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Search Results: 1 - 10 of 24785 matches for " Zhen Fan "
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Uniform Bound of the Highest Energy for the 3D Incompressible Elastodynamics
Zhen Lei,Fan Wang
Mathematics , 2015, DOI: 10.1007/s00205-014-0815-0
Abstract: This article concerns the time growth of Sobolev norms of classical solutions to the 3D incompressible isotropic elastodynamics with small initial displacements.
The Southern Oscillation / Northern Oscillation Cycle Associated with Sea Surface Temperature in the Equatorial Pacific
Chen Lieting,Fan Zhen,
Chen Lieting
,Fan Zhen

大气科学进展 , 1993,
Abstract: This paper analyzed the time evolution of the global 1000 hPa height anomalies related to the sea surface tem-perature (SST) in the eastern equatorial Pacific by using ECMWF data in the period 1979-1988, in which two Pacific warm events, 1982/83 and 1986/87, are included. It is found that there are distinct evidences of eastward propaga-tion of alternate positive / negative height anomalies not only in the tropical South Pacific but also in the tropical North Pacific. The former is associated with the Southern Oscillation (SO) and the latter is associated with the so-called Northern Oscillation (NO).It is noteworthy that the alternate positive / negative anomaly centers associated with SO and NO can be traced back to the middle and higher latitudes of the South Indian Ocean and the East Asian continent respectively, which may be significant for the understanding of the causes and mechanism of SO and NO and for the monitoring of ENSO.Furthermore, these evolution processes have a strong symmetry about the Northern and the Southern Hemi-sphere. The whole SO / NO cycle takes about 3.5 years from extreme positive to negative index pattern and again from extreme negative to positive index pattern, It is suggested that the anomalous cold air activities over East Asia and Australia and the polar vortex activities over the northern and the southern Pacific seem to have dominant role on the SO / NO cycle.
Crystal Engineering Based on Polymeric Hydrogen-Bonded Supramolecules by Self-Assembling of 9, 10-Bis(3,5- dihydroxyphenyl)anthracene and 2,2′,4,4′- Tetrahydroxybenzophenone with Bipyridines
Xiaokang Li,Lvyin Zhen,Yulan Fan,Xiaolin Fan,Qingdao Zeng
International Journal of Molecular Sciences , 2007, DOI: 10.3390/i8030241
Abstract: 9, 10-bis(3,5-dihydroxyphenyl)anthracene (BDHA) and 2,2′,4,4′-tetrahydroxybenzophenone (THB) are crystallized with bipyridine bases 4,4 ?-bipyridyl(bipy), 1,2-bis(4-pyridyl)ethane (bipy-eta), 1,2-di(4-pyridyl)ethylene (dipy-ete), 1,3-di(4-pyridyl)propane (dipy-pra), 4,4 ?-dipyridyl sulfide (dipy-sul), and 4,4 ?-dipyridyl disulfide(dipy-dis) to afford molecular complexes (BDHA)·(bipy)2 1, (BDHA)·(bipy-eta)2 2,(BDHA)0.5·(dipy-pra)·CH3CH2OH 3, (BDHA)0.5·(dipy-sul)·H2O 4, (BDHA)0.5·(dipy-dis)·CH3CH2OH 5 and (THB)·(dipy-ete)2·H2O 6. The crystal structures of 1–6 have beendetermined by single-crystal X-ray diffraction. All these molecular complexes exhibitpolymeric supramolecular structures via O–H···N or O–H···O hydrogen-bonding. 1 and 2form infinitely rectangular macrocycles linked with one another, whose sizes are ca.12.477 ?× 4.802 ? and ca.14.575 ? × 4.809 ?, respectively. 3, 5 and 6 form the one-dimensionalzigzag chain structure. 4 forms a ladder structure, and two dipy-sul molecules were includedin a frame.
Enhanced Thermal Conductivity of Carbon Nanotube Arrays by Carbonizing Impregnated Phenolic Resins  [PDF]
Dongmei Hu, Hongyuan Chen, Zhenzhong Yong, Minghai Chen, Xiaohua Zhang, Qingwen Li, Zhen Fan, Zhihai Feng
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.48055
Abstract:

A carbonization method is reported to improve the thermal conductivity of carbon nanotube (CNT) arrays. After being impregnated with phenolic resins, CNT arrays were carbonized at a temperature up to 1400°C. As a result, pyrolytic carbon was formed and connected non-neighboring CNTs. The pyrolysis improved the room temperature conductivity from below 2 W/m·K up to 11.8 and 14.6 W/m·K with carbonization at 800°C and 1400°C, respectively. Besides the light mass density of 1.1 g/cm3, the C/C composites demonstrated high thermal stability and a higher conductivity up to 21.4 W/m·K when working at 500°C.

