Spatio-Temporal Cluster Detection and Local Moran Statistics of Point Processes

Moran\u27s index is a statistic that measures spatial dependence, quantifying the degree of dispersion or clustering of point processes and events in some location/area. Recognizing that a single Moran\u27s index may not give a sufficient summary of the spatial autocorrelation measure, a local indicator of spatial association (LISA) has gained popularity. Accordingly, we propose extending LISAs to time after partitioning the area and computing a Moran-type statistic for each subarea. Patterns between the local neighbors are unveiled that would not otherwise be apparent. We consider the measures of Moran statistics while incorporating a time factor under simulated multilevel Palm distribution, a generalized Poisson phenomenon where the clusters and dependence among the subareas are captured by the rate of increase of the process over time. Event propagation is built under spatial nested sequences over time. The Palm parameters, Moran statistics and convergence criteria are calculated from an explicit algorithm in a Markov chain Monte Carlo simulation setting and further analyzed in two real datasets

Anforderungen an Musik-Discovery-Systeme: Handreichungen zur Optimierung von Benutzeroberflächen

This is an English language version of the German language article cited below. “Discovery” has become a library buzzword but it refers to a traditional concept: enabling users to find library information and materials. Discovery was first facilitated by print indexes and card catalogs, then later by online library catalogs and search engines. Today, the discovery environment is changing rapidly both within libraries and externally. Within the library realm, FRBR, RDA, discovery tools, and faceted browsing are key factors related to these changes in the way our users navigate searches and encounter library data. The newest discovery interfaces aim to remove barriers between different types of data and incorporate aspects of non-library online searching environments familiar to users. When discovery interfaces work well, everyone benefits: the library’s collections are more fully exposed, and users do not have to adhere to nor struggle with the shortcomings of complicated search vocabularies and strategies. Discovery is optimized

The Luminosities of Protostars in the Spitzer c2d and Gould Belt Legacy Clouds

Motivated by the long-standing "luminosity problem" in low-mass star formation whereby protostars are underluminous compared to theoretical expectations, we identify 230 protostars in 18 molecular clouds observed by two Spitzer Space Telescope Legacy surveys of nearby star-forming regions. We compile complete spectral energy distributions, calculate Lbol for each source, and study the protostellar luminosity distribution. This distribution extends over three orders of magnitude, from 0.01 Lsun - 69 Lsun, and has a mean and median of 4.3 Lsun and 1.3 Lsun, respectively. The distributions are very similar for Class 0 and Class I sources except for an excess of low luminosity (Lbol < 0.5 Lsun) Class I sources compared to Class 0. 100 out of the 230 protostars (43%) lack any available data in the far-infrared and submillimeter (70 um < wavelength < 850 um) and have Lbol underestimated by factors of 2.5 on average, and up to factors of 8-10 in extreme cases. Correcting these underestimates for each source individually once additional data becomes available will likely increase both the mean and median of the sample by 35% - 40%. We discuss and compare our results to several recent theoretical studies of protostellar luminosities and show that our new results do not invalidate the conclusions of any of these studies. As these studies demonstrate that there is more than one plausible accretion scenario that can match observations, future attention is clearly needed. The better statistics provided by our increased dataset should aid such future work.Comment: Accepted for publication in AJ. 21 pages, 10 figures, 4 table

Snow-avalanche boulder fans in Jotunheimen, southern Norway: Schmidt-hammer exposure-age dating, geomorphometrics, dynamics and evolution

Eleven snow-avalanche boulder fans were dated from two high-alpine sites in Jotunheimen using Schmidt-hammer exposure-age dating (SHD) and lichenometry. Average exposure ages of the surface boulders ranged from 2285 ± 725 to 7445 ± 1020 years and demonstrate the potential of SHD for dating active landforms and diachronous surfaces. Application of GIS-based morphometric analyses showed that the volume of rock material within 10 of the fans is accounted for by 16-68 % of the combined volume of their respective bedrock chutes and transport zones. It is inferred that the fans were deposited entirely within the Holocene, mainly within the early- to mid Holocene, by frequent avalanches carrying very small debris loads. Relatively small transport-zone volumes are consistent with avalanches of low erosivity. Excess chute volumes appear to represent subaerial erosion in the Younger Dryas and possibly earlier. Debris supply to the fans was likely enhanced by early-Holocene paraglacial processes following deglaciation, and by later permafrost degradation associated with the mid-Holocene Thermal Maximum. The latter, together with the youngest SHD age from one of the fans, may presage a similar increase in geomorphic activity in response to current warming trends

Detecting sub-MeV neutrons in solid plastic scintillator with gamma-ray discrimination

