239 research outputs found
Simultaneous initiation of radical and cationic polymerization reactions using the "G1" copper complex as photoredox catalyst: Applications of free radical/cationic hybrid photopolymerization in the composites and
WOS:000469902800007This investigation presents the use of a photoredox catalyst "G1" as a photoinitiating system for free radical/cationic hybrid polymerization under mild irradiation conditions. The G1 system (G1/iodonium salt/N-vinylcarbazole), can simultaneously initiate the free radical and cationic polymerization reactions upon exposure to a visible (405 nm) light from a Light Emitting Diode (LED) source. The multicomponent G1 system is able to simultaneously generate radical and cationic species through a catalytic photoredox process. The curing of thin samples (25 mu m), thick samples (1.4 mm) as well as the manufacture of hybrid system/glass fibers composites ( 2 to 4 mm thickness) was realized and the influence of the ratio of cationic/radical monomer blends on the polymerization kinetics was studied. The use of G1 in visible light photoinitiating system for the access to composites and 3D printing experiments was particularly outlined. G1 was also shown to have low levels of migration from the cured materials. When compared to reference materials ("F1", a similar copper complex and an anthracene derivative, dibutoxy anthracene), G1 showed better polymerization efficiency. The initiation efficiency was investigated through the real-time Fourier transform infrared (RT-FTIR) spectroscopy and optical pyrometry. Dynamical Mechanical Analysis has been used to determine the glass temperature transition of the cured hybrid system as a complementary technique
Precise Control of Band Filling in NaxCoO2
Electronic properties of the sodium cobaltate NaxCoO2 are systematically
studied through a precise control of band filling. Resistivity, magnetic
susceptibility and specific heat measurements are carried out on a series of
high-quality polycrystalline samples prepared at 200 C with Na content in a
wide range of 0.35 =< x =< 0.70. It is found that dramatic changes in
electronic properties take place at a critical Na concentration x* that lies
between 0.58 and 0.59, which separates a Pauli paramagnetic and a Curie-Weiss
metals. It is suggested that at x* the Fermi level touches the bottom of the
a1g band at the gamma point, leading to a crucial change in the density of
states across x* and the emergence of a small electron pocket around the gamma
point for x > x*.Comment: 4 pages, 5 figures, submitted to J. Phys. Soc. Jp
Bulk antiferromagnetism in single crystals
Susceptibility, specific heat, and muon spin rotation measurements on
high-quality single crystals of have revealed bulk
antiferromagnetism with N\'{e}el temperature K and an
ordered moment perpendicular to the layers. The magnetic order
encompasses nearly 100% of the crystal volume. The susceptibility exhibits a
broad peak around 30 K, characteristic of two-dimensional antiferromagnetic
fluctuations. The in-plane resistivity is metallic at high temperatures and
exhibits a minimum at .Comment: published versio
Magnetic and Metal-Insulator Transitions in beta-Na0.5CoO2 and gamma-K0.5CoO2 -NMR and Neutron Diffraction Studies-
Co-oxides beta-Na0.5CoO2 and gamma-K0.5CoO2 have been prepared by the Na
de-intercalation from alpha-NaCoO2 and by the floating-zone method,
respectively. It has been found that successive phase transitions take place at
temperatures Tc1 and Tc2 in both systems. The appearance of the internal
magnetic field at Tc1 with decreasing temperature T indicates that the
antiferromagnetic order exists at T < Tc1, as in gamma-Na0.5CoO2. For
beta-Na0.5CoO2, the transition temperatures and the NMR parameters determined
from the data taken for magnetically ordered state are similar to those of
gamma-Na0.5CoO2, indicating that the difference of the stacking ways of the
CoO2 layers between these systems do not significantly affect their physical
properties. For gamma-K0.5CoO2, the quantitative difference of the physical
quantities are found from those of beta- and gamma-Na0.5CoO2. The difference
between the values of Tci (i = 1 and 2) of these systems might be explained by
considering the distance between CoO2 layers.Comment: 8 pages, 14 figures, 1 Tabl
Impurity-induced transition and impurity-enhanced thermopower in the thermoelectric oxide NaCo_{2-x}Cu_x$O_4
Various physical quantities are measured and analysed for the Cu-substituted
thermoelectric oxide NaCo_{2-x}Cu_xO_4. As was previously known, the
substituted Cu enhances the thermoelectric power, while it does not increase
the resistivity significantly. The susceptibility and the electron
specific-heat are substantially decreased with increasing x, which implies that
the substituted Cu decreases the effective-mass enhancement. Through a
quantitative comparison with the heavy fermion compounds and the valence
fluctuation systems, we have found that the Cu substitution effectively
increases the coupling between the conduction electron and the magnetic
fluctuation. The Cu substitution induces a phase transition at 22 K that is
very similar to a spin-density-wave transition.Comment: 8 pages, 7 figures, submitted to Phys. Rev.
