Experimental and Numerical Investigation of Flow Properties of Supersonic Helium-Air Jets

Heated high speed subsonic and supersonic jets operating on- or off-design are a source of noise that is not yet fully understood. Helium-air mixtures can be used in the correct ratio to simulate the total temperature ratio of heated air jets and hence have the potential to provide inexpensive and reliable flow and acoustic measurements. This study presents a combination of flow measurements of helium-air high speed jets and numerical simulations of similar helium-air mixture and heated air jets. Jets issuing from axisymmetric convergent and convergent-divergent nozzles are investigated, and the results show very strong similarity with heated air jet measurements found in the literature. This demonstrates the validity of simulating heated high speed jets with helium-air in the laboratory, together with the excellent agreement obtained in the presented data between the numerical predictions and the experiments. The very close match between the numerical and experimental data also validates the frozen chemistry model used in the numerical simulation

Does Function Follow Organizational Form? Evidence From the Lending Practices of Large and Small Banks

Theories based on incomplete contracting suggest that small organizations may do better than large organizations in activities that require the processing of soft information. We explore this idea in the context of bank lending to small firms, an activity that is typically thought of as relying heavily on soft information. We find that large banks are less willing than small banks to lend to informationally 'difficult' credits, such as firms that do not keep formal financial records. Moreover, controlling for the endogeneity of bank-firm matching, large banks lend at a greater distance, interact more impersonally with their borrowers, have shorter and less exclusive relationships, and do not alleviate credit constraints as effectively. All of this is consistent with small banks being better able to collect and act on soft information than large banks.

Does Function Follow Organzizational Form? Evidence From the Lending Practices of Large and Small Banks

Theories based on incomplete contracting suggest that small organizations may do better than large organizations in activities that require the processing of soft information. We explore this idea in the context of bank lending to small firms, an activity that is typically thought of as relying heavily on soft information. We find that large banks are less willing than small banks to lend to informationally “difficult†credits, such as firms that do not keep formal financial records. Moreover, controlling for the endogeneity of bank-firm matching, large banks lend at a greater distance, interact more impersonally with their borrowers, have shorter and less exclusive relationships, and do not alleviate credit constraints as effectively. All of this is consistent with small banks being better able to collect and act on soft information than large banks. The opinions in this paper do not necessarily reflect those of the Federal Reserve Board or its staff. This work has been supported by the National Science Foundation (Rajan, Stein), and the George J. Stigler Center for Study of the State and Economy (Rajan). Thanks also to seminar participants at Yale, the Federal Reserve Bank of New York, Tulane, Babson, the University of Illinois, the Federal Reserve Bank of Chicago Bank Structure Conference, the NBER and the Western Finance Association meetings, as well as to Abhijit Banerjee, Michael Kremer, David Scharfstein, Andrei Shleifer, Greg Udell, Christopher Udry and James Weston for helpful comments and suggestions.

Assessing The Health Of Fringing Salt Marshes Along The Fore River And Its Tributaries

Casco Bay has experienced two significant oil spills in recent history - the Tamano Tanker spill in 1972 and the Julie N spill in 1996. In addition, the Fore River and its tributaries have experienced numerous small spills over the years, including the August 2002 fuel oil spill (2,900 gallons) and the April 2003 jet fuel spill (6,000 gallons). The impacts of these spills on the fringing salt marshes that line the edges of the Fore River and its tributaries are not well understood. Are these salt marshes resilient enough to withstand these impacts and still act as healthy marshes should? Or are they functioning at lower levels, compared to other fringing salt marshes in Casco Bay? The salt marshes that line the Fore River provide an important suite of functions and values to the citizens of southern Maine. The results of this study will help resource managers in their efforts to protect these important and unique natural resources

A Comprehensive Wetland Program For Fringing Salt Marshes In The York River, Maine

The overall goal of this project was to assist the Town of York, Maine, in its efforts to monitor and protect the fringing salt marshes along the York River. In particular, the project focused on potential impacts to the marshes due to shoreline development pressures. Specific objectives included (1) gathering baseline data about the marshes (2) developing a set of indicators to be used in future monitoring, and (3) generating management recommendations

Copyright and the Use of Images as Biodiversity Data [Forum paper]

