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Water deficits can cause chlorophyll degradation which decreases the total concentration of chlorophyll a and b (Chls). Few studies have investigated the effectiveness of spectral indices under water-stressed conditions. Chlorophyll meters have been extensively used for a wide variety of leaf chlorophyll and nitrogen estimations. Since a chlorophyll meter works by sensing leaves absorptance and transmittance, the reading of chlorophyll concentration will be affected by changes in transmittance as if there were a water deficit in the leaves. The overall objective of this paper was to develop a novel and reliable reflectance-based model for estimating Chls of fresh and water-stressed leaves using the reflectance at the absorption bands of chlorophyll a and b and the red edge spectrum. Three independent experiments were designed to collect data from three leaf sample sets for the construction and validation of Chls estimation models. First, a reflectance experiment was conducted to collect foliar Chls and reflectance of leaves with varying water stress using the ASD FieldSpec spectroradiometer. Second, a chlorophyll meter (SPAD-502) experiment was carried out to collect foliar Chls and meter readings. These two data sets were separately used for developing reflectance-based or absorptance-based Chls estimation models using linear and nonlinear regression analysis. Suitable models were suggested mainly based on the coefficient of determination (R2). Finally, an experiment was conducted to collect the third data set for the validation of Chls models using the root mean squared error (RMSE) and the mean absolute error (MAE). In all of the experiments, the observations (real values) of the foliar Chls were extracted from acetone solution and determined by using a Hitachi U-2000 spectrophotometer. The spectral indices in the form of reflectance ratio/difference/slope derived from the Chl b absorption bands (ρ645 and ρ455) provided Chls estimates with RMSE around 0.40–0.55 mg g−1 for both fresh and water-stressed samples. We improved Chls prediction accuracy by incorporating the reflectance at red edge position (ρREP) in regression models. An effective chlorophyll indicator with the form of (ρ645–ρ455)/ρREP proved to be the most accurate and stable predictor for foliar Chls concentration. This model was derived with an R2 of 0.90 (P < 0.01) from the training samples and evaluated with RMSE 0.35 and 0.38 mg g−1 for the validation samples of fresh and water-stressed leaves, respectively. The average prediction error was within 14% of the mean absolute error.

The current study aims at exploring the beneficial effect of silica fume (SF) and acrylic emulsion polymer (PR) on the enhanced properties of polypropylene fiber reinforced concrete (FRC) with the supplementary cementitious binder comprised of the Portland cement, slag, silica fume and fly ash. The compressive strength and impact-abrasion resistance were used for the estimation of engineering properties while the water absorption performance, surface electricity resistance, and rapid chloride penetration resistance were used for estimation of durability. Experimental results showed that a sole addition of SF increased the compressive strengths but decreased the abrasion-impact resistances of modified FRCs, which was just opposite to the influence of a sole addition of PR. A sole addition of either the SF or PR could moderately improve the durability of modified FRCs, respectively. However, due to the beneficial effect of the complementary interaction between SF and the optimal amount of PR, the mechanical properties and durability of modified FRCs seemed to become significantly improved.

In the present paper, the low-velocity impact of an elastic rod with a flat end upon a viscoelastic Timoshenko type beam has been considered. Viscoelastic properties of the beam out of the contact zone are described by the standard linear solid model with integer derivatives, while inside this zone they are governed by the fractional derivative standard linear solid model. The contact force for a concrete target has been defined experimentally at the concrete age of 7, 14, 28, 56, and 91 days. It has been found that an average maximum of the contact force increases with concrete age, whereas the contact duration decreases. Moreover, the most remarkable changes of both, contact force and contact time, occur at the concrete age earlier than 14 days, after that the rate of changes slows down. Experimental results have a good coincidence with theoretical expectations.

Ground granulated blast-furnace slag (GGBS) is commonly used as partial cement replacement in concrete production. Although the use of GGBS has many advantages, it possesses a lower initial hydration rate that leads to lower early strength. Therefore, an attempt to use sodium silicate to activate the GGBS was carried out to promote the early strength of cement-GGBS blended paste. Based on experimental results, incorporation of 5 and 10% of sodium silicate slightly reduced the flowability and final setting time of blended paste. For hardened properties, the addition of sodium silicate reduced the strength at early age until 28 days. The modulus of elasticity of activated paste with sodium silicate was lower at early age, however at 28 days the result was comparable with the control specimen. The addition of sodium silicate decreased the ultrasonic pulse velocity (UPV) value at early age, however, at 28 days, 5% sodium silicate specimen had a higher UPV value than the control specimen. The different trend between UPV test and compressive strength test was suggested due to the inhomogeneous structure of activated blended paste that had a different mechanism during destructive test (compressive strength test) and non-destructive test (UPV test).

An elastic Bernoulli–Euler beam model is developed for thermal-mechanical vibration and buckling instability of a single-walled carbon nanotube (SWCNT) conveying fluid and resting on an elastic medium by using the theories of thermal elasticity mechanics and nonlocal elasticity. The differential quadrature method is adopted to obtain the numerical solutions to the model. The effects of temperature change, nonlocal parameter and elastic medium constant on the vibration frequency and buckling instability of SWCNT conveying fluid are investigated. It can be concluded that at low or room temperature, the first natural frequency and critical flow velocity for the SWCNT increase as the temperature change increases, on the contrary, while at high temperature the first natural frequency and critical flow velocity decrease with the increase of the temperature change. The first natural frequency for the SWCNT decreases as the nonlocal parameter increases, both the first natural frequency and critical flow velocity increase with the increase of the elastic medium constant.

