Growth Threshold Research Articles

Identification of the optimal growth chart and threshold for the prediction of antepartum stillbirth.

To evaluate the effect of the choice growth chart and threshold used to define small for gestational age (SGA) on the predictive value of SGA for placenta-related or unexplained antepartum stillbirth. A retrospective cohort study of all women with a singleton pregnancy who gave birth > 24week gestation in a single center (2000-2016). The exposure of interest was SGA, defined as birth weight < 10th or < 25th centile according to three fetal growth charts (Hadlock et al., Radiology 181:129-133, 1991; intergrowth-21st (IG21), WHO 2017, and a Canadian birthweight-based reference-Kramer et al., Pediatrics 108:E35, 2001). The outcome of interest was antepartum stillbirth due to placental dysfunction or unknown etiology. Cases of stillbirth attributed to other specific etiologies were excluded. A total of 49,458 women were included in the cohort. There were 103 (0.21%) cases of stillbirth due to placental dysfunction or unknown etiology. For cases in the early stillbirth cluster (≤ 30weeks), the detection rate was high and was similar for the three ultrasound-based fetal growth charts of Hadlock, IG21, and WHO (range 83.3-87.0%). In contrast, the detection rate of SGA for cases in the late stillbirth cluster (> 30weeks) was low, being highest for WHO and Hadlock (36.7% and 34.7%, respectively), and lowest for IG21 (18.4%). Using a threshold of the 25th centile increased the detection rate for stillbirth by approximately 15-20% compared with that achieved by the 10th centile cutoff. At > 30week gestation, the Hadlock or WHO fetal growth charts provided the best balance between detection rate and false positive rate for stillbirth.

Sentiment‐Apt investors and UK sector returns

AbstractThis paper examines the relationship between sentiment‐apt investors and UK stock returns at industry level over the period January 1988 to December 2017. Using two new sentiment proxies (laggards to leaders and growth opportunity index) for 10 discrete sector groupings, we provide novel evidence on how returns in the UK stock market react to the activities of sentiment‐disposed investors. First, using threshold nonlinear regression, we document a significant relationship between the laggards to leaders sentiment proxy and sectoral returns. Our findings reveal that aggregate returns in the sector are affected by activities of investors who embark on profit‐taking when there is an increase in the proportion of lagging to leading stocks beyond the threshold value. Secondly, when using the growth opportunity sentiment proxy, we report that the increase in growth above the growth threshold value has a significant impact on sector returns. This study further confirms significant impact of non‐threshold variables on sector groupings. Our findings are robust, having been subjected to a range of robustness checks.

A short and long crack growth model based on 2-parameter driving force and crack growth thresholds

The propagation life of short cracks has a great influence on the accurate fatigue life prediction. A new crack growth model is proposed to provide a unified modeling framework for integrating short and long crack propagation in the formulation of the crack driving force to account for multiple crack growth controlling parameters. Crack propagation rates and fatigue lives predicted by the model are compared with crack growth and fatigue life data sets of 2024-T3, 7075-T561 aluminum and Ti-6Al-4V titanium alloys. Predicted results are found to be in good agreement with crack growth data and fatigue life data for these materials.

The Effect of Stress Ratios on the Very High Cycle Fatigue Behavior of 9%Cr Turbine Steel at 630 °C.

Effects of the stress ratio on the very high cycle fatigue behaviors of 9%Cr turbine steel have been investigated at 630 °C. The experimental results show that the S–N curve has a continuous downward trend and has no fatigue limit with the increasing in the cycles at 630 °C. Meanwhile, according to the analysis of microstructure, there are two failure modes that were observed at different stress ratios (R = −1 and 0.1), including surface crack failure and internal crack failure, respectively. Besides, the theoretical threshold value of the crack growth is compared with the calculated value of the fracture surface. To decrease the difference between the threshold value of internal crack initiation and the corresponding theoretical value, a new model for the crack growth threshold of the interior-induced fracture at different stress ratios is proposed and discussed.

