589 research outputs found
New Silhouette Disks with Reflection Nebulae and Outflows in the Orion Nebula and M43
We report the detection of several new circumstellar disks seen in silhouette
in the outskirts of the Orion nebula and M43, detected as part of our Halpha
survey of Orion with the HST/ACS. Several of the disks show bipolar reflection
nebulae, microjets, or temporal variability. Two disks in our sample are large
and particularly noteworthy: A nearly edge-on disk, d216-0939, is located
several arcminutes northwest of M43 and resembles the famous HH30 disk/jet
system in Taurus. It drives the 0.15 pc long bipolar outflow HH667, and
exhibits a remarkable asymmetric reflection nebula. With a diameter of 1200 AU,
it is as large as the giant edge-on silhouette disk d114-426 in the core of the
Orion Nebula. The large disk d253-1536 is located in a binary system embedded
within an externally-ionized giant proplyd in M43. The disk exhibits
distortions which we attribute to tidal interactions with a companion. The
bipolar jet HH668 emerges orthogonal to the disk, and a bow shock lies 54''
south of this binary system along the outflow axis. Proper motions over 1.4 yr
confirm that these emission knots are moving away from d253-1536, with speeds
as high as 330 km/s in the HH668 microjet, and slower motion farther from the
star.Comment: 19 pages, Fig 2 in color, accepted by A
Restoration of Bison (\u3ci\u3eBison bison\u3c/i\u3e) to Agate Fossil Beds National Monument, A Feasibility Study
Executive Summary
Agate Fossil Beds National Monument is a 3,057-acre park located in western Nebraska. The unit is comprised of northern mixed-grass prairie vegetation, typical of the Northern Great Plains. Weather, fire, and grazing are generally considered to be the ecological drivers of prairie ecosystems and critical for prairie health. However, grazing has essentially been absent since the 1960s. In 2014, a Department of the Interior report explicitly listed the park as a high priority for bison restoration. This report evaluates the feasibility, management options, benefits, and challenges of restoring bison to Agate Fossil Beds National Monument.
A potential bison pasture encompasses about 2,676 acres within the park, essentially the area east of Highway 29. Assuming 2,676 acres are available to bison, a forage intake rate of 2.667%, a natural sex and age structure for the herd, an average bison weight of 1,000 pounds, and an allocation of 33% of annual plant productivity to bison consumption, the park could support 166 bison in the fall in a normal-precipitation year including calves, or about 136 yearlings and adults. Using the same assumptions the dry year carrying capacity is 129 animals and the wet year carrying capacity is 219 animals (including calves). Changes in other assumptions and objectives result in different modeled carrying capacities ranging from 52 to 443 animals, demonstrating the latitude available to management. Using the assumptions listed above, if the portion of the park that encompasses the visitor center, park housing, and a private in-holding is excluded from the bison pasture (an area of about 300 acres) then the carrying capacity is reduced to about 147 bison in the fall.
If bison were restored to the park they would occur in a closed system absent of natural predation to affect population growth. Assuming a starting population of 40 yearlings (at a 50:50 sex ratio), the herd would reach carrying capacity about 9-11 years later. Numerous anthropogenic options are available to manage the herd size; however, the most conventional and feasible consists of the park periodically rounding up and transferring live animals to other entities such as Native American tribes. This approach is used by many NPS units with bison. Tradeoffs exist between the frequency of the removal operations and the quantity and age-sex classes of the animals removed in a cull. For example, assuming a goal of a long-term average population of 166 bison in the fall, an annual cull of 70% of the yearlings (about 23 animals) would maintain the herd at that level as would a cull conducted every third year that removed 40% of all age and sex classes (removing about 81 animals total). The greater the duration between culls the greater the variability in herd size, e.g., a cull every fifth year that removes 60% of the herd results in a population that fluctuates between 99 and 202 animals. Other considerations in selecting a culling strategy include ecological objectives, bison genetic goals, available funding and infrastructure, drought, and availability and desires of the recipients of the bison.
