Optical Properties of Quantum-Dot-Doped Liquid Scintillators

Semiconductor nanoparticles (quantum dots) were studied in the context of liquid scintillator development for upcoming neutrino experiments. The unique optical and chemical properties of quantum dots are particularly promising for the use in neutrinoless double beta decay experiments. Liquid scintillators for large scale neutrino detectors have to meet specific requirements which are reviewed, highlighting the peculiarities of quantum-dot-doping. In this paper, we report results on laboratory-scale measurements of the attenuation length and the fluorescence properties of three commercial quantum dot samples. The results include absorbance and emission stability measurements, improvement in transparency due to filtering of the quantum dot samples, precipitation tests to isolate the quantum dots from solution and energy transfer studies with quantum dots and the fluorophore PPO.Comment: version 2, minor text update

Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection

Over the course of several decades, organic liquid scintillators have formed the basis for successful neutrino detectors. Gadolinium-loaded liquid scintillators provide efficient background suppression for electron antineutrino detection at nuclear reactor plants. In the Double Chooz reactor antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded scintillator is utilized for the first time. Its large scale production and characterization are described. A new, light yield matched metal-free companion scintillator is presented. Both organic liquids comprise the target and "Gamma Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table

Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection

Over the course of several decades, organic liquid scintillators have formed the basis for successful neutrino detectors. Gadolinium-loaded liquid scintillators provide efficient background suppression for electron antineutrino detection at nuclear reactor plants. In the Double Chooz reactor antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded scintillator is utilized for the first time. Its large scale production and characterization are described. A new, light yield matched metal-free companion scintillator is presented. Both organic liquids comprise the target and "Gamma Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table

Large scale Gd-beta-diketonate based organic liquid scintillator production for antineutrino detection

Over the course of several decades, organic liquid scintillators have formed the basis for successful neutrino detectors. Gadolinium-loaded liquid scintillators provide efficient background suppression for electron antineutrino detection at nuclear reactor plants. In the Double Chooz reactor antineutrino experiment, a newly developed beta-diketonate gadolinium-loaded scintillator is utilized for the first time. Its large scale production and characterization are described. A new, light yield matched metal-free companion scintillator is presented. Both organic liquids comprise the target and "Gamma Catcher" of the Double Chooz detectors.Comment: 16 pages, 4 figures, 5 table

A Link Between Plant Stress and Hydrodynamics? Indications From a Freshwater Macrophyte

Live plants are increasingly used in hydraulic laboratories to investigate flow-vegetation interactions. In such experiments, they are often exposed to stressful handling and storage that can cause strong physiological responses and modifications in plant biomechanics. Little is known about the potential effect of these impacts on the performance of plants during hydraulic experiments. In this multidisciplinary study with a freshwater macrophyte (Potamogeton natans) we assess whether the duration and the conditions in which plants are stored in a laboratory prior to testing can impact plant stress, biomechanics and hydrodynamics, and quantify this impact. Plant stress was evaluated using chlorophyll fluorescence analysis (and the maximum quantum yield of photosystem II as specific indicator). Plant hydrodynamics were assessed using the drag coefficient calculated from drag force measurements at two flow scenarios. The results show that different plant handling/storage procedures can have a significant impact on plant hydrodynamics even within a short time frame, with a variation of the mean drag coefficient of approximately 30% across groups, which is comparable to the variation found across different species of freshwater macrophytes in previous studies. Plants with the highest level of stress were also characterized by the lowest drag coefficient across the groups considered, suggesting a potential link between plant stress and hydrodynamics

Effects of various generations of iterative CT reconstruction algorithms on low-contrast detectability as a function of the effective abdominal diameter: A quantitative task-based phantom study.

