Experimental Testing Program in Elementary Chemistry: A Preliminary Report

An experimental testing program is described which utilizes questions that are partly computer composed, in addition to a section composed by the instructor, and a retesting option to the student. Results from a trial of the program for one term indicate that (1) course grades were improved, (2) the student withdrawal failure rate was unaffected, and (3) the employed students took greater advantage of the retest than did the unemployed students

Part Rabbit, Part girl, Part Hole

The first issue of The September Issues and I was asked by the editor and photographer Mary Rozzi to create a visual response for their pages. The September Issues gives women creatives the opportunity to express themselves freely, explore their identities, and build a community without any constraints—a place where art, beauty, fashion, and topical issues can be discussed from a purely feminine perspective; a community that reflects the diversity and power of global femininity. The magazine aims to share ideas of identity, discover ritual and ceremony; celebrate and champion women pioneers of the past and present, and those yet to come—exchanging the story of women’s lives through visual and intellectual vocabularies. Politically, the world is fragmented. Recent events have demonstrated that change is most definitely the only thing we can be sure of in this moment. The September Issues want to be an active part of that change. We want to empower women by celebrating their achievements, and strive for the creation of an influential voice of equality in our future society. There was no brief. It was a magazine completed by women about women. A speculative tribe, linked invisibly by one common thread. I chose to continue the series of photographs shown at The Stanley Picker Gallery in The Liquid Game that follows the objects of and close to the earth as symbols and representations of the body. A codified place. Future memories. Abstract resistance. And this was the text to accompany the two images

Development of a Multi-Class Bicyclist Route Choice Model Using Revealed Preference Data

Existing regional travel forecasting systems are not typically set up to forecast usage of bicycle infrastructure and are insensitive to bicyclists\u27 route preferences in general. We collected revealed preference, GPS data on 162 bicyclists over the course of several days and coded the resulting trips to a highly detailed bicycle network model. We then use these data to estimate bicyclist route choice models. As part of this research, we developed a sophisticated choice set generation algorithm based on multiple permutations of labeled path attributes, which seems to out-perform comparable implementations of other route choice set generation algorithms. The model was formulated as a Path-Size Logit model to account for overlapping route alternatives. The estimation results show compelling intuitive elasticities for route choice attributes, including the effects of distance and delay; avoiding high-volumes of vehicular traffic, stops and turns, and elevation gain; and preferences for certain bike infrastructure types, particularly at bridge crossings and off-street paths. Estimation results also support segmentation by commute versus non-commute trip types, but are less clear when it comes to gender. The final model will be implemented as part of the regional travel forecasting system for Portland, Oregon, U.S.A

Regulation of the galactose pathway in Saccharomyces cerevisiae: induction of uridyl transferase mRNA and dependency on GAL4 gene function

In Saccharomyces cerevisiae, utilization of galactose requires four inducible enzyme activities. Three of these activities (galactose-1-phosphate uridyl transferase, EC 2.7.7.10; uridine diphosphogalactose 4-epimerase, EC 5.1.3.2; and galactokinase, EC 2.7.1.6) are specified by three tightly linked genes (GAL7, GAL10, and GAL1, respectively) on chromosome II, whereas the fourth, galactose transport, is specified by a gene (GAL2) located on chromosome XII. Although classic genetic analysis has revealed both positive and negative regulatory genes that coordinately affect the appearance of all four enzyme activities, neither the basic events leading to the appearance of enzyme activities nor the roles of the regulatory genes have yet been determined. Regulation of inducible enzyme activity could be mediated by events related to transcription, translation, or enzyme activation. For the purpose of studying galactose pathway induction and its regulation, we have developed an immunoprecipitation assay that enables us to detect the GAL7 specified uridyl transferase polypeptide in yeast extracts and among the polypeptides synthesized in an RNA-dependent in vitro translation system. Use of this immunoprecipitation assay in conjunction with in vivo labeling experiments demonstrates the presence of [(3)H]leucine-labeled transferase in extracts prepared from cells grown in galactose but not from cells grown in glucose. This galactose-specific induction of transferase polypeptide is mediated by the de novo appearance of a functional mRNA species whose synthetic capacity is detectable by the combination of in vitro translation and immunoprecipitation. The appearance of functional transferase mRNA depends on wild-type expression of the positive regulatory gene, GAL4. Cells carrying a nonsense (amber) mutation in the GAL4 gene fail to produce the transferase mRNA, whereas a nonsense suppressor of the GAL4 amber mutant regains the galactose-specific mRNA response. Our results establish that the induction of the GAL7 specified uridyl transferase activity is mediated by de novo appearance of a functional mRNA and that this galactose-specific response is dependent on a wild-type GAL4 gene product

