144 research outputs found
Restructuring Schools for Early Adolescent Learners
Much discussion about educational reform does little to address factors that truly affect teaching and learning
Target Motion Estimation Techniques in Single-Channel SAR
—Synthetic Aperture Radar (SAR) systems are versatile, high-resolution radar imagers useful for providing detailed intelligence, surveillance, and reconnaissance, especially when atmospheric conditions are non-ideal for optical imagers. However, targets in SAR images are smeared when they are moving. Along-track interferometry is a commonly-used method for extracting the motion parameters of moving targets but requires a dualaperture SAR system, which may be power- size- or cost prohibitive. This paper presents a method of estimating target motion parameters in single-channel SAR data given geometric target motion constraints. This estimation method includes an initial estimate, computation of the SAR ambiguity function, and application of the target motion constraints
An Introduction to Synthetic Aperture Radar: a High-Resolution Alternative to Optical Imaging
Optical methods for data collection on spacecraft and aircraft have been in use for many decades. In the late 1970s, radar became a standard component in space-borne remote sensing systems. Radar imagers are especially useful for space-borne and airborne applications because in the microwave frequency band, they operate independent of atmospheric conditions like clouds, rain, snow, fog, daylight, etc. unlike optical imagers. Synthetic Aperture Radar (SAR) systems are radar imagers that exploit the collection of many independent samples of targets in a particular scene to produce intrinsically highresolution images and have several key advantages over airborne optical imagers
Identification of histoplasma -specific peptides in human urine
pre-printHistoplasmosis is a severe dimorphic fungus infection, which is often difficult to diagnose due to similarity in symptoms to other diseases and lack of specific diagnostic tests. Urine samples from histoplasma-antigen-positive patients and appropriate controls were prepared using various sample preparation strategies including immunoenrichment, ultrafiltration, high-abundant protein depletion, deglycosylation, reverse-phase fractions, and digest using various enzymes. Samples were then analyzed by nanospray tandem mass spectrometry. Accurate mass TOF scans underwent molecular feature extraction and statistical analysis for unique disease makers, and acquired MS/MS data were searched against known human and histoplasma proteins. In human urine, some 52 peptides from 37 Histoplasma proteins were identified with high confidence. This is the first report of identification of a large number of Histoplasma-specific peptides from immunoassay-positive patient samples using tandem mass spectrometry and bioinformatics techniques. These findings may lead to novel diagnostic markers for histoplasmosis in human urine
The death of massive stars - II. Observational constraints on the progenitors of type Ibc supernovae
The progenitors of many type II core-collapse supernovae have now been
identified directly on pre-discovery imaging. Here we present an extensive
search for the progenitors of type Ibc supernovae in all available
pre-discovery imaging since 1998. There are 12 type Ibc supernovae with no
detections of progenitors in either deep ground-based or Hubble Space Telescope
archival imaging. The deepest absolute BVR magnitude limits are between -4 and
-5. We compare these limits with the observed Wolf-Rayet population in the
Large Magellanic Cloud and estimate a 16 per cent probability we have failed to
detect such a progenitor by chance. Alternatively the progenitors evolve
significantly before core-collapse or we have underestimated the extinction
towards the progenitors. Reviewing the relative rates and ejecta mass estimates
from lightcurve modelling of Ibc SNe, we find both incompatible with Wolf-Rayet
stars with initial masses >25Msun being the only progenitors. We present binary
evolution models that fit these observational constraints. Stars in binaries
with initial masses <20Msun lose their hydrogen envelopes in binary
interactions to become low mass helium stars. They retain a low mass hydrogen
envelope until approximately 10,000 years before core-collapse; hence it is not
surprising that galactic analogues have been difficult to identify.Comment: Accepted by MNRAS. 31 pages, 12 figures, 8 table
Orchestrator Telemetry Processing Pipeline
