Board Independence and Firm Financial Performance: Evidence from Nigeria

This study examined the relationship between board independence and firm financial performance, using data of varying sample size (ranging from 89 firms for regression to 205 firms for descriptive analysis) obtained from the Nigerian Stock Exchange for the period 1996 through 2004. The key results were that share ownership was highly concentrated inNigeria, and this structure tended to engender board structureswith close family affiliations in which the chief executive officers (CEOs) were activemembers of audit committees.While family affiliation of board members was found to support firm growth, we found evidence that audit committee membership of chief executives hurt firm performance. We also found that foreign chief executives performed better than their local counterparts. These results suggested the need for Nigerian firms to adopt better corporate governance mechanisms in order to make the boards of directors more independent, avoid unnecessary intervention of CEOs in important committees, and in that way aid financial performance.

Polycyclic Aromatic Hydrocarbons (PAHs) Occurrence and Toxicity in Camellia sinensis and Herbal Tea

This study describes a survey of polycyclic aromatic hydrocarbon (PAH) concentrations in 23 green, herbal, and black tea brands widely consumed in Nigeria by determining the levels of benzo[a]pyrene, chrysene (PAH2), benzo[a]pyrene,chrysene, benz[a]anthracene, benzo[b]fluoranthene (PAH4), benzo[a]pyrene, benz[a]anthracene, benzo[k]fluoranthene, chrysene, benzo[b]fluoranthene,dibenz[ah]anthracene, benzo[ghi]per-ylene and indeno[1,2,3-cd]pyrene (PAH8). Toxic equivalence factor and mutagenic equivalence factor were applied to evaluate the toxic equivalence and mutagenic equivalence quotients relative to benzo[a]pyrene. The concentrations of PAHs indicate that Regulation 835/2011/EC was not fulfilled by benzo[a]anthracene, B[a]A, benzo[a]pyrene, B[a]P, benzo[b]fluoranthene, B[b]F, and chrysene, CHR. The PAH4 levels ranged from 1.28 to 44.57, 4.34 to 11.20, and 0.76 to 34.82 μg/kg in green, black, and herbal tea products, respectively. On the other hand, the PAH8 concentration varied between 1.63 and 65.73, 5.02 and 68.83, and 12.43 and 24.92 μg/kg in green, herbal, and black tea samples. The PAH4 and PAH8 provide more reliable indicators for determination of PAH contamination and risk characterization in food than PAH

On The Effect of Electron-Hole Recombination in Disordered GaAs-Aa1-xALAs Multi-quantum Well Structure

The disordered electron-hole recombination in multi-quantum well was investigated using analytical method based on the rate equations. The results show extreme broad distribution of the recombination time which depends exponentially on the distances between the recombining excitons. The energies at each localised state shows an energy splitting between the electronic ground state and the first excited state of 0.0038eV

Trace Metal Contamination Characteristics and Health Risks Assessment of Commelina africana L. and Psammitic Sandflats in the Niger Delta, Nigeria

The purpose of this study was to investigate and quantify trace metal concentrations in Commelina africana L. and psammitic sandflats from an intertidal coastal ecosystem in Niger Delta, Nigeria, and to evaluate their spatial distribution, degree of contamination, and source apportionment.The environmental risks associated with soil contamination were elaborately assessed using potential ecological risk index, sediment quality guidelines, and enrichment relative to background levels. The mean concentrations of Cd, Cr, Ni, Pb, and Zn in sandflat soil samples are 0.76 ± 9.0 × 10−2, 7.39 ± 8.7 × 10−1, 2.28 ± 0.35, 0.024 ± 4.0 × 10−3, and 74.51 ± 2.55mg/kg, respectively. Metal levels indicate strong variability with sampling sites. The order of trace metal concentrations in the Commelina africana L. samples is Zn > Ni > Cr > Pb > Cd.The concentrations varied with the sample locations; and the levels of Pb (0.05 to 0.08mg/kg) at all locations are found to be significantly below permissible level of 0.3mg/kg. Potential sources of metal loadings may be associated with localised or diffused anthropogenic activities.The average carcinogenic risks are below 1.0 × 10−6 threshold values, and the sandflat soils are not considered to pose significant health effects to children and adult males and females. However, the carcinogenicity and noncarcinogenicity risks ranking decrease following the order children > adult males > adult females. Comparatively, the hazard quotient and hazard index indicate that the psammitic sandflats might pose a health risk to children in future

Characterisation of Polychlorinated Biphenyls in Coastal Inland Seawater, Nigeria

