1,830 research outputs found
Unveiling interactions between DNA and cytotoxic 2-arylpiperidinyl-1,4-naphthoquinone derivatives: A combined electrochemical and computational study
Indexación: Scopus.Three 2-arylpiperidinyl-1,4-naphthoquinone derivatives were synthesized and evaluated in vitro to determine their cytotoxicity on cancer and normal cell lines. In order to establish their possible action mechanism, the electrochemical behaviour of these quinones was examined using cyclic voltammetry (CV) as technique by using a three-electrode setup: a glassy carbon, Ag/AgCl (in 3 M KCl), and platinum wire as working, reference, and counter electrodes, respectively. Kinetic studies were done to determine the control of the reduction reaction and the number of transferred electrons in the process. Furthermore, the addition of dsDNA to the quinone solutions allowed for the observation of an interaction between each quinone and dsDNA as the current-peaks became lower in presence of dsDNA. Otherwise, motivated to support the aforementioned results, electronic structure calculations at the TPSS-D3/6-31+G(d,p) level of theory were carried out in order to find the most favourable noncovalently bonded complexes between quinones and DNA. Noncovalent complexes formed between DNA and 2-arylpiperidinyl-1,4-naphthoquinones and stabilized by π-stacking interactions along with the well-known hydrogen-bonded complexes were found, with the former being more stable than the latter. These results suggest that the intercalation of these quinone derivatives in DNA is the most likely action mechanism. © 2018 King Saud Universityhttps://www.sciencedirect.com/science/article/pii/S1878535218300893?via%3Dihu
Temperature - pressure phase diagram of CeCoSi: Pressure induced high-temperature phase
We have studied the temperature-pressure phase diagram of CeCoSi by
electrical-resistivity experiments under pressure. Our measurements revealed a
very unusual phase diagram. While at low pressures no dramatic changes and only
a slight shift of the Ne\'{e}l temperature ( K) are observed,
at about 1.45 GPa a sharp and large anomaly, indicative of the opening of a
spin-density-wave (SDW) gap, appears at a comparatively high temperature K. With further increasing pressure shifts rapidly to low
temperatures and disappears at about 2.15 GPa, likely continuously in a quantum
critical point, but without evidence for superconductivity. Even more
surprisingly, we observed a clear shift of to higher temperatures upon
applying a magnetic field. We discuss two possible origins for , either
magnetic ordering of Co or a meta-orbital type of transition of Ce.Comment: 6 pages, 5 figure
Remarkable magnetostructural coupling around the magnetic transition in CeCoFeSi
We report a detailed study of the magnetic properties of
CeCoFeSi under high magnetic fields (up to 16 Tesla)
measuring different physical properties such as specific heat, magnetization,
electrical resistivity, thermal expansion and magnetostriction.
CeCoFeSi becomes antiferromagnetic at 6.7 K.
However, a broad tail (onset at 13 K) in the specific heat
precedes that second order transition. This tail is also observed in the
temperature derivative of the resistivity. However, it is particularly
noticeable in the thermal expansion coefficient where it takes the form of a
large bump centered at . A high magnetic field practically washes out that
tail in the resistivity. But surprisingly, the bump in the thermal expansion
becomes a well pronounced peak fully split from the magnetic transition at
. Concurrently, the magnetoresistance also switches from negative to
positive just below . The magnetostriction is considerable and
irreversible at low temperature (
410 at 2 K) when the magnetic interactions dominate. A broad
jump in the field dependence of the magnetostriction observed at low may be
the signature of a weak ongoing metamagnetic transition. Taking altogether, the
results indicate the importance of the lattice effects in the development of
the magnetic order in these alloys.Comment: 5 pages, 6 figure
Valence fuctuation and magnetic ordering in EuNi2(P1-xGex)2 single crystals
Unusual phases and phase transitions are seen at the magnetic-nonmagnetic
boundary in Ce, Eu and Yb-based compounds. EuNiP is a very unusual
valence fluctuating Eu system, because at low temperatures the Eu valence stays
close to 2.5 instead of approaching an integer value. Eu valence and thus the
magnetic property in this system can be tuned by Ge substitution in P site as
EuNiGe is known to exhibit antiferromagnetc (AFM) ordering of
divalent Eu moments with = 30 K. We have grown
EuNi(PGe) (0.0 0.5) single crystals and
studied their magnetic, thermodynamic and transport properties. Increasing Ge
doping to 0.4 results in a well-defined AFM ordered state with = 12
K for = 0.5. Moreover, the reduced value of magnetic entropy for = 0.5
at suggests the presence of valance fluctuation/ Kondo effect in this
compound. Interestingly, the specific heat exhibits an enhanced Sommerfeld
coefficient upon Ge doping. Subsequently, electronic structure calculations
lead to a non-integral valence in EuNiP but a stable divalent Eu
state in EuNiGe which is in good agreement with experimental results.Comment: 7 pages, 8 figure
High-resolution resonant inelastic soft X-ray scattering as a probe of the crystal electrical field in lanthanides demonstrated for the case of CeRh2Si2
