Flight experience with a pivoting traversing boundary-layer probe

A pivoting traversing boundary layer probe was evaluated in flight on an F-104 airplane. The evaluation was performed at free stream Mach numbers from 0.8 to 2.0. The unit is described, and operating problems and their solutions are discussed. Conventional boundary layer profiles containing variations in flow angle within the viscous layer are shown for free stream Mach numbers of 0.8, 1.6, and 2.0. Although the unit was not optimized for size and weight, it successfully measured simultaneously flow angularity, probe height, and pitot pressure through the boundary layer

RNA secondary structure design

We consider the inverse-folding problem for RNA secondary structures: for a given (pseudo-knot-free) secondary structure find a sequence that has that structure as its ground state. If such a sequence exists, the structure is called designable. We implemented a branch-and-bound algorithm that is able to do an exhaustive search within the sequence space, i.e., gives an exact answer whether such a sequence exists. The bound required by the branch-and-bound algorithm are calculated by a dynamic programming algorithm. We consider different alphabet sizes and an ensemble of random structures, which we want to design. We find that for two letters almost none of these structures are designable. The designability improves for the three-letter case, but still a significant fraction of structures is undesignable. This changes when we look at the natural four-letter case with two pairs of complementary bases: undesignable structures are the exception, although they still exist. Finally, we also study the relation between designability and the algorithmic complexity of the branch-and-bound algorithm. Within the ensemble of structures, a high average degree of undesignability is correlated to a long time to prove that a given structure is (un-)designable. In the four-letter case, where the designability is high everywhere, the algorithmic complexity is highest in the region of naturally occurring RNA.Comment: 11 pages, 10 figure

Gradel

A major problem facing Computer Science faculty members at Cedarville University is grading student assignments. Specifically, grading programming assignments can be a repetitive, time-consuming process which makes it prime for automation. Professors need a web application that takes student code, compiles it, and compares the output to what the professors provides as correct. Gradel, a senior design project, allows students to submit their code online and receive instant feedback based on professor-designed test cases. Furthermore, professors need to be able to keep track of what grades students earn on their projects, which is functionality Gradel provides. In addition to allowing professors to create courses for typical class use, Gradel also allows professors to create contests, such as the annual programming competition that takes place on campus every year. Gradel has been used for several sections of a class and this year’s contest, and the results are extremely promising

Discourses of sexual relationships in a sample of German and British young people: a Q methodological study

Young people live in an environment which sexualises young people, particularly women, along traditional gender roles. This, in parallel with a silence about positive sexuality in policy development, means that sexual double standards prevail in young people’s lives. The aim of this study was to explore the discourses young women and men from two European countries, Germany and England, draw on when making sense of sexual relationships, and how these are steeped in the local cultural climate and messages. The study used Q methodology and included 65 German and English young people between 16 and 19 years of age. Six accounts emerged: sex as responsible, intimate and shared experience; sex as joint fun; ideal versus reality; sex has to be responsible, consensual and shared; caring relationships offer the perfect context for fulfilling sex; and equality between partners. The importance of cultural context in the availability of specific dominant and alternative discourses is discussed with a focus on how this influences young people’s sense-making with regard to sexuality and sexual relationships. Future directions for research are highlighted

Kraft odor problem

Title from folder label.Project report form no. 1 dated 9-22-48. William Shockley -- Project report form no. 1 dated February 16, 1949. / J. R. Peckham -- Project report form no. Final dated April 16, 1949. Final report on the work done on the kraft odor problem / F. E. Brauns -- Project report form no. 2 dated April 20, 1949. / John R. Peckham -- Project report form no. 5 dated July 1, 1949 / Charles Peckham -- Project report form no. 3 dated July 26, 1949. Prehydrolysis of wood / John Peckham -- Project report form no. 4 dated August 3, 1949 / John R. Peckham

Fluctuation-Facilitated Charge Migration along DNA

We propose a model Hamiltonian for charge transfer along the DNA double helix with temperature driven fluctuations in the base pair positions acting as the rate limiting factor for charge transfer between neighboring base pairs. We compare the predictions of the model with the recent work of J.K. Barton and A.H. Zewail (Proc.Natl.Acad.Sci.USA, {\bf 96}, 6014 (1999)) on the unusual two-stage charge transfer of DNA.Comment: 4 pages, 2 figure

Two-level system with a thermally fluctuating transfer matrix element: Application to the problem of DNA charge transfer

Charge transfer along the base-pair stack in DNA is modeled in terms of thermally-assisted tunneling between adjacent base pairs. Central to our approach is the notion that tunneling between fluctuating pairs is rate-limited by the requirement of their optimal alignment. We focus on this aspect of the process by modeling two adjacent base pairs in terms of a classical damped oscillator subject to thermal fluctuations as described by a Fokker-Planck equation. We find that the process is characterized by two time scales, a result that is in accord with experimental findings.Comment: original file is revtex4, 10 pages, three eps figure

Groundwater quality: global challenges, emerging threats and novel approaches

Improving our understanding of groundwater quality threats to human health and the environment is essential to protect and manage groundwater resources effectively. This essay highlights some global groundwater quality challenges, describes key contaminant groups and threats of emerging concern, including antimicrobial resistance, and discusses novel approaches to assessing groundwater quality. Groundwater quality monitoring needs to improve significantly in order to effectively identify and mitigate threats to groundwater from historical, current and future pollution