35 research outputs found
Improving data quality for 3D electron diffraction (3D ED) by Gatan Image Filter and a new crystal tracking method
3D ED is an effective technique to determine the structures of submicron- or
nano-sized crystals. In this paper, we implemented energy-filtered 3D ED using
a Gatan Energy Filter (GIF) in both selected area electron diffraction mode and
micro/nanoprobe mode. We explained the setup in detail, which improves the
accessibility of energy-filtered 3D ED experiments as more electron microscopes
are equipped with a GIF than an in-column filter. We also proposed a crystal
tracking method in STEM mode using live HAADF image stream. This method enables
us to collect energy-filtered 3D ED datasets in STEM mode with a larger tilt
range without foregoing any frames. In order to compare the differences between
energy-filtered 3D ED and normal 3D ED data, three crystalline samples have
been studied in detail. We observed that the final R1 will improve 20% to 30%
for energy-filtered datasets compared with unfiltered datasets and the
structure became more reasonable. We also discussed the possible reasons that
lead to the improvement
A Comparison of Structure Determination of Small Organic Molecules by 3D Electron Diffraction at Cryogenic and Room Temperature
3D electron diffraction (3D ED), also known as micro-crystal electron diffraction (MicroED), is a rapid, accurate, and robust method for structure determination of submicron-sized crystals. 3D ED has mainly been applied in material science until 2013, when MicroED was developed for studying macromolecular crystals. MicroED was considered as a cryo-electron microscopy method, as MicroED data collection is usually carried out in cryogenic conditions. As a result, some researchers may consider that 3D ED/MicroED data collection on crystals of small organic molecules can only be performed in cryogenic conditions. In this work, we determined the structure for sucrose and azobenzene tetracarboxylic acid (H4ABTC). The structure of H4ABTC is the first crystal structure ever reported for this molecule. We compared data quality and structure accuracy among datasets collected under cryogenic conditions and room temperature. With the improvement in data quality by data merging, it is possible to reveal hydrogen atom positions in small organic molecule structures under both temperature conditions. The experimental results showed that, if the sample is stable in the vacuum environment of a transmission electron microscope (TEM), the data quality of datasets collected under room temperature is at least as good as data collected under cryogenic conditions according to various indicators (resolution, I/σ(I), CC1/2 (%), R1, Rint, ADRA
The relationship between depressive mood and non-suicidal self-injury among secondary vocational school students: the moderating role of borderline personality disorder tendencies
BackgroundNon-suicidal self-injury (NSSI) has become an important public health issue of global concern, often occurring in adolescents, and depressive mood is closely related to NSSI. In addition, NSSI is considered a symptom of borderline personality disorder. It has been found that adolescents in secondary vocational schools are more vulnerable to behavior and emotional disorders than those in general high schools. This study investigated the risk factors associated with NSSI affecting secondary vocational school students and analyzed the role of borderline personality disorder tendencies in promoting the occurrence of NSSI among students with depressive moods.MethodsA total of 1,848 Chinese secondary vocational students completed a self-report questionnaire. The homemade NSSI behavior questionnaire, Patient Health Questionnaire-9 and Personality Diagnostic Questionnaire-4 were used in this survey. Binary logistic regression and PROCESS software analysis were used to explore the influencing factors associated with NSSI and to test for moderating effects.ResultsFemale (OR = 3.412, 95% CI 2.301–5.060), drinking history (OR = 2.007, 95% CI 1.383–2.911), history of suicidal death exposure (OR = 3.161, 95% CI 1.999–4.999), depressive mood (OR = 2.436, 95% CI 1.668–3.558) and borderline personality disorder tendencies (OR = 2.558, 95% CI = 1.764–3.711) were independent risk factors for NSSI. Borderline personality disorder tendencies (B = 0.047, p = 0.000) moderated the relationship between depressive mood and NSSI. The stronger the borderline personality tendencies, the more NSSI behavior occurred when they were depressive.ConclusionsBorderline personality disorder tendencies in secondary vocational school adolescents significantly enhance the association of depressive mood with NSSI. There is a moderating role for borderline personality disorder tendencies in depressive mood and NSSI
