6,295 research outputs found
Nomenclature of Some Pennsylvanian Upper Cherokee (Desmoinesian Series) Coals of Iowa
The nomenclatural history of some Upper Cherokee coals of Iowa is reviewed, beginning with the 1870 geological survey. The Lacona, Panora, Wheeler, Marshall, and Lonsdale coals were named by St. John. The two more important coal beds, the Panora and Wheeler, are discussed in detail. The Panora, described in Guthrie County, was in 1927 renamed Whitebreast by A. L. Lugn for exposures in Lucas County within half a mile of St. John\u27s type section of the Wheeler Coal. At the time of description both coals were measured at each type section in NE¼ sec. 33, T. 73 N., R. 22 W., Lucas County, Iowa, and in April 1969 both coals were still exposed, although the Whitebreast was found only at the Wheeler locality and the Wheeler at the Whitebreast locality. The Bevier Coal has been interpreted to split, the lower bench then called the Wheeler and the upper bench called the Bevier. A palynological investigation of these coal beds by Habib indicated that the lower bench of the split Bevier is not the Wheeler Coal. The Bevier Coal is poorly documented in Iowa. The Lacona Coal occurs 20 to 40 feet below the Whitebreast and may be of only local importance. The Marshall and Lonsdale coal beds occur in the Marmaton Group above the Cherokee
The status of traditional Scottish animal breeds and plant varieties and the implications for biodiversity
The aim of this scoping study was to evaluate the effects on Scottish biodiversity of
changes in the use of traditional breeds and varieties. The overall objectives were:
a) The evaluation of the importance of genetic loss from the reduction in use of these
breeds and varieties, for example, the loss of unusual characteristics that might have
been of particular local use.
b) An assessment of the impacts of reduction in the ability to conduct further breeding or
research on rare and traditional varieties and breeds.
c) Identification of the loss of certain farming techniques associated with particular
varieties and breeds.
d) An assessment of possible losses of biodiversity associated with reduction in the use of
these breeds and varieties and the farming systems associated with them
The Nonexistence of Instrumental Variables
The method of instrumental variables (IV) and the generalized method of moments (GMM) has become a central technique in health economics as a method to help to disentangle the complex question of causality. However the application of these techniques require data on a sufficient number of instrumental variables which are both independent and relevant. We argue that in general such instruments cannot exist. This is a reason for the widespread finding of weak instruments.
The accuracy of flap thickness and diameter in LASIK using a femtosecond laser
PURPOSE: To evaluate the resultant thickness of the WaveLight FS200 (Alcon Vision, LLC) created LASIK flap compared to intended thickness at the surgical visit, using the WaveLight EX500 (Alcon Vision, LLC) pachymeter and the resultant flap diameter compared to intended diameter.
METHODS: This single arm, prospective, single surgeon study assessed the accuracy of the intended flap thickness and diameter, after successful bilateral LASIK surgery. The WaveLight FS200 femtosecond laser was used to create all flaps with an intended thickness of 120 μm. Flap thickness was calculated by subtracting the stromal bed thickness after flap lift from the preoperative corneal thickness using the WaveLight EX500 on-board optical pachymeter. Flap diameter was determined using digital analysis.
RESULTS: A total of 58 subjects (116 eyes) completed the study. The calculated mean flap thickness was 120.6 ± 9.0 μm (range 102 to 143 μm) using the EX500 pre- and post-flap pachymetry measurements. There was no statistically significant difference between the planned and achieved flap thickness (p \u3e 0.05). The mean difference in flap diameter between planned and actual was 0.02 ± 0.05 mm. Corneal thickness measured by Pentacam at up to 2 months preoperatively versus EX500 just prior to surgery was similar, with EX500 measuring 2 μm less on average than the Pentacam.