Conversion of 3,4-Dihydroxypyrrolidine-2,5-Dione to Maleimide through Tosylation and Mechanism Study by DFT  [PDF]
Maocai Yan, Zhen Zhang, Jinhui Zhou, Wei Li, Shuai Fan, Zhaoyong Yang
Computational Chemistry (CC) , 2018, DOI: 10.4236/cc.2018.63004
Abstract:
Pyrrolidine-2,5-dione and maleimide are important scaffolds of many organic substances, and their derivatives are now attracting more and more interests from researchers in organic synthesis, medicinal chemistry, and drug development. Tosyloxy (-OTs) group is an important functional group widely used in organic synthesis, because it can be readily prepared from alcohols and is an excellent leaving group. However, surprisingly, substances bearing tosyloxy groups on pyrrolidine-2,5-dione or maleimide scaffolds are very rare. In this study, we discovered that, when treated with TsCl/Et3N,?trans-3,4-dihydroxypyrrolidine-2,5- dione will eliminate a TsOH molecule to form monotosyloxymaleimide. Thermodynamic and kinetic factors affecting this reaction were investigated by theoretical computation using density functional theory (DFT), and the possible reaction mechanism was proposed based on the computation results. Our results showed that tosylates of trans -3,4-dihydroxypyrrolidine- 2,5-dione, either monotosylate or ditosylate, are thermodynamically instable and may spontaneously convert to maleimides. This knowledge could be useful in understanding the properties of pyrrolidine-2,5-diones and maleimides, as well as the related organic synthesis.
Preparation of nanoparticles with an environment-friendly approach

