Tai X.S.,Weifang University |
Li Y.F.,Weifang University |
Zhao W.H.,Qinghai Normal University
Journal of Chemical and Pharmaceutical Research | Year: 2014
A novel complex, [Mg(L)2(H2O)2]·(H2O) [L= 3-amino-2-pyrazinecarboxylic acid] was synthesized in ethanol/H2O (v:v=3:1) with magnesium chloride hexahydrate and 3-amino-2-pyrazinecarboxylic acid as raw materials. It was characterized by elemental analysis, IR and X-ray single crystal diffraction analysis. The crystal of the title complex [Mg(L)2(H2O)2]·(H2O) belongs to orthorhombic, space group P-1 with a= 2.9288(6) nm, b= 0.82286(16) nm, c= 1.2132(2) nm, α= β= γ= 90°, V= 2.9238(10) nm3, Z=8, Dc= 1.611 μg·m-3, μ= 0.173 mm-1, F(000)= 1472, and final R1= 0.0247, wR2= 0.0697. X-ray analysis reveals that the complex comprises a six-coordinated magnesium (II) center, with a N2O4 distorted octahedron coordination environment. The molecules are connected by hydrogen bonds and π-π stacking to form one dimensional chain structure.
Liu F.,Qinghai Normal University |
Feng Z.,Xinjiang University
Holocene | Year: 2012
Our review of recently published climatic proxy sequences shows that the most dramatic climate tranistion of the mid Holocene (~8500-~3500 cal. yr BP) occurred at the middle- to late-Holocene transition at ~4000 cal. yr BP. In northern China, an abrupt climatic shift at ~4000 cal. yr BP was recorded in the eastern margin of the Tibetan Plateau, in the western part of the Chinese Loess Plateau and in the vast Inner Mongolian Plateau. In southern China, the ~4000 cal. yr BP event was also abrupt, but it is expressed as one of several quasi-cyclic events in most of the records. We propose that the cumulative effects of insolation-dictated declining trend in tropical SST and the geologically documented increasing trend of ENSO activity were the first-order causes of the cooling and the associated drying during the past 6000 years. Superimposed on the first-order causes were the second-order causes, i.e. the additive effects of the 'Bond Event 3'-associated lower insolation and the increasingly drying-resulted negative feedback of 'air-land interactions'. The second-order causes made ~4000 cal. yr BP the tipping point when the resultant drying had destroyed many Chinese Neolithic cultures. Our review of published archaeological literature shows that six of the seven well-documented Chinese Neolithic cultures collapsed at ~4000 cal. yr BP with the exception of the Henan Longshan Culture that evolved to the more advanced Erlitou Culture. The indicators of the cultural collapse include (1) the number of archaeological sites was significantly reduced, (2) the quality of the archaeological artifacts of the succeeding culture is lower than that of the preceding culture, (3) more sophisticated architectures disappeared, and (4) agricultural cultures were replaced by pastoralism or by agro-pastoralism in northern China. © The Author(s) 2012.
Hu C.,Shaanxi Normal University |
Hu C.,Qinghai Normal University |
Liu P.,Shaanxi Normal University
Journal of Alloys and Compounds | Year: 2013
Highly reactive amorphous SiO2 nanospheres were successfully synthesized at room temperature in atmosphere with a mean particle size of 174 nm by a Sol-Gel method. SiO2 ceramics were prepared using SiO 2 nanospheres and their microwave dielectric properties were investigated at different temperatures. Phase evolution, sintering characteristics and microstructures were detected by differential thermal analysis (DTA-TG) analysis, X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). Excellent microwave properties of εr ∼ 3.52, Q·f ∼ 92400 GHz and τf ∼ -14.5 ppm/°C, were obtained finally. The optimum sintering temperature of SiO2 ceramics was reduced 125 °C by aqueous Sol-Gel process compared to a conventional solid-state method. The Q·f and εr values of SiO2 ceramics are sensitive to the measured temperatures, which was explained by a simple composite dielectric model. © 2012 Elsevier B.V. All rights reserved.
Zhang W.Y.,Dalian Jiaotong University |
Gao H.,Dalian Jiaotong University |
Xu Y.,Qinghai Normal University
Journal of the European Ceramic Society | Year: 2011
Diopside-albite glass-ceramics were fabricated by sintering the powder mixtures of crystallization promoters and waste glass. Two kinds of promoters were synthesized using kaolin clay, talc and chemical reagents. The crystalline phases were formed by a reactive crystallization between promoters and glass during sintering. The effect of promoter components, additions and sintering temperatures on the crystallizing and densifying behavior, microstructures and mechanical properties of glass-ceramics was investigated. The results showed that the higher densities and better mechanical properties were obtained for the glass-ceramics with 12-15% crystallization promoters sintered at 950 °C for 2 h © 2011 Elsevier Ltd.
