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Gravitational Instanton, Inflation and Cosmological Constant
She-Sheng Xue 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.2I
Quantum fluctuations of unstable modes about gravitational instantons cause an instability of flat space at finite temperature, leading to the spontaneous process of nucleating quantum black holes. The density of vacuum energy gain in such a process gives the cosmological term in the Einstein equation. This naturally results in the inflationary phase of the early Universe. While the reheating phase is attributed to the Hawking radiation of these quantum black holes. In the Standard cosmology era, this cosmological term depends on the reheating temperature and asymptotically approaches the cosmological constant in the matter domination phase, which is consistent with current observations.
IN SITU UNZIPPING OF CARBON NANOTUBES TO FORM GRAPHENE NANORIBBONS
YONG-SHENG ZHOU,PAN JIN,TENG GUO,YING-CHUN ZHU,GAO-HUI DU,BING-SHE XU 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2014 NANO Vol.9 No.1
We report the one step facile synthesis of graphene nanoribbons (GNRs) by unzipping carbonnanotubes (CNTs) from glucose (C 6 H 12 O 6 ) precursor, using a simple chemical vapor depositionmethod. Some nanotubes are partially cut resulting in a GNR – CNT hybrid whereas others arefully cut to form GNRs. The average length of GNRs achieved by this method is typically in therange of 1 – 10 ? m. The formation of GNRs is ascribed to the in situ oxygen-driven unzipping ofCNTs. The process is free from aggressive oxidants and utilizes the in situ unzipping. Thismethod o®ers an alternative approach for making GNRs, compared to previously used techniquesto synthesize GNRs.
Effective Lagrangian of Quantum Electrodynamics
Remo Ruffini,She-Sheng Xue 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.2I
From the Euler-Heisenberg formula, we calculate the exact real part of the one-loop effective Lagrangian of quantum electrodynamics in a constant electromagnetic field and determine its strongfield limit.
Luo, You,She, Dong-Li,Xiong, Hu,Fu, Sheng-Jun,Yang, Li Asian Pacific Journal of Cancer Prevention 2015 Asian Pacific journal of cancer prevention Vol.16 No.14
Purpose: To evaluate and update evidence for prognostic effects of kidney-sparing (KS) management and nephroureterectomy (NU) for upper tract urothelial carcinomas. Materials and Methods: Pubmed, Embase and the Cochrane Library were retrieved for the identification of comparative studies of kidney-sparing procedure and nephroureterectomy for upper tract urothelial carcinoma prior to December 2014. The data were extracted independently by 2 reviewers and the quality of the included studies was assessed. Review Manager 5.3 and STATA 13 were used to perform the meta-analysis. Results: Twenty-three observational studies including 1,587 KS and 3,996 NU were evaluated. The results of the meta-analysis showed that nephroureterectomy had no significant benefit with regard to intravesical recurrence (IRFS), metastasis (MFS), cancer specific survival (CSS) and overall survival (OS) except the total tumor recurrence (RFS) when compared with kidney sparing management. The respectively pooled outcomes were HR 1.36 (0.69-2.68, P=0.38) for IRFS, 1.09 (0.59-2.01, P=0.78) for MFS, 1.17 (0.77-1.79, P=0.47) for CSS, 1.50 (0.90-2.48, P=0.12) for OS and 1.61 (1.03-2.51, P=0.04) for RFS. Conclusions: On the whole, kidney-sparing management had equivalent prognostic effect on upper tract urothelial carcinoma as the standard nephroureterectomy except in tumor recurrence. However, the results should be interpreted with caution for lack of stage and grade stratification and multi-center randomized controlled trials are still needed to verify our results.
On the Dyadosphere of Black Holes
Giuliano Preparata,Remo Ruffini,She-Sheng Xue 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
Basic energy requirements of Gamma Ray Burst(GRB) sources can be easily accounted for by a pair creation process occurring in the ``Dyadosphere" of a Black Hole endowed with an electromagnetic field (abbreviated to EMBH for ``electromagnetic Black Hole"). This includes the recent observations of GRB971214 by Kulkarni {\it et al}. The ``Dyadosphere" is defined as the region outside the horizon of an EMBH where the electromagnetic field exceeds the critical value for $e^+ e^-$ pair production. In a very short time of $\sim O({\hbar\over mc^2})$, very large numbers of pairs are created there. Further evolution, then, leads naturally to a relativistically expanding pair-electromagnetic-pulse (PEM-pulse). Specific examples of Dyadosphere parameters are given for $10M_{\odot}$ and $10^5M_{\odot}$ EMBH's. This process does occur for EMBH with charge-to-mass ratio larger than $2.2\times 10^{-5}$ and strictly smaller than one. From a fundamental point of view, this process represents the first mechanism proved capable of extracting large amounts of energy from a Black Hole with an extremely high efficiency (close to $100$ \%).
