maximum slope
Recently Published Documents

Abstract A portable near infrared spectroscopy (NIRS) system was used to evaluate alterations in cerebral total hemoglobin concentration (HbT) in individuals with orthostatic hypotension (OH) and orthostatic intolerance (OI) symptoms. We enrolled 238 healthy participants (mean age, 47.9 years) and assessed the presence of OH (orthostatic blood pressure (BP) drop of systolic BP ≥ 20 mmHg or diastolic BP ≥ 10 mmHg within 3 minutes of supine-to-stand) and OI symptoms using the OH questionnaire. The participants were categorized into three groups based on the presence of OH and OI symptoms: the classic OH (OH-BP) group, symptom alone (OH-Sx) group, and control group. Random case-control matching sets (age, sex, hypertension, and diabetes mellitus) were constructed consisting of 16 OH-BP and 69 OH-Sx-control sets. We measured the time-derivative of HbT change in the prefrontal cortex during the squat-to-stand maneuver. There were no differences in demographics, baseline BP, and heart rate among the matched sets. Among the NIRS parameters, the peak-time of maximum slope variation was significantly longer in the OH-Sx and OH-BP groups than in the matched control groups during transition to the standing position after squatting. Our results suggested that OH and OI symptoms are associated with dynamic alteration in cerebral HbT.

Abstract OBJECTIVE To develop a method based on CT angiography and the maximum slope model (MSM) to measure regional lung perfusion in anesthetized ponies. ANIMALS 6 ponies. PROCEDURES Anesthetized ponies were positioned in dorsal recumbency in the CT gantry. Contrast was injected, and the lungs were imaged while ponies were breathing spontaneously and while they were mechanically ventilated. Two observers delineated regions of interest in aerated and atelectatic lung, and perfusion in those regions was calculated with the MSM. Measurements obtained with a computerized method were compared with manual measurements, and computerized measurements were compared with previously reported measurements obtained with microspheres. RESULTS Perfusion measurements obtained with the MSM were similar to previously reported values obtained with the microsphere method. While ponies were spontaneously breathing, mean ± SD perfusion for aerated and atelectatic lung regions were 4.0 ± 1.9 and 5.0 ± 1.2 mL/min/g of lung tissue, respectively. During mechanical ventilation, values were 4.6 ± 1.2 and 2.7 ± 0.7 mL/min/g of lung tissue at end expiration and 4.1 ± 0.5 and 2.7 ± 0.6 mL/min/g of lung tissue at peak inspiration. Intraobserver agreement was acceptable, but interobserver agreement was lower. Computerized measurements compared well with manual measurements. CLINICAL RELEVANCE Findings showed that CT angiography and the MSM could be used to measure regional lung perfusion in dorsally recumbent anesthetized ponies. Measurements are repeatable, suggesting that the method could be used to determine efficacy of therapeutic interventions to improve ventilation-perfusion matching and for other studies for which measurement of regional lung perfusion is necessary.

Abstract Aim In liver CT perfusion, the dual-input maximum slope (DI-MS) method is commonly used to estimate perfusion to aid diagnosis of tumors. The DI-MS method relies on a model that assumes the splenic time-to-peak (TTP) separates arterial and portal venous perfusion, and occurs prior to venous perfusion. In this preclinical study, we examined how the timeliness of splenic TTP affects DI-MS perfusion calculations of liver tumors. Materials and Methods We analyzed imaging data obtained from 11 New Zealand White rabbits bearing a single implanted VX2 tumor in liver. A liver 320-slice CT perfusion protocol (5,400 images per study) was used to generate images. Times for arterial and portal slopes were recorded, and hepatic arterial perfusion (HAP), portal perfusion (HPP) and perfusion index (HPI) for liver and tumor were separately calculated using manual and automated methods. T-test comparisons and Bland-Altman plot analyses were performed. Results Mean tumor TTP occurred at 9.79 s (SD=3.41) and splenic TTP at 9.75 s (SD=4.47, p=0.98). In 3/11 (27.27%) cases, tumor SP occurred prior to spleen (mean difference=1.33 s, SD=1.15 s). In these cases, mean automated HPP values were 43.8% (SD=52.48) higher compared to manually computed ones. There were statistically significant differences between automated and manual methods for normal liver and tumor HPI and HPP (p<0.01 and p<0.0001, respectively), but not HAP values (p=0.125 and p=0.78, respectively). There was also a statistically significant variation between methods for tumor HPP and HPI (p=0.001, respectively). Conclusion In 320-slice CT perfusion of liver in this preclinical model, we observed that tumor TTP occurred prior to splenic TTP in 27.27% of tumors in liver. This temporal relationship affects tumor perfusion calculations and should be identified to address potential deviations of model assumptions.

