8,911 research outputs found
Satellite land use acquisition and applications to hydrologic planning models
A developing operational procedure for use by the Corps of Engineers in the acquisition of land use information for hydrologic planning purposes was described. The operational conditions preclude the use of dedicated, interactive image processing facilities. Given the constraints, an approach to land use classification based on clustering seems promising and was explored in detail. The procedure is outlined and examples of application to two watersheds given
A study of the use of remote sensing data in hydrologic engineering models
There are no author-identified significant results in this report
X-ray and EUV Observations of Simultaneous Short and Long Period Oscillations in Hot Coronal Arcade Loops
We report decaying quasi-periodic intensity oscillations in the X-ray (6-12
keV) and extreme ultraviolet (EUV) channels (131, 94, 1600, 304 \AA) observed
by the Fermi GBM (Gamma-ray Burst Monitor) and SDO/AIA, respectively, during a
C-class flare. The estimated period of oscillation and decay time in the X-ray
channel (6-12 keV) was about 202 s and 154 s, respectively. A similar
oscillation period was detected at the footpoint of the arcade loops in the AIA
1600 and 304 \AA channels. Simultaneously, AIA hot channels (94 and 131 \AA)
reveal propagating EUV disturbances bouncing back and forth between the
footpoints of the arcade loops. The period of the oscillation and decay time
were about 409 s and 1121 s, respectively. The characteristic phase speed of
the wave is about 560 km/s for about 115 Mm loop length, which is roughly
consistent with the sound speed at the temperature about 10-16 MK (480-608
km/s). These EUV oscillations are consistent with the SOHO/SUMER Doppler-shift
oscillations interpreted as the global standing slow magnetoacoustic wave
excited by a flare. The flare occurred at one of the footpoints of the arcade
loops, where the magnetic topology was a 3D fan-spine with a null-point.
Repetitive reconnection at this footpoint could cause the periodic acceleration
of non-thermal electrons that propagated to the opposite footpoint along the
arcade and precipitating there, causing the observed 202-s periodicity. Other
possible interpretations, e.g. the second harmonics of the slow mode are also
discussed.Comment: ApJ (in press), 13 pages, 6 figure
Dynamics of Bond Market Integration between Existing And Accession EU Countries
In this paper, we use a set of complementary techniques to examine the time-varying level of integration of European government bond markets. We consider daily bond returns and prices over the 1998-2003 period. Strong contemporaneous and dynamic linkages are found between individual European Union (EU) markets and the German market. However, there is no such evidence for the three accession markets of the Czech Republic, Hungary and Poland. The UKās market is also considered. In general, the degree of integration for the accession markets is weak and stable, with little evidence of further deepening despite the increased political integration.Bond Indices, Cointegration, GARCH Models, Integration, Kalman Filter
Quantitative and empirical demonstration of the Matthew effect in a study of career longevity
The Matthew effect refers to the adage written some two-thousand years ago in
the Gospel of St. Matthew: "For to all those who have, more will be given."
Even two millennia later, this idiom is used by sociologists to qualitatively
describe the dynamics of individual progress and the interplay between status
and reward. Quantitative studies of professional careers are traditionally
limited by the difficulty in measuring progress and the lack of data on
individual careers. However, in some professions, there are well-defined
metrics that quantify career longevity, success, and prowess, which together
contribute to the overall success rating for an individual employee. Here we
demonstrate testable evidence of the age-old Matthew "rich get richer" effect,
wherein the longevity and past success of an individual lead to a cumulative
advantage in further developing his/her career. We develop an exactly solvable
stochastic career progress model that quantitatively incorporates the Matthew
effect, and validate our model predictions for several competitive professions.
We test our model on the careers of 400,000 scientists using data from six
high-impact journals, and further confirm our findings by testing the model on
the careers of more than 20,000 athletes in four sports leagues. Our model
highlights the importance of early career development, showing that many
careers are stunted by the relative disadvantage associated with inexperience.Comment: 13 pages, 7 figures, 4 Tables; Revisions in response to critique and
suggestions of referee
Presence of rd8 mutation does not alter the ocular phenotype of late-onset retinal degeneration mouse model.
