33,546 research outputs found
Antimicrobial peptides and complement in neonatal hypoxia-ischemia induced brain damage
Hypoxic-ischemic encephalopathy (HIE) is a clinical condition in the neonate, resulting from oxygen deprivation around the time of birth. HIE affects 1-5/1000 live births worldwide and is associated with the development of neurological deficits, including cerebral palsy, epilepsy, and cognitive disabilities. Even though the brain is considered as an immune-privileged site, it has innate and adaptive immune response and can produce complement (C) components and antimicrobial peptides (AMPs). Dysregulation of cerebral expression of AMPs and C can exacerbate or ameliorate the inflammatory response within the brain. Brain ischemia triggers a prolonged inflammatory response affecting the progression of injury and secondary energy failure and involves both innate and adaptive immune systems, including immune-competent and non-competent cells. Following injury to the central nervous system (CNS), including neonatal hypoxia-ischemia (HI), resident microglia, and astroglia are the main cells providing immune defense to the brain in a stimulus-dependent manner. They can express and secrete pro-inflammatory cytokines and therefore trigger prolonged inflammation, resulting in neurodegeneration. Microglial cells express and release a wide range of inflammation-associated molecules including several components of the complement system. Complement activation following neonatal HI injury has been reported to contribute to neurodegeneration. Astrocytes can significantly affect the immune response of the CNS under pathological conditions through production and release of pro-inflammatory cytokines and immunomodulatory AMPs. Astrocytes express β-defensins, which can chemoattract and promote maturation of dendritic cells (DC), and can also limit inflammation by controlling the viability of these same DC. This review will focus on the balance of complement components and AMPs within the CNS following neonatal HI injury and the effect of that balance on the subsequent brain damage
2-Diazoacetoacetic acid, an efficient and convenient reagent for the synthesis of alpha-diazo-beta-ketoesters
The formation of various alpha-diazo acetoacetic esters can be obtained in a single transformation with good to excellent yields using readily available 2-diazoacetoacetic acid
Fundamental Oscillation Periods of the Interlayer Exchange Coupling beyond the RKKY Approximation
A general method for obtaining the oscillation periods of the interlayer
exchange coupling is presented. It is shown that it is possible for the
coupling to oscillate with additional periods beyond the ones predicted by the
RKKY theory. The relation between the oscillation periods and the spacer Fermi
surface is clarified, showing that non-RKKY periods do not bear a direct
correspondence with the Fermi surface. The interesting case of a FCC(110)
structure is investigated, unmistakably proving the existence and relevance of
non-RKKY oscillations. The general conditions for the occurrence of non-RKKY
oscillations are also presented.Comment: 34 pages, 10 figures ; to appear in J. Phys.: Condens. Mat
Exchange coupling between magnetic layers across non-magnetic superlattices
The oscillation periods of the interlayer exchange coupling are investigated
when two magnetic layers are separated by a metallic superlattice of two
distinct non-magnetic materials. In spite of the conventional behaviour of the
coupling as a function of the spacer thickness, new periods arise when the
coupling is looked upon as a function of the number of cells of the
superlattice. The new periodicity results from the deformation of the
corresponding Fermi surface, which is explicitly related to a few controllable
parameters, allowing the oscillation periods to be tuned.Comment: 13 pages; 5 figures; To appear in J. Phys.: Cond. Matte
Preserving the validity of the Two-Higgs Doublet Model up to the Planck scale
We examine the constraints on the two Higgs doublet model (2HDM) due to the
stability of the scalar potential and absence of Landau poles at energy scales
below the Planck scale. We employ the most general 2HDM that incorporates an
approximately Standard Model (SM) Higgs boson with a flavor aligned Yukawa
sector to eliminate potential tree-level Higgs-mediated flavor changing neutral
currents. Using basis independent techniques, we exhibit robust regimes of the
2HDM parameter space with a 125 GeV SM-like Higgs boson that is stable and
perturbative up to the Planck scale. Implications for the heavy scalar spectrum
are exhibited.Comment: 36 pages, 4 figures, 4 tables (Version 3: typographical error in eq.
(A.28) corrected
Nontopological self-dual Maxwell-Higgs vortices
We study the existence of self-dual nontopological vortices in generalized
Maxwell-Higgs models recently introduced in Ref. \cite{gv}. Our investigation
is explicitly illustrated by choosing a sixth-order self-interaction potential,
which is the simplest one allowing the existence of nontopological structures.
We specify some Maxwell-Higgs models yielding BPS nontopological vortices
having energy proportional to the magnetic flux, , and whose profiles
are numerically achieved. Particularly, we investigate the way the new
solutions approach the boundary values, from which we verify their
nontopological behavior. Finally, we depict the profiles numerically found,
highlighting the main features they present.Comment: 6 pages, 4 figure
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