On the use of information theory for the analysis of synchronous nociceptive withdrawal reflexes and somatosensory evoked potentials elicited by graded electrical stimulation.

PubMed

Arguissain, Federico G; Biurrun Manresa, José A; Mørch, Carsten D; Andersen, Ole K

2015-01-30

To date, few studies have combined the simultaneous acquisition of nociceptive withdrawal reflexes (NWR) and somatosensory evoked potentials (SEPs). In fact, it is unknown whether the combination of these two signals acquired simultaneously could provide additional information on somatosensory processing at spinal and supraspinal level compared to individual NWR and SEP signals. By using the concept of mutual information (MI), it is possible to quantify the relation between electrical stimuli and simultaneous elicited electrophysiological responses in humans based on the estimated stimulus-response signal probability distributions. All selected features from NWR and SEPs were informative in regard to the stimulus when considered individually. Specifically, the information carried by NWR features was significantly higher than the information contained in the SEP features (p<0.05). Moreover, the joint information carried by the combination of features showed an overall redundancy compared to the sum of the individual contributions. Comparison with existing methods MI can be used to quantify the information that single-trial NWR and SEP features convey, as well as the information carried jointly by NWR and SEPs. This is a model-free approach that considers linear and non-linear correlations at any order and is not constrained by parametric assumptions. The current study introduces a novel approach that allows the quantification of the individual and joint information content of single-trial NWR and SEP features. This methodology could be used to decode and interpret spinal and supraspinal interaction in studies modulating the responsiveness of the nociceptive system. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of the effects of the alpha-2 agonists detomidine, romifidine and xylazine on nociceptive withdrawal reflex and temporal summation in horses.

PubMed

Rohrbach, Helene; Korpivaara, Toni; Schatzmann, Urs; Spadavecchia, Claudia

2009-07-01

To evaluate and compare the antinociceptive effects of the three alpha-2 agonists, detomidine, romifidine and xylazine at doses considered equipotent for sedation, using the nociceptive withdrawal reflex (NWR) and temporal summation model in standing horses. Prospective, blinded, randomized cross-over study. Ten healthy adult horses weighing 527-645 kg and aged 11-21 years old. Electrical stimulation was applied to the digital nerves to evoke NWR and temporal summation in the left thoracic limb and pelvic limb of each horse. Electromyographic reflex activity was recorded from the common digital extensor and the cranial tibial muscles. After baseline measurements a single bolus dose of detomidine, 0.02 mg kg(-1), romifidine 0.08 mg kg(-1), or xylazine, 1 mg kg(-1), was administered intravenously (IV). Determinations of NWR and temporal summation thresholds were repeated at 10, 20, 30, 40, 60, 70, 90, 100, 120 and 130 minutes after test-drug administration alternating the thoracic limb and the pelvic limb. Depth of sedation was assessed before measurements at each time point. Behavioural reaction was observed and recorded following each stimulation. The administration of detomidine, romifidine and xylazine significantly increased the current intensities necessary to evoke NWR and temporal summation in thoracic limbs and pelvic limbs of all horses compared with baseline. Xylazine increased NWR thresholds over baseline values for 60 minutes, while detomidine and romifidine increased NWR thresholds over baseline for 100 and 120 minutes, respectively. Temporal summation thresholds were significantly increased for 40, 70 and 130 minutes after xylazine, detomidine and romifidine, respectively. Detomidine, romifidine and xylazine, administered IV at doses considered equipotent for sedation, significantly increased NWR and temporal summation thresholds, used as a measure of antinociceptive activity. The extent of maximal increase of NWR and temporal summation thresholds was comparable, while the duration of action was drug-specific.

NOAA Weather Radio - Using NWR SAME

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Transmitter Outages FAQ NWR - Special Needs ESPAÑOL Español Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el

NOAA Weather Radio - EAS Description

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing ±ol Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR

NOAA Weather Radio - Outage Reporting

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing ±ol Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR

NOAA Weather Radio

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR SAME

NOAA Weather Radio - NWR Voices

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Transmitter Outages FAQ NWR - Special Needs ESPAÑOL Español Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el

NOAA Weather Radio - Reception Problems

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing ±ol Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR

Spatial encoding in spinal sensorimotor circuits differs in different wild type mice strains

PubMed Central

Thelin, Jonas; Schouenborg, Jens

2008-01-01

Background Previous studies in the rat have shown that the spatial organisation of the receptive fields of nociceptive withdrawal reflex (NWR) system are functionally adapted through experience dependent mechanisms, termed somatosensory imprinting, during postnatal development. Here we wanted to clarify 1) if mice exhibit a similar spatial encoding of sensory input to NWR as previously found in the rat and 2) if mice strains with a poor learning capacity in various behavioural tests, associated with deficient long term potention, also exhibit poor adaptation of NWR. The organisation of the NWR system in two adult wild type mouse strains with normal long term potentiation (LTP) in hippocampus and two adult wild type mouse strains exhibiting deficiencies in corresponding LTP were used and compared to previous results in the rat. Receptive fields of reflexes in single hindlimb muscles were mapped with CO2 laser heat pulses. Results While the spatial organisation of the nociceptive receptive fields in mice with normal LTP were very similar to those in rats, the LTP impaired strains exhibited receptive fields of NWRs with aberrant sensitivity distributions. However, no difference was found in NWR thresholds or onset C-fibre latencies suggesting that the mechanisms determining general reflex sensitivity and somatosensory imprinting are different. Conclusion Our results thus confirm that sensory encoding in mice and rat NWR is similar, provided that mice strains with a good learning capability are studied and raise the possibility that LTP like mechanisms are involved in somatosensory imprinting. PMID:18495020

NOAA Weather Radio - County Coverage by State

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing ±ol Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR

NOAA Weather Radio - Deaf and Hard of Hearing

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing ±ol Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR

NOAA Weather Radio - Station Search

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR SAME Programación en Español NOAA

NOAA Weather Radio - Viewing Outages

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Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR Recepción Explicacion de NWR SAME Programación en Español

Subspecific affinity of black bears in the White River National Wildlife Refuge

USGS Publications Warehouse

Warrillow, J.; Culver, M.; Hallerman, E.; Vaughan, M.

2001-01-01

The black bear population of the White River National Wildlife Refuge (NWR) is adjacent to populations of black bear in Louisiana (Urusus americanus luteolus) which are listed as threatened under the U.S. Endangered Species Act. Wildlife management plans can pose restrictions on bear harvests and timber extraction; therefore the management plan for the White River NWR is sensitive to subspecific classification of its bear population. The objective of this study was to analyze genetic variation in the White River NWR and seven adjacent populations of black bears to assess the subspecific affinity of the White River NWR population. Here we report the variation at seven microsatellite DNA loci among eight black bear populations. The patterns of genetic variation gave strong support for distinguishing a southern group of black bears comprised of the White River, Arkansas; Tensas River, Louisiana; Upper Atchafalaya, Louisiana; Lower Atchafalaya, Louisiana; and Alabama/Mississippi populations. Phylogenetic analysis of individual variation suggested that historical black bear introductions into Arkansas and Louisiana affected gene pools of certain southern receiving populations, but did not significantly change interpopulation relatedness. Phylogenetic inferences at both the population and individual levels support the hypothesis that the White River NWR population of black bears belongs to the U. a. luteolus subspecies.

Subspecific affinity of black bears in the White River National Wildlife Refuge.

PubMed

Warrillow, J; Culver, M; Hallerman, E; Vaughan, M

2001-01-01

The black bear population of the White River National Wildlife Refuge (NWR) is adjacent to populations of black bear in Louisiana (Urusus americanus luteolus) which are listed as threatened under the U.S. Endangered Species Act. Wildlife management plans can pose restrictions on bear harvests and timber extraction; therefore the management plan for the White River NWR is sensitive to subspecific classification of its bear population. The objective of this study was to analyze genetic variation in the White River NWR and seven adjacent populations of black bears to assess the subspecific affinity of the White River NWR population. Here we report the variation at seven microsatellite DNA loci among eight black bear populations. The patterns of genetic variation gave strong support for distinguishing a southern group of black bears comprised of the White River, Arkansas; Tensas River, Louisiana; Upper Atchafalaya, Louisiana; Lower Atchafalaya, Louisiana; and Alabama/Mississippi populations. Phylogenetic analysis of individual variation suggested that historical black bear introductions into Arkansas and Louisiana affected gene pools of certain southern receiving populations, but did not significantly change interpopulation relatedness. Phylogenetic inferences at both the population and individual levels support the hypothesis that the White River NWR population of black bears belongs to the U. a. luteolus subspecies.

Pain processing in atypical Parkinsonisms and Parkinson disease: A comparative neurophysiological study.

PubMed

Avenali, Micol; Tassorelli, Cristina; De Icco, Roberto; Perrotta, Armando; Serrao, Mariano; Fresia, Mauro; Pacchetti, Claudio; Sandrini, Giorgio

2017-10-01

Pain is a frequent non-motor feature in Parkinsonism but mechanistic data on the alteration of pain processing are insufficient to understand the possible causes and to define specifically-targeted treatments. we investigated spinal nociception through the neurophysiological measure of the threshold (TR) of nociceptive withdrawal reflex (NWR) and its temporal summation threshold (TST) comparatively in 12 Progressive Supranuclear Palsy (PSP) subjects, 11 Multiple System Atrophy (MSA) patients, 15 Parkinson's disease (PD) subjects and 24 healthy controls (HC). We also investigated the modulatory effect of L-Dopa in these three parkinsonian groups. We found a significant reduction in the TR of NWR and in the TST of NWR in PSP, MSA and PD patients compared with HC. L-Dopa induced an increase in the TR of NWR in the PSP group while TST of NWR increased in both PSP and PD. Our neurophysiological findings identify a facilitation of nociceptive processing in PSP that is broadly similar to that observed in MSA and PD. Specific peculiarities have emerged for PSP. Our data advance the knowledge of the neurophysiology of nociception in the advanced phases of parkinsonian syndromes and on the role of dopaminergic pathways in the control on pain processing. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Waterfowl migration on Klamath Basin National Wildlife Refuges 1953-2001

USGS Publications Warehouse

Gilmer, David S.; Yee, Julie L.; Mauser, David M.; Hainline, James M.

2004-01-01

The Klamath Basin National Wildlife Refuge (NWR) complex, located in northeastern California and southern Oregon, is situated on a major Pacific Flyway migration corridor connecting waterfowl breeding grounds in the north with major wintering grounds in California and Mexico. The complex comprises five waterfowl refuges including Lower Klamath NWR, Tule Lake NWR, Upper Klamath NWR, Klamath Marsh NWR, and Clear Lake NWR, and one bald eagle refuge, Bear Valley NWR. Lower Klamath and Tule Lake NWRs are the largest refuges in the complex; historically, they supported some of the greatest autumn and spring concentrations of migrating waterfowl in North America. Starting in 1953, standardized waterfowl surveys from small aircraft have been conducted in autumn through spring. This report summarizes waterfowl migration activity (i.e., abundance, species composition, distribution on refuges, and chronology) over four time periods—the long-term (1953-2001), early (1953-76), recent (1977-2001), and the most recent (1998-2001)—to describe changing patterns of migration on Klamath Basin refuges from autumn 1953 to spring 2001.Over the long term, waterfowl abundance (birds per day) on the refuge complex averaged about 1.0 million in autumn and about 360,000 in spring. A record peak count of 5.8 million waterfowl was recorded September 24-25, 1958. Average abundance of autumn staging waterfowl for the refuge complex, after reaching record levels in the 1950s and early 1960s, began a decline that lasted until the 1980s. A gradual recovery occurred during the 1990s, but autumn abundance has not recovered to pre-1970 levels. In contrast to autumn, average spring abundance was generally lower in the early decades but has gradually increased through the 1990s, particularly on Lower Klamath NWR.Dabbling ducks represented an average of 68% of all waterfowl in autumn and 55% in spring for the long term. Northern pintail (Anas acuta) was dominant, representing 62% of all dabblers in autumn and 51% in spring. A significant decline in pintail abundance starting in the late 1950s altered waterfowl composition on Klamath Basin refuges. As pintail declined, other species such as mallard (Anas platyrhynchos) and green-winged teal (Anas crecca) increased in abundance. Although Arctic nesting geese, including white-fronted (Anser albifrons), cackling Canada (Branta canadensis minima), white geese (lesser snow [Chen caerulescens caerulescens], and Ross’s [Chen rossii]) have become less prominent in recent decades, they reached an historically high abundance during autumn in the 1960s and 1970s, particularly on Tule Lake NWR.Tule Lake NWR supported the highest average autumn waterfowl populations until surpassed by Lower Klamath NWR around 1980. During the recent period (1977-2001), Lower Klamath NWR accounted for 60% of all waterfowl using the refuge complex in autumn and 61% in spring. Habitat diversity and wetland productivity contributed to its greater waterfowl abundance. Tule Lake NWR supported the most geese over the long term, 79% in autumn and 66% in spring; however, total waterfowl abundance on this refuge in autumn has been in decline, likely because of reduced diversity and productivity of sumps in the refuge. Upper Klamath, Klamath Marsh, and Clear Lake NWRs accounted for less than 8% of total waterfowl use in autumn and spring but provided diverse habitats for migrants.Waterfowl use-days on Klamath Basin refuges typically peaked in mid-autumn, decreased as migrants passed through the basin, and then reached a lesser peak during spring passage. Waterfowl abundance reached a pronounced peak in autumn during the early period (1953-76), but spring peak buildup was much less pronounced. For the recent period the autumn peak was more subdued.Waterfowl abundance, species composition, and distribution on Klamath Basin refuges have fluctuated over the decades and have been influenced by events such as productivity on breeding grounds and habitat conditions on wintering grounds that cause shifts in migration patterns. A major challenge for the future appears to be the availability of adequate water for wetland management on Klamath Basin refuges.

Why computational models are better than verbal theories: the case of nonword repetition.

PubMed

Jones, Gary; Gobet, Fernand; Freudenthal, Daniel; Watson, Sarah E; Pine, Julian M

2014-03-01

Tests of nonword repetition (NWR) have often been used to examine children's phonological knowledge and word learning abilities. However, theories of NWR primarily explain performance either in terms of phonological working memory or long-term knowledge, with little consideration of how these processes interact. One theoretical account that focuses specifically on the interaction between short-term and long-term memory is the chunking hypothesis. Chunking occurs because of repeated exposure to meaningful stimulus items, resulting in the items becoming grouped (or chunked); once chunked, the items can be represented in short-term memory using one chunk rather than one chunk per item. We tested several predictions of the chunking hypothesis by presenting 5-6-year-old children with three tests of NWR that were either high, medium, or low in wordlikeness. The results did not show strong support for the chunking hypothesis, suggesting that chunking fails to fully explain children's NWR behavior. However, simulations using a computational implementation of chunking (namely CLASSIC, or Chunking Lexical And Sub-lexical Sequences In Children) show that, when the linguistic input to 5-6-year-old children is estimated in a reasonable way, the children's data are matched across all three NWR tests. These results have three implications for the field: (a) a chunking account can explain key NWR phenomena in 5-6-year-old children; (b) tests of chunking accounts require a detailed specification both of the chunking mechanism itself and of the input on which the chunking mechanism operates; and (c) verbal theories emphasizing the role of long-term knowledge (such as chunking) are not precise enough to make detailed predictions about experimental data, but computational implementations of the theories can bridge the gap. © 2013 John Wiley & Sons Ltd.

Bats of Ouray National Wildlife Refuge

USGS Publications Warehouse

Ellison, Laura E.

2011-01-01

Ouray National Wildlife Refuge (NWR) is located in the northeast corner of Utah along the Green River and is part of the Upper Colorado River System and the Colorado Plateau. The Colorado Plateau is home to 19 species of bats, some of which are quite rare. Of those 19 species, a few have a more southern range and would not be expected to be found at Ouray NWR, but it is unknown what species occur at Ouray NWR or their relative abundance. The assumption is that Ouray NWR provides excellent habitat for bats, since the riparian habitat consists of a healthy population of cottonwoods with plenty of older, large trees and snags that would provide foraging and roosting habitat for bats. The more than 4,000 acres of wetland habitat, along with the associated insect population resulting from the wetland habitat, would provide ideal foraging habitat for bats. The overall objective of this project is to conduct a baseline inventory of bat species occurring on the refuge using mist nets and passive acoustic monitoring.

NOAA Weather Radio - SAME

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Station Search Coverage Maps Outages View Outages Report Outages Information General Information Receiver Information Reception Problems NWR Alarms Automated Voices FIPS Codes NWR - Special Needs SAME USING SAME SAME FIPS (Federal Information Processing Standards) code changes and / or SAME location code changes

ERCMExpress. Volume 2, Issue 4

ERIC Educational Resources Information Center

US Department of Education, 2006

2006-01-01

This issue of ERCMExpress alerts readers of the All-Hazard NOAA weather radio (NWR) network upgrade. In 2004, The National Oceanic and Atmospheric Administration NOAA and the U.S. Department of Homeland Security (DHS) collaborated to enable DHS to disseminate homeland security-related information over the NWR network. DHS's goal was to produce an…

NOAA Weather Radio

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Station Search Coverage Maps Outages View Outages Report Outages Information General Information Receiver Information Reception Problems NWR Alarms Automated Voices FIPS Codes NWR - Special Needs SAME USING SAME SAME Search For Go NWS All NOAA Frequently Asked Questions This site offers a wealth of information on NOAA

NOAA Weather Radio - All Hazards

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Station Search Coverage Maps Outages View Outages Report Outages Information General Information Receiver Information Reception Problems NWR Alarms Automated Voices FIPS Codes NWR - Special Needs SAME USING SAME SAME Weather Service (NWS) warnings, watches, forecasts and other non-weather related hazard information 24

75 FR 35080 - Tampa Bay Refuges, FL

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-21

... species. It contains 7 mangrove islands encompassing about 394 acres. The refuge is comprised of Little... Tarpon and Little Bird Keys. Pinellas NWR provides important mangrove habitat for most long-legged wading species, especially the reddish egret. All of the mangrove islands of Pinellas NWR are closed to all...

Bilingual Performance on Nonword Repetition in Spanish and English

ERIC Educational Resources Information Center

Summers, Connie; Bohman, Thomas M.; Gillam, Ronald B.; Pena, Elizabeth D.; Bedore, Lisa M.

2010-01-01

Background: Nonword repetition (NWR) involves the ability to perceive, store, recall and reproduce phonological sequences. These same abilities play a role in word and morpheme learning. Cross-linguistic studies of performance on NWR tasks, word learning, and morpheme learning yield patterns of increased performance on all three tasks as a…

Non-Word Repetition in Adolescents with Specific Language Impairment (SLI)

ERIC Educational Resources Information Center

Ebbels, Susan H.; Dockrell, Julie E.; van der Lely, Heather K. J.

2012-01-01

Background: Non-word repetition (NWR) difficulties are common, but not universal, among children with specific language impairment (SLI). However, older children and adolescents with SLI have rarely been studied. Studies disagree on the relationship between NWR difficulties and difficulties with other areas of language and literacy. There is also…

NOAA Weather Radio - Outage Reporting

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is not listed at Current Outages, the problem may be possibly be with your receiver. If your NWR receiver is not working properly or you need assistance in programming your NWR receiver, please click here information we may not be able to troubleshoot the problem fully. COVERAGE County Coverage Listings State

75 FR 80524 - Watercress Darter National Wildlife Refuge, Jefferson County, AL

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-22

... Darter NWR, near the city of Bessemer, Jefferson County, Alabama, was established by the Service in 1980... occur in the city of Bessemer, Alabama. Watercress Darter NWR is a small system that can be greatly..., watershed, and biota exchange pathways. Extensive resource sharing and networking with other protected areas...

Why Computational Models Are Better than Verbal Theories: The Case of Nonword Repetition

ERIC Educational Resources Information Center

Jones, Gary; Gobet, Fernand; Freudenthal, Daniel; Watson, Sarah E.; Pine, Julian M.

2014-01-01

Tests of nonword repetition (NWR) have often been used to examine children's phonological knowledge and word learning abilities. However, theories of NWR primarily explain performance either in terms of phonological working memory or long-term knowledge, with little consideration of how these processes interact. One theoretical account that…

76 FR 33339 - Grays Harbor National Wildlife Refuge (NWR) and Black River Unit of Nisqually NWR; Comprehensive...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-08

... effects will climate change and sea level rise have on Refuge habitats and species? Invasive species control. Invasive species degrade habitat for shorebirds, migratory birds, and many other fish and wildlife. How can we reduce the incidence and spread of invasive species? Visitor experiences and education...

Vascular flora of Izembek National Wildlife Refuge, westernmost Alaska Peninsula, Alaska

USGS Publications Warehouse

Talbot, S. S.; Talbot, S.L.; Schofield, W.B.

2006-01-01

The vascular flora of Izembek National Wildlife Refuge (NWR), where few previous collections had been reported, was collected and recorded at sites selected to represent the totality of environmental variation. A total of 349 species (339 native and 10 introduced) was identified. To provide a comparative phytogeographic framework, we analyzed data from published reports that categorized vascular plant distribution patterns from a circumpolar, North American, and Alaskan perspective. The native flora of the Izembek NWR primarily includes species of circumpolar (38%), eastern Asian (23%), Eurasian (18%), and North American (13%) distribution. The most important longitudinal distributional classes in North America consist of transcontinental (62%) and extreme western species (31%). The annotated list of species in Izembek NWR expands the range of many species, filling a distributional gap in Hulte??n's Western Pacific Coast district. Forty notable range extensions are reported. The flora of Izembek NWR is primarily made up of boreal species and lacks many of the species considered to be Arctic. Comparison with the Raunkiaer life-form spectrum similarly points to the boreal.

Linking working memory and long-term memory: a computational model of the learning of new words.

PubMed

Jones, Gary; Gobet, Fernand; Pine, Julian M

2007-11-01

The nonword repetition (NWR) test has been shown to be a good predictor of children's vocabulary size. NWR performance has been explained using phonological working memory, which is seen as a critical component in the learning of new words. However, no detailed specification of the link between phonological working memory and long-term memory (LTM) has been proposed. In this paper, we present a computational model of children's vocabulary acquisition (EPAM-VOC) that specifies how phonological working memory and LTM interact. The model learns phoneme sequences, which are stored in LTM and mediate how much information can be held in working memory. The model's behaviour is compared with that of children in a new study of NWR, conducted in order to ensure the same nonword stimuli and methodology across ages. EPAM-VOC shows a pattern of results similar to that of children: performance is better for shorter nonwords and for wordlike nonwords, and performance improves with age. EPAM-VOC also simulates the superior performance for single consonant nonwords over clustered consonant nonwords found in previous NWR studies. EPAM-VOC provides a simple and elegant computational account of some of the key processes involved in the learning of new words: it specifies how phonological working memory and LTM interact; makes testable predictions; and suggests that developmental changes in NWR performance may reflect differences in the amount of information that has been encoded in LTM rather than developmental changes in working memory capacity.

Factors affecting settling, survival, and viability of black bears reintroduced to Felsenthal National Wildlife Refuge, Arkansas

USGS Publications Warehouse

Wear, B.J.; Eastridge, R.; Clark, J.D.

2005-01-01

We used radiotelemetry and population modeling techniques to examine factors related to population establishment of black bears (Ursus americanus) reintroduced to Felsenthal National Wildlife Refuge (NWR), Arkansas. Our objectives were to determine whether settling (i.e., establishment of a home range at or near the release site), survival, recruitment, and population viability were related to age class of reintroduced bears, presence of cubs, time since release, or number of translocated animals. We removed 23 adult female black bears with 56 cubs from their winter dens at White River NWR and transported them 160 km to man-made den structures at Felsenthal NWR during spring 2000–2002. Total movement and average circuity of adult females decreased from 1 month, 6 months, and 1 year post-emergence (F2,14 =19.7, P < 0.001 and F2,14 =5.76, P=0.015, respectively). Mean first-year post-release survival of adult female bears was 0.624 (SE = 0.110, SEinterannual = 0.144), and the survival rate of their cubs was 0.750 (SE = 0.088, SEinterannual = 0.109). The homing rate (i.e., the proportion of bears that returned to White River NWR) was 13%. Annual survival for female bears that remained at the release site and survived >1-year post-release increased to 0.909 (SE = 0.097, SEinterannual=0.067; Z=3.5, P < 0.001). Based on stochastic population growth simulations, the average annual growth rate (λ) was 1.093 (SD = 0.053) and the probability of extinction with no additional stockings ranged from 0.56-1.30%. The bear population at Felsenthal NWR is at or above the number after which extinction risk declines dramatically, although additional releases of bears could significantly decrease time to population reestablishment. Poaching accounted for at least 3 of the 8 adult mortalities that we documented; illegal kills could be a significant impediment to population re-establishment at Felsenthal NWR should poaching rates escalate.

Working memory span in Persian-speaking children with speech sound disorders and normal speech development.

PubMed

Afshar, Mohamad Reza; Ghorbani, Ali; Rashedi, Vahid; Jalilevand, Nahid; Kamali, Mohamad

2017-10-01

The aim of this study was to compare working memory span in Persian-speaking preschool children with speech sound disorder (SSD) and their typically speaking peers. Additionally, the study aimed to examine Non-Word Repetition (NWR), Forward Digit Span (FDS) and Backward Digit Span (BDS) in four groups of children with varying severity levels of SSD. The participants in this study comprised 35 children with SSD and 35 typically developing (TD) children -matched for age and sex-as a control group. The participants were between the age range of 48 and 72 months. Two components of working memory including phonological loop and central executive were compared between two groups. We used two tasks (NWR and FDS) to assess phonological loop component, and one task (BDS) to assess central executive component. Percentage of correct consonants (PCC) was used to calculate the severity of SSD. Significant differences were observed between the two groups in all tasks that assess working memory (p < 0.001). In addition, the comparison of the phonological loop of working memory between the various severity groups indicated significant differences between different severities of both NWR and FDS tasks among the SSD children (p < 0.001). Nevertheless, comparison of the central executive between various severity groups, which was assessed with the BDS task, did not show any significant differences (p > 0.05). The result showed that PCC scores in TD children were associated with NWR (p < 0.001), FDS (p = 0.001), and BDS (p < 0.001). Furthermore, PCC scores in SSD children were associated with NWR and FDS (p < 0.001), but not with BDS (p > 0.05). The working memory skills were weaker in SSD children, in comparison to TD children. In addition, children with varying levels of severity of SSD differed in terms of NWR and FSD, but not BDS. Copyright © 2017 Elsevier B.V. All rights reserved.

75 FR 68377 - Tamarac National Wildlife Refuge, Becker County, and Tamarac Wetland Management District, Minnesota

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-05

... Tamarac National Wildlife Refuge (NWR) and Tamarac Wetland Management District (WMD). Goals and objectives... complete the CCP process for Tamarac NWR and WMD, which we began by publishing a notice of intent on (72 FR... Federally-designated wilderness acres. The Tamarac WMD consists of 8,577 acres of wetland easements...

Bilingual Children's Performance on Three Nonword Repetition Tasks: The Role of Language Experience and Ability

ERIC Educational Resources Information Center

Huls, Simone

2017-01-01

Nonword repetition (NWR) tasks represent one assessment tool for Specific Language Impairment (SLI). The use of such tasks has been established and verified for monolingual children. However, the diagnostic accuracy of NWR tasks for bilingual children has had variable results and must address several unique characteristics of this population. Gaps…

75 FR 55600 - Sonny Bono Salton Sea National Wildlife Refuge Complex (Sonny Bono Salton Sea National Wildlife...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-09-13

...] Sonny Bono Salton Sea National Wildlife Refuge Complex (Sonny Bono Salton Sea National Wildlife Refuge... Bono Salton Sea National Wildlife Refuge (NWR) Complex, which consists of the Sonny Bono Salton Sea NWR... any of the following methods. E-mail: [email protected] . Include ``Sonny Bono Salton Sea...

Words are not enough: nonword repetition as an indicator of arcuate fasciculus integrity during brain tumor resection.

