Unravelling Quasi-Continuous 14C Profiles by Laser Ablation AMS

Radiocarbon ◽  
2019 ◽  
Vol 62 (2) ◽  
pp. 453-465 ◽  
Author(s):  
C Yeman ◽  
M Christl ◽  
B Hattendorf ◽  
L Wacker ◽  
C Welte ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Ion Source ◽  
Integration Time ◽  
Finite Width ◽  
Scanning Velocity ◽  
Ablation Volume ◽  
Evaluation Protocol ◽  
Novel Method ◽  
Target Memory

ABSTRACTLaser ablation (LA) accelerator mass spectrometry (AMS) is a novel method for rapid online radiocarbon (14C) analysis of carbonates. The quasi-continuous 14C profiles obtained with this technique demand a customized data evaluation protocol to relate the acquired 14C data to the analyzed sample. We take into account the mixing effects due to the minimal counting (integration) time of the AMS, the finite width of the laser beam and the gas washout of the ablation volume. Thereby we mathematically describe our LA setup with a system function that acts on the produced CO/CO2 (COX) from the sample resulting in a mixing of the 14C profiles obtained by AMS analysis. Furthermore, we analyze the long-term target memory effect in the gas ion source and establish a routine for correction. The correction routine is tested with a stalagmite comprising a growth stop that is analyzed at different scanning velocities indicating that only the slow scanning velocity can provide the necessary resolution to determine the width of the growth stop of 365 μm.

Thermogenesis of white adipocytes: a novel method allowing long-term microcalomrimetric investigations

1991 ◽  
Vol 23 (2) ◽  
pp. 181-187 ◽  
Author(s):  
Hartfried Böttcher ◽  
Jürgen Nittinger ◽  
Sabine Engel ◽  
Peter Fürst
Keyword(s):  
White Adipocytes ◽  
Novel Method

scholarly journals Maturity, Indebtedness, and Default Risk

2012 ◽  
Vol 102 (6) ◽  
pp. 2674-2699 ◽  
Author(s):  
Satyajit Chatterjee ◽  
Burcu Eyigungor
Keyword(s):  
Standard Deviation ◽  
Default Risk ◽  
Sovereign Debt ◽  
External Debt ◽  
Equilibrium Price ◽  
Short Term ◽  
Price Function ◽  
Output Ratio ◽  
Novel Method

We advance quantitative-theoretic models of sovereign debt by proving the existence of a downward sloping equilibrium price function for long-term debt and implementing a novel method to accurately compute it. We show that incorporating long-term debt allows the model to match Argentina's average external debt-to-output ratio, average spread on external debt, the standard deviation of spreads, and simultaneously improve upon the model's ability to account for Argentina's other cyclical facts. We also investigated the welfare properties of maturity length and showed that if the possibility of self-fulfilling rollover crises is taken into account, long-term debt is superior to short-term debt. (JEL E23, E32, F34, O11, O19)

scholarly journals Measurements of hydroperoxy radicals (HO<sub>2</sub>) at atmospheric concentrations using bromide chemical ionisation mass spectrometry

2019 ◽  
Vol 12 (2) ◽  
pp. 891-902 ◽  
Author(s):  
Sascha R. Albrecht ◽  
Anna Novelli ◽  
Andreas Hofzumahaus ◽  
Sungah Kang ◽  
Yare Baker ◽  
...  
Keyword(s):  
Water Vapour ◽  
Mass Spectrometer ◽  
Ion Source ◽  
Detection Sensitivity ◽  
Detection Methods ◽  
Integration Time ◽  
Key Species ◽  
Atmospheric Concentrations ◽  
Chemical Ionisation ◽  
Ionisation Mass