Intrinsic Electronic Structure and Nodeless Superconducting Gap of Observed by Spatially-Resolved Laser-Based Angle Resolved Photoemission Spectroscopy
The spatially-resolved laser-based high resolution ARPES measurements have
been performed on the optimally-doped
(Y123) superconductor. For the first time, we found the region from the cleaved
surface that reveals clear bulk electronic properties. The intrinsic Fermi
surface and band structures of Y123 are observed. The Fermi surface-dependent
and momentum-dependent superconducting gap is determined which is nodeless and
consistent with the d+is gap form
Electronic Origin of High-Tc Maximization and Persistence in Trilayer Cuprate Superconductors
In high temperature cuprate superconductors, it was found that the
superconducting transition temperature Tc depends on the number of CuO2 planes
(n) in the structural unit and the maximum Tc is realized in the trilayer
system (n=3). It was also found that the trilayer superconductors exhibit an
unusual phase diagram that Tc keeps nearly constant in the overdoped region
which is in strong contrast to the Tc decrease usually found in other cuprate
superconductors. The electronic origin of the Tc maximization in the trilayer
superconductors and its high Tc persistence in the overdoped region remains
unclear. By taking high resolution laser-based angle resolved photoemission
(ARPES) measurements, here we report our revelation of the microscopic origin
of the unusual superconducting properties in the trilayer superconductors. For
the first time we have observed the trilayer splitting in Bi2Sr2Ca2Cu3O10+d
(Bi2223) superconductor. The observed Fermi surface, band structures,
superconducting gap and the selective Bogoliubov band hybridizations can be
well described by a three-layer interaction model. Quantitative information of
the microscopic processes involving intra- and interlayer hoppings and pairings
are extracted. The electronic origin of the maximum Tc in Bi2223 and the
persistence of the high Tc in the overdoped region is revealed. These results
provide key insights in understanding high Tc superconductivity and pave a way
to further enhance Tc in the cuprate superconductors
Orbital-Dependent Electron Correlation in Double-Layer Nickelate La3Ni2O7
The latest discovery of high temperature superconductivity near 80K in
La3Ni2O7 under high pressure has attracted much attention. Many proposals are
put forth to understand the origin of superconductivity. The determination of
electronic structures is a prerequisite to establish theories to understand
superconductivity in nickelates but is still lacking. Here we report our direct
measurement of the electronic structures of La3Ni2O7 by high-resolution
angle-resolved photoemmission spectroscopy. The Fermi surface and band
structures of La3Ni2O7 are observed and compared with the band structure
calculations. A flat band is formed from the Ni-3dz2 orbitals around the zone
corner which is 50meV below the Fermi level. Strong electron correlations are
revealed which are orbital- and momentum-dependent. Our observations will
provide key information to understand the origin of high temperature
superconductivity in La3Ni2O7.Comment: 18 pages, 4 figure
Nodal s± pairing symmetry in an iron-based superconductor with only hole pockets
The origin of high-temperature superconductivity in iron-based superconductors is still not understood; determination of the pairing symmetry is essential for understanding the superconductivity mechanism. In the iron-based superconductors that have hole pockets around the Brillouin zone centre and electron pockets around the zone corners, the pairing symmetry is generally considered to be s±, which indicates a sign change in the superconducting gap between the hole and electron pockets. For the iron-based superconductors with only hole pockets, however, a couple of pairing scenarios have been proposed, but the exact symmetry is still controversial. Here we determine that the pairing symmetry in KFe2As2—which is a prototypical iron-based superconductor with hole pockets both around the zone centre and around the zone corners—is also of the s± type. Our laser-based angle-resolved photoemission measurements have determined the superconducting gap distribution and identified the locations of the gap nodes on all the Fermi surfaces around the zone centres and the zone corners. These results unify the pairing symmetry in hole-doped iron-based superconductors and point to spin fluctuation as the pairing glue in generating superconductivity