25 research outputs found
An Inflationary Model in String Theory
We construct a model of inflation in string theory after carefully taking
into account moduli stabilization. The setting is a warped compactification of
Type IIB string theory in the presence of D3 and anti-D3-branes. The inflaton
is the position of a D3-brane in the internal space. By suitably adjusting
fluxes and the location of symmetrically placed anti-D3-branes, we show that at
a point of enhanced symmetry, the inflaton potential V can have a broad
maximum, satisfying the condition V''/V << 1 in Planck units. On starting close
to the top of this potential the slow-roll conditions can be met. Observational
constraints impose significant restrictions. As a first pass we show that these
can be satisfied and determine the important scales in the compactification to
within an order of magnitude. One robust feature is that the scale of inflation
is low, H = O(10^{10}) GeV. Removing the observational constraints makes it
much easier to construct a slow-roll inflationary model. Generalizations and
consequences including the possibility of eternal inflation are also discussed.
A more careful study, including explicit constructions of the model in string
theory, is left for the future.Comment: 27 pages, LaTeX, 1 eps figure. v2: references adde
Genetic analysis reveals that PAX6 is required for normal transcription of pancreatic hormone genes and islet development
We present genetic and biochemical evidence that PAX6 is a key regulator of pancreatic islet hormone gene transcription and is required for normal islet development. In embryos homozygous for a mutant allele of the Pax6 gene, Small eye (Sey(Neu)), the numbers of all four types of endocrine cells in the pancreas are decreased significantly, and islet morphology is abnormal. In the remaining islet cells, hormone production, particularly glucagon production, is markedly reduced because of decreased gene transcription. These effects appear to result from a lack of PAX6 protein in the mutant embryos. Biochemical studies identify wild-type PAX6 protein as the transcription factor that binds to a common element in the glucagon, insulin, and somatostatin promoters, and show that PAX6 transactivates the glucagon and insulin promoters
The effects of Spirulina on anemia and immune function in senior citizens
Anemia and immunological dysfunction (i.e. immunosenescence) are commonly found in older subjects and nutritional approaches are sought to counteract these phenomena. Spirulina is a filamentous and multicellular bule-green alga capable of reducing inflammation and also manifesting antioxidant effects. We hypothesized that Spirulina may ameliorate anemia and immunosenescence in senior citizens with a history of anemia. We enrolled 40 volunteers of both sexes with an age of 50 years or older who had no history of major chronic diseases. Participants took a Spirulina supplementation for 12 weeks and were administered comprehensive dietary questionnaires to determine their nutritional regimen during the study. Complete cell count (CCC) and indoleamine 2,3-dioxygenase (IDO) enzyme activity, as a sign of immune function, were determined at baseline and weeks 6 and 12 of supplementation. Thirty study participants completed the entire study and the data obtained were analyzed. Over the 12-week study period, there was a steady increase in average values of mean corpuscular hemoglobin in subjects of both sexes. In addition, mean corpuscular volume and mean corpuscular hemoglobin concentration also increased in male participants. Older women appeared to benefit more rapidly from Spirulina supplements. Similarly, the majority of subjects manifested increased IDO activity and white blood cell count at 6 and 12 weeks of Spirulina supplementation. Spirulina may ameliorate anemia and immunosenescence in older subjects. We encourage large human studies to determine whether this safe supplement could prove beneficial in randomized clinical trials