Search

Background/Aim: Breast-cancer metastasis to the brain is an intractable disease. To discover improved therapy for this disease, we developed a precise non-invasivelyimageable orthotopic nude-mouse model, using very-narrowband- width laser fluorescence excitation. Materials and Methods: Female nu/nu nude mice, aged 4-8 weeks, were inoculated through the midline of the skull with triple-negative human MDA-MB-231 breast cancer cells (5×105) expressing red fluorescent protein (RFP). The mice were imaged with the Analytik Jena UVP Biospectrum Advanced at 520 nm excitation with peak emission at 605 nm. Results: Three weeks after injection of MDA-MB-231-RFP cells in the brain, noninvasive fluorescence images of the breast tumor growing on the brain were obtained. The images of the tumor were very bright, with well-defined margins with no detectable skin autofluorescence background. Images obtained at various angles showed that the extent of the tumor margins could be precisely measured. A skin flap over the skull confirmed that the tumor was growing on the surface of the brain which is a frequent occurrence in breast cancer. Conclusion: A precise orthotopic model of RFP-expressing breast-cancer metastasis to the brain was developed that could be non-invasively imaged with very-narrow-band-width laser excitation, resulting in an ultra-bright, ultra-low-background signal. The model will be useful in discovering improved therapeutics for this recalcitrant disease. [ABSTRACT FROM AUTHOR]

An experiment to search for 2ε-, εβ+- and 2β+-decays of 106Cd, using a 215 g cadmium tungstate scintillation crystal enriched at 66 % by 106Cd (106CdWO4) is carried out at the Gran Sasso underground laboratory (Italy). Events in the 106CdWO4 detector are recorded in (anti)coincidences with two large-volume CdWO4 scintillation counters. The design of the detector system, calibration and background measurements, methods, and results of data analysis to determine key detector characteristics are described. The experimental data are compared with Monte Carlo simulation results, and a background model is constructed. The radioactive contamination of the setup components is studied. The sensitivity of the experiment approaches the level of theoretical predictions for the 2νεβ+-decay channel, while for other possible 2β-decay channels it is already on the level of lim T1/2 ∼ 1021-1022 years.

Radionuclide verification is one of the four monitoring technologies used in International Monitoring System of Comprehensive Nuclear-Test-Ban Treaty (CTBT). The activity of radionuclides concerned by CTBT generally performs at the low-level. An anti-cosmic ray γ spectrometer system with a HPGe detector was developed by using a combination of active and passive shielding techniques in order to improve the detection sensitivity and reduce the affections of background. By adjusting the system with a delay time and testing anti-coincidence count loss correction, compared with the original γ spectrum, the integral background in the energy range of 15-2 700 keV is reduced by a factor of 8. The detection sensitivity is greatly improved by using the anti-coincidence method. For 140Ba, the minimum detectable activity (MDA) is 10 mBq by using the anti-cosmic ray γ spectrometer for 7 d measurement, which meets the technical requirements for certification of nuclide laboratory under the CTBT. It is not only of great significance for CTBT radionuclide verification, but also important for radiation environment monitoring.

An experiment to search for 2ε-, εβ+ - and 2β+ -decays of 106Cd, using a 215 g cadmium tungstate scintillation crystal enriched at 66 % by 106Cd (106CdWO4) is carried out at the Gran Sasso underground laboratory (Italy). Events in the 106CdWO4 detector are recorded in (anti)coincidences with two large-volume CdWO4 scintillation counters. The design of the detector system, calibration and background measurements, methods, and results of data analysis to determine key detector characteristics are described. The experimental data are compared with Monte Carlo simulation results, and a background model is constructed. The radioactive contamination of the setup components is studied. The sensitivity of the experiment approaches the level of theoretical predictions for the 2Vεβ + -decay channel, while for other possible 2β-decay channels it is already on the level of lim T1/2 ~ 1021 - 1022 years. [ABSTRACT FROM AUTHOR]

Deep underground environments are ideal for low background searches due to the attenuation of cosmic rays by passage through the earth. However, they are affected by backgrounds from γ-rays emitted by 40K and the 238U and 232Th decay chains in the surrounding rock. The LUX-ZEPLIN (LZ) experiment will search for dark matter particle interactions with a liquid xenon TPC located within the Davis campus at the Sanford Underground Research Facility, Lead, South Dakota, at the 4850-foot level. In order to characterise the cavern background, in-situ γ-ray measurements were taken with a sodium iodide detector in various locations and with lead shielding. The integral count rates (0–3300 keV) varied from 596 Hz to 1355 Hz for unshielded measurements, corresponding to a total flux from the cavern walls of 1.9 ± 0.4 γ cm−2s−1. The resulting activity in the walls of the cavern can be characterised as 220 ± 60 Bq/kg of 40K, 29 ± 15 Bq/kg of 238U, and 13 ± 3 Bq/kg of 232Th.

