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1
Kim, G. B., S. Choi, F. A. Danevich, A. Fleischmann, C. S. Kang, H. J. Kim, S. R. Kim, et al. "A CaMoO4Crystal Low Temperature Detector for the AMoRE Neutrinoless Double Beta Decay Search." Advances in High Energy Physics 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/817530.
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We report the development of a CaMoO4crystal low temperature detector for the AMoRE neutrinoless double beta decay(0νββ)search experiment. The prototype detector cell was composed of a 216 g CaMoO4crystal and a metallic magnetic calorimeter. An overground measurement demonstrated FWHM resolution of 6–11 keV for full absorption gamma peaks. Pulse shape discrimination was clearly demonstrated in the phonon signals, and 7.6 σof discrimination power was found for theαandβ/γseparation. The phonon signals showed rise-times of about 1 ms. It is expected that the relatively fast rise-time will increase the rejection efficiency of two-neutrino double beta decay pile-up events which can be one of the major background sources in0νββsearches.
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Metzger, Bloen, Ouamar Rahli, and Xiaolong Yin. "Heat transfer across sheared suspensions: role of the shear-induced diffusion." Journal of Fluid Mechanics 724 (April 29, 2013): 527–52. http://dx.doi.org/10.1017/jfm.2013.173.
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AbstractSuspensions of non-Brownian spherical particles undergoing shear provide a unique system where mixing occurs spontaneously at low Reynolds numbers. Through a combination of experiments and simulations, we investigate the effect of shear-induced particle diffusion on the transfer of heat across suspensions. The influence of particle size, particle volume fraction and applied shear are examined. By applying a heat pulse to the inner copper wall of a Couette cell and analysing its transient temperature decay, the effective thermal diffusivity of the suspension, $\alpha $, is obtained. Using index matching and laser-induced fluorescence imaging, we measured individual particle trajectories and calculated their diffusion coefficients. Simulations that combined a lattice Boltzmann technique to solve for the flow and a passive Brownian tracer algorithm to solve for the transfer of heat are in very good agreement with experiments. Fluctuations induced by the presence of particles within the fluid cause a significant enhancement (${\gt }200\hspace{0.167em} \% $) of the suspension transport properties. The effective thermal diffusivity was found to be linear with respect to both the Péclet number ($\mathit{Pe}= \dot {\gamma } {d}^{2} / {\alpha }_{0} \leq 100$) and the solid volume fraction ($\phi \leq 40\hspace{0.167em} \% $), leading to a simple correlation $\alpha / {\alpha }_{0} = 1+ \beta \phi \mathit{Pe}$ where $\beta = 0. 046$ and ${\alpha }_{0} $ is the thermal diffusivity of the suspension at rest. In our Couette cell, the enhancement was found to be optimum for a volume fraction, $\phi \approx 40\hspace{0.167em} \% $, above which, due to steric effects, both the particle diffusion motion and of the effective thermal diffusion dramatically decrease. No such correlation was found between the average particle rotation and the thermal diffusivity of the suspension, suggesting that the driving mechanism for enhanced transport is the translational particle diffusivity. Movies are available with the online version of the paper.
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Pavan, M. "CUORE/CUORICINO: Double Beta Decay with low temperature detectors." Nuclear Physics B - Proceedings Supplements 168 (June 2007): 60–62. http://dx.doi.org/10.1016/j.nuclphysbps.2007.02.007.
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Kang, W. G., J. H. Choi, E. J. Jeon, J. I. Lee, H. J. Kim, S. K. Kim, Y. D. Kim, et al. "Ultra-low gamma-ray measurement system for neutrinoless double beta decay." Applied Radiation and Isotopes 81 (November 2013): 290–93. http://dx.doi.org/10.1016/j.apradiso.2013.03.057.
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Poda, Denys, and Andrea Giuliani. "Low background techniques in bolometers for double-beta decay search." International Journal of Modern Physics A 32, no. 30 (October 30, 2017): 1743012. http://dx.doi.org/10.1142/s0217751x17430126.
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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.
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Folan, L. M., V. I. Tsifrinovich, and V. A. Sheverev. "The low-temperature rate of electron capture beta decay in magnetic materials." Journal of Applied Physics 79, no. 8 (1996): 5716. http://dx.doi.org/10.1063/1.362228.
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Kim, Sang Goon, Jin-A. Jeon, H. B. Kim, H. L. Kim, So Ra Kim, Yong-Hamb Kim, D. H. Kwon, Min Kyu Lee, Y. C. Lee, and K. R. Woo. "Low Temperature Property Study of MMCs Used for Neutrinoless Double Beta Decay." IEEE Transactions on Applied Superconductivity 31, no. 5 (August 2021): 1–5. http://dx.doi.org/10.1109/tasc.2021.3066179.
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Jo, H. S., S. Choi, F. A. Danevich, A. Fleischmann, J. A. Jeon, C. S. Kang, W. G. Kang, et al. "Status of the AMoRE Experiment Searching for Neutrinoless Double Beta Decay Using Low-Temperature Detectors." Journal of Low Temperature Physics 193, no. 5-6 (May 1, 2018): 1182–89. http://dx.doi.org/10.1007/s10909-018-1925-0.
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KLAPDOR-KLEINGROTHAUS, H. V., I. V. KRIVOSHEINA, and I. V. TITKOVA. "THEORETICAL INVESTIGATION OF PULSE SHAPES OF DOUBLE BETA EVENTS IN A 76Ge DETECTOR, THEIR DEPENDENCE ON PARTICLE PHYSICS PARAMETERS, AND THEIR SEPARABILITY FROM BACKGROUND GAMMA EVENTS." Modern Physics Letters A 21, no. 16 (May 30, 2006): 1257–78. http://dx.doi.org/10.1142/s0217732306020524.
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For the first time the expected pulse shapes to be observed for neutrinoless double beta events in a big 76 Ge detector have been calculated starting from their Monte Carlo calculated time history and spatial energy distribution. It is shown that with the spatial resolution of a large size Ge detector for the majority of 0νββ events it is not possible to differentiate between the contributions of different particle physics parameters entering into the 0νββ decay process — in the mass mechanism the effective neutrino mass and the right-handed weak current parameters λ, η. It is shown that on the other hand it is possible in a 76 Ge double beta decay experiment to reject a background of larger sizes (high multiplicity) gamma events by selecting low size (low multiplicity) events. First comparison of the theoretical ββ pulses to events from the line observed at3,4Qββ shows very good agreement. It is shown further that a rather good radial position determination of ββ events in the detector is possible. By the same type of calculation it is shown that use of the pulse shapes of the 1592 keV double escape line of the 2614 keV γ-transition from 228 Th for calibrating a neuronal net for search of events of neutrinoless double beta decay should be helpful.
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Poda, Denys. "Scintillation in Low-Temperature Particle Detectors." Physics 3, no. 3 (July 1, 2021): 473–535. http://dx.doi.org/10.3390/physics3030032.
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Inorganic crystal scintillators play a crucial role in particle detection for various applications in fundamental physics and applied science. The use of such materials as scintillating bolometers, which operate at temperatures as low as 10 mK and detect both heat (phonon) and scintillation signals, significantly extends detectors performance compared to the conventional scintillation counters. In particular, such low-temperature devices offer a high energy resolution in a wide energy interval thanks to a phonon signal detection, while a simultaneous registration of scintillation emitted provides an efficient particle identification tool. This feature is of great importance for a background identification and rejection. Combined with a large variety of elements of interest, which can be embedded in crystal scintillators, scintillating bolometers represent powerful particle detectors for rare-event searches (e.g., rare alpha and beta decays, double-beta decay, dark matter particles, neutrino detection). Here, we review the features and results of low-temperature scintillation detection achieved over a 30-year history of developments of scintillating bolometers and their use in rare-event search experiments.
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Osinski, Bolesław L., and Leslie M. Kay. "Granule cell excitability regulates gamma and beta oscillations in a model of the olfactory bulb dendrodendritic microcircuit." Journal of Neurophysiology 116, no. 2 (August 1, 2016): 522–39. http://dx.doi.org/10.1152/jn.00988.2015.
