Molecular Adaptations for Sensing and Securing Prey and Insight into Amniote Genome Diversity from the Garter Snake Genome

Colubridae represents the most phenotypically diverse and speciose family of snakes, yet no well-assembled and annotated genome exists for this lineage. Here, we report and analyze the genome of the garter snake, Thamnophis sirtalis, a colubrid snake that is an important model species for research in evolutionary biology, physiology, genomics, behavior, and the evolution of toxin resistance. Using the garter snake genome, we show how snakes have evolved numerous adaptations for sensing and securing prey, and identify features of snake genome structure that provide insight into the evolution of amniote genomes. Analyses of the garter snake and other squamate reptile genomes highlight shifts in repeat element abundance and expansion within snakes, uncover evidence of genes under positive selection, and provide revised neutral substitution rate estimates for squamates. Our identification of Z and W sex chromosome-specific scaffolds provides evidence for multiple origins of sex chromosome systems in snakes and demonstrates the value of this genome for studying sex chromosome evolution. Analysis of gene duplication and loss in visual and olfactory gene families supports a dim-light ancestral condition in snakes and indicates that olfactory receptor repertoires underwent an expansion early in snake evolution. Additionally, we provide some of the first links between secreted venom proteins, the genes that encode them, and their evolutionary origins in a rear-fanged colubrid snake, together with new genomic insight into the coevolutionary arms race between garter snakes and highly toxic newt prey that led to toxin resistance in garter snakes

Genres of high-stakes writing assessments and the construct of writing competence

High-stakes writing assessments currently exert a strong influence on the writing curriculum and instruction in schools across the United States. Under these circumstances it is important to examine the construct of writing competence on which these assessments are based, as well as the extent to which this construct supports the goals of secondary education. In this paper we conduct an exploratory analysis of the genre demands of high-stakes writing assessments from three states – California, Texas, and New York – with the aim of discerning, comparing, and evaluating the role that genre knowledge plays in the construct of writing competence measured by these assessments. Our method of inquiry includes both task analysis of the prompts and genre analysis of high-scoring benchmark papers written in response to these prompts. For the analysis of benchmark papers we employed both structural analysis and quantitative counts of key linguistic features to characterize the genres represented in these assessment tasks. Our results suggest a lack of alignment between the genres of the benchmark papers designated as exemplary and the genre demands of the prompts to which they were written. Exceptions to this pattern were most common on the New York assessments, which contextualize writing tasks in tests of subject–matter knowledge. Findings from our exploratory analysis lead us to argue for greater consistency and clarity of expectations in the design of high-stakes writing exams, and for the design oLanguage Use in Past and Presen

Genre and thinking in academic writing tasks

Genre-based approaches to teaching writing have made important strides in heightening students’ awareness of audience and purpose but have paid less attention to the ways in which expectations for written performance in school context are embedded in expectations for certain kinds of discipline-based thinking. In this paper we present a study that explored how a group of high school students studying history and literature within an interdisciplinary framework experience the thinking demands associated with a particular kind of writing characteristic of both subjects: analytic exposition.We found that the task of articulating interpretive thematic statements is a significant challenge for these students, in some cases because the nature of interpretative understanding remains elusive to them and in others because they struggle with finding the language to express this understanding in a concise form. A separate but related finding has to do with opportunities for interpretive insight that arose from writing in genres other than conventional analytic exposition, for example, narrative, descriptive, and imaginative writing. We conclude our discussion by recommending further investigation of ways in which alternatives to analytic exposition may be used as bridges to mastery of this important academic genre.Language Use in Past and Presen

Effect of UBM and BCB layers on the thermo-mechanical reliability of Wafer Level Chip Scale Package (WLCSP)

Cracking of the silicon chip of a wafer level chip scale package (WLCSP) is encountered during a thermal cycle test (TCT). This paper attempts to examine the failure mechanism. Both numerical and experimental efforts were devoted to investigate the problem. A series of finite element models with different combinations of material properties and geometric configurations were developed. The results showed that both the under bump metallization (UBM) and the dielectric layer Benzocyclobuten (BCB) contributed significantly to the stress level induced inside the silicon chip. In addition, solder ball pull tests were performed. The silicon cratering failure mode was reproduced which confirmed the failure mechanism as proposed by the finite element analysis. The effects of all relevant constituent materials on the chip are discussed in detail. Suggestions for the product design improvement are provided at the end of the paper. ©2009 IEEE

Effects of corner and edgebond epoxy adhesives on board level solder joint reliability of BGA mezzanine connectors

In this paper, the button shear tests of seven kinds of epoxy used for corner/edge bonding of BGA mezzanine connectors are performed firstly for determining adhesive strength between the epoxies and each relevant surface material. The effect of corner/edge bonding epoxy on the board level solder joint reliability of BGA connectors is also investigated including mechanical drop and 4-point bending tests. In addition, the pre-conditioning effect of thermal aging (1000 hours at 125°C) and accelerated temperature cycling (ATC, -40∼125°C, 500 cycles) on the reliability of connectors with corner/edge bonding epoxy is discussed. The failure modes and fracture strengths of the button shear and boardlevel tests are cross-referenced for comparison and assessed for correlation. The results from the present study not only contribute to the characterization and selection of corner/edge bonding epoxies for BGA connectors, but also improve the understanding of the corresponding relationship between simple button shear and the more complex and costly boardlevel reliability tests. © 2010 IEEE