Determination of rare earths in low grade uranium ores and SRM-rock by instrumental neutron activation analysis

An instrumental neutron activation analysis technique has been developed for simultaneous determination of 10 REE in low grade U/Zr ores and other geological materials. The samples were irradiated with reactor neutrons for 2 min to 8 hrs followed by a cooling of 30 min to 3 weeks. The γ-ray activity was measured with a semi-planar Ge(Li) detector. A precision of 5% has been obtained by the repeated analysis of NBS-SRM. The technique is relatively simple and adaptable on the routine basis.     

The influence of high uniaxial stress on the ΓI,C conduction band effective mass of gallium arsenide

From a study of the Zeeman splitting of the shallow donor states, the variation of the effective mass in the Γ_IC conduction band minimum of gallium arsenide has been measured as a function of applied uniaxial stress. The effective mass is found to be proportional to the stress, the percentage increase being (0.23 ± 0.06), (0.115 ± 0.015) and (0.075 ± 0.015) kbar^?1 for 〈100〉, 〈110〉 and 〈111〉 stress respectively. The precision inherent in the far-infrared technique employed is greater than that of previous experimental methods.     

Calculation of centrifugal distortion constants for diatomic molecules from RKR potentials

Expressions are developed for computing the centrifugal distortion constants D_v, H_v, and L_v directly from the Rydberg-Klein-Rees rotationless potential of a diatomic molecule. These expressions involve summations over integrals of the wavefunctions of all neighboring vibrational levels. Application is made to the X¹Σ⁺ state of CO and the $\text{X}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ state of O₂. In these applications, we have neglected the contributions of the continuum wavefunctions. For higher vibrational levels, particularly those near the dissociation limit, this approximation would be expected to fail. For the lowest vibrational levels of an electronic state, this method gives the same results for D_v, H_v, and L_v as the Dunham relations. However, for intermediate vibrational levels the present method is an improvement since expressions for only a few coefficients of the Dunham expansion are available. The use of D_v and H_v values calculated from Rydberg-Klein-Rees potentials in an iterative improvement of the reduction of spectroscopic data is described.     

Resolution of the discrepancies concerning the optical and microwave values for B0 and D0 of the X 3Σg− state of O2

The discrepancies concerning the optical and microwave values of B₀ and D₀ for the X${}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ state of O₂ have been removed by a nonlinear least-squares fit to all of the lines of the O₂, $\text{b}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}\text{-X}{}^3\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{?}}$ Red Atmospheric bands recorded by Babcock and Herzberg (Astrophys. J., 108, 167, 1948). The resulting values for B₀″ and D₀″ are in excellent agreement with the Raman and microwave values. Improved values are determined for B₁″, D₁″, γ₁″ (spin-rotation), and ?₁″ (spin-spin). Both γ_v″ and ?_v″ increase in magnitude from v″ = 0 to v″ = 1. Improved Dunham Y_i0 and Y_i1 expansion coefficients are determined for the $\text{b}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ state, from which the Rydberg-Klein-Rees potential is constructed.     

Filter-paper test for microgram detection of aliphatic amines

A new simple, sensitive and selective test for the detection of microgram amounts of aliphatic amines with diphenylcarbazide-soaked Whatman No. 1 filter paper as the detection medium is described. A feature of the study is the observation that the reaction does not take place in solution in the absence of the filter paper.     

Study of excited fragment emission from the electron impact dissociation of volatile mercury(II) halides

Emission resulting, from collisions of 5–200 eV electrons with gaseous H_gX₂, and CH₃H_gX (X = Cl, Br. I) was characterized in the 3800–5600 A region. HgX BX emission dominates and absolute cross section as a function of electron energy were determined. The formation of electronically excited Hg atoms, and the trend of the cross sections with the nature of the halogen atom are discussed in terms of a simple charge transfer model.     

Simple regge pole model for the reactionπ − p →η’n

The most recently measured differential cross-section data forπ ⁻ p → η’n has been fitted by using a simple Regge pole model with phenomenological residue functions. It has also been observed that this inelastic process has the scaling property.     

Synthesis and absolute configuration of (+)-2,3,3-trimethyl-2-hydroxybutanoic acid

The absolute configuration of (+)-2,3,3-trimethyl-2-hydroxybutanoic acid, a key intermediate in the synthesis of the HIV-protease inhibitor 1a (isomer A), has been confirmed as (R) on the basis of X-ray analysis.     

Transfer of radioactivity from soil to vegetation in Rechna Doab, Pakistan

In Rechna Doab, samples of the most common vegetation, perennial grass Desmostachya bipinnata (dab), were collected along with soil samples from 29 sites. Natural radioactivity of 22?Ra, 232Th/22?Ac and ??K was measured by using high purity germanium-based gamma ray spectrometer. Activity concentration levels of 22?Ra, 232Th/22?Ac and ??K in soil were found to be 46.8 ± 6.2 (36.0-57.6), 61.4 ± 5.9 (48.2-73.2) and 644.8 ± 73.9 (537.7-868.4) Bq kg?1 (dry mass), respectively, and those in vegetation were 2.74 ± 1.70 (1.00-6.39), 2.24 ± 0.59 (1.56-2.61) and 172.72±113.37 (53.14-469.24) Bq kg?1 (dry mass), respectively. The measured values of the activity concentration in vegetation are comparable with some other international data. Calculated soil to vegetation transfer factors of 22?Ra, 22?Ac and ??K were 0.06 ± 0.03 (0.02-0.14), 0.04 ± 0.01 (0.03-0.04) and 0.26 ± 0.16 (0.09-0.69). The mean outdoor absorbed dose rate in air for the area under study was determined as 8.22 nGy h?1 and the mean indoor absorbed dose rate in air was 11.52 nGy h?1. The total annual effective dose to the general public from the vegetation was found to be (0.02-0.16) mSv, which is below the recommended limit value of 1 mSv y?1 for the general public. The dab vegetation under study was found to be radiologically safe for the population and environment.     

Highly efficient and high output power of erbium doped fiber laser in a linear cavity configuration

A simple Erbium Doped Fiber Laser (EDFL) in linear cavity configuration is reported. The cavity design is based on an FBG as a back reflector, and a loop back optical circulator with an output coupler as the front reflector. Different coupling ratios of the coupler are tested and 50: 50 provides the highest coupling output power of 22.06 dBm (160.7 mW). The pump power conversion efficiency is about 95% when pumping with two pump lasers at 1460 and 1490 nm with combined pumping power of 545 mW. The laser output has a measured linewidth of 0.0179 nm.