Characterization of a circular thin film plasma source for atomic emission spectroscopy

A plasma source for analytical atomic emission spectroscopy is described based on the electrical vaporization by capacitive discharge of a thin Ag film deposited on a polycarbonate membrane filter. The source is designed for the rapid, direct analysis of solid powder samples collected by filtration from fluid media. A concentric electrode system consisting of a ring-shaped graphite electrode placed on the thin film surface and a pointed graphite rod located under the membrane substrate results in a plasma with cylindrical symmetry and a radial current path. Discharge current vs time and intensity vs time profiles are compared for the concentric electrode geometry and the linear geometry used in previous studies. Two values of tank circuit inductance also are compared. Both neutral-atom and ion line radiation from an Mn sample are more intense when the center electrode is initially cathodic. The inside diameter of the ring-shaped electrode and thus the surface area of the Ag film exposed to the plasma have relatively little effect on the intensity of continuum background and line radiation from a sample deposited near the center of the film. Particle size effects, while significant, are smaller than with the linear electrode geometry. Analytical curves are presented for several lines using both a low-inductance and a high-inductance discharge. Log-log slopes range from about 0.85 to 1.05 for ion lines. Detection limits are somewhat poorer than with the linear geometry.     

A note on the normal approximation error for randomly weighted self-normalized sums

Let X = {X _n } _n≥1 and Y = {Y _n } _n≥1 be two independent random sequences. We obtain rates of convergence to the normal law of randomly weighted self-normalized sums $$\psi _n \left( {X,Y} \right) = \sum\nolimits_{i = 1}^n {{{X_i Y_i } \mathord{\left/ {\vphantom {{X_i Y_i } {V_n , V_n }}} \right. \kern-\nulldelimiterspace} {V_n , V_n }}} = \sqrt {Y_1^2 + \cdots + Y_n^2 } .$$ . These rates are seen to hold for the convergence of a number of important statistics, such as for instance Student’s t-statistic or the empirical correlation coefficient.     

In situ measurement of localization error in particle tracking microrheology

A method is presented to estimate the static error ?? in a multiple particle tracking microrheology experiment. This in situ estimate of ?? is measured under the same conditions of the material under test, and without any additional experiments. The correction of the mean-squared displacement by the in situ method is potentially more reliable than methods that rely on characterizing ?? in a separate gel sample. With the true mean-squared displacements accessible at short lag times, experimental artifacts introduced by static error can be distinguished from true rheological properties, even in highly viscous (>10,000 mPa?s) samples.     

Quantum interference between the third and fourth exciton states in semiconducting carbon nanotubes using resonance Raman spectroscopy

We exploit an energy level crossover effect [Haroz et al., Phys. Rev. B 77, 125405 (2008)] to probe quantum interference in the resonance Raman response from carbon nanotube samples highly enriched in the single semiconducting chiralities of (8,6), (9,4), and (10,5). UV Raman excitation profiles of G-band spectra reveal unambiguous signatures of interference between the third and fourth excitonic states (E(33) and E(44)). Both constructive and destructive responses are observed and lead to anomalous intensity ratios in the LO and TO modes. Especially large anomalies for the (10,5) structure result from nearly identical energies found for the two E(ii) transitions. The interference patterns demonstrate that the sign of the exciton-phonon coupling matrix elements changes for the LO mode between the two electronic states, and remains the same for the TO mode. Significant non-Condon contributions to the Raman response are also found.     

Zur Bestimmung und Trennung des Mangans

Ohne Zusammenfassung     

Iodide‐Induced Shuttling of a Halogen‐ and Hydrogen‐Bonding Two‐Station Rotaxane

The first example of utilizing halogen‐bonding anion recognition to facilitate molecular motion in an interlocked structure is described. A halogen‐bonding and hydrogen‐bonding bistable rotaxane is prepared and demonstrated to undergo shuttling of the macrocycle component from the hydrogen‐bonding station to the halogen‐bonding station upon iodide recognition. In contrast, chloride‐anion binding reinforces the macrocycle to reside at the hydrogen‐bonding station.     

Synthetic and structural studies of some chloro-substituted methyl 2,1-benzisoxazole-3-carboxylates and related compounds

Methyl 5-chloro- and 5,7-dichloro-2,1-benzisoxazole-3-carboxylates have been synthesized by treatment of o-nitromandelic and 5-chloro-2-nitroamandelic methyl esters, respectively, with thionyl chloride under appropriate reaction conditions. The structural assignments of both heterocyclic products were based on elemental and spectral analyses, and their conversion to the corresponding 5-chloro- and 5,7-dichloro substituted 2,1-benzisoxazole-3-carboxylic acids and isatins. Methyl α-chloro-o-nitrophenylacetate and o-nitrophenylcarbomethoxymethinyl sulfite were also obtained from reactions of methyl o-nitromandelate and thionyl chloride. A possible reaction mechanism involving two consecutive nucleophilic substitutions of methyl o-nitromandelate with thionyl chloride was proposed to account for the formation of methyl 5-chloro-2,1-benzisoxazole-3-carboxylate.     

Subjective effects of traffic noise exposure: reliability and seasonal effects

Repeated interview surveys were made in suburban residential areas of London. At six selected sites, four sets of interviews were conducted at different times of year and at a further two sites two sets of interviews were conducted during summer months. At all sites traffic noise levels were measured over 24 hours at each interview phase with a microphone 1 m from the dwelling facade at first floor level. Seasonal weather data were also collected. In the course of the repeated interviews the initial sample of 364 respondents was reduced to 222. The questionnaire included two types of noise nuisance scale, questions bearing on the typicality of road traffic conditions, and on the opening and closing of windows. The results confirm others already reported but in addition, show that if annoyance scores are averaged over repeated occasions a highly significant increase in reliability is obtained, and the proportion of score variance accounted for by noise increases significantly. No evidence was found of seasonal changes in traffic noise levels and annoyance scores did not vary significantly despite significant differences in the proportion of windows open at different times of the year.