1-Acetyl-3-[benzoyl(4-methoxy­phenyl)­methyl­ene]-2,3-di­hydro-1H-indol-2-one

In the title compound, C₂₅H₁₉NO₄, the indole moiety is not completely planar, the heterocyclic ring being distorted very slightly towards a half-chair conformation. The benzoyl and 4-­methoxy­phenyl substituents are individually almost planar and are in a bisecting and nearly perpendicular configuration, respectively, with respect to the plane of the indole moiety. The molecular and packing structures in the crystal are stabilized by intramolecular and intermolecular C—H⋯O interactions.     

Application of the DLCA model to “natural” gels: The allophanic soils

Volcanic soil comprises weathering products such as allophane, originating from a leaching process of volcanic ashes and glasses. These soils are interesting in terms of mitigation of the greenhouse effect (C sequestration), because they are known for accumulating more C than non-volcanic soils. Allophanes are natural amorphous silicates and have physical features very close to those of synthetic gels. Knowledge of the allophanic soil structure is required to understand the sequestration mechanism. In this paper, nitrogen adsorption-desorption experiments, measured on allophanic soil samples, show that the hydraulic diameter (Dh) is shifted towards smaller size while the pore volume (Vp) and specific surface area (S) increase, when the allophane content of the soil increases. We introduce a numerical model to simulate the structure of this “natural gel”. The algorithm is based on Diffusion-Limited Cluster-Cluster Aggregation in which larger particles hinder the DLCA. As a function of the relative content of allophane (gel) and larger particles, the textural properties (Vp, S, Dh) of the different simulated structure are calculated using a simple triangulation method. Numerical results are in good agreement with experimental data and from the simulated data, we can derive the permeability evolution as a function of the allophane content. We show that at the scale of the allophanic aggregates the calculated permeability is low and could be an important parameter to explain the larger C content of allophanic soils. Because of the low allophanic aggregate permeability, the fluid exchanges and chemical reactions are slow. This gel-allophane analogy and DLCA model allow proposing a different approach to describe the properties of these peculiar soils.     

Green,One-Pot,Multicomponent Synthesis of Fused-Ring 2-Aminothiazoles

A facile, green, and efficient Fe(III) chloride, one-pot, multicomponent reaction (MCR) for synthesis of 2-aminothiazole-based compounds is reported. Considering the medicinal importance of fused ring 2-aminothiazoles, this process provides an easy route to the synthesis of this class of compound. Detailed mechanism of the reaction has been discussed.     

Novel chiral pyrrolidinone scaffolds derived from threonine with antibacterial activity

The synthesis of chiral pyrrolidinones derived from threonine, making use of a Dieckmann or aldol ring closure, is described. Compounds were found to exhibit antibacterial activity, for which the correlation with various physiochemical parameters was examined. This chiral tetramate scaffold may provide a useful template for fragment-based drug design providing rapid access to novel antibacterial compound libraries.     

On some representations of sample variance

The usual formula for variance depending on rounding off the sample mean lacks precision, especially when computer programs are used for the calculation. The well-known simplification of the total sums of squares does not always give benefit. Since the variance of two observations is easily calculated without the use of a sample mean, and the variance of a sample of n observations is the average of the variances of observations based on n(n-1)/2 distinct subsets of units of size 2 from the sample, it is argued that this sense of pairing may result in precision. Some other forms of variance are presented which provide some insight into it. The contribution of a new observation of variance is highlighted, which is important in sequential sampling. Notions are illustrated with examples.     

Study of the vibrational characteristics of the homonuclear diatomic nuclear schrödinger equation with a numerov method using a number of empirical potential functions

Many empirical potential energy functions have been modeled to represent the potential energy function of a diatomic molecule along whole range of internuclear distance coordinate, whereby one can determine certain molecular constants. Here we employ various potential functions such as Morse, Rydberg, Varshni(II), Varshni(III), Varshni(VI), Pöschl-Teller, Hulburt-Hirschfelder, Lippincott, Frost-Musulin, Linnet, and Rosen-Morse, and the Numerov method to solve the nuclear Schrödinger equation for F2, as an example of a homonuclear diatomic molecule. Herewith, the vibrational and vibration-rotation energy levels are obtained and excellent accuracy is achieved. The potential of employing the Numerov method in engineering physics computations is emphasized.     

Phase Noise Quenching in a Four-Level Laser

In the presence of usual transmission losses, it is shown that phase noise in a four-level laser can be reduced below the Schawlow-Townes limit when lasing levels are coupled to a squeezed vacuum reservoir. The squeezed vacuum coupled to the lasing mode modifies the phase diffusion rate and dominates the contribution from transmission losses. It is predicted to obtain phase stability in the system and phase noise vanishes for larger squeezing. Gain of the laser remains positive under these conditions.     

The 143 and 300 K polymorphs of hexa­methyl­enetetraminium 2,4-di­nitro­phenolate monohydrate

The title compound, 3,5,7-tri­aza-1-azoniatri­cyclo­[3.3.1.1^3,7]­decane 2,4-di­nitro­phenolate monohydrate, C₆H₁₃N₄⁺·C₆H₃N₂O₅⁻·H₂O, the 1:1 hydrate adduct of hexa­methyl­enetetr­amine (HMT) and 2,4-di­nitro­phenol, undergoes a temperature phase transition. In the room-temperature phase, the adduct crystallizes in the monoclinic P2₁/m space group, whereas in the low-temperature phase, the adduct crystallizes in the triclinic P space group. This phase transition is reversible, with the transition temperature at 273 K, and the phase transition is governed by hydrogen bonds and weak interactions. In both these temperature-dependent polymorphs, the crystal structure is alternately layered with sheets of hexa­methyl­enetetr­amine and sheets of di­nitro­phenol stacked along the c axis. The hexa­methyl­enetetr­amine and di­nitro­phenol moieties are linked by intermolecular hydrogen bonds. The water mol­ecule in the adduct plays an important role, forming O—H⋯O hydrogen bonds which, together with C—H⋯O hydrogen bonds, bridge the adducts into molecular ribbons. Extra hydrogen bonds and weak interactions exist for the low-temperature polymorph and these interconnect the molecular ribbons into a three-dimensional packing structure. Also in these two temperature-dependent polymorphs, di­nitro­phenol acts as a hydrogen-bond acceptor and HMT acts as a hydrogen-bond donor.