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The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) has been designed for a direct detection search for particle dark matter using a single-phase liquid argon target. The projected cross section sensitivity for DEAP-3600 to the spin-independent scattering of Weakly Interacting Massive Particles (WIMPs) on nucleons is 10−46cm2 for a 100 GeV/c2 WIMP mass with a fiducial exposure of 3 tonne-years. This paper describes the physical properties and construction of the DEAP-3600 detector.

The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) has been designed for a direct detection search for particle dark matter using a single-phase liquid argon target. The projected cross section sensitivity for DEAP-3600 to the spin-independent scattering of Weakly Interacting Massive Particles (WIMPs) on nucleons is 10−46cm2 for a 100 GeV/c2 WIMP mass with a fiducial exposure of 3 tonne-years. This paper describes the physical properties and construction of the DEAP-3600 detector.

Recent advancements in low-energy rare-event searches rely on the use of cryogenic calorimeters in order to reach extremely low energy thresholds. When attempting to accurately characterize their responses within the region of interest (ROI) these detectors face severe challenges due to the fact that traditional radioactive calibration sources produce signals above the ROI and cannot be used in low background environments. LANTERN, an optical calibration system, can instead be used to accurately study the ROI of cryogenic detectors. It utilizes LED pulses to generate photon signals to perform detector calibration. LANTERN's current LED matrix allows for a fast characterization of up to 64 calorimeters independently, spanning energies from a few eV to hundreds of keV. Its minimal electronics and optics make it a cost-effective and customizable solution and it will be employed by the BULLKID, NUCLEUS and CRAB experiments. [ABSTRACT FROM AUTHOR]

A search for the neutrinoless quadruple beta decay of 136Xe was conducted with the liquid-xenon detector XMASS-I using 327 kg ×800.0 days of the exposure. The pulse shape discrimination based on the scintillation decay time constant which distinguishes γ-rays including the signal and β-rays was used to enhance the search sensitivity. No significant signal excess was observed from the energy spectrum fitting with precise background evaluation, and we set a lower limit of the half life of 3.7 × 1024 years at 90% confidence level. This is the first experimental constraint of the neutrinoless quadruple beta decay of 136Xe.

Astronomical detection at infrared wavelengths is crucial in astrophysics due to the critical information in this wavelength range. Blocked impurity band (BIB) infrared detectors are desirable for space-based astronomical observation due to their broad response range, low dark currents, high quantum efficiencies, and excellent radiation resistance. In this review, typical BIB device structures and device physics development are first introduced. Subsequently, we discuss progress in Si-based BIB detectors with different doping types and emphasize their applications in space-based infrared detection. Additionally, we discuss recent efforts on pixel performance optimization, response extension, and higher operating temperature devices. Finally, we conclude by proposing the challenges and perspectives of BIB detectors with improved detection performances. [ABSTRACT FROM AUTHOR]

False positives and high background are key problems in nucleic acid amplification-based methods. Herein, a triple amplification and low background sensing platform is developed, termed double CRISPR/Cas12a-drived hyperbranched rolling circle amplification (D-Cas12a/HRCA). By introducing two kinds of CRISPR/Cas12a, we effectively avoid background signal and improve sensitivity. The target miRNA is firstly recognized by a padlock probe to trigger the rolling circle amplification (RCA), which generates mass of long ssDNA and achieves the first amplification. The ssDNA can unlock the cis- and trans-cleavage activity of CRISPR/Cas12a (Cas12a/crRNA-1). Therefore, the cis-cleaved ssDNA and trans-cleaved primer 2 (neighboring C3 inhibitor modification) are used as template and primer for the next hyperbranched rolling circle amplification (HRCA, secondary amplification), respectively. The above amplification products (dsDNA, ssDNA) are recognized again by the CRISPR/Cas12a (third amplification) and output fluorescence or visualization signals. Compared with traditional RCA/Cas12a or HRCA/Cas12a, D-Cas12a/HRCA shows higher sensitivity with lower background. This assay achieves sensitive detection of miRNA-21 low to 10.02 fM. The lateral flow detection strips enable miRNA-21 detection with a LOD of 100 fM, showing the potential of CRISPR/Cas-based technology in POCT detection. More importantly, the platform is consistent with RT-qPCR in detecting miRNA-21 extracted from different cell lines. • D-Cas12a/HRCA is a triple amplification with high sensitivity. • The two kinds of CRISPR/Cas12a enable detection with ultra-low background. • Fluorescence or visualization signals are achieved. • The actual detection results were consistent with RT-qPCR. [ABSTRACT FROM AUTHOR]

