6,374 research outputs found
Advanced crime scene mapping and technology course design
The purpose of this project is to develop an Advanced Crime Scene Mapping and Technology course that aims to strengthen crime scene documentation and mapping skills, enhance cognitive abilities, and introduce students to advanced digital technologies that are gaining popularity in several forensic science disciplines. In particular, recent advancements in 3D laser scanning, mapping, and drone technology have presented the fields of crime scene investigation and reconstruction with many exciting new possibilities for potential uses. However, due to several limitations regarding the cost of equipment and training, the availability of resources, time constraints, and limited knowledge, it is often difficult for agencies to integrate new tools into their investigative processes. This course endeavors to help alleviate some of these issues by providing students with a basic knowledge and understanding of relevant new technologies while keeping them firmly grounded in the fundamental principles of crime scene processing and reconstruction. The content and structure of this course are designed to be flexible so it can accommodate rapid changes in technological advancements and device regulations. As such, complete instructions and tutorials are not included for specific brands of equipment and software, but instead focus on general concepts and procedures that can be generally applied to most similar devices
Impact of Pre-Columbian Agriculture, Climate Change, and Tectonic Activity Inferred From a 5,700-Year Paleolimnological Record from Lake Nicaragua
Lake Nicaragua, the largest lake in Central America, is a promising site for paleolimnological study of past climate change, tectonic and volcanic activity, and pre-Columbian agriculture in the region. It is near the northern limit of the Intertropical Convergence Zone (ITCZ), which brings the rainy season to the tropics, so effects of decreasing precipitation due to southern migration of the ITCZ through the Holocene should be observable. Because fault zones and an active volcano lie within the lake, the long-term impact of tectonic and volcanic activity can also be examined. Finally, the fertile volcanic soils near the lake may have encouraged early agriculture. We analyzed diatoms, biogenic silica (BSi), total organic carbon (TOC), water content, volcanic glass, and magnetic susceptibility in a sediment core from Lake Nicaragua with eleven accelerator mass spectroscopy radiocarbon dates, spanning ~5,700 years. Sediment accumulation rates decreased from the bottom to the top of the core, indicating a general drying trend through the Holocene. An increase in eutrophic diatom abundance suggests that pre-Columbian agriculture impacted the lake as early as ~5,400 cal yr BP. Above a horizon of coarser grains deposited sometime between ~5,200 and 1,600 cal yr BP, planktonic diatoms increased and remained dominant to the top of the core, indicating that water depth permanently increased. Although magnetic susceptibility peaked and water content dipped at the coarse horizon, volcanic glass fragments did not increase, suggesting that the coarse horizon and subsequent increase in water depth were caused by tectonic rather than by volcanic activity. Decreased accumulation rates of BSi and TOC indicate that water became clearer when depth increased
The infrared imaging spectrograph (IRIS) for TMT: electronics-cable architecture
The InfraRed Imaging Spectrograph (IRIS) is a first-light instrument for the
Thirty Meter Telescope (TMT). It combines a diffraction limited imager and an
integral field spectrograph. This paper focuses on the electrical system of
IRIS. With an instrument of the size and complexity of IRIS we face several
electrical challenges. Many of the major controllers must be located directly
on the cryostat to reduce cable lengths, and others require multiple bulkheads
and must pass through a large cable wrap. Cooling and vibration due to the
rotation of the instrument are also major challenges. We will present our
selection of cables and connectors for both room temperature and cryogenic
environments, packaging in the various cabinets and enclosures, and techniques
for complex bulkheads including for large detectors at the cryostat wall
Carbon and Strontium Abundances of Metal-Poor Stars
We present carbon and strontium abundances for 100 metal-poor stars measured
from R7000 spectra obtained with the Echellette Spectrograph and Imager
at the Keck Observatory. Using spectral synthesis of the G-band region, we have
derived carbon abundances for stars ranging from [Fe/H] to
[Fe/H]. The formal errors are dex in [C/Fe]. The strontium
abundance in these stars was measured using spectral synthesis of the resonance
line at 4215 {\AA}. Using these two abundance measurments along with the barium
abundances from our previous study of these stars, we show it is possible to
identify neutron-capture-rich stars with our spectra. We find, as in other
studies, a large scatter in [C/Fe] below [Fe/H]. Of the stars with
[Fe/H], 94% can be classified as carbon-rich metal-poor stars. The Sr
and Ba abundances show that three of the carbon-rich stars are
neutron-capture-rich, while two have normal Ba and Sr. This fraction of carbon
enhanced stars is consistent with other studies that include this metallicity
range.Comment: ApJ, Accepte
The Stellar Metallicity Distribution Function of the Galactic Halo from SDSS Photometry
We explore the stellar metallicity distribution function of the Galactic halo
based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using
observations of several star clusters and validated by comparisons with
