89 resultados para Dark adsorptions
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Nd:silicate glass was implanted at room temperature by 6.0 MeV C3+ ions with a dose of 2.0 x 10(15) ions cm(-2). A waveguide with thickness of about 6.3 mu m was formed. The prism-coupling method was used to observe the dark modes of the waveguide at 633 nm and 1539 nm, respectively. There are three dark modes at 633 nm, of which one is the enhanced-index mode. The propagation loss of the enhanced-index mode in the waveguide measured at 633 nm is 0.42 dB cm(-1) after annealing at 217 degrees C for 35 min. The reflectivity calculation method was applied to simulate the refractive index profiles in the waveguide. The mode optical near-field output at 633 nm was presented.
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abstract = {TiO2/ormosil planar waveguide was prepared by sol-gel method at low thermal treatment temperature ( less than or equal 200°C). Scanning electron microscope, FT-IR spectrometer, spectrophotometer, atomic force microscopy, thermal analyzer, and dark m-line spectroscopy were used with the method of scattering-detection to investigate optical and structural properties. High optical quality waveguide film was obtained. The propagation loss of film was 0.569 dB/cm at a wavelength of 632.8 nm.
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The dark-brown colored 5 at% Yb-doped YAlO3 (Yb:YAP) single crystal was grown successfully by temperature gradient technique (TGT) for the first time. The TGT-grown Yb:YAP crystal with the perovskite structure and excellent crystallization perfection were confirmed by the X-ray diffractions techniques. The dark-brown color of TGT-Yb:YAP crystal turned into the colorless after annealing in the air at 1200 degrees C for 10h. The absorption spectra, LD-excited infrared emission and X-ray excited luminescence spectra of the air-annealed Yb:YAP single crystal were investigated at the room temperature. The results indicate that the TGT-Yb:YAP single crystals can be used for the laser and scintillation applications. (c) 2005 Elsevier B.V. All rights reserved.
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ZnO crystals with dimensions of 30 x 38 x 8 turn 3 have been grown by the hydrothermal method using a mixed solution of KOH, LiOH and H2O2. The growing rates for +c(0001) and -c(000 (1) over bar) were 0.17 and 0.09 mm/day, respectively. The crystal color was very light green for +c sector and dark brown for -c sector. For the +c sector, the resistivity at room temperature was 80 0 cm, the carrier concentration was about 10(4)/cm(3), and the mobility was about 100 cm(2)/Vs. The full-width at half-maximum (FWHM) of double axis X-ray rocking curve for the polished Zn face cut from +c sector was 45 arcsec. The photoluminescence (PL) spectrum and the absorption spectrum of +c part of the crystals at room temperature were also reported and discussed in this paper. (c) 2008 Elsevier B.V. All rights reserved.
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Y2O3/SiO2 coatings were deposited on fused silica by electron beam evaporation. A continuous wave CO2 laser was used to condition parts of the prepared samples at different scanning speeds in the air. LAMBDA 900 spectrometer was used to investigate the changes of the transmittance and residual reflection spectrum. A Nomarski microscope under dark field was used to examine the changes of the micro defect density. The changes of the surface roughness and the microstructure of the film before and after conditioning were investigated by AFM and X-ray diffraction, respectively. We found that laser-induced damage threshold (LIDT) of the films conditioning at 30 mm/s scanning speed was increased by more than a factor of 3 over the thresholds of the as-deposited films. The conditioning effect was correlated with an irradiation-induced decrease of the defect density and absorption of the films. (c) 2005 Elsevier B.V. All rights reserved.
