2,447 research outputs found
Mapping X-ray heliometer for Orbiting Solar Observatory-8
An instrument combining mechanical collimators and proportional counter detectors was designed to record solar X-rays with energies of 2-30 keV with good temperal, spectral, and spatial resolution. The overall operation of the instrument is described to the degree needed by personnel who interact with the experimenter during SC/experiment interfacing, experiment testing, observatory integration and testing, and pre/post launch data processing. The general layout of the instrument is given along with a summary of the instrument characteristics
Energy Loss from a Moving Vortex in Superfluid Helium
We present measurements on both energy loss and pinning for a vortex
terminating on the curved surface of a cylindrical container. We vary surface
roughness, cell diameter, fluid velocity, and temperature. Although energy loss
and pinning both arise from interactions between the vortex and the surface,
their dependences on the experimental parameters differ, suggesting that
different mechanisms govern the two effects. We propose that the energy loss
stems from reconnections with a mesh of microscopic vortices that covers the
cell wall, while pinning is dominated by other influences such as the local
fluid velocity.Comment: 8 pages, 6 figure
Individual and situational determinants of altruism and helping behaviour
Studies which have attempted to assess the relative contributions of individual and situational determinants of helping behaviour and altruism have yielded diverse and contradictory data. The present investigation attempts to reconcile some of these inconsistent findings by examining the interaction of individual factors such as personality and sex with situational influences such as group size and task involvement. Explanations of helping behaviour and empirical studies are critically reviewed and methodological problems considered. The first four experiments take place in the laboratory and employ a simulated emergency representing a person falling off a ladder. Results indicate that individual factors may be more meaningful predictors of helping behaviour when examined in light of relevant situational effects. Differences in the helpfulness of low and high Machiavellians, as measured by Christie's Mach IV Inventory, seem to emerge only when face-to-face interaction, latitude for improvisation, and emotional involvement are possible. In such situations, groups of low Machs appear more likely than groups of high Machs to aid a distressed victim. However, when subjects are alone, not communicating, or in mixed-Mach groups, no differences in helping are found. The findings also demonstrate that group size effects on helping may be enhanced when communication channels are blocked, ambiguous emergencies are employed, and passive confederates pose as bystanders. The last two experiments pool previous findings and more naturalistic data to explore the consistency of the helpfulness of individual subjects across several situations. The results cast doubt on the existence of general helping dispositions. The findings suggest that seemingly irrelevant factors often ignored by researchers may play an important role in studies of helping behaviour. Contradictory results of previous research may be at least partly due to a number of inappropriate assumptions about the strength of single variables, and between-study comparisons may thus be unjustified
The Lockheed OSO-8 program. Analysis of data from the mapping X-ray heliometer experiment
The final report describes the extent of the analysis effort, and other activities associated with the preservation and documentation of the data set are described. The main scientific results, which are related to the behavior of individual solar activity regions in the energy band 1.5 - 15 keV, are summarized, and a complete bibliography of publications and presentations is given. Copies of key articles are also provided
Study of a novel range-dependent propogation effect with application to the axial injection of signals from the Kaneohe source
A novel range-dependent propagation effect occurs when a source is placed on the seafloor in shallow water with a downward refracting sound speed profile, and sound waves propagate down a slope into deep water. Under these conditions, small grazing-angle sound waves slide along the bottom downward and outward from the source until they reach the depth of the sound channel axis in deep water, where they are detached from the sloping bottom and continue to propagate outward near the sound channel axis. This mudslide effect is one of a few robust and predictable acoustic propagation effects that occur in range-dependent ocean environments. As a consequence of this effect, a bottom mounted source in shallow water can inject a significant amount of acoustic energy into the axis of the deep ocean sound channel that can then propagate to very long ranges. Numerical simulations with a full-wave range-dependent acoustic model show that the Kaneohe experiment had the appropriate source, bathymetry, and sound speed profiles that allows this effect to operate efficiently. This supports the interpretation that some of the near-axial acoustic signals, received near the coast of California from the bottom mounted source located in shallow water in Kaneohe Bay, Oahu, Hawaii, were injected into the sound channel of the deep Pacific Ocean by this mechanism. Numerical simulations suggest that the mudslide effect is robust
