Phosphorus fractions and alkaline phosphatase activity in sediments of a large eutrophic Chinese lake (Lake Taihu)

Spatial, vertical, and seasonal variations in phosphorus fractions and in alkaline phosphatase activity (APA) were investigated in sediments in a large-shallow eutrophic Chinese lake (Lake Taihu) in 2003-2004. The phosphorus content was highest in the most seriously polluted lake area. Iron-bound phosphorus (Fe(OOH)-P) dominated (47% on average) among the phosphorus fractions determined according to Golterman (Hydrobiologia 335:87-95, 1996). Notably, organically-bound P comprised a further significant additional portion (acid-soluble + hot NaOH-extractable organic P = 25%), which was highest at the most polluted sites. The Fe(OOH)-P content was the lowest in spring (April, 2004), suggesting that degradation of organic matter led to the release of iron-bound phosphates. Sediment APA showed a significant positive relationship with both organically-bound P and Fe(OOH)-P. Consequently, organically-bound P is an important portion of the sediment phosphorus in Lake Taihu. It is mainly derived from freshly-settled autochthonous particles and from external discharges. Organically-bound P induces APA and may lead to the release of bioavailable phosphates from the organic sediments, thereby accelerating lake eutrophication.

Effect of annealing on optical properties of InAs quantum dots grown by MOCVD on GaAs (100) vicinal substrates

Thermal annealing effect on InAs quantum dots grown on vicinal (100) GaAs substrates is studied in comparison with dots on exact (100) GaAs substrates. We find that annealing acts stronger effect on dots with vicinal substrates by greatly accelerating the degradation of material quality. as well as slightly increasing the blueshift of the emission wavelength and the narrowing of PL linewidth. It is attributed to the higher strain in the dots formed on the vicinal substrates.

Effect of GaAS(100) 2 degrees surface misorientation on the formation and optical properties of MOCVD grown InAs quantum dots

The influence of GaAS(1 0 0)2 degrees substrate misorientation on the formation and optical properties of InAs quantum dots (QDs) has been studied in compare with dots on exact GaAs(1 0 0) substrates. It is shown that, while QDs on exact substrates have only one dominant size, dots on misoriented substrates are formed in lines with a clear bimodal size distribution. Room temperature photoluminescence measurements show that QDs on misoriented substrates have narrower FWHM, longer emission wavelength and much larger PL intensity relative to those of dots on exact substrates. However, our rapid thermal annealing (RTA) experiments indicate that annealing shows a stronger effect on dots with misoriented substrates by greatly accelerating the degradation of material quality. (c) 2005 Elsevier B.V All rights reserved.

Optical characteristics of InAs quantum dots on GaAs matrix by using various InGaAs structures

The effects of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots (QDs) grown by molecular-beam epitaxy ( MBE) were investigated. The emission wavelength of 1317 nm was obtained by embedding InAs QDs in InGAs/GgAs quantum well. The temperature-dependent and timed-resolved photoluminescence (TDPL and TRPL) were used to study the dynamic characteristics of carriers. InGaAs cap layer may improve the quality of quantum dots for the strain relaxation around QDs, which results in a stronger PL intensity and an increase of PL peak lifetime up to 170 K. We found that InGaAs buffer layer may reduce the PL peak lifetime of InAs QDs, which is due to the buffer layer accelerating the carrier migration. The results also show that InGaAs cap layer can increase the temperature point when, the thermal reemission and nonradiative recombination contribute significantly to the carrier dynamics.

Reconstructing the interaction between dark matter and holographic dark energy

We reconstruct the interaction rate between dark matter and the holographic dark energy with the parametrized equation of states and the future event horizon as the infrared cutoff length. It is shown that the observational constraints from the 192 type Ia Supernovae (SnIa) and baryon acoustic oscillation (BAO) measurement permit the negative interaction in the wide region. Moreover, the usual phenomenological descriptions cannot describe the reconstructed interaction well for many cases. The other possible interaction is also discussed.

