Retention Period Research Articles

Formulation and Evaluation of Topically Retained Hydrogels Loaded with Timolol Maleate Microspheres for Extended Release in Treating Glaucoma

Conventional aqueous eye drop formulations have a shorter retention period and wash out of the precorneal region more easily. In this study, biodegradable microsphere-loaded hydrogels were developed to extend the time of residence and improve the drug bioavailability. The prepared microspheres were fabricated using PLGA as the biodegradable polymer and PVA as the surfactant. Hydrogels were prepared using Carbopol 940 and Gellan gum as gelling agents. Methods: The microspheres were created through a technique known as double emulsion solvent evaporation method. Evaluation included for its percentage yield, entrapment efficiency, particle size and surface morphology of the prepared microspheres. Timolol Maleate microsphere loaded hydrogel underwent assessments for pH, spreadability, rheological behaviour, sterility, antimicrobial efficacy, in vitro release studies, drug release kinetics and ocular irritation. Results: FTIR analysis confirmed compatibility between the drug and polymer. SEM observations indicated spherical microspheres with sizes ranging from 1 to 12 µm, suitable for ocular application. All formulations exhibited pH values between 4.2 and 5.0, with gelation occurring at 35°C to 38°C. Formulation F3 demonstrated optimal viscosity (1486 – 1850 cps) and good spreadability. Sterility tests were successful, and F3 displayed a drug release of 82.6% after 24 hours. Antimicrobial studies exhibited inhibition zones, and ocular tests on rabbits revealed no irritation. Stability analysis indicated no significant changes in pH or clarity. Conclusion: Based on physiological, rheological, and in vitro evaluations F3 was identified as the most suitable formulation for extended Timolol Maleate release via hydrogel, holding promise for effective glaucoma treatment.

Optimizing the Flood Limit Water Level of Reservoirs in Sediment-Laden Rivers under Changing Water and Sediment Conditions: A Case Study of the Xiaolangdi Reservoir

Optimizing the flood limit water level (FLWL) of reservoirs in sediment-laden rivers under changing water and sediment conditions is an important research topic that could improve comprehensive utilization benefits. Because reservoir operation has multiple objectives in sediment-laden rivers, this study established a water–sediment mathematical model, a comprehensive benefit evaluation model, and an evaluation index system. Taking the Xiaolangdi Reservoir of the Yellow River as an example, the operation mode of the FLWL under changing water and sediment conditions was studied. Under the scenarios of incoming sediment amounts of 300–800 million tons, when using the operation mode of gradually raising the FLWL, the sediment retention period was 4–13 years longer; the lower average annual siltation of the downstream channel and minimum bank-full discharge of the downstream channel after 50 years was larger by 150–260 m3/s than the operation mode of raising the FLWL at one time. However, with enhanced benefits of sediment blocking and siltation reduction, other benefits such as water resources supply, hydropower generation, and ecological improvement are reduced. The average annual number of days that do not meet the downstream water resources supply requirements, irrigation, and ecological improvement was increased by 0.64–2.16 days, and 91–197 million kW·h reduced average annual hydropower generation. The critical amount of incoming sediment was 350 million for conversion between the two FLWL operation modes, and it will increase to 450 million tons if the incoming runoff of the Yellow River increases by 20%. After constructing the Guxian Reservoir in the middle of the Yellow River, the critical amount of incoming sediment will increase to 600 million tons. This study is of great significance for improving the utilization efficiency of water resources and promoting the socio-economic development of river basins.

Enhancing microbial fuel cell performance for sustainable treatment of palm oil mill wastewater using carbon cloth anode coated with activated carbon

Microbial fuel cells (MFCs) are a viable source of clean and renewable energy from wastewater and gaining attention on a global scale. Thus, this research work focuses on the energy production from high-strength palm oil mill wastewater using MFCs. A state-of-the-art technique for improving the performance of MFCs by covering a carbon fibre anode with various sized powdered activated carbon (PAC) particles was investigated. In addition, the MFCs were tested at various hydraulic retention times (HRT) to assess the performance displayed by modified MFCs. Results showed that a relatively smaller amount of PAC with a diameter of 13 μm coated at the anode during the cultivation stage at a shorter hydraulic retention time (4 days) would produce 504.1 ± 8.7 mW m−3 of power, 39.9 ± 2.9% of chemical oxygen demand removal efficiency, and 299 ± 63 mL of biogas. While, MFC running at a longer hydraulic retention time (12 days) was able to produce more power and had better effluent quality than those operating at a shorter hydraulic retention period.

