1,954 research outputs found
Evolution of the L1 halo family in the radial solar sail CRTBP
We present a detailed investigation of the dramatic changes that occur in the
halo family when radiation pressure is introduced into the
Sun-Earth circular restricted three-body problem (CRTBP). This
photo-gravitational CRTBP can be used to model the motion of a solar sail
orientated perpendicular to the Sun-line. The problem is then parameterized by
the sail lightness number, the ratio of solar radiation pressure acceleration
to solar gravitational acceleration. Using boundary-value problem numerical
continuation methods and the AUTO software package (Doedel et al. 1991) the
families can be fully mapped out as the parameter is increased.
Interestingly, the emergence of a branch point in the retrograde satellite
family around the Earth at acts to split the halo family
into two new families. As radiation pressure is further increased one of these
new families subsequently merges with another non-planar family at
, resulting in a third new family. The linear stability of
the families changes rapidly at low values of , with several small
regions of neutral stability appearing and disappearing. By using existing
methods within AUTO to continue branch points and period-doubling bifurcations,
and deriving a new boundary-value problem formulation to continue the folds and
Krein collisions, we track bifurcations and changes in the linear stability of
the families in the parameter and provide a comprehensive overview of
the halo family in the presence of radiation pressure. The results demonstrate
that even at small values of there is significant difference to the
classical CRTBP, providing opportunity for novel solar sail trajectories.
Further, we also find that the branch points between families in the solar sail
CRTBP provide a simple means of generating certain families in the classical
case.Comment: 31 pages, 17 figures, accepted by Celestial Mechanics and Dynamical
Astronom
Do colonization by dark septate endophytes and elevated temperature affect pathogenicity of oomycetes?
Phialocephala subalpina is one of the most frequent dark septate root endophytes in tree roots but its function in forest ecosystems is largely unknown. A full-factorial infection experiment was performed, using six P. subalpina isolates, two pathogenic oomycetes (Phytophthora plurivora [syn. Phytophthora citricola s.l.] and Elongisporangium undulatum [syn. Pythium undulatum]) and two temperature regimes (17.9 and 21.6 °C) to examine the ability of P. subalpina to protect Norway spruce seedlings against root pathogens. Seedling survival, disease intensity and seedling growth were affected by P. subalpina genotype, temperature and pathogen species. Some P. subalpina isolates effectively reduced mortality and disease intensity caused by the two pathogens. Elevated temperature adversely affected seedling growth but did not aggravate the effect of the pathogens. Elongisporangium undulatum but not P. plurivora significantly reduced plant growth. Colonization density of P. subalpina measured by quantitative PCR was not affected by temperature or the presence of the pathogens. In conclusion, P. subalpina confers an indirect benefit to its host and might therefore be tolerated in natural ecosystems, despite negative effects on plant health and plant growt
The complete life cycle of Petrakia echinata
The teleomorph of Petrakia echinata (Peglion) Syd. & P. Syd. on leaves of Acer pseudoplatanus is described based on field collections, culture studies and ITS sequencing and was assigned to the genus Mycodidymella C.Z. Wei, Y. Harada & K. Katumoto. In addition, a Mycopappus anamorph and a presumed spermatial Phoma stage were observed and conspecificity with P. echinata was confirmed by culture morphology and ITS sequencing. The phylogenetic relationships between the Mycodidymella teleomorph of P. echinata and related taxa were studied using LSU nDNA sequences. The fungus causes brown spots on the leaves of the host plant, known as "Petrakia leaf blotch of sycamore maple
Administrative structures: Options for achieving success in perioperative medicine.
Without the appropriate administrative structure, even well-thought-out strategic plans or detailed process improvement initiatives will fail. Developing a strong foundation for governance and leadership is a critical element of any high-functioning organization, and it applies just as well in the perioperative setting. Yet, perioperative patient care teams and operating room (OR) management structures can be very complex, due to relationships both within the OR and between the OR and other departments. Frequently, reliable management of the perioperative process is lacking. We aim to provide an overview of the structural and elemental components and roles of perioperative management teams, as well as the administrative structure that guides them, since effective perioperative care teams and OR leaders are of paramount importance for any successful hospital
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