10 research outputs found
A non-dispersive Raman D-band activated by well-ordered interlayer interactions in rotationally stacked bi-layer Graphene
Raman measurements on monolayer graphene folded back upon itself as an
ordered but skew-stacked bilayer (i.e. with interlayer rotation) presents new
mechanism for Raman scattering in sp2 carbons that arises in systems that lack
coherent AB interlayer stacking. Although the parent monolayer does not exhibit
a D-band, the interior of the skewed bilayer produces a strong two-peak Raman
feature near 1350 cm-1; one of these peaks is non-dispersive, unlike all
previously observed D-band features in sp2 carbons. Within a double-resonant
model of Raman scattering, these unusual features are consistent with a skewed
bilayer coupling, wherein one layer imposes a weak but well-ordered
perturbation on the other. The discrete Fourier structure of the rotated
interlayer interaction potential explains the unusual non-dispersive peak near
1350 cm-1
Why It Takes So Long to Connect to a WiFi Access Point
Today's WiFi networks deliver a large fraction of traffic. However, the
performance and quality of WiFi networks are still far from satisfactory. Among
many popular quality metrics (throughput, latency), the probability of
successfully connecting to WiFi APs and the time cost of the WiFi connection
set-up process are the two of the most critical metrics that affect WiFi users'
experience. To understand the WiFi connection set-up process in real-world
settings, we carry out measurement studies on million mobile users from
representative cities associating with million APs in billion WiFi
sessions, collected from a mobile "WiFi Manager" App that tops the Android/iOS
App market. To the best of our knowledge, we are the first to do such large
scale study on: how large the WiFi connection set-up time cost is, what factors
affect the WiFi connection set-up process, and what can be done to reduce the
WiFi connection set-up time cost. Based on the measurement analysis, we develop
a machine learning based AP selection strategy that can significantly improve
WiFi connection set-up performance, against the conventional strategy purely
based on signal strength, by reducing the connection set-up failures from
to and reducing time costs of the connection set-up
processes by more than times.Comment: 11pages, conferenc
Photoluminescence from nanocrystalline graphite monofluoride
We synthesize and study the structural and optical properties of
nanocrystalline graphene monofluoride and graphite monofluoride, which are
carbon-based wide bandgap materials. Using laser excitations 2.41 - 5.08 eV, we
identify six emission modes of graphite monofluoride, spanning the visible
spectrum from red to violet. The energy and linewidth of the modes point to
defect-induced midgap states as the source of the photoemission. We discuss
possible candidates. Our findings open the window to electro-optical
applications of graphene fluoride.Comment: 11 pages including supporting information, 2 figure
H-infinity control with dynamic output feedback for uncertain impulsive systems
The problem of robust dynamic output feedback H∞ control is investigated for uncertain impulsive systems. Two types of impulses are considered: one is destabilizing, the other one is stabilizing. For each class of impulsive systems, sufficient conditions for robust stability and weighted limited L2 gain are developed. Furthermore, based on linear matrix inequalities, sufficient conditions for the existence of dynamic output feedback H∞ controller are derived. Finally, numerical examples are provided to demonstrate the effectiveness of the proposed design methods
Robust H∞ control of uncertain linear impulsive stochastic systems
This paper develops robust stability theorems and robust H ∞ control theory for uncertain impulsive stochastic systems. The parametric uncertainties are assumed to be time varying and norm bounded. Impulsive stochastic systems can be divided into three cases, namely, the systems with stable/stabilizable continuous-time stochastic dynamics and unstable/unstabilizable discrete-time dynamics, the systems with unstable/unstabilizable continuous dynamics and stable/stabilizable discrete-time dynamics, and the systems in which both the continuous-time stochastic dynamics and the discrete-time dynamics are stable/stabilizable. Sufficient conditions for robust exponential stability and robust stabilization for uncertain impulsive stochastic systems are derived in terms of an average dwell-time condition. Then, a linear matrix inequality-based approach to the design of a robust H∞ controller for each system is presented. Finally, the numerical examples are provided to demonstrate the effectiveness of the proposed approach
Inhibition of MORC2 Mediates HDAC4 to Promote Cellular Senescence through p53/p21 Signaling Axis
(1) Background: Colorectal cancer (CRC) is a common gastrointestinal malignancy, accounting for the second largest gastrointestinal tumor. MORC2, a newly discovered chromatin remodeling protein, plays an important role in the biological processes of various cancers. However, the potential mechanistic role of MORC2 in promoting proliferation of CRC carcinoma remains unclear. (2) Methods: The Cancer Genome Atlas database was analyzed using bioinformatics to obtain gene expression and clinical prognosis data. The cell proliferation was assessed by CCK8 and EdU assays, as well as xenograft. SA-beta-gal staining, Western blot, and ELISA assay were using to assess the cell senescence and potential mechanism. (3) Results: Our data showed that MORC2 expression was elevated in CRC patients. Depletion of MORC2 inhibited cellular proliferation both in vivo and in vitro. Further studies showed that the depletion of MORC2 enhanced p21 and p53 expression through decreasing HDAC4 and increasing pro-inflammatory factors IL-6 and IL-8, thus, promoting cellular senescence. (4) Conclusions: We concluded that increased MORC2 expression in CRC might play a critical role in tumorigenesis by regulating the cellular senescence, in addition, MORC2 could be a novel biomarker for clinical outcomes and prognosis and a treatment target for CRC
Evidence for Ambient-Temperature Reversible Catalytic Hydrogenation in Pt-Doped Carbons
In situ high-pressure Raman spectroscopy, with corroborating density functional calculations, is used to probe C-H chemical bonds formed when dissociated hydrogen diffuses from a platinum nanocatalyst to three distinct graphenic surfaces. At ambient temperature, hydrogenation and dehydrogenation are reversible in the combined presence of an active catalyst and oxygen heteroatoms. Hydrogenation apparently occurs through surface diffusion in a chemisorbed state, while dehydrogenation requires diffusion of the chemisorbed species back to an active catalyst
Evidence for Ambient-Temperature Reversible Catalytic Hydrogenation in Pt-doped Carbons
In situ high-pressure Raman spectroscopy, with corroborating
density
functional calculations, is used to probe C–H chemical bonds
formed when dissociated hydrogen diffuses from a platinum nanocatalyst
to three distinct graphenic surfaces. At ambient temperature, hydrogenation
and dehydrogenation are reversible in the combined presence of an
active catalyst and oxygen heteroatoms. Hydrogenation apparently occurs
through surface diffusion in a chemisorbed state, while dehydrogenation
requires diffusion of the chemisorbed species back to an active catalyst