Rusty nails adsorb trace plutonium from the environment

Discarded rusty iron objects in the environment adsorb trace plutonium mobilized by oxygenated surface waters (e.g. rain, snow melt). Radiochemical and mass spectrometric analysis of the surface oxide coating of modest collections of rusty nails retrieved from remote locations provides a global fallout plutonium signal of up to 2 × 10¹⁰ atoms of ²³⁹Pu per sample. The median ²³⁹Pu measurement for 10 samples from five locations was 2.82 × 10⁹ atoms. The average ²⁴⁰Pu/²³⁹Pu atom ratio was 0.176 ± 0.012, consistent with the value accepted for global fallout.     

β-Na（Y_（1.5-x-y）Na_（0.5））F_6：Yb_xTm_y纳米颗粒的合成及其上转换发光性质

本文采用水热合成法制备了β-Na（Y1.5-x-yNa0.5）F6：YbxTmy（x=0.2~1.0,y=0.001~0.008）纳米颗粒,并利用X射线粉末衍射仪、透射电子显微镜和F-4600荧光分光光度计表征了其样品的物相、形貌和发光性质.结果表明样品物相为六角相,颗粒平均直径约22nm,并探讨了Yb3＋和Tm3＋掺杂浓度对样品的上转换发光性质的影响,结果表明敏化剂Yb3＋的最佳掺杂浓度为60%,而激活剂Tm3＋的最佳掺杂浓度为0.6%.     

Thermal conductivity of open‐cell polyolefin foams

The thermal conductivity and the cellular structure of novel open‐cell polyolefin foams produced by compression molding and based on blends of an ethylene‐vinyl acetate copolymer (EVA) and a low‐density polyethylene (LDPE) have been studied in the temperature range between 24 and 50 °C. The experimental results have shown that the cellular structure of the analyzed materials has interconnected cells because of the presence of large and small holes in the cell walls, this structure being clearly different to the typical structure of open‐cell polyurethane foams. It has been found that at low temperatures the materials have a slightly higher thermal conductivity than closed‐cell polyolefin foams of similar densities. The different mechanisms of heat flow, conduction, convection, and radiation have been analyzed by using experimental measurements and a theoretical model. It has been proved that, in spite of having an open‐cell structure, the convention mechanism is negligible, being the radiation mechanism the one which made different the conductivity of materials with varying cellular structures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 212–221, 2008     

A least mean squares blind equalization techniques for OFDM systems

Classical multicarrier systems based on the discrete Fourier transform(dft) make use of aguard interval (gi) in order to enable a low complexity equalization scheme. Thisguard interval consists of a redundant prefix cyclically appended to each block of modulated symbols so as to exploit the cyclic convolution property of thedft. Therefore, besides decreasing the useful transmitted symbol rate, this technique is very specific todft-basedofdm systems. In order to implement a digital modulator, an oversampled version of the continuous signal that would be produced by the all-analog ideal modulator is often computed. This amounts to appending null symbols to the block of symbols to be modulated. This work shows that forcing the presence of these null symbols at the appropriate places on the receiver side is sufficient to equalize the channel. Here, a linear equalizer is adapted by minimizing a quadratic criterion based on the energy of the subband signals that should be zero. Since no knowledge about theuseful data is required, this method performs blind equalization. Moreover, it requires neither a guard interval nor any reference symbol. As a result, for a given channel bitrate budget, the data rate is increased     

A physics based model for the RTD quantum capacitance

A simple derivation of the form for the compact model of the quantum capacitance in a resonant tunneling diode (RTD) is presented. The quantum capacitance is shown to reduce the resistive cutoff frequency. The implementation of the model into SPICE is described. The distorting effect of the strongly nonlinear quantum capacitance on an oscillator circuit is demonstrated in a SPICE simulation. The nonlinearity becomes important for the highest frequency applications when the RTD capacitance is comparable to the capacitance in the rest of the circuit.     

Majority-minority influence: identifying argumentative patterns and predicting argument-outcome links

In this paper, the authors investigate the argument activities of majority and minority faction in small group decision-making situations. We begin by identifying patterns of argument that characterize majority and minority communication in 34 discussions and then test several subgroup-outcome and argument-outcome links. Results indicate that winning and losing subgroups argue differently (as do minority and majority subgroups overall) and that consistency in argument is a strong predictor of subgroup success. Both theoretical and practical implications for subgroup influence in group decision making accrue from these findings.     

Absolutely isolated singularities of a differential equation

In this paper we solve the problemof desingularization of an absolutely isolatedsingularity of a differential equation, including thedicritical case. As an application, we prove thefiniteness of the number of dicritical points in theblowing up tree of an absolutely isolated singularity.