Flight Sequences Research Articles

The reverse flight of a monarch butterfly (Danaus plexippus) is characterized by a weight-supporting upstroke and postural changes.

Butterflies are agile fliers which use inactive and active upstrokes (US). The active US plays a secondary role to the downstroke (DS), generating both thrust and negative vertical force. However, whether their active halfstroke function is fixed or facultative has not been clarified. We showed that during multiple backward flights of an individual, postural adjustments via body angles greater than 90°, with pitch-down and pitch-up motions in the DS and US, respectively, reoriented the stroke plane and caused the reversal of the aerodynamic functions of the halfstrokes compared with forward flight. The US and DS primarily provided weight support and horizontal force, respectively, and a leading edge vortex (LEV) was formed in both halfstrokes. The US's LEV was a Class II LEV extending from wingtip to wingtip, previously reported albeit during the DS in forward flight. The US's net force contribution increased from 32% in forward to 60% in backward flight. Likewise, US weight support increased from 8 to 85%. Despite different trajectories, body postures and force orientations among flight sequences in the global frame, the halfstroke-average forces pointed in a uniform direction relative to the body in both forward and backward flight.

Optimizing flight equencing and gate assignment considering terminal configuration and walking time

Operating airline hub-and-spoke networks (HSN) rather than direct flights among city pairs may significantly reduce supplier cost; however, passengers' travel time may significantly increase due to increased transfer and in-flight time. The costs considered in this study are hub-related and incurred by passengers and aircraft (i.e., passenger transfer, flight dwelling, and gate occupancy). The objective is to minimize the total cost by optimizing flight sequence (i.e., arrivals and departures) and gate assignment, while considering transfer speed, transfer demand, flight size, gate size and terminal configuration. A real-world HSN whose hub airport (HA) is located at Xianyang International Airport (XIY) in Xi'an, China is analyzed. The optimized solutions and their relations to various model parameters are explored.

Macrophage subsets in atherosclerosis as defined by single-cell technologies.

Macrophages play a major role in the pathogenesis of atherosclerosis. Many studies have shone light on the different phenotypes and functions that macrophages can acquire upon exposure to local cues. The microenvironment of the atherosclerotic plaque contains a plethora of macrophage‐controlling factors, such as cytokines, oxidised low‐density lipoproteins and cell debris. Previous research has determined macrophage function within the plaque mainly by using immunohistochemistry and bulk analysis. The recent development and rapid progress of single‐cell technologies, such as cytometry by time of flight and single‐cell RNA sequencing, now enable comprehensive mapping of the wide range of cell types and their phenotypes present in atherosclerotic plaques. In this review we discuss recent advances applying these technologies in defining macrophage subsets residing in the atherosclerotic arterial wall of mice and men. Resulting from these studies, we describe three main macrophage subsets: resident‐like, pro‐inflammatory and anti‐inflammatory foamy TREM2hi macrophages, which are found in both mouse and human atherosclerotic plaques. Furthermore, we discuss macrophage subset‐specific markers and functions. More insights into the characteristics and phenotype of immune cells within the atherosclerotic plaque may guide future clinical approaches to treat disease. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Abstract 53: Aerial Drone versus Ground Search for Delivery of an Automated External Defibrillator (AED) for Out-of-hospital Cardiac Arrest: A Comparison of Elapsed Time and Bystander Experience in a Community Setting

