From Neutral Aniline to Aniline Trication: A Computational and Experimental Study

We report density functional theory computations and photoionization mass spectrometry measurements of aniline and its positively charged ions. The geometrical structures and properties of the neutral, singly, doubly, and triply positively charged aniline are computed using density functional theory with the generalized gradient approximation. At each charge, there are multiple isomers closely spaced in total energy. Whereas the lowest energy states of both neutral and cation have the same topology C6H5–NH2, the dication and trication have the C5NH5–CH2 topology with the nitrogen atom in the meta and para positions, respectively. We compute the dissociation pathways of all four charge states to NH or NH+ and NH2 or NH2+, depending on the initial charge of the aniline precursor. Dissociation leading to the formation of NH (from the neutral and cation) and NH+ (from the dication and trication) proceeds through multiple transition states. On the contrary, the dissociation of NH2 (from the neutral, cation) and NH2+ (from the dication and trication) is found to proceed without an activation energy barrier. The trication was found to be stable toward abstraction on NH+ and NH2+by 0.96 eV and 0.18 eV, respectively, whereas the proton affinity of the trication is substantially higher, 1.98 eV. The mass spectra of aniline were recorded with 1300 nm, 20 fs pulses over the peak intensity range of 1 x 1013 W cm-2 to 3 x 1014W cm-2. The analysis of the mass spectra suggests high stability of both dication and trication to fragmentation. The formation of the fragment NH+ and NH2+ ions is found to proceed via Coulomb explosion

Decoherence on a two-dimensional quantum walk using four- and two-state particle

We study the decoherence effects originating from state flipping and depolarization for two-dimensional discrete-time quantum walks using four-state and two-state particles. By quantifying the quantum correlations between the particle and position degree of freedom and between the two spatial ($x-y$) degrees of freedom using measurement induced disturbance (MID), we show that the two schemes using a two-state particle are more robust against decoherence than the Grover walk, which uses a four-state particle. We also show that the symmetries which hold for two-state quantum walks breakdown for the Grover walk, adding to the various other advantages of using two-state particles over four-state particles.Comment: 12 pages, 16 figures, In Press, J. Phys. A: Math. Theor. (2013

Quantum walks: a comprehensive review

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important result: the computational universality of both continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing Journa

Looking back and moving forward: 50 years of soil and soil fertility management research in sub-Saharan Africa

Article purchased; Published online: 02 Nov 2017Low and declining soil fertility has been recognized for a long time as a major impediment to intensifying agriculture in sub-Saharan Africa (SSA). Consequently, from the inception of international agricultural research, centres operating in SSA have had a research programme focusing on soil and soil fertility management, including the International Institute of Tropical Agriculture (IITA). The scope, content, and approaches of soil and soil fertility management research have changed over the past decades in response to lessons learnt and internal and external drivers and this paper uses IITA as a case study to document and analyse the consequences of strategic decisions taken on technology development, validation, and ultimately uptake by smallholder farmers in SSA. After an initial section describing the external environment within which soil and soil fertility management research is operating, various dimensions of this research area are covered: (i) ‘strategic research’, ‘Research for Development’, partnerships, and balancing acts, (ii) changing role of characterization due to the expansion in geographical scope and shift from soils to farms and livelihoods, (iii) technology development: changes in vision, content, and scale of intervention, (iv) technology validation and delivery to farming communities, and (v) impact and feedback to the technology development and validation process. Each of the above sections follows a chronological approach, covering the last five decades (from the late 1960s till today). The paper ends with a number of lessons learnt which could be considered for future initiatives aiming at developing and delivering improved soil and soil fertility management practices to smallholder farming communities in SSA

Sero-Epidemiology as a Tool to Screen Populations for Exposure to Mycobacterium ulcerans

Sero-epidemiological analyses revealed that a higher proportion of sera from individuals living in the Buruli ulcer (BU) endemic Densu River Valley of Ghana contain Mycobacterium ulcerans 18 kDa small heat shock protein (shsp)-specific IgG than sera from inhabitants of the Volta Region, which was regarded so far as BU non-endemic. However, follow-up studies in the Volta Region showed that the individual with the highest anti-18 kDa shsp-specific serum IgG titer of all participants from the Volta Region had a BU lesion. Identification of more BU patients in the Volta Region by subsequent active case search demonstrated that sero-epidemiology can help identify low endemicity areas. Endemic and non-endemic communities along the Densu River Valley differed neither in sero-prevalence nor in positivity of environmental samples in PCR targeting M. ulcerans genomic and plasmid DNA sequences. A lower risk of developing M. ulcerans disease in the non-endemic communities may either be related to host factors or a lower virulence of local M. ulcerans strains

Distribution of Mycobacterium ulcerans in Buruli Ulcer Endemic and Non-Endemic Aquatic Sites in Ghana

