Curvilinear Model Research Articles

Small size does not confer male agility advantages in a sexually-size dimorphic spider.

Selection pressures leading to extreme, female-biased sexual size dimorphism (SSD) in spiders continue to be debated. It has been proposed that males of sexually size dimorphic spiders could be small because gravity constrains adult agility (locomotor abilities). Accordingly, small males should achieve higher vertical climbing speeds and should be more prone to bridge. The curvilinear model of the gravity hypothesis predicts a negative relationship between vertical climbing speed and male body size only over a threshold of 7.6 mm, 42.5 mg. Because males of most species with extreme SSD fall well below this threshold, the relationship between male size and agility at this scale remains vague. Here, we tested three hypotheses on how male size, mass and age (after maturation) relate to vertical climbing and bridging ability in Nephilingis cruentata, a highly sexually dimorphic orb-weaver with males well below the size threshold. We placed males of different sizes and adult ages in a vertical platform and recorded their climbing speeds. Contrary to the original study testing male bridging ability as binary variable, we measured the duration of the crossing of the bridging thread, as well as its sagging distance. Male body size and mass positively related to the vertical climbing speed and to the distance of the sagging thread during bridging, but had no influence on the bridging duration. The detected positive correlation between male size/mass and vertical climbing speed goes against our first prediction, that small males would have vertical climbing advantage in Nephilingis cruentata, but agrees with the curvilinear model. Against our second prediction, small males were not faster during bridging. Finally, in agreement with our third prediction, threads sagged more in heavier males. These results suggest that small male size confers no agility advantages in Nephilingis cruentata.

Solute transport in shallow water flows using the coupled curvilinear Lattice Boltzmann method

A novel form of coupled curvilinear lattice Boltzmann model (CCLBM) for solving the solute transport in shallow water flows, imposed by the complex geometry, is developed and applied. Shallow water equations, transformed into curvilinear coordinate system, are solved using the lattice Boltzmann equation with multiple-relaxation-time (MRT-LBM), while the curvilinear form of the 2D advection-diffusion equation is solved applying the Bhatnagar-Gross-Krook (BGK-LBM) approach. Corresponding forms of equilibrium distribution function for both the shallow water and the advection-diffusion equation is derived using the D2Q9 lattice. The physical flow domain of arbitrary geometry in the horizontal plane is covered with adequate curvilinear mesh, while the calculation procedure for flow and transport is carried out in the D2Q9 square lattice, applying the basic form of the boundary condition method on water-solid and open boundaries as well. The coupled flow and pollution transport is tested using a straight inclined channel, irrigation channel with a parabolic cross section in a 90° bend, and a segment of the Danube River. In the cases of the straight inclined channels analytic solution is used as a comparative base, while for the bent channel previously obtained velocity measurements are utilized for flow calibration, where a mathematical model based on traditional CFD procedures is used for pollution transport validation. Unsteady flow and salinity transport in the Danube River is calibrated and modelled using velocity and salinity measurements, along with the results obtained by the traditionally based CFD model. The high level of agreement between the results obtained by the proposed model and the corresponding analytical values and measurements indicates that the presented curvilinear form of the LBM is capable of solving very complex environmental problems.