Background: An estimated 350,000 individuals experience out-of-hospital cardiac arrest (OHCA) in the United States (US) annually; only approximately 10% survive. The probability of survival after OHCA doubles when a bystander uses an automated external defibrillator (AED) before emergency management services arrives; however, bystander AED use is less than 2% in the US. We conducted a series of randomized trials in a community setting comparing the delivery of an AED by aerial drone to that of a bystander searching for and retrieving an AED from fixed locations in the area. Methods: We conducted 35 simulation trials of an OHCA using a life-sized manikin accompanied by two participants, paired by gender and age (18-34, 35-49, 50-65 years), in a community setting, with seven trials per zone in five distinct zones. Zones represented different environmental challenges to drone navigation and pedestrian acquisition of an AED and varied in number of fixed AEDs in the area (range 1-8 AEDs in a 600 ft radius from the OHCA site). We used a DJI Matrice 600 Pro drone, modified to carry a standard AED, flying autonomously from a preprogrammed flight path to the OHCA site. Drone launch sites varied by zone and ranged from 800 to 1300 ft from the OHCA site. We randomized participants either to call a mock 9-1-1 telecommunicator who would initiate the drone’s flight sequence, or to conduct a ground search to locate and retrieve an AED from a fixed location. We compared the delivery time of an AED by drone to that of an AED acquired by ground search. We conducted pre- and post-trial interviews with each participant to query perceptions. Results: We conducted 18 trials with women and 17 with men. These included 15, 11, and 9 trials across the three age strata, respectively. The average time (minutes: seconds) from onset of the simulated OHCA to AED delivery was 1:21 faster by drone (4:45, standard deviation (SD) = 0.34) compared to ground search (6:06, SD = 3:21). In 71% of trials (n=25 of 35), the drone delivered the AED to the event site within 5 minutes, compared to 51% (n=18 of 35) of ground searches (p=0.09). Median AED delivery time was faster by drone than by ground search in four of the five zones (range 0:17 to 2:56). Ground search was faster than the drone in one zone with 7 AEDs within 600 ft of the simulated OHCA event site and the shortest average distance to an AED (254 ft) of all the five zones. Among participants randomized to call for the drone, 89% reported that they felt comfortable as the drone approached, and 72% reported having no safety concerns. Nearly half of participants randomized to conduct a ground search reported difficulty finding an AED. Conclusion: Our study suggests that drone delivery of an AED to the site of an OHCA is feasible and acceptable in a community setting. Drones may provide more timely access to early defibrillation compared to bystander search and acquisition of an AED from the surrounding area.

Negotiating leisure etiquette in the context of drones

ABSTRACT The purpose of this paper is to explore leisure etiquette as negotiated through the lens of recreational drones. While drones have experienced spectacular growth in terms of sales and revenue, there remains very little known about how the nuances of recreational drone users negotiate codes of conduct to guide their leisure activities and behavior. Drawing from the overarching notion of leisure etiquette, this research explores the context of two groups of leisure drone users operating in Brisbane, Australia and Singapore. Through participant observation and social media content analysis, the research found that participants negotiated etiquette through three elements – Keeping time, sequence of flights and self-regulation of usage behavior. This research elucidates how leisure etiquette is better understood from the increased presence of recreational drones and offers practical steps for governance and regulations related to technologically-mediated leisure spaces.

Identification of Non-tuberculous Mycobacteria by Partial Gene Sequencing and Matrix Assisted Laser Desorption Ionisation Time of Flight at a Tertiary Care Hospital in Telangana, India

