Tunnel Spaces Research Articles

Numerical simulation and theoretical study on the impact of wind-sand flow of high-speed trains in long tunnel space

When high-speed trains (HST) run in enclosed spaces such as long tunnels, the thermal accumulation of their suspension devices is continuous and cannot be effectively dissipated. In addition, previous experiments or simulations for the heat dissipation of HST in tunnel spaces did not consider the impact of sand. To clarify the impact of HWS-LT on the heat accumulation of HST equipment cabin, this study used the CFD method to numerically simulate the impact of different wind-sand flow concentrations or no-sand wind on the cooling of equipment in the long tunnel space. Firstly, the sand particles in the wind-sand flow gather at the tunnel entrance and enter the equipment cabin with the train as it enters the tunnel. This boundary condition is more in line with actual engineering situations. Secondly, both flows show asymmetric intrusion into the cabin due to the asymmetrical tunnel arrangement, but the sand particles in the wind-sand flow are affected by the vortices and tunnel walls, resulting in more asymmetric flow and some particles being trapped in the grids or filters, leading to outflow ρQ < inflow ρQ. Under the wind-sand flow condition, the temperature of some equipment surfaces shows more significant increases than under the no-sand wind. Finally, contrary to popular perception, the wind-sand flow carrying sand particles can dissipate heat more effectively than no-sand wind, and the higher the volume fraction φ within a certain concentration range, the better the heat dissipation effect. This is because the wind-sand flow has a higher specific heat capacity, which can remove some heat from the contact point between the sand particles and the equipment wall upon contact. The higher sand particle concentration increases the contact frequency and contact area between the sand particles and the equipment wall, and the heat transfer pathway and heat dissipation efficiency are improved.

Electroacoustic modeling of speech intelligibility for a new road tunnel

This paper presents the process of electroacoustic design and modeling for tunnel public address (PA) system for the North East Link (NEL) road tunnel in Melbourne. The tunnel includes over 6km of twin-bore tunnels, with varying cross-sections along its length. The different tunnel spaces addressed in the design include mainline tunnel bores, interchanges, ramps, as well as pedestrian cross-passages and egress passages. This paper outlines how large data sets from CAD models were managed using a new automation method (Grasshopper 3D) throughout the design process to produce and maintain detailed electroacoustic modeling in Odeon software. In particular, this paper explores new and novel modeling methods adopted to address design constraints and to achieve a PA system capable of producing adequate speech intelligibility for emergency evacuation within very challenging acoustic environments.

Generating Topologically Consistent BIM Models of Utility Tunnels from Point Clouds.

The development and utilization of urban underground space is an important way to solve the "great urban disease". As one of the most important types of urban underground foundations, utility tunnels have become increasingly popular in municipal construction. The investigation of utility tunnels is a general task and three-dimensional laser scanning technology has played a significant role in surveying and data acquisition. However, three-dimensional laser scanning technology suffers from noise and occlusion in narrow congested utility tunnel spaces, and the acquired point clouds are imperfect; hence, errors and redundancies are introduced in the extracted geometric elements. The topology of reconstructed BIM objects cannot be ensured. Therefore, in this study, a hierarchical segmentation method for point clouds and a topology reconstruction method for building information model (BIM) objects in utility tunnels are proposed. The point cloud is segmented into facades, planes, and pipelines hierarchically. An improved mean-shift algorithm is proposed to extract wall line features and a local symmetry-based medial axis extraction algorithm is proposed to extract pipelines from point clouds. A topology reconstruction method that searches for the neighbor information of wall and pipeline centerlines and establishes collinear, perpendicular, and intersecting situations is used to reconstruct a topologically consistent 3D model of a utility tunnel. An experiment on the Guangzhou's Nansha District dataset successfully reconstructed 24 BIM wall objects and 12 pipelines within the utility tunnel, verifying the efficiency of the method.

