BT Concentration Research Articles

Transient modeling of column adsorption–desorption processes for pre-concentration of D-1,2,4-butanetriol

D-1,2,4-Butanetriol (BT) is one of the important platform chemicals mainly used in the pharmaceutical and military fields. However, the content of BT in its fermentation broth is less than 1 wt%. The purification of BT by distillation is a high energy-consumption process. In this paper, a solvent desorption method was used to pre-concentrate BT with ethanol as a desorbent. This work focused on establishing a transient chromatographic column model to explore vividly the pre-concentration behaviors of BT during column adsorption/desorption processes. First, by analysis of the hydrophobicity and molecular size of the solutes and the micropore size of resin, the adsorption mechanisms were proposed as size exclusion and hydrophobic interaction, while desorption equilibrium was supposed to competitive adsorption. Secondly, the effects of the different ethanol concentrations on the enrichment of BT concentration were investigated systematically. The results showed about 1.46 bed volumes of absolute ethanol could desorb BT completely with 1.5 times BT concentration in the fixed bed system. Finally, a general rate model (GRM) was used to predict the dynamic adsorption/desorption processes successfully. The transient process of BT pre-concentration in the presence of desorbent ethanol was vividly displayed by Matlab, which revealed the individual behaviors of BT and ethanol during the adsorption/desorption process. It further proved the competitive adsorption could be the reason for the BT pre-concentration.

Development and Performance Evaluation of Cellulose Acetate-Bentonite Mixed Matrix Membranes for CO2 Separation

Membrane science is a state-of-the-art environmentally green technology that ascertains superior advantages over traditional counterparts for CO2 capture and separation. In this research, mixed matrix membranes (MMMs) comprising cellulose acetate (CA) with various loadings of bentonite (Bt) clay were fabricated by adopting the phase-inversion technique for CO2/CH4 and CO2/N2 separation. The developed pristine and MMMs were characterized for morphological, thermal, structural, and mechanical analyses. Several techniques such as scanning electron microscopy, thermogravimetric analysis, Fourier transformed infrared spectroscopy, and nano-indentation investigations revealed the promising effect of Bt clay in MMMs as compared to pristine CA membrane. Nano-indentation test identified that elastic modulus and hardness of the MMM with 1 wt. loading was increased by 64% and 200%, respectively, compared to the pristine membrane. The permeability decreased with the incorporation of Bt clay due to uniform dispersion of filler attributed to enhanced tortuosity for the gas molecules. Nevertheless, an increase in gas separation performance was observed with Bt addition up to 1 wt. loading. The opposite trend prevailed with increasing Bt concentration on the separation performance owing to filler agglomeration and voids creation. The maximum value of ideal selectivity (CO2/CH4) was achieved at 2 bar pressure with 1 wt. % Bt loading, which is 79% higher than the pristine CA membrane. For CO2/N2, the ideal selectivity was 123% higher compared to the pristine membrane with 1 wt. % Bt loading at 4 bar pressure.

The structure and optical properties of PVA-BaTiO3 nanocomposite films

Abstract This paper aims to synthesize barium titanate (BaTiO3) nanocrystalline particles and to fabricate polyvinyl alcohol (PVA) films hosting BaTiO3 in order to enhance structural and optical properties. The tartrate precursor process is used to produce BaTiO3 nanocrystalline. By means of cast solution, the PVA – BaTiO3 nanocomposite films are prepared. The polymer films are described by X-ray diffractometer (XRD), Fourier-Transform Infrared (FTIR), UV–vis spectroscopy, and photoluminescence spectroscopy (PL). The study of XRD and FTIR indicates that complexity is established between BaTiO3 nanoparticles and PVA matrix. Furthermore, XRD analyzes emphasize a reduction in the crystallinity of polymer films by increasing of BaTiO3 nanoparticles within the matrix of PVA. It is noticed that as the BaTiO3 nanoparticles concentration increases in the PVA matrix, the optical band gap decreases while the Urbach energy increases. The PL spectra for PVA-BT films showed a photoemission peak at about 750 nm. This peak decreases in intensity and broadened with the increase of the BT concentration in the PVA matrix, which is related to the defects produced and causes disordering in the polymer matrix. The extinction coefficient, refractive index, optical conductivity and dielectric constants of the polymer films are also improved.

