2,937 research outputs found
Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation
We report experimentally and theoretically the behavior of freestanding
graphene subject to bombardment of energetic ions, investigating the ability of
large-scale patterning of freestanding graphene with nanometer sized features
by focused ion beam technology. A precise control over the He+ and Ga+
irradiation offered by focused ion beam techniques enables to investigate the
interaction of the energetic particles and graphene suspended with no support
and allows determining sputter yields of the 2D lattice. We find strong
dependency of the 2D sputter yield on the species and kinetic energy of the
incident ion beams. Freestanding graphene shows material semi-transparency to
He+ at high energies (10-30 keV) allowing the passage of >97% He+ particles
without creating destructive lattice vacancy. Large Ga+ ions (5-30 keV), in
contrast, collide far more often with the graphene lattice to impart
significantly higher sputter yield of ~50%. Binary collision theory applied to
monolayer and few-layer graphene can successfully elucidate this collision
mechanism, in great agreement with experiments. Raman spectroscopy analysis
corroborates the passage of a large fraction of He+ ions across graphene
without much damaging the lattice whereas several colliding ions create single
vacancy defects. Physical understanding of the interaction between energetic
particles and suspended graphene can practically lead to reproducible and
efficient pattern generation of unprecedentedly small features on 2D materials
by design, manifested by our perforation of sub-5-nm pore arrays. This
capability of nanometer scale precision patterning of freestanding 2D lattices
shows practical applicability of the focused ion beam technology to 2D material
processing for device fabrication and integration.Comment: 31 pages of main text (with 4 figures) plus 4 pages of supporting
information (with 2 figures). Original article submitted to a journal for
consideration for publicatio
Physics of the interior of a black hole with an exotic scalar matter
We use a numerical code to consider the nonlinear processes arising when a
Reissner-Nordstrom black hole is irradiated by an exotic scalar field (modelled
as a free massless scalar field with an opposite sign for its energy-momentum
tensor). These processes are quite different from the processes arising in the
case of the same black hole being irradiated by a pulse of a normal scalar
field. In our case, we did not observe the creation of a spacelike strong
singularity in the T-region of the space-time. We investigate the antifocusing
effects in the gravity field of the exotic scalar field with the negative
energy density and the evolution of the mass function. We demonstrate the
process of vanishing of the black hole when it is irradiated by a strong pulse
of an exotic scalar field.Comment: 16 pages, 16 figures. Text has been rewritten and restructured,
Penrose diagrams have been added, appendix with convergence tests has been
added. Co-author has been added. Conclusions are unchange
Differential cartilaginous tissue formation by human synovial membrane, fat pad, meniscus cells and articular chondrocytes
Objective: To identify an appropriate cell source for the generation of meniscus substitutes, among those which would be available by arthroscopy of injured knee joints. Methods: Human inner meniscus cells, fat pad cells (FPC), synovial membrane cells (SMC) and articular chondrocytes (AC) were expanded with or without specific growth factors (Transforming growth factor-betal, Fibroblast growth factor-2 and Plate let-derived growth factor bb, TFP) and then induced to form three-dimensional cartilaginous tissues in pellet cultures, or using a hyaluronan-based scaffold (Hyaff(R)-11), in culture or in nude mice. Human native menisci were assessed as reference. Results: Cell expansion with TFP enhanced glycosaminoglycan (GAG) deposition by all cell types (up to 4.1-fold) and messenger RNA expression of collagen type II by FPC and SMC (up to 472-fold) following pellet culture. In all models, tissues generated by AC contained the highest fractions of GAG (up to 1.9 were positively stained for collagen type II (specific of the inner avascular region of meniscus), type IV (mainly present in the outer vascularized region of meniscus) and types I, III and VI (common to both meniscus regions). Instead, inner meniscus, FPC and SMC developed tissues containing negligible GAG and no detectable collagen type II protein. Tissues generated by AC remained biochemically and phenotypically stable upon ectopic implantation. Conclusions: Under our experimental conditions, only AC generated tissues containing relevant amounts of GAG and with cell phenotypes compatible with those of the inner and outer meniscus regions. Instead, the other investigated cell sources formed tissues resembling only the outer region of meniscus. It remains to be determined whether grafts based on AC will have the ability to reach the complex structural and functional organization typical of meniscus tissue. (C) 2006 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights rese
Cell-based therapy for the treatment of female stress urinary incontinence:an early cost–effectiveness analysis