PubMed

Sierpowska, Joanna; Gabarrós, Andreu; Fernandez-Coello, Alejandro; Camins, Àngels; Castañer, Sara; Juncadella, Montserrat; Morís, Joaquín; Rodríguez-Fornells, Antoni

2017-02-01

OBJECTIVE Subcortical electrical stimulation during brain surgery may allow localization of functionally crucial white matter fibers and thus tailoring of the tumor resection according to its functional limits. The arcuate fasciculus (AF) is a white matter bundle connecting frontal, temporal, and parietal cortical areas that is often disrupted by left brain lesions. It plays a critical role in several cognitive functions related to phonological processing, but current intraoperative monitoring methods do not yet allow mapping of this tract with sufficient precision. In the present study the authors aimed to test a new paradigm for the intraoperative monitoring of the AF. METHODS In this report, the authors studied 12 patients undergoing awake brain surgery for tumor resection with a related risk of AF damage. To preserve AF integrity and the cognitive processes sustained by this tract in the intraoperative context, the authors used real word repetition (WR) and nonword repetition (NWR) tasks as complements to standard picture naming. RESULTS Compared with the errors identified by WR or picture naming, the NWR task allowed the detection of subtle errors possibly related to AF alterations. Moreover, only 3 patients demonstrated phonological paraphasias in standard picture naming, and in 2 of these patients the paraphasias co-occurred with the total loss of WR and NWR ability. Before surgery, lesion volume predicted a patient's NWR performance. CONCLUSIONS The authors suggest that monitoring NWR intraoperatively may complement the standard naming tasks and could permit better preservation of the important language production functions subserved by the AF.

The clinical examination of non-word repetition tasks in identifying Persian-speaking children with primary language impairment.

PubMed

Kazemi, Yalda; Saeednia, Soodeh

2017-02-01

This study aimed to examine the diagnostic accuracy of a non-word repetition (NWR) test in identifying Persian-speaking preschool children with specific/primary language impairment (PLI). Children with PLI show consistently poorer performance in non-word repetition tasks than their typically developing language (TDL) counterparts. It is assumed that the ability to repeat non-words triggers language skills and that the absence of this ability may be responsible for language impairment in PLI children. Twenty preschool children with PLI participated in this study and were compared with 31 peers whose language skills were developing typically. The TDL children were randomly selected from daycare centers, and the children with PLI were referred by qualified speech-language pathologists from speech therapy clinics. A Persian NWR test was administered and scored using two levels of scoring: item-level scoring and syllable-level scoring. Data were analyzed in two phases. The first phase aimed to determine any differences between the two groups of children in terms of NWR ability. The second phase examined the diagnostic measures of the test. The results of first phase documented that both scoring methods for the NWR test significantly differentiated between children with PLI and their normal peers. The second phase indicated that both scoring methods for the NWR test have good sensitivity and specificity in differentiating Persian-speaking children with PLI from their normal peers. Non-word repetition can be a reliable clinical marker of PLI in Persian-speaking preschool children. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Non-Word Repetition in Adolescents with Specific Language Impairment and Autism Plus Language Impairments: A Qualitative Analysis

ERIC Educational Resources Information Center

Riches, N. G.; Loucas, T.; Baird, G.; Charman, T.; Simonoff, E.

2011-01-01

Non-word repetition (NWR) was investigated in adolescents with typical development, Specific Language Impairment (SLI) and Autism Plus language Impairment (ALI) (n = 17, 13, 16, and mean age 14;4, 15;4, 14;8 respectively). The study evaluated the hypothesis that poor NWR performance in both groups indicates an overlapping language phenotype…

77 FR 49011 - Texas Mid-Coast National Wildlife Refuge Complex, Brazoria, Fort Bend, Matagorda, and Wharton...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-15

.... The Complex, which includes Brazoria, San Bernard, and Big Boggy National Wildlife Refuges (NWRs), is... Drop-off, Viewing, or Pickup: You may drop off comments during regular business hours (8 a.m. to 4:30 p... Bernard NWR, which was established in 1968, and encompasses 52,400 acres; and Big Boggy NWR, which was...

Linking Working Memory and Long-Term Memory: A Computational Model of the Learning of New Words

ERIC Educational Resources Information Center

Jones, Gary; Gobet, Fernand; Pine, Julian M.

2007-01-01

The nonword repetition (NWR) test has been shown to be a good predictor of children's vocabulary size. NWR performance has been explained using phonological working memory, which is seen as a critical component in the learning of new words. However, no detailed specification of the link between phonological working memory and long-term memory…

English Language Learners' Nonword Repetition Performance: The Influence of Age, L2 Vocabulary Size, Length of L2 Exposure, and L1 Phonology.

PubMed

Duncan, Tamara Sorenson; Paradis, Johanne

2016-02-01

This study examined individual differences in English language learners' (ELLs) nonword repetition (NWR) accuracy, focusing on the effects of age, English vocabulary size, length of exposure to English, and first-language (L1) phonology. Participants were 75 typically developing ELLs (mean age 5;8 [years;months]) whose exposure to English began on average at age 4;4. Children spoke either a Chinese language or South Asian language as an L1 and were given English standardized tests for NWR and receptive vocabulary. Although the majority of ELLs scored within or above the monolingual normal range (71%), 29% scored below. Mixed logistic regression modeling revealed that a larger English vocabulary, longer English exposure, South Asian L1, and older age all had significant and positive effects on ELLs' NWR accuracy. Error analyses revealed the following L1 effect: onset consonants were produced more accurately than codas overall, but this effect was stronger for the Chinese group whose L1s have a more limited coda inventory compared with English. ELLs' NWR performance is influenced by a number of factors. Consideration of these factors is important in deciding whether monolingual norm referencing is appropriate for ELL children.

MX Siting Investigation. Preliminary Geotechnical Investigation. Proposed Operational Base Site, Coyote Spring Valley, Nevada. Volume I. Synthesis.

DTIC Science & Technology

1980-12-23

slopes, location of potential aggregate sources, types of I foundations for the various structures and their aliowahle bearing pressures , and...limestone and dolomite are generally gray and dark gray, thick-bedded to massive, and are commonly I jointed. Bedding is defined by differential erosion...limestone and dolomite occurs about 1 1/2 miles (2.4 km) north of State Route 7 on the western side of Pahranagat Wash (Drawing 5-1). It has the same general

Identifying language impairment in bilingual children in France and in Germany.

PubMed

Tuller, Laurice; Hamann, Cornelia; Chilla, Solveig; Ferré, Sandrine; Morin, Eléonore; Prevost, Philippe; Dos Santos, Christophe; Abed Ibrahim, Lina; Zebib, Racha

2018-05-23

The detection of specific language impairment (SLI) in children growing up bilingually presents particular challenges for clinicians. Non-word repetition (NWR) and sentence repetition (SR) tasks have proven to be the most accurate diagnostic tools for monolingual populations, raising the question of the extent of their usefulness in different bilingual populations. To determine the diagnostic accuracy of NWR and SR tasks that incorporate phonological/syntactic complexity as discussed in recent linguistic theory. The tasks were developed as part of the Language Impairment Testing in Multilingual Settings (LITMUS) toolkit, in two different national settings, France and Germany, and investigated children with three different home languages: Arabic, Portuguese and Turkish. NWR and SR tasks developed in parallel were administered to 151 bilingual children, aged 5;6-8;11, in France and in Germany, to 64 children in speech-language therapy (SLT) and to 87 children not in SLT, whose first language (L1) was Arabic, Portuguese or Turkish. Children were also administered standardized language tests in each of their languages to determine likely clinical status (typical development (TD) or SLI), and parents responded to a questionnaire including questions about early and current language use (bilingualism factors) and early language development (risk factors for SLI). Monolingual controls included 47 TD children and 29 children with SLI. Results were subjected to inter-group comparisons, to diagnostic accuracy calculation, and to correlation and multiple regression analyses. In accordance with previous studies, NWR and SR identified SLI in the monolingual children, yielding good to excellent diagnostic accuracy. Diagnostic accuracy in bilingual children was fair to good, generally distinguishing children likely to have SLI from children likely to have TD. Accuracy was necessarily linked to the determination of clinical status, which was based on standardized assessment in each of the child's languages. Positive early development, a composite risk factor for SLI, and not variables related to language exposure and use, generally emerged as the strongest predictor of performance on the two tasks, constituting additional, independent support for the efficacy of NWR and SR in identifying impairment in bilingual children. NWR and SR tasks informed by linguistic theory are appropriate for use as part of the diagnostic process for identifying language impairment in bilingual children for whom the language of assessment is different from the home language, in diverse sociolinguistic contexts. © 2018 Royal College of Speech and Language Therapists.

Community Survey Results for Rappahannock River Valley National Wildlife Refuge: Completion Report

USGS Publications Warehouse

Sexton, Natalie R.; Stewart, Susan C.; Koontz, Lynne

2008-01-01

This report provides a summary of results for the survey of residents of communities adjacent to Rappahannock River Valley NWR conducted from the spring through the summer in 2006. This research was commissioned by the Northeast Region of the U.S. Fish and Wildlife Service in support of the Rappahannock River Valley NWR CCP and conducted by the Policy Analysis and Science Assistance Branch (PASA) of the U.S. Geological Survey/Fort Collins Science Center.

NOAA Weather Radio - EAS Event Codes

Science.gov Websites

Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Transmitter Outages FAQ NWR - Special Needs ESPAÑOL Español Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el

NOAA Weather Radio - Station Listing

Science.gov Websites

Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Outages FAQ NWR - Special Needs ESPAÑOL Español Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor

NOAA Weather Radio

Science.gov Websites

Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing interés abajo de dentro de la lista entera del archivo nacional Transmisores de NWR en los Estados ±ol Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES

NOAA Weather Radio

Science.gov Websites

recepción confiable en algunas localidades debido a bloqueos de las señales y/o distancia excesiva de la mensajes NOTA: Servicio de NWR para un condado depende de recepción confiable la señal, la cual cobertura de NWR, o cobertura parcial, serán indicados. Algunos condados o partes de condados

NOAA Weather Radio - Información General

Science.gov Websites

logo La Radio de Canada NWR receiver logo recepción COVERAGE County Coverage Listings State Coverage Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Search For Go NWS All NOAA Información General NWR receiver logo Información de Fondo (incluyendo

NOAA Weather Radio - General Information

Science.gov Websites

Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing - Special Needs ESPAÑOL Español Condado de cobertura Listado de estación Lista de Emisora y Cobertura Acerca de NWR ESTACIONES NACIONAL Información General Información Para el consumidor receptor NWR

The Role of Phonological Working Memory and Environmental Factors in Lexical Development in Italian-Speaking Late Talkers: A One-Year Follow-Up Study.

PubMed

Marini, Andrea; Ruffino, Milena; Sali, Maria Enrica; Molteni, Massimo

2017-12-20

This follow-up study assessed (a) the influence of phonological working memory (pWM), home literacy environment, and a family history of linguistic impairments in late talkers (LTs); (b) the diagnostic accuracy of a task of nonword repetition (NWR) in identifying LTs; and (c) the persistence of lexical weaknesses after 10 months. Two hundred ninety-three children were assessed at approximately 32 (t1) and 41 (t2) months. At t1, they were administered the Italian adaptation of the Language Development Survey, an NWR task (used to assess pWM), and questionnaires assessing home literacy environment and family history of language impairments. Thirty-three LTs were identified. The linguistic skills of the participants were evaluated at t2 by administering tasks assessing Articulation, Naming, Semantic Fluency, and Lexical Comprehension. At t2, LTs performed more poorly as compared with age-matched typically developing peers in articulatory and naming skills, had reduced lexical comprehension abilities, and had limited lexical knowledge. Their performance on the NWR task at t1 correlated with the extension of their vocabularies at t2 (as estimated with a Semantic Fluency task). The Language Development Survey recently adapted to Italian is sensitive to LTs. Former LTs still have a mild lexical delay at approximately 40 months. As an indirect measure of pWM, the task of NWR is an early indicator of future lexical deficits.

Natural uranium and strontium isotope tracers of water sources and surface water-groundwater interactions in arid wetlands: Pahranagat Valley, Nevada, USA

USGS Publications Warehouse

Paces, James B.; Wurster, Frederic C.

2014-01-01

Near-surface physical and chemical process can strongly affect dissolved-ion concentrations and stable isotope compositions of water in wetland settings, especially under arid climate conditions. In contrast, heavy radiogenic isotopes of strontium (87Sr/86Sr) and uranium (234U/238U) remain largely unaffected and can be used to help identify unique signatures from different sources and quantify end-member mixing that would otherwise be difficult to determine. The utility of combined Sr and U isotopes are demonstrated in this study of wetland habitats on the Pahranagat National Wildlife Refuge, which depend on supply from large-volume springs north of the Refuge, and from small-volume springs and seeps within the Refuge. Water budgets from these sources have not been quantified previously. Evaporation, transpiration, seasonally variable surface flow, and water management practices complicate the use of conventional methods for determining source contributions and mixing relations. In contrast, 87Sr/86Sr and 234U/238U remain unfractionated under these conditions, and compositions at a given site remain constant. Differences in Sr- and U-isotopic signatures between individual sites can be related by simple two- or three-component mixing models. Results indicate that surface flow constituting the Refuge’s irrigation source consists of a 65:25:10 mixture of water from two distinct regionally sourced carbonate aquifer springs, and groundwater from locally sourced volcanic aquifers. Within the Refuge, contributions from the irrigation source and local groundwater are readily determined and depend on proximity to those sources as well as water management practices.

Natural uranium and strontium isotope tracers of water sources and surface water-groundwater interactions in arid wetlands - Pahranagat Valley, Nevada, USA

NASA Astrophysics Data System (ADS)

Paces, James B.; Wurster, Frederic C.

2014-09-01

Near-surface physical and chemical process can strongly affect dissolved-ion concentrations and stable-isotope compositions of water in wetland settings, especially under arid climate conditions. In contrast, heavy radiogenic isotopes of strontium (87Sr/86Sr) and uranium (234U/238U) remain largely unaffected and can be used to help identify unique signatures from different sources and quantify end-member mixing that would otherwise be difficult to determine. The utility of combined Sr and U isotopes are demonstrated in this study of wetland habitats on the Pahranagat National Wildlife Refuge, which depend on supply from large-volume springs north of the Refuge, and from small-volume springs and seeps within the Refuge. Water budgets from these sources have not been quantified previously. Evaporation, transpiration, seasonally variable surface flow, and water management practices complicate the use of conventional methods for determining source contributions and mixing relations. In contrast, 87Sr/86Sr and 234U/238U remain unfractionated under these conditions, and compositions at a given site remain constant. Differences in Sr- and U-isotopic signatures between individual sites can be related by simple two- or three-component mixing models. Results indicate that surface flow constituting the Refuge's irrigation source consists of a 65:25:10 mixture of water from two distinct regionally sourced carbonate-aquifer springs, and groundwater from locally sourced volcanic aquifers. Within the Refuge, contributions from the irrigation source and local groundwater are readily determined and depend on proximity to those sources as well as water management practices.

Channel Response to Low-Elevation Desert Fire: The King Valley Fire of 2005

USGS Publications Warehouse

Webb, Robert H.; Griffiths, Peter G.; Wallace, Cynthia S.A.; Boyer, Diane E.

2007-01-01

In late September to early October 2005, a fire swept north from the Yuma Proving Grounds and into the Kofa National Wildlife Refuge (NWR), traveling mainly along desert wash systems and low-relief alluvial fans. This fire burned 9,975 ha, moving through xeroriparian systems in washes as well as low-elevation desert ecosystems in King Valley, a major area of designated wilderness in the southern part of the Kofa NWR. Using satellite imagery, we determined that 9,255 ha of the Kofa NWR in King Valley burned. The fine-fuel loading for the fire was mostly a native forb (Plantago insularis), and the desert environment that was burned was mostly low-cover creosote bush (Larrea tridentata) scrub with scattered palo verde (Cercidium microphyllum). The wash environments had significant tree cover, including ironwood (Olneya tesota), blue palo verde (Cercidium floridum), desert willow (Chilopsis linearis), and/or smoke tree (Psorothamnus spinosa). This report presents monitoring data collected in June 2006 and January-February 2007 on the effects of this fire on channel morphology in King Valley.

NOAA Weather Radio

Science.gov Websites

Search For Go NWS All NOAA NWR Recepción El área de la recepción nominal para un receptor de Radio cosas afectan la recepción de señas de la radio. Por ejemplo, las extensiones grandes de agua de sal de NWR. Siga leyendo si está dentro del área pero tiene dificultad con recepción. Su seña de la

NOAA Weather Radio

Science.gov Websites

televisión afuera o dentro de la casa. Todos éstos pueden mejorar recepción a cualquier radio de FM , incluso NWR. Cualquier pregunta específica sobre la recepción (o falta de ella) en su sitio debe Search For Go NWS All NOAA NWR Recepción El área de la recepción nominal para un receptor de Radio

An experimental animal model for percutaneous procedures used in trigeminal neuralgia.

PubMed

Herta, Johannes; Wang, Wei-Te; Höftberger, Romana; Breit, Sabine; Kneissl, Sibylle; Bergmeister, Helga; Ferraz-Leite, Heber

2017-07-01

This study describes an experimental rabbit model that allows the reproduction of percutaneous operations that are used in patients with trigeminal neuralgia (TN). Attention was given to an exact anatomical description of the rabbit's middle cranial fossa as well as the establishment of conditions for a successful procedure. Morphometric measurements were taken from 20 rabbit skulls and CT scans. The anatomy of the trigeminal nerve, as well as its surrounding structures, was assessed by bilateral dissection of 13 New Zealand white rabbits (NWR). An ideal approach of placing a needle through the foramen ovale to reach the TG was sought. Validation of correct placement was realized by fluoroscopy and confirmed by dissection. Precise instructions for successful reproduction of percutaneous procedures in NWR were described. According to morphological measurements, for balloon compression of the trigeminal ganglion (TG) the maximal diameter of an introducing cannula is 1.85 mm. The diameter of an empty balloon catheter should not exceed 1.19 mm, and the length of the inflatable part of the balloon can range up to 4 mm. For thermocoagulation the needle electrodes must not exceed an external diameter of 1.39, mm and the length of the non-insolated tip can range up to 4 mm. Glycerol rhizolysis can be achieved because the trigeminal cistern in the NWR is a closed space that allows a long dwelling time (>10 min) of the contrast agent. An experimental NWR model intended for the reproduction of percutaneous procedures on the TG has been meticulously described. This provides a tool that enables further standardized animal research in the field of surgical treatment of TN.

A comprehensive review of observational and site evaluation data of migrant whooping cranes in the United States, 1943-1999

USGS Publications Warehouse

Austin, Jane E.; Richert, Amy L.

2001-01-01

This report is a comprehensive analysis of existing observational data (1943–99) and site evaluation data (1977–99) for locations used by whooping cranes (Grus americana) during migration through the United States portion of the Wood Buffalo–Aransas flyway. The apparent migration path, as outlined by the distribution of whooping crane observations, is very similar to that delineated in earlier reports, following a relatively straight line north-northwest from Aransas National Wildlife Refuge (NWR) to central North Dakota then curving northwest along the Missouri Coteau to the North Dakota–Saskatchewan border. The distribution of spring and fall observations were relatively similar, except for the higher frequency of fall observations on Quivira NWR and Cheyenne Bottoms State Wildlife Area in Kansas, Salt Plains NWR in Oklahoma, and in Texas. Timing of spring and fall migrations also appears similar to that described earlier and shows no changes over the 57-year period of data collection. Regardless of season, most sightings included 1–3 whooping cranes, but groups with as many as 14 and 19 cranes have been sighted in spring and fall, respectively.

Twelve Months of Air Quality Monitoring at Ash Meadows National Wildlife Refuge, Southwestern Rural Nevada, U.S.A (EMSI April 2007)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Engelbrecht, Johann P; Shafer, David S; Campbell, Dave

The one year of air quality monitoring data collected at the Ash Meadows National Wildlife Refuge (NWR) was the final part of the air quality "Scoping Studies" for the Environmental Monitoring Systems Initiative (EMSI) in southern and central Nevada. The objective of monitoring at Ash Meadows was to examine aerosol and meteorological data, seasonal trends in aerosol and meteorological parameters as well as to examine evidence for long distance transport of some constituents. The 9,307 hectare refuge supports more than 50 springs and 24 endemic species, including the only population of the federally listed endangered Devil’s Hole pupfish (Cyprinodon diabolis)more » (U.S. Fish and Wildlife Service, 1990). Ash Meadows NWR is located in a Class II air quality area, and the aerosol measurements collected with this study are compared to those of Interagency Monitoring of Protected Visual Environments (IMPROVE) sites. Measurements taken at Ash Meadows NWR over a period of 12 months provide new baseline air quality and meteorological information for rural southwestern Nevada, specifically Nye County and the Amargosa Valley.« less

Lexical and phonological variability in preschool children with speech sound disorder.

PubMed

Macrae, Toby; Tyler, Ann A; Lewis, Kerry E

2014-02-01

The authors of this study examined relationships between measures of word and speech error variability and between these and other speech and language measures in preschool children with speech sound disorder (SSD). In this correlational study, 18 preschool children with SSD, age-appropriate receptive vocabulary, and normal oral motor functioning and hearing were assessed across 2 sessions. Experimental measures included word and speech error variability, receptive vocabulary, nonword repetition (NWR), and expressive language. Pearson product–moment correlation coefficients were calculated among the experimental measures. The correlation between word and speech error variability was slight and nonsignificant. The correlation between word variability and receptive vocabulary was moderate and negative, although nonsignificant. High word variability was associated with small receptive vocabularies. The correlations between speech error variability and NWR and between speech error variability and the mean length of children's utterances were moderate and negative, although both were nonsignificant. High speech error variability was associated with poor NWR and language scores. High word variability may reflect unstable lexical representations, whereas high speech error variability may reflect indistinct phonological representations. Preschool children with SSD who show abnormally high levels of different types of speech variability may require slightly different approaches to intervention.

Effects of open marsh water management on numbers of larval salt marsh mosquitoes

USGS Publications Warehouse

James-Pirri, Mary-Jane; Ginsberg, Howard S.; Erwin, R. Michael; Taylor, Janith

2009-01-01

Open marsh water management (OMWM) is a commonly used approach to manage salt marsh mosquitoes than can obviate the need for pesticide application and at the same time, partially restore natural functions of grid-ditched marshes. OMWM includes a variety of hydrologic manipulations, often tailored to the specific conditions on individual marshes, so the overall effectiveness of this approach is difficult to assess. Here, we report the results of controlled field trials to assess the effects of two approaches to OMWM on larval mosquito production at National Wildlife Refuges (NWR). A traditional OMWM approach, using pond construction and radial ditches was used at Edwin B. Forsythe NWR in New Jersey, and a ditch-plugging approach was used at Parker River NWR in Massachusetts. Mosquito larvae were sampled from randomly placed stations on paired treatment and control marshes at each refuge. The proportion of sampling stations that were wet declined after OMWM at the Forsythe site, but not at the Parker River site. The proportion of samples with larvae present and mean larval densities, declined significantly at the treatment sites on both refuges relative to the control marshes. Percentage of control for the 2 yr posttreatment, compared with the 2 yr pretreatment, was >90% at both treatment sites.

Soluble trace elements and total mercury in Arctic Alaskan snow

USGS Publications Warehouse

Snyder-Conn, E.; Garbarino, J.R.; Hoffman, G.L.; Oelkers, A.

1997-01-01

Ultraclean field and laboratory procedures were used to examine trace element concentrations in northern Alaskan snow. Sixteen soluble trace elements and total mercury were determined in snow core samples representing the annual snowfall deposited during the 1993-94 season at two sites in the Prudhoe Bay oil field and nine sites in the Arctic National Wildlife Refuge (Arctic NWR). Results indicate there were two distinct point sources for trace elements in the Prudhoe Bay oil field - a source associated with oil and gas production and a source associated with municipal solid-waste incineration. Soluble trace element concentrations measured in snow from the Arctic NWR resembled concentrations of trace elements measured elsewhere in the Arctic using clean sample-collection and processing techniques and were consistent with deposition resulting from widespread arctic atmospheric contamination. With the exception of elements associated with sea salts, there were no orographic or east-west trends observed in the Arctic NWR data, nor were there any detectable influences from the Prudhoe Bay oil field, probably because of the predominant easterly and northeasterly winds on the North Slope of Alaska. However, regression analysis on latitude suggested significant south-to-north increases in selected trace element concentrations, many of which appear unrelated to the sea salt contribution.

Plasma steroid concentrations and male phallus size in juvenile alligators from seven Florida lakes

USGS Publications Warehouse

Guillette, L.J.; Woodward, A.R.; Crain, D.A.; Pickford, D.B.; Rooney, A.A.; Percival, H.F.

1999-01-01

Neonatal and juvenile alligators from contaminated Lake Apopka in central Florida exhibit abnormal plasma sex steroid concentrations as well as morphological abnormalities of the gonad and phallus. This study addresses whether similar abnormalities occur in juvenile alligators inhabiting six other lakes in Florida. For analysis, animals were partitioned into two subsets, animals 40-79 cm total length (1-3 years old) and juveniles 80-130 cm total length (3-7 years old). Plasma testosterone (T) concentrations were lower in small males from lakes Apopka, Griffin, and Jessup than from Lake Woodruff National Wildlife Refuge (NWR). Similar differences were observed in the larger juveniles, with males from lakes Jessup, Apopka, and Okeechobee having lower plasma T concentrations than Lake Woodruff males. Plasma estradiol-17?? (E2) concentrations were significantly elevated in larger juvenile males from Lake Apopka compared to Lake Woodruff NWR. When compared to small juvenile females from Lake Woodruff NWR, females from lakes Griffin, Apopka, Orange, and Okeechobee had elevated plasma E2 concentrations. Phallus size was significantly smaller in males from lakes Griffin and Apopka when compared to males from Lake Woodruff NWR. An association existed between body size and phallus size on all lakes except Lake Apopka and between phallus size and plasma T concentration on all lakes except lakes Apopka and Orange. Multiple regression analysis, with body size and plasma T concentration as independent covariables, explained the majority of the variation in phallus size on all lakes. These data suggest that the differences in sex steroids and phallus size observed in alligators from Lake Apopka are not limited to that lake, nor to one with a history of a major pesticide spill. Further work examining the relationship of sex steroids and phallus size with specific biotic and abiotic factors, such as antiandrogenic or estrogenic contaminants, is needed.

Robust Path Tracking of Autonomous Underwater Vehicles Using Sliding Modes

DTIC Science & Technology

1990-12-01

MDB REAL MQN , MWN ,MDSN REAL QHADOTQHAT,THADOT,THAT C C YAW HYDRODYNAMIC COEFFICIENTS C REAL NPDOT,NRDOTNPQ , NQR REAL NVDOT , NP ,NR ,NVQ REAL NWP...NRDOT--3.4E-3-,NPQ .s-2.1E-2 , NQR .s2.7E-3, & NVDOT-1.2E-3 , NP --8.4E-4 ,NR --1.6E-2 ,NVQ - -1.E-2, -& NWP --1.75-2 , NWR -7.4E-3 ,NV -.-7.4E-3 ,NVW... NQR *Q*R)- +(RHO/2)*L**4*(NP*U*P+ & NR*U*R + NVQ*V*Q-+NWP*W*P + NWR*W*R) +(RHO/2)*L**3*(NV* & -U*V + NVW*V*W +-NDR*U**2*D R) +-YAW + (XG*WEIGHT- &XB

Predictors of Reading in Urdu: Does Deep Orthography Have an Impact?

PubMed Central

Farukh, Ammara; Vulchanova, Mila

2014-01-01

The aim of this study was to establish the extent to which rapid automatized naming (RAN) and non-word repetition (NWR) tasks predict reading fluency and reading accuracy in Urdu. One hundred sixty (8–9 years) children attending two types of schools (Urdu and English medium schools) were distributed into two groups, a control and a reading disability group on the basis of teacher’s report. The results confirmed the role of RAN in predicting reading fluency in both groups. The role of NWR as a predictor of accuracy was also confirmed, although the strength of the relationship was modulated by RAN in the reading disability group. There are no tests available to identify children with reading problems in Urdu. Our study supports the validity of NWR and RAN tasks for the purposes of screening for reading deficits. The performance results also confirm the original grouping based on teacher reports. The study further highlights the importance of medium of instruction and increased oral language input in learning to read. © 2014 The Authors. Dyslexia published by John Wiley & Sons Ltd. Key Messages Reliability of teacher reports in screening for reading difficulties in the classroom. Appropriateness of non-word repetition and rapid automatized naming tasks for establishing reading problems in Urdu. School type and exposure to instruction influences reading skills. PMID:24664499

Biological Diversity, Ecological Health and Condition of Aquatic Assemblages at National Wildlife Refuges in Southern Indiana, USA

PubMed Central

Morris, Charles C.; Robb, Joseph R.; McCoy, William

2015-01-01

Abstract The National Wildlife Refuge system is a vital resource for the protection and conservation of biodiversity and biological integrity in the United States. Surveys were conducted to determine the spatial and temporal patterns of fish, macroinvertebrate, and crayfish populations in two watersheds that encompass three refuges in southern Indiana. The Patoka River National Wildlife Refuge had the highest number of aquatic species with 355 macroinvertebrate taxa, six crayfish species, and 82 fish species, while the Big Oaks National Wildlife Refuge had 163 macroinvertebrate taxa, seven crayfish species, and 37 fish species. The Muscatatuck National Wildlife Refuge had the lowest diversity of macroinvertebrates with 96 taxa and six crayfish species, while possessing the second highest fish species richness with 51 species. Habitat quality was highest in the Muscatatuck River drainage with increased amounts of forested habitats compared to the Patoka River drainage. Biological integrity of the three refuges ranked the Patoka NWR as the lowest biological integrity (mean IBI reach scores = 35 IBI points), while Big Oaks had the highest biological integrity (mean IBI reach score = 41 IBI points). The Muscatatuck NWR had a mean IBI reach score of 31 during June, which seasonally increased to a mean of 40 IBI points during summer. Watershed IBI scores and habitat condition were highest in the Big Oaks NWR. PMID:25632261

Noninvasive assessment of the facilitation of the nociceptive withdrawal reflex by repeated electrical stimulations in conscious dogs.