Efficient recovery of bio-based 1,2,4-butanetriol by using boronic acid anionic reactive extraction

Effective isolation of 1,2,4-butanetriol (BT) from the fermentation broth with low BT concentration was achieved based on anionic reactive extraction with a combined extractant consisted of boronic acid carrier and trioctylmetylammonium Aliquat® 336 (A336) dissolved in the organic phase. The influence of various diluents, pH values, the ratio of phenylboronic acid derivatives (PBAD) to BT (αPBAD/BT), and A336 to BT (βA336/BT) on extraction property was investigated in detail. For model BT solutions, satisfactory extraction efficiency of 92% was obtained under the conditions of αPBAD/BT = 1.5, βA336/BT = 2, with dichloromethane as a diluent. Aqueous hydrochloric acid solutions were employed to strip BT from the organic phase. For actual fermentation broth, the extraction and stripping efficiency under the optimum conditions were 74% and 69%, respectively. Besides, compared with the original fermentation broth, 1,2,4-butanetriol has been concentrated by 4.6 times with the reactive extraction coupled hydrolysis.

Observation of enhanced electrostrictive strain in (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3 lead-free ceramics

Herein, the author reports the observation of composition dependent piezoelectric and electrostrictive behaviour in lead free (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: NBT-BT-BAO [x = 0.01, 0.03, 0.05, 0.07, 0.09] ceramics synthesized through standard solid state reaction route. X-ray diffraction analysis of the samples confirms existence of structural phase transition from monoclinic to pseudocubic with increase of BT and BAO concentration supported by Raman spectroscopic analysis. A flipping from piezoelectric (x≤ 0.03) to near-electrostrictive (x≥ 0.05) characteristics has been realized from strain vs electric field measurements. Especially, (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: x = 0.05 showed an enhanced strain of 0.33 %, Smax/Emax of 425 pm/V and an electrostrictive co-efficient (Q33) of 0.034 m4C−2 could be attributed to the presence of MPB by the co-existence of monoclinic and pseudocubic phases. Further, minimal temperature dependence of the electrostrictive strain is inferred from temperature dependent polarization and strain measurements.

Pathogenicity of indigenous soil isolate of Bacillus thuringiensis to Helicoverpa armigera H\xfcbner 1809 (Lepidoptera: Noctuidae)

This study evaluated the pathogenicity of indigenous soil isolate of Bacillus thuringiensis (Bt) strains, applied without and along with 1.0% MgCl2 salt, to Helicoverpa armigera Hübner (Lepidoptera: Noctuidae). Toxicity and effect of Bt isolate on larval development (weight) were assessed using in vitro bioassays. Six concentrations of the tested Bt with salt (i.e., 1.0 × 107, 0.5 × 105, 1.0 × 105, 1.5 × 105, and 2.0 × 105 cfu/ml), five without salt (i.e., 0.5 × 105, 1.0 × 105, 1.5 × 105, and 2.0 × 105 cfu/ml), and control were bioassayed against third-instar larvae of H. armigera under a complete randomized design (CRD), with four replications. Results revealed that both larval mortality and weight changes were significantly affected by time (F5, 19 = 35.98; P < 0.001 and F5, 19 = 11.01; P < 0.001, respectively) and treatments (F5, 19 = 27.45; P < 0.001 and F5, 19 = 25.07; P < 0.001). The highest larval mortality (91.1%) was exhibited by the highest concentration (1.0 × 107 cfu/ml), followed by 2.0 × 105 cfu/ml concentration, without salt (88.9%) and with salt (66.7%). Median lethal concentration (LC50) values of isolated Bt strain were 1.7 and 1.27 × 105 cfu/ml, without salt, and 1.80 and 1.13 × 105 cfu/ml, with salt, at 96 and 120 h, respectively. Regarding the impact of Bt isolate on larval development, treatment with the highest concentration (1.0 × 107 cfu/ml) had the most significant and negative impact on larval weight change (R2 = 0.53), followed by 2.0 × 105 cfu/ml Bt concentration (R2 = 0.40). There was no obvious synergistic or additive effect, but rather an inhibition was observed on the pathogenicity potential or larvicidal effect of Bt isolate.

