Quantum simulator to emulate lower-dimensional molecular structure.

Bottom-up quantum simulators have been developed to quantify the role of various interactions, dimensionality, and structure in creating electronic states of matter. Here, we demonstrated a solid-state quantum simulator emulating molecular orbitals, based solely on positioning individual cesium atoms on an indium antimonide surface. Using scanning tunneling microscopy and spectroscopy, combined with ab initio calculations, we showed that artificial atoms could be made from localized states created from patterned cesium rings. These artificial atoms served as building blocks to realize artificial molecular structures with different orbital symmetries. These corresponding molecular orbitals allowed us to simulate two-dimensional structures reminiscent of well-known organic molecules. This platform could further be used to monitor the interplay between atomic structures and the resulting molecular orbital landscape with submolecular precision.

A novel vertebrate system for the examination and direct comparison of the relative biological effectiveness for different radiation qualities and sources.

PURPOSE: The recent rapid increase of hadron therapy applications requires the development of high performance, reliable in vivo models for preclinical research on the biological effects of high linear energy transfer (LET) particle radiation. AIM: The aim of this paper was to test the relative biological effectiveness (RBE) of the zebrafish embryo system at two neutron facilities. MATERIAL AND METHODS: Series of viable zebrafish embryos at 24-hour post-fertilization (hpf) were exposed to single fraction, whole-body, photon and neutron (reactor fission neutrons () and (p (18 MeV)+Be, = 3.5 MeV) fast neutron) irradiation. The survival and morphologic abnormalities of each embryo were assessed at 24-hour intervals from the point of fertilization up to 192 hpf and then compared to conventional 6 MV photon beam irradiation results. RESULTS: The higher energy of the fast neutron beams represents lower RBE (ref. source LINAC 6 MV photon). The lethality rate in the zebrafish embryo model was 10 times higher for 1 MeV fission neutrons and 2.5 times greater for p (18 MeV)+Be cyclotron generated fast neutron beam when compared to photon irradiation results. Dose-dependent organ perturbations (shortening of the body length, spine curvature, microcephaly, micro-ophthalmia, pericardial edema and inhibition of yolk sac resorption) and microscopic (marked cellular changes in eyes, brain, liver, muscle and the gastrointestinal system) changes scale together with the dose response. CONCLUSION: The zebrafish embryo system is a powerful and versatile model for assessing the effect of ionizing radiation with different LET values on viability, organ and tissue development.

Investigation of alternative production routes of 99mTc: deuteron induced reactions on 100 Mo.

Activation cross sections of deuteron induced nuclear reactions on enriched (100)Mo have been studied up to 50 MeV using the stacked foil irradiation technique and gamma spectroscopy. The excitation functions for production of (99m)Tc, (ind99)Mo, (ind98m)Nb, (ind97mg)Nb radioisotopes were measured for the first time and compared with the results of the ALICE-D, EMPIRE-D and TALYS codes. Production possibilities of the medically important (99m)Tc are discussed.

Investigation of activation cross sections of deuteron induced reactions on indium up to 40 MeV for production of a 113 Sn/113m In generator.

(113)Sn (115.09 d) is the parent nuclide of the (113)Sn/(113m)In generator system. (113m)In (99.476 min) is used in diagnostic nuclear medicine and as an Auger-electron emitter is a candidate for internal radiotherapy. Excitation functions of the (nat)In(d,x) (113 mg)Sn, (116 m)In, (ind115m)In, (114m)In, (ind113m)In, (cum111)In, (115g)Cd,(111m)Cd reactions were measured up to 40 MeV for the first time. The experimental results were compared with the curves calculated with the ALICE-D and EMPIRE-D theoretical model codes and curves given in the EAF-2007 and TENDL-2009 databases. Thick target yields, impurity levels and specific activities for the optimal energy range were deduced and compared with the same parameters of other charged particle production routes of (113)Sn.

Study of activation cross sections of proton induced reactions on barium: Production of 131Ba-->131Cs.