The concentrations of polychlorinated biphenyls (PCBs) were determined in samples of surface seawater collected from five (5) different locations along the coastline of a tropical lagoon. The surface water samples were analysed using gas chromatography coupled with electron capture detector (GC-ECD) with fifteen (15) PCB congeners detected across the studied area. The chlorobiphenyls levels are in the order Ebute Ero > Oko Baba > Ijora > Lagos Island > Unilag lagoon front with levels 107.89, 53.15, 34.90, 27.78, and 2.15 mg/L, respectively. The enhanced average concentration of PCBs at the Ebute Ero site is due to the predominance of PCB-180 and PCB-185. A negative correlation was found between the total PCB concentration and the level of dissolved oxygen. Although, the results indicated fairly high levels of PCBs, the anthropogenic contributions from industrial releases and domestic activities may be largely associated with the detected concentrations of the di-, tetra-, penta-, hexa-, hepta-, and octa-chlorobiphenyl

Chemical constituents from the stem bark of Pentaclethra macrophylla Benth (Fabaceae)

Background: Plants have served as source of lead discovery in drug development; there is the need to look into our ethnomedicinal plants for the purpose of identifying bioactive antibacterial agents to combat the growing antibacterial resistance to current drugs.Objective: The present study investigated the antibacterial activity of the extract and soluble fractions of Pentaclethra macrophylla against some selected pathogens and isolation of active constituents using chromatography and spectroscopic techniques.Materials and methods: The pulverized stem bark of P. macrophylla was extracted to exhaustion with 70% methanol and the combined crude methanol extract after removal of solvent was partitioned with ethyl acetate and n-butanol to give ethyl acetate and n-butanol soluble fractions. Antibacterial activity was evaluated on the crude methanol extract,ethylacetate and n-butanol fractions against five pathogenic bacteria using agar diffusion assay method. The active ethylacetate and n-butanol fractions were subjected to Column chromatography and subsequent purification over sephadex LH-20 afforded compounds I, II and III. The structures of these compounds were elucidated using NMR and MS and are reported in this plant for the first time.Results: Antibacterial activity showed that the extract and fractions at 10mg/mL showed activity against B. subtilis with zones of inhibition of 8.0 ± 2.89, 16.0 ±1.73 and 9.5 ± 1.78 respectively for 70% methanol extract, ethyl acetate, and n-butanol fractions. Ethyl acetate soluble fraction at (10mg/mL) had a good activity against B. subtilis and S. aureus with inhibition zones of 16.0 and13.5mm compared with Levofloxacin (1.5μg/mL) having zones diameter of 21.1 and 16.6mm, however, none of the extract or fractions showed activity against K. pneumonae. Compound I was identified as methyl gallate, compound II: Bergenin and compound III: 11-O-galloylbergenin. The structures of these compounds were elucidated using NMR and ESI-MS and compared with literature.Conclusion: Finding from this work showed that the ethylacetate fraction is the most active and compounds I, II were isolated from the fraction, while the n-butanol furnished compound III. These compounds are being reported for the first time in this plant and have been known to possess antibacterial activity, thereby given credence to the ethnomedicinal use of this plant against infections.Keywords: Pentaclethra macrophylla, Antibacterial, Methyl gallate, Bergenin, 11-O-galloylbergeni

Structural and electrochemical properties of Reduced Graphene Oxide (RGO) synthesised using an improved modified hummers method as electrode material for electronics applications

High quality reduced graphene oxide (RGO) nanosheets were prepared from natural graphite using an improved modified Hummers method. The morphological, structural and electrochemical properties of the RGO were characterised by scanning electron microscope (SEM), Raman spectroscopy, X-ray diffraction (XRD) analysis, Cyclic Voltammetry (CV) analysis and Electrochemical Impedance Spectroscopy (EIS) analysis. The SEM image of the RGO showed that, there was a small increase in the number of grain boundaries, indicating a collapse of the surface coalescence of the graphene oxide. The XRD peak at 24.56˚ corresponds to the (002) diffraction plane with the interlayer spacing along the c-axis of 2.0989 Ǻ. The Raman shift for the reduced graphene oxide gives the ID/IG intensity ratio of 1.04. The RGO exhibited good electrochemical characteristics with energy density and power density of 19.2 Whkg-1 and 149.3 Wkg-1 respectively.Keywords: Reduce Graphene Oxide, Structural Properties, Morphological Properties, electrochemical propertie

Structural Characterization of Lithium Doped Nzp Na1-xLixZr(PO4)3(x=0.00-0.75)

