C2 Configuration Research Articles

Sequential hybridisation of wire and powder-based additive manufacturing of Inconel 718: Mechanical and microstructural characterization

The present study combines the Wire-based DED (W-DED) and Powder-based DED (P-DED) to achieve a high deposition rate and higher feature resolution, respectively, within the single component. The research puts forward a novel Wire-Power (WP) Hybrid DED process, which is realized by sequential deposition of feedstock in Wire and then in Powder form. Based on the deposition-extraction combination, three sample configurations, C1 (Y-X), C2 (X-X) and C3 (Y-Z), were fabricated and characterized for the mechanical properties and microstructural aspects. OM images revealed defect-free P-DED and W-DED interface, while the EBSD analysis showed grain size variations owing to differences in the cooling rates. The Ultimate Tensile Strength (UTS) values of C1 and C2 configurations are about 132.2 and 139.7 % higher in comparison to C3. Low cycle fatigue results showed that the C2 sustained a higher number of completely reversed cycles to failure in comparison to the other configurations. The impact energy absorbed by C3 is the highest, affirming the strong W–P interface.

Influence of location of twin-adiabatic blocks on magnetohydrodynamics-based double-diffusive convection and entropy generation for a liquid metal

This research deals with a rectangular cavity encompassing two adiabatic rectangular and impermeable obstacles at various positions. This study serves as a platform to explore the interplay between diverse flow-governing parameters, such as the buoyancy ratio (N = −1, 0, and +1), Hartmann number (Ha = 0, 50, and 100), Lewis number (Le = 1, 5, and 10), Rayleigh number (Ra = 103 and 104), and geometric arrangements of twin-blocks (C1, C2, and C3) to help in developing insights into such complex transport phenomenon driven under the influence of buoyancy and concentration. The arrangements are chosen such that C1 and C3 represent the off-center position of the first obstacle, while C2 represents the in-line position with the second obstacle. The influence of liquid sodium–potassium alloy (Pr = 0.054) on fluid flow, heat, and mass transfer, and entropy generation characteristics due to double-diffusive natural convection in the twin obstacle-filled rectangular enclosure are observed using the lattice Boltzmann method. The results reveal that the maximum amount of heat and mass transfer occurs at the C2 position, making it the most efficient for heat and mass transfer among all. In contrast, the C2 configuration is a thermodynamically inefficient arrangement as entropy generation is maximum, while the C3 configuration is obtained to be more efficient thermodynamically. Furthermore, the results reveal that the average total entropy generation is directly related to the Lewis number, while it has an inverse relation with the Hartmann number.

Experimental analysis of heat transfer characteristics using ultrasonic acoustic waves

In this experimental work, heat transfer intensification using ultrasonic waves was investigated. A heat source, consisting in a parallelepiped aluminum block in which two electrical heating cartridges of 160 W each were mounted to heat four liters of distilled water contained in a tank made of Plexiglas. To demonstrate the effectiveness of heat transfer enhancement with the use of ultrasounds, three different configurations were analyzed. In the first one, considered as a reference case, the heat transfer was studied without ultrasound field. In the second configuration, ultrasonic acoustic waves were generated using one transducer vibrating at a fixed frequency of 40 kHz with a total power of 60 W. In the last configuration, ultrasounds were generated with two similar transducers mounted on two opposite walls of the water tank while maintaining the same power and frequency. The effect of the distance separating the heat source to the trans-ducers on the convective heat transfer coefficients and the average temperature of the water in the tank were analyzed in detail. The results revealed that the natural convection heat transfer in the water tank was intensified by means of low frequency acoustic waves. Indeed, it was shown, particularly, that more the distance between the transducer and the heater is low more the heat transfer improvement is better. The heat transfer enhancement factor was estimated to 2.5 on the surface facing the transducer while it was only about 1.2 on the opposite surface in C2 configura-tion. In C3 configuration, the heat transfer enhancement factor is nearly the same with, however, more homogenous water temperature. The acoustic cavitation and streaming were identified as the main phenomena leading to these results. This study successfully demonstrated the feasibility of heat transfer intensification using low frequency ultrasonic waves.

Prevalence and Morphology of C-Shaped Canals in Mandibular First and Second Molars of an Iranian Population: A Cone-Beam Computed Tomography Assessment.

