清代湖广邻私述略

在清代,作为两淮最为重要的行盐口岸,湖广与其他各行盐口岸一样,长期以来一直为私盐所困扰。在名目繁多的私盐当中,邻私的侵害尤为剧烈。邻私的入侵,与制度、价格和地理等因素密切相关。在划界行盐的食盐专卖体制下,质优价廉的邻私借助优越的地理优势大量向湖广地区侵灌。邻私的活跃,给淮盐在湖广口岸的销售构成了极大的冲击。面对邻私的步步逼进,清政府不得不通过设关置卡等措施来加大对邻私的防范和打击力度。但由于受腐败吏治的影响,上述措施收效甚微。

近代山东私盐的泛滥及其成因

为了维护专商引岸制度,近代山东私盐界定宽泛,使用多重标准,具有很大不合理性,导致私盐泛滥成灾,其中场私、邻私、硝私、军私等危害较大。究其原因,主要有四点:盐政管理弊端丛生、度量衡制度紊乱、缉私力量不统一、私盐对官盐具有优势。可见,销售制度的固化与消费需求的灵活性之间形成了一对难以调和的矛盾。

Impact of seasonal tide variation on saltwater intrusion in the Changjiang River estuary

An improved 3-D ECOM-si model was used to study the impact of seasonal tide variation on saltwater intrusion into the Changjiang River estuary, especially at the bifurcation of the North Branch （NB） and the South Branch （SB）. The study assumes that the fiver discharge and wind are constant. The model successfully reproduced the saltwater intrusion. During spring tide, there is water and salt spillover （WSO and SSO） from the NB into the SB, and tidally averaged （net） water and salt fluxes are 985 m3/s and 24.8 ton/s, respectively. During neap tide, the WSO disappears and its net water flux is 122 m3/s. Meanwhile, the SSO continues, with net salt flux of 1.01 ton/s, much smaller than during spring tide. Because the tidal range during spring tide is smaller in June than in March, overall saltwater intrusion is weaker in June than in March during that tidal period. However, the WSO and SSO still exist in June. Net water and salt fluxes in that month are 622 m3/s and 15.35 ton/s, respectively, decreasing by 363 m3/s and 9.45 ton/s over those in March. Because tidal range during neap tide is greater in June than in March, saltwater intrusion in June is stronger than in March during that tidal period. The WSO and SSO appear in June, with net water and salt fluxes of 280 m3/s and 8.55 ton/s, respectively, increasing by 402 m3/s and 7.54 ton/s over those in March. Saltwater intrusion in the estuary is controlled by the fiver discharge, semi-diurnal flood-ebb tide, semi-monthly spring or neap tide, and seasonal tide variation.

Assessment of hemodynamics in precancerous lesion of hepatocellular carcinoma:Evaluation with MR perfusion

AIM: To investigate the hemodynamic changes in a precancerous lesion model of hepatocellular carcinoma (HCC). METHODS: Hemodynamic changes in 18 Wistar rats were studied with non-invasive magnetic resonance (MR) perfusion. The changes induced by diethylnitrosamine (DEN) developed into liver nodular lesions due to hepatic cirrhosis during the progression of carcinogenesis. The MR perfusion data [positive enhancement integral (PEI)] were compared between the nodular lesions corresponding well with MR images and pathology and their surrounding hepatic parenchyma. RESULTS: A total of 46 nodules were located by MR imaging and autopsy, including 22 dysplastic nodules (DN), 9 regenerative nodules (RN), 10 early HCCs and 5 overt HCCs. Among the 22 DNs, 6 were low-grade DN (lGDN) and 16 were high-grade DN (HGDN). The average PEI of RN, DN, early and overt HCC was 205.67 ± 31.17, 161.94 ± 20.74, 226.09 ± 34.83, 491.86 ± 44.61 respectively, and their liver parenchyma nearby was 204.84 ± 70.19. Comparison of the blood perfusion index between each RN and its surrounding hepatic parenchyma showed no statistically significant difference (P = 0.06). There were significant differences in DN (P = 0.02). During the late hepatic arterial phase, the perfusion curve in DN declined. DN had an iso-signal intensity at the early hepatic arterial phase and a low signal intensity at the portal venous phase. Of the 10early HCCs, 4 demonstrated less blood perfusion and 6 displayed minimally increased blood flow compared to the surrounding parenchyma. Five HCCs showed significantly increased blood supply compared to the surrounding parenchyma (P = 0.02). CONCLUSION: Non-invasive MR perfusion can detect changes in blood supply of precancerous lesions.