Diversifying and normalising cycling in London, UK: An exploratory study on the influence of infrastructure

This article examines the extent to which protected infrastructure is associated with greater diversity and normalisation of cycling. In the UK, cyclists are predominantly male and often wear distinctive cycle clothing rather than everyday clothes. This is not the case in higher-cycling countries such as the Netherlands and Germany. It has been argued that the UK's demographic skewing may be partly due to poor quality infrastructure which can be off-putting for many, but particularly for women, children and older people. Route choice studies tend to confirm that women are more likely than men to choose routes with greater levels of separation from motor traffic. Other work suggests that if cycling feels unsafe, cyclists may wear specialised cycle clothing such as helmets, which then may itself support a perception of cycling as dangerous. This small-scale exploratory study examines age, gender, and use of specialist clothing in relation to infrastructure type, comparing a recently improved route with separate space for cyclists to parallel busy streets without protected cycle infrastructure. The separated route showed better, though still unequal, demographic balance and a reduced tendency for cyclists to wear helmets and sporty clothing, though not high-visibility items. Infrastructure type is only one factor in route choice, particularly if there is relatively little good infrastructure along key desire lines. However this paper suggests that infrastructure for cycling could help to improve perceptions of safety and the need to wear specialist cycle clothing. In turn this could promote a better demographic balance and normalise cycling

Spectroscopic investigation of nitrogenase: EPR and MCD studies of the FeMo cofactor and the P-cluster

Little is known about substrate binding and reduction of nitrogenase. EPR spectroscopy is used here to observe intermediate states generated by different substrates. Two different spin states (S=3/2 and S=1/2) were exhibited for each substrate, which may result from different binding of the substrate to the cofactor (side-on or terminal binding) or the difference of the substrate binding to either Fe or Mo of the cofactor. Parallel studies were performed on a variant MoFe protein, alpha-195Gln, which exhibited different signals from the wild-type suggesting that the substituted amino acid maybe necessary to reach some mechanistic states that the wild-type MoFe protein can reach. Electron transfer between the Fe protein and the MoFe protein was investigated to help determine the initial electron transfer pathway in nitrogenase. The altered Fe protein, L127-deletion Fe protein, is permanently in the complex-ready conformation and complexes with the MoFe protein to allow one electron transfer. The MCD studies suggest the presence of a second paramagnetic center in addition to the resting state cofactor. The second paramagnetic center may result from an electron delocalized over the entire P-cluster or its return to the Fe protein. The P-cluster is suggested to play a role in the electron transfer from the Fe protein to the cofactor. Apo-proteins were used to provide information about the function and the maturation of the P-cluster. One apo-protein, nifB-deletion MoFe protein, exhibits redox characteristics analogous to the wild-type MoFe protein, i.e., both as-isolated proteins have the P-cluster in the state P0 and could be oxidized to P+2. The second apo-protein, nifH-deletion MoFe protein, demonstrated different characteristics. The as-isolated form appears to be in the P+1 state and can be oxidized to a previously unobserved state now suggested to be S=2.0. These results indicate that nifH-deletion MoFe protein P-clusters electronically differ from the mature fully functioning P-cluster in the nifB-deletion and wild-type MoFe proteins suggesting that NifH is necessary for the maturation of the P-cluster

DNA looping: the consequences and its control

The formation of DNA loops by proteins and protein complexes is ubiquitous to many fundamental cellular processes, including transcription, recombination, and replication. Here we review recent advances in understanding the properties of DNA looping in its natural context and how they propagate to the cellular behavior through gene regulation. The results of connecting the molecular properties with cellular physiology indicate that looping of DNA in vivo is much more complex and easier than predicted from current models and reveals a wealth of previously unappreciated details