Quantum slow-roll and quantum fast-roll inflationary initial conditions: CMB quadrupole suppression and further effects on the low CMB multipoles

Quantum fast-roll initial conditions for the inflaton which are different from the classical fast-roll conditions and from the quantum slow-roll conditions can lead to inflation that last long enough. These quantum fast-roll initial conditions for the inflaton allow for kinetic energies of the same order of the potential energies and nonperturbative inflaton modes with nonzero wavenumbers. Their evolution starts with a transitory epoch where the redshift due to the expansion succeeds to assemble the quantum excited modes of the inflaton in a homogeneous (zero mode) condensate, and the large value of the Hubble parameter succeeds to overdamp the fast-roll of the redshifted inflaton modes. After this transitory stage the effective classical slow-roll epoch is reached. Most of the efolds are produced during the slow-roll epoch and we recover the classical slow-roll results for the scalar and tensor metric perturbations plus corrections. These corrections are important, both for scalar and for tensor perturbations, if scales which are horizon-size today exited the horizon by the end of the transitory stage and as a consequence the lower CMB multipoles get suppressed (fast-roll) or enhanced (precondensate). These two types of corrections can compete and combine in a scale dependent manner. They arise as natural consequences of the quantum nonperturbative inflaton dynamics, and provide a consistent and contrastable model for the origin of the suppression of the quadrupole and for other departures of the low CMB multipoles from the slow-roll inflation-LambdaCMB model which are to be contrasted to the TE and EE multipoles and to the forthcoming and future CMB data.Comment: LaTeX, 14 pages, 3 figure

Two component dark matter

We explain the PAMELA positron excess and the PPB-BETS/ATIC e+ + e- data using a simple two component dark matter model (2DM). The two particle species in the dark matter sector are assumed to be in thermal equilibrium in the early universe. While one particle is stable and is the present day dark matter, the second one is metastable and decays after the universe is 10^-8 s old. In this model it is simple to accommodate the large boost factors required to explain the PAMELA positron excess without the need for large spikes in the local dark matter density. We provide the constraints on the parameters of the model and comment on possible signals at future colliders.Comment: 6 pages, 2 figures, discussion clarified and extende

Structure Formation, Melting, and the Optical Properties of Gold/DNA Nanocomposites: Effects of Relaxation Time

We present a model for structure formation, melting, and optical properties of gold/DNA nanocomposites. These composites consist of a collection of gold nanoparticles (of radius 50 nm or less) which are bound together by links made up of DNA strands. In our structural model, the nanocomposite forms from a series of Monte Carlo steps, each involving reaction-limited cluster-cluster aggregation (RLCA) followed by dehybridization of the DNA links. These links form with a probability $p_{eff}$ which depends on temperature and particle radius $a$. The final structure depends on the number of monomers (i. e. gold nanoparticles) $N_m$, $T$, and the relaxation time. At low temperature, the model results in an RLCA cluster. But after a long enough relaxation time, the nanocomposite reduces to a compact, non-fractal cluster. We calculate the optical properties of the resulting aggregates using the Discrete Dipole Approximation. Despite the restructuring, the melting transition (as seen in the extinction coefficient at wavelength 520 nm) remains sharp, and the melting temperature $T_M$ increases with increasing $a$ as found in our previous percolation model. However, restructuring increases the corresponding link fraction at melting to a value well above the percolation threshold. Our calculated extinction cross section agrees qualitatively with experiments on gold/DNA composites. It also shows a characteristic ``rebound effect,'' resulting from incomplete relaxation, which has also been seen in some experiments. We discuss briefly how our results relate to a possible sol-gel transition in these aggregates.Comment: 12 pages, 10 figure

Angiotensin II induction of PDGF-C expression is mediated by AT1 receptor-dependent Egr-1 transactivation