YAO Kefu,PENG Zhen,FAN Xiaolin,

环境科学学报(英文版) , 2009,
Abstract: Developing various approaches for preparing high performance materials has long been topics and tasks both for scientists and for engineers.Despite that many methods have been developed for preparing nanomaterials,developing simple and environment-friendly ways for preparing nanomaterials is very attractive.A simple approach of synthesizing Fe3O4 nanoparticles by arc-discharge submerging in water was reported.The results showed that by this method Fe3O4 nanoparticles can be synthesized in large scale.The as-prepared Fe3O4 nanoparticles exhibit uniform spherical shape and their diameters varied with arc-discharging parameters.The experimental results showed that the size of the synthesized Fe3O4 nanoparticles can be controlled through adjusting the processing parameters.Since no vacuum system has been used,the synthesizing process is greatly simplified.In addition,only cheap deionized water and industrial iron bar are used and no pollution or harmful by-products are found in the synthesis process.It indicated that the present approach is a simple,low-cost and environment-friendly for preparing nanoparticles.
1, 9-Pyrazoloanthrones Downregulate HIF-1α and Sensitize Cancer Cells to Cetuximab-Mediated Anti-EGFR Therapy
Yang Lu,Xinqun Li,Haiquan Lu,Zhen Fan
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0015823
Abstract: Cetuximab, a monoclonal antibody that blocks the epidermal growth factor receptor (EGFR), is currently approved for the treatment of several types of solid tumors. We previously showed that cetuximab can inhibit hypoxia-inducible factor-1 alpha (HIF-1α) protein synthesis by inhibiting the activation of EGFR downstream signaling pathways including Erk, Akt, and mTOR. 1, 9-pyrazoloanthrone (1, 9 PA) is an anthrapyrazolone compound best known as SP600125 that specifically inhibits c-jun N-terminal kinase (JNK). Here, we report 1, 9 PA can downregulate HIF-1α independently of its inhibition of JNK. This downregulatory effect was abolished when the oxygen-dependent domain (ODD) of HIF-1α (HIF-1α-ΔODD, the domain responsible for HIF-1α degradation) was experimentally deleted or when the activity of HIF-1α prolyl hydroxylase (PHD) or the 26S proteasomal complex was inhibited, indicating that the 1, 9 PA downregulates HIF-1α by promoting PHD-dependent HIF-1α degradation. We found that the combination of 1, 9 PA and cetuximab worked synergistically to induce apoptosis in cancer cells in which cetuximab or 1, 9 PA alone had no or only weak apoptotic activity. This synergistic effect was substantially decreased in cancer cells transfected with HIF-1α-ΔODD, indicating that downregulation of HIF-1α was the mechanism of this synergistic effect. More importantly, 1, 9 PA can downregulate HIF-1α in cancer cells that are insensitive to cetuximab-induced inhibition of HIF-1α expression due to overexpression of oncogenic Ras (RasG12V). Our findings suggest that 1, 9 PA is a lead compound of a novel class of drugs that may be used to enhance the response of cancer cells to cetuximab through a complementary effect on the downregulation of HIF-1α.
Differential responses to doxorubicin-induced phosphorylation and activation of Akt in human breast cancer cells
Xinqun Li, Yang Lu, Ke Liang, Bolin Liu, Zhen Fan
Breast Cancer Research , 2005, DOI: 10.1186/bcr1259
Abstract: The levels of Akt phosphorylation and activity were measured by Western blot analysis with an anti-Ser473-phosphorylated Akt antibody and by in vitro Akt kinase assay using glycogen synthase kinase-3 as a substrate.Within 24 hours after exposure to doxorubicin, MCF7, MDA468 and T47D cells showed a drug-dose-dependent increase in the levels of phosphorylated Akt; in contrast, SKBR3 and MDA231 cells showed a decrease in the levels of phosphorylated Akt, and minimal or no changes were detected in MDA361, MDA157 and BT474 cells. The doxorubicin-induced Akt phosphorylation was correlated with increased kinase activity and was dependent on phosphoinositide 3-kinase (PI3-K). An increased baseline level of Akt was also found in MCF7 cells treated with ionizing radiation. The cellular responses to doxorubicin-induced Akt phosphorylation were potentiated after the expression of Akt upstream activators including HER2, HER3 and focal adhesion kinase.Taken together with our recent published results showing that constitutive Akt mediates resistance to chemotherapy or radiotherapy, our present data suggest that the doxorubicin-induced phosphorylation and activation of Akt might reflect a cellular defensive mechanism of cancer cells to overcome doxorubicin-induced cytotoxic effects, which further supports the current efforts of targeting PI3-K/Akt for enhancing the therapeutic responses of breast cancer cells to chemotherapy and radiotherapy.Cancer cells with an inherent or acquired capability to resist induction of apoptosis at some point(s) in the signal cascade pathway leading to cell death generally tend to be resistant to chemotherapy or radiotherapy. The serine–threonine protein kinase Akt has received much interest in recent years because it suppresses apoptosis induced by chemotherapy or radiotherapy through interaction with several critical molecules that regulate or execute apoptosis. For instance, after activation, Akt could do the following: it phosphorylates the proapo
Responses of cancer cells with wild-type or tyrosine kinase domain-mutated epidermal growth factor receptor (EGFR) to EGFR-targeted therapy are linked to downregulation of hypoxia-inducible factor-1α
Yang Lu, Ke Liang, Xinqun Li, Zhen Fan
Molecular Cancer , 2007, DOI: 10.1186/1476-4598-6-63
Abstract: We found that, compared with previously studied response markers, including EGFR per se and three EGFR downstream signal molecules (ERK, Akt, and STAT3), which showed variable post-treatment changes in levels of phosphorylation and no consistent link of the changes to therapeutic responses, HIF-1α showed a selective decrease in protein levels only in responsive cell lines. To demonstrate a critical role of HIF-1α downregulation by EGFR-targeted treatment, we introduced a constitutively expressed HIF-1α mutant (HIF-1α/ΔODD) that is resistant to cetuximab-induced downregulation in a cetuximab-responsive cell line (A431); we found that the HIF-1α/ΔODD-transfected cells remained sensitive to cetuximab-induced inhibition of Akt and ERK phosphorylation but were remarkably less responsive to cetuximab-induced growth inhibition compared with corresponding control cells.Our data indicates that downregulation of HIF-1α is associated with positive therapeutic responses of cancer cells to EGFR-targeted therapy and suggest further investigation using HIF-1α as an indicator of tumor response to EGFR-targeted therapy in preclinical studies and in the clinical setting.Epidermal growth factor receptor (EGFR) has been implicated in the development and progression of a diverse type of solid tumors. Over the past two decades, experimental cancer therapies targeting EGFR have been studied extensively [1-4]. Recent clinical studies have found that targeting EGFR with receptor-blocking monoclonal antibodies such as cetuximab and panitumumab, or with small-molecule EGFR tyrosine kinase inhibitors (TKIs) such as gefitinib and erlotinib, is effective against several types of solid tumors [5-9]. TKI is particularly effective against a subset of non-small cell lung cancers (NSCLCs) that have several somatic mutations in the EGFR tyrosine kinase domain [10-12]. However, many patients do not experience favorable responses to EGFR-targeted therapy, regardless of positive or even high EGFR express
Radiolarian record to paleoecological environment change events over the past 1.2 MaBP in the southern South China Sea
Lihong Yang,Muhong Chen,Rujian Wang,Fan Zhen
Chinese Science Bulletin , 2002, DOI: 10.1360/02tb9326
Abstract: This note studies the Radiolarian fossil groups since 1.2 MaBP in ODP leg 184 site 1143, the southern South China Sea (SCS). The result shows that radiolarian abundance experienced a significant variation: before 0.9 MaBP it remained at the extremely low level, but increased with low extent between 0.9–0.65 Ma, which corresponded to the Mid-Pleistocene Transition stage, and it increased rapidly after 0.65 MaBP. During the whole process, the average abundance became higher and higher in each stage, and showed regularly periodic fluctuations. The obvious increase after 0.65 MaBP is inferred to result from the enhanced upwelling in this region, which was induced by the intensified monsoon circulation after the “Mid-Pleistocene Transition”. An outstanding result of the spectral analyses is that a long oscillation of ~ 0.2 Ma cycle was found in the records of radiolarian abundance and complex diversity, which corresponds well to the result of other paleoceanographic indexes. This probably indicated a special cycle characteristic of paleoecological environment evolution in this area. In addition, all of the radiolarian indexes show an obvious boundary in about 0.47 MaBP, indicating the abrupt variation of the community structure and radiolarian abundance level before and after 0.47 MaBP. So we suppose that there existed a distinct change event of oceanic ecology environment during that period.
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