The Ontogeny of Masticatory Muscle Architecture in Microcebus murinus

Many studies pertaining to the masticatory apparatus have focused on the mandibular adductors (the temporalis, masseter, and medial pterygoid) ‐ the muscles that work cooperatively to produce bite force. Specifically, the architectural properties of these muscles have been correlated with diet. For instance, felids that eat relatively large prey have relatively longer fascicles to allow for the necessary gape. Primate diet also correlates with muscle architecture and, in some instances (e.g., tree gouging in Callithrix), the mode of foraging. However, there is little known about the ontogenetic development of these muscles. To characterize age‐related changes, we used an intraspecific sample of 28 specimens from a captive colony, spanning the entire lifespan of the small Malagasy primate, Microcebus murinus.We dissected each of the jaw adductors and obtained their masses as well as linear morphometrics. We then chemically dissected them using 35% nitric acid for 15–30 hours until their constituent fascicles could be separated. Then the reaction was neutralized in 50% glycerol and fascicles were photographed and measured using ImageJ (NIH) and all logged variables were statistically analyzed in JMP (SAS).A quadratic curvilinear model is significant when muscle mass is regressed against age with p‐values <0.01 for each adductor. The trends demonstrate that the muscle mass of the adductors peak during early to mid‐adulthood with a point of inflection occurring at late adulthood to early senescence. When physiological cross‐sectional area (PCSA) is scaled against age, a quadratic model represents the data significantly better for the masseter and medial pterygoid with p‐values <0.01. However, a linear model is more appropriate when characterizing changes in the PCSA of temporalis as the quadratic model was found to be insignificant. The general trend for changes in PCSA for masseter and medial pterygoid are consistent with the patterns observed in muscle mass, but temporalis PCSA does not appear to atrophy significantly with age. When fiber length is scaled against age for each mandibular adductor, the curvilinear relationship was observed to be a good fit with p‐values <0.05. However, for the temporalis and medial pterygoid this trend appears to be driven by the inclusion of a low outlier. When this specimen is excluded, the trend line is horizontal suggesting that, once fiber length reaches maximum length early in life, it remains relatively constant. The trend for medial pterygoid also suggests that fiber length peaks early in life; however, it also indicates a point of inflection occurring in early adulthood.From these results, representing the most complete ontogenetic sample of primate masticatory muscle architecture, we have successfully characterized myological changes across the lifespan of M. murinus. Our findings suggest that the changes in PCSA are driven mostly by changes in muscle mass including growth through early adulthood and slight but clear reduction into senescence, while masticatory fascicle lengths remain surprisingly constant throughout life.Support or Funding InformationThis project was supported by the NSF (IOS‐15‐57125 and BCS‐14‐40599).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Job-related emotions and job burnout among civil servants: examining the shape of the relationship in cross-sectional and longitudinal models

The relationship between positivity, i.e., the proportion of positive and negative emotions, and job burnout may be of a curvilinear shape. From a theoretical point of view, it is a causal relationship, since positivity can be regarded as a proximal dimension of occupational well-being, and burnout as a distal one. However, previous studies have been mostly cross-sectional and have tested only linear relationships between these variables. Therefore, the aim of the study is to examine the shape of the relationship between positivity and burnout using both cross-sectional and longitudinal designs, on the example of civil servants. The study involved 238 civil servants (73.5% of whom were women). Positivity was assessed with the Job-related Affective Well-being Scale. Exhaustion and disengagement, 2 components of job burnout, were measured twice, at a 4-month interval, using the Oldenburg Burnout Inventory. The cross-sectional models assuming the curvilinear relationship between positivity and job burnout were better fitted to the data than models with the linear relationship only. Thus, positivity was curvilinearly related to both exhaustion and disengagement, with an inflection point around 2. In the longitudinal models, for exhaustion the curvilinear model was again better fitted to the data, while for disengagement it was the linear model. The relationship between positivity and exhaustion was curvilinear among the civil servants. This may indicate personal costs of maintaining a high ratio of positive to negative emotions at work. Nevertheless, the role of positivity for disengagement seems more complex, with a possible long-term protective function. Med Pr. 2019;70(2):201-11.

Motor Skills Learning and Generalization with Adapted Curvilinear Gaussian Mixture Model

This paper is intended to solve the motor skills learning, representation and generalization problems in robot imitation learning. To this end, we present an Adapted Curvilinear Gaussian Mixture Model (AdC-GMM), which is a general extension of the GMM. The proposed model can encode data more compactly. More critically, it is inherently suitable for representing data with strong non-linearity. To infer the parameters of this model, a Cross Entropy Optimization (CEO) algorithm is proposed, where the cross entropy loss of the training data is minimized. Compared with the traditional Expectation Maximization (EM) algorithm, the CEO can automatically infer the optimal number of components. Finally, the generalized trajectories are retrieved by an Adapted Curvilinear Gaussian Mixture Regression (AdC-GMR) model. To encode observations from different frames, the sophisticated task parameterization (TP) technique is introduced. All above proposed algorithms are verified by comprehensive tasks. The CEO is evaluated by a hand writing task. Another goal-directed reaching task is used to evaluate the AdC-GMM and AdC-GMR algorithm. A novel hammer-over-a-nail task is designed to verify the task parameterization technique. Experimental results demonstrate the proposed CEO is superior to the EM in terms of encoding accuracy and the AdC-GMM can achieve more compact representation by reducing the number of components by up to 50%. In addition, the trajectory retrieved by the AdC-GMR is smoother and the approximation error is comparable to the Gaussian process regression (GPR) even far fewer parameters need to be estimated. Because of this, the AdC-GMR is much faster than the GPR. Finally, simulation experiments on the hammer-over-a-nail task demonstrates the proposed methods can be deployed and used in real-world applications.

