Factors Associated With an Abnormal Blood Pressure Response During Exercise After Coarctation Repair

Background Although resting blood pressures following aortic arch repair or the extended end-to-end anastomosis (EEA) repair for coarctation can be physiologic, factors associated with an abnormal blood pressure response after exercise are unknown. We measured blood pressure gradients following exercise in children who had undergone previous repair in accordance with a surgical selection algorithm and sought to identify factors associated with an abnormal blood pressure response. Methods In accordance with our practice's surgical algorithm for repair of coarctation, infants were stratified to aortic arch repair when the distal transverse arch-to-left carotid artery ratio (DTA:LCA) ≤ 1.0, or when a brachiocephalic trunk or intra-cardiac lesion requiring repair was present. A thoracotomy and EEA were otherwise used. A follow-up exercise stress test (EST) measured the arm:leg blood pressure gradient after exercise, and a gradient ≥ 20 mm Hg was defined as an abnormal blood pressure response. Results Thirty-seven infants who had previously undergone coarctation repair (aortic arch repair-19, EEA-18) completed an EST at 12.3 ± 2.2 years of age. Thirteen (35%) children (aortic arch repair-5, EEA-8; p = .3) exhibited an abnormal blood pressure response. Factors associated with an abnormal blood pressure response included: smaller DTA:LCA ratios prior to repair (1.0 ± .2 vs. 1.2 ± .3; p = .04) and greater body weight at the time of EST (57.5 ± 19.1 vs. 40.9 ± 15.6 kg; p = .03). Conclusion An abnormal blood pressure response following exercise is associated with smaller DTA:LCA ratios at the time of repair and increased weight during follow-up suggesting that patients with these factors warrant close observation.

Role of Central Atom on the Pressure Response of 2D Perovskites Containing a Long Alkyl Chain (Decylammonium, DA): DA2PbI4 and DA2GeI4

The application of an external pressure on Metal Halide Perovskite (MHPs) has become a fascinating way of tuning their optical properties, achieving also novel features. Here, the pressure response of 2D MHPs including a long alkyl chain made of ten carbon atoms, namely decylammonium (DA), has been investigated as a function of the central atom in DA2PbI4 and DA2GeI4. The two systems share a common trend in the phase stability, displaying a transition from an orthorhombic to a monoclinic phase around 2 GPa, followed by a phase separation in two monoclinic phases characterized by different c-axis. The optical properties show rather different behavior due to the presence of Pb or Ge. DA2PbI4 shows a progressive red shift of the band gap from 2.28 eV at ambient conditions, to 1.64 eV at 11.5 GPa, with a narrow PL emission composed by two components, with the second one appearing in concomitance with the phase separation and significantly shifted to lower energy. On the other hand, DA2GeI4, changes from a non-PL system at ambient pressure, to a clear broadband emitter centered around 730 nm (FWHM ~ 170 nm), with a large stoke shift, and an intensity maximum at about 3.7 GPa. This work sheds light on the structural stability of 2D perovskites characterized by extended alkyl chains, to date limited to four carbon atoms, and shows the pressure-induced emergence of broad emission in a novel lead-free perovskite, DA2GeI4. The evidence of wide emission by a moderate pressure in a germanium-based 2D MHP represents a novel result which may open the design, by chemical pressure, of efficient wide or even white lead-free emitters.

Analysis of Pressure Response Characteristics and Influencing Factors of the Automatic Pressure Regulating Valve in Electronic-Controlled Pneumatic Braking System of Commercial Vehicle

Automatic pressure regulating valve is the core pressure regulating element in electronic-controlled pneumatic braking system of commercial vehicle, its pressure response characteristics directly affect the real-time and rapid pressure regulation. In this paper, the influence of structural parameters of high-speed solenoid valve on its pressure response characteristics is studied. By analyzing the working principle and structure of high-speed solenoid valve, the mathematical model was established by AMESim. Through the combination of simulation and experiment the correctness of the model is verified. Finally, according to the influence law of key structural parameters in high-speed solenoid valve on the pressure response characteristics of automatic pressure regulating valve, a set of optimized parameters are obtained to realize the improvement and optimization of the pressure response characteristics of the automatic pressure regulating valve.

Using Dynamic Pressure Response for Erosion Detection in Hydraulic Tubes and Hoses

Numerical simulations were performed to study the feasibility of erosion detection in hydraulic tubes and hoses using fluid dynamic pressure response analysis. Reflected pressure signals caused by wall thinning were studied to locate and quantify pipe defects. Simulations were conducted for steel pipes as well as hoses. Results showed that for a steel pipe, since the stiffness of the fluid is much less than the pipe material’s, a very big change of wall thickness is needed to have a meaningful change in wave propagation speed and therefore the dynamic pressure response. For hoses, the wall stiffness is much less than steel pipes, hence it is more feasible to detect changes in stiffness. A dataset of 10 000 dynamic pressure impulse responses from samples with randomly generated eroded geometries was calculated to train a gated recurrent unit (GRU) neural network. Results showed that under perfect conditions (no noise), we are able to detect an eroded section’s location, length, and change in wave propagation speed with relative errors of 2.69%, 4.88%, and 3.79%, respectively. The changes in the wave propagation speed was also categorized into three classes of low, mild, and severe erosion with the accuracy of 97.3%. Under more practical conditions including sensor noise, the accuracy of erosion detection is degraded, especially in the case of steel tubing. By retraining the model with noisy data, the drop in the accuracy is compensated to about 96%.