PubMed

Bergadano, Alessandra; Andersen, Ole K; Arendt-Nielsen, Lars; Spadavecchia, Claudia

2007-08-01

To investigate the facilitation of the nociceptive withdrawal reflex (NWR) by repeated electrical stimuli and the associated behavioral response scores in conscious, nonmedicated dogs as a measure of temporal summation and analyze the influence of stimulus intensity and frequency on temporal summation responses. 8 adult Beagles. Surface electromyographic responses evoked by transcutaneous constant-current electrical stimulation of ulnaris and digital plantar nerves were recorded from the deltoideus, cleidobrachialis, biceps femoris, and cranial tibial muscles. A repeated stimulus was given at 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, and 1.1 x I(t) (the individual NWR threshold intensity) at 2, 5, and 20 Hz. Threshold intensity and relative amplitude and latency of the reflex were analyzed for each stimulus configuration. Behavioral reactions were subjectively scored. Repeated sub-I(t) stimuli summated and facilitated the NWR. To elicit temporal summation, significantly lower intensities were needed for the hind limb, compared with the forelimb. Stimulus frequency did not influence temporal summation, whereas increasing intensity resulted in significantly stronger electromyographic responses and nociception (determined via behavioral response scoring) among the dogs. In dogs, it is possible to elicit nociceptive temporal summation that correlates with behavioral reactions. These data suggest that this experimental technique can be used to evaluate nociceptive system excitability and efficacy of analgesics in canids.

Stratigraphy and morphology of the barrier platform of Breton Island, Louisiana: deltaic, marine and human influences

USGS Publications Warehouse

Flocks, James G.; Kindinger, Jack G.; Miselis, Jennifer L.; Locker, Stanley D.

2015-01-01

Breton Island, located at the southern end of the Chandeleur Islands, Louisiana, is part of the Breton National Wildlife Refuge (NWR). Breton NWR is recognized as an important bird habitat and is host to one of Louisiana's largest historical brown pelican nesting colonies. Loss of island area through relative sea-level rise, storm impact, and impeded and diminishing sediment supply is reducing the available habitat, and restoration is necessary if the island is to remain emergent. Physical investigation of the Breton Island platform has provided new insight into the geologic framework. The data reveal a complex system that is undergoing both long-term and short-term change. Results of the study help to resolve uncertainties in island evolution and will assist in effective restoration of the island.

Teaching change to local youth: Plant phenology, climate change and citizen science at Hakalau Forest National Wildlife Refuge

NASA Astrophysics Data System (ADS)

Litton, C. M.; Laursen, S. C.; Phifer, C.; Giardina, C. P.

2012-12-01

Plant phenology is a powerful indicator of how climate change affects native ecosystems, and also provides an experiential outdoor learning opportunity for promoting youth conservation education and awareness. We developed a youth conservation education curriculum, including both classroom and field components, for local middle and high school students from Hawaii. The curriculum is focused on linking plant phenology and climate change, with emphasis on ecologically and culturally important native trees and birds at Hakalau Forest National Wildlife Refuge (NWR), on the Island of Hawaii. In this curriculum, students: (i) visit Hakalau Forest NWR to learn about the ecology of native ecosystems, including natural disturbance regimes and the general concept of change in forest ecosystems; (ii) learn about human-induced climate change and its potential impact on native species; and (iii) collect plant phenology measurements and publish these data on the USA National Phenology Network website. This youth conservation education curriculum represents a close collaboration between Hakalau Forest NWR; the Friends of Hakalau Forest NWR; the College of Tropical Agriculture and Human Resources at the University of Hawaii at Manoa; the USDA Forest Service; and Imi Pono no Ka Aina, an environmental education and outreach program for the Three Mountain Alliance Watershed Partnership. In the Winter and Spring of 2011-2012, we developed classroom and field portions of the curriculum. In the Spring and Summer of 2012, we recruited four groups of participants, with a total of ~40 students, who visited the refuge to participate in the curriculum. Preliminary phenology observations based upon ~4 months of measurements show low to medium levels of flowering, fruiting and leaf flush. However, the real science value of this program will come over years to decades of accumulated student activity. From this, we anticipate the emergence of a unique tropical montane forest dataset on plant phenology for Hakalau Forest NWR. This work would not otherwise exist in Hawaii as we are the first and only site in Hawaii participating in the USA National Phenology Network. In turn, the education and outreach value of this program is immediate, as participating students are exposed to: (i) native ecosystems that they would never otherwise have the opportunity to visit; (ii) the concept of plant phenology and its utility for monitoring native ecosystems; and (iii) the concept of change, including anthropogenic climate change. The curriculum we have developed in Hawaii can be easily replicated elsewhere by: (i) selecting local species with high cultural and ecological value; (ii) devising phenology collection methods tailored to these local species, and student backgrounds and educational levels; and (iii) building sustainable partnerships between community conservation groups and government agencies.

A detailed 2,000-year late holocene pollen record from lower Pahranagat Lake, Southern Nevada, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hemphill, M L; Wigand, P E

Preliminary analysis of 128 pollen samples and seven radiocarbon dates from a 5-meter long, 10-cm diameter sediment core retrieved from Lower Pahranagat Lake (elevation - 975 in), Lincoln County, Nevada, gives us a rare, continuous, record of vegetation change at an interval of every 14 years over the last 2,000 years. During this period increasing Pinus (pine) pollen values with respect to Juniperus Ouniper pollen values reflect the increasing dominance of pinyon in southern Nevada woodlands during the last 2,000 years. Today Pinus pollen values indicate that pinyon pine is more frequent in the southern Great Basin since the endmore » of the Neoglacial 2,000 years ago. During the same time frame, a general decrease in Poaceae (grass) pollen values with respect to Artemisia (sagebrush) pollen values reflect the general trend of increasing dominance of steppe and desert scrub species with respect to grasses. Variations in these two species reflect not only the generally more xeric nature of climate during the last 2,000 years, but also periods of summer shifted rainfall - 1,500 years ago that encouraged both a period of grass and pinyon expansion. The ratio of aquatic to littoral pollen types indicates generally deeper water conditions 2 to 1 ka and more variable, but predominately more marshy, conditions at the site during most of the last 1 ka. Investigation of ostracodes from the same record being conducted by Dr. R. Forester at the USGS corroborate the pollen record by evidencing shifts between open and closed hydrologic systems including lake, marsh and even stream habitats. Analysis of an additional 10 meters of core recovered in the summer of 1994 with a basal date of 5.6 ka promises to provide the best record of middle through late Holocene vegetation and climate history for southern Nevada.« less

Vasculoprotective and vasodilatation effects of herbal formula (Sahatsatara) and piperine in spontaneously hypertensive rats.

PubMed

Booranasubkajorn, Suksalin; Huabprasert, Sukit; Wattanarangsan, Jantanee; Chotitham, Pruksa; Jutasompakorn, Pinpilai; Laohapand, Tawee; Akarasereenont, Pravit; Tripatara, Pinpat

2017-01-15

The herbal formula (Sahatsatara, STF), the Thai traditional poly-herbal recipe, has been used for treatment of muscle pain, anti-flatulence and numbness on hands and feet, with the caution when used in hypertensive patients. However, there is no scientific evidence to prove its effects on cardiovascular system. Piperine is the proposed major active compound in STF. It is shown to have antihypertensive effect in the L-NAME-induced endothelial dysfunction rats. This study investigated the pharmacokinetics, mechanism of action, as well as the hemodynamic and vasoactive effect and toxicity of STF and piperine using spontaneously hypertensive rats (SHR) and normal Wistar rats (NWR). The amount of piperine in STF was measured by ultra performance liquid chromatography (UPLC). SHR and NWR were gavaged with piperine (50mg/kg/day) or STF (100, 300, or 1000mg/kg/day) alone or together with L-NAME (in drinking water) for 28 days. Hemodynamic effects were monitored by noninvasive tail cuff every 7 days. Vasorelaxation effect on the thoracic aorta in organ chamber was observed through force transducer at the end of the experiment. Biochemical parameters for kidney and liver toxicity were measured. In addition, pharmacokinetic study was performed using non-compartment analysis. The amount of piperine in STF was 1.29%w/w. Both STF and piperine did not affect blood pressure and heart rate in both SHR and NWR. Interestingly, STF and piperine increased acetylcholine-induced vasorelaxation of isolated thoracic aorta and have vascoluprotective effect in nitric oxide (NO) impaired rats. No liver or kidney toxicity was found in this study. Non-compartment pharmacokinetic analysis showed that the time to reach maximum concentration (T max ) of plasma piperine after administration of piperine and STF were 3.9 and 1.7h, respectively. This result suggested that piperine in the recipe had better absorption than the pure standard piperine. STF had no effect on blood pressure in both SHR and NWR. However, it was able to relax isolated thoracic aorta and had the potential for vasculoprotective effect in hypertensive and NO impaired condition. The effects of STF were comparable to those of piperine. Copyright © 2016 Elsevier GmbH. All rights reserved.

Visitor reponse to demonstration fees at National Wildlife Refuges

USGS Publications Warehouse

Taylor, J.G.; Vaske, J.J.; Shelby, L.B.; Donnelly, M.P.; Browne, Cassandra M.

2002-01-01

In response to a request from the United States Fish and Wildlife Service, we examined the likelihood of visitors changing their plans for future visits to National Wildlife Refuges (NWR) because of changes in entrance or use fees. We obtained data for this study from 3,173 respondents from 14 NWRs between 1998 and 2000. Overall, only 8% of all respondents reported potential displacement as a likely response to fee changes. Bivariate analyses indicated that displacement was related to the NWR visited, participation in consumptive or nonconsumptive activities, amount of fees paid, and respondents' income, but the strength of these relationships was weak. Beliefs about the fee program and attitude toward fees paid were better predictors of displacement potential. Multivariate log-linear analysis highlighted significant interactions among the variables and complexity of understanding the displacement process.

Evening flights of female northern pintails from a major roost site

USGS Publications Warehouse

Cox, R.R.; Afton, A.D.

1996-01-01

We monitored evening flights of female Northern Pintails (Anas acuta) from Lacassine National Wildlife Refuge (NWR) in southwestern Louisiana during winters of 1991-1992 and 1992-1993. We analyzed the influence of female age, winter, and date within wintering period on three flight parameters: distance, duration, and departure time. Flight distance and duration increased with date within wintering period, and age differences in flight distance and duration were not consistent between winters. Females departed 12 min later, on average, on clear, moonlit evenings than on overcast, moonless evenings, and 4 min later when winds were light rather than heavy. After controlling for variation due to environmental conditions, immature females departed Lacassine NWR 1.3 min earlier, on average, than did adults. Flight parameters of females did not differ between hunting and non-hunting time periods. Estimated daily transit costs ranged from 27-54% of basal metabolic rate, 7-19% of daily energy expenditure, and 8-20% of daily dietary intake of rice (Oryza sativa). Our findings that flight distance and duration increased with date within wintering period were consistent with predictions of refuging theory, but alternative hypotheses also could explain these results. Evening flights of Northern Pintails roosting on Lacassine NWR were greater in distance and duration than those reported for most other species of wintering waterfowl. We recommend that proximity of refuges to feeding sites be considered in conservation and management plans for wintering Northern Pintails and other refuging waterfowl.

Nantucket National Wildlife Refuge alternative transportation study

DOT National Transportation Integrated Search

2014-10-01

This study for the Fish and Wildlife Service (FWS) identifies and analyzes options for enhancing alternative transportation access to the Nantucket National Wildlife Refuge (Nantucket NWR) at Great Point in Nantucket, Massachusetts. The study team de...

75 FR 19988 - Watercress Darter National Wildlife Refuge, Jefferson County, AL

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-16

... prominent as development activities occur in the city of Bessemer, Alabama. Watercress Darter NWR is a small.... Extensive resource sharing and networking with other protected areas, State and local government agencies...

MONTHLY REPORT OF DEVELOPMENT, SEPTEMBER 1963

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1964-10-31

Methods for separating germanium from Taiga carbonaceous shale by flotation and salt roasting are described. The recovery of vanadium from Beaverlodge mill tailings by carbonate leaching is briefly discussed. Methods of chemical analysis are also discussed. (N.W.R.)

Hawaiian forest bird trends: using log-linear models to assess long-term trends is supported by model diagnostics and assumptions (reply to Freed and Cann 2013)

USGS Publications Warehouse

Camp, Richard J.; Pratt, Thane K.; Gorresen, P. Marcos; Woodworth, Bethany L.; Jeffrey, John J.

2014-01-01

Freed and Cann (2013) criticized our use of linear models to assess trends in the status of Hawaiian forest birds through time (Camp et al. 2009a, 2009b, 2010) by questioning our sampling scheme, whether we met model assumptions, and whether we ignored short-term changes in the population time series. In the present paper, we address these concerns and reiterate that our results do not support the position of Freed and Cann (2013) that the forest birds in the Hakalau Forest National Wildlife Refuge (NWR) are declining, or that the federally listed endangered birds are showing signs of imminent collapse. On the contrary, our data indicate that the 21-year long-term trends for native birds in Hakalau Forest NWR are stable to increasing, especially in areas that have received active management.

Evidence of estrogenic endocrine disruption in smallmouth and largemouth bass inhabiting Northeast U.S. national wildlife refuge waters: A reconnaissance study.

PubMed

Iwanowicz, L R; Blazer, V S; Pinkney, A E; Guy, C P; Major, A M; Munney, K; Mierzykowski, S; Lingenfelser, S; Secord, A; Patnode, K; Kubiak, T J; Stern, C; Hahn, C M; Iwanowicz, D D; Walsh, H L; Sperry, A

2016-02-01

Intersex as the manifestation of testicular oocytes (TO) in male gonochoristic fishes has been used as an indicator of estrogenic exposure. Here we evaluated largemouth bass (Micropterus salmoides) or smallmouth bass (Micropterus dolomieu) form 19 National Wildlife Refuges (NWRs) in the Northeast U.S. inhabiting waters on or near NWR lands for evidence of estrogenic endocrine disruption. Waterbodies sampled included rivers, lakes, impoundments, ponds, and reservoirs. Here we focus on evidence of endocrine disruption in male bass evidenced by gonad histopathology including intersex or abnormal plasma vitellogenin (Vtg) concentrations. During the fall seasons of 2008-2010, we collected male smallmouth bass (n=118) from 12 sites and largemouth bass (n=173) from 27 sites. Intersex in male smallmouth bass was observed at all sites and ranged from 60% to 100%; in male largemouth bass the range was 0-100%. Estrogenicity, as measured using a bioluminescent yeast reporter, was detected above the probable no effects concentration (0.73ng/L) in ambient water samples from 79% of the NWR sites. Additionally, the presence of androgen receptor and glucocorticoid receptor ligands were noted as measured via novel nuclear receptor translocation assays. Mean plasma Vtg was elevated (>0.2mg/ml) in male smallmouth bass at four sites and in male largemouth bass at one site. This is the first reconnaissance survey of this scope conducted on US National Wildlife Refuges. The baseline data collected here provide a necessary benchmark for future monitoring and justify more comprehensive NWR-specific studies. Published by Elsevier Inc.

Potential environmental contaminant risks to avian species at important bird areas in the northeastern United States

USGS Publications Warehouse

Rattner, B.A.; Ackerson, B.K.

2008-01-01

Environmental contaminants can have profound effects on birds, acting from the molecular through population levels of biological organization. An analysis of potential contaminant threats was undertaken at 52 Important Bird Areas (IBAs) within the northeastern Atlantic coast drainage. Using geographic information system methodology, data layers describing or integrating contamination (impaired waters, fish or wildlife consumption advisories, toxic release inventory sites, and estimates of pesticide use) were overlaid on buffered IBA boundaries, and the relative threat at each site was ranked. The most threatened sites include Jefferson National Forest (NF), Stewart B. McKinney National Wildlife Refuge (NWR), Great Dismal Swamp NWR, Blue Ridge Parkway, Shenandoah National Park (NP), Adirondack Park, Edwin B. Forsythe NWR, George Washington NF, Green Mountain NF, Long Island Piping Plover Beaches, and Merrymeeting Bay. These sites exhibited moderate to high percentages of impaired waters and had fish consumption advisories related to mercury and polychlorinated biphenyls, and were located in counties with substantial pesticide use. Endangered, threatened and Watch List bird species are present at these sites. The Contaminant Exposure and Effects--Terrestrial Vertebrates database was searched within buffered IBA boundaries, and for a moderate number of sites there was concordance between the perceived risk and contaminant exposure. Several of the IBAs with apparently substantial contaminant threats had no avian ecotoxicological data (e.g., George Washington NF, Shenandoah NP). Based upon this screening level risk assessment, contaminant biomonitoring is warranted at such sites, and data generated from these efforts should foster natural resource management activities.

Evidence of estrogenic endocrine disruption in smallmouth and largemouth bass inhabiting Northeast U.S. National Wildlife Refuge waters: A reconnaissance study

USGS Publications Warehouse

Iwanowicz, Luke R.; Blazer, Vicki S.; Pinkney, A.E.; Guy, C.P.; Major, A.M.; Munney, K.; Mierzykowski, S.; Lingenfelser, S.; Secord, A.; Patnode, K.; Kubiak, T.J.; Stern, C.; Hahn, Cassidy M.; Iwanowicz, Deborah; Walsh, Heather L.; Sperry, Adam J.

2016-01-01

Intersex as the manifestation of testicular oocytes (TO) in male gonochoristic fishes has been used as an indicator of estrogenic exposure. Here we evaluated largemouth bass (Micropterus salmoides) or smallmouth bass (Micropterus dolomieu) form 19 National Wildlife Refuges (NWRs) in the Northeast U.S. inhabiting waters on or near NWR lands for evidence of estrogenic endocrine disruption. Waterbodies sampled included rivers, lakes, impoundments, ponds, and reservoirs. Here we focus on evidence of endocrine disruption in male bass evidenced by gonad histopathology including intersex or abnormal plasma vitellogenin (Vtg) concentrations. During the fall seasons of 2008–2010, we collected male smallmouth bass (n=118) from 12 sites and largemouth bass (n=173) from 27 sites. Intersex in male smallmouth bass was observed at all sites and ranged from 60% to 100%; in male largemouth bass the range was 0–100%. Estrogenicity, as measured using a bioluminescent yeast reporter, was detected above the probable no effects concentration (0.73 ng/L) in ambient water samples from 79% of the NWR sites. Additionally, the presence of androgen receptor and glucocorticoid receptor ligands were noted as measured via novel nuclear receptor translocation assays. Mean plasma Vtg was elevated (>0.2 mg/ml) in male smallmouth bass at four sites and in male largemouth bass at one site. This is the first reconnaissance survey of this scope conducted on US National Wildlife Refuges. The baseline data collected here provide a necessary benchmark for future monitoring and justify more comprehensive NWR-specific studies.

Literature Review and Database of Relations Between Salinity and Aquatic Biota: Applications to Bowdoin National Wildlife Refuge, Montana

USGS Publications Warehouse

Gleason, Robert A.; Tangen, Brian A.; Laubhan, Murray K.; Finocchiaro, Raymond G.; Stamm, John F.

2009-01-01

Long-term accumulation of salts in wetlands at Bowdoin National Wildlife Refuge (NWR), Mont., has raised concern among wetland managers that increasing salinity may threaten plant and invertebrate communities that provide important habitat and food resources for migratory waterfowl. Currently, the U.S. Fish and Wildlife Service (USFWS) is evaluating various water management strategies to help maintain suitable ranges of salinity to sustain plant and invertebrate resources of importance to wildlife. To support this evaluation, the USFWS requested that the U.S. Geological Survey (USGS) provide information on salinity ranges of water and soil for common plants and invertebrates on Bowdoin NWR lands. To address this need, we conducted a search of the literature on occurrences of plants and invertebrates in relation to salinity and pH of the water and soil. The compiled literature was used to (1) provide a general overview of salinity concepts, (2) document published tolerances and adaptations of biota to salinity, (3) develop databases that the USFWS can use to summarize the range of reported salinity values associated with plant and invertebrate taxa, and (4) perform database summaries that describe reported salinity ranges associated with plants and invertebrates at Bowdoin NWR. The purpose of this report is to synthesize information to facilitate a better understanding of the ecological relations between salinity and flora and fauna when developing wetland management strategies. A primary focus of this report is to provide information to help evaluate and address salinity issues at Bowdoin NWR; however, the accompanying databases, as well as concepts and information discussed, are applicable to other areas or refuges. The accompanying databases include salinity values reported for 411 plant taxa and 330 invertebrate taxa. The databases are available in Microsoft Excel version 2007 (http://pubs.usgs.gov/sir/2009/5098/downloads/databases_21april2009.xls) and contain 27 data fields that include variables such as taxonomic identification, values for salinity and pH, wetland classification, location of study, and source of data. The databases are not exhaustive of the literature and are biased toward wetland habitats located in the glaciated North-Central United States; however, the databases do encompass a diversity of biota commonly found in brackish and freshwater inland wetland habitats.

AN IMPROVED SOCKING TECHNIQUE FOR MASTER SLAVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parsons, T.C.; Deckard, L.E.; Howe, P.W.

1962-10-29

A technique for socking a pair of standard Model 8 master-slave manipulators is described. The technique is primarily concerned with the fabrication of the bellows section, which provides for Z motion as well as wris movement and rotation. (N.W.R.)

ARCHITECTURAL AND CIVIL STANDARDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

Hanford Atomic Production Operation specification guides and standards for architectural and civil engineering are presented. Information includes construction of roads, railroads, roofs, signs, buildings, building equipment, sewers, fences, safety systems, and drainage systems. Details of this manual are given in TID-4100 (Suppl.). (N.W.R.)

Antinociceptive effects, metabolism and disposition of ketamine in ponies under target-controlled drug infusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knobloch, M.; Portier, C.J.; Levionnois, O.L.

2006-11-01

Ketamine is widely used as an anesthetic in a variety of drug combinations in human and veterinary medicine. Recently, it gained new interest for use in long-term pain therapy administered in sub-anesthetic doses in humans and animals. The purpose of this study was to develop a physiologically based pharmacokinetic (PBPk) model for ketamine in ponies and to investigate the effect of low-dose ketamine infusion on the amplitude and the duration of the nociceptive withdrawal reflex (NWR). A target-controlled infusion (TCI) of ketamine with a target plasma level of 1 {mu}g/ml S-ketamine over 120 min under isoflurane anesthesia was performed inmore » Shetland ponies. A quantitative electromyographic assessment of the NWR was done before, during and after the TCI. Plasma levels of R-/S-ketamine and R-/S-norketamine were determined by enantioselective capillary electrophoresis. These data and two additional data sets from bolus studies were used to build a PBPk model for ketamine in ponies. The peak-to-peak amplitude and the duration of the NWR decreased significantly during TCI and returned slowly toward baseline values after the end of TCI. The PBPk model provides reliable prediction of plasma and tissue levels of R- and S-ketamine and R- and S-norketamine. Furthermore, biotransformation of ketamine takes place in the liver and in the lung via first-pass metabolism. Plasma concentrations of S-norketamine were higher compared to R-norketamine during TCI at all time points. Analysis of the data suggested identical biotransformation rates from the parent compounds to the principle metabolites (R- and S-norketamine) but different downstream metabolism to further metabolites. The PBPk model can provide predictions of R- and S-ketamine and norketamine concentrations in other clinical settings (e.g. horses)« less

Impact of West Nile virus and other mortality factors on American white pelicans at breeding colonies in the northern plains of North America

USGS Publications Warehouse

Sovada, M.A.; Pietz, P.J.; Converse, K.A.; Tommy, King D.; Hofmeister, Erik K.; Scherr, P.; Ip, Hon S.

2008-01-01

American white pelicans (Pelecanus erythrorhynchos) are colonial-nesting birds and their breeding sites are concentrated in a few small areas, making this species especially vulnerable to factors that can influence productivity, such as disease, disturbance, predation, weather events and loss of nesting habitat. Nearly half of the American white pelican population breeds at four colonies in the northern plains: Chase Lake National Wildlife Refuge (NWR) in North Dakota, Bitter Lake (Waubay NWR) in South Dakota, Medicine Lake NWR in Montana, and Marsh Lake in Minnesota. Thus, sustained productivity at these colonies is crucial to the health of the entire species. During the latter half of the 2002 and 2003 breeding seasons, unusually high mortality of pelican chicks was observed at these colonies. West Nile virus (WNv) was identified as one source of these losses. In 2004-2007 we monitored three major colonies in the northern plains to assess mortality of chicks during the late breeding season. We documented severe weather events, disturbance, and WNv as factors contributing to chick mortality. Before WNv arrived in the region in 2002, chick mortality after mid-July was ???4%, and then jumped to as high as 44% in the years since WNv arrived. WNv kills older chicks that are no longer vulnerable to other common mortality factors (e.g., severe weather, gull predation) and typically would have survived to fledge; thus WNv appears to be an additive mortality factor. Persistence of lower productivity at American white pelican colonies in the northern plains might reduce the adult breeding population of this species in the region.

Selecting habitat management strategies on refuges

USGS Publications Warehouse

Schroeder, Richard L.; King, Wayne J.; Cornely, John E.

1998-01-01

This report is a joint effort of the Biological Resources Division, U.S. Geological Survey and the U.S. Fish and Wildlife Service (FWS) to provide National Wildlife Refuge (NWR) managers guidance on the selection and evaluation of habitat management strategies to meet stated objectives. The FWS recently completed a handbook on writing refuge management goals and objectives (U.S. Fish and Wildlife Service 1996a). the National Wildlife Refuge System Improvement Act of 1997 requires that National Wildlife Refuge System (NWRS) lands be managed according to approved Comprehensive Conservation Plans to guide management decisions and devise strategies for achieving refuge unit purposes and meeting the NWRS mission. It is expected that over the next several years most refuges will develop new or revised refuge goals and objectives for directing their habitat management strategies. This paper outlines the steps we recommend in selecting and evaluating habitat management strategies to meet specific refuge habitat objectives. We selected two examples to illustrate the process. Although each refuge is unique and will require specific information and solutions, these two examples can be used as guidance when selecting and evaluating habitat management strategies for other refuge resources: Example 1. Management of floodplain woods habitat for forest interior birds. The biological recourse of concern is the quality and quantity of floodplain woods habitat for eastern forest interior birds in the Cypress Creek NWR (U.S. Fish and Wildlife Service 1996b). Example 2. Management of habitat for biodiversity: Historical landscape proportions. The biological resource of concern is the change in diversity associated with man-induced changes in the distribution and abundance of habitat types at the Minnesota Valley NWR (U.S. Fish and Wildlife Service 1996c).

[Book review] Return of the Whooping Crane

USGS Publications Warehouse

Ellis, D.H.; Smith, D.G.

1990-01-01

Fewer than 40 years ago, Life magazine ran an article decrying the plight of Whooping Cranes (Grus americana) on their wintering grounds at Aransas National Wildlife Refuge (Aransas) along the Gulf Coast. The small flock of approximately 20 birds that summered at Wood Buffalo National Park (Wood Buffalo) in Canada and wintered on the Texas coast at Aransas comprised the entire wild population of the species-a population that at the time seemed to be drifting inexorably to- ward extinction. Today, the Aransas/Wood Buffalo flock numbers more than 140 birds, there are more than 30 birds in captivity at the Patuxent Wildlife Research Center (Patuxent), and another 20-plus birds at the International Crane Foundation in Baraboo, Wisconsin. There are also a dozen wild birds in an experimental flock (termed the Rocky Mountain flock by Doughty) that winters at Bosque Del Apache National Wildlife Refuge (NWR) in New Mexico and summers in the mountain valleys centered on Grays Lake NWR in Idaho.