Four-dimensional Newton's constant in brane world with a sloping extra dimension

We show the four-dimensional Newton's constant obtained naturally from five-dimensional brane world with a tinily sloping extra dimension, which is independent of the bulk Weyl tensor. The corresponding universe is stiff fluid dominated when the slope of extra dimension is very small. Otherwise, the universe may be undergoing a self-acceleration at present epoch and have a decelerated phase in very recent past.

Charge stripping accumulation of light heavy ions in HIRFL-CSR main ring

The charge stripping injection method has been adopted for the accumulation of light heavy ions in HIRFL-CSR. This method has some special requirements for the accelerating particles, and at the same time the structure of the injection orbit has to be changed. In this paper, the design of the orbit has been presented, as well as the calculation of the beam line matching. According to the result of commissioning, stripping injection can accumulate the beam to a higher current.

An untuned MA-loaded cavity for HIRFL-CSR

In order to realize high energy density physics and plasma physics research at HIRFL-CSR, a magnetic alloy (MA)-loaded cavity has been studied. According to the theoretical calculation and simulation for the MA-loaded cavity, we achieved a better result. The MA-loaded cavity had a higher Qf value, with a higher shunt impedance and a higher accelerating gradient. The accelerating gradient was about 95 kV/m at 1.8003 MHz, 130 kV/m at 0.9000 MHz. Compared with the ferrite-loaded cavities that are used at HIRFL-CSR, with about 10 kV/m accelerating gradient, the MA-loaded cavity obviously has an advantage. The results of the theoretical calculation and the simulation, which meet the design requirements are in good agreement.

Preliminary study of a niobium quarter-wave prototype cavity for a heavy-ion superconducting linac

Superconducting quarter-wave resonators, due to their compactness and their convenient shape for tuning and coupling, are very attractive for low-beta beam acceleration. In this paper, two types of cavities with different geometry have been numerically simulated: the first type with larger capacitive load in the beam line and the second type of lollipop-shape for 100 MHz, beta=0.06 beams; then the relative electromagnetic parameters and geometric sizes have been compared. It is found that the second type, whose structural design is optimized with the conical stem and shaping drift-tube, can support the better accelerating performance. At the end of the paper, some structural deformation effects on frequency shifts and appropriate solutions have been discussed.

Design optimization of the APF DTL in the SSC-linac

A linear accelerator as a new injector for the SSC (Separated Sector Cyclotron) of the HIRFL (Heavy ton Research Facility Lanzhou) is being designed. The DTL (Drift-Tube-Linac) has been designed to accelerate U-238(34+) from 0.140 MeV/u to 0.97 MeV/u. To the first accelerating tank which accelerates U-238(34+) to 0.54 MeV/u, the approach of Alternating-Phase-Focusing (APF) is applied. The phase array is obtained by coupling optimization software Dakota and beam optics code LINREV. With the hybrid of Multi-objective Genetic Algorithm (MOGA) and a pattern search method, an optimum array of asynchronous phases is determined. The final growth, both transversely and longitudinally, can meet the design requirements. In this paper, the deign optimization of the APF DTL is presented.

An untuned MA-loaded cavity for HIRFL-CSR

In order to realize high energy density physics and plasma physics research at HIRFL-CSR, a magnetic alloy (MA)-loaded cavity has been studied. According to the theoretical calculation and simulation for the MA-loaded cavity, we achieved a better result. The MA-loaded cavity had a higher mu Q f value, with a higher shunt impedance and a higher accelerating gradient. The accelerating gradient was about 95 kV/m at 1.8003 MHz, 130 kV/m at 0.9000 MHz. Compared with the ferrite-loaded cavities that are used at HIRFL-CSR, with about 10 kV/m accelerating gradient, the MA-loaded cavity obviously has an advantage. The results of the theoretical calculation and the simulation, which meet the design requirements are in good agreement.