Analysis of Maintenance Techniques for a Three-Dimensional Digital Twin-Based Railway Facility with Tunnels

In accordance with the paradigm of the 4th and Industrial Revolution, the introduction of building information modeling is expected in all areas related to railroad construction, operation and management, along with the establishment of a metaverse platform that combines big data, the Internet of Things, and artificial intelligence. The performance of tasks related to the safety and maintenance of railway facilities is aided by the use of digital systems free from physical and temporal constraints. Three-dimensional (3D) modeling and other 4th industrial technologies, such as unmanned aerial vehicles (UAVs) and light detection and ranging (LiDAR), are increasingly implemented in many types of infrastructure. With respect to railroads, the use of these methods to monitor tunnel spaces has been hindered by the limitations of modeling with UAV and inadequate Global Positioning System reception. Here, we conducted the domestic application of 4th industrial technologies to a railway tunnel; we addressed these problems using a BLK360, a fixed LiDAR device that combines two-dimensional panoramic images and a 3D point cloud method. The outcomes of this research will benefit railway operation managers by providing a platform combining a two-dimensional panoramic virtual reality (VR) image and a 3D model developed from a 3D scan framework for the maintenance of existing railway facilities (tunnels). Our approach was optimized for the maintenance and operational management of railroad facilities, as demonstrated for tunnels, because it continuously acquires time-series data that is appropriate for the maintenance of the corresponding space. In the future, this approach can be used for test tracks and operational lines.

Lanthanide-Aromatic Iminodiacetate Frameworks with Helical Tubes: Structure, Properties, and Low-Temperature Heat Capacity.

A series of lanthanide coordination polymers [LnL(H2O)2]n [Ln = Pr (1), Nd (2), Sm (3), Eu (4), and Gd (5), H3L = N-(4-carboxy-benzyl)iminodiacetic acid] was hydrothermally prepared and structurally characterized. All the five compounds have been confirmed as 3D Ln-CPs with one-dimensional helical tunnels composed of four helical chains, although there are different coordination geometries around Ln3+. Enantiomeric helixes in 1–3, and absolute left-handed and right-handed helical chains in 4 and 5, respectively, lead to different tunnel spaces. Their conformations can also be featured by different space groups and unit cell dimensions. Photoluminescence measurement on 3 and 4 show characteristic emission peaks of Sm3+ and Eu3+ ions, respectively. The low-temperature heat capacity of 1–4 has been investigated in the temperature range of 1.9–300 K. Their heat capacity values are nearly equal below 10 K and display a crossover with the value order Cp,m(2) > Cp,m(1) ≈ Cp,m(4) > Cp,m(3) above 10 K. The measured heat capacities have been fitted, and the corresponding thermodynamic functions were consequently calculated based on the fitting parameters. The standard molar entropies at 298.15 K have been determined to be (415.71 ± 4.16), (451.32 ± 4.51), (308.53 ± 3.09), and (407.62 ± 4.08) J·mol–1·K–1 for 1, 2, 3, and 4, respectively.

A real-time forecast of tunnel fire based on numerical database and artificial intelligence

The extreme temperature induced by fire and hot toxic smokes in tunnels threaten the trapped personnel and firefighters. To alleviate the potential casualties, fast while reasonable decisions should be made for rescuing, based on the timely prediction of fire development in tunnels. This paper targets to achieve a real-time prediction (within 1 s) of the spatial-temporal temperature distribution inside the numerical tunnel model by using artificial intelligence (AI) methods. A CFD database of 100 simulated tunnel fire scenarios under various fire location, fire size, and ventilation condition is established. The proposed AI model combines a Long Short-term Memory (LSTM) model and a Transpose Convolution Neural Network (TCNN). The real-time ceiling temperature profile and thousands of temperature-field images are used as the training input and output. Results show that the predicted temperature field 60 s in advance achieves a high accuracy of around 97%. Also, the AI model can quickly identify the critical temperature field for safe evacuation (i.e., a critical event) and guide emergency responses and firefighting activities. This study demonstrates the promising prospects of AI-based fire forecasts and smart firefighting in tunnel spaces.

