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The title compound, [Li4O4(C12H8BO)4(C4H10O)4], features a Li4O4 cube. Each Li atom in the cube is additionally coordinated by a diethyl ether molecule and each O atom in the cube carries a 9-oxa-10-boraanthracene residue. The crystal studied was a non-merohedral twin [twin law (-1 0 0 / 0 0 1 / 0 1 0); the contribution of the major twin component refined to 0.553 (3)] emulating apparent tetragonal symmetry, whereas the actual crystal system is just orthorhombic.
Mol-ecules of the title compound, [Zn(8)(C(6)F(5))(8)O(4)(C(4)H(10)O)(4)], are located on a special position of site symmetry [Formula: see text]. As a result, there is just one quarter-mol-ecule in the asymmetric unit. The title compound features a Zn(4)O(4) cube. Each Zn atom in the cube carries a pentafluorophenyl substituent. Each O atom is bonded to a further Zn atom, which is connected to a pentafluorophenyl substituent and the O atom of a diethyl ether mol-ecule. All ether C atoms are disordered over two sets of sites with a site occupation factor of 0.51 (2) for the major occupied site.
The neutron capture cross section of some unstable nuclei is especially relevant for s-process nucleosynthesis studies. This magnitude is crucial to determine the local abundance pattern, which can yield valuable information of the s-process stellar environment. In this work we describe the neutron capture (n,γ) measurement on two of these nuclei of interest, 204Tl and 171Tm, from target production to the final measurement, performed successfully at the n_TOF facility at CERN in 2014 and 2015. Preliminary results on the ongoing experimental data analysis will also be shown. These results include the first ever experimental observation of capture resonances for these two nuclei.
The slow neutron capture process (s-process) is responsible for producing about half of the elemental abundances heavier than iron in the universe. Neutron capture cross sections on stable isotopes are a key nuclear physics input for s-process studies. The 72Ge(n, γ) cross section has an important influence on production of isotopes between Ge and Zr during s-process in massive stars and therefore experimental data are urgently required. 72Ge(n, γ) was measured at the neutron time-of-flight facility n_TOF (CERN) for the first time at stellar energies. The measurement was performed using an enriched 72GeO2 sample at a flight path of 185m with a set of liquid scintillation detectors (C6D6). The motivation, experiment and current status of the data analysis are reported.
Introduction: Definitive chemoradiation (CRT) followed by high-dose-rate (HDR) brachytherapy (BT) represents state-of-the-art treatment for locally-advanced cervical cancer. Despite use of this treatment paradigm, disease-related outcomes have stagnated in recent years, indicating the need for biomarker development and improved patient stratification. Here, we report the association of Polo-like kinase (PLK) 3 expression and Caspase 8 T273 phosphorylation levels with survival among patients with cervical squamous cell carcinoma (CSCC) treated with CRT plus BT.
Methods: We identified 74 patients with FIGO Stage Ib to IVb cervix squamous cell carcinoma. Baseline immunohistochemical scoring of PLK3 and pT273 Caspase 8 levels was performed on pre-treatment samples. Correlation was then assessed between marker expression and clinical endpoints, including cumulative incidences of local and distant failure, cancer-specific survival (CSS) and overall survival (OS). Data were then validated using The Cancer Genome Atlas (TCGA) dataset.
Results: PLK3 expression levels were associated with pT273 Caspase 8 levels (p = 0.009), as well as N stage (p = 0.046), M stage (p = 0.026), and FIGO stage (p = 0.001). By the same token, pT273 Caspase 8 levels were associated with T stage (p = 0.031). Increased PLK3 levels corresponded to a lower risk of distant relapse (p = 0.009), improved CSS (p = 0.001), and OS (p = 0.003). Phospho T273 Caspase 8 similarly corresponded to decreased risk of distant failure (p = 0.021), and increased CSS (p < 0.001) and OS (p < 0.001) and remained a significant predictor for OS on multivariate analysis. TCGA data confirmed the association of low PLK3 expression with resistance to radiotherapy and BT (p < 0.05), as well as increased propensity for metastasis (p = 0.019). Finally, a combined PLK3 and pT273 Caspase 8 score predicted for decreased distant relapse (p = 0.005), and both improved CSS (p < 0.001) and OS (p < 0.001); this combined score independently predicted distant failure (p = 0.041) and CSS (p = 0.003) on multivariate analyses.
Conclusion: Increased pre-treatment tumor levels of PLK3 and pT273 Caspase 8 correspond to improved disease-related outcomes among cervical cancer patients treated with CRT plus BT, representing a potential biomarker in this context.
