A simple route to the synthesis of high-quality NiO nanoparticles

Dispersed nickel oxide nanoparticles were obtained by a simple and low-cost method using a mixture of gelatin as organic precursor and NiCl₂ · 6H₂O as Ni source. The average particle size was estimated from X-ray powder diffraction (XRPD) peaks using the Rietveld refinement. The values ranged from 3.2 to 79 nm. We observed that the particle size changes as a function of synthesis time, with a notable decrease after the addition of NaOH to the solution. Field emission scanning electron microscopy (FE-SEM) measurements show that particles have well defined shapes and are dispersed in an organic matrix. X-ray absorption near edge spectroscopy (XANES) shows also the formation of fcc NiO nanoparticles structures.     

Demonstration of high extinction ratio modal interference in a two-mode fiber and its applications for all-fiber comb filter and high-temperature sensor

We show that high extinction ratio (>20 dB) modal interference in a two-mode dispersion compensating fiber can be utilized to build a compact, easy-to-fabricate tunable all-fiber optical comb filter. Wavelength tunability over the full free spectral range of the comb filter is demonstrated with an electrical power of 115mW using an on-fiber thin film micro-heater deposited directly on the fiber. In another configuration, the comb filter is used as a temperature sensor with dynamic range of >300 °C and sensitivity of <0.1 °C. The temperature sensor is capable of measuring a temperature as high as 500 °C.     

A two time scale analysis of gyroscopic motion with friction

The motion of a symmetric rigid body having one fixed point and subject to frictional forces is considered. The frictional forces are due to a surrounding dissipative medium and are accounted for by a model wherein the frictional torque is proportional to the angular velocity. A two time scale perturbation technique is used to analyze and characterize possible motions. The results of calculations which illustrate some of these motions are provided. These results show full agreement with qualitative observations.

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Résumé On considère le mouvement d'un corps rigide symétrique ayant un point fixe et sujet à des forces de friction. Les forces de friction sont dues à un milieu dissipatif et sont représentées par un modèle où le moment de friction est proportionnel à la vitesse angulaire. On utilise une technique de perturbations à double échelle pour l'analyse et la charactérisation des mouvements possibles. On donne des résultats numériques illustrant certains de ces mouvements. Ces résultats sont en accord complet avec les observations qualitatives.

     

Lifetime measurements and decay of superdeformed bands in Hg isotopes

The lifetimes of states in Superdeformed (SD) bands in ^192,194Hg have been measured using the Doppler shift attenuation method. Intrinsic quadrupole moments have been extracted for band 1 of ¹⁹²Hg and for bands 1, 2, and 3 of ¹⁹⁴Hg. It was found that the quadrupole moments for the “identical” SD bands in these nuclei are the same. In the same experiment, one-step transitions linking SD states to yrast and near yrast states for bands 1 and 3 of ¹⁹⁴Hg have been identified. From this observation, excitation energies, spins and probable parities have been assigned to SD states in these bands.     

Using Metaphors to Unpack Student Beliefs About Mathematics

This paper reports on an exploratory study of the mathematical beliefs of a group of ninth and tenth grade students at a large, college preparatory, private school in the Southeastern United States. These beliefs were revealed using contemporary metaphor theory. A thematic analysis of the students' metaphors for mathematics indicated that students had well developed and complex views about mathematics including math as: an Interconnected Structure, a Hierarchical Structure, a Journey of Discovery, an Uncertain Journey, and a Tool. Another prevalent theme revealed by the metaphors was that students believe perseverance is needed for success in mathematics. The data also suggest an impact of gender and tracking on students beliefs about mathematics. Creating metaphors for mathematics provided a catalyst for student reflection, class discussion, and qualitative data, which could aid program evaluation. Several areas for future research were identified through this exploratory study.     

Tilting and shearing determination in the alignment of a Mach-Zehnder interferometer by zone plates

An easy and accurate method to detect the kind of disarrangement and its magnitude in the adjustment process of a Mach-Zehnder interfermeter by means of an equilateral hyperbolic zone plate is explained.     

Hydrogen bonding in nylon 66 and model compounds

Fourier-transform infrared spectroscopy was used to study the hydrogen bond-breaking process in nylon 66 and two model compounds. The resulting enthalpy and entropy values indicated that while there is no interaction between adjacent amide groups in the polymer chain, there is, nevertheless, a substantial cooperative effect in the transverse hydrogen bond direction. We have also established that any analysis of hydrogen bond breaking in semicrystalline polymers (i.e., nylon 66) below the melting point should include a crystallinity correction factor. Extrapolation of our data above the melting point of nylon 66 yielded a 26% retention of hydrogen bonding.     

Calculation of conductance spectra of silver clusters on graphite

The transport properties of Ag_n clusters, 40<n< 100, deposited on crystalline graphite and probed with a tunneling tip are analyzed by using non-equilibrium Green’s functions. Current–voltage characteristics are computed accounting for self-consistent charge redistribution in the cluster caused by coupling to the surface and the external bias. The differential conductance is compared to the density of states of the supported clusters at equilibrium, highlighting the effects of charging and substrate properties on the measured spectrum. PACS 61.46.+w; 73.63.-b; 68.43.-h; 73.22.-f     

Nuclear k T in d+Au collisions from multi-particle jet reconstruction at STAR

This paper presents the most recent nuclear k _T measurements from STAR derived from multi-particle jet reconstruction of d+Au and p+p collisions at √s=200 GeV. Since jets reconstructed from multiple particles are relatively free of fragmentation biases, nuclear k _Tcan be measured with greater certainty in this way than with traditional di-hadron correlations. Multiparticle jet reconstruction can also be used for a direct measurement of the fragmentation function.