The response of performance in grower and finisher pigs to diets formulated to different tryptophan to lysine ratios

Three experiments were conducted to determine the optimal dietary standardized ileal digestible (SID) Trp to Lys ratio (Trp:Lys) for grower-finisher pigs with body weight of 20–50 (Experiment (Exp.) 1), 50–80 (Exp. 2), and 80–110 kg (Exp. 3). A total of 4032 Duroc × Yorkshire × Landrace barrows and gilts were used in the experiments with a randomized complete blocked design. For each experiment, 1344 pigs were randomly assigned into 6 dietary treatments (SID Trp:Lys levels: 0.150, 0.165, 0.180, 0.195, 0.210, and 0.225) with 8 replicate pens per treatment (14 barrows and 14 gilts per pen). Synthetic Trp was used to adjust the dietary SID Trp:Lys, while the Lys content in all 6 diets remained fixed in each experiment. In Exp. 1, the average daily gain (ADG), average daily feed intake (ADFI), gain to feed ratio (G:F), and serum urea N (SUN) were increased quadratically (P < 0.01) as the SID Trp:Lys increased from 0.150 to 0.225. The optimal SID Trp:Lys for ADG estimated using broken-line and curvilinear-plateau models were 0.171 and 0.188, respectively. For G:F, the break-points were 0.192 and 0.207 for the linear and quadratic models, respectively. In Exp. 2, a quadratic increase was observed in ADG, ADFI, G:F, and SUN as the SID Trp:Lys increased from 0.150 to 0.225 (P < 0.05). The optimal SID Trp:Lys for ADG estimated using the broken-line and curvilinear-plateau models were 0.183 and 0.200, respectively. The break-points for G:F estimated using broken-line and curvilinear-plateau models were 0.195 and 0.213, respectively. In Exp. 3, the ADG, G:F, and SUN increased quadratically with increasing SID Trp:Lys, while ADFI increased linearly (P < 0.05). The optimal SID Trp:Lys for ADG estimated using the broken-line and curvilinear-plateau models were 0.184 and 0.201, respectively. Likewise for G:F, the best ratios were 0.174 and 0.198 for the linear and curvilinear models, respectively. In summary, the optimal Trp:Lys for ADG estimated using the broken-line model in pigs weighing 20 to 50, 50 to 80, and 80 to 110 kg were 0.171, 0.183, and 0.184, respectively. The optimal Trp:Lys for G:F estimated using the broken-line model in pigs weighing 20 to 50, 50 to 80, and 80 to 110 kg were 0.192, 0.195, and 0.174, respectively.

Meta-Analysis of the Curvilinear Relationship between Rate of Delivery and Message Persuasiveness

&lt;em&gt;For five decades researchers investigated whether increasing the speed of the delivery of a persuasive message produces more message comprehension and attitude change. The experimental literature on this issue appears inconsistent, with many mediating variables introduced in an effort to reconcile disparate findings. This meta-analysis seeks to determine how persuasion is influenced by the rate of message delivery. The data provide support for a curvilinear model, indicating that persuasion is maximal for moderate speech rates. Results are discussed in terms of source credibility and mechanisms of message processing.&lt;/em&gt;

A linear model for relative motion in an elliptical orbit based on a spherical coordinate system

When compared with Cartesian coordinates, curvilinear coordinates have shown significant superior accuracy when applied to a linear model for relative motion in a circular reference orbit. Experts assume the same superiority for an elliptical reference orbit. However, the curvilinear model in an elliptical reference orbit has not been established, and the superiority has not been proved. After a strictly theoretical derivation this paper establishes a linear model with spherical coordinates for relative motion in an elliptical reference orbit. The differential equation has the same form as the Lawden or Tschauner-Hempel equation and can be easily solved with the solutions from the literature. In addition both the theoretical derivation and the numerical examples prove the model's superior accuracy in leader-follower formation and formations with a large along-track distance. The proposed model reduces the approximate limits of close relative motion, and it is expected to be applied in the propagation, guidance, and control for longer term relative motion with large along-track distances.

