A colorimetric method of estimating hydrolyzable chlorine in lindane (γ-hexachlorocyclohexane)

A rapid colorimetric method of determining hydrolyzable chlorine content of lindane has been developed. The region of maximum absorption, Beer's law is obeyed between 80 and 320 μg/ml of solution. The sensitivity of this method is compared with Volhard's titration method and is found to be superior. With the above method, the insecticide can be estimated in pure form with an accuracy of ±0.8 to 1.9%.     

On some properties of sets with positive measures

Summary Steinhaus (2) gave eleven theorems on distance sets of sets with positive measure. The author of this paper has shown here that all these theorems hold good if ratio sets are considered for sets with positive measure instead of their distance sets.

---

Riassunto Steinhaus (2) dà vari teoremi sugli insiemi delle distanze relative agli insiemi con misura positiva. In questa Nota l'autore dimostra che tutti i sudetti teoremi valgono ancora se per gli insiemi con misura positiva si considerano, invece degli insiemi delle distanze, gli insemi dei rapporti.

     

Multivariate interval interpolation

The problem of multivariate interval interpolation has been defined. Two algorithms for the computation of a multivariate interval interpolating polynomial have been proposed. The algorithms have been compared among themselves with respect to the number of interval arithmetic operations required to compute them and the width of the computed intervals. One of the algorithms is recommended for fast computation and the other for obtaining the most accurate results.     

Study of tau decays to six pions and a neutrino

The tau decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are B(tau(-)-->2pi(-)pi(+)3pi(0)nu(tau)) = (2.2+/-0.3+/-0.4)x10(-4) and B(tau(-)-->3pi(-)2pi(+)pi(0)nu(tau)) = (1.7+/-0.2+/-0.2)x10(-4). A search for substructure in these decays shows that they are saturated by intermediate states with eta or omega mesons. We present the first observation of the decay tau(-)-->2pi(-)pi(+)omega(nu)tau and the branching fraction is measured to be (1.2+/-0.2+/-0.1)x10(-4). The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions.     

Study of steady state and time resolved photoluminescence of thiol capped CdS nanocrystalline powders dispersed in N,N-dimethylformamide

The microwave (MW) assisted synthesis of thiol capped cadmium sulfide (CdS) nanocrystallites/quantum dots (QDs) was performed through the reaction of cadmium acetate with thiourea in N,N-dimethylformamide (DMF) by keeping the MW irradiation time fixed (40 s) in the presence of a thiol containing capping agent. Three capping agents, namely, benzyl mercaptan (BM), 1-butanethiol (BT) and 2-mercaptoethanol (ME) were used. The concentration of the precursors was varied to check the change in the average size of the thiol capped CdS nanocrystals formed. The nanocrystallites were characterized by usual procedure. The UV-vis absorption spectra and the photoluminescence (PL) spectra of the CdS nanocrystalline powders dispersed in DMF were studied. It was observed that with increase in concentration of the capping agent (BM), there is a shift in the nature of emission (PL) from trap associated PL to the band edge luminescence in the case of BM capped CdS nanocrystalline powders dispersed in DMF possibly due to better surface passivation. The relative PL quantum yield of the thiol capped CdS nanocrystalline powders dispersed in DMF was calculated under various experimental conditions. Time-correlated single-photon counting experiments were performed to study the time-resolved photoluminescence of the CdS nanocrystalline powders dispersed in DMF. The observed emission decay profiles have been simulated using the multiexponential model. The emission decay profiles for thiol capped CdS nanocrystalline powders dispersed in DMF depend on the nature of the capping agents (thiols) used to passivate the CdS nanocrystallites. The time resolved PL studies show that the average values of PL lifetime are related to the size and size distribution of the prepared thiol capped CdS nanocrystallites.     

