Population Imaging of Central Sensitization

Capsaicin applied locally to the skin causes central sensitization that results in allodynia, a state in which pain is elicited by innocuous stimuli. Here, we used two-photon calcium imaging of neurons in the dorsal spinal cord to visualize central sensitization across excitatory interneurons and spinal projection neurons. To distinguish among excitatory neuron subtypes, we developed CICADA, a cell profiling approach that leverages the expression of distinct Gq-coupled receptors. We then identified capsaicin-responsive and capsaicin-sensitized neuronal populations. Capsaicin-sensitized neurons showed emergent responses to low threshold input and increased receptive field sizes consistent with the psychophysical phenomenon that allodynia is observed across an extended secondary zone. Finally, we identified spinal projection neurons that showed a shift in tuning toward low threshold input. These experiments provide a population-level view of central sensitization and a framework with which to model somatosensory integration in the dorsal horn.

Design and Validation of a Novel Test-Rig for RQL Flame Dynamics Studies

In this paper a novel test-rig for the investigation of low-frequency thermoacoustic instabilities in aero-engines with air-staging RQL (rich-quench-lean) is presented. The new approach is to separate the rich primary zone from the lean secondary zone to allow for an isolated thermoacoustic characterization of each combustion zone. In addition the test-rig offers the possibility to combine both zones to judge the transferability of the findings from the separated to the compact configuration. The high modularity of the test-rig is already considered in the design-phase and allows a cost and time efficient manufacturing. Heat losses in the primary zone and the transition duct between the two zones play a crucial role for the functionality of the facility and are estimated during design to guarantee a stable re-ignition in the secondary zone. The main design steps in the secondary zone for achieving complete burn-out of the hot primary combustion gases are described. The realization of the acoustic excitation via loudspeakers is described and damping measures to improve combustor stability are explained. The operation of both zones, their acoustic behavior and the operational limits of the test-rig are demonstrated experimentally. They include first thermoacoustic measurement data of naturally occurring instabilities, the corresponding eigenfrequencies and the validation of the test-rig design. Finally an outlook on the future work in the research project concludes this paper.

Study of Adiabatic Flame Temperature of a Jet Combustor using a Non-Circular Inlet

An experimental investigation on heat transfer at various zones of the combustion chamber has been carried out using a non-circular inlet at the flame tube. With an aim to improve the turbulent level in flow, the non-circular section used here is an elliptical one. In addition to this, two rectangular tabs are placed at major axis of the ellipse to achieve an efficient mixing of fuel and air. Fuel used for combustion is kerosene while LPG gas is used for pre ignition. Fuel is fed to the chamber by gravity system and it has been atomized by two fish tank pumps. Ignition of the fuel is done by spark plug with a separate setup. The setup comprises of growler and CDI coil which are powered electrically. During the experiment, combustion has been initiated by allowing the air from blower to the chamber. The fuel is sprayed into the flame tube through fuel injector placed at a specified distance. After the proper mixing of fuel and air, the mixture is ignited by spark plug setup. Initially LPG gas was used for preheating followed by kerosene for combustion. Fuel tank has been calibrated for mass flow rate. The experiment has been carried out for different intervals of time and the heat transferred from the flame tube wall and chamber wall is been measured using an infrared gun (ray gun) by pointing laser on the wall. The temperatures at different zones have been measured. It is seen that the overall heat transfer at secondary zone is minimum when compared with other zones for the same period of time. This indicates that if the fuel injector is placed before the secondary zone, then a maximum flame temperature can be obtained. This leads to an improvement in efficiency of the combustion chamber.

Capsaicin-Induced Changes in Electrical Pain Perception Threshold Can Be Used to Assess the Magnitude of Secondary Hyperalgesia in Humans

Objectives Areas of secondary hyperalgesia can be assessed using quantitative sensory testing (QST). Delivering noxious electrocutaneous stimulation could provide added benefit by allowing multiple measurements of the magnitude of hyperalgesia. We aimed to characterize the use of electrical pain perception (EPP) thresholds alongside QST as a means by which to measure changes in pain thresholds within an area of secondary mechanical hyperalgesia. Methods EPP and heat pain thresholds (HPTs) were measured at five distinct points at baseline and following 1% capsaicin cream application, one within a central zone and four within a secondary zone. Areas of secondary mechanical hyperalgesia were mapped using QST. In a further 14 participants, capsaicin-induced reduction in EPP thresholds was mapped using a radial lines approach across 24 points. Results There was a reduction in EPP threshold measured at the four points within the secondary zone, which was within the mapped area of mechanical secondary hyperalgesia. The magnitude of secondary hyperalgesia could be split into a mild (∼4% reduction) and severe (∼21% reduction) area within an individual subject. There was no reduction in HPT within the secondary zone, but there was a reduction in both HPT and EPP threshold within the primary zone. EPP mapping revealed differences in the magnitude and spread of hyperalgesia across all subjects. Conclusions Measuring capsaicin-induced reduction in EPP thresholds can be used to map hyperalgesic areas in humans. This semi-automated approach allows rapid assessment of the magnitude of hyperalgesia, both within an individual subject and across a study population.