Structural Insight into the Abnormal Capacity of a Co-Substituted Tunnel-Type Na0.44MnO2 Cathode for Sodium-Ion Batteries.

Tunnel-type (T-type) Na0.44MnO2 (NMO) is a promising cathode material for sodium-ion batteries (SIBs) owing to its high rate performance and cycling stability compared to manganese-based layered oxides. However, the low specific capacity still restricts its practical applications. Herein, a Co-doped T-type NMO is synthesized through a facile solid-state reaction method and utilized as a cathode material for SIBs. A T-type Na0.44Mn0.9925Co0.0075O2 (NMO-3) electrode can deliver a high reversible capacity of 138 mAh g-1 at 0.1C, a superior rate capability (133, 130, 121, 106, and 93 mAh g-1 at 0.5, 1, 2, 5, and 10C, respectively), and excellent cycling stability (85.2% at 10C after 500 cycles). The substitution of Co3+ by Mn3+ leads to the enlargement of small and S-shaped tunnel spaces, which facilitates the insertion/deinsertion of Na+ into/from NMO-3 and greatly enhances its rate capability and cycling stability. Moreover, the reduced energy barriers for Na+ diffusion in small tunnels make the inactive Na+ easier to be deintercalated, which should be responsible for its high specific capacity that exceeds the theoretical capacity of T-type NMO.

Vector P‐ and S‐wave pre‐stack reverse‐time migration for tunnel spaces

ABSTRACTMigration is considered to be a key step in the data processing of the seismic advancement predictions of tunnels, and it directly affects the final interpretations. Therefore, with the goal of addressing the limitations of the current acoustic reverse‐time migration processes, as well as deepening the understanding of the interactions between different wave modes in traditional elastic reverse‐time migration, a vector P‐ and S‐wave reverse‐time migration method is proposed in this study. Consideration is given to the actual tunnel spaces, and forward calculations and reverse‐time extrapolations of the wavefields are carried out based on the first‐order velocity‐stress elastic wave equation of P‐ and S‐wave separation and a high‐order staggered‐grid algorithm. The imaging conditions of a source‐normalized cross‐correlation are used to realize the imaging. Then, a Laplace filtering method is adopted to suppress the low‐frequency artefacts. Numerical simulations of the weak interlayer and karst cave models show that the proposed method had the ability to more effectively suppress noise and achieve high‐precision imaging of tunnel spaces, when compared with using horizontal or vertical components to directly obtain the images. The positions and shapes within the tunnel spaces can be accurately imaged regardless of whether they are lithologic interfaces or local geological bodies. This is found to improve the resolution and accuracy of the tunnel advancement predictions. Finally, the proposed method is successfully applied to the real data processing, and the effects are found to be satisfactory.

Discovery of New‐Structured Post‐Spinel MgFe2O4: Crystal Structure and High‐Pressure Phase Relations

AbstractPhase relations in MgFe2O4 at 20–27 GPa and 1,000–1,200 °C were investigated, and a novel post‐spinel phase of MgFe2O4 (space group, Pnma) was identified. This phase has a Z‐shape framework of edge‐sharing (Mg,Fe)O6 octahedra, with other Mg and Fe cations randomly occupying one tetrahedral and two octahedral sites in tunnel spaces within the framework. This structure is similar to Nax (Fe,Ti)xTi2‐xO4 phase (0.75 ≤ x ≤ 0.9) with (Fe,Ti)O6 Z‐shape framework and tricapped‐prism sites for Na. Compression data showed ~6% volume reduction at 16–20 GPa. The recovered phase may have transformed during decompression from the Nax (Fe,Ti)xTi2‐xO4‐type structure due to cations in the tunnel spaces shifting, probably because of cation‐size misfit. The novel phase may be found in impact craters and shocked meteorites and may serve as an indicator of shock P‐T conditions. Without crystal structure refinement, post‐spinel phases are likely to be misidentified due to similar crystallographic features.

