1,192 research outputs found
The European Union and China: Adversaries or Allies
Historically Europe and China have caused great changes in the world, both with and against each other. Should one look at the landscape of the world today, they would clearly see the influence of Europe and China. It is undeniable that these states have enormous potential, and will make a global difference in the near future. However their recently acquired Partnership lacks clarity on both sides despite its paramount importance.
The thesis is a study to answer the question “What is the Sino-EU relationship?” and “How will it affect the changing world?” Using an examination of their histories, perceptions, foreign policies, differences of concepts, and view of each other, this study will analyze the current situation and provide predictions for the coming years
Direct dating of mid-crustal shear zones with synkinematic allanite:new in situ U-Th-Pb geochronological approaches applied to the Mont Blanc massif
International audienceDating the timing of motion on crustal shear zones is of tremendous importance for understanding the assembly of orogenic terranes. This objective is achieved in this paper by combining petrological and structural observations with novel developments in in situ U-Th-Pb geochronology of allanite. A greenschist facies shear zone within the Mont Blanc Massif is documented. Allanite is synkinematic and belongs to the mylonitic assemblage. LA-ICP-MS U-Th-Pb isotope analyses of allanite reveal high contents and highly radiogenic isotopic compositions of the common-Pb component. The use of measured Pb-isotope compositions of associated minerals (feldspars and chlorite) is critical for accurate common-Pb correction, and provides a powerful mechanism for linking allanite growth to the metamorphic assemblage. A mean 208Pb/232Th age of 29.44 ± 0.95 Ma is accordingly taken for synkinematic allanite crystallisation under greenschist facies conditions. This age reflects the timing of the Mont Blanc underthrusting below the Penninic Front and highlights the potential of directly dating deformation with allanite
Increased Affinity for RNA Targets Evolved Early in Animal and Plant Dicer Lineages through Different Structural Mechanisms
Understanding the structural basis for evolutionary changes in protein function is central to molecular evolutionary biology and can help determine the extent to which functional convergence occurs through similar or different structural mechanisms. Here, we combine ancestral sequence reconstruction with functional characterization and structural modeling to directly examine the evolution of sequence-structure-function across the early differentiation of animal and plant Dicer/DCL proteins, which perform the first molecular step in RNA interference by identifying target RNAs and processing them into short interfering products. We found that ancestral Dicer/DCL proteins evolved similar increases in RNA target affinities as they diverged independently in animal and plant lineages. In both cases, increases in RNA target affinities were associated with sequence changes that anchored the RNA's 5'phosphate, but the structural bases for 5'phosphate recognition were different in animal versus plant lineages. These results highlight how molecular-functional evolutionary convergence can derive from the evolution of unique protein structures implementing similar biochemical mechanisms
Exceeding octave tunable Terahertz waves with zepto-second level timing noise
Spectral purity of any millimeter wave (mmW) source is of the utmost interest
in low-noise applications. Optical synthesis via photomixing is an attractive
source for such mmWs, which usually involves expensive spectrally pure lasers
with narrow linewidths approaching monochromaticity due to their inherent
fabrication costs or specifications. Here, we report an alternative option for
enhancing the spectral purity of inexpensive semiconductor diode lasers via a
self-injection locking technique through corresponding Stokes waves from a
fiber Brillouin cavity exhibiting greatly improved phase noise levels and large
wavelength tunability of ~1.8 nm. We implement a system with two self-injected
diode lasers on a common Brillouin cavity aimed at difference frequency
generation in the mmW and THz region. We generate tunable sub-mmW (0.3 and 0.5
THz) waves by beating the self-injected two wavelength Stokes light on a
uni-travelling carrier photodiode and characterize the noise performance. The
sub-mmW features miniscule timing noise levels in the zepto-second (zs.Hz^-0.5)
scale outperforming the state of the art dissipative Kerr soliton based
micro-resonator setups while offering broader frequency tunability. These
results suggest a viable inexpensive alternative for mmW sources aimed at
low-noise applications featuring lab-scale footprints and rack-mounted
portability while paving the way for chip-scale photonic integration.Comment: 31 page
Brillouin laser-driven terahertz oscillator up to 3 THz with femtosecond-level timing jitter
The terahertz (THz) frequency range, spanning 0.1 to 10 THz, is a field ripe
for innovation with vast, developing potential in areas like wireless
communication and molecular spectroscopy. Our work introduces a dual-wavelength
laser design that utilizes stimulated Brillouin scattering in an optical fiber
cavity to effectively generate two highly coherent optical Stokes waves with
differential phase noise inherently mitigated. To guarantee robust operation,
the Stokes waves are optically injected into their respective pump lasers,
which also serves to greatly improve the resulting coherence. The frequency
difference between the two wavelengths is converted into THz waves through a
uni-traveling-carrier photodiode. This innovative design facilitates the
generation of THz waves with phase noise levels of less than -100 dBc/Hz,
translating to timing noise below 10~ at 10
kHz Fourier frequency, over a carrier frequency range from 300 GHz to 3 THz.
This development in phase noise reduction establishes a new benchmark in the
spectral purity of tunable THz sources. Such advances are pivotal for
applications to move beyond oscillator constraints
Eye lens β-crystallins are predicted by native ion mobility-mass spectrometry and computations to form compact higher-ordered heterooligomers
Eye lens crystallin proteins maintain the refractive properties of the lens but are not replaced after denucleation. Rolland et al. use native ion mobility-mass spectrometry, kinetics experiments, and computations to reveal that b-crystallins form heterodimers. These likely assemble into compact heterooligomers that enable the very high protein concentrations found in lens tissue
60 Gbps real-time wireless communications at 300 GHz carrier using a Kerr microcomb
Future wireless communication infrastructure will rely on terahertz systems
that can support an increasing demand for large-bandwidth, ultra-fast wireless
data transfer. In order to satisfy this demand, compact, low-power, and low
noise sources of terahertz radiation are being developed. A promising route to
achieving this goal is combining photonic-integrated optical frequency combs
with fast photodiodes for difference frequency generation in the THz. Here, we
demonstrate wireless communications using a 300 GHz carrier wave generated via
photomixing of two optical tones originating from diode lasers that are
injection locked to a dissipative Kerr soliton frequency microcomb. We achieve
transfer rates of 80 Gbps using homodyne detection and 60 Gbps transmitting
simultaneously both data and clock signals in a dual-path wireless link. This
experimental demonstration paves a path towards low-noise and integrated
photonic millimeter-wave transceivers for future wireless communication
systems
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