Development of 222Rn Emanation Sources with Integrated Quasi 2π Active Monitoring

In this work, a novel approach for the standardization of low-level 222Rn emanation is presented. The technique is based on the integration of a 222Rn source, directly, with an α-particle detector, which allows the residual 222Rn to be continuously monitored. Preparation of the device entails thermal physical vapor deposition of 226RaCl2 directly onto the surface of a commercially available ion implanted Si-diode detector, resulting in a thin-layer geometry. This enables continuous collection of well resolved α-particle spectra of the nuclei, decaying within the deposited layer, with a detection efficiency of approximately 0.5 in a quasi 2π geometry. The continuously sampled α-particle spectra are used to derive the emanation by statistical inversion. It is possible to achieve this with high temporal resolution due to the small background and the high counting efficiency of the presented technique. The emanation derived in this way exhibits a dependence on the relative humidity of up to 15% in the range from 20% rH to 90% rH. Traceability to the SI is provided by employing defined solid-angle α-particle spectrometry to characterize the counting efficiency of the modified detectors. The presented technique is demonstrated to apply to a range covering the release of at least 1 to 210 222Rn atoms per second, and it results in SI-traceable emanation values with a combined standard uncertainty not exceeding 2%. This provides a pathway for the realization of reference atmospheres covering typical environmental 222Rn levels and thus drastically improves the realization and the dissemination of the derived unit of the activity concentration concerning 222Rn in air.

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Collection and counting efficiency

10.1093/oso/9780199565092.003.0010 ◽

2017 ◽

Author(s):

A. G. Wright

Keyword(s):

Quantum Efficiency ◽

Standard Method ◽

Shot Noise ◽

Count Rate ◽

Detection Efficiency ◽

Collection Efficiency ◽

Counting Efficiency ◽

Single Electron ◽

Anode Current ◽

Secondary Electrons

Standards laboratories can provide a photocathode calibration for quantum efficiency, as a function of wavelength, but their measurements are performed with the photomultiplier operating as a photodiode. Each photoelectron released makes a contribution to the photocathode current but, if it is lost or fails to create secondary electrons at d1, it makes no contribution to anode current. This is the basis of collection efficiency, F. The anode detection efficiency, ε‎, allied to F, refers to the counting efficiency of output pulses. The standard method for determining F involves photocurrent, anode current, count rate, and the use of highly attenuating filters; F may also be measured using methods based on single-electron responses (SERs), shot noise, or the SER at the first dynode.

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The quest for AMS of 182Hf – why poor gas gives pure beams

EPJ Web of Conferences ◽

10.1051/epjconf/202023202003 ◽

2020 ◽

Vol 232 ◽

pp. 02003

Author(s):

Martin Martschini ◽

Johannes Lachner ◽

Silke Merchel ◽

Alfred Priller ◽

Peter Steier ◽

...

Keyword(s):

Detection Efficiency ◽

Ion Source ◽

Negative Ion ◽

Complete Suppression ◽

Buffer Gas ◽

Novel Approach ◽

First Results ◽

Ion Laser ◽

R Process ◽

Ion Yields

The long-lived radioisotope 182Hf (T1/2 = 8.9 Ma) is of high astrophysical interest as its potential abundance in environmental archives would provide insight into recent r-process nucleosynthesis in the vicinity of our solar system. Despite substantial efforts, it could not be measured at natural abundances with conventional AMS so far due to strong isobaric interference from stable 182W. Equally important is an increase in ion source efficiency for the anions of interest. The new Ion Laser InterAction Mass Spectrometry (ILIAMS) technique at VERA tackles the problem of elemental selectivity in AMS with a novel approach. It achieves near-complete suppression of isobar contaminants via selective laser photodetachment of decelerated anion beams in a gas-filled radio-frequency quadrupole (RFQ) ion cooler. The technique exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Alternatively, these differences in EA can also facilitate anion separation via chemical reactions with the buffer gas. We present first results with this approach on AMS-detection of 182Hf. With He +O2 mixtures as buffer gas in the RFQ, suppression of 182WF5− vs 180HfF 5− by >105 has been demonstrated. Mass analysis of the ejected anion beam identified the formation of oxyfluorides as an important reaction channel. The overall Hf-detection efficiency at VERA presently is 1.4% and the W-corrected blank value is 182Hf/180Hf = (3.4 ± 2.1)×10−14. In addition, a survey of different sample materials for highest negative ion yields of HfF 5− with Cs-sputtering has been conducted.

