Transient Attenuation Research Articles

Robust Control of Chat-PM: A Switched Singular System with Mode-dependent Bounded Nonlinearity

This paper is concerned with the robust control of the composite hybrid aerial-terrestrial precise manipulator (Chat-PM), a quadrotor-based robot with aerial/terrestrial movement and payload transportation capabilities. Given the distinct dynamics between aerial and terrestrial locomotion modes, Chat-PM is modeled as a type of switched singular system. A nonlinear term is contained in the system to model the coupling between translational and rotational movements of Chat-PM, which is proven to be norm-bounded and mode-dependent. Besides, the estimation error of the robotic arm's interaction force/torque is treated as the disturbance of the system. By means of the mixed H2/H∞ approach, numerically testable stability criterion are obtained, based on which the existence conditions for controllers with satisfactory transient and disturbance attenuation performance are provided. Compared to traditional studies assuming the nonlinearity term to be mode-independent, the conservatism in the controller design is reduced. Experimental results are provided to demonstrate the effectiveness of the proposed approach.

Temperature dependent radiative and non-radiative recombination lifetimes of luminescent amorphous silicon oxynitride systems

In our previous work, we deeply researched the absolute photoluminescence (PL) quantum yields of luminescent modulating a-SiNxOy films with various N/Si atom ratios under different measurement temperatures. In this work, we further systematically studied the temperature dependent kinetic processes of radiative and non-radiative recombinations in a-SiNxOy systems in the visible light range. First, we investigated the structure of a-SiNxOy films and obtained the concentrations of both trivalent Si and N-Si-O defects related dangling bonds through XPS, FTIR and EPR measurements. Then we further tested the transient fluorescence attenuation of a-SiNxOy films detected at different emission wavelengths. We found that the PL lifetimes of a-SiNxOy films vary with the change of N-Si-O defect state concentrations, which is different from the typical PL decay characteristics of band tail related a-SiNx films previously reported. By combining the resulting PL IQE values with the ns-PL lifetimes, we further intensively redetermined the radiative and non-radiative recombination lifetimes of a-SiNxOy systems. The related radiative recombination rates were obtained (kr∼108 s−1), which can be compared to the results in the direct band gap.

Visceral adipose tissue, epicardial fat, and hepatic steatosis in polycystic ovary syndrome: a study of ectopic fat stores and metabolic dysfunction.

In polycystic ovary syndrome (PCOS), ectopic fat accumulation remains debatable. Therefore, intra-abdominal, hepatic, and epicardial fat were compared between PCOS women and body mass index (BMI)-matched controls and their associations with metabolic and hormonal parameters were explored. Furthermore, the performance of echocardiographic epicardial adipose tissue thickness (EATT) and hepatic steatosis measurement using transient elastography-based controlled attenuation parameter (TE-CAP) in screening abdominal visceral adipose tissue (VAT) was originally evaluated. Women aged 18-39 years with BMI < 35 kg/m² were recruited. PCOS was defined by the Rotterdam criteria. All participants underwent clinical and laboratory exams, dual-energy X-ray absorptiometry (DXA), TE-CAP, and echocardiography. A receiver operating characteristic curve was applied to evaluate the accuracy and optimal cutoff values of TE-CAP and EATT in predicting DXA-measured VAT. The study included 35 women with PCOS and 37 controls. PCOS women exhibited higher levels of androgens, insulin resistance (IR) parameters, LDL-cholesterol, triglycerides, VAT, and EATT. VAT correlated with IR and triglycerides, whereas EATT correlated with HDL-cholesterol. In PCOS women aged 18-29, the cutoff values of CAP and EATT for VAT were 198.0 and 3.07, respectively, with CAP showing higher area under the curves (AUC). In PCOS women aged 30-39, the cutoff values were 209.5 and 3.36, respectively, with EATT showing higher AUC. VAT correlates with more metabolic parameters in PCOS than TE-CAP or EATT. TE-CAP is useful for VAT screening in PCOS patients aged 18-39 years, whereas EATT is effective and outperforms CAP in those aged 30-39 years.