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Odors evoke gamma (40–100 Hz) and beta (20–30 Hz) oscillations in the local field potential (LFP) of the mammalian olfactory bulb (OB). Gamma (and possibly beta) oscillations arise from interactions in the dendrodendritic microcircuit between excitatory mitral cells (MCs) and inhibitory granule cells (GCs). When cortical descending inputs to the OB are blocked, beta oscillations are extinguished whereas gamma oscillations become larger. Much of this centrifugal input targets inhibitory interneurons in the GC layer and regulates the excitability of GCs, which suggests a causal link between the emergence of beta oscillations and GC excitability. We investigate the effect that GC excitability has on network oscillations in a computational model of the MC-GC dendrodendritic network with Ca2+-dependent graded inhibition. Results from our model suggest that when GC excitability is low, the graded inhibitory current mediated by NMDA channels and voltage-dependent Ca2+ channels (VDCCs) is also low, allowing MC populations to fire in the gamma frequency range. When GC excitability is increased, the activation of NMDA receptors and other VDCCs is also increased, allowing the slow decay time constants of these channels to sustain beta-frequency oscillations. Our model argues that Ca2+ flow through VDCCs alone could sustain beta oscillations and that the switch between gamma and beta oscillations can be triggered by an increase in the excitability state of a subpopulation of GCs.
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Lee, M. H. "AMoRE: a search for neutrinoless double-beta decay of 100Mo using low-temperature molybdenum-containing crystal detectors." Journal of Instrumentation 15, no. 08 (August 7, 2020): C08010. http://dx.doi.org/10.1088/1748-0221/15/08/c08010.
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Degoda, V. Ya, F. A. Danevich, N. Coron, I. M. Ivanov, Ya P. Kogut, E. P. Makarov, P. de Marcillac, et al. "Luminescence of ZnMoO4 Crystals Developed for the LUMINEU Double Beta Decay Experiment." Solid State Phenomena 230 (June 2015): 184–92. http://dx.doi.org/10.4028/www.scientific.net/ssp.230.184.
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Scintillation efficiency of ZnMoO4 crystals is one of the main characteristics for application in cryogenic double beta decay experiments. Luminescence of ZnMoO4 crystals developed from deeply purified molybdenum under X-ray irradiation of different doses was studied in the temperature interval from 1.4 K to 295 K. Emission spectra, dependence of luminescence intensity on dose and temperature, phosphorescence and thermally stimulated luminescence were investigated. Two emission bands were identified: recombination luminescence at ~ 600 nm and exciton luminescence at ~ 500 nm. We have found that concentration of shallow traps in the material is much greater than the concentration of deep traps. Furthermore only shallow traps absorb a small part of the luminescence and cause the low scintillation efficiency of the sample.
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Yates, S. W., E. E. Peters, B. P. Crider, S. Mukhopadhyay, and A. P. D. Ramirez. "Relevance of the Nuclear Structure of the Stable Ge Isotopes to the Neutrino-less Double-Beta Decay of 76Ge." EPJ Web of Conferences 232 (2020): 04011. http://dx.doi.org/10.1051/epjconf/202023204011.
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Gamma-ray detection following the inelastic neutron scattering reaction on isotopically enriched material was used to study the nuclear structure of 74Ge. From these measurements, low-lying, low-spin excited states were characterized, new states and their decays were identified, level lifetimes were measured with the Doppler-shift attenuation method (DSAM), multipole mixing ratios were established, and transition probabilities were determined. New structural features in 74Ge were identified, and the reanalysis of older 76Ge data led to the placement of the 2+ member of the intruder band. In addition, a number of previously placed states in 74Ge were shown not to exist. A procedure for future work, which will lead to meaningful data for constraining calculations of the neutrinoless double-beta decay matrix element, is suggested.
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Ranitzsch, P. C. O., D. Arnold, J. Beyer, L. Bockhorn, J. J. Bonaparte, C. Enss, K. Kossert, et al. "MetroMMC: Electron-Capture Spectrometry with Cryogenic Calorimeters for Science and Technology." Journal of Low Temperature Physics 199, no. 1-2 (December 9, 2019): 441–50. http://dx.doi.org/10.1007/s10909-019-02278-4.
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AbstractAccurate decay data of radionuclides are necessary for many fields of science and technology, ranging from medicine and particle physics to metrology. However, data that are in use today are mostly based on measurements or theoretical calculation methods that are rather old. Recent measurements with cryogenic detectors and other methods show significant discrepancies to both older experimental data and theory in some cases. Moreover, the old results often suffer from large or underestimated uncertainties. This is in particular the case for electron-capture (EC) decays, where only a few selected radionuclides have ever been measured. To systematically address these shortcomings, the European metrology project MetroMMC aims at investigating six radionuclides decaying by EC. The nuclides are chosen to cover a wide range of atomic numbers Z, which results in a wide range of decay energies and includes different decay modes, such as pure EC or EC accompanied by $$\gamma $$γ- and/or $$\beta ^{+}$$β+-transitions. These will be measured using metallic magnetic calorimeters (MMCs), cryogenic energy-dispersive detectors with high-energy resolution, low-energy threshold and high, adjustable stopping power that are well suited for measurements of the total decay energy and X-ray spectrometry. Within the MetroMMC project, these detectors are used to obtain X-ray emission intensities of external sources as well as fractional EC probabilities of sources embedded in a $$4\pi $$4π absorber. Experimentally determined nuclear and atomic data will be compared to state-of-the-art theoretical calculations which will be further developed within the project. This contribution introduces the MetroMMC project and in particular its experimental approach. The challenges in EC spectrometry are to adapt the detectors and the source preparation to the different decay channels and the wide energy range involved, while keeping the good resolution and especially the low-energy threshold to measure the EC from outer shells.
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Vermeeren, L., W. Leysen, L. Pichon, V. Salou, and G. Helleux. "THERMOCOAX rhodium SPND sensitivity dispersion and validation of the sensitivity calculation model." EPJ Web of Conferences 225 (2020): 04015. http://dx.doi.org/10.1051/epjconf/202022504015.
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This paper describes the neutron irradiation tests of 7 THERMOCOAX Self-Powered Neutron detectors (SPNDs) in the BR1 reactor at SCK•CEN. The SPNDs were fabricated according to the same specifications, but from different fabrication batches. The SPND signals were recorded during stepwise power-up of the reactor, proving the linearity of the SPND response within a wide thermal neutron flux range: from as low as 0.8·109 n/(cm2) to 2.6·1011 n/(cm2s). Intercomparison of the SPND signals shows a very small spread, confirming the repeatability of the THERMOCOAX fabrication processes. The overall neutron sensitivities of the seven SPNDs agreed within a 1% margin. The experimental data were analyzed in terms of prompt and various delayed responses. Prompt contributions to the signal are due to external gamma induced processes and to processes involving gamma rays emitted instantaneously upon neutron capture. The main contribution in a rhodium SPND is due to activation of the rhodium emitter and beta emission during decay of the activated rhodium and leads to a delayed response with a characteristic time of a few minutes. Activation and subsequent beta decay in other materials present in the SPND lead to additional minor delayed signal contributions. The partial SPND sensitivities due to all these processes were calculated using an MCNPX based model and were compared with experimental sensitivities based on the recorded data. The results were in fair agreement; for the overall SPND neutron sensitivity an agreement within a 1% margin was achieved.
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Bisnovatyi-Kogan, G. S., and A. F. Illarionov. "Low Energy Lines in Spectra of Gamma Bursts." International Astronomical Union Colloquium 115 (1990): 63–69. http://dx.doi.org/10.1017/s0252921100012148.
