16O Reaction Research Articles

Installation of First Medium Energy Medical Cyclotron in Bangladesh at National Institute of Nuclear Medicine and Allied Sciences (NINMAS) for PET radiopharmaceuticals Production

PET-CT (positron emission tomography and computed tomography) is a gold-standard cancer imaging tool for diagnosis and management, as well as prognostic information based on treatment. Positron-emitting radionuclide 18F (Fluorine) is generated by accelerating particles to energies high enough to cause a certain nuclear reaction 18O(p,n)18F within the particle accelerator, the cyclotron. Mannose triflate is converted to 2-[18F] Fluoro-2-deox-D-yglucose ([18F]FDG) via nucleophilic reaction. Under the ownership of Bangladesh Atomic Energy Commission installed a medium energy (18/9 MeV, IBA) Cyclotron at National Institute of Nuclear Medicine and Allied Sciences (NINMAS). The facility was established in the oncology Building (Block F) of Bangabandhu Sheikh Mujib Medical University (BSMMU). Cyclotron vault and the Control room are located in the underground i.e. basement floor. Each wall of the cyclotron vault and ceiling is made of concrete with a density of 2.35 g/cm3 and a thickness sufficient to shield gamma and neutron radiation. On the ground floor, there are Synthesis room, Quality control laboratory, and the Decontamination room. PET-CT rooms are located on the first floor. Identification, Radionuclide purity (Gamma spectrum detection and half-life measurement), Radiochemical Purity, Chemical purity, Residual solvent measurement, pH measurement, Sterility, and bacterial endotoxins (LAL test) are performed to maintain the quality of the product. The current uses of the Cyclotron are mostly for the synthesis of 18F-FDG. Bangladesh J. Nuclear Med. 24(1&2): 48-50, 2021

The impact of the uncertainties in the 12C(α, γ)16O reaction rate on the evolution of low- to intermediate-mass stars

ABSTRACT One of the largest uncertainties in stellar evolutionary computations is the accuracy of the considered reaction rates. The 12C(α, γ)16O reaction is particularly important for the study of low- and intermediate-mass stars as it determines the final C/O ratio in the core which influences the white dwarf (WD) cooling evolution. Thus, there is a need for a study of how the computations of WDs and their progenitors that are made to date may be affected by the uncertainties of the 12C(α, γ)16O reaction rates. In this work, we compute fully evolutionary sequences using the mesa code with initial masses in the range of 0.90 ≤ Mi/M⊙ ≤ 3.05. We consider different adopted reaction rates, obtained from the literature, as well as the extreme limits within their uncertainties. As expected, we find that previous to the core helium burning (CHB) stage, there are no changes to the evolution of the stars. However, the subsequent stages are all affected by the uncertainties of the considered reaction rate. In particular, we find differences to the convective core mass during the CHB stage which may affect pulsation properties of subdwarfs, the number of thermal pulses during the asymptotic giant branch and trends between final oxygen abundance in the core and the progenitor masses of the remnant WDs.

Direct measurement of the 19F(p, αγ)16O reaction in JUNA

The 19F(p, αγ)16O reaction is of crucial importance for Galactic 19F abundances and CNO cycle loss in first generation Population III stars. Due to its extremely small cross sections, the 19F(p, αγ)16O reaction has not been measured in the low energy part of the Gamow window(70-200 keV). As a day-one campaign, the experiment was performed under the extremely low cosmicray-induced background environment of the China JinPing Underground Laboratory(CJPL), one of the deepest underground laboratories in the world. The γ-ray yields were measured over Ec.m. =72.4–344 keV, covering the full Gamow window for the first time. The direct experimental data will help people to expound the fluorine over-abundances, energy generation, as well as heavy-element nuclosynthesis scenario in asymptotic giant branch (AGB) stars, with the astrophysical model on the firm ground.

