FPGA-based digital chaotic anti-interference lidar system.

We use the chaotic signal generated by a field-programmable gate array (FPGA) to establish a digital chaotic pulse lidar system, which can achieve mid-range detection and high ranging accuracy without a complex optical structure. We employ the FPGA to generate random sequences with different modulation rates based on different chaotic iterative equations and initial values. By selecting the initial value and improved logistic equations, we successfully achieve centimeter-level ranging accuracy. Experiments have proved that the digital chaotic lidar system can effectively resist the interference of chaotic signals, square wave signals, and sine wave signals with modulation frequencies of 10 MHz, 100 MHz, 200 MHz, and 1 GHz, showing its strong anti-interference capability.

Improved l-Leucine Production in Corynebacterium glutamicum by Optimizing the Aminotransferases.

The production of branched-chain amino acids (BCAAs) is still challenging, therefore we rationally engineered Corynebacterium glutamicum FA-1 to increase the l-leucine production by optimizing the aminotransferases. Based on this, we investigated the effects of the native aminotransferases, i.e., branched-chain amino acid aminotransferase (BCAT; encoded by ilvE) and aspartate aminotransferase (AspB; encoded by aspB) on l-leucine production in C. glutamicum. The strain FA-1△ilvE still exhibited significant growth without leucine addition, while FA-1△ilvE△aspB couldn't, which indicated that AspB also contributes to L-leucine synthesis in vivo and the yield of leucine reached 20.81 ± 0.02 g/L. It is the first time that AspB has been characterized for l-leucine synthesis activity. Subsequently, the aromatic aminotransferase TyrB and the putative aspartate aminotransferases, the aspC, yhdR, ywfG gene products, were cloned, expressed and characterized for leucine synthesis activity in FA-1△ilvE△aspB. Only TyrB was able to synthesize l-leucine and the l-leucine production was 18.55 ± 0.42 g/L. The two putative branched-chain aminotransferase genes, ybgE and CaIlvE, were also cloned and expressed. Both genes products function efficiently in BCAAs biosynthesis. This is the first report of a rational modification of aminotransferase activity that improves the l-leucine production through optimizing the aminotransferases.

Visible-Light Induced Direct Synthesis of Polysubstituted Furans from Cyclopropyl Ketones.

In this article, a photoredox protocol for the synthesis of furans via oxidative coupling of olefin generated in situ from cyclopropyl ketones with ketonic oxygen atom is presented. Moreover, bromination of furans in the presence of overstoichiometric oxidant has been achieved with high regioselectivity.

Fe- and Co-P4-embedded graphenes as electrocatalysts for the oxygen reduction reaction: theoretical insights.

Encouraged by the great promise of metal-nitrogen-carbon (M-N-C) materials in replacing Pt for catalyzing the oxygen reduction reaction (ORR), metal-P species were successfully introduced into carbon matrices in experiments and have exhibited high catalytic activity for the ORR. Here, by means of comprehensive density functional theory (DFT) computations, we investigated the origin and the mechanism of the ORR occurring on Fe- and Co-P-embedded graphenes. Our computations have revealed that the Fe- and Co-P4 moiety-embedded graphenes possess good stability and high chemical reactivity for O2 activation, thus facilitating the subsequent ORR steps, and a more efficient 4e pathway in both acidic and alkaline media is more energetically favorable. Furthermore, by analyzing the computed free energy profiles, the Fe-P4 species-embedded graphene is a more efficient electrocatalyst for the ORR in an alkaline medium than the Co-P4 species-embedded graphene. Our DFT computations will be useful for gaining deeper insight into the high activity of metal-P species.

Numerical Simulation of Monodisperse Lube Oil Multiple Droplet Evaporation and Autoignition under Nonconstant Cylinder Conditions of Low-Speed Two-Stroke Gas Engines.

The possibility of lube oil droplets' existence in cylinders for two-stroke low-speed gas engines is higher because of the much higher lube oil consumption rate. Some droplets are directly injected into cylinders by lube oil injectors, and some are blown into cylinders through the scavenging ports. Autoignition of cylinder oil droplets is the main cause of preignition. This research study indicates that under in-cylinder conditions, overlarge single droplets cannot autoignite due to the long evaporation time, and overly small single droplets cannot autoignite because of the low vapor concentration. To find out what kinds of oil droplet groups could autoignite and cause preignition, 3-D computational fluid dynamics simulation in OpenFOAM was carried out. The model predictions were validated against the experimental results, including the evaporation rate of n-heptane droplets and the ignition delay of lube oil droplets. Also, the simulation was used to investigate the characteristics of multiple droplets under different ambient temperatures and pressures. The evaporation lifetime and the ignition delay of a large single droplet are dozens of times longer than that of multiple droplets, which confirms that the droplet group is more dangerous than a large single droplet. The evaporation rate and ignition delay are affected by the distance and number of droplets. A larger number causes a lower average evaporation rate. A smaller distance causes a shorter ignition delay. The local vapor concentration and temperature could be greatly reduced due to the existence of multiple evaporation and ignition cores. Additionally, these findings of multiple droplets were confirmed under nonconstant cylinder conditions of a natural gas engine. This research provides a guide to design the lube oil injectors and scavenging ports so as to reduce the preignition caused by lube oil autoignition.

