Market-Based Alternatives for Managing Congestion at New York’s LaGuardia Airport

We summarize the results of a project that was motivated by the expiration of the “High Density Rule,” which defined the slot controls employed at New York’s LaGuardia Airport for more than 30 years. The scope of the project included the analysis of several administrative measures, congestion pricing options and slot auctions. The research output includes a congestion pricing procedure and also the specification of a slot auction mechanism. The research results are based in part on two strategic simulations. These were multi-day events that included the participation of airport operators, most notably the Port Authority of New York and New Jersey, FAA and DOT executives, airline representatives and other members of the air transportation community. The first simulation placed participants in a stressful, high congestion future scenario and then allowed participants to react and problem solve under various administrative measures and congestion pricing options. The second simulation was a mock slot auction in which participants bid on LGA arrival and departure slots for fictitious airlines.Auctions, airport slot auctions, combinatorial auctions

Parameterized Supply Function Bidding: Equilibrium and Efficiency

We consider a model where a finite number of producers compete to meet an infinitely divisible but inelastic demand for a product. Each firm is characterized by a production cost that is convex in the output produced, and firms act as profit maximizers. We consider a uniform price market design that uses supply function bidding: firms declare the amount they would supply at any positive price, and a single price is chosen to clear the market. We are interested in evaluating the impact of price-anticipating behavior both on the allocative efficiency of the market and on the prices seen at equilibrium. We show that by restricting the strategy space of the firms to parameterized supply functions, we can provide upper bounds on both the inflation of aggregate cost at the Nash equilibrium relative to the socially optimal level, as well as the markup of the Nash equilibrium price above the competitive level: as long as N > 2 firms are competing, these quantities are both upper bounded by 1 + 1/(N − 2). This result holds even in the presence of asymmetric cost structure across firms. We also discuss several extensions, generalizations, and related issues.National Science Foundation (U.S.) (Graduate Research Fellowship)National Science Foundation (U.S.) (grant ECS-0312921

Market-Based Alternatives for Managing Congestion at New York’s LaGuardia Airport

In the paper, we summarize the results of a project that was motivated by the expiration of the “High Density Rule,” which defined the slot controls employed at New York’s LaGuardia Airport for more than 30 years. The scope of the project included the analysis of several administrative measures, congestion pricing options and slot auctions. The research output includes a congestion pricing procedure and also the specification of a slot auction mechanism. The research results are based in part on two strategic simulations. These were multi-day events that included the participation of airport operators, most notably the Port Authority of New York and New Jersey, FAA and DOT executives, airline representatives and other members of the air transportation community. The first simulation placed participants in a stressful, high congestion future scenario and then allowed participants to react and problem solve under various administrative measures and congestion pricing options. The second simulation was a mock slot auction in which participants bid on LGA arrival and departure slots for fictitious airlines

Structured feedback on students’ concept maps: the proverbial path to learning?

Good conceptual knowledge is an essential requirement for health professions students, in that they are required to apply concepts learned in the classroom to a variety of different contexts. However, the use of traditional methods of assessment limits the educator’s ability to correct students’ conceptual knowledge prior to altering the educational context. Concept mapping (CM) is an educational tool for evaluating conceptual knowledge, but little is known about its use in facilitating the development of richer knowledge frameworks. In addition, structured feedback has the potential to develop good conceptual knowledge. The purpose of this study was to use Kinchin’s criteria to assess the impact of structured feedback on the graphical complexity of CM’s by observing the development of richer knowledge frameworks. Fifty-eight physiotherapy students created CM’s targeting the integration of two knowledge domains within a case-based teaching paradigm. Each student received one round of structured feedback that addressed correction, reinforcement, forensic diagnosis, benchmarking, and longitudinal development on their CM’s prior to the final submission. The concept maps were categorized according to Kinchin’s criteria as either Spoke, Chain or Net representations, and then evaluated against defined traits of meaningful learning. The inter-rater reliability of categorizing CM’s was good. Pre-feedback CM’s were predominantly Chain structures (57%), with Net structures appearing least often. There was a significant reduction of the basic Spoke- structured CMs (P = 0.002) and a significant increase of Net-structured maps (P < 0.001) at the final evaluation (post-feedback). Changes in structural complexity of CMs appeared to be indicative of broader knowledge frameworks as assessed against the meaningful learning traits. Feedback on CM’s seemed to have contributed towards improving conceptual knowledge and correcting naive conceptions of related knowledge. Educators in medical education could therefore consider using CM’s to target individual student development