75 FR 22832 - Lake Wales Ridge National Wildlife Refuge, Highlands and Polk Counties, FL

Federal Register 2010, 2011, 2012, 2013, 2014

2010-04-30

... would continue to focus on maintaining existing habitats for rare, threatened, and endangered species... Island NWR Complex provides fire program staff); (2) rare, threatened, and endangered species monitoring... actions that include managing habitats for rare, threatened, and endangered species. Both Federal- and...

77 FR 7176 - Great Bay National Wildlife Refuge, Rockingham County, NH

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-10

... Concord, New Hampshire, that is managed primarily for the federally endangered Karner blue butterfly. The... and the Karner blue butterfly easement have been managed by staff located at Parker River NWR in... partnership with the New Hampshire Fish and Game Department (NHFG). Management on the Karner blue butterfly...

COMPARISON OF THERMAL EFFICIENCIES FOR A MERCURY-STEAM BINARY VAPOR CYCLE AND THE RANKINE CYCLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prem, L.L.

1961-05-19

A comparison of the thermal efficiencies of the mercurysteam binary vapor cycle and the Rankine cycle shows that the binary cycle efficiency is greater. A temperatureentropy diagram and a schematic layout of the binary cycle are presented for clarity. (N.W.R.)

77 FR 15121 - Final Land Protection Plan and Final Environmental Assessment for Everglades Headwaters National...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-14

... Wildlife Refuge and Conservation Area AGENCY: Fish and Wildlife Service, Interior. ACTION: Notice of... Headwaters National Wildlife Refuge (NWR) and Conservation Area in Polk, Osceola, Highlands, and Okeechobee.... We established the refuge and conservation area to support a connected conservation landscape; to...

A Nonword Repetition Task to Assess Bilingual Children's Phonology

ERIC Educational Resources Information Center

dos Santos, Christophe; Ferré, Sandrine

2018-01-01

Children with specific language impairment (SLI) are particularly sensitive to phonological complexity in their language. Their performance drops when there are specific phonological structures or when complexity increases. A nonword repetition (NWR) test, which aims to assess the phonology of bilingual speakers with and without SLI, should…

Associations among Nonword Repetition and Phonemic and Vocabulary Awareness: Implications for Intervention

ERIC Educational Resources Information Center

Tattersall, Patricia J.; Nelson, Nickola Wolf; Tyler, Ann A.

2015-01-01

Prior research has shown possible relations among nonword repetition (NWR), vocabulary, and phonological processing skills in children with and without language impairment. This study was designed to investigate whether relationships would differ for students with primary language impairment (PLI) and typical language (TL) and whether they would…

78 FR 70318 - Cat Island National Wildlife Refuge; West Feliciana Parish, Louisiana; Notice of Intent To...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-25

...-FF04R02000] Cat Island National Wildlife Refuge; West Feliciana Parish, Louisiana; Notice of Intent To... comprehensive conservation plan (CCP) and associated National Environmental Policy Act (NEPA) documents for Cat... NEPA documents for Cat Island National Wildlife Refuge NWR, West Feliciana Parish, Louisiana, in a...

NOAA Weather Radio - Receiver Consumer Information

Science.gov Websites

retail outlets such as electronics, department, sporting goods, and boat and marine accessory stores and stores with an electronics department. NWR broadcasts are in the Public Service VHF frequencies, just Electronics, Inc 5185 Cliffwood Drive Montclair CA 91763 Customer Support: 866-KAITO76 (866-524-8676) Fax:(909

78 FR 23949 - Sunkhaze Meadows National Wildlife Refuge and Carlton Pond Waterfowl Production Area, Penobscot...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-23

... Maine Coastal Islands NWR, 9 Water Street, Rockland, ME 04841. For more information on locations for... newsletters updating the public on our progress with the CCP. We received comments on topics such as the potential effects of climate change, improving biological connectivity, forest management, potential...

77 FR 57107 - Bandon Marsh, Nestucca Bay, and Siletz Bay National Wildlife Refuges, Coos, Tillamook, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-17

... observation, photography, and interpretation from the observation deck and associated gravel trail, with no... waterfowl hunting season. Additional trails and parking lots would be constructed. Some administrative and... eco-tourism or natural resource-based visitor centers. Nestucca Bay NWR Alternative A: No Action Under...

76 FR 14984 - Sunkhaze Meadows National Wildlife Refuge, Penobscot, Kennebec, and Waldo Counties, ME, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-18

..., wildlife observation and photography, and environmental education and interpretation. We will review and... Sunkhaze Meadows NWR and Carlton Pond WPA. We will conduct the environmental review of this project and..., including American woodcock, red-winged blackbird, and bobolink. The Sandy Stream Unit is mainly comprised...

THE CONTAMINANT-ASSOCIATED STRESS RESPONSE AND ITS RELATIONSHIP TO PLASMA STRESS AND SEX STERIOD CONCENTRATIONS IN THE FLORIDA GAR, LEPISOSTEUS PLATYRHINCUS

EPA Science Inventory

Contaminants can alter the stress response. This study examined the stress response, defined by plasma cortisol concentration, and its relationship to plasma estradiol-17b and testosterone concentrations in adult gar collected from Lake Apopka, Orange Lake and Lake Woodruff NWR, ...

Nonword Repetition Problems in Children with Specific Language Impairment: A Deficit in Accessing Long-Term Linguistic Representations?

ERIC Educational Resources Information Center

Leclercq, Anne-Lise; Maillart, Christelle; Majerus, Steve

2013-01-01

Children with specific language impairment (SLI) consistently show poor nonword repetition (NWR) performance. However, the reason for these difficulties remains a matter of intensive debate. Nonword repetition is a complex psycholinguistic task that heavily relies upon phonological segmentation and phonological knowledge, and even lexical…

Reactions of Solvated Ions Final Report

DOE R&D Accomplishments Database

Taube, H.

1962-09-24

Brief summaries are presented on isotopic dilution studies on salts dissolved in CH{sub 3}OH, studies on metal and metal salts in solvents of the amine type, and studies on phosphato complexes of the pentammine Co(III) series. A list of papers published on reactions of solvated ions is included. (N.W.R.)

PROGRESS ON THE STUDY OF BETA TREATMENT OF URANIUM, DECEMBER 1, 1960-MARCH 30, 1961

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.B.

The variables affecting the beta treatment of uranium are described. Results are included on the effects of time at beta temperature, the influence of air delay before quenching, and the effects of 800 l C annealing. A description of x-ray automation equipment is presented. (N.W.R.)

Nonword Repetition and Vocabulary Use in Toddlers

ERIC Educational Resources Information Center

Stokes, Stephanie F.; Moran, Catherine; George, Anjali

2013-01-01

Purpose: There is general consensus that the ability to repeat nonsense words is related to vocabulary size in young children, but there is considerable debate about the nature of the relationship and the mechanisms that underlie it. Research with adults has proposed a shared neural substrate for nonword repetition (NWR) and language production,…

78 FR 38011 - Endangered and Threatened Species; Notice of Intent To Prepare a Recovery Plan for Oregon Coast...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-06-25

... and Threatened Species; Notice of Intent To Prepare a Recovery Plan for Oregon Coast Coho Salmon... Oregon Coast coho salmon (Oncorhynchus kisutch) Evolutionarily Significant Unit (ESU) (OC coho) and... which can be accessed at http://www.nwr.noaa.gov/protected_species/salmon_steelhead/recovery_planning...

Development of a decision support tool for water and resource management using biotic, abiotic, and hydrological assessments of Topock Marsh, Arizona

USGS Publications Warehouse

Holmquist-Johnson, Christopher; Hanson, Leanne; Daniels, Joan; Talbert, Colin; Haegele, Jeanette

2016-05-23

Topock Marsh is a large wetland adjacent to the Colorado River and the main feature of Havasu National Wildlife Refuge (Havasu NWR) in southern Arizona. In 2010, the U.S. Fish and Wildlife Service (FWS) and Bureau of Reclamation began a project to improve water management capabilities at Topock Marsh and protect habitats and species. Initial construction required a drawdown, which caused below-average inflows and water depths in 2010–11. U.S. Geological Survey Fort Collins Science Center (FORT) scientists collected an assemblage of biotic, abiotic, and hydrologic data from Topock Marsh during the drawdown and immediately after, thus obtaining valuable information needed by FWS.Building upon that work, FORT developed a decision support system (DSS) to better understand ecosystem health and function of Topock Marsh under various hydrologic conditions. The DSS was developed using a spatially explicit geographic information system package of historical data, habitat indices, and analytical tools to synthesize outputs for hydrologic time periods. Deliverables include high-resolution orthorectified imagery of Topock Marsh; a DSS tool that can be used by Havasu NWR to compare habitat availability associated with three hydrologic scenarios (dry, average, wet years); and this final report which details study results. This project, therefore, has addressed critical FWS management questions by integrating ecologic and hydrologic information into a DSS framework. This DSS will assist refuge management to make better informed decisions about refuge operations and better understand the ecological results of those decisions by providing tools to identify the effects of water operations on species-specific habitat and ecological processes. While this approach was developed to help FWS use the best available science to determine more effective water management strategies at Havasu NWR, technologies used in this study could be applied elsewhere within the region.

Diagnostic accuracy of repetition tasks for the identification of specific language impairment (SLI) in bilingual children: evidence from Russian and Hebrew.

PubMed

Armon-Lotem, Sharon; Meir, Natalia

2016-11-01

Previous research demonstrates that repetition tasks are valuable tools for diagnosing specific language impairment (SLI) in monolingual children in English and a variety of other languages, with non-word repetition (NWR) and sentence repetition (SRep) yielding high levels of sensitivity and specificity. Yet, only a few studies have addressed the diagnostic accuracy of repetition tasks in bilingual children, and most available research focuses on English-Spanish sequential bilinguals. To evaluate the efficacy of three repetition tasks (forward digit span (FWD), NWR and SRep) in order to distinguish mono- and bilingual children with and without SLI in Russian and Hebrew. A total of 230 mono- and bilingual children aged 5;5-6;8 participated in the study: 144 bilingual Russian-Hebrew-speaking children (27 with SLI); and 52 monolingual Hebrew-speaking children (14 with SLI) and 34 monolingual Russian-speaking children (14 with SLI). Parallel repetition tasks were designed in both Russian and Hebrew. Bilingual children were tested in both languages. The findings confirmed that NWR and SRep are valuable tools in distinguishing monolingual children with and without SLI in Russian and Hebrew, while the results for FWD were mixed. Yet, testing of bilingual children with the same tools using monolingual cut-off points resulted in inadequate diagnostic accuracy. We demonstrate, however, that the use of bilingual cut-off points yielded acceptable levels of diagnostic accuracy. The combination of SRep tasks in L1/Russian and L2/Hebrew yielded the highest overall accuracy (i.e., 94%), but even SRep alone in L2/Hebrew showed excellent levels of sensitivity (i.e., 100%) and specificity (i.e., 89%), reaching 91% of total diagnostic accuracy. The results are very promising for identifying SLI in bilingual children and for showing that testing in the majority language with bilingual cut-off points can provide an accurate classification. © 2016 Royal College of Speech and Language Therapists.

Perceptual and cerebro-spinal responses to graded innocuous and noxious stimuli following aerobic exercise.

PubMed

Micalos, P S; Harris, J; Drinkwater, E J; Cannon, J; Marino, F E

2015-11-01

The aim of this study was to evaluate the effect of aerobic exercise on perceptual and cerebro-spinal responses to graded electrocutaneous stimuli. The design comprised 2 x 30 min of cycling exercise at 30% and 70% of peak oxygen consumption (VO2 peak) on separate occasions in a counter-balanced order in 10 healthy participants. Assessment of nociceptive withdrawal reflex threshold (NWR-T), pain threshold (PT), and somatosensory evoked potentials (SEPs) to graded electrocutaneous stimuli were performed before and after exercise. Perceptual magnitude ratings and SEPs were compared at 30%PT, 60%PT, 100%PT before (Pre), 5 min after (Post1), and 15 min after (Post2) aerobic exercise. There was no difference in the NWR-T and the PT following exercise at 30% and 70% of VO2 peak. ANOVA for the perceptual response within pooled electrocutaneous stimuli show a significant main effect for time (F2,18=5.41, P=0.01) but no difference for exercise intensity (F1,9=0.02, P=0.88). Within-subject contrasts reveal trend differences between 30%PT and 100%PT for Pre-Post1 (P=0.09) and Pre-Post2 (P=0.02). ANOVA for the SEPs peak-to-peak signal amplitude (N1-P1) show significant main effect for time (F2,18=4.04, P=0.04) but no difference for exercise intensity (F1,9=1.83, P=0.21). Pairwise comparisons for time reveal differences between Pre-Post1 (P=0.06) and Pre-Post2 (P=0.01). There was a significant interaction for SEPs N1-P1 between exercise intensity and stimulus intensity (F2,18=3.56, P=0.05). These results indicate that aerobic exercise did not increase the electrocutaneous threshold for pain and the NWR-T. Aerobic exercise attenuated perceptual responses to innocuous stimuli and SEPs N1-P1 response to noxious stimuli.

Changes in carbon uptake and release cause by insect outbreaks in the Colorado Rocky Mountains from 2000 through 2010

NASA Astrophysics Data System (ADS)

Moore, D. J.; Wilkes, P.; Quaife, T. L.; Trahan, N. A.; Monson, R. K.; Stephens, B. B.

2010-12-01

A large scale insect outbreak has progressively infected North American Forests in the Rocky Mountains over the last 8 years causing the death of millions of trees. Loss of mature trees on this scale is likely to compromise the ability of these ecosystems to sequester carbon. While a reduction of live leaf area likely leads to reduced carbon uptake gross primary productivity (GPP) the impact of the outbreak on ecosystem respiration (RE) is not clear. We investigated the response of both GPP (2000 through 2010) and RE (2005-2010) to insect out break by contrasting two locations in the Rocky Mountains, the Fraser Experiment Forest (FEF; 39.91 N, 105.88 W) which has been heavily impacted by insects and Niwot Ridge (NWR; 40.05 N, 105.58 W) where the outbreak has not yet occurred. We used a modified estimate of GPP based on enhanced vegetation index (EVI) calibrated using eddy covariance measured at NWR to examine the impact of the beetle outbreak across the region. We found that while GPP decreased significantly at Fraser after the insect outbreak did not show a time dependent decline at NWR. Since 2005 near continuous atmospheric CO2 has been measured at the bottom of FEF. We used the diurnal variation in the CO2 concentration measured at the bottom of Fraser Valley as a proximate measurement of RE. We found that from 2005 through 2009 there was a decline in apparent RE while in 2010 apparent RE increased relative to 2009. Direct measurements of soil CO2 efflux appear to bear out this trend. Barring a large shift in temperature it is possible that the increase in apparent RE in 2010 may be the result of mobilization of N or potentially recovery of GPP from regenerating vegetation. The relative changes in GPP and RE are investigated from 2005 through 2010.

Western Pond Turtle Head-starting and Reintroduction; 2003-2004 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Leuven, Susan; Allen, Harriet; Slavin, Kate

This report covers the results of the western pond turtle head-starting and reintroduction project for the period of October 2003-September 2004. Wild hatchling western pond turtles from the Columbia River Gorge were reared at the Woodland Park and Oregon Zoos in 2003 and 2004 as part of the recovery effort for this Washington State endangered species. The objective of the program is to reduce losses to introduced predators like bullfrogs and largemouth bass by raising the hatchlings to a size where they are too large to be eaten by most of these predators. Sixty-nine turtles were over-wintered at the Woodlandmore » Park Zoo and 69 at the Oregon Zoo. Of these, 136 head-started juvenile turtles were released at three sites in the Columbia Gorge in 2004. Two were held back to attain more growth in captivity. Thirty-four were released at the Klickitat ponds, 19 at the Klickitat lake, 21 at the Skamania site, and 62 at Pierce National Wildlife Refuge (NWR). This brought the total number of head-start turtles released since 1991 to 246 for the Klickitat ponds, 114 for the Klickitat lake, 167 for the Skamania pond complex, and 250 at Pierce NWR. In 2004, 32 females from the two Columbia Gorge populations were equipped with transmitters and monitored for nesting activity. Twenty-one of the females nested and produced 85 hatchlings. The hatchlings were collected in September and October and transported to the Woodland Park and Oregon zoos for rearing in the head-start program. Data collection for a four-year telemetry study of survival and habitat use by juvenile western pond turtles at Pierce NWR concluded in 2004. Radio transmitters on study animals were replaced as needed until all replacements were in service; afterward, the turtles were monitored until their transmitters failed. The corps of study turtles ranged from 39 in August 2003 to 2 turtles at the end of August 2004. These turtles showed the same seasonal pattern of movements between summer water and upland winter habitats observed in previous years. During the 2004 field season trapping effort, 345 western pond turtles were captured in the Columbia Gorge, including 297 previously head-started turtles. These recaptures, together with confirmed nesting by head-start females and visual resightings, indicate the program is succeeding in boosting juvenile recruitment to increase the populations. Records were also collected on 224 individual painted turtles captured in 2004 during trapping efforts at Pierce NWR, to gather baseline information on this native population. Bonneville Power Administration (BPA) funded approximately 60% of program activities in the Columbia River Gorge from October 2003 through September 2004.« less

77 FR 21797 - Hopper Mountain, Bitter Creek, and Blue Ridge National Wildlife Refuges, Ventura, Kern, San Luis...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-11

..., and visitor and volunteer opportunities. Alternatives for Blue Ridge NWR Under Alternative B...-FF08R00000] Hopper Mountain, Bitter Creek, and Blue Ridge National Wildlife Refuges, Ventura, Kern, San Luis... Conservation Plan (CCP) and Environmental Assessment (EA) for the Hopper Mountain, Bitter Creek, and Blue Ridge...

USFWS demonstration fees

USGS Publications Warehouse

Taylor, Jonathan; Vaske, Jerry; Donnelly, Maureen; Shelby, Lori

2002-01-01

This study examined National Wildlife Refuge (NWR) visitors' reactions to changes in fees implemented as part of the fee demonstration program. Visitors' evaluations of the fees paid were examined in addition to their beliefs about fees and the fee demonstration program, and the impact of fees paid on their intention to return. All results were analyzed relative to socio-demographic characteristics.

78 FR 21397 - Don Edwards San Francisco Bay National Wildlife Refuge, Alameda, Santa Clara, and San Mateo...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-04-10

...) 792-5828. Mail: U.S. Fish and Wildlife Service, San Francisco Bay NWR Complex, 1 Marshlands Road... the San Francisco Bay National Wildlife Refuge Complex, 1 Marshlands Road, Fremont, CA 94555 (510) 792... and environmental education. We announce our decision and the availability of the FONSI for the final...

77 FR 51552 - The Great Lakes Islands National Wildlife Refuges in Michigan and Wisconsin

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-24

... Draft CCP/EA'' in the subject line of the message. Fax: [cir] Attention: Refuge Manager, Gravel/Green Bay NWRs, 920-387- 2973. [cir] Attention: Refuge Manager, Huron/Harbor Island/MI Islands (N) NWRs, 906-586-3800. [cir] Attention: Refuge Manager, Michigan Islands (S) NWR, 989-777- 9200. U.S. Mail: [cir...

Short-Term Memory Performance in 7- and 8-Year-Old Children: The Relationship between Phonological and Pitch Processing

ERIC Educational Resources Information Center

Flagge, Ashley Gaal; Estis, Julie M.; Moore, Robert E.

2016-01-01

Purpose: The relationship between short-term memory for phonology and pitch was explored by examining accuracy scores for typically developing children for 5 experimental tasks: immediate nonword repetition (NWR), nonword repetition with an 8-s silent interference (NWRS), pitch discrimination (PD), pitch discrimination with an 8-s silent…

76 FR 16637 - J.N. “Ding” Darling NWR, Lee County, FL; Final Comprehensive Conservation Plan and Finding of No...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-24

..., quantity, and timing of flows and from climate change and sea level rise. Resource protection will be... designations, including Wilderness Area, Research Natural Area, Marine Protected Area, Florida Important Bird Area, and Outstanding Florida Water. Annual visitation to the refuge exceeds 700,000. We announce our...

Electrophysiology of Perception and Processing of Phonological Information as Indices of Toddlers' Language Performance

ERIC Educational Resources Information Center

Harwood, Vanessa; Preston, Jonathan; Grela, Bernard; Roy, Dooti; Harold, Olivia; Turcios, Jacqueline; Andrada, Kiyomi; Landi, Nicole

2017-01-01

Purpose: The toddler years are a critical period for language development and growth. We investigated how event-related potentials (ERPs) to repeated and novel nonwords are associated with clinical assessments of language in young children. In addition, nonword repetition (NWR) was used to measure phonological working memory to determine the…

Computer Simulations of Developmental Change: The Contributions of Working Memory Capacity and Long-Term Knowledge

ERIC Educational Resources Information Center

Jones, Gary; Gobet, Fernand; Pine, Julian M.

2008-01-01

Increasing working memory (WM) capacity is often cited as a major influence on children's development and yet WM capacity is difficult to examine independently of long-term knowledge. A computational model of children's nonword repetition (NWR) performance is presented that independently manipulates long-term knowledge and WM capacity to determine…

BOILING NUCLEAR SUPERHEATER (BONUS) POWER STATION. Final Summary Design Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1962-05-01

The design and construction of the Boiling Nuclear Superheater (BONUS) Power Station at Punta Higuera on the seacoast at the westernmost tip of Puerto Rico are described. The reactor has an output of 17.5 Mw(e). This report will serve as a source of information for personnel engaged in management, evaluation, and training. (N.W.R.)

76 FR 43339 - Hunt Fee at Caddo Lake National Wildlife Refuge, TX

Federal Register 2010, 2011, 2012, 2013, 2014

2011-07-20

... Fee at Caddo Lake National Wildlife Refuge, TX AGENCY: Fish and Wildlife Service, Interior. ACTION...), announce our intent to implement a hunt fee at Caddo Lake National Wildlife Refuge (Refuge), located in.... Caddo Lake NWR is within RMU 16 where deer densities increased from 8.7 to 15.1 deer per 1,000 acres and...

75 FR 67095 - Charles M. Russell National Wildlife Refuge and UL Bend National Wildlife Refuge, Montana

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-01

...] Charles M. Russell National Wildlife Refuge and UL Bend National Wildlife Refuge, Montana AGENCY: Fish and... conservation plan (CCP) and environmental impact statement (EIS) for Charles M. Russell and UL Bend National... are extending the comment period for review of the draft CCP and EIS for Charles M. Russell NWR and UL...

77 FR 67829 - Charles M. Russell National Wildlife Refuge and UL Bend National Wildlife Refuge, MT...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-14

...-FXRS1266066CCP0S3-123] Charles M. Russell National Wildlife Refuge and UL Bend National Wildlife Refuge, MT... final comprehensive conservation plan (CCP) and final environmental impact statement (EIS) for Charles M....gov . Include ``Request copy of Charles M. Russell NWR ROD'' in the subject line of the message. U.S...

Nonword Repetition: The Relative Contributions of Phonological Short-Term Memory and Phonological Representations in Children with Language and Reading Impairment

ERIC Educational Resources Information Center

Rispens, Judith; Baker, Anne

2012-01-01

Purpose: This study investigates the relative contributions of phonological short-term memory and phonological representations to nonword repetition (NWR). This was evaluated in children with specific language impairment (SLI) and/or reading impairment (RI); it was also studied from a developmental perspective by comparing 2 groups of typically…

77 FR 9692 - Keālia Pond National Wildlife Refuge and Kakahai`a National Wildlife Refuge, Maui County, HI...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-02-17

...: Glynnis Nakai, Project Leader, Maui National Wildlife Refuge Complex, P.O. Box 1042, K[imacr]hei, Hawai`i 96753. In-Person Viewing or Pickup: Call (808) 875-1582 to make an appointment during regular business... FURTHER INFORMATION CONTACT: Glynnis Nakai, Project Leader, Maui NWR Complex, phone number (808) 875-1582...

Transportation Observations, Considerations, and Recommendations for Monomoy National Wildlife Refuge Provided by the Interagency Transportation Assistance Group (TAG)/Alternative Transportation in Parks and Public Lands (ATPPL) Program Chatham, MA July 1

DOT National Transportation Integrated Search

2007-07-17

A field investigation of the current transportation infrastructure and issues at Monomoy National Wildlife Refuge (NWR) by the interagency Transportation Assistance Group (TAG) was conducted July 17-19, 2007, on behalf of the U.S. Fish and Wildlife S...

Diagnostic Accuracy of Repetition Tasks for the Identification of Specific Language Impairment (SLI) in Bilingual Children: Evidence from Russian and Hebrew

ERIC Educational Resources Information Center

Armon-Lotem, Sharon; Meir, Natalia

2016-01-01

Background: Previous research demonstrates that repetition tasks are valuable tools for diagnosing specific language impairment (SLI) in monolingual children in English and a variety of other languages, with non-word repetition (NWR) and sentence repetition (SRep) yielding high levels of sensitivity and specificity. Yet, only a few studies have…

Word Recognition and Nonword Repetition in Children with Language Disorders: The Effects of Neighborhood Density, Lexical Frequency, and Phonotactic Probability

ERIC Educational Resources Information Center

Rispens, Judith; Baker, Anne; Duinmeijer, Iris

2015-01-01

Purpose: The effects of neighborhood density (ND) and lexical frequency on word recognition and the effects of phonotactic probability (PP) on nonword repetition (NWR) were examined to gain insight into processing at the lexical and sublexical levels in typically developing (TD) children and children with developmental language problems. Method:…

Viability of male gametes in common carp (Cyprinus carpio) along the Lower Colorado River from the Cibola National Wildlife Refuge (NWR), Havasu NWR, and Lake Mohave of Lake Mead National Recreation Area

USGS Publications Warehouse

Jenkins, Jill A.; Goodbred, Steven L.

2005-01-01

To contribute to an investigation on possible endocrine impacts in three sites along the lower Colorado River in Arizona, especially in male fishes, this study addressed the null hypothesis that aquatic species in southern sites did not exhibit evidence of endocrine disruption as compared with those in nonimpacted sites. The results presented are intended to provide managers with science-based information and interpretations about the reproductive condition of biota in their habitat along the lower Colorado River to minimize any potential adverse effects to trust fish and wildlife resources and to identify water resources of acceptable quality. In particular, these data can inform decision making about wastewater discharges into the Colorado River that directly supplies water to Arizona refuges located along the river. These data are integral to the USFWS proposal entitled 'AZ - Endocrine Disruption in Razorback Sucker and Common Carp on National Wildlife Refuges along the Lower Colorado River' that was proposed to assess evidence of endocrine disruption in carp and razorback suckers downstream of Hoover Dam.

Final Shaw AFB Chaff and Flare Environmental Assessment

DTIC Science & Technology

2003-12-01

Resources Conservation Service NWR National Wildlife Refuge SAT Surface Attack Tactics SCL South Carolina Lakes SEAD Suppression of Enemy Air Defenses...provide many recreational opportunities for tourists and local residents. Fishing is the most popular sport on both water bodies ( SCL 2003). The...flares with expired shelf lives or defects are returned to the supply depot responsible for their disposal. Final disposal of unusable chaff and

77 FR 56229 - White River National Wildlife Refuge, AR; Final Comprehensive Conservation Plan and Finding of No...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-12

... DEPARTMENT OF THE INTERIOR Fish and Wildlife Service [FWS-R4-R-2011-N267; FXRS12650400000-123...: You may obtain a copy of the CCP by writing to: Mr. Dennis Sharp, Refuge Manager, White River NWR, 57... Process The National Wildlife Refuge System Administration Act of 1966 (16 U.S.C. 668dd-668ee...

PROGRESS ON THE STUDY OF BETA TREATMENT OF URANIUM, AUGUST 1, 1961-NOVEMBER 30, 1961

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell, R.B.; Wolff, A.K.

Variables affecting the texture and grain size of uranium during beta treatment are summarized. The effects of composition (ingot versus dingot), prior delta condition, prior texture, pre-quenching air delay, rod or tube size, quenching medium and applied stress on grain size, distontion, and G/sub 3/ gradients in the final beta-treated shapes are described. (N.W.R.)

THE CRYSTALLOGRAPHIC INVESTIGATION OF AuCl /center dot/ PCl$sub 3$ AND IBOGAINE /center dot/ HBr

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arai-wessel, G.J.

1960-01-01

The structure of the two compounds is completely dlfferent, one being an inorganic complex and the other being an organic alkaloid complex. The difference in crystal constitution caused a difference in behavior with regard to radiation, requiring the use of specific crysthllographic methods for each. Interferences involved in determining their crystal structure are compared and discussed. (N.W.R.)

