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Bujumbura, Burundi

The University of Burundi is located in Bujumbura, Burundi. It is the only public university in Burundi. Most of its facilities are deteriorating and significantly damaged due to civil war. In its infancy, it was owned and operated by the Roman Catholic Church. Its enrollment is approximately 13,000. Wikipedia.

Liu Y.,CAS Changchun Institute of Applied Chemistry | Sun X.,Qingdao Agricultural University | Gahungu G.,University of Burundi | Qu X.,CAS Changchun Institute of Applied Chemistry | And 2 more authors.
Journal of Materials Chemistry C | Year: 2013

A DFT/TDDFT investigation was performed on the electronic structures, basic photophysical properties and potential OLED applications of a series of Ir(iii) complexes [(fpmb)2Ir(fptz)] (1a), [(dfpmb)2Ir(fptz)] (2a), [(fpmb)2Ir(bptz)] (3a), [(dfpmb)2Ir(bptz)] (4a) [where H2fpmb = 1-(4-fluorophenyl)-2,3-dihydro-3-methyl-1H-benzo[d] imidazole; H2dfpmb = 1-(2,4-fluorophenyl)-2,3-dihydro-3-methyl-1H- benzo[d]imidazole; fptzH = 2-(5-(trifluoromethyl)-2H-1,2,4-triazol-3-yl) pyridine; bptzH = 4-tert-butyl-2-(5-(trifluoromethyl)-2H-1,2,4-triazol-3-yl) pyridine] and [(fbmb)2Ir(fptz)] (1b), [(dfbmb)2Ir(fptz)] (2b), [(fbmb)2Ir(bptz)] (3b), [(dfbmb)2Ir(bptz)] (4b) [where H2fbmb = 1-(4-fluorobenzyl)-2,3-dihydro-3-methyl-1H-benzo[d] imidazole; H2dfbmb = 1-(2,4-fluorobenzyl)-2,3-dihydro-3-methyl-1H- benzo[d]imidazole] bearing two conjugated and nonconjugated carbene ligands respectively and one blue-emitting chromophore that possesses a much larger ligand energy gap. It is found that the photophysical properties of these complexes are greatly affected by the properties of the adopted ligands. From 1b to 4b, the insertion of a saturated σ-bond methylene spacer into the carbene ligand renders an increase of the HOMO-LUMO energy gap, but relatively weak absorption intensities. The emission spectra are slightly influenced by the switch between conjugated and nonconjugated ligands. Furthermore, on the basis of the calculations, the significantly higher quantum yield of 2b and 3b with respect to 3a is also explained with the assistance of their larger metal contribution to the lowest excited states (MLCT%) and smaller S 1-T2 splitting energies (ΔES1-T 2). Besides, the designed complexes 1b and 4b are considered to be potential candidates as blue-emitting materials with good charge transfer properties and high quantum efficiency. © 2013 The Royal Society of Chemistry.

Nkurunziza H.,University of Burundi | Gebhardt A.,Klagenfurt University | Pilz J.,Klagenfurt University
Malaria Journal | Year: 2011

Background: Malaria is a major public health issue in Burundi in terms of both morbidity and mortality, with around 2.5 million clinical cases and more than 15,000 deaths each year. It is still the single main cause of mortality in pregnant women and children below five years of age. Because of the severe health and economic burden of malaria, there is still a growing need for methods that will help to understand the influencing factors. Several studies/researches have been done on the subject yielding different results as which factors are most responsible for the increase in malaria transmission. This paper considers the modelling of the dependence of malaria cases on spatial determinants and climatic covariates including rainfall, temperature and humidity in Burundi. Methods. The analysis carried out in this work exploits real monthly data collected in the area of Burundi over 12 years (1996-2007). Semi-parametric regression models are used. The spatial analysis is based on a geo-additive model using provinces as the geographic units of study. The spatial effect is split into structured (correlated) and unstructured (uncorrelated) components. Inference is fully Bayesian and uses Markov chain Monte Carlo techniques. The effects of the continuous covariates are modelled by cubic p-splines with 20 equidistant knots and second order random walk penalty. For the spatially correlated effect, Markov random field prior is chosen. The spatially uncorrelated effects are assumed to be i.i.d. Gaussian. The effects of climatic covariates and the effects of other spatial determinants are estimated simultaneously in a unified regression framework. Results: The results obtained from the proposed model suggest that although malaria incidence in a given month is strongly positively associated with the minimum temperature of the previous months, regional patterns of malaria that are related to factors other than climatic variables have been identified, without being able to explain them. Conclusions: In this paper, semiparametric models are used to model the effects of both climatic covariates and spatial effects on malaria distribution in Burundi. The results obtained from the proposed models suggest a strong positive association between malaria incidence in a given month and the minimum temperature of the previous month. From the spatial effects, important spatial patterns of malaria that are related to factors other than climatic variables are identified. Potential explanations (factors) could be related to socio-economic conditions, food shortage, limited access to health care service, precarious housing, promiscuity, poor hygienic conditions, limited access to drinking water, land use (rice paddies for example), displacement of the population (due to armed conflicts). © 2011 Nkurunziza et al; licensee BioMed Central Ltd.

