Claussen and Long give an overview of metallobleomucin activation and DNA cleavage, highlighting the key points recently reviewed and followed by an examination of the current understanding of ...metallobleomycin structure and DNA recognition.
We demonstrate vertical-incidence electroabsorption modulators for free-space optical interconnects. The devices operate via the quantum-confined Stark effect in Ge/SiGe quantum wells grown on ...silicon substrates by reduced pressure chemical vapor deposition. The strong electroabsorption contrast enables use of a moderate-Q asymmetric Fabry-Perot resonant cavity, formed using a film transfer process, which allows for operation over a wide optical bandwidth without thermal tuning. Extinction ratios of 3.4 dB and 2.5 dB are obtained for 3 V and 1.5 V drive swings, respectively, with insertion loss less than 4.5 dB. For 60 ?m diameter devices, large signal modulation is demonstrated at 2 Gbps, and a 3 dB modulation bandwidth of 3.5 GHz is observed. These devices show promise for high-speed, low-energy operation given further miniaturization.
Background: Previous studies questioned the link between early childhood anemia and detrimental child development. Objective: A population-based study was conducted to examine the association between ...early childhood anemia and mild or moderate metal retardation at 10 y of age. Design: The present study linked early childhood nutrition data collected by the Special Supplemental Program for Women, Infants, and Children (WIC) and school records. Hemoglobin values were used to determine the relation between anemia in early life and children's placement in special education classes for mild or moderate mental retardation. Subjects were all participants in the WIC program. A computer program was used to link data from birth, WIC, and school records. Results: Logistic regression showed an increased likelihood of mild or moderate mental retardation associated with anemia, independent of birth weight, maternal education, sex, race-ethnicity, the mother's age, or the child's age at entry into the WIC program. Conclusion: These findings support the proposition that efforts to prevent mild and moderate mental retardation should include providing children with adequate nutrition during early childhood.
Background: Studies of changes in engineering students’ perceptions of ethics and social responsibility over time have often resulted in mixed results or shown only small longitudinal shifts. ...Comparisons across different studies have been difficult due to the diverse frameworks that have been used for measurement and analysis in research on engineering ethics and have revealed major gaps between the measurement tools and instruments available to assess engineering ethics and the complexity of ethical and social responsibility constructs. Purpose/Hypothesis: The purpose of this study was to understand how engineering students’ views of ethics and social responsibility change over the four years of their undergraduate degrees and to explore the use of reflexive principlism as an organizing framework for analyzing these changes. Design/Method: We used qualitative interviews of engineering students to explore multiple facets of their understanding of ethics and social responsibility. We interviewed 33 students in their first and fourth years of their undergraduate studies. We then inductively analyzed the pairs of interviews, using the reflexive principlism framework to formulate our findings. Results: We found that engineering students in their fourth year of studies were better able to engage in balancing across multiple ethical principles and specification of said ethical principles than they could as first year students. They most frequently referenced nonmaleficence and, to a lesser degree, beneficence as relevant ethical principles at both time points, and were much less likely to reference justice and autonomy. Conclusions: This work shows the potential of using reflexive principlism as an analytical framework to illuminate the nuanced ways that engineering students’ views of ethics and social responsibility change and develop over time. Our findings suggest reflexive principlism may also be useful as a pedagogical approach to better equip students to specify and balance all four principles when ethical situations arise.
Background: Prior work has shown the importance of engineering identity formation for student success and persistence in engineering. While research has explored how engineering identity is formed, ...less attention has been given to liminal engineering identities—identities that exist between two commonly identified ones, such as the identity of being an engineering student and that of being an engineering professional—and the qualities of liminality that might impact this identity formation. Purpose/Hypothesis: This paper addresses the research question, “How do engineering students talk about their liminal engineering identities?” Design/Method: Through eleven focus groups held with engineering students at two U.S. universities, evidence of liminal engineering identities emerged. Focus group data was analyzed iteratively using an inductive analysis process due to the emergent nature of this study. Results: Our analysis found six categories for the reasons and justifications students gave for their liminal engineering identities: Mindsets and Related Personal Characteristics; Knowledge; Experience; Engineering Coursework and Degrees; the “Real World”; and Other People. We found that these categories sat on a continuum between an internal or self-driven sense of identity and an external or other-driven sense of identity. Conclusions: This work applies the concept of liminal identity to engineering education, emphasizing that engineering identity is more than an either/or prospect. It makes evident the intricate and intersecting ways in which students construct and justify their emerging engineering identities, and illuminates the reasons students give for refraining from fully adopting an engineering identity.
