Nuclear Reactions: A Challenge for Few- and Many-Body Theory

A current interest in nuclear reactions, specifically with rare isotopes concentrates on their reaction with neutrons, in particular neutron capture. In order to facilitate reactions with neutrons one must use indirect methods using deuterons as beam or target of choice. For adding neutrons, the most common reaction is the (d,p) reaction, in which the deuteron breaks up and the neutron is captured by the nucleus. Those (d,p) reactions may be viewed as a three-body problem in a many-body context. This contribution reports on a feasibility study for describing phenomenological nucleon-nucleus optical potentials in momentum space in a separable form, so that they may be used for Faddeev calculations of (d,p) reactions.Comment: to appear in the Proceedings of HITES 2012: Conference on `Horizons of Innovative Theories, Experiments, and Supercomputing in Nuclear Physics', June 4-7, 2012, New Orleans, Louisian

6^6Li in a Three-Body Model with Realistic Forces: Separable vs. Non-separable Approach

{\bf Background:} Deuteron induced reactions are widely used to probe nuclear structure and astrophysical information. Those (d,p) reactions may be viewed as three-body reactions and described with Faddeev techniques. {\bf Purpose:} Faddeev equations in momentum space have a long tradition of utilizing separable interactions in order to arrive at sets of coupled integral equations in one variable. However, it needs to be demonstrated that their solution based on separable interactions agrees exactly with solutions based on non-separable forces. {\bf Results:} The ground state of $^6$Li is calculated via momentum space Faddeev equations using the CD-Bonn neutron-proton force and a Woods-Saxon type neutron(proton)-$^4$He force. For the latter the Pauli-forbidden $S$-wave bound state is projected out. This result is compared to a calculation in which the interactions in the two-body subsystems are represented by separable interactions derived in the Ernst-Shakin-Thaler framework. {\bf Conclusions:} We find that calculations based on the separable representation of the interactions and the original interactions give results that agree to four significant figures for the binding energy, provided an off-shell extension of the EST representation is employed in both subsystems. The momentum distributions computed in both approaches also fully agree with each other

Barriers to anti-retroviral therapy adherence among adolescents aged 10 to 19 years living with HIV in sub-Saharan Africa: A mixed-methods systematic review protocol

Background: Antiretroviral therapy (ART) adherence is fundamental in achieving viral load suppression and consequently attaining positive health outcomes among people living with HIV. However, ART adherence is sub-optimum among adolescents living with HIV (ALHIV) thus the high AIDS-related mortality even after World Health Organization (WHO) revised HIV treatment eligibility guidelines in 2010, 2013 and 2016. Consolidated trends of barriers to ART adherence among ALHIV aged 10 to 19 years in sub-Saharan countries post each eligibility guidelines revision to date are unknown. Methods and analysis: We will conduct comprehensive search of peer-reviewed and grey literature databases publishing observational studies reporting data adherence and barriers to ART among ALHIV on ART. We will further search the reference lists of included studies and other relevant reviews. We will also do a citation search for included studies in the review. We will search in the following databases PubMed, Cochrane Review, Scopus on Excerpta Medica Database (Embase) and Cumulated Index to Nursing and Allied Health Literature (CINAHL). Furthermore WHO, Joint United Nations Programme on HIV/AIDS (UNAIDS) websites, conference proceedings and country reports will be searched to identify relevant literature. Data will be extracted from eligible studies and synthesis will be through categorizing studies by year of study, barriers, and outcomes. Meta-analysis and meta-synthesis will be conducted for quantitative and qualitative data, respectively. Where meta-synthesis is impossible, narrative synthesis will be conducted. We will only include studies conducted between 2010 and 2022 within sub-Saharan Africa countries. Discussion: Adherence to ART at a high level is required to achieve adequate viral suppression and improve quality of life in ALHIV. The knowledge of barriers to ART among ALHV may aid in the design of interventions aimed at improving ART adherence

Barriers and facilitators to anti-retroviral therapy adherence among adolescents aged 10 to 19 years living with HIV in sub-Saharan Africa: A mixed-methods systematic review and meta-analysis

Background: Human Immunodeficiency Virus (HIV) significantly affects adolescents globally, with the sub-Saharan Africa (SSA) reporting a high burden of the disease. HIV testing, treatment, and retention to care are low among adolescents. We conducted a mixed-method systematic review to assess anti-retroviral therapy (ART) adherence; barriers and facilitators to ART adherence and ART outcomes among adolescents living with HIV and on ART in sub-Saharan Africa. Methods: We conducted searches in four scientific databases for studies conducted between 2010 and March 2022 to identify relevant primary studies. Studies were screened against inclusion criteria and assessed for quality, and data was extracted. Meta-analysis of rates and odd ratios was used to plot the quantitative studies and meta-synthesis summarized the evidence from qualitative studies. Results: A total of 10 431 studies were identified and screened against the inclusion/ exclusion criteria. Sixty-six studies met the inclusion criteria (41 quantitative, 16 qualitative, and 9 mixed-methods study designs). Fifty-three thousand two hundred and seventeen (53 217) adolescents (52 319 in quantitative studies and 899 in qualitative studies) were included in the review. Thirteen support focused interventions for improved ART adherence were identified from quantitative studies. The plotted results from the meta-analysis found an ART adherence rate of 65% (95%CI 56–74), viral load suppression was 55% (95%CI 46–64), un-suppressed viral load rate of 41% (95%CI 32–50), and loss to follow up of 17% (95%CI 10–24) among adolescents. Meta-synthesis found six themes of barriers to ART (social, patient-based, economic, health system-based, therapy-based, and cultural barriers) in both the qualitative and quantitative studies, and three themes of facilitators to ART were also identified (social support, counselling, and ART education and secrecy or confidentiality) from qualitative studies. Conclusion: ART adherence remains low among adolescents in SSA despite multiple interventions implemented to improve ART adherence. The low adherence rate may hinder the attainment of the UNAIDS 2030 targets. Additionally, various barriers to ART adherence due to lack of support have been reported among this age group. However, interventions aimed at improving social support, educating, and counselling adolescents may improve and sustain ART adherence

Optical potentials for the rare-isotope beam era

We review recent progress and motivate the need for further developments in nuclear optical potentials that are widely used in the theoretical analysis of nucleon elastic scattering and reaction cross sections. In regions of the nuclear chart away from stability, which represent a frontier in nuclear science over the coming decade and which will be probed at new rare-isotope beam facilities worldwide, there is a targeted need to quantify and reduce theoretical reaction model uncertainties, especially with respect to nuclear optical potentials. We first describe the primary physics motivations for an improved description of nuclear reactions involving short-lived isotopes, focusing on its benefits for fundamental science discoveries and applications to medicine, energy, and security. We then outline the various methods in use today to build optical potentials starting from phenomenological, microscopic, and ab initio methods, highlighting in particular the strengths and weaknesses of each approach. We then discuss publicly-available tools and resources facilitating the propagation of recent progresses in the field to practitioners. Finally, we provide a set of open challenges and recommendations for the field to advance the fundamental science goals of nuclear reaction studies in the rare-isotope beam era.Comment: This paper is the outcome of the Facility for Rare Isotope Beams Theory Alliance (FRIB - TA) topical program "Optical Potentials in Nuclear Physics" held in March 2022 at FRIB. Its content is non-exhaustive, was chosen by the participants and reflects their efforts related to optical potential