In the present study, we propose a simplified nonlinear fluid model to characterize the complex nonlinear response of some viscoelastic materials. Recently, the viscoelastic modeling has been utilized by many researchers to simulate some parts of human body in bioengineering and to represent many material properties in mechanical engineering, electronic engineering and construction engineering. Occasionally it is almost impossible to evaluate the constant parameters in the model in the deterministic sense, therefore, the damping coefficient of the dashpot and the spring constants of the linear and nonlinear springs are considered as stochastic to model the stochastic properties of the viscoelastic materials. After some transformations, the closed-form solution can be obtained for the mean value of the displacement of the simplified nonlinear fluid model, subjected to constant rate of displacement. Based on the closed-form solution, the proposed method generates the stochastic dynamic response of the simplified nonlinear model, which plays an important role in performing the reliability analysis of the nonlinear system.

BackgroundEffective paediatric basic life support improves survival and outcomes. Current cardiopulmonary resuscitation (CPR) training involves 4-yearly courses plus annual updates. Skills degrade by 3–6 months. No method has been described to motivate frequent and persistent CPR practice. To achieve this, we explored the use of competition and a leaderboard, as a gamification technique, on a CPR training feedback device, to increase CPR usage and performance.ObjectiveTo assess whether self-motivated CPR training with integrated CPR feedback improves quality of infant CPR over time, in comparison to no refresher CPR training.DesignRandomised controlled trial (RCT) to assess the effect of self-motivated manikin-based learning on infant CPR skills over time.SettingA UK tertiary children's hospital.Participants171 healthcare professionals randomly assigned to self-motivated CPR training (n=90) or no refresher CPR training (n=81) and followed for 26 weeks.InterventionThe intervention comprised 24 h a day access to a CPR training feedback device and anonymous leaderboard. The CPR training feedback device calculated a compression score based on rate, depth, hand position and release and a ventilation score derived from rate and volume.Main outcome measureThe outcome measure was Infant CPR technical skill performance score as defined by the mean of the cardiac compressions and ventilations scores, provided by the CPR training feedback device software. The primary analysis considered change in score from baseline to 6 months.ResultsOverall, the control group showed little change in their scores (median 0, IQR −7.00–5.00) from baseline to 6 months, while the intervention group had a slight median increase of 0.50, IQR 0.00–33.50. The two groups were highly significantly different in their changes (p<0.001).ConclusionsA significant effect on CPR performance was demonstrated by access to self-motivated refresher CPR training, a competitive leaderboard and a CPR training feedback device.

A stochastic spectral method is proposed to estimate the nonlinear parameters of a system subjected to random excitation. Sometimes, it is impossible to measure the excitation process; therefore, estimation must then be based on the response measurement only, in conjunction with a stochastic model of the excitation. The concept of this method is to establish an objecting function involving the unknown parameters through frequency domain analysis, and then we can minimize the objecting function to estimate the unknown parameters by using standard nonlinear optimization algorithm. Finally, the validation of the proposed method is accomplished through many simulations and it can be concluded that the proposed method is applicable to a variety of different problems.

In capacity-planning systems, various sources of uncertainty and imprecision are encountered. In most cases, the uncertainty is determined by the subjective beliefs of managers linguistically. However, the measurement of mangers’ judgments is difficult and vague. Therefore, a fuzzy logic-based approach is proposed to deal with capacity-planning problems in the presence of the uncertain demand, set-up resources, and the capacity constraints. Firstly, fuzzy numbers are used to represent uncertain data. Secondly, fuzzy if-then rules are employed to model vaguely defined relations between fuzzy numbers. Then, the computational aspects of fuzzy models and interpretations of inference results are illustrated by a numerical case. Finally, three examples are used to verify the proposed representation and inference mechanism.

The cytotoxic effects of ginkgetin, a natural biflavone isolated from Selaginella moellendorffii Hieron, were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in three different human cell lines: ovarian adenocarcinoma (OVCAR-3), cervical carcinoma (HeLa) and foreskin fibroblast (FS-5). The concentrations of ginkgetin required to induce 50% death (EC50) in OVCAR-3, HeLa, and FS-5 were 3.0, 5.2, and 8.3 microg/ml, respectively. Morphological changes in cells and their nuclei, DNA fragmentation with a characteristic pattern of inter-nucleosomal ladder, and double-stranded DNA breaks were detected following treatment with 3 microg/ml of this biflavone for 24 h. Incubation with 5 microg/ml ginkgetin led to increased intracellular levels of hydrogen peroxide as early as 30 min. The cytotoxicity of ginkgetin was partially inhibited by pretreating cells with vitamin C, vitamin E or catalase. Catalase not only afforded the best protective effect among three antioxidants, but also reduced both the DNA fragmentation and double-stranded DNA breakage induced by ginkgetin. Moreover, the involvement of caspase(s) in ginkgetin-induced apoptosis was demonstrated by the activation of caspase 3 after drug treatment and the suppression of cell death by a broad-spectrum caspase inhibitor, benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk). However, the protective effects of z-VAD-fmk and catalase were not additive. Taken together, our results indicated that the apoptosis induced by ginkgetin (especially at 5 microg/ml) is mediated mainly through the activation of caspase(s) by the hydrogen peroxide generated possibly through autooxidation of this biflavone.