[Ammonia volatilization under different nitrogen and water treatments of tomato-watermelon rotation system in solar greenhouse in Losses Plateau, China]. / æ—¥å ‰æ¸©å®¤ç•ªèŒ„-西瓜轮作系统不同水氮处理氨挥发特征.

To understand the characteristics of ammonia volatilization in Losses Plateau, an experiment was conducted in a typical solar greenhouse involving four treatments. Intermittent ventilation chamber method was used to measure NH3 volatilization over the period of tomato-watermelon rotation. The results showed that nitrogen transformation was rapid in solar greenhouse system. The peak NH3 volatilization rate appeared one to two days after fertilization with the range from 0.26 to 2.02 kg N·hm-2·d-1. The NH3 volatilization lasted for about one week in all treatments. No significant differences were recorded in terms of cumulative NH3 volatilization among all nitrogen fertilizer input treatments. The cumulative NH3 losses further increased about 46.7% in two seasons under the same nitrogen application rate, however when irrigation application was decreased. The average NH3 vola-tilization rate and cumulative NH3 losses in watermelon season were higher compared to tomato season, which might be attributed to high temperature during watermelon season. Soil NH4+-N content, water filled pore space, soil temperature of 0-5 cm layer and air temperature all had extremely significant effect on NH3 volatilization rate, while a negative correlation was observed between soil pH and NH3 volatilization rate. Between the different cropping seasons, the rate of NH3 volatilization and cumulative NH3 losses were different, and decreased with decreases in nitrogen input, while reduced irrigation volume increased NH3 volatilization under the same nitrogen application rate.

[Effects of nitrogen fertilizer application on carbon dioxide emissions from soils with different inorganic carbon contents.] / æ°®è‚¥å¯¹ä¸åŒæ— æœºç¢³å«é‡åœŸå£¤äºŒæ°§åŒ–ç¢³é‡Šæ”¾çš„å½±å“.

The application of nitrogen (N) fertilizer results in decreases of soil pH, but its effects on CO2 emission from soils with different inorganic carbon contents remain unclear. An closed-jar incubation experiment was conducted to examine the effects of N fertilizer and nitrification inhibitor (DCD) on soil pH and CO2 emissions from three soil types with different contents of soil inorganic carbon (SIC), including paddy soil (PS), lime concretion black soil (CS), and eum-orthic anthrosols (AS). There were three treatments for each soil type, including control (N0), 0.2 g·kg-1 N fertilizer (N0.2), and its combination with DCD (N0.2+DCD). Soil pH, contents of mineral N (NH4+, NO3-), and CO2 emissions were measured. The results showed that N fertilizer addition significantly reduced soil pH and increased soil CO2 cumulative emissions in each type of soil. Compared to control, the CO2 cumulative emissions after 49 days incubation from the three soil types were enhanced by 39.4%, 23.4%, and 71.8% for PS, CS, AS soils, respectively. The soil pH of N0.2+DCD for three soil types were significantly higher than N0.2 after 49 days incubation, indicating that DCD application inhibited soil nitrification process. There were no significant differences in the mean CO2 cumulative emissions of PS and CS soils between N0.2 and N0.2+DCD treatments; however, N0.2+DCD treatment significantly reduced cumulative CO2 emissions from AS soil by 12.5%. Soil inorganic carbon can effectively buffer soil acidification caused by N fertilizer addition. The CO2 emission in calcareous soil following N addition is not only derived from the mineralization of soil organic carbon, but also from the dissolution of inorganic carbon. Given the large differences in soil inorganic carbon content in different regions of China, the problem of soil acidification and soil inorganic carbon pool consumption caused by long-term large amount of N fertilizer inputs deserve more attention.

Rising time restoration for nuclear pulse using a mathematic model.

The rising time of a nuclear pulse is slowed before being digitized because of the effect of distributed capacitance and resistance. This results in the waveform distortion of a shaped pulse. In this study, the effect of distributed capacitance and resistance is equivalent to the result of RC network. The mathematical model of the network is established to restore the rising time of the input nuclear pulse. Experimental results show that the leading edge of the nuclear pulse becomes steep after rising time restoration, and the shape of the shaped pulse is also improved. The energy spectrum obtained with rising time restoration is compared with that without rising time restoration. The comparison result indicates that using rising time restoration can extend the measurement range of pulse amplitude without affecting the energy resolution of the system.