Taxonomy is the discipline responsible for charting the world’s organismic diversity, understanding ancestor/descendant relationships, and organizing all species according to a unified taxonomic classification system. Taxonomists document the attributes (characters) of organisms, with emphasis on those can be used to distinguish species from each other. Character information is compiled in the scientific literature as text, tables, and images. The information is presented according to conventions that vary among taxonomic domains; such conventions facilitate comparison among similar species, even when descriptions are published by different authors. There is considerable uncertainty within the taxonomic community as to how to re-use images that were included in taxonomic publications, especially in regard to whether copyright applies. This article deals with the principles and application of copyright law, database protection, and protection against unfair competition, as applied to images. We conclude that copyright does not apply to most images in taxonomic literature because they are presented in a standardized way and lack the individuality that is required to qualify as ‘copyrightable works’. There are exceptions, such as wildlife photographs, drawings and artwork produced in a distinctive individual form and intended for other than comparative purposes (such as visual art). Further exceptions may apply to collections of images that qualify as a database in the sense of European database protection law. In a few European countries, there is legal protection for photographs that do not qualify as works in the usual sense of copyright. It follows that most images found in taxonomic literature can be re-used for research or many other purposes without seeking permission, regardless of any copyright declaration. In observance of ethical and scholarly standards, re-users are expected to cite the author and original source of any image that they use

Platelet-derived growth factor stimulates Src-dependent mRNA stabilization of specific early genes in fibroblasts.

The Src family of protein-tyrosine kinases (SFKs) participates in a variety of signal transduction pathways, including promotion of cell growth, prevention of apoptosis, and regulation of cell interactions and motility. In particular, SFKs are required for the mitogenic response to platelet-derived growth factor (PDGF). However, it is not clear whether there is a discrete SFK-specific pathway leading to enhanced gene expression or whether SFKs act to generally enhance PDGF-stimulated gene expression. To examine this, we treated quiescent NIH3T3 cells with PDGF in the presence or absence of small molecule inhibitors of SFKs, phosphatidylinositol 3-kinase (PI3K), and MEK1/2. Global patterns of gene expression were analyzed by using Affymetrix Gene-Chip arrays, and data were validated by using reverse transcription-PCR and ribonuclease protection assay. We identified a discrete set of immediate early genes induced by PDGF and inhibited in the presence of the SFK-selective inhibitor SU6656. A subset of these SFK-dependent genes was induced by PDGF even in the presence of the MEK1/2 inhibitor U0126 or the PI3K inhibitor LY294002. By using ribonuclease protection assays and nuclear run-off assays, we further determined that PDGF did not stimulate the rate of transcription of these SFK-dependent immediate early genes but rather promoted mRNA stabilization. Our data suggest that PDGF regulates gene expression through an SFK-specific pathway that is distinct from the Ras-MAPK and PI3K pathways, and that SFKs signal gene expression by enhancing mRNA stability.Peer reviewe

Spatiotemporal dynamics of the postnatal developing primate brain transcriptome.

Developmental changes in the temporal and spatial regulation of gene expression drive the emergence of normal mature brain function, while disruptions in these processes underlie many neurodevelopmental abnormalities. To solidify our foundational knowledge of such changes in a primate brain with an extended period of postnatal maturation like in human, we investigated the whole-genome transcriptional profiles of rhesus monkey brains from birth to adulthood. We found that gene expression dynamics are largest from birth through infancy, after which gene expression profiles transition to a relatively stable state by young adulthood. Biological pathway enrichment analysis revealed that genes more highly expressed at birth are associated with cell adhesion and neuron differentiation, while genes more highly expressed in juveniles and adults are associated with cell death. Neocortex showed significantly greater differential expression over time than subcortical structures, and this trend likely reflects the protracted postnatal development of the cortex. Using network analysis, we identified 27 co-expression modules containing genes with highly correlated expression patterns that are associated with specific brain regions, ages or both. In particular, one module with high expression in neonatal cortex and striatum that decreases during infancy and juvenile development was significantly enriched for autism spectrum disorder (ASD)-related genes. This network was enriched for genes associated with axon guidance and interneuron differentiation, consistent with a disruption in the formation of functional cortical circuitry in ASD

Mixcoin Anonymity for Bitcoin with accountable mixes (Full version)

Abstract. We propose Mixcoin, a protocol to facilitate anonymous payments in Bitcoin and similar cryptocurrencies. We build on the emergent phenomenon of currency mixes, adding an accountability mechanism to expose theft. We demonstrate that incentives of mixes and clients can be aligned to ensure that rational mixes will not steal. Our scheme is efficient and fully compatible with Bitcoin. Against a passive attacker, our scheme provides an anonymity set of all other users mixing coins contemporaneously. This is an interesting new property with no clear analog in better-studied communication mixes. Against active attackers our scheme offers similar anonymity to traditional communication mixes.