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AbstractWe connect the phenomenon of gamma ray bursts with nuclear explosions on the old neutron stars. The matter of the neutron star in the non-equilibrium layer at depths of 30 m ≤ h ≥ 100 m consists of superheavy (A ≥ 300) nuclei with a surplus of neutrons (A/Z = 3 ÷ 4). These nuclei are metastable and exist only at high pressure. After the starquake some of the matter from non-equilibrium layer may move upwards and its nuclei become unstable. The β-decay is followed by a chain reaction of fission and nuclear explosion. The gamma ray burst is observed as radiation of the star surface heated to high temperature. Some mass may be ejected, forming expanding cloud. It consists mainly of the iron Fe56 with small (≤ 1%) additions of heavy elements (Ba, I, …) arising from the fission. The passage of stellar gamma radiation through the expanding plasma clouds leads to the formation of short-lived spectral features. Strong absorption of the soft gamma rays on K-electrons of Fe56 must be observed in the early stages. The gamma quanta with energies ε = 40–70 keV beyond the K-edge of the heavy elements (Ba, I, …) are absorbed in the later stages. A wide Kα line (εα = 30 keV) appears simultaneously. The free-free emission of expanding hot plasma cloud may be observed as a short flash in optical band.
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Niemeyer, Terlize Cristina, Carlos Roberto Grandini, and Sandra G. Schneider. "Low-Frequency High-Temperature Internal Friction in Ti-13Nb-13Zr Alloy." Key Engineering Materials 319 (September 2006): 103–8. http://dx.doi.org/10.4028/www.scientific.net/kem.319.103.
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Recent studies have been done to achieve biomedical alloys containing non-toxic elements and presenting low elastic moduli. It has been reported that Ti-Nb-Zr alloys rich in beta phase, especially Ti-13Nb-13Zr, have potential characteristics for substituting conventional materials such as Ti-6Al-4V, stainless steel and Co alloys. The aim of this work is to study the internal friction (IF) of Ti-13Nb-13Zr (TNZ) alloy due to the importance of the absorption impacts in orthopedic applications. The internal friction of this alloy produced by arc melting was measured using an inverted torsion pendulum with the free decay method. The measurements were performed from 77 to 700 K with heating rate of 1 K/min, in a vacuum better than 10-5 mBar. The results show a relaxation structure at high temperature strongly dependent on microstructure of the material. Qualitative discussions are presented for the experimental results, and the possibility of using the TNZ as a high damping material is briefly mentioned.
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Andreev, Anatolii V., Roman V. Volkov, Vyacheslav M. Gordienko, Aleksandr M. Dykhne, Pavel M. Mikheev, Andrei B. Savel'ev, Evgenii V. Tkalya, O. V. Chutko, and Alexander A. Shashkov. "Detection of the gamma decay of an isomeric low-lying181Ta level excited in a high-temperature near-surface laser plasma." Quantum Electronics 29, no. 3 (March 31, 1999): 191–92. http://dx.doi.org/10.1070/qe1999v029n03abeh001447.
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Draguhn, A., and U. Heinemann. "Different mechanisms regulate IPSC kinetics in early postnatal and juvenile hippocampal granule cells." Journal of Neurophysiology 76, no. 6 (December 1, 1996): 3983–93. http://dx.doi.org/10.1152/jn.1996.76.6.3983.
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1. Monosynaptic inhibitory postsynaptic currents (IPSCs) were recorded from early postnatal and juvenile dentate granule cells in rat brain slices at room temperature. The focally evoked currents were mediated by gamma-aminobutyric acid-A (GABAA) receptors. 2. IPSCs were characterized by a steep rising phase and a slower, monoexponential decay time course. The decay time constant was potential dependent and average values ranged from 33 ms at a holding potential of -60 mV to 58 ms at a holding potential of +40 mV. 3. IPSCs were studied in tissue from animals between postnatal day (p) 3 and p25. All kinetic parameters as well as the mean current amplitude were unchanged during this ontogenetic period. 4. In juvenile granule cells from animals aged 13–16 days, addition of the GABA uptake blocker (R)-N-[4,4-bis (3-methyl-2-thienyl) but-3-en1-yl] nipecotic acid (tiagabine) (10 microM) prolonged the decaying phase of the IPSCs. The current decay remained monoexponential but the time constant increased to 250% of control values. Mean current amplitudes remained largely unchanged. 5. In contrast, tiagabine had no effect on IPSCs in early postnatal tissue. The decay time constant remained unchanged in cells recorded from animals aged p4-p6. Other uptake blockers were also ineffective during the first postnatal week, whereas beta-alanine, NNC-711, and L-2,3-diaminoproprionic acid enhanced the decay time constant in the older tissue (p13-p16). 6. Hypoosmolaric extracellular solution was applied to restrict the extracellular space. In juvenile tissue (p13-p16), IPSCs were not affected by this treatment, whereas early postnatal granule cells (p4-p6) displayed clearly prolonged IPSC decay time constants (165% of control). 7. We conclude that the mechanism governing the kinetics of evoked IPSCs in granule cells changes during ontogenesis. Whereas in early postnatal tissue the transmitter leaves the postsynaptic site by diffusion, GABA uptake becomes time limiting after 2 wk of postnatal development.
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Baratta, Edmong J., David G. Easterly, S. A. Bell, C.-S. Cheng, J. Daly, G. C. Fuhrmann, J. B. Kapish, et al. "Determination of Iodine-131 at Low Levels in Milk: Collaborative Study." Journal of AOAC INTERNATIONAL 84, no. 2 (March 1, 2001): 507–11. http://dx.doi.org/10.1093/jaoac/84.2.507.
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Abstract The official method for the determination of iodine-131 in milk has a lower limit of detection (LLD) of 10 pCi/L (0.37 Bq/L). The Nuclear Regulatory Commission had recommended that a method claiming to have an LLD of <0.3 pCi/L (<1.1E-02 Bq/L) be used. That method, which is capable of measuring iodine-131 below the level of detection of the Official Method, was collaboratively studied. The method uses a palladium iodide precipitate to concentrate the iodine-131 and measures (counts) its 364 keV gamma energy in coincidence with the beta decay or with a low-background beta-counting system. The study was performed by using 3 concentrations of iodine- 131 in milk: 2.6, 5.0, and 8.0 pCi/L (9.62E-02, 1.85E-01, and 2.96E-01 Bq/L, respectively). Eleven laboratories agreed to participate in the study. Eight laboratories submitted data for the study. The averages of the results were 2.68, 5.30, and 8.12 pCi/L (9.92E-02, 1.96E-01, and 3.00E-01 Bq/L, respectively), respectively. The intra- and interlaboratory variations were acceptable. The method was adopted First Action by AOAC INTERNATIONAL.
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Khan, Arshad, Pabitra Aryal, Hongjoo Kim, Moo Hyun Lee, and Yeongduk Kim. "PbMoO4 Synthesis from Ancient Lead and Its Single Crystal Growth for Neutrinoless Double Beta Decay Search." Crystals 10, no. 3 (February 27, 2020): 150. http://dx.doi.org/10.3390/cryst10030150.
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A powder synthesis of PbMoO4 (PMO) from ancient lead (Pb) and deeply purified commercial MoO3 powders was performed using a wet chemistry technique to achieve the low radioactivity scintillator for neutrinoless double beta decay search in 100Mo. The synthesized powders were used to grow single crystals of PbMoO4 by the Czochralski technique in an Ar environment. The luminescence and scintillation properties were measured with excitations using UV, X- and γ-rays in the temperature range of 10–300 K. Annealing of the grown PMO crystal in an air atmosphere significantly enhanced the scintillation light yield compared to that measured before annealing. The scintillation light yield of grown PMO crystal at 10 K was found to be 127% to that of a reference PMO crystal under 662 keV γ-rays excitation from a 137Cs source. The background measurement of the grown crystal performed at 50 K shows a lower internal activity from 210Pb compared to that of reference PMO (grown from modern Pb) crystal. These preliminary performances show that the PMO crystal grown from ancient Pb and deeply purified MoO3 powders has a great potential to be used as a cryogenic scintillator for the neutrinoless double beta decay search in 100Mo.
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Guo, Shuang-Xi, Sheng-Qi Zhou, Xian-Rong Cen, Ling Qu, Yuan-Zheng Lu, Liang Sun, and Xiao-Dong Shang. "The effect of cell tilting on turbulent thermal convection in a rectangular cell." Journal of Fluid Mechanics 762 (December 2, 2014): 273–87. http://dx.doi.org/10.1017/jfm.2014.655.