Pre-surgical Weight Loss Predicts Post-surgical Weight Loss Trajectories in Adolescents Enrolled in a Bariatric Program.

Adolescent obesity is markedly increasing worldwide and bariatric surgery is emerging as an effective treatment option. However, a subset of patients fails to achieve significant weight loss or show post-surgical weight regain. Efforts have been made to identify different post-surgical weight trajectories and their possible predictors. Furthermore, the role of pre-surgical intervention programs in optimizing post-surgical results has been a subject of debate. This study aimed to evaluate the impact of a 3-month lifestyle-oriented pre-surgical program for adolescent candidates for bariatric surgery on pre-surgical weight loss (body mass index (BMI) on completion - BMI at admission), and to identify predictors of different post-surgical weight loss trajectories. Forty-eight adolescent bariatric surgery candidates were enrolled in a lifestyle- and behavior-oriented bariatric program consisting of a 3-month pre-surgical outpatient intervention and a 6-month post-surgical follow-up. Mean BMI decreased by 1.82 points (SD = 1.83) during the program's pre-surgical intervention phase, a 3.8% average drop in participants' BMI; post-surgical weight loss trajectories were significantly associated in a curvilinear model with pre-surgical weight loss; optimal post-surgical results were associated with moderate pre-surgical weight loss, and inversely associated with maternal history of obesity, early-life weight loss attempts, and comorbid learning disorders. Moderate weight loss in a pre-surgical lifestyle-oriented intervention program predicts optimal post-surgical weight loss. Additionally, by assessing risk factors and pre-surgical weight loss patterns, it may be possible to identify sub-populations of adolescents undergoing bariatric surgery at risk of achieving sub-optimal long-term results.

Optimal experimental design that minimizes the width of simultaneous confidence bands

We propose an optimal experimental design for a curvilinear regression model that minimizes the band-width of simultaneous confidence bands. Simultaneous confidence bands for curvilinear regression are constructed by evaluating the volume of a tube about a curve that is defined as a trajectory of a regression basis vector (Naiman, 1986). The proposed criterion is constructed based on the volume of a tube, and the corresponding optimal design that minimizes the volume of tube is referred to as the tube-volume optimal (TV-optimal) design. For Fourier and weighted polynomial regressions, the problem is formalized as one of minimization over the cone of Hankel positive definite matrices, and the criterion to minimize is expressed as an elliptic integral. We show that the Möbius group keeps our problem invariant, and hence, minimization can be conducted over cross-sections of orbits. We demonstrate that for the weighted polynomial regression and the Fourier regression with three bases, the tube-volume optimal design forms an orbit of the Möbius group containing D-optimal designs as representative elements.

Evaluation of standardized ileal digestible lysine requirement for 8-20kg pigs fed low crude protein diets.

Two experiments were conducted to determine the standardized ileal digestible lysine (SID Lys) requirement for weaned pigs fed with low crude protein (CP) diet. In Experiment 1, 144 pigs were fed a normal CP (20%) diet with 12.3g/kg SID Lys and five low CP (18.5%) diets providing SID Lys levels of 9.8, 11.1, 12.3, 13.5, and 14.8g/kg, respectively, for 28days. Reducing dietary CP from 20% to 18.5% enhanced (p<0.05) the growth performance. The average daily gain (ADG) and gain to feed ratio (G:F) increased (linear and quadratic; p<0.05), serum urea nitrogen (SUN) decreased (linear and quadratic; p<0.05) as SID Lys increased. The SID Lys levels required to maximize ADG and optimize G:F were 12.8 and 13.1g/kg using a curvilinear plateau model, and to minimize SUN was 13.4g/kg using a two-slope broken-line model, which averaged 13.1g/kg SID Lys. In Experiment 2, 18 pigs were used in a 12-day N balance trial and received the same diets of Experiment 1. Total N excretion was decreased when dietary CP reduced and further decreased when SID Lys increased. Collectively, 1.5% dietary CP reduction improved the growth performance and decreased the N excretion; the optimal SID Lys requirement was at 13.1g/kg of 8-20kg pigs fed with 18.5% CP diet.