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用热蒸发方法沉积了薄膜滤光片.并将样品分别在去离子水中浸泡10天和30天.通过分光光度计、光学暗场显微镜、及扫描电子显微镜等多种测试手段,对诱导透射滤光片在潮湿环境下的稳定性进行了研究.实验发现,在潮湿环境下滤光片产生的膜层分离都是从薄膜中微缺陷点处开始发生和发展的,微缺陷是影响滤光片环境稳定性的重要原因之一,其中杂质和针孔是滤光片中两种最常见的微缺陷.EDS能谱分析进一步表明,薄膜中杂质缺陷成分即为Al2O3膜料本身,所以不能推测,薄膜沉积中的喷溅可能是微缺陷产生的根本原因,抑制喷溅可以有效提高薄膜滤光
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利用发根农杆菌(Agrobacterium rhizogenes)1601,1000,1500,15834,A4,均成功地转化了中药青蒿(Artemisia annua L.)并且建立了pRi1601,pRi15834,pRiA4诱导的发根培养。pRi1601,pRi15834的发根诱导率比其它质粒高。太老或太幼的叶片不利子发根的诱导;发根主要从叶脉的伤口处萌发;带顶芽或带侧芽的叶片容易诱导根,但不一定是发根。光照有利于发根的诱导和发根的生长。以每个发根的“绝对生长速率”(Gtowth Ratio,GR)和绝对“侧根”数量(Number of Side Roots,NSR),通过大量的发根系的筛选,建立了8个发根系,1601-L-1, 1601-L-2, 1601-L-3, 1601-L-4, 15834-L-1, 1601-P-I, 16 01-P-2,15834-L-2。Southern分子检测表明,160l-1-1,1801-L-2, 1601-L-3,1601-L-4,1601-P-1,1601-P-2均为转化子。8个建立的发根系之间无论生长或者QHS的合成存在明显的差异。比较光/暗(16/8hrs),25℃条件下培养的16 01-L-1,1601-L-2,1601-L-3,1601-L-4,1601-P-l,和1601-P-2,其中16 01-L-3的生长最快,160l-L-1的生长最慢;但是,1601-L-1的QHS的含量最高(可达1. 048%),1601-1-3的QHS的含量最低。160Z-L-3,15834 -L-1和2583:1-L-2的生长速率相差不大。用盛有l000mLMS液体培养基的3000mL的锥形瓶扩大培养1601-L -3,15834-L-1和15834-L-2,转速为ll0rlpm,培养过程中发根容易形成发根球(Hairy Root Balis,HRB),HRB的形成严重影响发根的生长和QHs的合成,HpLC分析表明扩大培养发根中QHS的含量比较低。 改变MS基本培养基中的无机离子的浓度,研究不同无机离子对发根生长和QHS的合成的影响。 l、KN03为18.79×10-3M时有利于1601- L-1生长,为14. 84×10-3M时有利于QHS的合成。NH-4N0-3浓度在10.93-12. 49×10—3M范围内有利于1601-L-1生长,在0-20.62×10-3M范围内对QHS的合成影响不大,大于20. 62×lO-3M不利QHS的合成。培养基中NH-4+/N0-3-比值为0. 37-0. 4-0.52:1时有利于发根的生长,比值为0.52 - 0.58:1时有利于QHS的合成。 2、H-2P0-4-浓度为2.498×10-3M时有利于发根的生长在0-2. 498×l0-3M范围内,随着浓度的提高,促进发根的生长。培养基中的H2P4 -的浓度在0-1.249×lO-3M的范围内,随着浓度的提高,促进QHS的合成,为1.249×10-3M时QHS的含量最高。 3、培养基中最适16 01-L-1生长的Ca-2+浓度为0.198- 0.766×10-3M,大于或小于该浓度范围,显著地抑制发根的生长。但是,在0-3.695×10-3M范围内,随着培养基中Ca-2+浓度提高,促进QHS的合成,最适Ca-2+浓度为3.695×l0-3M。 4、培养基中不加Mg-2+时,完全抑制发根生长,在0. 142×10-3M-7.506×l0-3M浓度范围内,对发根生长影响没有明显的差别。但是,HPLC和UV分析发根中QHS含量,培养基中不加Mg-2+时,发根中QHS含量最高。 5、培养基中的Fe-2+浓度在0. 25 -1.0×10-3M范围内,同时有利于16 01- L-1的生长和QHS的形成。 6、培养基中最适合予16 01- L-3生长的KI浓度为2.5ppm,大于或小予该浓度均显著地抑制发根的生长,培养基中加入KI明显地降低发根中的QHS的含量。 7、H2BO3对l601-L-l生长影响不大,HPLC分析QHS的含量,培养基中的H3BO3浓度为100ppm和400ppm,QHS的含量分别为1.69mg/g和1.80mg/g(DW)。 