Effects of delayed BCG vaccination on cellular immune responses in HIV-exposed infants

Includes abstract. Includes bibliographical references

R&D narrative disclosure, corporate governance and market value:evidence from France

We investigate the impact of R&D narrative disclosure on the market value of equity for a sample of French companies during the period 2000–2004. Using 3SLS estimation on a panel data of 98 French firms, we find, ceteris paribus, positive (but insignificant) association between R&D voluntary disclosure and the market value of equity. Both R&D intensity and R&D capitalization lead French firms to disclose more R&D narrative information. However, they impact differently the relationship between R&D-related disclosure and market value. Indeed, a positive and significant association is found when we control for R&D capitalization. In contrast, when controlling for R&D intensity, we find a negative association. We also find that equity-based compensation and audit committee independence are the most important drivers for R&D narrative disclosure.

Provisioning over the business cycle:Some insights from the microfinance industry

This paper investigates the drivers of provisioning in MFIs and their provisioning behaviour over the business cycle. Based on an international sample of MFIs extracted from the MIX database over the 2001–2014 period, we uncover a negative relationship between MFIs' provisioning and the business cycle. Our finding corroborates the fact that MFIs do not build their loan loss provisions (LLP) during economic booms when profit and earnings are high. Since they provision more during downturns, they are more likely to suffer from unexpected losses and experience failure. This is in sharp contrast with the current Basel III countercyclical buffer requirement suggesting that financial institutions, especially banks, should build sufficient buffer in booms so that they can avoid costly capital adjustment when the economy contracts. Deeper analyses suggest however that this behaviour mainly concerns profit-oriented and deposit-taking/regulated MFIs, with business model and target close to conventional banking. This suggests that bank-like and regulated MFIs' loan loss provisions follow similar behavioral patterns to those of the conventional banking sector during the boom-and-bust cycles.</p

Low-temperature alkaline activation of feldspathic solid solutions: Development of high strength geopolymers

Most of the natural solid solutions, as a result of the history of their formation and crystallization, present a fraction of amorphous or metastable materials that may easily be dissolved or activated in alkaline media. In this work, trachyte, granite, pegmatite and sand for comparison are used as principal solid precursors for the design of high strength geopolymers. The particularity of the solid-solution based geopolymers is the high fraction of crystalline phases incongruently dissolved that may react essentially at the surface, thus developing very resistant bonds. While working with 100 wt% of solid solution is almost unrealistic for the production of geopolymers, it was found that 15 to 30 wt% of metakaolin in replacement of the solid-solution powder conducts to low porosity (10 vol.%), high flexural strength (20-30 MPa) and compact microstructure. Preliminary resonance-based mechanical tests showed that the elastic modulus of the investigated samples ranged between 11-15 GPa, as also confirmed by instrumented micro-indentations. It was concluded that a high strength and durable matrix are a result of chemico-mechanical equilibrium of phases contained within the composites including the pore volume and pore-size distribution, which are significant for the life cycle of geopolymer composites

Gestion des risques et performance des institutions de microfinance

L’objectif de cet article est d’analyser la relation entre la gestion des risques et la performance financière des institutions de microfinance. Les dispositifs analysés relèvent des choix des contrats de crédit et de la régulation prudentielle. La performance est appréhendée sous trois dimensions. Elle renvoie à la rentabilité économique, à la performance opérationnelle et à la qualité du portefeuille. Sur la base d’un échantillon de 148 institutions de microfinance durant la période 2001-2006, notre étude montre que la spécialisation sur un type de contrat améliore la qualité du portefeuille. Plus précisément, les contrats de crédit de groupe améliorent la qualité du portefeuille et influencent négativement la rentabilité économique et la performance opérationnelle, indiquant que le choix des contrats de crédit de groupe conduit les institutions de microfinance à arbitrer entre la rentabilité et la qualité du portefeuille. Enfin, la régulation n’influence en aucune mesure les trois dimensions de la performance susmentionnées.The objective of this paper is to analyze the relationship between risk management and performance of microfinance institutions (MFIs). The devices tested are the choices of credit contracts and prudential regulation. Performance is understood in three dimensions. It refers to profitability, operational performance and portfolio quality. Based on a sample of 148 microfinance institutions in the period 2001-2006, our study shows that specialization on a type of contract improves the quality of the portfolio. Specifically, the group-lending contracts improve quality of portfolio and negatively influence the economic and operational performance, indicating that the choice of credit agreements group led microfinance institutions to a trade-off between profitability and portfolio quality. Finally, the regulation does not influence the three dimensions of performance