Mu-Opioid Receptor (MOR) Dependence of Pain in Chemotherapy-Induced Peripheral Neuropathy.

We recently demonstrated that transient attenuation of Toll-like receptor 4 (TLR4) in dorsal root ganglion (DRG) neurons, can both prevent and reverse pain associated with chemotherapy-induced peripheral neuropathy (CIPN), a severe side effect of cancer chemotherapy, for which treatment options are limited. Given the reduced efficacy of opioid analgesics to treat neuropathic, compared with inflammatory pain, the cross talk between nociceptor TLR4 and mu-opioid receptors (MORs), and that MOR and TLR4 agonists induce hyperalgesic priming (priming), which also occurs in CIPN, we determined, using male rats, whether (1) antisense knockdown of nociceptor MOR attenuates CIPN, (2) and attenuates the priming associated with CIPN, and (3) CIPN also produces opioid-induced hyperalgesia (OIH). We found that intrathecal MOR antisense prevents and reverses hyperalgesia induced by oxaliplatin and paclitaxel, two common clinical chemotherapy agents. Oxaliplatin-induced priming was also markedly attenuated by MOR antisense. Additionally, intradermal morphine, at a dose that does not affect nociceptive threshold in controls, exacerbates mechanical hyperalgesia (OIH) in rats with CIPN, suggesting the presence of OIH. This OIH associated with CIPN is inhibited by interventions that reverse Type II priming [the combination of an inhibitor of Src and mitogen-activated protein kinase (MAPK)], an MOR antagonist, as well as a TLR4 antagonist. Our findings support a role of nociceptor MOR in oxaliplatin-induced pain and priming. We propose that priming and OIH are central to the symptom burden in CIPN, contributing to its chronicity and the limited efficacy of opioid analgesics to treat neuropathic pain.

Molecular Characteristics and Functional Identification of a Key Alpha-Amylase-Encoding Gene AMY11 in Musa acuminata.

Alpha-amylase (AMY) plays a significant role in regulating the growth, development, and postharvest quality formation in plants. Nevertheless, little is known about the genome-wide features, expression patterns, subcellular localization, and functional regulation of AMY genes (MaAMYs) in the common starchy banana (Musa acuminata). Twelve MaAMY proteins from the banana genome database were clustered into two groups and contained a conserved catalytic domain. These MaAMYs formed collinear pairs with the AMYs of maize and rice. Three tandem gene pairs were found within the MaAMYs and are indicative of putative gene duplication events. Cis-acting elements of the MaAMY promoters were found to be involved in phytohormone, development, and stress responses. Furthermore, MaAMY02, 08, 09, and 11 were actively expressed during fruit development and ripening. Specifically, MaAMY11 showed the highest expression level at the middle and later stages of banana ripening. Subcellular localization showed that MaAMY02 and 11 were predominately found in the chloroplast, whereas MaAMY08 and 09 were primarily localized in the cytoplasm. Notably, transient attenuation of MaAMY11 expression resulted in an obvious increase in the starch content of banana fruit, while a significant decrease in starch content was confirmed through the transient overexpression of MaAMY11. Together, these results reveal new insights into the structure, evolution, and expression patterns of the MaAMY family, affirming the functional role of MaAMY11 in the starch degradation of banana fruit.

Decreased Beta Power and OFC-STN Phase Synchronization during Reactive Stopping in Freely Behaving Rats.