Introduction: Non-tuberculous Mycobacteria (NTM) pulmonary disease is often unrecognised or misdiagnosed as Mycobacterium tuberculosis (MTB), Multi-Drug Resistant Tuberculosis (MDRTB), because of similar clinical presentation in counties with high burden of Tuberculosis (TB) including India. In India due to lack of awareness among clinicians and lack of laboratory facilities to diagnose these infections, its prevalence is largely unknown. Aim: To evaluate the efficacy of identification of NTM species by Matrix Assisted Laser Desorption Ionisation Time of Flight (MALDI-TOF) and Heat Shock Protein (hSP65) gene sequencing and to determine their Antimicrobial Susceptibility Testing (AST). Materials and Methods: All the clinical specimens from pulmonary and extra-pulmonary TB suspects at Nizam’s Institute of Medical Sciences, Hyderabad, Telangana, India, over a period of one year i.e., from June 2017 to May 2018 were included in the study. The specimens were subjected to microscopy, culture and GeneXpert. The NTMs isolated in the culture were further characterised genotypically by MALDI-TOF and hsp65 gene sequencing. The identified NTM isolates were subjected to AST. All the methods were followed as per the standard protocols. Data was analysed using SPSS 25. Results: A total of 1085 samples were processed out of which Mycobacteria was detected in 201 cases (18.5%). Among the culture positives, MTB complex was detected in 146 cases (13.5%) and NTM in 55 (5.06%). Mycobacterium abscessus was the predominant isolate. The most common co-morbidities were bronchiectasis and Chronic Obstructive Pulmonary Disease (COPD). Linezolid, clarithromycin, moxifloxacin and amikacin showed high sensitivity. Conclusion: Molecular assay helps in rapid identification which can lead to targeted therapy and can thus combat antimicrobial resistance. The MALDI-TOF and hsp65 gene sequencing also offers quick results at a low cost and is easy to perform hence it can be considered as an alternate diagnostic tool for identification.

Stochastic Runway Scheduling Problem With Partial Distribution Information of Random Parameters

Air traffic flow management is one of the most important operations in terminal airports heavily relying on advanced intelligence transportation techniques. This work considers a two-stage runway scheduling problem given a set of flights with uncertain arrival times. The first-stage problem is to identify a sequence of aircraft weight classes (e.g., Heavy, Large and Small) that minimizes runway occupying time (i.e., makespan). Then the second-stage decision is dedicated to scheduling the flights as punctually as possible after their arrival times realized, which translates into determining a sequence of flights for each aircraft category such that the total deviation time imposed on the flights is minimized. Instead of an exactly known probability distribution, information on uncertain parameters is limited (i.e., ambiguous), such as means, mean absolute deviations and support set of random parameters derived from historical data. Under this information on the random parameters, an ambiguous mixed-integer stochastic optimization model is proposed. For such a problem, we approximately construct a worst-case discrete probability distribution with three possible realizations per random parameter, and adopt a hybrid sample average approximation algorithm in which genetic algorithms are used to replace commercial solvers. To illustrate the effectiveness and efficiency of the proposed model and algorithm, extensive numerical experiments are carried out.

Susceptibility to Flight Simulator-Induced Spatial Disorientation in Pilots and Non-Pilots

ABSTRACT Objective: This study aimed to investigate whether pilots and non-pilots differ in their susceptibility to spatial disorientation (SD) during a flight in various disorienting scenarios, and in coping with SD. Background: Pilot selection is relevant in assessing pilots’ susceptibility to SD. However, SD-related accidents indicate that it may not be fully effective. Method: A set of 12 flight sequences (six containing an SD conflict, three with vestibular and three with visual illusions) was flown by military pilots (N = 20; age: M = 31.6; SD = 8.22) and non-pilots (N = 20; age: M = 30.95; SD = 7.72) in a flight simulator specially designed for SD research and training. The number and mean magnitude of control reversal errors (CREs) were calculated along with the effects of SD conflict on flight performance. Results: With two exceptions, in all SD-conflict flights, the mean number of CREs increased. For mean magnitudes of CREs, the same effects were not observed. Pilots and non-pilots differed in disorientation conditions (M = 4.5 ± 1.95 vs M = 2.6 ± 2.41) only in one profile (shape constancy illusion). In the other two (false horizon and leans illusions), the applied SD cues significantly affected their flight performance. Conclusion: Although the effects of SD cues on flight performance were observed, the applied disorientation scenario would not be useful in the pilot selection procedure. To provide the criteria to select pilot candidates, other disorientation scenarios, or even a different flight simulator should be considered.