CONCLUSION: The results suggest that the WaveLight FS200 laser is reliable for LASIK flap thickness and diameter and accurately created flaps at the intended thickness and the intended diameter
Genetic characterization of clinical and environmental Vibrio parahaemolyticus from the Northeast USA reveals emerging resident and non-indigenous pathogen lineages
Gastric infections caused by the environmentally transmitted pathogen, Vibrio parahaemolyticus, have increased over the last two decades, including in many parts of the United States (US). However, until recently, infections linked to shellfish from the cool northeastern US waters were rare. Cases have risen in the Northeast, consistent with changes in local V. parahaemolyticus populations toward greater abundance or a shift in constituent pathogens. We examined 94 clinical isolates from a period of increasing disease in the region and compared them to 200 environmental counterparts to identify resident and non-indigenous lineages and to gain insight into the emergence of pathogenic types. Genotyping and multi-locus sequence analysis (MLSA) of clinical isolates collected from 2010 to 2013 in Massachusetts, New Hampshire, and Maine revealed their polyphyletic nature. Although 80% of the clinical isolates harbored the trh hemolysin either alone or with tdh, and were urease positive, 14% harbored neither hemolysin exposing a limitation for these traits in pathogen detection. Resident sequence type (ST) 631 strains caused seven infections, and show a relatively recent history of recombination with other clinical and environmental lineages present in the region. ST34 and ST674 strains were each linked to a single infection and these strain types were also identified from the environment as isolates harboring hemolysin genes. Forty-two ST36 isolates were identified from the clinical collection, consistent with reports that this strain type caused a rise in regional infections starting in 2012. Whole-genome phylogenies that included three ST36 outbreak isolates traced to at least two local sources demonstrated that the US Atlantic coastal population of this strain type was indeed derived from the Pacific population. This study lays the foundation for understanding dynamics within natural populations associated with emergence and invasion of pathogenic strain types in the region
Time resolved structural dynamics of butadiyne-linked porphyrin dimers
In this work the timescales and mechanisms associated with the structural dynamics of butadiyne-linked porphyrin dimers are investigated through time resolved narrowband pump / broadband probe transient absorption spectroscopy. Our results confirm previous findings that the broadening is partly due to a distribution of structures with different (dihedral) angular conformations. Comparison of measurements with excitations on the red and blue sides of the Q-band unravel the ground and excited state conformational re-equilibration timescales. Further comparison to a planarized dimer, through addition of a ligand, provide conclusive evidence for the twisting motion performed by the porphyrin dimer in solution
No-till Forage Establishment in Alaska
We assessed the effectiveness of no-till forage establishment at six Alaska locations: Anchor Point, Sterling, Point MacKenzie, Palmer, Delta Junction, and Fairbanks. Directly seeding grass into established grass stands generally did not improve forage yields or quality. Seeding rate had little effect on establishment of newly seeded forages in no-till. Grass yields were depressed when companion crop yields were high, and they typically did not recover in subsequent years. Red clover established well, producing high yields of good quality forage under no-till at Point MacKenzie, but established poorly at Anchor Point and Delta Junction. These results indicated that no-till seeding of most forage crops into declining grass stands is not likely to be successful in Alaska with current available technology
Use of Whole Genome Phylogeny and Comparisons in the Development of a Multiplex-PCR Assay to Identify Sequence Type 36 Vibrio parahaemolyticus
Vibrio parahaemolyticus sequence type (ST) 36 strains that are native to the Pacific Ocean have recently caused multi-state outbreaks of gastroenteritis linked to shellfish harvested from the Atlantic Ocean. Whole genome comparisons of 295 genomes of V. parahaemolyticus, including several traced to northeastern US sources, were used to identify diagnostic loci: one putatively encoding an endonuclease (prp), and two others potentially conferring O-antigenic properties (cps and flp). The combination of all three loci was present only in one clade of closely-related strains, of ST36, ST59 and one additional unknown sequence type. However, each locus was also identified outside this clade, with prp and flp occurring in only two non-clade isolates, and cps in four. Based on the distribution of these loci in sequenced genomes, prp could identify clade strains with \u3e99% accuracy, but the addition of one more locus would increase accuracy to 100%. Oligonucleotide primers targeting prp and cps were combined in a multiplex PCR method that defines species using the tlh locus, and determines presence of both the tdh and trh hemolysin-encoding genes which are also present in ST36. Application of the method in vitro to a collection of 94 clinical isolates collected over a four year period in three Northeastern US, and 87 environmental isolates, revealed the prp and cps amplicons were only detected in clinical isolates identified as belonging to the ST36-clade, and in no environmental isolates from the region. The assay should improve detection and surveillance, thereby reducing infections
Archeological Testing at 41TR170, along the Clear Fork of the Trinity River, Tarrant County, Texas
Archeologists from Geo-Marine, Inc., were subcontracted through Prewitt and Associates, Inc., of Austin to conduct National Register of Historic Places evaluative testing at archeological site 41TR170, located in Tarrant County, Texas. This work (Geo-Marine project number 30353.06.02) was conducted for the Environmental Affairs Division of the Texas Department of Transportation under contract/work authorization 57524SA006. The archeological remains are located on and in the alluvial terrace of the Clear Fork of the Trinity River, within the proposed 130-meter-wide right-of-way of State Highway 121 in southwestern Fort Worth. The work was conducted to comply with Section 106 of the National Historic Preservation Act of 1969, as amended (Public Law 89-665); the Department of Transportation Act of 1966 (Public Law 89-670); and the Antiquities Code of Texas, as incorporated into Title 98, Chapter 191, of the Natural Resources Code of Texas of 1977, as amended. The work was conducted under Texas Antiquities Permit Number 3699 issued by the Texas Historical Commission.