During natural behavior, an action often needs to be suddenly stopped in response to an unexpected sensory input-referred to as reactive stopping. Reactive stopping has been mostly investigated in humans, which led to hypotheses about the involvement of different brain structures, in particular the hyperdirect pathway. Here, we directly investigate the contribution and interaction of two key regions of the hyperdirect pathway, the orbitofrontal cortex (OFC) and subthalamic nucleus (STN), using dual-area, multielectrode recordings in male rats performing a stop-signal task. In this task, rats have to initiate movement to a go-signal, and occasionally stop their movement to the go-signal side after a stop-signal, presented at various stop-signal delays. Both the OFC and STN show near-simultaneous field potential reductions in the beta frequency range (12-30 Hz) compared with the period preceding the go-signal and the movement period. These transient reductions (∼200 ms) only happen during reactive stopping, which is when the stop-signal was received after action initiation, and are well timed after stop-signal onset and before the estimated time of stopping. Phase synchronization analysis also showed a transient attenuation of synchronization between the OFC and STN in the beta range during reactive stopping. The present results provide the first direct quantification of local neural oscillatory activity in the OFC and STN and interareal synchronization specifically timed during reactive stopping.

Assessing hepatic steatosis by magnetic resonance in potential living liver donors

To determine the accuracy of magnetic resonance imaging-proton density fat fraction (MRI-PDFF) measurements for detecting liver fat content in potential living liver donors and to compare these results using liver biopsy findings. A total of 139 living liver donors (men/women: 83/56) who underwent MRI between January 2017 and September 2021 were included in this analysis retrospectively. The PDFFs were measured using both MR spectroscopy (MRS) and chemical shift-based MRI (CS-MRI) for each donor in a blinded manner. Significant positive correlations were found between liver biopsy and MRS-PDFF and CS-MRI PDFF in terms of hepatic steatosis detection [r = 0.701, 95% confidence interval (CI): 0.604–0.798, r = 0.654, 95% CI: 0.544–0.765, P < 0.001, respectively). A weak level correlation was observed between liver biopsy, MRI methods, and vibration-controlled transient elastography attenuation parameters in 42 available donors. Based on receiver operating characteristic (ROC) analysis, MRS-PDFF and CS-MRI PDFF significantly distinguished >5% of histopathologically detected hepatic steatosis with an area under the ROC curve (AUC) of 0.837 ± 0.036 (P < 0.001, 95% CI: 0.766–0.907) and 0.810 ± 0.036 (P < 0.001, 95% CI: 0.739–0.881), respectively. The negative predictive values (NPVs) of MRS-PDFF and CS-MRI PDFF were 88.3% and 81.3%, respectively. In terms of distinguishing between clinically significant hepatic steatosis (≥10% on histopathology), the AUC of MRS-PDFF and CS-MRI were 0.871 ± 0.034 (P < 0.001 95% CI: 0.804–0.937) and 0.855 ± 0.036 (P < 0.001, 95% CI: 0.784–0.925), respectively. The NPVs of MRS-PDFF and CS-MRI were 99% and 92%, respectively. The methods of MRS-PDFF and CS-MRI PDFF provide a non-invasive and accurate approach for assessing hepatic steatosis in potential living liver donor candidates. These MRI PDFF techniques present a promising clinical advantage in the preoperative evaluation of living liver donors by eliminating the requirement for invasive procedures like liver biopsy.

The U-net-based ice pore parameter extraction method for establishing the SAW icing sensing mechanism

The porous ice layer formed upon the SAW (surface acoustic wave) propagation path will produce transient acoustic attenuation, and a new icing sensing method can be constructed based on this feature. Obtaining the pore characteristics of an ice layer is a prerequisite and basis for deriving the sensing mechanism of SAW icing. Employing the U-net network, a segmentation model of frozen pores is developed by collecting frozen images and calibrating sample data sets for training in this work. The MIOU and the MPA of the model reach 92.16 % and 95.15 % respectively. Then, the watershed algorithm and post-processing were used to accurately obtain the pore characteristic parameters (porosity, pore number, and average pore area) of the ice layer. On this basis, applying the Biot's theory for two-phase porous media, a theoretical model of the SAW icing sensing mechanism was established, and the acoustic sensing response under different icing types was theoretically simulated. To prove the accuracy of the theoretical simulation, a SAW sensor using a waveguide structure of SU-8/ST-90 °X quartz operating at 80 MHz was constructed and evaluated experimentally. The results demonstrate that the acoustic sensing responses of different ice types are completely consistent with the theoretical results. This fully verifies the accuracy of the ice pore parameters extracted in this work and also confirms the feasibility of using pore microscopic information to achieve ice detection and ice type discrimination.