Construction-Based Optimization Approaches to Airline Crew Rostering Problem

An airline crew rostering problem (ACRP) is one of the most important problems in an airline planning process. It aims at determining an optimal assignment of pairings, which refer to sequences of flights starting from and ending at the same crew base, to aircrew to form roster lines. In practice, ACRP is subject to various types of constraints. We present a constraint-implicit mathematical model taking into account the basic, horizontal, and vertical constraints. In order to solve a kind of ACRP, we propose a construction-based variable neighborhood search (VNS) framework that can build rosters effectively. Three construction methods, i.e., crew-by-crew, pairing-by-pairing, and orthogonal constructions, are introduced. To evaluate our approaches, we conduct extensive experiments on two scenarios (intense and light workload) of instances originated from a Chinese airline company and make comparisons among different VNS approaches. The computational results show that the proposed approaches are capable of producing high-quality solutions in both scenarios.

Second-Order Parabolic Equation to Model, Analyze, and Forecast Thermal-Stress Distribution in Aircraft Plate Attack Wing–Fuselage

During a flight, the steel plate attack wing–fuselage of an aircraft is subjected to cyclical thermal stress caused by flight altitude variation that could compromise the functionality of the plate. Thus, it is compulsory after a sequence of flights to evaluate the state of plate health. In this work, we propose a new dynamic model on the basis of the physical transmission of heat by conduction governed by a second-order parabolic partial differential equation with suitable initial and boundary conditions to analyze and forecast thermal stresses in the plate of a P64 OSCAR B airplane. Developing this model in the COMSOL Multi-Physics® environment, a finite-element technique was applied to achieve the thermal-stress map on the plate. The achieved results, equivalent to those obtained by a campaign of infrared thermographic experiment measurements (not yet used in the aeronautical industry), highlight the evolution of the thermal load of the steel plate attack wing–fuselage, adding evidence of possible incoming fatigue phenomena to identify in advance if the steel plate must be replaced.

Low thrust Earth–Moon transfer trajectories via lunar capture set

A cislunar cargo spacecraft with low-thrust propulsion traveling between the Earth and the Moon is essential for sustainable, long-term manned lunar exploration. In low-thrust Earth–Moon transfer (LTEMT), lunar capture is the primary prerequisite for spacecraft subject to the circular restricted three-body model. Therefore, this study identifies sufficient conditions for lunar capture, which are determined by the Jacobi integral and Hill’s region. This paper proposes a guidance scheme that includes thrust direction, thrust efficiency, and a five-stage flight control sequence based on the variation of the Jacobi integral. The LTEMT problem is then converted to an initial value problem of a differential equation with three parameters. Lunar capture set theories (LCSTs), which are convenient for identifying lunar capture sets, are presented and proved according to the continuous properties of the ordinary differential equation. Finally, the solutions of the LTEMT trajectories departing from a geosynchronous orbit with an altitude of approximately 35,827 km are discussed for different thrust accelerations and cut-off values of the thrust efficiency. The robustness is analyzed assuming that navigation and switching time errors are present to demonstrate the adaptability of this method. The results reveal that the proposed guidance scheme and LCSTs can provide technical support for future cislunar cargo missions.

Influence of the Variable Loading Factor on the Masticatory System and the Temporomaxilar Joint and Its Correlation with the Clinic

The integral analysis of the Temporomandibular Joint (TMJ) and the osteo-ligament-articular and muscular structures was carried out together with their associated neural network. This determined the high degree of correlation of the factors that affect the dynamic-functional balance of the Temporomandibular System (TMS) and the self-dynamics of the System. Finite element studies were used to represent the effects of load factors (G forces) in the laboratory and over military combat aircraft, to try to extrapolate the results to field work. The dynamic parameters of the TMJ were measured, using a variable load factor (force G) imposed on the pilots in a sequence of military flights. The application of sustained load factor allowed to visualize in a short period of time, what would take a researcher years to observe, about the typical anomalies of the temporomandibular system and the associated dynamic structures in a patient, besides being able to study the relaxation time that the masticatory system needs, in order to recover its physiological stability, understanding which are the adaptation mechanisms for it. It was determined that not only asymmetric efforts (responsible for the multiple positions of each tooth or dental prosthesis), are responsible for generating harmful loads on the Temporomandibular System, but also have a high degree of correlation, in general, with the damage caused at the TMJ, due to alterations in biomechanical lever systems. Therefore, the methodology of dental treatments must be reconsidered, starting from functional recovery, through appropriate biomechanical mechanisms, to then give way to the corresponding dental rehabilitation, which will result in the functional stability of the masticatory system, dental-prosthetic rehabilitation and the balance integral of the body understanding the masticatory system, as an integral part of a Whole (Holistic Vision).