Epigenetic neural glioblastoma enhances synaptic integration and predicts therapeutic vulnerability
(2023)
Neural-tumor interactions drive glioma growth as evidenced in preclinical models, but clinical validation is nascent. We present an epigenetically defined neural signature of glioblastoma that independently affects patients survival. We use reference signatures of neural cells to deconvolve tumor DNA and classify samples into low- or high-neural tumors. High-neural glioblastomas exhibit hypomethylated CpG sites and upregulation of genes associated with synaptic integration. Single-cell transcriptomic analysis reveals high abundance of stem cell-like malignant cells classified as oligodendrocyte precursor and neural precursor cell-like in high-neural glioblastoma. High-neural glioblastoma cells engender neuron-to-glioma synapse formation in vitro and in vivo and show an unfavorable survival after xenografting. In patients, a high-neural signature associates with decreased survival as well as increased functional connectivity and can be detected via DNA analytes and brain-derived neurotrophic factor in plasma. Our study presents an epigenetically defined malignant neural signature in high-grade gliomas that is prognostically relevant.
Background: Dexamethasone (Dex) is the most common corticosteroid to treat edema in glioblastoma (GBM) patients. Recent studies identified the addition of Dex to radiation therapy (RT) to be associated with poor survival. Independently, Tumor Treating Fields (TTFields) provides a novel anti-cancer modality for patients with primary and recurrent GBM. Whether Dex influences the efficacy of TTFields, however, remains elusive.
Methods: Human GBM cell lines MZ54 and U251 were treated with RT or TTFields in combination with Dex and the effects on cell counts and cell death were determined via flow cytometry. We further performed a retrospective analysis of GBM patients with TTFields treatment +/- concomitant Dex and analysed its impact on progression-free (PFS) and overall survival (OS).
Results: The addition of Dex significantly reduced the efficacy of RT in U251 and MZ54 cells. TTFields (200 kHz/250 kHz) induced massive cell death in both cell lines. Concomitant treatment of TTFields and Dex did not reduce the overall efficacy of TTFields. Further, in our retrospective clinical analysis, we found that the addition of Dex to TTFields therapy did not influence PFS nor OS.
Conclusion: Our translational investigation indicates that the efficacy of TTFields therapy in patients with GBM and primary GBM cell lines is not affected by the addition of Dex.
Accurate measurement of the standard 235U(n,f) cross section from thermal to 170 keV neutron energy
(2020)
An accurate measurement of the 235U(n,f) cross section from thermal to 170 keV of neutron energy has recently been performed at n_TOF facility at CERN using 6Li(n,t)4He and 10B(n,α)7Li as references. This measurement has been carried out in order to investigate a possible overestimation of the 235U fission cross section evaluation provided by most recent libraries between 10 and 30 keV. A custom experimental apparatus based on in-beam silicon detectors has been used, and a Monte Carlo simulation in GEANT4 has been employed to characterize the setup and calculate detectors efficiency. The results evidenced the presence of an overestimation in the interval between 9 and 18 keV and the new data may be used to decrease the uncertainty of 235U(n,f) cross section in the keV region.
Accurate neutron capture cross section data for minor actinides (MAs) are required to estimate the production and transmutation rates of MAs in light water reactors with a high burnup, critical fast reactors like Gen-IV systems and other innovative reactor systems such as accelerator driven systems (ADS). Capture reactions of 244Cm open the path for the formation of heavier Cm isotopes and of heavier elements such as Bk and Cf. In addition, 244Cm shares nearly 50% of the total actinide decay heat in irradiated reactor fuels with a high burnup, even after three years of cooling.
Experimental data for this isotope are very scarce due to the difficulties of providing isotopically enriched samples and because the high intrinsic activity of the samples requires the use of neutron facilities with high instantaneous flux. The only two previous experimental data sets for this neutron capture cross section have been obtained in 1969 using a nuclear explosion and, more recently, at J-PARC in 2010. The neutron capture cross sections have been measured at n_TOF with the same samples that the previous experiments in J-PARC. The samples were measured at n_TOF Experimental Area 2 (EAR-2) with three C6D6 detectors and also in Experimental Area 1 (EAR-1) with the Total Absorption Calorimeter (TAC). Preliminary results assessing the quality and limitations of these new experimental datasets are presented for the experiments in both areas. Preliminary yields of both measurements will be compared with evaluated libraries for the first time.
233U is the fissile nuclei in the Th-U fuel cycle with a particularily small neutron capture cross setion which is on average about one order of magnitude lower than its fission cross section. Hence, the measurement of the 233U(n, γ) cross section relies on a method to accurately distinguish between capture and fission γ-rays. A measurement of the 233U α-ratio has been performed at the n_TOF facility at CERN using a so-called fission tagging setup, coupling n_TOF 's Total Absorption Calorimeter with a novel fission chamber to tag the fission γ-rays. The experimental setup is described and essential parts of the analysis are discussed. Finally, a preliminary 233U α-ratio is presented.