Western Pond Turtle Head-starting and Reintroduction, 2005-2006 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Leuven, Susan; Allen, Harriet; Slavens, Kate

This report covers the results of the western pond turtle head-starting and reintroduction project for the period of October 2005-September 2006. Wild hatchling western pond turtles from the Columbia River Gorge were reared at the Woodland Park and Oregon zoos in 2005 and 2006 as part of the recovery effort for this Washington State endangered species. The objective of the program is to reduce losses to introduced predators like bullfrogs and largemouth bass by raising the hatchlings to a size where they are too large to be eaten by most of these predators. Twenty-six turtles were placed at the Woodlandmore » Park Zoo and 62 at the Oregon Zoo in fall 2005. These turtles joined two that were held back from release in summer 2005 due to their small size. All 90 juvenile turtles were released at three sites in the Columbia Gorge in 2006. Twenty-eight juvenile turtles were released at the Klickitat ponds, 22 at the Klickitat lake, 21 at the Skamania site, and 19 at Pierce National Wildlife Refuge (NWR). This brought the total number of head-start turtles released since 1991 to 944; 285 for the Klickitat ponds, 158 for the Klickitat lake, 227 for the Skamania pond complex, and 274 at Pierce NWR. In 2006, 20 females from the Klickitat population were equipped with transmitters and monitored for nesting activity. Fifteen nests were located and protected; these produced 55 hatchlings. The hatchlings were collected in September and transported to the Oregon and Woodland Park zoos for rearing in the head-start program. One wild hatchling captured in spring 2006 was placed in the head-start program to attain more growth in captivity. During the 2006 field season trapping effort, 414 western pond turtles were captured in the Columbia Gorge, including 374 previously head-started turtles. These recaptures, together with confirmed nesting by head-start females and visual resightings, indicate the program is succeeding in boosting juvenile recruitment to increase the populations. Records were also collected on 179 individual painted turtles captured in 2006 during trapping efforts at Pierce NWR, to gather baseline information on this native population.« less

Western Pond Turtle Head-starting and Reintroduction; 2004-2005 Annual Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Leuven, Susan; Allen, Harriet; Slavin, Kate

This report covers the results of the western pond turtle head-starting and reintroduction project for the period of October 2004-September 2005. Wild hatchling western pond turtles from the Columbia River Gorge were reared at the Woodland Park and Oregon Zoos in 2004 and 2005 as part of the recovery effort for this Washington State endangered species. The objective of the program is to reduce losses to introduced predators like bullfrogs and largemouth bass by raising the hatchlings to a size where they are too large to be eaten by most of these predators. Thirty-five turtles were placed at the Woodlandmore » Park Zoo and 53 at the Oregon Zoo. Of these, 77 head-started juvenile turtles were released at three sites in the Columbia Gorge in 2005. Four were held back to attain more growth in captivity. Eleven were released at the Klickitat ponds, 22 at the Klickitat lake, 39 at the Skamania site, and 5 at Pierce National Wildlife Refuge (NWR). This brought the total number of head-start turtles released since 1991 to 257 for the Klickitat ponds, 136 for the Klickitat lake, 206 for the Skamania pond complex, and 255 at Pierce NWR. In 2005, 34 females from the two Columbia Gorge populations were equipped with transmitters and monitored for nesting activity. Twenty-four nests were located and protected; these produced 90 hatchlings. The hatchlings were collected in September and transported to the Oregon and Woodland Park zoos for rearing in the head-start program. During the 2005 field season trapping effort, 486 western pond turtles were captured in the Columbia Gorge, including 430 previously head-started turtles. These recaptures, together with confirmed nesting by head-start females and visual resightings, indicate the program is succeeding in boosting juvenile recruitment to increase the populations. Records were also collected on 216 individual painted turtles captured in 2005 during trapping efforts at Pierce NWR, to gather baseline information on this native population. Bonneville Power Administration (BPA) funded approximately 75% of program activities in the Columbia River Gorge from October 2004 through September 2005.« less

Native plant propagation and habitat restoration at Hakalau Forest National Wildlie Refuge, Hawaii

Treesearch

Baron Horiuchi; Jack Jeffrey

2002-01-01

Hakalau Forest NWR was established in 1985 under the authority of the Endangered Species Act to preserve and protect five species of endangered forest birds and their rain forest habitat. While most of the 32,730 acre refuge is closed canopy forest, over one hundred years of cattle grazing, logging and burning have convened about 5,000 acres (2,023 ha) of upper...

78 FR 27989 - Bandon Marsh, Nestucca Bay, and Siletz Bay National Wildlife Refuges, Coos, Tillamook, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-05-13

... hunting program on the Bandon Marsh Unit, hunting would be allowed on 300 acres of the Ni-les'tun Unit 3... conflicts with the waterfowl hunting season. A portion of the Ni-les'tun Unit would be open to wildlife... acreage at the Ni-les'tun Unit has been changed from 300 to 299 acres. Nestucca Bay NWR The objective...

75 FR 73121 - Bandon Marsh, Nestucca Bay, and Siletz Bay National Wildlife Refuges, Coos, Tillamook, and...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-11-29

..., Oregon. The 582-acre Ni-les'tun Unit, established in 2000, includes 400 acres of historic salt marsh that is currently being restored to tidal action. The Ni-les'tun Unit is located on the east side of... * * *'' (95 Stat. 1709, dated Dec 29, 1981). The Ni- les'tun Unit was added to Bandon Marsh NWR in order to (1...

Herpetofauna of lowland bottomlands of southeastern Arizona: a comparison of sites

Treesearch

Philip C. Rosen; William R. Radke; Dennis J. Caldwell

2005-01-01

We intensively sampled the riparian herpetofauna at three sites in southeastern Arizona, a canyon site, Leslie Canyon, and two lowland sites, San Bernardino NWR and Empire-Ci¨¦nega Creek at Las Ci¨¦negas National Conservation Area. We also compiled a list of herpetofaunal records for the original lowland riparian area at Tucson using museum records. The herpetofaunas...

The Role of Phonological Working Memory and Environmental Factors in Lexical Development in Italian-Speaking Late Talkers: A One-Year Follow-Up Study

ERIC Educational Resources Information Center

Marini, Andrea; Ruffino, Milena; Sali, Maria Enrica; Molteni, Massimo

2017-01-01

Purpose: This follow-up study assessed (a) the influence of phonological working memory (pWM), home literacy environment, and a family history of linguistic impairments in late talkers (LTs); (b) the diagnostic accuracy of a task of nonword repetition (NWR) in identifying LTs; and (c) the persistence of lexical weaknesses after 10 months. Method:…

Secondary Craters

NASA Image and Video Library

2016-12-21

This image of a southern mid-latitude crater was intended to investigate the lineated material on the crater floor. At the higher resolution of HiRISE, the image reveals a landscape peppered by small impact craters. These craters range from about 30 meters in diameter down to the resolution limit (about 2 meter diameter in this image acquired by averaging 2x2 picture elements). Such dense clusters of small craters are frequently formed by secondary craters, caused by the impact of material that was excavated and ejected from the surface of Mars during the creation of a larger nearby crater by the impact of a comet or an asteroid. Secondary impact craters are both interesting and vexing. They are interesting because they show the trajectories of the material that was ejected from the primary impact with the greatest speeds, typically material from near the surface of the blast zone. Secondary craters are often found along the traces of crater rays, linear features that extend radially from fresh impact craters and can reach many crater diameters in length. Secondary craters can be useful when crater rays are visible and the small craters can be associated with a particular primary impact crater. They can be used to constrain the age of the surface where they fell, since the surface must be older than the impact event. The age of the crater can be approximately estimated from the probability of an impact that produced a crater of such a size within a given area of Mars over a given time period. But these secondary craters can also be perplexing when no crater rays are preserved and a source crater is not easily identifiable, as is the case here. The impact that formed these secondary craters took place long enough ago that their association with a particular crater has been erased. They do not appear along the trace of a crater ray that is still apparent in visible or thermal infrared observations. These secondary craters complicate the task of estimating the age of the lineated material on the crater floor. It is necessary to distinguish secondary craters from the primary impacts that we rely upon to estimate the ages of Martian surfaces. The large number of small craters clustered together here is typical of crater rays elsewhere on Mars and suggests that these are indeed, secondary impact craters. http://photojournal.jpl.nasa.gov/catalog/PIA14450

NOAA Weather Radio

Science.gov Websites

Programación Español Listado de estación Explicacion de SAME Coverage Station Listing County Listing Search For Go NWS All NOAA Lista de Emisora y Cobertura Seleccione aquí para radiofrecuencias (La lista Transmitter Outages FAQ NWR - Special Needs ESPAÑOL Español Condado de cobertura Listado de estación Lista

Potential use of weather radar to study movements of wintering waterfowl

USGS Publications Warehouse

Randall, Lori A.; Diehl, Robert H.; Wilson, Barry C.; Barrow, Wylie C.; Jeske, Clinton W.

2011-01-01

To protect and restore wintering waterfowl habitat, managers require knowledge of routine wintering waterfowl movements and habitat use. During preliminary screening of Doppler weather radar data we observed biological movements consistent with routine foraging flights of wintering waterfowl known to occur near Lacassine National Wildlife Refuge (NWR), Louisiana. During the winters of 2004–2005 and 2005–2006, we conducted field surveys to identify the source of the radar echoes emanating from Lacassine NWR. We compared field data to weather radar reflectivity data. Spatial and temporal patterns consistent with foraging flight movements appeared in weather radar data on all dates of field surveys. Dabbling ducks were the dominant taxa flying within the radar beam during the foraging flight period. Using linear regression, we found a positive log-linear relationship between average radar reflectivity (Z) and number of birds detected over the study area (P r2 = 0.62, n = 40). Ground observations and the statistically significant relationship between radar data and field data confirm that Doppler weather radar recorded the foraging flights of dabbling ducks. Weather radars may be effective tools for wintering waterfowl management because they provide broad-scale views of both diurnal and nocturnal movements. In addition, an extensive data archive enables the study of wintering waterfowl response to habitat loss, agricultural practices, wetland restoration, and other research questions that require multiple years of data.

Deficits in comprehending wh-questions in children with hearing loss - the contribution of phonological short-term memory and syntactic complexity.

PubMed

Penke, Martina; Wimmer, Eva

2018-01-01

The aim of the study is to investigate if German children with hearing loss (HL) display persisting problems in comprehending complex sentences and to find out whether these problems can be linked to limitations in phonological short-term memory (PSTM). A who-question comprehension test (picture pointing) and a nonword repetition (NWR) task were conducted with 21 German children with bilateral sensorineural HL (ages 3-4) and with age-matched 19 normal hearing (NH) children. Follow-up data (ages 6-8) are reported for 10 of the children with HL. The data reveal that the comprehension of who-questions as well as PSTM was significantly more impaired in children with HL than in children with NH. For both groups of participants, there were no correlations between question comprehension scores and performance in the NWR test. Syntactic complexity (subject vs. object question) affected question comprehension in children with HL, however, these problems were overcome at school age. In conclusion, the data indicate that a hearing loss affects the comprehension of complex sentences. The observed problems did, however, not persist and were, therefore, unlikely to be caused by a genuine syntactic deficit. For the tested wh-questions, there is no indication that syntactic comprehension problems of children with HL are due to limitations in PSTM.

Degradation studies of Martian impact craters

NASA Technical Reports Server (NTRS)

Barlow, N. G.

1991-01-01

The amount of obliteration suffered by Martian impact craters is quantified by comparing measurable attributes of the current crater shape to those values expected for a fresh crater of identical size. Crater diameters are measured from profiles obtained using photoclinometry across the structure. The relationship between the diameter of a fresh crater and a crater depth, floor width, rim height, central peak height, etc. was determined by empirical studies performed on fresh Martian impact craters. We utilized the changes in crater depth and rim height to judge the degree of obliteration suffered by Martian impact craters.

The Global Contribution of Secondary Craters on the Icy Satellites

NASA Astrophysics Data System (ADS)

Hoogenboom, T.; Johnson, K. E.; Schenk, P.

2014-12-01

At present, surface ages of bodies in the Outer Solar System are determined only from crater size-frequency distributions (a method dependent on an understanding of the projectile populations responsible for impact craters in these planetary systems). To derive accurate ages using impact craters, the impactor population must be understood. Impact craters in the Outer Solar System can be primary, secondary or sesquinary. The contribution of secondary craters to the overall population has recently become a "topic of interest." Our objective is to better understand the contribution of dispersed secondary craters to the small crater populations, and ultimately that of small comets to the projectile flux on icy satellites in general. We measure the diameters of obvious secondary craters (determined by e.g. irregular crater shape, small size, clustering) formed by all primary craters on Ganymede for which we have sufficiently high resolution data to map secondary craters. Primary craters mapped range from approximately 40 km to 210 km. Image resolution ranges from 45 to 440 m/pixel. Bright terrain on Ganymede is our primary focus. These resurfaced terrains have relatively low crater densities and serve as a basis for characterizing secondary populations as a function of primary size on an icy body for the first time. Although focusing on Ganymede, we also investigate secondary crater size, frequency, distribution, and formation, as well as secondary crater chain formation on icy satellites throughout the Saturnian and Jovian systems principally Rhea. We compare our results to similar studies of secondary cratering on the Moon and Mercury. Using Galileo and Voyager data, we have identified approximately 3,400 secondary craters on Ganymede. In some cases, we measured crater density as a function of distance from a primary crater. Because of the limitations of the Galileo data, it is necessary to extrapolate from small data sets to the global population of secondary craters. Nonetheless, we confirm that secondary craters on Ganymede have narrow size-frequency distributions and that they correlate with primary crater diameter. From these data we will evaluate the contribution of secondary craters over a range of crater diameters.

Evidence for self-secondary cratering of Copernican-age continuous ejecta deposits on the Moon

NASA Astrophysics Data System (ADS)

Zanetti, M.; Stadermann, A.; Jolliff, B.; Hiesinger, H.; van der Bogert, C. H.; Plescia, J.

2017-12-01

Crater size-frequency distributions on the ejecta blankets of Aristarchus and Tycho Craters are highly variable, resulting in apparent absolute model age differences despite ejecta being emplaced in a geologic instant. Crater populations on impact melt ponds are a factor of 4 less than on the ejecta, and crater density increases with distance from the parent crater rim. Although target material properties may affect crater diameters and in turn crater size-frequency distribution (CSFD) results, they cannot completely reconcile crater density and population differences observed within the ejecta blanket. We infer from the data that self-secondary cratering, the formation of impact craters immediately following the emplacement of the continuous ejecta blanket by ejecta from the parent crater, contributed to the population of small craters (< 300 m diameter) on ejecta blankets and must be taken into account if small craters and small count areas are to be used for relative and absolute model age determinations on the Moon. Our results indicate that the cumulative number of craters larger than 1 km in diameter per unit area, N(1), on the continuous ejecta blanket at Tycho Crater, ranges between 2.17 × 10-5 and 1.0 × 10-4, with impact melt ponds most accurately reflecting the primary crater flux (N(1) = 3.4 × 10-5). Using the cratering flux recorded on Tycho impact melt deposits calibrated to accepted exposure age (109 ± 1.5 Ma) as ground truth, and using similar crater distribution analyses on impact melt at Aristarchus Crater, we infer the age of Aristarchus Crater to be ∼280 Ma. The broader implications of this work suggest that the measured cratering rate on ejecta blankets throughout the Solar System may be overestimated, and caution should be exercised when using small crater diameters (i.e. < 300 m on the Moon) for absolute model age determination.

Moon-Mercury: Relative preservation states of secondary craters

USGS Publications Warehouse

Scott, D.H.

1977-01-01

Geologic mapping of the Kuiper quadrangle of Mercury and other geologic studies of the planet indicate that secondary craters are much better preserved than those on the moon around primary craters of similar size and morphology. Among the oldest recognized secondary craters on the moon associated with craters 100 km across or less are those of Posidonius, Atlas and Plato; these craters have been dated as middle to late Imbrian in age. Many craters on Mercury with dimensions, morphologies and superposed crater densities similar to these lunar craters have fields and clusters of fresher appearing secondary craters. The apparent differences between secondary-crater morphology and parent crater may be due in part to: (1) rapid isostatic adjustment of the parent crater; (2) different impact fluxes between the two planets; and (or) (3) to the greater concentration of Mercurian secondaries around impact areas, thereby accentuating crater forms. Another factor which may contribute to the better state of preservation of Mercurian secondaries relative to the moon is the difference in crater ejecta velocities on both bodies. These velocities have been calculated for fields of secondary craters at about equal ranges from lunar and Mercurian parent craters. Results show that ejection velocities of material producing most of the secondary craters are rather low (<1 km/s) but velocities on Mercury are about 50% greater than those on the moon for equivalent ranges. Higher velocities may produce morphologically enhanced secondary craters which may account for their better preservation with time. ?? 1977.

Geology of five small Australian impact craters

USGS Publications Warehouse

Shoemaker, E.M.; Macdonald, F.A.; Shoemaker, C.S.

2005-01-01

Here we present detailed geological maps and cross-sections of Liverpool, Wolfe Creek, Boxhole, Veevers and Dalgaranga craters. Liverpool crater and Wolfe Creek Meteorite Crater are classic bowlshaped, Barringer-type craters, Liverpool was likely formed during the Neoproterozoic and was filled and covered with sediments soon thereafter. In the Cenozoic, this cover was exhumed exposing the crater's brecciated wall rocks. Wolfe Creek Meteorite Crater displays many striking features, including well-bedded ejecta units, crater-floor faults and sinkholes, a ringed aeromagnetic anomaly, rim-skirting dunes, and numerous iron-rich shale balls. Boxhole Meteorite Crater, Veevers Meteorite Crater and Dalgaranga crater are smaller, Odessa-type craters without fully developed, steep, overturned rims. Boxhole and Dalgaranga craters are developed in highly follated Precambrian basement rocks with a veneer of Holocene colluvium. The pre-existing structure at these two sites complicates structural analyses of the craters, and may have influenced target deformation during impact. Veevers Meteorite Crater is formed in Cenozoic laterites, and is one of the best-preserved impact craters on Earth. The craters discussed herein were formed in different target materials, ranging from crystalline rocks to loosely consolidated sediments, containing evidence that the impactors struck at an array of angles and velocities. This facilitates a comparative study of the influence of these factors on the structural and topographic form of small impact craters. ?? Geological Society of Australia.

Avian disease assessment in seabirds and non-native passerines birds at Midway Atoll NWR

USGS Publications Warehouse

LaPointe, Dennis A.; Atkinson, Carter T.; Klavitter, John L.

2013-01-01

Midway Atoll in the Northwestern Hawaiian Islands supports the largest breeding colony of Laysan albatross (Phoebastria immutabilis) in the world and is a proposed site for the translocation of endangered Northwestern Hawaiian Island passerine birds such as the Nihoa finch (Telespiza ultima), Nihoa millerbird (Acrocephalus familiaris kingi), or Laysan finch (Telespiza cantans). On the main Hawaiian Islands, introduced mosquito-borne avian malaria (Plasmodium relictum) and avian pox (Avipoxvirus) have contributed to the extinction and decline of native Hawaiian avifauna. The mosquito vector (Culex quinquefasciatus) is present on Sand Island, Midway Atoll, where epizootics of Avipoxvirus have been reported among nestling Laysan albatross, black-footed albatross (Phoebastria nigripes), and red-tailed tropicbirds (Phaethon rubricauda) since 1963. Two introduced passerines, the common canary (Serinus canaria) and the common myna (Acridotheres tristis), are also present on Sand Island and may serve as reservoirs of mosquito-borne pathogens. Assessing disease prevalence and transmission potential at Midway Atoll National Wildlife Refuge (NWR) is a critical first step to translocation of Nihoa endemic passerines. In May 2010 and April 2012 we surveyed Midway Atoll NWR for mosquitoes and evidence of mosquito-borne disease. Although we did not observe active pox infections on albatross nestlings in May 2010, active infections were prevalent on albatross nestlings in April 2012. Presumptive diagnosis of Avipoxvirus was confirmed by PCR amplification of the Avipoxvirus 4b core protein gene from lesions collected from 10 albatross nestlings. Products were sequenced and compared to 4b core protein sequences from 28 Avipoxvirus isolates from the Hawaiian Islands and other parts of the world. Sequences from all Midway isolates were identical and formed a clade with other Avipoxvirus isolates from seabirds that was distinct from other Avipoxvirus isolates from the Hawaiian Islands. Tissue from three presumptive avian pox lesions from common canaries tested negative for Avipoxvirus. Blood samples from 124 canaries and 61 mynas tested negative for Plasmodium by one or more diagnostic tests based on microscopy, serology, or PCR diagnostics. Prevalence of Avipoxvirus infection was highest among albatross nestlings (94.6%) in the vicinity of the septic tanks where adult C. quinquefasciatus reached their highest densities, and data from all sites suggest a positive correlation between mosquito abundance and Avipoxvirus prevalence. Adult C. quinquefasciatus were also locally abundant around fishless, constructed wetlands. Since 1996, infrastructure removal and source reduction efforts by the refuge have greatly reduced the availability of underground and container habitats for larval mosquitoes on Sand Island. However, the creation of artificial wetlands and a central septic system on Sand Island has resulted in new, highly productive larval mosquito habitat for C. quinquefasciatus. Despite the presence of endemic Avipoxvirus in albatross nestlings and the introduction of mosquito vectors and two susceptible passerine species in the last century, we found no evidence of the avian malaria Plasmodium relictum or a passerine-infecting Avipoxvirus on Midway Atoll NWR that would interfere with the successful translocation of endemic Northwestern Hawaiian Island passerines. Without eradication of mosquitoes from Midway Atoll, however, periodic epizootics of Avipoxvirus among nestling seabirds will likely continue, and the introduction of malaria and passerine strains of Avipoxvirus from migratory birds will remain a long-term threat to passerine restoration programs.

Lunar Cratering Chronology: Calibrating Degree of Freshness of Craters to Absolute Ages

NASA Astrophysics Data System (ADS)

Trang, D.; Gillis-Davis, J.; Boyce, J. M.

2013-12-01

The use of impact craters to age-date surfaces of and/or geomorphological features on planetary bodies is a decades old practice. Various dating techniques use different aspects of impact craters in order to determine ages. One approach is based on the degree of freshness of primary-impact craters. This method examines the degradation state of craters through visual inspection of seven criteria: polygonality, crater ray, continuous ejecta, rim crest sharpness, satellite craters, radial channels, and terraces. These criteria are used to rank craters in order of age from 0.0 (oldest) to 7.0 (youngest). However, the relative decimal scale used in this technique has not been tied to a classification of absolute ages. In this work, we calibrate the degree of freshness to absolute ages through crater counting. We link the degree of freshness to absolute ages through crater counting of fifteen craters with diameters ranging from 5-22 km and degree of freshness from 6.3 to 2.5. We use the Terrain Camera data set on Kaguya to count craters on the continuous ejecta of each crater in our sample suite. Specifically, we divide the crater's ejecta blanket into quarters and count craters between the rim of the main crater out to one crater radii from the rim for two of the four sections. From these crater counts, we are able to estimate the absolute model age of each main crater using the Craterstats2 tool in ArcGIS. Next, we compare the degree of freshness for the crater count-derived age of our main craters to obtain a linear inverse relation that links these two metrics. So far, for craters with degree of freshness from 6.3 to 5.0, the linear regression has an R2 value of 0.7, which corresponds to a relative uncertainty of ×230 million years. At this point, this tool that links degree of freshness to absolute ages cannot be used with craters <8km because this class of crater degrades quicker than larger craters. A graphical solution exists for correcting the degree of freshness for craters <8 km in diameter. We convert this graphical solution to a single function of two independent variables, observed degree of freshness and crater diameter. This function, which results in a corrected degree of freshness is found through a curve-fitting routine and corrects the degree of freshness for craters <8 km in diameter. As a result, we are able to derive absolute ages from the degree of freshness of craters with diameters from about ≤20 km down to a 1 km in diameter with a precision of ×230 million years.

Craters on Crater

NASA Image and Video Library

2006-10-10

Several craters were formed on the rim of this large crater. The movement of material downhill toward the floor of the large crater has formed interesting patterns on the floors of the smaller craters

Using THEMIS thermal infrared observations of rays from Corinto crater to study secondary crater formation on Mars

NASA Astrophysics Data System (ADS)

Williams, J. P.

2017-12-01

Corinto crater (16.95°N, 141.72°E), a 13.8 km diameter crater in Elysium Planitia, displays dramatic rays in Mars Odyssey's Thermal Emission Imaging System (THEMIS) nighttime infrared imagery where high concentrations of secondary craters have altered the thermophysical properties of the martian surface. The THEMIS observations provide a record of secondary crater formation in the region and ray segments are identified up to 2000 km ( 145 crater radii) distance [1][2]. Secondary craters are likely to have the largest influence on model surfaces ages between 0.1 to a few Myr as there is the potential for one or two sizeable craters to project secondary craters onto those surfaces and thus alter the crater size-frequency distribution (CSFD) with an instantaneous spike in crater production [3]. Corinto crater is estimated to be less than a few Ma [4] placing the formation of its secondaries within this formative time period. Secondary craters superposed on relatively young impact craters that predate Corinto provide observations of the secondary crater populations. Crater counts at 520 and 660 km distance from Corinto (38 and 48 crater radii respectively), were conducted. Higher crater densities were observed within ray segments, however secondary craters still influenced the CSFD where ray segments were not apparent, resulting in steepening in the CSFD. Randomness analysis confirms an increase in clustering as diameters decrease suggesting an increasing fraction of secondary craters at smaller diameters, both within the ray and outside. The counts demonstrate that even at nearly 50 crater radii, Corinto secondaries still influence the observed CSFD, even outside of any obvious rays. Crater populations used to derive model ages on many geologically young regions on Mars, such as glacial and periglacial landforms related to obliquity excursions that occur on 106 - 107 yr cycles, should be used cautiously and analyzed for any evidence, either morphologic or statistical, for secondary cratering that may potentially influence the derived age. [1] Williams et al. (2017) MAPS, in press. [2] Bloom et al. (2014) Mars 8th, #1289. [3] Hartmann and Daubar (2017), MAPS, 52, 493- 510. [4] Hundal et al. (2017), LPSC, #1726.

A global catalogue of Ceres impact craters ≥ 1 km and preliminary analysis

NASA Astrophysics Data System (ADS)

Gou, Sheng; Yue, Zongyu; Di, Kaichang; Liu, Zhaoqin

2018-03-01

The orbital data products of Ceres, including global LAMO image mosaic and global HAMO DTM with a resolution of 35 m/pixel and 135 m/pixel respectively, are utilized in this research to create a global catalogue of impact craters with diameter ≥ 1 km, and their morphometric parameters are calculated. Statistics shows: (1) There are 29,219 craters in the catalogue, and the craters have a various morphologies, e.g., polygonal crater, floor fractured crater, complex crater with central peak, etc.; (2) The identifiable smallest crater size is extended to 1 km and the crater numbers have been updated when compared with the crater catalogue (D ≥ 20 km) released by the Dawn Science Team; (3) The d/D ratios for fresh simple craters, obviously degraded simple crater and polygonal simple crater are 0.11 ± 0.04, 0.05 ± 0.04 and 0.14 ± 0.02 respectively. (4) The d/D ratios for non-polygonal complex crater and polygonal complex crater are 0.08 ± 0.04 and 0.09 ± 0.03. The global crater catalogue created in this work can be further applied to many other scientific researches, such as comparing d/D with other bodies, inferring subsurface properties, determining surface age, and estimating average erosion rate.

Crater Mound Formation by Wind Erosion on Mars

NASA Astrophysics Data System (ADS)

Steele, L. J.; Kite, E. S.; Michaels, T. I.

2018-01-01

Most of Mars' ancient sedimentary rocks by volume are in wind-eroded sedimentary mounds within impact craters and canyons, but the connections between mound form and wind erosion are unclear. We perform mesoscale simulations of different crater and mound morphologies to understand the formation of sedimentary mounds. As crater depth increases, slope winds produce increased erosion near the base of the crater wall, forming mounds. Peak erosion rates occur when the crater depth is ˜2 km. Mound evolution depends on the size of the host crater. In smaller craters mounds preferentially erode at the top, becoming more squat, while in larger craters mounds become steeper sided. This agrees with observations where smaller craters tend to have proportionally shorter mounds and larger craters have mounds encircled by moats. If a large-scale sedimentary layer blankets a crater, then as the layer recedes across the crater it will erode more toward the edges of the crater, resulting in a crescent-shaped moat. When a 160 km diameter mound-hosting crater is subject to a prevailing wind, the surface wind stress is stronger on the leeward side than on the windward side. This results in the center of the mound appearing to "march upwind" over time and forming a "bat-wing" shape, as is observed for Mount Sharp in Gale crater.