Research on the Problem of Sorting Parallel Runway Aircraft in Terminal Area Based on Genetic Algorithm

Serious air traffic congestion often occurs in busy airports and terminal areas, which seriously interferes with the normal operation of flights, resulting in a large number of flight delays, causing huge economic losses to airlines, and also the affecting the safe operation of flights in the terminal area. This study takes the two-runway airport as the research object, establishes the parallel runway arrival flight sequencing model and designs the double-encoded genetic algorithm, uses a pair of chromosomes to determine the runway allocation and landing sequence number of the arriving flight, and arranges the flight landing sequence and the runway. The simulation experiments were carried out on 10 flights that were about to land at a certain time in the airport, the experimental results show that the algorithm achieves flight sorting and runway allocation optimization, compared with the current FCFS (First Come First Served) algorithm, it can effectively reduce flight delay time and improve the utilization efficiency of the airport terminal area.

Angiographic contrast mechanism comparison between Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) sequence and Time of Flight (TOF) sequence for intracranial artery

PurposeTo theoretically compare the MR angiography (MRA) contrast mechanism of Time of Flight (TOF) and Simultaneous Non-contrast Angiography and intraPlaque hemorrhage (SNAP) for intracranial artery imaging with in-vivo validation. MethodsThe contrast ratio (CR) of SNAP and TOF was simulated under different blood velocities and travel distance that the blood had flown through. The CR and the slope of CR with respect to blood velocity of SNAP and TOF were compared in theoretical simulation. Two healthy subjects (a 60 years old female and a 29 years old male) were imaged on a 3 T MR scanner with SNAP, TOF and phase contrast (PC) images as the validation set. The measured CR from the images in validation set was compared with the theoretically simulated CR by Person's correlation coefficient. The ratio of CR difference to velocity difference in the validation set was compared between TOF and SNAP with Student's t-test. Thirty patients (21 males, age: 48 ± 13.8 years) with carotid artery atherosclerotic plaque were imaged with both TOF and SNAP as the comparison test. Between TOF and SNAP, the CR and total artery length were compared with Student's t-test, and the prevalence of stenosis was compared with Cohen's kappa in comparison test. ResultsThe theoretically simulated CR was significantly correlated with in-vivo measured CR from the validation set for TOF (p < 0.001) and SNAP (p < 0.001). The simulation revealed that the CR of SNAP was higher than that of TOF when the blood velocity and travel distance were within the range to have effective MRA contrast. Similarly, the in-vivo comparison test showed that SNAP had higher CR (p < 0.001 for all tested intracranial arteries) and longer total artery length (1.4 ± 0.4 m vs 1.2 ± 0.2 m, p < 0.001) than TOF. The stenosis detection performance was similar between TOF and SNAP (Cohen's kappa 0.72; 95% confidence interval: 0.51–0.93). Moreover, compared with TOF, SNAP showed higher slope of CR with respect to velocity in simulation (0.06 ± 0.02 s/cm vs 0.02 ± 0.05 s/cm, p < 0.001), and higher ratio of CR difference to velocity difference in validation test (0.47 ± 0.38 s/cm vs 0.19 ± 0.38 s/cm, p = 0.001). ConclusionsCompared with TOF, the SNAP shows better performance to visualize distal intracranial artery and worse performance to visualize ICA, and is more sensitive to blood velocity.

