155 research outputs found
Spectroscopic imaging of single atoms within a bulk solid
The ability to localize, identify and measure the electronic environment of
individual atoms will provide fundamental insights into many issues in
materials science, physics and nanotechnology. We demonstrate, using an
aberration-corrected scanning transmission microscope, the spectroscopic
imaging of single La atoms inside CaTiO3. Dynamical simulations confirm that
the spectroscopic information is spatially confined around the scattering atom.
Furthermore we show how the depth of the atom within the crystal may be
estimated.Comment: 4 pages and 3 figures. Accepted in Phys.Rev.Let
Polar-Graded Multiferroic SrMnO3 Thin Films
Engineering defects and strains in oxides provides a promising route for the quest of thin film materials with coexisting ferroic orders, multiferroics, with efficient magnetoelectric coupling at room temperature. Precise control of the strain gradient would enable custom tailoring of the multiferroic properties but presently remains challenging. Here we explore the existence of a polar-graded state in epitaxially strained antiferromagnetic SrMnO3 thin films, whose polar nature was predicted theoretically and recently demonstrated experimentally. By means of aberration-corrected scanning transmission electron microscopy we map the polar rotation of the ferroelectric polarization with atomic resolution, both far from and near the domain walls, and find flexoelectricity resulting from vertical strain gradients. The origin of this particular strain state is a gradual distribution of oxygen vacancies across the film thickness, according to electron energy loss spectroscopy. Herein we present a chemistry-mediated route to induce polar rotations in oxygen-deficient multiferroic films, resulting in flexoelectric polar rotations and with potentially enhanced piezoelectricity
SNP genotyping elucidates the genetic diversity of Magna Graecia grapevine germplasm and its historical origin and dissemination
Background: Magna Graecia is the ancient name for the modern geopolitical region of South Italy extensively populated by Greek colonizers, shown by archeological and historical evidence to be the oldest wine growing region of Italy, crucial for the spread of specialized viticulture around Mediterranean shores. Here, the genetic diversity of Magna Graecia grape germplasm was assessed and its role in grapevine propagation around the Mediterranean basin was underlined. Results: A large collection of grapevines from Magna Graecia was compared with germplasm from Georgia to the Iberian Peninsula using the 18 K SNP array. A high level of genetic diversity of the analyzed germplasm was determined; clustering, structure analysis and DAPC (Discriminant Analysis of Principal Components) highlighted the genetic relationships among genotypes from South Italy and the Eastern Mediterranean (Greece). Gene flow from east (Georgia) to west (Iberian Peninsula) was identified throughout the large number of detected admixed samples. Pedigree analysis showed a complex and well-structured network of first degree relationships, where the cultivars from Magna Graecia were mainly involved. Conclusions: This study provided evidence that Magna Graecia germplasm was shaped by historical events that occurred in the area due to the robust link between South Italian and Greek genotypes, as well as, by the availability of different thermal resources for cultivars growing in such different winegrowing areas. The uniqueness of this ampelographic platform was mainly an outcome of complex natural or human-driven crosses involving elite cultivars
Recommended from our members
High-K dielectric sulfur-selenium alloys.
Upcoming advancements in flexible technology require mechanically compliant dielectric materials. Current dielectrics have either high dielectric constant, K (e.g., metal oxides) or good flexibility (e.g., polymers). Here, we achieve a golden mean of these properties and obtain a lightweight, viscoelastic, high-K dielectric material by combining two nonpolar, brittle constituents, namely, sulfur (S) and selenium (Se). This S-Se alloy retains polymer-like mechanical flexibility along with a dielectric strength (40 kV/mm) and a high dielectric constant (K = 74 at 1 MHz) similar to those of established metal oxides. Our theoretical model suggests that the principal reason is the strong dipole moment generated due to the unique structural orientation between S and Se atoms. The S-Se alloys can bridge the chasm between mechanically soft and high-K dielectric materials toward several flexible device applications
The secret life of garnets: a comprehensive, standardized dataset of garnet geochemical analyses integrating localities and petrogenesis
Integrating mineralogy with data science is critical to
modernizing Earth materials research and its applications to geosciences.
