No abstract

[1] We present estimates of nitrogen (N) inputs to the Changjiang River basin for the period 1968-1997. The total N input is approximately 7.8 Â 10 9 kg in 1997, which is a threefold increase over 1968 levels. N fixation was often a dominant input before 1978, providing about 2.2 Â 10 9 kg year À1 , while N fertilizer dominated N input after 1983, supplying an additional input of some 4.4 Â 10 9 kg year À1 . More than 40% of total N inputs is converted into manure N, and half of total manure N is returned to agricultural soil. We estimate that the river nitrate concentration and flux have increased about tenfold from 1968 to 1997. Our study suggests that the percent of N inputs to the basin that are exported by the river as NO 3 -N has increased steadily over the 30-year period and that about 30% of total N input is transported through the river. The integrated N input, budget, and storage have been linked to the increasing temporal trends of Changjiang River nitrate. N fertilizer application and human population density, as well as manure N production in the basin, are good predictors of the river's nitrate concentration and flux. Therefore, how N balance is kept (especially for effective application of N fertilizer) is a crucial problem to the sustainable development of the basin.

Key points The present study showed that anodal and cathodal transcranial direct current stimulation (tDCS) can respectively increase and decrease the amplitude of visually evoked field potentials in the stimulated visual cortex of cats, with the effect lasting for ∼60–70 min. We directly measured tDCS‐induced changes in the concentration of inhibitory and excitatory neurotransmitters in the visual cortex using the enzyme‐linked immunosorbent assay method and showed that anodal and cathodal tDCS can selectively decrease the concentration of GABA and glutamate in the stimulated cortical area. Anodal and cathodal tDCS can selectively inhibit the synthesis of GABA and glutamate by suppressing the expression of GABA‐ and glutamate‐synthesizing enzymes, respectively. Abstract Transcranial direct current stimulation (tDCS) evokes long‐lasting neuronal excitability in the target brain region. The underlying neural mechanisms remain poorly understood. The present study examined tDCS‐induced alterations in neuronal activities, as well as the concentration and synthesis of GABA and glutamate (GLU), in area 21a (A21a) of cat visual cortex. Our analysis showed that anodal and cathodal tDCS respectively enhanced and suppressed neuronal activities in A21a, as indicated by a significantly increased and decreased amplitude of visually evoked field potentials (VEPs). The tDCS‐induced effect lasted for ∼60–70 min. By contrast, sham tDCS had no significant impact on the VEPs in A21a. On the other hand, the concentration of GABA, but not that of GLU, in A21a significantly decreased after anodal tDCS relative to sham tDCS, whereas the concentration of GLU, but not that of GABA, in A21a significantly decreased after cathodal tDCS relative to sham tDCS. Furthermore, the expression of GABA‐synthesizing enzymes GAD65 and GAD67 in A21a significantly decreased in terms of both mRNA and protein concentrations after anodal tDCS relative to sham tDCS, whereas that of GLU‐synthesizing enzyme glutaminase (GLS) did not change significantly after anodal tDCS. By contrast, both mRNA and protein concentrations of GLS in A21a significantly decreased after cathodal tDCS relative to sham tDCS, whereas those of GAD65/GAD67 showed no significant change after cathodal tDCS. Taken together, these results indicate that anodal and cathodal tDCS may selectively reduce GABA and GLU syntheses and thus respectively enhance and suppress neuronal excitability in the stimulated brain area.

Discovering differentially expressed proteins in various biological samples requires proteome quantification methods with accuracy, precision, and wide dynamic range. This study describes a mass defect-based pseudo-isobaric dimethyl labeling (pIDL) method based on the subtle mass defect differences between 12 C/ 13 C and 1 H/ 2 H. Lys-C protein digests were labeled with CD 2 O/ 13 CD 2 O and reduced with NaCNBD 3 /NaCNBH 3 as heavy and light isotopologues, respectively. The fragment ion pairs with mass differences of 5.84 mDa were resolved by high-resolution tandem mass spectrometry (MS/MS) and used for quantification. The pIDL method described here resulted in highly accurate and precise quantification results with approximately 100-fold dynamic range. Furthermore, the pIDL method was extended to 4-plex proteome quantification and applied to the quantitative analysis of proteomes from Hca-P and Hca-F, two mouse hepatocarcinoma ascites syngeneic cell lines with low and high lymph node metastasis rates.M ethods of stable-isotope incorporation with mass spectrometry (MS)-based proteome quantification have advanced rapidly in the past decade. Peptide samples can be differentially tagged with heavy or light isotopes by metabolic labeling 1,2 or chemical labeling. 3,4 The mass differences can be distinguished at either the MS or tandem mass spectrometry (MS/MS) level. Dimethyl labeling, 3 a chemical labeling method, is widely used for proteome quantification at the MS level. Several advantages of this method include quick reaction, high labeling efficiency, low cost, and applicability to different types of samples including tissues, cells, and body fluids. 5 Isobaric tags for relative and absolute quantitation (iTRAQ), 4 an MS/MS-based method, allows the proteome quantification of up to eight samples simultaneously and provides more precise quantification results than the MS level quantification method. 6,7 Although these strategies have been widely used for proteome quantification, their accuracy and dynamic range are limited by the signal-tonoise ratio and the increased MS spectral complexity leads to fewer quantified proteins for MS level-based quantification approaches. 8 In addition, ratio distortion caused by precursor interference is common for MS/MS level-based quantification methods. 9,10 To solve these problems, several innovative methods have been recently developed. Isobaric peptide termini labeling (IPTL) 11−13 is an elegant solution in which the amino groups of the N-termini and C-termini of Lys-C protein digests were crosswise labeled with heavy/light isotope reagents according to the slightly different chemical properties of α-and ε-NH 2 . Fragment ion pairs specific to the labeled peptides were used for peptide/protein quantification. Although IPTL improved the quantification accuracy compared to other reported MS/ MS level methods, the side reactions that are inherent in the multistep labeling can adversely affect quantification accuracy and dynamic range. 12 NeuCode SILAC 14 is another st...

