The determination of potassium and sodium in coal ash

Methods are described for the rapid determination of sodium and potassium in coal ash. The ash is decomposed by a Lawrence Smith ignition: sodium is determined as sodium zinc uranyl acetate (gravimetncally or titrimctrically) on an aliquot of the aqueous extract, and potassium is determined gravunctrically as potassium tetraphenylboron on a second aliquot.Other methods for completing the determination were examined but were less satisfactory. The flame photometer method although less reproducible than other methods is extremely rapid and is probably accurate enough for routine purposes.     

Submicro methods for the analysis of organic compounds: The determination of sulphide and disulphide groups

Summary Bromination methods are described for determination of sulphide and disulphide groups in organic samples weighing onlyca. 50g. Direct titration with visual end-point indication is suitable in some cases, but a back-titration method is of more general application. The accuracy obtained is of the same order as on much larger scales of working.

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Zusammenfassung Bromierungsverfahren zur Bestimmung von Sulfid- und Disulfidgruppen in Einwaagen von nur etwa 50g organischer Substanz wurden beschrieben. In manchen Fällen eignet sich die direkte Titration mit visueller Endpunktbestimmung, aber die Rücktitration ist allgemeiner anwendbar. Die Genauigkeit ist von der gleichen Größenordnung wie bei wesentlich größeren Einwaagen.

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Résumé On décrit les méthodes de bromation pour le dosage des groupements sulfures et disulfures dans les échantillons organiques, sur environ 50g de prise d'essai. Le titrage avec indication visuelle du point équivalent convient dans certains cas, mais une méthode avec titrage en retour se montre d'une application plus générale. La précision que l'on obtient est du même ordre de grandeur que pour le travail à échelle beaucoup plus grande.

     

The determination of Nickel in Iron and Steel by Atomic absorption spectrophotometry

A procedure is described for the determination of 0.005 to 2% of nickel in low and high alloy irons and steels by atomic absorption spectrophotometry. The sample is dissolved in phosphoric-sulphuric acid and atomised in an atomic absorption spectrophotometer. The method is rapid and free from interferences; preliminary separations are not required and results obtained on standard samples are in good agreement with certificate values.     

The determination of manganese in iron and steel by atomic absorption spectrophotometry

A procedure is described for the determination of 0.001–2% of manganese in low and high alloy irons and steels by atomic absorption spertrophotometry. The sample is dissolved in phosphoric-sulphuric acid and atomised in an atomic absorption spectrophotometer. The method is rapid, free from interferences, preliminary separations are not required and results obtained on standard samples agree closely with stated certificate values.     

Disrupted functional connectivity in social anxiety disorder: a resting-state fMRI study

Dysfunction of the corticolimbic circuitry has been highlighted in social anxiety disorder (SAD) during social stimuli. However, few studies have investigated functional connectivity in SAD during the resting state, which may improve our understanding of SAD pathophysiology. The aim of this study was to investigate whether whole-brain functional connectivity might be aberrant in SAD patients, and if so, whether these changes are related to the measured clinical severity. Seventeen SAD patients and 19 healthy controls participated in resting-state functional magnetic resonance imaging. The brain was first divided into 90 paired brain regions and functional connectivity was then estimated by temporal correlation between each of these regions. Furthermore, connections that were significantly disrupted in SAD patients were correlated with clinical severity measured using the Liebowitz Social Anxiety Scale. Compared with healthy controls, SAD patients showed decreased positive connections within the frontal lobe and decreased negative connections between the frontal and occipital lobes. In particular, the weaker negative connections between the frontal lobe, which mainly involved the right median prefrontal cortex, and the occipital lobe had a significant positive correlation with the severity of SAD symptoms. The results support the hypothesis that some abnormalities of functional connectivity exist in SAD patients, which relate to the frontal cortex and occipital cortex. In addition, decreased functional connectivity between the frontal and occipital lobes and within the frontal lobe might be related to abnormal information processing and reflect disturbed neural organization resulting in defective social cognition, which could represent an early imaging biomarker for SAD.     

Pre-concentration of short-lived radionuclides using manganese dioxide precipitation from surface waters

Rapid determination of ²²²Rn and ²²⁰Rn progeny (²¹⁴Pb, ²¹²Pb, ²¹⁴Bi, ²¹²Bi) is achievable using manganese dioxide (MnO₂) precipitation with analysis by γ-spectrometry. This is of interest to environmental monitoring programmes that utilise gross activity methods to screen for anthropogenic radionuclides. The contribution from these naturally occurring radionuclides (NOR) varies, and is difficult to experimentally measure due to short half-lives (t _½ = 19.9 m–10.64 h) and low environmental activity (<0.1 Bq L^?1). The extraction efficiency of the technique is above 90%, and above 80% for other nuclides (²³²Th, ²³⁸U, ²³⁵U, ²²⁸Ac, ²²⁶Ra, ²²⁴Ra, ²¹⁰Pb, ⁵⁴Mn). Short-lived NOR have been measured at two surface water locations, and indicates elevated ²¹⁴Bi activity of 4.0 ± 1.1 Bq L^?1.     

The micro and semimicro determination of alkoxyl groups

An examination has been made of the sources of error associated with the determination of alkoxyl groups. Several features of other methods have been incorporated in a simple apparatus, and a modified procedure is presented for both the micro and semimicro determination of methoxyl and ethoxyl groups.     

The 1h92 proton orbit size in 209Bi

Angular distributions of α-particles from the reaction ²⁰⁹Bi(t, α)²⁰⁸Pb (ground state) have been measured at bombarding energies E_t = 8.5 MeV and E_t = 9.0 MeV. Zero-range (ZR) DWBA analyses of the data are used to determine the radial extent of the wave function of the $\text{lh}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ orbit in which the transferred proton is bound in ²⁰⁹Bi. The applicability of the sub-Coulomb ZR DWBA treatment is investigated by comparison of ZR and exact finite-range DWBA calculations. A value of the (t, α) normalization constant of (20.8 ± 3.1) × 10⁴ MeV² · fm³, based on forward dispersion relations, has been obtained from this comparison. The asymptotic amplitude of the wave function is measured directly and the rms radius is extracted via a Woods-Saxon model. A value of √〈r²〉 = 6.10_?0.08^+0.12 fm, corresponding to a point proton and to a local Woods-Saxon potential, is obtained. The rms radius and radial wave function of the $\text{1}\text{h}{}_{\mathrm{<mtext>9</mtext><mtext>2</mtext>}}$ proton are compared with the results of electron scattering and muonic atom data on targets of ²⁰⁹Bi and ²⁰⁸Pb and with the results of Hartree-Fock calculations.     

Quantum cryptography without switching

We propose a new coherent state quantum key distribution protocol that eliminates the need to randomly switch between measurement bases. This protocol provides significantly higher secret key rates with increased bandwidths than previous schemes that only make single quadrature measurements. It also offers the further advantage of simplicity compared to all previous protocols which, to date, have relied on switching.