Optimization of thermal environment during crystal growth of large-sized Nd : YAG by Temperature Gradient Technique

A finite-element model is employed to analysis the thermal environments in Temperature Gradient Technique (TGT) furnace during the growth of large-sized Nd:YAG crystal. The obtained results show that when the crucible is located at the lower position inside of the heater, a flatter solid-liquid interface is established, which makes it easier to obtain the core-free Nd:YAG crystal. Meanwhile, the lower crucible position can induce higher axial temperature gradient, which is beneficial to the release of latent heat. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectroscopic properties of Ce : YAP scintillation crystal grown by temperature gradient technique

Spectroscopic properties of Ce-doped yttrium orthoaluminate (Ce:YAlO3 or Ce:YAP) crystals grown by temperature gradient technique (TGT) were investigated, and the effects of the growth conditions on the properties were analyzed.. Methods of optical absorption (OA), photoluminescence (PL), photoluminescence decay (PLD), X-ray excited luminescence (XL) and cathodeluminescence (CL) were used in these investigations. The results showed that the absorption band peak at 202, 394 and 532 nm originated from F and F+ color center induced by the weak reducing growth atmosphere, green emission band near 500 ran derived from Ce3+ -Ce3+ pairs and band at 650 similar to 850 run from some unintentional impurity in crystals.

Growth of highly sensitive thermoluminescent crystal alpha-Al2O3 : C by the temperature gradient technique

In this work, an alpha-Al2O3:C crystal with highly sensitive thermoluminescence was directly grown by the temperature gradient technique (TGT) using Al2O3 and graphite powders as raw materials. The optical and luminescent properties and the dosimetric characteristics of the crystal were investigated. An as-grown alpha-Al2O3:C crystal shows a single glow peak at 462 K and a blue emission peak at 415 nm. The thermoluminescence (TL) response of the crystal shows a linear-sublinear-saturation characteristic. In the dose range from 5 x 10(-6) to 10Gy, the alpha-Al2O3:C crystal shows excellent linearity, and saturation was observed at about 30Gy. The sensitivity of the crystal decreases as the heating rate increases. (c) 2008 Elsevier B.V. All rights reserved.

植生克雷伯氏菌（Klebsiella planticola 19-1）nifA-like基因的克隆

植生克雷伯氏菌(Klebsiella planticola 19-1)是从新疆鄯善地区玉米根际分离得到的一株联合固氮菌。在40℃高温下有较强的乙炔还原活性。 本工作利用Southern Blot分子杂交技术, 以Klebsiella pneumoniae的nifA为探针，证明了在K．planticola 19-1中存在nifA-like基因，由nifH-lacZ实验推论其nifA-like基因产物对高温相对稳定。经过大质粒电泳和Southern Blot分子杂交，发现nifA-like基因定位于染色体外的大质粒上。本工作进一步克隆了含有K．plonticola 19-1的nifA-like基因的DNA片段，做了它的限制性酶切图谱，并将nifA-like基因初步定位。