Effects of Electron Temperature Anisotropy on Proton-beam Instability in the Solar Wind

Abstract Solar wind observations often show that the drift velocity of a proton beam relative to a background proton decreases with the heliocentric distance. Proton-beam instability has been suggested to play an important role in the deceleration of the proton-beam velocity; the effects of electron temperature anisotropy on the proton-beam instability have not been examined. Based on a general kinetic dispersion relation solver for magnetized plasma (PDRK), we investigate the effects of electron temperature anisotropy on the oblique Alfvén/ion-cyclotron (A/IC) and parallel magnetosonic/whistler (M/W) instabilities driven by proton beams in the solar wind. The results show that the growth rates, real frequencies, and threshold conditions for both instabilities are sensitive to the electron temperature anisotropy T e⊥/T e∣∣ and the parallel electron beta β e∣∣. In the low-beta regime with , where is a critical plasma beta for which the threshold velocities of both instabilities are equal, the growth rate of the oblique A/IC instability is weakly dependent on the electron temperature anisotropy. In the high-beta regime with , the growth rate of the parallel M/W instability increases with decreasing T e⊥/T e∣∣. Moreover, the threshold velocities of both instabilities are shifted to lower values as T e⊥/T e∣∣ decreases, especially for the parallel M/W instability in the regime with β e∣∣ ≥ 1. The theoretical results for the threshold velocity together with the observed parallel electron beta and/or electron temperature anisotropy are used to explain the observed proton-beam drift velocity in the solar wind.

Restrictions of Historical Tissues on Urban Growth, Self-Sustaining Agglomeration in Walled Cities of Chinese Origin

This article uses a fractal observation to help delineate the constraints placed by multiple city walls on the growth of historical East Asian cities. By applying advanced technologies from economic geography and fractal indices, a staged scaling process within urban dimension coherence can be applied to both indices. In this study, a discovery is proposed based on the urban organism concept that is capable of indicating a proportional intra-urban structure from a fundamental wall-bounded urban element (local specificity) to other greater walled spatial properties (global variables). This local specificity potentially performs approximate scaling regularities, and spatially denotes an average historical threshold of urban growth for its overall size, with similar scaling law constraints. This finding involves territorial, urban planning, and ancient architectural perspectives, providing a historical and local response to the expansion of contemporary cities. By employing growing fractal estimation, data processing enables the logarithmic city size to be obtained by measuring each wall’s specific features using the Ordinary Least Squares (OLS) method. On the basis of two-dimensional allometric scaling patches, a spatial unfolding mechanism is utilized to reproduce these dynamic changes with city walls as a result of the human trajectories in time geography.

Shaped‐Charge Jet‐Initiation of Covered RDX‐Based Aluminized Explosives and Effect of Temperature

AbstractUnderstanding the shaped‐charge jet‐initiation mechanism of covered explosives and the effect of explosive temperature is important for ammunition safety. We devised a method of using a shaped‐charge jet‐penetrating cover to shock‐initiate heated explosives. This method achieves uniform temperature control of explosives via heating the upper and lower ends and preserves heat on the side of the explosive charge. We experimentally tested the method on hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX)‐based aluminized explosives (61 wt.% RDX, 30 wt.% Al, 9 wt.% binder) at different temperatures and cover thicknesses. The jet‐penetration behavior and explosive detonation‐wave growth were observed via X‐ray photography, and the effect of explosive temperature on jet initiation was analyzed. A numerical model of the shaped‐charge jet‐initiating explosive was set up by considering the temperature change of the explosive and analyzing the detonation‐wave growth and initiation thresholds of different explosive temperatures under jet shock initiation. Under a thin cover, the explosive showed prompt impact initiation by the jet; the initiation occurred very near to the explosive surface. However, for a thick cover, the explosion was initiated by a bow wave formed at a certain distance from the upper surface of the explosive, and a retonation wave was observed. The temperature of RDX‐based aluminized explosives affects the two jet‐initiation mechanisms. The shock sensitivity of the explosives to the jet decreased with increasing temperature, but the shock sensitivity increased when the temperature exceeded a certain value. A simulation method was established that can be used to predict shaped‐charge jet initiation at different explosive temperatures. We obtained the relationship between the cover thickness and run‐to‐detonation distance under jet shock initiation, which provides a theoretical basis for safety analysis and evaluation of a warhead charge that is attacked by a shaped‐charge jet.

