Development of a method for recovery of 233U from thorium oxalate cake in reconversion step of reprocessing of irradiated thorium rods

A method is developed for the selective leaching of ²³³U from a thorium oxalate cake. The leaching capacity of ammonium carbonate and nitric acid have been investigated, showing that (NH₄)₂CO₃ leads to higher recovery. The maximum leaching efficiency is obtained using 0.5% ammonium carbonate, with a minimal thorium pick-up. A uranium recovery of 94% is obtained after three consecutive contact experiments in carbonate media, with minimal thorium uptake in the leachate. This process was applied to an actual plant stream, allowing the reduction of the ²³³U -activity from 5.64 to 0.3 Ci/g of thorium oxalate cake.     

Galactose-Grafted 2D Nanosheets from the Self-Assembly of Amphiphilic Janus Dendrimers for the Capture and Agglutination of Escherichia coli

High aspect ratio, sugar-decorated 2D nanosheets are ideal candidates for the capture and agglutination of bacteria. Herein, the design and synthesis of two carbohydrate-based Janus amphiphiles that spontaneously self-assemble into high aspect ratio 2D sheets are reported. The unique structural features of the sheets include the extremely high aspect ratio and dense display of galactose on the surface. These structural characteristics allow the sheet to act as a supramolecular 2D platform for the capture and agglutination of E. coli through specific multivalent noncovalent interactions, which significantly reduces the mobility of the bacteria and leads to the inhibition of their proliferation. Our results suggest that the design strategy demonstrated here can be applied as a general approach for the crafting of biomolecule-decorated 2D nanosheets, which can perform as 2D platforms for their interaction with specific targets.     

Indirect electrochemical oxidation of substituted polycyclic aromatic hydrocarbons to corresponding para-quinones with potassium bromide in water–chloroform medium

Indirect electrochemical synthesis of quinone derivatives of a series of substituted anthracene and naphthalene by the electrolysis of aqueous solution of potassium bromide (3.0 M) using Pt anode at constant current density (40 mA/cm²) has been carried out. These reactions resulted in good to excellent yields of the corresponding para-quinones as confirmed by physical and spectral data.     

Shock Processing of Amino Acids Leading to Complex Structures—Implications to the Origin of Life

The building blocks of life, amino acids, are believed to have been synthesized in the extreme conditions that prevail in space, starting from simple molecules containing hydrogen, carbon, oxygen and nitrogen. However, the fate and role of amino acids when they are subjected to similar processes largely remain unexplored. Here we report, for the first time, that shock processed amino acids tend to form complex agglomerate structures. Such structures are formed on timescales of about 2 ms due to impact induced shock heating and subsequent cooling. This discovery suggests that the building blocks of life could have self-assembled not just on Earth but on other planetary bodies as a result of impact events. Our study also provides further experimental evidence for the ‘threads’ observed in meteorites being due to assemblages of (bio)molecules arising from impact-induced shocks.     

Residual Dipolar-Coupling-Based Conformational Comparison of Noncovalent Ubiquitin Homodimer with Covalently Linked Diubiquitin

Although the conformation of the polymer chain of Ubiquitin (Ub) mainly depends on the type of isopeptide linkage connecting two Ub molecules, the non-covalent (noncovalent) interaction between two Ub molecules within the chain could also tune their conformational preference. Here, we studied the conformation of noncovalently formed Ub dimers in solution using residual dipolar couplings (RDCs). Comparing the RDC derived alignment tensor of the noncovalently formed dimer with the two most abundant (K11 and K48) covalent linked Ub dimers revealed that the conformation of K11 linked and noncovalent Ub dimers were similar. Between the various NMR and crystal structures of K11 linked Ub dimers, RDC tensor analysis showed that the structure of K11 linked dimer crystalized at neutral pH is similar to noncovalent dimer. Analogous to the experimental study, the comparison of predicted order matrix of various covalent Ub dimers with that of the experimentally determined order matrix of noncovalent Ub dimer also suggests that the conformation of K11 linked dimers crystalized at neutral pH is similar to the noncovalent dimer.     

Impedance spectroscopic studies of planetary ball-milled lithium titanium phosphate material

The ac electrical conductivity properties of LiTi₂(PO₄)₃ (LTP) polycrystalline material in two different crystallite sizes are compared. Micrometer sized LTP is prepared by conventional solid-state reaction. LTP crystallites of 71 nm size are prepared by solid-state reaction of 40 h planetary milled stoichiometric mixture. The XRD and SEM are used as characterization techniques. Electrical properties are studied using impedance spectroscopic technique. Ball-milled LTP shows one order increase in grain-interior conduction compared to microcrystalline LTP at 388 K. The increase in conduction results from decreased crystallite size.     

Photophysical investigation of 3-substituted 4-alkyl and/or 7-acetoxy coumarin derivatives—A study of the effect of substituents on fluorescence

In the present work an array of novel substituted 2H-chromen-2-one (coumarin) derivatives has been subjected to photophysical analysis. Though the influence of the electron-donating groups such as amino, substituted amino, hydroxyl, alkoxy groups, etc. at position 7 of the coumarin ring system has been extensively studied, the luminescent properties of the coumarin moieties with an acetoxy substituent have not been explored. Herein it is attempted to study the variation of fluorescence behavior of substituted coumarin derivatives with change of nature and position of the substituents on the 2H-chromen-2-one skeleton. Effect of a methyl substituent at position 4 which imposes abnormal photophysical behavior to the chromenone unit has also been briefly described.     

Experimental investigation on the flow instability behavior of a multi-channel boiling natural circulation loop at low-pressures

Natural circulation as a mode of heat removal is being considered as a prominent passive feature in the innovative nuclear reactor designs, particularly in boiling-water-reactors, due to its simplicity and economy. However, boiling natural circulation system poses many challenges to designer due to occurrence of various kinds of instabilities such as excursive instability, density wave oscillations, flow pattern transition instability, geysering and metastable states in parallel channels. This problem assumes greater significance particularly at low-pressures i.e. during startup, where there is great difference in the properties of two phases. In light of this, a parallel channel loop has been designed and installed that has a geometrical resemblance to the pressure-tube-type boiling-water-reactor, to investigate into the behavior of boiling natural circulation. The loop comprises of four identical parallel channels connected between two common plenums i.e. steam drum and header. The recirculation path is provided by a single downcomer connected between steam drum and header. Experiments have been conducted over a wide range of power and pressures (1–10 bar). Two distinct unstable zones are observed with respect to power i.e. corresponding to low power (Type-I) and high power (Type-II) with a stable zone at intermediate powers. The nature of oscillations in terms of their amplitude and frequency and their evolution for Type-I and Type-II instabilities are studied with respect to the effect of heater power and pressure. This paper discusses the evolution of unstable and stable behavior along with the nature of flow oscillation in the channels and the effect of pressure on it.     

An improved edge bound on the interval number of a graph

The upper bound on the interval number of a graph in terms of its number of edges is improved. Also, the interval number of graphs in hereditary classes is bounded in terms of the vertex degrees.