Second-order Exponential Model Research Articles

Edaphoclimatic variation and harvest seasonality as determining factors of multidimensional quality in avocado cv. hass grown in the tropics

The increase in cultivated areas in tropical zones such as Colombia for avocado cv. Hass and the lack of knowledge on edaphoclimatic relationships with factors associated with quality led to the present research. The aim of this research was to establish the relationship of soil, climatic, spatial factors (plot location), and harvest seasonality (principal and transitory) with the multidimensional quality of avocado cv. Hass planted under tropical conditions. This research was carried out on eight farms located in three producing subregions. Soil, environmental and harvest data were recorded for three years (2015–2017) in each plot. Avocado fruit samples were used to determine the parameters of macronutrient, fatty acids, minerals, and vitamin E. Descriptive, inferential statistics, multivariate analysis, effect size, second-order exponential model, and causal relationships were used to determine variables associated with soil, climate, harvest seasonality, and spatial location, and to determine quality parameters. The results established a relationship between nutritional quality and the origin region. Similarly, it was possible to identify parameters associated with differential quality with a robust statistical methodology to propose origin as a differentiating factor for quality. This study provided useful information for the value chain that selected the best areas for avocado crops according to market expectations and nutritional quality criteria.

Physiological system analysis of the kidney by high-temporal-resolution monitoring of an oxygenation step response.

Examine the feasibility of characterizing the regulation of renal oxygenation using high-temporal-resolution monitoring of the response to a step-like oxygenation stimulus. For mapping, multi-echo gradient-echo imaging was used (temporal resolution = 9seconds). A step-like renal oxygenation challenge was applied involving sequential exposure to hyperoxia (100% O2 ), hypoxia (10% O2 + 90% N2 ), and hyperoxia (100% O2 ). In vivo experiments were performed in healthy rats (N = 10) and in rats with bilateral ischemia-reperfusion injury (N = 4). To assess the step response of renal oxygenation, a second-order exponential model was used (model parameters: amplitude [A], time delay [Δt], damping constant [D], and period of the oscillation [T]) for renal cortex, outer stripe of the outer medulla, inner stripe of the outer medulla, and inner medulla. The second-order exponential model permitted us to model the exponential recovery and the superimposed oscillation following renal oxygenation stimulus. The in vivo experiments revealed a difference in Douter medulla between healthy controls (D < 1, indicating oscillatory recovery) and ischemia-reperfusion injury (D > 1, reflecting aperiodic recovery). The increase in Douter medulla by a factor of 3.7 (outer stripe of the outer medulla) and 10.0 (inner stripe of the outer medulla) suggests that this parameter might be rather sensitive to (patho)physiological oxygenation changes. This study demonstrates the feasibility of monitoring the dynamic oxygenation response of renal tissues to a step-like oxygenation challenge using high-temporal-resolution mapping. Our results suggest that the implemented system analysis approach may help to unlock questions regarding regulation of renal oxygenation, with the ultimate goal of providing imaging means for diagnostics and therapy of renal diseases.

Could the pulmonary [formula omitted] off-transient response to maximal short-term exercise be better characterized by a triexponential decay?

The off-transient pulmonary oxygen uptake (V˙O2) response to a single bout of intense, exhaustive exercise has been characterized over the years by a second-order exponential model. In this paper, we report the superiority of a third-order exponential decay in describing the V˙O2 off-kinetics after a maximal cycling exercise lasting 60-s. Our findings are in accordance with a biphasic pattern of phosphocreatine resynthesis when muscle pH is affected.

Determination of strain, site occupancy, photoluminescent, and thermoluminescent-trapping parameters of Sm3+-doped NaSrB5O9 microstructures

Monoclinic NaSrB5O9:Sm3+ phosphors were synthesized by a conventional solid-state reaction method in air. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies revealed that the Sm3+ ions preferably occupy Sr2+ cation sites in the NaSrB5O9 host lattice. The doping-dependent crystallite size and lattice strain on the X-ray peak broadening of the NaSrB5O9:Sm3+ phosphor was determined by the Scherrer and Williamson–Hall (W–H) methods. Trigonally and tetrahedrally coordinated boron atoms in the phosphors were confirmed by confocal Raman analysis. Under near-UV excitation (402nm), the NaSrB5O9:Sm3+ phosphors emitted reddish-orange light at 604 nm that corresponds to the 4G5/2→6H7/2 transition. The concentration quenching mechanism between the two Sm3+ ions within the host was proved to be the dipole-dipole interaction, and the critical distance was found to be 22.29Å. The fitted luminescence decay curves in terms of a second-order exponential model suggest that the Sm3+ ions possess two different kinds of environments in the host lattice, which was supported by XPS analysis. The defects acting as trapping centers were investigated by thermoluminescence glow curves. The γ-irradiated NaSrB5O9:Sm3+ phosphors show two major dosimetric glow peaks centered at about 188.83 and 378.66°C, indicating two different kinds of trapping centers in the phosphors.

Periodic Breathing in Heart Failure Explained by Dynamic and Static Properties of Respiratory Control.

OBJECTIVEThe respiratory operating point is determined by the interplay between the controller and plant subsystem elements within the respiratory chemoreflex feedback system. This study aimed to establish the methodological basis for quantitative analysis of the open-loop dynamic properties of the human respiratory control system and to apply the results to explore detailed mechanisms of the regulation of respiration and the possible mechanism of periodic breathing in chronic heart failure.METHODS AND RESULTSIn healthy volunteers, we measured arterial CO2 partial pressure (PaCO2) and minute ventilation to estimate the dynamic properties of the controller ( relation) and plant ( relation). The dynamic properties of the controller and plant approximated first- and second-order exponential models, respectively, and were described using parameters including gain, time constant, and lag time. We then used the open-loop transfer functions to simulate the closed-loop respiratory response to an exogenous disturbance, while manipulating the parameter values to deviate from normal values but within physiological ranges. By increasing both the product of gains of the two subsystem elements (total loop gain) and the lag time, the condition of system oscillation (onset of periodic breathing) was satisfied.CONCLUSIONWhen abnormality occurs in a part of the respiratory chemoreflex system, instability of the control system is amplified and may result in the manifestation of respiratory abnormalities such as periodic breathing.

Estimation of Grasping Force from Features of Intramuscular EMG Signals with Mirrored Bilateral Training

This study investigates the use of features extracted from intramuscular electromyography (EMG) for estimating grasping force in the ipsilateral and contralateral (mirrored) hand, during bilateral grasping tasks. This is relevant since force estimation using mirror tasks is a potentially useful pathway for the clinical training of unilateral amputees. Bilateral grasping force and intramuscular EMG (wire electrodes) of the right forearm were measured in 10 able-bodied subjects. The features extracted from the EMG signal were the root mean square, the global discharge rate, the standard sample entropy, and the constraint sample entropy (CSE). The association between the EMG features and force was modeled using a first-order polynomial model, a second-order exponential model, and an artificial neural network (ANN). The accuracies of estimation of ipsilateral and mirrored grasping force were not significantly different (e.g., R(2) = 0.89 ± 0.02 for ipsilateral and 0.88 ± 0.017 for mirrored, when using CSE and the ANN). It was concluded that it is possible to use just one channel of intramuscular EMG for force estimation. This result suggests that intramuscular EMG signals may be suitable for proportional myoelectric control and that training of the association between intramuscular EMG features and force can be performed using mirror tasks, which is a needed condition for applications in unilateral amputees.