The Majorana collaboration is constructing the Majorana Demonstrator at the Sanford Underground Research Facility at the Homestake gold mine, in Lead, SD. The apparatus will use Ge detectors, enriched in isotope 76Ge, to demonstrate the feasibility of a large-scale Ge detector experiment to search for neutrinoless double beta decay. The long half-life of this postulated process requires that the apparatus be extremely low in radioactive isotopes whose decays may produce backgrounds to the search. The radioassay program conducted by the collaboration to ensure that the materials comprising the apparatus are sufficiently pure is described. The resulting measurements from gamma-ray counting, neutron activation and mass spectroscopy of the radioactive-isotope contamination for the materials studied for use in the detector are reported. We interpret these numbers in the context of the expected background for the experiment.

BackgroundThe expected signal rate of rare decay experiments, such as instance dark matter and neutrino less double beta decay experiments, is extremely low, which requires that the detector building materials have extremely low radioactivity. Low radioactive background control is one of the essential works in the rare decay experiments. 226Ra and 228Ra produced in the early decay chain of 238U and 232Th have low boiling point and high vapor pressure, removing the element Ra can break the 238U decay chain and keep a low radioactivity of 232Th-late for a long time.PurposeThis study aims to investigate vacuum melting technique for low background titanium to reduce the impurity of isotopes that have negative impact on rare decay experiments and creating a low background environment for the detector running.MethodsFirstly, the low background material samples were acquired by manual separation of radionuclides using physical and chemical methods. Then, radioactive impurity elements, such as K, Cs, Ra, Pb, Po and Rn with low boiling point and high vapor pressure, were volatilized in environment with high temperature and high vacuum level. Finally, radioactivity of these testing samples were measured by two sets of high-purity germanium γ spectrometer with measurement time extended to 7 days.ResultsMeasurement results show signs of removal of radioactive isotopes by smelting-vacuum method, and the impurity in pure titanium smelted in vacuum electron beam furnace can reach the levels of (0.13±0.69) mBq∙kg-1 for 232Th-228Ac, and (0.07±0.29) mBq∙kg-1 for 238U-222Rn, respectively.ConclusionsThe smelting-vacuum method could provide reliable low background material for the container of the next generation PandaX detector.

We have searched for exotic neutrino-electron interactions that could be produced by a neutrino millicharge, by a neutrino magnetic moment, or by dark photons using solar neutrinos in the XMASS-I liquid xenon detector. We observed no significant signals in 711 days of data. We obtain an upper limit for neutrino millicharge of 5.4×10−12e at 90% confidence level assuming all three species of neutrino have common millicharge. We also set flavor-dependent limits assuming the respective neutrino flavor is the only one carrying a millicharge, 7.3×10−12e for νe, 1.1×10−11e for νμ, and 1.1×10−11e for ντ. These limits are the most stringent yet obtained from direct measurements. We also obtain an upper limit for the neutrino magnetic moment of 1.8×10−10 Bohr magnetons. In addition, we obtain upper limits for the coupling constant of dark photons in the U(1)B−L model of 1.3×10−6 if the dark photon mass is 1×10−3 MeV/c2, and 8.8×10−5 if it is 10 MeV/c2.

