Dynamic Prefetching of Data Tiles for Interactive Visualization

In this paper, we present ForeCache, a general-purpose tool for exploratory browsing of large datasets. ForeCache utilizes a client-server architecture, where the user interacts with a lightweight client-side interface to browse datasets, and the data to be browsed is retrieved from a DBMS running on a back-end server. We assume a detail-on-demand browsing paradigm, and optimize the back-end support for this paradigm by inserting a separate middleware layer in front of the DBMS. To improve response times, the middleware layer fetches data ahead of the user as she explores a dataset. We consider two different mechanisms for prefetching: (a) learning what to fetch from the user's recent movements, and (b) using data characteristics (e.g., histograms) to find data similar to what the user has viewed in the past. We incorporate these mechanisms into a single prediction engine that adjusts its prediction strategies over time, based on changes in the user's behavior. We evaluated our prediction engine with a user study, and found that our dynamic prefetching strategy provides: (1) significant improvements in overall latency when compared with non-prefetching systems (430% improvement); and (2) substantial improvements in both prediction accuracy (25% improvement) and latency (88% improvement) relative to existing prefetching techniques

Spatial and Temporal Stability of Airglow Measured in the Meinel Band Window at 1191.3 nm

We report on the temporal and spatial fluctuations in the atmospheric brightness in the narrow band between Meinel emission lines at 1191.3 nm using an R=320 near-infrared instrument. We present the instrument design and implementation, followed by a detailed analysis of data taken over the course of a night from Table Mountain Observatory. The absolute sky brightness at this wavelength is found to be 5330 +/- 30 nW m^-2 sr^-1, consistent with previous measurements of the inter-band airglow at these wavelengths. This amplitude is larger than simple models of the continuum component of the airglow emission at these wavelengths, confirming that an extra emissive or scattering component is required to explain the observations. We perform a detailed investigation of the noise properties of the data and find no evidence for a noise component associated with temporal instability in the inter-line continuum. This result demonstrates that in several hours of ~100s integrations the noise performance of the instrument does not appear to significantly degrade from expectations, giving a proof of concept that near-IR line intensity mapping may be feasible from ground-based sites.Comment: 15 figures, submitted to PAS

Siamese Neural Networks for Skin Cancer Classification and New Class Detection using Clinical and Dermoscopic Image Datasets

Skin cancer is the most common malignancy in the world. Automated skin cancer detection would significantly improve early detection rates and prevent deaths. To help with this aim, a number of datasets have been released which can be used to train Deep Learning systems - these have produced impressive results for classification. However, this only works for the classes they are trained on whilst they are incapable of identifying skin lesions from previously unseen classes, making them unconducive for clinical use. We could look to massively increase the datasets by including all possible skin lesions, though this would always leave out some classes. Instead, we evaluate Siamese Neural Networks (SNNs), which not only allows us to classify images of skin lesions, but also allow us to identify those images which are different from the trained classes - allowing us to determine that an image is not an example of our training classes. We evaluate SNNs on both dermoscopic and clinical images of skin lesions. We obtain top-1 classification accuracy levels of 74.33% and 85.61% on clinical and dermoscopic datasets, respectively. Although this is slightly lower than the state-of-the-art results, the SNN approach has the advantage that it can detect out-of-class examples. Our results highlight the potential of an SNN approach as well as pathways towards future clinical deployment.Comment: 10 pages, 5 figures, 5 table

Evaluations of in-traffic performance of high-intensity discharge headlamps

This study evaluated subjects' impressions of performance of high-intensity discharge (HID) headlamps after in-traffic experience, with an emphasis on colour appearance of red stop signs. In the first of two tasks, subjects drove (or rode) for half an hour on a variety of roads in a car equipped with either HID or tungsten-halogen low-beam headlamps. Instructions did not mention colour appearance. The second task involved a direct comparison of HID and tungsten-halogen headlamps. In this task, subjects drove (or rode) twice along a 7-minute route in a residential area, and they were instructed to pay attention to the colour appearance of stop signs and other objects. The main finding from Task 1 is that subjects who experienced HID headlamps did not report more (or fewer) spontaneous negative comments on colour appearance of stop signs or other objects than did subjects who experienced tungsten-halogen headlamps. Furthermore, the evaluations of the overall performances of the two types of headlamps were not different. In the direct comparison of Task 2 there was no evidence of problems with colour appearance when using HID headlamps. Moreover, subjects preferred HID headlamps in terms of the overall performance, and in making stop signs and other objects stand out from their background. However, this preference for HID headlamps was present only for subjects who had the relatively extended exposure to the HID headlamps in Task 1. The present results provide no evidence for problems with colour appearance of stop signs and other objects when using HID headlamps. Furthermore, the study provides evidence that observers perceive HID headlamps as helping stop signs and other objects to stand out from their background. The results imply that given a somewhat extended exposure to HID headlamps, drivers would prefer them over current tungsten-halogen headlamps.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68417/2/10.1177_096032719402600402.pd