[Study on the High Speed and Precision Gaussian Function Fitting Algorithm for Nuclear Single Spectral Peak].

In nuclear spectrum, Gaussian function least square fitting is a commonly used method. Usually the method has high precision, but it is very much sensitive to noise, which causes that the residual vector is larger near the peak in the Gaussian function. To solve the problem, Gaussian function least square fitting was deduced particularly, and the causes are analyzed. As a result, Gaussian function weighted least square fitting is proposed, i.e., a weight factor, which had an opposite tendency to the data weight reduction tendency after taking logarithm, or it had the same tendency to the origin data. This was introduced based on Gaussian function least square fitting to reduce noise sensitivity. In the process of solving Gaussian parameter, to improve the real-time performance, the solution process of inverse matrix was transferred to the solution process of simple equations because the computation of inverse matrix was time consuming. Gaussian function parameter, amplitude, center value and variance, were given with the fast calculation formulas. By applying these two methods to the practical fitting of 55Fe characteristic X-ray single spectrum peak, respectively, the results show that Gaussian function weighted least square fitting is more satisfactory. It indicates the proposed method can decrease the noise sensitivity and reduce the residual vector near the peak; in addition, the fitting precision is also improved. What's more, the real-time performance is improved by applying fast calculation formulas, which makes it possible to apply the proposed method to portable equipment efficiently.

Study on Heavy Metal Detection in Soil with Improved EDXRF.

Due to the low precision and accuracy of trace heavy metals detection wiith traditional energy dispersive X-ray fluorescence (EDXRF) system, an improved EDXRF system is proposed. In order to reduce the influence of reflected rays, the sample is irradiated with the incident X-rays vertically, and the detector is placed in parallel with the sample's section. The sample is connected with detector through collimator. With improved EDXRF measures certified reference materials, the results show that the detection limit of the improved EDXRF system for Mo，Zn，Cu，Pb，Zr，Nb is 0.4，6.68，1.97，6.84，1.60，7.59 mg·kg-1 respectively and the logarithm deviation of each element in the standard samples is between 0 and 0.05. The RSD%(GBW) is less than 7 as the element content is more than three times of the detection limit, and it is below 15 when the element content is less than three times of the detection limit. The soil samples collected from Da Xing'an Ling region are applied to verify the improved EDXRF system. The proposed EDXRF system can improve the measurement accuracy of trace heavy metal detection in soil, satisfying the requirements of geologic exploration.

[Effects of long-term different fertilizations on biomass and nutrient content of maize root].

Taking two long-term local field trials at the south edge of the Loess Plateau, which were found in 1990 and 2003, respectively, as test subjects, the effects of different fertilization practices on the maize root biomass and nutrient content were investigated in this paper. Maize roots in the 0-20 cm top soil post-maize harvest from the different fertilization practices were collected by hand in October 2011. The results showed that compared with control without fertilization and N, NK, or PK treatments, the NP, NPK, fertilizers plus manure (M1NPK and M2NPK) or plus straw return (SNPK) treatments significantly increased the dry mass of maize root. The C, N, P and K contents in maize roots in the NP, NPK, M1 NPK, M2NPK and SNPK treatments were also significantly higher than those of control, especially in the NPK plus organic manure treatments (M1 NPK and M2NPK) in the trial. Compared with the N fertilizer free treatment (N0), root biomass in the 120 kg N · hm(-2) (N120) and 240 kg N · hm(-2) ( N240) fertilization treatments increased by 38% and 45%, respectively, but there was no significant difference between N120 and N240 treatments. Nitrogen fertilizer application (N120 and N240) also improved the C, N, P and K contents in maize root. The water soluble organic C and total soluble N contents of maize root in the NP, NPK, M1NPK, M2NPK, SNPK and the N120 and N240 treatments were greater than those of control and other treatments. Otherwise, the cellulose and lignin contents in maize roots declined in the NPK, M1NPK, M2NPK, and SNPK treatments compared with other treatments. So the root C/N and lignin/N ratios in the control, PK and N0 treatments were significantly higher than those in the NP, NPK, M1NPK, M2NPK and SNPK treatments. We concluded that the optimum fertilization (e. g., NP, NPK, MNPK and SNPK treatments) could increase maize root growth and nutrient content and improve soil fertility and carbon sequestration through root residue into soil.