Combining Benders’ Decomposition and Column Generation for Integrated Crew Pairing and Personalized Crew Assignment Problems

The airline crew scheduling problem, because of its size and complexity, is usually solved in two phases: the crew pairing problem and the crew assignment problem. A pairing is a sequence of flights, connections, and rests starting and ending at the same crew base. The crew pairing problem consists of determining a minimum-cost set of feasible pairings such that each flight is covered exactly once. In the crew assignment problem, the goal is to construct monthly schedules from these pairings for a given set of pilots and copilots independently, while respecting all the safety and collective agreement rules. However, this sequential approach may lead to significantly suboptimal solutions because it does not take into account the crew assignment constraints and objective during the building of the pairings. In this paper, first, we propose an extension of the crew pairing problem that incorporates pilot and copilot vacation requests at the crew pairing stage. Second, we introduce a model that completely integrates the crew pairing and crew assignment problems simultaneously for pilots and copilots. To solve this integrated problem, we develop a method that combines Benders’ decomposition and column generation. We conduct computational experiments with real-world data from a major U.S. carrier.

Amsterdam to Dublin Eventually Delayed? LSTM and Transfer Learning for Predicting Delays of Low Cost Airlines

Flight delays impact airlines, airports and passengers. Delay prediction is crucial during the decision-making process for all players in commercial aviation, and in particular for airlines to meet their on-time performance objectives. Although many machine learning approaches have been experimented with, they fail in (i) predicting delays in minutes with low errors (less than 15 minutes), (ii) being applied to small carriers i.e., low cost companies characterized by a small amount of data. This work presents a Long Short-Term Memory (LSTM) approach to predicting flight delay, modeled as a sequence of flights across multiple airports for a particular aircraft throughout the day. We then suggest a transfer learning approach between heterogeneous feature spaces to train a prediction model for a given smaller airline using the data from another larger airline. Our approach is demonstrated to be robust and accurate for low cost airlines in Europe.

Auditory Verbal Working Memory Load Effects on a Simulator-Induced Spatial Disorientation Event.

INTRODUCTION: Working memory is an essential executive function for flying an aircraft and its limitations may jeopardize flight safety. This function is particularly critical when pilots have to struggle with spatial disorientation (SD) cues. This research aimed to assess the combined effect of the auditory N-back task (NBT) and simulator-induced SD cues on pilots' flight performance.METHODS: Using an SD simulator, 39 male military pilots (control N = 20; age M = 31.6; SD = 8.22, experimental N = 19; age M = 26.9; SD = 8.67) were exposed to 12 flight sequences, where 6 contained an SD conflict-3 with vestibular illusions and 3 with visual illusions. Additionally, the pilots from the experimental group were asked to perform an auditory NBT involving sound stimuli (the sequential letter memory task) as they performed during oriented and disoriented flight conditions.RESULTS: Pilots' flight performance from the NBT group were significantly worse than the control group in the approach and landing profiles involving visual illusions (for both nonconflict and conflict flight), and in the profile involving the false horizon illusion (only for the conflict flight). No increase in a pilot's susceptibility to SD was observed with any other profiles.DISCUSSION: The current study provides support that pilots' cognitive workload can negatively impact flight performance. Pilots are not always aware of altered flight parameters, which may indicate that they have lost spatial orientation, mainly as a result of visual illusion. If problems occur in maintaining proper flight parameters, pilots should direct all available mental resources to regain their orientation and withdraw from any other parallel tasks.Lewkowicz R, Stróżak P, Bałaj B, Francuz P. Auditory verbal working memory load effects on a simulator-induced spatial disorientation event. Aerosp Med Hum Perform. 2019; 90(6):531-539.

