27 research outputs found
Evolution of the surface atomic structure of multielement oxide films: curse or blessing?
Atomically resolved scanning tunneling microscopy (STM) and x-ray
photoelectron spectroscopy (XPS) are used to gain atomic-scale insights into
the heteroepitaxy of lanthanum-strontium manganite (LSMO,
LaSrMnO, 0.2) on SrTiO(110). LSMO
is a perovskite oxide characterized by several composition-dependent surface
reconstructions. The flexibility of the surface allows it to incorporate
nonstoichiometries during growth, which result in composition-dependent surface
atomic structures. This happens up to a critical point, where phase separation
occurs, clusters rich in the excess cations form at the surface, and films show
a rough morphology. To limit the nonstoichiometry introduced by non-optimal
growth conditions, it proves useful to monitor the changes in surface atomic
structures as a function of the PLD parameters and tune the latter accordingly.Comment: 8 pages, 5 figure
Thin graphene oxide nanoflakes modulate glutamatergic synapses in the amygdala cultured circuits: exploiting synaptic approaches to anxiety disorders
Anxiety disorders (ADs) are nervous system maladies involving changes in the amygdala synaptic circuitry, such as an upregulation of excitatory neurotransmission at glutamatergic synapses. In the field of nanotechnology, thin graphene oxide flakes with nanoscale lateral size (s-GO) have shown outstanding promise for the manipulation of excitatory neuronal transmission with high temporal and spatial precision, thus they were considered as ideal candidates for modulating amygdalar glutamatergic transmission. Here, we validated an in vitro model of amygdala circuitry as a screening tool to target synapses, towards development of future ADs treatments. After one week in vitro, dissociated amygdalar neurons reconnected forming functional networks, whose development recapitulated that of the tissue of origin. When acutely applied to these cultures, s-GO flakes induced a selective modification of excitatory activity. This type of interaction between s-GO and amygdalar neurons may form the basis for the exploitation of alternative approaches in the treatment of ADs
How water binds to microcline feldspar (001)
Microcline feldspar (KAlSiO) is a common mineral with important roles
for Earth's ecological balance. It participates in the carbon, potassium, and
water cycles, contributing to CO sequestration, soil formation, and
atmospheric ice nucleation. To understand the fundamentals of these processes,
it is essential to establish microcline's surface atomic structure and its
interaction with the omnipresent water molecules. This work presents
atomic-scale results on microcline's lowest-energy surface and its interaction
with water, combining ultrahigh vacuum investigations by non-contact atomic
force microscopy and X-ray photoelectron spectroscopy with density functional
theory calculations. An ordered array of hydroxyls bonded to silicon or
aluminum readily forms on the cleaved surface at room temperature. The distinct
proton affinities of these hydroxyls influence the arrangement and orientation
of the first water molecules binding to the surface, holding potential
implications for the subsequent condensation of water.Comment: 14 pages, 5 figure
Tuning a two-impurity Kondo system by a moir\'e superstructure
Two-impurity Kondo models are paradigmatic for correlated spin-fermion
systems. Working with Mn atoms on Au(111) covered by a monolayer of MoS, we
tune the inter-adatom exchange via the adatom distance and the adatom-substrate
exchange via the location relative to a moir\'e structure of the substrate.
Differential-conductance measurements on isolated adatoms exhibit Kondo peaks
with heights depending on the adatom location relative to the moir\'e
structure. Mn dimers spaced by a few atomic lattice sites exhibit split Kondo
resonances. In contrast, adatoms in closely spaced dimers couple
antiferromagnetically, resulting in a molecular-singlet ground state. Exciting
the singlet-triplet transition by tunneling electrons, we find that the
singlet-triplet splitting is surprisingly sensitive to the moir\'e structure.
We interpret our results theoretically by relating the variations in the
singlet-triplet splitting to the heights of the Kondo peaks of single adatoms,
finding evidence for coupling of the adatom spin to multiple conduction
electron channels
Water Structures Reveal Local Hydrophobicity on the In2O3(111) Surface
Clean oxide surfaces are generally hydrophilic. Water molecules anchor at
undercoordinated surface metal atoms that act as Lewis-acid sites, and they are
stabilized by H bonds to undercoordinated surface oxygens. The large unit cell
of In2O3(111) provides surface atoms in various configurations, which leads to
chemical heterogeneity and a local deviation from this general rule.
