Γ-ray Singles Research Articles

Dual-threshold Time-over-Threshold nonlinearity correction for PET detectors

The Time-over-Threshold (ToT) analog-to-digital signal processing approach provides a power-efficient and cost-effective technique to extract all relevant information from detectors in high-energy physics and Positron Emission Tomography (PET) imaging. In this work, three calibration methods were investigated to correct the inherent nonlinear response of the ToT data using 1) γ-ray sources of various energies, 2) internal electronic gain variation in the LabPET II ASIC in combination with a single energy γ-ray source, and 3) internal gain variation along with an embedded pulse charge generator in replacement of a γ-ray source. The electronic gain calibration technique was shown to achieve equivalent correction accuracy as the γ-ray sources calibration. Furthermore, this method has the advantage of allowing a faster calibration requiring only one single γ-ray source (e.g., 511 keV) and a quick automated routine to sweep the internal gain. The last technique would be the most convenient method, provided that the signal pulse shape would be similar to the detector signal responding to a typical γ-ray event. Whereas the concept was demonstrated with a step pulse, extensive processing would be required to recover the nonlinearity correction factors for the detector pulse shape. After calibration, the 511-keV energy resolution of typical LabPET II detectors was only slightly degraded, by less than 12% and 8% for methods 1) and 2), respectively, relative to a conventional ADC-based data acquisition system. The feasibility of fast and accurate calibration for the nonlinearity correction of ToT data in PET imaging was demonstrated, making a daily quality control within reach.

Integrative Analysis for the Roles of lncRNAs in the Immune Responses of Mouse PBMC Exposed to Low-Dose Ionizing Radiation.

It is well accepted that low-dose ionizing radiation (LDIR) modulates a variety of immune responses that have exhibited the properties of immune hormesis. Alterations in messenger RNA (mRNA) and long noncoding RNA (lncRNA) expression were to crucially underlie these LDIR responses. However, lncRNAs in LDIR-induced immune responses have been rarely reported, and its functions and molecular mechanisms have not yet been characterized. Here, we used microarray profiling to determine lncRNA in BALB/c mice exposed to single (0.5 Gy×1) and chronic (0.05 Gy×10) low-dose γ-rays radiation (Co60). We observed that a total of 8274 lncRNAs and 7240 mRNAs were altered in single LDIR, while 2077 lncRNAs and 796 mRNAs in chronic LDIR. The biological functions of these upregulated mRNAs in both 2 groups using Gene Ontology functional and pathway enrichment analysis were significantly enriched in immune processes and immune signaling pathways. Subsequently, we screened out the lncRNAs involved in regulating these immune signaling pathways and examined their potential functions by lncRNAs-mRNAs coexpression networks. This is the first study to comprehensively identify lncRNAs in single and chronic LDIR responses and to demonstrate the involvement of different lncRNA expression patterns in LDIR-induced immune signaling pathways. Further systematic research on these lncRNAs will provide new insights into our understanding of LDIR-modulated immune hormesis responses.

Research of radiation resistance delivery through paracrine effects on non-small cell lung cancer