Enhancing Dynamic Performance in K-Rb-21Ne Co-Magnetometers through Atomic Density Optimization

The K-Rb-21Ne co-magnetometer exhibits poorer dynamic performance due to the larger equivalent magnetic field generated by alkali metal atoms. In this study, the impact of the atomic number density of alkali metal atoms and noble gas atoms in the cell on the dynamic performance of the atomic ensemble is investigated quantitatively. Relationships between the slow-decay term in the transient response attenuation of the Spin-Exchange Relaxation-Free (SERF) co-magnetometer to interference magnetic fields and the number densities of noble gas atoms as well as alkali metal atoms are established. Based on the established model, the relationship between the number density of 21Ne atoms and dynamic performance is investigated using cells with five different noble gas pressures. Then, we investigate the impact of the number density of alkali metal atoms using a cell with a pressure of 2.1 atm at different temperatures. The results indicate that, as the number density of alkali metal atoms or noble gas atoms in the cell increases, the dynamic performance of the system improves, which provides a theoretical basis for the design of cell parameters for SERF co-magnetometers.

P549 Liver stiffness assessed with TE-CAP tends to increase with longer duration of disease in Crohn’s disease: A prospective cohort study for the evaluation of hepatic abnormalities in inflammatory bowel disease

Abstract Background Intestinal mucosal injury is supposed to cause liver disease and abnormal liver profiles are frequently observed in inflammatory bowel disease (IBD) patients. Therefore, we investigated the hepatic manifestations of IBD in Korea. Methods A prospective cohort for the evaluation of hepatic abnormalities in IBD was established at Kosin University Gospel Hospital, Busan, Korea in 2018. From December 2018 to June 2023, patients who diagnosed with IBD were consecutively enrolled and conducted both abdominal sonography and transient elastography-controlled attenuation parameter (TE-CAP) with liver function tests, viral tests, lipid profiles, and fecal calprotectin. Results Three hundred twelve (138 Crohn's disease, CD, 174 ulcerative colitis, UC, and 200 men) patients were enrolled. Mean ages (years old) were 46.4 in UC and 37.5 in CD. Mean body mass indexes, BMIs were 23.1 in UC and 21.9 in CD. Mean CAP (dB/m) score was 222.439 (±55.375) [UC 232.408 (±53.476), CD 209.869 (±55.358)]. Mean E (kPa) value was 4.481 (±1.801) [UC 4.496 (±2.028), CD 4.461 (±1.474)]. Mean fecal calprotectins were 982 in UC and 1160 in CD. The mean durations of disease (months) were 36.8 in UC and 44.0 in CD. In abdominal sonography, abnormal findings in gallbladder were found 38/169 (22.4%) in UC and 38/137 (27.7%) in CD (P=0.834). (Table 1) HBs Ag positivity was 7/173 (4.0%) in UC, 5/138 (3.6%) in CD (P=0.847). Anti-HBs was positive in 115/173 (66.4%) in UC and 68/138 (49.2%) in CD (P=0.002). Anti-HBc IgG was positive in 46/112 (29.1%) in UC and 17/130 (13.0%) in CD (P=0.001). Anti-HCV was positive in 0/173 (0.0%) in UC and 3/138 (2.1%) in CD (P=0.051). In UC patients, CAP value was associated with BMI (r=0.498, P&amp;lt;0.0001), triglyceride (TG) (r=0.264, P&amp;lt;0.0001), and low-density lipoprotein (LDL) (r=0.162, P=0.033). E value was related to BMI (r=0.267, P&amp;lt;0.0001). In CD patients, CAP value was associated with BMI (r=0.661, P&amp;lt;0.0001), total cholesterol (r=0.290, P=0.001), TG (r=0.286, P=0.001), LDL (r=0.217, P=0.011) and fecal calprotectin (r=-0.343, P&amp;lt;0.0001). E value was associated with total bilirubin (r=0.369, P&amp;lt;0.0001), ALP (r=0.236, P=0.005), r-GTP (r=0.318, P&amp;lt;0.0001), AST (r=0.384, P&amp;lt;0.0001), ALT (r=0.277, P&amp;lt;0.001) and disease duration (r=0.239, P=0.005). In CD patients with a disease duration of more than 1 year, the E value was confirmed to increase gradually as the disease period lengthened (r=0.346, P=0.004). (Figure 1) Conclusion In CD patients, liver stiffness tends to increase with longer duration of disease or active liver inflammation. Both UC and CD patients, fatty liver may occur attributed to abnormal metabolic profiles. In addition, there is a need to encourage HBV vaccination in IBD patients in HBV endemic area, especially in UC patients.