Rock spatial densities on the rims of the Tycho secondary craters in Mare Nectaris

NASA Astrophysics Data System (ADS)

Basilevsky, A. T.; Michael, G. G.; Kozlova, N. A.

2018-04-01

The aim of this work is to check whether the technique of estimation of age of small lunar craters based on spatial density of rock boulders on their rims described in Basilevsky et al. (2013, 2015b) and Li et al. (2017) for the craters < 1 km in diameter is applicable to the larger craters. The work presents the rock counts on the rims of four craters having diameters 1000, 1100, 1240 and 1400 m located in Mare Nectaris. These craters are secondaries of the primary crater Tycho, whose age was found to be 109 ± 4 Ma (Stoffler and Ryder, 2001) so this may be taken as the age of the four craters, too. Using the dependence of the rock spatial densities at the crater rims on the crater age for the case of mare craters (Li et al., 2017) our measured rock densities correspond to ages from ∼100 to 130 Ma. These estimates are reasonably close to the given age of the primary crater Tycho. This, in turn, suggests that this technique of crater age estimation is applicable to craters up to ∼1.5 km in diameter. For the four considered craters we also measured their depth/diameter ratios and the maximum angles of the crater inner slopes. For the considered craters it was found that with increasing crater diameter, the depth/diameter ratios and maximum angles of internal slopes increase, but the values of these parameters for specific craters may deviate significantly from the general trends. The deviations probably result from some dissimilarities in the primary crater geometries, that may be due to crater to crater differences in characteristics of impactors (e.g., in their bulk densities) and/or differences in the mechanical properties of the target. It may be possible to find secondaries of crater Tycho in the South pole area and, if so, they may be studied to check the specifics and rates of the rock boulder degradation in the lunar polar environment.

NOAA Weather Radio

Science.gov Websites

para un condado depende de recepción de la seña fiable, que típicamente se extiende en un radio de 40 millas del transmisor, asumiendo terreno plano. Condados sin la cobertura de NWR o cobertura obstáculos de la seña y/o la distancia excesiva del transmisor. Usted puede referirse directamente a

Successive Formation of Impact Craters

NASA Image and Video Library

2012-02-16

This image from NASA Dawn spacecraft shows two overlapping impact craters on asteroid Vesta. The rims of the craters are both reasonably fresh but the larger crater must be older because the smaller crater cuts across the larger crater rim.

The self-secondary crater population of the Hokusai crater on Mercury

NASA Astrophysics Data System (ADS)

Xiao, Zhiyong; Prieur, Nils C.; Werner, Stephanie C.

2016-07-01

Whether or not self-secondaries dominate small crater populations on continuous ejecta deposits and floors of fresh impact craters has long been a controversy. This issue potentially affects the age determination technique using crater statistics. Here the self-secondary crater population on the continuous ejecta deposits of the Hokusai crater on Mercury is unambiguously recognized. Superposition relationships show that this population was emplaced after both the ballistic sedimentation of excavation flows and the subsequent veneering of impact melt, but it predated the settlement and solidification of melt pools on the crater floor. Fragments that formed self-secondaries were launched via impact spallation with large angles. Complex craters on the Moon, Mercury, and Mars probably all have formed self-secondaries populations. Dating young craters using crater statistics on their continuous ejecta deposits can be misleading. Impact melt pools are less affected by self-secondaries. Overprint by subsequent crater populations with time reduces the predominance of self-secondaries.

Interior and Ejecta Morphologies of Impact Craters on Ganymede

NASA Astrophysics Data System (ADS)

Barlow, Nadine G.; Klaybor, K.; Katz-Wigmore, J.

2006-09-01

We are utilizing Galileo SSI imagery of Ganymede to classify impact crater interior and ejecta morphologies. Although we are in the early stages of compiling our Catalog of Impact Craters on Ganymede, some interesting trends are beginning to emerge. Few craters display obvious ejecta morphologies, but 68 craters are classified as single layer ejecta and 3 as double layer ejecta. We see no obvious correlation of layered ejecta morphologies with terrain or latitude. All layered ejecta craters have diameters between 10 and 40 km. Sinuosity ("lobateness") and ejecta extent ("ejecta mobility ratio") of Ganymede layered ejecta craters are lower than for martian layered ejecta craters. This suggests less mobility of ejecta materials on Ganymede, perhaps due to the colder temperatures. Interior structures being investigated include central domes, peaks, and pits. 57 dome craters, 212 central peak craters, and 313 central pit craters have been identified. Central domes occur in 50-100 km diameter craters while peaks are found in craters between 20 and 50 km and central pit craters range between 29 and 74 km in diameter. The Galileo Regio region displays higher concentrations of central dome and central pit craters than other regions we have investigated. 67% of central pit craters studied to date are small pits, where the ratio of pit diameter to crater diameter is <0.2. Craters containing the three interior structures preferentially occur on darker terrain units, suggesting that an ice-silicate composition is more conducive to interior feature formation than pure ice alone. Results of this study have important implications not only for the formation of specific interior and ejecta morphologies on Ganymede but also for analogous features associated with Martian impact craters. This research is funded through NASA Outer Planets Research Program Award #NNG05G116G to N. G. Barlow.

Simultaneous impact and lunar craters

NASA Technical Reports Server (NTRS)

Oberbeck, V. R.

1972-01-01

The existence of large terrestrial impact crater doublets and crater doublets that have been inferred to be impact craters on Mars suggests that simultaneous impact of two or more bodies can occur at nearly the same point on planetary surfaces. An experimental study of simultaneous impact of two projectiles near one another shows that doublet craters with ridges perpendicular to the bilateral axis of symmetry result when separation between impact points relative to individual crater diameter is large. When separation is progressively less, elliptical craters with central ridges and peaks, and circular craters with deep round bottoms are produced. These craters are similar in structure to many of the large lunar craters. Results suggest that the simultaneous impact of meteoroids near one another may be an important mechanism for the production of central peaks in large lunar craters.

Volatile-rich Crater Interior Deposits on Mars: An Energy Balance Model of Modification

NASA Technical Reports Server (NTRS)

Russell, Patrick S.; Head, James W.; Hecht, Michael H.

2003-01-01

Several craters on Mars are partially filled by material emplaced by post-impact processes. Populations of such craters include those in the circumsouth polar cap region, in Arabia Terra, associated with the Medusae Fossae Formation, and in the northern lowlands proximal to the north polar cap. In this study, crater fill material refers to an interior mound, generally separated from the interior walls of the crater by a trough that may be continuous along the crater s circumference (i.e. a ring-shaped trough), or may only partially contact the crater walls (i.e. a crescent-shaped trough). The fill deposit is frequently off-center from the crater center and may be asymmetric, (i.e. not circular) in plan view shape. Here we test the hypothesis that asymmetries in volatile fill shape, profile, and center-location within a crater result from asymmetries in local energy balance within the crater due mainly to variation of solar insolation and radiative effects of the crater walls over the crater interior. We first focus on Korolev crater in the northern lowlands. We can then apply this model to other craters in different regions. If asymmetry in morphology and location of crater fill are consistent with radiative-dominated asymmetries in energy budget within the crater, then 1) the volatile-rich composition of the fill is supported (this process should not be effective at shaping volcanic or sedimentary deposits), and 2) the dominant factor determining the observed shape of volatile-rich crater fill is the local radiative energy budget within the crater (and erosive processes such as eolian deflation are not necessary).

Crater dimensions from apollo data and supplemental sources

USGS Publications Warehouse

Pike, R.J.

1976-01-01

A catalog of crater dimensions that were compiled mostly from the new Apollo-based Lunar Topographic Orthophotomaps is presented in its entirety. Values of crater diameter, depth, rim height, flank width, circularity, and floor diameter (where applicable) are tabulated for a sample of 484 craters on the Moon and 22 craters on Earth. Systematic techniques of mensuration are detailed. The lunar craters range in size from 400 m to 300 km across and include primary impact craters of the main sequence, secondary impact craters, craterlets atop domes and cones, and dark-halo craters. The terrestrial craters are between 10 m and 22.5 km in diameter and were formed by meteorite impact. ?? 1976 D. Reidel Publishing Company.

Methods of Estimating Initial Crater Depths on Icy Satellites using Stereo Topography

NASA Astrophysics Data System (ADS)

Persaud, D. M.; Phillips, C. B.

2014-12-01

Stereo topography, combined with models of viscous relaxation of impact craters, allows for the study of the rheology and thermal history of icy satellites. An important step in calculating relaxation of craters is determining the initial depths of craters before viscous relaxation. Two methods for estimating initial crater depths on the icy satellites of Saturn have been previously discussed. White and Schenk (2013) present the craters of Iapetus as relatively unrelaxed in modeling the relaxation of craters of Rhea. Phillips et al. (2013) assume that Herschel crater on Saturn's satellite Mimas is unrelaxed in relaxation calculations and models of Rhea and Dione. In the second method, the depth of Herschel crater is scaled based on the different crater diameters and the difference in surface gravity on the large moons to predict the initial crater depths for Rhea and Dione. In the first method, since Iapetus is of similar size to Dione and Rhea, no gravity scaling is necessary; craters of similar size on Iapetus were chosen and their depths measured to determine the appropriate initial crater depths for Rhea. We test these methods by first extracting topographic profiles of impact craters on Iapetus from digital elevation models (DEMs) constructed from stereo images from the Cassini ISS instrument. We determined depths from these profiles and used them to calculate initial crater depths and relaxation percentages for Rhea and Dione craters using the methods described above. We first assumed that craters on Iapetus were relaxed, and compared the results to previously calculated relaxation percentages for Rhea and Dione relative to Herschel crater (with appropriate scaling for gravity and crater diameter). We then tested the assumption that craters on Iapetus were unrelaxed and used our new measurements of crater depth to determine relaxation percentages for Dione and Rhea. We will present results and conclusions from both methods and discuss their efficacy for determining initial crater depth. References: Phillips, C.B., et al. (2013). Lunar Planet Sci. XLIV, abstract 2766. White, O.L., and P.L. Schenk. Icarus 23, 699-709, 2013. This work was supported by the NASA Outer Planets Research Program grant NNX10AQ09G and by the NSF REU Program.

Elevation and igneous crater modification on Venus: Implications for magmatic volatile content

NASA Technical Reports Server (NTRS)

Wichman, R. W.

1993-01-01

Although most impact craters on Venus preserve nearly pristine crater rim and ejecta features, a small number of craters have been identified showing clear evidence of either igneous intrusion emplacement (floor-fracturing) beneath the crater floor or of volcanically embayed exterior ejecta deposits. Since the volcanically embayed craters consistently occur at higher elevations than the identified floor-fractured craters, this report proposes that igneous crater modification on Venus is elevation dependent. This report describes how regional variations in magmatic neutral buoyancy could produce such elevation dependent crater modification and considers the implications for typical magmatic volatile contents on Venus.

Size-Frequency Distribution of Small Lunar Craters: Widening with Degradation and Crater Lifetime

NASA Astrophysics Data System (ADS)

Ivanov, B. A.

2018-01-01

The review and new measurements are presented for depth/diameter ratio and slope angle evolution during small ( D < 1 km) lunar impact craters aging (degradation). Comparative analysis of available data on the areal cratering density and on the crater degradation state for selected craters, dated with returned Apollo samples, in the first approximation confirms Neukum's chronological model. The uncertainty of crater retention age due to crater degradational widening is estimated. The collected and analyzed data are discussed to be used in the future updating of mechanical models for lunar crater aging.

Physical properties of lunar craters

NASA Astrophysics Data System (ADS)

Joshi, Maitri P.; Bhatt, Kushal P.; Jain, Rajmal

2017-02-01

The surface of the Moon is highly cratered due to impacts of meteorites, asteroids, comets and other celestial objects. The origin, size, structure, age and composition vary among craters. We study a total of 339 craters observed by the Lunar Reconnaissance Orbiter Camera (LROC). Out of these 339 craters, 214 craters are known (named craters included in the IAU Gazetteer of Planetary Nomenclature) and 125 craters are unknown (craters that are not named and objects that are absent in the IAU Gazetteer). We employ images taken by LROC at the North and South Poles and near side of the Moon. We report for the first time the study of unknown craters, while we also review the study of known craters conducted earlier by previous researchers. Our study is focused on measurements of diameter, depth, latitude and longitude of each crater for both known and unknown craters. The diameter measurements are based on considering the Moon to be a spherical body. The LROC website also provides a plot which enables us to measure the depth and diameter. We found that out of 214 known craters, 161 craters follow a linear relationship between depth (d) and diameter (D), but 53 craters do not follow this linear relationship. We study physical dimensions of these 53 craters and found that either the depth does not change significantly with diameter or the depths are extremely high relative to diameter (conical). Similarly, out of 125 unknown craters, 78 craters follow the linear relationship between depth (d) and diameter (D) but 47 craters do not follow the linear relationship. We propose that the craters following the scaling law of depth and diameter, also popularly known as the linear relationship between d and D, are formed by the impact of meteorites having heavy metals with larger dimension, while those with larger diameter but less depth are formed by meteorites/celestial objects having low density material but larger diameter. The craters with very high depth and with very small diameter are perhaps formed by the impact of meteorites that have very high density but small diameter with a conical shape. Based on analysis of the data selected for the current investigation, we further found that out of 339 craters, 100 (29.5%) craters exist near the equator, 131 (38.6%) are in the northern hemisphere and 108 (31.80%) are in the southern hemisphere. This suggests the Moon is heavily cratered at higher latitudes and near the equatorial zone.

Operation Sun Beam, Shot Small Boy. Project Officers report. Project 1. 9. Crater measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rooke, A.D.; Davis, L.K.; Strange, J.N.

1985-09-01

The objectives of Project 1.9 were to obtain the dimensions of the apparent and true craters formed by the Small Boy event and to measure the permanent earth deformation occurring beyond the true crater boundary. Measurements were made of the apparent crater by aerial stereophotography and ground survey and of the true crater and subsurface zones of residual deformation by the excavation and mapping of an array of vertical, colored sand columns which were placed along one crater diameter prior to the shot. The results of the crater exploration are discussed, particularly the permanent compression of the medium beneath themore » true crater which was responsible for the major portion of the apparent and true crater volumes. Apparent and true crater dimensions are compared with those of previous cratering events.« less

Geomorphology of crater and basin deposits - Emplacement of the Fra Mauro formation

NASA Technical Reports Server (NTRS)

Morrison, R. H.; Oberbeck, V. R.

1975-01-01

Characteristics of continuous deposits near lunar craters larger than about 1 km wide are considered, and it is concluded that (1) concentric dunes, radial ridges, and braided lineations result from deposition of the collision products of ejecta from adjacent pairs of similarly oriented secondary-crater chains and are, therefore, concentrations of secondary-crater ejecta; (2) intracrater ridges are produced within preexisting craters surrounding a fresh primary crater by ricocheting and focusing of secondary-crater ejecta from the preexisting craters' walls; and (3) secondary cratering has produced many of the structures of the continuous deposits of relatively small lunar craters and is the dominant process for emplacement of most of the radial facies of the continuous deposits of large lunar craters and basins. The percentages of Imbrium ejecta in deposits and the nature of Imbrium sculpturing are investigated.

Cratering on Ceres: Implications for its crust and evolution

USGS Publications Warehouse

Hiesinger, H.; Marchi, S.; Schmedemann, N.; Schenk, P.; Pasckert, J. H.; Neesemann, A.; O'Brien, D. P.; Kneissl, T.; Ermakov, A.; Fu, R.R.; Bland, M. T.; Nathues, A.; Platz, T.; Williams, D.A.; Jaumann, R.; Castillo-Rogez, J. C.; Ruesch, O.; Schmidt, B.; Park, R.S.; Preusker, F.; Buczkowski, D.L.; Russell, C.T.; Raymond, C.A.

2016-01-01

Thermochemical models have predicted that Ceres, is to some extent, differentiated and should have an icy crust with few or no impact craters. We present observations by the Dawn spacecraft that reveal a heavily cratered surface, a heterogeneous crater distribution, and an apparent absence of large craters. The morphology of some impact craters is consistent with ice in the subsurface, which might have favored relaxation, yet large unrelaxed craters are also present. Numerous craters exhibit polygonal shapes, terraces, flowlike features, slumping, smooth deposits, and bright spots. Crater morphology and simple-to-complex crater transition diameters indicate that the crust of Ceres is neither purely icy nor rocky. By dating a smooth region associated with the Kerwan crater, we determined absolute model ages (AMAs) of 550 million and 720 million years, depending on the applied chronology model.

Centrifuge impact cratering experiment 5

NASA Technical Reports Server (NTRS)

1984-01-01

Transient crates motions, cratering flow fields, crates dynamics, determining impact conditions from total crater welt, centrifuge quarter-space cratering, and impact cratering mechanics research is documented.

Geomorphology and Geology of the Southwestern Margaritifer Sinus and Argyre Regions of Mars. Part 4: Flow Ejecta Crater Distribution

NASA Technical Reports Server (NTRS)

Parker, T. J.; Pieri, D. C.

1985-01-01

Flow ejecta craters - craters surrounded by lobate ejecta blankets - are found throughout the study area. The ratio of the crater's diameter to that of the flow ejecta in this region is approximately 40 to 45%. Flow ejecta craters are dominantly sharply defined craters, with slightly degraded craters being somewhat less common. This is probably indicative of the ejecta's relatively low resistence to weathering and susceptibility to burial. Flow ejecta craters here seem to occur within a narrow range of crater sizes - the smallest being about 4km in diameter and the largest being about 27km in diameter. Ejecta blankets of craters at 4km are easily seen and those of smaller craters are simply not seen even in images with better than average resolution for the region. This may be due to the depth of excavation of small impacting bodies being insufficient to reach volatile-rich material. Flow ejecta craters above 24km are rare, and those craters above 27km do not display flow ejecta blankets. This may be a result of an excavation depth so great that the volatile content of the ejecta is insufficient to form a fluid ejecta blanket. The geomorphic/geologic unit appears also to play an important role in the formation of flow ejecta craters. Given the typical size range for the occurrence of flow ejecta craters for most units, it can be seen that the percentage of flow ejecta craters to the total number of craters within this size range varies significantly from one unit to the next. The wide variance in flow ejecta crater density over this relatively small geographical area argues strongly for a lithologic control of their distribution.

Spatial distribution of impact craters on Deimos

NASA Astrophysics Data System (ADS)

Hirata, Naoyuki

2017-05-01

Deimos, one of the Martian moons, has numerous impact craters. However, it is unclear whether crater saturation has been reached on this satellite. To address this issue, we apply a statistical test known as nearest-neighbor analysis to analyze the crater distribution of Deimos. When a planetary surface such as the Moon is saturated with impact craters, the spatial distribution of craters is generally changed from random to more ordered. We measured impact craters on Deimos from Viking and HiRISE images and found (1) that the power law of the size-frequency distribution of the craters is approximately -1.7, which is significantly shallower than those of potential impactors, and (2) that the spatial distribution of craters over 30 m in diameter cannot be statistically distinguished from completely random distribution, which indicates that the surface of Deimos is inconsistent with a surface saturated with impact craters. Although a crater size-frequency distribution curve with a slope of -2 is generally interpreted as indicating saturation equilibrium, it is here proposed that two competing mechanisms, seismic shaking and ejecta emplacement, have played a major role in erasing craters on Deimos and are therefore responsible for the shallow slope of this curve. The observed crater density may have reached steady state owing to the obliterations induced by the two competing mechanisms. Such an occurrence indicates that the surface is saturated with impact craters despite the random distribution of craters on Deimos. Therefore, this work proposes that the age determined by the current craters on Deimos reflects neither the age of Deimos itself nor that of the formation of the large concavity centered at its south pole because craters should be removed by later impacts. However, a few of the largest craters on Deimos may be indicative of the age of the south pole event.

Cratering history of Miranda: Implications for geologic processes

USGS Publications Warehouse

Plescia, J.B.

1988-01-01

Miranda's surface is divisible into cratered terrain and coronae. The cratered terrain is the most heavily cratered of the terrains and presumably is the oldest. The frequency of craters in the cratered terrain is variable and related to position on the satellite. The coronae are also variably cratered. Elsinore and Arden Coronae have similar crater frequencies and may have formed simultaneously. They are of intermediate agompared to the cratered terrain and to Inverness Corona, which is the youngest major terrain. Graben formation appears to have occured both before and after the formation of the coronae reflecting periods of global expansion. Miranda's surfaces are, in general, the least cratered and therefore inferred to be the youngest within the Uranian system. ?? 1988.

Impact craters on Venus: An overview from Magellan observations

NASA Technical Reports Server (NTRS)

Schaber, G. G.; Strom, R. G.; Moore, H. J.; Soderblom, L. A.; Kirk, R. L.; Chadwick, D. J.; Dawson, D. D.; Gaddis, L. R.; Boyce, J. M.; Russell, J.

1992-01-01

Magellan has revealed an ensemble of impact craters on Venus that is unique in many important ways. We have compiled a database describing 842 craters on 89 percent of the planet's surface mapped through orbit 2578 (the craters range in diameter from 1.5 to 280 km). We have studied the distribution, size-frequency, morphology, and geology of these craters both in aggregate and, for some craters, in more detail. We have found the following: (1) the spatial distribution of craters is highly uniform; (2) the size-density distribution of craters with diameters greater than or equal to 35 km is consistent with a 'production' population having a surprisingly young age of about 0.5 Ga (based on the estimated population of Venus-crossing asteroids); (3) the spectrum of crater modification differs greatly from that on other planets--62 percent of all craters are pristine, only 4 percent volcanically embayed, and the remainder affected by tectonism, but none are severely and progressively depleted based on size-density distribution extrapolated from larger craters; (4) large craters have a progression of morphologies generally similar to those on other planets, but small craters are typically irregular or multiple rather than bowl shaped; (5) diffuse radar-bright or -dark features surround some craters, and about 370 similar diffuse 'splotches' with no central crater are observed whose size-density distribution is similar to that of small craters; and (6) other features unique to Venus include radar-bright or -dark parabolic arcs opening westward and extensive outflows originating in crater ejecta.

Tabular comparisons of the Flynn Creek impact crater, United States, Steinheim impact crater, Germany and Snowball explosion crater, Canada

NASA Technical Reports Server (NTRS)

Roddy, D. J.

1977-01-01

A tabular outline of comparative data is presented for 340 basic dimensional, morphological, and structural parameters and related aspects for three craters of the flat-floored, central uplift type, two of which are natural terrestrial impact craters and one is a large-scale experimental explosion crater. The three craters are part of a general class, in terms of their morphology and structural deformation that is represented on each of the terrestrial planets including the moon. One of the considered craters, the Flynn Creek Crater, was formed by a hypervelocity impact event approximately 360 m.y. ago in what is now north central Tennessee. The impacting body appears to have been a carbonaceous chondrite or a cometary mass. The second crater, the Steinheim Crater, was formed by an impact event approximately 14.7 m.y. ago in what is now southwestern Germany. The Snowball Crater was formed by the detonation of a 500-ton TNT hemisphere on flat-lying, unconsolidated alluvium in Alberta, Canada.

Experimental simulation of impact cratering on icy satellites

NASA Technical Reports Server (NTRS)

Greeley, R.; Fink, J. H.; Gault, D. E.; Guest, J. E.

1982-01-01

Cratering processes on icy satellites were simulated in a series of 102 laboratory impact experiments involving a wide range of target materials. For impacts into homogeneous clay slurries with impact energies ranging from five million to ten billion ergs, target yield strengths ranged from 100 to 38 Pa, and apparent viscosities ranged from 8 to 200 Pa s. Bowl-shaped craters, flat-floored craters, central peak craters with high or little relief, and craters with no relief were observed. Crater diameters increased steadily as energies were raised. A similar sequence was seen for experiment in which impact energy was held constant but target viscosity and strength progressively decreases. The experiments suggest that the physical properties of the target media relative to the gravitationally induced stresses determined the final crater morphology. Crater palimpsests could form by prompt collapse of large central peak craters formed in low target strength materials. Ages estimated from crater size-frequency distributions that include these large craters may give values that are too high.

Terrace width variations in complex Mercurian craters and the transient strength of cratered Mercurian and lunar crust

NASA Technical Reports Server (NTRS)

Leith, Andrew C.; Mckinnon, William B.

1991-01-01

The effective cohesion of the cratered region during crater collapse is determined via the widths of slump terraces of complex craters. Terrace widths are measured for complex craters on Mercury; these generally increase outward toward the rim for a given crater, and the width of the outermost major terrace is generally an increasing function of crater diameter. The terrace widths on Mercury and a gravity-driven slump model are used to estimate the strength of the cratered region immediately after impact (about 1-2 MPa). A comparison with the previous study of lunar complex craters by Pearce and Melosh (1986) indicates that the transient strength of cratered Mercurian crust is no greater than that of the moon. The strength estimates vary only slightly with the geometric model used to restore the outermost major terrace to its precollapse configuration and are consistent with independent strength estimates from the simple-to-complex crater depth/diameter transition.

Craters on Earth, Moon, and Mars: Multivariate classification and mode of origin

USGS Publications Warehouse

Pike, R.J.

1974-01-01

Testing extraterrestrial craters and candidate terrestrial analogs for morphologic similitude is treated as a problem in numerical taxonomy. According to a principal-components solution and a cluster analysis, 402 representative craters on the Earth, the Moon, and Mars divide into two major classes of contrasting shapes and modes of origin. Craters of net accumulation of material (cratered lunar domes, Martian "calderas," and all terrestrial volcanoes except maars and tuff rings) group apart from craters of excavation (terrestrial meteorite impact and experimental explosion craters, typical Martian craters, and all other lunar craters). Maars and tuff rings belong to neither group but are transitional. The classification criteria are four independent attributes of topographic geometry derived from seven descriptive variables by the principal-components transformation. Morphometric differences between crater bowl and raised rim constitute the strongest of the four components. Although single topographic variables cannot confidently predict the genesis of individual extraterrestrial craters, multivariate statistical models constructed from several variables can distinguish consistently between large impact craters and volcanoes. ?? 1974.

Application of high explosion cratering data to planetary problems

NASA Technical Reports Server (NTRS)

Oberbeck, V. R.

1977-01-01

The present paper deals with the conditions of explosion or nuclear cratering required to simulate impact crater formation. Some planetary problems associated with three different aspects of crater formation are discussed, and solutions based on high-explosion data are proposed. Structures of impact craters and some selected explosion craters formed in layered media are examined and are related to the structure of lunar basins. The mode of ejection of material from impact craters is identified using explosion analogs. The ejection mode is shown to have important implications for the origin of material in crater and basin deposits. Equally important are the populations of secondary craters on lunar and planetary surfaces.

Paradigm lost: Venus crater depths and the role of gravity in crater modification

NASA Technical Reports Server (NTRS)

Sharpton, Virgil L.

1992-01-01

Previous to Magellan, a convincing case had been assembled that predicted that complex impact craters on Venus were considerably shallower than their counterparts on Mars, Mercury, the Moon, and perhaps even Earth. This was fueled primarily by the morphometric observation that, for a given diameter (D), crater depth (d) seems to scale inversely with surface gravity for the other planets in the inner solar system. The unpredicted depth of fresh impact craters on Venus argues against a simple inverse relationship between surface gravity and crater depth. Factors that could contribute to deep craters on Venus include (1) more efficient excavation on Venus, possibly reflecting rheological effects of the hot venusian environment; (2) more melting and efficient removal of melt from the crater cavity; and (3) enhanced ejection of material out of the crater, possibly as a result of entrainment in an atmosphere set in motion by the passage of the projectile. The broader issue raised by the venusian crater depths is whether surface gravity is the predominant influence on crater depths on any planet. While inverse gravity scaling of crater depths has been a useful paradigm in planetary cratering, the venusian data do not support this model and the terrestrial data are equivocal at best. The hypothesis that planetary gravity is the primary influence over crater depths and the paradigm that terrestrial craters are shallow should be reevaluated.

