Measurement of solar energy radiation at Nsukka and the determination of the regression coefficients

Solar radiation for Nsukka, latitude 6.8°N, longitude 7.35°E, located 488 m above sea level, was collected for 11 yr using a Gunn-Bellani instrument, and the data obtained were restandardized using an Eppley precision pyranometer. The sunshine data during this period were also obtained using a Campbell-Stokes sunshine recorder.

It is observed that the insolation level for the month of November during the period of measurement is the highest, with an average of 17.50 MJ/m². The level of insolation during this month varied sinusoidally with an amplitude of 3.84 MJ/m². The clearness index, k_T, is 0.53, and there is an indication that the atmosphere was persistently laden with dust. August has the least insolation level with an average of 11.86 MJ/m² and a k_T of 0.32. The atmosphere during this month was always covered with cloud. This work confirmed the assertion by Awachie and co-workers that dust and haze attenuate insolation less than cloud cover. The Nsukka weather is rated to be heavily overcast, and over 90% of the total solar radiation is diffuse, with an average k_T value of 0.43.

The average regression coefficients a and b for Nsukka are 0.21 and 0.51 respectively. These values do not agree with the general relations and values already quoted by some workers. The predicted insolation values for Nsukka using these coefficients in the Angstrom type of formula agree with the measured data with an error of 0.7%. This level of accuracy compares well with those obtained when the insolation values are predicted for each year using the values of a and b deduced for the respective year. Furthermore, there was an indication that the level of accuracy obtained using average values of a and b might increase if a longer period is considered. Thus, with reliable average values of a and b obtained over a reasonably long period, and knowledge of the bright sunshine hours, the measurement of solar radiation in a location, for design purposes, may not be necessary.     

Extragradient Algorithm for Solving Pseudomonotone Equilibrium Problem with Bregman Distance in Reflexive Banach Spaces

Networks and Spatial Economics - Using the Bregman distance technique, we study the approximation of solution of pseudomonotone equilibrium problem using modified extragradient method in a real...     

Preparation and evaluation of charged solid lipid nanoparticles of tetrandrine for ocular drug delivery system: pharmacokinetics,cytotoxicity and cellular uptake studies

In this study, tetrandrine-loaded cationic solid lipid nanoparticles (TET-CNP) and solid lipid nanoparticles (TET-NP) were prepared by the emulsion evaporation-solidification at low temperature method. The particle size, zeta potential, and entrapment efficiency of TET-CNP and TET-NP were characterized. The results showed that the TET-CNP and TET-NP had average diameters of (15.29?±?1.34) nm and (18.77?±?1.23) nm with zeta potentials of (5.11?±?1.03) mV and (?8.71?±??1.23) mV and entrapment efficiencies of (94.1?±?2.37)% and (95.6?±?2.43)%, respectively. In vitro release studies indicated that the TET-CNP and TET-NP retained the drug entity better than tetrandrine ophthalmic solutions (TET-SOL). In the pharmacokinetics studies, the AUC values of TET-CNP and TET-NP were 1.96-fold and 2.00-fold higher than that of TET-SOL (?p?C_max values of TET-CNP and TET-NP were 2.45-fold and 2.53-fold higher than that of the TET-SOL (p?相似文献   

Universal fungus-specific primer systems and group-specific hybridization oligonucleotides for 18S rDNA

We designed two primer systems that amplify a fragment of the gene coding for the small ribosomal subunit (18S rRNA). A broadly reactive, yet fungus-specific, primer cocktail comprises two previously published primers, TR1 and TR2, which specifically amplify dermatophytes, and two newly designed primers, CA1 and AF2, which specifically amplify Candida and Aspergillus respectively. This primer cocktail amplifies a DNA fragment of approximately 578 basepairs (bp) in length (from position 838 to 1415), which contains variable, possibly species-specific regions (V5, partly V7). Another newly designed primer, UF1 (universal fungal primer 1), along with the eukaryotic primer S3 amplifies a 926-bp fragment (from position 263 to 1188) that includes the variable regions V3, V4 and V5. Both primer systems amplified DNA from Saccharomyces cerevisiae, Candida albicans, Cryptococcus neoformans, Aspergillus fumigatus, Penicillium marneffei, Fusarium oxysporum and Trichophyton mentagrophytes, but not the DNA from Prototheca zopfii, Escherichia coli or humans. The previously published oligonucleotides TR and HC, which are specific for dermatophytes and Histoplasma respectively, and the newly designed group-specific oligonucleotides, CA and AF, hybridized with T. mentagrophytes, Histoplasma capsulatum, C. albicans and A. fumigatus respectively, but not with the other six fungi or with the three controls.     