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AbstractIn this study the influence of cell tilting on flow dynamics and heat transport is explored experimentally within a rectangular cell (aspect ratios ${\it\Gamma}_{x}=1$ and ${\it\Gamma}_{y}=0.25$). The measurements are carried out over a wide range of tilt angles ($0\leqslant {\it\beta}\leqslant {\rm\pi}/2\ \text{rad}$) at a constant Prandtl number ($\mathit{Pr}\simeq 6.3$) and Rayleigh number ($\mathit{Ra}\simeq 4.42\times 10^{9}$). The velocity measurements reveal that the large-scale circulation (LSC) is sensitive to the symmetry of the system. In the level case, the high-velocity band of the LSC concentrates at about a quarter of the cell width from the boundary. As the cell is slightly tilted (${\it\beta}\simeq 0.04\ \text{rad}$), the position of the high-velocity band quickly moves towards the boundary. With increasing ${\it\beta}$, the LSC changes gradually from oblique ellipse-like to square-like, and other more complicated patterns. Oscillations have been found in the temperature and velocity fields for almost all ${\it\beta}$, and are strongest at around ${\it\beta}\simeq 0.48\ \text{rad}$. As ${\it\beta}$ increases, the Reynolds number ($\mathit{Re}$) initially also increases, until it reaches its maximum at the transition angle ${\it\beta}=0.15\ \text{rad}$, after which it gradually decreases. The cell tilting causes a pronounced reduction of the Nusselt number ($\mathit{Nu}$). As ${\it\beta}$ increases from 0 to 0.15, 1.05 and ${\rm\pi}/2\ \text{rad}$, the reduction of $\mathit{Nu}$ is approximately 1.4 %, 5 % and 18 %, respectively. Over the ranges of $0\leqslant {\it\beta}\leqslant 0.15\ \text{rad}$, $0.15\leqslant {\it\beta}\leqslant 1.05\ \text{rad}$ and $1.05\leqslant {\it\beta}\leqslant {\rm\pi}/2\ \text{rad}$, the decay slopes are $8.57\times 10^{-2}$, $3.27\times 10^{-2}$ and $0.24\ \text{rad}^{-1}$, respectively.
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Divari, Paraskevi C., and John D. Vergados. "Heavy Sterile Neutrino in Dark Matter Searches." Advances in High Energy Physics 2018 (2018): 1–14. http://dx.doi.org/10.1155/2018/1479313.
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Sterile neutrinos are possible dark matter candidates. We examine here possible detection mechanisms, assuming that the neutrino has a mass of about 50 keV and couples to the ordinary neutrino. Even though this neutrino is quite heavy, it is nonrelativistic with a maximum kinetic energy of 0.1 eV. Thus new experimental techniques are required for its detection. We estimate the expected event rate in the following cases: (i) measuring electron recoil in the case of materials with very low electron binding; (ii) low temperature crystal bolometers; (iii) spin induced atomic excitations at very low temperatures, leading to a characteristic photon spectrum; (iv) observation of resonances in antineutrino absorption by a nucleus undergoing electron capture; (v) neutrino induced electron events beyond the end point energy of beta decaying systems, for example, in the tritium decay studied by KATRIN.
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Boschi, A., L. Uccelli, M. Pasquali, A. Duatti, A. Taibi, G. Pupillo, and J. Esposito. "188W/188Re Generator System and Its Therapeutic Applications." Journal of Chemistry 2014 (2014): 1–14. http://dx.doi.org/10.1155/2014/529406.
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The188Re radioisotope represents a useful radioisotope for the preparation of radiopharmaceuticals for therapeutic applications, particularly because of its favorable nuclear properties. The nuclide decay pattern is through the emission of a principle beta particle having 2.12 MeV maximum energy, which is enough to penetrate and destroy abnormal tissues, and principle gamma rays (Eγ=155 keV), which can efficiently be used for imaging and calculations of radiation dose.188Re may be conveniently produced by188W/188Re generator systems. The challenges related to the double neutron capture reaction route to provide only modest yield of the parent188W radionuclide indeed have been one of the major issues about the use of188Re in nuclear medicine. Since the specific activity of188W used in the generator is relatively low (<185 GBq/g), the elutedRe188O4-can have a low radioactive concentration, often ineffective for radiopharmaceutical preparation. However, several efficient postelution concentration techniques have been developed, which yield clinically usefulRe188O4-solutions. This review summarizes the technologies developed for the preparation of188W/188Re generators, postelution concentration of the188Re perrhenate eluate, and a brief discussion of new chemical strategies available for the very high yield preparation of188Re radiopharmaceuticals.
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Greene, John P., Matthew Gott, Richard L. Fink, and Igor Pavlovsky. "Rhenium and iridium targets prepared using a novel graphene loading technique." EPJ Web of Conferences 229 (2020): 06001. http://dx.doi.org/10.1051/epjconf/202022906001.
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For accelerator targets, graphene films are an excellent material choice due to their high thermal conductivity, high temperature tolerance, low outgassing, mechanical integrity, and ease of handling. A variety of targets have been produced using graphene material as a backing or a host matrix. One of the unique advantages of the graphene film fabrication process is the capability to embed target materials, including refractory metals, in the nanoparticle form into a host graphene matrix during target preparation. Targets of natIr and natRe have been fabricated as nanoparticle loaded graphene targets for use in nuclear physics research. We have obtained beam time to evaluate target performance as well as production yields and nuclear decay properties via the natRe(a,2n)186Ir and natIr(a,3n)194Au reactions, respectively. These rhenium and iridium targets will be irradiated using the ATLAS accelerator and gamma rays measured in-place using the high-precision gamma-ray spectroscopy capabilities of Gammasphere and further analyzed using a multi-parameter detector system. Future plans include the preparation of isotopic targets of these two elements.
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Leeuwenkamp, O. R., W. J. van der Vijgh, B. C. Hüsken, P. Lips, and J. C. Netelenbos. "Quantification of strontium in plasma and urine with flameless atomic absorption spectrometry." Clinical Chemistry 35, no. 9 (September 1, 1989): 1911–14. http://dx.doi.org/10.1093/clinchem/35.9.1911.
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Abstract This analytical method for determination of Sr in plasma and urine involves flameless atomic absorption spectrophotometry (FAAS). Drying, charring, and atomization were optimized with respect to temperature, temperature ramp, and duration for Sr in dilute HNO3 and Sr in plasma diluted 20-fold with dilute HNO3. Calibration curves (r greater than 0.995) were linear in the concentration range 5-250 micrograms/L for Sr in various media, with intercepts negligibly small except for the calibration curves in 1:1-diluted plasma and undiluted urine. The estimated detection limits for Sr in 20-fold-diluted plasma and 50-fold-diluted urine were 2 and 3 micrograms/L, respectively. Endogenous Sr in plasma and urine was estimated at 16 (SD 8) micrograms/L and 158 (SD 26) micrograms/L (n = 6), respectively. Intra- and interassay CVs were 9.1% and 5.3% for 20-fold-diluted plasma at a Sr concentration of 25 micrograms/L, and 6.9% and 4.8% at a concentration of 250 micrograms/L. The respective CVs were 8.2% and 1.2% for 50-fold-diluted urine at the low concentration, and 4.0% and 4.6% at the high concentration. In a pharmacokinetic pilot study of 2.5 mmol of Sr orally administered to a healthy volunteer, the peak plasma concentration of Sr, 4.4 mg/L, decayed bi-exponentially [t1/2, alpha = 24 h, t1/2, beta = 77 h]; the estimated first-order absorption rate constant was 0.005 min-1; and the observed decay (day 0-6) of the urinary Sr/creatinine ratio closely paralleled the plasma decay [t1/2 = 70 h].
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Ивашин, Н. В., and С. Н. Терехов. "Спектры РКР и механизмы тушения флуоресценции beta-нитро-тетрафенилпорфирина." Журнал технической физики 126, no. 3 (2019): 285. http://dx.doi.org/10.21883/os.2019.03.47368.288-18.