A native herbaceous community exerts a strong allelopathic effect on the woody range-expander Betula fruticosa

Biological invasions by alien and range-expanding native plant species can suppress native plants through allelopathy.However,the homeland security hypothesis suggests that some native plants can resist invasion by producing allelopathic compounds that inhibit the growth of invasive plants.Most research has focused on allelopathic interactions between individual native and invasive plant species,with less emphasis on how allelopathy helps entire native communities resist invasions.Additionally,limited knowledge exists about allelopathic interactions between range-expanding native species and recipient native communities,and their influence on invasion success.To bridge this knowledge gap,we conducted two greenhouse competition experiments to test reciprocal allelopathic effects between a native woody range-expanding species,Betula fruticosa,and a community of four native herbaceous species(Sanguisorba officinalis,Gentiana manshurica,Sium suave and Deyeuxia angustifolia)in China.We assessed whether B.fruticosa and the native community differed in their competitive effects and responses,and whether these were influenced by activated carbon,which neutralizes allelochemicals in the soil.Activated carbon reduced the suppressive effects of the native community on the above-ground biomass of B.fruticosa,which indicates that the native community exerted a strong allelopathic effect on B.fruticosa.In contrast,activated carbon only marginally enhanced the suppressive effects of B.fruticosa on the native community,which indicates that allelopathy is not the primary mechanism by which B.fruticosa exerts its suppression.Overall,these findings support the homeland security hypothesis and suggest that biotic resistance from the native herbaceous community may limit the invasion success of the woody range-expander B.fruticosa.

Mammalian herbivory in post-fire chaparral impacts herbaceous composition but not N and C cycling

Aims Classical theory predicts that herbivores impact herb assemblages and soil nitrogen(N)cycling through selective plant consumption and the deposition of N-rich waste,with effects dependent upon ecosystem N availability.Herbivores are predicted to accelerate N cycling when N availability is high and decelerate cycling when availability is low.However,experimental tests of these theories in natural systems are limited and have yielded contradictory results.California’s widespread chaparral shrublands provide a tractable system in which to test these theories.They are prone to periodic crown fire,which temporarily removes living shrub cover,deposits mineral N on soils and allows diverse herbaceous assemblages to dominate the landscape for 3–5 years.Chaparral is also increasingly vulnerable to herbaceous invasion;mammalian herbivory may limit the establishment of non-native herbs in the shrub understory.Methods We implemented a 2-year herbivore-exclosure experiment(Hopland,CA)to assess the impact of mammalian herbivory during early post-fire chaparral succession,both on herbaceous plant assemblages and soil N and C cycling.We predicted that,in high-N post-fire conditions,mammalian herbivory would not demonstrate a strong preference for N-fixing herbs,would accelerate N cycling and would reduce the abundance of non-native herbs.Important Findings Excluding mammalian herbivores increased herb standing biomass by 54%,but changed neither the relative abundance of N-fixing vs.non-N-fixing herbs nor any measure of N or C cycling.Herbivore impacts on nutrient cycling may not be significant over the 2-year time scale of the experiment and physical effects of herbivore activity could have counteracted the influence of plant litter and animal dung/urine inputs.Mammalian herbivores concentrated their feeding on typical non-native herbs,slightly decreasing their relative abundance;however,mammalian herbivory was not sufficient to stem the invasion of chaparral by invasive herbs or alter C and N cycling over the first 2 years after fire.

Soil Erosion as Affected by Polyacrylamide Application Under Simulated Furrow Irrigation with Saline Water

The reduction of soil and water losses under furrow irrigation with saline water is important to environmental protection and agricultural production. The objective of this study was to determine the effect of polyacrylamide (PAM) application on soil infiltration and erosion under simulated furrow irrigation with saline water. Polyacrylamide was applied by dissolving it in irrigation water at the rates of 1.5, 7.5, and 15.0 mg L-1 or spreading it as a powder on soil surface at the rates of 0.3, 1.5, 3.0, and 6.0 g m-2, respectively. The electrolyte concentration of tested irrigation water was 10 and 30 mmolc L-1 and its sodium adsorption ratio (SAR) was 0.5, 10.0, and 20.0 (mmolc L-1)0.5. Distilled water was used as a control for irrigation water quality. Results indicated that the electrolyte concentration and SAR generally did not significantly affect soil and water losses after PAM application. Infiltration rate and total infiltration volume decreased with the increase of PAM application rate. Polyacrylamide application in both methods significantly reduced soil erosion, but PAM application rate did not significantly affect it. The solution PAM application was more effective in controlling soil erosion than the powdered PAM application, but the former exerted a greater adverse influence on soil infiltration than the latter. Under the same total amounts, the powdered PAM application resulted in a 38.2%-139.6% greater infiltration volume but a soil mass loss of 1.3-3.4 times greater than the solution PAM application.