The conservation of bison genetics is a high priority within the NPS. Frequent smaller culls better conserve bison genetics as the population does not experience the deep nadirs caused by the removal of large numbers of animals necessitated by less frequent culls. The larger the herd the better genetic diversity is conserved, all else being equal. Genetic diversity could be better conserved if an Agate Fossil Beds herd was managed as a metapopulation with other NPS herds. The park could also choose to manage bison in partnership neighbors, one of whom owns about 5,000 acres. Such a partnership would greatly increase the size of the herd, ecological function, and genetic conservation.
The potential benefits of restoring bison to Agate Fossil Beds National Monument include:
1) restoring a native species to the park,
2) restoring an ecological process to the park that enhances the conservation of biodiversity,
3) improving visitor experience and understanding,
4) benefitting local communities via increased tourism,
5) restoring a Native American ethnographic and cultural resource,
6) contributing to meeting DOI and NPS bison goals,
7) establishing a metapopulation that contributes to agency and global conservation of bison genetic diversity,
8) establishing a genetically pure bison herd (assuming the needed technology is completed),
9) establishing a satellite herd that provides redundancy in case of a catastrophe to another NPS herd(s),
10) being a repository for Yellowstone National Park or other park bison, if needed.
The challenges to bison restoration at the park include the cost and potential impacts of bison-associated infrastructure and maintenance, the need to hire staff with natural resource expertise, and the need to foster support within the agency and with stakeholders. Depending on the location of the bison pastures the park may also need to address private inholdings within the park administrative boundary, impacts on paleontological resources, issues associated with a county road, and impacts to the park administrative areas and structures. The small size of the park makes a well-designed prescribed fire program and an active vegetation monitoring program especially important to assure park goals are being met.
This feasibility study primarily provides a scientific evaluation of restoring bison to Agate Fossil Beds National Monument. Ultimately a full evaluation that considers other concerns and impacts (e.g. cultural resources) would need to be conducted as part of an environmental assessment and management plan. This report tries to facilitate that process wherever possible by analyzing and presenting a range of values. An environmental assessment would also need to consider action alternatives that were not fully vetted here, such as introducing cattle in lieu of bison for purposes of restoring the grazing process. From an ecological and conservation perspective there would be many benefits to restoring bison to the park, and it would be very feasible
BOOK REVIEWS: American Serengeti: The Last Big Animals of the Great Plains. Dan Flores.
Before describing what Flores’ book is, I must state what it is not. It is not a technical book designed for scholarly readers. Sources are not fully cited, and the bibliography is of limited scope. Nor is it a comprehensive book of all the megafauna of the Great Plains. Although chapters are devoted to extant species such as American bison (Bison bison), pronghorn (Antilocapra americana), and coyote (Canis latrans), there are only passing references to mule and white-tailed deer (Odocoileus hemionus and O. virginianus, respectively), elk (Cervus canadensis), and bighorn sheep (Ovis canadensis). Rather, Flores devotes chapters to grizzly bears (Ursus arctos) and wolves (Canus lupus), two species that are essentially absent from the current Great Plains. Interestingly, the modern horse (Equus caballus), recently returned to the region by Europeans, is afforded a chapter. The somewhat arbitrary list of species could have been selected by the author because he viewed them as the epitome of Great Plains wildlife, or because they best told the story of the relationship that humans have had with large Great Plains animals, or because the author simply had a personal interest in those species. Flores mentions, but doesn’t weigh in on the sensitive topic of what caused the extinction of most of the region’s megafauna about 10,000 years ago (e.g., aboriginal people), when the Great Plains truly rivaled the Serengeti in terms of large animal diversity.