Objective To investigate the role and possible mechanisms of paracrine in radiation tolerance of non-small cell lung cancer (NSCLC) by observing the effects of radiation-resistant NSCLC H460R cell secretion on the radiosensitivity of parental H460 cells. Methods H460 cells were inoculated and cultured, and then divided into control group, conditional culturing group, irradiation group and irradiation combined conditional culturing group. One-time irradiation with 137Cs γ-rays was conducted with a dose rate of 1.02 Gy/min. Effect of H460R conditioned media on the radiation sensitivity of H460 cells was observed by clonogenic assay. The percentage of phospho-histone histone H2AX (γH2AX) positive cells was detected by immunofluorescence staining. The cyclical changes of the cells were detected by flow cytometry. The expression of DNA damage-associated proteins γH2AX and Rad51 were detected by Western Blot. Results The results showed that compared with the single γ-rays irradiation, the number of cell clones was significantly increased in the H460R cells after γ-rays irradiation combined with conditional culturing treatment at different doses of 2, 4, and 6 Gy, and the differences were statistically significant (2,4 Gy: all P<0.05; 6 Gy: P<0.01). The results of immunofluorescence staining showed that the percentage of γH2AX positive cells in the conditional culturing group was higher than that in the control group [(39.40±2.51)% vs. (25.21±2.05)%], and the difference was statistically significant (P<0.01). This value in the irradiation combined conditional culturing group was lower than that in irradiated group [(60.48±2.79)% vs. (80.65±2.05)%], and the difference was statistically significant (P<0.001). The flow cytometry analysis showed that the percentage of cells in G2/M phase for the irradiation (4 Gy) combined conditional culturing group was higher than that of irradiated group [(26.83±1.42)% vs. (15.73±1.29)%], and the difference was statistically significant (P<0.001). The Western Blot results showed that γH2AX and Rad51 protein expression in the irradiation (4 Gy) combined conditional culturing group respectively was lower and higher than that in irradiated group. Conclusion In the tumor microenvironment, radiation-resistant H460R cells can enhance the radioresistance of H460 cells by paracrine, which may be related to the promotion of DNA repair ability after irradiation Key words: Non-small cell lung cancer; Paracrine; Radioresistance; DNA repair

Исследование содержания уридиловых нуклеотидов и активности аспартаткарбамоилтрансферазы в тканях облученных крыс при введении оротовой кислоты и перфторана

Purpose: Study of uridylic nucleotides content and aspartate carbamoyltransferase which was a key enzyme on the pathway for the synthesis of pyrimidine nucleotides in tissues of irradiated animals upon administration of orotic acid and perftorane was conducted.&#x0D; Material and methods: Studies were performed on random-bred albino rats subjected to a single γ-ray exposure at a total dose of 6 Gy. Orotic acid was injected as potassium salt in a dose of 60 mg / kg, perftoran salt in a dose of 1 ml / 100 g water.&#x0D; Results: A decrease in the content of UTP and UDP, as well as an increase in UMP after irradiation, especially on the 7th day, was established. The most pronounced changes in the studied biochemical parameters take place in the mucosa of the small intestine. The administration of orotic acid and perftorane to irradiated animals contributes to a significant correction of both the nucleotide content and the activity of aspartate carbamoyltransferase.&#x0D; Conclusion: The radiation leads to some decrease in the content of UDP and UTP. Changes in the content of nucleotides and activity of aspartate carbamoyltransferase in the mucosa of the small intestine are more pronounced in comparison with liver tissue. The combined administration of orotic acid and perftorane promotes the normalization of the content of nucleotides, and the activity of aspartate carbamoyltransferase in the liver and mucous membrane of the small intestine of irradiated animals.

Search for the Ga73 ground-state doublet splitting in the β decay of Zn73

The existence of two close-lying nuclear states in ⁷³Ga has recently been experimentally determined: a 1/2⁻ spin-parity for the ground state was measured in a laser spectroscopy experiment, while a J_π = 3/2⁻ level was observed in transfer reactions. This scenario is supported by Coulomb excitation studies, which set a limit for the energy splitting of 0.8 keV. In this work, we report on the study of the excited structure of ⁷³Ga populated in the β decay of ⁷³Zn produced at ISOLDE, CERN. Using β-gated, γ-ray singles, and γ –γ coincidences, we have searched for energy differences to try to delimit the ground-state energy splitting, providing a more stringent energy difference limit. Three new half-lives of excited states in ⁷³Ga have been measured using the fast-timing ;method with LaBr₃(Ce) detectors. From our study, we help clarify the excited structure of ⁷³G and we extend the existing ⁷³Zn decay to ⁷³Ga with 8 new energy levels and 35 γ transitions. We observe a 195-keV transition consistent with a γ ray de-exciting a short-lived state in the β-decay parent ⁷³Zn.