Platelet-derived growth factors are a family of mitogens and chemoattractants comprising of four ligand genes (A-, B-, C-, D-chains) implicated in many physiologic and pathophysiologic processes, including atherosclerosis, fibrosis and tumorigenesis. Our understanding of the molecular mechanisms, which regulate PDGF-C transcription remains incomplete. Transient transfection analysis, conventional and quantitative real-time PCR revealed the induction of PDGF-C transcription and mRNA expression in smooth muscle cells (SMCs) exposed to the peptide hormone angiotensin (ATII), which induces Egr-1. Occupancy of a G + C-rich element in the proximal region of the PDGF-C promoter was unaffected by ATII. Instead we discovered, using both nuclear extracts and recombinant proteins with EMSA and ChIP analyses, the existence of a second Egr-1-binding element located 500 bp upstream. ATII induction of PDGF-C transcription is mediated by the angiotensin type 1 receptor (AT1R) and Egr-1 activation through this upstream element. DNAzyme ED5 targeting Egr-1 blocked ATII-inducible PDGF-C expression. Moreover, increased PDGF-C expression after exposure to ATII depends upon the differentiation state of the SMCs. This study demonstrates the existence of this novel ATII-AT1R-Egr-1-PDGF-C axis in SMCs of neonatal origin, but not in adult SMCs, where ATII induces Egr-1 but not PDGF-C

Intrinsic Morphology of Ultra-diffuse Galaxies

With the published data of apparent axis ratios for 1109 ultra-diffuse galaxies (UDGs) located in 17 low-redshift (z~ 0.020 - 0.063) galaxy clusters and 84 UDGs in 2 intermediate-redshift (z~ 0.308 - 0.348) clusters, we take advantage of a Markov Chain Monte Carlo approach and assume a ubiquitous triaxial model to investigate the intrinsic morphologies of UDGs. In contrast to the conclusion of Burkert (2017), i.e., the underlying shapes of UDGs are purely prolate ($C=B<A$), we find that the data favor the oblate-triaxial models ($C<B\lesssim A$) over the nearly prolate ones. We also find that the intrinsic morphologies of UDGs are relevant to their stellar masses/luminosities, environments, and redshifts. First, for the low-redshift UDGs in the same environment, the more-luminous ones are always thicker than the less-luminous counterparts, possibly due to the more voilent internal supernovae feedback or external tidal interactions for the progenitors of the more-luminous UDGs. The UDG thickness dependence on luminosity is distinct from that of the typical quiescent dwarf ellipticals (dEs) and dwarf spheroidals (dSphs) in the local clusters and groups, but resembles that of massive galaxies; in this sense, UDGs may not be simply treated as an extension of the dE/dSph class with similar evolutionary histories. Second, for the low-redshift UDGs within the same luminosity range, the ones with smaller cluster-centric distances are more puffed-up, probably attributed to tidal interactions. Finally, the intermediate-redshift cluster UDGs are more flattened, which plausibly suggests a `disky' origin for high-redshift, initial UDGs.Comment: Accepted for publication in ApJ; new versio

The potential of hematopoietic growth factors for treatment of Alzheimer's disease: a mini-review

There are no effective interventions that significantly forestall or reverse neurodegeneration and cognitive decline in Alzheimer's disease. In the past decade, the generation of new neurons has been recognized to continue throughout adult life in the brain's neurogenic zones. A major challenge has been to find ways to harness the potential of the brain's own neural stem cells to repair or replace injured and dying neurons. The administration of hematopoietic growth factors or cytokines has been shown to promote brain repair by a number of mechanisms, including increased neurogenesis, anti-apoptosis and increased mobilization of bone marrow-derived microglia into brain. In this light, cytokine treatments may provide a new therapeutic approach for many brain disorders, including neurodegenerative diseases like Alzheimer's disease. In addition, neuronal hematopoietic growth factor receptors provide novel targets for the discovery of peptide-mimetic drugs that can forestall or reverse the pathological progression of Alzheimer's disease