Using Tunnel Air Heat in the Heat and Cold Supply Systems of Subway Facilities

An imbalance of thermal operating conditions in a subway has a negative effect on the microclimate in tunnels and stations and eventually leads to accumulation of “thermal pollution” of the soil strata surrounding the subway tunnels and facilities. In turn, such “thermal pollution” results in less intense heat removal to the soil and in air overheating in stations. One of the efficient methods for achieving better energy efficiency of the climate systems and for improving the microclimate in the Moscow Subway’s underground facilities is to use heat pump systems with recovery of the tunnel air heat for supplying heat and cold for station complexes. The article presents the main results obtained from experimental investigations of the thermal operating conditions at some stations of the Moscow Subway. In particular, air temperature in the subway tunnel spaces was measured in the summer and winter seasons. As a result, the main factors influencing the temperature operating conditions in the subway tunnels have been revealed. Based on the results of the experiments, it can be recommended to put heat pumps into operation in the tunnels for setting up a comfortable microclimate in the subway. As an example, the results from testing this process solution are presented through analyzing the efficiency of the heat pump-based heat supply system of the Salar’evo experimental station’s complex. The analysis of the Salar’evo station’s heat pump-based heat supply system has demonstrated its successful operation in the subway along with good compatibility between the subway systems and heat pump unit at the design and operation stages. Application of heat pump equipment in the heat and cold supply systems of subway facilities is not only significantly cheaper than the conventional technology in terms of one-time capital investments but also makes it possible to save more than 80% of energy in the course of operation.

The digging dynamics of ant tunnels: movement, encounters, and nest space

Underground ant nests are constructed by decentralised self-organisation wherein the ants respond to local stimuli and produce coordinated structures through globally regulated behaviours. One such regulation is the reduction in digging effort that occurs when available nest space has reached an adequate size. Tunnels have a distinct configuration relative to other nest elements and the processes regulating their excavation are poorly understood. We examined the relationship between digging effort and tunnel space by presenting groups of 10 Acromyrmex lundi workers with either short or long tunnel spaces and demonstrated that they will dig significantly less over time in a tunnel that is already long compared to one that is short. Additionally, we provided the same treatment to groups of 100 workers and found no significant effect of length, suggesting that group size has an important impact on tunnel excavation dynamics. Automated tracking was then used to examine tunnel digging in greater detail. Groups of 10 Atta colombica ants were tracked while excavating sand in a tunnel apparatus. There was a significant correlation between mean walking speed and excavation rate. Additionally, the ants would maintain a consistent level of proximity with each other over time. This suggests that as tunnel space expands, several factors combine to lower the chance of ants encountering the tunnel digging face and taking up excavation.

Temporal Bone Histopathology of X-linked Inherited Alport Syndrome.

ObjectiveTo describe the histopathologic findings within the human cochlea in X‐linked Alport syndrome.Study DesignHistopathologic analysis of cellular elements within the human cochlea by light microscopy.Materials and MethodsA right and a left cochleae of a man with genetically confirmed X‐linked Alport syndrome was studied post‐mortem. The temporal bones underwent standard processing for histologic examination. The slides were examined by light microscopy. Graphic reconstruction of the cochlea was performed to quantify hair cells, pathologic changes of the stria vascularis, and loss of cochlear neuronal cells.ResultsThere was severe loss of inner hair cells and all three rows of outer hair cells in the apical two turns of the cochlea. The stria vascularis and spiral ligament showed areas of marked loss which became more prominent from base to apex in each ear. The spiral ganglion cell count in the Rosenthal's canal exhibited loss of 20% to 45% compared to matched historical controls. There was a zone of separation between the organ of Corti and the basilar membrane extending along the basal surface of Deiters cells, Hensen cells, Claudius cells and external sulcus cells. The tunnel of Corti and the space of Nuel were filled with cellular elements along the cochlea.ConclusionThe histopathologic findings of cochlear involvement in Alport's syndrome are basement membrane separation from the cells of the organ of Corti, outer and inner hair cell loss, and cellular infilling of the tunnel and extracellular spaces of the organ of Corti. These observations contribute to our understanding of the mechanism of sensorineural hearing loss in these patients.Level of Evidence