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AbstractThe study of the excited states and photophysical characteristics of β-nitro-tetraphenylporphyrin (TPP–NO_2) has been carried out using resonance Raman scattering (RRS) spectroscopy and methods of the density functional theory. The appearance of new lines, the intensity of which depends on the composition of the matrix and excitation wavelength, has been found in the TPP–NO_2 RRS spectra in the low-temperature matrix. The calculation of the vibrational states of TPP–NO_2 allowed the linking of the additional lines with the asymmetric vibrations of the nitro group and valence C–C vibrations of the phenyl ring (Ph1) that was nearest to it. The activation of these modes is related to the specific features of the TPP–NO_2 geometry in the charge transfer (CT) state from Ph1 to the porphyrin macrocycle. It has been concluded on the basis of the analysis of the data of the study of the RRS spectra and the results of calculations that use the СAM-B3LYP and wB97XD functionals that the CT states do not play a significant role in the TPP–NO_2 fluorescence quenching, as previously assumed. The fluorescence quenching owes to strengthening channels of internal and inter-conversion by reducing the energy gaps Δ E ( S _1 – T _1) and Δ E ( S _1 – S _0) as well as increasing the spin-orbit coupling between the S _1 and T _1 states. It has been shown that TPP–NO_2 is characterized by conformational heterogeneity both in the ground and in the excited states, which explains the absence of the monoexponentiality of fluorescence decay kinetics.
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Vucina, Jurij, and Ruben Han. "Production and therapeutic application of rhenium isotopes, rhenium-186 and rhenium-188: Radioactive pharmaceuticals of the future." Medical review 56, no. 7-8 (2003): 362–65. http://dx.doi.org/10.2298/mpns0308362v.
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Introduction In contemporary nuclear medicine, alpha, pure beta or beta-gamma emitters are used for targeted therapy. Use of pure and combined alpha/beta emitters in oncology, endocrinology, rheumatology and, a short while ago, interventional cardiology, has refined as an important alternative to more common therapeutic regimens. Two radioisotopes of rhenium, rhenium-186 and rhenium-188, are of particular interest. Production of Rhenium-186 and Rhenium-188 Rhenium-186 is routinely produced in nuclear reactors by direct neutron activation of metallic rhenium enriched with 185Re via 185Re(n,)186Re nuclear reaction. For production of 188Re the target is 186W. 188W is produced by double neutron capture which gives 188Re due to beta decay. Separation of 188Re is performed in generators by column chromatography, extraction or by gel technology. The best results are obtained using chromatographic 188W/188Re generator in which 188W is adsorbed on aluminum. Rhenium-188 is eluted in saline solution. Radiopharmaceuticals labeled with rhenium radioisotopes and their clinical applications There are several fields of applications of radiopharmaceuticals labeled with 186,188Re. For bone pain palliation the most often used are 186Re-HEDP and 188Re-DMSA. For synovectomy, 186Re-sulphide in kit form is already commercially available. Endovascular radiation therapy is performed by using 188Re-perrhenate or 188Re-MAG3. Labeling of peptides and antibodies with 188Re is also reported. Application of rhenium radioisotopes depends on their specific activity. Rhenium-186,188 of low specific activity can be used only for labeling of particles or diphosphonates. However, labeling of peptides or antibodies can be performed only by using 188Re of high specific activity. Conclusion 188Re is expected to have wide applications after development of a chromatographic 188W/188Re generator. One of the advantages of rhenium is its chemical similarity with technetium. So technetium analogues labeled with 186,188Re can be developed for several specific applications.
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Forster, Amanda L., Zois Tsinas, and Mohamad Al-Sheikhly. "Effect of Irradiation and Detection of Long-Lived Polyenyl Radicals in Highly Crystalline Ultra-High Molar Mass Polyethylene (UHMMPE) Fibers." Polymers 11, no. 5 (May 27, 2019): 924. http://dx.doi.org/10.3390/polym11050924.
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To improve properties such as thermal conductivity, low temperature thermal strain, and creep resistance of ultra-high molar mass polyethylene (UHMMPE) fibers, several researchers have previously undertaken efforts to crosslink these fibers using radiation. Ionizing radiation is commonly used to crosslink bulk UHMMPE in other applications, such as artificial joints. However, UHMMPE fibers differ from bulk UHMMPE in that they have a higher crystallinity (approximately 85% to 90%) and are very highly oriented during manufacturing in which the fibers are stretched 50 to 100 times their original length. Thus, the amorphous fraction of the UHMMPE fibers is also highly ordered. Several experiments were conducted to crosslink the UHMMPE fibers using both low dose rate (gamma) and high dose rate (electron beam) irradiation, all in the absence of oxygen. In all cases, the tensile strength of the fiber was greatly reduced by the irradiation. The oxidation index was also measured for the irradiated samples, and oxidation was not found to play a major role in the reduction of tensile strength in the fibers after irradiation. While this work did not achieve the desired result of improving the mechanical properties of the UHMMPE fiber, a significant result was found. The electron paramagnetic resonance (EPR) spectrum of the UHMMPE fibers was measured shortly after irradiation, and a mixture of allyl and alkyl radicals were detected. The irradiated samples were stored in dark ambient conditions for at least six years, then reexamined using EPR for free radical characterization. Surprisingly, the gamma-irradiated samples showed clear evidence of long-lived polyenyl radicals present in the material. Free radicals are very reactive species that will typically migrate to the surface of the crystalline domain and decay in a relatively short time through various reactions in the amorphous regions. It is hypothesized herein that due to the high crystallinity and large anisotropy of the highly drawn UHMMPE fiber, the polyenyl radicals were trapped in the crystal phase and were unable to migrate and decay. An experiment was performed to test this hypothesis, by which samples of the irradiated fibers were heated to temperatures above first the alpha relaxation and then melting point of polyethylene, and EPR measurements were taken. Results showed that the polyenyl radical signal persisted below the Tm, but was rapidly eliminated upon melting of the crystals. These experiments support the hypothesis that the long-lived polyenyl radicals are trapped in the crystalline region of the polyethylene fibers.
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Pedlosky, Joseph. "Time-Dependent Response to Cooling in a Beta-Plane Basin." Journal of Physical Oceanography 36, no. 11 (November 1, 2006): 2185–98. http://dx.doi.org/10.1175/jpo2967.1.
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Abstract The time-dependent response of an ocean basin to the imposition of cooling (or heating) is examined in the context of a quasigeostrophic, two-layer model on the beta plane. The focus is on the structure and magnitude of the vertical motion and its response to both a switch-on forcing and a periodic forcing. The model employed is a time-dependent version of an earlier model used to discuss the intensification of sinking in the region of the western boundary current. The height of the interface of the two-layer model serves as an analog of temperature, and the vertical velocity at the interface consists of a cross-isopycnal velocity modeled in terms of a relaxation to a prescribed interface height, an adiabatic representation of eddy thickness fluxes parameterized as lateral diffusion of thickness, and the local vertical motion of the interface itself. The presence of time dependence adds additional dynamical features to the problem, in particular the emergence of low-frequency, weakly damped Rossby basin modes. If the buoyancy forcing is zonally uniform the basin responds to a switch-on of the forcing by coming into steady-state equilibrium after the passage of a single baroclinic Rossby wave. If the forcing is nonuniform in the zonal direction, a sequence of Rossby basin modes is excited and their decay is required before the basin achieves a steady state. For reasonable parameter values the boundary layers, in which both horizontal and vertical circulations are closed, are quasi-steady and respond to the instantaneous state of the interior. As in the steady problem the flow is sensitive to small nonquasigeostrophic mass fluxes across the perimeter of the basin. These fluxes generally excite basin modes as well. The basin modes will also be weakly excited if the beta-plane approximation is relaxed. The response to periodic forcing is also examined, and the sensitivity of the response to the structure of the forcing is similar to the switch-on problem.
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Valberg, P. A., and D. F. Albertini. "Cytoplasmic motions, rheology, and structure probed by a novel magnetic particle method." Journal of Cell Biology 101, no. 1 (July 1, 1985): 130–40. http://dx.doi.org/10.1083/jcb.101.1.130.
