One-pot synthesis of 6-aryl-2,3-dihydro-4H-pyran-4-ones by cyclocondensation of 1,3-diketone dianions with aldehydes

6-Aryl-2,3-dihydro-4H-pyran-4-ones were prepared in one step by cyclocondensation of 1,3-diketone dianions with aldehydes. The use of hydrochloric acid (10%) for the aqueous work-up proved to be very important.     

AC conductivity evolution in bulk and grain boundary response of sodium tungstate Na<Subscript>2</Subscript>WO<Subscript>4</Subscript>

The Na₂WO₄ compound has been obtained by the conventional solid-state reaction and characterized by X -ay powder diffraction. The title material crystallizes in the cubic system with Fd-3m space group. The electrical properties of the compound have been studied using complex impedance spectroscopy in the frequency range 200 Hz–5 MHz and temperature range 586–679 K. Two semicircles are observed in impedance plot indicating the presence of two relaxation processes in the compound associated with the grain and grain boundary. The relaxation behavior of the grain and grain boundary of the Na₂WO₄ are also obtained from the analyzed electrical modulus data. AC conductivity measured follows the power-law dependence σ_AC～ω^s typical for charge transport. Therefore, the experimental results are analyzed with various theoretical models. Temperature dependence of the power law exponent s strongly suggests that tunneling of large polarons is the dominant transport process. The mechanism of conduction is probably due from the displacements of the Na+ ion in the tunnel-type cavities along [111] direction.     

NIR vibrational overtone spectra of toluidines-evidence for steric and electronic effects in o-toluidine

The near infrared vibrational overtone absorption spectra of liquid phase toluidines are reported. The analysis of the observed CH and NH local mode mechanical frequency values shows that there exists steric and electronic interaction between the amino and methyl groups in o-toluidine. This observation supports the conclusions drawn from structural studies of toluidines by resonance two-photon ionization (R2PI) spectroscopy, ab initio calculations and laser induced fluorescence studies reported earlier.     

Vibrational overtone spectra of chloroanilines--evidence for intramolecular hydrogen bonding in o-chloroaniline

The near infrared vibrational overtone absorption spectra of liquid phase aniline and chloroanilines are reported. The analysis of the observed CH and NH local mode mechanical frequency values shows that intramolecular hydrogen bonding occurs between NH2 group and chlorine atom in o-chloroaniline. This observation supports the conclusion drawn from microwave spectroscopic studies reported earlier.     

Calibrating a J2 plasticity material model using a 2D inverse finite element procedure

Material models are the key ingredients to accurately capture the global mechanical response of structural systems. The use of finite element analysis has proven to be effective in simulating nonlinear engineering applications. However, the choice of the appropriate material model plays a big role in the value of the numerical predictions. Such models are not expected to exactly reproduce global experimental response in all cases. Alternatively, the measured global response at specific domain or surface points can be used to guide the nonlinear analysis to successively extract a representative material model. By selecting an initial set of stress–strain data points, the load–displacement response at the monitoring points is computed in a forward incremental analysis without iterations. This analysis retains the stresses at the integration points. The corresponding strains are not accurate since the computed displacements are not anticipated to match the measured displacements at the monitoring points. Therefore, a corrective incremental displacement analysis is performed at the same load steps to adjust for displacements and strains everywhere by matching the measured displacements at the monitoring points. The stress–strain vectors at the most highly stressed integration point are found to establish an improved material model. This model is used within a multi-pass incremental nonlinear finite element analysis until the discrepancy between the measured and the predicted structural response at the monitoring points vanishes. The J2 flow theory of plasticity is used as a constitutive framework to build the tangent elastic–plastic matrices. The applicability of the proposed approach is demonstrated by solving 2D inverse continuum problems. The comparisons presented support the effectiveness of the proposed approach in accurately calibrating the J2 plasticity material model for such problems.     