Mediatory role of K, Cu and Mo over Ru/SiO2 catalysts for glycerol hydrogenolysis
Xiaoyuan Liao,Kewen Li,Xiaomin Xiang,Sheng-Guang Wang,Xichun She,Yulei Zhu,Yongwang Li 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.2
SiO2 supported ruthenium catalysts with and without modifiers were prepared, characterized and tested for glycerol hydrogenation. Addition of K, Cu and Mo affects the reducibility and acidity of the Ru/SiO2catalyst. Characterization data shows that Cu and Mo-modified Ru/SiO2 have stronger acidity. On the contrary, K element on a passive effect on the acidity of Ru based catalyst had been observed. A comparison with the pure Ru/SiO2 indicates the Cu-promoted specimen has better selective to the desired products, acetol, 1,2-propanediol and ethyl glycol, although the reactivity is slightly lower.
Schwinger mechanism in electromagnetic field in de Sitter spacetime
Bavarsad, Ehsan,Pyo Kim, Sang,Stahl, Clé,ment,Xue, She-Sheng,Gwak, B.,Kang, G.,Kim, C.,Kim, H.-C.,Lee, C.-H.,Lee, J.,Lee, S.,Lee, W. EDP Sciences 2018 The European Physical Journal Conferences Vol.168 No.-
<P>We investigate Schwinger scalar pair production in a constant electromagnetic field in de Sitter (dS) spacetime. We obtain the pair production rate, which agrees with the Hawking radiation in the limit of zero electric field in dS. The result describes how a cosmic magnetic field affects the pair production rate. In addition, using a numerical method we study the effect of the magnetic field on the induced current. We find that in the strong electromagnetic field the current has a linear response to the electric and magnetic fields, while in the infrared regime, is inversely proportional to the electric field and leads to infrared hyperconductivity.</P>
( Hong Chen Zheng ),( Ming Zhe Sun ),( Ling Cai Meng ),( Hai Sheng Pei ),( Xiu Qing Zhang ),( Zheng Yan ),( Wen Hui Zeng ),( Jing Sheng Zhang ),( Jin Rong Hu ),( Fu Ping Lu ),( Jun She Sun ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.4
High levels of extracellular xylanase activity (211.79 IU/mg) produced by Paenibacillus sp. NF1 were detected when it was submerged-cultured. After three consecutive purification steps using Octyl-Sepharose, Sephadex G75, and Q-Sepharose columns, a thermostable xylanase (XynNF) was purified to homogeneity and showed a molecular mass of 37 kDa according to SDS-PAGE. The specific activity of the purified XynNF was up to 3,081.05 IU/mg with a 14.55-fold purification. The activity of XynNF was stimulated by Ca2+, Ba2+, DTT, and β-mercaptoethanol, but was inhibited by Fe3+, Zn2+, Fe2+, Cu2+, SDS, and EDTA. The purified XynNF displayed a greater affinity for oat spelt xylan with the maximal enzymatic activity at 60°C and pH 6.0. XynNF, which was shown to be cellulose-free, with high stability at high temperature (70°C-80°C) and low pH range (pH 4.0-7.0), is potentially valuable for various industrial applications. The enzyme hydrolyzed oat spelt xylan to yield mainly xylooligosaccharides (95.8%) of 2-4 degree of polymerization (DP2-4). Moreover, the majority of the xylooligosacharides (DP2- 4) products was xylobiose (61.5%). The thermostable xylanase (XynNF) thus seems potentially usefull in the production of xylooligosaccharides.
Effect of a magnetic field on Schwinger mechanism in de Sitter spacetime
Bavarsad, Ehsan,Kim, Sang Pyo,Stahl, Clé,ment,Xue, She-Sheng American Physical Society 2018 Physical review. D Vol.97 No.2
<P>We investigate the effect of a uniform magnetic field background on scalar QED pair production in a four-dimensional de Sitter spacetime (dS(4)). We obtain a pair production rate which agrees with the known Schwinger result in the limit of Minkowski spacetime and with Hawking radiation in dS spacetime in the zero electric field limit. Our results describe how the cosmic magnetic field affects the pair production rate in cosmological setups. In addition, using the zeta function regularization scheme we calculate the induced current and examine the effect of a magnetic field on the vacuum expectation value of the current operator. We find that, in the case of a strong electromagnetic background the current responds as E . B, while in the infrared regime, it responds as B/E, which leads to a phenomenon of infrared hyperconductivity. These results for the induced current have important applications for the cosmic magnetic field evolution.</P>