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The motions of magnetic particles contained within organelles of living cells were followed by measuring magnetic fields generated by the particles. The alignment of particles was sensed magnetometrically and was manipulated by external fields, allowing non-invasive detection of particle motion as well as examination of cytoplasmic viscoelasticity. Motility and rheology data are presented for pulmonary macrophages isolated from lungs of hamsters 1 d after the animals had breathed airborne gamma-Fe2O3 particles. The magnetic directions of particles within phagosomes and secondary lysosomes were aligned, and the weak magnetic field produced by the particles was recorded. For dead cells, this remanent field was constant, but for viable macrophages, the remanent field decreased rapidly so that only 42% of its initial magnitude remained 5 min after alignment. A twisting field was applied perpendicular to the direction of alignment and the rate at which particles reoriented to this new direction was followed. The same twisting was repeated for particles suspended in a series of viscosity standards. Based on this approach, the low-shear apparent intracellular viscosity was estimated to be 1.2-2.7 X 10(3) Pa.s (1.2-2.7 X 10(4) poise). Time-lapse video microscopy confirmed the alignment of ingested particles upon magnetization and showed persistent cellular motility during randomization of alignment. Cytochalasin D and low temperature both reduced cytoplasmic activity and remanent-field decay, but affected rheology differently. Magnetic particles were observed in association with the microtubule organizing center by immunofluorescence microscopy; magnetization did not affect microtubule distribution. However, both vimentin intermediate filaments and f-actin reorganized after magnetization. These data demonstrate that magnetometry of isolated phagocytic cells can probe organelle movements, rheology, and physical properties of the cytoskeleton in living cells.
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Van der Kloot, W., and J. Molgo. "Facilitation and delayed release at about 0 degree C at the frog neuromuscular junction: effects of calcium chelators, calcium transport inhibitors, and okadaic acid." Journal of Neurophysiology 69, no. 3 (March 1, 1993): 717–29. http://dx.doi.org/10.1152/jn.1993.69.3.717.
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1. We studied two-pulse facilitation and delayed release at 0 degree C, because at low temperature facilitation is enhanced and extended whereas delayed release is increased. Our major goal was to test, by a number of approaches, the residual Ca2+ hypothesis of facilitation and delayed release. 2. As we increased the interval between pulses from 30 to 100–200 ms facilitation declined steeply. As we lengthened the interval further facilitation declined more slowly. In our entire series facilitation was still seen at 700 ms, in some preparations facilitation was apparent at 2 s. 3. We measured delayed release in preparations in which excitation-contraction was uncoupled. The decline in the rate of delayed release following the endplate potential (EPP) is similar to the decay of facilitation, both at 0 and 22 degrees C. 4. When we replaced the Ca2+ in the Ringer by Sr2+, facilitation persisted for a longer time, there was significant facilitation 2 s after an EPP. Delayed release also continued longer; the time courses for the decline of facilitation and delayed release were very similar. 5. We measured delayed release after EPPs triggered by electrotonic depolarization in isotonic CaCl2 solution or in Ringer in which the Na+ was replaced by methylamine (these solutions also contained 3,4-diaminopyridine). The time course of delayed release was very similar to that in Ringer. 6. We found that delayed release also facilitated, in the sense that the number of delayed releases, and the rate at which they were released, increased markedly after a second or third closely spaced EPP. The facilitation of delayed release and of EPPs were quantitatively similar. 7. We soaked preparations for 2 h in 200 microM bis-(aminophenoxy) ethane-tetraacetic acid (BAPTA/AM), a cell permeable Ca2+ chelator. In about one-half of these preparations facilitation was clearly diminished, judging from the EPPs evoked by a series of four to five stimuli at 30-ms intervals. The summed results from those preparations in which facilitation was reduced at 30 ms showed that it was also reduced at longer intervals. There was a comparable shortening in delayed release. Facilitation was significantly reduced when we pretreated with ethylene glycol bis-(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid tetraacetoxymethyl ester (EGTA/AM), another cell-permeable Ca2+ chelator. 8. It has been reported that in BAPTA loaded preparations facilitation during trains of EPPs transiently reappears after exposure to the ionophore X-537A, which presumably elevates intracellular [Ca2+].(ABSTRACT TRUNCATED AT 400 WORDS)
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Brofferio, Chiara, Oliviero Cremonesi, and Stefano Dell'Oro. "Neutrinoless Double Beta Decay Experiments With TeO2 Low-Temperature Detectors." Frontiers in Physics 7 (June 13, 2019). http://dx.doi.org/10.3389/fphy.2019.00086.
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Adams, D. Q., C. Alduino, K. Alfonso, F. T. III Avignone, O. Azzolini, G. Bari, F. Bellini, et al. "Search for double-beta decay of $$\mathrm {^{130}Te}$$ to the $$0^+$$ states of $$\mathrm {^{130}Xe}$$ with CUORE." European Physical Journal C 81, no. 7 (July 2021). http://dx.doi.org/10.1140/epjc/s10052-021-09317-z.
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AbstractThe CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay ($$0\nu \beta \beta $$ 0 ν β β ) in the isotope $$\mathrm {^{130}Te}$$ 130 Te . In this work we present the latest results on two searches for the double beta decay (DBD) of $$\mathrm {^{130}Te}$$ 130 Te to the first $$0^{+}_2$$ 0 2 + excited state of $$\mathrm {^{130}Xe}$$ 130 Xe : the $$0\nu \beta \beta $$ 0 ν β β decay and the Standard Model-allowed two-neutrinos double beta decay ($$2\nu \beta \beta $$ 2 ν β β ). Both searches are based on a 372.5 kg$$\times $$ × yr TeO$$_2$$ 2 exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique signature, which can be searched for with low background by studying coincident events in two or more bolometers. The closely packed arrangement of the CUORE crystals constitutes a significant advantage in this regard. The median limit setting sensitivities at 90% Credible Interval (C.I.) of the given searches were estimated as $$\mathrm {S^{0\nu }_{1/2} = 5.6 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 0 ν = 5.6 × 10 24 yr for the $${0\nu \beta \beta }$$ 0 ν β β decay and $$\mathrm {S^{2\nu }_{1/2} = 2.1 \times 10^{24} \, \mathrm {yr}}$$ S 1 / 2 2 ν = 2.1 × 10 24 yr for the $${2\nu \beta \beta }$$ 2 ν β β decay. No significant evidence for either of the decay modes was observed and a Bayesian lower bound at $$90\%$$ 90 % C.I. on the decay half lives is obtained as: $$\mathrm {(T_{1/2})^{0\nu }_{0^+_2} > 5.9 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 0 ν > 5.9 × 10 24 yr for the $$0\nu \beta \beta $$ 0 ν β β mode and $$\mathrm {(T_{1/2})^{2\nu }_{0^+_2} > 1.3 \times 10^{24} \, \mathrm {yr}}$$ ( T 1 / 2 ) 0 2 + 2 ν > 1.3 × 10 24 yr for the $$2\nu \beta \beta $$ 2 ν β β mode. These represent the most stringent limits on the DBD of $$^{130}$$ 130 Te to excited states and improve by a factor $$\sim 5$$ ∼ 5 the previous results on this process.
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Belli, P., R. Bernabei, F. Cappella, R. Cerulli, F. A. Danevich, A. Di Marco, A. Incicchitti, et al. "First search for double- $ \beta$ decay of platinum by ultra-low background HP Ge $ \gamma$ spectrometry." European Physical Journal A 47, no. 8 (August 2011). http://dx.doi.org/10.1140/epja/i2011-11091-6.
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Jansen, Sabine, Wolfgang König, Bernd Schmidt, and Florian Theil. "Surface Energy and Boundary Layers for a Chain of Atoms at Low Temperature." Archive for Rational Mechanics and Analysis, December 21, 2020. http://dx.doi.org/10.1007/s00205-020-01587-3.
