Characterisation of fire retardant poly(phenylene ether) high impact polystyrene in the UL-94 test

The distribution of the temperature and the morphology of the charred material formed in the combustion of blends of poly(phenylene ether) (PPE) with high impact polystyrene (HIPS), carried out in the UL94 test, were examined. The effect of the fire retardant triphenyl phosphate is shown to be the decrease of time of burning, of temperature of the specimen and of zone involved in combustion, without apparent modification of the char structure. Hypothesis on gas and condensed phase fire retardant mechanisms are discussed.     

Biofortification—A Frontier Novel Approach to Enrich Micronutrients in Field Crops to Encounter the Nutritional Security

Globally, many developing countries are facing silent epidemics of nutritional deficiencies in human beings and animals. The lack of diversity in diet, i.e., cereal-based crops deficient in mineral nutrients is an additional threat to nutritional quality. The present review accounts for the significance of biofortification as a process to enhance the productivity of crops and also an agricultural solution to address the issues of nutritional security. In this endeavor, different innovative and specific biofortification approaches have been discussed for nutrient enrichment of field crops including cereals, pulses, oilseeds and fodder crops. The agronomic approach increases the micronutrient density in crops with soil and foliar application of fertilizers including amendments. The biofortification through conventional breeding approach includes the selection of efficient genotypes, practicing crossing of plants with desirable nutritional traits without sacrificing agricultural and economic productivity. However, the transgenic/biotechnological approach involves the synthesis of transgenes for micronutrient re-translocation between tissues to enhance their bioavailability. Soil microorganisms enhance nutrient content in the rhizosphere through diverse mechanisms such as synthesis, mobilization, transformations and siderophore production which accumulate more minerals in plants. Different sources of micronutrients viz. mineral solutions, chelates and nanoparticles play a pivotal role in the process of biofortification as it regulates the absorption rates and mechanisms in plants. Apart from the quality parameters, biofortification also improved the crop yield to alleviate hidden hunger thus proving to be a sustainable and cost-effective approach. Thus, this review article conveys a message for researchers about the adequate potential of biofortification to increase crop productivity and nourish the crop with additional nutrient content to provide food security and nutritional quality to humans and livestock.     

Speaker Recognition Using Constrained Convolutional Neural Networks in Emotional Speech

Speaker recognition is an important classification task, which can be solved using several approaches. Although building a speaker recognition model on a closed set of speakers under neutral speaking conditions is a well-researched task and there are solutions that provide excellent performance, the classification accuracy of developed models significantly decreases when applying them to emotional speech or in the presence of interference. Furthermore, deep models may require a large number of parameters, so constrained solutions are desirable in order to implement them on edge devices in the Internet of Things systems for real-time detection. The aim of this paper is to propose a simple and constrained convolutional neural network for speaker recognition tasks and to examine its robustness for recognition in emotional speech conditions. We examine three quantization methods for developing a constrained network: floating-point eight format, ternary scalar quantization, and binary scalar quantization. The results are demonstrated on the recently recorded SEAC dataset.     

Reversible C=C Bond Activation by an Intramolecularly Coordinated Antimony(I) Compound

The reaction of N,C,N-chelated stibinidene ArSb ( 1 ) (Ar=C₆H₃-2,6-(CH=NtBu)₂) with selected N-alkyl/aryl-maleimides RN(C(O)CH)₂ (R=Me, tBu, Ph) gave the addition products with bridged bicyclic [2.2.1] structure containing an antimony atom at the bridgehead position, fused with a 6-membered benzene and a 5-membered N-alkyl/aryl-pyrrolidine ring. These compounds were completely characterized. More importantly, additional studies showed that these reactions are reversible in solution, thereby representing an unprecedented reversible activation of a C=C bond by an antimony(I) compound.     

Weak solutions for steady compressible Navier-Stokes-Fourier system in two space dimensions

We consider steady compressible Navier-Stokes-Fourier system in a bounded two-dimensional domain. We show the existence of a weak solution for arbitrarily large data for the pressure law p(ϱ, ϑ) ∼ ϱ ^γ + ϱϑ if γ > 1 and p(ϱ, ϑ) ∼ ϱ ln ^α (1 + ϱ) + ϱϑ if γ = 1, α > 0, depending on the model for the heat flux.     

