128 research outputs found
Data fusion with artificial neural networks (ANN) for classification of earth surface from microwave satellite measurements
A data fusion system with artificial neural networks (ANN) is used for fast and accurate classification of five earth surface conditions and surface changes, based on seven SSMI multichannel microwave satellite measurements. The measurements include brightness temperatures at 19, 22, 37, and 85 GHz at both H and V polarizations (only V at 22 GHz). The seven channel measurements are processed through a convolution computation such that all measurements are located at same grid. Five surface classes including non-scattering surface, precipitation over land, over ocean, snow, and desert are identified from ground-truth observations. The system processes sensory data in three consecutive phases: (1) pre-processing to extract feature vectors and enhance separability among detected classes; (2) preliminary classification of Earth surface patterns using two separate and parallely acting classifiers: back-propagation neural network and binary decision tree classifiers; and (3) data fusion of results from preliminary classifiers to obtain the optimal performance in overall classification. Both the binary decision tree classifier and the fusion processing centers are implemented by neural network architectures. The fusion system configuration is a hierarchical neural network architecture, in which each functional neural net will handle different processing phases in a pipelined fashion. There is a total of around 13,500 samples for this analysis, of which 4 percent are used as the training set and 96 percent as the testing set. After training, this classification system is able to bring up the detection accuracy to 94 percent compared with 88 percent for back-propagation artificial neural networks and 80 percent for binary decision tree classifiers. The neural network data fusion classification is currently under progress to be integrated in an image processing system at NOAA and to be implemented in a prototype of a massively parallel and dynamically reconfigurable Modular Neural Ring (MNR)
Medical Student Motivation to Work in E-learning
Nowadays information technology is widley used in studying process thus enabling students to acquire knowledge in a convenient place and time. It is a novel approach and a challenge for both – the students and the faculty of Latvian University Riga Medical College (LU RMK). In order to provide and develope e-learning environment LU RMK has launched a Project whose main objective is „to develop guidelines and video training materials in the e-environment for students and faculty staff in order to provide a more efficient studying process”. Implementation of the project has been started with a pilot study „Medical students’ motivation to work in e-environment”, designed to explore students’ motivation and factors affecting the work of the e environment. Methods: A pilot study using a quantitative method – a survey. To achieve the goal 209 students have been surveyed in the LU RMK
Alpha-synuclein oligomers alter the spontaneous firing discharge of cultured midbrain neurons
The aim of this work was to monitor the effects of extracellular α-synuclein on
the firing activity of midbrain neurons dissociated from substantia nigra TH-GFP
mice embryos and cultured on microelectrode arrays (MEA). We monitored the
spontaneous firing discharge of the network for 21 days after plating and the
role of glutamatergic and GABAergic inputs in regulating burst generation and
network synchronism. Addition of GABAA, AMPA and NMDA antagonists did not
suppress the spontaneous activity but allowed to identify three types of neurons that
exhibited different modalities of firing and response to applied L-DOPA: high-rate
(HR) neurons, low-rate pacemaking (LR-p), and low-rate non-pacemaking (LR-np)
neurons. Most HR neurons were insensitive to L-DOPA, while the majority of LR-
p neurons responded with a decrease of the firing discharge; less defined was the
response of LR-np neurons. The effect of exogenous α-synuclein (α-syn) on the
firing discharge of midbrain neurons was then studied by varying the exposure
time (0–48 h) and the α-syn concentration (0.3–70 μM), while the formation of
α-syn oligomers was monitored by means of AFM. Independently of the applied
concentration, acute exposure to α-syn monomers did not exert any effect on
the spontaneous firing rate of HR, LR-p, and LR-np neurons. On the contrary,
after 48 h exposure, the firing activity was drastically altered at late developmental
stages (14 days in vitro, DIV, neurons): α-syn oligomers progressively reduced the
spontaneous firing discharge (IC50 = 1.03 ÎĽM), impaired burst generation and
network synchronism, proportionally to the increased oligomer/monomer ratio.