medium-resolution spectroscopic values over a wide range of metal abundance. We
estimate distances and metallicities for individual main-sequence stars in the
multiply scanned SDSS Stripe 82, at heliocentric distances in the range 5 - 8
kpc and |b| > 35 deg, and find that the in situ photometric metallicity
distribution has a shape that matches that of the kinematically-selected local
halo stars from Ryan & Norris. We also examine independent kinematic
information from proper-motion measurements for high Galactic latitude stars in
our sample. We find that stars with retrograde rotation in the rest frame of
the Galaxy are generally more metal poor than those exhibiting prograde
rotation, which is consistent with earlier arguments by Carollo et al. that the
halo system comprises at least two spatially overlapping components with
differing metallicity, kinematics, and spatial distributions. The observed
photometric metallicity distribution and that of Ryan & Norris can be described
by a simple chemical evolution model by Hartwick (or by a single Gaussian
distribution); however, the suggestive metallicity-kinematic correlation
contradicts the basic assumption in this model that the Milky Way halo consists
primarily of a single stellar population. When the observed metallicity
distribution is deconvolved using two Gaussian components with peaks at [Fe/H]
~ -1.7 and -2.3, the metal-poor component accounts for ~20% - 35% of the entire
halo population in this distance range.Comment: Accepted for publication in Ap
Variation in prey delivered to common Black-Hawk (Buteogallus anthracinus) nests in Arizona drainage basins
Understanding how raptor diets vary across local and regional scales can be important when human actions have the potential to alter prey abundances. We combined data on prey delivered to 16 Common Black-Hawk (Buteogallus anthracinus) nests in three tributaries of the Verde River, Arizona, in 2008 and 2009 with similar data reported previously (1994) for three other Arizona drainage basins to better understand variation in diet composition within and across drainage basins. Within the three drainage basins studied in 2008 and 2009, nests clustered into two groups: those along Fossil Creek, where fish and amphibians were common, and those in Wet Beaver and Oak Creek drainage basins, where reptiles and nonnative crayfish were more abundant. When data from all six drainage basins were combined, drainage basins again clustered into two groups, with prey deliveries in one cluster dominated by fish and amphibians and in the other cluster by reptiles. These results confirm the opportunistic nature of prey use by Common Black-Hawks and highlight the variation in diet that can occur both within and among drainage basins. Management targeting the eradication of nonnative crayfish or the reintroduction of native amphibians and fish could alter prey availability for this raptor species
Metallicity Mapping with gri Photometry: The Virgo Overdensity and the Halos of the Galaxy
We describe the methodology required for estimation of photometric estimates
of metallicity based on the SDSS gri passbands, which can be used to probe the
properties of main-sequence stars beyond ~ 10 kpc, complementing studies of
nearby stars from more metallicity-sensitive color indices that involve the u
passband. As a first application of this approach, we determine photometric
metal abundance estimates for individual main-sequence stars in the Virgo
Overdensity, which covers almost 1000 square degrees on the sky, based on a
calibration of the metallicity sensitivity of stellar isochrones in the gri
filter passbands using field stars with well-determined spectroscopic metal
abundances. Despite the low precision of the method for individual stars,
internal errors of in [Fe/H] ~ +/- 0.1 dex can be achieved for bulk stellar
populations. The global metal abundance of the Virgo Overdensity determined in
this way is = -2.0 +/- 0.1 (internal) +/- 0.5 (systematic), from
photometric measurements of 0.7 million stars with heliocentric distances from
~ 10 kpc to ~ 20 kpc. A preliminary metallicity map, based on results for 2.9
million stars in the northern SDSS DR-7 footprint, exhibits a shift to lower
metallicities as one proceeds from the inner- to the outer-halo population,
consistent with recent interpretation of the kinematics of local samples of
stars with spectroscopically available metallicity estimates and full space
motions.Comment: 4 pages, 2 figures, to appear in IAU Symp. 26
Relationship Between Supervisors\u27 Servant Leadership and Police Officers Job Satisfaction
Recent police killings of unarmed African Americans in the United States and the subsequent protests and demonstrations against police brutality have resulted in more focus on the importance of collaborative relationships between law enforcement agencies and their communities. This quantitative correlational research study was conducted in one southern United States police department that incorporated a servant leadership philosophy, including its leaders being publicly heralded for their servant leadership practices that positively impacted its relationship with its community. The study examined if a relationship existed between perceived servant leadership of law enforcement leaders and line police officers’ job satisfaction. The study’s participants n=31 completed the Servant Leadership Scale to measure servant leadership characteristics and Job Descriptive Index to measure employee job satisfaction. Results indicated a statistically significant relationship between servant leadership and employee job satisfaction of the police officers in the department
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