Oxygen Formation in the Light of Gamma-Beams: [Precision Measurements of the 12C(α, γ) Reaction with Gamma-Beams and a Time Projection Chamber

The carbon/oxygen (C/O) ratio at the end of stellar helium burning is not known with sufficient accuracy due to the large uncertainty in the cross-section of the 12C(α, γ)16O reaction. We developed a new method to measure this reaction that is significantly different from the experimental efforts of the past four decades. Data were measured with vanishingly small background, inside one detector, that also serves as an active target (AT-TPC). Angular distributions of the 12C(α, γ)16O reaction were obtained by measuring the inverse 16O(γ, α)12C reaction with gamma-beams (from the HIγS facility) and an optical readout time projection chamber (O-TPC) detector. We agree with current world data on the measured total reaction cross-section. We further evidence the strength of our method with angular distributions measured over the 1–resonance at Ecm ~ 2.4 MeV. We extract the E1-E2 mixing phase angle (ϕ12) over this resonance and obtained values that follow the trend of prediction based on unitarity of the scattering amplitude. Our technique promises to yield results that will surpass the quality of the currently available data. We continue these measurements to lower energies at the HIγS facility of TUNL at Duke University, and anticipate measurements down to Ecm = 1.1 MeV at the ELI-NP, the EU facility in Romania..

Final results on the 13C(α,n)16O cross section at low energies at LUNA

It is well established that the 13C(α, n)16O reaction (Q=2.215 MeV) is the major neutron source feeding the s-process in low mass (1−3M⊙) Asymptotic Giant Branch (AGB) stars. In the last decades, several measurements have been performed. Nevertheless, no dataset reaches the Gamow window (140 keV <Ec.m.<250 keV). This is due to the exponential drop of the cross section σ(E) with decreasing energy. The consequence is that the reaction rate becomes so low that the cosmic background becomes predominant in surface laboratories. A recent measurement was carried out in deep underground laboratory of Laboratori Nazionali del Gran Sasso (LNGS) in the framework of the LUNA experiment. To measure the 13C(α, n)16O cross section at low energies, a multiple effort has been performed to suppress the background in the setup, to maximise the detector efficiency and to keep under control the target modification under an intense stable beam provided by the LUNA accelerator (<I>= 200 µA). Thanks to these accuracies, the 13C(α, n)16O cross section was measured in the center of mass energy range 230 keV <Ecm<305 keV with a maximum 20% overall uncertainty. This allowed to constrain the reaction rate at T=0.1 GK at 15% uncertainty and to lead the way for new possible astrophysical consequences.

Observing Intermediate-mass Black Holes and the Upper Stellar-mass gap with LIGO and Virgo

Abstract Using ground-based gravitational-wave detectors, we probe the mass function of intermediate-mass black holes (IMBHs) wherein we also include BHs in the upper mass gap at ∼60–130 M ⊙. Employing the projected sensitivity of the upcoming LIGO and Virgo fourth observing run (O4), we perform Bayesian analysis on quasi-circular nonprecessing, spinning IMBH binaries (IMBHBs) with total masses 50–500 M ⊙, mass ratios 1.25, 4, and 10, and dimensionless spins up to 0.95, and estimate the precision with which the source-frame parameters can be measured. We find that, at 2σ, the mass of the heavier component of IMBHBs can be constrained with an uncertainty of ∼10%–40% at a signal-to-noise ratio of 20. Focusing on the stellar-mass gap with new tabulations of the 12C(α, γ)16O reaction rate and its uncertainties, we evolve massive helium core stars using MESA to establish the lower and upper edges of the mass gap as ≃ 59 − 13 + 34 M ⊙ and ≃ 139 − 14 + 30 M ⊙ respectively, where the error bars give the mass range that follows from the ±3σ uncertainty in the 12C(α, γ)16O nuclear reaction rate. We find that high resolution of the tabulated reaction rate and fine temporal resolution are necessary to resolve the peak of the BH mass spectrum. We then study IMBHBs with components lying in the mass gap and show that the O4 run will be able to robustly identify most such systems. Finally, we reanalyze GW190521 with a state-of-the-art aligned-spin waveform model, finding that the primary mass lies in the mass gap with 90% credibility.

Development of irradiation-resistant enriched 12C targets for astrophysical [formula omitted] reaction measurements

The production of irradiation-resistant enriched 12C target is one of the key technologies in the direct measurement of the 12C(α,γ)16O reaction at energies of astrophysical interest. In this work, we produced the enriched Ti12C targets on Ta substrates via the filter cathodic vacuum arc (FCVA) technology. The target stability under the bombardment of a high-intensity 4He beam was investigated by monitoring the γ-ray yields of the 12C(p,γ)13N reaction regularly. A 25% deterioration of 12C in the target was observed after bombardment by a 740 keV, 500 μA 4He2+ beam with a charge of 280 C, which is stronger than the implanted targets developed before. Furthermore, the 13C/12C ratio in the Ti12C target was measured to be (1.1±0.3)×10−4, which can meet the requirement of the 12C(α,γ)16O measurement at the China JinPing underground Laboratory (CJPL).