A three-stage field tactic was used during the testing of the site. Stage 1, conducted between March 15 and 29, 2005, consisted of archeological monitoring of the mechanical excavation of 28 backhoe trenches, followed by geomorphological field studies of the trench profiles. Trenches were placed both north and south of a relic channel of the Clear Fork of the Trinity River; the present channel was formed in the late 1960s by river-straightening channelization efforts. Efforts were made to ensure archeological sampling of all feature- and artifact-bearing areas previously identified in trenches dug during the 2000 archeological survey. The second stage, which occurred between March 21 and April 29, 2005, involved the manual excavation of 10 test units to depths of 2 meters below surface using standard 10-centimeter-thick levels. The purpose of this phase was to assess the reliability of the backhoe trench monitoring activities and to locate occupation zones worthy of further excavations. The third stage of field investigations was conducted between May 2 and June 3, 2005, and consisted of the mechanical stripping of the overburden above target occupation surfaces and the manual excavation of three block excavations, each 9 square meters, to a depth of 40 centimeters below surface. Upon completion of the fieldwork, a fourth stage comprised a limited analysis to document the nature of the recovered assemblage and to make National Register recommendations about the site, and a final stage was to design a plan for further study or analysis that would then be based on the results of an interim report.
The geomorphic investigations, coupled with the processing of eight radiocarbon dates, ascertained that the upper 2 meters of the Clear Fork sediments date to the past 2,900 years. All trenches contained evidence of the regionally dominant West Fork paleosol that is buried under a thin layer of recent alluvium. Beneath the West Fork paleosol were grayish and yellowish clayey strata, and stringers of pea-sized gravels could be correlated to many of the trenches onsite. The substrate for a series of trenches dug into the south edge of the site encountered cemented gravels that likely date to the Pleistocene age. These gravels extend above the Holocene alluvial sediments onsite and provide some minor relief above the floodplain. Although some bioturbation has blurred boundaries between the West Fork paleosol and more recent sediments, the degree of sediment movement is not as pronounced as observed in many other parts of Texas.
The excavations generally documented a series of low-density, highly stratified occupations that could not be correlated with any great assurance. The site context and integrity of deposits are generally excellent. Nevertheless, the paucity of remains in most areas is generally insufficient to provide data necessary to address many regional research questions. Site 41TR170 is not unique in this regard, because many sites within the Trinity River basin seem to be short-term specialized logistical extractive activity areas rather than campsites. Two areas of 41TR170, however, seem to be exceptions to low-density, brief occupations and contain a range of features unlike any previously encountered or recorded in the Clear Fork of the Trinity River.