Temporal dependency in the picosecond regime of laser damage growth.

Based on squared top-hat beam irradiations, we investigate how a change of the pulse duration in the picosecond regime affects the phenomenon of laser damage growth on dielectric mirrors. We first confirm two major previously reported experimental results with a Gaussian beam that are the existence of a growth threshold fluence smaller than the laser-induced damage threshold (LIDT) and the linear evolution, characterized by a growth coefficient, of the damage area with the number of irradiations when growth occurs. We then express the growth coefficient with the fluence and the growth threshold in particular. Changing the pulse duration ultimately allows us to refine this expression a step further which leads us to establish an empirical growth law for the damage area. The temporal dependency displayed within this law appears to be very close to the one found for the LIDT which evidences the deterministic nature of laser damage growth in short pulse regimes.

Description and analysis of a mathematical model of population growth of Aedes aegypti

This article proposes a mathematical model based on ordinary nonlinear differential equations that describes the dynamics of population growth of the mosquito Aedes aegypti throughout its life cycle. Then, a modification is made to the model by implementing a time delay, initially constant and then distributed over time. In addition, h, the population growth threshold, is established, the equilibrium points (trivial equilibrium, coexistence equilibrium) of the population are found and an analysis of local stability of the coexistence equilibrium is performed. If $$h>1$$ , this results in the population of adult aquatic mosquitoes persisting in the environment, approaching a equilibrium of coexistence, regardless of whether the time delay is considered or not. Finally, numerical simulations are carried out using Matlab software using the functions ode45 and dde23, with a value of $$ h>1 $$ , which allow the solutions of the initial model of ordinary differential equations to be compared to the solutions when the delay is implemented.

Keeping the lid on infection spread

Coronavirus From February to April 2020, many countries introduced variations on social distancing measures to slow the ravages of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Publicly available data show that Germany has been particularly successful in minimizing death rates. Dehning et al. quantified three governmental interventions introduced to control the outbreak. The authors predicted that the third governmental intervention—a strict contact ban since 22 March—switched incidence from growth to decay. They emphasize that relaxation of controls must be done carefully, not only because there is a 2-week lag between a measure being enacted and the effect on case reports but also because the three measures used in Germany only just kept virus spread below the growth threshold. Science , this issue p. [eabb9789][1] [1]: /lookup/doi/10.1126/science.abb9789

Exploring the inhibition boundaries of mixed cultures of purple phototrophic bacteria for wastewater treatment in anaerobic conditions

The development of novel wastewater platforms should include the analysis of the most critical functional factors including the effects of toxic or inhibitory substances. Due to the novelty of purple phototrophic bacteria (PPB)-based wastewater treatment systems, this analysis has not been done yet in mixed cultures. In this work, various relevant chemical compounds, including aromatic (phenol, 2,4,6-trichlorophenol or 246TCP, 4-nitrophenol or 4CP, sulfathiazole) and aliphatic organics (methanol, trichlorethylene or TCE, oleic acid, ethanol, propionic acid), inorganic salts (ammonium, ClO3−, Na+), and metals (Fe3+, Fe2+, Cu2+, Zn2+, Ni2+, Al3+), as well as pH, are analyzed for their effect on mixed PPB cultures in anaerobic photoheterotrophic conditions using acetate as the model organic substrate. The most toxic substances detected were 246TCP, 4NP, Cu2+, Fe2+ and Ni2+, (Ki for activity: 23 ± 2, 97 ± 12, 3.1 ± 0.4, 13 ± 3, 13 ± 1 mg/L, and Ki (or toxicity threshold) for growth: 17 ± 2, (119), 3.5 ± 0.4, (4.8), (22.9) mg/L, respectively). Some substances inhibited the activity more than the growth (sulfathiazole, Ni2+ and Fe3+), or the growth more than the activity (TCE, 4NP and Fe2+). In addition, some organic substrates, such as phenol, ethanol and propionate, specifically inhibited the acetate uptake, being noncompetitive in the case of phenol and ethanol, and most likely competitive in the case of propionate. These findings are relevant for the wastewater treatment and resource recovery applications of the PPB technology, as well as for the upgrading of current models (Photo-Anaerobic Model). In addition, the data will open possibilities to promote the production of specific compounds (as PHA or single-cell proteins) by selectively inhibiting some parts of the PPB metabolism.