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AbstractWe analyze the surface energy and boundary layers for a chain of atoms at low temperature for an interaction potential of Lennard–Jones type. The pressure (stress) is assumed to be small but positive and bounded away from zero, while the temperature $$\beta ^{-1}$$ β - 1 goes to zero. Our main results are: (1) As $$\beta \rightarrow \infty $$ β → ∞ at fixed positive pressure $$p>0$$ p > 0 , the Gibbs measures $$\mu _\beta $$ μ β and $$\nu _\beta $$ ν β for infinite chains and semi-infinite chains satisfy path large deviations principles. The rate functions are bulk and surface energy functionals $$\overline{{\mathcal {E}}}_{\mathrm {bulk}}$$ E ¯ bulk and $$\overline{{\mathcal {E}}}_\mathrm {surf}$$ E ¯ surf . The minimizer of the surface functional corresponds to zero temperature boundary layers; (2) The surface correction to the Gibbs free energy converges to the zero temperature surface energy, characterized with the help of the minimum of $$\overline{{\mathcal {E}}}_\mathrm {surf}$$ E ¯ surf ; (3) The bulk Gibbs measure and Gibbs free energy can be approximated by their Gaussian counterparts; (4) Bounds on the decay of correlations are provided, some of them uniform in $$\beta $$ β .
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Djamal, Mitra. "Preliminary Study of Double Beta Decay: Simulation of CaMoO4 Scintillation Detector Response Function to the Gamma Ray Radiation." KnE Engineering 1, no. 1 (September 5, 2016). http://dx.doi.org/10.18502/keg.v0i0.479.
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<p class="TTPAbstract">CaMoO<sub>4</sub> crystal is a material candidate forthe scintillation detector and double beta decay experiment to determinea neutrino mass. The objective of this work is to analyze the response function of CaMoO<sub>4 </sub>using Monte Carlo GEANT4 simulation. Penelope-low energy method was used as an interaction type for the electromagnetic process. The simulation results show that the presence of the photopeak energies of gamma ray from Cs-137, Co-60 and K-40 sources can be identified and observed in the energy 0.662 MeV, 1.17 MeV, 1.33 MeV and 1.5 MeV. The photoelectric cross section interaction of CaMoO<sub>4 </sub>is lower than NaI(Tl), but in other hand the incoherent cross section is vice versa.</p>
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Djamal, Mitra. "Preliminary Study of Double Beta Decay: Simulation of CaMoO4 Scintillation Detector Response Function to the Gamma Ray Radiation." KnE Engineering 1 (September 5, 2016). http://dx.doi.org/10.18502/keg.v1i1.479.
Full textAbstract:
<p class="TTPAbstract">CaMoO<sub>4</sub> crystal is a material candidate forthe scintillation detector and double beta decay experiment to determinea neutrino mass. The objective of this work is to analyze the response function of CaMoO<sub>4 </sub>using Monte Carlo GEANT4 simulation. Penelope-low energy method was used as an interaction type for the electromagnetic process. The simulation results show that the presence of the photopeak energies of gamma ray from Cs-137, Co-60 and K-40 sources can be identified and observed in the energy 0.662 MeV, 1.17 MeV, 1.33 MeV and 1.5 MeV. The photoelectric cross section interaction of CaMoO<sub>4 </sub>is lower than NaI(Tl), but in other hand the incoherent cross section is vice versa.</p>
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Furis, Madalina, Fei Chen, Alexander N. Cartwright, Hong Wu, and William J. Schaff. "Room-Temperature Time–Resolved Photoluminescence Studies of UV Emission from GaN/AlN Quantum Wells." MRS Proceedings 743 (2002). http://dx.doi.org/10.1557/proc-743-l11.14.
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ABSTRACTRoom temperature time-resolved photoluminescence (TRPL) studies of multiple quantum well (MQW) structures of the binaries GaN and AlN grown by molecular beam epitaxy are reported. The eventual application of these structures is for GaN intersubband IR light emitters. However, as an initial study, the structures are evaluated at UV to investigate materials parameters relevant to IR light emission. The nominally 0.9, 1.3 and 1.5 nm GaN quantum wells are clad by 6nm of AlN on top of a thick AlN buffer grown on sapphire. All samples consisted of 20 quantum wells. The observed peak energy of the emission spectrum is in excellent agreement with a model that includes the strong confinement present in these structures and the existence of the large built-in piezoelectric field and spontaneous polarization present inside the wells. Furthermore, consistent with screening of the in-well field as carriers are injected in the well, a clear blue shift of the emission is observed at short times after carrier injection. Subsequently, as the carriers recombine, the peak emission red-shifts and the screening of the field is reduced. Moreover, the observed lifetimes were energy dependent as should be expected from field dependent elongation of lifetimes due to spatial separation of the injected carriers. Specifically, the decay time at high energies can be fitted by a stretched exponential with a beta value of 0.8 which is consistent with carrier spatial separation. The lifetimes obtained from the fitting are of the order of 1ns, longer than the reported recombination lifetimes in similar GaN/AlGaN MQW's. On the low energy side of the PL feature the intensity time decay becomes exponential with lifetimes ranging from 3 to 10ns. The strong UV emission at room temperature makes these structures promising for UV emitters.
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Muluvhahothe, Mulalo M., Grant S. Joseph, Colleen L. Seymour, Thinandavha C. Munyai, and Stefan H. Foord. "Repeated surveying over 6 years reveals that fine-scale habitat variables are key to tropical mountain ant assemblage composition and functional diversity." Scientific Reports 11, no. 1 (January 8, 2021). http://dx.doi.org/10.1038/s41598-020-80077-8.
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AbstractHigh-altitude-adapted ectotherms can escape competition from dominant species by tolerating low temperatures at cooler elevations, but climate change is eroding such advantages. Studies evaluating broad-scale impacts of global change for high-altitude organisms often overlook the mitigating role of biotic factors. Yet, at fine spatial-scales, vegetation-associated microclimates provide refuges from climatic extremes. Using one of the largest standardised data sets collected to date, we tested how ant species composition and functional diversity (i.e., the range and value of species traits found within assemblages) respond to large-scale abiotic factors (altitude, aspect), and fine-scale factors (vegetation, soil structure) along an elevational gradient in tropical Africa. Altitude emerged as the principal factor explaining species composition. Analysis of nestedness and turnover components of beta diversity indicated that ant assemblages are specific to each elevation, so species are not filtered out but replaced with new species as elevation increases. Similarity of assemblages over time (assessed using beta decay) did not change significantly at low and mid elevations but declined at the highest elevations. Assemblages also differed between northern and southern mountain aspects, although at highest elevations, composition was restricted to a set of species found on both aspects. Functional diversity was not explained by large scale variables like elevation, but by factors associated with elevation that operate at fine scales (i.e., temperature and habitat structure). Our findings highlight the significance of fine-scale variables in predicting organisms’ responses to changing temperature, offering management possibilities that might dilute climate change impacts, and caution when predicting assemblage responses using climate models, alone.
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Muluvhahothe, Mulalo M., Grant S. Joseph, Colleen L. Seymour, Thinandavha C. Munyai, and Stefan H. Foord. "Repeated surveying over 6 years reveals that fine-scale habitat variables are key to tropical mountain ant assemblage composition and functional diversity." Scientific Reports 11, no. 1 (January 8, 2021). http://dx.doi.org/10.1038/s41598-020-80077-8.
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AbstractHigh-altitude-adapted ectotherms can escape competition from dominant species by tolerating low temperatures at cooler elevations, but climate change is eroding such advantages. Studies evaluating broad-scale impacts of global change for high-altitude organisms often overlook the mitigating role of biotic factors. Yet, at fine spatial-scales, vegetation-associated microclimates provide refuges from climatic extremes. Using one of the largest standardised data sets collected to date, we tested how ant species composition and functional diversity (i.e., the range and value of species traits found within assemblages) respond to large-scale abiotic factors (altitude, aspect), and fine-scale factors (vegetation, soil structure) along an elevational gradient in tropical Africa. Altitude emerged as the principal factor explaining species composition. Analysis of nestedness and turnover components of beta diversity indicated that ant assemblages are specific to each elevation, so species are not filtered out but replaced with new species as elevation increases. Similarity of assemblages over time (assessed using beta decay) did not change significantly at low and mid elevations but declined at the highest elevations. Assemblages also differed between northern and southern mountain aspects, although at highest elevations, composition was restricted to a set of species found on both aspects. Functional diversity was not explained by large scale variables like elevation, but by factors associated with elevation that operate at fine scales (i.e., temperature and habitat structure). Our findings highlight the significance of fine-scale variables in predicting organisms’ responses to changing temperature, offering management possibilities that might dilute climate change impacts, and caution when predicting assemblage responses using climate models, alone.