I think it fair to say that this isn’t really a book about the large animals of the Great Plains, but rather, is about the people and cultures that essentially destroyed one Great Plains ecosystem and replaced it with another. Ultimately, this is a book about societies, cultural attitudes toward nature, and the psyche of the people who pulled the triggers. For that goal, it succeeds
Observations of Bobcats, Lynx rufus, Hunting Black-Tailed Prairie Dogs, Cynomys ludovicianus, in Western South Dakota
There is a paucity of scientific literature describing Bobcat (Lynx rufus) hunting strategies. I document 13 observations of Bobcats hunting Black-tailed Prairie Dogs (Cynomys ludovicianus) in western South Dakota. In all cases the Bobcats stationed themselves next to a prairie dog mound in an attempt to ambush prairie dogs emerging from their burrows. In eight cases the Bobcats successfully captured a prairie dog emerging from the burrow, in one case the Bobcat turned and captured a prairie dog that had walked up behind it, and in the other cases the Bobcats lunged at the burrow openings, but did not capture a prairie dog. There were two variations of the tactic: in some cases Bobcats entered a colony prior to prairie dog emergence and stationed themselves next to a mound, whereas in other cases Bobcats stationed themselves next to a burrow that a prairie dog had just escaped to. One Bobcat appeared to have waited next to the same mound for at least 7.5 hr. Prairie dogs may comprise a large portion of a Bobcat's winter diet in landscapes where prairie dog colonies exist in close proximity to badlands or woody cover
High-Tech-Gründungen in Deutschland: Hemmnisse junger Unternehmen
Die Anzahl von Unternehmensgründungen in den High-Tech-Sektoren ist im Jahr 2009 im Vergleich zum Vorjahr gestiegen. Mit einer Zunahme um knapp 20% auf 14.000 lag die Anzahl der High- Tech-Gründungen deutlich über dem Tiefpunkt des Jahres 2008. Die Gründungstätigkeit in der Gesamtwirtschaft nahm ebenfalls zu. Die Anzahl wirtschaftsaktiver Gründungen insgesamt stieg um knapp 8% auf 205.000 Gründungen. Der starke Anstieg der Anzahl der Unternehmensgründungen ist auf eine Änderung der institutionellen Rahmenbedingungen zurückzuführen. So trat am 1.11.2008 das Gesetz zur Modernisierung des GmbH-Rechts und zur Bekämpfung von Missbräuchen (MoMiG) in Kraft, das mit der Einführung der haftungsbeschränkten Unternehmergesellschaft (der sog. Mini-GmbH) für viele, insbesondere kleine Unternehmen eine attraktive Rechtsform schaffte. Ohne die Einführung der Unternehmergesellschaft wäre die Entwicklung der Gründungstätigkeit zwar schwächer ausgefallen, aber mit einem geschätzten Anstieg der Anzahl der Unternehmensgründungen im High-Tech-Sektor von mindestens 3% trotzdem erfreulich positiv ausgefallen. Die Einführung der Unternehmergesellschaft führte zu einem Bruch in der Zeitreihe der Entwicklung der Gründungstätigkeit, da nun sehr viel mehr Kleinunternehmen erfasst werden als bisher üblich. Aufgrund dieses Bruches ist der Vergleich des Jahres 2009 mit den Vorjahren nur eingeschränkt möglich, so dass die Entwicklung der Gründungstätigkeit ohne Berücksichtigung der Unternehmergesellschaften eine wohl sinnvollere Orientierung für die Abschätzung der Dynamik der Gründungstätigkeit im Jahr 2009 gibt
PATRIMONIO INMATERIAL DE LA NACIÓN - Lenguas colombianas
¿Lenguas colombianas?, dirán ante un título como éste muchos colombianos todavía empecinados en creer que lo único que vale la pena en nuestro país –y en el subcontinente latinoamericano– es lo que nos ha legado Europa, la lengua española por ejemplo, y que las manifestaciones vernáculas de este territorio son, a lo sumo, reminiscencias de un pasado que aún nos abochorna, con ‘dialectos’ o ‘jergas’ –que no lenguas– hablados por las sociedades indígenas y afrocolombianas; con ‘hechicerías’ –que no prácticas religiosas–, como consideramos sus creencias; y con ‘artesanías’ –que no arte–, como llamamos a su cultura material, testimonios todos de esa milenaria memoria ancestral americana que se resiste a morir junto con sus portadores