Revisiting the deforestation-induced EKC hypothesis: the role of democracy in Bangladesh

This paper aimed at evaluating the validity of the deforestation-induced Environmental Kuznets Curve hypothesis controlling for the democracy between 1971 and 2018 in Bangladesh. The cointegration results provide statistical evidence of long-run associations between economic growth, deforestation propensities and the quality of democracy. The elasticity estimates certify the validity of the EKC hypothesis for all the three indicators of deforestation used in this paper: forest area coverage, deforestation rate and net forest depletion rate. Moreover, controlling for democracy lowers the threshold level of growth beyond which the marginal impact of growth results in environmental betterment by reducing the deforestation propensities in Bangladesh. Moreover, democracy and economic growth are also seen to exert a combined impact on the growth-deforestation nexus. The estimated growth thresholds are above the current real GDP level of Bangladesh which reasons the nation’s deforestation woes. Finally, the causality results also affirm causal associations between economic growth, deforestation and the quality of democracy. Thus, these findings impose key policy implications keeping into cognizance the sustainable economic and environmental development goals of Bangladesh.

Defect tolerance and hydrogen susceptibility of the fatigue limit of an additively manufactured Ni-based superalloy 718

The sensitivity of the fatigue limit of an additively manufactured, Ni-based superalloy 718 sample to surface finishing conditions and solute hydrogen was investigated via a series of tension–compression fatigue tests. The results revealed that neither defects nor hydrogen diminished the fatigue limit of the sample. The high defect tolerance of this material is attributed to a large unit of crack initiation in the coarse grain, which eclipses the detrimental effect of AM-process-induced defects. Also, from the results, it is inferred that hydrogen has little effect on the crack propagation rate and the crack growth threshold of the material.

Optimal Inflation Threshold and Economic Growth: Ordinal Regression Model Analysis

The study investigates the relationship between the inflation rate and economic growth to find out the optimal inflation threshold for economic growth. Therefore, this study applied an ordinary least square model (OLS) and the ordinal regression model, and collected the time-series data from 1996 to 2017 to test the relationship between inflation and economic growth in the short-term and long-term. The sample fits the model and is statistically significant. The study showed that 96.6% of correlation between inflation rate and economic growth are close and 4.5% of optimal inflation threshold is appropriate for economic growth. It finds that the optimal inflation threshold is base to perform economic growth, besides the inflation rate is positively related to economic growth. The results support the monetary policy appropriately. This study identifies issues for Government to consider: have a comprehensive solution among macroeconomic policies, monetary policy, fiscal policy and other policies to control and maintain the inflation and stimulate growth; have appropriate policies to regulate inflation to stimulate economic growth over the long term; set a priority goal for sustainable economic growth; not pursue economic growth by maintaining the inflation rate in the long term, but take appropriate measures to stabilize the inflation at the optimal inflation threshold.