A nap consolidates generalized perceptual learning

Previous research has demonstrated that a night's sleep can consolidate rote and generalized perceptual learning. Over a waking retention period following training, performance gains from learning significantly decline, but sleep can restore performance to levels found immediately after learning. Furthermore, when sleep precedes a waking retention period following training, performance is protected against loss. Other research demonstrating that rote learning can be consolidated by a night's sleep has shown that a relatively brief nap can consolidate rote learning. This suggests that short periods of sleep can produce consolidation, indicating that consolidation may not require successive sleep cycles over an entire night to emerge. However, previous research has demonstrated that there can be differences in sleep-dependent consolidation for rote and generalized learning. In this study, we investigated whether an opportunity for a 90-min midday nap was sufficient to consolidate generalized perceptual learning of synthetic speech. We recruited 75 participants from the University of Chicago community (mean age of 20.83) who completed a pretest, training, and posttest in the morning on perception of synthetic speech. Training and testing in this manner are known to result in substantial generalized learning of synthetic speech. Participants then returned in the afternoon and were either given an opportunity for a 90-min nap or remained awake for 90-min. Participants were then given another posttest later that evening, never hearing the same words twice during the experiment. Results demonstrated that participants who did not nap showed significant loss of learning at the evening posttest. In contrast, individuals who napped retained what they learned, and did not show loss of learning at the evening posttest. These results are consistent with the view that an opportunity for a 90-min midday nap can consolidate generalized learning, as only individuals with consolidated learning should be able to retain what they learned despite an intervening waking retention period. This is the first demonstration that generalized skill learning is subject to sleep-dependent consolidation in short durations of sleep and does not require a full night of sleep. This work has implications for understanding the basic neural mechanisms that operate to stabilize short-term learning experiences.

Optimization of Pilot scale Biogas Plant for mixed food wastes with cow dung by anaerobic digestion process

<p>The primary aim of this research is to identify the best anaerobic digestion process yield for generating biogas from mixed food waste in the combination of cow manure. For the biogas generation experiment, certain biodegradable domestic organic wastes gathered from restaurants, waste storage facilities, the fruit-and-vegetable market and manure from cows. Organic waste collection; 38g of mixed food waste, cow dung waste and its mixture collected from Yaaballo town. To match the digester's input size and to make digestion easier, all wastes were broken down into little (5 mm) pieces by using a mortar and pestle. Organic materials were kept in plastic bags till anaerobic digestion got started. Because high temperatures stimulated the growth of methanogenic bacteria in the digester, the findings from the research indicated that Mixed Food Waste and Cow Dung Waste produced the most biogas (44ml) at 45⁰C in a short retention period. The temperature, PH, and retention time all significantly (P0.05) affect the production of biogas, according to the ANOVA results. It is possible to combine organic materials with equal amounts of high and low C:N ratios to get the ideal C:N ratios for digester use. The pH stability and increased methanogenic activities achieved by changing the C:N ratio of organic waste to provide the greatest biogas generation in Mixed Food Waste and Cow Dung Waste. For the best yield, the combination of diverse organic waste and the effects of various parameters on biogas production should be thoroughly studied.</p>

Numerical optimization of hydrothermal liquefaction process for the production of bio-oil and bio-char from Citrus maxima peel waste and product characterization.

