Barite Accumulation rates across Paleocene-Eocene Thermal Maximum (PETM)

Barite accumulation rates (BAR) have been measured from 12 DSDP/ODP site globally (DSDP site 525, 549 and ODP site 690, 738, 1051, 1209, 1215, 1220, 1221, 1263,1265 and 1266A) to reconstruct the export production across Paleocene Eocene Thermal Maximum (PETM) around 55.9 million year ago. Our results suggesting a general increase in export productivity. We propose that changes in marine ecosystems, resulting from high atmospheric partial pressure of CO2 and ocean acidification, led to enhanced carbon export from the photic zone to depth, thereby increasing the efficiency of the biological pump. We estimate that an annual carbon export flux out of the euphotic zone and into the deep ocean waters could have amounted to about 15 Gt during the PETM. About 0.4% of this carbon is expected to have entered the refractory dissolved organic pool, where it could be sequestered from the atmosphere for tens of thousands of years. Our estimates are consistent with the amount of carbon redistribution expected for the recovery from the PETM.

Sapientia, 2000, Vol. LV, nº 208 (número completo)

Contenido: Estructuras mentales y principios racionales / Lorenzo Vicente Burgoa – Autonomía moral y deliberación en Santo Tomás de Aquino / Ciro E. Schmidt Andrade – Thomas Aquinas and the reality of time / Steven C. Snyder – Fe y razón en Ramón Llull / Marc Egea I Ger – Idealismo y personalismo en Husserl / Francisco Leocata – El discurso no consensuado de Jürgen Habermas / Marisa Villalba de Tablón – Hacia el tercer milenio : el clima posmoderno y la recuperación de la naturaleza humana del hombre (observaciones tomistas) / William R. Darós – Razón, voluntad y praxis / María Celestina Donadío Maggi de Gandolfi – Meditación sobre la felicidad / Alberto Caturelli – “Y llegarán a ser virtuosos” : ley jurídica positiva penal y educación / Héctor H. Hernández – Todos los hombres desean la felicidad / Ignacio E. M. Andereggen – Justicia y derecho en Ley Natural y Derechos Naturales de John Finnis / Carlos I. Massini Correas – El itinerario antiguo y medieval de la negación nominalista de la metafísica / Mario Enrique Sacchi – Notas y comentarios -- Bibliografía

退火对He注入及随后~(208)Pb~(27+)辐照的Al_2O_3单晶PL谱的影响

利用高能离子研究了110keV的He+注入Al2O3单晶及随后230MeV的208Pb27+辐照并在不同温度条件下退火样品的光致发光的特性.从测试结果可以清楚地看到在375nm,390nm,413nm和450nm出现了强烈的发光峰.经过600K退火2h后测试结果显示,390nm发光峰增强剧烈,而别的发光峰显示不明显.在900K退火条件下,390nm的发光峰开始减弱相反在510nm出现了较强的发光峰,到1100K退火完毕后390nm的发光峰完全消失,而510nm的发光峰相对增强.从辐照样品的FTIR谱中看到,波数在460—510cm-1间的吸收是振动模式,经过离子辐照后,吸收带展宽,随着辐照量的增大,Al2O3振动吸收峰消失,说明Al2O3振动模式被完全破坏.1000—1300cm-1之间为Al-O-Al桥氧的伸缩振动模式,辐照后吸收带向高波数方向移动.退火后的FTIR谱变化不大.

高温注氦及随后230MeV的~(208)Pb~(27+)辐照Al_2O_3的光致发光谱的研究

主要研究了110keV的He~+高温注入Al_2O_3单晶及1.1MeV/u的~(208)Pb~(27+)辐照注氦Al_2O_3样品的光致发光的特性。从测试结果可以清楚地看到在375nm,413nm和450nm处出现了强烈的发光峰。并且在600K,5×10~(16) ions/cm~2剂量点,样品的发光峰是最强的。这表明He~+注入Al_2O_3后使带隙中深的辐射中心复合的效率大幅度提高,极大的增强了其发光强度,而且发光伴随着蓝移现象。而经过高能~(208)Pb~(27+)辐照后的样品,在390nm出现了新的发光峰,从FTIR谱中我们能够看到,可能是~(208)Pb~(27+)辐照相对沉积膜出现一定的晶化,其中含有许多纳米尺寸的Al_2O_3晶粒所致。