Background/aim: Breast-cancer metastasis to the brain is an intractable disease. To discover improved therapy for this disease, we developed a precise non-invasively-imageable orthotopic nude-mouse model, using very-narrow-band-width laser fluorescence excitation., Materials and Methods: Female nu/nu nude mice, aged 4-8 weeks, were inoculated through the midline of the skull with triple-negative human MDA-MB-231 breast cancer cells (5×10 5 ) expressing red fluorescent protein (RFP). The mice were imaged with the Analytik Jena UVP Biospectrum Advanced at 520 nm excitation with peak emission at 605 nm., Results: Three weeks after injection of MDA-MB-231-RFP cells in the brain, non-invasive fluorescence images of the breast tumor growing on the brain were obtained. The images of the tumor were very bright, with well-defined margins with no detectable skin autofluorescence background. Images obtained at various angles showed that the extent of the tumor margins could be precisely measured. A skin flap over the skull confirmed that the tumor was growing on the surface of the brain which is a frequent occurrence in breast cancer., Conclusion: A precise orthotopic model of RFP-expressing breast-cancer metastasis to the brain was developed that could be non-invasively imaged with very-narrow-band-width laser excitation, resulting in an ultra-bright, ultra-low-background signal. The model will be useful in discovering improved therapeutics for this recalcitrant disease., (Copyright © 2024, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Abstract A search for Weakly Interacting Massive Particles (WIMPs) was conducted with the single-phase liquid-xenon detector XMASS through inelastic scattering in which 129Xe nuclei were excited, using an exposure (327 kg × 800.0 days) 48 times larger than that of our previous study. The inelastic excitation sensitivity was improved by detailed evaluation of background, event classification based on scintillation timing that distinguished γ -rays and β -rays, and simultaneous fitting of the energy spectra of γ -like and β -like samples. No evidence of a WIMP signal was found. Thus, we set the upper limits of the inelastic channel cross section at 90% confidence level, for example, 4.1 × 10 − 39 cm 2 for a 200 GeV/ c 2 WIMP. This result provides the most stringent limits on the SD WIMP-neutron interaction and is better by a factor of 7.7 at 200 GeV/ c 2 than the existing experimental limit. [ABSTRACT FROM AUTHOR]

Abstract An application of a modern noble pixel detector, XRPIX series, for solar KSVZ axion search experiment is being developed. A low radioactive background is necessary in the detector volume for the axion search. We surveyed the radioactivity of all peripheral components mounted on the detector using an HPGe detector. The results are used as an input for a GEANT4 Monte Carlo simulation to study the background in the experiment. This paper describes the expected background and the simulated sensitivity of stacked XRPIX detector currently under development. [ABSTRACT FROM AUTHOR]

Abstract The Dark matter Experiment using Argon Pulse-shape discrimination (DEAP) has been designed for a direct detection search for particle dark matter using a single-phase liquid argon target. The projected cross section sensitivity for DEAP-3600 to the spin-independent scattering of Weakly Interacting Massive Particles (WIMPs) on nucleons is 10 − 46 cm 2 for a 100 GeV/ c 2 WIMP mass with a fiducial exposure of 3 tonne-years. This paper describes the physical properties and construction of the DEAP-3600 detector. [ABSTRACT FROM AUTHOR]

Abstract Glucose oxidase (GOx) based biosensor is an effective method to determine glucose level. However, the biosensors embedded with high electroactive species suffered from high background signal levels, which leading to relative low sensitivity for glucose sensing. In this work, a novel 3D network materials based glucose biosensor with low background signal was constructed, which demonstrated high sensitivity and selectivity towards glucose assay. Here, the combination of ionic liquid modified graphene sheets (GS-IL) and Au nanorods (Au NRs) acted as high electroactive catalyst, and thiol-containing silica sol-gel served as a nonconductive matrix to self-assembly of GS-IL and Au NRs to form the three-dimensional (3D) network materials. Meanwhile, the doping amount of the sol-gel had significant influences on electrochemical performance of the 3D network materials based biosensor. As a result, optimized 3.75% doping 3D network materials were selected to construct the glucose biosensor, which exhibited low background signal and high sensitivity. This biosensor was successfully applied in monitoring the glucose levels of serum and brain microdialysate samples. Highlights • The novel 3D network materials based glucose biosensor exhibiting high sensitivity with low background signal was designed. [ABSTRACT FROM AUTHOR]