Abstract. Hydroxyl and hydroperoxy radicals are key species for the understanding of atmospheric oxidation processes. Their measurement is challenging due to their high reactivity; therefore, very sensitive detection methods are needed. Within this study, the measurement of hydroperoxy radicals (HO2) using chemical ionisation combined with a high-resolution time-of-flight mass spectrometer (Aerodyne Research Inc.) employing bromide as the primary ion is presented. The sensitivity reached is equal to 0.005×108 HO2 cm−3 for 106 cps of bromide and 60 s of integration time, which is below typical HO2 concentrations found in the atmosphere. The detection sensitivity of the instrument is affected by the presence of water vapour. Therefore, a water-vapour-dependent calibration factor that decreases approximately by a factor of 2 if the water vapour mixing ratio increases from 0.1 % to 1.0 % needs to be applied. An instrumental background, most likely generated by the ion source that is equivalent to a HO2 concentration of (1.5±0.2)×108 molecules cm−3, is subtracted to derive atmospheric HO2 concentrations. This background can be determined by overflowing the inlet with zero air. Several experiments were performed in the atmospheric simulation chamber SAPHIR at the Forschungszentrum Jülich to test the instrument performance in comparison to the well-established laser-induced fluorescence (LIF) technique for measurements of HO2. A highly linear correlation coefficient of R2=0.87 is achieved. The slope of the linear regression of 1.07 demonstrates the good absolute agreement of both measurements. Chemical conditions during experiments allowed for testing the instrument's behaviour in the presence of atmospheric concentrations of H2O, NOx, and O3. No significant interferences from these species were observed. All of these facts demonstrate a reliable measurement of HO2 by the chemical ionisation mass spectrometer presented.

Laser Ablation of Metastatic Lesions of the Lung: Long-Term Outcome

2009 ◽  
Vol 192 (3) ◽  
pp. 785-792 ◽  
Author(s):  
Christian Rosenberg ◽  
Ralf Puls ◽  
Katrin Hegenscheid ◽  
Jens Kuehn ◽  
Tom Bollman ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Term Outcome ◽  
Long Term Outcome ◽  
Metastatic Lesions

Synthesis technique of diamondlike carbon films by laser ablation ion source in atmosphere

1992 ◽  
Author(s):  
Kaoru Suzuki ◽  
Tetsuya Taniyama ◽  
Junji Nakata ◽  
Takaya Masutani
Keyword(s):  
Laser Ablation ◽  
Carbon Films ◽  
Ion Source ◽  
Synthesis Technique ◽  
Diamondlike Carbon

scholarly journals Lifelong Zero-Shot Learning

2020 ◽  
Author(s):  
Kun Wei ◽  
Cheng Deng ◽  
Xu Yang
Keyword(s):  
Fine Tuning ◽  
Training Set ◽  
Continuous Training ◽  
Evaluation Protocol ◽  
Multiple Datasets ◽  
Real World Applications ◽  
Knowledge Distillation ◽  
Novel Method ◽  
Previous Training ◽  
Current Stage

Zero-Shot Learning (ZSL) handles the problem that some testing classes never appear in training set. Existing ZSL methods are designed for learning from a fixed training set, which do not have the ability to capture and accumulate the knowledge of multiple training sets, causing them infeasible to many real-world applications. In this paper, we propose a new ZSL setting, named as Lifelong Zero-Shot Learning (LZSL), which aims to accumulate the knowledge during the learning from multiple datasets and recognize unseen classes of all trained datasets. Besides, a novel method is conducted to realize LZSL, which effectively alleviates the Catastrophic Forgetting in the continuous training process. Specifically, considering those datasets containing different semantic embeddings, we utilize Variational Auto-Encoder to obtain unified semantic representations. Then, we leverage selective retraining strategy to preserve the trained weights of previous tasks and avoid negative transfer when fine-tuning the entire model. Finally, knowledge distillation is employed to transfer knowledge from previous training stages to current stage. We also design the LZSL evaluation protocol and the challenging benchmarks. Extensive experiments on these benchmarks indicate that our method tackles LZSL problem effectively, while existing ZSL methods fail.

Laser-ablation-based ion source characterization and manipulation for laser-driven ion acceleration

2018 ◽  
Vol 60 (5) ◽  
pp. 054002 ◽  
Author(s):  
P Sommer ◽  
J Metzkes-Ng ◽  
F-E Brack ◽  
T E Cowan ◽  
S D Kraft ◽  
...  
Keyword(s):  
Laser Ablation ◽  
Ion Source ◽  
Ion Acceleration ◽  
Source Characterization

scholarly journals A novel method for producing NH4+ reagent ions in the hollow cathode glow discharge ion source of PTR-MS instruments

2020 ◽  
Vol 447 ◽  
pp. 116254 ◽  
Author(s):  
Markus Müller ◽  
Felix Piel ◽  
Rene Gutmann ◽  
Philipp Sulzer ◽  
Eugen Hartungen ◽  
...  
Keyword(s):  
Glow Discharge ◽  
Hollow Cathode ◽  
Ion Source ◽  
Novel Method
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