Concentration Time Research Articles

Modeling run-off flow hydrographs using remote sensing data: an application to the Bashar basin, Iran

Abstract Precipitation is hard to access in countries like Iran, due to inadequate number of rain gauge stations. Remote sensing provides an alternative source of rainfall estimation. In this study, the effectiveness of the HEC-HMS model was evaluated using GPM (Global Precipitation Measurement Mission) satellite and rain gauge station data. The model was calibrated and validated using 5 flood events' data of a hydrometric station at the outlet of Bashar basin. Important flood parameters including peak discharge (QP), flood volume (V) and time of concentration (TC) were used to evaluate and compare the application of satellite and ground station data in the model, using various statistical indices. The accuracy of QP and V estimations using rain gauge data was higher than those obtained by satellite data. However, the difference between mean relative error (MRE) in QP estimation was about 1% (9.9% and 10.6% for rain gauge and satellite data, respectively). Conversely, higher accuracies were met for TC estimation using satellite (with MRE 9.1% and 10.2% for GPM and rain gauge data, respectively). Such results imply the sole utilization of satellite precipitation data is reliable for modeling hydrological key parameters, which can be helpful in areas with limited ground station coverage.

Alternative streamflow-based approach to estimate catchment response time in medium to large catchments: case study in Primary Drainage Region X, South Africa

Event-based estimates of the design flood in ungauged catchments are normally based on a single catchment response time parameter expressed as either the time of concentration (TC), lag time (TL) and/or time to peak (TP). In small, gauged catchments, a simplified convolution process between a single observed hyetograph and hydrograph is generally used to estimate these time parameters. In medium to large heterogeneous, gauged catchments, such a simplification is neither practical nor applicable, given that the variable antecedent soil moisture status resulting from previous rainfall events and spatially non-uniform rainfall hyetographs can result in multi-peaked hydrographs. In ungauged catchments, time parameters are estimated using either empirical or hydraulic methods. In South Africa (SA), unfortunately, the majority of the empirical methods recommended for general use were developed and verified in catchments ≤ 0.45 km² without using any local data. This paper presents the further development and verification of the streamflow-based approach developed by Gericke (2016) to estimate observed TP values and to derive a regional empirical TP equation in Primary Drainage Region X, SA. A semi-automated hydrograph analysis tool was developed to extract and analyse complete hydrographs for time parameter estimation using primary streamflow data from 51 flow-gauging sites. The observed TP values were estimated using three methods: (i) duration of total net rise of a multi-peaked hydrograph, (ii) triangular-shaped direct runoff hydrograph approximations, and (iii) linear catchment response functions. The combined use of these methods incorporated the high variability of event-based time parameters, and Method (iii), in conjunction with an ensemble-event approach sampled from the time parameter distributions, should replace the event-based approaches to enable the improved calibration of empirical time parameter equations. The conceptual approach used to derive the regional empirical TP equation should also be adopted when regional equations need to be derived at a national scale in SA.

Characteristics and Estimation of the Time of Concentration for Small Forested Catchments in Steep Mountainous Terrain

Accurate modeling of flood flow hydrographs for small forested catchments in steep mountainous terrain is challenging because of large errors in the estimation of response time using existing empirical equations. The time of concentration (TC) for a catchment is a widely used time parameter for estimating peak discharges in hydrological designs. In this study, we developed an estimated TC using readily available mountain catchment variables, a small catchment, steep slope, and narrow valley, using empirical equations. For our approach, we used directly measured data from 39 forested catchments (area: 0.02–9.69 km2) during 3648 observed rainfall events over a 10-year observation period. Based on the uncertainties inherent in the empirical equation, the estimated TC values were compared and analyzed through multiple regression and two different modified empirical modelling equations using our observed catchment parameters. The mean TC was significantly correlated with catchment size and stream length but negatively correlated with stream slope (p < 0.01). As a result, the mean TC estimated using the three modelling equations with catchment variables was qualitatively similar and had relative differences ranging from −12.5 to 15.5 min (−49 to 56%). Therefore, the models (particularly modeling equations with multiple regression, a modified empirical formula, and modified SCS Lag) can efficiently determine the TC and can be used in any small forested catchment in steep mountainous terrain.

DEM Computation of Flood Catchment Areas: Determining the Run-off and Maximum Discharge Time of Concentration in Uyo Urban

Rainfall runoff modelling is a vital and an essential paradigm in flood risk management. This research sought to determine the run-off and maximum discharge time of concentration (TC) in Uyo Urban to help facilitate adequate and proper flood risk and management plan in the area. The topographic map and 3D surface of the catchment area were generated and the rational method employed to determine the time of concentration of runoff as well as the maximum discharge while Hydrology extension in ArcGIS 10.3 was used to model the river basin from DEM and identify locations. Detailed analysis of 39 years (1977-2015) rainfall data was recorded to determine inter-annual variability, monthly distribution pattern, mean total annual rainfall, mean maximum daily rainfall and standardized anomaly index (SAI). The computed discharge was calculated. The results of the analyses indicate a total discharge of 1573.54m3/s and takes approximately 40 minutes of runoff time evident of prolonged rainstorms in areas like IBB Avenue as opposed to the short-lived rainfalls that causes flash floods in areas like Brook Street. This means that it takes a longer time of about 2 km to travel to the analysed site to cause flood. The study recommends the need for creation of more risk awareness and flood warning signs to further educate the people.

