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Desertification in north China is ongoing despite the endeavours to mitigate it over the past 50 years. Overall examination of the context of desertification and defects of desertification-combating programmes is a prerequisite for desertification control, which is now attracting general concern in China. The physiographic circumstances of north China, including the dry, continental, mid-latitude climate, easily erodible soil surface and water shortage, provide the background to desertification. Climatic aridity and the evolution of land use and land management in recent decades have produced great stress on the land. The ineffectiveness of anti-desertification measures ascribed to inadequate scientific involvement in decision-making, neglect of the human dimension and the lack of a well-organized desertification monitoring system are discussed in this paper.

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The phthalocyanines are promising second-generation photosensitizers that are being evaluated for the photodynamic therapy (PDT) of malignant tumors. In vivo studies with the silicon phthalocyanine Pc 4 have shown that it is highly effective at causing regression of RIF-1 tumors in C3H/HeN mice in PDT protocols. Because cutaneous photosensitivity is the major complication of photosensitizers used for PDT, experiments were performed to evaluate the effect of inhibitors of the inflammatory response (cyproheptadine, dexamethasone, pentoxifylline, and tumor necrosis factor alpha [TNF-alpha] antibodies) on Pc 4-induced cutaneous photosensitivity and tumor regression. The C3H/HeN mice were injected with either Pc 4 or Photofrin and were exposed to 86 J/cm2 of filtered radiation emitted from a solar simulator. Animals were irradiated at 1, 3, 7, 10, 14 and 28 days postinjection. Cutaneous photosensitivity was assessed using the murine ear-swelling response. Cyproheptadine, dexamethasone, pentoxifylline and TNF-alpha antibodies were administered prior to illumination to assess their ability to block Pc 4-induced cutaneous photosensitivity and to evaluate whether such treatment adversely influenced Pc 4 PDT-induced tumor regression. Compared to Photofrin, Pc 4 produced cutaneous photosensitivity that was transient, resolving within 24 h, and that could be elicited for only 10 days after administration. In contrast, Photofrin caused photosensitivity that required 4 days to resolve and could be elicited for at least 1 month after it was administered. The Pc 4-induced cutaneous photosensitivity could be blocked by corticosteroids and an inhibitor of vasoactive amines (cyproheptadine). The TNF-alpha gene transcription was found to increase in keratinocytes following treatment with Pc 4 and light. The anti-TNF-alpha antibodies and pentoxifylline, an inhibitor of cytokine transcription, also prevented cutaneous photosensitivity, implicating TNF-alpha in the pathogenesis of Pc 4-induced cutaneous photosensitivity. None of these agents had any effect on Pc 4 PDT-induced tumor regression. Cyproheptadine, dexamethasone, pentoxifylline and TNF-alpha antibodies may be valuable pharmacologic agents in the management of cutaneous photosensitivity associated with PDT without altering the efficacy of this new therapeutic modality. The findings suggest that it should be possible to devise PDT protocols that block cutaneous photosensitivity without impairing the anti-tumor response to the agents.

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Net photosynthesis (P n ), transpiration (E), stomatal conductance (g s ), internal CO 2 concentration (C i ), and water use efficiency (WUE) were examined on 215 species from eight plant functional types (PFTs) along a precipitation gradient in northeast China (the Northeast China Transect, or NECT). Among the eight PFTs, meadow steppe grasses had the highest rates of net photosynthesis and forest grasses the lowest and the following order of P n was noted: meadow steppe grasses >typical steppe grasses >steppe shrubs >desert grasses >forest trees >forest shrubs >desert shrubs >forest grasses (P<0.05). Transpiration tended to be the highest in the steppe grasses and lowest in forest shrubs. Transpiration also decreased rapidly with the appearance of C 3 desert species at the desert end. The forest tree PFT had lower P n , E, g s than the steppe PFTs, whereas WUE values were somewhat greater in the forest tree PFT than the desert shrubs and grasses. Low C i values along the steppe section (from 400 to 1100 km, east to west) indicated the presence of C 4 species. Of all the PFTs, only shrubs and herbs were noted at all points along the transect. No clear relationship between P n , E, g s , WUE of herb and shrub PFTs and annual precipitation was noted -low values were found at both the high and low precipitation ends of the transect. Highest values were noted when precipitation was intermediate.

The results of an investigation into the relationship between surface sediment subfossil chironomid distribution and water quality are presented. Data from 30 lakes in the middle and lower reaches of the Yangtze River indicate that the nutrient gradient was the major factor affecting the distribution of chironomids across these sites. Canonical correspondence analysis (CCA) revealed that of 12 summer water environmental variables, total Phosphorus was most important, accounting for 20.1% of the variance in the chironomid data. This was significant enough to allow the development of quantitative inference models. A TP inference model was developed using weighted averaging (WA), partial least squares (PLS) and weighted averaging partial least squares (WA-PLS). An optimal two-component WA-PLS model provided a high jack-knifed coefficient of prediction for conductivity r 2 jack = 0.76, with a low root mean squared error of prediction (RMSEP jack = 0.13). Using this model it is possible to produce long-term quantitative records of past water quality for lacustrine sites across the middle and lower reaches of the Yangtze River, which has important implications for future lake management and ecological restoration.