大功率电子加速器的预研与束流传输的研究

电子束辐照烟道气脱除502和NOx技术是一项将辐射物理和辐射化学紧密结合的高新技术。该项技术自1970年被提出后，经历了20多年的逐步发展，已进入了工业装置阶段。目前，在美国、德国、日本、波兰和我国的成都热电厂等处建立了中试厂和工业示范厂。当前在国际上，对一该项目的关键部件电子加速器有两种方案：即日新公司的高压变压器方案和以俄罗斯新西伯利亚核物理研究所的ElV型加速器为代表的谐振变压器型。根据目前国内的实际状况和满足我所及在兰州各研究所的物理实验的需要，中利4院近代物理所在已有技术力量的基础上，并在国家计委的大力支持下，立项研制大功率谐振变压器型电子加速器。这篇论文首先对1.5Mev/300mA三相谐振变压器型电子加速器的高压电极表面电场强度、分布电容、电感、三相谐振频率等作了预研。在此基础上，着重对强流静电加速管轴上电位和电场分布、平面电子枪的实际电流密度、电极膜孔透镜对束流的聚焦性能、加速管中电子轨迹和出射斜率、球面阴极的电子光学特性等作了详细的计算和分析，从计算得到的结果来看，所设计的电场能够满足束流传输的要求。另外，还对加速管非均匀场对电子负载的抑制作用，离子反轰阴极作了初步研究。论文的另一个重点是研究了静电加速管中强流电子束的空间电荷效应。根据实际情况，合理地建立了物理模型。并对模型上的4个不同位置的束内外径向电位分布、空间电荷对轴＿L电位的影响，以及空间电荷力对束流传输的影响等进行了详尽的理论计算和分析。在对轴上电场分布进行分析时，发现可以将电场沿轴向分为3个区域，并认真对每个区域的作用作了详细的分析说明。特别指出了，强流静电加速管的设计关键在加速管的前端，与弱流加速管相比，前者的变化幅度要大得多。论文最后对大功率电子加速器部件的加工和三相谐振变压器高压发生器模拟实验结果给予了介绍和分析。

辽西油松纯林可持续经营途径探讨

Under the direction of Sustainable Development, some key issues of forestry in Western Liaoning Province were analyzed in this paper. "Planting Broad-leaved Trees and Accelerating Conifers" (PBTAC) was put forward as the effective approach to sustainable management on the Pure Plantation of Pinus tabulaeformis and the unique path of forestry sustainable development in Western Liaoning Province. The concept, aim, and notices of "PBTAC" were also analyzed and discussed.

燕儿沟流域水保治理措施优化配置示范研究

作为综合治理试验示范区 ,燕儿沟流域在水土保持技术措施配置中 ,坚持以土地利用结构调整为中心的综合治理方略 ,贯彻强化基本农田建设、退耕还林 (草 )的指导思想 ,强调降雨就近拦蓄 ,合理利用土地 ,减少水土流失 ,取得最大效益。同时 ,在配置实施过程中兼顾退耕与基本农田建设同步 ,发展粮食与水土保持同步的主导思想 ,探索生态环境建设的合理模式 ,并取得了可喜成效

Sol-gel synthesis and characterization of SiO2@NaGd(WO4)(2): Eu3+ core-shell-structured spherical phosphor particles

Monodisperse, core-shell-structured SiO2@NaGd(WO4)(2):Eu3+ particles were prepared by the sol-gel method. The samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, photoluminescence (PL), and low-voltage cathodoluminescence (CL) as well as time-resolved PL spectra and lifetimes. PL and CL study revealed that the core-shell-structured SiO2@NaGd (WO4)(2):Eu3+ particles show strong red emission dominated by the D-5(0) - F-7(2) transition of Eu3+ at 614 nm with a lifetime of 0.74 ms. The PL and CL emission intensity can be tuned by the coating number of NaGd(WO4)(2):Eu3+ phosphor layers on SiO2 and by accelerating voltage and the filament current, respectively.