Heat requirements for loquat fruit development may be assessed with a Beta model approach

In Mediterranean areas, loquat trees (Eriobotrya japonica Lindl.) typically bloom in fall and fruits develop during the winter period, reaching their ripening in spring. So far, little interest has been driven towards models capable of estimating heat requirements for the accomplishment of fruit development in the winter period. In this work, we verified whether in Mediterranean areas the heat accumulation (GDH) needed for loquat fruit growth, may be precisely described using a Beta model, a flexible mathematical function which, in the past, has been successfully used in peach. BBCH phenological stages of ‘Algerie’ trees were recorded in two experimental sites: Palermo, Italy (38°04’N, 13°22’E, 150 m a.s.l.), and Callosa d’En Sarria, Alicante, Spain (38°39’N, 00°07’W, 150 m a.s.l.). The original data pool included maximum and minimum daily temperatures from a total of sixteen years, nine from Palermo and seven from Callosa. Firstly, the model was tested taking into account phenological data from all the years. However, due to anomalous data, some years were excluded. Temperatures and phenological data – Julian days (JD) from anthesis to ripening date – were used as input to run a Visual Basic computer program for the computation of growing degree hours (GDH). The program was used to randomly change the triplet of cardinal temperatures (i.e., base (Tb), optimal (To) and critical (Tc)) used to construct the Beta model. More than a thousand random sets of cardinal temperatures were generated to optimize the model. The target was to minimize the coefficients of variation (CV) of harvest dates (JD) among years and locations. The best resulting model, having Tb=4.8°C, To=9.0°C and Tc=42.2°C, yielded an average accumulation of 67542 GDH, and CV=2.36%. On average, the model generated an error of 5 days (SE ±1) between real harvest time and forecasts. Tb and To were selected within very narrow intervals, implying a high level of estimation accuracy. Thus, in future studies further curvilinear models have to be studied in order to estimate loquat heat requirements with minimal errors. In conclusion, although further attempts must be carried out in order to refine a loquat fruit growth phenoclimatic model, the approach used in this work may represent a further step to predict loquat harvest date.

Validation of the nonhydrostatic General Curvilinear Coastal Ocean Model (GCCOM) for stratified flows

While global- and basin-scale processes can be captured quite well with computationally-inexpensive hydrostatic models, smaller-scale features such as shoaling nonlinear internal waves and bores, coastal fronts, and other convective processes require the use of a nonhydrostatic model to accurately capture dynamics. Here the nonhydrostatic capabilities of the General Curvilinear Coastal Ocean Model (GCCOM) in a stratified environment are introduced. GCCOM is a three-dimensional, nonhydrostatic Large Eddy Simulation (LES), rigid lid model that has the ability to run in a fully three-dimensional general curvilinear coordinate system. This model was previously validated for unstratified flows with curvilinear coordinates. Here, recent advances of the model to simulate stratified flows are presented, focusing on sigma coordinate grids with both flat bottom geometry and a local gently sloping seamount. In particular, a suite of test cases widely used as benchmarks for assessing the nonhydrostatic capabilities for gravity-driven flows and internal waves is presented: an internal seiche in a flat bottom tank, the classic lock release and gravity current experiment, and a field-scale internal wave beam experiment consisting of an oscillating tidal flow over a topographic ridge. GCCOM shows excellent agreement with the benchmark test cases and is able to accurately resolve complex nonhydrostatic phenomena in stratified flows. Future studies will utilize the model capabilities for realistic field-scale internal wave simulations.

Use of Refined Finite Element Models for Solving the Contact Thermoalasticity Problem of Gas Turbine Rotors

A refined mathematical model of gas turbine engine rotors using three-dimensional finite elements of a curvilinear form is developed. All the calculations were performed for rotors, which are widely used in power machine building and shipbuilding. The fact is that such components have a constructive heterogeneity that can hardly be correctly explained using well-known finite elements and their shape functions. On the other hand, the mathematical model should be as simple as possible with a view to its wide use in the process of designing a rotor. Therefore, a new refined finite-element mathematical model was developed, consisting of three-dimensional curvilinear hexahedral finite elements. It was used to calculate the displacement field caused by the complex action of the heat flux and contact load at the junction of rotor elements. This approach makes it possible to describe the entire rotor as a superposition of the developed curvilinear finite element models and make the calculation process more correct and compact. To solve this problem, a system of matrix equations was compiled. It is based on the use of energy balance dependences in the mechanical contact interaction of rotor elements, as well as the heat balance under the influence of non-stationary heat flow. When creating a numerical algorithm for solving the problem, the direct decomposition of Cholesky was used. To make the solution more compact, the Sherman scheme was used. All the calculations of displacement and temperature fields were carried out for two widely used types of joints, which are used to create such rotors, namely: joints with clearance and interference.