In the frame of a systematic study of charged particle production routes of the therapeutic radioisotope (131)Cs, excitation functions of the (nat)Ba(p,x)(135,132mg)La, (ind135m,cum133m,cum133mg,cum131mg)Ba and (136mg,134mg,132,cum129)Cs reactions were measured in the 30-70 MeV energy range using stacked foil irradiation technique, activation method and gamma spectroscopy. Comparisons with new results of the ALICE-IPPE and EMPIRE-II codes and with existing data obtained with TALYS code are shown. From the measured cross section data integral yields were calculated and compared with experimental integral yield data reported in the literature. Potential use of proton induced reactions on Ba for production of (131)Cs is discussed.

New measurements and evaluation of excitation functions for (p,xn), (p,pxn) and (p,2pxn) reactions on (133)Cs up to 70MeV proton energy.

Cross sections for production of the therapeutic radioisotope (131)Cs via the (133)Cs(p,3n)(131)Ba-->(131)Cs route were investigated at cyclotrons. Excitation functions of the (133)Cs(p,x)(133m,133mg,131mg,129g,129m,128)Ba, (132,129cum,127cum)Cs and (129m(ind),127cum,125cum)Xe nuclear reactions were measured up to 70MeV proton energy. The experimental data were compared to the results of model calculations performed by means of ALICE-IPPE, EMPIRE-II and TALYS computer codes. Good overall agreement was observed. On the basis of the measured excitation functions integral yields were deduced. Charged particle production routes of (131)Cs are discussed.

Experimental study of the excitation functions of proton induced nuclear reactions on (167)Er for production of medically relevant (167)Tm.

(167)Tm (T(1/2)=9.25d) is a candidate radioisotope for medical therapy and diagnostics due to its Auger-electron and low-energy X- and gamma-ray emission. Excitation functions of the (167)Er(p,n)(167)Tm reaction and (168)Er(p,n)(168)Tm, (167)Er(p,2n)(166)Tm, (166)Er(p,2n)(165)Tm disturbing reactions were measured up to 15MeV by using the stacked foil irradiation technique and gamma-ray spectroscopy. The measured excitation functions agree well with the results of ALICE-IPPE, EMPIRE-II and TALYS nuclear reaction model codes. The thick target yield of (167)Tm in the 15-8MeV energy range is 6.9MBq/microAh. A short comparison of charged particle production routes of (167)Tm is given.

Study of excitation functions of alpha-particle induced nuclear reactions on holmium for 167Tm production.

(167)Tm is a candidate radioisotope for both nuclear medicine diagnostics and therapy due to its emitted Auger-electrons, low energy X- and gamma-rays. In the frame of a systematic study of excitation functions for production of medically relevant radioisotopes by charged particle induced reactions on rare earths, the (165)Ho(alpha,2n)(167)Tm reaction and the (165)Ho(alpha,n)(168)Tm, (165)Ho(alpha,3n)(166)Tm, (165)Ho(alpha,4n)(165)Tm side reactions were measured up to 40 MeV by the stacked foil irradiation technique and gamma-ray spectroscopy. The measured results were compared to the ALICE-IPPE and EMPIRE-II theoretical curves. Thick target yields, impurity levels and specific activities were deduced and compared with the same parameters for other charged particle production routes of (167)Tm.

Cross section measurements of the (131)Xe(p,n) reaction for production of the therapeutic radionuclide (131)Cs.

(131)Cs is an X-ray emitter radioisotope gaining interest in prostate brachytherapy. It is generally produced via the (130)Ba(n,gamma)(131)Ba-->(131)Cs process in thermal-flux reactors. Here we investigate its cyclotron production possibilities. Excitation function of the (131)Xe(p,n)(131)Cs reaction was measured up to 35MeV using the stacked gascell technique and high-resolution X-ray spectrometry. The experimental data were compared with results of the ALICE-IPPE and EMPIRE-II codes and curves taken from the PADF and TENDL database. The calculated integral yield was 17MBq/microAh in the energy range E(p)=20-->7MeV. Comparison of cyclotron and reactor production routes was given.

