The charge and discharge voltage profiles obtained with the conventional constant current-constant voltage charging and pulse charging protocols at low temperatures were studied. There are two peaks in the charge and subsequent discharge voltage profiles, which suggests that lithium plating can occur in two stages during the low-temperature charging. The first stage may occur shortly after the charging at −20°C while the second stage occurs in the later part of charging. The lithium deposited on the negative surface during the low-temperature charging can rapidly diffuse into the graphite negative at room temperature while it cannot diffuse into the graphite negative at −20°C. It appears that the lithium solid diffusion in the graphite negative is the ultimate rate-limiting factor for charging lithium-ion cells at low temperatures. The effects on cell properties such as cell capacity, rate capability, impedance, and cycle life from low-temperature charging with different charging protocols were also studied. Directions for improving the low-temperature charge capability of the lithium-ion cells and designing low-temperature charging protocols are discussed.

Pseudomonas syringae pv. tomato, the causal agent of bacterial speck of tomato, has recently become an increasing problem in California due to the evolution and prevalence of highly aggressive race 1 strains. In resistant plant genotypes, the type III effectors AvrPto and AvrPtoB are recognized by the tomato proteins Pto and Prf. We investigated the prevalence of avrPto and avrPtoB in strains collected over the last 13 years in California. All race 1 strains retained avrPtoB but did not express AvrPtoB protein at detectable levels in vitro. However, deletion of avrPtoB indicated that this effector protein is still expressed at low levels in race 1 during infection. avrPto was detected in four race 1 strains but a key amino acid polymorphism prevents this new protein from interacting with and eliciting Pto-mediated resistance. Growth curve analyses demonstrate that this new avrPto allele is still functional and can enhance P. syringae virulence on tomato. Multilocus sequence typing was used to resolve phylogenetic relationships and revealed that the majority of race 0 and 1 strains were most closely related to P. syringae T1. Collectively, these data support the hypothesis that existing P. syringae populations evolved to overcome genetic resistance by altering the expression and sequence of avrPto and avrPtoB effectors.

The purpose of the study was to ascertain the influence of subject matter expertise on teachers’ pedagogical content knowledge. Data were collected through multiple, extended interviews with 10 teachers with expertise in at least 1 subject area in physical education. Each teacher was interviewed 4 times for approximately 1 hour, focusing on the teacher’s familiarity with 2 content areas (1 expert and 1 nonexpert) and their experiences teaching the subjects. Data were analyzed using the constant comparative technique. The findings were presented with reference to Grossman’s (1990) definition of pedagogical content knowledge. Subject experts identified their largest pedagogical problem as student motivation, while nonexperts believed finding appropriate activities was their greatest challenge. Subject experts were more comfortable and enthusiastic about pedagogical duties and could accommodate a greater range of abilities. The experts and nonexperts revealed no differences in curricular selection, perceptions of students’ understanding of the subject, or evaluation criteria.

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Across the educational systems of the world, few issues have received more attention in recent years than the problem of ensuring that elementary-and secondary-school classrooms are all staffed with adequately qualified teachers (Mullis et al., 2000; OECD, 1994 OECD, , 2005Wang et al., 2003). Even in nations where students routinely score high on international exams, the issue of teacher quality is the subject of much concern. This is not surprising. Elementary and secondary schooling is mandatory in almost all nations and children are legally placed in the care of teachers for a significant portion of their lives. It is widely believed that the quality of teachers and teaching are among the most important factors shaping the learning and growth of students. Moreover, this impact goes beyond student academic achievement. Across the world, observers routinely tie the performance of teachers to numerous, larger societal goals and problems--economic competitiveness and productivity, juvenile delinquency, moral and civic culture, and so on. In addition, the largest single component of the cost of education in any country typically is teacher compensation. Along with a general consensus among many nations that the quality of teachers and teaching is a vital resource, there is accordingly much concern surrounding how equitably this resource is distributed within educational systems. Indeed, some nations suffer from an apparent paradox--that despite an overall overproduction and oversupply of new teachers, there nevertheless appear to be substantial numbers of students without access to qualified teachers. This brief summarizes the results from a collaborative, comparative study of the qualifications of elementary and secondary teachers undertaken by a group of scholars, policy makers and senior education officials from six nations and one region: United