520 research outputs found
Theory and operation of the real-time data acquisition system for the NASA-LaRC differential absorption lidar (DIAL)
The improvement of computer hardware and software of the NASA Multipurpose Differential Absorption Lidar (DIAL) system is documented. The NASA DIAL system has undergone development and experimental deployment at NASA/Langley Res. Center for the remote measurement of atmospheric trace gas concentrations from ground and aircraft platforms. A viable DIAL system was developed capable of remotely measuring O3 and H2O concentrations from an aircraft platform. The DIAL Data Acquisition System (DAS) has undergone a number of improvements also. Due to the participation of the DIAL in the Global Tropospheric Experiment, modifications and improvements of the system were tested and used both in the lab and in air. Therefore, this is an operational manual for the DIAL DAS
Pennsylvanian Spiriferacea and Spiriferinacea of Kansas
36 p., 22 fig.http://paleo.ku.edu/contributions.htm
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Effect of Time-of-Flight and Regularized Reconstructions on Quantitative Measurements and Qualitative Assessments in Newly Diagnosed Prostate Cancer With 18F-Fluorocholine Dual Time Point PET/MRI.
Recent technical advances in positron emission tomography/magnetic resonance imaging (PET/MRI) technology allow much improved time-of-flight (TOF) and regularized iterative PET reconstruction regularized iterative reconstruction (RIR) algorithms. We evaluated the effect of TOF and RIR on standardized uptake values (maximum and peak SUV [SUVmax and SUVpeak]) and their metabolic tumor volume dependencies and visual image quality for 18F-fluorocholine PET/MRI in patients with newly diagnosed prostate cancer. Fourteen patients were administered with 3 MBq/kg of 18F-fluorocholine and scanned dynamically for 30 minutes. Positron emission tomography images were divided to early and late time points (1-6 minutes summed and 7-30 minutes summed). The values of the different SUVs were documented for dominant PET-avid lesions, and metabolic tumor volume was estimated using a 50% isocontour and SUV threshold of 2.5. Image quality was assessed via visual acuity scoring (VAS). We found that incorporation of TOF or RIR increased lesion SUVs. The lesion to background ratio was not improved by TOF reconstruction, while RIR improved the lesion to background ratio significantly ( P < .05). The values of the different VAS were all significantly higher ( P < .05) for RIR images over TOF, RIR over non-TOF, and TOF over non-TOF. In conclusion, our data indicate that TOF or RIR should be incorporated into current protocols when available
Segregation and Tiebout Sorting: Investigating the Link between Investments in Public Goods and Neighborhood Tipping
Segregation has been a recurring social concern throughout human history. While much progress has been made to our understanding of the mechanisms driving segregation, work to date has ignored the role played by location-specific amenities. Nonetheless, policy remedies for reducing group inequity often involve place-based investments in minority communities. In this paper, we introduce an exogenous location-specific public good into a model of group segregation. We characterize the equilibria of the model and derive the comparative statics of improvements to the local public goods. We show that the dynamics of neighborhood tipping depend on the levels of public goods. We also show that investments in low-public good communities can actually increase segregation.