[The study of baseline estimated in digital XRF analyzer].

For the digital X-ray fluorescence analyzer, the voltage of the instability baseline will directly affect the performance of the instrument, resulting in decreased energy resolution. In order to solve this problem, Kalman filtering algorithm was used for pulse signal baseline estimate in the digital X-ray fluorescence. Whether using the classic Kalman filter, or the simplified sage-husa, or the improved sage-husa, their baseline filtering effects were all poor. So, it is necessary to improve and optimize existing algorithms. The method of Double-Forgotten was put forward to establish a new model of adaptive Kalman filter algorithm based on the sage-husa. The experiment results show that a very good filtering effect was obtained using the mathematical model of the baseline filter. The algorithm solved the problem of filtering divergence, avoided slow convergence of baseline and realized the pulse baseline restoration, and improved the instrumental energy resolution.

[Effects of combined application of maize- and horsebean straws on the straws decomposition and soil nutrient contents].

A laboratory incubation experiment was conducted to study the straw decomposition and soil nutrient contents after single and combined applications of maize- and horsebean straws. With the single application of maize straw, the mineralization rates of the straw and soil organic C were lower, and the immobilization of soil mineral N sustained longest. Combined application of maize- and horsebean straws promoted the mineralization of the straws organic C and soil immobilized N. Both single and combined application of the straws increased the contents of soil microbial biomass C and N significantly. It was suggested that a combined application of gramineous and leguminous straws could promote the straws decomposition and harmonize the soil nutrient supply.

[Methods of detector response function establishment in X-ray fluorescence spectra analysis].

During the measurement and analysis process of X-ray fluorescence spectra, it is very helpful to improve the analyze speed, accuracy and automaticity of X-ray fluorescence spectra analysis by establishing detector response function(DRF), which represents the shape of full energy peak and can provide former basic data for subsequent X-ray analysis technique. For the theory and model of semiconductor DRF in X-ray energy spectrum measurements, methods of three typical detector response function model establishment, key parameters of full energy peak standard deviation and Fano factor calculation, etc. are discussed, and meanwhile, the summarization and contrast of existing studies are shown in this paper. Finally, the suggestion for modeling methods of DRF in X-ray fluorescence spectra measurements is provided.

[Decomposition of different plant litters in Loess Plateau of Northwest China].

Taking the litters of species Hippophae rhamnoides, Medicago sativa, Populus simonii, Robinia pseudoacaci, Salix psammophila, and Stipa bungeana in the Loess Plateau of Northeast China as test objects, and by using mesh bags, this paper studied the dynamic changes of the litters mass, carbon, and nitrogen during decomposition after buried in the field in semiarid region. The litters buried were from one, two, or three of the plant species, and mixed thoroughly with equal proportion of masses. During decomposition, the mass loss rate, total carbon and nitrogen release rates, and total soluble carbon and nitrogen contents of different litters were higher at the early than at the later decomposition stage. After 412 d decomposition, the average mass loss rate of the litters was in the order of mixed litters of three plant species > mixed litters of two plant species > one plant species litter. By the end of this experiment, the average release rates of the litter total carbon and nitrogen ranked as one plant species litter > mixed litters of two plant species > mixed litters of three plant species, the litter soluble organic carbon content was mixed litters of two plant species > mixed litters of three plant species > one plant species litter, while the litter soluble total nitrogen content was mixed litters of three plant species > mixed litters of two plant species > one plant species litter. Correlation analysis showed that the litter mass loss rate had definite correlation with the litter soluble organic matter, especially soluble organic carbon. From the viewpoint of mass loss rate, the mixture of the litters of P. simonii, H. rhamnoide, and M. sativa was the optimum. It was suggested that in the process of returning farmland into forestland and grassland in the gully and valley region of Loess Plateau, it would be required to rationally increase plant species diversity to improve soil fertility.