Aim: To perform an early cost–effectiveness analysis of in vitro expanded myoblasts (IVM) and minced myofibers versus midurethral slings (MUS) for surgical treatment of female stress urinary incontinence. Methods: Cost–effectiveness and sensitivity analyses were performed using a decision tree comprising previously published data and expert opinions. Results & conclusion: In the base case scenario, MUS was the cost-effective strategy with a negative incremental cost–effectiveness ratio compared with IVM and a positive incremental cost–effectiveness ratio compared with minced myofibers. However, the sensitivity analysis indicates that IVM may become an alternative providing greater effect at a higher cost. With the possibility of becoming more effective, IVM treatment would be advantageous over MUS given its reduced invasiveness and lower risks of complications. </jats:p
Lentiviral gene transfer into the dorsal root ganglion of adult rats
<p>Abstract</p> <p>Background</p> <p>Lentivector-mediated gene delivery into the dorsal root ganglion (DRG) is a promising method for exploring pain pathophysiology and for genetic treatment of chronic neuropathic pain. In this study, a series of modified lentivector particles with different cellular promoters, envelope glycoproteins, and viral accessory proteins were generated to evaluate the requirements for efficient transduction into neuronal cells <it>in vitro </it>and adult rat DRG <it>in vivo</it>.</p> <p>Results</p> <p><it>In vitro</it>, lentivectors expressing enhanced green fluorescent protein (EGFP) under control of the human elongation factor 1α (EF1α) promoter and pseudotyped with the conventional vesicular stomatitis virus G protein (VSV-G) envelope exhibited the best performance in the transfer of EGFP into an immortalized DRG sensory neuron cell line at low multiplicities of infection (MOIs), and into primary cultured DRG neurons at higher MOIs. <it>In vivo</it>, injection of either first or second-generation EF1α-EGFP lentivectors directly into adult rat DRGs led to transduction rates of 19 ± 9% and 20 ± 8% EGFP-positive DRG neurons, respectively, detected at 4 weeks post injection. Transduced cells included a full range of neuronal phenotypes, including myelinated neurons as well as both non-peptidergic and peptidergic nociceptive unmyelinated neurons.</p> <p>Conclusion</p> <p>VSV-G pseudotyped lentivectors containing the human elongation factor 1α (EF1α)-EGFP expression cassette demonstrated relatively efficient transduction to sensory neurons following direct injection into the DRG. These results clearly show the potential of lentivectors as a viable system for delivering target genes into DRGs to explore basic mechanisms of neuropathic pain, with the potential for future clinical use in treating chronic pain.</p
Effects of Gold Substrates on the Intrinsic and Extrinsic Activity of High-Loading Nickel-Based Oxyhydroxide Oxygen Evolution Catalysts
We systematically investigate the
effects of Au substrates on the
oxygen evolution activities of cathodically electrodeposited nickel
oxyhydroxide (NiOOH), nickel–iron oxyhydroxide (NiFeOOH), and
nickel–cerium oxyhydroxide (NiCeOOH) at varying loadings from
0 to 2000 nmol of metal/cm<sup>2</sup>. We determine that the geometric
current densities, especially at higher loadings, were greatly enhanced
on Au substrates: NiCeOOH/Au reached 10 mA/cm<sup>2</sup> at 259 mV
overpotential, and NiFeOOH/Au achieved 140 mA/cm<sup>2</sup> at 300
mV overpotential, which were much greater than those of the analogous
catalysts on graphitic carbon (GC) substrates. By performing a loading
quantification using both inductively coupled plasma optical emission
spectrometry and integration of the Ni<sup>2+/3+</sup> redox peak,
we show that the enhanced activity is predominantly caused by the
stronger physical adhesion of catalysts on Au. Further characterizations
using impedance spectroscopy and <i>in situ</i> X-ray absorption
spectroscopy revealed that the catalysts on Au exhibited lower film
resistances and higher number of electrochemically active metal sites.
We attribute this enhanced activity to a more homogeneous electrodeposition
on Au, yielding catalyst films with very high geometric current densities
on flat substrates. By investigating the mass and site specific activities
as a function of loading, we bridge the practical geometric activity
to the fundamental intrinsic activity
A giant stem-group chaetognath
Chaetognaths, with their characteristic grasping spines, are the oldest known pelagic predators, found in the lowest Cambrian (Terreneuvian). Here, we describe a large stem chaetognath, Timorebestia koprii gen. et sp. nov., from the lower Cambrian Sirius Passet Lagerstätte, which exhibits lateral and caudal fins, a distinct head region with long antennae and a jaw apparatus similar to Amiskwia sagittiformis. Amiskwia has previously been interpreted as a total-group chaetognathiferan, as either a stem-chaetognath or gnathostomulid. We show that T. koprii shares a ventral ganglion with chaetognaths to the exclusion of other animal groups, firmly placing these fossils on the chaetognath stem. The large size (up to 30 cm) and gut contents in T. koprii suggest that early chaetognaths occupied a higher trophic position in pelagic food chains than today
A giant stem-group chaetognath.
Chaetognaths, with their characteristic grasping spines, are the oldest known pelagic predators, found in the lowest Cambrian (Terreneuvian). Here, we describe a large stem chaetognath, gen. et sp. nov., from the lower Cambrian Sirius Passet Lagerstätte, which exhibits lateral and caudal fins, a distinct head region with long antennae and a jaw apparatus similar to . has previously been interpreted as a total-group chaetognathiferan, as either a stem-chaetognath or gnathostomulid. We show that shares a ventral ganglion with chaetognaths to the exclusion of other animal groups, firmly placing these fossils on the chaetognath stem. The large size (up to 30 cm) and gut contents in suggest that early chaetognaths occupied a higher trophic position in pelagic food chains than today
- …