, prolongs ...patient survival by several months, and combination treatment with gemcitabine and other anti-cancer drugs in the clinic do not show any significant effects on overall survival. Thus, identification of a drug that resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine and a better understanding of the molecular mechanisms of gemcitabine resistance are critical to develop new therapeutic options for pancreatic cancer. Here, we report that zidovudine resensitizes gemcitabine-resistant pancreatic cancer to gemcitabine as shown by screening a compound library, including clinical medicine, using gemcitabine-resistant cells. In analyzing the molecular mechanisms of zidovudine effects, we found that the epithelial-to-mesenchymal transition (EMT)-like phenotype and downregulation of human equilibrative nucleoside transporter 1 (hENT1) are essential for the acquisition of gemcitabine resistance, and zidovudine restored these changes. The chemical biology investigations also revealed that activation of the Akt-GSK3β-Snail1 pathway in resistant cells is a key signaling event for gemcitabine resistance, and zidovudine resensitized resistant cells to gemcitabine by inhibiting this activated pathway. Moreover, our in vivo study demonstrated that co-administration of zidovudine and gemcitabine strongly suppressed the formation of tumors by gemcitabine-resistant pancreatic cancer and prevented gemcitabine-sensitive pancreatic tumors from acquiring gemcitabine-resistant properties, inducing an EMT-like phenotype and downregulating hENT1 expression. These results suggested that co-treatment with zidovudine and gemcitabine may become a novel therapeutic strategy for pancreatic cancer by inhibiting chemoresistance-specific signaling.
Single crystals have high atomic electric fields as much as 1011 V/m, which correspond to magnetic fields of ∼103 T. These fields can be utilized to convert x-rays into axionlike particles (ALPs) ...coherently similar to x-ray diffraction. In this paper, we perform the first theoretical calculation of the Laue-case conversion in crystals based on the Darwin dynamical theory of x-ray diffraction. The calculation shows that the Laue-case conversion has longer interaction length than the Bragg case, and that ALPs in the keV range can be resonantly converted by tuning an incident angle of x-rays. ALPs with mass up to O(10 keV) can be searched by light-shining-through-a-wall (LSW) experiments at synchrotron x-ray facilities.
We report the first direct measurement of the hyperfine transition of the ground state positronium. The hyperfine structure between ortho-positronium and para-positronium is about 203 GHz. We develop ...a new optical system to accumulate about 10 kW power using a gyrotron, a mode converter, and a Fabry-Pérot cavity. The hyperfine transition has been observed with a significance of 5.4 standard deviations. The transition probability is measured to be A = 3.1(-1.2)(+1.6) × 10(-8) s(-1) for the first time, which is in good agreement with the theoretical value of 3.37 × 10(-8) s(-1).
Abstract Adult neurogenesis occurs in the subgranular zone (SGZ) of the dentate gyrus, where primary neuronal progenitors that express glial fibrillary acidic protein (GFAP) develop into granule ...neurons. Here, we used transgenic mice with mouse GFAP promoter-controlled enhanced green fluorescent protein (mGFAP-EGFP Tg mice) to examine how astrocyte-like progenitors differentiate into neuron-committed progenitors. Bromodeoxyuridine (BrdU) analysis indicated that proliferating cells in the neurogenic SGZ transiently expressed EGFP and GFAP, and finally differentiated into cells positive for the neuronal marker, Hu (Hu+). Most proliferating EGFP+ cells showed expression of the stem cell marker, Sox2, and formed clusters of two to four cells containing GFAP+/EGFP+ and GFAP−/EGFP+ cells. No GFAP−/EGFP+ cells were detected in non-neurogenic regions, such as CA1 and CA3 of the pyramidal cell layer. Together with the assumption that exogeneous EGFP has a higher stability than that of endogenous GFAP in the degradation process, it is highly probable that the GFAP−/EGFP+ cells were daughter cells or immediate progeny derived from GFAP+/EGFP+ cells. The subpopulation of proliferating GFAP+/EGFP+ cells expressed proneural protein Mash1 and neuronal marker Hu, while the proliferating GFAP−/EGFP+ cells expressed additional immature neuronal markers, such as polysialic acid-neural cell adhesion molecule (PSA-NCAM) and doublecortin. Therefore, these results suggest that through a few cell divisions, GFAP+ progenitors give rise to neuronal progenitors via neuron-committed early intermediate progenitors that express both GFAP and Hu (and/or Mash1). The findings of the present study also indicated that mGFAP-EGFP Tg mice are useful animals for identifying the daughter cells or immediate progeny derived from GFAP+ neural progenitors.
Search for CP violation in positronium decay Yamazaki, T; Namba, T; Asai, S ...
Physical review letters,
2010-Feb-26, 20100226, 2010-02-26, Letnik:
104, Številka:
8
Journal Article
Recenzirano
CP violation in the quark sector has been well established over the last decade, but has not been observed in the lepton sector. We search for CP violating decay processes in positronium, using the ...angular correlation of (S x k{1})(S x k{1}x k{2}), where S is the positronium spin and k{1}, k{2} are the directions of the positronium decay photons. To a sensitivity of 2.2x10{-3}, no CP violation has been found, which is at the level of the CP violation amplitude in the K meson. A 90% confidence interval of the CP violation parameter (C{CP}) was determined to be -0.0023<C{CP}<0.0049. This result is a factor 7 more strict than that of the previous experiment.
We report the first results of a search for real photon–photon scattering using X rays. A novel system is developed to split and collide X-ray pulses by applying interferometric techniques. A total ...of 6.5×105 pulses (each containing about 1011 photons) from an X-ray Free-Electron Laser are injected into the system. No scattered events are observed, and an upper limit of 1.7×10−24 m2 (95% C.L.) is obtained on the photon–photon elastic scattering cross section at 6.5 keV.
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