Cyclic ammonium salts of dithiocarbamic acid: stable alternative reagents for the synthesis of S-alkyl carbodithioates from organyl thiocyanates in water

Carbodithioate esters are important functional organosulfur compounds widely used in diverse fields such as pharmaceuticals, agrochemicals and material sciences. Common preparative methods include reaction of alkyl halides, carbon disulfide and bases under both metal-free and metal-catalyzed conditions. However, organyl thiocyanates have not been previously explored, possibly because of their conversion to organyl disulfides under basic conditions. Here, we report an efficient and practical method for the preparation of libraries of carbodithioate esters from organyl thiocyanates by reacting with cyclic amine-based dithiocarbamic acid salts in water. The protocol is found to be applicable in general to various thiocyanates such as benzyl/aroyl methyl/cinnamyl and so on. Other notable features include no by-products such as disulfides, metal- and alkali-free, aqueous conditions, and finally easy and near-quantitative formation of cyclic amine-based dithiocarbamic acid salt as a stable alternative reagent.     

Carbon nanotube reinforced hydroxyapatite composite for orthopedic application: A review

Application of hydroxyapatite (HA) in orthopedic implants suffers from its low fracture toughness and poor wear resistance. Carbon nanotube (CNT), with its high stiffness and mechanical strength, is an attractive reinforcement for HA to surmount these issues. The last 7–8 years have seen a number of studies to explore the efficiency of CNT reinforcement in strengthening HA, in the form of composites and coatings. Impressive improvement in the fracture toughness and wear resistance of HA with CNT reinforcement and beneficial effects on biocompatibility has sparked further research interests, for possible clinical applications. This review article aims to cover a wide span of this exciting and expanding research arena – from detailed technical discussions on HA–CNT system, their processing techniques and the influence of CNT dispersion in the HA matrix. Role of CNT in the improvement of mechanical properties and tribological behavior of the composite has been discussed in light of different processing techniques. Other important issues related to HA–CNT system, e.g., phase transformation and crystallinity of HA and HA–CNT interfacial bonding has been stressed upon. Biocompatibility of HA–CNT composites, which is extremely important for its intended orthopedic application, has been summarized with an overview of the present status. An in-depth analysis of the information presented in this review facilitates a better understanding of the current state of HA–CNT research and allows framing guidelines toward future research direction for its successful clinical application.     

Identification and characterization of metabolic properties of bacterial populations recovered from arsenic contaminated ground water of North East India (Assam)

Diversity of culturable bacterial populations within the Arsenic (As) contaminated groundwater of North Eastern state (Assam) of India is studied. From nine As contaminated samples 89 bacterial strains are isolated. 16S rRNA gene sequence analysis reveals predominance of Brevundimonas (35%) and Acidovorax (23%) along with Acinetobacter (10%), Pseudomonas (9%) and relatively less abundant (<5%) Undibacterium, Herbaspirillum, Rhodococcus, Staphylococcus, Bosea, Bacillus, Ralstonia, Caulobacter and Rhizobiales members. High As(III) resistance (MTC 10–50 mM) is observed for the isolates obtained from As(III) enrichment, particularly for 3 isolates of genus Brevundimonas   (MTC 50 mM). In contrast, high resistance to As(V) (MTC as high as 550 mM) is present as a ubiquitous property, irrespective of isolates' enrichment condition. Bacterial genera affiliated to other groups showed relatively lower degree of As resistance [MTCs of 15–20 mM As(III) and 250–350 mM As(V)]. As(V) reductase activity is detected in strains with high As(V) as well as As(III) resistance. A strong correlation could be established among isolates capable of reductase activity and siderophore production as well as As(III) tolerance. A large number of isolates (nearly 50%) is capable of anaerobic respiration using alternate inorganic electron acceptors [As(V), Se(VI), Fe(III), ₃NO²⁻${{\text{NO}}_3}^{2\mathrm{-}}$, ₄SO²⁻${{\text{SO}}_4}^{2\mathrm{-}}$, S₂O₃²⁻${{\text{S}}_2{\text{O}}_3}^{2\mathrm{-}}$]. Ability to utilize different carbon sources ranging from C2–C6 compounds along with some complex sugars is also observed. Particularly, a number of strains is found to possess ability to grow chemolithotrophically using As(III) as the electron donor. The study reports for the first time the identity and metabolic abilities of bacteria in As contaminated ground water of North East India, useful to elucidate the microbial role in influencing mobilization of As in the region.     

Oviposition Preference and Performance of a Specialist Herbivore Is Modulated by Natural Enemies,Larval Odors,and Immune Status

Journal of Chemical Ecology - Insect herbivores frequently must balance host plant quality and the risk of attack by their natural enemies when making oviposition decisions. Yet, which factor is...     

Stopping power of Mylar for heavy ions up to copper

The stopping powers of Mylar for several heavy ions covering Z=11 to 29 in the energy range 0.3 to 2.3 MeV/n have been measured using the elastic recoil detection technique and twin detector system. The technique provided a unique method to generate a variety of variable energy ion species utilizing a fixed energy 140 MeV Ag¹³⁺ primary beam from the Pelletron accelerator facility at Nuclear Science Center, New Delhi, India. Most of these measurements are new. The experimentally measured stopping power values have been compared with those calculated using LSS theory, Ziegler et al. formulation and Northcliffe and Schilling tabulations. Merits and demerits of these formulations are highlighted. Stopping power calculations using the Hubert et al. formulation have been extended successfully beyond its recommended range of validity, i.e. 2.5–500 MeV/n down to energies as low as 0.5 MeV/n.     

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A₂B₂O₇, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La₂Zr₂O₇ (LZO) and La₂Hf₂O₇ (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu³⁺ ions. Based on our earlier work, LHO-based nanophosphors display higher photo- and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO-based nanophosphors. Moreover, under electronic O²⁻→Zr⁴⁺/Hf⁴⁺ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu³⁺-doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu³⁺ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays.     

Performance Evaluation and Biodegradation Study of Polyvinyl Chloride Films with Castor Oil-based Plasticizer

In the present study, a renewable resource-based plasticizer was synthesized by the lipase-catalyzed esterification reaction of furfuryl alcohol (FA) and castor oil fatty acid (COFA). The resultant ester (FA-COFA ester) was used as secondary plasticizers to the polyvinyl chloride (PVC) films. The PVC films were formulated using the combination of a conventional plasticizer di-butyl phthalate (DBP) and FA-COFA ester as a secondary plasticizer at different concentrations. Films were characterized by X-ray diffraction analysis, scanning electron microscopy, thermal analysis, mechanical performance, and migration stability. A biodegradability study of the PVC films showed increased degradability with increasing concentration of the FA-COFA ester in the PVC film. The study showed that ester of FA and COFA could be a substitute of DBP by as much as 80% of the total plasticizer with improved elongation and tensile properties, and such a kind of sustainable resource-based PVC blend films could be used as a good packaging material with biodegradable property.