Effects of environmental conditions on the axial tension–compression fatigue behavior of carbon/epoxy plain-weave laminates containing flaws

The objective of this work is to investigate the effects of environmental conditions on the axial fatigue behavior of a carbon/epoxy plain-weave laminate with an embedded flaw subjected to a partially reversed cyclic load (stress ratio R = −0.1) in tension–compression. This specific material is more commonly used in aerospace engineering for the manufacturing of aircraft structural parts, which are directly exposed to various environmental conditions during service. Specific environmental and loading conditions that are appropriate to simulate real-life conditions are considered to observe and collect information about the material's behavior. For the investigation, dry and wet coupons were submitted to room temperature, 82 and 121 ℃ under loading frequencies of 7 and 15 Hz. A maximum allowable strain increase criterion is used to monitor the flaw growth threshold or delamination onset, during fatigue testing. The ultrasonic imaging (C-scan) technique is used to verify and confirm the delamination onset. Results show that the delamination onset strain increase criterion, along with fatigue life, generally decreased as the operating temperature and humidity were increased and that frequency had little effect on the delamination onset fatigue life. The S– N curves obtained from the tension–compression fatigue data were then compared to those of a previous work carried out in tension–tension fatigue loading. Results show a clear degradation in the delamination onset fatigue life of the coupons tested under tension–tension cyclic loading when the minimum tensile component of the cyclic load was replaced with a compressive load of the same magnitude.

New assessment indicator of habitat suitability for migratory bird in wetland based on hydrodynamic model and vegetation growth threshold

Abstract Migratory birds are indicator organisms for the health of wetland ecosystems. Choosing the key environmental indicators is vital to the assessment of habitat suitability for migratory birds. In the study, hydroperiod was used to predict wetland suitability for migratory birds. It control growth of vegetation used for migratory birds’ food and could predicted by hydrodynamic model. This study presents a new indicator for assessing migratory bird habitat suitability in wetland, continuous flooding time (CFT), based on two-dimensional (2D) hydrodynamic model and vegetation growth threshold. In Poyang Lake wetland (the largest migratory bird wintering based in Asia), variation in CFT amongst different hydrological years (wet, dry and normal flow years) was calculated by using the 2D hydrodynamic model based on incompressible Reynolds Average Navier-Stokes (N-S) equation. The habitat suitability for migratory birds were calculated based on the vegetation growth threshold (CFT) of Carex spp., Phalaris arundinacea and Polygonum criopolitanum in the typical (hydrological) years. Results show that migratory birds have the largest suitable area (with High and Very High suitability) in 2009 (normal flow year). The suitable area in severe drought (flood) year is significantly less than the area in normal dry (wet)year. The average of the suitable CFTs (with High and Very High suitability) are almost equal in 2007 (dry year) and 2002 (wet year). The suitable CFT is between 120 and 240 days, and the average of the suitable CFT is 170.39, 190.26 and 173.49 days in 2007 (dry year), 2009 (normal flow year) and 2002 (wet year), respectively. Overall, the study provides a valuable evaluation indicator of habitat suitability for migratory bird, however the use of the indicator must depend on a certain study of the vegetation growth threshold and the feeding habit of migratory birds for the study area. The proposed indicator can further improve the comprehensive evaluation system for wetland migratory birds and provide a scientific reference of the water environment planning and ecological management for the scheduled Poyang lake dam.

Growth, photoluminescence, lifetime, and laser damage threshold studies of 1, 3, 5-triphenylbenzene (TPB) single crystal for scintillation application

The 1, 3, 5-triphenylbenzene (TPB) single crystal has been grown using slow cooling seed rotation technique. Optical transmittance of the grown crystal was obtained from UV–Visible analysis. The grown TPB crystal has good transmission in the entire visible region with a lower cutoff wavelength of 330 nm. The solubility of TPB material was determined using toluene as a solvent with different temperatures. The full width at half maximum is 18 arcsec, which indicates that the crystal is of good quality. The TPB crystal was excited (λexc) at 307 nm, and the corresponding emission (λem) has been observed at 352 nm. The laser-induced damage threshold (LDT) value of grown crystal is 1.25 GW/cm2. Third-order nonlinear optical susceptibility χ(3) is determined using the Z-scan technique as 3.07422 × 10–09 esu. The TPB crystal proves its suitability for scintillation applications and optoelectronic device fabrications.

