Migrating songbirds recalibrate their magnetic compass daily from twilight cues

Night migratory songbirds can use stars, sun, geomagnetic field, and polarized light for orientation when tested in captivity. We studied the interaction of magnetic, stellar, and twilight orientation cues in free-flying songbirds. We exposed Catharus thrushes to eastward-turned magnetic fields during the twilight period before takeoff and then followed them for up to 1100 kilometers. Instead of heading north, experimental birds flew westward. On subsequent nights, the same individuals migrated northward again. We suggest that birds orient with a magnetic compass calibrated daily from twilight cues. This could explain how birds cross the magnetic equator and deal with declination.     

Honey bee orientation: a backup system for cloudy days

On cloudy days, honey bees are known to navigate to familiar food sources and orient their dances accurately. This capacity could be based on a magnetic compass sense, an ability to perceive the sun or patterns of polarized light through the clouds, or on the bees' memory of the diurnal course of the sun with respect to local landmarks. Experiments pitting these alternatives against one another demonstrate that the navigational backup system of bees is based on memory.     

Reproductive effort, molting latitude, and feather color in a migratory songbird

Toward the end of the breeding season, migratory songbirds face crucial tradeoffs between the timing of reproduction, molt, and migration. Using stable hydrogen isotopes, we show that male American redstarts investing in high levels of reproduction late in the season adopt a unique strategy of combining molt and migration. Tail feathers molted during migration also reflect less orange-red light, indicating reduced carotenoid concentration. Thus, we show how reproduction in a migratory animal can influence both life history strategies (location of molt) and social signals (feather color) during subsequent periods of the annual cycle.     

Oceili: a celestial compass in the desert ant cataglyphis

In addition to multifaceted lateral compound eyes, most insects possess three frontal eyes called ocelli. Each ocellus has a single lens, as does the vertebrate eye. The ocelli of some flying insects, locusts and dragonflies, have been shown to function as horizon detectors involved in the visual stabilization of course. In a walking insect, the desert ant Cataglyphis, it is now shown that the ocelli can read compass information from the blue sky. When the ant's compound eyes are occluded and both sun and landmarks are obscured, the ocelli, using the pattern of polarized light in the sky as a compass cue, help in guiding the ant back home.     

Illuminating the circadian clock in monarch butterfly migration

Migratory monarch butterflies use a time-compensated Sun compass to navigate to their overwintering grounds in Mexico. Here, we report that constant light, which disrupts circadian clock function at both the behavioral and molecular levels in monarchs, also disrupts the time-compensated component of flight navigation. We further show that ultraviolet light is important for flight navigation but is not required for photic entrainment of circadian rhythms. Tracing these distinct light-input pathways into the brain should aid our understanding of the clock-compass mechanisms necessary for successful migration.     

Decline of DDT residues in migratory songbirds

Analyses of ten species of migratory songbirds killed when the birds flew into television towers in Florida showed a progressive decline in the concentration of DDT and its metabolites (DDD and DDE) in their fat depots for the period 1964 to 1973. This decline is apparently correlated with the decreased usage of DDT in the United States during the same time.     

Reconstruction of zebrafish early embryonic development by scanned light sheet microscopy

A long-standing goal of biology is to map the behavior of all cells during vertebrate embryogenesis. We developed digital scanned laser light sheet fluorescence microscopy and recorded nuclei localization and movement in entire wild-type and mutant zebrafish embryos over the first 24 hours of development. Multiview in vivo imaging at 1.5 billion voxels per minute provides "digital embryos," that is, comprehensive databases of cell positions, divisions, and migratory tracks. Our analysis of global cell division patterns reveals a maternally defined initial morphodynamic symmetry break, which identifies the embryonic body axis. We further derive a model of germ layer formation and show that the mesendoderm forms from one-third of the embryo's cells in a single event. Our digital embryos, with 55 million nucleus entries, are provided as a resource.     

Navigation of single homing pigeons: airplane observations by radio tracking

Navigation of homing pigeons was investigated by tracking their homeward flights from a light airplane. Released on successive days from a single training point 35 miles (56 kilometers) from home, individual pigeons, each carrying a transmitter, were repeatedly tracked back to theirloft. No two tracks covered the same ground for even short distances, yet all tracks were within 10 miles of a straight line. Results from further releases north and south of the training point suggest that pigeons often use three methods in sequence to find home: compass orientation, bi-coordinate navigation, and orientation by familiar landmarks.     