Martian Low-Aspect-Ratio Layered Ejecta (LARLE) craters: Distribution, characteristics, and relationship to pedestal craters

NASA Astrophysics Data System (ADS)

Barlow, Nadine G.; Boyce, Joseph M.; Cornwall, Carin

2014-09-01

Low-Aspect-Ratio Layered Ejecta (LARLE) craters are a unique landform found on Mars. LARLE craters are characterized by a crater and normal layered ejecta pattern surrounded by an extensive but thin outer deposit which terminates in a sinuous, almost flame-like morphology. We have conducted a survey to identify all LARLE craters ⩾1-km-diameter within the ±75° latitude zone and to determine their morphologic and morphometric characteristics. The survey reveals 140 LARLE craters, with the majority (91%) located poleward of 40°S and 35°N and all occurring within thick mantles of fine-grained deposits which are likely ice-rich. LARLE craters range in diameter from the cut-off limit of 1 km up to 12.2 km, with 83% being smaller than 5 km. The radius of the outer LARLE deposit displays a linear trend with the crater radius and is greatest at higher polar latitudes. The LARLE deposit ranges in length between 2.56 and 14.81 crater radii in average extent, with maximum length extending up to 21.4 crater radii. The LARLE layer is very sinuous, with lobateness values ranging between 1.45 and 4.35. LARLE craters display a number of characteristics in common with pedestal craters and we propose that pedestal craters are eroded versions of LARLE craters. The distribution and characteristics of the LARLE craters lead us to propose that impact excavation into ice-rich fine-grained deposits produces a dusty base surge cloud (like those produced by explosion craters) that deposits dust and ice particles to create the LARLE layers. Salts emplaced by upward migration of water through the LARLE deposit produce a surficial duricrust layer which protects the deposit from immediate removal by eolian processes.

Morphometry of impact craters on Mercury from MESSENGER altimetry and imaging

NASA Astrophysics Data System (ADS)

Susorney, Hannah C. M.; Barnouin, Olivier S.; Ernst, Carolyn M.; Johnson, Catherine L.

2016-06-01

Data acquired by the Mercury Laser Altimeter and the Mercury Dual Imaging System on the MESSENGER spacecraft in orbit about Mercury provide a means to measure the geometry of many of the impact craters in Mercury's northern hemisphere in detail for the first time. The combination of topographic and imaging data permit a systematic evaluation of impact crater morphometry on Mercury, a new calculation of the diameter Dt at which craters transition with increasing diameter from simple to complex forms, and an exploration of the role of target properties and impact velocity on final crater size and shape. Measurements of impact crater depth on Mercury confirm results from previous studies, with the exception that the depths of large complex craters are typically shallower at a given diameter than reported from Mariner 10 data. Secondary craters on Mercury are generally shallower than primary craters of the same diameter. No significant differences are observed between the depths of craters within heavily cratered terrain and those of craters within smooth plains. The morphological attributes of craters that reflect the transition from simple to complex craters do not appear at the same diameter; instead flat floors first appear with increasing diameter in craters at the smallest diameters, followed with increasing diameter by reduced crater depth and rim height, and then collapse and terracing of crater walls. Differences reported by others in Dt between Mercury and Mars (despite the similar surface gravitational acceleration on the two bodies) are confirmed in this study. The variations in Dt between Mercury and Mars cannot be adequately attributed to differences in either surface properties or mean projectile velocity.

Variations in interior morphology of 15-20 km lunar craters - Implications for a major subsurface discontinuity

NASA Technical Reports Server (NTRS)

De Hon, R. A.

1980-01-01

Craters vary in morphology as a function of crater diameter, age, and mode of origin. This study concentrates on the morphology of young lunar impact craters within a limited size range. Elimination of morphologic variations generally attributed to crater size or age leaves a small population which should nearly reflect the varying properties of the lunar substrate. The sample consists of 17 craters 15-20 km in diameter with both simple and complex morphologies. While depth/diameter ratios do not obviously differ between mare and highland subsets, apparent depth, rim height, and profile data do differ distinctly. Highland craters tend to be deep, simple, and bowl-shaped. Mare craters tend to be shallow and flat-floored. Rim heights of complex mare craters are typically greater than those of simple craters. Differences of highland and mare crater morphologies are attributed to variations in the thickness of the lunar megaregolith. Highland craters in this size range do not penetrate the megaregolith. The depth and morphology of complex craters are controlled by the discontinuity at the transition from highly brecciated megaregolith to more coherent crystalline material of the upper crust.

Relative depths of simple craters and the nature of the lunar regolith

NASA Astrophysics Data System (ADS)

Stopar, Julie D.; Robinson, Mark S.; Barnouin, Olivier S.; McEwen, Alfred S.; Speyerer, Emerson J.; Henriksen, Megan R.; Sutton, Sarah S.

2017-12-01

We assessed the morphologies of more than 930 simple impact craters (diameters 40 m-10 km) on the Moon using digital terrain models (DTMs) of a variety of terrains in order to characterize the variability of fresh crater morphology as a function of crater diameter. From Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) DTMs, we determined depth-to-diameter (d/D) ratios for an extremely fresh set of these craters with diameters less than 400 m and found that their d/D ratios range from 0.11 to 0.17. Using both NAC and Kaguya Terrain Camera DTMs, we also determined the d/D ratios for the set of fresh simple craters larger than 400 m in diameter. The d/D ratios of these larger craters are typically near 0.21, as expected of gravity-dominated crater excavation. Fresh craters less than ∼400 m in diameter, on the other hand, exhibit significantly lower d/D ratios. Various possible factors affect the morphologies and relative depths (d/D ratios) of small strength-dominated craters, including impactor and target properties (e.g., effective strength, strength contrasts, porosity, pre-existing weaknesses), impact angle and velocity, and degradation state. While impact conditions resulting from secondary impacts can also affect crater morphologies, we found that d/D ratio alone was not a unique discriminator of small secondary craters. To investigate the relative influences of degradation and target properties on the d/D ratios of small strength-dominated craters, we examined a subset of fresh craters located on the geologically young rim deposits of Tycho crater. These craters are deeper and steeper than other craters of similar diameter and degradation state, consistent with their relative freshness and formation in the relatively coherent, melt-rich deposits in this region. The d/D ratios of globally distributed small craters of similar degradation state and size range, on the other hand, are relatively shallow with lower average wall slopes, consistent with crater excavation in a weak or poorly cohesive layer. The widespread predominance of these small, shallow craters is consistent with the pervasive, poorly cohesive upper regolith.

Marine-target craters on Mars? An assessment study

USGS Publications Warehouse

Ormo, J.; Dohm, J.M.; Ferris, J.C.; Lepinette, A.; Fairen, A.G.

2004-01-01

Observations of impact craters on Earth show that a water column at the target strongly influences lithology and morphology of the resultant crater. The degree of influence varies with the target water depth and impactor diameter. Morphological features detectable in satellite imagery include a concentric shape with an inner crater inset within a shallower outer crater, which is cut by gullies excavated by the resurge of water. In this study, we show that if oceans, large seas, and lakes existed on Mars for periods of time, marine-target craters must have formed. We make an assessment of the minimum and maximum amounts of such craters based on published data on water depths, extent, and duration of putative oceans within "contacts 1 and 2," cratering rate during the different oceanic phases, and computer modeling of minimum impactor diameters required to form long-lasting craters in the seafloor of the oceans. We also discuss the influence of erosion and sedimentation on the preservation and exposure of the craters. For an ocean within the smaller "contact 2" with a duration of 100,000 yr and the low present crater formation rate, only ???1-2 detectable marine-target craters would have formed. In a maximum estimate with a duration of 0.8 Gyr, as many as 1400 craters may have formed. An ocean within the larger "contact 1-Meridiani," with a duration of 100,000 yr, would not have received any seafloor craters despite the higher crater formation rate estimated before 3.5 Gyr. On the other hand, with a maximum duration of 0.8 Gyr, about 160 seafloor craters may have formed. However, terrestrial examples show that most marine-target craters may be covered by thick sediments. Ground penetrating radar surveys planned for the ESA Mars Express and NASA 2005 missions may reveal buried craters, though it is uncertain if the resolution will allow the detection of diagnostic features of marine-target craters. The implications regarding the discovery of marine-target craters on Mars is not without significance, as such discoveries would help address the ongoing debate of whether large water bodies occupied the northern plains of Mars and would help constrain future paleoclimatic reconstructions. ?? Meteoritical Society, 2004.

Occurrence and mechanisms of impact melt emplacement at small lunar craters

NASA Astrophysics Data System (ADS)

Stopar, Julie D.; Hawke, B. Ray; Robinson, Mark S.; Denevi, Brett W.; Giguere, Thomas A.; Koeber, Steven D.

2014-11-01

Using observations from the Lunar Reconnaissance Orbiter Camera (LROC), we assess the frequency and occurrence of impact melt at simple craters less than 5 km in diameter. Nine-hundred-and-fifty fresh, randomly distributed impact craters were identified for study based on their maturity, albedo, and preservation state. The occurrence, frequency, and distribution of impact melt deposits associated with these craters, particularly ponded melt and lobate flows, are diagnostic of melt emplacement mechanisms. Like larger craters, those smaller than a few kilometers in diameter often exhibit ponded melt on the crater floor as well as lobate flows near the crater rim crest. The morphologies of these deposits suggest gravity-driven flow while the melt was molten. Impact melt deposits emplaced as veneers and ;sprays;, thin layers of ejecta that drape other crater materials, indicate deposition late in the cratering process; the deposits of fine sprays are particularly sensitive to degradation. Exterior melt deposits found near the rims of a few dozen craters are distributed asymmetrically around the crater and are rare at craters less than 2 km in diameter. Pre-existing topography plays a role in the occurrence and distribution of these melt deposits, particularly for craters smaller than 1 km in diameter, but does not account for all observed asymmetries in impact melt distribution. The observed relative abundance and frequency of ponded melt and flows in and around simple lunar craters increases with crater diameter, as was previously predicted from models. However, impact melt deposits are found more commonly at simple lunar craters (i.e., those less than a few kilometers in diameter) than previously expected. Ponded melt deposits are observed in roughly 15% of fresh craters smaller than 300 m in diameter and 80% of fresh craters between 600 m and 5 km in diameter. Furthermore, melt deposits are observed at roughly twice as many non-mare craters than at mare craters. We infer that the distributions and occurrences of impact melt are strongly influenced by impact velocity and angle, target porosity, pre-existing topography, and degradation. Additionally, areally small and volumetrically thin melt deposits are sensitive to mixing with solid debris and/or burial during the modification stage of impact cratering as well as post-cratering degradation. Thus, the production of melt at craters less than ∼800 m in diameter is likely greater than inferred from the present occurrence of melt deposits, which is rapidly affected by ongoing degradation processes.

Apollo 12 Mission image - High oblique view of crater Copernicus and Carpathian Mt. range

NASA Image and Video Library

1969-11-19

AS12-47-6876 (November 1969) --- An Apollo 12 high-oblique view of the lunar nearside looking northeast toward the crater Copernicus (in center near horizon), as photographed from lunar orbit. The shaded crater in the foreground is Reinhold. Reinhold B is the crater next to Reinhold which as the small crater in the center of it. Also, visible is the keyhole-shaped crater Fauth near the crater Copernicus.

An assessment of crater erosional histories on the Earth and Mars using digital terrain models.

NASA Astrophysics Data System (ADS)

Paul, R. L.; Muller, J.-P.; Murray, J. B.

The research will examine quantitatively the geomorphology of both Terrestrial and Martian craters. The erosional and sub-surface processes will be investigated to understand how these affect a crater's morphology. For example, the Barringer crater in Arizona has an unusual shape. The Earth has a very high percentage of water both in the atmosphere as clouds or rain and under the surface. The presence of water will therefore affect a crater's formation and its subsequent erosional modification. On Mars there is little or no water present currently, though recent observations suggest there may be near-surface ice in some areas. How do craters formed in the Martian environment therefore differ from Terrestrial ones? How has the structure of Martian craters changed in areas of possible fluvial activity? How does the surface material affect crater formation? How does the Earth's fluvial activity affect a crater's evolution? At present, four measurements of circularity have been used to describe a crater (Murray & Guest, 1972). These parameters will be re-examined to see how effectively they describe Terrestrial and Martian craters using high resolution DTMs which were not available at the time of the original study. The model described by Forsberg-Taylor et al. 2004, and others will also be applied to results obtained from the chosen craters to assess how effectively these craters are described. Both hypsometric curves and hydrological analysis will be used to assess crater evolution. A suitable criterion for the selection of Terrestrial and Martian craters is essential for this type of research. Terrestrial craters have been selected in arid or semi-arid terrain with crater diameters larger than one kilometre. Craters less than five million years old would be ideal. However, this was too restrictive and so a variety of crater ages have had to be used. Eight terrestrial craters have been selected in arid or semi-arid areas for study, using the Earth Impact Database and ICEDS. These are: Barringer, Arizona, U.S.A; Goat Paddock, West Australia; Ouarkziz, Algeria; Roter Kamm, Namibia; Talemzane, Algeria; Tenoumer, Mauritania; Tswaing, South Africa 1 and Upheaval Dome, Utah, U.S.A. Comparable Martian craters are in the process of being chosen using the USGS PIGWAD database and the Morphological Catalogue of the Craters of Mars. Digital Terrain Models of each crater using SRTM DEMs and data from the recent Mars Express HRSC will be used at various resolutions (30m upwards) to provide three dimensional models to assess the capabilities of measuring erosional effects. There is also available ASTER DEMs and ASTER Level 1A for terrestrial craters and MOLA tracks for Martian craters. Both laboratory and theoretical models of crater shape and erosion features will provide a better understanding of the processes observed. This will enable us to develop a better explanation of why craters are the shape they are. References. Barlow N., 1987, Crater Size-Frequency Distribution and a Revised Martian Relative Chronology, Icarus, 75, 285-305. Barlow, N., 1995, The degradation of impact craters in Maja Valles and Arabia Mars, Journal GeoPhys. Res., 100, 23307-23316. Earth Impact Database http://www.unb.ca/passc/ImpactDatabase/ Earth PIGWAD database http://webgis.wr.usgs.gov/website/mars%5Fcrater%5Fhtml/viewer.htm ICEDS http://iceds.ge.ucl.ac.uk/ Morphology Catalogue of the Craters of Mars http://selena.sai.msu.ru/Home/Mars_Cat/Mars_Cat.htm Murray J.B, Guest J.E, 1970, Circularities of craters and related structures on Earth and Moon, Modern Geology, 1, 149-159. Forsberg-Taylor N., Howard A.D., 2004, Crater degradation in the Martian Highlands: Morphometric Analysis of the Sinus Sabaeus region and simulation modelling suggest fluvial processes, Journal GeoPhys Res., 109, E05002. 2

Small Rayed Crater Ejecta Retention Age Calculated from Current Crater Production Rates on Mars

NASA Technical Reports Server (NTRS)

Calef, F. J. III; Herrick, R. R.; Sharpton, V. L.

2011-01-01

Ejecta from impact craters, while extant, records erosive and depositional processes on their surfaces. Estimating ejecta retention age (Eret), the time span when ejecta remains recognizable around a crater, can be applied to estimate the timescale that surface processes operate on, thereby obtaining a history of geologic activity. However, the abundance of sub-kilometer diameter (D) craters identifiable in high resolution Mars imagery has led to questions of accuracy in absolute crater dating and hence ejecta retention ages (Eret). This research calculates the maximum Eret for small rayed impact craters (SRC) on Mars using estimates of the Martian impactor flux adjusted for meteorite ablation losses in the atmosphere. In addition, we utilize the diameter-distance relationship of secondary cratering to adjust crater counts in the vicinity of the large primary crater Zunil.

Regional variations in degradation and density of Martian craters.

NASA Technical Reports Server (NTRS)

Mcgill, G. E.; Wise, D. U.

1972-01-01

Martian craters visible on Mariner 6 and 7 imagery show a spectrum of topographic types from very fresh to highly degraded. A method of numerical scoring of rim, wall, and floor is proposed to yield a degradation number to classify each crater. Plots of degradation class vs density of large craters are similar for all four regions studied, whereas similar plots for small craters show marked differences between regions. The data suggest general continuity of crater formation and degradation, along with locally sporadic formation and/or degradation of the smallest craters classified. Deucalionis Regio, with an excess of fresh, small craters, experienced an episode of small crater formation (or nondegradation) most recently; Margaritifer Sinus was similarly disturbed at some more remote time. Meridiani Sinus and Hellespontus-Noachis show little or no sign of excess fresh, small craters.

Rampart craters on Ganymede: Their implications for fluidized ejecta emplacement

NASA Astrophysics Data System (ADS)

Boyce, Joseph; Barlow, Nadine; Mouginis-Mark, Peter; Stewart, Sarah

2010-04-01

Some fresh impact craters on Ganymede have the overall ejecta morphology similar to Martian double-layer ejecta (DLE), with the exception of the crater Nergal that is most like Martian single layer ejecta (SLE) craters (as is the terrestrial crater Lonar). Similar craters also have been identified on Europa, but no outer ejecta layer has been found on these craters. The morphometry of these craters suggests that the types of layered ejecta craters identified by Barlow et al. (2000) are fundamental. In addition, the mere existence of these craters on Ganymede and Europa suggests that an atmosphere is not required for ejecta fluidization, nor can ejecta fluidization be explained by the flow of dry ejecta. Moreover, the absence of fluidized ejecta on other icy bodies suggests that abundant volatiles in the target also may not be the sole cause of ejecta fluidization. The restriction of these craters to the grooved terrain of Ganymede and the concentration of Martian DLE craters on the northern lowlands suggests that these terrains may share key characteristics that control the development of the ejecta of these craters. In addition, average ejecta mobility (EM) ratios indicate that the ejecta of these bodies are self-similar with crater size, but are systematically smaller on Ganymede and Europa. This may be due to the effects of the abundant ice in the crusts of these satellites that results in increased ejection angle causing ejecta to impact closer to the crater and with lower horizontal velocity.

Impact Craters: Size-Dependent Degration Rates

NASA Astrophysics Data System (ADS)

Ravi, S.; Mahanti, P.; Meyer, H. M.; Robinson, M. S.

2017-12-01

From superposition relations, Shoemaker and Hackman (1) devised the lunar geologic timescale with Copernican and Eratosthenian as the most recent periods. Classifying craters into the two periods is key to understanding impactor flux and regolith maturation rates over the last 3 Ga. Both Copernican and Eratosthenian craters exhibit crisp morphologies (sharp rims, steep slopes), however, only the former exhibit high reflectance rays and ejecta (1). Based on the Optical Maturity Parameter (OMAT; 2), Grier et al. (3) classified 50 fresh craters (D >20 km) into 3 categories - young (OMAT >0.22), intermediate, and old (OMAT <0.16). In our previous work, Copernican craters (D > 10) were identified (4) from a catalogue of 11,875 craters (5). In this work; we compare two size ranges (D: 5 km - 10 km and 10 km to 15 km) of 177 Copernican craters based on the average OMAT, measured near the crater rim (3). OMAT is measured at the crater rim (as opposed to further away from the crater) to minimize the influence of spatial variation of OMAT (6) in our investigation. We found that OMAT values are typically lower for smaller craters (5km < D < 10km) in comparison to larger craters (10km < D < 15km). However, when compared against morphological freshness (as determined by d/D for simpler craters), the smaller craters were fresher (higher d/D value). Since the OMAT value decreases with age, craters with higher d/D value (morphologically fresher) should have higher OMAT, but this is not the case. We propose that quicker loss of OMAT (over time) for smaller craters compared to decrease in d/D with crater ageing, is responsible for the observed decreased OMAT for smaller craters. (1) Shoemaker and Hackman, 1962 (2) Lucey et al., 2000 (3) Grier et al., 2001 (4) Ravi et al., 2016 (5) Reinhold et al., 2015 (6) Mahanti et al., 2016

Ancient fluvial processes in the equatorial highlands of Mars

NASA Technical Reports Server (NTRS)

Craddock, Robert A.; Maxwell, Ted A.

1991-01-01

Martian highland craters typically lack ejecta deposits, have no noticeable rim, and are flat floored. In addition, crater size frequency distribution curves show that highland craters have depleted populations less than 20 km in diameter. A variety of processes have been suggested to explain these observations including deposition of aeolian or volcanic materials up to the crater rim crests, thermal creep, terrain softening, and mass wasting. However, none of these processes adequately explains both the crater morphology and population distribution. In order to explain both the Martian highland crater morphology and population distribution, a fluvial process is proposed which is capable of removing the loose crater rim material. The resulting effect is to decrease the crater diameter, thereby causing the population curves to bendover. The eroded material is redistributed, burying or partially burying smaller diameter craters before complete erosion. This material may also be deposited into local topographic lows, creating the depositional basins observed. A fluvial process explains both sets of observations: crater morphology and crater population distribution curves.

Multivariate analyses of crater parameters and the classification of craters

NASA Technical Reports Server (NTRS)

Siegal, B. S.; Griffiths, J. C.

1974-01-01

Multivariate analyses were performed on certain linear dimensions of six genetic types of craters. A total of 320 craters, consisting of laboratory fluidization craters, craters formed by chemical and nuclear explosives, terrestrial maars and other volcanic craters, and terrestrial meteorite impact craters, authenticated and probable, were analyzed in the first data set in terms of their mean rim crest diameter, mean interior relief, rim height, and mean exterior rim width. The second data set contained an additional 91 terrestrial craters of which 19 were of experimental percussive impact and 28 of volcanic collapse origin, and which was analyzed in terms of mean rim crest diameter, mean interior relief, and rim height. Principal component analyses were performed on the six genetic types of craters. Ninety per cent of the variation in the variables can be accounted for by two components. Ninety-nine per cent of the variation in the craters formed by chemical and nuclear explosives is explained by the first component alone.

Phobos - Surface density of impact craters

NASA Technical Reports Server (NTRS)

Thomas, P.; Veverka, J.

1977-01-01

Revised crater counts for Phobos are presented which are based on uniform Mariner 9 imagery and Duxbury's (1974) map of the satellite. The contiguous portion of the satellite's surface on which all craters down to the limiting resolution of 0.2 to 0.3 km in diameter would be expected to be identified is delineated and found to contain 87 identifiable craters larger than 0.2 km in diameter. Analysis of the crater size distribution shows that the surface appears to be saturated for craters exceeding 1 km in diameter but the crater counts definitely fall below the saturation curve for smaller craters. Reasons for this fall-off are considered, and it is noted that too few craters are visible in Mariner 9 images of Deimos to permit meaningful crater counts on that satellite's surface. It is concluded that, contrary to a previous assertion, the surfaces of Phobos and Deimos are not known to be saturated with craters larger than 0.2 km in diameter.

On the SLq(2) extension of the standard model and the concept of charge

NASA Astrophysics Data System (ADS)

Finkelstein, Robert J.

2017-01-01

Our SLq(2) extension of the standard model is constructed by replacing the elementary field operators, Ψ(x), of the standard model by Ψ̂mm‧j(x)D mm‧j where Dmm‧j is an element of the (2j + 1)-dimensional representation of the SLq(2) algebra, which is also the knot algebra. The allowed quantum states (j,m,m‧) are restricted by the topological conditions (j,m,m‧) = 1 2(N,w,r + o) postulated between the states of the quantum knot (j,m,m‧) and the corresponding classical knot (N,w,r + o) where the (N,w,r) are (the number of crossings, the writhe, the rotation) of the 2d projection of the corresponding oriented classical knot. Here, o is an odd number that is required by the difference in parity between w and r. There is also the empirical restriction on the allowed states (j,m,m‧) = 3(t,-t 3,-t0)L that holds at the j = 3 2 level, connecting quantum trefoils 3 2,m,m‧ with leptons and quarks 1 2,-t3,-t0L. The so-constructed knotted leptons and quarks turn out to be composed of three j = 1 2 particles which unexpectedly agree with the preon models of Harrari and Shupe. The j = 0 particles, being electroweak neutral, are dark and plausibly greatly outnumber the quarks and leptons. The SLq(2) or (j,m,m‧) measure of charge has a direct physical interpretation since 2j is the total number of preonic charges while 2m and 2m‧ are the numbers of writhe and rotation sources of preonic charge. The total SLq(2) charge of a particle, measured by writhe and rotation and composed of preons, sums the signs of the counterclockwise turns (+1) and clockwise turns (-1) that any energy-momentum current makes in going once around the knot. In this way, the handedness of the knot reduces charge to a geometric concept similar to the way that curvature of space-time encodes mass and energy. According to this model, the leptons and quarks are j = 3 2 particles, the preons are j = 1 2 particles, and the j = 0 particles are candidates for dark matter. It is possible to understand q as a simple deformation parameter or as the ratio e/g of the electroweak to the gluon coupling constants.

On the usefulness of optical maturity for relative age classification of fresh craters

NASA Astrophysics Data System (ADS)

Ravi, S.; Meyer, H. M.; Mahanti, P.; Robinson, M. S.

2016-12-01

Copernican and Eratosthenian craters represent the two most recent geologic periods in the lunar timescale, and their characterization is essential for understanding impact crater flux over the last 3 Gy. Craters from both periods exhibit crisp morphologies, but Copernican craters are 'rayed craters' per Wilhelms (1) classification scheme. Distinguishing compositional from maturity rays is possible using compositional estimates and the optical maturity parameter (OMAT; 2). From OMAT estimates, Grier et al. (3) classified 50 fresh craters (diameter (D) > 20 km) into young (OMAT > 0.22), intermediate, and old (OMAT < 0.16) classes. In this work we analyze morphology and optical maturity for a population of 12,000 craters (D> 10 km; 60 to investigate the applicability of OMAT for relative age classification among Copernican craters. Craters obtained from (4,5) were initially classified based on crispness of morphology (LROC WAC observations (6)) and then were then analyzed based on OMAT values averaged from rim out to one crater radius (n=2000). We found that typically craters larger than Copernicus (D = 95 km) were had lower OMAT values than Copernicus (OMAT = 0.17) except for Vavilov, Pythagorus, Fizeau and Moretus which had OMAT > 0.17. These large craters are clearly affected by rays from small, nearby craters. We estimate that at least 250 craters (D > 10 km; OMAT > 0.22) on the Moon are Copernican (> 2% of all craters analyzed) and of these at least 100 are as optically immature (or more so) than Tycho crater (OMAT >= 0.24). A calibration curve (OMAT vs Absolute Model Age) obtained for craters with known ages showed that OMAT <=0.15 displays little change with AMA and are thus unsuitable for estimating relative ages. Normalization by crater size was found to reduce the uncertainty associated with the relation between AMA and OMAT. 1) Wilhelms (1987), The Geologic History of the Moon, USGS, pp. 1348. 2) Lucey et al (2000), JGR, 105, 20377-20386. 3) Grier et al. (2001), JGR, 106, 847-862. 4) Povilaitis et al. (2013), NLSI, Session 5B. 5) Head et al. (2010), Science, 239, 1504-1506. 6) Boyd et al. (2013), AGU, P13B-1744.

Gully formation in terrestrial simple craters: Meteor Crater, USA and Lonar Crater, India

NASA Astrophysics Data System (ADS)

Kumar, P.; Head, J. W.; Kring, D. A.

2007-12-01

Geomorphic features such as gullies, valley networks, and channels on Mars have been used as a proxy to understand the climate and landscape evolution of Mars. Terrestrial analogues provide significant insight as to how the various exogenic and endogenic processes might contribute to the evolution of these martian landscapes. We describe here a terrestrial example from Meteor Crater, which shows a spectacular development of gullies throughout the inner wall in response to rainwater precipitation, snow melting and groundwater discharge. As liquid water has been envisaged as one of the important agents of landscape sculpturing, Meteor Crater remains a useful landmark, where planetary geologists can learn some lessons. We also show here how the lithology and structural framework of this crater controls the gully distribution. Like many martian impact craters, it was emplaced in layered sedimentary rocks with an exceptionally well-developed centripetal drainage pattern consisting of individual alcoves, channels and fans. Some of the gullies originate from the rim crest and others from the middle crater wall, where a lithologic transition occurs. Deeply incised alcoves are well-developed on the soft sandstones of the Coconino Formation exposed on the middle crater wall, beneath overlying dolomite. In general, the gully locations are along crater wall radial fractures and faults, which are favorable locales of groundwater flow and discharge; these structural discontinuities are also the locales where the surface runoff from rain precipitation and snow melting can preferentially flow, causing degradation. Like martian craters, channels are well developed on the talus deposits and alluvial fans on the periphery of the crater floor. In addition, lake sediments on the crater floor provide significant evidence of a past pluvial climate, when groundwater seeped from springs on the crater wall. Caves exposed on the lower crater level may point to percolation of surface runoff and selective discharge through fractures on the crater wall. Similar relationships are seen at Lonar Crater, India. Although these hydrological processes continue at Meteor Crater today, conditions at the crater are much more arid than they were soon after impact, reflecting a climatic shift similar in direction to that inferred for Mars.

Impact craters on Titan

USGS Publications Warehouse

Wood, Charles A.; Lorenz, Ralph; Kirk, Randy; Lopes, Rosaly; Mitchell, Karl; Stofan, Ellen; ,

2010-01-01

Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles.