To investigate how various generations of iterative reconstruction (IR) algorithms impact low-contrast detectability (LCD) in abdominal computed tomography (CT) for different patient effective diameters, using a quantitative task-based approach. Investigations were performed using an anthropomorphic abdominal phantom with two optional additional rings to simulate varying patient effective diameters (25, 30, and 35 cm), and containing multiple spherical targets (5, 6, and 8 mm in diameter) with a 20-HU contrast difference. The phantom was scanned using routine abdominal protocols (CTDI <sub>vol</sub> , 5.9-16 mGy) on four CT systems from two manufacturers. Images were reconstructed using both filtered back-projection (FBP) and various IR algorithms: ASiR 50%, SAFIRE 3 (both statistical IRs), ASiR-V 50%, ADMIRE 3 (both partial model-based IRs), or Veo (full model-based IR). Section thickness/interval was 2/1 mm or 2.5/1.25 mm, except 0.625/0.625 mm for Veo. We assessed LCD using a channelized Hotelling observer with 10 dense differences of Gaussian channels, with the area under the receiver operating characteristic curve (AUC) as a figure of merit. For the smallest phantom (25-cm diameter) and smallest lesion size (5-mm diameter), AUC for FBP and the various IR algorithms did not significantly differ for any of the tested CT systems. For the largest phantom (35-cm diameter), Veo yielded the highest AUC improvement (8.5%). Statistical and partial model-based IR algorithms did not significantly improve LCD. In abdominal CT, switching from FBP to IR algorithms offers limited possibilities for achieving significant dose reductions while ensuring a constant objective LCD

The hydrodynamic drag of full scale trees

River hydrodynamicsOverbank flows and vegetatio

A Link Between Plant Stress and Hydrodynamics? Indications From a Freshwater Macrophyte

Live plants are increasingly used in hydraulic laboratories to investigate flow-vegetation interactions. In such experiments, they are often exposed to stressful handling and storage that can cause strong physiological responses and modifications in plant biomechanics. Little is known about the potential effect of these impacts on the performance of plants during hydraulic experiments. In this multidisciplinary study with a freshwater macrophyte (Potamogeton natans) we assess whether the duration and the conditions in which plants are stored in a laboratory prior to testing can impact plant stress, biomechanics and hydrodynamics, and quantify this impact. Plant stress was evaluated using chlorophyll fluorescence analysis (and the maximum quantum yield of photosystem II as specific indicator). Plant hydrodynamics were assessed using the drag coefficient calculated from drag force measurements at two flow scenarios. The results show that different plant handling/storage procedures can have a significant impact on plant hydrodynamics even within a short time frame, with a variation of the mean drag coefficient of approximately 30% across groups, which is comparable to the variation found across different species of freshwater macrophytes in previous studies. Plants with the highest level of stress were also characterized by the lowest drag coefficient across the groups considered, suggesting a potential link between plant stress and hydrodynamics

Degradation of the cancer genomic DNA deaminase APOBEC3B by SIV Vif

APOBEC3B is a newly identified source of mutation in many cancers, including breast, head/neck, lung, bladder, cervical, and ovarian. APOBEC3B is a member of the APOBEC3 family of enzymes that deaminate DNA cytosine to produce the promutagenic lesion, uracil. Several APOBEC3 family members function to restrict virus replication. For instance, APOBEC3D, APOBEC3F, APOBEC3G, and APOBEC3H combine to restrict HIV-1 in human lymphocytes. HIV-1 counteracts these APOBEC3s with the viral protein Vif, which targets the relevant APOBEC3s for proteasomal degradation. While APOBEC3B does not restrict HIV-1 and is not targeted by HIV-1 Vif in CD4-positive T cells, we asked whether related lentiviral Vif proteins could degrade APOBEC3B. Interestingly, several SIV Vif proteins are capable of promoting APOBEC3B degradation, with SIVmac239 Vif proving the most potent. This likely occurs through the canonical polyubiquitination mechanism as APOBEC3B protein levels are restored by MG132 treatment and by altering a conserved E3 ligase-binding motif. We further show that SIVmac239 Vif can prevent APOBEC3B mediated geno/cytotoxicity and degrade endogenous APOBEC3B in several cancer cell lines. Our data indicate that the APOBEC3B degradation potential of SIV Vif is an effective tool for neutralizing the cancer genomic DNA deaminase APOBEC3B. Further optimization of this natural APOBEC3 antagonist may benefit cancer therapy