scholarly journals High-Sensitivity Radiocarbon Dating in the 50,000 to 70,000 bp Range without Isotopic Enrichment

Radiocarbon ◽  
1992 ◽  
Vol 34 (3) ◽  
pp. 351-359 ◽  
Author(s):  
Austin Long ◽  
Robert M. Kalin
Keyword(s):  
Memory Effect ◽  
Liquid Scintillation ◽  
High Sensitivity ◽  
Isotopic Enrichment ◽  
Counting System ◽  
Systematic Analysis ◽  
Critical Elements ◽  
Background Material ◽  
Acetylene Production

Calculations show the possibility of detecting 14C remaining after 10 or 11 decay half-lives in natural materials, such as wood, using commercially available liquid scintillation (LS) detectors. Assuming in-situ14C production has contributed insignificantly to the measured 14C, one can calculate finite ages approaching 70 ka. In practice, defensible finite age determinations involve careful considerations of several critical elements in the procedure. These critical elements are: 1) the integrity of the sample itself, in terms of younger contaminants and of in situ-produced 14C; 2) the availability of “dead” background material; 3) chemical blank in laboratory preparation of, in this case, benzene; and 4) stability of background and efficiency of the LS counting system. High-sensitivity 14C dating reveals a low level of memory effect 14C in benzene synthesized in the laboratory from anthracite or marble. This level of 14C activity is equivalent to that found in 53 ka old wood, and thus, is not distinguishable from petrochemical benzene used in routine dating. If careful control of laboratory conditions can maintain this 14C blank constant, reproducible dating beyond 53 ka would be possible. Although we have not completed a systematic analysis of the origins of memory effect, lithium reactors used in acetylene production and organic solvents in wood pretreatment are likely sources.

scholarly journals Robust Radiocarbon Dating of Wood Samples by High-Sensitivity Liquid Scintillation Spectroscopy in the 50–70 kyr Age Range

Radiocarbon ◽  
2007 ◽  
Vol 49 (2) ◽  
pp. 379-391 ◽  
Author(s):  
Alan G Hogg ◽  
L Keith Fifield ◽  
Jonathan G Palmer ◽  
Chris S M Turney ◽  
Rex Galbraith
Keyword(s):  
Liquid Scintillation ◽  
High Sensitivity ◽  
Background Count ◽  
Suitable Material ◽  
Time Period ◽  
Laboratory Procedures ◽  
Counting Statistics ◽  
Age Range ◽  
Background Counting

Although high-sensitivity liquid scintillation (LS) spectroscopy is theoretically capable of producing finite radiocarbon ages in the 50,000- to 70,000-yr range, there is little evidence in the literature that meaningful dates in this time period have been obtained. The pressing need to undertake calibration beyond 26 kyr has resulted in the regular publication of 14C results in excess of 50 kyr, yet very little effort has been made to demonstrate their accuracy or precision. There is a paucity of systematic studies of the techniques required to produce reliable dates close to background and the methods needed to assess contamination from either in situ sources or laboratory handling and processing. We have studied the requirements for producing accurate and reliable dates beyond 50 kyr. Laboratory procedures include optimization of LS spectrometers to obtain low and stable non-14C background count rates, use of low-background counting vials, large benzene volumes, long counting times, and preconditioning of vacuum lines. We also discuss the need for multiple analyses of a suitable material containing no original 14C (background blank) and the application of an appropriate statistical model to compensate for variability in background contamination beyond counting statistics. Accurate and reproducible finite ages >60 kyr are indeed possible by high-sensitivity LS spectroscopy, but require corroborating background blank data to be defensible.

scholarly journals Automated Design of Probes for rRNA-Targeted FluorescenceIn SituHybridization Reveals the Advantages of Using Dual Probes for Accurate Identification

2014 ◽  
Vol 80 (16) ◽  
pp. 5124-5133 ◽  
Author(s):  
Erik S. Wright ◽  
L. Safak Yilmaz ◽  
Andrew M. Corcoran ◽  
Hatice E. Ökten ◽  
Daniel R. Noguera
Keyword(s):  
High Sensitivity ◽  
High Specificity ◽  
Target Group ◽  
Accurate Identification ◽  
Systematic Analysis ◽  
Single Probe ◽  
Common Technique ◽  
Generation Sequencing ◽  
Rrna Sequences