[Contents and biodegradation of soluble organic carbon in different plant residues from the Loess Plateau].

Soluble organic carbon (SOC) in plant residues extracted by water or different extractants is an active component, and has important roles in carbon and nitrogen biogeochemical process in soil ecosystem. Reestablishing the vegetation on the Loess Plateau is changing the types and amounts of the plant residues into soil ecosystem. Therefore, our objective was to evaluate the contents and biodegradation of SOC of residues of different species from this region. Six species of plant residues were sampled from Shenmu, North of the Loess Plateau, and the contents of SOC in two sizes residues (2 mm and 1 cm length) was extracted with two extractants (distilled water and 0.01 mol x L(-1) CaCl2). And a 7-day incubation experiment (25 degrees C) was conducted to compare the biodegradability of SOC of the different plant residues. The contents of SOC in the different plant species ranged from 4.21 g x kg(-1) to 76.25 g x kg(-1), and the rates of SOC to total carbon (SOC/TC) of the plant residues were in range of 0.99% and 19.84%. The order about the average content of SOC and SOC/TC of the different plant species was trees > shrubs > grasses. After 7-day of incubation, rates of biodegradation of SOC in different plant residues ranged from 34. 7% to 75. 1% (averaged 56.3%). The proportion of complex structure SOC increased significantly in solution at the end of incubation, indicated the rapid biodegradation of labile composition in the residues.

[Soluble organic carbon in plant litters on Loess Plateau: content and biodegradability].

The litters of eight plant species from the Loess Plateau were cut into pieces with 2 mm and 1 cm in size, and extracted with distilled water and 0.01 mol x L(-1) CaCl2 to determine the soluble organic carbon (SOC) content. In the meantime, a 7-day indoor incubation test was conducted at (25 +/- 3) degrees C to investigate their biodegradability. The SOC content and the ratio of SOC to total carbon (SOC/TC) in the litters were 18.20-156.82 g x kg(-1) and 4.21%-32.84%, respectively. Shrub litter had a slightly higher SOC content than tree litter, while grass litter had the lowest SOC content. After 7-day incubation, the biodegradation rate of SOC in the plant litters ranged from 44.5% to 80.6% (62.9% on average), and decreased in the order of shrub > tree > grass. By the end of the incubation, the proportion of soluble organic matter in solution had a significant increasing trend, which was related to the rapid biodegradation of labile composition in the litters. The higher content and higher biodegradation rate of SOC in plant litters might play important roles in nutrient cycling and energy flow during the vegetation restoration on Loess Plateau.

[Effects of fertilization on carbon/nitrogen ratio of maize straw and its minereffects of fertilization on carbon/nitrogen ratio of maize straw and its mineralization in soil.alization in soil].

Maize straws were collected from different treatments of two long-term fertilization studies, their carbon (C)/nitrogen (N) ratios were determined, and their C and N mineralization rates in soil were compared in an aerobic incubation test. The results showed that comparing with no fertilization, applying chemical fertilizers (NPK) or chemical fertilizers plus manure (MNPK) increased the N content and decreased the C/N ratio of maize straw. The amounts of mineralized and immobilized C and N of the straws from different fertilization treatments differed with incubation time. The straws from treatments NPK, MNPK, and N240 had significantly higher C mineralization rates than that from the treatment without fertilization. After incubation for 60 days, the straw from treatment NPK had the highest C mineralization rate (13.24% of added organic C), and the immobilized N from the straws of fertilized plots, especially of MNPK plot, was lesser, compared to unfertilized plots. Adding maize straw into soil increased the metabolic quotient (qCO2) of soil microorganisms, but the difference among the treatments was not significant. During incubation, the amounts of soil microbial biomass C and N from different treatments differed with time. Therefore, in agricultural practices, the differences in the nutrient contents of straw due to different fertilization should be considered when the straw was to be added into soil.

Nonlinear Dynamics and Chaos of Microcantilever-Based TM-AFMs with Squeeze Film Damping Effects.

