Formation and Propagation of Local Traffic Jam

Large scale traffic congestion often stems from local traffic jam in single road or intersection. In this paper, macroscopic method was used to explore the formation and propagation of local traffic jam. It is found that (1) the propagation of traffic jam can be seen as the propagation of traffic signal parameters, that is, virtual split and virtual green time; (2) for a road with endogenous flow, entrance location influences the jam propagation. With the same demand (upstream links flow and entrance flow), the upstream got more influence; (3) when a one-lane road is thoroughly congested, virtual signal parameters everywhere are the same as that at stop line; for a basic road, the virtual signals work in a cooperative manner; (4) phase sequence is one important parameter that influences traffic performances during peak hour where spill back of channelization takes place. The same phase plan for left-turn flow and through flow would be preferred; (5) signal coordination plays an important role in traffic jam propagation and hence effective network signal parameters should be designed to prevent jam from propagation to the whole network. These findings would serve as a basis for future network traffic congestion control

Study on the Calculation Models of Bus Delay at Bays Using Queueing Theory and Markov Chain

Traffic congestion at bus bays has decreased the service efficiency of public transit seriously in China, so it is crucial to systematically study its theory and methods. However, the existing studies lack theoretical model on computing efficiency. Therefore, the calculation models of bus delay at bays are studied. Firstly, the process that buses are delayed at bays is analyzed, and it was found that the delay can be divided into entering delay and exiting delay. Secondly, the queueing models of bus bays are formed, and the equilibrium distribution functions are proposed by applying the embedded Markov chain to the traditional model of queuing theory in the steady state; then the calculation models of entering delay are derived at bays. Thirdly, the exiting delay is studied by using the queueing theory and the gap acceptance theory. Finally, the proposed models are validated using field-measured data, and then the influencing factors are discussed. With these models the delay is easily assessed knowing the characteristics of the dwell time distribution and traffic volume at the curb lane in different locations and different periods. It can provide basis for the efficiency evaluation of bus bays. Document type: Articl

Orbital-angular-momentum dependent speckles for spatial mode sorting and multiplexed data transmission

Characterizing the orbital angular momentum (OAM) of a vortex beam is critically important for OAM-encoded data transfer. However, in typical OAM-based applications where vortex beams transmit through diffusers, the accompanying scattering effect tends to be either deliberately prevented, or characterized and then modulated actively based on complex wavefront shaping and interferometry techniques. Here, we aim to investigate the characteristics of blurred speckles obtained after a vortex beam transmits through a ground glass diffuser. It is theoretically and experimentally demonstrated that a cross-correlation annulus can be identified by implementing the cross-correlation operation between speckle patterns corresponding to vortex beams with different OAM values. Besides, it is worth noting that, the size of the cross-correlation annulus is determined by the absolute value of the topological charge difference between the two corresponding vortex beams. Based on this mechanism, the OAM modes can be easily sorted from the incoherently measured OAM-dependent speckles as well as their cross-correlation. Furthermore, to make full use of the orthogonal feature of the OAM-dependent speckles, demultiplexing of OAM-encoded data transfer is verified using a ground glass diffuser. Both 8-bit grayscale and 24-bit RGB OAM-encoded data transfers are carried out in experiments with superior error rates. We can conclude that the OAM-dependent speckles can be not only utilized as a competitive candidate for the OAM mode sorting function in a simple way but also provide an efficient method for the demultiplexing of OAM-encoded data transfer in a practical application

Bis(2-carboxybenzo­ato-κO 1)bis­[1-cyclo­propyl-6-fluoro-4-oxo-7-(piperazin-4-ium-1-yl)-1,4-dihydro­quinoline-3-carboxyl­ato-κ2 O 3,O 4]manganese(II) dihydrate

The title compound, [Mn(C17H18FN3O3)2(C8H5O4)2]·2H2O or [Mn(cfH)2(1,2-Hbdc)2]·2H2O (cfH = ciprofloxacin = 1-cyclo­propyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-piperazin­yl)-3-quinoline carb­oxy­lic acid, 1,2-bdc = benzene-1,2-dicarboxyl­ate), has been prepared under hydro­thermal conditions. The Mn2+ atom, located on an inversion centre, exhibits a distorted octa­hedral geometry, coordinated by four O atoms from two symmetry-related zwitterionic ciprofloxacin ligands in the equatorial positions and two O atoms of two 1,2-Hbdc ligands in the axial positions. The complex mol­ecules are linked into a two-dimensional network through N—H⋯O and OW—H⋯O hydrogen bonds. A strong intramolecular hydrogen bond between the carboxyl/carboxylate groups of the 1,2-Hbdc anion is also present. The layers are further extended through off-set aromatic π–π stacking inter­actions of cfH groups [centroid–centroid distance of 3.657 (2) Å] into the final three-dimensional supra­molecular arrays

Structural mechanism for bacterial oxidation of oceanic trimethylamine into trimethylamine N -oxide

Trimethylamine (TMA) and trimethylamine N-oxide (TMAO) are widespread in the ocean and are important nitrogen source for bacteria. TMA monooxygenase (Tmm), a bacterial flavin-containing monooxygenase (FMO), is found widespread in marine bacteria and is responsible for converting TMA to TMAO. However, the molecular mechanism of TMA oxygenation by Tmm has not been explained. Here, we determined the crystal structures of two reaction intermediates of a marine bacterial Tmm (RnTmm) and elucidated the catalytic mechanism of TMA oxidation by RnTmm. The catalytic process of Tmm consists of a reductive half-reaction and an oxidative half-reaction. In the reductive half-reaction, FAD is reduced and a C4a-hydroperoxyflavin intermediate forms. In the oxidative half-reaction, this intermediate attracts TMA through electronic interactions. After TMA binding, NADP+ bends and interacts with D317, shutting off the entrance to create a protected micro-environment for catalysis and exposing C4a-hydroperoxyflavin to TMA for oxidation. Sequence analysis suggests that the proposed catalytic mechanism is common for bacterial Tmms. These findings reveal the catalytic process of TMA oxidation by marine bacterial Tmm and first show that NADP+ undergoes a conformational change in the oxidative half-reaction of FMOs

Metastasis of nasopharyngeal carcinoma: What we know and do not know

Nasopharyngeal carcinoma (NPC) has the highest metastatic rate among head and neck cancers, with its underlying mechanism not yet fully unveiled. High- versus low-metastasis, NPC cell lines have been established. The footpad-popliteal lymph node metastasis model and other in vivo models have been stably used to study NPC metastasis. The histological appearance and the expression of epithelial-to-mesenchymal transition (EMT) markers might be helpful in selecting high-risk NPC patients for developing post-treatment metastasis. Tested EMT markers and their protein expression levels that correlate with patient disease-free survival in large patient cohorts include E-cadherin, N-cadherin, CD44, Twist, Snail, and Cyclin D1. Epstein-Barr virus (EBV) infection can trigger NPC metastasis from multiple angles via multiple signaling pathways. High endothelial venules are commonly seen in NPC tissues, with their role in NPC metastasis requiring clarification. The molecules that promote and inhibit NPC metastasis are introduced, with a focus on cytokines SPINK6, serglycin, interleukin 8 (IL8), Wnt family member 5A (WNT5A), and chemokine C-C motif ligand 2 (CCL2). Two videos showing NPC cells with and without SPINK6 knocked down are presented. Future directions for studying NPC metastasis are also discussed