The complex anatomy of C-shaped canals poses challenges for clinicians compared to teeth with normal root canal anatomy. This study is aimed at evaluating the frequency and morphology of C-shaped canals in the mandibular first and second molars among an Iranian population using cone-beam computed tomography (CBCT). This cross-sectional study evaluated 369 CBCT scans from the archives of a radiology clinic in Ardabil, Iran. The sample included 248 mandibular first molars and 478 mandibular second molars. The presence of C-shaped canals and their classification, according to Fan et al., were evaluated at four levels: orifice, coronal, middle, and apical. Prevalence based on gender and tooth type was also assessed. A total of 199 (53.9%) males and 170 (46.1%) females were evaluated. C-shaped canals were found in 11 (8 males/3 females) out of 248 (4.4%) first molars and in 20 (11 males/9 females) out of 478 (3.7%) second molars. The C2 configuration was most prevalent in the orifice, coronal, and middle levels of both molar types, while C3 and C4 morphologies were most commonly found apically in the second and first molars, respectively. A significant difference in configuration was found only at the coronal level between molar types. A significant association between gender and configuration was observed only at the orifice level of the second molars. No other significant differences were found (P > 0.05). C-shaped canal configurations should be expected in 4.4% of mandibular first molars and 3.7% of the second molars in this Iranian population, with a predominance of the C2 configuration in the orifice, coronal, and middle levels.

Prevalence of Root Canal Configuration of Mandibular Second Molar Using Cone-Beam Computed Tomography in a Sample of Iraqi Patients

Introduction: The purpose of this study was to find out the prevalence of C-shaped canals configurations in mandibular 2nd molar and to investigate the gender prevalence. Materials and Methods: A sample of 1200 patients’ cone beam computed tomography (CBCT) scans were screened and evaluated by a maxillofacial radiologist assessed the axial, sagittal, and coronal sections. Inclusion criteria applied to 801 patients (452 females and 349 male) aged 14–75 years were included in this study with total of 1567 mandibular 2nd molar was evaluated. Inclusion criteria: Available CBCT images of mandibular posterior teeth with at least one mandibular 2nd molar in the scan, absence of root canal treatment, absence of coronal or post coronal restorations, absence of root resorption or periapical lesions, and high-quality images. Canal configuration was classified by criteria’s which described by Fan et al. (2004): (i) Fused roots, (ii) a longitudinal groove on the buccal or lingual surface of the root, and (iii) at least one cross-section of the canal belongs to the C1, C2, or C3 configuration. Results: Considering 801 patients, 97 (12.1%) patients females 57 (7.1%) and 40 (5%) males had a C-shaped canal with no statistical difference between females and males (P > 0.05). Conclusion: The occurrence of C- shaped canal mandibular 2nd molar is approximately 12.1% and no significant difference was found by gender.

Synthesis of Rare 6-Deoxy-d-/l-Heptopyranosyl Fluorides: Assembly of a Hexasaccharide Corresponding to Campylobacter jejuni Strain CG8486 Capsular Polysaccharide.

Campylobacter jejuni is the leading cause of human diarrheal diseases and has been designated as one of highly resistant pathogens by the World Health Organization. The C. jejuni capsular polysaccharides feature broad existence of uncommon 6dHepp residues and have proven to be potential antigens to develop innovative antibacterial glycoconjugation vaccines. To address the lack of synthetic methods for rare 6dHepp architectures of importance, we herein describe a novel and efficient approach for the preparation of uncommon d-/l-6dHepp fluorides that have power as glycosylating agents. The synthesis is achieved by a C1-to-C5 switch strategy relying on radical decarboxylative fluorination of uronic acids arising from readily available allyl d-C-glycosides. To further showcase the application of this protocol, a structurally unique hexasaccharide composed of →3)-β-d-6didoHepp-(1→4)-β-d-GlcpNAc-(1→ units, corresponding to the capsular polysaccharide of C. jejuni strain CG8486 has been assembled for the first time. The assembly is characterized by highly efficient construction of the synthetically challenging β-(1,2-cis)-d-ido-heptopyranoside by inversion of the C2 configuration of β-(1,2-trans)-d-gulo-heptopyranoside, which is conveniently obtained by anchimerically assisted stereoselective glycosylation of the orthogonally protected 6dgulHepp fluoride. Ready accessibility of 6dHepp fluorides and the resulting glycans could serve as a rational starting point for the further development of synthetic vaccines fighting Campylobacter infection.

