Rapid planetesimal formation in turbulent circumstellar disks

During the initial stages of planet formation in circumstellar gas disks, dust grains collide and build up larger and larger bodies. How this process continues from metre-sized boulders to kilometre-scale planetesimals is a major unsolved problem: boulders are expected to stick together poorly, and to spiral into the protostar in a few hundred orbits owing to a 'headwind' from the slower rotating gas. Gravitational collapse of the solid component has been suggested to overcome this barrier. But even low levels of turbulence will inhibit sedimentation of solids to a sufficiently dense midplane layer, and turbulence must be present to explain observed gas accretion in protostellar disks. Here we report that boulders can undergo efficient gravitational collapse in locally overdense regions in the midplane of the disk. The boulders concentrate initially in transient high pressure regions in the turbulent gas, and these concentrations are augmented a further order of magnitude by a streaming instability driven by the relative flow of gas and solids. We find that gravitationally bound clusters form with masses comparable to dwarf planets and containing a distribution of boulder sizes. Gravitational collapse happens much faster than radial drift, offering a possible path to planetesimal formation in accreting circumstellar disks.     

Corporate Social Responsibility as a Messy Problem: Linking Systems and Sensemaking Perspectives

Corporate social responsibility (CSR) has become an essential topic with regard to the relationship between business and the wider society. It is a complex and controversial phenomenon that can best be addressed via systems theory and the sensemaking perspective. This paper proposes a way to link a dialectical systems perspective with communications that includes the sensemaking and dialogic collective approaches, which help to build systems of organised activities that aim to find solutions to complex problems from a holistic perspective. Companies are increasingly aware that if they wish to be successful actors in their business and societal relationships, the traditional sole focus on maximising profit is counterproductive, especially in terms of sustaining their value chains. A holistic approach to CSR and the value chain involves companies integrating their stakeholders along their value chains, especially at the downstream and upstream extremes (their customers and suppliers). This paper illustrates its theoretical perspectives with a case study of JYSK, a multinational company based in Denmark, which demonstrates how the company based its actual management of CSR on its willingness to learn from its own actions and from the actions of others.     

DNA synthesis and distribution of first and second divisions in 72-h-cultures of human leukocytes

Zusammenfassung Lymphocyten eines gesunden Erwachsenen lassen ohne Stimulation keine messbare DNS-Synthese erkennen. Nach Stimulation durch Phytohaemagglutinin finden am 2. und 3. Tag je eine Phase intensiver DNS-Synthese statt, was auf die Anwesenheit von mindestens zwei verschiedenen Zellpopulationen hinweist.

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Grateful acknowledgment is made to Dr.A. Brøgger and Dr.P. Eker for their kind advice and criticism.     

Gravitational haemodynamics and oedema prevention in the giraffe

Because it is so tall, the giraffe, Giraffa camelopardalis, provides an important animal model for investigating adaptive mechanisms to orthostatic (gravitational) pressure changes. Previous physiological studies of the giraffe have concentrated on arterial blood pressures in the heart and neck. Briefly, these investigations revealed that arterial pressure near the giraffe heart is about twice that in humans, to provide more normal blood pressure and perfusion to the brain. Another important question is that of how giraffes avoid pooling of blood and tissue fluid (oedema) in dependent tissues of their extremities. As monitored by radiotelemetry, the blood and tissue fluid pressures that govern transcapillary exchange vary greatly with exercise. These pressures, combined with a tight skin layer, move fluid upward against gravity. Other mechanisms that prevent oedema include precapillary vasoconstriction and low permeability of capillaries to plasma proteins.     

An abundance of small exoplanets around stars with a wide range of metallicities

The abundance of heavy elements (metallicity) in the photospheres of stars similar to the Sun provides a 'fossil' record of the chemical composition of the initial protoplanetary disk. Metal-rich stars are much more likely to harbour gas giant planets, supporting the model that planets form by accumulation of dust and ice particles. Recent ground-based surveys suggest that this correlation is weakened for Neptunian-sized planets. However, how the relationship between size and metallicity extends into the regime of terrestrial-sized exoplanets is unknown. Here we report spectroscopic metallicities of the host stars of 226 small exoplanet candidates discovered by NASA's Kepler mission, including objects that are comparable in size to the terrestrial planets in the Solar System. We find that planets with radii less than four Earth radii form around host stars with a wide range of metallicities (but on average a metallicity close to that of the Sun), whereas large planets preferentially form around stars with higher metallicities. This observation suggests that terrestrial planets may be widespread in the disk of the Galaxy, with no special requirement of enhanced metallicity for their formation.     

Three new records for diatoms from the Great Basin, USA

Three diatom species recently collected from Great Basin localities represent new records of these taxa from this region of western North America. Cocconeis scutellum   Ehr. and Melosira dubia   Kuetz. were collected from a thermal spring in Tooele County, Utah. Nitzschia hustedtiana   Salah was collected from newly flooded marshes at the south end of the Great Salt Lake, Tooele Countv, Utah.     

基于像元和对象分类的城区植被高分辨率遥感制图比较研究

本研究利用高空间分辨率遥感影像和LiDAR数据,参照美国USGS植被分类体系,在两种不同分类层次上,评价了基于像元和基于对象分类两种方法的城区植被覆盖专题制图效果.采用传统的基于像元监督最大似然分类时,在下层分类层次,分类总精度仅为70.5%,Kappa系数为63.5%.当在上层分类层次进行分类时,分类精度相对下层分类层次有明显提高,总精度达84%,Kappa系数为75.8%.而采用面向对象的分类方法时,在下层分类层次,分类总精度为86%,Kappa系数为82.3%.在上层分类层次,总精度达90.8%,Kappa系数为86.2%.研究结果表明,在城区两种不同植被分类层次,面向对象分类结果都取得了优于基于像元的分类结果.     

The bacterium Thioploca ingrica on wet walls in Zion National Park, Utah

Hanging gardens and wet wall habitats have been studied for the past several years in many arid regions of the Intermountain West. One unusual large wet wall habitat in Zion National Park was found to be covered with a mucilaginous red-colored growth of the filamentous gliding bacterium Thioploca ingrica Visloukh. This is the only habitat we have examined where the predominant matrix-forming organism was a bacterium rather than an alga.