8、Cu-2+对1601-L-3的生长影响显著,最适合1601-L-3生长的Cu-2+浓度为1.00ppm,在0 -1.00ppm的浓度范围内,随着培养基中的Cu+浓度的提高,发根的生物量不断增加。培养基中QHS合成的最适Cu2+浓度为0.05ppm,大于或小于该浓度均显著地抑制发根中QHS的合成。 比较光培养和暗培养对发根生长的影响,结果表明光照明显地促进1601-L-l的生长,暗培养明显不利于发根的生长。最适合于发根生长的温度为25℃,大于35℃显著地抑制发根的生长,影响发根的根尖细胞的正常分裂。 改变培养基中的蔗糖浓度和在发根培养的不同时期给培养基中添加蔗糖,试验结果表明蔗糖作为碳源对1601-L-3和1601-L-1的生长具有显著的影响。 (1)培养基中缺少蔗糖显著地抑制发根的生长。 (2)发根培养的前5天时间内,蔗糖浓度为30- 60glL昀培养基最有利于发根的生长,50glL的培养基中的发根生长最快,培养基中的蔗糖浓度大于60g/L小于30g/L时,发根的生物量增加较少。 (3)发根培养至第15天时,蔗糖浓度为60g/L的培养基最有利予发根的生物量的增加。发根培养至30天时,蔗糖浓度为60-90g/L的培养基,发根的生物量的增加相差不大,但是为蔗糖浓度为30-40g/L的培养基中的发根生物量一倍。 (4)发根培养过程中,分别于第5和15天给蔗糖浓度为30g/L的培养基中添加一次或二次蔗糖,使培养基中的蔗糖终浓度相当于60g/L或90g/L,培养至30天时,添加蔗糖的培养基中的发根的干重生物量相当于不添加蔗糖培养基中的发根生物量一倍,相当于初始蔗糖浓度为60g/L和90g/L培养基中发根的生物量。 (5)随着培养基中蔗糖浓度的提高,发根干重/鲜重比显著增加。培养基中的蔗糖的消耗量与发根生物量的增加呈正相关,蔗糖消耗越多,发根生物量的增加越大。 比较pH值对发根生长和QHS合成的影响表明,灭菌前pH值在5.O-6.5范围内的培养基适合予1601-L-1的生长,小于5.O不利于发根的生长,pH5.8有利于1601-1-1生长和QHS的生物合成。发根收获时培养基中的pH值一般为4.5-5.2. pH7.O抑制发根的生长,pHl0.O对发根具有强烈的致死作用。发根在培养过程中,对培养基中的pH值具有显著的调节作用,发根能在很短的时间内(24- 48hrs)使pl:l值为5.8、6.4、7.0培养基降低到pH4. 5-5.2,pH为5.8的培养基有利于QHS合成。 比较不同基本培养基对发根生长和QHS合成的影响,试验结果表明N6、DCR、Litvay培养基有利于1601-L-1的生长,WS、White、B5培养基不利于发根的生长。DCR培养基中的QHS含量最高。 根据三水平试验选用三水平正交表来安排试验的原则,选用三水平正交表L7(3-),研究多因子效应对发根生长和QHS合成的影响,试验结果表明,Mg2+,Fe2+,Mn-2+,NH4NO3,KN03 ,KI,Ca-2+为发根生长的主要因子,NH4N03,KNOs,Mg2+,Ca2+,肌醇为QHS合成的主要因子。 通过TLC分析发根中QHS和其它化学成分,同时比较发根和无菌苗及野生植株的化学成分,发根和无菌苗均能合成包括QHS在内的野生青蒿叶片中的大部分非挥发性的化台 物。 研究青蒿植株在发育过程中QHS的含量的变化以及发根、无菌苗和野生青蒿中QHS的合成,HP分析结果表明,l、不同的单株青蒿之间的QHS量相差很大。2、同一植株幼 叶的QHS含量比老叶的QHS含量高。3、不同单株青蒿之间达到最高QHS含量的时间不一样,开花期或开花之前。4、无菌苗(带根)或者不带根丛生芽均能合成QHS,但是带根的无菌蕾的QHS量比丛生芽中的QIS的含量高。5、不同发根农杆菌转化的发根系1601-L-1和15834-L-1都能合成QHS。
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杜鹃花属(Rhododendron L.)植物分布广泛,研究发现所有的杜鹃花科植物都能形成一种特殊的菌根——杜鹃花类菌根(Ericoid Mycorrhiza)。杜鹃花类菌根对杜鹃花科植物在营养胁迫的环境下生长起到重要的作用。近几年,对杜鹃花类菌根的生物学和生态功能的研究越来越重视。我国是杜鹃花属植物资源最为丰富的国家,因此研究杜鹃花属植物菌根真菌多样性,充分利用杜鹃花特有的菌根资源,促进杜鹃花迁地保护成功具有重大的意义。 本研究以分布较广并且是中国特有的杜鹃花属植物——大白花杜鹃(Rhododendron decorum Franch.)的野生植株为研究对象,应用直接扩增根中真菌ITS区的分子鉴定方法和T-RFLP(末端限制性片段长度多态性)的分析方法,来研究其菌根真菌的多样性;并结合生态化学计量学特征分析、宿主遗传相似性及其群落组成分析等内容,探讨大白花杜鹃的菌根真菌-宿主植物-根际土壤三者之间的关系。