偏振波谱光态矢量光照参量对东亚飞蝗偏光响应效应的影响

为明确偏振波谱光态光照参量对蝗虫趋偏响应效应的影响作用,获取蝗虫偏振诱导光场的技术特征,研制蝗虫偏振诱导光源,利用蝗虫偏光响应试验装置测试了蝗虫对紫、蓝部分偏光及线偏光的响应特征,以此优选波谱偏振光态矢量的作用模式,分析偏振波谱光态光照参量对蝗虫偏光响应机制的影响,探讨蝗虫偏光波谱矢量敏感模式变化的原因。结果表明,部分偏光中,紫波谱未引起而蓝波谱导致蝗虫视响应与视趋性敏感矢量发生改变;线偏光中,紫、蓝波谱均影响蝗虫趋偏响应效应的矢量敏感模式,且波谱相同,部分偏光矢量置向模式对蝗虫的操控诱导、视趋强度的调控性优于线偏光,而偏振矢量光态相同,紫波谱的作用效果强于蓝波谱。蝗虫趋偏响应效应与偏振波谱、偏振光态的异质作用效应有关,且线偏紫波谱120°左右置向矢量对蝗虫的诱导效果最强(94.5%),而紫波谱部分偏光左60°及右150°矢量对蝗虫视趋强度的作用效果最强(68.5%);部分偏光矢量置向模式的作用效果与波谱光致性视敏偏振效应有关,且蓝波谱中偏振度越高而光照度越低,矢量模式的操控诱导性越强,紫波谱中偏振度越低而光照度越强,矢量模式对蝗虫趋偏聚集程度的作用效果越强。从而,线偏与部分偏光不同矢量光照交替刺激模式可提高蝗虫趋偏响应敏感性。     

Decagonal and quasi-crystalline tilings in medieval Islamic architecture

The conventional view holds that girih (geometric star-and-polygon, or strapwork) patterns in medieval Islamic architecture were conceived by their designers as a network of zigzagging lines, where the lines were drafted directly with a straightedge and a compass. We show that by 1200 C.E. a conceptual breakthrough occurred in which girih patterns were reconceived as tessellations of a special set of equilateral polygons ("girih tiles") decorated with lines. These tiles enabled the creation of increasingly complex periodic girih patterns, and by the 15th century, the tessellation approach was combined with self-similar transformations to construct nearly perfect quasi-crystalline Penrose patterns, five centuries before their discovery in the West.     

Canopy orientation: a new kind of orientation in ants

Celestial cues, such as the sun or patterns of polarized sky light, appear to have no detectable effect in the precise homing orientation of foragers of Paltothyreus tarsatus. Field and laboratory experiments reveal that canopy patterns are a major influence in the home range orientation of this ponerine ant, a common species in African forests. Canopy orientation appears to be well suited to the restrictive lighting conditions of tropical forests.     

Migration along orthodromic sun compass routes by arctic birds

Flight directions of birds migrating at high geographic and magnetic latitudes can be used to test bird orientation by celestial or geomagnetic compass systems under polar conditions. Migration patterns of arctic shorebirds, revealed by tracking radar studies during an icebreaker expedition along the Northwest Passage in 1999, support predicted sun compass trajectories but cannot be reconciled with orientation along either geographic or magnetic loxodromes (rhumb lines). Sun compass routes are similar to orthodromes (great circle routes) at high latitudes, showing changing geographic courses as the birds traverse longitudes and their internal clock gets out of phase with local time. These routes bring the shorebirds from high arctic Canada to the east coast of North America, from which they make transoceanic flights to South America. The observations are also consistent with a migration link between Siberia and the Beaufort Sea region by way of sun compass routes across the Arctic Ocean.     

惠州鸟类资源调查

2005年3月～2012年12月,惠州记录到鸟类18目、58科、299种。其中,雀形目鸟类27科、151种,占总数的50.50%;非雀行目鸟类31科、148种,占总数的49.50%。国家重点保护鸟类Ⅰ级2种,Ⅱ级37种。我国特有种2种。CITES记录的鸟类11种,《中国濒危物种红皮书》中的鸟类23种。留鸟157种,占总数的52.51%;冬候鸟90种,占总数的30.10%;夏候鸟37种,占总数的12.37%;旅鸟或迷鸟15种,占总数的5.02%。东洋界种155种,占总数的51.84%;古北界种107种,占总数的35.79%;广布种37种,占总数的12.37%。鸣禽151种,占总数的50.50%;湿地水鸟73种,占总数的24.7%。麻雀、白喉红臀鹎等15种鸟类是惠州的优势种,占总数的5.01%。     