ABSTRACTFluorescencein situhybridization (FISH) is a common technique for identifying cells in their natural environment and is often used to complement next-generation sequencing approaches as an integral part of the full-cycle rRNA approach. A major challenge in FISH is the design of oligonucleotide probes with high sensitivity and specificity to their target group. The rapidly expanding number of rRNA sequences has increased awareness of the number of potential nontargets for every FISH probe, making the design of new FISH probes challenging using traditional methods. In this study, we conducted a systematic analysis of published probes that revealed that many have insufficient coverage or specificity for their intended target group. Therefore, we developed an improved thermodynamic model of FISH that can be applied at any taxonomic level, used the model to systematically design probes for all recognized genera of bacteria and archaea, and identified potential cross-hybridizations for the selected probes. This analysis resulted in high-specificity probes for 35.6% of the genera when a single probe was used in the absence of competitor probes and for 60.9% when up to two competitor probes were used. Requiring the hybridization of two independent probes for positive identification further increased specificity. In this case, we could design highly specific probe sets for up to 68.5% of the genera without the use of competitor probes and 87.7% when up to two competitor probes were used. The probes designed in this study, as well as tools for designing new probes, are available online (http://DECIPHER.cee.wisc.edu).

TO SEPARATELY ASSESS THE DIAGNOSTIC POTENTIAL OF TVS & MRI IN THE TERMS OF SENSITIVITY AND SPECIFICITY BY CORRELATING THE IMAGING FINDINGS WITH HISTOPATHOLOGY

2020 ◽  
Vol 4 (6) ◽  
Author(s):  
Suraj Mathur
Keyword(s):  
Transvaginal Ultrasound ◽  
High Sensitivity ◽  
Imaging Evaluation ◽  
Medical College ◽  
Conventional Mri ◽  
Diagnostic Potential ◽  
Adc Mapping ◽  
Malignant Lesions ◽  
Sensitivity Specificity

This prospective study was done in the Department of Radio diagnosis Govt. Medical College, Kozhikode. A total of 65 patients who were referred to our department with clinical suspicion of endometrial lesions and incidentally detected endometrial lesions on ultrasonography underwent transvaginal ultrasound and subsequent Imaging evaluation of pelvis MRI has very high sensitivity (95%) and specificity (98%) and is almost as accurate (97%) as histopathology in differentiating benign from malignant lesions. Addition of DWI with ADC mapping to conventional MRI increases its accuracy even more. However there is inherent limitation to MRI in detecting carcinoma in situ and micrometastasis. Keywords: TVS, MRI, Sensitivity, Specificity, Histopathology.

scholarly journals Spatial expression pattern of serine proteases in the blood fluke Schistosoma mansoni determined by fluorescence RNA in situ hybridization

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Lenka Ulrychová ◽  
Pavel Ostašov ◽  
Marta Chanová ◽  
Michael Mareš ◽  
Martin Horn ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Schistosoma Mansoni ◽  
Rna Sequencing ◽  
Serine Proteases ◽  
Expression Patterns ◽  
High Sensitivity ◽  
Host Parasite Interactions ◽  
Highly Sensitive ◽  
Host Parasite

Abstract Background The blood flukes of genus Schistosoma are the causative agent of schistosomiasis, a parasitic disease that infects more than 200 million people worldwide. Proteases of schistosomes are involved in critical steps of host–parasite interactions and are promising therapeutic targets. We recently identified and characterized a group of S1 family Schistosoma mansoni serine proteases, including SmSP1 to SmSP5. Expression levels of some SmSPs in S. mansoni are low, and by standard genome sequencing technologies they are marginally detectable at the method threshold levels. Here, we report their spatial gene expression patterns in adult S. mansoni by the high-sensitivity localization assay. Methodology Highly sensitive fluorescence in situ RNA hybridization (FISH) was modified and used for the localization of mRNAs encoding individual SmSP proteases (including low-expressed SmSPs) in tissues of adult worms. High sensitivity was obtained due to specifically prepared tissue and probes in combination with the employment of a signal amplification approach. The assay method was validated by detecting the expression patterns of a set of relevant reference genes including SmCB1, SmPOP, SmTSP-2, and Sm29 with localization formerly determined by other techniques. Results FISH analysis revealed interesting expression patterns of SmSPs distributed in multiple tissues of S. mansoni adults. The expression patterns of individual SmSPs were distinct but in part overlapping and were consistent with existing transcriptome sequencing data. The exception were genes with significantly low expression, which were also localized in tissues where they had not previously been detected by RNA sequencing methods. In general, SmSPs were found in various tissues including reproductive organs, parenchymal cells, esophagus, and the tegumental surface. Conclusions The FISH-based assay provided spatial information about the expression of five SmSPs in adult S. mansoni females and males. This highly sensitive method allowed visualization of low-abundantly expressed genes that are below the detection limits of standard in situ hybridization or by RNA sequencing. Thus, this technical approach turned out to be suitable for sensitive localization studies and may also be applicable for other trematodes. The results suggest that SmSPs may play roles in diverse processes of the parasite. Certain SmSPs expressed at the surface may be involved in host–parasite interactions. Graphic abstract