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Using response action with intelligent intrusion detection and prevention system against web application malware

Information Management & Computer Security ◽

10.1108/imcs-02-2013-0007 ◽

2014 ◽

Vol 22 (5) ◽

pp. 431-449 ◽

Cited By ~ 8

Author(s):

Ammar Alazab ◽

Michael Hobbs ◽

Jemal Abawajy ◽

Ansam Khraisat ◽

Mamoun Alazab

Keyword(s):

Intrusion Detection ◽

Intrusion Detection System ◽

Web Application ◽

Web Applications ◽

Detection Efficiency ◽

Detection System ◽

Content Type ◽

Novel Approach ◽

Prevention System ◽

Intrusion Detection And Prevention

Purpose – The purpose of this paper is to mitigate vulnerabilities in web applications, security detection and prevention are the most important mechanisms for security. However, most existing research focuses on how to prevent an attack at the web application layer, with less work dedicated to setting up a response action if a possible attack happened. Design/methodology/approach – A combination of a Signature-based Intrusion Detection System (SIDS) and an Anomaly-based Intrusion Detection System (AIDS), namely, the Intelligent Intrusion Detection and Prevention System (IIDPS). Findings – After evaluating the new system, a better result was generated in line with detection efficiency and the false alarm rate. This demonstrates the value of direct response action in an intrusion detection system. Research limitations/implications – Data limitation. Originality/value – The contributions of this paper are to first address the problem of web application vulnerabilities. Second, to propose a combination of an SIDS and an AIDS, namely, the IIDPS. Third, this paper presents a novel approach by connecting the IIDPS with a response action using fuzzy logic. Fourth, use the risk assessment to determine an appropriate response action against each attack event. Combining the system provides a better performance for the Intrusion Detection System, and makes the detection and prevention more effective.

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Gradient Artefact Correction and Evaluation of the EEG Recorded Simultaneously with fMRI Data Using Optimised Moving-Average

Journal of Medical Engineering ◽

10.1155/2016/9614323 ◽

2016 ◽

Vol 2016 ◽

pp. 1-17 ◽

Cited By ~ 4

Author(s):

José L. Ferreira ◽

Yan Wu ◽

René M. H. Besseling ◽

Rolf Lamerichs ◽

Ronald M. Aarts

Keyword(s):

Moving Average ◽

Fmri Data ◽

Accurate Information ◽

High Temporal Resolution ◽

Eeg Signal ◽

Novel Approach ◽

Aas Method ◽

Average Filter ◽

Artefact Correction

Over the past years, coregistered EEG-fMRI has emerged as a powerful tool for neurocognitive research and correlated studies, mainly because of the possibility of integrating the high temporal resolution of the EEG with the high spatial resolution of fMRI. However, additional work remains to be done in order to improve the quality of the EEG signal recorded simultaneously with fMRI data, in particular regarding the occurrence of the gradient artefact. We devised and presented in this paper a novel approach for gradient artefact correction based upon optimised moving-average filtering (OMA). OMA makes use of the iterative application of a moving-average filter, which allows estimation and cancellation of the gradient artefact by integration. Additionally, OMA is capable of performing the attenuation of the periodic artefact activity without accurate information about MRI triggers. By using our proposed approach, it is possible to achieve a better balance than the slice-average subtraction as performed by the established AAS method, regarding EEG signal preservation together with effective suppression of the gradient artefact. Since the stochastic nature of the EEG signal complicates the assessment of EEG preservation after application of the gradient artefact correction, we also propose a simple and effective method to account for it.

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Counting Single DNA Molecules in a Capillary with Radial Focusing

Australian Journal of Chemistry ◽

10.1071/ch02192 ◽

2003 ◽

Vol 56 (3) ◽

pp. 149 ◽

Cited By ~ 18

Author(s):

Jinjian Zheng ◽

Edward S. Yeung

Keyword(s):

Single Molecule ◽

Detection Efficiency ◽

Signal To Noise Ratio ◽

Sampling Rate ◽

Ccd Camera ◽

Counting Efficiency ◽

Spherical Particles ◽

Dna Molecules ◽

Single Dna Molecules ◽

Relative Standard

For single-molecule detection, usually a small detection volume of 10 pL or less is used to improve the signal-to-noise ratio. Detection of every molecule in a sample requires that the sample be driven through a well-defined volume to facilitate laser excitation. We report a novel approach to count single DNA molecules with nearly 100% efficiency. By applying an electric field across a 40 cm long, 75 × 75 µm2 square capillary together with hydrodynamic flow from cathode to anode, we were able to concentrate more than 95% of DNA molecules into a 10 µm region at the centre of the capillary. The YOYO-1 labelled λ-DNA molecules were imaged with an intensified CCD camera. We found that the single DNA molecule detection efficiency in a 10–17 M solution was 114 ± 21%. The mobility of the DNA molecules after radial focusing was relatively constant, with relative standard deviations ranging from 0.8% to 1.4%. This allowed us to match the sampling rate to the length of the detection window to maximize counting efficiency. Analysis of a 40.2 nL injected plug of 2 × 10–14 M λ-DNA gave a result of 492 ± 73 molecules, which agreed well with the estimated value of 484. This method should be generally useful for counting deformable molecules or non-spherical particles at extremely low concentrations.

