Classification of phase singularities for complex scalar waves

Motivated by the importance and universal character of phase singularities which are clarified recently, we study the local structure of equi-phase loci near the dislocation locus of complex valued planar and spatial waves, from the viewpoint of singularity theory of differentiable mappings, initiated by H. Whitney and R. Thom. The classification of phase-singularities are reduced to the classification of planar curves by radial transformations due to the theory of A. du Plessis, T. Gaffney, and L. Wilson. Then fold singularities are classified into hyperbolic and elliptic singularities. We show that the elliptic singularities are never realized by any Helmholtz waves, while the hyperbolic singularities are realized in fact. Moreover, the classification and realizability of Whitney's cusp, as well as its bifurcation problem are considered in order to explain the three points bifurcation of phase singularities. In this paper, we treat the dislocation of linear waves mainly, developing the basic and universal method, the method of jets and transversality, which is applicable also to non-linear waves.Comment: 17 pages, 5 figure

Singularities of improper affine spheres and surfaces of constant Gaussian curvature

We study the equation for improper (parabolic) affine spheres from the view point of contact geometry and provide the generic classification of singularities appearing in geometric solutions to the equation as well as their duals. We also show the results for surfaces of constant Gaussian curvatureand for developable surfaces. In particular we confirm that generic singularities appearing in such a surface are just cuspidal edges and swallowtails.Comment: 20 pages, 1 figure

Synthesis and characterization of reactive dye-cassava mesocarp cation exchange resins

The synthesis of triazine based reactive dyes was carried out. The resultant dyes were characterized by thin layers chromatography, molecular weight, infrared and ultra- violet spectroscopy, and used in dyeing cassava mesocarp to produce dye modified cellulosic substrates. The dyed substrates weretested for dye fixation, fastness (acid, alkali, wash) and solvent stability. Results obtained show that the dyes have excellent dyeing properties attributable to chemical bond formation between the dye molecules and the hydroxyl groups of the substrate (cassava mesocarp). The satisfactory fastness properties and good dye fixation on the substrate are of importance in the preparation of stable and efficient dye modified cellulosic ion exchange resins

Evaluation of phosphorus fertilizer rates for maize and sources for cowpea on different soil types in southwestern Nigeria

Flexible phosphorus (P) fertilizer rate recommendation could be based on variations in soil characteristics that affect yield responses. Experiments were conducted in the Department of Agronomy, LAUTECH, on the effects of P rates on maize and P sources on cowpea in four soil types. On average, soil types and P rates influenced maize height and grain yield. Iwo and Egbeda soils supported taller plants than Itagunmodi soil. Phosphorus fertilization enhanced height and grain yield compared with no P. To optimize maize grain yield for Itagunmodi and Egbeda soils, application of 15 kg P2O5 ha-1 was sufficient while for Majeroku and Iwo, it was 30 and 75 kg P2O5 ha-1, respectively. Cowpea grain yield and P uptake were significantly affected by soil types and P sources. Iwo and Egbeda soils supported higher grain weights and P uptake than Itagunmodi and Majeroku soils. Triple super phosphate (TSP) and no P supported higher grain weights and P uptake than rock phosphate (RP) and single super phosphate (SSP)

Prescribing practices in two health care facilities in Warri, Southern Nigeria: A comparative study

Purpose: Inappropriate prescribing has been identified in many health facilities in developing countries. The purpose of this study was to evaluate the prescribing practices in two health care facilities in Warri located in south-south geopolitical region of Nigeria and identify factors influencing the practices. Method: WHO Prescribing Indicators were applied to evaluate 2000 prescription records, retrospectively, from a private and a public hospital in Warri. Factors influencing the prescribing practices in the facilities were identified through informal interviews of 10 prescribers in the facilities. Using a self-administered questionnaire administered to 40 prescribers in the facilities, we also evaluated the order of importance of the factors affecting drug prescribing. Results: Average number of drugs per encounter in the health facilities is 3.4 (3.9 in the public hospital and 2.8 in the private hospital). Generic prescribing was generally low (54% in the public hospital and 16% in the private hospital) while the percentage of encounters with antibiotics prescribed was high (75% in the public hospital and 55% in the private hospital). Antimalarials, antihypertensives, antidiarrhoeals and analgesics accounted for 47.4%, 7.5%, 1.0% and 18.2%, respectively. The overuse of drugs and generic prescribing were significantly lower in the private hospital than in the public hospital. Major factors influencing prescribing practices included drug availability, clinician\'s level of training, cost of drugs, feedback from patients and socio-economic status of patients. Conclusion: Polypharmacy, overuse of antibiotics and low rate generic prescribing still occur in the health facilities studied. Drug availability, clinician\'s level of training, cost of drugs, feedback from patients and socio-economic status of patients are major factors influencing prescribing in the facilities. Keywords: Drug prescribing, Indicators, Practices, Southern Nigeria Tropical Journal of Pharmaceutical Research 2003; 2(1): 175-18