Comparison between the penetration characteristics of methyl bromide and ethanedinitrile through the bark of pine (Pinus radiata D.Don) logs.

Ethanedinitrile (EDN) is a fumigant being commercialized worldwide as an alternative phytosanitary treatment to methyl bromide (MB) for forest products. The penetration characteristics of MB and EDN were measured through the bark of wooden blocks (100 × 100 × 50 mm) cut from the upper (average bark thickness 5 ± 2 mm) and lower (average bark thickness 25 ± 5 mm) trunk of recently felled pine (Pinus radiata D.Don) trees. Doses of 48 g m-3 MB and 50 g m-3 EDN were applied to chambers at 10 and 20°C for 10h. Penetration of MB was influenced by the interaction between fumigation time and temperature, with concentrations increasing at a higher rate at 20°C compared with at 10°C. After 10h, an average concentration of 8.05 ± 0.89 g m-3 had penetrated the bark of log sections at 20°C, whereas 5.20 ± 0.89 g m-3 was measured at 10°C. By contrast, the factors examined in this study did not significantly impact the penetration of EDN. Concentration × time (CT) values for MB under the bark were 35.20 ± 2.30 g h m-3 at 10°C and 55.85 ± 9.58 g h m-3 at 20°C; whereas for EDN, CT values were 19.50 ± 6.80 g h m-3 at 10°C and 19.08 ± 4.10g h m-3 at 20°C. MB can achieve a higher concentration under the bark of log sections during simulated fumigations, but all of the factors examined affected the ability of MB to penetrate the bark of wooden blocks. By comparison, the penetration of EDN through the bark is more consistent than MB under laboratory conditions. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Analisis Banjir Genangan di Kawasan Tembalang dan Sekitarnya

Semarang City has a low and flat topography in several areas so that it has a high risk of inundation during the rainy season with a spatial distribution in the city center area. In 2022 inundation floods have inundated 877.66 hectares, one of which is in the Tembalang area and its surroundings with a height of around 275 MDPL which occurred in 20 locations with an area of around 33.62 hectares, where the area is the downstream part of the Babon Watershed. The results of the analysis of rain in the Babon watershed area for 20 years show that it is relatively stable, not too much variation, where the results of calculating the rational flood discharge for 2022 with a return period of 2 years are around 25.80 m³/s. Furthermore, the morphometric analysis of the watershed shows that the shape of the Babon watershed is relatively elongated with a circularity ratio <0.50, the density index of the river is 0.25 – 10 km/km² which is in the medium density category with a relatively long Time Concentration (TC) of around 3.2 hours so that it is less thus impacting flooding downstream. The Babon watershed runoff coefficient is affected by land cover conditions, where the interpretation results show that there was a change in land cover from 2002 – 2022 for the area of built-up land which increased by 708.44 hectares and the vegetation area decreased by 486.77 hectares. Analysis of channel capacity shows that there is potential for overflow from existing channels in 7 sub-watersheds which will result in inundation. The conclusion of this study shows that rainfall over the past 20 years has been relatively stable and the morphometry of the watershed has not had much impact on downstream flooding, the main river capacity of the Babon DAS is still sufficient to accommodate the planned flood discharge with a return period of 25 years. So that inundation that occurs is more caused by changes in land cover and drainage capacity in the downstream.

Computation of Time of Concentration Based on Two-Dimensional Hydraulic Simulation

Time of concentration (TC) is a parameter in runoff estimation, used to study and design different types of projects in watersheds. Any error in TC calculation leads to an inaccurate estimation of the design flow, which can lead to over-sizing or under-sizing of designed facilities that can have great economic and environmental consequences. Therefore, choosing the correct method to estimate TC is of great importance. Due to the diversity of estimation methods in the literature, the obtained TC values are different. This study aims to present a new method to calculate TC, based on its main concept, i.e., the time required for a water parcel to reach its outlet from the farthest hydrological point of a watershed. A two-dimensional hydraulic simulation was used to model the water parcel travel. A watershed was selected as a case study, and its time of concentration was determined by salt solution tracing. The field measurement results were used for calibration of the numerical simulation model. Meanwhile, 31 empirical relations in the literature were reviewed to determine the most accurate ones. Estimated TC values were compared with the measured ones, and the relative error percentage was used to evaluate the accuracy of the result. In the empirical TC methods, the maximum error was above 300%, and the minimum error was 6.7% for the field studied area. The relative errors of hydraulic simulation outputs were between 3 and 27%. The results showed that only three empirical methods, namely Simas and Hawkins, SCSlag, and Yen and Chow, had the least errors respectively equal to 6.7%, 8.660%, and 13.5%, which can be recommended for the studied area and those with similar hydrological characteristics. On the other hand, hydraulic simulation is also introduced as an efficient method to determine TC which can be used in any desired watershed.