Removal of toluidine blue by manganese/graphene coated titaniferous sand and optimization of decolouration process via Box-Behnken design

An adequate modification of a titaniferous sand fraction by manganese/graphene coating (GMnTS) was carried out. Indeed, the surface of titaniferous sand (TS) with a particle size less than 100 μm was functionalized by chemical precipitation of manganese oxide on which were coated graphene oxide nano-sheets. Modified Hummer method was used to produce a stable suspension of graphene oxide. In this study, the adsorption affinity was tested using toluidine blue (BT) as an aquatic contaminant. According to the Langmuir model, GMnTS has an adsorption capacity about 12 times higher than that of unmodified titaniferous sand. This is a coating rate of about 0.73 ± 0.02 %. The response surface methodology based on Box–Behnken design was applied to optimize the linear and interactive effects of four factors (BT concentration, pH, solid/liquid ratio and KCl concentration) influencing the discoloration process by GMnTS.

High-energy storage performance in lead-free (0.8-x)SrTiO3-0.2Na0.5Bi0.5TiO3-xBaTiO3 relaxor ferroelectric ceramics

lead-free (0.8-x)SrTiO3-0.2Na0.5Bi0.5TiO3-xBaTiO3 ceramics (abbreviated as (0.8-x)ST-0.2NBT-xBT) were prepared by the conventional solid-state sintering method, and their crystal structure, dielectric properties, relaxor behavior and energy-storage property were investigated as a function of BT concentration. X-ray diffraction results reveal a pure perovskite structure with a pseudo-cubic phase. The dielectric measurements exhibit a relaxor behavior for all samples and the Tm gradually increases (from −49.67 °C to 67.91 °C) with increasing x. The pinched polarization-electric field (P-E) loops were observed in the samples with x ≤ 0.40 and the maximum polarization (Pm) increased from 11.37 μC/cm2 to 20.79 μC/cm2 at 8 kV/mm while x = 0.20–0.55. The maximum discharge energy-storage density (Jd) (1.78 J/cm3) is obtained in x = 0.35 ceramic with a relatively high Pm (29.19 μC/cm2) under an electric field of 17 kV/mm, which makes (0.8-x)ST-0.2NBT-xBT ceramics may be promising lead-free materials in practical high energy storage application.

Exploring new methodologies for the identification of the morphotropic phase boundary region in the (BiNa)TiO3-BaTiO3 lead free piezoceramics: Confocal Raman Microscopy

On ferroelectrics materials, the piezoelectric activity is enhanced near the so-called morphotropic phase boundary (MPB) separating the rhombohedral and tetragonal phases in the binary phase diagram. Here, we report the identification of the morphotropic phase boundary (MPB) region in the (1-x)Na0.5Bi0.5TiO3–xBaTiO3 (BNT-BT) ceramic system by Confocal Raman Microscopy (CRM), emphasizing on the relationships between structure and piezoelectric properties. CRM results reveal the presence of the morphotropic phase boundary, between rhombohedral and tetragonal structures when BT concentration is close to 0.06–0.07. Raman spectroscopy can be used to rapidly identify the MPB on ferroelectric ceramics as seen in our model system (BNT-BT-based ceramics), since Raman spectra can be taken in few seconds, being then a very useful technique for material testing on industrial processes. Specifically, the methodology here showed represents an interesting way to correlate the micro and nanostructure with the properties in lead-free piezoceramics, which are controlled in part by the distribution of their different crystal phases. We believe that our results can benefit the understanding of BNT-BT ceramics expanding its applications range.