Studies on dyed coconut (Cocos nucifera) pollens for removal of Cu (II) and Zn (II) from aqeoues solution

The ability of undyed and dyed coconut pollens to remove Cu(II) and Zn(II) from single ion solutions was been studied. The experiments were carried out using coconut pollens (1.0 g) undyed coconut pollens, UDCP, and dyed coconut pollens, DCPI, DCPII and DCPIII of different particle sizes: 0.40, 0.63 and 0.80 mm, respectively. The amount of Cu(II) adsorbed on UDCP, DCPI, DCPII and DCPIII were 69.20, 97.90, 94.70 and 93.10%, respectively, while that of zinc adsorbed on these adsorbents were 87.15,98.30, 92.55 and 90.05%, respectively. These results show that dyed coconut pollens is effective in removing Cu(II) and Zn(II) from aqueous solutions

Effect of normal and pre-eclamptic pregnancies on plasma cholinesterase in Nigerian women

Background: Pre-eclampsia can be devastating and life-threatening for both mother and baby, particularly in developing countries. It is a major cause of maternal and foetal mortality and morbidity. Early diagnosis and management are very important to the reduction of mortality and morbidity. A sensitive diagnostic and prognostic marker will therefore be of great value. There is paucity of data on the effect of pre-eclamptic pregnancy on plasma cholinesterase activity especially in Nigerians. Objective: Our aim was to determine the changes in plasma cholinesterase concentration in normal and pre-eclamptic pregnancies in Nigerians. Setting: Antenatal Clinic and Prenatal Diagnostic and Therapy Centre in a Tertiary University Teaching Hospital in Lagos. Patients and Methods: Plasma cholinesterase concentration was determined using a colorimetric method in 30 healthy non-pregnant, 30 healthy pregnant, 30 and 27 pregnant women with mild and severe pre-eclampsia, respectively, between 28 and 41 weeks of gestation. Cholinesterase activity was re-assessed 6 weeks postpartum. Results: The mean plasma cholinesterase levels in healthy non-pregnant women, women with normal pregnancy, pregnant women with mild pre-eclampsia and those with severe pre-eclampsia were 3594±1042, 2135±422, 1781±330 and 1630±326 (m/L), respectively. Six weeks postpartum, the mean cholinesterase levels in the normal pregnant, mild eclamptic and severe eclamptic groups were 3212±346, 3157±750 and 2864±700 (/L), respectively. Conclusions: Our study suggests that normal pregnancy, mild and severe pre-eclampsia cause a significant (p< 0.01) reduction in plasma cholinesterase activity compared to non-pregnant state, with the greatest decrease in severe pre-eclamptic pregnancy. This decline does not return to normal non-pregnant state in subjects with severe pre-clampsia within six weeks postpartum. The place of plasma cholinesterase concentration as a diagnostic and prognostic marker in pre-eclamptic and eclamptic pregnancies should be further explored. Keywords: Cholinesterase, Eclampsia, Pre-eclampsia, Pregnancy, Succinylcholine

High performance liquid chromatographic determination of proguanil after derivatisation with sodium benzoxazole-2-sulphonate

A simple, fast and reproducible method for the determination of proguanil using high performance liquid chromatographic with UV/Fluorescence detection is described. Proguanil was derivatised to its corresponding derivative [(N1-(4-chlorophenyl)-N5-(1 -methyl ethyl) imidocarbonimideamide-Nbenzoxazole]. The derivatisation reaction was conducted in methanol at 60&#176;C using sodium benzoxazole-2-sulphonate under alkaline conditions. The resulting derivative was extracted with chloroform after which the extract was observed under UV lamp at 254 nm before TLC and HPLC analysis. Similarly, the derivatisation process was adapted for derivatisation of proguanil in urine sample. The reaction proceeded smoothly and rapidly. The extraction process was not cumbersome and eliminated the need for costly extraction and evaporation equipments. The resulting derivative fluorensced intensely under UV lamp. Direct HPLC analysis of the reaction mixture was found possible without interferences from excess reagent and endogeneous compounds like ammonium salts. The derivative eluted in less than seven minutes thus making the method suitable for routine use. The calibration plot was linear over the concentration range. A correlation regression of the order of 0.94 was obtained from the calibration curve which indicated a strong relationship between the instrument response and the concentration of proguanil. The discussion also summarizes the derivatisation chemistry that have not being fully explored to date but may find utility in future development of highly sensitive analytical methods for biquanide drugs

Equilibrium and kinetics studies of metal ion adsorption on dyed coconut pollens

Batch equilibration studies were conducted to determine the nature of adsorption of Zn (II) and Cu (II) onto dyed coconut pollens. The nature of adsorption of metal ions was explained using the Langmuirequation. The calculated values of equilibrium parameter indicated favourable adsorption by the adsorbents. Also the calculated values of fractional attainment of equilibrium , the intraparticle diffusion rate constant, Ka show that adsorption of metal ions is particle diffusion controlled. The adsorbent produced from coconut fibre can be used to remove heavy metals from aqueous solution with high efficiency