In an area located about 60 meters north of the relic river channel, Block 2 exposed part of a deeply buried (180–220 centimeters below surface) ashy zone with abundant charcoal flecks and burned clay daub that occasionally retained impressions of sticks and small posts. Three burned rock features (small pits, scattered rocks, and rock dump concentrations) were found within this ashy zone, but they were not associated with the genesis of the ash. Bone preservation in this zone was good (numbering 121 specimens), but only one stone tool and four pieces of manufacture/maintenance debris were found. Based on the stratigraphic position and the recovery of one unclassified dart point, this feature is possibly Transitional Archaic in affiliation. Indeed, four radiocarbon dates from two features and the top and bottom of the ashy zone reaffirm that the occupation dates between A.D. 540 and 710 (two sigma dates, tree-ring calibrated), and relates to the Transitional Archaic period. The genesis of the thick ashy zone is problematic and not well understood. The radiocarbon dates suggest that the 40-centimeter-thick ashy zone did not develop instantaneously but rather apparently accumulated over a span of about 180 years (ca. 1,270 and 1,450 years ago). Even though a few rock features and some relatively high density of bone are preserved in this ashy sediment, the low density of remains suggests that the deposit cannot be considered an occupation midden. The age range also suggests that this is not a burned architectural structure. The formation process resulting in a 40-centimeter-thick ashy zone remains unknown.
In an area almost 150 meters south of the relic channel, an extensive area of burned rock covering at least 12-x-12 meters was encountered. Noncontiguous Blocks 1 and 3 were opened to explore the variability of burned rock features and ascertain the kinds of remains present. The recovery of two dart points (a Trinity and a Yarbrough) at comparable depths of 90 to 130 centimeters below surface suggests that this area along the edge of the Pleistocene gravel terrace was repeatedly occupied during the Late Archaic period. Among the burned rock features revealed in Block 3 was one large incipient burned rock oven with a pit measuring 2.54 meters in diameter surrounded by a discard ring of burned rocks that were only some 20 centimeters thick. Another cluster of burned rock more deeply buried in the sediments suggests multiple occupations. In adjacent Block 1 were two smaller (possible) pit ovens about 1 meter in diameter, an elongated pile of rock stored for reuse, a few rake-off piles or dumps, and one area of fitted burned rock that might have served as a large griddle-like feature. Tools and chipped stone debris were moderately abundant in Block 1, but rare in Block 3. Bone preservation in this area was very poor, although several hundred fragments of scattered freshwater mussel shell were present. Analysis of shell umbos or hinges indicates that about 59 shells were present in Block 1 and only 50 hinges in Block 3; none were concentrated into discrete discard features. The size, density, and morphological variability of the burned rock features are unlike anything previously seen in the Trinity River basin. Four radiocarbon dates from Blocks 1 and 3 suggest that the series of occupations date between A.D. 540 and 780 (2-sigma dates, tree-ring calibrated). Indeed the radiocarbon dates indicate that the activities resulting in the accumulation of dense burned rock features exposed in Blocks 1 and 3 are culturally contemporaneous with the activities occurring in the thick ashy zone located some 170 to 210 meters apart, even though they undoubtedly represent multiple reuse of the area. The two areas may not have been occupied simultaneously, for the low artifact density suggests that comparable groups of people from the Transitional Archaic period made the distinctly different occupational signatures in the two areas.
The testing phase of work at 41TR170 has documented considerable variability in feature forms during the Transitional Archaic period for the Trinity River basin. Test probes also strongly suggest that many more burned rock features occur parallel to the Pleistocene gravel terrace. In this regard, the testing has not exhausted the information potential related to the spatial patterning in activities by these people. However, the associated stone, shell, and bone artifact assemblages are relatively meager. Similarly, extensive flotation has failed to find any macrobotanical remains other than a single nutshell and small amounts of wood charcoal. Efforts to retrieve lipids samples from the burned rock feature proved to be successful, but the results were not very helpful in providing insight into the diversity of feature activities. Although examination of more burned rock features may stumble on examples of cooking accidents that preserve ancient foodstuff, the current robust level of testing suggests that the information content from the site is relatively limited. For this reason, even though the site is of considerable interest from a regional perspective, the site seemingly does not have the potential to make further contributions to the knowledge of the region. Thus, site 41TR170 fails to meet the standards of Criterion D or any other significance standard required for assessing National Register eligibility. Site 41TR170 is recommended as not eligible for National Register inclusion, and no further archeological investigations are recommended
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