Simulation of CO Emission in Primary and Secondary Zone of a Small Gas Turbine Combustion Chamber Using CFD and Reactors Network

In this paper the influence of various parameters of the primary and secondary zones of a small-sized combustion chamber on its environmental characteristics was studied. The study of the environmental characteristics of the combustion chamber was carried out in two ways. The first method consisted of two steps. The first step was a 3D simulation of combustion processes using FGM combustion model. The second step was based on results of the first step using reactors network implemented in the ANSYS Fluent 18.2 software. The construction of the reactors network in this approach occurred automatically according to a temperature and mixture fraction. The number of reactors in the result was about 500. The second method was a simple model of a reactors network in which the primary zone was simulated by a perfectly stirred reactor, and the secondary zone was a plug flow reactor. Methane was used as a fuel. The influence of the residence time of the mixture and fuel-air equivalence ratio in each zone on the emission of CO and NOx at the combustion chamber exit was studied. The residence time and fuel-air equivalence ratio for the first method were changed using the design parameters of the combustion chamber. For a simple reactors network, these parameters are set as input data, so this method can be used at the preliminary design stage. As a result of the work, a method was obtained that allows to find the parameters of the primary and secondary zones of the combustion chamber in order to minimize pollutant emissions at the preliminary design stage.

Numerical Investigation of Influence of Multi-Line Fuel Injection (Methane) on a Tubular Combustor Emissions of Micro Gas Turbine

This work presents a technique for design optimization of a gas turbine tubular combustor. This technique is based on the use of computational fluid dynamics (CFD) with CFX solver to reduce emission gases by using multi-line of fuel injection in secondary zone. This research relates the mass fraction of the multi-line of fuel injection as well as the equivalence ratio of the tubular combustion chamber designed for methane fuel. By using k-ε as turbulent model and Probability Density Function (PDF) Flamelet as combustion model. The operating casing data of micro size gas turbine are used, the validation of fuel flow mixing and combustion analyses were carried out with a focus on species concentration in the combustor outlet section. With variant fuel mass flow rate fraction in fuel lines (F2/F1), It was found that, with the new design NO reduced about 56% for the mass fraction 3 in high equivalence ratio and about 30%for the mass fraction 1 for a low equivalence ratio, while reduction in outlet temperature profile (pattern factor) is about 45% → 35%.

Microseismicity-derived fracture network characterization of unconventional reservoirs by topology

The advent of horizontal drilling technology, combined with multistaged hydraulic fracturing to create a complex fracture network within the relatively impermeable rock mass, has made natural gas production from tight reservoirs economically feasible. Understanding of the generated fracture network properties, such as its spatial distribution, extension, connection, and ability to percolate, plays a significant role in evaluation of the stimulation efficiency, optimizing analytical frac models, and ultimately enhancing completion programs. We have developed a unique approach to understand the influence of fractures on fluid flow and production from impermeable reservoirs and evaluate completion effectiveness. We characterize the microseismicity-derived discrete fracture network in a North American shale-gas reservoir using modified scanline and topology methods. Using concepts of node and branch classification and assessing the number of connections (fracture intersections), the network connectivity is established volumetrically. The zones of permeability enhancement are then identified using the connection per branch and line ([Formula: see text] and [Formula: see text]), tied to percolation thresholds of the fracture system. These zones consist of a primary zone with a high proportion of doubly connected fractures, a secondary zone populated with partially connected fractures, and a tertiary or unstimulated zone dominated by isolated fractures. These divisions are reflected in the deformation that is observed in the reservoir as measured through a cluster-based description of the microseismicity. The primary and secondary zones are considered spanning fracture clusters, and they take part in production, whereas the tertiary zone is recognized as nonspanning fractures, and though it may enhance the bulk permeability of the rock mass, it is unlikely to contribute to reservoir production.