Clinical research of fibroscan ‒ TE-CAP at noninvasive diagnosis of hepatic steatosis in children

Background & aimsThe authors assess the diagnostic accuracy of the Transient Elastography-Controlled Attenuation Parameter (TE-CAP) in children of Southern China. Methods105 obese or overweight children and adolescents were enrolled in the diagnostic test of TE-CAP assessment of hepatic steatosis using MRI-PDFF. Hepatic steatosis grades S0-S3 were classified. Statistical correlation, agreement and consistency between methods were evaluated. The diagnostic efficiency of TE-CAP was evaluated. The authors used the cutoff value of TE-CAP to detect hepatic steatosis in another 356 children. ResultsThe Area Under Curve (AUC) of TE-CAP for grade ≥ S1, ≥ S2, and ≥ S3 steatosis were 0.975, 0.984, and 0.997, respectively. For detecting ≥ S1 steatosis, TE-CAP had a sensitivity of 96 % and a specificity of 97 %. For detecting ≥ S2 steatosis, TE-CAP had a sensitivity of 97 % and a specificity of 93 %. For detecting ≥ S3 steatosis, TE-CAP had a sensitivity of 1 and a specificity of 94 %. TE-CAP and MRI-PDFF had a linear correlation (r = 0. 0.87, p < 0.001). The hepatic steatosis was identified in 40.2 % (143/356) of children in which the obesity and overweight were 69.8 % (113/162) and 40.0 % (18/45). ConclusionTE-CAP showed excellent diagnostic accuracy in pediatric hepatic steatosis.

Exploring the function of MaPHO1 in starch degradation and its protein interactions in postharvest banana fruits

Banana is a quintessential fruit known for its starch conversion process. During development, substantial starch accumulates in banana fruit and subsequently undergoes rapid degradation, contributing to flavor development during postharvest ripening. However, the genes orchestrating this crucial starch degradation process have not been comprehensively studied thus far. Through temporal transcriptomic analysis, we screened 63 active genes that were actively expressed in association with starch degradation during the ripening of banana fruits. The results found that phosphorolytic enzymes primarily regulate starch degradation at the early to middle stages of fruit ripening and that hydrolytic enzymes significantly contribute to starch degradation at the later stage. The expression of Musa acuminata starch phosphorylase 1 (MaPHO1) was the highest at the early to middle stages of banana ripening, characterized by the insertion of an L80 domain. While MaPHO1 was predominately found in the chloroplast, MaPHO2 was localized to the cell membrane. Starch accumulation was significantly increased by transient attenuation of MaPHO1 expression, whereas a drastic reduction in starch content was triggered by transient overexpression of MaPHO1, affirming its functional role in banana fruit ripening. By constructing a co-expression network, 29 categories, including 74 proteins interacting with MaPHO1 were identified. Tripartite interactions between MaPHO1 and both glucan, water dikinase 1 (GWD1) and enolase 1 (ENO1) were revealed by further validation through yeast two-hybrid and glutathione-S-transferase pull-down analyses.

Electroencephalography as a diagnostic tool for late-onset efavirenz neurotoxicity syndrome.