High-Tech-Gründungen in Deutschland: Optimismus trotz Krise
Unternehmensgru¨ndungen haben in der wirtschaftspolitischen Diskussion einen großen Stellenwert, wird ihnen doch gemeinhin ein wichtiger Beitrag zur Schaffung neuer, zukunftsorientierter Arbeitsplätze unterstellt. Eine höhere gesamtwirtschaftliche Effizienz, ein beschleunigter Strukturwandel und nicht zuletzt eine größere Produkt- und Technologievielfalt sind nur einige Effekte, durch die Unternehmensgru¨ndungen die langfristige Wettbewerbsfähigkeit einer Volkswirtschaft positiv beeinflussen (Fritsch, 2008). Insbesondere bei Unternehmensgru¨ndungen in High-Tech-Sektoren wird eine starke Verknu¨pfung mit der Wettbewerbsfähigkeit einer Volkswirtschaft angenommen, da sie im Mittel häufiger Forschung und Entwicklung (FuE) betreiben und stärker auf neue Technologien fokussiert sind als Gru¨ndungen in anderen Wirtschaftsbereichen. Weil High-Tech-Gru¨ndungen häufig als Vorreiter Marktnischen besetzen oder neue Märkte etablieren, bergen sie eine gesteigerte Innovationskraft und können die Orientierung der Volkswirtschaft auf neue, Erfolg versprechende technologische Entwicklungen mit Wachstumspotenzial lenken. Diese Funktion von High-Tech-Gru¨ndungen könnte in der Wirtschaftskrise von unmittelbarer Bedeutung sein. Gerade in Krisen werden oft die Weichen fu¨r zuku¨nftige Märkte gestellt, da sich radikale Innovationen und neue Technologien eher in Krisenzeiten durchsetzen und von etablierten Unternehmen aufgegriffen und weiterentwickelt werden – dies hat die Weltwirtschaftskrise von 1929 gelehrt. In Kooperation mit Microsoft hat das ZEW bereits in den Vorjahren ausgewählte Aspekte von High- Tech-Gru¨ndungen beleuchtet. Im Jahr 2006 stand die Beschreibung der Charakteristika von High- Tech-Gru¨ndungen im Vordergrund. Die Evaluierung des Zugangs von High-Tech-Unternehmen zu Wissens- und Finanzierungsressourcen sowie die Rolle von Frauen im High-Tech-Gru¨ndungsgeschehen waren Inhalte der Studie des Jahres 2007, während im Jahr 2008 die Exporttätigkeit junger High-Tech-Unternehmen thematisiert wurde. Kernpunkt der diesjährigen Studie ist zu klären, wie die aktuelle globale Wirtschaftskrise junge High-Tech-Unternehmen trifft
Parude Bú’O’ fiesta de la pubertad’ entre los emberá: investigación acción participante en etnolingüística
spa: A través del análisis y la traducción hecha por el lingüista Aguirre Licht de una canción antigua de la comunidad, que habla sobre la fiesta de
pubertad de la niña emberá, y con la participación activa de indígenas emberá, busca mostrar, en primer lugar, algunos de los problemas que
se presentan cuando se traducen narraciones vernáculas de lengua indígena a la lengua nacional; en segundo lugar, señalar las ventajas del
análisis de contenido para la traducción de textos literarios cuando hay una participación activa de los indígenas y, por último, explicar
algunos de los aportes de la etnolingüística en la recuperación, revitalización y proyección cultural de minorías étnicas que aún conservan su
lengua y cuyos protagonistas son, en primera instancia, sus hablante
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Cas9+ conditionally-immortalized macrophages as a tool for bacterial pathogenesis and beyond.
Macrophages play critical roles in immunity, development, tissue repair, and cancer, but studies of their function have been hampered by poorly-differentiated tumor cell lines and genetically-intractable primary cells. Here we report a facile system for genome editing in non-transformed macrophages by differentiating ER-Hoxb8 myeloid progenitors from Cas9-expressing transgenic mice. These conditionally immortalized macrophages (CIMs) retain characteristics of primary macrophages derived from the bone marrow yet allow for easy genetic manipulation and a virtually unlimited supply of cells. We demonstrate the utility of this system for dissection of host genetics during intracellular bacterial infection using two important human pathogens: Listeria monocytogenes and Mycobacterium tuberculosis
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