Ensuring the stability of all‐inorganic halide perovskite light‐emitting diodes (LEDs) has become an obstacle that needs to be broken for commercial applications. Currently, lead halide perovskite CsPbX3 (X = Br, I, Cl) nanocrystals (NCs) are considered as alternative materials for future fluorescent lighting devices due to their combination of superior optical and electronic properties. However, the temperature of the surface of the LEDs will increase after long‐term power‐on work, which greatly affects the optical stability of CsPbX3 NCs. In order to overcome this bottleneck issue, a strategy of annealing perovskite materials in liquid is proposed, and the changes in photoluminescence and electroluminescence (EL) behaviors before and after annealing are studied. The results show that the luminescence stability of the annealed perovskite materials is significantly improved. Moreover, the EL stability of different perovskite LED devices under long‐term operation is monitored, and the performance of the annealed materials is particularly outstanding. The results have proved that this convenient and low‐cost liquid annealing strategy is suitable for large‐scale postprocessing of perovskite materials, granting them stable fluorescence emission, which will bring a new dawn to the commercialization of next‐generation optoelectronic devices.
We present a re-engineered version of the laser frequency comb that has proven a few-cm/s calibration repeatability on the HARPS spectrograph during past campaigns. The new design features even better performance characteristics. The newly arranged oscillator, filter cavities and fiber injection for spectral broadening allow robust long term operation, controlled from a remote site. Its automation features enable easy operation for non-experts. The system is being prepared for installation on the HARPS spectrograph in fall of 2014, and will subsequently become available to the astronomical community.
The type-I polyketide ansamitocin P-3 (AP-3) is a potent antitumor agent. Its production is most likely hampered by the required multiple substrate supplies and complicated post-PKS modifications in Actinosynnema pretiosum subsp. pretiosum ATCC 31280. For titer improvement, gene ansa30, encoding for a glycosyltransferase competing for the N-demethyl-AP-3 (PND-3) intermediate for AP-3 biosynthesis, was initially inactivated. In the mutant NXJ-22, the AP-3 titer was increased by 66% along with an obvious accumulation of PND-3, indicating that the N-methylation is a rate-limiting step. Alternatively, when abundant upstream intermediate 19-chloroproansamitocin was fed into a PKS mutant, 3-O-acylation was further identified along with the N-methylation as the rate-limiting steps. Subsequent overexpression of N-methyltransferase gene asm10 in NXJ-22 resulted in a 93% increase of AP-3 and a corresponding 92% decrease of PND-3. Additional supplementation of L-methionine, the precursor for SAM biosynthesis, substantially decreased the accumulation of PND-3. In parallel, the 3-O-acylation bottleneck was relieved by feeding with L-valine to NXJ-22, resulting in a 126% increase of AP-3. Eventually, a combined asm10 overexpression and supplementation of L-methionine and L-valine resulted in a 5-fold increase of AP-3, from 42 ± 2 mg L to 246 ± 6 mg L , without any noticeable accumulation of PND-3.
Laser frequency combs (LFCs) are well on their way to becoming the next-generation calibration sources for precision astronomical spectroscopy 1-6 . This development is considered key in the hunt for low-mass rocky exoplanets around solar-type stars whose discovery with the radial-velocity method requires cm/s Doppler precision 7 . In order to prove such precise calibration with an LFC, it must be compared to another calibrator of at least the same precision. Being the best available spectrograph calibrator, this means comparing it to a second -fully independent -LFC. This test had long been pending, but our installation of two LFCs at the ultra-stable spectrograph HARPS presented the so far unique opportunity for simultaneous calibrations with two separate LFCs. Although limited in time, the test results confirm the 1 cm/s stability that has long been anticipated by the astronomical community.
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