To examine electroencephalogram (EEG) as a diagnostic tool for late-onset efavirenz (EFV) neurotoxicity syndrome (LENS), an uncommon but severe and potentially fatal complication of EFV therapy. We conducted a Retrospective case-control study. EEGs from confirmed cases of LENS (clinical syndrome and plasma EFV >4ug/mL) recorded from June 2016 to May 2021 were compared with control EEGs from the same time-period. Controls were adults (18-70 years) with a similar indication for EEG (eg. encephalopathy or confusion), dysrhythmia generalised grade II, and LENS excluded. EEGs were reviewed by two blinded interpreters given a description of the characteristic EEG changes, ie. persistent, diffuse, high voltage, bisynchronous, monomorphic 4-7 Hz theta frequency waveforms with transient attenuation on eye opening. Interpreters were asked to determine whether EEGs showed definite, probable or no changes. Thirteen LENS cases were compared with 50 control EEGs. Interpreter 1 labelled 11/13 LENS cases as having define or probable changes, and interpreter 2 labelled 10/13. Interpreter 1 labelled probable changes in 1/50 controls and interpreter 2 in 3/50. Neither interpreter labelled any controls as having definite changes. Interrater reliability was good with 95% agreement and a Cohen's kappa of 0.83. Sensitivity of EEG under these conditions for the diagnosis of LENS was 85% and 77% for interpreters 1 and 2 respectively, and specificity was 98% and 94%. EEG is a useful tool in the diagnosis of LENS which can be used to aid clinical decisions while awaiting EFV levels, or in low-resource settings where EFV levels are not available.

Transient hepatic attenuation difference (THAD) or fat sparing? Aberrant right gastric vein (ARGV) determining a pseudolesion at the border of the IInd/IIIrd liver segments. Review of developmental concepts.

The aberrant right gastric vein (ARGV) is a rare anatomical variation. It can be responsible for unexplained hyperdensities in the hepatic parenchyma on CT scans, also known as third inflow effects. We present two cases sharing similar vascular pattern and slightly different imagistic findings on ultrasound and computer-tomography performed studies. Both ultrasonographies showed a nodular-geographic hypoechoic area within a hyperechogenic fatty liver. Further CT evaluation showed in both cases a hyperattenuating homogenous area clearly visible on all four phases at the border of the IInd/IIIrd hepatic segment, that enhance especially on the portal venous phase, with no slow-fill, wash-out, central scar or rim-like features. The areas were considered to be focal fat sparing areas in diffuse fatty liver or a perfusion disorder due to the presence of an aberrant right gastric vein. The aim of this paper is to discuss the embryological aspects which are the groundwork for this vascular anomaly and to correlate the findings with imagistic aspects. These two ARGV produced pseudolesions, understood as focal fat sparing areas within diffuse fatty livers. These pseudolesions mimic liver tumours, therefore it is important to look for such an aberrant vessel in order to rule out other diagnoses.

Noise Characteristics and Denoising Methods of Long-Offset Transient Electromagnetic Method

The advantages of the long-offset transient electromagnetic method include deep detection and sensitive response to resistivity anomalies. It is widely used in underground mineral resources exploration, fluid identification in petroleum reservoirs, hydraulic fracturing, and dynamic residual oil and gas monitoring. After the primary field signal is turned off, grounded electrodes or coils are used to observe the secondary eddy field. The secondary field signal decays quickly and has a large dynamic range and a wide frequency band but is easily affected by various natural and human electromagnetic interferences. Therefore, noise reduction and distortion correction are important issues in the processing of transient electromagnetic data. This paper proposes a systematic noise interference suppression process. Multi-period and positive–negative bipolar signal stackings were used to remove random noise and suppress DC offset signals. Then, a time-domain inverse digital recursive method was applied to remove characteristic frequency signals, e.g., power frequency signals and their harmonic interference. A standard noise-free signal was constructed through forward modeling simulation and verified by adding different types of noise. Finally, high-quality transient electromagnetic secondary field attenuation signals were obtained through overlapping windowing technology. We applied this algorithm to obtain electromagnetic data from dynamic monitoring of hydraulic fracturing in Fuling shale gas and from a copper–iron metal mine in Daye City, demonstrating its effectiveness.

