Student Difficulties with Accessing and Using Mathematical Knowledge

This article examines the issue of why students fail to activate and use mathematical knowledge during problem solving when it is known that they possess the required knowledge. This issue is explored by analyzing problem-solving attempts of a high-achieving student and a low-achieving student in the domain of plane geometry. On the basis of these data and other literature, three major sources of mathematical knowledge-access difficulties are identified that might be considered by classroom teachers, including a student's (1) dispositional state, (2) management of the problem-solving process, and (3) state of organization of his or her mathematical knowledge. It is argued that teaching practices that place emphasis on careful management of problem-solving activity could help students activate and extend the use of mathematical knowledge acquired in lesson activities.     

Constraints on three flavor neutrino mixing

We summarize the constraints on three flavor neutrino mixing coming from data. We first map out the allowed region in the three neutrino parameter space using solar and atmospheric neutrino data. We then incorporate the results of reactor and long baseline experiments in our analysis and show that the parameter space is drastically reduced. We conclude by pointing out that the results of Borexino and SNO will further help in constraining the parameter space.     

Photoionization of Al IV (neon-type) from its ground 2s 22p 6 1 S e and excited 2s 22p 53p 3,1 P 0 3 S e states using the R-matrix method

The R-matrix method is used to calculate the total photoionization cross-sections from the ground 2s ²2p ^{6 1} S ^e and the first three excited 2s ²2p ⁵3p ^3,1 S ^e states of Al IV, for photon energies ranging from the first ionization threshold to just above the second threshold of the residual ion Al V. The two lowest LS terms of Al V − 2s ²2p ^{5 2} P ⁰, 2s2p ^{6 2} S ^e, 2s2p ^{6 2} S ^e, represented by sophisticated configuration interaction wavefunctions, are included in the R-matrix calculation. The resulting cross-sections are affected by Rydberg series of resonances converging to the 2s2p ^{6 2} S ^e excited threshold.     

Structure and electrochemical performance of LiV x Mn2 − x O4 (0 ≤ x ≤ 0.20) cathode materials for rechargeable lithium ion batteries

LiMn₂O₄ and vanadium-substituted LiV _x Mn_2???x O₄ (x?=?0.05, 0.10 0.15 and 0.20) cathode materials were synthesized by sol–gel method using aqueous solutions of metal nitrates and tartaric acid as chelating agent at 600 °C for 10 h. The structure and electrochemical properties of the synthesized materials were characterized by using X-ray diffraction, SEM, TEM and charge–discharge studies. X-ray powder diffraction analysis was changed in lattice parameters with increasing vanadium content suggesting the occupation of the substituent within LiMn₂O₄ interlayer spacing. TEM and SEM analyses show that LiV_0.15Mn_1.85O₄ has a smaller particle size and more regular morphological structure with narrow size distribution than LiMn₂O₄. It is concluded that the structural stability and cycle life improvement were due to many factors like better crystallinity, smaller particle size and uniform distribution compared to the LiMn₂O₄ cathode material. The LiV_0.15Mn_1.85O₄ cathode material has improved the structural stability and excellent electrochemical performances of the rechargeable lithium ion batteries.     

Excitations of optomechanically driven Bose Einstein condensates in a cavity: Photodetection measurements

We present a detailed study to analyze the Dicke quantum phase transition within the thermodynamic limit for an optomechanically driven Bose-Einstein condensate in a cavity. The photodetection-based quantum optical measurements have been performed to study the dynamics and excitations of this optomechanical Dicke system. For this, we discuss the eigenvalue analysis, fluorescence spectrum and the homodyne spectrum of the system. It has been shown that the normal phase is negligibly affected by the mechanical mode of the mirror while it has a significant effect in the superradiant phase. We have observed that the eigenvalues and the spectra both exhibit distinct features that can be identified with the photonic, atomic and phononic branches. In the fluorescence spectra, we further observe an asymmetric coherent energy exchange between the three degrees of freedom of the system in the superradiant phase arising as a result of optomechanical interaction and Bloch-Siegert shift.     

Exchange corrected Eikonal-Born approximation for elastic scattering of electrons by Helium

Differential cross-sections for elastic scattering of electron from Helium atom have been calculated using the Eikonal-Born Series method with the inclusion of exchange effect evaluated by Glauber Model. The results obtained for 300 eV incident electrons are compared with other theoretical calculations and with recent experimental data.     

Compensation differences between male and female CEOs for publicly traded firms: a nonparametric analysis

A recent article in the popular press suggested that gender is one determining factor of corporate executives' pay. The average compensation for the top 20 men was more than 10 times larger than for the top 20 women. We would expect, however, that direct compensation from salary and bonuses would be similar for both genders given the public nature of the data. There have been few academic articles on the topic of gender pay differences among top executives. One paper found marginally significant statistical evidence that women CEOs are paid more than their male counterparts. In this paper, we extend the literature by looking at compensation differences of male and female CEOs. Our sample includes over 40 female CEOs for publicly traded companies and matched pairs of comparable male CEOs. In addition, we use data envelopment analysis to derive a gap measure representing the difference between male and female compensation. The results suggest that there is a statistical difference between male and female potential compensation.     

Alpha particle induced reactions on copper and tantalum

Alpha particle induced reactions in the target elements copper and tantalum were studied. The excitation functions of⁶³Cu(α, n) +⁶⁵Cu(α, 3n),⁶⁵Cu(α, 2n),¹⁸¹Ta(α, 2n) and¹⁸¹Ta(α, 4n) were measured up to 75 MeV.Eight new energy point cross-sections were measured for the first time. The experimental results were compared with the predictions of updated hybrid model (ALICE/85/300) as well as with index model using the initial exciton numbern ₀=4 (4poh) and level density parameter,a=A/8. A general agreement was found for all the reactions with both the models.     

Microscopic TV holography for MEMS deflection and 3-D surface profile characterization

Recent industrial demands for greater product quality in the fields of microelements and micro-electro-mechanical systems (MEMS) generate new challenges for metrology. The fast-growing MEMS industry requires a robust non-destructive quantitative measurement system for the characterization of their performance, reliability and integrity. A microscopic TV holographic system using a long working distance microscope with an extended zoom range has been developed for microelements and MEMS deformation and 3-D surface profile analysis. The system is capable of evaluating both rough and smooth surfaces. Noisy wrapped phase map is a usual problem in speckle interferometry. We have compared several phase-shifting algorithms for evaluation of speckle phase for their usefulness in generating less-noisy phase maps. The experimental results on a MEMS pressure sensor for out-of-plane deflection and 3-D surface profile analysis are presented.