A coexistence of multi-relaxor states in 0.5BiFeO3–0.5BaTiO3

Here we report our investigations on a pseudo-cubic 0.5BiFeO3–0.5BaTiO3 ceramic (0.5BF–0.5BT) in which ferroelectric relaxor and antiferromagnetic and magnetic relaxor orders coexist. The temperature dependence of ferroelectric hysteresis loops and dielectric data confirms the existence of the ferroelectric relaxor state. The temperature of the maximum dielectric constant (Tm) at 1MHz and electric freezing temperature (Tf) are 584K and ~250K, respectively. The magnetic data imply that a Neel transition occurs below 174K. Most importantly, a magnetic relaxor order appears below ~6K. The magnetic states of 0.5BF–0.5BT are rather different from those of BF–BT ceramics with the low BT concentration.

Growth of NBT–BT single crystals by flux method and their structural, morphological and electrical characterizations

In this paper, one of the important, eco-friendly polycrystalline material, (1−x)(Na0.5Bi0.5)TiO3 (NBT) – xBaTiO3 (BT) of different compositions (x=0.07, 0.06 and 0.05wt%) around the morphotropic phase boundary (MPB) were synthesized by solid state reaction technique. And the single crystals with 13×7×7mm3, 12×12×7mm3 and 10×7×4mm3 dimensions were grown by self flux method. The morphology, crystal structure and unit-cell parameters have been studied and the monoclinic phase has been identified for 0.07wt% of BT. Higher BT concentration changes the crystal habit and the mechanism has been studied clearly. Raman spectroscopy at room-temperature confirms the presence of functional groups. The quality of the as grown single crystals was examined by high resolution x-ray diffraction analysis. The dielectric properties of the as grown crystals were investigated in the frequency range of 20Hz–2MHz from room temperature to 450°C. The broad dielectric peak and frequency dispersion demonstrates the relaxor behavior of grown crystals. The dielectric constant (εr), transition temperature (Tm), and depolarization temperature (Td) of the grown crystals are found to be comparatively good. The diffusive factor (γ) from Curie–Weiss law confirms the as grown NBT–BT single crystals are relaxor in nature.

Synthesis, structural, morphological and electrical properties of NBT–BT ceramics for piezoelectric applications

In this paper, the synthesis of ferroelectric (1−x)(Na0.5Bi0.5)TiO3 (NBT)–xBaTiO3 (BT) ceramics of different compositions (x=0.07, 0.06wt%) around the morphotropic phase boundary (MPB) by solid state reaction technique has been reported. From the Scanning Electron Microscopy (SEM) analysis, the pebble-like morphology of the synthesized ceramics has been changed to regular cube-like morphology for higher BT concentration. The phase coexistence and crystal structure have been determined by using X-ray powder diffraction. Presence of functional groups has been identified by Raman Spectroscopy at room-temperature. The dielectric properties of the ceramics were investigated in the frequency range of 200Hz–2MHz from room temperature to 500°C. The broad dielectric peak and frequency dispersion demonstrate the relaxor behavior of ceramics. The dielectric constant (εr), transition temperature (Tm), depolarization temperature (Td) and diffusive factor (γ) are found to be comparatively good and tabulated for 5kHz. The ac conductivity follows jump relaxation model at low frequency and double power at high frequency and temperature. For these ceramics P–E loops with high remnant polarization were obtained at room temperature. The d33 values for NBT–BT 94/6 and NBT–BT 93/7 were 85 and 102pC/N respectively. The open circuit g – constants have been calculated and it is high for NBT–BT 93/7.