New systematic features in the neutron-deficient Au isotopes

A recently developed portable, on-line capability for γ-ray and conversion-electron spectroscopy, HIGH-TATRA is demonstrated with its application to the study of 183Hg 183Au at ISOLDE. Key details of the low-energy level scheme of the neutron-deficient nuclide 183Au populated in this decay are presented. A broad energy germanium detector is employed to achieve this (the first-ever use of such a device in decay-scheme spectroscopy), by way of a combination of high-gain γ-ray singles spectroscopy and γ–γ coincidence spectroscopy. Further, by combining the γ-ray detectors with a liquid-nitrogen-cooled Si(Li) detector operated under high vacuum, conversion-electron singles and e–γ coincidences are obtained. These data lead to the determination of transition multipolarities and the location of a highly converted (E0 + M1 + E2) transition in the 183Au decay scheme, suggesting a possible new shape coexisting structure in this nucleus. Identification of new intruder and normal states fixes their relative energies in 183Au for the first time. New systematic features in the odd-Au isotopes are presented.

Total prompt γ-ray emission in fission

The total prompt γ-ray energy distributions were measured for the neutron-induced fission of 235U, 239,241Pu at incident neutron energy of 0.025 eV–100 keV, and the spontaneous fission of 252Cf using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments by a parallel-plate avalanche counter. Corrections were made to the measured distribution by unfolding the two-dimension spectrum of total prompt γ-ray energy vs multiplicity using a simulated DANCE response matrix. A summary of this work is presented with the emphasis on the comparison of total prompt fission γ-ray energy between our results and previous ones. The mean values of the total prompt γ-ray energy ⟨Eγ,tot⟩, determined from the unfolded distributions, are ∼20% higher than those derived from measurements using single γ-ray detector for all the fissile nuclei studied.

A method for imaging and spectroscopy using γ-rays and magnetic resonance.

Magnetic resonance imaging (MRI) provides fine spatial resolution, spectral sensitivity and a rich variety of contrast mechanisms for diagnostic medical applications. Nuclear imaging using γ-ray cameras offers the benefits of using small quantities of radioactive tracers that seek specific targets of interest within the body. Here we describe an imaging and spectroscopic modality that combines favourable aspects of both approaches. Spatial information is encoded into the spin orientations of tiny amounts of a polarized radioactive tracer using pulses of both radio-frequency electromagnetic radiation and magnetic-field gradients, as in MRI. However, rather than detecting weak radio-frequency signals, imaging information is obtained through the detection of γ-rays. A single γ-ray detector can be used to acquire an image; no γ-ray camera is needed. We demonstrate the feasibility of our technique by producing images and spectra from a glass cell containing only about 4 × 10(13) atoms (about 1 millicurie) of the metastable isomer (131m)Xe that were polarized using the laser technique of spin-exchange optical pumping. If the cell had instead been filled with water and imaged using conventional MRI, then it would have contained more than 10(24) water molecules. The high sensitivity of our modality expands the breadth of applications of magnetic resonance, and could lead to a new class of radioactive tracers.

An inversion decomposition test based on Monte Carlo response matrix on the γ-ray spectra from NaI(Tl) scintillation detector

The NaI(Tl) scintillation detector has a number of unique advantages, including wide use, high light yield, and its low price. It is difficult to obtain the decomposition of instrument response spectrum because of limitations associated with the NaI(Tl) scintillation detector’s energy resolution. This paper, based on the physical process of γ photons released from decay nuclides, generating an instrument response spectrum, uses the Monte Carlo method to simulate γ photons with NaI(Tl) scintillation detector interaction. The Monte Carlo response matrix is established by different single energy γ-rays with detector effects. The Gold and the improved Boosted-Gold iterative algorithms have also been used in this paper to solve the response matrix parameters through decomposing tests, such as simulating a multi-characteristic energy γ-ray spectrum and simulating synthesized overlapping peaks γ-ray spectrum. An inversion decomposition of the γ instrument response spectrum for measured samples (U series, Th series and U–Th mixed sources, among others) can be achieved under the response matrix. The decomposing spectrum can be better distinguished between the similar energy characteristic peaks, which improve the error levels of activity analysis caused by the overlapping peak with significant effects.