Different effects were found on early-stage developed neurons (9 DIV), whose firing
discharge remained unaltered, regardless of the applied α-syn concentration and
the exposure time. Our findings unravel, for the first time, the variable effects of
exogenous α-syn at different stages of midbrain network development and provide
new evidence for the early detection of neuronal function impairment associated to
aggregated forms of α-syn
Multi-wavelength study of the gravitational lens system RXS J1131-1231: III. Long slit spectroscopy: micro-lensing probes the QSO structure
(ABRIDGED)
Aims: We discuss and characterize micro-lensing among the 3 brightest lensed
images (A-B-C) of the gravitational lens system RXS J1131-1231 (a quadruply
imaged AGN) by means of long slit optical and NIR spectroscopy. Qualitative
constraints on the size of different emission regions are derived.
Methods: We decompose the spectra into their individual emission components
using a multi-component fitting approach. A complementary decomposition of the
spectra enables us to isolate the macro-lensed fraction of the spectra
independently of any spectral modelling.
Results: -1. The data support micro-lensing de-amplification of images A and
C. Not only is the continuum emission microlensed in those images but also a
fraction of the Broad Line emitting Region (BLR).-2. Micro-lensing of a very
broad component of MgII emission line suggests that the corresponding emission
occurs in a region more compact than the other components of the emission line.
-3. We find evidence that a large fraction of the FeII emission arises in the
outer parts of the BLR. We also find very compact emitting region in the ranges
3080-3540 A and 4630-4800 A that is likely associated with FeII. -4. The OIII
narrow emission line regions are partly spatially resolved. This enables us to
put a lower limit of 110h^{-1} pc on their intrinsic size. -5. Analysis of MgII
absorption found in the spectra indicates that the absorbing medium is
intrinsic to the quasar, has a covering factor of 20%, and is constituted of
small clouds homogeneously distributed in front of the continuum and BLRs. -6.
Two neighbour galaxies are detected at redshifts z=0.10 and z=0.289. These
galaxies are possible members of galaxy groups reported at those redshifts.Comment: Accepted by Astronomy and Astrophysics. Small modifications to match
the final versio
The long-term X-ray variability properties of AGN in the Lockman Hole region
We present the results from a detailed X-ray variability analysis of 66 AGN
in the Lockman Hole, which have optical spectroscopic identifications. We
compare, quantitatively, their variability properties with the properties of
local AGN, and we study the "variability-luminosity" relation as a function of
redshift, and the "variability-redshift" relation in two luminosity bins. We
use archival data from the last 10 XMM observations of the Lockman Hole field
to extract light curves in the rest frame, 2-10 keV band. We use the
"normalized excess variance" to quantify the variability amplitude. Using the
latest results regarding the AGN power spectral shape and its dependence on
black hole mass and accretion rate, we are able to compute model
"variability-luminosity" curves, which we compare with the relations we
observe. When we consider all the sources in our sample, we find that their
variability amplitude decreases with increasing redshift and luminosity. These
global anti-correlations are less pronounced when we split the objects in
various luminosity and redshift bins. We do not find a significant correlation
between variability amplitude and spectral slope. The "variability-luminosity"
relation that we detect has a larger amplitude when compared to that of local
AGN. We also find that, at a given luminosity, the variability amplitude
increases with redshift up to z~1, and then stays roughly constant. Our results
imply that the AGN X-ray mechanism operates in the same way at all redshifts.