Effect of Na content and hydration on the excitation spectrum of the cobaltite Na_xCoO_2 yH_2O
We report on a Raman scattering study on the superconducting cobaltite
as function of Na content and hydration (x1/3,
3/4 and y0, 2/3, 4/3). The observed phonon scattering and scattering
continua are analyzed in terms of lattice strain due to the structural misfit
and disorder. Hydration, due to the intercalation of one or two layers,
releases a part of this strain. Our Raman data suggest a connection between
disorder on the partly occupied Na sites, the split off of the level
from the other states of and superconductivity.Comment: 10 pages, 4 figures, for further information see
http://www.peter-lemmens.d
Unconventional magnetic transition and transport behavior in Na0.75CoO2
Here we report an unconventional magnetic and transport phenomenon in a
layered cobalt oxide, NaxCoO2. Only for x = 0.75, a magnetic transition of the
second order was clearly detected at Tm ~ 22 K where an apparent specific-heat
jump, an onset of extremely small spontaneous magnetization, and a kink in
resistivity came in. Moreover large positive magnetoresistance effect was
observed below Tm. These features of the transition strongly indicate the
appearance of an unusual electronic state that may be attributed to the
strongly-correlated electrons in Na0.75CoO2.Comment: 5 pages, 6 figures, to appear in Phys. Rev.
Achieving Controlled Biomolecule-Biomaterial Conjugation
The conjugation of biomolecules can impart materials with the bioactivity necessary to modulate specific cell behaviors. While the biological roles of particular polypeptide, oligonucleotide, and glycan structures have been extensively reviewed, along with the influence of attachment on material structure and function, the key role played by the conjugation strategy in determining activity is often overlooked. In this review, we focus on the chemistry of biomolecule conjugation and provide a comprehensive overview of the key strategies for achieving controlled biomaterial functionalization. No universal method exists to provide optimal attachment, and here we will discuss both the relative advantages and disadvantages of each technique. In doing so, we highlight the importance of carefully considering the impact and suitability of a particular technique during biomaterial design
Cholangiocarcinoma 2020: the next horizon in mechanisms and management
| Cholangiocarcinoma (CCA) includes a cluster of highly heterogeneous biliary malignant
tumours that can arise at any point of the biliary tree. Their incidence is increasing globally,
currently accounting for ~15% of all primary liver cancers and ~3% of gastrointestinal malignancies.
The silent presentation of these tumours combined with their highly aggressive nature and
refractoriness to chemotherapy contribute to their alarming mortality, representing ~2% of all
cancer-related deaths worldwide yearly. The current diagnosis of CCA by non-invasive approaches
is not accurate enough, and histological confirmation is necessary. Furthermore, the high
heterogeneity of CCAs at the genomic, epigenetic and molecular levels severely compromises
the efficacy of the available therapies. In the past decade, increasing efforts have been made to
understand the complexity of these tumours and to develop new diagnostic tools and therapies
that might help to improve patient outcomes. In this expert Consensus Statement, which is
endorsed by the European Network for the Study of Cholangiocarcinoma, we aim to summarize
and critically discuss the latest advances in CCA, mostly focusing on classification, cells of origin,
genetic and epigenetic abnormalities, molecular alterations, biomarker discovery and treatments.
Furthermore, the horizon of CCA for the next decade from 2020 onwards is highlighted
Interfacial Reactions in Model NiTi Shape Memory Alloy Fiber-Reinforced Sn Matrix “Smart” Composites
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