Experiments (TPD, XPS, ncAFM) agree quantitatively with DFT calculations and
show a series of distinct phases. The first three water molecules dissociate at
one specific area of the unit cell and desorb above room temperature. The next
three adsorb as molecules in the adjacent region. Three more water molecules
rearrange this structure and an additional nine pile up above the OH groups.
Despite offering undercoordinated In and O sites, the rest of the unit cell is
unfavorable for adsorption and remains water-free. The first water layer thus
shows ordering into nanoscopic 3D water clusters separated by hydrophobic
pockets
Non-alcoholic to metabolic associated fatty liver disease: Cardiovascular implications of a change in terminology in patients living with HIV
Background and Aims:
It has recently been suggested that the definition of non-alcoholic fatty liver disease (NAFLD) be changed to Metabolic Associated FLD (MAFLD) to better reflect the complex metabolic aspects of this syndrome. We compared the ability of MAFLD and NAFLD to correctly identify high CV risk patients, sub-clinical atherosclerosis or a history of prior CV events (CVEs) in patients living with HIV (PWH).
Methods:
Single center, cross-sectional study of PWH on stable anti-retrovirals. NAFLD was diagnosed by transient liver elastography; published criteria were used to diagnose MAFLD (JHepatol.2020;73(1):202-209). Four mutually exclusive groups were considered: low (<7.5%) vs high (>7.5%) ASCVD risk, subclinical CVD (carotid IMT ≥1 mm and/or coronary calcium score >100), and prior CVEs. The association of NAFLD and MAFLD with the CVD risk groups was explored via a multinominal model adjusted for age, sex, liver fibrosis, HIV duration, nadir CD4 and current CD4 cell count.
Results:
We included 1249 PWH (mean age 55 years, 74% men, median HIV duration 24 years). Prevalence of overweight/obesity and diabetes was 40% and 18%. Prevalence of NAFLD and MAFLD and overlapping groups are shown in Fig 1A. Fig 1B shows distribution of NAFLD/MAFLD in the 4 patient categories (p-for-trend <0.001). Both MAFLD and NAFLD were significantly associated with an increased risk of CVD compared to the reference level (ASCVD<7.5%) (all p-values <0.004; Fig 2).
Conclusions:
NAFLD and MAFLD perform equally in detecting CVD or its risk. The proposed change in terminology may not help to identify PWH requiring enhanced surveillance and preventative interventions for cardiovascular disease
Data demonstrating the anti-oxidant role of hemopexin in the heart
The data presented in this article are related to the research article entitled Hemopexin counteracts systolic dysfunction induced by heme-driven oxidative stress (G. Ingoglia, C. M. Sag, N. Rex, L. De Franceschi, F. Vinchi, J. Cimino, S. Petrillo, S. Wagner, K. Kreitmeier, L. Silengo, F. Altruda, L. S. Maier, E. Hirsch, A. Ghigo and E. Tolosano, 2017) [1]. Data show that heme induces reactive oxygen species (ROS) production in primary cardiomyocytes. H9c2 myoblastic cells treated with heme bound to human Hemopexin (Hx) are protected from heme accumulation and oxidative stress. Similarly, the heme-driven oxidative response is reduced in primary cardiomyocytes treated with Hx-heme compared to heme alone. Our in vivo data show that mouse models of hemolytic disorders, β-thalassemic mice and phenylhydrazine-treated mice, have low serum Hx associated to enhanced expression of heme- and oxidative stress responsive genes in the heart. Hx-/- mice do not show signs of heart fibrosis or overt inflammation. For interpretation and discussion of these data, refer to the research article referenced above. Keywords: Heme, Hemopexin, Heart, Oxidative stres
The effect of different InO(111) surface terminations on CO adsorption
InO-based catalysts have shown high activity and selectivity for
CO hydrogenation to methanol, however the origin of the high performance of
InO is still unclear. To elucidate the initial steps of CO
hydrogenation over InO, we have combined X-ray Photoelectron
Spectroscopy (XPS) and Density Functional Theory (DFT) calculations to study
the adsorption of CO on the InO(111) crystalline surface with
different terminations, namely the stoichiometric, the reduced, and the
hydroxylated surface, respectively. The combined approach confirms that the
reduction of the surface results in the formation of In ad-atoms and that water
dissociates on the surface at room temperature. A comparison of the
experimental spectra and the computed core-level-shifts (using methanol and
formic acid as benchmark molecules) suggests that CO adsorbs as a carbonate
on all surface terminations. We find that CO adsorption is hindered by
hydroxyl groups on the hydroxylated surface.Comment: 49 pages, 18 figure