Subbarrier fusion and elastic scattering cross-sections based on modified Thomas-Fermi method potentials

The nucleon density distributions and nucleus-nucleus interaction potentials for the reactions 16O+92Zr and 16O+116Sn were calculated using the modified Thomas-Fermi method, taking into account all terms up to members of the second order by ħ in the quasiclassical decomposition of the kinetic energy. As a nucleon-nucleon interaction, density depended Skyrme forces were used. Based on the obtained potentials, the cross-sections of subbarrier fusion and elastic scattering were calculated. It is shown that the obtained cross-sections of the reactions agree well with the latest experimental data.

Utilization of thermal neutron induced in-situ chain reactions and the (n,p) reaction with fast neutrons for compositional characterization of lithium titanate

A methodology has been developed for the complete compositional characterization of lithium titanate (LTO) using neutron activation, which is quite challenging and no literature report is available so far. The concept of thermal neutron induced in-situ chain reactions 6Li(n,α)3H and 16O(3H,n)18F has been used for the determination of Li and O through the measurement of 18F activity. The method is capable of analyzing Li and O in percentage level as reported in the present analysis of two types of lithium titanate samples. Spectroscopic interference of the elements which can directly or indirectly affect the outcome, were evaluated meticulously. Determination of Ti was carried out using fast neutron activation through the product isotopes like 47Sc, 48Sc, generated via (n,p) nuclear reactions. Fast neutron activation methodology seems to be advantageous for Ti determination over thermal neutron activation, as it offers self validation through different isotopes and multiple gamma lines.

Precision measurements on oxygen formation in stellar helium burning with gamma-ray beams and a Time Projection Chamber

The carbon/oxygen (C/O) ratio at the end of stellar helium burning is the single most important nuclear input to stellar evolution theory. However, it is not known with sufficient accuracy, due to large uncertainties in the cross-section for the fusion of helium with 12C to form 16O, denoted as 12C(α, γ)16O. Here we present results based on a method that is significantly different from the experimental efforts of the past four decades. With data measured inside one detector and with vanishingly small background, angular distributions of the 12C(α, γ)16O reaction were obtained by measuring the inverse 16O(γ, α)12C reaction with gamma-beams and a Time Projection Chamber (TPC) detector. We agree with current world data for the total reaction cross-section and further evidence the strength of our method with accurate angular distributions measured over the 1− resonance at Ecm ~ 2.4 MeV. Our technique promises to yield results that will surpass the quality of the currently available data.

The intermediate neutron capture process

Context. Carbon-enhanced metal-poor (CEMP) r/s-stars show surface-abundance distributions characteristic of the so-called intermediate neutron capture process (i-process) of nucleosynthesis. We previously showed that the ingestion of protons in the convective helium-burning region of a low-mass low-metallicity star can explain the surface abundance distribution observed in CEMP r/s stars relatively well. Such an i-process requires detailed reaction network calculations involving hundreds of nuclei for which reaction rates have not yet been determined experimentally. Aims. We investigate the nuclear physics uncertainties affecting the i-process during the asymptotic giant branch (AGB) phase of low-metallicity low-mass stars by propagating the theoretical uncertainties in the radiative neutron capture cross sections, as well as the 13C(α,n)16O reaction rate, and estimating their impact on the surface-abundance distribution. Methods. We used the STAREVOL code to follow the evolution of a 1 M⊙ [Fe/H] = − 2.5 model star during the proton ingestion event occurring at the beginning of the AGB phase. In the computation, we adopt a nuclear network of 1160 species coupled to the transport processes and different sets of radiative neutron capture cross sections consistently calculated with the TALYS reaction code. Results. It is found that considering systematic uncertainties on the various nuclear ingredients affecting the radiative neutron capture rates, surface elemental abundances are typically predicted within ±0.4 dex. The 56 ≲ Z ≲ 59 region of the spectroscopically relevant heavy-s elements of Ba-La-Ce-Pr as well as the r-dominated Eu element remain relatively unaffected by nuclear uncertainties. In contrast, the inclusion of the direct capture contribution impacts the rates in the neutron-rich A ≃ 45, 100, 160, and 200 regions, and the i-process production of the Z ≃ 45 and 65–70 elements. Uncertainties in the photon strength function also impact the overabundance factors by typically 0.2–0.4 dex. Nuclear level densities tend to affect abundance predictions mainly in the Z = 74 − 79 regions. The uncertainties associated with the neutron-producing reaction 13C(α,n)16O and the unknown β-decay rates are found to have a low impact on the overall surface enrichment. Conclusions. The i-process nucleosynthesis during the early AGB phase of low-metallicity low-mass stars remains sensitive to nuclear uncertainties, substantially affecting theoretical predictions of still unknown radiative neutron capture cross sections. Improved descriptions of direct neutron capture based on shell model calculations or experimental constraints from (d, p) reactions could help to decrease the uncertainties in the estimated rates. Similarly, constraints on the photon strength functions and nuclear level densities, for example through the Oslo method, in the neutron-rich region of A ≃ 100 and 160 would increase the predictive power of the present simulations.