Data were compiled on 95 650 garnet sample analyses from a variety of
sources, ranging from large repositories (EarthChem, RRUFF, MetPetDB) to
individual peer-reviewed literature. An important feature is the inclusion
of mineralogical “dark data” from papers published prior to 1990. Garnets
are commonly used as indicators of formation environments, which directly
correlate with their geochemical properties; thus, they are an ideal subject
for the creation of an extensive data resource that incorporates
composition, locality information, paragenetic mode, age, temperature,
pressure, and geochemistry. For the data extracted from existing databases
and literature, we increased the resolution of several key aspects,
including petrogenetic and paragenetic attributes, which we extended from
generic material type (e.g., igneous, metamorphic) to more specific rock-type names (e.g., diorite, eclogite, skarn) and locality information,
increasing specificity by examining the continent, country, area, geological
context, longitude, and latitude. Likewise, we utilized end-member and
quality index calculations to help assess the garnet sample analysis
quality. This comprehensive dataset of garnet information is an open-access
resource available in the Evolutionary System of Mineralogy Database (ESMD)
for future mineralogical studies, paving the way for characterizing
correlations between chemical composition and paragenesis through natural
kind clustering (Chiama et al., 2022; https://doi.org/10.48484/camh-xy98). We encourage scientists to contribute their own
unpublished and unarchived analyses to the growing data repositories of
mineralogical information that are increasingly valuable for advancing
scientific discovery.</p
Genetic dynamics in untreated CLL patients with either stable or progressive disease: A longitudinal study
Clonal evolution of chronic lymphocytic leukemia (CLL) often follows chemotherapy and is associated with adverse outcome, but also occurs in untreated patients, in which case its predictive role is debated. We investigated whether the selection and expansion of CLL clone(s) precede an aggressive disease shift. We found that clonal evolution occurs in all CLL patients, irrespective of the clinical outcome, but is faster during disease progression. In particular, changes in the frequency of nucleotide variants (NVs) in specific CLL-related genes may represent an indicator of poor clinical outcome
Circulating MicroRNA-15a Associates With Retinal Damage in Patients With Early Stage Type 2 Diabetes
: Circulating microRNAs are potential biomarkers of type 2 diabetes mellitus (T2DM) and related complications. Here, we investigated the association of microRNA-15a with early retinal damage in T2DM. A cohort of untreated subjects screened for intermediate/high risk of T2DM, according to a score assessment questionnaire, and then recognized to have a normal (NGT) or impaired (IGT) glucose tolerance or T2DM was studied. The thickness of the ganglion cell complex (GCC), an early marker of retinal degeneration anteceding overt retinopathy was assessed by Optical Coherence Tomography. Total and extracellular vesicles (EV)-associated microRNA-15a quantity was measured in plasma by real time PCR. MicroRNA-15a level was significantly higher in subjects with IGT and T2DM compared with NGT. MicroRNA-15a abundance was correlated to body mass index and classical diabetes biomarkers, including fasting glucose, HbA1c, insulinemia, and HOMA-IR. Moreover, GCC thickness was significantly reduced in IGT and T2DM subjects compared with NGT controls. Importantly, total microRNA-15a correlated with GCC in IGT subjects, while in T2DM subjects, EV-microRNA-15a negatively correlated with GCC, suggesting that microRNA-15a may monitor initial retinal damage. The assessment of plasma microRNA-15a may help refining risk assessment and secondary prevention in patients with preclinical T2DM
Direct Observation of an Interface Dipole between Two Metallic Oxides Caused by Localized Oxygen Vacancies
Oxygen vacancies are increasingly recognized to play a role in phenomena
observed at transition-metal oxide interfaces. Here we report a study of
SrRuO3/La0.7Sr0.3MnO3 (SRO/LSMO) interfaces using a combination of quantitative
aberration-corrected scanning transmission electron microscopy, electron energy
loss spectroscopy, and density-functional calculations. Cation displacements
are observed at the interface, indicative of a dipole-like electric field even
though both materials are nominally metallic. The observed displacements are
reproduced by theory if O vacancies are present in the near-interface LSMO
layers. The results suggest that atomic-scale structural mapping can serve as a
quantitative indicator of the presence of O vacancies at interfaces
Spatial symmetry constraint of charge-ordered kagome superconductor CsVSb
Elucidating the symmetry of intertwined orders in exotic superconductors is
at the quantum frontier. Recent surface sensitive studies of the topological
kagome superconductor CsVSb discovered a cascade 4a superlattice
below the charge density wave (CDW) ordering temperature, which can be related
to the pair density modulations in the superconducting state. If the 4a
phase is a bulk and intrinsic property of the kagome lattice, this would form a
striking analogy to the stripe order and pair density wave discovered in the
cuprate high-temperature superconductors, and the cascade ordering found in
twisted bilayer graphene. High-resolution X-ray diffraction has recently been
established as an ultra-sensitive probe for bulk translational
symmetry-breaking orders, even for short-range orders at the diffusive limit.
Here, combining high-resolution X-ray diffraction, scanning tunneling
microscopy and scanning transmission electron microscopy, we demonstrate that
the 4a superstructure emerges uniquely on the surface and hence exclude the
4a phase as the origin of any bulk transport or spectroscopic anomaly.
Crucially, we show that our detected 222 CDW order breaks the
bulk rotational symmetry to C2, which can be the driver for the bulk nematic
orders and nematic surface superlattices including the 4a phase. Our
high-resolution data impose decisive spatial symmetry constraints on emergent
electronic orders in the kagome superconductor CsVSb
- …