Fast Segmentation of the Left Atrial Appendage in 3-D Transesophageal Echocardiographic Images.

Left atrial appendage (LAA) has been generally described as "our most lethal attachment," being considered the major source of thromboembolism in patients with nonvalvular atrial fibrillation. Currently, LAA occlusion can be offered as a treatment for these patients, obstructing the LAA through a percutaneously delivered device. Nevertheless, correct device sizing is not straightforward, requiring manual analysis of peri-procedural images. This approach is suboptimal, time demanding, and highly variable between experts, which can result in lengthy procedures and excess manipulations. In this paper, a semiautomatic LAA segmentation technique for 3-D transesophageal echocardiography (TEE) images is presented. Specifically, the proposed technique relies on a novel segmentation pipeline where a curvilinear blind-ended model is optimized through a double stage strategy: 1) fast contour evolution using global terms and 2) contour refinement based on regional energies. To reduce its computational cost, and thus make it more attractive to real interventions, the B-spline explicit active surface framework was used. This novel method was evaluated in a clinical database of 20 patients. Manual analysis performed by two observers was used as ground truth. The 3-D segmentation results corroborated the accuracy, robustness to the variation of the parameters, and computationally attractiveness of the proposed method, taking approximately 14 s to segment the LAA with an average accuracy of ~0.9 mm. Moreover, a performance comparable to the interobserver variability was found. Finally, the advantages of the segmented model were evaluated, while semiautomatically extracting the clinical measurements for device selection, showing a similar accuracy but with a higher reproducibility when compared to the current practice. Overall, the proposed segmentation method shows potential for an improved planning of LAA occlusion, demonstrating its added value for normal clinical practice.

Temperaturas cardinales de desarrollo del teocintle (Zea spp.)

El teocintle representa una fuente importante de genes para el mejoramiento del maíz (Zea mays L.); sin embargo, poco se ha avanzado en la caracterización de sus respuestas a diversas condiciones ambientales, incluyendo el desarrollo del teocintle en función de la temperatura, siendo ésta una variable clave para su adaptación y distribución. La temperatura base (Tb), temperatura óptima (To) y temperatura umbral máxima (Tu) son conocidas también como temperaturas cardinales del desarrollo y son particulares para cada especie, genotipo y etapa fenológica. El objetivo del presente estudio fue determinar las temperaturas cardinales de poblaciones de los teocintles Zea perennis, Zea diploperennis, Zea mays subsp. mexicana razas Chalco, Durango, Mesa Central y Nobogame y Zea mays subsp. parviglumis o raza Balsas. Se utilizaron datos de experimentos de campo realizados entre 1986 y 2005 donde se monitorearon datos de días a antesis (F), datos de temperatura y precipitación. Se utilizaron modelos lineales y curvilíneos para explicar la variación de la tasa de desarrollo de la etapa siembra-antesis (1/F) en función de la variación de la temperatura media (Tm) del período siembra-floración. Los resultados mostraron que la relación entre Tm y 1/F es descrita por una función curvilínea, ajustándose en todos los casos un modelo cuadrático-exponencial, con un valor de r2&gt; 0.73. El valor de Tb varió de 8.02 a 14.31 °C, el de To entre 23.5 y 31.67 °C y el de Tu entre 29.43 y 40.61 °C. Se concluye que los valores de temperaturas cardinales del teocintle varían entre y dentro de razas, lo que indica adaptación a diversas condiciones térmicas para las razas de teocintle estudiadas.