Impact craters on Titan

USGS Publications Warehouse

Wood, C.A.; Lorenz, R.; Kirk, R.; Lopes, R.; Mitchell, Ken; Stofan, E.

2010-01-01

Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles. ?? 2009 Elsevier Inc.

An investigation of the cratering-induced motions occurring during the formation of bowl-shaped craters. [using high explosive charges as the cratering source

NASA Technical Reports Server (NTRS)

Piekutowski, A. J.

1980-01-01

The effects of the dynamic processes which occur during crater formation were examined using small hemispherical high-explosive charges detonated in a tank which had one wall constructed of a thick piece of clear plexiglas. Crater formation and the motions of numerous tracer particles installed in the cratering medium at the medium-wall interface were viewed through the wall of this quarter-space tank and recorded with high-speed cameras. Subsequent study and analysis of particle motions and events recorded on the film provide data needed to develop a time-sequence description of the formation of a bowl-shaped crater. Tables show the dimensions of craters produced in a quarter-space tank compared with dimensions of craters produced in normal half-space tanks. Crater growth rate summaries are also tabulated.

The Lord of the Rings - Deep Learning Craters on the Moon and Other Bodies

NASA Astrophysics Data System (ADS)

Silburt, Ari; Ali-Dib, Mohamad; Zhu, Chenchong; Jackson, Alan; Valencia, Diana; Kissin, Yevgeni; Tamayo, Daniel; Menou, Kristen

2018-01-01

Crater detection has traditionally been done via manual inspection of images, leading to statistically significant disagreements between scientists for the Moon's crater distribution. In addition, there are millions of uncategorized craters on the Moon and other Solar System bodies that will never be classified by humans due to the time required to manually detect craters. I will show that a deep learning model trained on the near-side of the Moon can successfully reproduce the crater distribution on the far-side, as well as detect thousands of small, new craters that were previously uncharacterized. In addition, this Moon-trained model can be transferred to accurately classify craters on Mercury. It is therefore likely that this model can be extended to classify craters on all Solar System bodies with Digital Elevation Maps. This will facilitate, for the first time ever, a systematic, accurate, and reproducible study of the crater records throughout the Solar System.

Ceres and the terrestrial planets impact cratering record

NASA Astrophysics Data System (ADS)

Strom, R. G.; Marchi, S.; Malhotra, R.

2018-03-01

Dwarf planet Ceres, the largest object in the Main Asteroid Belt, has a surface that exhibits a range of crater densities for a crater diameter range of 5-300 km. In all areas the shape of the craters' size-frequency distribution is very similar to those of the most ancient heavily cratered surfaces on the terrestrial planets. The most heavily cratered terrain on Ceres covers ∼15% of its surface and has a crater density similar to the highest crater density on <1% of the lunar highlands. This region of higher crater density on Ceres probably records the high impact rate at early times and indicates that the other 85% of Ceres was partly resurfaced after the Late Heavy Bombardment (LHB) at ∼4 Ga. The Ceres cratering record strongly indicates that the period of Late Heavy Bombardment originated from an impactor population whose size-frequency distribution resembles that of the Main Belt Asteroids.

A proposed origin for palimpsests and anomalous pit craters on Ganymede and Callisto

NASA Technical Reports Server (NTRS)

Croft, S. K.

1983-01-01

The hypothesis that palimpsests and anomalous pit craters are essentially pristine crater forms derived from high-velocity impacts and/or impacts into an ice crust with preimpact temperatures near melting is explored. The observational data are briefly reviewed, and an impact model is proposed for the direct formation of a palimpsest from an impact when the modification flow which produces the final crater is dominated by 'wet' fluid flow, as opposed to the 'dry' granular flow which produces normal craters. Conditions of 'wet' modification occur when the volume of impact melt remaining in the transient crater attains a volume comparable to the transient crater. The normal crater-palimpsest transition is found to occur for sufficiently large impacts or sufficiently fast impactors. The range of crater diameters and morphological characteristics inferred from the impact model is consistent with the observed characteristics of palimpsests and anomalous pit craters.

A first-order model for impact crater degradation on Venus

NASA Technical Reports Server (NTRS)

Izenberg, Noam R.; Arvidson, Raymond E.; Phillips, Roger J.

1993-01-01

A first-order impact crater aging model is presented based on observations of the global crater population of Venus. The total population consists of 879 craters found over the approximately 98 percent of the planet that has been mapped by the Magellan spacecraft during the first three cycles of its mission. The model is based upon three primary aspects of venusian impact craters: (1) extended ejecta deposits (EED's); (2) crater rims and continuous ejecta deposits; and (3) crater interiors and floors.

Martian Central Pit Craters

NASA Technical Reports Server (NTRS)

Hillman, E.; Barlow, N. G.

2005-01-01

Impact craters containing central pits are rare on the terrestrial planets but common on icy bodies. Mars is the exception among the terrestrial planets, where central pits are seen on crater floors ( floor pits ) as well as on top of central peaks ( summit pits ). Wood et al. [1] proposed that degassing of subsurface volatiles during crater formation produced central pits. Croft [2] argued instead that central pits might form during the impact of volatile-rich comets. Although central pits are seen in impact craters on icy moons such as Ganymede, they do show some significant differences from their martian counterparts: (a) only floor pits are seen on Ganymede, and (b) central pits begin to occur at crater diameters where the peak ring interior morphology begins to appear in terrestrial planet craters [3]. A study of craters containing central pits was conducted by Barlow and Bradley [4] using Viking imagery. They found that 28% of craters displaying an interior morphology on Mars contain central pits. Diameters of craters containing central pits ranged from 16 to 64 km. Barlow and Bradley noted that summit pit craters tended to be smaller than craters containing floor pits. They also noted a correlation of central pit craters with the proposed rings of large impact basins. They argued that basin ring formation fractured the martian crust and allowed subsurface volatiles to concentrate in these locations. They favored the model that degassing of the substrate during crater formation was responsible for central pit formation due to the preferential location of central pit craters along these basin rings.

Why do complex impact craters have elevated crater rims?

NASA Astrophysics Data System (ADS)

Kenkmann, Thomas; Sturm, Sebastian; Krueger, Tim

2014-05-01

Most of the complex impact craters on the Moon and on Mars have elevated crater rims like their simple counterparts. The raised rim of simple craters is the result of (i) the deposition of a coherent proximal ejecta blanket at the edge of the transient cavity (overturned flap) and (ii) a structural uplift of the pre-impact surface near the transient cavity rim during the excavation stage of cratering [1]. The latter occurs either by plastic thickening or localized buckling of target rocks, as well as by the emplacement of interthrust wedges [2] or by the injection of dike material. Ejecta and the structural uplift contribute equally to the total elevation of simple crater rims. The cause of elevated crater rims of large complex craters [3] is less obvious, but still, the rim height scales with the final crater diameter. Depending on crater size, gravity, and target rheology, the final crater rim of complex craters can be situated up to 1.5-2.0 transient crater radii distance from the crater center. Here the thickness of the ejecta blanket is only a fraction of that occurring at the rim of simple craters, e.g. [4], and thus cannot account for a strong elevation. Likewise, plastic thickening including dike injection of the underlying target may not play a significant role at this distance any more. We started to systematically investigate the structural uplift and ejecta thickness along the rim of complex impact craters to understand the cause of their elevation. Our studies of two lunar craters (Bessel, 16 km diameter and Euler, 28 km diameter) [5] and one unnamed complex martian crater (16 km diameter) [6] showed that the structural uplift at the final crater rim makes 56-67% of the total rim elevation while the ejecta thickness contributes 33-44%. Thus with increasing distance from the transient cavity rim, the structural uplift seems to dominate. As dike injection and plastic thickening are unlikely at such a distance from the transient cavity, we propose that reverse faulting induced by radially outward directed maximum stresses during the excavation flow may be responsible for the elevation of complex crater rims. This hypothesis is tested at terrestrial craters whose apparent crater rims are often confined by circumferential faults [7]. References:[1] Shoemaker, E. M. (1963) The Solar System, 4, 301-336. [2] Poelchau M.H. et al. (2009), JGR, 114, E01006. [3] Settle, M., and Head, J.W., (1977), Icarus, 31, 123. [4] McGetchin, T. R., et al., (1973), EPSL, 20, 226.[5] Krüger T. et al. (2014), LPSC 45, #1834. [6] Sturm, S. et al. (2014), LPSC 45, 1801. [7] Turtle, E. et al. (2005), GSA-SP. 384, 1.

Low-velocity impact craters in ice and ice-saturated sand with implications for Martian crater count ages.

USGS Publications Warehouse

Croft, S.K.; Kieffer, S.W.; Ahrens, T.J.

1979-01-01

We produced a series of decimeter-sized impact craters in blocks of ice near 0oC and -70oC and in ice-saturated sand near -70oC as a preliminary investigation of cratering in materials analogous to those found on Mars and the outer solar satellites. Crater diameters in the ice-saturated sand were 2 times larger than craters in the same energy and velocity range in competent blocks of granite, basalt and cement. Craters in ice were c.3 times larger. Martian impact crater energy versus diameter scaling may thus be a function of latitude. -from Authors

Experimental Simulations of Large-Scale Collisions

NASA Technical Reports Server (NTRS)

Housen, Kevin R.

2002-01-01

This report summarizes research on the effects of target porosity on the mechanics of impact cratering. Impact experiments conducted on a centrifuge provide direct simulations of large-scale cratering on porous asteroids. The experiments show that large craters in porous materials form mostly by compaction, with essentially no deposition of material into the ejecta blanket that is a signature of cratering in less-porous materials. The ratio of ejecta mass to crater mass is shown to decrease with increasing crater size or target porosity. These results are consistent with the observation that large closely-packed craters on asteroid Mathilde appear to have formed without degradation to earlier craters.

Shallow and deep fresh impact craters in Hesperia Planum, Mars

NASA Technical Reports Server (NTRS)

Mouginis-Mark, Peter J.; Hayashi, Joan N.

1993-01-01

The depths of 109 impact craters about 2-16 km in diameter, located on the ridged plains materials of Hesperia Planum, Mars, have been measured from their shadow lengths using digital Viking Orbiter images (orbit numbers 417S-419S) and the PICS computer software. On the basis of their pristine morphology (very fresh lobate ejecta blankets, well preserved rim crests, and lack of superposed impact craters), 57 of these craters have been selected for detailed analysis of their spatial distribution and geometry. We find that south of 30 deg S, craters less than 6.0 km in diameter are markedly shallower than similar-sized craters equatorward of this latitude. No comparable relationship is observed for morphologically fresh craters greater than 6.0 km diameter. We also find that two populations exist for older craters less than 6.0 km diameter. When craters that lack ejecta blankets are grouped on the basis of depth/diameter ratio, the deeper craters also typically lie equatorward of 30 S. We interpret the spatial variation in crater depth/diameter ratios as most likely due to a poleward increase in volatiles within the top 400 m of the surface at the times these craters were formed.

Lunar and Venusian radar bright rings

NASA Technical Reports Server (NTRS)

Thompson, T. W.; Saunders, R. S.; Weissman, D. E.

1986-01-01

Twenty-one lunar craters have radar bright ring appearances which are analogous to eleven complete ring features in the earth-based 12.5 cm observations of Venus. Radar ring diameters and widths for the lunar and Venusian features overlap for sizes from 45 to 100 km. Radar bright areas for the lunar craters are associated with the slopes of the inner and outer rim walls, while level crater floors and level ejecta fields beyond the raised portion of the rim have average radar backscatter. It is proposed that the radar bright areas of the Venusian rings are also associated with the slopes on the rims of craters. The lunar craters have evolved to radar bright rings via mass wasting of crater rim walls and via post-impact flooding of crater floors. Aeolian deposits of fine-grained material on Venusian crater floors may produce radar scattering effects similar to lunar crater floor flooding. These Venusian aeolian deposits may preferentially cover blocky crater floors producing a radar bright ring appearance. It is proposed that the Venusian features with complete bright ring appearances and sizes less than 100 km are impact craters. They have the same sizes as lunar craters and could have evolved to radar bright rings via analogous surface processes.

The Explorer's Guide to Impact Craters

NASA Technical Reports Server (NTRS)

Chuang, F.; Pierazzo, E.; Osinski, G.

2005-01-01

Impact cratering is a fundamental geologic process of our solar system. It competes with other processes, such as plate tectonics, volcanism, fluvial, glacial and eolian activity, in shaping the surfaces of planetary bodies. In some cases, like the Moon and Mercury, impact craters are the dominant landform. On other planetary bodies impact craters are being continuously erased by the action of other geological processes, like volcanism on Io, erosion and plate tectonics on the Earth, tectonic and volcanic resurfacing on Venus, or ancient erosion periods on Mars. The study of crater populations is one of the principal tools for understanding the geologic history of a planetary surface. Among the general public, impact cratering has drawn wide attention through its portrayal in several Hollywood movies. Questions that are raised after watching these movies include: How do scientists learn about impact cratering? , and What information do impact craters provide in understanding the evolution of a planetary surface? Fundamental approaches used by scientists to learn about impact cratering include field work at known terrestrial craters, remote sensing studies of craters on various solid surfaces of solar system bodies, and theoretical and laboratory studies using the known physics of impact cratering.

The phanerozoic impact cratering rate: Evidence from the farside of the Moon

USGS Publications Warehouse

McEwen, A.S.; Moore, Johnnie N.; Shoemaker, E.M.

1997-01-01

The relatively recent (< 1 b.y.) flux of asteroids and comets forming large craters on the Earth and Moon may be accurately recorded by craters with bright rays on the Moon's farside. Many previously unknown farside rayed craters are clearly distinguished in the low-phase-angle images returned by the Clementine spacecraft. Some large rayed craters on the lunar nearside are probably significantly older than 1 Ga; rays remain visible over the maria due to compositional contrasts long after soils have reached optical maturity. Most of the farside crust has a more homogeneous composition and only immature rays are visible. The size-frequency distribution of farside rayed craters is similar to that measured for Eratosthenian craters (up to 3.2 b.y.) at diameters larger than 15 km. The areal density of farside rayed craters matches that of a corrected tabulation of nearside Copernican craters. Hence the presence of bright rays due to immature soils around large craters provides a consistent time-stratigraphic basis for defining the base of the Copernican System. The density of large craters less than ???3.2 b.y. old is ???3.2 times higher than that of large farside rayed craters alone. This observation can be interpreted in two ways: (1) the average cratering rate has been constant over the past 3.2 b.y. and the base of the Copernican is ???1 Ga, or (2) the cratering rate has increased in recent geologic time and the base of the Copernican is less than 1 Ga. We favor the latter interpretation because the rays of Copernicus (800-850 m.y. old) appear to be very close to optical maturity, suggesting that the average Copernican cratering rate was ???35% higher than the average Eratosthenian rate. Other lines of evidence for an increase in the Phanerozoic (545 Ga) cratering rate are (1) the densities of small craters superimposed on Copernicus and Apollo landing sites, (2) the rates estimated from well-dated terrestrial craters (??? 120 m.y.) and from present-day astronomical observations, and (3) the Proterozoic rate suggested by the crater record of Australia. The hypothesis most consistent with several key observations is that the cratering rate has increased by ???2x during the past ???300 m.y. Copyright 1997 by the American Geophysical Union.

Styles of crater gradation in Southern Ismenius Lacus, Mars

NASA Technical Reports Server (NTRS)

Grant, J. A.; Schultz, P. H.

1991-01-01

Preserved morphology around selected impact craters together with results from study of long term gradational evolution are used to assess processes responsible for crater modification in southern Ismenius Lacus. Results are compared with the gradational styles of selected terrestrial craters. Although most craters in the region display complex primary morphologies, some first order comparisons with the gradational styles around simple terrestrial craters may be valid. Nearly complete high resolution coverage provides a basis for studying morphologic features at scales comparable to those observed in LANDSAT TM images of terrestrial craters. It is concluded that the relative importance of gradational processes differs around the terrestrial and Martian craters considered here: Martian rimless morphologies are produced by mass wasting, eolian deposition/erosion, and limited fluvial incisement resulting in downwasting and significant backwasting of crater walls.

Crater Age and Hydrogen Content in Lunar Regolith from LEND Neutron Data

NASA Astrophysics Data System (ADS)

Sanin, Anton; Starr, Richard; Litvak, Maxim; Petro, Noah; Mitrofanov, Igor

2017-04-01

We are presenting an analysis of Lunar Exploration Neutron Detector (LEND) epithermal neutron count rates for a large set of mid-latitude craters. Epithermal neutron count rates for crater interiors measured by the LEND Sensor for Epithermal Neutrons (SETN) were compared to crater exteriors for 322 craters. An increase in relative count rate at about 9-sigma confidence level was found, consistent with a lower hydrogen content. A smaller subset of 31 craters, all located near three Copernican era craters, Jackson, Tycho, and Necho, also shows a significant increase in Optical Maturity parameter implying an immature regolith. The increase in SETN count rate for these craters is greater than the increase for the full set of craters by more than a factor of two.

Crater Age and Hydrogen Content in Lunar Regolith from LEND Neutron Data

NASA Technical Reports Server (NTRS)

Starr, Richard D.; Litvak, Maxim L.; Petro, Noah E.; Mitrofanov, Igor G.; Boynton, William V.; Chin, Gordon; Livengood, Timothy A.; McClanahan, Timothy P.; Sanin, Anton B.; Sagdeev, Roald Z.;

Crater gradation in Gusev crater and Meridiani Planum, Mars

NASA Astrophysics Data System (ADS)

Grant, J. A.; Arvidson, R. E.; Crumpler, L. S.; Golombek, M. P.; Hahn, B.; Haldemann, A. F. C.; Li, R.; Soderblom, L. A.; Squyres, S. W.; Wright, S. P.; Watters, W. A.

2006-01-01

The Mars Exploration Rovers investigated numerous craters in Gusev crater and Meridiani Planum during the first ~400 sols of their missions. Craters vary in size and preservation state but are mostly due to secondary impacts at Gusev and primary impacts at Meridiani. Craters at both locations are modified primarily by eolian erosion and infilling and lack evidence for modification by aqueous processes. Effects of gradation on crater form are dependent on size, local lithology, slopes, and availability of mobile sediments. At Gusev, impacts into basaltic rubble create shallow craters and ejecta composed of resistant rocks. Ejecta initially experience eolian stripping, which becomes weathering-limited as lags develop on ejecta surfaces and sediments are trapped within craters. Subsequent eolian gradation depends on the slow production of fines by weathering and impacts and is accompanied by minor mass wasting. At Meridiani the sulfate-rich bedrock is more susceptible to eolian erosion, and exposed crater rims, walls, and ejecta are eroded, while lower interiors and low-relief surfaces are increasingly infilled and buried by mostly basaltic sediments. Eolian processes outpace early mass wasting, often produce meters of erosion, and mantle some surfaces. Some small craters were likely completely eroded/buried. Craters >100 m in diameter on the Hesperian-aged floor of Gusev are generally more pristine than on the Amazonian-aged Meridiani plains. This conclusion contradicts interpretations from orbital views, which do not readily distinguish crater gradation state at Meridiani and reveal apparently subdued crater forms at Gusev that may suggest more gradation than has occurred.

Moon-Mercury: Large impact structures, isostasy and average crustal viscosity

USGS Publications Warehouse

Schaber, G.G.; Boyce, J.M.; Trask, N.J.

1977-01-01

Thirty-five craters and basins larger than 200 km in diameter are recognized on the imaged portion (45%) of Mercury. If the unimaged portion of the planet is similarly cratered, a total of 78 such impact features may be present. Sixty-two craters and basins 200 km in diameter are recognized on the moon, a body with only half the cross-sectional area of Mercury. If surface areas are considered, however, Mercury is cratered only 70% as densely as the moon. The density of impact craters with diameters greater than 400 km on Mercury is only 30% of that on the moon, and for craters with diameters between 400 and 700 km, the density on Mercury is only 21% of the lunar crater density. The size-frequency distribution curve for the large Mercurian craters follows the same cumulative -2 slope as the lunar curve but lies well below the 10% surface saturation level characteristic of the lunar curve. This is taken as evidence that the old heavily cratered terrain on Mercury is, at least presently, not in a state of cratering equilibrium. The reduced density of large craters and basins on Mercury relative to the moon could be either a function of the crater-production rates on these bodies or an effect of different crustal histories. Resurfacing of the planet after the basin-forming period is ruled out by the presence of 54 craters and basins 100 km in diameter and larger (on the imaged portion of Mercury) that have either well-defined or poorly-defined secondary-crater fields. Total isostatic compensation of impact craters ???800 km in diameter indicates that the average viscosity of the Mercurian crust over the past 4+ aeons was the same as that for the moon (???1026.5 P). This calculated viscosity and the distribution of large craters and basins suggest that either the very early crustal viscosity on Mercury was less than that of the moon and the present viscosity greater, or the differences in large crater populations on the two bodies is indeed the result of variations in rates of crater production. ?? 1977.

Modeling turbulent flows in the atmospheric boundary layer of Mars: application to Gale crater, Mars, landing site of the Curiosity rover

NASA Astrophysics Data System (ADS)

Anderson, William; Day, Kenzie; Kocurek, Gary

2016-11-01

Mars is a dry planet with a thin atmosphere. Aeolian processes - wind-driven mobilization of sediment and dust - are the exclusive mode of landscape variability on Mars. Craters are common topographic features on the surface of Mars, and many craters on Mars contain a prominent central mound (NASA's Curiosity rover was landed in Gale crater). Using density-normalized large-eddy simulations, we have modeled turbulent flows over crater-like topographies that feature a central mound. We have also run one simulation of flow over a digital elevation map of Gale crater. Resultant datasets suggest a deflationary mechanism wherein vortices shed from the upwind crater rim are realigned to conform to the crater profile via stretching and tilting. This was accomplished using three-dimensional datasets (momentum and vorticity) retrieved from LES. As a result, helical vortices occupy the inner region of the crater and, therefore, are primarily responsible for aeolian morphodynamics in the crater. We have also used the immersed-boundary method body force distribution to compute the aerodynamic surface stress on the crater. These results suggest that secondary flows - originating from flow separation at the crater - have played an important role in shaping landscape features observed in craters (including the dune fields observed on Mars, many of which are actively evolving). None.

Modeling turbulent flows in the atmospheric boundary layer of Mars: application to Gale crater, Mars, landing site of the Curiosity rover

NASA Astrophysics Data System (ADS)

Anderson, William

2017-04-01

Mars is a dry planet with a thin atmosphere. Aeolian processes - wind-driven mobilization of sediment and dust - are the exclusive mode of landscape variability on Mars. Craters are common topographic features on the surface of Mars, and many craters on Mars contain a prominent central mound (NASA's Curiosity rover was landed in Gale crater). Using density-normalized large-eddy simulations, we have modeled turbulent flows over crater-like topographies that feature a central mound. We have also run one simulation of flow over a digital elevation map of Gale crater. Resultant datasets suggest a deflationary mechanism wherein vortices shed from the upwind crater rim are realigned to conform to the crater profile via stretching and tilting. This was accomplished using three-dimensional datasets (momentum and vorticity) retrieved from LES. As a result, helical vortices occupy the inner region of the crater and, therefore, are primarily responsible for aeolian morphodynamics in the crater. We have also used the immersed-boundary method body force distribution to compute the aerodynamic surface stress on the crater. These results suggest that secondary flows - originating from flow separation at the crater - have played an important role in shaping landscape features observed in craters (including the dune fields observed on Mars, many of which are actively evolving).

What Dominates a Craters Size, the Largest Single Explosion of the Formation Process or the Cumulative Energy of Many? Results of Multiblast Crater Evolution Experiments

NASA Astrophysics Data System (ADS)

Sonder, I.; Graettinger, A. H.; Valentine, G. A.

2015-12-01

Craters of explosive volcanic eruptions are products of many explosions. Such craters are different than products of single events such as meteorite impacts or those produced by military testing because they typically result from multiple, rather than single, explosions. We analyzed the evolution of experimental craters that were created by several detonations of chemical explosives in layered aggregates. A method to calculate an effective explosion depth for non-flat topography (e.g. for explosions below existing craters) is derived, showing how multi-blast crater sizes differ from the single blast case. It is shown that sizes of natural caters (radii, volumes) are not characteristic of the number of explosions, and therefore not characteristic for the total acting energy, that formed a crater. Also the crater size is not simply related to the largest explosion in a sequence, but depends upon that explosion and the energy of that single blast and on the cumulative energy of all blasts that formed the crater. The two energies can be combined to form an effective number of explosions that is characteristic for the crater evolution. The multi-blast crater size evolution implies that it is not correct to estimate explosion energy of volcanic events from crater size using previously published relationships that were derived for single blast cases.

Lonar Lake, India: An impact Crater in basalt

USGS Publications Warehouse

Fredriksson, K.; Dube, A.; Milton, D.J.; Balasundaram, M.S.

1973-01-01

Discovery of shock-metamorphosed material establishes the impact origin of Lonar Crater. Coarse breccia with shatter coning and microbreccia with moderately shocked fragments containing maskelynite were found in drill holes through the crater floor. Trenches on the rim yield strongly shocked fragments in which plagioclase has melted and vesiculated, and bombs and spherules of homogeneous rock melt. As the only known terrestrial impact crater in basalt, Lonar Crater provides unique opportunities for comparison with lunar craters. In particular, microbreccias and glass spherules from Lonar Crater have close analogs among the Apollo specimens.

Cratering on Mars. I - Cratering and obliteration history. II Implications for future cratering studies from Mariner 4 reanalysis

NASA Technical Reports Server (NTRS)

Chapman, C. R.

1974-01-01

It is pointed out that Mars is especially well adapted to statistical studies of crater morphologies for deciphering its geological history. A framework for understanding planetary geomorphological histories from the diameter-frequency relations of different morphological classes of craters described by Chapmam et al. (1970) is extended in order to understand Martian cratering, erosional, and depositional history. The cratering-obliteration history derived is compared with global interpretations considered by Hartman (1973) and Soderblom et al. (1974). An idealized dust-filling model is employed.

Impact Craters of Venus with D Greater Than 5 km Classified Based on Degree of Preservation of the Associated Radar-Dark Deposits

NASA Technical Reports Server (NTRS)

Basilevsky, A. T.; Head, J. W.; Setyaeva, I. V.

2003-01-01

This is a further continuation of work, which studied craters greater than or equal to 30 km in diameter. That work subdivided craters based on character of the associated radar dark deposits. It was suggested and then confirmed that the most pristine deposits of that sort are radar-dark parabolas. Non-parabolic radar-dark halos represent the next stage of the deposit evolution and then with time they disappear. So presence and character of crater-associated dark deposit can be used for estimates of the crater age and then for dating other features. Previous work classified craters into: 1) craters with dark parabola (DP), 2) with clear dark halo (CH), 3) with faint halo (FH) and 4) with no dark halo (NH). It was found that abundances of craters superposed on regional plains (whose mean age is close to the planet mean surface age T) and belonging to DP, CH, FH and NH classes were correspondingly 15, 30, 30 and 25%. From that it was concluded that DP craters are not older than 0.1-0.15T; CH craters formed during the time interval from approx. 0.5T until 0.1-0.15T ago, and the FH and NH craters formed prior to approx. 0.5T ago. It was shown that the DP, CH, FH and NH percentages show only slight apparent dependence on the crater geographic latitudes and no noticeable dependence on the crater size. The present study analyzes a much larger population (all D greater than or equal to 5 km craters) to investigate better the latitude effect and to study if within this larger crater population the size effect exists.

Evidence for rapid topographic evolution and crater degradation on Mercury from simple crater morphometry

NASA Astrophysics Data System (ADS)

Fassett, Caleb I.; Crowley, Malinda C.; Leight, Clarissa; Dyar, M. Darby; Minton, David A.; Hirabayashi, Masatoshi; Thomson, Bradley J.; Watters, Wesley A.

2017-06-01

Examining the topography of impact craters and their evolution with time is useful for assessing how fast planetary surfaces evolve. Here, new measurements of depth/diameter (d/D) ratios for 204 craters of 2.5 to 5 km in diameter superposed on Mercury's smooth plains are reported. The median d/D is 0.13, much lower than expected for newly formed simple craters ( 0.21). In comparison, lunar craters that postdate the maria are much less modified, and the median crater in the same size range has a d/D ratio that is nearly indistinguishable from the fresh value. This difference in crater degradation is remarkable given that Mercury's smooth plains and the lunar maria likely have ages that are comparable, if not identical. Applying a topographic diffusion model, these results imply that crater degradation is faster by a factor of approximately two on Mercury than on the Moon, suggesting more rapid landform evolution on Mercury at all scales.