Orchestrator is a software application infrastructure for telemetry monitoring, logging, processing, and distribution. The architecture has been applied to support operations of a variety of planetary rovers. Built in Java with the Eclipse Rich Client Platform, Orchestrator can run on most commonly used operating systems. The pipeline supports configurable parallel processing that can significantly reduce the time needed to process a large volume of data products. Processors in the pipeline implement a simple Java interface and declare their required input from upstream processors. Orchestrator is programmatically constructed by specifying a list of Java processor classes that are initiated at runtime to form the pipeline. Input dependencies are checked at runtime. Fault tolerance can be configured to attempt continuation of processing in the event of an error or failed input dependency if possible, or to abort further processing when an error is detected. This innovation also provides support for Java Message Service broadcasts of telemetry objects to clients and provides a file system and relational database logging of telemetry. Orchestrator supports remote monitoring and control of the pipeline using browser-based JMX controls and provides several integration paths for pre-compiled legacy data processors. At the time of this reporting, the Orchestrator architecture has been used by four NASA customers to build telemetry pipelines to support field operations. Example applications include high-volume stereo image capture and processing, simultaneous data monitoring and logging from multiple vehicles. Example telemetry processors used in field test operations support include vehicle position, attitude, articulation, GPS location, power, and stereo images
Identification of Histoplasma-Specific Peptides in Human Urine
Histoplasmosis is a severe dimorphic fungus infection, which is often difficult to diagnose due to similarity in symptoms to other diseases and lack of specific diagnostic tests. Urine samples from histoplasma-antigen-positive patients and appropriate controls were prepared using various sample preparation strategies including immunoenrichment, ultrafiltration, high-abundant protein depletion, deglycosylation, reverse-phase fractions, and digest using various enzymes. Samples were then analyzed by nanospray tandem mass spectrometry. Accurate mass TOF scans underwent molecular feature extraction and statistical analysis for unique disease makers, and acquired MS/MS data were searched against known human and histoplasma proteins. In human urine, some 52 peptides from 37 Histoplasma proteins were identified with high confidence. This is the first report of identification of a large number of Histoplasma-specific peptides from immunoassay-positive patient samples using tandem mass spectrometry and bioinformatics techniques. These findings may lead to novel diagnostic markers for histoplasmosis in human urine
The birth place of the type Ic Supernova 2007gr
We report our attempts to locate the progenitor of the peculiar type Ic SN
2007gr in HST pre-explosion images of the host galaxy, NGC 1058. Aligning
adaptive optics Altair/NIRI imaging of SN 2007gr from the Gemini (North)
Telescope with the pre-explosion HST WFPC2 images, we identify the SN position
on the HST frames with an accuracy of 20 mas. Although nothing is detected at
the SN position we show that it lies on the edge of a bright source, 134+/-23
mas (6.9 pc) from its nominal centre. Based on its luminosity we suggest that
this object is possibly an unresolved, compact and coeval cluster and that the
SN progenitor was a cluster member, although we note that model profile fitting
favours a single bright star. We find two solutions for the age of this assumed
cluster; 7-/+0.5 Myrs and 20-30 Myrs, with turn-off masses of 28+/-4 Msun and
12-9 Msun respectively. Pre-explosion ground-based K-band images marginally
favour the younger cluster age/higher turn-off mass. Assuming the SN progenitor
was a cluster member, the turn-off mass provides the best estimate for its
initial mass. More detailed observations, after the SN has faded, should
determine if the progenitor was indeed part of a cluster, and if so allow an
age estimate to within ~2 Myrs thereby favouring either a high mass single star
or lower mass interacting binary progenitor.Comment: 12 pages, 3 figures, resolution of fig 1. has been reduced, some
revision based on referee's comments, Accepted ApJL 27 Nov 200
Spatial Query for Planetary Data
Science investigators need to quickly and effectively assess past observations of specific locations on a planetary surface. This innovation involves a location-based search technology that was adapted and applied to planetary science data to support a spatial query capability for mission operations software. High-performance location-based searching requires the use of spatial data structures for database organization. Spatial data structures are designed to organize datasets based on their coordinates in a way that is optimized for location-based retrieval. The particular spatial data structure that was adapted for planetary data search is the R+ tree
Cliffbot Maestro
Cliffbot Maestro permits teleoperation of remote rovers for field testing in extreme environments. The application user interface provides two sets of tools for operations: stereo image browsing and command generation
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