Among objects with the same luminosity in our sample, the black hole mass
decreases and the accretion rate increases with larger redshift.Comment: 11 pages, 5 figures, accepted for publication in A&
Prediction of near-term risk of developing breast cancer using computerized features from bilateral mammograms
Alpha-synuclein oligomers alter the spontaneous firing discharge of cultured midbrain neurons
The aim of this work was to monitor the effects of extracellular α-synuclein on the firing activity of midbrain neurons dissociated from substantia nigra TH-GFP mice embryos and cultured on microelectrode arrays (MEA). We monitored the spontaneous firing discharge of the network for 21 days after plating and the role of glutamatergic and GABAergic inputs in regulating burst generation and network synchronism. Addition of GABAA, AMPA and NMDA antagonists did not suppress the spontaneous activity but allowed to identify three types of neurons that exhibited different modalities of firing and response to applied L-DOPA: high-rate (HR) neurons, low-rate pacemaking (LR-p), and low-rate non-pacemaking (LR-np) neurons. Most HR neurons were insensitive to L-DOPA, while the majority of LR-p neurons responded with a decrease of the firing discharge; less defined was the response of LR-np neurons. The effect of exogenous α-synuclein (α-syn) on the firing discharge of midbrain neurons was then studied by varying the exposure time (0–48 h) and the α-syn concentration (0.3–70 μM), while the formation of α-syn oligomers was monitored by means of AFM. Independently of the applied concentration, acute exposure to α-syn monomers did not exert any effect on the spontaneous firing rate of HR, LR-p, and LR-np neurons. On the contrary, after 48 h exposure, the firing activity was drastically altered at late developmental stages (14 days in vitro, DIV, neurons): α-syn oligomers progressively reduced the spontaneous firing discharge (IC50 = 1.03 μM), impaired burst generation and network synchronism, proportionally to the increased oligomer/monomer ratio. Different effects were found on early-stage developed neurons (9 DIV), whose firing discharge remained unaltered, regardless of the applied α-syn concentration and the exposure time. Our findings unravel, for the first time, the variable effects of exogenous α-syn at different stages of midbrain network development and provide new evidence for the early detection of neuronal function impairment associated to aggregated forms of α-syn
Analysis of laminated composite skew shells using higher order shear deformation theory
Short Stories, Tall Tales
It is often said that the truth should never get in the way of a good story. I use painting and drawing to override truth, open a door to imagined lives, reflect on the past from a new perspective, and look to the future from my current perspective. Thedrawings and paintings in this exhibitioncombine elements of personal history, historical art references, popular culture, and music, drawing heavily from American iconography. I use the format of the still life to create idiosyncratic parings of objects and images documenting memories of growing up in Missouri. Some of the images are short stories. Others are tall tales.
I come from a hundred-year line of gravestone makers, and for eight years I worked in cemeteries setting gravestones. What has stuck with me from that period of my life—aside from a fear of my own death—is the realization that I can use my experiences of growing-up in small-town Maryville, Missouri— to discuss more universal themes such as love, death, family, and the mystery of the unknown. The approach and technique of short story telling that all gravestones implement has also stuck with me.
You can’t fit a life story on the face of a headstone. The challenge one faces is to focus only on a few elements: quotes and anecdotes, pictures and symbols, all of which exist in shallow space. The way I compose objects in my drawings and paintings are executed in a similar manner. I create a narrative within each piece by limiting the number of objects in each composition. This creates a standoff within the picture, focusing the viewer to find relationships between the object and image, and allowing the elements in the painting to supersede their literal presence for a symbolic one.
I use multiple images—such as family photographs, copies of famous paintings, and album cover art, to open greater possibilities of how the viewer reads the work’s narrative. The paintings in this exhibition each contain a kind of stage—represented by either a shelf, tabletop, or counter space. Distilling the number of objects within this shallow space allows me to create a set of forms in the painting that carry symbolic, aesthetic, and compositional relationships.
The combinations and comparisons of images and objects in my works at first glance may strike one as funny, absurd, or seemingly unrelated. For example, the painting Life Cycle contains a magazine cut out of Gustave Courbet’s image, Origin of the World, and is set next to an image of a man grabbing the antlers of a freshly killed deer, and blank check signed by myself. The painting is a memento mori: which means “remember you must die”, a subject that many still life painters have touched on throughout history. In Life Cycle, Courbet’s image becomes a stand in for birth, the deer’s corpse represents death, and the signed blank check is a reminder to spend your life wisely.
Short Stories, Tall Tales presents narratives with universal themes of life, love, and death. I hope to give the viewer a way into my world through instances and emotions that echo their own experience.
Advisor: Matthew Sontheime
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