Architected material analogs for shape memory alloys

Architected material analogs for shape memory alloys

Prevalence of C-shaped second mandibular molar canals in the population of central Serbia: A cone-beam computed tomography study

Background/Aim. C-shaped canals are a complex morphological variation of the tooth root canal system that, if present, could greatly affect the outcome of endodontic therapy. The prevalence of these canal configurations varies between the populations of different ethnic and geographical origins. Therefore, the goal of this study was to analyze the prevalence and morphology of mandibular second molar C-shaped canals in the population of Central Serbia. Methods. The study included a total of 1 99 mandibular second molars receiving a cone-beam computed tomography (CBCT) examination and determining the presence of C-shaped canal systems, their configuration, minimal wall thickness and its relative position on axial cross-sections at the coronal, middle, and apical level. Results. The prevalence of C-shaped mandibular second molars was 5.53%. C1 canal configuration was the most frequent at the coronal cross-section, while C2 configuration was the most frequent at middle and apical cross-sections. Minimal wall thickness decreased going apically, with the mean value of 1.01 mm at the coronal, 0.87 mm at the middle, and 0 .67 mm at the apical cross-sections. Minimal wall thickness was mostly directed lingually at all cross-sectional levels. Conclusion. C-shaped canals should be expected in mandibular second molars of the population of Central Serbia. CBCT was shown to be the most valuable technique to determine C-shaped canals and facilitate understanding of the C-shaped canal morphology; its implementation could improve the success of endodontic therapy, especially if the complex root canal configuration is present.

Silver Single Atom in Carbon Nitride Catalyst for Highly Efficient Photocatalytic Hydrogen Evolution.

Single atom catalysts (SACs) with the maximized metal atom efficiency have sparked great attention. However, it is challenging to obtain SACs with high metal loading, high catalytic activity, and good stability. Herein, we demonstrate a new strategy to develop a highly active and stable Ag single atom in carbon nitride (Ag-N2 C2 /CN) catalyst with a unique coordination. The Ag atomic dispersion and Ag-N2 C2 configuration have been identified by aberration-correction high-angle-annular-dark-field scanning transmission electron microscopy (AC-HAADF-STEM) and extended X-ray absorption. Experiments and DFT calculations further verify that Ag-N2 C2 can reduce the H2 evolution barrier, expand the light absorption range, and improve the charge transfer of CN. As a result, the Ag-N2 C2 /CN catalyst exhibits much better H2 evolution activity than the N-coordinated Ag single atom in CN (Ag-N4 /CN), and is even superior to the Pt nanoparticle-loaded CN (PtNP /CN). This work provides a new idea for the design and synthesis of SACs with novel configurations and excellent catalytic activity and durability.

Organometallic binuclear Pd(II) complex: Synthesis, crystal structure and in-vitro antitumor activity study

A novel planar chiral ferrocene cyclopalladated compound (C2) was synthesized and fully characterized. The absolute configuration of C2 has been determined by single-crystal X-ray analysis. The cytotoxic activities of C2 and cisplatin were evaluated against liver (MHCC97 and HepG2), mouse breast (4 T1) and ovarian granulosa (KGN) cancer cell lines. C2 was about 23 times more potent than cisplatin in the suppression of KGN cells.

Laminar Mixed Convection of Water-Based Alumina Nanofluid in a Cylindrical Enclosure with a Rotating End Wall: A Numerical Investigation

Steady-state laminar mixed convection of water-based alumina nanofluids in cylindrical enclosures with a rotating top cover has been numerically analyzed for different Reynolds numbers (500–3000), Richardson numbers (0–1) and nanoparticle volume fractions (1–5%) for an aspect ratio of unity. Two different configurations have been considered for this analysis in order to obtain physical insights into the fluid flow and heat transfer in cylindrical enclosures with a rotating end cover. In one configuration (i.e. C1 configuration), the rotating top wall is kept at a higher temperature than the bottom wall, whereas the bottom wall is heated in the second configuration (i.e. C2 configuration). The mean Nusselt number in the case of mixed convection has been found to assume higher values in the C2 configuration than in the C1 configuration for a given set of values of Reynolds number, Richardson number and nanoparticle volume fraction. It has also been found that mean Nusselt number monotonically decreases with increasing nanoparticle volume fraction regardless of Richardson number values in the C2 configuration, whereas the mean Nusselt number decreases (increases) with increasing nanoparticle volume fraction for fully forced convection (mixed convection) in the C1 configuration. The simulation data has been used to propose a correlation for the mean Nusselt number for both C1 and C2 configurations.