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Efficient MoWO3/VO2/MoS2/Si UV Schottky photodetectors; MoS2 optimization and monoclinic VO2 surface modifications

Scientific Reports ◽

10.1038/s41598-020-72990-9 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Mohamed A. Basyooni ◽

Shrouk E. Zaki ◽

Mohamed Shaban ◽

Yasin Ramazan Eker ◽

Mucahit Yilmaz

Keyword(s):

Physical Vapor Deposition ◽

Deposition Time ◽

Transition Metal Dichalcogenides ◽

Metallic Phase ◽

Silicon Substrates ◽

Strongly Correlated ◽

High Quality ◽

Novel Approach ◽

Metal Dichalcogenides ◽

P Type

Abstract The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from < 1 to > 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s)MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 108 Jones detectivity, and ~ 1.0 × 1010 quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.

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Investigations of the effect of (Cr1−x, Alx)N coatings’ micro Structure on Impact Toughness

MRS Proceedings ◽

10.1557/proc-843-t1.2 ◽

2004 ◽

Vol 843 ◽

Cited By ~ 2

Author(s):

K. Bobzin ◽

E. Lugscheider ◽

O. Knotek ◽

M. Maes

Keyword(s):

Wear Resistance ◽

Impact Toughness ◽

Physical Vapor Deposition ◽

Test Methods ◽

Coated Materials ◽

Novel Approach ◽

Deposition Parameters ◽

Impact Tester ◽

The Impact ◽

Load Behavior

ABSTRACTOriginated from the tooling industry, PVD (Physical Vapor Deposition) coating development focused on increasing the wear resistance. Nowadays, a steadily increasing market is evolving by coating machine parts. The requirements that have to be met due to the needs of this new market segment focus on tribological behavior. This means, that the focus of wear resistance is shifted towards properties like coefficient of friction, wetting behavior and the response of coatings towards dynamic loads. For many tribological applications, coatings are exposed to severe alternating loads, which are usually left out in common test methods. The approach of common coating test methods are based on the static behavior of deposited coatings. The impact tester is a testing device with a novel approach to dynamic load behavior of both bulk and coated materials. In this paper, the effect of the coatings' microstructure and Young's modulus on the impact toughness was investigated. A change in microstructure was provoked by changing deposition parameters like aluminum content. In a second stage these coatings were then tested with respect to their response to high alternating loads. For this purpose both load and number of impacts were varied.

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Fast transient networks in spontaneous human brain activity

eLife ◽

10.7554/elife.01867 ◽

2014 ◽

Vol 3 ◽

Cited By ~ 234

Author(s):

Adam P Baker ◽

Matthew J Brookes ◽

Iead A Rezek ◽

Stephen M Smith ◽

Timothy Behrens ◽

...

Keyword(s):

Functional Connectivity ◽

Brain Activity ◽

High Temporal Resolution ◽

Resting State Networks ◽

Novel Approach ◽

Dorsal Attention Network ◽

Functional Brain Networks ◽

Brain States ◽

Brain Functional Connectivity ◽

Transient Networks

To provide an effective substrate for cognitive processes, functional brain networks should be able to reorganize and coordinate on a sub-second temporal scale. We used magnetoencephalography recordings of spontaneous activity to characterize whole-brain functional connectivity dynamics at high temporal resolution. Using a novel approach that identifies the points in time at which unique patterns of activity recur, we reveal transient (100–200 ms) brain states with spatial topographies similar to those of well-known resting state networks. By assessing temporal changes in the occurrence of these states, we demonstrate that within-network functional connectivity is underpinned by coordinated neuronal dynamics that fluctuate much more rapidly than has previously been shown. We further evaluate cross-network interactions, and show that anticorrelation between the default mode network and parietal regions of the dorsal attention network is consistent with an inability of the system to transition directly between two transient brain states.

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Quantification of infiltration into sewers based on time series of pollutant loads

Water Science & Technology ◽

10.2166/wst.2005.0078 ◽

2005 ◽

Vol 52 (3) ◽

pp. 209-218 ◽

Cited By ~ 17

Author(s):

O. Kracht ◽

W. Gujer

Keyword(s):

Time Series ◽

Recent Measurement ◽

High Temporal Resolution ◽

Detailed Data ◽

Pollutant Concentrations ◽

Novel Approach ◽

Automated Sensors ◽

Polluted Waters ◽

Measurement Campaigns ◽

Analysis Of Time Series

We introduce the concepts of a novel approach that allows for the quantification of infiltrating non-polluted waters by a combined analysis of time series of pollutant concentrations and discharged wastewater volume. The methodology is based on the use of automated sensors for the recording of the pollutant concentrations. This provides time series in a high temporal resolution that are suitable for a detailed data analysis and discussion on the underlying assumptions. The procedure is demonstrated on two examples from recent measurement campaigns in Switzerland.

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