Detection System for Scanning Electron Microscope

The kind of information and the quality of the backscattered electron (BSE) images depend upon numerous features of the detector. Therefore, various types of detectors should be used simultaneously to obtain as much of information as possible. The detection system presented here contains a large area semiconductor detector and a BSE to secondary electrons (SE) converter system. These two different kinds of detectors give different BSE images. After subtracting the signal of a semiconductor detector from that of a converter system, an image with good topography and reduced material contrast can be achieved

The Effect of Urbanization on Ant Abundance and Diversity: A Temporal Examination of Factors Affecting Biodiversity.

Numerous studies have examined the effect of urbanization on species richness and most studies implicate urbanization as the major cause of biodiversity loss. However, no study has identified an explicit connection between urbanization and biodiversity loss as the impact of urbanization is typically inferred indirectly by comparing species diversity along urban-rural gradients at a single time point. A different approach is to focus on the temporal rather than the spatial aspect and perform “before and after” studies where species diversity is cataloged over time in the same sites. The current study examined changes in ant abundance and diversity associated with the conversion of natural habitats into urban habitats. Ant abundance and diversity were tracked in forested sites that became urbanized through construction and were examined at 3 time points - before, during, and after construction. On average, 4.3±1.2 unique species were detected in undisturbed plots prior to construction. Ant diversity decreased to 0.7±0.8 species in plots undergoing construction and 1.5±1.1 species in plots 1 year after construction was completed. With regard to species richness, urbanization resulted in the permanent loss of 17 of the 20 species initially present in the study plots. Recovery was slow and only 3 species were present right after construction was completed and 4 species were present 1 year after construction was completed. The second objective examined ant fauna recovery in developed residential lots based on time since construction, neighboring habitat quality, pesticide inputs, and the presence of invasive ants. Ant diversity was positively correlated with factors that promoted ecological recovery and negatively correlated with factors that promoted ecological degradation. Taken together, these results address a critical gap in our knowledge by characterizing the short- and long-term the effects of urbanization on the loss of ant biodiversity

Signal Mixing Technique for Backscattered Electrons in the Scanning Electron Microscope

Signal mixing technique using asymetrically placed backscattered electron detectors in a scanning electron microscope is presented in this paper. Two types of detectors have been used: a low-take off angle ring scintillation detector (placed around the specimen) and a wide-angle semiconductor detector (placed above the specimen). It has been shown that the discussed configuration gives good real topography in all directions on the specimen surface and also reduces significantly the pseudo-topography effect of flat grain boundaries

PAIRED COMPETITION ANALYSIS USING MIXED MODELS

Urban and rural colonies of odorous house ants (Tapinoma sessile) have very different social structures. Urban colonies are very large with hundreds of cohabiting queens, while rural colonies are small with only one queen. To investigate whether worker ant aggressiveness varies across these two colony types, an experiment was performed using an aggression assay, in which 50 ants from each of two colonies were placed in a petri dish and allowed to fight. The response was the total number of dead ants within 24 hours. Because the ants were all the same species and not marked by colony, the number of dead ants per colony could not be determined. A total of 138 colony pairings, involving six urban (U) and seven rural (R) colonies, were used in the experiment. Interest was in comparing the three types of pairings (UU, UR, and RR) to see if there is an ordering based on aggressiveness (e.g., μUU \u3c μUR \u3c μRR). A linear mixed model is proposed to account for the fact that multiple assays involve ants from the same colony (i.e., to account for between colony variation in aggressiveness). However, the incorporation of random colony factors is not feasible for this study because of the UU and RR assays. As a result, we perform this mixed model analysis by specifying the covariance matrix (i.e., using the LINEAR covariance structure). A simulation study is used to assess the Type I and Type II errors of this mixed model approach relative to the standard one-way ANOVA. We conclude with an analysis of the real data set

Electron Beam Induced Current Studies of Defect Induced Conductivity Inversion

Defect induced inversion of conductivity type was studied both at the surface and at a network of interfacially confined misfit dislocations in heteroepitaxial Si(Ge) on Si structures. The inversion was achieved by controlled contamination with Au and Ni metallic impurities introduced by diffusion from backside evaporated layers. A theoretical explanation of the defect electrical activity and the inversion effect is presented, along with temperature dependent beam induced current observations

The effectiveness and stability of impurity/defect interactions and their impact on minority carrier lifetime. Annual subcontract report, 1 August 1990--31 July 1991

This report covers the investigation and understanding of electrical activity of ``clean`` and metallic impurity decorated defects. A heterostructure containing a controlled number of deliberately introduced misfit dislocations is used as a model system to simulate a variety of defect/impurity interactions in photovoltaic materials. In addition, a noncontact laser/microwave deep-level transient spectroscopy technique is applied to characterize the minority carrier lifetime and determine the energy levels of defects. 59 refs

Sustainable Management of Water Resources

The Dawn spacecraft arrived at dwarf planet Ceres in spring 2015 and imaged its surface from four successively lower polar orbits at ground sampling dimensions between ∼1.3 km/px and ∼35 m/px. To understand the geological history of Ceres a mapping campaign was initiated to produce a set of 15 quadrangle-based geological maps using the highest-resolution Framing Camera imagery. Here we present the geological map of the Ac-10 Rongo Quadrangle, which is located at the equator encompassing the region from 22°N to 22°S and 288° to 360°E. The total relief within the quadrangle is 11.1 km with altitudes ranging from about −7.3 km to +3.8 km. We identified nine geological units based on surface morphology and surface textural characteristics. The dominant and most widespread unit is the cratered terrain (crt) representing ancient reworked crustal material. Its consistent formation age across the quadrangle is 1.8 Ga. Two edifices (unit th), Ahuna Mons and an unnamed tholus within Begbalel Crater, are interpreted to be of (cryo)volcanic origin. The southwest portion of the quadrangle is dominated by ejecta material (Ye) emplaced during the formation of the 260-km diameter Yalode impact basin at about 580 Ma. Rayed crater ejecta material (cr) is dominant in the eastern part of the quadrangle but also occurs in isolated patches up to a distance of 455 km from the 34 km diameter source crater Haulani. The remaining five geological units also represent impact crater materials: degraded rim (crdeg), bright crater (cb), hummocky floor (cfh), talus (ta), and crater (c) materials. Widespread Yalode and Haulani ejecta materials can potentially be utilised as stratigraphic markers. Therefore, it is essential to consistently map their full areal extent and to date their formations using impact crater statistics

NASA Planetary Mission Concept Study: Assessing: Dwarf Planet Ceres' past and Present Habitability Potential

The Dawn mission revolutionized our understanding of Ceres during the same decade that has also witnessed the rise of ocean worlds as a research and exploration focus. We will report progress on the Planetary Mission Concept Study (PMCS) on the future exploration of Ceres under the New Frontiers or Flagship program that was selected for NASA funding in October 2019. At the time this writing, the study was just kicked off, hence this abstract reports the study plan as presented in the proposal