Effects of wall heating on laminar mixed convection in a cylindrical enclosure with a rotating end wall

Steady-state laminar mixed convection in a cylindrical enclosure has been numerically analysed for different values of Reynolds, Richardson and Prandtl numbers given by 500≤Re≤3000, 0≤Ri≤1 and 10≤Pr≤500 respectively. The aspect ratio (i.e. height: radius = AR = H/R) of the cylindrical container is considered to be unity (i.e. AR = H/R = 1). The bottom and top covers of the cylindrical enclosure are kept at different temperatures (TC<TH), while the cylindrical surface is taken to be adiabatic. The simulations for rotating top and bottom cover configurations yield the same numerical values of the mean Nusselt number Nu¯ when the thermal boundary conditions are kept unaltered. For this reason, only rotating top hot wall (i.e. C1 configuration) and rotating top cold wall (i.e. C2 configuration) have been considered for this analysis. The mean Nusselt number Nu¯ has been found to assume higher values in the C2 configuration than in the C1 configuration. Moreover, it has been found that the variation of the mean Nusselt number with Richardson number in the C2 configuration is qualitatively different from that in the C1 configuration. The simulation data has been used to propose a correlation for Nu¯ for the range of Re,Ri and Pr considered here for both C1 and C2 configurations. In addition to this, a regime diagram has been proposed for the C2 configuration in order to demarcate different flow regimes.

MP4 Study of the Anharmonic Coupling of the Shared Proton Stretching Vibration of the Protonated Water Dimer in Equilibrium and Transition States.

The structure and harmonic and anharmonic IR spectra of the protonated water dimer (PWD) were calculated in C1, C2, and Cs symmetry at the MP4/acc-pVTZ level of theory. We found that structure and IR spectra are practically identical in C2 and C1 symmetry, demonstrating that an equilibrium C1 configuration of the PWD is not realized. Anharmonic coupling of the shared proton stretching vibration with all other modes in the PWD in C2 and Cs symmetry was the focus of this investigation. For this purpose, 28 two-dimensional potential energy surfaces (2D PES) were built at the MP4/acc-pVTZ level of theory and the corresponding vibrational Schrödinger equations were solved using the DVR method. Differences in the coupling of the investigated mode with other modes in the C2 and Cs configurations, along with some factors that determine the red- or blue-shift of the stretching vibration frequency, were analyzed. We obtained a rather reasonable value of the stretching frequency of the bridging proton (1058.4 cm-1) unperturbed by Fermi resonance. The Fermi resonance between the fundamental vibration ν7 and the combined vibration ν2 + ν6 of the same symmetry was analyzed through anharmonic second-order perturbation theory calculations, as well as by 3D PES constructed using Q2, Q6, and Q7 as normal coordinates. A significant (up to 50%) transfer of intensity from the fundamental vibration to the combined one was found. We have estimated the frequency of the bridging proton stretching vibration in the Cs configuration of the PWD based on calculations of the intrinsic anharmonicity and anharmonic double modes interactions at the MP4/acc-pVTZ level of theory (1261 cm-1).

Calcium complexation and acid-base properties of l-gulonate, a diastereomer of d-gluconate.

The Ca(ii)-complexation and acid-base properties of l-gulonic acid (HGul), a diastereomer of d-gluconic acid (HGluc) differing only in the configurations of C2 and C5 have been investigated via1H and 13C NMR spectroscopies, Ca-ISE- and pH-potentiometry, polarimetry and freezing point depression. Data obtained for Gul-/HGul have been compared with those of Gluc-/HGluc. It was found that some properties (acid dissociation constant, the stoichiometry and formation constants of the Ca(ii)-complexes) were insensitive to the difference in the configuration. In solutions with pH close to neutral, the presence of the complexes CaGul+ and CaGul20 was unambiguously proven, with formation constants of log K1,1 = 0.88 ± 0.02 and log β1,2 = 1.51 ± 0.03 (I = 1 M, T = 25 °C). The formation of Ca(Gluc)20 was also observed by others, which implies that the formation of the charge neutral 1 : 2 Ca(ii)-complex of sugar carboxylates is more common than was previously believed. The stability of these species was found not to vary significantly in the ionic strength range of 1-4 M. Polarimetric measurements attested that the structure of Gul- did not change markedly upon complexation. NMR experiments suggest the coordination of C2-OH and C3-OH groups (beside COO-). DFT calculations support the existence of two coordination isomers, in which Ca2+ is attached to the COO-, C2-OH and C3-OH (in agreement with NMR), as well as to the COO-, C3-OH and C4-OH groups.

