912 research outputs found
Electrical and optical properties of fluid iron from compressed to expanded regime
Using quantum molecular dynamics simulations, we show that the electrical and
optical properties of fluid iron change drastically from compressed to expanded
regime. The simulation results reproduce the main trends of the electrical
resistivity along isochores and are found to be in good agreement with
experimental data. The transition of expanded fluid iron into a nonmetallic
state takes place close to the density at which the constant volume derivative
of the electrical resistivity on internal energy becomes negative. The study of
the optical conductivity, absorption coefficient, and Rosseland mean opacity
shows that, quantum molecular dynamics combined with the Kubo-Greenwood
formulation provides a powerful tool to calculate and benchmark the electrical
and optical properties of iron from expanded fluid to warm dense region
COMPUTER TEACHING STRATEGY BASED ON BIG DATA ENVIRONMENT FROM THE PERSPECTIVE OF EDUCATIONAL PSYCHOLOGY
COMPUTER TEACHING STRATEGY BASED ON BIG DATA ENVIRONMENT FROM THE PERSPECTIVE OF EDUCATIONAL PSYCHOLOGY
A Local Concentration-based Descriptor Predicting the Stacking Fault Energy of Refractory High Entropy Alloys
Stacking fault energy (SFE) is an essential parameter for characterizing
mechanical properties. However, in high entropy alloys (HEAs), the local
chemical environment varies significantly across different stacking fault
planes, resulting in a substantial fluctuation of SFE values rather than a
unique value, which prohibits the prediction of the local SFE. Herein, we
proposed an effective descriptor based on the local concentration ratio near
stacking fault to quantitatively predict the local SFE of refractory HEAs. We
find that the role of a given element in determining SFE strongly depends on
its valence-electron number relative to other components and the contribution
of its s- and d-electrons to its cohesive properties, which can be understood
in the framework of the tight-binding model. Notably, the descriptor not only
unifies the local nature of SFE from simple alloys to HEAs but also helps to
quickly design HEAs as the involved parameters are easily accessible.Comment: 20 pages,10 figure
Dimensionless ratios: characteristics of quantum liquids and their phase transitions
Dimensionless ratios of physical properties can characterize low-temperature
phases in a wide variety of materials. As such, the Wilson ratio (WR), the
Kadowaki-Woods ratio and the Wiedemann\--Franz law capture essential features
of Fermi liquids in metals, heavy fermions, etc. Here we prove that the phases
of many-body interacting multi-component quantum liquids in one dimension (1D)
can be described by WRs based on the compressibility, susceptibility and
specific heat associated with each component. These WRs arise due to additivity
rules within subsystems reminiscent of the rules for multi-resistor networks in
series and parallel --- a novel and useful characteristic of multi-component
Tomonaga-Luttinger liquids (TLL) independent of microscopic details of the
systems. Using experimentally realised multi-species cold atomic gases as
examples, we prove that the Wilson ratios uniquely identify phases of TLL,
while providing universal scaling relations at the boundaries between phases.
Their values within a phase are solely determined by the stiffnesses and sound
velocities of subsystems and identify the internal degrees of freedom of said
phase such as its spin-degeneracy. This finding can be directly applied to a
wide range of 1D many-body systems and reveals deep physical insights into
recent experimental measurements of the universal thermodynamics in ultracold
atoms and spins.Comment: 12 pages (main paper), (6 figures
Adv3D: Generating 3D Adversarial Examples in Driving Scenarios with NeRF
Deep neural networks (DNNs) have been proven extremely susceptible to
adversarial examples, which raises special safety-critical concerns for
DNN-based autonomous driving stacks (i.e., 3D object detection). Although there
are extensive works on image-level attacks, most are restricted to 2D pixel
spaces, and such attacks are not always physically realistic in our 3D world.
Here we present Adv3D, the first exploration of modeling adversarial examples
as Neural Radiance Fields (NeRFs). Advances in NeRF provide photorealistic
appearances and 3D accurate generation, yielding a more realistic and
realizable adversarial example. We train our adversarial NeRF by minimizing the
surrounding objects' confidence predicted by 3D detectors on the training set.
Then we evaluate Adv3D on the unseen validation set and show that it can cause
a large performance reduction when rendering NeRF in any sampled pose. To
generate physically realizable adversarial examples, we propose primitive-aware
sampling and semantic-guided regularization that enable 3D patch attacks with
camouflage adversarial texture. Experimental results demonstrate that the
trained adversarial NeRF generalizes well to different poses, scenes, and 3D
detectors. Finally, we provide a defense method to our attacks that involves
adversarial training through data augmentation. Project page:
https://len-li.github.io/adv3d-we
N′-(2-Methoxybenzylidene)nicotinohydrazide
The title compound, C14H13N3O2, was prepared by the reaction of 2-methoxybenzyaldehyde with nicotinic acid hydrazide in methanol. The dihedral angle between the benzene and pyridine rings is 5.9 (3)°. In the crystal structure, molecules are linked by intermolecular N—H⋯O hydrogen bonds, leading to the formation of chains along the c axis; adjacent chains are linked via C—H⋯O and C—H⋯N hydrogen bonds
HIF-1α Contributes to Hypoxia-induced Invasion and Metastasis of Esophageal Carcinoma via Inhibiting E-cadherin and Promoting MMP-2 Expression
Hypoxia-inducible factor-1α (HIF-1α) has been found to enhance tumor invasion and metastasis, but no study has reported its action in esophageal carcinoma. The goal of this study was to explore the probable mechanism of HIF-1α in the invasion and metastasis of esophageal carcinoma Eca109 cells in vitro and in vivo. mRNA and protein expression of HIF-1α, E-cadherin and matrix metalloproteinase-2 (MMP-2) under hypoxia were detected by RT-PCR and Western blotting. The effects of silencing HIF-1α on E-cadherin, MMP-2 mRNA and protein expression under hypoxia or normoxia were detected by RT-PCR and Western blotting, respectively. The invasive ability of Eca109 cells was tested using a transwell chambers. We established an Eca109-implanted tumor model and observed tumor growth and lymph node metastasis. The expression of HIF-1α, E-cadherin and MMP-2 in xenograft tumors was detected by Western blotting. After exposure to hypoxia, HIF-1α protein was up-regulated, both mRNA and protein levels of E-cadherin were down-regulated and MMP-2 was up-regulated, while HIF-1α mRNA showed no significant change. SiRNA could block HIF-1α effectively, increase E-cadherin expression and inhibit MMP-2 expression. The number of invading cells decreased after HIF-1α was silenced. Meanwhile, the tumor volume was much smaller, and the metastatic rate of lymph nodes and the positive rate were lower in vivo. Our observations suggest that HIF-1α inhibition might be an effective strategy to weaken invasion and metastasis in the esophageal carcinoma Eca109 cell line
3,8-Dimethylquinazoline-2,4(1H,3H)-dione
In the title compound, C10H10N2O2, all non-H atoms are approximately co-planar with an r.m.s. deviation of 0.016 Å. In the crystal, molecules are linked into inversion dimers by pairs of N—H⋯O hydrogen bonds. Chains along [010] are buiilt up by π–π interactions [centroid–centroid distance = 3.602 (1) Å] between the benzene and piperazine rings of adjacent molecules
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