In Atomic force microscope (AFM) examination of a vibrating microcantilever, the nonlinear tip-sample interaction would greatly influence the dynamics of the cantilever. In this paper, the nonlinear dynamics and chaos of a tip-sample dynamic system being run in the tapping mode (TM) were investigated by considering the effects of hydrodynamic loading and squeeze film damping. The microcantilever was modeled as a spring-mass-damping system and the interaction between the tip and the sample was described by the Lennard-Jones (LJ) potential. The fundamental frequency and quality factor were calculated from the transient oscillations of the microcantilever vibrating in air. Numerical simulations were carried out to study the coupled nonlinear dynamic system using the bifurcation diagram, Poincaré maps, largest Lyapunov exponent, phase portraits and time histories. Results indicated the occurrence of periodic and chaotic motions and provided a comprehensive understanding of the hydrodynamic loading of microcantilevers. It was demonstrated that the coupled dynamic system will experience complex nonlinear oscillation as the system parameters change and the effect of squeeze film damping is not negligible on the micro-scale.

[Effects of long-term fertilization and fallowing on soil nitrogen mineralization and exogenous NO3(-) -N transformation].

Soil samples were collected from a 17-year fertilization experiment site in southern Loess Plateau to study the effects of different fertilizations and fallowing on the characteristics of soil nitrogen mineralization, and the transformation of exogenous NO3(-) -N in sterilized and non-sterilized soil samples. The results showed that a combined application of manure and chemical NPK and long-term fallowing increased the contents of soil organic matter, total N, and mineralized N, as well as the N mineralization rate significantly, compared with the control. Applying chemical NPK increased soil inorganic N content, but had less effects on the contents of soil organic matter, total N and mineralized N, as well as the N mineralization rate. Autoclaved sterilization resulted in a significant increase of soil NH4(+) -N content, while soil NO3(-) -N content remained relatively constant whether sterilization or not, suggesting that under the conditions of our incubation, abiotic and biological factors had no significant effects on the transformation of exogenous NO3 (-) -N.

[Adsorption characteristics of soluble organic carbon and nitrogen in two cultivated soils].

In this paper, soluble organic carbon (SOC) and nitrogen (SON) were extracted from manure, and their adsorption characteristics in Argosols and Anthrosols in Guanzhong region of Shaanxi Province were investigated. The results showed that the adsorption of SON and SOC in the two soils could be fitted by initial mass isotherm model, and the adsorbed amounts of SON and SOC had a significant linear relationship with the initial concentrations of SON and SOC added into soils. The partition coefficient, m of the initial mass isotherm model, indicated that Argosols had a higher adsorbility than Anthrosols. The average adsorption rates of SON and SOC in Anthrosols were 24.3% and 18.8%, and those in Argosols were 38.3% and 18.6%, respectively. The low adsorption rates of SON and SOC indicated their high mobility in the two soils, and more SON was adsorbed than SOC suggested the higher potential of SOC leaching from soil.

[Studies on triterpenoids from Potentilla chinensis].

OBJECTIVE: To investigate the chemical constituents of Potentilla chinensis. METHOD: Silica gel column chromatography and Sephadex LH - 20 gel column chromatography were employed for the isolation and purfication. The structures were identified on the basis of spectral data and chemical evidence. RESULT: Six compounds were isolated and identified as follows: 3-hydroxy-11-ursen-28, 13-olide, 11, 12-dehydroursolic acid lactone (1), 3-O-acetyl pomolic acid (2), betulinic acid (3), 3-oxo-12-ursen-28-oic acid (4), ursolic acid (5), oleanic acid (6). CONCLOUSION: All these compounds were isolated from P. chinensis for the first time, compound 1, 2, 4 were isolated from this genus for the first time.

[Study on chemical constituents of Potentilla chinensis Ser].

Five compounds (I - V) were isolated from Potentilla chinensis Ser. On the basis of spectral data and chemical evidence. I - V were identified as 2alpha-hydroxyoleanolic acid (I), 2alpha-hydroxyursolic acid (II), 5, 7, 4'-trihydroxyflavone (IIl), beta-sitosterol (IV), daucostarine (V). All these compounds were isolated from Potentilla chinensis Ser for the first time.