13C-NMR glycosylation effects in (1→3)-linked furanosyl-pyranosides

Synthesis, theoretical conformational analysis (molecular mechanics and DFT calculations) and NMR spectral data including the 13C-NMR glycosylation effects for six pairs of isomeric furanosyl-(1→3)-pyranosides with different anomeric and absolute configurations of furanosyl units as well as configurations of C2 and C4 in the pyranoside units are described. The determined 13C-NMR glycosylation effects were shown to correlate with the pattern of intramolecular interactions around the inter-unit bonds.

Acceptor specificity of amylomaltase from Corynebacterium glutamicum and transglucosylation reaction to synthesize palatinose glucosides

Acceptor specificity for intermolecular transglucosylation reaction of amylomaltase from Corynebacterium glutamicum was investigated using starch as glucosyl donor and various saccharide acceptors. Maltooligosaccharides (G1–G4), mannose, palatinose and sucrose were efficient acceptors; the best one was glucose. This amylomaltase preferred hexose sugar containing the same configuration of C2-, C4- and C6-hydroxyl groups as glucopyranose. Palatinose was chosen as suitable acceptor for the synthesis of palatinose glucosides (PGs). The optimal condition was to incubate 5U/ml amylomaltase with 7.5mM palatinose and 1.0% (w/v) soluble potato starch at 30°C for 24h. In addition to PGs, maltooligosaccharides were also produced as by product. The product yield was 67.9%, in which the ratio of PGs to maltooligosaccharides was 1:1. Then PGs were separated by Bio-Gel-P2 column chromatography and analyzed by HPAEC. PG1–PG13 were identified with PG1 and PG2 as major products. NMR analysis showed that the PGs produced are novel products, PG1 and PG2 were a tri- and tetra-saccharide with the structure [O-α-d-glucopyranosyl-(1→4)]n-O-α-d-glucopyranosyl-(1→6)-d-fructofuranose, where n=1–2. PG was less sweet than palatinose and sucrose, more hygroscopic with similar prebiotic activity as palatinose. PGs thus have potential to replace sucrose or palatinose in food products for health benefits.

Micro–computed Tomographic Analysis of Mandibular Second Molars with C-shaped Root Canals

IntroductionThe goal of the present study was to evaluate the morphometric aspects of the internal anatomy of the root canal system of mandibular second molars with C-shaped canals. MethodsFifty-two extracted second mandibular molars with C-shaped canals, fused roots, and radicular grooves were selected from a Brazilian population. The samples were scanned with a micro–computed tomographic scanner at a voxel size of 19.6 μm. The root canal cross sections were recorded as C1, C2, C3, and C4 root canal configurations according to the modified Melton classification. Morphometric parameters, including the major and minor diameters of the root canals, the aspect ratio, the roundness, and the tridimensional configuration (merging, symmetric, and asymmetric), were evaluated. ResultsThe 3-dimensional reconstruction images of the teeth indicated an even distribution within the sample. The analysis of the prevalence of the different cross-sectional configurations of the C-shaped molars revealed that these were predominantly of the C4 and C3 configurations (1 mm from the apex) and the C1 and C2 configurations in the cervical third. According to the morphometric parameters, the C1 and the distal aspect of the C2 configurations exhibited the lowest roundness values and higher values for the area, major diameter, and aspect ratio in the apical third. ConclusionsMandibular molars with C-shaped root canals exhibited similar distributions of symmetric, asymmetric, and merging type canals. The C1 configuration and the distal aspect of the C2 configuration exhibited the highest area values, low roundness values, and large apical diameters.

