12,593 research outputs found
Bus Rapid Transit: A Handbook for Partners, MTI Report 06-02
In April 2005, the Caltrans Division of Research and Innovation (DRI) asked MTI to assist with the research for and publication of a guidebook for use by Caltrans employees who work with local transit agencies and jurisdictions in planning, designing, and operating Bus Rapid Transit (BRT) systems that involve state facilities. The guidebook was also to assist to transit operators, local governments, community residents, and other stakeholders dealing with the development of BRT systems. Several areas in the state have experienced such projects ( San Diego , Los Angeles , San Francisco , and Alameda County ) and DRI wished to use that experience to guide future efforts and identify needed changes in statutes, policies, and other state concerns. Caltrans convened a Task Team from the Divisions of Research and Innovation, Mass Transportation, and Operations, together with stakeholders representing many of those involved with the BRT activities around the state. Prior to MTIâs involvement, this group produced a white paper on the topic, a series of questions, and an outline of the guidebook that MTI was to write. The MTI team conducted case studies of the major efforts in California, along with less developed studies of some of the other BRT programs under development or in early implementation phases around the state. The purpose was to clarify those issues that need to be addressed in the guidebook, as well as to compile information that would identify items needing legislative or regulatory action and items that Caltrans will need to address through district directives or other internal measures. A literature scan was used to develop a bibliography for future reference. The MTI team also developed a draft Caltrans directorâs policy document, which provides the basis for Caltransâ actions. This ultimately developed to be a project within a project. MTI submitted a draft document to Caltrans as a final product from the Institute. Task team members and Caltrans staff and leadership provided extensive review of the draft Bus Rapid Transit: A Handbook for Partners. Caltrans adopted a new Directorâs Policy and published the document, BRT Caltrans. The MTI âwraparoundâ report presented below discusses in more detail the process that was followed to produce the draft report. The process was in many ways as much a project as the report itself
Investigation of Gate Current in Neutron irradiated Al\u3csub\u3ex\u3c/sub\u3eGa\u3csub\u3e1-x\u3c/sub\u3eN/GaN Heterogeneous Field Effect Transistors Using Voltage and Temperature Dependence
The gate current of Al27Ga73N/GaN heterogeneous field effect transistors (HFETs) is investigated using current-voltage (IV) and current-temperature (IT) measurement demonstrating that trap assisted tunneling (TAT) is the primary current mechanism. A thermionic trap assisted tunneling (TTT) model is used with variables of Schottky barrier height, trap energy, donor density and trap density. This results in a sigma of 1.38x10-8 A for IT data measured between 85K and 290K and for IV data measured between 0.0 V and -4.0 V. High energy (\u3e0.5 MeV) neutron irradiation confirms an increase of gate current with fluence. An increase in magnitude of threshold voltage is also observed. The TTT model suggests that increased trap density is responsible for increased gate current at a fluence of 1.2x1012. An increase in trap density from the unirradiated fit value of 4.593x1021 to 5.737x1021 traps/m3 and an increase in the position of traps in the energy band from 0.896 to 0.9028 V results in a fit with Ï of 1.77x10-9 A. An increase in donor defect density is modeled resulting in a sigma of 5.00x10-9 A and an increase in threshold voltage magnitude consistent with the observed change in measured IV behavior
Evolution of Cooperative Thought, Theory, and Purpose
The evolution of agricultural cooperative thought, theory, and purpose in the United States is reviewed from the standpoint of the reemergence of interest in how cooperatives can provide some of the security and benefits that might be lost with gradual phasing out of federal government farm support programs. By accomplishing group action for self-help, the early development of cooperatives drew considerable attention from economists, social theorists, and politicians. Alternative schools of cooperative thought developed, but most proponents of cooperatives regarded them as having enormous potential to provide a public service role in building a more economically stable and democratic society This paper also surveys how cooperative theory was developed more rigorously in the post-WWII period. It has provided better analytical tools for understanding how and why cooperatives have changed in response to technological and economic developments, as well as to social trends, like individualism. Given the new perspectives on cooperative theory and the scope of changes in how cooperatives operate and are structured, cooperatives have even greater potential for coordinating self-help actions, but this potential needs the support of cooperative education services.Agribusiness,