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An Empirical Examination of Service Dominant Logic: The Theory of the Network
Marketing scholars question the ability of the 4Ps to explain higher order phenomena in modern marketing. Scholars contend that marketing's historical framework, based in product centric economic theory, constrains the 4Ps ability to form a foundation for a general theory of marketing. The focus on value embedded in product fails to explain knowledge-based intangible sources of competitive advantage. In response to this concern a new dominant logic for marketing called service-dominant logic (S-D Logic) has been proposed. However, not all scholars are supportive of S-D Logic. Still nescient, S-D Logic lacks a theoretic model, operationalized constructs, and relationships between those constructs. This study addresses those deficiencies by: (1) generation of a grounded theory of a performance-oriented network; (2) empirical assessment of the S-D Logic literature; and (3) development of an inductively generated theory of S-D Logic to include constructs, relationships, outcomes, and hypothesis. This investigation provides an important set of research findings. The resultant service-oriented network theory suggests a theoretic structure for S-D Logic. Use of grounded theory provides a strong empirical foundation based in a leading edge multi-national market segment composed corporations and programs worth hundreds of billions of dollars. The analysis drew upon 44 field interviews and follow-up exchanges. Multiple member checking sessions generated practitioner confirmation of the research conclusions. The work provides actionable theoretical and practical implications. This investigation provides a link between S-D Logic as a foundation for a general theory of marketing and initial model of suggestive of such theory. For the practitioner the service-oriented network model provides actionable constructs. The antecedents identified are largely influencable by inter-firm leadership and provides them a mechanism to tailor the specific service-oriented strategy to support the desired network value propositions
Reassessment of vertebrate ichnotaxa from the Upper Carboniferous āFern Ledgesā, Lancaster Formation, Saint John, New Brunswick, Canada
Vertebrate ichnotaxa described by George Frederic Matthew in 1910 from the Upper Carboniferous (Lower Pennsylvanian) āFern Ledgesā of Saint John, New Brunswick, were dismissed as dubious trackways by previous authors. Thus, three new ichnospecies Matthew described appeared in the 1975 Treatise on Invertebrate Paleontology as āunrecognized or unrecognizableā and were mostly forgotten by vertebrate ichnologists. These traces include Hylopus (?) variabilis, Nanopus (?) vetustus and Bipezia bilobata. One ichnospecies, Hylopus (?) variabilis, here is retained as a valid tetrapod footprint ichnotaxon and reassigned to the ichnogenus Limnopus as a new combination, together with other poorly preserved specimens Matthew labeled, but never described. Nanopus (?) vetustus and Bipezia bilobata named by Matthew in the same paper, have been reexamined and remain as nomina dubia.
A Novel Diagnostic Aid for Detection of Intra-Abdominal Adhesions to the Anterior Abdominal Wall Using Dynamic Magnetic Resonance Imaging
Introduction. Abdominal adhesions can cause serious morbidity and complicate subsequent operations. Their diagnosis is often one of exclusion due to a lack of a reliable, non-invasive diagnostic technique. Development and testing of a candidate technique are described below. Method. During respiration, smooth visceral sliding motion occurs between the abdominal contents and the walls of the abdominal cavity. We describe a technique involving image segmentation and registration to calculate shear as an analogue for visceral slide based on the tracking of structures throughout the respiratory cycle. The presence of an adhesion is attributed to a resistance to visceral slide resulting in a discernible reduction in shear. The abdominal movement due to respiration is captured in sagittal dynamic MR images. Results. Clinical images were selected for analysis, including a patient with a surgically confirmed adhesion. Discernible reduction in shear was observed at the location of the adhesion while a consistent, gradually changing shear was observed in the healthy volunteers. Conclusion. The technique and its validation show encouraging results for adhesion detection but a larger study is now required to confirm its potential
Investigative Ophthalmology (j Visual Science Articles Membrane Skeleton Protein 4.1 in Inner Segments of Retinal Cones
The role of the spectrin-based membrane skeleton in regulation of cell morphology and immobilization of integral membrane proteins is well established in erythrocytes and is currently being investigated in other eukaryotic cells
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Evolution of the melt source during protracted crustal anatexis: An example from the Bhutan Himalaya
The chemical compositions of magmatic zircon growth zones provide powerful insight into evolving magma compositions due to their ability to record both time and the local chemical environment. In situ U-Pb and Hf isotope analyses of zircon rims from OligoceneāMiocene leucogranites of the Bhutan Himalaya reveal, for the first time, an evolution in melt composition between 32 and 12 Ma. The data indicate a uniform melt source from 32 Ma to 17 Ma, and the progressive addition of an older source component to the melt from at least ca. 17 Ma. Age-corrected ĪµHf ratios decrease from between ā10 and ā15 down to values as low as ā23 by 12 Ma. Complementary whole-rock Nd isotope data corroborate the Hf data, with a progressive decrease in ĪµNd(t) from ca. 18 to 12 Ma. Published zircon and whole-rock Nd data from different lithotectonic units in the Himalaya suggest a chemical distinction between the younger Greater Himalayan Series (GHS) and the older Lesser Himalayan Series (LHS). The time-dependent isotopic evolution shown in the leucogranites demonstrates a progressive increase in melt contribution from older lithologies, suggestive of increasing LHS involvement in Himalayan melting over time. The time-resolved data are consistent with LHS material being progressively accreted to the base of the GHS from ca. 17 Ma, facilitated by deformation along the Main Central thrust. From 17 Ma, decompression, which had triggered anatexis in the GHS since the Paleogene, enabled melting in older sources from the accreted LHS, now forming the lowermost hanging wall of the thrust
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