Morphological evidence for geologically young thaw of ice on Mars: a review of recent studies using high-resolution imaging data

Liquid water is generally only meta-stable on Mars today; it quickly freezes, evaporates or boils in the cold, dry, thin atmosphere (surface pressure is about 200 times lower than on Earth). Nevertheless, there is morphological evidence that surface water was extensive in more ancient times, including the Noachian Epoch (~4.1 Ga to ~3.7 Ga bp), when large lakes existed and river-like channel networks were incised, and early in the Hesperian Epoch (~3.7 Ga to ~2.9 Ga bp), when megafloods carved enormous channels and smaller fluvial networks developed in association with crater-lakes. However, by the Amazonian Epoch (~3.0 Ga to present), most surface morphogenesis associated with liquid water had ceased, with long periods of water sequestration as ice in the near-surface and polar regions. However, inferences from observations using imaging data with sub-metre pixel sizes indicate that periglacial landscapes, involving morphogenesis associated with ground-ice and/or surface-ice thaw and liquid flows, has been active within the last few million years. In this paper, three such landform assemblages are described: a high-latitude assemblage comprising features interpreted to be sorted clastic stripes, circles and polygons, non-sorted polygonally patterned ground, fluvial gullies, and solifluction lobes; a mid-latitude assemblage comprising gullies, patterned ground, debris-covered glaciers and hillslope stripes; and an equatorial assemblage of linked basins, patterned ground, possible pingos, and channel-and-scarp features interpreted to be retrogressive thaw-slumps. Hypotheses to explain these observations are explored, including recent climate change, and hydrated minerals in the regolith ‘thawing’ to form liquid brines at very low temperatures. The use of terrestrial analogue field sites is also discussed

Protective Mechanisms for Depression among Racial/Ethnic Minority Youth: Empirical Findings, Issues, and Recommendations

We (1) review empirical studies that report findings regarding putative protective mechanisms when exposed to risk of depression in African American and Hispanic adolescents; (2) identify key protective mechanisms for different risk contexts that garner empirical support; (3) synthesize the mechanisms identified as protective against depression among racial/ethnic minority adolescents; and (4) discuss improved methods for advancing understanding of resilience against depression in minority youth. The studies were selected from PsycINFO searches that met the following inclusion criteria: participants between 12 and 21 years of age, inclusions of racial/ethnic minority members, examining protection through an interaction with a risk factor, and outcome measures of depression, depressed mood, or depressive symptomatology. We found 39 eligible studies; 13 of which included multiple racial/ethnic groups. The following were supported as protective mechanisms, at least preliminarily, for at least one racial/ethnic group and in at least one risk context: employment, extracurricular activities, father–adolescent closeness, familism, maternal support, attending predominately minority schools, neighborhood composition, non-parent support, parental inductive reasoning, religiosity, self-esteem, social activities, and positive early teacher relationships. To investigate protective mechanisms more comprehensively and accurately across individual, social, and community levels of influence, we recommend incorporating multilevel modeling or multilevel growth curve analyses and large diverse samples

Percutaneous pelvic osteotomy and intertrochanteric varus shortening osteotomy in nonambulatory GMFCS level IV and V cerebral palsy patients

This study evaluated the outcome of severe cerebral palsy patients (Gross Motor Function Classification System level IV and V) treated by simultaneous percutaneous pelvic osteotomy and intertrochanteric varus shortening osteotomy for hip subluxation or dislocation between 2002 and 2011. Twenty-four patients (30 hips) with an average age of 9.4 years (5-16.5) were reviewed at a mean follow-up of 35.9 months (6-96). Percutaneous pelvic osteotomy lasted on average 30 min/patient per side (25-40) and was always performed through a skin incision of 2-3 cm. The migration percentage and acetabular angle were assessed on plain radiographs. The mean Reimers' migration percentage improved from 67.1% (42-100) preoperatively to 7.7% (0-70) at the last follow-up and the mean acetabular angle improved from 31.8° (22-48) to 15.7° (5-27). Five patients presented complications: one redislocation, one bone graft dislodgement, and three with avascular necrosis of the femoral head. This study should be considered as a pilot study. These results indicate that this combined approach is an effective, reliable, and minimally invasive alternative method for the treatment of spastic dislocated hips in severe cerebral palsy patients with an outcome similar to standard techniques reported in the literature