Fault diagnosis in bipolar HVDC systems based on traveling wave theory by monitoring data from one terminal

This paper proposes a method for detecting, classifying and locating incident faults on transmission line (TL) of a bipolar HVDC system. This method is based on the traveling waves theory and uses the redundant discrete wavelet transform to filter voltage signals monitored at only one system terminal. The model represents the Brazilian HVDC system of the Madeira River, which is simulated in the Alternative Transient Program (ATP). Different fault scenarios are analyzed, being generated by varying type, resistance and fault location. Moreover, in order to make the simulation more realistic, the TL is modeled based on frequency dependent parameters. Thereby, the impacts of line parameter uncertainties and transient attenuation on the proposed method are analyzed. From the obtained results, it is concluded that the method correctly detects all fault types through the use of a self-adaptive detection threshold. Furthermore, it is verified that the self-adaptive threshold detects the fault times instants with an efficiency superior to the fixed threshold. In the classification step, all faults were correctly classified through rules elaborated based on the voltage variation level. Finally, the total average errors of fault location represents only 0.047% of the TL extension. Moreover, it is verified that fault location errors for pole:pole faults were inferior to those obtained for pole:ground faults, being the efficiency of the method inversely proportional to the fault resistance.

A fast transient tracking differentiator for high-precision motion systems

High-quality velocity signal plays an important role in fast and precise motion systems, but most commercially available motion systems are not commonly equipped with velocity sensors; hence, full access to the system states is impossible. A fast transient tracking differentiator is proposed in this article for obtaining the noise-less time derivative from a noisy measurement. The fast transient tracking differentiator is conceived within the framework of tracking differentiator methodology and is accomplished by integrating a power-like function with a smooth hyperbolic sine function. Tracking differentiator theory and Lyapunov direct method are employed to show the global asymptotic convergence. Advantages of the proposed fast transient tracking differentiator include the easy implementation with intuitive structure and high computational efficiency and faster transient and higher noise attenuation for both small and large initial estimation errors. The proposed fast transient tracking differentiator can be applied to a large class of motion systems by cascading to a robust output feedback proportional–derivative control for fast and high-precision positioning with position measurement only. Numerical simulation and real-time experimental comparisons demonstrate that the proposed approach provides an easygoing model-free output feedback solution for fast and accurate velocity reconstruction and high-performance positioning of uncertain motion systems with position measurement only.

A unified analytical model for the flight distance of flying microdroplet before solidification

Heat dissipation and solidification of a flying microdroplet are omnipresent in nature and industrial applications. The current study lacks a model to determine the critical flight distance before the microdroplet solidification, which is crucial for powder production and microdroplet jet printing in additive manufacturing. This study investigated the transient velocity and temperature attenuation of a flying microdroplet. Both the velocity and temperature of the microdroplet were found to be decayed exponentially with the flying time. Based on energy conversion and flying velocity integration, an analytical model was proposed to determine the critical flight distances that the microdroplet begins and ends to solidify. Moreover, the parameters affecting the critical flight distance were unified into a nondimensional formula. Finally, we validated the proposed models experimentally through the deposited morphologies of copper microdroplets induced by laser pulses.

Hypoxia induces dichotomous and reversible attenuation of T cell responses through reactive oxygen species-dependent phenotype redistribution and delay in lymphoblast proliferation