Mycobacterium ulcerans, the causative agent of Buruli ulcer, is an emerging environmental bacterium in Australia and West Africa. The primary risk factor associated with Buruli ulcer is proximity to slow moving water. Environmental constraints for disease are shown by the absence of infection in arid regions of infected countries. A particularly mysterious aspect of Buruli ulcer is the fact that endemic and non-endemic villages may be only a few kilometers apart within the same watershed. Recent studies suggest that aquatic invertebrate species may serve as reservoirs for M. ulcerans, although transmission pathways remain unknown. Systematic studies of the distribution of M. ulcerans in the environment using standard ecological methods have not been reported. Here we present results from the first study based on random sampling of endemic and non-endemic sites. In this study PCR-based methods, along with biofilm collections, have been used to map the presence of M. ulcerans within 26 aquatic sites in Ghana. Results suggest that M. ulcerans is present in both endemic and non-endemic sites and that variable number tandem repeat (VNTR) profiling can be used to follow chains of transmission from the environment to humans. Our results suggesting that the distribution of M. ulcerans is far broader than the distribution of human disease is characteristic of environmental pathogens. These findings imply that focal demography, along with patterns of human water contact, may play a major role in transmission of Buruli ulcer

Evolving national pharmacovigilance systems in Africa

Introduction: Various authors have described the challenges associated with African pharmacovigilance systems. However, the last decades have seen growth of these systems. The thesis provides insight into the emergence and growth of African pharmacovigilance systems by looking at different elements of the system. Focus will be on examining the role of the national pharmacovigilance centre, the participation and awareness of reporters and evaluators and lastly, the feasibility of generating evidence on the safety and use of medicines in low resource settings in Africa. Results:Chapter 2.1 characterized Adverse Drug Reaction (ADR) reporting activities in Africa and compared them with the rest of the world. We found that ADR reporting in Africa has grown from 25,000 in 2010to 103,499 in 2015. The characteristics of African ADRs are different from the rest of the world in terms of products and ADRs reported. In Chapter 2.2 we provided a broader view on the functioning of national pharmacovigilance centres in Africa by examining their resources, relationships and organisational capacity. We found that strategic leaders of national centres often attributed successful pharmacovigilance activities to availability of political and technical resources, while unsuccessful activities were often attributed to a lack of financial and human resources. In order to increase reporting of ADRs to the national centre, we assessed the awareness of Ghanaian patients about ADRs and ADR reporting (Chapter 3.1) which revealed that of the 491 participants in our study, 38% had experienced an ADR of which 67% reported the ADR to someone, 68% of them reported it to a doctor. However, only 3% of the 491 participants were aware of the Ghana-Food and Drug Authority’s patient reporting system. There is limited knowledge on the use of local data for decision making in Africa. In Chapter 3.2 through literature review we showed that no major drug safety decisions have been taken by public health programmes based on data collected in Africa. Data on the use and safety of medicines may be needed to make decisions for products used in Africa hence in Chapter 4.1 we applied a cohort event monitoring methodology to assess the ADRs of Injectable Artesunate (Inj AS) and found that,the overall incidence of ADRs was 17.9% (197/1103) which is similar to that listed in the public assessment reports published by the WHO. In Chapter 4.2 the data collected through the cohort event monitoring was used to assess prescribing practices of African health care professionals and investigate if these are in line with the WHO treatment guidelines. We found that Inj AS is the most commonly prescribed medicine in the management of severe malaria in Ghana and Uganda. However, only 27.6% (329 out of 1191) of patients received at least three doses if Inj AS followed by a full course of oral ACT as recommended by WHO. Conclusion: Most African countries have met the WHO minimum requirements for formal national pharmacovigilance systems. However, with pharmacovigilance activities expanding, various system structures and relationships between system participants need to be further strengthened

The contribution of Ghanaian patients to the reporting of adverse drug reactions : a quantitative and qualitative study

BACKGROUND: Under-reporting of adverse drug reactions (ADRs) is a major challenge for pharmacovigilance in Africa. This study sets out to assess the level of awareness of Ghanaian patients about ADRs and ADR-reporting and explores how different patients in Ghana recognize an ADR and the steps they take when they experience an ADR. METHODS: This was a two-part study consisting of a survey to quantify the awareness of Ghanaian patients on ADRs and ADR-reporting, and in-depth interviews to explore how patients recognize an ADR and the steps they take thereafter. Participants were selected from 28 health care facilities (HCF) in rural and urban areas in 4 out of the 10 administrative regions of Ghana. Chi-square tests were used to examine associations between demographic variables and i) awareness of ADRs and ADR-reporting, ii) ADR experience and iii) awareness of the Ghana Food and Drug Authority (Ghana-FDA) and its patient reporting system (PRS). Only participants that indicated they experienced an ADR were included for the in-depth interviews. Data was investigated for participants' awareness of ADRs, ADR reporting and steps taken when they experience ADRs. RESULTS: Of the total 572 participants enrolled in the study, 14% indicated they were unaware of ADRs and were excluded. Of the remaining 491 participants, 38% had experienced an ADR, of which 67% reported the ADR, 68% of them reported it to a doctor. Only 3% of the 491 participants were aware of the Ghana-FDA's PRS. The interview phase consisted of 33 patients who had experienced an ADR. Three key findings from the interview phase were; most participants recognized an ADR themselves, the symptoms of the ADR were the most mentioned reason for reporting and participants experienced a wide variety of obstacles in ADR-reporting. CONCLUSIONS: Most Ghanaian patients appear unaware of or unable/unwilling to use formal national channels for ADR reporting like the Ghana-FDA PRS. Motivation for ADR reporting appeared mainly personal and not communal. These findings warrant further attention in order to increase patient reporting of ADRs