主要结果如下: (1)通过用直接扩增真菌ITS区序列,揭示了大白花杜鹃根部真菌的多样性,本研究发现,野生大白杜鹃根部的真菌种类比较丰富,至少有26个ITS-taxa,包括子囊菌和担子菌共5个真菌目:Helotiales、Lecanorales(≡Agyriales)、Onygenales、Sebacinales和Thelephorales,其中包括典型的ERM真菌——树粉孢属Oidiodendron sp.(Myxotrichaceae)真菌。另外还发现了黑色有隔内生菌(Dark septate endophyte,DSE)以及一些未命名的子囊菌。担子菌在本研究中占有较大比例,尤其是蜡壳耳菌目真菌;此外还有较典型的外生菌根真菌——革菌目真菌。 (2)大白花杜鹃野生植株与栽培植株在菌根真菌种类组成上,有一定的相似性;在忽略种源差异等条件下相较而言,前者的物种丰富度远高于后者。 (3)大白花杜鹃菌根真菌多样性和丰富度同它的根际土壤与叶片的C、N、P含量以及C/N、N/P、土壤pH值、宿主的海拔高度等都没有显著的相关关系。 (4)在大白花杜鹃的菌根真菌群落组成方面,整体上保持了相当程度的相似性,同时还保持了一定水平的差异;大白杜鹃菌根真菌的种类是丰富的,优势度指数表明其多样性水平很高。 (5)大白花杜鹃的遗传距离与其菌根真菌群落组成结构有极显著的相关关系,宿主的种内遗传差异可能对菌根真菌群落物种组成产生选择偏好。 (6)大白花杜鹃的群落组成与其菌根真菌群落组成有极为显著的关联性,伴生种的菌根类型可能会影响宿主植物菌根真菌的物种组成结构。
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被子植物成熟的种子一般不合有叶绿素,但是莲(Nelumbo nucifera Gaertn.)的胚芽却具有鲜明的绿色,本文较详细地研究了莲胚芽不同于一般被子植物叶组织的色素和光台系统组成,并通过对莲胚芽成熟发育过程中的叶绿素合成和光合系统发育进行分析,探讨了莲胚芽光合特性形成的原因,最后对莲胚芽在黑暗中萌发能发育并建成光合系统的现象进行了研究,主要的结果如下: 1,莲胚芽不仅含有叶绿素和光合系统,而且其色素和光台系统组成均与莲叶以及其它被子植物的叶组织不同。莲胚芽的Chla/b值约为0.8左右,远远低于正常高等植物的Chla/b值(~3):莲胚芽的色素组成中不含有β-胡萝卜素;莲胚芽的光合系统没有电子传递活性,快速荧光动力学测定结果表明莲胚芽只有较高的固定荧光F。没有可变荧光Fv;原位低温荧光光谱检测表明莲胚芽只在679nm处有一个荧光发射主峰,没有正常的PSII和PSI荧光发射峰(683nm、692nm和730nm);部分变性的叶绿素蛋白复合物凝胶电泳分析结果表明莲胚芽叶绿体类囊体膜上只存在LHCII 一种叶绿素蛋白复合物(其中单体和二聚体形式的LHCII均有发现);Western Blots检测结果表明莲胚芽的LHCII组成比较单一,同时确证了莲胚芽不含有PSI的核心和天线蛋白组分。莲胚芽LHCII和莲叶LHCII在SDS-PAGE图谱上迁移距离相同,但是光谱分析表明二者不仅在Chla、Chlb的相对含量上不同,而且在叶绿素分子与蛋白的结合状态上也存在差异,这些差异主要是由一部分Chla分子造成的,Chlb分子在二者中的结合状态则比较~致。 2,对莲胚芽成熟过程中的光合系统发育进行研究,结果表明这个过程可以分为建成期(0-20天)、稳定期(20-30天)和降解期(30—40天)三个阶段。在建成期和稳定期内,莲胚芽外面的包被物可能不是完全遮光的,所以莲胚芽能感受到环境光信号,其叶绿素合成已经光合系统建成集中在此阶段内进行:在莲’胚芽成熟后期,莲胚芽外面的包被组织开始木质化,光信号无法再穿透它们,莲胚芽的光合系统发育进入降解期,叶绿素合成停止,己建成的光合系统开始降解,到莲胚芽成熟时,除LHCIl外,光合系统其余的叶绿素蛋白复合物都被降解了,所以莲胚芽具有不同于一般祓子植物叶组织的色素和光合系统组成。对莲胚芽的成熟发育过程进行遮光处理,结果发现遮光发育的莲胚芽发生明显黄化,这表明莲胚芽的叶绿素合成也离不开光照,在莲总基因组中检测不到编码DPOR的三个基因的同源序列,确证了莲胚芽不具有在黑暗中合成叶绿素的能力。 3,在黑暗中萌发生长的莲胚芽能够在相当长的时间内保持其叶绿素稳定,特别是Chla的含量在暗生长10天以内基本没有变化;原位低温荧光光谱检测表明暗萌发过程中莲苗有PSII和PSI的荧光发射峰形成,暗生长10天左右的莲苗具有比较明显的光合系统荧光发射峰,但是与自然光照下的发育过程相比,暗萌发莲苗的光合系统荧光发射峰出现较慢,而且PSI的荧光发射相对较弱;暗萌发莲苗在转绿以及冻融过程中的原位低温荧光光谱变化表明莲苗在黑暗中建成的光合系统不完善并且不稳定;对莲胚芽、暗萌发莲苗以及莲叶的叶绿体吸收光谱进行比较,结果显示暗萌发莲苗的叶绿体发育阶段介于莲胚芽和莲叶之间;叶绿素蛋白复合物凝胶电泳分离,SDS-PAGE,Western Blots免疫检测、以及叶绿素荧光诱导动力学结果均确证暗萌发莲苗有光合系统的发育,特别是PSI的出现;对暗萌发莲苗的光化学活性进行分析,结果表明暗中建成的PSII和PSI均具有电子传递活性:但是放氧复合物的发育不完全,对莲胚芽暗萌发过程光合系统建成的原因进行分析,推测叶绿素可能起了至关重要的作用,光对于莲胚芽萌发过程中的光合系统发育来说可能并不是必需的。