We have measured the capture cross section of the 155Gd and 157Gd isotopes between 0.025 eV and 1 keV. The capture events were recorded by an array of 4 C6D6 detectors, and the capture yield was deduced exploiting the total energy detection system in combination with the Pulse Height Weighting Techniques. Because of the large cross section around thermal neutron energy, 4 metallic samples of different thickness were used to prevent problems related to self-shielding. The samples were isotopically enriched, with a cross contamination of the other isotope of less than 1.14%. The capture yield was analyzed with an R-Matrix code to describe the cross section in terms of resonance parameters. Near thermal energies, the results are significantly different from evaluations and from previous time-of-flight experiments. The data from the present measurement at n_TOF are publicly available in the experimental nuclear reaction database EXFOR.
Feasibility, design and sensitivity studies on innovative nuclear reactors that could address the issue of nuclear waste transmutation using fuels enriched in minor actinides, require high accuracy cross section data for a variety of neutron-induced reactions from thermal energies to several tens of MeV. The isotope 241Am (T1/2= 433 years) is present in high-level nuclear waste (HLW), representing about 1.8 % of the actinide mass in spent PWR UOx fuel. Its importance increases with cooling time due to additional production from the β-decay of 241Pu with a half-life of 14.3 years. The production rate of 241 Am in conventional reactors, including its further accumulation through the decay of 241Pu and its destruction through transmutation/incineration are very important parameters for the design of any recycling solution. In the present work, the 241 Am(n,f) reaction cross-section was measured using Micromegas detectors at the Experimental Area 2 of the n_TOF facility at CERN. For the measurement, the 235U(n,f) and 238U(n,f) reference reactions were used for the determination of the neutron flux. In the present work an overview of the experimental setup and the adopted data analysis techniques is given along with preliminary results.
Measurement of the 244Cm and 246Cm neutron-induced capture cross sections at the n_TOF facility
(2019)
The neutron capture reactions of the 244Cm and 246Cm isotopes open the path for the formation of heavier Cm isotopes and heavier elements such as Bk and Cf in a nuclear reactor. In addition, both isotopes belong to the minor actinides with a large contribution to the decay heat and to the neutron emission in irradiated fuels. There are only two previous 244Cm and 246Cm capture cross section measurements: one in 1969 using a nuclear explosion [1] and the most recent data measured at J-PARC in 2010 [2]. The data for both isotopes are very scarce due to the difficulties in performing the measurements: high intrinsic activity of the samples and limited facilities capable of providing isotopically enriched samples.
We have measured both neutron capture cross sections at the n_TOF Experimental Area 2 (EAR-2) with three C6 D6 detectors and also at Area 1 (EAR-1) with the TAC. Preliminary results assessing the quality and limitations (back-ground subtraction, measurement technique and counting statistics) of this new experimental datasets are presented and discussed.
Study of the photon strength functions and level density in the gamma decay of the n + 234U reaction
(2019)
The accurate calculations of neutron-induced reaction cross sections are relevant for many nuclear applications. The photon strength functions and nuclear level densities are essential inputs for such calculations. These quantities for 235U are studied using the measurement of the gamma de-excitation cascades in radiative capture on 234U with the Total Absorption Calorimeter at n_TOF at CERN. This segmented 4π gamma calorimeter is designed to detect gamma rays emitted from the nucleus with high efficiency. This experiment provides information on gamma multiplicity and gamma spectra that can be compared with numerical simulations. The code DICEBOXC is used to simulate the gamma cascades while GEANT4 is used for the simulation of the interaction of these gammas with the TAC materials. Available models and their parameters are being tested using the present data. Some preliminary results of this ongoing study are presented and discussed.
233U is of key importance among the fissile nuclei in the Th-U fuel cycle. A particularity of 233U is its small neutron capture cross-section, which is on average about one order of magnitude lower than the fission cross-section. The accuracy in the measurement of the 233U capture cross-section depends crucially on an efficient capture-fission discrimination, thus a combined set-up of fission and γ-detectors is needed. A measurement of the 233U capture cross-section and capture-to-fission ratio was performed at the CERN n_TOF facility. The Total Absorption Calorimeter (TAC) of n_TOF was employed as γ-detector coupled with a novel compact ionization chamber as fission detector. A brief description of the experimental set-up will be given, and essential parts of the analysis procedure as well as the preliminary response of the set-up to capture are presented and discussed.
New neutron cross section measurements of minor actinides have been performed recently in order to reduce the uncertainties in the evaluated data, which is important for the design of advanced nuclear reactors and, in particular, for determining their performance in the transmutation of nuclear waste. We have measured the 241Am(n,γ) cross section at the n_TOF facility between 0.2 eV and 10 keV with a BaF2 Total Absorption Calorimeter, and the analysis of the measurement has been recently concluded. Our results are in reasonable agreement below 20 eV with the ones published by C. Lampoudis et al. in 2013, who reported a 22% larger capture cross section up to 110 eV compared to experimental and evaluated data published before. Our results also indicate that the 241Am(n,γ) cross section is underestimated in the present evaluated libraries between 20 eV and 2 keV by 25%, on average, and up to 35% for certain evaluations and energy ranges.