This research study aims to potential utilization of Citrus maxima peel waste and optimize the hydrothermal liquefaction process for the production of bio-oil (BO) and bio-char (BC). The effect of several HTL processing variables on BO yield (%) and BC yield (%), including temperature, retention period, and slurry concentration, has been examined using central composite design (CCD) (a three-level three-factor design). The optimized values of HTL process variables were found to be 240°C (temperature), 52min (retention time), and 7% (slurry concentration) and the corresponding responses were 5.794% (BO yield) and 29.450% (BC yield). The values obtained from the RSM-CCD model as the predicted values agreed with the experimental values (5.93% and 30.14%). Further the BO and BC obtained under optimized conditions and CPP were analyzed to identify the variations by 1H-NMR, GC-MS, FT-IR, and CHNO-S.

The Effect of Modeling Methods on Mirror Neuron Activity and a Motor Skill Acquisition and Retention.

Mirror neurons have been suggested as a potential neural mechanism of observational learning. This study aims to investigate the effect of self-modeling, skilled model, and learning model on mu rhythm suppression and golf putting acquisition and retention. The study was conducted on 45 male volunteer students (aged 19.4±0.37 years) in three experimental groups, self-modeling, skilled, and learning models with six sessions of physical and observational training in three periods of pre-test, acquisition, and retention. In the pre-test, after the initial familiarity with the skill, participants performed 10 golf putting actions while scores were recorded. Then, electrical brain waves in C3, C4, and Cz regions were recorded during the observation of 10 golf putting actions by their group-related models. The acquisition period consisted of golf putting training during six sessions, each consisting of six blocks of 10 trials. Before each training block, participants observed golf putting related to their group 10 times in the form of a video. Acquisition and delayed retention tests were also performed by recording scores of 10 golf putting actions, as well as recording electrical brain waves while observing the skill performed by the related model. Mixed analysis of variance (ANOVA) showed that the mu rhythm suppression in the pre-test was more in the self-modeling group compared to the skilled model and learning model groups, but this suppression was not significantly different in all three groups in the acquisition and retention tests. In putting task variables, all three groups that had no significant difference in the pre-test period made considerable progress in learning the desired skill from the pre-test to the acquisition test, and this progress was somewhat stable until the retention test. Also, both in the acquisition and retention periods, the self-modeling group showed better performance than the other two groups; however, no significant difference was observed between these groups. These results suggest that the model-observer similarity is a crucial factor in modeling interventions and can affect the rate of mu rhythm suppression.

A review on Activated Carbon Prepared from Agricultural Waste using Conventional and Microwave Activation

In the recent years the research on the activated carbon preparation from agro-waste and byproducts have been increased due to their potency for agro-waste elimination. This paper presents a literature review on the synthesis of activated carbon from agro-waste using microwave irradiation method for heating. The applicable approach is highlighted, as well as the effects of activation conditions including carbonization temperature, retention period, and impregnation ratio. The review reveals that the agricultural wastes heated using a chemical process and microwave energy can produce activated carbon with a surface area that is significantly higher than that using the conventional heating method.

Sleep consolidates stimulus-response learning.

Performing a motor response to a sensory stimulus creates a memory trace whose behavioral correlates are classically investigated in terms of repetition priming effects. Such stimulus-response learning entails two types of associations that are partly independent: (1) an association between the stimulus and the motor response and (2) an association between the stimulus and the classification task in which it is encountered. Here, we tested whether sleep supports long-lasting stimulus-response learning on a task requiring participants (1) for establishing stimulus-classification associations to classify presented objects along two different dimensions ("size" and "mechanical") and (2) as motor response (action) to respond with either the left or right index finger. Moreover, we examined whether strengthening of stimulus-classification associations is preferentially linked to nonrapid eye movement (non-REM) sleep and strengthening of stimulus-action associations to REM sleep. We tested 48 healthy volunteers in a between-subjects design comparing postlearning retention periods of nighttime sleep versus daytime wakefulness. At postretention testing, we found that sleep supports consolidation of both stimulus-action and stimulus-classification associations, as indicated by increased reaction times in "switch conditions"; that is, when, at test, the acutely instructed classification task and/or correct motor response for a given stimulus differed from that during original learning. Polysomnographic recordings revealed that both kinds of associations were correlated with non-REM spindle activity. Our results do not support the view of differential roles for non-REM and REM sleep in the consolidation of stimulus-classification and stimulus-action associations, respectively.