Nonlinear buckling finite element analysis of stiffened B–Al plates

Nonlinear buckling behavior of stiffened composite B–Al plates was analyzed by means of finite element analysis (FEA) method. In the method, the composite material was taken as B matrix into which Al fibers were embedded in different configurations. The laminated B–Al material in the form of rectangular plates was subjected to lateral compressive loading. It is observed that stiffeners have significant effect on the buckling behavior of plates under compressive loading and for various geometrical configurations. The stiffeners used in the modeling are one-sided and have rectangular cross-sections. It is found that there are physically important loading intervals and the critical buckling modes make transitions back and forth between stable and unstable states. Bifurcation buckling regions resulting from various configurations of fiber orientations and different plate aspect ratios are determined. The whole analysis is performed by using ANSYS finite element computations. Only the buckling patterns of stiffened plate configurations under simply supported boundary conditions are studied. Distributions of compressive stresses (σx) vs in-plane contractions (u) and compressive stresses (σx) vs out-of plane deflections (δ) are obtained. Nonlinear analysis of the C2 fiber configuration yields the safest critical buckling stress amongst C1, C2, C3 and C4 configurations. It is concluded that FEA method for the nonlinear buckling analysis generates accurate results.

Micro-computed tomography evaluation of the removal of calcium hydroxide medicament from C-shaped root canals of mandibular second molars.

To use micro-computed tomography (μ-CT) to evaluate the amount of calcium hydroxide [Ca(OH)2 ] remaining in the C-shaped root canals of mandibular second molars after attempting to remove it with passive ultrasonic and sonic irrigation. Thirty mandibular second molars, 15 in C1 and 15 in C2 configurations as first identified by μ-CT, were divided into three groups (five C1 and five C2 in each group) for the three irrigation methods. All teeth were prepared to ProTaper Universal F2 and filled with Ca(OH)2 paste. The Ca(OH)2 was removed with F2 files and irrigation without agitation or with agitation using either EndoActivator or ultrasonics. μ-CT was used to measure the initial amount of Ca(OH)2 present. After removal of Ca(OH)2, μ-CT imaging was used to assess the percentage of volume of residual Ca(OH)2 in the canal. Data were analysed using one-way anova test. There was no significant difference in the mean volume of the root canal systems after instrumentation amongst the three groups. The three irrigation techniques left 2-17% of Ca(OH)2 in the root canals after removal. The mean volume of the remaining Ca(OH)2 was higher in the group without agitation than in the groups with sonic or ultrasonic agitation (P<0.05). In the apical third, 68% of the canal space remained occupied by Ca(OH)2 when no agitation was used, whereas 28% and 31% remained filled by Ca(OH)2 in the EndoActivator and ultrasonic groups, respectively. There was no significant difference in the amount of residual Ca(OH)2 between the EndoActivator and ultrasonic groups. The proportion of remaining Ca(OH)2 in the apical canals was higher than in the middle and coronal canals in all groups (P<0.05). A considerable proportion of the apical canal space remained filled with Ca(OH)2 in the C-shaped root canals after instrumentation and conventional needle irrigation. Although combining rotary instrumentation and irrigation with sonic or ultrasonic agitation reduced the amount of residual Ca(OH)2 in the C-shaped root canals, the large amount of calcium hydroxide in the critical apical area remains a concern. Alternative strategies should be considered in medication of the apical canal in C-shaped teeth.

Structural requirement and stereospecificity of tetrahydroquinolines as potent ecdysone agonists

Tetrahydroquinoline (THQ)-type compounds are a class of potential larvicides against mosquitoes. The structure–activity relationships (SAR) of these compounds were previously investigated (Smith et al., Bioorg. Med. Chem. Lett.2003, 13, 1943–1946), and one of cis-forms (with respect to the configurations of 2-methyl and 4-anilino substitutions on the THQ basic structure) was stereoselectively synthesized. However, the absolute configurations of C2 and C4 were not determined. In this study, four THQ-type compounds with cis configurations were synthesized, and two were submitted for X-ray crystal structure analysis. This analysis demonstrated that two enantiomers are packed into the crystal form. We synthesized the cis-form of the fluorinated THQ compound, according to the published method, and the enantiomers were separated via chiral HPLC. The absolute configurations of the enantiomers were determined by X-ray crystallography. Each of the enantiomers was tested for activity against mosquito larvae in vivo and competitive binding to the ecdysone receptor in vitro. Compared to the (2S,4R) enantiomer, the (2R,4S) enantiomer showed 55 times higher activity in the mosquito larvicidal assay, and 36 times higher activity in the competitive receptor binding assay.