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Sugar intake among German adolescents: trends from 1990-2016 based on biomarker excretion in 24-h urine samples
Trend analyses based on dietary records suggest decreases in the intakes of total (TS), added (AS) and free sugar (FS) since 2005 among children and adolescents in Germany. In terms of age trends, TS intake decreased with increasing age. However, self-reported sugar intake in epidemiological studies is criticized, as it may be prone to bias due to selective underreporting. Furthermore, adolescents are more susceptible to underreporting than children. We thus analyzed time and age trends in urinary fructose excretion (FE), sucrose excretion (SE) and the sum of both (FE+SE) as biomarkers for sugar intake among 8.5-16.5-year-old adolescents. Urinary sugar excretion was measured by UPLC-MS/MS in 997 24-h urine samples collected from 239 boys and 253 girls participating in the DONALD study cohort between 1990 and 2016. Time and age trends of log-transformed FE, SE and FE+SE were analyzed using polynomial mixed-effects regression models. Between 1990 and 2016 FE as well as FE+SE decreased (linear time trend: p=0.0272 and p<0.0001, respectively). A minor increase in excretion during adolescence was confined to FE (linear age trend: p=0.0017). The present 24-h excretion measurements support a previously reported dietary-record based decline in sugar intake since 2005. However, the previous seen dietary record-based decrease in TS from childhood to late adolescence was not confirmed by our biomarker analysis, suggesting a constant sugar intake for the period of adolescence
Long-range electron transfer in structurally engineered pentaammineruthenium (histidine-62) cytochrome c
In many biological processes, long-range electron transfer (ET) plays a key role. When the three-dimensional structures of proteins are accurately known, use of modified proteins and protein-protein complexes provides an experimental approach to study ET rates between two metal centers. For Ru(His)- modified proteins, the introduction of histidine residues at any desired surface location by site-directed mutagenesis opens the way for systematic investigations of ET pathways
Quantifying and resolving multiple vector transformants in S. cerevisiae plasmid libraries
<p>Abstract</p> <p>Background</p> <p>In addition to providing the molecular machinery for transcription and translation, recombinant microbial expression hosts maintain the critical genotype-phenotype link that is essential for high throughput screening and recovery of proteins encoded by plasmid libraries. It is known that <it>Escherichia coli </it>cells can be simultaneously transformed with multiple unique plasmids and thusly complicate recombinant library screening experiments. As a result of their potential to yield misleading results, bacterial multiple vector transformants have been thoroughly characterized in previous model studies. In contrast to bacterial systems, there is little quantitative information available regarding multiple vector transformants in yeast. <it>Saccharomyces cerevisiae </it>is the most widely used eukaryotic platform for cell surface display, combinatorial protein engineering, and other recombinant library screens. In order to characterize the extent and nature of multiple vector transformants in this important host, plasmid-born gene libraries constructed by yeast homologous recombination were analyzed by DNA sequencing.</p> <p>Results</p> <p>It was found that up to 90% of clones in yeast homologous recombination libraries may be multiple vector transformants, that on average these clones bear four or more unique mutant genes, and that these multiple vector cells persist as a significant proportion of library populations for greater than 24 hours during liquid outgrowth. Both vector concentration and vector to insert ratio influenced the library proportion of multiple vector transformants, but their population frequency was independent of transformation efficiency. Interestingly, the average number of plasmids born by multiple vector transformants did not vary with their library population proportion.</p> <p>Conclusion</p> <p>These results highlight the potential for multiple vector transformants to dominate yeast libraries constructed by homologous recombination. The previously unrecognized prevalence and persistence of multiply transformed yeast cells have important implications for yeast library screens. The quantitative information described herein should increase awareness of this issue, and the rapid sequencing approach developed for these studies should be widely useful for identifying multiple vector transformants and avoiding complications associated with cells that have acquired more than one unique plasmid.</p
Whole genome sequencing-based mapping and candidate identification of mutations from fixed zebrafish tissue