Student conceptions about energy transformations: progression from general chemistry to biochemistry
Students commencing studies in biochemistry must transfer and build on concepts they learned in chemistry and biology classes. It is well established, however, that students have difficulties in transferring critical concepts from general chemistry courses; one key concept is âenergy.â Most previous work on studentsâ conception of energy has focused on their understanding of energy in the context of physics (including the idea of âworkâ) and/or their understanding of energy in classical physical and inorganic chemistry contexts (particularly Gibbs Free Energy changes, the second law of thermodynamics, and equilibrium under standard conditions within a closed system). For biochemistry, students must go beyond those basic thermodynamics concepts of work, standard energy changes, and closed systems, and instead they must consider what energy flow, use, and transformation mean in living, open, and dynamic systems. In this study we explored studentsâ concepts about free energy and flow in biological chemical reactions and metabolic pathways by surveys and in-depth interviews. We worked with students in general chemistry classes and biochemistry courses in both an Australian and a US tertiary institution. We address three primary questions (i) What are the most common alternative conceptions held by students when they explain energy-related phenomena in biochemistry?, (ii) What information do students transfer from introductory chemistry and biology when they are asked to consider energy in a biological reaction or reaction pathway?, and (iii) How do students at varying levels of competence articulate their understandings of energy in pathways and biological reactions? The answers to these questions are used to build a preliminary learning progression for understanding âenergyâ in biochemistry. We also propose crucial elements of content knowledge that instructors could apply to help students better grasp this threshold concept in biochemistry
Accuracy of clinical staging for T2N0 oesophageal cancer: systematic review and meta-analysis
Oesophageal cancer is the sixth commonest cause of overall cancer mortality. Clinical staging utilizes multiple imaging modalities to guide treatment and prognostication. T2N0 oesophageal cancer is a treatment threshold for neoadjuvant therapy. Data on accuracy of current clinical staging tests for this disease subgroup are conflicting. We performed a meta-analysis of all primary studies comparing clinical staging accuracy using multiple imaging modalities (index test) to histopathological staging following oesophagectomy (reference standard) in T2N0 oesophageal cancer. Patients that underwent neoadjuvant therapy were excluded. Electronic databases (MEDLINE, Embase, Cochrane Library) were searched up to September 2019. The primary outcome was diagnostic accuracy of combined T&N clinical staging. Publication date, first recruitment date, number of centers, sample size and geographical location main histological subtype were evaluated as potential sources of heterogeneity. The search strategy identified 1,199 studies. Twenty studies containing 5,213 patients met the inclusion criteria. Combined T&N staging accuracy was 19% (95% CI, 15â24); T staging accuracy was 29% (95% CI, 24â35); percentage of patients with T downstaging was 41% (95% CI, 33â50); percentage of patients with T upstaging was 28% (95% CI, 24â32) and percentage of patients with N upstaging was 34% (95% CI, 30â39). Significant sources of heterogeneity included the number of centers, sample size and study region. T2N0 oesophageal cancer staging remains inaccurate. A significant proportion of patients were downstaged (could have received endotherapy) or upstaged (should have received neoadjuvant chemotherapy). These findings were largely unchanged over the past two decades highlighting an urgent need for more accurate staging tests for this subgroup of patients
Estimates of measles case fatality ratios: a comprehensive review of community-based studies.
BACKGROUND: Global deaths from measles have decreased notably in past decades, due to both increases in immunization rates and decreases in measles case fatality ratios (CFRs). While some aspects of the reduction in measles mortality can be monitored through increases in immunization coverage, estimating the level of measles deaths (in absolute terms) is problematic, particularly since incidence-based methods of estimation rely on accurate measures of measles CFRs. These ratios vary widely by geographic and epidemiologic context and even within the same community from year-to-year. METHODS: To understand better the variations in CFRs, we reviewed community-based studies published between 1980 and 2008 reporting age-specific measles CFRs. RESULTS: The results of the search consistently document that measles CFRs are highest in unvaccinated children under age 5 years; in outbreaks; the lowest CFRs occur in vaccinated children regardless of setting. The broad range of case and death definitions, study populations and geography highlight the complexities in extrapolating results for global public health planning. CONCLUSIONS: Values for measles CFRs remain imprecise, resulting in continued uncertainty about the actual toll measles exacts
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