Total promptγ-ray emission in fission

The total prompt γ-ray energy distributions were measured for the neutron-induced fission of 235 U, 239,241 Pu at incident neutron energy of 0.025 eV–100 keV, and the spontaneous fission of 252 Cf using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments by a parallel-plate avalanche counter. Corrections were made to the measured distribution by unfolding the two-dimension spectrum of total prompt γ-ray energy vs multiplicity using a simulated DANCE response matrix. A summary of this work is presented with the emphasis on the comparison of total prompt fission γ-ray energy between our results and previous ones. The mean values of the total prompt γ-ray energy ⟨Eγ,tot⟩, determined from the unfolded distributions, are ∼20% higher than those derived from measurements using single γ-ray detector for all the fissile nuclei studied.

β− Decay of 150Ce to Odd–Odd 150Pr

The β− decay of 150Ce having a half-life of 6.05(7) s produced by the thermal-neutron-induced fission of 235U has been studied using the on-line isotope separator at the Kyoto University Research Reactor. A decay scheme containing 18 excited levels and 55 γ-rays was constructed from γ-ray singles and γ–γ coincidence measurements. Of these, 9 levels and 37 γ-rays were newly placed. The dominant β-feeding observed at the 110 keV level of 150Pr was found to be an allowed unhindered spin-flip transition. On the basis of the systematics of the neighboring nuclides, the Gallagher–Moszkowski coupling rules, and the selection rules for the β-decay of deformed nuclei, the Nilsson configurations of the ground and 110 keV states in 150Pr were newly proposed to be π5/2+[413]–ν3/2−[521] and π5/2−[532]–ν3/2−[532], respectively.

The nonlinear light output of NaI(Tl) detectors in the Modular Total Absorption Spectrometer

A new detector array, the Modular Total Absorption Spectrometer (MTAS), was commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Lab (ORNL). Total absorption gamma spectra measured with MTAS are expected to improve beta-feeding patterns and beta strength functions in fission products. MTAS is constructed out of hexagonal NaI(Tl) detectors with a unique central module surrounded by 18 identical crystals assembled in three rings. The total NaI(Tl) mass of MTAS is over 1000kg. The response of the central and other 18 MTAS modules to γ-radiation was simulated using the GEANT4 toolkit modified to analyze the nonlinear light output of NaI(Tl). A detailed description of the GEANT4 modifications made is discussed. Simulated energy resolution of MTAS modules is found to agree well with the measurements for single γ transitions of 662keV (137Cs) with 8.2% full width half maximum (FWHM), 835keV (54Mn) with FWHM of 7.5% FWHM, and 1115keV (65Zn) with FWHM of 6.5%. Simulations of single and multiple γ-rays from 60Co are also discussed.

High-Statistics Study of theβ+/EC-Decay of110In

A study of the 110In β+/EC decay was performed at the TRIUMF Isotope Separator and Accelerator (ISAC) facility to probe the nuclear structure of 110Cd. The data were collected in scaled-down γ-ray singles, γ − γ coincidence, and γ-electron coincidence mode. The data were sorted and a random-background subtracted γ − γ matrix was created containing a total of 850 million events. We expanded the level scheme of 110Cd significantly by identifying 75 levels under 3.8 MeV, including 12 new ones, and increased the number of previously observed transitions from these levels to 273. The γ-ray branching intensities have been extracted through an analysis of the coincidence intensities. The branching ratios were combined with a reanalysis of lifetimes measurements obtained in an (n, n'γ) reaction with monoenergetic neutrons for the calculation of B(E2) values and these results have lead to the proposal of a γ-soft rotor, or O(6) nucleus, rather than a vibrational, or U(5) pattern for the nature of the low-lying, low-spin levels in 110Cd.