Construction Mechanical Mechanism of Shallow Subway Tunnel Group with Large-Span Variable Cross Section

The number of tunnel crossings or line switchings in the vicinity of subway transfer stations is increasing with the construction of subway tunnels. The construction interaction of the subway tunnel group with variable cross section and the time and space effects of strata deformation has become a major problem that limits the development of subway tunnel spaces. Thus, this study analyzed the deformation law of the upper strata and surrounding rocks in a subway tunnel group with large-span variable cross section caused by different construction processes using ABAQUS numerical simulation analysis. The research focused on the construction interaction mechanism and stratum deformation law of such a subway tunnel group and considered Shenzhen Metro Line 7 as the study subject. The stratum deformation law caused by twin tunnels excavation was referred. Results showed that (1) the construction process significantly influenced the construction safety of tunnel groups with large-span variable cross section; (2) constructing small cross-sectional tunnels first increases the lateral deformation and settlement of the vault in large cross-sectional tunnels, which are far from small cross-sectional tunnels, but reduces the settlement of the vault in the small cross-sectional tunnels and the lateral deformation of the surrounding rock between the large and small cross-sectional tunnels, which benefits tunnel groups with large-span variable cross section; and (3) as shown by the comparison of the final numerical simulation data that in which the large cross-sectional tunnel was constructed after the completion of the small cross-sectional tunnel construction had the lowest project risk.

Evacuation speed in full-scale darkened tunnel filled with smoke

Tunnel fires create dense black smoke that covers ceiling lights and darkens tunnel spaces. The present study investigates experimentally the evacuation speed in a full-scale tunnel filled with smoke and clarifies the relation between the extinction coefficient (up to 1.6m−1) and normal walking speed. In this study, participants were exposed to smoke in a full-scale experimental tunnel that was darkened by turning off the ceiling lights, and the extinction coefficient was varied from 0.18 to 1.6m−1. The maximum, minimum, and mean normal walking speeds were almost constant up to 1.0m−1 but decreased slightly at higher extinction coefficients. At 0.30m−1, the maximum emergency-evacuation speed through the dark tunnel is less than that when the ceiling lights are on and corresponds to 2.6m/s, thereby indicating a fast walking speed even at small extinction coefficients. However, the maximum emergency-evacuation speeds at coefficients exceeding 0.48m−1 for light and dark conditions are almost identical. The minimum and mean emergency-evacuation speeds decrease at extinction coefficients of approximately 1.0m−1. Additionally, normal walking speed and emergency-evacuation curves are calculated from the current experimental results to compare the effect of ceiling lights with that of a darkened space. The results indicate that the normal walking speed and emergency-evacuation speed are influenced by the darkened space.

A novel method for evaluation of fire prevention by using water curtain with large droplets

Based on the ability to attenuate thermal radiation of droplets, water curtain plays an important role in fire prevention in the oil and gas terminal, traffic tunnel and other outdoor spaces. Radiation transfer characteristics of large droplets are determined by the Mie theory, and the Two-flux model is used to simplify the radiative transfer equation. Combined with an empirical formula to calculate the droplet diameter, a novel method is given for calculating the transmissivity of water curtain. Based on the method, influences of both the pressure and the width of water curtain on the transmissivity are fit for exponential relationship. Compared with experimental data, an ideal agreement is found between calculation results and experimental data for both single pipe water curtain and double pipe water curtain, only in the case of triplex pipe water curtain the deviation between calculation and experiment is more than 25%. A better calculation result can be obtained under the condition of the optical thin media. The method is effective in the scope of that the transmitted radiation is stronger than the environmental radiation.