Measurement of radon concentrations and their annual effective doses in soils and rocks of Jaintiapur and its adjacent areas,Sylhet, North-east Bangladesh

Journal of Radioanalytical and Nuclear Chemistry - The study investigates the measurement of radon concentration in soils and rocks as a natural tracer for exploring uranium mineralization, first...     

Dielectric relaxation spectroscopy and electro-optical studies of a new,partially fluorinated orthoconic antiferroelectric liquid crystal material exhibiting V-shaped switching

In this paper we report the results from detailed electro-optical and dielectric studies in various antiferroelectric and ferroelectric phases of an orthoconic antiferroelectric liquid crystal (OAFLC) material . The material possesses high tilt and high spontaneous polarisation. Such an OAFLC, because of its high tilt, provides an excellent dark state. The material exhibits V-shaped switching in the SmC* phase. Dielectric studies reveal the existence of another phase during heating in the range between 78.6 and 92°C which did not appear in the DSC curve and in polarising microscopy. This phase has been identified as the SmC_γ* phase and is extremely sensitive with respect to the cell conditions, aligning material, purity, etc. Three dielectric modes have been assigned in the above-mentioned temperature range and their origins are discussed.     

Analysis of pseudo jahn–teller distortion based on natural bond orbital theory: Case study for silicene

Ground state (GS) instability of nondegenerate molecules in high symmetric structures is understood through Pseudo Jahn–Teller mixing of the electronic states through the vibronic coupling. The general approach involves setting up of a Pseudo Jahn–Teller (PJT) problem wherein one or more symmetry allowed excited states couple to the GS to create vibrational instability along a normal mode. This faces two major complications namely (1) estimating the adiabatic potential energy surfaces for the excited states which are often difficult to describe in case the excited states have charge-transfer or multi-excitonic (ME) character and (2) finding out how many such excited states (all satisfying the symmetry requirements for vibronic coupling) of increasing energies need to be coupled with the GS for a particular PJT problem. An analogous alternative approach presented here for the well-known case of symmetry breaking of planar (D_6h) hexasilabenzene (Si₆H₆) to the buckled (D_3d) structure involves identifying the second-order donor–acceptor, hyperconjugative interactions (E²_{i → j}) that stabilize the distorted structure. Following the recent work of Nori-Shargh and Weinhold, one observes that the orbitals involved in the vibronic coupling between the S₀/S_n states and those for the donor (filled)–acceptor (empty) interactions are identical. In fact, deletion of any particular pair of E²_{i → j} interaction creates vibrational instability in the buckled structure and as a corollary, deleting it for the planar structure removes its instability. The one-to-one correlation between the natural bond orbital theory and PJT theory assists in an intuitive identification of the relevant (few) excited states from a manifold of computed ones that cause symmetry breaking by vibronic coupling. © 2019 Wiley Periodicals, Inc.     

Nonisothermal crystallization kinetics and microstructure evolution of calcium lanthanum metaborate glass

This paper reports results on the crystallization kinetics of 35.5CaO–7.25La₂O₃–57.25B₂O₃ glass under nonisothermal conditions based on the studies carried out from the differential thermal analysis upon using various well-established models. The crystalline phases formed during the optimized ceramization process have been confirmed from the X-ray diffraction. The activation energies of the first (formation of CaLaB₇O₁₃) and second (formation of LaBO₃) crystallization events have been estimated using the conventional methods of Kissinger, Augis–Bennett, Ozawa, and Matusita, and the results are found to be in good agreement with each other. The Avrami exponents that are determined by these models for the crystallization of CaLaB₇O₁₃ and LaBO₃ are found to be in the range of (1.81–2.35) and (4.03–4.65), respectively. This indicates that the formation of CaLaB₇O₁₃ is dominated by a surface crystallization, whereas LaBO₃ is formed by three-dimensional bulk crystallization with an increased rate of nucleation. This observation is further validated by microstructural investigation, which shows the formation of CaLaB₇O₁₃ phase as a surface layer and a bulk crystallization of LaBO₃ in optimally ceramized samples.