Effect of elevated temperature on rice husk ash based self-compacting alkali activated slag concrete mixes under different cooling regimes

Here an attempt has been made to develop self-compacting alkali activated slag concrete mix using Rice Husk Ash as Binder. Investigation on the mechanical properties and residual strength when subjected to temperature of 200,400,600,800°C retention period1hour. The Rice husk ash Self Compacting Alkali Activated Slag Concrete mixes was made with GGBS, Rice husk ash and Lime as the binder, with its content varying from 550 to 650 kg/m3of fresh concrete. The W/B ratio of mixes varied in 0.7-0.88 range. The alkaline solutions had Na2O percentages in the range 5-7 with constant activator modulus maintained at 1. Final mix considered had lower water content, higher percentage of RHA and higher compressive strength. Trails showed Processed Rice Husk Ash30%, lime20% and GGBS50% for binder content 600kg/m3 and 6% Na2O dosage showed greater compressive strength and lower water binder ratio compared to other trail mixes. Results showed the slump flow, L–Box, U-box and V-Funnel as greater than 650mm, 0.85, 20mm and 10s resp. Fire damage of RSAASC was measured by subjecting to elevated temperature between 200-800°C for a retention period of 1hour. Cooled to room using furnace cooling, air cooling and sudden cooling. Results indicated reduced compressive strength with increased temperature.

Interactive Privacy Management: Toward Enhancing Privacy Awareness and Control in the Internet of Things

The balance between protecting user privacy while providing cost-effective devices that are functional and usable is a key challenge in the burgeoning Internet of Things (IoT). In traditional desktop and mobile contexts, the primary user interface is a screen; however, in IoT devices, screens are rare or very small, invalidating many existing approaches to protecting user privacy. Privacy visualizations are a common approach for assisting users in understanding the privacy implications of web and mobile services. To gain a thorough understanding of IoT privacy, we examine existing web, mobile, and IoT visualization approaches. Following that, we define five major privacy factors in the IoT context: type, usage, storage, retention period, and access. We then describe notification methods used in various contexts as reported in the literature. We aim to highlight key approaches that developers and researchers can use for creating effective IoT privacy notices that improve user privacy management (awareness and control). Using a toolkit, a use case scenario, and two examples from the literature, we demonstrate how privacy visualization approaches can be supported in practice.

A new method for the analysis of access period experiments, illustrated with whitefly-borne cassava mosaic begomovirus.

Reports of low transmission efficiency, of a cassava mosaic begomovirus (CMB) in Bemisia tabaci whitefly, diminished the perceived importance of whitefly in CMB epidemics. Studies indicating synergies between B. tabaci and CMB prompt a reconsideration of this assessment. In this paper, we analysed the retention period and infectiousness of CMB-carrying B. tabaci as well as B. tabaci susceptibility to CMB. We assessed the role of low laboratory insect survival in historic reports of a 9d virus retention period. To do this, we introduced Bayesian analyses to an important class of experiment in plant pathology. We were unable to reject a null hypothesis of life-long CMB retention when we accounted for low insect survival. Our analysis confirmed low insect survival, with insects surviving on average for around three days of transfers from the original infected plant to subsequent test plants. Use of the new analysis to account for insect death may lead to re-calibration of retention periods for other important insect-borne plant pathogens. In addition, we showed that B. tabaci susceptibility to CMB is substantially higher than previously thought. We also introduced a technique for high resolution analysis of retention period, showing that B. tabaci infectiousness with CMB was increasing over the first five days of infection.