Li D.-C.,Zhejiang Ocean University |
Geng S.-L.,Qinghai Normal University
Information Sciences | Year: 2014
This paper aims to solve the problem of multiple-objective linear optimization model subject to a system of inf-→ composition fuzzy relation equations, where → is R-, S- or QL-implications generated by continuous Archimedean t-norm (s-norm). Since the feasible domain of inf-→ relation equations constraint is nonconvex, these traditional mathematical programming techniques may have difficulty in computing efficient solutions for this problem. Therefore, we firstly investigate the solution sets of a system of inf-→ composition fuzzy relation equations in order to characterize the feasible domain of this problem. And then employing the smallest solution of constraint equation, we yield the optimal values of linear objective functions subject to a system of inf-→ composition fuzzy relation equations. Secondly, the two-phase approach is applied to generate an efficient solution for the problem of multiple-objective linear optimization model subject to a system of inf-→ composition fuzzy relation equations. Finally, a procedure is represented to compute the optimal solution of multiple-objective linear programming with inf-→ composition fuzzy relation equations constraint. In addition, three numerical examples are provided to illustrate the proposed procedure. © 2014 Elsevier Inc. All rights reserved.
Ma K.,Qinghai Normal University
Proceedings of 2016 IEEE International Conference on Big Data Analysis, ICBDA 2016 | Year: 2016
According to the security policy research in distributed data and information storage, considered from the data access patterns, this paper designs a system with new storage model and query mechanism for distributed platform and big data. This system can provide data sharing integrity check, while giving a hot backup solution, to improve the safety and maintainability of the cluster, and take a viable option for data migration and recovery when the cluster fails. © 2016 IEEE.
Song C.,Qinghai Normal University
Proceedings of 2016 IEEE International Conference on Big Data Analysis, ICBDA 2016 | Year: 2016
Association rule data mining is an important part in the field of data mining data mining, its algorithm performance directly affects the efficiency of data mining and the integrity, effectiveness of ultimate data mining results. Based on the existing association rule mining algorithms, this paper studies and analyzes their efficiency and effectiveness, and according to the efficiency defects of Apriorialgorithm, proposes an improved algorithm. This algorithm can reduce the data base I /Operation time, improve mining efficiency. © 2016 IEEE.
Fang L.,Nankai University |
Li H.,Qinghai Normal University
Computers and Operations Research | Year: 2013
The calculation of cost efficiency requires complete and accurate information on the input prices at each decision making unit (DMU). In practice, however, exact knowledge of the relevant prices is difficult to come by, and prices may be subject to variation in the short term. To estimate the cost efficiency while taking price uncertainty into account, cone-ratio DEA models incorporating the available price information as weight restrictions can be applied. However, the literature lacks a clear explanation regarding the exact relationships between these two models. In this paper, through a duality study, we establish both the theoretical properties of these relationships and the characteristics of their efficiency solutions between cone-ratio DEA models and CE models, assuming there are imprecise price data. Based on the duality study, we also develop a new approach and design a lexicographic order algorithm to estimate the lower bounds of the cost efficiency measure. Our computational experiments indicate that the proposed models are robust and that the proposed algorithm is computationally simple. © 2012 Elsevier Ltd. All rights reserved.
Tai X.,Weifang University |
Zhao W.,Qinghai Normal University
Materials | Year: 2013
A novel Ca(II) coordination polymer, [CaL(4,4'-bipyridyl)(H2O)4]n (L = 1,6-naphthalenedisulfonate), was synthesized by reaction of calcium perchlorate with 1,6-naphthalenedisulfonic acid disodium salt and 4,4'-bipyridyl in CH3CH2OH/H2O. It was characterized by elemental analysis, IR, molar conductivity and thermogravimetric analysis. X-ray crystallography reveals that the Ca(II) coordination polymer belongs to the orthorhombic system, with space group P212121. The geometry of the Ca(II) ion is a distorted CaNO6 pengonal bipyramid, arising from its coordination by four water molecules, one nitrogen atom of 4,4'-bipyridyl molecule, and two oxygen atoms from two L ligands. The complex molecules form a helical chain by self-assembly. The antitumor activity of 1,6-naphthalenedisulfonic acid disodium salt and the Ca(II) coordination polymer against human hepatoma smmc-7721 cell line and human lung adenocarcinoma A549 cell line reveals that the Ca(II) coordination polymer inhibits cell growth of human lung adenocarcinoma A549 cell line with IC50 value of 27 μg/mL, and is more resistive to human lung adenocarcinoma A549 cell line as compared to 1,6-naphthalenedisulfonic acid disodium salt. © 2013 by the authors.