Low-energy resonances in the O18 ( p,γ)19F reaction

Background: Shell hydrogen burning during the asymptotic giant branch (AGB) phase through the oxygen isotopes has been indicated as a key process that is needed to understand the observed O18/O16 relative abundance in presolar grains and in stellar atmospheres. This ratio is strongly influenced by the relative strengths of the reactions O18(p,α)N15 and O18(p,γ)F19 in low-mass AGB stars. While the former channel has been the focus of a large number of measurements, the (p,γ) reaction path has only recently received some attention and its stellar reaction rate over a wide temperature range rests on only one measurement. Purpose: Our aim is the direct measurement of states in F19 as populated through the reaction O18(p,γ)F19 to better determine their influence on the astrophysical reaction rate, and more generally to improve the understanding of the nuclear structure of F19. Method: Branchings and resonance strengths were measured in the proton energy range Eplab=150–400keV, using a high-purity germanium detector inside a massive lead shield. The measurement took place in the ultra-low-background environment of the Laboratory for Underground Nuclear Astrophysics (LUNA) experiment at the Gran Sasso National Laboratory, leading to a highly increased sensitivity. Results: The uncertainty of the γ branchings and strengths was improved for all four resonances in the studied energy range; many new transitions were observed in the case of the 334keV resonance, and individual γ decays of the 215keV resonance were measured for the first time. In addition a number of transitions to intermediate states that decay through α emission were identified. The strengths of the observed resonances are generally in agreement with literature values. Conclusions: Our measurements substantially confirm previous determinations of the relevant resonance strengths. Therefore the O18(p,γ)F19 reaction rate does not change with respect to the reaction rate reported in the compilations commonly adopted in the extant computations of red-giant branch and AGB stellar models. Nevertheless, our measurements definitely exclude a nonstandard scenario for the fluorine nucleosynthesis and a nuclear physics solution for the O18 depletion observed in Group 2 oxygen-rich stardust grains.3 MoreReceived 18 June 2020Revised 12 April 2021Accepted 6 July 2021DOI:https://doi.org/10.1103/PhysRevC.104.025802©2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasH & He burningNuclear astrophysicsNuclear reactionsRadiative captureProperties6 ≤ A ≤ 19Nuclear Physics

Neutron yield and energy spectrum of 13C(alpha,n)16O reaction in liquid scintillator of KamLAND: A Nedis-2m simulation

The 13C (α,n)16O reaction cross-section is important data for nuclear physics, astrophysical, and neutrino physics experiments, however, they exhibit uncertainties due to the discrepancies in the experimental data. In this study, using the Nedis-2m program code, the energy spectrum of α-induced neutrons in a thin carbon target was calculated and the corresponding reaction cross-section was refined in the alpha particle energy range of 5–8 MeV. The results were used to calculate the intensity and energy spectrum of background neutrons produced in the liquid scintillator of KamLAND. The results will be useful in a variety of astrophysical and neutrino experiments especially those based on LS or Gd-LS detectors.