PurposeA spontaneous frameshift mutation, c.3481delC, in the Crb1 gene is the underlying cause of dysplasia and retinal degeneration in rd8 mice. The rd8 mutation is found in C57BL/6N but not in C57BL/6J mouse sub-strains. The development of ocular pathology in single knockout Ccl2-/-, Cx3cr1-/- and in double knockout Ccl2-/-, Cx3cr1-/- mice raised on a C57BL/6 background has been reported to depend on the presence of a rd8 mutation. In this study, we investigated the influence of the rd8 mutation on the retinal pathology that we previously described in the late-onset retinal degeneration (L-ORD) mouse model with a heterozygous S163R mutation in the C1q-tumor necrosis factor-related protein-5Ctrp5+/- gene that was generated on a C57BL/6J background.MethodsMouse lines carrying the Ctrp5 S163R and rd8 mutations (Ctrp5+/-;rd8/rd8), corresponding controls without the rd8 mutation (Ctrp5+/-;wt/wt), and wild-type mice with and without the rd8 mutation (Wtrd8/rd8 and Wtwt/wt, respectively) were generated by systematic breeding of mice in our L-ORD mouse colony. Genotyping the mice for the rd8 (del C at nt3481 in Crb1) and Ctrp5 S163R mutations was performed with allelic PCR or sequencing. Retinal morphology was studied with fundus imaging, histology, light microscopy, electron microscopy, and immunohistochemistry.ResultsGenotype analysis of the mice in L-ORD mouse colony detected the rd8 mutation in the homozygous and heterozygous state. Fundus imaging of wild-type mice without the rd8 mutation (Wtwt/wt) revealed no autofluorescence (AF) spots up to 6-8 months and few AF spots at 21 months. However, the accumulation of AF lesions accelerated with age in the Ctrp5+/- mice that lack the rd8 mutation (Ctrp5+/-;wt/wt). The number of AF lesions was significantly increased (p<0.001), and they were small and uniformly distributed throughout the retina in the 21-month-old Ctrp5+/-;wt/wt mice when compared to the age-matched controls. Wild-type and Ctrp5+/- mice with the rd8 mutation (Wtrd8/rd8 and Ctrp5+/-;rd8/rd8, respectively) revealed an integrated retinal architecture with well-defined outer segments/inner segments (OS/IS), outer nuclear layer (ONL), outer plexiform layer (OPL), and inner nuclear layer (INL). The presence of pseudorosette structures reported in the rd8 mice between the ONL and the INL in the ventral quadrant of the retina was not observed in all genotypes studied. Further, the external limiting membrane was continuous in the Ctrp5+/-;rd8/rd8 and Wtrd8/rd8 mice. Evaluation of the retinal phenotype revealed that the Ctrp5+/-;wt/wt mice developed characteristic L-ORD pathology including age-dependent accumulation of AF spots, development of sub-retinal, sub-RPE, and basal laminar deposits, and Bruch's membrane abnormalities at older age, while these changes were not observed in the age-matched littermate WTwt/wt mice.ConclusionsThe Wtrd8/rd8 and Ctrp5+/-;rd8/rd8 mice raised on C57BL/6J did not develop early onset retinal changes that are characteristic of the rd8 phenotype, supporting the hypothesis that manifestation of rd8-associated pathology depends on the genetic background. The retinal pathology observed in mice with the Ctrp5+/-;wt/wt genotype is consistent with the L-ORD phenotype observed in patients and with the phenotype we described previously. The lack of rd8-associated retinal pathology in the Ctrp5+/-;wt/wt mouse model raised on the C57BL/6J background and the development of the L-ORD phenotype in these mice in the presence and absence of the rd8 mutation suggests that the pathology observed in the Ctrp5+/-;wt/wt mice is primarily associated with the S163R mutation in the Ctrp5 gene
Midazolam Efficacy Against Acute Hydrogen Sulfide-Induced Mortality and Neurotoxicity.
