Use of the liquid-liquid interface for generating ultrathin nanocrystalline films of metals, chalcogenides, and oxides

The air-water interface has traditionally been employed to prepare particle assemblies and films of metals and semiconductors. The interface between water and an organic liquid, however, has not been investigated sufficiently for possible use in preparing nanocrystals and thin films of materials. In this article, we demonstrate the use of the liquid-liquid interface as a medium for preparing ultrathin films of metals, chalcogenides and oxides. The method involves the reaction at the interface between a metal-organic compound in the organic layer and an appropriate reagent for reduction, sulfidation, etc. in the aqueous layer. Some of the materials discussed are nanocrystalline films of gold, CuS, CuSe, CuO, and Cu(OH)2 formed at the liquid-liquid interface. The results reported in this article should demonstrate the versatility and potential of the liquid-liquid interface for preparing nanomaterials and ultrathin films and encourage further research in this area.     

Interfacial stabilization of organic-aqueous two-phase microflows for a miniaturized DNA extraction module

Organic-aqueous liquid (phenol) extraction is one of many standard techniques to efficiently purify DNA directly from cells. The cell components naturally distribute themselves into the two fluid phases in order to minimize interaction energies of the biological components with the surrounding solvents. The membrane components and protein partition to the interface between the organic and aqueous phases while the DNA stays in the aqueous phase. The aqueous phase is then removed with a purified DNA sample. This work studies the first steps towards miniaturizing this liquid extraction technique in a microfluidic device. The first step is to understand how the two liquid phases behave in microchannels. Due to the interfacial tension between the two liquid phases, novel approaches must be examined in order to obtain interfacial stability under flow conditions. The stability of the organic-aqueous interface is improved by reducing the interfacial tension between the two phases by incorporating a surfactant into the aqueous phase. The variation of the interfacial tension as a function of surfactant concentration is also quantified in this work. This has led to the ability to create stable stratified microflows in both a dual inlet and three inlet microfluidic systems. Also, the first step in understanding biological interactions at the organic-aqueous interface is investigated using a fluorescently labeled bovine serum albumin protein.     

Thermodynamics and heat transfer study of a circular tube embedded with novel perforated angular-cut alternate segmental baffles

Journal of Thermal Analysis and Calorimetry - Baffles are used for heat transfer enhancement in heat exchanger tubes. However, they also increase the friction factor in the flow channel....     

Synthesis,molecular docking and dynamics study of novel epoxide derivatives of 1,2,4-trioxanes as antimalarial agents

Structural Chemistry - Malaria infection continues to pose a substantial threat to human health in the twenty-first century. The parasites’ resistance against conventional antimalarial drugs...     

Synthetic collagen heterotrimers: structural mimics of wild-type and mutant collagen type I

Collagen type I is an AAB heterotrimer assembled from two alpha1 chains and one alpha2 chain. Missense mutations in either of these chains that substitute a glycine residue in the ubiquitous X-Y-Gly repeat with a bulky amino acid leads to osteogenesis imperfecta (OI) of varying severity. These mutations have been studied in the past using collagen-like peptide homotrimers as a model system. However, homotrimers, which by definition will contain glycine mutations in all the three chains, do not accurately mimic the mutations in their native form and result in an exaggerated effect on stability and folding. In this article, we report the design of a novel model system based upon collagen-like heterotrimers that can mimic the glycine mutations present in either the alpha1 or alpha2 chains of type I collagen. This design utilizes an electrostatic recognition motif in three chains that can force the interaction of any three peptides, including AAA (all same), AAB (two same and one different), or ABC (all different) triple helices. Therefore, the component peptides can be designed in such a way that glycine mutations are present in zero, one, two, or all three chains of the triple helix. With this design, we for the first time report collagen mutants containing one or two glycine substitutions with structures relevant to native forms of OI. Furthermore, we demonstrate the difference in thermal stability and refolding half-life times between triple helices that vary only in the frequency of glycine mutations at a particular position.     

Triethylammonium acetate (TEAA): a recyclable inexpensive ionic liquid promotes the chemoselective aza- and thia-Michael reactions

A new, highly efficient, inexpensive, recyclable, mild, convenient, and green protocol for chemoselective aza/thia-Michael addition reactions of amines/thiols to α,β-unsaturated compounds using triethylammonium acetate (TEAA) ionic liquid was developed. The catalyst can be recycled ten times and obviate the need for toxic and expensive catalysts. Correspondence: Akhilesh K. Verma, Green Organic Chemistry Research Laboratory, Dr. B.R. Ambedkar Center for Biomedical Research, University of Delhi, Delhi 110007, India.     

Oxidative Intramolecular 1,2-Amino-Oxygenation of Alkynes under AuI/AuIII Catalysis: Discovery of a Pyridinium-Oxazole Dyad as an Ionic Fluorophore

Oxidative intramolecular 1,2-amino-oxygenation reactions, combining gold(I)/gold(III) catalysis, is reported. The reaction provides efficient access to a structurally unique ionic pyridinium-oxazole dyad with tunable emission wavelengths. The application of these fluorophores as potential biomarkers has been investigated.     

The case for the cosmological constant

I present a short overview of current observational results and theoretical models for a cosmological constant. The main motivation for invoking a small cosmological constant (or A-term) at the present epoch has to do with observations of high redshift Type Ia supernovae which suggest an accelerating universe. A flat accelerating universe is strongly favoured by combining supernovae observations with observations of CMB anisotropies on degree scales which give the ‘best-fit’ values Θ_A ⋍ 0.7 and Θ _m ⋍ 0.3. A time dependent cosmological A-term can be generated by scalar field models with exponential and power law potentials. Some of these models can alleviate the ‘fine tuning’ problem which faces the cosmological constant.     

Thermodynamics of Formation of Binary and Ternary Nitrides in the System Ce/Mn/N

Drop solution calorimetry in high‐temperature oxide melts has been shown to be very useful to study the energetics of nitride formation. This methodology was used to determine the enthalpies of formation from the elements of binary and ternary nitrides in the Ce/Mn/N system. The resulting values in kJ mol^–1 are; δH (CeN) = –340.19 ± 6.80, δ(H (Mn₃N_1.95, η‐Mn₃N₂ type) = –192.68 ± 7.57, δH (Mn₆N_5.40, θ‐Mn₆N₅ type) = –430.80 ± 10.93 and δH (Ce₂MnN₃) = –928.18 ± 9.46. The results show the role of inductive effects in Ce₂MnN₃ leading to a higher energetic stability compared to binary components.