ASTROPHYSICS. Atom-interferometry constraints on dark energy.

If dark energy, which drives the accelerated expansion of the universe, consists of a light scalar field, it might be detectable as a "fifth force" between normal-matter objects, in potential conflict with precision tests of gravity. Chameleon fields and other theories with screening mechanisms, however, can evade these tests by suppressing the forces in regions of high density, such as the laboratory. Using a cesium matter-wave interferometer near a spherical mass in an ultrahigh-vacuum chamber, we reduced the screening mechanism by probing the field with individual atoms rather than with bulk matter. We thereby constrained a wide class of dark energy theories, including a range of chameleon and other theories that reproduce the observed cosmic acceleration.

Effects of brief stress exposure during early postnatal development in Balb/CByJ mice: II. Altered cortical morphology.

Early life experience can significantly determine later mental health status and cognitive function. Neonatal stress, in particular, has been linked to the etiology of mental health disorders as divergent as mood disorder, schizophrenia, and autism. Our study uses a Balb/CByJ mouse model to test the hypothesis, that neonatal stress will alter development and subsequent environmental modulation of neocortex. Using a split litter design, we generated stressed mice (STR) and within litter controls (LMC) along with age-matched, untreated animals (AMC), to serve as across litter controls. Short, daily exposure to a psychosocial/physical stressor, during the first week of life, resulted by adulthood in significant changes in neocortical thickness and architecture, which were further modulated by exposure to behavioral testing. Surprisingly, cortical size in LMC mice was also affected. These observations were compared to the effects of environmental enrichment in the same mouse strain. Our data indicate that LMC and STR males share with environmentally enriched males, an increase in thickness in infra-granular cortical layers, while STR also display a stress selective decrease in supragranular layers, in response to behavioral training as adults.

Biological and biomechanical assessment of a long-term bioresorbable silk-derived surgical mesh in an abdominal body wall defect model.

BACKGROUND: The patient's own repair of a body wall defect would be enhanced by a mechanically robust, physically tailorable, bioresorbable mesh scaffold that: (1) supports rapid host tissue ingrowth and development, while (2) reducing the complications associated with permanent synthetic and allogenic and xenogenic biological implants. METHODS: A full-thickness 1-cm-diameter abdominal wall defect was made in 36 Sprague-Dawley rats, which were divided according to the implant material used; SeriFascia surgical mesh (test) and Mersilene mesh (control). Histopathology, histomorphometry, tissue ingrowth, and biomechanical analysis were performed 30 and 94 days post-implantation. RESULTS: The biological response to the test and control groups were equivalent, with significantly greater tissue ingrowth observed in the test group (P < 0.05). A significant 33 and 57% reduction of test device mass was observed at 30 and 94 days, respectively. The ultimate burst load for the test group defect decreased after 30 days to the initial strength of the control mesh and remained constant for the duration of the study. CONCLUSION: SeriFascia surgical mesh initially bioresorbed at an ideal rate that supported the transfer of load-bearing responsibility to developing host repair tissue. The results indicate the development of functional native tissue that could potentially minimize any long-term complication associated with presently available mesh implants.