Further Estimate of Complete Trigonometric Sums

1 IntroductionLet q be a positive integer, and f(x) = akxk ... alx ac (k>3)be apolynomial with integral coefficients such that (a,, "',ah, q) = 1 and writeIn 1940. Hua Lookeng['] first proyed thatwhere the constant implied by aO" depends only on k and e. This is a1significant result, because the main order(1 -- i)is the best possible. Afterwards, some mathematicians are interested in the improvements of theconstant implied by aO" .Various estimates are as follows:The purpose of this p…     

Wind Measurement with a Wind Profiling Radar

The first troposphere wind profiling radar in China has been in operation. The paper describes the radar parameters and characteristics with some experimental results presented.     

Twenty-five years of change in scleractinian coral communities of Daya Bay （northern South China Sea） and its response to the 2008 AD extreme cold climate event

Coral reefs worldwide are becoming increasingly and detrimentally impacted upon by a variety of factors including significant climate changes, such as global warming and increased El Nino-Southern Oscillation activity. Generally, the persistence of coral reefs, especially at low-latitudes, is governed, in part, by sea surface temperatures not exceeding the critical limit （-30℃） at which mass mortality can occur. Thus, it is thought that corals living at high-latitudes （i.e., currently cooler sea surface temperatures） will likely respond more favourably to hypothesized future temperature increases than corals living at low-latitudes （i.e., currently warmer sea surface temperatures）. Consequently, high-latitude coral communities may have the potential to act as regions of refugia for many coral species in the face of potential future global warming. The Daya Bay （22°31′--22°50′N）, northern South China Sea, contains several high-latitude non-reefal coral communities and represents one of the most northerly distributions of scleractinian corals within the region. Significantly, Daya Bay has experienced dramatic warming in both air and sea surface temperatures throughout the past 50 years. In this paper, we analyze 25 years of change in the Daya Bay coral communities, based both on historic surveys and our latest 2006--2008 regional ecological surveys. Our results suggest that, contrary to predictions, there have been significant declines in coral cover within the Daya Bay during the past 25 years （i.e., 76.6% coral cover in 1983/1984 to only 15.3% coral cover by 2008）. Such changes also reflect a significant shift in the most abundant coral species, from Acropora pruinosa to Favites abdita. Most of the modern coral communities became established between 15 and 30 years ago, corresponding to a period of increased winter sea surface temperature. However, very few colonies have become established within the last 15 years, despite a more intense period of warming. By taking into account additional factors, we hypothesize that direct anthropogenic impacts, rather than climatic events, have both restricted the development, and drove the decline, of Daya Bay coral communities in the last 15 years. The Daya Bay has also been subjected to occasional extreme cold events during the past 50 years, with the most recent occurring in early 2008 （13 January-13 February）. During the 2008 cold event, the lowest air temperature reaches only 6.6℃, and the mean sea surface temperature for February fall to 〈 14℃, including six continuous days at 12.3℃. Significantly, the sea surface temperatures fall below the hypothesized critical lower temperature threshold （-13℃） that commonly leads to mass mortality in scleractinian coral communities. Surprisingly, our coral community surveys, conducted both before （August 2007） and after （late February 2008） the extreme 2008 cold event, demonstrate that the Daya Bay coral ecosystems are barely impacted upon during the cold period. Those observations suggest that the Daya Bay scleractinian coral communities have developed adaptations to low sea surface temperatures. Overall, our data support the hypothesis that high-latitude coral communities, such as Daya Bay, have the potential to act as areas of refugia for scleractinian corals in the advent of potential future global warming.     

Approaches for improving the performance of filament-type resistive switching memory

Resistive random access memory (RRAM) has received significant research interest because of its promising potential in terms of down-scaling,high density,high speed and low power. However,its endurance,retention and uniformity are still imperfect. In this article,the physical mechanisms of filament-type RRAM and the approaches for improving the switching performance,including doping,process optimization and interface engineering,are introduced.     

Purification of Murine Monoclonal IgM Antibody

ＩｎｔｒｏｄｕｃｔｉｏｎＩｏｎｅｘｃｈａｎｇｅｉｓｔｈｅｍｏｓｔｆｒｅｑｕｅｎｔｌｙｕｓｅｄｃｈｒｏｍａｔｏｇｒａｐｈｉｃｔｅｃｈｎｉｑｕｅｆｏｒｔｈｅｓｅｐａｒａｔｉｏｎａｎｄｐｕｒｉｆｉｃａｔｉｏｎｏｆｃｈａｒｇｅｄｂｉｏｍｏｌｅｃｕｌｅｓ ,ｅｓｐｅｃｉａｌｌｙｗｈｅｒｅａｓｍａｌｌａｍｏｕｎｔｏｆｐｒｏｔｅｉｎｉｓｔｏｂｅｅｘｔｒａｃｔｅｄｆｒｏｍａｌａｒｇｅｖｏｌｕｍｅ[1 3] .Ｇｅｌｆｉｌｔｒａｔｉｏｎｉｓａｔｅｃｈｎｉｑｕｅｔｈａｔｃａｎｎｏｔｏｎｌｙｓｅｐａｒａｔｅｐｒｏｔｅｉｎｓ ,…     

Transgenic rescue of defective Cd36 ameliorates insulin resistance in spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) display several features of the human insulin-resistance syndromes. Cd36 deficiency is genetically linked to insulin resistance in SHR. We show that transgenic expression of Cd36 in SHR ameliorates insulin resistance and lowers serum fatty acids. Our results provide direct evidence that Cd36 deficiency can promote defective insulin action and disordered fatty-acid metabolism in spontaneous hypertension.     

Vortex dynamics in superconducting MgB2 and prospects for applications

The recently discovered superconductor magnesium diboride, MgB2, has a transition temperature, Tc, approaching 40 K, placing it intermediate between the families of low- and high-temperature superconductors. In practical applications, superconductors are permeated by quantized vortices of magnetic flux. When a supercurrent flows, there is dissipation of energy unless these vortices are 'pinned' in some way, and so inhibited from moving under the influence of the Lorentz force. Such vortex motion ultimately determines the critical current density, Jc, which the superconductor can support. Vortex behaviour has proved to be more complicated in high-temperature superconductors than in low-temperature superconductors and, although this has stimulated extensive theoretical and experimental research, it has also impeded applications. Here we describe the vortex behaviour in MgB2, as reflected in Jc and in the vortex creep rate, S, the latter being a measure of how fast the 'persistent' supercurrents decay. Our results show that naturally occurring grain boundaries are highly transparent to supercurrents, a desirable property which contrasts with the behaviour of the high-temperature superconductors. On the other hand, we observe a steep, practically deleterious decline in Jc with increasing magnetic field, which is likely to reflect the high degree of crystalline perfection in our samples, and hence a low vortex pinning energy.     

Dynamic learning rates algorithm for BPNN to forecast time series of dam security

Time series data of dam security have a large number of observed values and should be forecasted accurately in time. Neural networks have the powerful approach ablilities of arbitrary functions and have been broadly utilized in many domains. In this paper, a dynamic learning rate training algorithm of back-propagation neural networks for time series forecasting is proposed and the networks with this algorithm are built to forecast time series of dam security. The application results demonostrate the efficiency of modelling and the effictiveness of forecasting.     

Synthesis and crystal structure of the trimetallic erbium tetrahydride complex [Li(THF)_4][{(Bu~tCp)_2Er(μ-H)}_3-(μ_3-H)]

~~Synthesis and crystal structure of the trimetallic erbium tetrahydride complex [Li(THF)_4][{(Bu~tCp)_2Er(μ-H)}_3-(μ_3-H)]~~