The mating-specific Gα interacts with a kinesin-14 and regulates pheromone-induced nuclear migration in budding yeast

As a budding yeast cell elongates toward its mating partner, cytoplasmic microtubules connect the nucleus to the cell cortex at the growth tip. The Kar3 kinesin-like motor protein is then thought to stimulate plus-end depolymerization of these microtubules, thus drawing the nucleus closer to the site where cell fusion and karyogamy will occur. Here, we show that pheromone stimulates a microtubule-independent interaction between Kar3 and the mating-specific Gα protein Gpa1 and that Gpa1 affects both microtubule orientation and cortical contact. The membrane localization of Gpa1 was found to polarize early in the mating response, at about the same time that the microtubules begin to attach to the incipient growth site. In the absence of Gpa1, microtubules lose contact with the cortex upon shrinking and Kar3 is improperly localized, suggesting that Gpa1 is a cortical anchor for Kar3. We infer that Gpa1 serves as a positional determinant for Kar3-bound microtubule plus ends during mating. © 2009 by The American Society for Cell Biology

Antifungal coatings by caspofungin immobilization onto biomaterials surfaces via a plasma polymer interlayer

Published Online: 14 October 2015Not only bacteria but also fungal pathogens, particularly Candida species, can lead to biofilm infections on biomedical devices. By covalent grafting of the antifungal drug caspofungin, which targets the fungal cell wall, onto solid biomaterials, a surface layer can be created that might be able to provide long-term protection against fungal biofilm formation. Plasma polymerization of propionaldehyde (propanal) was used to deposit a thin (∼20 nm) interfacial bonding layer bearing aldehyde surface groups that can react with amine groups of caspofungin to form covalent interfacial bonds for immobilization. Surface analyses by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed the intended grafting and uniformity of the coatings, and durability upon extended washing. Testing for fungal cell attachment and ensuing biofilm formation showed that caspofungin retained activity when covalently bound onto surfaces, disrupting colonizing Candida cells. Mammalian cytotoxicity studies using human primary fibroblasts indicated that the caspofungin-grafted surfaces were selective in eliminating fungal cells while allowing attachment and spreading of mammalian cells. These in vitro data suggest promise for use as antifungal coatings, for example, on catheters, and the use of a plasma polymer interlayer enables facile transfer of the coating method onto a wide variety of biomaterials and biomedical devices.Stefani S. Griesser, Marek Jasieniak, Bryan R. Coad, and Hans J. Griesse

Engineering the Controlled Assembly of Filamentous Injectisomes in E. coli K-12 for Protein Translocation into Mammalian Cells.

Bacterial pathogens containing type III protein secretion systems (T3SS) assemble large needle-like protein complexes in the bacterial envelope, called injectisomes, for translocation of protein effectors into host cells. The application of these molecular syringes for the injection of proteins into mammalian cells is hindered by their structural and genomic complexity, requiring multiple polypeptides encoded along with effectors in various transcriptional units (TUs) with intricate regulation. In this work, we have rationally designed the controlled expression of the filamentous injectisomes found in enteropathogenic Escherichia coli (EPEC) in the nonpathogenic strain E. coli K-12. All structural components of EPEC injectisomes, encoded in a genomic island called the locus of enterocyte effacement (LEE), were engineered in five TUs (eLEEs) excluding effectors, promoters and transcriptional regulators. These eLEEs were placed under the control of the IPTG-inducible promoter Ptac and integrated into specific chromosomal sites of E. coli K-12 using a marker-less strategy. The resulting strain, named synthetic injector E. coli (SIEC), assembles filamentous injectisomes similar to those in EPEC. SIEC injectisomes form pores in the host plasma membrane and are able to translocate T3-substrate proteins (e.g., translocated intimin receptor, Tir) into the cytoplasm of HeLa cells reproducing the phenotypes of intimate attachment and polymerization of actin-pedestals elicited by EPEC bacteria. Hence, SIEC strain allows the controlled expression of functional filamentous injectisomes for efficient translocation of proteins with T3S-signals into mammalian cells