Asian Journal of Physical and Chemical Sciences

The aim of this study is to determine the occupational hazards due to exposure to gamma radiations from oil and gas facilities. In-situ measurement of radiation exposure rate of some Oil Field Facilities in Rivers State, Nigeria  carried out using Digilert 200 and Radalert 100 nuclear radiation monitor and a geographical positioning system (Garmin GPSMAP 76S). The average exposure rates of the facilities range from 0.010±0.002 to 0.015±0.001, for indoor and 0.014±0.003 to 0.027±0.003  for outdoor. The mean absorbed dose rates for indoor varied from 92.1 to 121.1 nGyh^-1 while the mean outdoor absorbed dose varied from 120.4 to 234.2 nGyh^-1. The estimated indoor annual effective dose varied from 0.14 to 0.19 mSvy^-1 while the outdoor annual effective dose varied from 0.23 to 0.36 m Svy^-1.The estimated indoor excess lifetime cancer risk (ELCR) range from 0.56× to 0.65x10^-3 and outdoor ranged from 0.65×5 to 1.26×. The respective mean values of absorbed dose, AEDE and ELCR for indoor and outdoor measurements at the different locations exceeded the world permissible values of 60, 70 and 0.29× respectively. The result of this work indicated that used oilfield pipe market recorded the highest exposure rate. This could be due to radiations from scales on the pipes and may pose health challenged for long term exposure.

The gross alpha and beta activity concentration in drinkable water and soil/sediment from oil spilled communities of Delta state have been carried out using calibrated MPC 2000 Protean ORTEC desktop gross alpha/beta counter. A total of 22 water samples (11 River water and 11 well water) and 22 soil/sediment (11 soil and 11 sediment) were collected in 2-litre plastic containers with about 1% air space left for thermal expansion and black polyethene bags respectively. All the samples were prepared following international standard organization (ISO) procedure. The result showed that gross alpha activity in River water ranged from 0.013±0.005 to 0.0783±0.015 Bql^-1 while the gross beta activity concentration in River water ranged from 0.0073±0.015 to 0.0928 ±0.024 Bql^-1. The gross alpha and beta activity in ground (well) water ranged from 0.018±0.006 to 0.0817±0.014 Bql^-1 and 0.0126 ±0.013 to 0.173±0.063 Bql^-1 respectively. The mean gross alpha and beta activity in soil and sediment are 12.0±1.0 and 23.27±3.0 Bq/kg and 23.0±4.0 and 21.73± 15.0 Bq/kg respectively. The total annual effective dose estimated from both alpha and beta emitting radionuclides in water resources sampled, ranged between 0.007 to 0.063 mSvy^-1 in river water and 0.021 to 0.102 mSvy^-1 for well water. The annual gonadal dose resulting from gross alpha and beta activity in surface and ground water ranges from 0.019 to 0.238 mSvy^-1 and 0.037 to 0.406 mSvy^-1 respectively. The highest gonad dose of 0.238 mSvy^-1 and 0.439 mSvy^-1 was obtained in surface water (OTU₁) and ground water (OTU₂) respectively. The estimated excess lifetime cancer risks range from 0.024 x 10^-3 to 0.220 x 10^-3 and 0.039 x 10^-3 to 0.358 x 10^-3 for river and well water respectively. The result showed a significant relationship in both surface and ground water with regression values of 0.66 and 0.84 respectively. This implies that the same radionuclide is responsible for both alpha and beta activities in the water studied. The result of this study show that all the water resources sampled pose no immediate health risk to the populace though, there is little radioactive contamination of the sampled water arising from oil spillages and may be effluent discharge into the surface water. Following no threshold model, the water sampled need to be treated to remove the radionuclide in it through ion exchange technology or reverse osmosis technology before consuming to avoid long term internal exposure.

Background: There has been recent shift from the core issue of Michaelian kinetics to issues regarding various kinds of quasi-steady-state assumptions. Derivable equations with which to determine reverse rate constant for the dissociation of enzyme-substrate complex (ES) is given less attention.

Objectives: The objectives of this research are: 1) to derive other equations from differential equations whose evaluation leads to MM equation and 2) quantify based on derived equations the kinetic parameters given less attention and duration of catalytic events.

Methods: A major theoretical research and experimentation using Bernfeld method.