Hydration and Dehydration Transformation Mechanism of Cefaclor Pseudopolymorphs

Hydration/dehydration phase transitions of active pharmaceutical ingredients (API) are often accompanied with changes of physicochemical properties, such as solubility, stability, and bioavailability. Therefore, three dimensional structural investigation of the hydration / dehydration mechanism of API is important for pharmaceutical research and development. By relative humidity control, Cefaclor hydrate crystal dehydrates non-stoichiometrically from dihydrate to anhydrous form A. Unexpectedly, its monohydrate form transformed into new 1.9 hydrate by slurry treatment (methanol / water) which dehydrated into another anhydrous form B through hemihydrate by heating. In this study, these hydration and dehydration presudo-polymorphic transitions of Cefaclor are investigated by the crystal structure analyses. Crystal structures of anhydrous and partially dehydrated forms were determined by structure determination from powder diffraction data technique because such dehydration phase transitions were resulted in a disintegration of single crystal form. In the first dehydration route, hydrates and the anhydrous form A have similar crystal structure, which is referred as `isomorphic desolvation'. Interestingly, the anhydrous form A has void spaces which corresponds to the water molecule position in the hydrate form. Thus, in hydration / dehydration phase transitions, water molecules move in and out of the void without changing the crystal structures, and the anhydrous form A can hydrate even in low R.H. condition. In the second route, the 1.9 hydrate, hemihydrate and the anhydrate form B have three crystallographically independent molecules forming similar T-shape building block pattern. There are tunnel spaces along b axis between the blocks. In the hydration / dehydration process, the blocks slide each other to open and close the channel. This mechanism explains another non-stoichiometric dehydration in this route.

Na-Fe-S-O System As Cathode Materials for Na-Ion Batteries: An Ab Initio Study

Sodium-ion rechargeable batteries have been attracting increasing interest as a cost effective alternative to lithium-ion batteries, particular for larger energy storage systems. However, sodium system has the intrinsic drawback of having lower voltage than lithium one. Exploration of cathode materials containing polyanions can led to high voltages and therefore is a meaningful remedy. Experiences gained in the studies of lithium battery show that sulphates (Li2Fe(SO4)2) deliver the highest voltage (3.83 V vs Li/Li+) among polyanions such as phosphates and silicates due to the high formal charge of S and inductive effects[1]. The Na-Fe-S-O system also has the advantage of composing of elements high in natural abundances and low in costs.In exploring the Na-Fe-S-O system, our group found some new phases[2]. One of these can extract nearly all the Na atoms in the formula unit at an average voltage of 3.6 V vs Na/Na+. This is a significant improvement over the known Fe2(SO4)3 in the Nasicon phase[3], where only one Na atom can be inserted and at a lower voltage of 3.4 V vs Na/Na+. The rate capability and cycling performance are also very satisfactory. The new structure consists of peculiar edge sharing Fe2O10subunits forming tunnel spaces partially occupied by Na ions.In order to understand the structural origin of the excellent performance of this material we carried out ab initio study employing density functional theory. Migration activation energy (Ea ) calculations found that Na ions are very mobile in the structure with Ea as low as 0.14 eV (Figure). This accounts for the high rate performance and hints at the application as solid-state electrolytes. On the voltage aspect, emphasis will be put on the origin of the higher voltage of the present system in comparison to the Nasicon phase. Theory for the trend of voltage in cathode material employing different polyanions is well known, however, it is highly controversial for polymorphs of compounds with the same chemical compositions. Phase behavior at different state of charge will also be discussed.

