2,314 research outputs found
Determining layer number of two dimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrate
Transition-metal dichalcogenide (TMD) semiconductors have been widely studied
due to their distinctive electronic and optical properties. The property of TMD
flakes is a function of its thickness, or layer number (N). How to determine N
of ultrathin TMDs materials is of primary importance for fundamental study and
practical applications. Raman mode intensity from substrates has been used to
identify N of intrinsic and defective multilayer graphenes up to N=100.
However, such analysis is not applicable for ultrathin TMD flakes due to the
lack of a unified complex refractive index () from monolayer to bulk
TMDs. Here, we discuss the N identification of TMD flakes on the SiO/Si
substrate by the intensity ratio between the Si peak from 100-nm (or 89-nm)
SiO/Si substrates underneath TMD flakes and that from bare SiO/Si
substrates. We assume the real part of of TMD flakes as that of
monolayer TMD and treat the imaginary part of as a fitting
parameter to fit the experimental intensity ratio. An empirical ,
namely, , of ultrathin MoS, WS and WSe
flakes from monolayer to multilayer is obtained for typical laser excitations
(2.54 eV, 2.34 eV, or 2.09 eV). The fitted of MoS has
been used to identify N of MoS flakes deposited on 302-nm SiO/Si
substrate, which agrees well with that determined from their shear and
layer-breathing modes. This technique by measuring Raman intensity from the
substrate can be extended to identify N of ultrathin 2D flakes with N-dependent
. For the application purpose, the intensity ratio excited by
specific laser excitations has been provided for MoS, WS and
WSe flakes and multilayer graphene flakes deposited on Si substrates
covered by 80-110 nm or 280-310 nm SiO layer.Comment: 10 pages, 4 figures. Accepted by Nanotechnolog
Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material
Two-dimensional (2D) transition metal dichalcogenide (TMD) nanosheets exhibit
remarkable electronic and optical properties. The 2D features, sizable
bandgaps, and recent advances in the synthesis, characterization, and device
fabrication of the representative MoS, WS, WSe, and MoSe TMDs
make TMDs very attractive in nanoelectronics and optoelectronics. Similar to
graphite and graphene, the atoms within each layer in 2D TMDs are joined
together by covalent bonds, while van der Waals interactions keep the layers
together. This makes the physical and chemical properties of 2D TMDs layer
dependent. In this review, we discuss the basic lattice vibrations of
monolayer, multilayer, and bulk TMDs, including high-frequency optical phonons,
interlayer shear and layer breathing phonons, the Raman selection rule,
layer-number evolution of phonons, multiple phonon replica, and phonons at the
edge of the Brillouin zone. The extensive capabilities of Raman spectroscopy in
investigating the properties of TMDs are discussed, such as interlayer
coupling, spin--orbit splitting, and external perturbations. The interlayer
vibrational modes are used in rapid and substrate-free characterization of the
layer number of multilayer TMDs and in probing interface coupling in TMD
heterostructures. The success of Raman spectroscopy in investigating TMD
nanosheets paves the way for experiments on other 2D crystals and related van
der Waals heterostructures.Comment: 30 pages, 23 figure
Collaborative Graph Neural Networks for Attributed Network Embedding
Graph neural networks (GNNs) have shown prominent performance on attributed
network embedding. However, existing efforts mainly focus on exploiting network
structures, while the exploitation of node attributes is rather limited as they
only serve as node features at the initial layer. This simple strategy impedes
the potential of node attributes in augmenting node connections, leading to
limited receptive field for inactive nodes with few or even no neighbors.
Furthermore, the training objectives (i.e., reconstructing network structures)
of most GNNs also do not include node attributes, although studies have shown
that reconstructing node attributes is beneficial. Thus, it is encouraging to
deeply involve node attributes in the key components of GNNs, including graph
convolution operations and training objectives. However, this is a nontrivial
task since an appropriate way of integration is required to maintain the merits
of GNNs. To bridge the gap, in this paper, we propose COllaborative graph
Neural Networks--CONN, a tailored GNN architecture for attribute network
embedding. It improves model capacity by 1) selectively diffusing messages from
neighboring nodes and involved attribute categories, and 2) jointly
reconstructing node-to-node and node-to-attribute-category interactions via
cross-correlation. Experiments on real-world networks demonstrate that CONN
excels state-of-the-art embedding algorithms with a great margin
Hemiballism-hemichorea induced by ketotic hyperglycemia: case report with PET study and review of the literature
Hemiballism-hemichorea (HB-HC) is commonly used to describe the basal ganglion dysfunction in non-ketotic hyperglycemic elderly patients. Here we report two elderly female patients with acute onset of involuntary movements induced by hyperglycemia with positive urine ketones. We described the computed tomography and magnetic resonance imaging findings in these two patients, which is similar to that of non-ketotic hyperglycemic HB-HC patients. FDG-PET was performed and the glucose metabolism in the corresponding lesion in these two patients was contradictory with each other. We tried to clarify the underlying mechanisms of HB-HC and explain the contradictory neuroradiological findings in FDG-PET as being performed at different clinical stages
A qualitative study on the clinical safety and user experiences of female condoms for anal intercourse among men who have sex with men in Shanghai, China