Investigation of the relationship between the condensed structure and the chemically bonded water content in the network of geopolymer cements

The main objective of this work was to investigate the relationship between the condensed structure and the chemically bonded water content in the metakaolin-based geopolymer network. The kaolinite clay used in this work as an aluminosilicate source was transformed to metakaolin by calcination at 700 °C. The powder of the waste glass and the silica fume were used as silica sources for the synthesis of the hardeners. The obtained hardeners were characterized by infrared spectroscopy and MAS-NMR 29Si. The metakaolin and the hardeners were used for producing geopolymers cements. The synthesized products were characterized by X-ray diffractometry, infrared spectroscopy, mercury intrusion porosimetry, scanning electron microscopy, MAS-NMR 29Si and 27Al, thermal analyses (TG and DSC) and compressive strength. The results show that the compressive strength of geopolymer cements using hardener from silica fume and the one from waste glass are 62 and 26 MPa, respectively. The microstructure (SEM observations) geopolymer cements obtained using hardener from silica fume are homogeneous, compact and dense with an average pore diameter around 10 nm. Whereas, the one obtained using hardener from waste glass are heterogeneous and contains larger pores (170 nm). MAS-NMR 29Si and 27Al results show that the specimen obtained using hardener from the silica fume contains more aluminum in four-fold coordination in its network than waste glass geopolymer, GWG. This indicates a higher degree of crosslinking of poly(sialate-siloxo) chains which could lead to a smaller pore sizes and a higher water uptake in the structure of the sample. The amount of chemically bonded water contained in the network of geopolymer cements using hardeners from waste glass and silica fume were 6.82 and 11.23%, respectively, as determined from weigth loss in the range 100-300 °C. All these results indicate that the higher content of chemically bonded water in the network of geopolymer obtained using hardener from silica fume is related to the much smaller average pore size diameter and the hydrophilic character of aluminum, which reveals obviously better mechanical and microstructural properties of the specimen. This could indicate here a higher degree of condensation using silica fume based hardeners for geopolymerisation. Please click Additional Files below to see the full abstract

Water resistance and thermal behavior of metakaolin-phosphate-based geopolymer cements

The main target of this work was to investigate the thermal behavior and water resistance of geopolymer cement made from metakaolin as an aluminosilicate source using phosphoric acid solution (10&nbsp;M) as a hardener. The obtained geopolymer cements were cured at room temperature for 28&nbsp;days, the one part was treated at 200°C, 400°C, 600°C, 800°C and 1000°C, and the others were soaked in water for 28&nbsp;days. The geopolymer cements were characterized by microstructural properties using X-ray diffractometry, infrared spectroscopy, microstructure, physical property based on water resistance and thermo-mechanical properties (thermal analysis, compressive strength). The results show that the compressive strength of the unheated geopolymer cement was 87.96&nbsp;MPa. The ones soaked in water revealed a strength of 40.71&nbsp;MPa. This indicates that the specimens soaked in water lose about 54% of their strengths. The X-ray patterns of heated geopolymer cements showed the formation of crystalline phases even at relatively low temperatures. It was typically found that the compressive strength of metakaolin-phosphate-based geopolymer cements decreases due to the hydrolysis of Si-O-P bonds in the presence of water

Meta-halloysite to improve compactness in iron-rich laterite-based alkali activated materials