Dissemination of genetically diverse NDM-1, -5, -7 producing-Gram-negative pathogens isolated from pediatric patients in Pakistan.

Aim: To determine the prevalence of New Delhi metallo-β-lactamase (NDM)-producing Gram-negative pathogens isolated from children's samples. Materials & methods: Carbapenem-resistant clinical isolates (n=117) were confirmed by VITEK® 2 compact system, matrix-assisted laser desorption ionization-time of flight and multilocus sequence typing.MIC (μg/ml) of various antibiotics was determined by VITEK2 compact system. Molecular characterization of the isolates was performed by PCR, DNA sequencing,PFGE and DNA hybridization. Results: Out of 117 carbapenemase producers, 37 (31.6%) and 29 (24.7%) were Klebsiella pneumoniae and Acinetobacter baumannii, respectively. 72 (61.5%) isolates were NDM positive and among these60, 9 and 3 were NDM-1, -5 and -7, respectively. Majority of the NDM-producing K. pneumoniaebelonged to ST11and ST273while most of theEscherichiacoli belonged to ST405 and ST101. blaNDM were mainly located on 150kb plasmids. MIC displayed high resistance against β-lactams drugs including carbapenems,and the most sensitive drugs were tigecycline and colistin. Conclusion: Dissemination of blaNDM-producing pathogens, particularly in children clinical settings, is a matter of great public health concern.

High-dimensional immune atlas of second trimester human intestinal immunity

Abstract It has long been postulated that newborn’s immune system is immature. To this end, a third of neonatal deaths are due to infections. Similarly, newborns tend to have reduced immune responses to vaccines. Nevertheless, most newborns are healthy. There is limited direct human studies focusing on utero fetal mucosal immune development. Therefore, there is a critical need to investigate fetal mucosal immunity. Using cytometry time of flight (CyTOF) and next-generation sequencing of B and T-cell receptor (B/TCR) repertoires of small (S) and large intestines (LI), we show that intestinal immunity is diverse and functional as early as 16 weeks gestation (GA). Similarly, BCR and TCR repertoires are as diverse in early fetal as in full term samples, though an increase in CDR3β length and distance-from-germline correlates with advanced GA. Innate immunity is dominated by antigen presenting cells, including CD103+DCs, innate lymphoid cells and natural killer cells. B-cells are also present in all tissue examined, with follicular and transitional B-cells enriched in the fetal and CD69+IgM+B-cell in neonatal tissue. Finally, there is high complexity in T-cells, representing &amp;gt;50% of immune cells with similar frequencies at all developmental stages and locations studied. Contrary to our assumption, the majority of T-cells are of central and effector memory subsets. Even more surprisingly, functional tissue resident memory T-cells are abundant and functional in fetal and neonatal samples. Our data provide the foundation for a mucosal immune atlas of second trimester human development and challenge the paradigm that the neonatal immune system is immature, suggesting that development occurs significantly earlier than previously reported.

Update on MR imaging of the pulmonary vasculature

Magnetic resonance imaging (MRI) plays an increasingly important role in the non-invasive evaluation of the pulmonary vasculature. MR angiographic (MRA) techniques provide morphological information, while MR perfusion techniques provide functional information of the pulmonary vasculature. Contrast-enhanced MRA can be performed at high spatial resolution using 3D T1-weighted spoiled gradient echo sequence or at high temporal resolution using time-resolved techniques. Non-contrast MRA can be performed using 3D steady state free precession, double inversion fast spin echo, time of flight or phase contrast sequences. MR perfusion can be done using dynamic contrast-enhanced technique or using non-contrast techniques such as arterial spin labelling and time-resolved imaging of lungs during free breathing with Fourier decomposition analysis. MRI is used in the evaluation of acute and chronic pulmonary embolism, pulmonary hypertension and other vascular abnormalities, congenital anomalies and neoplasms. In this article, we review the different MR techniques used in the evaluation of pulmonary vasculature and its clinical applications.