Sunscreens - Which and what for?

It is well established that sun exposure is the main cause for the development of skin cancer. Chronic continuous UV radiation is believed to induce malignant melanoma, whereas intermittent high-dose UV exposure contributes to the occurrence of actinic keratosis as precursor lesions of squamous cell carcinoma as well as basal cell carcinoma. Not only photocarcinogenesis but also the mechanisms of photoaging have recently become apparent. In this respect the use of sunscreens seemed to prove to be more and more important and popular within the last decades. However, there is still inconsistency about the usefulness of sunscreens. Several studies show that inadequate use and incomplete UV spectrum efficacy may compromise protection more than previously expected. The sunscreen market is crowded by numerous products. Inorganic sunscreens such as zinc oxide and titanium oxide have a wide spectral range of activity compared to most of the organic sunscreen products. It is not uncommon for organic sunscreens to cause photocontact allergy, but their cosmetic acceptability is still superior to the one given by inorganic sunscreens. Recently, modern galenic approaches such as micronization and encapsulation allow the development of high-quality inorganic sunscreens. The potential systemic toxicity of organic sunscreens has lately primarily been discussed controversially in public, and several studies show contradictory results. Although a matter of debate, at present the sun protection factor (SPF) is the most reliable information for the consumer as a measure of sunscreen filter efficacy. In this context additional tests have been introduced for the evaluation of not only the protective effect against erythema but also protection against UV-induced immunological and mutational effects. Recently, combinations of UV filters with agents active in DNA repair have been introduced in order to improve photoprotection. This article reviews the efficacy of sunscreens in the prevention of epithelial and nonepithelial skin cancer, the effect on immunosuppression and the value of the SPF as well as new developments on the sunscreen market. Copyright (C) 2005 S. Karger AG, Basel

Identification of the Biotransformation Products of 2-Ethylhexyl 4-(N,N-Dimethylamino)benzoate

Nowadays, 2-ethylhexyl 4-(N,N-dimethylamino)benzoate (EDP) is one of the most widely used UV filters in sunscreen cosmetics and other cosmetic products. However, undesirable processes such as percutaneous absorption and biological activity have been attributed to this compound. The in vitro metabolism of EDP was elucidated in the present work. First of all, the phase I biotransformation was studied in rat liver microsomes and two metabolites, N,N-dimethyl-p-aminobenzoic acid (DMP) and N-monomethyl-p-aminobenzoic acid (MMP), were identified by GC-MS analysis. Secondly, the phase II metabolism was investigated by means of LC-MS. The investigated reactions were acetylation and glucuronidation working with rat liver cytosol and with both human and rat liver microsomes, respectively. Analogue studies with p-aminobenzoic acid (PABA) were carried out in order to compare the well established metabolic pathway of PABA with the unknown biotransformation of EDP. In addition, a method for the determination of EDP and its two phase I metabolites in human urine was developed. The methodology requires a solid-phase extraction prior to LC-MS analysis. The method is based on standard addition quantification and has been fully validated. The repeatability of the method, expressed as relative standard deviation, was in the range 3.4–7.4% and the limit of detection for all quantified analytes was in the low ng mL−1 range

EFFECT OF TOPOGRAPHIC AND GEOLOGIC HETEROGENEITIES ON THE DISTRIBUTION PATTERN OF AQUIFERS IN AKWA IBOM STATE, SOUTHEASTERN NIGERIA

Geologic heterogeneities and topographic variations in relation to aquifer distribution ad occurrence in Akwa Ibom State have been assessed based on geologic and geophysical studies sixty-six sounding points together with electric log responses of representative wells together with surface geologic data have been integrated and used in deciphering subsurface variations in hydrologic unit in the state. The results show that three aquiferous units, made up of medium to coarse grained whitish sands exist within a depth range of 72 to 98 meters and having resistivities less than 1500 ohm metres. These aquifers are clearly defined in those locations close to the coast and in the hinterlands whereas towards the northern parts of the state they appear to pinch-out or dip downward to much greater depths. Measurements of elevation across the study area show a drastic decrease in altitude tending toward the mean sea level within the hinterland and coastal regions, whereas towards the northern part, relatively higher elevations-exist. The increase in altitude in addition to the occurrence of thick columns of compacted shales greatly account for the scarcity of aquiferous zones in this northern part of the study area contrary to the localities within and surrounding the coastal and central regions. KEY WORDS: Heterogeneities, aquifer, topography, pinch-out, hydrologic. Global Jnl Geological Sciences. Vol.2(1) 2004: 125-13

Diplog analysis of paleocurrent and depositional energy of Miocene reservoir sands in the northwestern Niger Delta

Dipmeter log is an invaluable tool in the description of paleocurrent and depositional energy associated with subsurface sediments due to its high depth resolution and uniqueness as a method for studies of this kind. Interpretation of dip patterns and variations in dip amounts, in conjunction with composite log and biostratigraphic data, shows that the Lower to Middle Miocene sand reservoirs identified in two onshore wells in the Niger Delta were deposited under high to low energy conditions. The paleocurrent directions are mainly to the southwest, northwest, and southeast. Transporting water currents, waves, tides, and longshore currents dictated both paleocurrent directions and depositional energy. The interaction of these nearshore influences and the resulting pattern of sedimentation of the reservoir sands reinforce the conclusions drawn from studies conducted on Quaternary sediments along the Nigerian southwest coast and on Cretaceous sediments in the adjoining Anambra Basin. The levels of depositional energy deduced are indicative of the bathymetry of the reservoirs and their petrophysical properties. High-energy deposits occur in shallower water depths than the low energy deposits and are likely to be better sorted and more permeable. High variability in energy levels in some sand zones have been shown to correlate with depth intervals having repeated sequences of very thin reservoir sands often separated by minor shale beds. KEY WORDS: Dips, paleocurrent, energy, deposition, reservoir Global Jnl of Pure and Applied Sciences Vol.10(4) 2004: 635-64

Aeromagnetic modelling in evaluating the hydrocarbon potential of the basement of the Calabar Flank, southeastern Nigeria

No Abstract

Basinal Structure Of Yola Arm Of The Upper Benue Trough Nigeria; Evidence From Aeromagnetic Data

Aeromagnetic data interpretation of the Yola arm of the Upper Benue Trough has previously been carried out. However, no detail modeling of the Crustal Structures has been undertaken. Two composite reduced Aeromagnetic maps on a scale of 1:250,000 were digitized and processed using computer techniques. Analytical Signal, Power Spectrum and Upward Continuation methods were used prior to modeling of the subsurface structures. Forward and inverse modelings were done to determine the subsurface basin configuration. The result shows two sub-basins; the Lau and Yola sub-basins. The variations in sediment thickness within the Lau sub-basin is in the range of 2.0 – 4.5 km and in the Yola sub-basin 2.0 – 3.0 km respectively. The basin configurations from the modeled profiles depict that of horst and graben features resulting to variation in sediment thickness evident in Lau (Barwa to Yanga) subsector and Yola (Muleng) axis. The upward continuation revealed lineament trends in the NE-SW Yola (Muleng) axis and NW-SE Lau (Barwa to Yanga) subsector. Keywords: Upper Benue Trough, Basin configuration upward continuation, Analytical signal, power spectrum. Global Journal of Geological Sciences Vol. 6 (2) 2008: pp. 175-18