Ndayiragije F.,University of Burundi | Van Assche W.,Catholic University of Leuven
Journal of Physics A: Mathematical and Theoretical | Year: 2013

Multiple Meixner polynomials are polynomials in one variable which satisfy orthogonality relations with respect to r > 1 different negative binomial distributions (Pascal distributions). There are two kinds of multiple Meixner polynomials, depending on the selection of the parameters in the negative binomial distribution. We recall their definition and some formulas and give generating functions and explicit expressions for the coefficients in the nearest neighbor recurrence relation. Following a recent construction of Miki, Tsujimoto, Vinet and Zhedanov (for multiple Meixner polynomials of the first kind), we construct r > 1 non-Hermitian oscillator Hamiltonians in r dimensions which are simultaneously diagonalizable and for which the common eigenstates are expressed in terms of multiple Meixner polynomials of the second kind. © 2013 IOP Publishing Ltd.

Li Z.,Central China Normal University | Claver H.,Central China Normal University | Claver H.,University of Burundi
Optics Letters | Year: 2013

In this Letter, we show that digital optical phase conjugation might be utilized to construct a new kind of wavelength- selective switches. When incorporated with a multimode interferometer, these switches have wide bandwidth, high tolerance for fabrication error, and low polarization dependency. They might help to build large-scale multiwavelength nonblocking switching systems, or even to fabricate an optical cross-connecting or routing system on a chip. © 2013 Optical Society of America.

Liu Y.,CAS Changchun Institute of Applied Chemistry | Gahungu G.,University of Burundi | Sun X.,Qingdao Agricultural University | Qu X.,CAS Changchun Institute of Applied Chemistry | Wu Z.,CAS Changchun Institute of Applied Chemistry
Journal of Physical Chemistry C | Year: 2012

A DFT/TDDFT investigation was applied to understand the unusual properties of the recently synthesized blue-emitting Ir(III) complexes [Ir(PMe 2Ph)(dppit)(py2pz)] (1) [PMe2Ph = dimethylphenylphosphine; dppit = diphenyl phenylphosphonite; py2pz = 3,5-di(2-pyridyl)pyrazole] and [Ir(PMe2Ph)(dppit)(bptz)] (2) [bptz =3-tert-butyl-5-(2-pyridyl) triazolate], which are successfully used as emitters in organic light-emitting diodes (OLEDs). The influence of N-substitution on optical and electronic properties of Ir(III) complexes was also explored by introducing a N atom on the pyridine moiety of Nâ̂§N ligands for 1 and 2. The calculated results reveal that introduction of N substitution leads to a blue shift for 1a, 1b, 1c, and 1d (a, b, c, d indicate different positions for N substitution) and slightly red shift for 2a-2d in absorption spectra compared with that of 1 and 2, respectively. The N substitution at different positions on Nâ̂§N ligands may also be an efficient approach of tuning emitting color for 1 and 2. The 1-position substituent (1a and 2a) leads to an obvious blue shift of emission spectra compared with 1 and 2, while a significant red shift is observed for the 3-substituted derivatives 1c and 2c. It is believed that the larger 3MLCT-3MC energy gap and higher μS1 value, as well as the smaller ΔES1-T1 for 1a/2a, are good indications for the higher quantum efficiency compared with that of experimental structures 1/2. These new structure-property relationships can provide improved design and optimization of OLED devices based on blue-emitting phosphorescent Ir(III) complexes. © 2012 American Chemical Society.

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