RESUMO
The LEXI and SMILE missions will provide soft X-ray images of the Earth's magnetosheath and cusps after their anticipated launch in 2023 and 2024, respectively. The IBEX mission showed the potential of an Energetic Neutral Atom (ENA) instrument to image dayside magnetosheath and cusps, albeit over the long hours required to raster an image with a single pixel imager. Thus, it is timely to discuss the two imaging techniques and relevant science topics. We simulate soft X-ray and low-ENA images that might be observed by a virtual spacecraft during two interesting solar wind scenarios: a southward turning of the interplanetary magnetic field and a sudden enhancement of the solar wind dynamic pressure. We employ the OpenGGCM global magnetohydrodynamics model and a simple exospheric neutral density model for these calculations. Both the magnetosheath and the cusps generate strong soft X-rays and ENA signals that can be used to extract the locations and motions of the bow shock and magnetopause. Magnetopause erosion corresponds closely to the enhancement of dayside reconnection rate obtained from the OpenGGCM model, indicating that images can be used to understand global-scale magnetopause reconnection. When dayside imagers are installed with high-ENA inner-magnetosphere and FUV/UV aurora imagers, we can trace the solar wind energy flow from the bow shock to the magnetosphere and then to the ionosphere in a self-standing manner without relying upon other observatories. Soft X-ray and/or ENA imagers can also unveil the dayside exosphere density structure and its response to space weather.
RESUMO
Omnivorous mammals are able to adaptively modulate rates of intestinal nutrient transport to match changes in diet. Because adaptive responses during suckling, when dietary composition is relatively constant, have not been adequately determined, we measured in vitro sugar and amino acid uptake [nmol/(mg tissue.min)] in suckling pigs fed milk replacers with either lactose (LAC) or a 60:40 mixture of maltodextrin and sucrose (MDS). The MDS-fed pigs initially grew slower, but had intestinal dimensions similar to those of LAC-fed siblings when normalized to body weight. Carrier-mediated uptake for three monosaccharides (glucose, galactose, fructose) did not differ between LAC- and MDS-fed pigs at 5, 10, 15 and 20 d of age. Interdiet differences in rates of leucine and proline uptake, despite identical types and concentration of protein in both milk replacers, are indicative of non-specific responses to diet during suckling. Uptake capacities (grams of monosaccharide absorbed per 24 h) never exceeded estimates of monosaccharide intake by more than fourfold and were less than aldohexose intake during early suckling. Our results indicate 1) age-related changes in rates of nutrient uptake are genetically programmed and little influenced by diet; 2) any responses to diet are nonspecific and likely involve a shift in the timing of the genetic program; and 3) at birth and throughout suckling, pigs are capable of absorbing limited quantities of alternative nutrients.