Sodium zirconium phosphate (NZP) of composition Na1-xLixZr2(PO4)3 (x=0.0-0.75) have been synthesized using solid state reaction, with a view to minimizing the ZrO2 second phase normally present .The compositions have been characterized by XRD and SEM for phase composition, lattice parameters and density. No ZrO2 second phase was detected in some of the compositions, rather NasZr(PO4)3 and the density showed a systematic decrease with increase of Li. All The compositions belong to the rhombohedral crystal system and were indexed based on hexagonal lattice structure. The density of the composition x=0.00 as calculated from the XRD data is 3.02g/cm3.The grain sizes of the compositions are in the range 1-2&#956m, 2-5&#956m, 3-7 &#956m and 2&#956m for x=0,0.25,0.5 and 0.75, respectively. Keywords: solid state synthesis, NZP, XR

Polycyclic aromatic hydrocarbons in imported Sardinops sagax: Levels and health risk assessments through dietary exposure in Nigeria

Polycyclic aromatic hydrocarbons (PAHs) occurrence and assessment of dietary exposure from imported canned sardines (Sardinops sagax) commercially marketed in local stores and supermarkets in Nigeria were evaluated for the first time. PAHs determinations were performed using high performance liquid chromatography (HPLC) (Agilent 1290 model) equipped with UV-VIS diodes array detector (DAD) at l = 210 nm and 214 nm. The percentage recoveries were higher than 96%. The degree of contamination expressed as total concentration of PAH congeners ranged between 2.53 and 35.55 mg kg�1 dry weight (d. w.) at l = 210 nm, and 1.30 and 27.93 mg kg�1 (d.w.) at l = 214 nm. The carcinogenic (TEQBaP) and mutagenic toxicities (MEQBaP) of eight priority PAHs were evaluated. Benzo[a]pyrene, benzo[b] fluoranthene, benzo[k]fluoranthene and indeno[1,2,3-c,d] pyrene contributed significantly to the total carcinogenic equivalents of PAHs. The mutagenic equivalents were largely dominated by chrysene, benzo [b]fluoranthene, benzo[k]fluoranthene and benzo[a]pyrene and indeno[1,2,3-c,d]pyrene equivalence factors. The estimated lifetime average daily dose (LADD), average annual excess risk (AR), excess cancer rate (ECR), and hazard quotient risk (HQ) were evaluated for adults, children and preteens exposure related risks. The LADD, ECR, AR and HQ of PAHs for carcinogenic and non-carcinogenic risks are relatively higher in preteens than children and adults

Production and characterization of xanthan gum by bacterial isolates

Xanthan gum is a microbial polymer synthesised by a plant pathogen of the Xanthomonas genus. Due to its rheological characteristics and water solubility, it is of enormous commercial significance and has been utilized as a thickening and stabilizing agent in a variety of industries. In this work, the potential for synthesizing xanthan gum in Xanthomonas species isolated from black rot spotted tomatoes, peppers, mango, and bananas was investigated. After washing the leaves in saline solution, a tenfold dilution was made, and aliquots (1 ml) were placed on a nutrient agar plate and incubated for 48 h at 25 °C. Gram staining was made on colonies that appeared yellow. An emulsification test was carried out on bacteria that were gram-negative rods. Potential xanthan gum producers include isolates displaying yellow colonies, gram-negative rods, and stable emulsions on carbon-enriched media. These requirements were satisfied by eight (61.5 %) of the isolates tested. Biochemical analysis of the isolates indicated that they were Xanthomonas species, and they were coded appropriately (BX2, BX3, PX4, MX6, PX7, MX8, TM9, TX11). The molecular analysis of the best two isolates (TM9 and BX3) revealed that they were Xanthomonas campestris and Stenotrophomonas maltophilia. After 96 h of incubation, Xanthomonas campestris and Stenotrophomonas maltophilia were the most effective xanthan gum producers, generating 2.10 g/l and 1.63 g/l of xanthan gum, respectively. The apparent viscosity (AV), emulsification index (IE24), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) were used to characterize the xanthan gums produced. The findings indicated little or no differences between commercially synthesized xanthan gum and produced xanthan gum. However, xanthan gum from Stenotrophomonas maltophilia has a higher apparent viscosity (660.6 mPas) that is above those of Xanthomonas campestris (526.1 mPas) and commercial xanthan gum (411.3 mPas), respectively. The gums showed structural similarities and exhibited good thermal stability. These findings indicate that Xanthomonas species are viable options for xanthan gum production