Short-term stability of anterior open bite treatment with clear aligners in adults

This study aimed to examine the stability of anterior open bite (AOB) treatment with clear aligners. This retrospective cohort study included 52 adult AOB patients (aged>18 years; 15 males, 37 females) who underwent nonextraction clear aligner treatment and were at least 1 year posttreatment. Eleven cephalometric measurements were evaluated at pretreatment, end of active treatment, and at least 1-year posttreatment. Overbite change, the primary outcome variable, and other cephalometric changes during treatment and retention were calculated, and repeated measures analysis of variance were performed. Stepwise multiple regression was used to make a prediction equation for open bite relapse. The mean retention period was 2.1 ± 1.1 years. The mean change in overbite during treatment was 3.3 ± 1.5 mm; 6% of patients presented relapse at least 1 year after treatment completion. The mean change of overbite (0.2 ± 0.5 mm) during the retention period was not statistically significant (P= 0.59). None of the 11 cephalometric measurements showed significant change during the retention period. The prediction model showed that only the coefficient for a tongue posture issue at the initial examination was statistically significant. AOB was successfully corrected in all 52 patients using only clear aligners with no additional adjunctive aids such as microimplants. When retained with maxillary and mandibular fixed retainers and maxillary and mandibular vacuum-formed retainers, there was no significant change in cephalometric measurements during the short-term retention period.

Effects of the EXECP Intervention on Motor Function, Muscle Strength and Joint Flexibility in Individuals with Cerebral Palsy.

Numerous exercise interventions to enhance motor function in cerebral palsy (CP) have been proposed, with varying degrees of effectiveness. Since motor function requires a combination of muscle strength, joint flexibility and motor coordination, we designed a supervised multicomponent exercise intervention (EXECP) for individuals with CP. Our aim was to evaluate the effects of the EXECP intervention and its retention after it ceased. The EXECP intervention combined strength training for the lower limbs and trunk muscles, passive stretching for the lower limb muscles and inclined treadmill gait training. Eighteen participants with CP (mean age: 14, 13 males) were tested twice before the three-month intervention and twice after the intervention, each test separated by three months. Seventeen typically developing age and sex-matched controls were tested twice. Motor function was assessed with the six minutes walking test (6MWT) and the gross motor function measure (GMFM) dimensions D and E. Passive joint flexibility was measured with goniometry. Isometric and concentric muscle strength were assessed at the knee, ankle and trunk joints. The EXECP intervention successfully increased 6MWT (p < 0.001), GMFM (p = 0.004) and muscle strength for knee and trunk muscles (p < 0.05), although no changes were observed for ankle joint muscles. Hip and knee joint flexibility also increased (p < 0.05). After the retention period, all tested variables except the 6MWT and knee joint flexibility regressed and were not different from the pre-tests. The improvements in strength, flexibility, and possibly motor coordination brought by the EXECP intervention were transferred to significant functional gains. The regression towards baseline after the intervention highlights that training must be a life-long decision for individuals with CP.

Assessing the benefits of real-time control to enhance rainwater harvesting at a building in Cape Town, South Africa

In the period 2015–2017, the City of Cape Town, South Africa, faced the possibility of taps running dry due to a prolonged drought. To mitigate the impacts of water scarcity, many households installed rainwater tanks to harvest water to use for non-potable purposes such as toilet flushing and washing. The installation of the rainwater tanks was mainly arbitrary, in response to perceived impact of water scarcity rather than a systematic needs assessment. This study was thus undertaken to determine the available opportunity to optimise the use of these rainwater tanks using real-time control (RTC) techniques. Many studies have demonstrated the potential of rainwater harvesting (RWH) systems to supplement potable water supply and minimize stormwater flows to downstream drainage networks. RTC technology can be used to enhance the performance of RWH systems in achieving these two objectives, by receiving a rainfall forecast and initiating pre-storm release in real time. In this study, RTC was applied on the RWH system at the New Engineering Building, University of Cape Town (UCT) to enhance water supply and increase rainwater retention period. The performance with RTC was compared with the conventional management of the RWH system. It was determined that RWH with RTC technology was generally superior in simultaneously achieving water supply and rainwater retention benefits compared to the conventional management approach. RTC provides an active operation which optimizes the performance of the system across varying conditions but requires an assiduous management process designed to meet set objectives. It was concluded that the active release mechanism employing RTC exhibited great potential; the system opens up the possibility of delivering a more robust and reliable system due to its ability to provide failure detection and centralised control. The system can readily be adapted to variation of local climatic conditions in the short and long term.