New cross-sections for production of 103Pd; review of charged particle production routes.

Production cross-sections of (103)Ag obtained by irradiating (nat)Pd and (nat)Cd with 70 MeV protons are presented and compared with ALICE-IPPE model calculations. Production of (103)Ag is of interest for the generation of (103)Pd widely used in brachytherapy. The investigated energy range of the (103)Rh(d,2n)(103)Pd reaction was extended up to 40 MeV and the results were compared with the curves of ALICE-IPPE, EMPIRE-II and GNASH theoretical codes. Thick target yields were calculated. An overview and analysis of the most important charged particle induced production routes of (103)Pd is presented. An explanation of the apparent discrepancy in the activity measurements for (103)Rh based on X- or gamma-ray is given.

Excitation functions of 3He- and alpha-particle induced nuclear reactions on natSb for production of medically relevant 123I and 124I radioisotopes.

Excitation functions were measured using the stacked foil irradiation technique from threshold energies to 28 MeV for (3)He- and to 21 MeV for alpha-particle induced nuclear reactions on natural antimony leading to the formation of (121,123,124)I radioisotopes. The measured excitation functions were compared with the contradicting results of the earlier investigations found in the literature and with the curves predicted by the ALICE-IPPE and EMPIRE-II codes. Integral yields were also calculated and compared with the experimental thick target yields reported in the literature.

Investigation of production of the therapeutic radioisotope 165 Er by proton induced reactions on erbium in comparison with other production routes.

The excitation function of the (nat)Er(p,xn)(165)Tm reaction resulting in production of (165)Er was measured up to 70 MeV by activation of stacked foils practically for the first time. The theoretical interpretation is based on the results of the ALICE-IPPE and EMPIRE-II codes. From the measured experimental cross section data integral production yield was calculated and compared with experimental integral yield data reported in the literature. Different production routes of the therapeutic radioisotope (165)Er were compared.

Investigations on landmine detection by neutron-based techniques.

Principles and techniques of some neutron-based methods used to identify the antipersonnel landmines (APMs) are discussed. New results have been achieved in the field of neutron reflection, transmission, scattering and reaction techniques. Some conclusions are as follows: The neutron hand-held detector is suitable for the observation of anomaly caused by a DLM2-like sample in different soils with a scanning speed of 1m(2)/1.5 min; the reflection cross section of thermal neutrons rendered the determination of equivalent thickness of different soil components possible; a simple method was developed for the determination of the thermal neutron flux perturbation factor needed for multi-elemental analysis of bulky samples; unfolded spectra of elastically backscattered neutrons using broad-spectrum sources render the identification of APMs possible; the knowledge of leakage spectra of different source neutrons is indispensable for the determination of the differential and integrated reaction rates and through it the dimension of the interrogated volume; the precise determination of the C/O atom fraction requires the investigations on the angular distribution of the 6.13MeV gamma-ray emitted in the (16)O(n,n'gamma) reaction. These results, in addition to the identification of landmines, render the improvement of the non-intrusive neutron methods possible.

Advantages and limitations of thermal and epithermal neutron activation analysis of bulk samples.

Systematic investigations have been carried out to extend the thermal neutron activation method for elemental analysis of bulk samples. A new method developed for the determination of the flux perturbation factor renders the thermal and epithermal neutron activation analyses of bulky samples of unknown compositions possible both in hydrogenous and in graphite moderators. The flux perturbation, F, depression, H, and self-absorption, G, factors are given for different samples. The limitation of the epithermal neutron activation analysis for hydrogenous bulky samples is also discussed.

Investigations on thermal neutron reflection by activation method.

The prompt neutron detection and the foil activation methods were compared for the determination of the reflection cross-section of thermal neutrons and the hydrogen content of bulk samples. The advantages and limitations of the two methods are discussed.