INVESTIGATION OF THE 16O(γ, p)3H3α REACTION AT THE ENERGIES BELOW THE MESON PRODUCTION THRESHOLD

The reaction 16O(γ, p)3H3 induced by bremsstrahlung photons of endpoint energy Emaxγ = 150 MeV has been studied by the method of a diffusion chamber in a magnetic field. The energy dependence of the total cross section has been measured in the energy range from the threshold and has been founded a broad resonance centered at 55 MeV. The rate of decrease in the cross section undergoes a change in the region around 55 MeV. A comparison was made with the cross section for reactions 4He(γ, p)3H and 12С(γ, р)3H2. The agreement between the shapes of distributions for the (γ, p)3H reactions is evident and was concluded that the mechanism of interaction of the γ-quantum with the nucleus is similar. The dependence of average kinetic energy of particles on the total kinetic energy was determined. In the whole energy interval, the distribution for a proton is more than the statistical distribution. Distribution of relative energy of the proton and 3H nucleus in their c.m.s. does not agree with the predictions of the mechanism of photon absorption by an α-particle cluster, but at energies above the maximum, it agrees with calculations within the framework of the quasi-deuteron model of photoabsorption.

Non-Resonant Reaction Rates of 13C(α,n)16O and 22Ne(α,n)25Mg reactions in AGB Stars

Both 13C 16O and 22Ne 25Mg reactions perform a cosmic role in the production of neutrons in AGB stars, which significantly contributes to the nucleosynthesis via the s-process. The astrophysical S-factor for both reactions has been calculated in this research, utilizing EMPIRE code and depending on two parameter sets for the optical potential: McFadden and Satchler (MFS), and Avrigeanu and Hodgson (AH) for the non-resonant region of the spectrum, and over a temperature range . The extrapolated S-factor at zero energy is derived to be and for 13C 16O, and for 22Ne 25Mg from using MFS and AH parameter sets respectively, and they show a reasonable agreement with the most recommended value. The differences in the S-factor, S(E), values obtained from these two adopted parameters set, were attributed to the variations of the real potential term's diffuseness parameter that affecting the reaction cross section, hence S-factor, and specifically at low energy region. Moreover, the present results imply an influential enhancement of the rates by the electron shielding effect at the low-temperature region in which 13C 16O reaction activated, and especially on 22Ne 25Mg reaction. In addition, for both adopted reactions and overall selected temperature range, the reaction rates using values based on MFS showed acceptable results with other previous compilations and reference libraries. While that obtained from AH exceed all other compilations even though the resonance contributions are currently unconsidered.

Differential cross section measurements of the 6.13 MeV gamma ray from proton-induced reaction of fluorine

Fundamental cross section measurements are essential for particle-induced gamma emission (PIGE) analysis. 19F(p,αγ2-0)16O can be utilized in PIGE analysis; however, differential cross section measurements for this reaction do not exist due to the difficulty in deconvolving overlapping peaks in the gamma spectrum. Although gamma yield measurements for this reaction exist (Dababneh et al., 1993), these can only be used for relative measurements. This work presents the 6.13 MeV gamma production differential cross sections for the 19F(p,αγ2-0)16O reaction in the incident proton kinetic energy range of 837 to 1517 keV. The yield of the 6.13 MeV gamma was obtained by subtracting the contribution of the 7.12 MeV double escape peak using the experimentally-determined ratio of the escape peaks. The corrected yields were converted to differential cross sections, which are presented here for the first time, as a contribution to the current knowledge and utilization of PIGE techniques.

