Traffic Lights Detection and Recognition Method Based on the Improved YOLOv4 Algorithm.

For facing of the problems caused by the YOLOv4 algorithm's insensitivity to small objects and low detection precision in traffic light detection and recognition, the Improved YOLOv4 algorithm is investigated in the paper using the shallow feature enhancement mechanism and the bounding box uncertainty prediction mechanism. The shallow feature enhancement mechanism is used to extract features from the network and improve the network's ability to locate small objects and color resolution by merging two shallow features at different stages with the high-level semantic features obtained after two rounds of upsampling. Uncertainty is introduced in the bounding box prediction mechanism to improve the reliability of the prediction of the bounding box by modeling the output coordinates of the prediction bounding box and adding the Gaussian model to calculate the uncertainty of the coordinate information. The LISA traffic light data set is used to perform detection and recognition experiments separately. The Improved YOLOv4 algorithm is shown to have a high effectiveness in enhancing the detection and recognition precision of traffic lights. In the detection experiment, the area under the PR curve value of the Improved YOLOv4 algorithm is found to be 97.58%, which represents an increase of 7.09% in comparison to the 90.49% score gained in the Vision for Intelligent Vehicles and Applications Challenge Competition. In the recognition experiment, the mean average precision of the Improved YOLOv4 algorithm is 82.15%, which is 2.86% higher than that of the original YOLOv4 algorithm. The Improved YOLOv4 algorithm shows remarkable advantages as a robust and practical method for use in the real-time detection and recognition of traffic signal lights.

The long-term efficacy of cryoballoon vs irrigated radiofrequency ablation for the treatment of atrial fibrillation: A meta-analysis.

OBJECTIVES: The main purpose of this meta-analysis was to compare the long-term efficacy of cryoballoon ablation (CBA) with irrigated radiofrequency catheter ablation (RFCA) for the treatment of atrial fibrillation (AF). METHODS: The Medline, Cochrane Library and Embase Database were searched for clinical studies published up to October 2014. Studies that fulfilled our predefined inclusion criteria were included. The primary clinical outcome was the proportion of patients free from AF (follow-up≥3months), and the secondary clinical outcomes included acute pulmonary vein (PV) isolated rate, fluoroscopy time, procedure time and complications. RESULTS: After a literature search in the major databases, three randomized controlled trials (RCTs) and eight retrospective trials with a total of 1216 patients were identified. Pool-analysis demonstrated that, as compared RFCA, CBA was associated with a similar proportion of patients free from AF at a mean 16.5months follow-up (66.9% vs 65.1%; relative risk [RR]: 1.01; 95% CI: 0.94 to 1.07, P=0.87). Acute PV isolation rate (RR: 0.92; 95% CI: 0.82 to 1.03) and fluoroscopy time (weighted mean difference WMD: -8.60; 95% CI: -18.29 to 3.69) were not statistically significant difference. The procedure time was shorter in CBA group ([WMD]: -31.94; 95% CI: -60.43 to -3.45). Transient phrenic nerve palsy was uniquely observed in the CBA group (5.4%, P<0.00001) and resolved in all during the follow-up period, total complication was similar in both groups (RR: 1.30; 95% CI: 0.91 to 1.85). CONCLUSIONS: CBA was as effective as RFCA for the treatment of atrial fibrillation during long-term follow-up with comparable procedural features.

Enantioselective nickel-catalyzed reductive coupling of alkynes and imines.

The nickel-catalyzed reductive coupling of alkynes and imines with Et(2)Zn as a reductant by using electron-rich phosphine ligands has been developed, affording various allylic amines with high yields and excellent chemoselectivities. Chiral induction was also achieved in this reductive coupling reaction when a nickel catalyst containing a chiral spiro phosphine ligand was used.

Nickel-catalyzed enantioselective alkylative coupling of alkynes and aldehydes: synthesis of chiral allylic alcohols with tetrasubstituted olefins.

A highly efficient nickel-catalyzed asymmetric alkylative coupling of alkynes, aldehydes, and dimethylzinc has been realized by using bulky spirobiindane phosphoramidite ligands, affording allylic alcohols with a tetrasubstituted olefin functionality in high yields, high regioselectivities, and excellent enantioselectivities.

The different roles of metal ions and water molecules in the recognition and catalyzed hydrolysis of ATP by phenanthroline-containing polyamines.

The phenanthroline bridging polyaza ligands L1, L2 and L3 can selectively and strongly bind nucleotides at physiological pH, and hence accelerate the hydrolysis rate of the bound ATP. It is interesting that a phosphoramidate intermediate at 2.88 ppm (should be added 5.63 ppm when compared with other models) was found in the hydrolysis process of L/ATP. By introduction of metal ions (critical Zn(2+) or hard Mg(2+), Ca(2+)) to the L/ATP system, recognition of the anionic substrates by the protonated ligands was greatly promoted. However, due to the different affinities of metal ions to the receptor and the substrate, ATP hydrolysis in Zn(2+)/L/ATP system and Mg(2+)(Ca(2+))/L/ATP system occurs through different mechanisms. By comparison with the M/ATP (M=Zn(2+), Mg(2+), Ca(2+)) system, the rates of ATP-hydrolysis in the Mg(2+)Ca(2+)/L/ATP system and the Zn(2+)/L/ATP system were enhanced and retarded, respectively. Moreover, the reasons contributing to large rate range of the L/ATP systems and M(2+)/L/ATP systems were given. The results show that metal ions vertically regulate the recognition and hydrolysis of ATP. On the other hand, water molecule participates in the hydrolysis reactions at different steps with different functions in the L/ATP systems and M(Zn(2+), Mg(2+), Ca(2+))L/ATP systems.

Recognition promoted by Zn2+ between phenanthroline bridging polyaza ligands and nucleotides--Zn2+ acts as 'messenger' between the receptor and substrate.

The stability constants of the supramolecular complexes formed between L ((a,b,c,d)) or their Zn(2+) complexes, and adenosine 5'-triphosphate (ATP) in aqueous solution were determined by potentiometric titrations (25 degrees C, I = 0.1 mol dm(-3) KNO(3)). The results show that protonated aliphatic-substituted L (a,d) and aromatic-substituted L (b,c) ligands and/or Zn(II) ion can efficiently recognition the substrate, ATP. All of the equilibrium studies, (1)H and (31)P nuclear magnetic resonance spectra indicate that multiple interactions, including coordination, pi-stacking, ion-pairing, H-bonding, and possible ion-pi-donor, hydrophobic and even van der Waals interactions exist in the Zn(II)-L-ATP systems. On the other hand, the recognition of the substrates by the protonated ligands was significantly promoted by the addition of Zn(II), which leads to coordination competition between the mixed ligands, L and nucleotide. In Zn(II)/L/ATP systems the tendency for phosphate chain to receive proton and metal ion increases, facilitating the cleavage of the phosphate chain of the nucleotide.