Two magnetoreception pathways in a migratory salamander

Male eastern red-spotted newts (Notophthalmus viridescens) under controlled laboratory conditions exhibit unimodal magnetic compass orientation either in a trained compass direction or in the direction of their home pond. If the vertical component of the magnetic field is inverted, newts exhibiting the simple-compass response undergo a 180 degree reversal in orientation, whereas newts orienting in the home direction are unaffected by this treatment. These results indicate that newts use an axial compass mechanism for simple-compass orientation similar to that found in migrating birds. However, a distinct magnetoreception pathway with polar response properties is involved in homing and is possibly linked in some way to the navigational map.     

Spatial orientation by Salamanders using plane-polarized light

Tiger salamanders (Ambystoma tigrinum) can perceive the plane of polarization in linearly polarized light and can learn to use that e-vector direction for spatial orientation in indoor orientation tests.     

河西走廊5种作物种植模式的产量潜力估算

采用联合国粮农组织(FAO)推荐的方法,通过光温系数的修正,计算了甘肃河西走廊单作小麦、单作玉米、单作豌豆、小麦间作玉米、豌豆间作玉米等5种作物种植模式的光温潜力.结果表明,大多数单作种植模式不能充分利用光热资源,间套作种植可以衍生作物覆盖时间,当前主要的作物间套作种植模式(小麦间作玉米、豌豆间作玉米)更有利于热量资源的充分发挥     

Changed lyotropic liquid crystalline structure due to polymerization of the amphiphilic component

Optical patterns in polarized light and x-ray reflections in the low-angle region were used to detect a shift from one liquid crystalline structure to another during polymerization. The polymerization took place in a Iotropic liquid crystal of water and sodium undecenoate, with a structure consisting of cylinders in a two-dimensional hexagonal close packing. After polymerization, a lamellar liquid crystalline structure was obtained.     

利用组织化学染色和偏振光显微镜检识植物组织中草酸钙结晶的研究

[目的]探讨利用组织化学染色和偏振光显微镜检识植物组织中草酸钙结晶的可行性。[方法]将闪光相思树（Acacia stellaticeps Kodela,Tindale ＆ D．Keith）叶状柄用乙二醇甲基丙烯酸酯包埋后制作半薄切片,分别用甲苯胺蓝和氨基黑10B对切片进行染色,利用偏振光显微镜在透射光和偏振光下对染色的切片进行观察和拍照,并且与在偏振光下观察和拍摄到的未染色切片进行对比。[结果]与单纯使用偏振光观察未染色切片和使用透射光观察甲苯胺蓝或氨基黑10B染色的切片以及使用偏振光观察氨基黑染色10B的切片相比．用偏振光观察甲苯胺蓝染色的切片能更准确地检识草酸钙结晶。[结论]该研究为检识植物组织中草酸钙结晶提供一种新的思路和方法。     

Bumblebee ocelli and navigation at dusk

Western bumblebees fly straight while homing by polarized light, but zigzag when they use landmarks. That flight difference was used to determine the roles of the dorsal ocelli and parts of the compound eyes in homing. Polarized light and ocelli can prolong foraging at twilight, when landmarks are no longer visible.     

海参捕捞装置导航中低成本陀螺仪的降噪研究与试验

针对MEMS陀螺仪输出信号中含有的随机漂移噪声造成海参捕捞装置惯性导航精度明显下降的问题,采用时间序列分析法和Kalman滤波算法,对MEMS陀螺仪随机漂移噪声的削减问题进行研究。以MEMS惯性测量单元的实测数据和三维电子罗盘测量的姿态角为样本,对本研究的低成本陀螺仪的降噪效果进行测试,试验结果表明:1)经过降噪处理后的陀螺仪随机漂移信号的方差比陀螺仪原始采样信号的方差降低1个数量级,显著改善了陀螺仪随机漂移数据的精密度;2)以高精度三维电子罗盘实测的姿态角作为参考基准,将降噪后的陀螺仪随机漂移数据导入捷联惯导姿态更新算法程序,在300s时间内,解算出的俯仰角、横滚角和航向角的均方根误差RMSE全部小于1°;与降噪前相比,相应的俯仰角、横滚角、航向角的RMSE分别降低了170.5、97.6和42.5倍,明显提高了惯性导航精度。