Windows through the dusty disks surrounding the youngest low-mass protostellar objects

The formation and evolution of young low-mass stars are characterized by important processes of mass loss and accretion occurring in the innermost regions of their placentary circumstellar disks. Because of the large obscuration of these disks at optical and infrared wavelengths in the early protostellar stages (class 0 sources), they were previously detected only at radio wavelengths using interferometric techniques. We have detected with the Infrared Space Observatory the mid-infrared (mid-IR) emission associated with the class 0 protostar VLA1 in the HH1-HH2 region located in the Orion nebula. The emission arises in three wavelength windows (at 5. 3, 6.6, and 7.5 micrometers) where the absorption due to ices and silicates has a local minimum that exposes the central part of the young protostellar system to mid-IR investigations. The mid-IR emission arises from a central source with a diameter of 4 astronomical units at an averaged temperature of approximately 700 K, deeply embedded in a dense region with a visual extinction of 80 to 100 magnitudes.     

The onset of planet formation in brown dwarf disks

The onset of planet formation in protoplanetary disks is marked by the growth and crystallization of sub-micrometer-sized dust grains accompanied by dust settling toward the disk mid-plane. Here, we present infrared spectra of disks around brown dwarfs and brown dwarf candidates. We show that all three processes occur in such cool disks in a way similar or identical to that in disks around low- and intermediate-mass stars. These results indicate that the onset of planet formation extends to disks around brown dwarfs, suggesting that planet formation is a robust process occurring in most young circumstellar disks.     

The formation and fragmentation of disks around primordial protostars

The very first stars to form in the universe heralded an end to the cosmic dark ages and introduced new physical processes that shaped early cosmic evolution. Until now, it was thought that these stars lived short, solitary lives, with only one extremely massive star, or possibly a very wide binary system, forming in each dark-matter minihalo. Here we describe numerical simulations that show that these stars were, to the contrary, often members of tight multiple systems. Our results show that the disks that formed around the first young stars were unstable to gravitational fragmentation, possibly producing small binary and higher-order systems that had separations as small as the distance between Earth and the Sun.     

Organic molecules and water in the planet formation region of young circumstellar disks

The chemical composition of protoplanetary disks is expected to hold clues to the physical and chemical processes that influence the formation of planetary systems. However, characterizing the gas composition in the planet formation region of disks has been a challenge to date. We report here that the protoplanetary disk within 3 astronomical units of AA Tauri possesses a rich molecular emission spectrum in the mid-infrared, indicating a high abundance of simple organic molecules (HCN, C2H2, and CO2), water vapor, and OH. These results suggest that water is abundant throughout the inner disk and that the disk supports an active organic chemistry.     

根结线虫诱导巨型细胞形成关键启动子的定位

为了找到根结线虫诱导的烟草根结内特异性强启动的启动子和了解巨型细胞被诱导形成的分子机理,用无启动子的报告基因(GUS)及旁边的Ds转座子,分离烟草根结内巨型细胞特意启动子.将p13DGUTs转烟草叶片,获得了转基因植株.通过根结线虫感染盆载转基因烟草后,分别检测根系、叶的报告基因的表达情况.结果显示,从转基因植株中筛选到只在根结巨型细胞内表达的转基因植株.     

Formation of giant planets by fragmentation of protoplanetary disks

The evolution of gravitationally unstable protoplanetary gaseous disks has been studied with the use of three-dimensional smoothed particle hydrodynamics simulations with unprecedented resolution. We have considered disks with initial masses and temperature profiles consistent with those inferred for the protosolar nebula and for other protoplanetary disks. We show that long-lasting, self-gravitating protoplanets arise after a few disk orbital periods if cooling is efficient enough to maintain the temperature close to 50 K. The resulting bodies have masses and orbital eccentricities similar to those of detected extrasolar planets.     

利用小麦ⅹ玉米诱导小麦单倍体形成的研究

利用小麦（Triticum aestivum L.）与玉米（Zea mays L.）进行远缘杂交,是获得小麦单倍体的一条重要途径,也是获得双单倍体（Double haploid,DH）植株、构建小麦遗传群体的重要途径之一。为创建小麦抗吸浆虫DH群体,在温室条件下对5个小麦抗、感吸浆虫杂交组合进行了单倍体诱导试验。结果表明：小麦不同基因型对诱导单倍体胚形成有较大影响;小麦授粉后适宜的2,4-D点药时间为6-36h;适宜的2,4-D药液为10-30mg/L;授粉后适宜的剥胚培养时间为14-16天,授粉后茎秆离体培养有较好的诱导效果,培养温度以20~25℃为宜。提出了在温室条件下高效诱导小麦单倍体植株的方法及条件。     

Puparium formation in flies: contraction to puparium induced by ecdysone

Larvae of the fly Calliphora erythrocephala (Meigen) were deprived surgically of their ring glands at an age prior to the appearance of ecdysone in the blood, and then injected with ecdysone. They contracted into the typical barrel-shaped puparium, before the onset of tanning. This proved that ecdysone controls the puparium contraction as well as tanning.     