The magnetic properties of rare earth compounds are usually well captured by
assuming a fully localized f shell and only considering the Hund's rule ground
state multiplet split by a crystal electrical field (CEF). Currently, the
standard technique for probing CEF excitations in lanthanides is inelastic
neutron scattering. Here we show that with the recent leap in energy
resolution, resonant inelastic soft X-ray scattering has become a serious
alternative for looking at CEF excitations with some distinct advantages
compared to INS. As an example we study the CEF scheme in CeRh2Si2, a system
that has been intensely studied for more than two decades now but for which no
consensus has been reached yet as to its CEF scheme. We used two new features
that have only become available very recently in RIXS, high energy resolution
of about 30 meV as well as polarization analysis in the scattered beam, to find
a unique CEF description for CeRh2Si2. The result agrees well with previous INS
and magnetic susceptibility measurements. Due to its strong resonant character,
RIXS is applicable to very small samples, presents very high cross sections for
all lanthanides, and further benefits from the very weak coupling to phonon
excitation. The rapid progress in energy resolution of RIXS spectrometers is
making this technique increasingly attractive for the investigation of the CEF
scheme in lanthanides
Quantum criticality in the cubic heavy-fermion system CeIn_{3-x}Sn_x
We report a comprehensive study of CeInSn single crystals close to the antiferromagnetic (AF) quantum critical
point (QCP) at by means of the low-temperature thermal
expansion and Gr\"uneisen parameter. This system represents the first example
for a {\it cubic} heavy fermion (HF) in which can be suppressed
{\it continuously} down to T=0. A characteristic sign change of the Gr\"uneisen
parameter between the AF and paramagnetic state indicates the accumulation of
entropy close to the QCP. The observed quantum critical behavior is compatible
with the predictions of the itinerant theory for three-dimensional critical
spinfluctuations. This has important implications for the role of the
dimensionality in HF QCPs.Comment: Physical Review Letters, to be publishe
From financing needs to criminal terrorism: The role of terrorist financing in crime-terror relations
After twenty years of national and international measures to combat financing of terrorism and money laundering, global terrorism has encountered greater restrictions to access the volume of economic resources it needs which has justified its collaboration with criminal organisations or conversion into criminal-terrorist organisations. This study seeks to analyse crime-terror relations by looking at the influence of the fight against terrorist financing in the evolution of global terrorist organisations, which have developed structures to establish a new range of relationships with transnational organised crime with unprecedented intensity. This article highlights some of the features that differentiate global terrorism from other types of terrorism, especially in terms of its objectives, organisational structures and funding possibilities, as well as pointing out a possible effect of the fight against terrorist financing in the relationship between terrorism and crime. Finally, it offers the different contexts where economic, political and social circumstances have created new cooperation models with organised crime groups.Tras veinte años de desarrollo de medidas nacionales e internacionales encaminadas a combatir la financiación del terrorismo y el blanqueo de capitales, el terrorismo global ha encontrado grandes restricciones para acceder al volumen de recursos económicos que necesita. Este estudio aborda la influencia de la lucha contra la financiación del terrorismo en la evolución de las organizaciones terroristas globales y en el cambio de la naturaleza y alcance de las relaciones entre el crimen organizado y el terrorismo. Asà mismo examina los diferentes contextos en los que las circunstancias económicas, polÃticas y sociales han propiciado la creación de nuevos modelos de cooperación de las organizaciones terroristas con los grupos criminales organizados.Ministerio de Ciencia e Innovación del Gobierno de España Ref. PID2020-116646RB-I0
Optical study of archetypical valence-fluctuating Eu-systems
We have investigated the optical conductivity of the prominent valence
fluctuating compounds EuIr2Si2 and EuNi2P2 in the infrared energy range to get
new insights into the electronic properties of valence fluctuating systems. For
both compounds we observe upon cooling the formation of a renormalized Drude
response, a partial suppression of the optical conductivity below 100 meV and
the appearance of a mid-infrared peak at 0.15 eV for EuIr2Si2 and at 0.13 eV
for EuNi2P2. Most remarkably, our results show a strong similarity with the
optical spectra reported for many Ce- or Yb-based heavy fermion metals and
intermediate valence systems, although the phase diagrams and the temperature
dependence of the valence differ strongly between Eu- and Ce-/Yb-systems. This
suggests that the hybridization between 4f- and conduction electrons, which is
responsible for the properties of Ce- and Yb-systems, plays an important role
in valence fluctuating Eu-systems
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