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Ödegaard-Jensen, Arvid, and Virginia Oversby. "Testing of Uranium Dioxide Containing Different Levels of Alpha Activity Under Anaerobic and Reducing Conditions." MRS Proceedings 1104 (2008). http://dx.doi.org/10.1557/proc-1104-nn03-09.
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AbstractSweden plans to dispose of spent nuclear reactor fuel in a deep geologic repository in granitic rock. The conditions in the repository in the long term will be reducing and water is not expected to contact the fuel until after more than 1000 years. At that time, most of the beta- and gamma-active nuclides will have decayed away and the radiation will be dominated by alpha decay. In order to simulate the radiolysis field for dissolution of spent fuel with age more than 1000 years we have used uranium dioxide containing 5% U-235 and 0, 5, or 10% U-233. The 10% U-233 gives an alpha activity appropriate to about 3000 years after disposal. Samples were testied in a synthetic groundwater with low ionic strength and with the chemical composition dominated by sodium bicarbonate and calcium chloride. Tests were run in triplicate using an atmosphere of nitrogen (1atm), hydrogen (10 bar), hydrogen (10 bar) plus an iron strip in the solution, nitrogen (1 atm) plus an iron strip in the solution, hydrogen (10 bar) plus an iron strip in the solution, hydrogen (10 bar) without the iron strip. Each of these test conditions was run for 2 consecutive periods of at least 21 days. The results showed that the dissolution behavior of the samples was the same for both nitrogen atmosphere and hydrogen atmosphere. The amount of U dissolved under these conditions clearly showed the enhancement of dissolution due to oxidation of the sample surface by radiolysis products. When an iron strip was added to the solution, the amount of dissolution decreased dramatically indicating that the Fe(II) ions released from the corroding iron were able to react with most of the radiolysis products before they could oxidize the uranium dioxide surface.
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He, Xiao-Gang, and Xiao-Dong Ma. "An EFT toolbox for baryon and lepton number violating dinucleon to dilepton decays." Journal of High Energy Physics 2021, no. 6 (June 2021). http://dx.doi.org/10.1007/jhep06(2021)047.
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Abstract In this paper we systematically consider the baryon (B) and lepton (L) number violating dinucleon to dilepton decays (pp → ℓ+ℓ′+, pn → $$ {\mathrm{\ell}}^{+}\overline{\nu}^{\prime } $$ ℓ + ν ¯ ′ , nn → $$ \overline{\nu}\overline{\nu}^{\prime } $$ ν ¯ ν ¯ ′ ) with ∆B = ∆L = −2 in the framework of effective field theory. We start by constructing a basis of dimension-12 (dim-12) operators mediating such processes in the low energy effective field theory (LEFT) below the electroweak scale. Then we consider their standard model effective field theory (SMEFT) completions upwards and their chiral realizations in baryon chiral perturbation theory (BχPT) downwards. We work to the first nontrivial orders in each effective field theory, collect along the way the matching conditions, and express the decay rates in terms of the Wilson coefficients associated with the dim-12 operators in the SMEFT and the low energy constants pertinent to BχPT. We find the current experimental limits push the associated new physics scale larger than 1 − 3 TeV, which is still accessible to the future collider searches. Through weak isospin symmetry, we find the current experimental limits on the partial lifetime of transitions pp → ℓ+ℓ′+, pn → $$ {\mathrm{\ell}}^{+}\overline{\nu}^{\prime } $$ ℓ + ν ¯ ′ imply stronger limits on nn → $$ \overline{\nu}\overline{\nu}^{\prime } $$ ν ¯ ν ¯ ′ than their existing lower bounds, which are improved by 2−3 orders of magnitude. Furthermore, assuming charged mode transitions are also dominantly generated by the similar dim-12 SMEFT interactions, the experimental limits on pp → e+e+, e+μ+, μ+μ+ lead to stronger limits on pn → $$ {\mathrm{\ell}}_{\alpha}^{+}{\overline{\nu}}_{\beta } $$ ℓ α + ν ¯ β with α, β = e, μ than their existing bounds. Conversely, the same assumptions help us to set a lower bound on the lifetime of the experimentally unsearched mode pp → e+τ+ from that of pn → $$ {e}^{+}{\overline{\nu}}_{\tau } $$ e + ν ¯ τ , i.e., $$ {\Gamma}_{pp\to {e}^{+}{\tau}^{+}}^{-1}\gtrsim 2\times {10}^{34} $$ Γ pp → e + τ + − 1 ≳ 2 × 10 34 yr.
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Burakov, Boris E., Maria A. Yagovkina, Vladimir M. Garbuzov, Alexander A. Kitsay, and Vladimir A. Zirlin. "Self-Irradiation of Monazite Ceramics: Contrasting Behavior of PuPO4 and (La,Pu)PO4 Doped with Pu-238." MRS Proceedings 824 (2004). http://dx.doi.org/10.1557/proc-824-cc4.1.
Full textAbstract:
AbstractTo investigate the behavior of monazite during accelerated radiation damage, which simulates effects of long term storage, 238Pu-doped polycrystalline samples of (La,Pu)PO4 and PuPO4 were synthesized for the first time ever and studied using powder X-ray diffraction (XRD) analysis and optical microscopy. The starting precursor materials were obtained by precipitation of La and (or) Pu from their aqueous nitrate solutions followed by calcination in air at 700°C for 1 hour, cold pressing, and sintering in air at 1200-1250°C for 2 hours. The 238Pu contents in ceramic samples measured using gamma spectrometry were (in wt.% el.): 8.1 for (La,Pu)PO4 and 7.2 for PuPO4. The (La,Pu)PO4 monazite remained crystalline at ambient temperature up to a cumulative dose of 1.19 × 1025 alpha decays/m3. In contrast, the PuPO4 monazite became nearly completely amorphous at a relatively low dose of 4.2 × 1024 alpha decays/m3. Swelling and crack formation due to the alpha decay damage was observed in the PuPO4 ceramic. Also, under self-irradiation this sample completely changed color from initial deep blue to black. The (La,Pu)PO4 monazite was characterized by a similar change in color from initial light blue to gray, however, no swelling or crack formation have so far been observed. The results of this study allow us to conclude that the radiation damage behavior of monazite strictly depends on the chemical composition. The justification of monazite-based ceramics as actinide waste forms requires additional investigation.
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"The possibility to obtain ZnSe crystals with high structural perfection for cryogenic bolometric technics." Journal of V. N. Karazin Kharkiv National University, Series "Physics", no. 30 (2019). http://dx.doi.org/10.26565/2222-5617-2019-30-3.
Full textAbstract:
In this work the samples of ZnSe zinc selenide crystal grown from the melt by Bridgman method from high-purity (chemical and radio) raw materials were studied for further use in experiments on the search for neutrinoless double beta decay. The microstructure of the test samples was studied. Chemical selective etching, first of all, has allowed to determine the nature of distribution and sizes of area twinning, as well as the etch pits along twins boundaries. It is shown the figures found by chemical etching are the dislocation exits to the studied crystal surface. The dislocation density was estimated by counting the dislocation etch pits on the plane perpendicular to the growth direction and was 104 cm-2. As a rule, thermophysical conditions of ZnSe crystal growth, as well as high concentration of foreign inclusions and impurities in the crystal significantly affect the formation of twins and growth dislocations and are the cause of the optical, electrical, and mechanical heterogeneity of the material. The optical and electrical characteristics of the samples were measured. The absorption bands observed in the optical transmission spectra of the visible and IR ranges gave important information about the presence of local defects and impurities in the crystal, namely in 470÷550 nm and 580÷650 nm regions – absorption by point defects and in 3÷15 μm region – Fe2+, CSe and CSe2 absorption. The total transmission level in the visible range reached 60 %, which is lower than the theoretical one and due to scattering by defects. The phonon thermal conductivity of ZnSe sample was measured in the temperature range 5÷298 K. Based on the approximation of obtained temperature dependences of the thermal conductivity, it was shown that the phonon mean free path at low temperatures is comparable with the distance between twins’ boundaries in the sample.