News Article | December 28, 2016
The first humans venturing onto the Tibetan Plateau, often called the “roof of the world,” faced one of the most brutal environments our species can endure. At an average elevation of over 4,500 meters, it is a cold and arid place with half the oxygen present at sea level. Science has long held that humans did not set foot in this alien place until 15,000 years ago, as suggested by archaeological evidence of the earliest known settlement on the northeastern fringe of the plateau 3,000 meters above sea level. But now new genetic data indicate this may have occurred much earlier—possibly as far back as the last ice age, 62,000 years ago. A better understanding of modern Tibetans’ genetic mix and diversity could help reconstruct the history of migration and population expansion in the region, and may help unravel the mystery of the ethnic origins of Tibetans—and of how humans have adapted to low-oxygen conditions at high altitudes. For the new study, researchers sequenced the entire genomes of 38 ethnic Tibetans and 39 Han Chinese (the country’s majority ethnic group), and compared the results with published genomic sequences of other ethnic groups around the world—information that allowed the team to pinpoint the common genetic origin of different populations and to get a better grasp on the history of migration in Tibet. “Tibetan-specific DNA sequences can be traced back to ancestors 62,000-38,000 years ago…This represents the earliest colonization of the Tibetan Plateau,” says Shuhua Xu, a population geneticist at the Chinese Institute of Sciences’ Shanghai Institutes for Biological Sciences. Xu’s work was published in September in the American Journal of Human Genetics, and presented at the American Society of Human Genetics’ annual meeting in Vancouver. Since that initial migration, as the ice age tightened its grip on the plateau, genetic mixing between Tibetans and non-Tibetans probably ground to a halt for tens of thousands of years—suggesting that movement into Tibet dropped to the minimum. “The migration routes were probably cut off by ice sheets,” Xu says. “It’s simply too harsh even for the toughest hunter-gatherers.” But about 15,000 to 9,000 years ago—after the so-called last glacial maximum (LGM), during which the Earth’s ice cover had reached its most extensive point and climate was at its harshest—people flocked into Tibet en masse. “It’s the most significant wave of migration that shaped the modern Tibetan gene pool,” Xu says. “We can really see rapid population expansion [on the plateau] during that time.” Interestingly, he adds, this was also when the common ancestor of Tibetans and Han Chinese split—contrary to a previous study suggesting that the divergence took place as late as 2,750 years ago. “This is the first study to sequence the entire genome of Tibetans, and the resolution is really impressive,” says Mark Aldenderfer, an archaeologist at the University of California, Merced, who was not involved in Xu’s study. The much earlier divergence between Tibetans and Han Chinese makes sense because there are continuous material cultures on the plateau since 15,000 years ago, he says. The study, Aldenderfer adds, “also provides fine details of how different populations from various directions may have combined their genes to ultimately create the people that we call Tibetans.” The data show that 94 percent of the present-day Tibetan genetic makeup came from modern humans—possibly those who ventured into Tibet in the second wave of migration—and the rest came from archaic hominins such as Denisovans, Neandertals and unknown groups. The modern part of the Tibetan genome shares 82 percent similarity with East Asians, 11 percent with Central Asians, and 6 percent with South Asians. “Among all ethic groups, Han Chinese are most closely related to Tibetans,” Xu says. The findings also reveal a startling genetic continuity since the plateau was first colonized 62,000 years ago. “This suggests that Tibet has always been populated—even during the toughest times as far as climate was concerned,” Xu says. That idea contradicts the commonly held notion that any early plateau dwellers would have been eliminated during harsh climate intervals such as LGM and another period known as the Younger Dryas between 12,900 and 11,600 years ago, says David Zhang, a geographer at the University of Hong Kong, who was not involved in Xu’s research. In 2002 Zhang and a colleague published a controversial study in Geophysical Review Letters showing marks of hands and feet from at least six individuals in rocks that were once soft mud, which was dated to 20,000 years ago at 4,000 meters above sea level in the heart of Tibet. Based on this they theorized that people were living in Tibet at the height of LGM, but the lack of archaeological finds near the site has cast doubt on this. “Many people don’t think it’s possible,” Aldenderfer says. “But there were plenty of places for [those early populations] to live where local conditions weren’t that bad, such as the big river valleys on the plateau.” The handprints and footprints were uncovered near one of the plateau’s many hot springs, which could have served as refuges for plants, animals and humans, he adds. Two independent archaeological studies presented at the 33rd International Geographical Congress, held in August in Beijing, also support the antiquity of Tibet settlement as suggested by Xu’s genetic data. A team led by archaeologist Guanghui Dong of Lanzhou University in Gansu province unveiled the earliest archaeological evidence of human presence—dating to 39,000-31,000 years ago—on the southeastern fringe of the Tibetan Plateau. The site, rich with stone tools and animal bones, lies at 2,500 meters above sea level at the bank of the Salween River. “This may represent one of the first steps of human colonization on the plateau,” Dong says. “Those hunter-gathers might then expand to the inner plateau along the river valley.” The second study pushes back the dates of human settlement above 4,000 meters by 4,000 years. Qinghai Normal University archaeologist Guangliang Hou and some of his colleagues recently excavated an archaeological site dated to 11,500 years ago, which is in line with the second and more important wave of migration that Xu’s study suggests. Hou said at the geographical congress that the site, close to a main tributary of the Yellow River, is teeming with charcoal—a telltale sign of fire use by humans. “This may have helped the plateau dwellers to survive the harsh conditions at such high elevations nearing the end of the Younger Dryas,” he says. “It’s increasingly clear that there has been much earlier and much more persistent human occupation of the plateau than we previously thought,” Aldenderfer says. He stresses, however, that pieces are still missing from the puzzle: “More excavations are required to close those gaps.”