School-Based Teacher Education in the United States : An Uneven Evolution

What does school-based teacher education mean in the United States? Certainly, it does not mean that funding, decision-making and management of programs are the province of individual school districts; in the United States, teacher education is firmly ensconced in higher education. The overwhelming majority of teachers are prepared in colleges and universities, licensed by individual states, and employed by local school districts. Law, tradition, and funding suggest that this general pattern will not change soon. While teacher education is located primarily in higher education institutions, school-based teacher education exists. It exists in many forms, ranging from student teaching and other field experiences in which students apply concepts and skills learned on campus to comprehensive partnerships among higher education institutions and local school districts for comprehensive initial and continuing teacher development. In this article, we explore several configurations of school-based teacher education. We first present brief scenarios that illustrate common schoolbased patterns, then describe several configurations currently in operation in the United States. We then summarise some of the issues inherent in school-based teacher education

Spatial median and directional data

We introduce the normalized spatial median as an estimator of location for rotationally symmetric distributions on the hypersphere. We investigate some of its asymptotic properties and use them to obtain confidence regions for the modal direction of a distribution on the hypersphere. These results are then applied to the von Mises-Fisher distribution and to a contamination model. It is seen that the normalized spatial median can perform more efficiently than the normalized mean in presence of outlier

Gas exchange, δ13C, and heterotrophy for Castilleja linariifolia and Orthocarpus tolmiei, facultative root hemiparasites on Artemisia tridentata

Journal ArticleGas exchange and carbon isotope ratios were measured on 2 facultative hemiparasites, Castilleja linarifolia Benth. (Indian paintbrush; Scrophulariaceae) and Orthocarpus tolmiei I-I. & A. (Tolmie owl clover; Scrophulariaceae), and their Artemisia tridentata L. (big sagebrush; Asteraceae) hosts. Photosynthetic rates differed greatly between years; rates in 1995 were more than double those in 1994, likely due to more precipitation and less water stress during 1995. Despite this difference in precipitation, photosynthetic rates for C. linariifolia were not different from those of their hosts for either year. However, carbon isotope ratios of C. linariifolia and O. tolmiei were up to 30/00 more negative than those of their A. tridentata hosts. Using measured δ13C ratios in conjunction with δ13C ratios predicted from gas-exchange measurements, we calculated that C. linariifolia derived, on average, 40% of its leaf carbon heterotrophically. Contrary to current suggestions that high photosynthetic rates of hemiparasites are an indication of reduced heterotrophy, C. linariifolia exhibited photosynthetic rates similar to autotrophic plants and used a substantial amount of host-derived carbon. Moreover, this evidence shows that manipulation of a heterotrophic carbon supply transcends obligate hemiparasites to include those plants whose parasitism is facultative

Fractional Angular Momenta, Gouy and Berry Phases in Relativistic Bateman-Hillion-Gaussian Beams of Electrons

A new Bateman-Hillion solution to the Dirac equation for a relativistic Gaussian electron beam taking explicit account of the four-position of the beam waist is presented. This solution has a pure Gaussian form in the paraxial limit but beyond it contains higher order Laguerre-Gaussian components attributable to the tighter focusing. One implication of the mixed mode nature of strongly diffracting beams is that the expectation values for spin and orbital angular momenta are fractional and are interrelated to each other by intrinsic spin-orbit coupling. Our results for these properties align with earlier work on Bessel beams [Bliokh et al., Phys. Rev. Lett. 107, 174802 (2011)] and show that fractional angular momenta can be expressed by means of a Berry phase. The most significant difference arises, though, due to the fact that Laguerre-Gaussian beams naturally contain Gouy phase, while Bessel beams do not. We show that Gouy phase is also related to Berry phase and that Gouy phase fronts that are flat in the paraxial limit become curved beyond it

Manifestation of a Ferroelectric Phase Transition

Temperature dependences of the dielectric properties of ultrathin polyvinylidene fluoride films prepared using the Langmuir-Blodgett method were studied by linear and nonlinear dielectric spectroscopy. It is shown that ultrathin Langmuir films of polyvinylidene fluoride exhibit a manifestation of a first-order ferroelectric phase transition, which can be assigned to the interaction between the spontaneous polarization and the surfaces bounding the film. As the film thickness increases, the effect of the surfaces decreases and the ferroelectric phase transition shifts to high temperatures to vanish altogether when the temperature region of the transition rises above the melting point

Mini‐review: The Promise of Piezoelectric Polymers

Recent advances provide new opportunities in the field of polymer piezoelectric materials. Piezoelectric materials provide unique insights to the fundamental understanding of the solid state. In addition, piezoelectric materials have a wide range of applications, representing billions of dollars of commercial applications. However, inorganic piezoelectric materials have limitations that polymer ferroelectric materials can overcome, if certain challenges can be addressed. This mini-review is a practical summary of the current research and future directions in the investigation and application of piezoelectric materials with an emphasis on polymeric piezoelectric materials. We will assume that the reader is well versed in the subject of polymers, however, not as familiar with piezoelectric materials

Polarization imaging in ferroelectric polymer thin film capacitors by pyroelectric scanning microscopy

A Pyroelectric Scanning Microscopy system, which uses laser-induced thermal modulation for mapping the pyroelectric response, has been used to image a bipolar domain pattern in a ferroelectric polymer thin film capacitor. This system has achieved a resolution of 660±28 nm by using a violet laser and high f-number microscope objective to reduce the optical spot size, and by operating at high modulation frequencies to reduce the thermal diffusion length. The results agree well with a thermal model implemented numerically using finite element analysis