Abstract A search for dark matter using an underground single-phase liquid xenon detector was conducted at the Kamioka Observatory in Japan, particularly for Weakly Interacting Massive Particles (WIMPs). We have used 705.9 live days of data in a fiducial volume containing 97 kg of liquid xenon at the center of the detector. The event rate in the fiducial volume after the data reduction was (4.2 ± 0.2) × 10 − 3 day − 1 kg − 1 ke V ee − 1 at 5 ke V ee , with a signal efficiency of 20%. All the remaining events are consistent with our background evaluation, mostly of the "mis-reconstructed events" originated from 210Pb in the copper plates lining the detector's inner surface. The obtained upper limit on a spin-independent WIMP-nucleon cross section was 2.2 × 10 − 44 cm 2 for a WIMP mass of 60 GeV/c 2 at the 90% confidence level, which was the most stringent limit among results from single-phase liquid xenon detectors. [ABSTRACT FROM AUTHOR]

We recently designed and developed a furnace for small-angle neutron scattering, enabling small-angle neutron scattering data with a very low background level to be obtained. The furnace consists of an internal heater and external vacuum chamber. The internal heater consists of an alumina tube around which a heating coil is wound. There are two open windows in the alumina tube for the incident and scattered neutron beams. In the vacuum chamber, there are two aluminium windows of thickness 0.5 mm. As a result, only these aluminium windows are in the path of the beam, and the background scattering from elements other than the sample is significantly reduced in the detected signals. The opening angle for the scattered beam is ±15°. This is adequate for the small-angles detector bank in TAIKAN (BL15) at the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC). [ABSTRACT FROM AUTHOR]

Abstract Hidden photons and axion-like particles are candidates for cold dark matter if they were produced non-thermally in the early universe. We conducted a search for both of these bosons using 800 live-days of data from the XMASS detector with 327 kg of liquid xenon in the fiducial volume. No significant signal was observed, and thus we set constraints on the α ′ / α parameter related to kinetic mixing of hidden photons and the coupling constant g A e of axion-like particles in the mass range from 40 to 120 keV/ c 2 , resulting in α ′ / α < 6 × 10 − 26 and g A e < 4 × 10 − 13. These limits are the most stringent over this mass range derived from both direct and indirect searches to date. [ABSTRACT FROM AUTHOR]

The Cryogenic Underground Test (CUTE) facility will be located 2 km underground in the SNOLAB laboratory, near Sudbury (Ontario, Canada). It is primarily designed to test the performances of cryogenic detectors of the Super-Cryogenic Dark Matter Search (SuperCDMS) experiment which will be installed next to CUTE. As a facility, it will also be accessible to scientists developing innovative cryogenic detectors for rare events search like dark matter or double-beta decay. The low temperature required to operate the cryogenic detectors is reached via an advanced dry dilution refrigerator from CryoConcept (France). The ‘Ultra Quiet Technique’ (UQT®) reduces the vibration transmission by using a proprietary gas-coupled thermal link between the two-stage pulse tube and the cryostat. In order to install the cryostat into a shielding water tank, we have developed a suspension system which decouples the cryostat from the environment with a low stiffness support, making a mechanical low-pass filter with a roll-off below 2 Hz for the vertical attenuation. We report the design choices made for the mechanical architecture to limit the vibration transmission and the material selection to achieve a low radioactive background rate in the detector. The expected background rate is less than 5 counts/day per kg of Ge detector in the 0-1 keV energy range. [ABSTRACT FROM AUTHOR]

CRISPR/Cas12a-based detection has been widely used for DNA targets, but always suffers from a relatively high background fluorescent signal, which potentially gives false positive results, and limits the accuracy and specificity of detection. To address this problem, violet phosphorene nanosheets (VPNSs) with excellent DNA adsorption and light absorption capacities were synthesized by liquid exfoliation from bulk violet phosphorus. The introduction of VPNSs into CRISPR/Cas12a-based detection decreased the relatively high background fluorescent signal by 32.7 %, and resulted in a background with the relative fluorescence unit of 2590.5 that was no longer visible via a visual readout, demonstrating that VPNSs are efficient fluorescence quenchers. By combining the detection with a smartphone-based fluorescence imaging system (FIS), a biosensor was developed for simultaneous detection of virulence genes iucA , iroB , peg-344 , rmpA and rmpA2 , and resistance gene tet (A) carried by tigecycline-resistant hypervirulent Klebsiella pneumoniae (HvKP). Upon optimization, the VPNSs-CRISPR/Cas12a-FIS biosensor detected 1 cfu of tigecycline-resistant HvKP in 60 min with a low background signal. The whole process was performed with portable devices including a block heater and an FIS, and the signal could be observed with either a smartphone or the naked eye. The biosensor provides new insights for exploration of low background, multiple target, and onsite analytical methods based on CRISPR/Cas12a. [Display omitted] • Violet phosphorene nanosheets in a biosensor decreased the background signal. • The onsite biosensor indicates hypervirulent K. pneumoniae with a visual readout. • The detection limit of the biosensor was 1 cfu and the whole process took 60 min. [ABSTRACT FROM AUTHOR]