Warm tachyon inflation and swampland criteria

In this study, the scenario of a two-component warm tachyon inflation is considered, where the tachyon field plays the role of the inflaton by driving the inflation. During inflation, the tachyon scalar field interacts with the other component of the Universe, which is assumed to be photon gas, i.e., radiation. The interacting term contains a dissipation coefficient, and the study is modeled based on two different and familiar choices of the coefficient that were studied in the literature. By employing the latest observational data, the acceptable ranges for the free parameters of the model are obtained. For any choice within the estimated ranges, there is an acceptable concordance between the theoretical predictions and observations. Although the model is established based on several assumptions, it is crucial to verify their validity for the obtained values of the free parameters of the model. It is found that the model is not self-consistent for all values of the ranges, and for some cases, the assumptions are violated. Therefore, to achieve both self-consistency and agreement with the data, the parameters of the model must be constrained. Subsequently, we consider the recently proposed swampland conjecture, which imposes two conditions on the inflationary models. These criteria rule out some inflationary models; however, warm inflation is among those that successfully satisfy the swampland criteria. We conduct a precise investigation, which indicates that the proposed warm tachyon inflation cannot satisfy the swampland criteria for some cases. In fact, for the first case of the dissipation coefficient, in which, there is dependency only on the scalar field, the model agrees with observational data. However, it is in direct tension with the swampland criteria. Nevertheless, for the second case, wherein the dissipation coefficient has a dependency on both the scalar field and temperature, the model exhibits acceptable agreement with observational data, and suitably satisfies the swampland criteria.     

Radiosynthesis and Biodistribution of <Superscript>99m</Superscript>Tc-Metronidazole as an <Emphasis Type="Italic">Escherichia coli</Emphasis> Infection Imaging Radiopharmaceutical

Bacterial infection poses life-threatening challenge to humanity and stimulates to the researchers for developing better diagnostic and therapeutic agents complying with existing theranostic techniques. Nuclear medicine technique helps to visualize hard-to-diagnose deep-seated bacterial infections using radionuclide-labeled tracer agents. Metronidazole is an antiprotozoal antibiotic that serves as a preeminent anaerobic chemotherapeutic agent. The aim of this study was to develop technetium-99m-labeled metronidazole radiotracer for the detection of deep-seated bacterial infections. Radiosynthesis of ^99mTc-metronidazole was carried by reacting reduced technetium-99m and metronidazole at neutral pH for 30 min. The stannous chloride dihydrate was used as the reducing agent. At optimum radiolabeling conditions, ~ 94% radiochemical was obtained. Quality control analysis was carried out with a chromatographic paper and instant thin-layer chromatographic analysis. The biodistribution study of radiochemical was performed using Escherichia coli bacterial infection-induced rat model. The scintigraphic study was performed using E. coli bacterial infection-induced rabbit model. The results showed promising accumulation at the site of infection and its rapid clearance from the body. The tracer showed target-to-non-target ratio 5.57 ± 0.04 at 1 h post-injection. The results showed that ^99mTc-MNZ has promising potential to accumulate at E. coli bacterial infection that can be used for E. coli infection imaging.     

Advancements in biocatalysis: From computational to metabolic engineering

Through several waves of technological research and un-matched innovation strategies, bio-catalysis has been widely used at the industrial level. Because of the value of enzymes, methods for producing value-added compounds and industrially-relevant fine chemicals through biological methods have been developed. A broad spectrum of numerous biochemical pathways is catalyzed by enzymes, including enzymes that have not been identified. However, low catalytic efficacy, low stability, inhibition by non-cognate substrates, and intolerance to the harsh reaction conditions required for some chemical processes are considered as major limitations in applied bio-catalysis. Thus, the development of green catalysts with multi-catalytic features along with higher efficacy and induced stability are important for bio-catalysis. Implementation of computational science with metabolic engineering, synthetic biology, and machine learning routes offers novel alternatives for engineering novel catalysts. Here, we describe the role of synthetic biology and metabolic engineering in catalysis. Machine learning algorithms for catalysis and the choice of an algorithm for predicting protein-ligand interactions are discussed. The importance of molecular docking in predicting binding and catalytic functions is reviewed. Finally, we describe future challenges and perspectives.     

An MCl inf4 p2− moiety (M = copper,zinc, cadmium and mercury) stabilized by bis(ethylenediamine)copper(II) cation

Summary New ionic bimetallic complexes of the type [Cu(en)₂]-[MCl₄], where M = Cu^II, Zn^II, Cd^II and Hg^II, were prepared by reacting bis(ethylenediamine)copper(II) dichloride (1 mol) with copper, zinc, cadmium and mercury dichlorides (1 mol) in absolute alcohol. Elemental analyses, conductivity and magnetic susceptibility measurements, and spectroscopic data (such as i.r., u.v.-vis. and e.p.r.) confirm that the compounds are 22 electrolytes in MeOH and that the copper(II) ion is paramagnetic, maintaining its square-planar geometry, while metal ions in the anionic moiety of the complexes achieve their usual tetrahedral environment. An augmented magnetic moment has been observed in the [Cu(en)₂] [CuCl₄] complex, which is attributed to the ferromagnetic effect and TIP.Author to whom all correspondence should be directed.