Copper mediated atom transfer radical cyclisation reactions

The effect of different N-pentyl-2-pyridylmethanimine (NPMI) derivatives upon the rate of copper(I) mediated atom transfer radical cyclisation (ATRC) of mono-bromo- and trichloro-acetamides were investigated. 6-Functionalised NPMI derivatives retarded the rate of ATRC due to steric effects, while for the 5-substituted analogues, inductively increasing the electron density of the pyridine nitrogen increased the rate of ATRC. Multidentate amine derived copper(l) halide complexes were found to mediate the ATRC of I-halo-N-propargylacetamides. The cyclisation of trichloro- and dichloroacetamide precursors leads to a,B-unsaturated y-Iactams containing the gem-dihalide functional group, while monohaloacetamides gave rise to either cyclised atom transfer or reduction products depending upon the solvent and catalyst used. The tripyridyJamine (TPA) copper(I) halide complex facilitates the efficient ATRC of bromo-enamides to give plactams exclusively with no formation of y-Iactams. Initial products result from 4-exo bromine atom transfer and subesqucnt elimination can be readily achieved to furnish the corresponding alkenes. A range of fused bicyclic lactams were prepared via copper(l) mediated 5-endo ATRC of halo-N-(cycloalk-1-enyl)acetamides and the use of this methodology for the synthesis of the Iycorane and erythrinane alkaloid skeletons was investigated

Atmospheric potential oxygen: New observations and their implications for some atmospheric and oceanic models

Measurements of atmospheric O2/N2 ratios and CO2 concentrations can be combined into a tracer known as atmospheric potential oxygen (APO ≈ O2/N2 + CO2) that is conservative with respect to terrestrial biological activity. Consequently, APO reflects primarily ocean biogeochemistry and atmospheric circulation. Building on the work of Stephens et al. (1998), we present a set of APO observations for the years 1996-2003 with unprecedented spatial coverage. Combining data from the Princeton and Scripps air sampling programs, the data set includes new observations collected from ships in the low-latitude Pacific. The data show a smaller interhemispheric APO gradient than was observed in past studies, and different structure within the hemispheres. These differences appear to be due primarily to real changes in the APO field over time. The data also show a significant maximum in APO near the equator. Following the approach of Gruber et al. (2001), we compare these observations with predictions of APO generated from ocean O2 and CO2 flux fields and forward models of atmospheric transport. Our model predictions differ from those of earlier modeling studies, reflecting primarily the choice of atmospheric transport model (TM3 in this study). The model predictions show generally good agreement with the observations, matching the size of the interhemispheric gradient, the approximate amplitude and extent of the equatorial maximum, and the amplitude and phasing of the seasonal APO cycle at most stations. Room for improvement remains. The agreement in the interhemispheric gradient appears to be coincidental; over the last decade, the true APO gradient has evolved to a value that is consistent with our time-independent model. In addition, the equatorial maximum is somewhat more pronounced in the data than the model. This may be due to overly vigorous model transport, or insufficient spatial resolution in the air-sea fluxes used in our modeling effort. Finally, the seasonal cycles predicted by the model of atmospheric transport show evidence of an excessive seasonal rectifier in the Aleutian Islands and smaller problems elsewhere. Copyright 2006 by the American Geophysical Union

Toward a Scalable Census of Dashboard Designs in the Wild: A Case Study with Tableau Public

Dashboards remain ubiquitous artifacts for presenting or reasoning with data across different domains. Yet, there has been little work that provides a quantifiable, systematic, and descriptive overview of dashboard designs at scale. We propose a schematic representation of dashboard designs as node-link graphs to better understand their spatial and interactive structures. We apply our approach to a dataset of 25,620 dashboards curated from Tableau Public to provide a descriptive overview of the core building blocks of dashboards in the wild and derive common dashboard design patterns. To guide future research, we make our dashboard corpus publicly available and discuss its application toward the development of dashboard design tools.Comment: *J. Purich and A. Srinivasan contributed equally to the wor

An improved comparison of atmospheric Ar/N2 time series and paired ocean-atmosphere model predictions

Ar/N2 variations in the atmosphere reflect ocean heat fluxes, air-sea gas exchange, and atmospheric dynamics. Here atmospheric Ar/N2 time series are compared to paired ocean-atmosphere model predictions. Agreement between Ar/N2 observations and simulations has improved in comparison to a previous study because of longer time series and the introduction of automated samplers at several of the atmospheric stations, as well as the refinement of the paired ocean-atmosphere models by inclusion of Ar and N2 as active tracers in the ocean component. Although analytical uncertainties and collection artifacts are likely to be mainly responsible for observed Ar/N2 outliers, air parcel back-trajectory analysis suggests that some of the variability in Ar/N2 measurements could be due to the low-altitude history of the air mass collected and, by extension, the local oceanic Ar/N2 signal. Although the simulated climatological seasonal cycle can currently be evaluated with Ar/N2 observations, longer time series and additional improvements in the signal-to-noise ratio will be required to test other model predictions such as interannual variability, latitudinal gradients, and the secular increase in atmospheric Ar/N2 expected to result from ocean warming. Copyright 2008 by the American Geophysical Union