AN INVESTIGATION OF THE EFFECT OF TOUGHNESS AND BRITTLENESS INDEXES ON AMPERE CONSUMPTION AND WEAR RATE OF A CIRCULAR DIAMOND SAW

The circular diamond saw (CDS) is one of the major sawing machines in dimension stone processing plants. Predicting the performance of a circular diamond saw is very important to estimate the cost and the planning of the stone process- ing plants. The performance of a CDS depends on some important factors such as machine and tool characteristics, physical and mechanical characteristics of rock and tool wear rate. In this research, it is aimed to investigate the relation- ship between ampere consumption, brittleness indexes and toughness with the wear rate of a CDS. This aim was pursued by using a fully instrumented cutting rig to cut 14 types of hard rock at constant feed rates, cut depths and peripheral speeds. Wear rate, toughness and brittleness indexes were evaluated using simple and multiple curvilinear regression analysis and predicted models were developed. The results indicated that there is a significant correlation between wear rate, ampere consumption and toughness. It is concluded that, the wear rate of a CDS can be reliably estimated using a multiple curvilinear model which includes ampere consumption and toughness.

Inter-network connectivity and amyloid-beta linked to cognitive decline in preclinical Alzheimer\u2019s disease: a longitudinal cohort study

BackgroundAmyloid-beta (Aβ) has a dose-response relationship with cognition in healthy adults. Additionally, the levels of functional connectivity within and between brain networks have been associated with cognitive performance in healthy adults. Aiming to explore potential synergistic effects, we investigated the relationship of inter-network functional connectivity, Aβ burden, and memory decline among healthy individuals and individuals with preclinical, prodromal, or clinical Alzheimer’s disease.MethodsIn this longitudinal cohort study (ADNI2), participants (55–88 years) were followed for a maximum of 5 years. We included cognitively healthy participants and patients with mild cognitive impairment (with or without elevated Aβ) or Alzheimer’s disease. Associations between memory decline, Aβ burden, and connectivity between networks across the groups were investigated using linear and curvilinear mixed-effects models.ResultsWe found a synergistic relationships between inter-network functional connectivity and Aβ burden on memory decline. Dose-response relationships between Aβ and memory decline varied as a function of directionality of inter-network connectivity across groups. When inter-network correlations were negative, the curvilinear mixed-effects models revealed that higher Aβ burden was associated with greater memory decline in cognitively normal participants, but when inter-network correlations were positive, there was no association between the magnitude of Aβ burden and memory decline. Opposite patterns were observed in patients with mild cognitive impairment. Combining negative inter-network correlations with Aβ burden can reduce the required sample size by 88% for clinical trials aiming to slow down memory decline.ConclusionsThe direction of inter-network connectivity provides additional information about Aβ burden on the rate of expected memory decline, especially in the preclinical phase. These results may be valuable for optimizing patient selection and decreasing study times to assess efficacy in clinical trials.

The effects of time frames on self-report.

BackgroundThe degree to which episodic and semantic memory processes contribute to retrospective self-reports have been shown to depend on the length of reporting period. Robinson and Clore (2002) argued that when the amount of accessible detail decreases due to longer reporting periods, an episodic retrieval strategy is abandoned in favor of a semantic retrieval strategy. The current study further examines this shift between retrieval strategies by conceptually replicating the model of Robinson and Clore (2002) for both emotions and symptoms and by attempting to estimate the exact moment of the theorized shift.MethodA sample of 469 adults reported the extent to which they experienced 8 states (excited, happy, calm, sad, anxious, angry, pain, stress) over 12 time frames (right now to in general). A series of curvilinear and piecewise linear multilevel growth models were used to examine the pattern of response times and response levels (i.e., rated intensity on a 1–5 scale) across the different time frames.ResultsReplicating previous results, both response times and response levels increased with longer time frames. In contrast to prior work, no consistent evidence was found for a change in response patterns that would suggest a shift in retrieval strategies (i.e., a flattening or decrease of the slope for longer time frames). The relationship between the time frames and response times/levels was similar for emotions and symptoms.ConclusionsAlthough the current study showed a pronounced effect of time frame on response times and response levels, it did not replicate prior work that suggested a shift from episodic to semantic memory as time frame duration increased. This indicates that even for longer time frames individuals might attempt to retrieve episodic information to provide a response. We suggest that studies relying on self-report should use the same well-defined time frames across all self-reported measures.

Is There an ‘Ideal’ Level of Gender Diversity? Testing Two Competing Curvilinear Models

The use of linear models presents important limitations to accurately representing the link between gender diversity and organizational performance. This study therefore investigates curvilinear mo...