As forward genetic screens in zebrafish become more common, the number of mutants that cannot be identified by gross morphology or through transgenic approaches, such as many nervous system defects, has also increased. Screening for these difficult-to-visualize phenotypes demands techniques such as whole-mount in situ hybridization (WISH) or antibody staining, which require tissue fixation. To date, fixed tissue has not been amenable for generating libraries for whole genome sequencing (WGS). Here, we describe a method for using genomic DNA from fixed tissue and a bioinformatics suite for WGS-based mapping of zebrafish mutants. We tested our protocol using two known zebrafish mutant alleles, gpr126st49 and egr2bfh227, both of which cause myelin defects. As further proof of concept we mapped a novel mutation, stl64, identified in a zebrafish WISH screen for myelination defects. We linked stl64 to chromosome 1 and identified a candidate nonsense mutation in the F-box and WD repeat domain containing 7 (fbxw7) gene. Importantly, stl64 mutants phenocopy previously described fbxw7vu56 mutants, and knockdown of fbxw7 in wild-type animals produced similar defects, demonstrating that stl64 disrupts fbxw7. Together, these data show that our mapping protocol can map and identify causative lesions in mutant screens that require tissue fixation for phenotypic analysis
Avenues of future research in homotransplantation of the liver with particular reference to hepatic supportive procedures, antilymphocyte serum, and tissue typing
Three general areas of research which bear on the developing field of liver transplantation are reviewed. These are: (1) the prospects of obtaining better immunosuppression with particular reference to heterologous antilymphocyte serum; (2) the possible use of antigen matching technics as an advanced indicator of donorrecipient histocompatibility; (3) a simlified system of extracorporeal transplntation designed to provide teporary hepatic support. © 1966
Stem-Boring Caterpillars of Switchgrass in the Midwestern United States
Lepidopteran stem borers were collected from switchgrass, Panicum virgatum L., tillers showing symptoms of infestation at seven locations in Illinois and Iowa, with additional observations made on larval and adult activity. Blastobasis repartella (Dietz) (Coleophoridae), whose only known host is switchgrass, was common in plots grown for \u3e5 yr, whereas the polyphagous stalk borer, Papaipema nebris (GuenĂ©e) (Noctuidae), was abundant in newly established (i.e., first- and second year) switchgrass. Haimbachia albescens Capps (Crambidae) was collected from two locations in Illinois, making switchgrass the first known host for this species. Entry holes made by B. repartella and H. albescens were usually 1-2 cm above the soil surface, precluding discrimination between these species based on external appearance of damage. Although P. nebris often entered stems within 5 cm of the soil surface, they also seemed to move between stems and were the only species entering stems at heights \u3e15 cm. Adults of B. repartella were active on and above the switchgrass canopy by 2130 hours, with peak activity at â0230 hours. Activity of B. repartella adults seemed greatly reduced on one night with relatively cool temperatures and low wind speeds. Data from switchgrass and giant ragweed, Ambrosia trifida L., suggest P. nebris larvae move out of switchgrass during July in search of hosts with larger diameter stems, although by then hosts such as corn, Zea mays L., or Miscanthus spp. may have outgrown the potential for serious damage. However, switchgrass could contribute to greater adult populations of P. nebris if thick-stemmed hosts such as giant ragweed are not managed
Stem-Boring Caterpillars of Switchgrass in the Midwestern United States
Lepidopteran stem borers were collected from switchgrass, Panicum virgatum L., tillers showing symptoms of infestation at seven locations in Illinois and Iowa, with additional observations made on larval and adult activity. Blastobasis repartella (Dietz) (Coleophoridae), whose only known host is switchgrass, was common in plots grown for \u3e5 yr, whereas the polyphagous stalk borer, Papaipema nebris (GuenĂ©e) (Noctuidae), was abundant in newly established (i.e., first- and second year) switchgrass. Haimbachia albescens Capps (Crambidae) was collected from two locations in Illinois, making switchgrass the first known host for this species. Entry holes made by B. repartella and H. albescens were usually 1-2 cm above the soil surface, precluding discrimination between these species based on external appearance of damage. Although P. nebris often entered stems within 5 cm of the soil surface, they also seemed to move between stems and were the only species entering stems at heights \u3e15 cm. Adults of B. repartella were active on and above the switchgrass canopy by 2130 hours, with peak activity at â0230 hours. Activity of B. repartella adults seemed greatly reduced on one night with relatively cool temperatures and low wind speeds. Data from switchgrass and giant ragweed, Ambrosia trifida L., suggest P. nebris larvae move out of switchgrass during July in search of hosts with larger diameter stems, although by then hosts such as corn, Zea mays L., or Miscanthus spp. may have outgrown the potential for serious damage. However, switchgrass could contribute to greater adult populations of P. nebris if thick-stemmed hosts such as giant ragweed are not managed
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