主要资源国家政治生态情况及其对铝土矿政策的影响

Vesuvius, dominating the densely-populated Neapolitan area, is one of the most dangerous volcanoes in the World. Its destructive power derives from energetic subplinian and plinian eruptions, such as the one which occurred in 79 A.D. Generally such large-scale events follow a long period of quiescence; a behaviour interpreted as the gradual build-up of magma volumes between periods of major activity. After the 1631 subplinian eruption until the last 1944 A.D. eruption, it experienced an almost continuous and less energetic explosive/effusive activity. The erupted magmas are characterized by undersaturated potassic to ultrapotassic nature, and compositional and Sr-isotopic variability. Furthermore geobarometric studies indicate two different crystallization depths located at 4 and >11 km, respectively. According to most of the recent literature, the eruptions were triggered by the injection in a shallower magma chamber, of isotopically distinct magma batches derived from heterogeneous mantle source(s) and/or contamination processes occurred within the deep reservoir. In our review of petrochemical data, we consider the period between the 3550 years BP plinian eruption and the 472 A.D. sub-plinian eruption, which includes 79 A.D. event, and the most recent period of activity which started in 1631 A.D. and lasted up to the 1944 A.D. eruption, characterized by a near continuous effusive/explosive activity. For both periods we identify a correlation between Sr-isotopical features of magmas and their crystallization depth. In particular, we show that pyroxenes have Sr-isotopic ratios lower than 0.7074 and an equilibrium crystallization depth of 22-11 km. Moreover feldspars have higher 87Sr/86Sr values (0.7075-7) and an equilibrium crystallization depth of about 4 km. Therefore the most radiogenic magmas did not derive from a deeper reservoir but their higher Sr-isotopic ratios have been acquired at a shallower depth likely by crustal contamination during magma evolution. In contrast, the lower Sr-isotope compositions characterise the less contaminated magmas coming from deeper crustal levels. On the basis of this evidence, the temporal Sr-isotopical variation of magma which erupted in the 1631-1944 A.D. period probably derives from the progressive withdrawal of the shallow magma chamber, which was completely empty before the 1805-1944 A.D. period of volcanism. Therefore the effusive and explosive events of the most recent 1805-1944 A.D. period were fed directly by the deep reservoir located at a depth exceding 11 km

在福建东南沿海局部地域献血员中检出HTLV-I

[目的 ]进一步阐明福建沿海 HTL V小流行区 HTL V- 的地理分布特点及毒株的基因类型。 [方法 ]对福建东南沿海莆田地区献血员以国产双抗原夹心法 EL ISA试剂筛选 ,对 EL ISA阳性血清用 Western blot(WB)进行确证。对抗体确证阳性者 ,采集外周血分离淋巴细胞用巢式 PCR扩增 HTL V- env区 gp46片段进行序列分析鉴定病毒亚型。 [结果 ]从 1998年 10月至 2 0 0 0年 4月止 ,共检测 45 6 4份标本 ,结果确证出 16例 HTL V- 抗体阳性者 ,感染率为 0 .35 %。HTL V- 抗体阳性者主要分布在某村献血人群中 ,并具有区域集中的特点。笏石秀屿一带某村献血员中感染率高达 4.7%。7例代表性毒株经病毒序列分析为 HTL V- C亚型 (COSMOPOL ITAN)。[结论 ]福建东南沿海某村献血员中发现 HTL V- 流行。提出在对某一地区人群进行 HTL V筛选时 ,既要注意整个地区“面”的筛查 ,又要注重某个村镇“点”的调查