Krull’s theory for the double gamma function

The Barnes’ G-function G(x) = 1/Γ₂, satisfies the functional equation logG(x + 1) − logG(x) = logΓ(x). We complement W. Krull’s work in Bemerkungen zur Differenzengleichung g(x + 1) − g(x) = φ(x), Math. Nachrichten 1 (1948), 365-376 with additional results that yield a different characterization of the function G, new expansions and sharp bounds for G on x > 0 in terms of Gamma and Digamma functions, a new expansion for the Gamma function and summation formulae with Polygamma functions.     

Understanding the role of surfactants on the preparation of ZnS nanocrystals

We have synthesized surface modified ZnS nanoparticles of size 2-3 nm using non-ionic surfactant-stabilized reverse emulsions. The non-ionic surfactants in the Span series, i.e. sorbitan monolaurate (Span 20) and sorbitan monooleate (Span 80) of hydrophilic-lipophilic balance (HLB) values of 8.6 and 4.3, respectively, have been used for the stabilization of emulsions. The role of these surfactants in controlling the size and properties of the ZnS nanoparticles has been discussed. The triethylamine (TEA) has been proved to be the effective surface modifying (capping) agent for the preparation of free-standing ZnS nanoparticles. The Span 20 with the higher HLB value of 8.6 has been found to be highly suitable in synthesizing TEA-capped ZnS nanoparticles of smaller size and higher photophysical characteristics compared to that of the Span 80 of lower HLB value of 4.3. A mechanism for the formation of TEA-capped ZnS nanoparticles from the surfactant-stabilized reverse emulsions has been proposed.     

Recent Advances in Asymmetric Catalysis Using p-Block Elements

The development of new methods for enantioselective reactions that generate stereogenic centres within molecules are a cornerstone of organic synthesis. Typically, metal catalysts bearing chiral ligands as well as chiral organocatalysts have been employed for the enantioselective synthesis of organic compounds. In this review, we highlight the recent advances in main group catalysis for enantioselective reactions using the p-block elements (boron, aluminium, phosphorus, bismuth) as a complementary and sustainable approach to generate chiral molecules. Several of these catalysts benefit in terms of high abundance, low toxicity, high selectivity, and excellent reactivity. This minireview summarises the utilisation of chiral p-block element catalysts for asymmetric reactions to generate value-added compounds.     

Gas-phase and solution conformations of the alpha-L-iduronic acid structural unit of heparin

The IdoA2S structural unit of heparin (subunit G) may oscillate among the three conformations (4C1, 1C4, and 2So). Only the twisted boat conformation allowed the biologically active pentasaccharide unit of heparin (DEFGH) to bind to antithrombin. Our work reports, in detail, the results of systematic large-scale theoretical investigations of the three basic conformations (4C1, 1C4, and 2So) of the IdoA2S structural unit of heparin, its anionic forms, and its sodium salt using the B3LYP/6-311++G(d, p) and B3LYP/6-31+G(d) model chemistries. According to our calculations, the most stable structure of these molecules corresponds to the 2So skew-boat conformation. This form is also the most stable in a water solution. The 2So conformation of neutral molecules is not maintained in the anionic species. With anions, both 1C4 and 4C1 conformations are present. The relative stability of individual species of the substituted iduronic acid affects extra stabilization by means of intramolecular hydrogen bonds. The calculated macroscopic pKa of 1,4-DiOMe IdoA2S are as follows: pKa = 0.25 for the terminal C(2)-OSO3H group, pKa = 3.67 for the terminal C(5)-CO2H group, and pKa = 14.00 for the C(3)-OH hydroxyl group. The computed Gibbs interaction energies, DeltaGdegrees , for the reaction 1,4-DiOMe IdoA2S(2-) + 2Na+ <==> 1,4-DiOMe IdoA2SNa2 (4C1, 1C4, and 2So conformations) are negative and span a rather small energy interval (from -1244 to -1290 kJ mol(-1)).