Investigation of the impact of atmospheric particles on solar radiation at Nsukka, Nigeria

Using a well-calibrated integrating nephelometer of sensitivity 10⁻⁷/m, we have successfully measured the scattering extinction coefficient of atmospheric fine particles, b_sp at Nsukka, Nigeria, at latitude 6.8°N and longitude 7.35°E and an elevation of 488 m above sea level.

The values of b_sp recorded are 10.0 × 10⁻⁴/m (maximum) and 0.17 × 10⁻⁴/m (minimum). We have also investigated the impact of the scattering extinction coefficient on solar radiation. Results of our investigation reveal that, for high b_sp, mean insolation is generally low, and the reverse is the case for low b_sp. It appears that there is no correlation between instantaneous (hourly) extinction coefficient and insolation for the period covered.     

Ribosomal genes of Histoplasma capsulatum var. duboisii and var. farciminosum

A total of 1704 basepairs of the 18S rDNA of Histoplasma capsulatum var. duboisii (HCD, strain CBS175.57) and H. capsulatum var. farciminosum (HCF, strain CBS478.64) were sequenced (EMBL accession no. Z75306 and no. Z75307). The 18S rDNA of HCD was 100% identical to a published sequence of H. capsulatum var. capsulatum (HCC). The 18S rDNA of HCF showed one transversional point mutation at the nucleotide position 114 (ref. Saccharomyces cerevisiae). Hybridization confirmed that, in the 18S rDNA of two out of five strains of HCF, guanine was substituted for cytosine at the nucleotide position 114. Furthermore, identical group 1C1 introns (403 bp) were found to be inserted after position 1165 in four out of five strains of HCF, including the two strains with point mutations in the 18S rDNA, and a slightly different group 1C1 intron (408 bp) was detected in one strain of HCC without this point mutation. Intraspecific sequence variability in the highly conserved 18S rDNA because of occurrence of introns and mutations as a possible source of error in molecular diagnostics is discussed. In addition, internal transcribed spacer regions between the 18S rDNA and the 5.8S rDNA (ITS1) of three strains of HCF, and one strain each of HCC and HCD showed significant sequence variability between varieties and strains of H. capsulatum.     

Performance of PVD Coated Carbide Inserts When Machining a Nimonic (C-263) Alloy at High Speed Conditions

Physicals Vapor Deposition (PVD) coated carbide inserts were used to machine a nickel-base, C-263, superalloy under severe cutting conditions. Test results show that the TiN/TiCN/TiN coated, inserts with positive, honed and chamfered edges (Tool A) outperformed similar tools with double positive edges and no edge protection (Tool B) in terms of tool life as well as lower flank wear rate when machining under roughing conditions. The double positive edges of Tool B inserts are more susceptible to chipping action due to reduced tool-chip and tool-workpiece contact lengths/areas and associated increase in applied stresses at the cutting edge during machining. Increase in cutting conditions and variation of the cutting edge geometry did not increase the surface roughness value due to the elastic recovery of the C-263 alloy. Prolonged machining causes appreciable increase in the feed force due to the rapid work hardening of the nimonic alloy as well as the formation of hard burrs during machining     

Behavior of Coated Carbide Tools in High Speed Machining of a Nickel Base Alloy

Multilayer TiN/TiCN/TiN and single-layer TiAIN PVD coated carbide tools were used to machine a nickel base, C-263, alloy at high-speed conditions in order to investigate their performance in terms of tool life, surface finish and component forces generated during machining. The test results show that the triple layer, TiN/TiCN/TiN, coated inserts gave longer tool life when machining at higher speed and depth of cut conditions while the single layer, TiA/N, coated inserts produced better surface finish. The feed forces recorded were generally higher than the cutting forces. This could perhaps be attributed to the adverse effect of burr formation and work hardening of the workpiece associated with prolonged machining. Analysis of the test results indicate that the difference in thermal properties and tribo-chemical behaviour of both the coating and substrate materials are the major factors influencing the tribo-contact at the tool-chip interface during machining. Wear mechanisms of the coating materials can also affect tool performance in terms of tool life, surface finish and component forces.     

Young's modulus of alkali halides from interionic potential energy functions

Journal of Materials Science Letters -