Improving the technical level of railway transport of industrial enterprises is expressed in the introduction of advanced types of traction (locomotives and electric locomotives), four and six-axle specialized cars, including self-unloading, automation and telemechanics. To increase the productivity of quarry trains at PJSC "Kryukiv Railway Car Building Plant" a six-axle dump car model 33-7141 for quarry railway transport was designed. The car is designed for transportation from quarries of open cut hard rocks, ore and other bulk and lump cargo with density (1.75-4.0) t/m3, as well as mechanized unloading on dumping sites or crushing units of opencast mining. A distinctive feature of innovative dump cars from typical ones is the increase of cargo weight by 10 t and axial load to 271.6 (27.7) kN (ts). In this regard, the issues of assessing the braking efficiency of a quarry train with innovative dump cars that meet the requirements for railway industrial transport are becoming relevant. The article presents the study results of the braking efficiency of a quarry train composition of 10 and 14 cars. Locomotive TEM7 and unit OPE1AM with one and two motor cars were considered as traction units. The maximum permissible speeds were determined in a given range of slopes of the railway track, and the maximum possible descent was set provided that the braking distance does not exceed or will be equal to 300. As a result of research, it was found that the maximum allowable deviations ranged from 34 ‰ to 38 ‰ depending on the number of cars and traction units. The speed of trains with innovative dump trucks on the site is 42 km/h. Key words: dump car, tipping wagon, maximum slope, permissible speed, braking distance, traction unit.

Abstract Micro-hydropower plants have become one of the alternative solutions to meet the electricity needs of people in remote villages that the public electricity company has not reached. However, the performance of a micro-hydro system has to be continuously developed. This research aims to improve the performance of a micro-hydro system by examining the effect of the slope of the penstock on the increase in electrical power. The penstock slope is varied with diverse angles, namely θ = 50 °, 60 °, 70 °, 80 °, and 90 °. Five simulations of water flow in the penstock for five slope angles were constructed using the open-source CFD software, i.e., OpenFOAM. We calculate the electric power for the five simulations aforementioned. The calculation results show that the variation of the penstock slope can affect the increase of the electric power of a micro-hydro system. The highest electric power occurs at a maximum slope, θ = 90 °.

Abstract Background Acute heart failure and cardiogenic shock remain highly morbid conditions despite prompt medical therapy in critical care settings. Mechanical circulatory support (MCS) is a promising therapy for these patients, yet remains managed with open-loop control. Continuous measure of cardiac function would support and optimize MCS deployment and weaning. The nature of indwelling MCS provides a platform for attaining this information. This study investigates how hysteresis modeling derived from MCS device signals can be used to assess contractility changes to provide continuous indication of changing cardiac state. Load-dependent MCS devices vary their operation with cardiac state to yield a device–heart hysteretic interaction. Predicting and examining this hysteric relation provides insight into cardiac state and can be separated by cardiac cycle phases. Here, we demonstrate this by predicting hysteresis and using the systolic portion of the hysteresis loop to estimate changes in native contractility. This study quantified this measurement as the enclosed area of the systolic portion of the hysteresis loop and correlated it with other widely accepted contractility metrics in animal studies (n = 4) using acute interventions that alter inotropy, including a heart failure model. Clinical validation was performed in patients (n = 8) undergoing Impella support. Results Hysteresis is well estimated from device signals alone (r = 0.92, limits of agreement: − 0.18 to 0.18). Quantified systolic area was well correlated in animal studies with end-systolic pressure–volume relationship (r = 0.84), preload recruitable stroke work index (r = 0.77), and maximum slope of left ventricular pressure (dP/dtmax) (r = 0.95) across a range of inotropic conditions. Comparable results were seen in patients with dP/dtmax (r = 0.88). Diagnostic capability from ROC analysis yielded AUC measurements of 0.92 and 0.90 in animal and patients, respectively. Conclusions Mechanical circulatory support hysteretic behavior can be well modeled using device signals and used to estimate contractility changes. Contractility estimate is correlated with other accepted metrics, captures temporal trends that elucidate changing cardiac state, and is able to accurately indicate changes in inotropy. Inherently available during MCS deployment, this measure will guide titration and inform need for further intervention.