An entrance window surrounded phoswich design of GAGG:Ce/CsI:Tl has been implemented for a low-background and Compton-suppressed detector. Not as the common phoswich detector does, the GAGG:Ce scintillator with the well-type CsI:Tl scintillator entrance window surrounded makes the efficient large-angle Compton suppression. This design also makes results measured by the phoswich detector have no degradation compared with the single GAGG:Ce detector. The Compton continuum and other backgrounds are reduced by identifying the gamma-ray energy depositions in different scintillators using the real-time rise time discrimination (RTD) method. The background rate is suppressed approximately 74%. The peak-to-total (P/T) ratio at 137Cs and 60Co point sources are 0.769 and 0.561, respectively. The Compton suppression is highly efficient at all the energy range of Compton continuums. The reduction of the Compton continuum and other backgrounds and the improvement of the P/T ratio will greatly expand the application range of the GAGG:Ce detector in low-intensity measurements. [ABSTRACT FROM AUTHOR]

Large-scale low-background detectors are increasingly used in rare-event searches as experimental collaborations push for enhanced sensitivity. However, building such detectors, in practice, creates an abundance of radioassay data especially during the conceptual phase of an experiment when hundreds of materials are screened for radiopurity. A tool is needed to manage and make use of the radioassay screening data to quantitatively assess detector design options. We have developed a Materials Database Application for the nEXO experiment to serve this purpose. This paper describes this database application, explains how it functions, and discusses how it streamlines the design of the experiment. [ABSTRACT FROM AUTHOR]

A double-cycle system has been developed for specifically detecting trace amounts of Pb2+ by significantly decreasing the background signal. The detection involves two types of RNA cleavage reactions: one using a Pb2+-specific GR5 DNAzyme (PbDz) and the other utilizing a newly constructed 10–23 DNAzyme with two hairpins embedded in its catalytic center (hpDz). The ring-structured hpDz (c-hpDz) exhibits significantly lower activity compared to the circular 10–23 DNAzyme without hairpin structures, which plays a crucial role in reducing the background signal. When Pb2+ is present, PbDz cleaves c-hpDz to its active form, which then disconnects the molecular beacon to emit the fluorescent signal. The method allows for rapid and sensitive Pb2+ detection within 40 min for 10 fM of Pb2+ and even as short as 10 min for 100 nM of Pb2+. Additionally, visual detection is possible through the non-crosslinking assembly of Au nanoparticles. The entire process can be performed in one pot and even one step, making it highly versatile and suitable for a wide range of applications, including food safety testing and environmental monitoring. [ABSTRACT FROM AUTHOR]

Inductively Coupled Plasma Mass Spectrometry (ICP-MS) allows for rapid, high-sensitivity determination of trace impurities, notably the primordial radioisotopes 238 U and 232 Th, in candidate materials for low-background rare-event search experiments. We describe the setup and characterisation of a dedicated low-background screening facility at University College London where we operate an Agilent 7900 ICP-MS. The impact of reagent and carrier gas purity is evaluated and we show that twice-distilled ROMIL-SpA TM -grade nitric acid and zero-grade Ar gas delivers similar sensitivity to ROMIL-UpA TM -grade acid and research-grade gas. A straightforward procedure for sample digestion and analysis of materials with U/Th concentrations down to 10 ppt g/g is presented. This includes the use of 233 U and 230 Th spikes to correct for signal loss from a range of sources and verification of 238 U and 232 Th recovery through digestion and analysis of a certified reference material with a complex sample matrix. Finally, we demonstrate assays and present results from two sample preparation and assay methods: a high-sensitivity measurement of ultra-pure Ti using open digestion techniques, and a closed vessel microwave digestion of a nickel–chromium-alloy using a multi-acid mixture. [ABSTRACT FROM AUTHOR]