Dielectric Performance of (1-x)Na0.5Bi0.5TiO3-xBaTiO3 Lead-Free Piezoelectric Ceramics Synthesized by Sol-Gel Combustion Method

Lead-free piezoelectric ceramics (1-x)Na0.5Bi0.5TiO3-xBaTiO3(x=0.04, 0.06, 0.08) was synthesized via sol–gel combustion method. Structural analysis was performed by using X-ray diffraction (XRD). The structural morphology of the nanoparticles was studied using scanning electron microscopy (SEM). The ceramics show a rhombohedral-tetragonal morphotropic phase boundary (MPB) in the range of x =0.04-0.08, which makes ceramics having superior dielectric and piezoelectric properties. There is a decrease of the grain size with increasing BT concentration, suggesting that dissolving BT into NBT inhibits the grain growth. And the multi-peak fitting result shows lattice constants of NBT have increased with the BT doped into NBT. Belong to the ionic polarization relaxation type, the low temperature dielectric anomalous peak shift towards a high temperature and the high temperature dielectric anomalous peak shift towards a lower temperature showed by the dielectric-temperature spectrum. Dielectric-temperature spectrum further determines that (1-x)NBT-xBT ceramics are relaxation ferroelectrics, and join BT makes the Curie temperature decreasing about 21 to 24°C. High piezoelectric properties with d33=148pC/N are observed in NBT-BT0.06.

Effects of Bacillus thuringiensis isolates and single nuclear polyhedrosis virus in combination and alone on Helicoverpa armigera

Cotton bollworm is a key pest of cotton and other crops in many parts of Asia. Evaluation of three native Bacillus thuringiensis isolates and HaSNPV on cotton bollworm was studied. Results revealed that KD-2 isolate was the superior isolate, that its LC50 was 1.2 × 107 spore ml−1 and LC50 of HaSNPV equal to 9.2 × 103 OB ml−1. Interactions on the mortality and debilitating effects between B. thuringiensis KD-2 isolate (3 × 106, 6 × 106, 1.21 × 107 and 1.8 × 107 spore ml−1) and HaSNPV (2.3 × 103, 4.6 × 103 and 9.2 × 103 OB ml−1) on second instars larvae of Helicoverpa armigera were evaluated in laboratory. The larvae of cotton bollworm were fed for 48 h on the treated diets. The results revealed that the Bt at 1.2 × 107 spore ml−1, mixed with all above-mentioned concentrations of HaSNPV, had antagonistic effects. However, the Bt at 1.8 × 107 spore ml−1, mixed with HaSNPV at 9.2 × 103 OB ml−1, had additive effect. The Bt at 6 × 106 spore ml−1 mixed with all above-mentioned concentrations of HaSNPV demonstrated additive effects. The Bt at 3 × 106 spore ml−1 had additive effect with HaNPV at 2.3 × 103 and 4.6 × 103 OB ml−1. The mortality observed in larvae infected with the combination of both Bt (3 × 106 spore ml−1) and HaSNPV (9.2 × 103 OB ml−1) was interpreted as synergist effect. Therefore, it could be concluded that combination of the lowest Bt concentration and the highest HaSNPV concentration had synergist effect on H. armigera second instar larvae.

Interaction of acid exudates in chickpea with biological activity of Bacillus thuringiensis towards Helicoverpa armigera