Massed Training is Logistically Superior to Distributed Training in Acquiring Basic Endovascular Skills

A "PROficiency based StePwise Endovascular Curricular Training" (PROSPECT) has proven its superiority over traditional training in a randomised controlled trial to acquire basic endovascular skills outside theatre, but real life adherence is low. This study aimed to compare the original distributed training format, where trainees learn at their own pace, with a massed training format offering the same content within a limited time span while exempt from clinical duties. Secondly, long term skills retention was evaluated. A multicentre, prospective study allocated participants to the distributed D-PROSPECT or to a massed, compact version (C-PROSPECT) based on logistics such as travel time, participant and instructor availability. A multiple choice question (MCQ) test (max. score 20) tested cognitive skills. Technical skills were assessed using a global rating scale (GRS) (max. score 55), examiner's checklist (max. score 85), and validated simulator metrics. Data were collected pre- and post-programme and at three, six, and 12 months after programme completion. Over four years and in two countries, D-PROSPECT was implemented in two centres and C-PROSPECT in three. A total of 22 participants completed D-PROSPECT with a 41% dropout rate, and 21 completed C-PROSPECT with 0% dropout rate. All participants showed significant improvement for all performance parameters after programme completion: MCQ test (median 14.5 vs. 18; p < .001), GRS (median 20 vs. 41; p < .001), examiner's checklist (median 49 vs. 78.5; p < .001), and simulation metrics (p < .001). Scores of C- or D-PROSPECT participants were not significantly different. No significant differences were seen between groups during the retention period. PROSPECT significantly improves the quality of simulated endovascular performances using a massed or distributed training format. A massed training format of PROSPECT may be preferred to decrease dropout during standardised training to obtain basic endovascular skills in existing surgical curricula.

Assessment of the outcomes and stability after mandibular incisor extraction in orthodontic patients: A systematic review and meta-analysis.

This study assessed the stability of the outcomes after mandibular incisor extraction (MIE) using intercanine width and peer assessment rating (PAR) scores in orthodontic patients. PubMed, Cochrane Library, Science Direct, Google Scholar, Ovid, and SciELO were systematically searched without restrictions until August 2022. A risk of bias assessment was performed using Newcastle-Ottawa Scale (NOS). The Grading of Recommendations, Assessment, Development, and Evaluation tool was used to assess the quality of evidence. Random effects meta-analysis was performed using RevMan software. Seven retrospective studies met the inclusion criteria and were included. Meta-analysis identified a statistically significant reduction in intercanine width with MIE after the retention period. The mean difference in post-retention changes concerning intercanine width (MD=0.14, 95% CI: -2.17-1.89; P<0.00001) was significantly higher in premolar extraction (PE) compared to incisor extraction and significantly less in non-extraction compared to incisor extraction (MD=0.72, 95% CI: -0.59-2.03; P<0.00001). Improvements in PAR scores from the start of treatment to the retention period indicated a high outcome standard (>70%) with MIE treatment, with no significant difference in the reduction percentage compared to premolar and non-extraction groups. With the existing retrospective studies of limited evidence, treatment outcomes with MIE were found to show good improvements in PAR scores. Some reduction in the intercanine width was evident after the retention period, which was observed even with the other two treatment modalities that were compared. Hence, with careful evaluation, MIE could be considered a valid treatment option.

Effect of vitamin D deficiency on postorthodontic relapse: An animal study.

