1,629 research outputs found
Working wetlands: classifying wetland potential for agriculture
Wetlands / Ecology / Natural resources / Social aspects / Case studies / Zanzibar / Tanzania / Zimbabwe / Swaziland
Formation of primordial black holes from non-Gaussian perturbations produced in a waterfall transition
We consider the process of primordial black hole (PBH) formation originated
from primordial curvature perturbations produced during waterfall transition
(with tachyonic instability), at the end of hybrid inflation. It is known that
in such inflation models, rather large values of curvature perturbation
amplitudes can be reached, which can potentially cause a significant PBH
production in the early Universe. The probability distributions of density
perturbation amplitudes in this case can be strongly non-Gaussian, which
requires a special treatment. We calculated PBH abundances and PBH mass spectra
for the model, and analyzed their dependence on model parameters. We obtained
the constraints on the parameters of the inflationary potential, using the
available limits on .Comment: v2: 11 pages, 4 figures. Several comments and references added.
Version accepted by Phys. Rev.
Wave generation through the interaction of a mode-2 internal solitary wave and a broad, isolated ridge
Parallel gene synthesis in a microfluidic device
The ability to synthesize custom de novo DNA constructs rapidly, accurately and inexpensively is highly desired by researchers, as synthetic genes and longer DNA constructs are enabling to numerous powerful applications in both traditional molecular biology and the emerging field of synthetic biology. However, the current cost of de novo synthesis—driven largely by reagent and handling costs—is a significant barrier to the widespread availability of such technology. In this work, we demonstrate, to our knowledge, the first gene synthesis in a microfluidic environment. The use of microfluidic technology greatly reduces reaction volumes and the corresponding reagent and handling costs. Additionally, microfluidic technology enables large numbers of complex reactions to be performed in parallel. Here, we report the fabrication of a multi-chamber microfluidic device and its use in carrying out the syntheses of several DNA constructs. Genes up to 1 kb in length were synthesized in parallel at minute starting oligonucleotide concentrations (10–25 nM) in four 500 nl reactors. Such volumes are one to two orders of magnitude lower than those utilized in conventional gene synthesis. The identity of all target genes was verified by sequencing, and the resultant error rate was determined to be 1 per 560 bases.Massachusetts Institute of Technology. Center for Bits and AtomsNational Science Foundation (U.S.) (CBA grant CCR-0122419
Inhibiting HIV-1 Entry Discovery of D-Peptide Inhibitors that Target the gp41 Coiled-Coil Pocket
AbstractThe HIV-1 gp41 protein promotes viral entry by mediating the fusion of viral and cellular membranes. A prominent pocket on the surface of a central trimeric coiled coil within gp41 was previously identified as a potential target for drugs that inhibit HIV-1 entry. We designed a peptide, IQN17, which properly presents this pocket. Utilizing IQN17 and mirror-image phage display, we identified cyclic, D-peptide inhibitors of HIV-1 infection that share a sequence motif. A 1.5 Å cocrystal structure of IQN17 in complex with a D-peptide, and NMR studies, show that conserved residues of these inhibitors make intimate contact with the gp41 pocket. Our studies validate the pocket per se as a target for drug development. IQN17 and these D-peptide inhibitors are likely to be useful for development and identification of a new class of orally bioavailable anti-HIV drugs
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