In this paper, the results of the experimental investigation were used to understand the effect of fine meta-halloysite on the reactivity, mechanical and microstructural properties of laterite-based geopolymers. Laterite was replaced by 0, 20, 30 and 50 wt% of meta-halloysite in order to improve the physico-chemical performance. Meta-halloysite was prepared by calcination of natural halloysite at 600 °C. The moduli (molar ratio SiO2/Na2O) of the activating solutions were 1.04, 0.92, and 0.75 with H2O/Na2O = 9.78, 10.45 and 12.04, respectively. The results indicated that calcined laterite has a high specific surface area (43.00 ± 0.12 m2/g), notwithstanding a high average particle size (d50 = 45.20 μm) compared to meta-halloysite with a smaller average particle size (d50 = 8.40 μm) and a specific surface (29.80 ± 0.16 m2/g). The compressive strength of geopolymers increased upon the addition of meta-halloysite from 12 MPa to 45 MPa at 28 days. While the setting time and water absorption decrease with increase in the of meta-halloysite content as well as with increase in Si/Al, Si/Fe, Al/Fe and Na/Al molar ratios used in the synthesis of geopolymers. The use of fine meta-halloysite resulted in better efficiency and improved mechanical performance of synthesized products

Engineering properties, phase evolution and microstructure of the iron-rich aluminosilicates-cement based composites: Cleaner production of energy efficient and sustainable materials

This paper investigates the direct transformation of laterites (natural iron-rich aluminosilicates) to cementitious composites with principal mineral phases being Gismondine and Stratlingite. The effects of particles size distribution and cement content (2 to 8 wt%) on the mechanical properties and microstructure of laterite-cement composites are assessed. Four grades of granulometry with various percentages of fine and coarse particles were considered. The Environment Scanning Electron Microscopy (ESEM), Mercury Intrusion Porosimetry (MIP), Fourier Transformed Infrared Spectroscopy (FT-IR) and X-ray Powder Diffractometry (XRD) were performed after 1, 90 and 365 days, to assess the phase's evolution, mechanical performance and the microstructure of the laterite-cement composites. It is found that fines particles, essentially pozzolanic and amorphous, are responsible for the bonding strength while coarse particles improve the compressive strength. Dense and compact microstructure, water absorption under 18% and flexural strength above 6 MPa (compressive strength &gt; 30 MPa) could be achieved as from 4 wt% of cement making the laterite-cement composite appropriate as building and construction materials. The choice of a highly corroded class of laterite and the selection of the particle size distribution allows the production of optimum composite that is presented as energy-efficient and sustainable. Thus, corroded or indurated laterites are considered as “green metakaolins” which do not require any energy for their transformation unlike clayey materials

Microstructure and mechanical, physical and structural properties of sustainable lightweight metakaolin-based geopolymer cements and mortars employing rice husk

This work focuses on an in-depth investigation of the formation of pores in the structure of lightweight geopolymer cements and mortars using rice husk as a foaming agent. The hardener used in this study was sodium waterglass. Metakaolin was replaced by 0, 10, 20, 30 and 40 % by mass of husk and the obtained powders were used to produce lightweight geopolymer cements and mortars. The formation of pores in the lightweight geopolymer cements was monitored using X-ray diffractometry and infrared spectroscopy while those in the mortars were assessed using apparent density and compressive strength measurements, mercury intrusion porosimetry and optical and scanning electron microscopy. The values for the compressive strength and apparent density were in the ranges of 28.92\u20130.75&nbsp;MPa and 1.88\u20131.70&nbsp;g/cm 3 , respectively. The results indicated that the values for the compressive strength and apparent density of geopolymer mortars decreased while those of the cumulative pore volume increased with increases in the metakaolin replacement level. Stereomicroscopic and scanning electron microscopic images showed the presence of rice husk and fibres of rice husk, respectively, in the networks. It was found that rice husk can be used as a foaming agent for producing sustainable lightweight geopolymer mortars