This study aims to evaluate the effect of vitamin D deficiency (VDD) on orthodontic tooth movement (OTM), retention, and relapse and to assess the effect of systemic administration of vitamin D (VD) in a rat model. A total of 32 male Wistar rats were divided into two groups, a control group of 11 rats and an experimental group of 21 rats with VDD, after enhancement using a custom diet. Of the VDD group, 11 rats were supplemented with systemic vitamin D3 and categorized as vitamin (VD supplement [VDS]) groups. The VDS group received 40,000 IU/kg via intramuscular injection on Days 1 and 15 of the orthodontic treatment period. A modified orthodontic appliance was fitted to apply 0.5 N of force to move the maxillary right first molars mesially for 14 days, followed by retention and relapse periods for 7 days. Space created during OTM was measured and reassessed after the retention and relapse periods. The relapse ratio was estimated, and histomorphometric analysis was performed to assess the number of osteoblasts, osteoclast bone cells, and bone area. A significant increase in the relapse ratio and a reduction in osteoblast cells and bone area were observed in the VDD group. By contrast, the amount of tooth movement was significantly higher together with osteoblast cells and bone marrow in VDS with a significant reduction in relapse ratio. VDD was associated with a significant reduction in osteoblast cell count and total bone area in addition to a significant increase in relapse ratio. Routine screening of VD may be beneficial before commencing orthodontic treatment.

Hydrodynamic modeling of ephemeral flow in the Iishana channel systems of the Cuvelai Basin—Northern Namibia

AbstractThe transboundary region of the Iishana system in the western Cuvelai Basin, between southern Angola and northern Namibia, is frequently affected by floods at irregular intervals. As a result, the predominantly rural, subsistence farming population has experienced crop failures, human, and economic losses. To date, very little is known about the generation of floods, flood concentration, and stormwater drainage dynamics in this region. In this study, 2D‐hydrodynamic modeling was applied to reconstruct one of the latest major flood events during the rainy season from November 2008 to March 2009 in order to study the runoff behavior and interconnectivity of the Iishana system. The model focused on the eastern part of the Iishana system, which was most affected by floods and flood damage due to the high population density in and around Oshakati, the regional capital. Two main streams were identified noteworthy because they merge and subsequently affect Oshakati. Regarding the simulated flood event water depths vary from 0.1 m to 14 m, with an average of 0.2 m, while water depths above 5 m were attributed to borrow pits. The inundation area ranged up to 1860 km2 and the amount of water left after the rainy season on March 25th, 2009, was determined between 0.116 and 0.547 km3, depending on the amount of evapotranspiration considered in the model. Thus, in the Angolan part of the Iishana system, significantly larger quantities of water are available for longer periods of time during the subsequent dry season, whereas the system in Namibia stores less water, resulting in a shorter water retention period.

LIQUID CHROMATOGRAPHY DEPENDENT STABILITY INDICATING METHODOLOGY: DEVELOPMENT AND AUTHENTICATION FOR FORMULATIONS OF CAPSULE TYPE CONTAINING TEGAFUR, GIMERACIL, AND OTERACIL

Objective: This investigation entitles the development and authentication of a rapid, selective and explicit RP-HPLC technique to assay tegafur (TGR), gimeracil (GMR), and oteracil (OTR) simultaneously in bulk and formulations of capsule type. Methods: The separation, detection and assessment of TGR, GMR and OTR were achieved using a C18 Agilent Zorbax (25 cm; 4.6 mm; 5 µm particle dimension) reverse phase column. The acetonitrile (40% by volume) and 0.1% triethylamine in distilled water (pH 2.5, 60% by volume) was utilized as mobile phase. The validation of the method and degradation study was performed as per the strategy given by ICH. Results: The retention periods in Agilent Zorbax column for OTR, TGR, and GMR were 2.458 min, 7.236 min and 8.629 min, respectively. Linearity was seen in the concentration series of 5.0-30.0 µg/ml (TGR), 1.45-8.70 µg/ml (GMR), and 3.95-23.70 µg/ml (OTR). The regression coefficient was greater than 0.999. The LOQ values were 0.606 µg/ml (TGR), 0.175 µg/ml (GMR), and 0.478 µg/ml (OTR). The percent comparative standard deviation (exactness) values were bestowed to be 0.243%-0.676%, 0.293%-1.894% and 0.269%-0.615% for TGR, GMR and OTR, respectively. The percent recoveries (accuracy) were in the range of 100.044%-100.493 for TGR, 99.730%-100.335% for GMR and 100.064%-100.543% for OTR. Conclusion: The research results of the degradation investigation proved the technique's specificity as well as stability indicating feature. The process could be used for routine evaluation of OTR, TGR, and GMR in formulations of capsule type.