We report on recent efforts to design a solid plastic scintillation hodoscope to measure neutron production cross sections at low energies. Our program includes not only the development of the detector itself, but also a set of auxiliary measurements which will help characterize its low-energy response. A novel scintillation counter has been developed to detect sub-MeV neutrons while rejecting gamma-ray backgrounds with good efficiency. The detector uses multiple layers of thin solid scintillator, with optical isolation between the adjacent layers. Incident low-energy neutrons produce ionizing recoil particles which remain within just one of the scintillator layers, while background gamma rays create electrons which most often cross the boundary between layers. By observing the trigger pattern within the layers, most gamma-ray backgrounds can be distinguished from the low-energy neutrons of interest. We report on the results of our Monte Carlo studies of this design, as well as on the operation of a prototype detector unit. We also have undertaken a new measurement of the neutron-proton total cross section below 1 MeV. Calculations of the efficiency for detecting low energy neutrons in plastic scintillator rely on accurate low energy n-p cross sections, yet surprisingly few such data currently exist. New measurements which span the region from 150 to 800 keV neutron (lab) energy are reported and discussed. Additionally, we have measured the light response of BC 418 scintillator for recoil proton energies as low as 100 keV. Recoil protons are produced at a known energy in the scintillator by placing it in a neutron beam and detecting in coincidence the elastically scattered neutrons at fixed angle. Our new results extend the energy range of previous measurements of the light response of solid organic scintillators, and may indicate a significantly modified response at the lowest observed energies.United States. Dept. of Energy (Grant No. DE-FG52-10NA29651

The Spitzer Survey of Interstellar Clouds in the Gould Belt. VI. The Auriga-California Molecular Cloud observed with IRAC and MIPS

We present observations of the Auriga-California Molecular Cloud (AMC) at 3.6, 4.5, 5.8, 8.0, 24, 70 and 160 micron observed with the IRAC and MIPS detectors as part of the Spitzer Gould Belt Legacy Survey. The total mapped areas are 2.5 sq-deg with IRAC and 10.47 sq-deg with MIPS. This giant molecular cloud is one of two in the nearby Gould Belt of star-forming regions, the other being the Orion A Molecular Cloud (OMC). We compare source counts, colors and magnitudes in our observed region to a subset of the SWIRE data that was processed through our pipeline. Using color-magnitude and color-color diagrams, we find evidence for a substantial population of 166 young stellar objects (YSOs) in the cloud, many of which were previously unknown. Most of this population is concentrated around the LkHalpha 101 cluster and the filament extending from it. We present a quantitative description of the degree of clustering and discuss the fraction of YSOs in the region with disks relative to an estimate of the diskless YSO population. Although the AMC is similar in mass, size and distance to the OMC, it is forming about 15 - 20 times fewer stars.Comment: (30 pages, 17 figures (2 multipage figures), accepted for publication in ApJ

A rock-surface microweathering index from Schmidt hammer R-values and its preliminary application to some common rock types in southern Norway

An index of the degree of rock-surface microweathering based on Schmidt hammer R-values is developed for use in the field without laboratory testing. A series of indices - I2 to In, where n is the number of successive blows with the hammer - is first proposed based on the assumption that the R-values derived from successive impacts on the same spot on a weathered rock surface converge on the value characteristic of an unweathered surface of the same lithology. Of these indices, the I5 index, which measures the difference between the mean R-value derived from first and fifth impacts as a proportion of the mean R-value from the fifth impact, is regarded as optimal: use of fewer impacts (e.g. in an I2 index) underestimates the degree of weathering whereas use of more impacts (e.g. in an I10 index) makes little difference and is therefore inefficient and may also induce an artificial weakening of the rock. Field tests of these indices on weathered glacially-scoured bedrock outcrops of nine common metamorphic and igneous rock types from southern Norway show, however, that even after ten impacts, successive R-values fail to approach the values characteristic of unweathered rock surfaces (e.g. bedrock from glacier forelands and road cuttings). An improved *I5 index is therefore preferred, in which the estimated true R-value of an unweathered rock surface is substituted. Weathered rock surfaces exposed to the atmosphere for ~10,000 years in southern Norway exhibit *I5 indices of 36-57%, values that reflect a similarly high degree of weathering irrespective of the rock type

Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

Schmidt-hammer exposure-age dating (SHD) of boulders on cryoplanation terrace treads and associated bedrock cliff faces revealed Holocene ages ranging from 0 ± 825 to 8890 ± 1185 yr. The cliffs were significantly younger than the inner treads, which tended to be younger than the outer treads. Radiocarbon dates from the regolith of 3854 to 4821 cal yr BP (2σ range) indicated maximum rates of cliff recession of ~0.1 mm/year, which suggests the onset of terrace formation prior to the last glacial maximum. Age, angularity and size of clasts, together with planation across bedrock structures and the seepage of groundwater from the cliff foot, all support a process-based conceptual model of cryoplanation terrace development in which frost weathering leads to parallel cliff recession and hence terrace extension. The availability of groundwater during autumn freeze-back is viewed as critical for frost wedging and/or the growth of segregation ice during prolonged winter frost penetration. Permafrost promotes cryoplanation by providing an impermeable frost table beneath the active layer, focusing groundwater flow, and supplying water for sediment transport by solifluction across the tread. Snowbeds are considered an effect rather than a cause of cryoplanation terraces and cryoplanation is seen as distinct from nivation