scholarly journals Comment on „Novel method for determining 234U/238U ages of Devils Hole 2 cave calcite“ by Li et al.

2020 ◽  
Author(s):  
Anonymous
Keyword(s):  
Devils Hole ◽  
Novel Method

scholarly journals Novel method for determining <sup>234</sup>U–<sup>238</sup>U ages of Devils Hole 2 cave calcite (Nevada)

Geochronology ◽  
2021 ◽  
Vol 3 (1) ◽  
pp. 49-58
Author(s):  
Xianglei Li ◽  
Kathleen A. Wendt ◽  
Yuri Dublyansky ◽  
Gina E. Moseley ◽  
Christoph Spötl ◽  
...  
Keyword(s):  
The Novel ◽  
Time Intervals ◽  
Δ13c Values ◽  
Devils Hole ◽  
Calcite Deposition ◽  
Dating Method ◽  
Novel Method ◽  
Multi Linear Regression ◽  
Δ18o And Δ13c

Abstract. Uranium–uranium (234U–238U) disequilibrium dating can determine the age of secondary carbonates over greater time intervals than the well-established 230Th–234U dating method. Yet it is rarely applied due to unknowns in the initial δ234U (δ234Ui) value, which result in significant age uncertainties. In order to understand the δ234Ui in Devils Hole 2 cave, Nevada, we have determined 110 δ234Ui values from phreatic calcite using 230Th–234U disequilibrium dating. The sampled calcite was deposited in Devils Hole 2 between 4 and 590 ka, providing a long-term look at δ234Ui variability over time. We then performed multi-linear regression among the δ234Ui values and correlative δ18O and δ13C values. The regression can be used to estimate the δ234Ui value of Devils Hole calcite based upon its measured δ18O and δ13C values. Using this approach and the measured present-day δ234U values of Devils Hole 2 calcite, we calculated 110 independent 234U–238U ages. In addition, we used newly measured δ18O, δ13C, and present-day δ234U values to calculate 10 234U–238U ages that range between 676 and 731 ka, thus allowing us to extend the Devils Hole chronology beyond the 230Th–234U-dated chronology while maintaining an age precision of ∼ 2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 ± 11 kyr ago. The novel method presented here may be applied to future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.

Novel method for determining 234U-238U ages of Devils Hole 2 cave calcite (Nevada)

2021 ◽  
Author(s):  
Xianglei Li ◽  
Kathleen A. Wendt ◽  
Yuri Dublyansky ◽  
Gina E. Moseley ◽  
Christoph Spötl ◽  
...  
Keyword(s):  
Linear Regression ◽  
The Novel ◽  
Time Intervals ◽  
Devils Hole ◽  
Calcite Deposition ◽  
Dating Method ◽  
Novel Method ◽  
Multi Linear Regression ◽  
Over Time

&lt;p&gt;Uranium-uranium (&lt;sup&gt;234&lt;/sup&gt;U-&lt;sup&gt;238&lt;/sup&gt;U) disequilibrium dating can determine the age of secondary carbonates over greater time intervals than the well-established &lt;sup&gt;230&lt;/sup&gt;Th-&lt;sup&gt;234&lt;/sup&gt;U dating method. Yet it is rarely applied due to unknowns in the initial d&lt;sup&gt;234&lt;/sup&gt;U (d&lt;sup&gt;234&lt;/sup&gt;U&lt;sub&gt;i&lt;/sub&gt;) value, which result in significant age uncertainties. In order to understand the d&lt;sup&gt;234&lt;/sup&gt;U&lt;sub&gt;i&lt;/sub&gt; in Devils Hole 2 cave, Nevada, we have determined 110 d&lt;sup&gt;234&lt;/sup&gt;U&lt;sub&gt;i&lt;/sub&gt; values from phreatic calcite using &lt;sup&gt;230&lt;/sup&gt;Th-&lt;sup&gt;234&lt;/sup&gt;U disequilibrium dating. The sampled calcite was deposited in Devils Hole 2 between 4 and 590 ka, providing a long-term look at d&lt;sup&gt;234&lt;/sup&gt;U&lt;sub&gt;i&lt;/sub&gt; variability over time. We then performed multi-linear regression among the d&lt;sup&gt;234&lt;/sup&gt;U&lt;sub&gt;i&lt;/sub&gt; values and correlative d&lt;sup&gt;18&lt;/sup&gt;O and d&lt;sup&gt;13&lt;/sup&gt;C values. The regression can be used to estimate the d&lt;sup&gt;234&lt;/sup&gt;U&lt;sub&gt;i&lt;/sub&gt; value of Devils Hole calcite based upon its measured d&lt;sup&gt;18&lt;/sup&gt;O and d&lt;sup&gt;13&lt;/sup&gt;C values. Using this approach and the measured present-day d&lt;sup&gt;234&lt;/sup&gt;U values of Devils Hole 2 calcite, we calculated 110 independent &lt;sup&gt;234&lt;/sup&gt;U-&lt;sup&gt;238&lt;/sup&gt;U ages. In addition, we used newly measured d&lt;sup&gt;18&lt;/sup&gt;O, d&lt;sup&gt;13&lt;/sup&gt;C, and present-day d&lt;sup&gt;234&lt;/sup&gt;U values to calculate 10 &lt;sup&gt;234&lt;/sup&gt;U-&lt;sup&gt;238&lt;/sup&gt;U ages that range between 676 and 731 ka, thus allowing us to extend the Devils Hole chronology beyond the &lt;sup&gt;230&lt;/sup&gt;Th-&lt;sup&gt;234&lt;/sup&gt;U-dated chronology while maintaining an age precision of ~2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 &amp;#177; 11 kyr ago. The novel method presented here may be applied to future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.&lt;/p&gt;

scholarly journals Supplementary material to "Novel method for determining <sup>234</sup>U-<sup>238</sup>U ages of Devils Hole 2 cave calcite"