Phase Distribution in a High Pressure Slurry Bubble Column via a Single Source Computed Tomography

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PROPOSAL FOR DIRECT SEARCH FOR STRONGLY BOUND STATES OF $p\bar p$, $n\bar p$ SYSTEMS WITH HIGH INTENSITY AND COLLECTIVE $\bar p$ BEAM

Here, we discuss the possibility of showing the existence of [Formula: see text] and [Formula: see text] bound states. Measurement of the single γ-ray from [Formula: see text] and [Formula: see text] systems at rest can directly confirm whether X(1860) and X(1835) are the resonances which are strongly coupled to [Formula: see text]. In addition to the neutral candidate, a charged resonance X- is also proposed to be searched for in [Formula: see text] channel. We find that the data from the Crystal Barrel experiment at LEAR/CERN can be used to confirm the X(1835) observed by BES collaboration. The possibility of measuring the γ spectrum below 100 MeV at the new experiment with cold high intensity [Formula: see text] beam at GSI is discussed. These new techniques can be used to probe the structure of the X(1860) and X(1835) in the future.

High-Spin States in Odd–Odd 140Pr Nucleus

High-spin level structure of doubly odd nucleus 140Pr has beeninvestigated via the 130Te(14N,4n)140Pr reactionat beam energies from 55 to 65 MeV. Measurements of γ-ray excitationfunctions, γ-ray singles and γ-γ-t coincidences wereperformed with twelve BGO(AC)HPGe detectors. The level scheme of140Pr, including 27 new levels and 42 new γ rays, has beenestablished for the first time. The level structure is compared withthose in the neighbouring odd–odd nuclei, and interpreted qualitatively.

Levels in 127La fed by the 127Ce beta-decay

The low-lying levels in 127La have been studied through the β-decay of 127Ce ( T1/2 = 29s) produced by bombarding a natMo target with a 185-MeV 35Cl beam. Reaction products were on-line mass-separated, and γ-ray singles and γ-γ coincidence measurements were performed. Conversion electrons were also measured and multipolarities of transitions have been derived. The half-life of the 210.9-keV level was determined to be (1.9±0.3)ns by the β-γ delayed coincidence technique. The level scheme obtained has been compared with calculations based on the Nilsson model.

High spin states of 141Pm

The high spin states in the N=80 odd- A 141Pm nucleus have been investigated by in-beam γ-spectroscopic techniques following the reaction 133Cs( 12C, 4n) 141Pm at E=65 MeV using a modest γ detector array, consisting of seven Compton-suppressed high purity germanium detectors and a multiplicity ball of 14 bismuth germanate elements. Thirty new γ rays have been assigned to 141Pm on the basis of γ-ray singles and γγ-coincidence data. The level scheme of 141Pm has been extended upto an excitation energy of 5.2 MeV and spin 35 2 ℏ and 16 new levels have been proposed. Spin-parity assignments for most of the newly proposed levels have been made on the basis of the deduced directional correlation orientation ratios for strong transitions. The meanlives of a few excited states have been determined from the pulsed beam- γγ coincidence data using the generalised centroid-shift method. The level structure is discussed in the light of known systematics of neighbouring N=80 isotonic nuclei.

Decay Studies on Neutron-Rich Isotope 151Ce

The β− decay of 151Ce produced by the thermal neutron-induced fission of 235U has been studied using an isotope separator on-line. From γ-ray singles, γ-γ coincidence and internal conversion electron measurements, the decay scheme of 151Ce with a half-life of 1.72(5) s was proposed for the first time.

The nuclear structure of 229Th

The γ-rays following the β − decay of 229Ac have been investigated by means of γ-ray singles and γγ-coincidence measurements using Ge detectors. Multipolarities of 40 transitions in 229Th have been established by measuring conversion electrons with a mini-orange electron spectrometer. The half-lives of the 146.35, 164.53 and 261.96 keV levels have been measured using the advanced time delayed βγγ(t) method. The low-lying states in 229Th and observed transition rates have been interpreted within the quasiparticle–phonon model with inclusion of Coriolis coupling. Two octupole correlated parity partner bands, with K π =5/2 ± and K π =3/2 ±, were identified in 229Th.