A facile and cost-effective fluorescence biosensor is constructed for the accurate and sensitive determination of DNA. The G-quadruplex-forming sequence in hairpin DNA sequence (H1) is originally locked. When target DNA is present, the hairpin structure of H1 can be unfolded and part of H1 hybridized with the target DNA to form a double-stranded DNA and a G-quadruplex. The hairpin DNA sequence (H2) hybridizes with the unfolded H1 and displaces the target DNA. Finally, the displaced target DNA again hybridizes with the H1 and initiates cycle amplification. Thus, the numerous G-quadruplexs at the H1 ends are formed, resulting in the fluorescent enhancement after binding with N-methyl mesoporphyrin IX (NMM). Lower background signal improves the accuracy of assay. The enzyme-free method can detect down to 40 pM and a linear range of 3 orders of magnitude. Moreover, this strategy has an ability to discriminate the target DNA from even single-base mismatched or other sequence. The proposed method has potential applications in DNA-based molecular diagnostics. [ABSTRACT FROM AUTHOR]

We report results from a systematic measurement campaign conducted to identify low radioactivity materials for the construction of the EXO-200 double beta decay experiment. Partial results from this campaign have already been reported in a 2008 paper by the EXO collaboration. Here we release the remaining data, collected since 2007, to the public. The data reported were obtained using a variety of analytic techniques. The measurement sensitivities are among the best in the field. Construction of the EXO-200 detector has been concluded, and Phase-I data was taken from 2011 to 2014. The detector’s extremely low background implicitly verifies the measurements and the analysis assumptions made during construction and reported in this paper. [ABSTRACT FROM AUTHOR]

Bolometers are low temperature particle detectors with high energy resolution and detection efficiency. Some types of bolometric detectors are also able to perform an efficient particle identification. A wide variety of radiopure dielectric and diamagnetic materials makes the bolometric technique favorable for applications in astroparticle physics. In particular, thanks to their superior performance, bolometers play an important role in the worldwide efforts on searches for neutrinoless double-beta decay. Such experiments strongly require an extremely low level of the backgrounds that can easily mimic the process searched for. Here, we overview recent progress in the development of low background techniques for bolometric double-beta decay searches. [ABSTRACT FROM AUTHOR]

Previous measurements have demonstrated the wealth of information that tritium (T) can provide on environmentally relevant processes. We present modifications to sample preparation approaches that enable T measurement by proportional counting on small sample sizes equivalent to 120 mg of water and demonstrate the accuracy of these methods on a suite of standardized water samples. We identify a current quantification limit of 92.2 TU which, combined with our small sample sizes, correlates to as little as 0.00133 Bq of total T activity. This enhanced method should provide the analytical flexibility needed to address persistent knowledge gaps in our understanding of both natural and artificial T behavior in the environment. [ABSTRACT FROM AUTHOR]

CdZnTe coplanar-grid (CPG) detector is used in the COBRA experiment to search for neutrinoless double beta decay. In the next phase of the experiment, significantly larger detectors with a volume of (20 \times 20 \times 15)~\text mm^3 and a coplanar-quad-grid will be used. This paper presents the results of a spatially resolved investigation of the performance of one detector of this type, focusing on its usability in a double-beta experiment. With these data, two modifications of the interaction depth formula, which is of great importance for background reduction in COBRA, are investigated for the first time with such a detector, and the results are compared with a detector with a conventional CPG. Furthermore, we report the mobility-lifetime product for electrons for each sector of the detector. [ABSTRACT FROM AUTHOR]

We developed a cryogenic phonon-scintillation detector to search for 0 νββ decay of 100 Mo. The detector module, a proto-type setup of the AMoRE experiment, has a scintillating 40 Ca 100 MoO 4 absorber composed of 100 Mo-enriched and 48 Ca-depleted elements. This new detection method employs metallic magnetic calorimeters (MMCs) as the sensor technology for simultaneous detection of heat and light signals. It is designed to have high energy and timing resolutions to increase sensitivity to probe the rare event. The detector, which is composed of a 200 g 40 Ca 100 MoO 4 crystal and phonon/photon sensors, showed an energy resolution of 8.7 keV FWHM at 2.6 MeV, with a weak temperature dependence in the range of 10-40 mK. Using rise-time and mean-time parameters and light/heat ratios, the proposed method showed a strong capability of rejecting alpha-induced events from electron events with as good as 20 σ separation. Moreover, we discussed how the signal rise-time improves the rejection efficiency for random coincidence signals. [ABSTRACT FROM AUTHOR]