Results and Discussion: The durations for ES dissociation (ESD) into free substrate, S and enzyme, E were much shorter than the duration of ESD into E and product, P in 3 minutes duration of assay with low [S]; it was the shortest and longest in 3 and 5 minutes durations respectively with high [S]. The durations of ESD into E and P was shortest in 3 minutes duration of assay with high [S]. The values of reverse rate constant, k_-1 for ESD into S and E in 3 minutes duration of assay with high [S] was » the rate constant, k₂ for product formation and they are much higher than in other duration of assay.

Conclusion: The equations for the determination of the durations of various events, in a given catalytic cycle were derived. The various time regimes for each event and the rate constant for the dissociation of the ES can be graphically and calculationally determined as the case may be. Substrate concentration regime and duration of assay affects rate constants.

Objective: To investigate the Phytochemical screening, antioxidant and antimicrobial activities of the essential oil and ethanol extract of Psidium guajava.

Methods: The leaf of Psidium guajavabelongs to the myrtle family (Myrtacease) which is used as herbal remedies for the cure of many ailments by natives in northern part of Nigeria, was collected in June, 2018 from the Professor’s Quarters of Modibbo Adama University of Technology (MAUTECH) Yola. The leaf was air dried, pulverized and extracted by simple overnight maceration technique and then analyzed. Fresh leaf of the aforementioned was extracted using modified steam distillation. The phytochemical screening of the ethanol extract was carried out using standard method.

Results: The result revealed the present of Tannin, Flavanoid, Alkaloid, Volatile oil, Triterpene, Saponin, Glycoside while phenolic compound was absent in the ethanol extract of Psidium guajava. The result of the antioxidant activity of the essential oil was screened using DPPH method and the IC₂₅ values of ascorbic acid (standard drug)  was 57.92 µl/m and Psidium guajava of the essential oil  was 46.55 µl/ml  respectively. Antibacterial activity was carried out using dics diffusion method and the results showed reasonable zone of inhibition against tasted organisms, with Staphylococcus epidemidis being the most inhibited (23 mm) and Proteus vulgari being the least inhibited (2 mm) with the ethanol extract of Psidium guajava. In contrast, Staphylococcus aureus was the most inhibited (13 mm) and Salmonella typhi showed the least inhibition (9mm) in the essential oil of Psidium guajava.

Conclusion: The result, thus support the use of the plants traditionally to treat chronic diarrhea, fever, diabetes, malaria and suggest its usage in the formulation of new antioxidant and antibacterial drugs.

Background: The equation of the difference between reverse and forward Gibbs free energy of activation (ΔΔG_ES^#) reflects Michaelis-Menten constant (K_M) in both directions; this may not be applicable to all enzymes even if the reverse reaction is speculatively Michaelian. Arrhenius activation energy, E_a and (E_a - ΔG_ES^#)/RT) are considered = ΔG_ES^# and K_M respectively. The equations are considered unlikely.

Objectives: The objectives of this research are: 1) To derive what is considered as an appropriate equation for the determination of the difference in ΔG_ES^# between the reverse and forward directions, 2) calculate the difference between the reverse and total forward ΔG_ES^#, and 3) show reasons why E_a ≠ ΔG_ES^#  in all cases.

Methods: A major theoretical research and experimentation using Bernfeld method.

Results and Discussion: A dimensionless equilibrium constant K_ES is given. Expectedly, the rate constants were higher at higher temperatures and the free energy of activation with salt was < the Arrhenius activation energy, E_a; ΔΔG_ES^#ranges between 67 - 68 kJ/mol.

Conclusion: The equations for the calculation of the difference in free energy of activation (ΔΔG_ES^#) between the forward and reverse directions and a dimensionless equilibrium constant for the formation of enzyme-substrate (ES) were derivable. The large positive value of the ΔΔG_ES^# shows that the forward reaction is not substantially spontaneous; this is due perhaps, to the nature of substrate. The equality of Arrhenius activation energy (E_a) and ΔG_ES^# may not be ruled out completely but it must not always be the case; the presence of additive like salt can increase the magnitude of E_a well above the values of the ΔG_ES^#. A dimensionless equilibrium constant for the net yield of ES seems to be a better alternative than K_M. The E_a unlike ΔG_ES^#  requires at least two different temperatures for its calculation.