Unseeded Crystal Growth of (100)-Oriented Grain-Boundary-Free Si Thin-Film by a Single Scan of the CW-Laser Lateral Crystallization of a-Si on Insulator

Laser crystallization of a-Si film on insulating substrate is a promising technology to fabricate three-dimensional integrations (3D ICs), flat panel displays (FPDs), or flexible electronics, because the crystallization can be performed on room temperature substrate to avoid damage to the underlying devices or supporting plane. Orientation-controlled grain-boundary-free films are required to improve the uniformity in electrical characteristics of field-effect-transistors (FETs)fabricated in those films. This paper describes the recently found simple method to obtain {100}-oriented grain-boundary-free Si thin-films stably, by using a single scan of continuous-wave (CW)-laser lateral crystallization of a-Si with a highly top-flat line beam with 532 nm wavelength at room temperature in air. It was difficult to control crystal orientations in the grain-boundary-free film crystallized by the artificial modulation of solid-liquid interface, and any other trial to obtain preferential surface orientation with multiple irradiations resulted in grain boundaries. The self-organized growth of the {100}-oriented grain-boundary-free films were realized by satisfying the following conditions: (1) highly uniform top-flat line beam, (2) SiO2 cap, (3) low laser power density in the vicinity of the lateral growth threshold, and (4) single scan crystallization. Higher scan velocity makes the process window wide for the {100}-oriented grain-boundary-free film. This crystallization is very simple, because it is performed by a single unseeded scan with a line beam at room temperature substrate in air.

Inferring change points in the spread of COVID-19 reveals the effectiveness of interventions.

As COVID-19 is rapidly spreading across the globe, short-term modeling forecasts provide time-critical information for decisions on containment and mitigation strategies. A major challenge for short-term forecasts is the assessment of key epidemiological parameters and how they change when first interventions show an effect. By combining an established epidemiological model with Bayesian inference, we analyze the time dependence of the effective growth rate of new infections. Focusing on COVID-19 spread in Germany, we detect change points in the effective growth rate that correlate well with the times of publicly announced interventions. Thereby, we can quantify the effect of interventions, and we can incorporate the corresponding change points into forecasts of future scenarios and case numbers. Our code is freely available and can be readily adapted to any country or region.

Water retention and warming effect of integrated rice management for the hilly areas of southwest China

AbstractSeasonal drought and low temperatures strongly limit rice (Oryza sativa L.) grain yield in the hilly areas of Southwest China. An integrated rice management (IRM) system was developed, which integrates ridge cultivation with plastic mulching, furrow irrigation, and triangular transplanting. A field experiment was conducted from 2011 to 2015. The effects of IRM on grain yield, yield components, soil moisture content (θ), and soil temperature (Tsoil) were evaluated. Compared with traditional rice management (TRM), IRM significantly improved grain yield by 29.9%. Furthermore, the yield of IRM (8181−9267 kg ha−1, CV: 7.6%) remained relatively stable. The rice tiller of TRM was highly related to the accumulated rainfall during the rice tillering stage in drought years (2011 and 2014). The water retention capability of IRM decreased the influence of interannual rainfall on rice growth and grain yield. In 2015, the θ in the 0−20‐cm layer was higher than the threshold for rice root growth over the rice‐growing season. Compared with TRM, Tsoil of the 0−20‐cm layer in IRM was 4.7 °C higher during the early tillering stage. The &gt;10 °C soil effective accumulated temperature in IRM was also higher, and the difference was highest at the maximum tillering stage. The warming effect of IRM, particularly during the tillering stage, stimulated early growth and stronger tillering. In summary, the water retention capacity and warming effect of IRM were key factors for the improvement of rice yield; most importantly, the yields were stabilized in both drought and rainy years.