Endothelial cell lumen and vascular guidance tunnel formation requires MT1-MMP–dependent proteolysis in 3-dimensional collagen matrices

AbstractHere we show that endothelial cells (EC) require matrix type 1-metalloproteinase (MT1-MMP) for the formation of lumens and tube networks in 3-dimensional (3D) collagen matrices. A fundamental consequence of EC lumen formation is the generation of vascular guidance tunnels within collagen matrices through an MT1-MMP-dependent proteolytic process. Vascular guidance tunnels represent a conduit for EC motility within these spaces (a newly remodeled 2D matrix surface) to both assemble and remodel tube structures. Interestingly, it appears that twice as many tunnel spaces are created than are occupied by tube networks after several days of culture. After tunnel formation, these spaces represent a 2D migratory surface within 3D collagen matrices allowing for EC migration in an MMP-independent fashion. Blockade of EC lumenogenesis using inhibitors that interfere with the process (eg, integrin, MMP, PKC, Src) completely abrogates the formation of vascular guidance tunnels. Thus, the MT1-MMP-dependent proteolytic process that creates tunnel spaces is directly and functionally coupled to the signaling mechanisms required for EC lumen and tube network formation. In summary, a fundamental and previously unrecognized purpose of EC tube morphogenesis is to create networks of matrix conduits that are necessary for EC migration and tube remodeling events critical to blood vessel assembly.

Control of microvascular tube assembly by endothelial cell‐pericyte interactions

Endothelial cell (EC) tube morphogenesis is controlled by downstream signals derived from a cell surface metalloproteinase, MT1‐MMP, the Rho GTPases, Cdc42 and Rac1, and the α2β1 integrin. These signals promote lumen formation and interconnection of neighboring cells to form multicellular tube networks in 3D collagen matrices. This process depends on Cdc42‐mediated signaling and involves the downstream effectors, Pak2, Pak4, the cell polarity protein, Par3, and the protein kinase C isoforms, epsilon and zeta. Also, during tube formation, ECs generate MT1‐MMP‐dependent proteolyzed spaces, termed vascular guidance tunnels, which represent physical imprints in the matrix allowing for rapid cellular movement and tube remodeling. In EC‐pericyte cocultures, marked recruitment of pericytes occurs into these vascular guidance tunnels and they are distributed in a polarized fashion along the ablumenal surface of EC tubes. These tunnels facilitate dynamic migration of ECs and pericytes, leading to deposition of basement membrane matrix components (only occurs with pericytes) and EC tube stabilization. Thus, EC microvascular tube assembly is a function of initial EC signaling and morphogenic events leading to vascular guidance tunnel formation and downstream stabilization signals catalyzed by EC‐pericyte interactions within these tunnel spaces. Supported by NIH grants HL59373 and HL79460.

Vascular guidance tunnels direct endothelial cell‐pericyte interactions and basement membrane matrix deposition

Endothelial cell (EC) tube morphogenesis in 3D extracellular matrices is controlled by EC intracellular vacuolation and vesicular fusion leading to lumen formation and interconnection of neighboring cells to form multicellular tube networks. These latter events require proteolysis in collagen matrices by MT1‐MMP. The EC generated proteolyzed spaces, termed vascular guidance tunnels, represent a physical imprint in the matrix allowing for cellular movement and tube remodeling within these spaces in an MMP‐independent manner. Over a period of days, time‐lapse and immunofluorescence microscopy shows marked recruitment of pericytes into these vascular guidance tunnels. The creation of a 2D plane within a 3D matrix environment allows for enhanced EC‐pericyte interactions, proteolytic independent movement and pericyte proliferation. Furthermore, it is only when pericytes are present within the vascular guidance tunnels that deposition of the basement membrane components collagen type IV, laminin, nidogens 1/2, and perlecan occurs. In the absence of pericytes, ECs produce each of these components, although they are not locally deposited. Pericyte proliferation within these tunnel spaces increases the ratio of pericytes to ECs leading to basement membrane matrix deposition and EC tube stabilization.