The gram pod borer, Helicoverpa armigera, is one of the most important constraints to chickpea production. High acidity of chickpea exudates is associated with resistance to pod borer, H. armigera; however, acidic exudates in chickpea might influence the biological activity of the bacterium, Bacillus thuringiensis (Bt), applied as a foliar spray or deployed in transgenic plants for controlling H. armigera. Therefore, studies were undertaken to evaluate the biological activity of Bt towards H. armigera on chickpea genotypes with different amounts of organic acids. Significantly lower leaf feeding, larval survival and larval weights were observed on ICC 506EB, followed by C 235, and ICCV 10 across Bt concentrations. Leaf feeding by the larvae and larval survival and weights decreased with an increase in Bt concentration. However, rate of decrease in leaf feeding and larval survival and weights with an increase in Bt concentration was greater on L 550 and ICCV 10 than on the resistant check, ICC 506EB, suggesting that factors in the resistant genotypes, particularly the acid exudates, resulted in lower levels of biological activity of Bt possibly because of antifeedant effects of the acid exudates. Antifeedant effects of acid exudates reduced food consumption and hence might reduce the efficacy of Bt sprays on insect-resistant chickpea genotypes or Bt-transgenic chickpeas, although the combined effect of plant resistance based on organic acids, and Bt had a greater effect on survival and development of H. armigera than Bt alone.

The role of temperature in enhancing the insecticidal activity of Bacillus thuringiensis against Spodoptera littoralis larvae

The present study scrutinised how far temperature would affect the velocity of the insecticidal activity of Bacillus thuringiensis, as the rapidity of pest control achievements is of a great concern. Third instar Spodoptera littoralis larvae were treated with Bt at three concentration levels under five different temperatures (15°C, 20°C, 25°C, 30°C and 35°C). LT50s were evaluated in each case. The LT50 values showed various levels of reductions as temperature and/or Bt concentration increased, indicating that the velocity of mortality (1/LT50) and/or the rapidity of Bt activity was almost temperature dependant. However, relatively high and low reduction percentages in the LT50 values on the elevation of 5°C were obtained at lower and higher temperature ranges, respectively. The temperature coefficient, Q 10 values, determined within narrow ranges (5°C) showed great reductions when temperature increased from 15°C to 20°C at all Bt concentrations. Raising temperature by 5°C above 20°C or 25°C almost caused similar Q 10 values indicating constant increase in the response of Bt activity within 20–30°C temperature range. Q 10 values over 30°C were comparatively very low. This proved that decrease in Q 10 values due to the rise of temperature was dependant on the starting temperature.

Respiration pattern and microbial use of field-grown transgenic Bt-maize residues

A 49-day incubation experiment was carried out with the addition of field-grown maize stem and leaf residues to soil at three different temperatures (5, 15, and 25 °C). The aim was to study the effects of two transgenic Bt-maize varieties in comparison to their two parental non- Bt varieties on the mineralization of the residues, on their incorporation into the microbial biomass and on changes in the microbial community structure. The stem and leaf residues of Novelis -Bt contained 3.9 μg g −1 dry weight of the Bt toxin Cry1Ab and those of Valmont -Bt only 0.8 μg g −1. The residues of the two parental non- Bt varieties Nobilis and Prelude contained higher concentrations of ergosterol (+220%) and glucosamine (+190%) and had a larger fungal C-to-bacterial C ratio (+240%) than the two Bt varieties. After adding the Bt residues, an initial peak in respiration of an extra 700 μg CO 2–C g −1 soil or 4% of the added amount was observed in comparison to the two non- Bt varieties at all three temperatures. On average of the four varieties, 19–38% of the maize C added was mineralized during the 49-day incubation at the three different temperatures. The overall mean increase in total maize-derived CO 2 evolution corresponded to a Q 10 value of 1.4 for both temperature steps, i.e. from 5 to 15 °C and from 15 to 25 °C. The addition of maize residues led to a strong increase in all microbial properties analyzed. The highest contents were always measured at 5 °C and the lowest at 25 °C. The variety-specific contents of microbial biomass C, biomass N, ATP and adenylates increased in the order Novelis -Bt ⩽ Prelude<Valmont -Bt ⩽ Nobilis. The mineralization of Novelis -Bt residues with the highest Bt concentration and lowest N concentration and their incorporation into the microbial biomass was significantly reduced compared to the parental non- Bt variety Nobilis. These negative effects increased considerably from 5 to 25 °C. The transgenic Bt variety Valmont did not show further significant effects except for the initial peak in respiration at any temperature.