Hydrogen sulfide (H2S) is a colorless, highly neurotoxic gas. It is not only an occupational and environmental hazard but also of concern to the Department of Homeland Security for potential nefarious use. Acute high-dose H2S exposure causes death, while survivors may develop neurological sequelae. Currently, there is no suitable antidote for treatment of acute H2S-induced neurotoxicity. Midazolam (MDZ), an anti-convulsant drug recommended for treatment of nerve agent intoxications, could also be of value in treating acute H2S intoxication. In this study, we tested the hypothesis that MDZ is effective in preventing/treating acute H2S-induced neurotoxicity. This proof-of-concept study had two objectives: to determine whether MDZ prevents/reduces H2S-induced mortality and to test whether MDZ prevents H2S-induced neurological sequelae. MDZ (4Ā mg/kg) was administered IM in mice, 5Ā min pre-exposure to a high concentration of H2S at 1000Ā ppm or 12Ā min post-exposure to 1000Ā ppm H2S followed by 30Ā min of continuous exposure. A separate experiment tested whether MDZ pre-treatment prevented neurological sequelae. Endpoints monitored included assessment of clinical signs, mortality, behavioral changes, and brain histopathological changes. MDZ significantly reduced H2S-induced lethality, seizures, knockdown, and behavioral deficits (pĀ <Ā 0.01). MDZ also significantly prevented H2S-induced neurological sequelae, including weight loss, behavior deficits, neuroinflammation, and histopathologic lesions (pĀ <Ā 0.01). Overall, our findings show that MDZ is a promising drug for reducing H2S-induced acute mortality, neurotoxicity, and neurological sequelae
Application of molecular biomarkers in epidemiology.
The principal conclusions and opportunities that can be drawn from this conference are as follows. The meeting demonstrated the large communication gap that still exists between most epidemiologists and laboratory scientists. This problem could be overcome if epidemiologists worked closely with laboratory scientists at the outset of any project so that a better understanding could be built between them. Epidemiologists need simple, well-characterized, reproducible assays that can be applied to hundreds or thousands of people. Most laboratory scientists have little interest in running large numbers of assays, but wish to continually refine their methods so that they stay on the "cutting edge" of basic research. This problem could be overcome if the new laboratory technology could be transferred to contract laboratories or small companies. Problems of technology transfer therefore need to be addressed. Current and new biomarkers need to be better validated in the field and by studying animal models. More information on the background expression of biomarkers in the general population is needed (i.e. what is the normal range?). Ethical issues, such as the possibility that biomarkers of susceptibility could be used to exclude people from the workplace, need to be addressed
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Broad spectrum proteomics analysis of the inferior colliculus following acute hydrogen sulfide exposure.
Acute exposure to high concentrations of H2S causes severe brain injury and long-term neurological disorders, but the mechanisms involved are not known. To better understand the cellular and molecular mechanisms involved in acute H2S-induced neurodegeneration we used a broad-spectrum proteomic analysis approach to identify key molecules and molecular pathways involved in the pathogenesis of acute H2S-induced neurotoxicity and neurodegeneration. Mice were subjected to acute inhalation exposure of up to750 ppm of H2S. H2S induced behavioral deficits and severe lesions including hemorrhage in the inferior colliculus (IC). The IC was microdissected for proteomic analysis. Tandem mass tags (TMT) liquid chromatography mass spectrometry (LC-MS/MS)-based quantitative proteomics was applied for protein identification and quantitation. LC-MS/MS identified 598, 562, and 546 altered proteomic changes at 2āÆh, and on days 2 and 4 post-H2S exposure, respectively. Of these, 77 proteomic changes were statistically significant at any of the 3 time points. Mass spectrometry data were subjected to Perseus 1.5.5.3 statistical analysis, and gene ontology heat map clustering. Expressions of several key molecules were verified to confirm H2S-dependent proteomics changes. Webgestalt pathway overrepresentation enrichment analysis with Panther engine revealed H2S exposure disrupted several biological processes including metabotropic glutamate receptor group 1 and inflammation mediated by chemokine and cytokine signaling pathways among others. Further analysis showed that energy metabolism, integrity of blood-brain barrier, hypoxic, and oxidative stress signaling pathways were also implicated. Collectively, this broad-spectrum proteomics data has provided important clues to follow up in future studies to further elucidate mechanisms of H2S-induced neurotoxicity
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