96 research outputs found
Frustration driven structural distortion in VOMoO4
Nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR),
magnetization measurements and electronic structure calculations in VOMoO4 are
presented. It is found that VOMoO4 is a frustrated two-dimensional
antiferromagnet on a square lattice with competing exchange interactions along
the side J1 and the diagonal J2 of the square. From magnetization measurements
J1+J2 is estimated around 155 K, in satisfactory agreement with the values
derived from electronic structure calculations. Around 100 K a structural
distortion, possibly driven by the frustration, is evidenced. This distortion
induces significant modifications in the NMR and EPR spectra which can be
accounted for by valence fluctuations. The analysis of the spectra suggests
that the size of the domains where the lattice is distorted progressively grows
as the temperature approaches the transition to the magnetic ground state at
Tc=42 K
Strong electronic correlations in LiZnPc organic metals
Nuclear magnetic resonance, electron paramagnetic resonance and magnetization
measurements show that bulk LiZnPc are strongly correlated one-dimensional
metals. The temperature dependence of the nuclear spin-lattice relaxation rate
and of the static uniform susceptibility on approaching room
temperature are characteristic of a Fermi liquid. Moreover, while for the electrons are delocalized down to low temperature, for a
tendency towards localization is noticed upon cooling, yielding an increase
both in and . The -dependence of the effective density of
states at the Fermi level displays a sharp enhancement for , at the half filling of the ZnPc lowest unoccupied molecular orbitals. This
suggests that LiZnPc is on the edge of a metal-insulator transition where
enhanced superconducting fluctuations could develop.Comment: 5 pages, 4 figure
Magnetic properties and spin dynamics in single molecule paramagnets Cu6Fe and Cu6Co
The magnetic properties and the spin dynamics of two molecular magnets have
been investigated by magnetization and d.c. susceptibility measurements,
Electron Paramagnetic Resonance (EPR) and proton Nuclear Magnetic Resonance
(NMR) over a wide range of temperature (1.6-300K) at applied magnetic fields,
H=0.5 and 1.5 Tesla. The two molecular magnets consist of
CuII(saldmen)(H2O)}6{FeIII(CN)6}](ClO4)38H2O in short Cu6Fe and the analog
compound with cobalt, Cu6Co. It is found that in Cu6Fe whose magnetic core is
constituted by six Cu2+ ions and one Fe3+ ion all with s=1/2, a weak
ferromagnetic interaction between Cu2+ moments through the central Fe3+ ion
with J = 0.14 K is present, while in Cu6Co the Co3+ ion is diamagnetic and the
weak interaction is antiferromagnetic with J = -1.12 K. The NMR spectra show
the presence of non equivalent groups of protons with a measurable contact
hyperfine interaction consistent with a small admixture of s-wave function with
the d-function of the magnetic ion. The NMR relaxation results are explained in
terms of a single ion (Cu2+, Fe3+, Co3+) uncorrelated spin dynamics with an
almost temperature independent correlation time due to the weak magnetic
exchange interaction. We conclude that the two molecular magnets studied here
behave as single molecule paramagnets with a very weak intramolecular
interaction, almost of the order of the dipolar intermolecular interaction.
Thus they represent a new class of molecular magnets which differ from the
single molecule magnets investigated up to now, where the intramolecular
interaction is much larger than the intermolecular one
Mesoscopic phase separation in NaCoO ()
NMR, EPR and magnetization measurements in NaCoO for are presented. While the EPR signal arises from Co magnetic
moments ordering at K, Co NMR signal originates from
cobalt nuclei in metallic regions with no long range magnetic order and
characterized by a generalized susceptibility typical of strongly correlated
metallic systems. This phase separation in metallic and magnetic insulating
regions is argued to occur below ( K). Above an
anomalous decrease in the intensity of the EPR signal is observed and
associated with the delocalization of the electrons which for were
localized on Co orbitals. It is pointed out that the in-plane
antiferromagnetic coupling cannot be the driving force for the phase
separation.Comment: 14 figure
The impact of plasma rich in growth factors on clinical and biological factors involved in healing processes after third molar extraction
A split-mouth randomized clinical trial to evaluate the performance of piezosurgery compared with traditional technique in lower wisdom tooth removal.
Armamenti, Conflitto, Decolonizzazione, Democrazia, Diritti Umani, Disarmo, Forze armate, Governo, Guerra, Guerra fredda, Ideologia, Imperialismo, Indipendenza, Internazionalismo, Nazionalismo, Nazione, Neocolonialismo, Organizzazioni Internazionali, Pace, Partito, Politica della sicurezza, Rivoluzione, Societ\ue0 civile, Stato, Sviluppo, Terrorismo, Terzo mondo, Umanitarismo
Third-molar extraction with ultrasound bone surgery: a case-control study.
The aim of this case-control study was to evaluate the postoperative period and healing between 2 surgical methods (traditional and ultrasound bone surgery) that are used for mandibular third-molar extraction.Fifteen patients with impaction of both of the lower third molars and indications for their extractions were used in this study. Bilateral-mandibular third-molar extractions were performed at the same surgical time: traditional surgery with burrs was used on 1 side (control site), and ultrasound surgery was used on the other side (test [T] site). After surgery, the patients were examined at 7 and 14 days and at 1 and 3 months to evaluate tissue healing. The following was assessed at every follow-up: pain, trismus, swelling, and alveolar bone level.The study included 15 patients, and 30 mandibular third-molar extractions were performed. We found only 1 postoperative complication: 1 patient had alveolitis in the control site. Complete recoveries without any complications were reported in all of the patients at the T sites.Complete recoveries without any complication were reported in all patients at the T sites. The only disadvantage of the piezoelectric technique was the length of operation time, which was increased by approximately 8 minutes; however, this effect was offset by reducing the morbidity.Our preliminary study showed that Piezosurgery is an excellent tool for reducing the risk of complications and improving the postoperative period
Effects of reaction atmosphere on physico-chemical properties of V-doped FeNb11O29
FeNb11O29, pure or doped with metal transition ions, is a very promising material with advanced multifunctionalities
and interesting applicative perspectives. It is isostructural with Nb12O29, one of the rare compounds
in which Nb displays a local magnetic moment and shows both antiferromagnetic ordering and metallic
conductivity at low temperatures. In this work we have synthesized and studied Fe0.8V0.2Nb11O29 monoclinic
powders. In particular we monitored the effects on structural, electronic and magnetic properties in samples
produced in different atmospheres to stabilize cations with different oxidation states.
We have demonstrated that the reaction atmosphere influences the phase homogeneity, the crystallite size
and the amount of paramagnetic centres, with a transformation of Fe3+ in Fe2+ when an inert atmosphere is
used, as proved by the absence, in this case, of any electron paramagnetic resonance signal. Also the Raman
spectra result to be affected due to the change of coordination polyhedra. Subsequent re-oxidation of reduced
powders brings to the monophasic iron niobate again containing Fe3+ demonstrating the reversibility of redox
process. This reversibility is accompanied by a complete restoring of monoclinic structure evidenced by X-ray
diffraction data and by Raman measurements, which allowed also to follow in situ the spectral changes induced
by laser heating
- …