The (n, γ) cross sections of the gadolinium isotopes play an important role in the study of the stellar nucleosynthesis. In particular, among the isotopes heavier than Fe, 154Gd together with 152Gd have the peculiarity to be mainly produced by the slow capture process, the so-called s-process, since they are shielded against the β-decay chains from the r-process region by their stable samarium isobars. Such a quasi pure s-process origin makes them crucial for testing the robustness of stellar models in galactic chemical evolution (GCE). According to recent models, the 154Gd and 152Gd abundances are expected to be 15-20% lower than the reference un-branched s-process 150Sm isotope. The close correlation between stellar abundances and neutron capture cross sections prompted for an accurate measurement of 154Gd cross section in order to reduce the uncertainty attributable to nuclear physics input and eventually rule out one of the possible causes of present discrepancies between observation and model predictions. To this end, the neutron capture cross section of 154Gd was measured in a wide neutron energy range (from thermal up to some keV) with high resolution in the first experimental area of the neutron time-of-flight facility n_TOF (EAR1) at CERN. In this contribution, after a brief description of the motivation and of the experimental setup used in the measurement, the preliminary results of the 154Gd neutron capture reaction as well as their astrophysical implications are presented.
Monte Carlo simulations and n-p differential scattering data measured with Proton Recoil Telescopes
(2020)
The neutron-induced fission cross section of 235U, a standard at thermal energy and between 0.15 MeV and 200 MeV, plays a crucial role in nuclear technology applications. The long-standing need of improving cross section data above 20 MeV and the lack of experimental data above 200 MeV motivated a new experimental campaign at the n_TOF facility at CERN. The measurement has been performed in 2018 at the experimental area 1 (EAR1), located at 185 m from the neutron-producing target (the experiment is presented by A. Manna et al. in a contribution to this conference). The 235U(n,f) cross section from 20 MeV up to about 1 GeV has been measured relative to the 1H(n,n)1H reaction, which is considered the primary reference in this energy region. The neutron flux impinging on the 235U sample (a key quantity for determining the fission events) has been obtained by detecting recoil protons originating from n-p scattering in a C2H4 sample. Two Proton Recoil Telescopes (PRT), consisting of several layers of solid-state detectors and fast plastic scintillators, have been located at proton scattering angles of 25.07° and 20.32°, out of the neutron beam. The PRTs exploit the ΔE-E technique for particle identification, a basic requirement for the rejection of charged particles from neutron-induced reactions in carbon. Extensive Monte Carlo simulations were performed to characterize proton transport through the different slabs of silicon and scintillation detectors, to optimize the experimental set-up and to deduce the efficiency of the whole PRT detector. In this work we compare measured data collected with the PRTs with a full Monte Carlo simulation based on the Geant-4 toolkit.
Since the start of its operation in 2001, based on an idea of Prof. Carlo Rubbia [1], the neutron time of-flight facility of CERN, n_TOF, has become one of the most forefront neutron facilities in the world for wide-energy spectrum neutron cross section measurements. Thanks to the combination of excellent neutron energy resolution and high instantaneous neutron flux available in the two experimental areas, the second of which has been constructed in 2014, n_TOF is providing a wealth of new data on neutron-induced reactions of interest for nuclear astrophysics, advanced nuclear technologies and medical applications. The unique features of the facility will continue to be exploited in the future, to perform challenging new measurements addressing the still open issues and long-standing quests in the field of neutron physics. In this document the main characteristics of the n_TOF facility and their relevance for neutron studies in the different areas of research will be outlined, addressing the possible future contribution of n_TOF in the fields of nuclear astrophysics, nuclear technologies and medical applications. In addition, the future perspectives of the facility will be described including the upgrade of the spallation target, the setup of an imaging installation and the construction of a new irradiation area.
Neutron-induced fission cross sections of isotopes involved in the nuclear fuel cycle are vital for the design and safe operation of advanced nuclear systems. Such experimental data can also provide additional constraints for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of fission models. In the present work, the 237Np(n,f) cross section was studied at the EAR2 vertical beam-line at CERN's n_TOF facility, over a wide range of neutron energies, from meV to MeV, using the time-of-flight technique and a set-up based on Micromegas detectors, in an attempt to provide accurate experimental data. Preliminary results in the 200 keV – 14 MeV neutron energy range as well as the experimental procedure, including a description of the facility and the data handling and analysis, will be presented.