The status monitoring of industrial process equipment is of great significance to its production energy efficiency and safety. A state monitoring system for complex surface structures based on the distributed FBG sensor network is proposed. The system adopts the FBG network and realizes the calculation of the stress field of the complex surface through the FBG layout design at different positions in the three-dimensional space. A 32-channel FBG sensor network is designed, and the light source, demodulation module, and processing system are selected and analyzed. On the basis of building the FBG sensor network, the stress field test was carried out on the industrial process equipment. For complex three-dimensional surface structures, an optical scanner is used for position offset calibration. Experiments show that when force is applied to the center point, the slope of the FBG at the best sensitive position is 0.715 pm/N; when force is applied on both sides, the maximum slope in the positive direction is 0.348 pm/N and the maximum slope in the negative direction is −0.381 pm/N. After data fusion correction is used, the average error of the three-dimensional position offset of the test data is 6.85%. It can be seen that the FBG network has the ability to monitor the state of complex surface structures in the industrial engineering equipment.

In assessing the severity of lower extremity arterial disease (LEAD), physicians rely on clinical judgements supported by conventional measurements of macrovascular blood flow. However, current diagnostic techniques provide no information about regional tissue perfusion and are of limited value in patients with chronic limb-threatening ischemia (CLTI). Near-infrared (NIR) fluorescence imaging using indocyanine green (ICG) has been used extensively in perfusion studies and is a possible modality for tissue perfusion measurement in patients with CLTI. In this prospective cohort study, ICG NIR fluorescence imaging was performed in patients with CLTI and control patients using the Quest Spectrum Platform® (Middenmeer, The Netherlands). The time–intensity curves were analyzed using the Quest Research Framework. Fourteen parameters were extracted. Successful ICG NIR fluorescence imaging was performed in 19 patients with CLTI and in 16 control patients. The time to maximum intensity (seconds) was lower for CLTI patients (90.5 vs. 143.3, p = 0.002). For the inflow parameters, the maximum slope, the normalized maximum slope and the ingress rate were all significantly higher in the CLTI group. The inflow parameters observed in patients with CLTI were superior to the control group. Possible explanations for the increased inflow include damage to the regulatory mechanisms of the microcirculation, arterial stiffness, and transcapillary leakage.

Abstract Rangeland is a valuable resource that can allow producers to cost effectively provide nutrients for grazing cattle. However, grazing behavior of cattle is adversely affected when the temperature humidity index is greater than 72. It is possible to select cattle that exhibit efficient grazing behavior even under mild heat stress. This study evaluated genetic associations with grazing behavior to help producers identify cows that will effectively use their rangeland pastures. Using genome-wide associations, this study identified single nucleotide polymorphisms (SNPs) associated with grazing time, walking time and max slope that cattle utilized while experiencing mild heat load. Data were collected from Angus X Hereford 2-year-old beef cows from UI herd over two years (37 grazing and walking minutes, 38 max slope). Genotypes were obtained using a Bovine GGP 50K SNP marker array and 41,686 markers were used in the analyses. Two SNPs on chromosome 11 are significantly (P = 5.01e-7, P = 6.46e-7) associated with grazing minutes and explain 0.52 proportion of variance (PVE). A SNP on chromosome 3 is significant for walking minutes (P=1.91e-6) with a PVE of 0.48. Additionally, a SNP on chromosome 14 is significantly (P = 8.50e-6) associated with max slope and has a PVE of 0.43. This ongoing project identified significant associations with grazing and walking minutes and maximum slope. This research will be strengthened with the addition of more animals over successive years. Some cattle spend more time grazing, walking, or at a higher elevation in mild heat load. Identifying genetic variants associated with grazing time, walking time, and maximum slope use while under heat stress can enable producers to select for cattle that best fit the rangeland available to them.

Abstract The detailed characterization of complex forms of atrial flutter relies on the correct interpretation of intra-atrial electrograms. For this, the near field components, which represent the local electrical activity, are decisive. However, far field components arising from distant electrical sources in the atria can obscure the diagnosis. We developed a method to separate and characterize atrial near field and atrial far field components from bipolar intra-atrial electrograms. First, a set of bipolar electrograms was created by simulating different propagation scenarios representing common clinical depolarization patterns. Second, near and far fields were detected as active segments using a non-linear energy operator-based approach. Third, the maximum slope and the spectral power were extracted as features for all active segments. Active segments were grouped accounting for both the timing and the location of their occurrence. In a last step, the active segments were classified in near and far fields by comparing their feature values to a threshold. All active segments were detected correctly. On average, near fields showed 15.1x larger maximum slopes and 40.4x larger spectral powers above 100 Hz than far fields. For 135 active segments detected in 72 bipolar electrograms, 5.2% and 6.7% were misclassified using the maximum slope and the spectral power, respectively. All active segments were classified correctly if only one near field segment was assumed to occur per electrogram. The separation of atrial near and atrial far fields was successfully developed and applied to in silico electrograms. These investigations provide a promising basis for a future clinical study to ultimately facilitate the precise clinical diagnosis of atrial flutter.