Goodness-of-fit test for isochrone fitting in the Gaia era

Context. The increasing precision in observational data made available by recent surveys means that the reliability of stellar models can be tested. For this purpose, a firm theoretical basis is crucial for evaluating the agreement of the data and theoretical predictions. Aims This paper presents a rigorous derivation of a goodness-of-fit statistics for colour-magnitude diagrams (CMD). We discuss the reliability of the underlying assumptions and their validity in real-world testing. Methods. We derived the distribution of the sum of squared Mahalanobis distances of stellar data and theoretical isochrone for a generic set of data and models. We applied this to the case of synthetic CMDs that were constructed to mimic real data of open clusters in the Gaia sample. Then, we analysed the capability of distinguishing among different sets of input physics and parameters that were used to compute the stellar models. To do this, we generated synthetic clusters from isochrones computed with these perturbed quantities, and we evaluated the goodness-of-fit with respect to the reference unperturbed isochrone. Results. We show that when r magnitudes are available for each of the N observational objects and p hyperparameters are estimated in the fit, the error distribution follows a χ2 distribution with (r − 1)N − p degrees of freedom. We show that the linearisation of the isochrone between support points introduces negligible deviation from this result. We investigated the possibility of detecting the effects on stellar models that are induced when the following physical quantities were varied: convective core overshooting efficiency, 14N(p, γ)15O reaction rate, microscopic diffusion velocities, outer boundary conditions, and colour transformation (bolometric corrections). We conducted the analysis at three different ages, 150 Myr, 1 Gyr, and 7 Gyr, and accounted for errors in photometry from 0.003 mag to 0.03 mag. The results suggest that it is possible to detect the effect induced by only some of the perturbed quantities. The effects induced by a change in the diffusion velocities or in the 14N(p, γ)15O reaction rate are too small to be detected even when the smallest photometric uncertainty is adopted. A variation in the convective core overshooting efficiency was detectable only for photometric errors of 0.003 mag and only for the 1 Gyr case. The effects induced by the outer boundary conditions and the bolometric corrections are the largest; the change in outer boundary conditions is detected for photometric errors below about 0.01 mag, while the variation in bolometric corrections is detectable in the whole photometric error range. As a last exercise, we addressed the validity of the goodness-of-fit statistics for real-world open cluster CMDs, contaminated by field stars or unresolved binaries. We assessed the performance of a data-driven cleaning of observations, aiming to select only single stars in the main sequence from Gaia photometry. This showed that this selection is possible only for a very precise photometry with errors of few millimagnitudes.

Thermonuclear 19F(p, α)16O Reaction Rate Revised and Astrophysical Implications

Abstract We have calculated the thermonuclear 19F(p, α γ )16O reaction rate in a wide temperature region of 0.001–10 GK by re-evaluating the available experimental data. Together with recently evaluated 19(p, α 0)16O and 19(p, α π )16O data, we have derived a new total reaction rate of 19F(p, α)16O using a Monte Carlo technique. The present rate is larger than the NACRE recommended one by factors of 36.4, 2.3, and 1.7 at temperatures of 0.01, 0.05, and 0.1 GK, respectively. This is because we have considered the enhanced low-energy astrophysical S factors in the (p, α γ ) channel, owing to the interference effect between an 11 keV resonance and the well-known 323 keV resonance. It shows that the (p, α γ ) channel dominates the total rate over the entire temperature region, except for a narrow region of 0.05–0.12 GK where the (p, α 0) channel dominates, contrary to the previous conclusion. We have investigated the impact of the 19F(p, α)16O reaction rate using a simple parametric model of extra mixing in low-mass AGB stars, which would lower the fluorine abundance produced and observed in these stars. However, models considering different temperature profiles and more sophisticated approaches, such as extra mixing induced by magnetic fields, are needed to verify the results of our preliminary tests. Interestingly, our new rate has a strong impact on destruction of 19F in the CNO cycle at low temperatures of 0.02–0.03 GK, and this general behavior needs to be analyzed further.

Differential cross sections and product ro-vibrational distributions for 16O+36O2 and 18O+32O2 exchange reactions

We report the rotational-state resolved integral cross sections and differential cross sections for 18O + 16O16O (v = 0, j = 1) →18O16O (v′ = 0, j′) + 16O and 16O + 18O18O (v = 0, j = 1) →18O16O (v′ = 0, j′) + 18O reactions obtained using time-independent quantum mechanical method on an ab initio potential energy surface of ozone [Dawes et al. J. Chem. Phys.135, 081102(2011)]. The results for both the reactions in the collision energy range of 0.001 – 0.1 eV are presented and discussed the isotopic effects found. The present results are compared with the earlier experimental and theoretical results reported in the literature.

Massive Star Modeling and Nucleosynthesis

After a brief introduction to stellar modeling, the main lines of massive star evolution are reviewed, with a focus on the nuclear reactions from which the star gets the needed energy to counterbalance its gravity. The different burning phases are described, as well as the structural impact they have on the star. Some general effects on stellar evolution of uncertainties in the reaction rates are presented, with more precise examples taken from the uncertainties of the 12C(α, γ)16O reaction and the sensitivity of the s-process on many rates. The changes in the evolution of massive stars brought by low or zero metallicity are reviewed. The impact of convection, rotation, mass loss, and binarity on massive star evolution is reviewed, with a focus on the effect they have on the global nucleosynthetic products of the stars.