2020 ◽  
Author(s):  
Xianglei Li ◽  
Kathleen A. Wendt ◽  
Yuri Dublyansky ◽  
Gina E. Moseley ◽  
Christoph Spötl ◽  
...  
Keyword(s):  
Devils Hole ◽  
Novel Method ◽  
Supplementary Material

scholarly journals Novel method for determining <sup>234</sup>U-<sup>238</sup>U ages of Devils Hole 2 cave calcite

2020 ◽  
Author(s):  
Xianglei Li ◽  
Kathleen A. Wendt ◽  
Yuri Dublyansky ◽  
Gina E. Moseley ◽  
Christoph Spötl ◽  
...  
Keyword(s):  
The Novel ◽  
Time Intervals ◽  
Devils Hole ◽  
Calcite Deposition ◽  
Dating Method ◽  
Novel Method ◽  
Linear Regressions ◽  
Over Time ◽  
Δ18o And Δ13c

Abstract. Uranium-uranium (234U-238U) dating can determine the age of secondary carbonates over greater time intervals than the well-established 230Th-234U dating method. Yet it is rarely applied due to unknowns surrounding the initial δ234U (δ234Ui) value, which result in significant age uncertainties. In order to understand the δ234Ui in Devils Hole 2 cave, we have precisely determined 110 δ234Ui values from phreatic calcite crusts using a 230Th-234U chronology. The sampled calcite crusts were deposited in Devils Hole 2 between 4 and 590 thousand years, providing a long-term look at δ234Ui variability over time. We then performed multi-linear regressions among the δ234Ui values and correlative δ18O and δ13C values. These regressions allow us to predict the δ234Ui value of Devils Hole calcite based upon its δ18O and δ13C. Using this approach and measured present-day &amp;felta;234U values, we calculate 110 independent 234U-238U ages of Devils Hole 2 cave deposits. In addition, we used newly measured δ18O, δ13C, and present-day δ234U values to calculate 10 234U-238U ages that range between 676 and 731 thousand years, thus allowing us to extend the Devils Hole chronology beyond the 230Th-234U-dated chronology while maintaining an age precision of ~2 %. Our results indicate that calcite deposition at Devils Hole 2 cave began no later than 736 &amp;pm; 11 thousand years ago. The novel method presented here may be used in future speleothem studies in similar hydrogeological settings, given appropriate calibration studies.

The removal and morphology of intact biofilms from implanted venous access devices

1995 ◽  
Vol 53 ◽  
pp. 1020-1021
Author(s):  
M.A. Gregory ◽  
G.P. Hadley
Keyword(s):  
Patient Selection ◽  
Surgical Oncology ◽  
Venous Access ◽  
Common Procedure ◽  
Indwelling Catheters ◽  
Careful Patient ◽  
Novel Method ◽  
The Subject ◽  
Vascular Catheters ◽  
Venous Access Devices

The insertion of implanted venous access systems for children undergoing prolonged courses of chemotherapy has become a common procedure in pediatric surgical oncology. While not permanently implanted, the devices are expected to remain functional until cure of the primary disease is assured. Despite careful patient selection and standardised insertion and access techniques, some devices fail. The most commonly encountered problems are colonisation of the device with bacteria and catheter occlusion. Both of these difficulties relate to the development of a biofilm within the port and catheter. The morphology and evolution of biofilms in indwelling vascular catheters is the subject of ongoing investigation. To date, however, such investigations have been confined to the examination of fragments of biofilm scraped or sonicated from sections of catheter. This report describes a novel method for the extraction of intact biofilms from indwelling catheters.15 children with Wilm’s tumour and who had received venous implants were studied. Catheters were removed because of infection (n=6) or electively at the end of chemotherapy.

Longitudinal Changes in Individual BrainAGE in Healthy Aging, Mild Cognitive Impairment, and Alzheimer’s Disease

GeroPsych ◽  
2012 ◽  
Vol 25 (4) ◽  
pp. 235-245 ◽  
Author(s):  
Katja Franke ◽  
Christian Gaser
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Healthy Aging ◽  
Brain Aging ◽  
Elderly Subjects ◽  
Additional Increase ◽  
Longitudinal Changes ◽  
Novel Method ◽  
The Brain

We recently proposed a novel method that aggregates the multidimensional aging pattern across the brain to a single value. This method proved to provide stable and reliable estimates of brain aging – even across different scanners. While investigating longitudinal changes in BrainAGE in about 400 elderly subjects, we discovered that patients with Alzheimer’s disease and subjects who had converted to AD within 3 years showed accelerated brain atrophy by +6 years at baseline. An additional increase in BrainAGE accumulated to a score of about +9 years during follow-up. Accelerated brain aging was related to prospective cognitive decline and disease severity. In conclusion, the BrainAGE framework indicates discrepancies in brain aging and could thus serve as an indicator for cognitive functioning in the future.

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