Satellite orbit considerations for a global change technology architecture trade study

A study was conducted to determine satellite orbits for earth observation missions aimed at obtaining data for assessing data global climate change. A multisatellite system is required to meet the scientific requirements for temporal coverage over the globe. The best system consists of four sun-synchronous satellites equally spaced in local time of equatorial crossing. This system can obtain data every three hours for all regions. Several other satellite systems consisting of combinations of sun-synchronous orbits and either the Space Station Freedom or a mid-altitude equatorial satellite can provide three to six hour temporal coverage, which is sufficient for measuring many of the parameters required for the global change monitoring mission. Geosynchronous satellites are required to study atmospheric and surface processes involving variations on the order of a few minutes to an hour. One or two geosynchronous satellites can be relocated in longitude to study processes over selected regions of earth

Temporal variation in sex allocation in the mealybug <em>Planococcus citri</em>:Adaptation, constraint, or both?

Sex ratio theory has been very successful in predicting under which circumstances parents should bias their investment towards a particular offspring sex. However, most examples of adaptive sex ratio bias come from species with well-defined mating systems and sex determining mechanisms, while in many other groups there is still an on-going debate about the adaptive nature of sex allocation. Here we study the sex allocation in the mealybug Planococcus citri, a species in which it is currently unclear how females adjust their sex ratio, even though experiments have shown support for facultative sex ratio adjustment. Previous work has shown that the sex ratio females produce changes over the oviposition period, with males being overproduced early and late in the laying sequence. Here we investigate this complex pattern further, examining both the robustness of the pattern and possible explanations for it. We first show that this sex allocation behaviour is indeed consistent across lines from three geographical regions. Second, we test whether females produce sons first in order to synchronize reproductive maturation of her offspring, although our data provide little evidence for this adaptive explanation. Finally we test the age at which females are able to mate successfully and show that females are able to mate and store sperm before adult eclosion. Whilst early-male production may still function in promoting protandry in mealybugs, we discuss whether mechanistic constraints limit how female allocate sex across their lifetime

Heterochromatin and the molecular mechanisms of 'parent-of-origin' effects in animals.

Twenty five years ago it was proposed that conserved components of constitutive heterochromatin assemble heterochromatinlike complexes in euchromatin and this could provide a general mechanism for regulating heritable (cell-to-cell) changes in gene expressibility. As a special case, differences in the assembly of heterochromatin-like complexes on homologous chromosomes might also regulate the parent-of-origin-dependent gene expression observed in placental mammals. Here, the progress made in the intervening period with emphasis on the role of heterochromatin and heterochromatin-like complexes in parent-of-origin effects in animals is reviewed

NACA Technical Notes

Report presenting flight testing of a fin-stabilized parabolic body of revolution (NACA RM-10) as a rocket-propelled model. Boundary-layer static-temperature profiles were determined around the body and from Mach number profiles obtained from a total-pressure rake. Results regarding boundary-layer profiles, skin-friction coefficients, and heat-transfer coefficients are provided

Chitosan in sparkling wines produced by the traditional method: influence of its presence during the \u201cPrise de Mousse\u201d.

Chitosan, a natural polysaccharide prepared from fungal origin, has been quite recently admitted in winemaking as clarifying, antimicrobic and contaminant reducing agent [1]. However, other features, such as antiradical and antibrowning activity have been recognized to this polymer [2]. Due to these latter characteristics, chitosan has been proposed as potential sulphite substitute. In the production of sparkling wines obtained following the traditional method, the second fermentation (Prise de Mousse) is a crucial step that needs to be carried out avoiding oxidation and/or sluggish or unwanted fermentations. Chitosan could have the potential to fulfils both the functions but, information about the impact of its presence during the fermentation are still notably scarce. In this work we tried to deepen such a subject by comparing the chemical and sensory characteristics of sparkling wines obtained with i) the presence of chitosan (20 g/HL) or ii) sulfure dioxide (60 mg/L), during the \u201cprise de mousse\u201d. Fixed, phenolic and volatile compounds demonstrated significant differences due to the presence of the two preservatives. Chitosan reduced the browning of wines without significantly modifying the fermentation kinetic. Sensory analysis further confirmed the differences emerged from volatile composition, highlighting that chitosan may positively impact on the final products while permitting to reduce the amount of sulfur dioxide used during winemaking