1,340 research outputs found
Hole polaron formation and migration in olivine phosphate materials
By combining first principles calculations and experimental XPS measurements,
we investigate the electronic structure of potential Li-ion battery cathode
materials LiMPO4 (M=Mn,Fe,Co,Ni) to uncover the underlying mechanisms that
determine small hole polaron formation and migration. We show that small hole
polaron formation depends on features in the electronic structure near the
valence-band maximum and that, calculationally, these features depend on the
methodology chosen for dealing with the correlated nature of the
transition-metal d-derived states in these systems. Comparison with experiment
reveals that a hybrid functional approach is superior to GGA+U in correctly
reproducing the XPS spectra. Using this approach we find that LiNiPO4 cannot
support small hole polarons, but that the other three compounds can. The
migration barrier is determined mainly by the strong or weak bonding nature of
the states at the top of the valence band, resulting in a substantially higher
barrier for LiMnPO4 than for LiCoPO4 or LiFePO4
Resistance to experimental infections with Haemonchus contortus in Romanov sheep
International audienc
Design of a cell selection mechanism to mitigate interference for cell-edge macro users in femto-macro heterogeneous network
The Femto-Macro heterogeneous network is a promising solution to improve the network capacity and coverage in mobile network. However interference may rise due to femtocell deployment nearby to macro user equipment (MUE) within macrocell network coverage. Femtocell offers main priority in resource allocation to its subscribed femto user equipment (FUE) rather than unsubscribed MUE. MUEs will suffer severe interference when they are placed near or within the femtocell area range especially at the cell edge. This phenomenon occurs due to the distance is far from its serving macro base station (MBS) to receive good signal strength. This paper presents a design of cell selection scheme for cell-edge MUE to select an optimal femto base station (FBS) as its primary serving cell in physical resource block allocation. In this study, the proposed cell selection consists of four main elements: measuring the closest FBS distance, Signal to Interference-plus-Noise-Ratio (SINR), physical resource block (PRB) availability and node density level for the selected base station. The main goal is to ensure cell-edge MUE has priority fairly with FUE in physical resource block allocation per user bandwidth demand to mitigate interference. Hence, the cell-edge MUE has good experienced on receiving an adequate user data rate to improve higher network throughput
Ab initio studies of electronic structure of defects in PbTe
Understanding the detailed electronic structure of deep defect states in
narrow band-gap semiconductors has been a challenging problem. Recently,
self-consistent ab initio calculations within density functional theory (DFT)
using supercell models have been successful in tackling this problem. In this
paper, we carry out such calculations in PbTe, a well-known narrow band-gap
semiconductor, for a large class of defects: cationic and anionic
substitutional impurities of different valence, and cationic and anionic
vacancies. For the cationic defects, we study a series of compounds
RPb2n-1Te2n, where R is vacancy or monovalent, divalent, or trivalent atom; for
the anionic defects, we study compounds MPb2nTe2n-1, where M is vacancy, S, Se
or I. We find that the density of states (DOS) near the top of the valence band
and the bottom of the conduction band get significantly modified for most of
these defects. This suggests that the transport properties of PbTe in the
presence of impurities can not be interpreted by simple carrier doping
concepts, confirming such ideas developed from qualitative and
semi-quantitative arguments
Evaluation of different formulations of gellan gum-based hydrogels for tissue engineering of intervertebral disc
Gellan gum based-hydrogels present advantageous features for application
as acellular and cellular nucleus pulposus (NP) substitutes due to
the possibility of fine-tuning its physico-chemical and biological properties.
In this study, ionic-crosslinked hydrogel discs were produced by
means of mixing a raw and chemically modified material, i.e., high acyl
gellan gum (HAGG) and methacrylated low acyl gellan gum (GG-MA),
respectively. The hydrogel discs were characterized in terms of its
mechanical properties and degradation/swelling ability. The biocompatibility
of the different hydrogel formulations was assessed in vitro
using NP rabbit cells isolated from the intervertebral disc. The biological
performance of the developed gellan gum-based hydrogels formulations
was evaluated by: (i) culturing of NP cells in the presence of the
hydrogel leachables, and (ii) seeding or encapsulation of the NP cells
within the hydrogels. The present work demonstrated that as HAGG
content increases, the modulus of the hydrogels decreases. Moreover,
the increase of the HAGG content induces a higher weight loss of the
GG-MA/HA-GG formulation as compared to GG-MA hydrogel. The in
vitro study revealed that hydrogels are non-cytotoxic and support the
encapsulation of rabbit NP cells. The methacrylated gellan gum and
formulations possessing high acyl gellan gum present tunable properties
that may be interesting for application as NP substitutes
Anti-Inflammatory properties of injectable Betamethasone-Loaded Tyramine-Modified Gellan Gum/Silk Fibroin Hydrogels
Rheumatoid arthritis is a rheumatic disease for which a healing treatment does not presently exist. Silk fibroin has been extensively studied for use in drug delivery systems due to its uniqueness, versatility and strong clinical track record in medicine. However, in general, natural polymeric materials are not mechanically stable enough, and have high rates of biodegradation. Thus, synthetic materials such as gellan gum can be used to produce composite structures with biological signals to promote tissue-specific interactions while providing the desired mechanical properties. In this work, we aimed to produce hydrogels of tyramine-modified gellan gum with silk fibroin (Tyâ GG/SF) via horseradish peroxidase (HRP), with encapsulated betamethasone, to improve the biocompatibility and mechanical properties, and further increase therapeutic efficacy to treat rheumatoid arthritis (RA). The Tyâ GG/SF hydrogels presented a β-sheet secondary structure, with gelation time around 2â 5 min, good resistance to enzymatic degradation, a suitable injectability profile, viscoelastic capacity with a significant solid component and a betamethasone-controlled release profile over time. In vitro studies showed that Tyâ GG/SF hydrogels did not produce a deleterious effect on cellular metabolic activity, morphology or proliferation. Furthermore, Tyâ GG/SF hydrogels with encapsulated betamethasone revealed greater therapeutic efficacy than the drug applied alone. Therefore, this strategy can provide an improvement in therapeutic efficacy when compared to the traditional use of drugs for the treatment of rheumatoid arthritis.Norte2020 project (“NORTE-08-5369-FSE000044”), REMIX project (GA 778078—REMIX—H2020-MSCA-RISE-2017) Gilson Lab, Chonbuk National
University, Republic of Korea and the Frontiers of technology for theranostics of cancer, metabolic and
neurodegenerative diseases (FROnTHERA), Structural Project NORTE-01-0145-FEDER-000023. The FCT
distinction attributed to J.M.O. under the Investigator FCT program (number IF/01285/2015) is also greatly
acknowledged. C.G. also wishes to acknowledge FCT for supporting her research (number SFRH/BPD/94277/201
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