We demonstrate the first vertical-incidence Ge/SiGe quantum well reflection modulators fabricated entirely on standard silicon substrates. These modulators could help enable massively parallel, ...free-space optical interconnects to silicon chips. An asymmetric Fabry-Perot resonant cavity is formed around the quantum well region by alkaline etching the backside of the Si substrate to leave suspended SiGe membranes, upon which high-index-contrast Bragg mirrors are deposited. Electroabsorption and electrorefraction both contribute to the reflectance modulation. The devices exhibit greater than 10 dB extinction ratio with low insertion loss of 1.3 dB. High-speed modulation with a 3 dB bandwidth of 4 GHz is demonstrated. The moderate-Q cavity (Q ~ 600) yields an operating bandwidth of more than 1 nm and permits operation without active thermal stabilization.
Maize (Zea mays L.) plants have been transformed to express a Cry1F insecticidal crystal protein originally isolated from Bacillus thuringiensis Berliner. This protein controls lepidopteran pests of ...maize, including the European corn borer, Ostrinia nubilalis (Hübner). As part of the safety assessment for crops containing transgenes, a compositional analysis of the food and feed is conducted. This analysis is designed to detect unintended changes in the nutrient and antinutrient content of the raw commodities produced by the crop due to the insertion of the genes into the genomic DNA of the plant (pleotropic effects). Samples of transgenic and nontransgenic maize forage and grain were collected from six field sites located in the U.S. and Canada. Forage samples were analyzed for proximates and minerals, and grain was further analyzed for fatty acids, amino acids, vitamins, secondary metabolites, and antinutrients. Results demonstrated that maize expressing the Cry1F protein was equivalent to nontransgenic maize with respect to these important components. Comparison of the variability within the nontransgenic and transgenic hybrid, as compared to composition values reported in the literature, suggest that factors other than transgenes may contribute more substantially to the composition of crops. Keywords: Cry1F; hybrid; maize; seed
Site-selective DNA cleavage by diastereoisomers of Ni(II)•Gly-Gly-His-derived metallopeptides was investigated through high-resolution gel analyses and molecular dynamics simulations. ...Ni(II)•l-Arg-Gly-His and Ni(II)•d-Arg-Gly-His (and their respective Lys analogues) targeted A/T-rich regions; however, the l-isomers consistently modified a subset of available nucleotides within a given minor groove site, while the d-isomers differed in both their sites of preference and their ability to target individual nucleotides within some sites. In comparison, Ni(II)•l-Pro-Gly-His and Ni(II)•d-Pro-Gly-His were unable to exhibit a similar diastereoselectivity. Simulations of the above systems, along with Ni(II)•Gly-Gly-His, indicated that the stereochemistry of the amino-terminal amino acid produces either an isohelical metallopeptide that associates stably at individual DNA sites (l-Arg or l-Lys) or, with d-Arg and d-Lys, a noncomplementary metallopeptide structure that cannot fully employ its side chain nor amino-terminal amine as positional stabilizing moieties. In contrast, amino-terminal Pro-containing metallopeptides of either stereochemistry, lacking an extended side chain directed toward the minor groove, did not exhibit a similar diastereoselectivity. While the identity and stereochemistry of amino acids located in the amino-terminal peptide position influenced DNA cleavage, metallopeptide diastereoisomers containing l- and d-Arg (or Lys) within the second peptide position did not exhibit diastereoselective DNA cleavage patterns; simulations indicated that a positively charged amino acid in this location alters the interaction of the metallopeptide equatorial plane and the minor groove leading to an interaction similar to Ni(II)•Gly-Gly-His.
We report a Ge/SiGe quantum well waveguide electroabsorption modulator that is monolithically integrated with silicon-on-insulator waveguides. The active quantum well section is selectively grown on ...a silicon-on-insulator substrate and has a footprint of 8 . The integrated device demonstrates more than 3.2-dB contrast ratio with 1-V direct voltage swing at 3.5 GHz. We also show the potential of this device to operate in the telecommunication C-band at room temperature.
Plant oils, including canola oil, are considered to be major sources of vitamin K as the second most substantial contributor of vitamin K to the human diet. Green leafy vegetables are the largest ...source of vitamin K. However, the effects of environment and germplasm on vitamin K levels in harvested canola seed have not been extensively investigated. To better understand these relationships, harvested canola seed from a range of diverse cultivars grown in different geographical locations in North and South America was assessed for levels of vitamin K. The analytical method developed to perform this measurement was based on C30 reversed-phase HPLC that could distinguish the biologically active trans-vitamin K1 from the inactive cis-isomer. Results demonstrated that for the majority of the canola cultivars evaluated, those cultivated in the North American sites had higher average vitamin K1 levels than those cultivated in the South American sites. Not all of the cultivars exhibited differences in response to the environment, suggesting that individual cultivar genetics also played a role in the variability of vitamin K1 levels observed in canola seed. Results from this study suggest that cultivar and environmental effects influence vitamin K1 levels in canola seed and provide a context to assess compositional variability of new cultivars.
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