7,000 research outputs found
Suppression of both superconductivity and structural transition in hole-doped MoTe induced by Ta substitution
Type-II Weyl semimetal MoTe exhibits a first-order structural transition
at 250~K and superconducts at 0.1~K at ambient
pressure. Both and can be manipulated by several tuning parameters,
such as hydrostatic pressure and chemical substitution. It is often reported
that suppressing enhances , but our study shows a different
behaviour when MoTe is hole-doped by Ta. When is suppressed by Ta
doping, is also suppressed. Our findings suggest that the suppression of
does not necessarily enhance superconductivity in MoTe. By connecting
with the findings of electron-doped MoTe, we argue that varying electron
carrier concentration can effectively tune . In addition, the Hall
coefficient is enhanced around the doping region, where is completely
suppressed, suggesting that the critical scattering around the structural
transition may also play a role in suppressing
Shareholder Litigation Rights and Corporate Acquisitions
We examine the effect of shareholder litigation rights on managers’ acquisition decisions. Our experimental design exploits a U.S. Ninth Circuit Court of Appeals ruling on July 2, 1999 that resulted in a reduction in shareholder class actions. We find that, since the ruling, firms in Ninth Circuit states acquire larger targets. Furthermore, acquirers’ returns are lower in these states, especially for those with weaker corporate governance. Further analysis shows that value destruction is the result of managers’ freedom to conduct empire-building acquisitions using overvalued equity. Overall, our findings indicate the importance of shareholder litigation as an external governance mechanism
Association between cyclo-oxygenase-2 overexpression and missense p53 mutations in gastric cancer
Wild-type p53 competitively binds to the promoter region of COX-2 in vitro and inhibits its transcription. We examined the association between p53 mutation and COX-2 expression in gastric cancer. COX-2 over-expression was seen in 19 (48.7%) cases. These tumours had more lymph-node metastasis (P = 0.048) and tended to have a poorer survival (P = 0.07). Missense mutations of p53 were detected in 20 (51.3%) patients and had a significantly stronger COX-2 expression than tumours without p53 mutation (P = 0.016). Our results suggest a link between p53 mutation and COX-2 overexpression in gastric cancer. © 2001 Cancer Research Campaign http://www.bjcancer.co
Frequent epigenetic inactivation of secreted frizzled-related protein 2 (SFRP2) by promoter methylation in human gastric cancer
The role of secreted frizzled-related protein (SFRP) genes in gastric cancer remains largely unknown. We determined the frequency and functional significance of SFRPs hypermethylation in human gastric cancer. The expression and methylation status of four SFRP members (SFRP1, 2, 4, and 5) in primary gastric cancer samples was screened. The biological effects of SFRP were analysed by flow cytometry, cell viability assay and in vivo tumour growth in nude mice. Among the four SFRPs, only SFRP2 was significantly downregulated in gastric cancer as compared to adjacent non-cancer samples (P<0.01). Promoter hypermethylation of SFRP2 was detected in 73.3% primary gastric cancer tissues, 37.5% of samples showing intestinal metaplasia and 20% adjacent normal gastric tissues. Bisulphite DNA sequencing confirmed the densely methylated SFRP2 promoter region. Demethylation treatment restored the expression of SFRP2 in gastric cancer cell lines. Forced expression of SFRP2 induced cell apoptosis, inhibited proliferation of gastric cancer cells and suppressed tumour growth in vivo. Moreover, methylated SFRP2 was detected in 66.7% of serum samples from cancer patients but not in normal controls. In conclusion, epigenetic inactivation of SFRP2 is a common and early event contributing to gastric carcinogenesis and may be a potential biomarker for gastric cancer
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