With the continual increase in the utilization of rare earth elements (REEs) for industrial and agricultural purposes in China, the research into the environmental biogeochemical behavior of REEs has become a pressing issue. The REEs' content in soil and various parts of wheat under different conditions in soil-plant systems were measured by INAA and ICP-MS. The results showed four aspects. (1) The mean value of total REEs in soil of China was 176.8 mg kg )1 . The mean ratio of SLREE/SHREE in soils was 8.0 and cerium accounts for 42% of the total REEs. The content of REEs in wheat seed ranged between 10 )11 and 10 )8 g g )1 , 3-4 orders of magnitude lower than that in soil. (2) The REEs contents in ryegrass, especially in roots, were significantly related to that of soil. The bioavailability of REEs in soil mainly depended on the exchangeable fraction of REEs, which was strongly affected by the physico-chemical properties of the soil. (3) Long-term foliage-dressing with Changle microfertilizer of REEs did not affect the contents and distribution patterns of REEs in soil. At the maturing stage of spring wheat, the REEs content was in the order of root > leaf >stem and crust. Compared with the control, foliage-dressing has a higher accumulation of REEs in root and leaf. However, no significant difference was found in stem and crust between the two treatments. (4) There was no significant accumulation with the soil-dressing method. When comparing controls in both foliage-and soil-dressing methods, no distinct residue of REEs in grains was found.

Abstract. During a two-year field study, an annual nutrient budget and cycles were developed for a small agricultural watershed. The study emphasized the integrated unit of the watershed in understanding the biogeochemistry. It was found that the total nutrient input was 39.1 x 104 kg nitrogen and 3.91 x 104 kg phosphorus in the year 1995, of which the greatest input of nutrients to the watershed was chemical fertilizer application, reaching 34.7 x 104 kg (676 kg/ha) nitrogen and 3.88 x 104 kg (76 kg/ha) phosphorus. The total nutrient output from the watershed was 13.55 x 104 kg nitrogen and 0.40 x 104 kg phosphorus, while the largest output of nitrogen was denitrification, accounting for 44.1% of N output; the largest output of phosphorus was sale of crops, accounting for 99.4% of P output. The results show that the nutrient input is larger than output, demonstrating that there is nutrient surplus within the watershed, a surplus which may become a potential source of nonpoint pollution to area waters. The research showed that both denitrification and volatilization of nitrogen are key ways of nitrogen loss from the watershed. This suggests that careful management of fertilizer application will be important for the sustainable development of agriculture.The research demonstrated that a multipond system within the watershed had high retention rate for both water and nutrients, benefiting the water, nutrient and sediment recycling in the terrestrial ecosystem and helping to reduce agricultural nonpoint pollution at its source. Therefore, this unique watershed system should be recommended due to its great potential relevance for sustainable agricultural development.

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Anomalous Hall effect (AHE) can be induced by intrinsic mechanism due to the band Berry phase and extrinsic one arising from the impurity scattering. The recently discovered magnetic Weyl semimetal Co3Sn2S2 exhibits a large intrinsic anomalous Hall conductivity (AHC) and a giant anomalous Hall angle (AHA). The predicted energy dependence of the AHC in this material exhibits a plateau at 1000 Ω-1 cm-1 and an energy width of 100 meV just below EF, thereby implying that the large intrinsic AHC will not significantly change against small-scale energy disturbances such as slight p-doping. Here, we successfully trigger the extrinsic contribution from alien-atom scattering in addition to the intrinsic one of the pristine material by introducing a small amount of Fe dopant to substitute Co in Co3Sn2S2. Our experimental results show that the AHC and AHA can be prominently enhanced up to 1850 Ω-1 cm-1 and 33%, respectively, owing to the synergistic contributions from the intrinsic and extrinsic mechanisms as distinguished by the TYJ model. In particular, the tuned AHA holds a record value in low fields among known magnetic materials. This study opens up a pathway to engineer giant AHE in magnetic Weyl semimetals, thereby potentially advancing the topological spintronics/Weyltronics.