High Sensitivity of PCR in Situ Hybridization for the Detection of Human Papillomavirus Infection in Uterine Cervical Neoplasias

2001 ◽  
Vol 82 (2) ◽  
pp. 350-354 ◽  
Author(s):  
Yuhong Xiao ◽  
Shigemi Sato ◽  
Takaaki Oguchi ◽  
Kaori Kudo ◽  
Yoshihito Yokoyama ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Human Papillomavirus ◽  
High Sensitivity ◽  
Human Papillomavirus Infection ◽  
Papillomavirus Infection ◽  
Pcr In Situ

scholarly journals Memory Effect on a LDH/zeolite A Composite: An XRD In Situ Study

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2102
Author(s):  
Breno G. P. Bezerra ◽  
Lindiane Bieseki ◽  
Mariele I. S. de Mello ◽  
Djalma R. da Silva ◽  
Cristiane B. Rodella ◽  
...  
Keyword(s):  
Memory Effect ◽  
Inert Atmosphere ◽  
Effect Study ◽  
Physical Mixture ◽  
Zeolite A ◽  
Three Samples ◽  
In Situ Experiments ◽  
Double Hydroxide ◽  
Rehydration Process

In this memory effect study, hydrotalcite-type compounds in the lamellar double hydroxide-like (LDH)/zeolite A composite material were analyzed using X-Ray Diffration XRD) in situ experiments. Three samples were analyzed: Al,Mg-LDH, Al,Mg-LDH/ZA composite, and a physical mixture (50/50 wt%) of zeolite A and Al,Mg-LDH. The Al,Mg-LDH sample was treated at 500 °C in an O2 atmosphere and subsequently rehydrated. The Al,Mg-LDH/ZA composites had three treatments: one was performed at 300 °C in a He atmosphere, and two treatments were performed with an O2 atmosphere at 300 and 500 °C. In the physical mixture, two treatments were carried out under O2 flow at 500 °C and under He flow at 300 °C. Both went through the rehydration process. All samples were also analyzed by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The results show that the LDH phase in the Al,Mg-LDH/ZA compounds has memory effects, and thus, the compound can be calcined and rehydrated. For the LDH in the composite, the best heat treatment system is a temperature of 300 °C in an inert atmosphere.

scholarly journals Dating the End of the Neolithic in an Eastern Sahara Oasis: Modeling Absolute Chronology

Radiocarbon ◽  
2012 ◽  
Vol 54 (3-4) ◽  
pp. 305-318 ◽  
Author(s):  
Michel Wuttmann ◽  
François Briois ◽  
Béatrix Midant-Reynes ◽  
Tiphaine Dachy
Keyword(s):  
Bayesian Modeling ◽  
Liquid Scintillation ◽  
Nile Valley ◽  
Archaeological Remains ◽  
Middle Holocene ◽  
Cultural Complex ◽  
Scintillation Method ◽  
First Time ◽  
Ostrich Eggshell

The Neolithic site KS043, excavated by the Institut français d'archéologie orientale (IFAO), is situated in the southern basin of the Kharga Oasis (Egypt). It is one of the very few stratified prehistoric sites of the eastern Sahara. The archaeological remains were found near artesian springs that provided water for pastoralists during the dry Middle Holocene. In situ settlement features provided well-preserved material (charcoal, ashy sediment, ostrich eggshell) sufficient to perform radiocarbon dating in the IFAO laboratory in Cairo by the conventional liquid scintillation method. In 2 cases, ostrich eggshell and charcoal within the same in situ context gave significantly different results of, respectively, ∼600 and ∼1200 yr younger dates for the ostrich eggshells. The strong discrepancy is here highlighted for the first time and we suggest that it may be linked with postdepositional phenomena in the vicinity of the artesian springs. A thorough review of 14C dates available for the Holocene in eastern Sahara shows that ostrich eggshells have been widely used. They seem slightly more prone to be discarded than other material but were never the object of a particular study in this context. Bayesian modeling shows that the Neolithic occupation at site KS043 spans a range from 5000 to 3950 cal BC (and concentrated around 4600–4350 cal BC). Characteristic flint tools and pottery relate this occupation to the end of the Neolithic and show links with the Tasian culture, confirming the timing of the presence of this cultural complex in the desert before its appearance in the Nile Valley.

Sign in / Sign up

Export Citation Format

Share Document