ObjectiveThis qualitative study aimed to understand the clinical safety, efficacy, and receptiveness of using the female condom (FC) during anal intercourse among men who have sex with men (MSM).MethodsSubjects for this study were recruited from a two-group crossover trial among MSM in Shanghai. The trial consisted of two phases, each including the use of condoms (FC vs. male condom), questionnaires, and in-depth one-on-one interviews. The two phases were separated by a washout period of 4 weeks. The minimum sample size for this study was determined in accordance with the principle of “information saturation.” The qualitative data were organized and analyzed using ATLAS.ti version 7.ResultsA total of 26 participants from the MSM population were recruited for this study, with 10 assuming the insertive role (i.e., “1”), 8 assuming the receptive role (i.e., “0”), and 8 being versatile (i.e., “0.5”). Each participant completed the crossover trial comprising two phases. The cumulative usage of FCs and male condoms (MCs) amounted to 115 and 127 times, respectively. During the reported sexual encounters, no participants reported incidents of condom rupture, slippage, or other malfunctions. A few participants reported experiencing slight chafing pain, primarily put forward by “0” participants. Apart from those reports, no instances of bleeding, swelling, or allergic reactions were reported. The efficiency of FC in disease prevention, the sexual partner’s willingness to use FC, the freshness of FC, and positive sexual experiences were the main reasons for the consistent use of FC for anal sex. Discomfort and pain during sexual activity, the loose design and thick material of FCs, and difficulties in placing FCs were the major obstacles to FC use among MSM. The elements referring to the forehead exhibited varied in importance among “1,”, “0,” and “0.5” participants. Regarding the willingness to use the FC in the future anal intercourse, 61.54% of participants expressed a positive inclination, 23.08% were uncertain, and 15.38% stated that they would not. “A better sense of security during anal sex” was the main factor affecting willingness among “0” participants and “the sexual pleasure that the FC brought” among “1” participants. Improving the design and technology of FCs and increasing the frequency of use and practice might improve the use skills, which will favor the willingness to use FCs among the MSM population.ConclusionFCs received positive user feedback from study participants, but distinctions were found in individuals in different sexual roles. Large-scale quantitative studies are needed to evaluate the clinical safety of the FC and its effectiveness in preventing the transmission of STDs during anal intercourse
Activation of an AMP-activated protein kinase is involved in post-diapause development of Artemia franciscana encysted embryos
<p>Abstract</p> <p>Background</p> <p>Cysts of <it>Artemia </it>can remain in a dormant state for long periods with a very low metabolic rate, and only resume their development with the approach of favorable conditions. The post-diapause development is a very complicated process involving a variety of metabolic and biochemical events. However, the intrinsic mechanisms that regulate this process are unclear.</p> <p>Results</p> <p>Herein we report the specific activation of an AMP-activated protein kinase (AMPK) in the post-diapause developmental process of <it>Artemia</it>. Using a phospho-AMPKα antibody, AMPK was shown to be phosphorylated in the post-diapause developmental process. Results of kinase assay analysis showed that this phosphorylation is essential for AMPK activation. Using whole-mount immunohistochemistry, phosphorylated AMPK was shown to be predominantly located in the ectoderm of the early developed embryos in a ring shape; however, the location and shape of the activation region changed as development proceeded. Additionally, Western blotting analysis on different portions of the cyst extracts showed that phosphorylated AMPKα localized to the nuclei and this location was not affected by intracellular pH. Confocal microscopy analysis of immunofluorescent stained cyst nuclei further showed that AMPKα localized to the nuclei when activated. Moreover, cellular AMP, ADP, and ATP levels in developing cysts were determined by HPLC, and the results showed that the activation of <it>Artemia </it>AMPK may not be associated with cellular AMP:ATP ratios, suggesting other pathways for regulation of <it>Artemia </it>AMPK activity.</p> <p>Conclusion</p> <p>Together, we report evidence demonstrating the activation of AMPK in <it>Artemia </it>developing cysts and present an argument for its role in the development-related gene expression and energy control in certain cells during post-diapause development of <it>Artemia</it>.</p
A Study of Wolf Pack Algorithm for Test Suite Reduction
Modern smart meter programs are iterating at an ever-increasing rate, placing higher demands on the software testing of smart meters. How to reduce the cost of software testing has become a focus of current research. The reduction of test overhead is the most intuitive way to reduce the cost of software testing. Test suite reduction is one of the necessary means to reduce test overhead. This paper proposes a smart meter test suite reduction technique based on Wolf Pack Algorithm. First, the algorithm uses the binary optimization set coverage problem to represent the test suite reduction of the smart meter program; then, the Wolf Pack Algorithm is improved by converting the positions of individual wolves into a 0/1 matrix; finally, the optimal test case subset is obtained by iteration. By simulating different smart meter programs and different size test suites, the experimental result shows that the Wolf Pack Algorithm achieves better results compared to similar algorithms in terms of the percentage of obtaining both the optimal solution and the optimal subset of test overhead
Polytypism and Unexpected Strong Interlayer Coupling of two-Dimensional Layered ReS2
The anisotropic two-dimensional (2D) van der Waals (vdW) layered materials,
with both scientific interest and potential application, have one more
dimension to tune the properties than the isotropic 2D materials. The
interlayer vdW coupling determines the properties of 2D multi-layer materials
by varying stacking orders. As an important representative anisotropic 2D
materials, multilayer rhenium disulfide (ReS2) was expected to be random
stacking and lack of interlayer coupling. Here, we demonstrate two stable
stacking orders (aa and a-b) of N layer (NL, N>1) ReS2 from ultralow-frequency
and high-frequency Raman spectroscopy, photoluminescence spectroscopy and
first-principles density functional theory calculation. Two interlayer shear
modes are observed in aa-stacked NL-ReS2 while only one interlayer shear mode
appears in a-b-stacked NL-ReS2, suggesting anisotropic-like and isotropic-like
stacking orders in aa- and a-b-stacked NL-ReS2, respectively. The frequency of
the interlayer shear and breathing modes reveals unexpected strong interlayer
coupling in aa- and a-b-NL-ReS2, the force constants of which are 55-90% to
those of multilayer MoS2. The observation of strong interlayer coupling and
polytypism in multi-layer ReS2 stimulate future studies on the structure,
electronic and optical properties of other 2D anisotropic materials
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