钙磷对RANKL诱导番鸭破骨细胞生成及活性的影响

分离了1~7日龄番鸭长骨骨髓细胞,与不同因子(Ⅰ组,对照;Ⅱ组,30 ng/ml sRANKL;Ⅲ组,30ng/ml sRANKL 6 mmol/L Ca 3 mmol/L P)共培养。倒置显微镜观察细胞形态,抗酒石酸酸性磷酸酶(TRAP)试剂盒进行组织化学染色,培养7 d后取象牙片用1%甲苯胺蓝染色,光镜及扫描电镜观察吸收陷窝,形态分析系统计算吸收陷窝面积。结果表明,第一次更换培养液后7 d,Ⅱ组多核OC数极显著低于对照组(P<0.01),Ⅲ组多核OC数极显著低于对照组和Ⅱ组(P<0.01)。Ⅱ组和Ⅲ组吸收陷窝数量明显多于对照组,陷窝深度明显深于对照组,陷窝面积极显著大于对照组(P<0.01),但Ⅱ、Ⅲ组陷窝面积大小差异不显著。故认为,钙磷(6 mmol/LCa 3 mmol/L P)对sRANKL诱导番鸭OC骨吸收活性无显著抑制效应,但能极显著抑制番鸭OC的生成,减少多核OC数量。     

Pattern formation in homogeneous polymer solutions induced by a continuous-wave visible laser

We report an unexpected nonphotothermal material organization induced by continuous-wave visible laser light at low power levels. This effect is observed along the laser beam propagation direction in fully transparent entangled solutions of common homopolymers featuring sufficiently high molecular mass and optical anisotropy along the chain backbone. The resulting formation of long-lived stringlike or dotlike patterns on the micrometer scale, probed by dark-field coherent imaging, depends on the molecular mass, architecture, solvent nature, and polymer concentration. Electrostrictive and alignment forces as well as chain cooperativity are responsible for the osmotic compression of the polymer solute. Subsequent waveguiding effects induce autoamplification and "pattern writing" upon prolonged illumination. This wave-medium coupling could potentially lead to photorefractive, microoptics, and nanotechnology applications.     

Postreplicative formation of cohesion is required for repair and induced by a single DNA break

Sister-chromatid cohesion, established during replication by the protein complex cohesin, is essential for both chromosome segregation and double-strand break (DSB) repair. Normally, cohesion formation is strictly limited to the S phase of the cell cycle, but DSBs can trigger cohesion also after DNA replication has been completed. The function of this damage-induced cohesion remains unknown. In this investigation, we show that damage-induced cohesion is essential for repair in postreplicative cells in yeast. Furthermore, it is established genome-wide after induction of a single DSB, and it is controlled by the DNA damage response and cohesin-regulating factors. We thus define a cohesion establishment pathway that is independent of DNA duplication and acts together with cohesion formed during replication in sister chromatid-based DSB repair.     

僵知饮对四氧嘧啶诱导大鼠糖尿病的试验研究

采用静脉注射四氧嘧啶诱导大鼠化学性糖尿病,观察僵知饮对动物血糖、血脂和氧自由基的影响,以期治疗实验性糖尿病。结果表明:与模型组比较,僵知饮组空腹时血糖、甘油三酯和脂质过氧化物均显著降低(P<0.05～0.01),而全血超氧化物歧化酶活性明显升高(P<0.01),说明僵知饮治疗实验动物化学性糖尿病不仅降糖效果优于甲苯磺丁脲,且有降血脂、改善氧自由基代谢紊乱等多方面的药理活性,从而有助于防治糖尿病的并发症。     

Ca2+-CaM系统在生长素诱导莴苣侧根原基形成中的作用

采用不同浓度的CaCl2、EGTA\,CPZ\,TFP和La(NO3)3处理莴苣幼苗种子根,结果表明,4 mg*L-1的氯化钙对莴苣幼苗侧根原基形成有促进作用,侧根原基数目为对照的2.1倍,并对生长素的促根效应有加合效应,可达17%以上;而钙离子专一性螯合剂乙醇双乙胺醚-N,N-四乙酸(EGTA)则起抑制作用,且其抑制作用能在一定程度上被氯化钙所恢复;钙调素抑制剂氯丙嗪(CPZ)和三氟拉嗪(TFP)也起抑制作用,抑制率最高可达40%左右;而钙离子通道阻断剂镧离子在很低浓度下却有促进作用,且与生长素处理有加合效应,其效应与钙离子类似.     

阿克苏红富士“冰糖心”形成的影响因素

摘要：采收时间、负载量、树势、树龄、土壤质地、品种、方位、套袋、乔矮化栽培等因素都会对阿克苏红富士“冰糖心”的形成产生影响。红富士在阿克苏10月上旬已开始形成糖心，10月26日糖心果率和糖心指数达到较高值，此后变化平缓；负载量高不利于糖心的形成；树势弱、树龄小较树势旺都易于糖心的产生；沙质土壤栽培、不套袋管理、矮化栽培也有利于冰糖心的形成；条红品种较片红品种更易形成糖心。