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磷脂酰甘油(PG)是光系统I(PSI)中唯一的磷脂,也是PSI重要的组成部分。在本工作中,我们通过改变PSI中PG的含量(体外重组至PG脂质体或专一性磷脂酶降解),研究了PG对PSI的调控作用。主要结果如下: 1. 外加PG导致PSI色素的结合状态和激子相互作用发生改变。吸收光谱中,Chl a特征峰蓝移且吸收降低。低温荧光光谱中,680nm处的峰逐渐明显,F730-735 /F680的比值下降,LHCI-730激发峰蓝移。可视CD光谱中Chl a、Chl b蓝移,它们的相互作用增强;类胡萝卜素分子发生红移。 2. PSI的重组引起了PSI蛋白质结构的改变,即蛋白的α-螺旋结构增加而无序结构含量减少。同时,PSI蛋白质内部的色氨酸残基处于更极性的环境。 3. PG对PSI的电子传递的影响具有浓度效应。低浓度时可以促进PSI的电子传递活性,而在相对较高浓度时抑制PSI的电子传递。 4. PLA2的处理导致PSI中PG的缺失,抑制了PSI反应中心P700的暗还原反应,即延长了其还原所用的时间。P700的暗还原反应存在快相和慢相两相反应。PG的缺失降低了这两相反应的反应速率,抑制了电子从质体蓝素(PC)到P700+的传递。
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Dalai-lamae (Ovis ammon dalai-lamae), Gobi (O. a. darwini), Kara Tau (O. a. nigrimontana) and Tibetan (O. a. hodgsoni) argali share a 2n = 56 diploid chromosome number and a karyotype consisting of 2 pairs of biarmed and 25 pairs of acrocentric autosomes, a large acrocentric X and a minute Y chromosome. The Giemsa-banding patterns of the largest pair of biarmed chromosomes were identical to those of the largest biarmed chromosomes in all wild sheep and domestic sheep of the genus Ovis. The banding patterns of the second pair of biarmed chromosomes (metacentric) were identical to the third pair of biarmed chromosomes in Ovis with 2n = 54 and to the third largest pair of chromosomes in the 2n = 52 karyotype of Siberian snow sheep (O. nivicola). The G-banded karyotypes of dalai-lamae, darwini, hodgsoni and nigrimontana are consistent with all subspecies of argali (O. ammon), except that the Y chromosome is acrocentric instead of metacentric as typical of the argaliform wild sheep and Ovis. The Dalai-lamae and Tibetan argali specimens exhibit the light-colored, long-haired ruffs and body coloration typical of argalis from the Tibetan Plateau. The Gobi argali, from the extreme western Gobi, is similar to the dark phase argali.