As T cells transit between blood, lymphoid organs, and peripheral tissues, they experience varied levels of oxygen/hypoxia in inflamed tissues, skin, intestinal lining, and secondary lymphoid organs. Critical illness among COVID-19 patients is also associated with transient hypoxia and attenuation of T cell responses. Hypoxia is the fulcrum of altered metabolism, impaired functions, and cessation of growth of a subset of T cells. However, the restoration of normal T cell functions following transient hypoxia and kinetics of their phenotype-redistribution is not completely understood. Here, we sought to understand kinetics and reversibility of dichotomous T cell responses under sustained and transient hypoxia. We found that a subset of activated T cells accumulated as lymphoblasts under hypoxia. Further, T cells showed the normal expression of activation markers CD25 and CD69 and inflammatory cytokine secretion but a subset exhibited delayed cell proliferation under hypoxia. Increased levels of reactive oxygen species (ROS) in cytosol and mitochondria were seen during dichotomous and reversible attenuation of T cell response under hypoxia. Cell cycle analysis revealed maximum levels of cytosolic and mitochondrial ROS in dividing T cells (in S, G2, or M phase). Hypoxic T cells also showed specific attenuation of activation induced memory phenotype conversion without affecting naïve and activated T cells. Hypoxia-related attenuation of T cell proliferation was also found to be reversible in an allogeneic leukocyte specific mixed lymphocyte reaction assay. In summary, our results show that hypoxia induces a reversible delay in proliferation of a subset of T cells which is associated with obliteration of memory phenotype and specific increase in cytosolic/mitochondrial ROS levels in actively dividing subpopulation. Thus, the transient reoxygenation of hypoxic patients may restore normal T cell responses.

434 TAKOTSUBO SYNDROME AFTER PACEMAKER IMPLANTATION

Abstract Introduction Takotsubo syndrome is a clinical syndrome characterized by typical anamnestic features together with typical ECG and echocardiographic findings. Comparing with the available literature not so many cases of takotsubo syndrome after pacemaker implantation can be found. Furthermore, there are only few articles talking about ECG features in these patient. The case we described allows to observe dynamic ECG alterations in a patient with electro-induced ventriculograms Case Description A 90-year-old male was admitted to the emergency room for important fatigue associated with severe bradycardia (25/min). His cardiovascular history was silent, and his past medical history was characterized by high blood pressure, chronic pulmonary obstructive disease and anemia due to iron deficiency. The ECG showed second degree AVB type 2, with phases of 2:1 AVB and paroxysmal third degree AVB on continuous monitoring. The routine blood tests showed normal T troponin and BNP was 420 pg/mL. The echocardiogram revealed normal biventricular dimensions and systolic function with moderate aortic valve stenosis. The patient underwent urgent permanent DDD pacemaker implantation without previous isoproterenol administration. During the procedure he referred important pain on the site of the wound, and he became confused and agitated. The procedure was complicated by massive pneumothorax that needed quick decompression. On the 2nd day after pacemaker implantation the ECG revealed electro-induced atrium-guided ventriculograms and began to modify with only mild ST-segment elevation in V2 and initial T-wave inversion from V3 to V6 and in I - II - aVF. On the next days, T-waves became deeper and QTc prolonged to 540 ms. These abnormalities were then gradually resolved on the 11th day. Mild transient attenuation of the amplitude of the QRS complexes in V2 – V3 leads on day 1 could be reported. Another echocardiogram was then performed, which showed new apical akinesis with “apical ballooning” aspect and EF of 40%. TnT and BNP values increased. Coronary angiogram was not performed due to patient rejection, so that coronaropathy could not be excluded with certainty. Nevertheless, the patient had only high blood pressure as cardiovascular risk factor and that the probability of the diagnosis of takotsubo cardiomyopathy was assessed of 76,9% by InterTAK diagnostic score, so that we considered Takotsubo syndrome the most likely diagnosis. Therefore, the patient's therapy was then optimized with an increase in the dosage of ACE inhibitors. At one month follow-up the ECG remained stable, and the echocardiogram showed a preserved ejection fraction (EF = 55%), without alterations of the segmental contractility. BNP and TnT values were normal. Therapy was left unmodified. Conclusions Takotsubo syndrome should be consider a rare but possible complication of pacemaker implantation. This is true especially for patients affected by frailty and cognitive impairment. There are no specific ECG criteria for takotsubo syndrome in patients with electro-induced ventriculograms, but anomalies of the repolarization are similar to those in patients with spontaneous ventricular activity. Transient attenuation of the QRS complexes voltages could be seen even just in the precordial leads and it is generally present in the very acute phase.