Soil Microbial and Faunal Community Responses toBtMaize and Insecticide in Two Soils

The effects of maize (Zea mays L.), genetically modified to express the Cry1Ab protein (Bt), and an insecticide on soil microbial and faunal communities were assessed in a glasshouse experiment. Soil for the experiment was taken from field sites where the same maize cultivars were grown to allow comparison between results under glasshouse conditions with those from field trials. Plants were grown in contrasting sandy loam and clay loam soils, half were sprayed with a pyrethroid insecticide (deltamethrin) and soil samples taken at the five-leaf stage, flowering, and maturity. The main effect on all measured parameters was that of soil type and there were no effects of Bt trait or insecticide on plant growth. The Bt trait resulted in more soil nematodes and protozoa (amoebae), whereas insecticide application increased plant Bt concentration and altered nematode community structure. The only significant effects on soil microbial community structure, microarthropods, and larvae of a nontarget root-feeding Dipteran, were due to soil type and plant growth stage. The results indicate that, although there were statistically significant effects of the Bt trait on soil populations, they were small. The relative magnitude of the effect could best be judged by comparison with the insecticide treatment, which was representative of current best practice. The Bt trait had no greater effect than the insecticide treatment. Results from this glasshouse experiment were in broad agreement with conclusions from field experiments using the same plant material grown in the same soils.

Effects of various concentrations ofBacillus thuringiensis-corn leaf material on food utilization byChilo partellus larvae of different ages

When herbivores feed on insect-resistant transgenic plants, food consumption and utilization are probably affected. Quantifying these parameters is of importance, because they may be associated with the performance of parasitoids, which are important antagonists of herbivorous pests. In this study, relative consumption rate (RCR), relative growth rate (RGR), approximate digestibility (AD), efficiency of conversion of digested food into body matter (ECD) and efficiency of conversion of ingested food into body matter (ECI) ofChilo partellus Swinhoe larvae (Lepidoptera: Crambidae) exposed to different concentrations of transgenic insect-resistantBacillus thuringiensis-corn (Bt-corn) tissue suspension, were investigated under laboratory conditions. For the control groups, different concentrations of control corn tissue suspension were used. In order to determine whether Bt effects were influenced by larval age, 4- and 17-day-old larvae were used. At all concentrations and for larvae of both ages, RGR, RCR, ECD and ECI values in the control were significantly higher than in the Bt group. Moreover, there was a gradual decrease in RCR, RGR and ECI values when Bt concentrations were increased. However, AD values at the lowest Bt concentration were significantly higher than in the control, whereas no significant differences between both groups could be detected at higher concentrations. In conclusion, the experiments showed that nutritional indices of herbivores exposed to transgenic insect-resistant plants could be quantified to determine the effects of these plants on target or non-target organisms. This could be one component in future evaluation of the effect of transgenic insect-resistant plants on the second and third trophic level.

Electromechanical and dielectric properties of Na 0.5Bi 0.5TiO 3–K 0.5Bi 0.5TiO 3–BaTiO 3 lead-free ceramics

Electromechanical and dielectric properties of (1–3 x)NBT–2 x KBT– xBT lead-free ceramics were investigated. XRD results show that the crystalline structure of the ceramics was perovskite. The morphotropic phase boundary (MPB) of the ternary system between rhombohedral and tetragonal locates in the range of x = 0.025–0.035. The preferred piezoelectric constant d 33 = 150 pC N −1 and planar electromechanical coupling factor k p = 0.298 are observed at x = 0.035, corresponding to a relatively large remanent polarization of P r = 35.0 μC cm −2 and a relatively low coercive field of E c = 4.55 kV mm −1. Temperature dependence of dielectric constant at different frequencies shows that the ferroelectric characteristic of (1–3 x)NBT–2 xKBT– xBT lead-free ceramics transforms from relaxor ferroelectric to normal ferroelectric with increasing of KBT and BT concentration.