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Whether mice perceive the depth of space dependent on the visual size of object targets was explored when visual cues such as perspective and partial occlusion in space were excluded. A mouse was placed on a platform the height of which is adjustable. The platform located inside a box in which all other walls were dark exception its bottom through that light was projected as a sole visual cue. The visual object cue was composed of 4x4 grids to allow a mouse estimating the distance of the platform relative to the grids. Three sizes of grids reduced in a proportion of 2/3 and seven distances with an equal interval between the platform and the grids at the bottom were applied in the experiments. The duration of a mouse staying on the platform at each height was recorded when the different sizes of the grids were presented randomly to test whether the Judgment of the mouse for the depth of the platform from the bottom was affected by the size information of the visual target. The results from all conditions of three object sizes show that time of mice staying on the platform became longer with the increase in height. In distance of 20 similar to 30 cm, the mice did not use the size information of a target to judge the depth, while mainly used the information of binocular disparity. In distance less than 20 cm or more than 30 cm, however, especially in much higher distance 50 cm, 60 cm and 70 cm, the mice were able to use the size information to do so in order to compensate the lack of binocular disparity information from both eyes. Because the mice have only 1/3 of the visual field that is binocular. This behavioral paradigm established in the current study is a useful model and can be applied to the experiments using transgenic mouse as an animal model to investigate the relationships between behaviors and gene functions.
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Bats (Chiroptera) are the second-most abundant mammalian order in the world, occupying a diverse range of habitats and exhibiting many different life history traits. In order to contribute to this highly underrepresented group we describe the sleep architecture of two species of frugivorous bat, the greater short-nosed fruit bat (Cynopterus sphinx) and the lesser dawn fruit bat (Eonycteris spelaea). Electroencephalogram (EEG) and electromyogram (EMG) data were recorded from multiple individuals (>= 5) by telemetry over a 72-h period in a laboratory setting with light/dark cycles equivalent to those found in the wild. Our results show that over a 24-h period both species spent more time asleep than awake (mean 15 h), less than previous reported for Chiroptera (20 h). C sphinx spent significantly more of its non-rapid eye movement sleep (NREM) and rapid eye movement sleep (REM) quotas during the light phase, while E. spelaea divided its sleep-wake architecture equally between both light and dark phases. Comparing the sleep patterns of the two species found that C. sphinx had significantly fewer NREM and REM episodes than E. spelaea but each episode lasted for a significantly longer period of time. Potential hypotheses to explain the differences in the sleep architecture of C. sphinx with E. spelaea, including risk of predation and social interaction are discussed. (C) 2010 Published by Elsevier B.V.
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A new species of Amolops is described from a mountainous area of southern Yunnan Province, China. The species is unique in having a dark purple dorsum with small light yellow spots. The spots are smaller than the smallest finger disk. Other characters tha
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Data on sleep-related behaviors were collected for a group of central Yunnan black crested gibbons (Nomascus concolor jingdongensis) at Mt. Wuliang, Yunnan, China from March 2005 to April 2006. Members of the group usually formed four sleeping units (adult male and juvenile, adult female with one semi-dependent black infant, adult female with one dependent yellow infant, and subadult male) spread over different sleeping trees. Individuals or units preferred specific areas to sleep; all sleeping sites were situated in primary forest, mostly (77%) between 2,200 and 2,400 m in elevation. They tended to sleep in the tallest and thickest trees with large crowns on steep slopes and near important food patches. Factors influencing sleeping site selection were (1) tree characteristics, (2) accessibility, and (3) easy escape. Few sleeping trees were used repeatedly by the same or other members of the group. The gibbons entered the sleeping trees on average 128 min before sunset and left the sleeping trees on average 33 min after sunrise. The lag between the first and last individual entering the trees was on average 17.8 min. We suggest that sleep-related behaviors are primarily adaptations to minimize the risk of being detected by predators. Sleeping trees may be chosen to make approach and attack difficult for the predator, and to provide an easy escape route in the dark. In response to cold temperatures in a higher habitat, gibbons usually sit and huddle together during the night, and in the cold season they tend to sleep on ferns and/or orchids.