Visible-Light-Induced Palladium-Catalyzed Intermolecular Narasaka-Heck Reaction at Room Temperature.

A palladium-catalyzed Narasaka-Heck reaction by a domino cross-coupling reaction with aromatic alkenes under blue LED irradiation at room temperature was developed. The undesired ß-hydride elimination of the hybrid alkyl palladium radical species was prohibited, enabling a broad range of oxime esters to undergo 5-exo cyclization and subsequent coupling with olefins. The practicality of the method was well illustrated by the construction of a nitrogen bridgehead tricycle as a core skeleton of alkaloids.

Visible-Light Promoted Selective Imination of Unactivated C-H Bonds via Copper-nitrene Intermediates for the Synthesis of 2H-Azirines.

A novel strategy to trap iminyl radicals with copper ions has been developed at room temperature, the resulted high-valent Cu(III) imine intermediate resets quickly to form nitrene and then to furnish a 2H-azirine. This protocol with dual copper/photoredox catalyst enables the selective imination of unactivated C-H bonds under mild conditions with a broader scope. Moreover, this method also uncovers a novel ring-expansion rearrangement from cyclobutyl oxime derivatives to give the α-acylamino cyclopentanones.

[Activity and role of tryptase after entrance of amniotic fluid into blood in rats].

OBJECTIVE: To investigate the activity and role of tryptase after entrance of amniotic fluid into blood in rats. METHODS: Thirty female Wistar rats (20 day pregnancy) were divided into the control group (10, injected with normal saline), amniotic group (10, injected with amniotic fluid), meconium group (10, injected with 1% meconium). After injection, pulmonary tissue was taken out. Tryptase activity was measured by special substrate. The histology of pulmonary tissue was determined by immunohistochemistry (HE). RESULTS: (1) Dropsy, hemorrhage, and infiltration of neutrophil (PMN), macrophage, leukomonocyte were observed in two experimental groups, but no such changes were found in control group. (2) After injection, tryptase activity in meconium group 176.4 +/- 8.6 and amniotic fluid group 165.4 +/- 7.4 was significantly higher than preexperimental groups 146.8 +/- 8.9 and 147.8 +/- 9.5, respectively (t = 7.58 and t = 4.64, P < 0.01); tryptase activity in control group was 145.3 +/- 10.6 before injection and 146.9 +/- 9.4 after injection, respectively, there was no difference (t = 0.37, P > 0.05). After injection, tryptase activity in meconium and amniotic fluid groups was significantly increased than that in control group (F = 30.66, P < 0.05). CONCLUSION: The activity of tryptase was significantly increased after entrance of amniotic fluid into blood in rats. Degranulation of mast cells to release tryptase may be the important cause of the pathophysiologic change after entrance of amniotic fluid into blood. These results suggest a role for mast cell activation in the mechanism of amniotic fluid embolism. This method is sensitive and effective for diagnosis of amniotic fluid embolism in clinic.

Inhibition of topoisomerase II by 8-chloro-adenosine triphosphate induces DNA double-stranded breaks in 8-chloro-adenosine-exposed human myelocytic leukemia K562 cells.

8-Chloro-cAMP and 8-chloro-adenosine (8-Cl-Ado) are known to inhibit proliferation of cancer cells by converting 8-Cl-Ado into an ATP analog, 8-chloro-ATP (8-Cl-ATP). Because type II topoisomerases (Topo II) are ATP-dependent, we infer that 8-Cl-Ado exposure might interfere with Topo II activities and DNA metabolism in cells. We found that 8-Cl-Ado exposure inhibited Topo II-catalytic activities in K562 cells, as revealed by decreased relaxation of the supercoiled pUC19 DNA and inhibited decatenation of the kinetoplast DNA (kDNA). In vitro assays showed that 8-Cl-ATP, but not 8-Cl-Ado, could directly inhibit Topo IIalpha-catalyzed relaxation and decatenation of substrate DNA. Furthermore, 8-Cl-ATP inhibited Topo II-catalyzed ATP hydrolysis and increased salt-stabilized closed clamp. In addition, 8-Cl-Ado exposure decreased bromo-deoxyuridine (BrdU) incorporation into DNA and led to enhanced DNA double-stranded breaks (DSBs) and to increased formation of gamma-H2AX nuclear foci in exposed K562 cells. Together, 8-Cl-Ado/8-Cl-ATP can inhibit Topo II activities in cells, thereby inhibiting DNA synthesis and inducing DNA DSBs, which may contribute to 8-Cl-Ado-inhibited proliferation of cancers.