Enhancing a Multi-Step Discharge Prediction with Deep Learning and a Response Time Parameter

Flood forecasting is among the most important precaution measures to prevent devastating disasters affecting human life, properties, and the overall environment. It is closely involved with precipitation and streamflow data forecasting tasks. In this work, we introduced a multi-step discharge prediction framework based on deep learning models. A simple feature representation technique using a correlation of backward lags was enhanced with a time of concentration (TC) concept. Recurrent neural networks and their variants, coupled with the TC-related features, provided superior performance with over 0.9 Nash–Sutcliffe model efficiency coefficient and substantially high correlation values for multiple forecasted points. These results were consistent among both the Upper Nan and the Loei river basins in Thailand, which were used as case studies in this work.

A comparative study of the time of concentration methods for designing urban drainage infrastructure

Abstract The time of concentration (ToC) is an important parameter in rainfall−runoff simulation for designing and evaluating an urban drainage system (UDS). There are several lumped and distributed methods available in the literature for estimating the ToC. However, these methods lead to significantly varied values. Therefore, it is imperative to choose an appropriate and best-suited method for estimating the ToC. This study analyses eight lumped approach-based and two distributed approach-based methods for estimating the ToC in an urban area of Gurugram, a satellite city in the National Capital Region (NCR) of Delhi in India. Considering the ToC obtained by the Natural Resource Conservation Service (NRCS) method as the ‘true’ value, the Carter method among lumped methods and the SWDM method between the distributed methods results in ToC values in agreement with the NRCS method. Furthermore, to study the impact of the underestimation or overestimation of ToC on drainage, the system is evaluated in terms of variation in flood volume, duration, peak discharge, and the time to peak for different ToC values. The simulations were carried out by setting the model in SWMM, and it was found that flood volume increases by 4.25 times and the duration increases by 7.25 times if the ToC is increased from 0.1 to 6.14 h. The results infer that ToC estimation methods significantly impact the design and performance of an urban drainage infrastructure.

Fumigation Monitoring and Modeling of Hopper-Bottom Railcars Loaded with Corn Grits

IntroductionBulk railcars are a common method of moving commodities in the USA. Allowances are given for the practice of treating railcars with fumigates during transit because the routes are limited access and not on public roads. Recent technology has become available for monitoring phosphine gas (PH3) fumigation on railcars which logs the phosphine concentration and temperature of the test point in the railcars.Materials and MethodsTwo hopper bottom railcar shipments of corn grit were monitored for phosphine during 8-day transit from mill to processor. Several phosphine-sensing units were used in each railcar and spaced across the top layer. Mathematical modeling of the railcar fumigation was carried out using computational fluid dynamic software. Because access to lower depths in the railcar was not available, supplement experiments were performed with small columns of corn grits (2.5 m height x 0.55 m diameter) to test for phosphine at greater depths. Also, in the grain columns, bioassays of both phosphine susceptible and resistant, adult Rhyzopertha dominica (F.), lesser grain borer, and Tribolium castaneum (Herbst), red flour beetle, were included at the 0 cm, 25 cm, and 60 cm below the surface.ResultsThe phosphine concentrations in the railcar headspace varied with time with phosphine spiking over 1600 ppm and gradually settling to over 300 ppm at the end of the 8 days. Total gas dosage was estimated as concentration*time (CT) over the 8 days as 115,000 and 125,000 ppm*h at the top of each railcar. The supplement grain column fumigation tests found significant phosphine penetration into the column at 2 m depth with ~380 ppm after 2 days which reduced to ~260 ppm after 8 days, and all insects, at all locations, were dead after 8 days. The CFD simulation models were shown to provide estimates of the phosphine concentration and distribution which matched well with the observed data, validating the CFD approach as a useful tool.DiscussionThe simulation models were shown to provide estimates of the phosphine concentration and distribution which matched well the observed data, validating the CFD approach as an efficient tool for future planning and analysis of similar fumigations.

Time of Concentration Estimated Using Some Methods and Application in The Ciliwung Watershed, Jakarta

Flood is one of the disasters that must be faced in the lowlands with poor drainage system, when there is high rainfall. Rainfall in the that upstream River can affect water level downstream River. Calculation of river discharge and forecast from that time that arrival from flood can Help prepare population to face that disaster. That method used in this lesson is a quantitative method with analysis from rainfall and planned flood repatriate. Then, time of concentration (TC) before calculated use that time traveling method, That Experience Resource Conservation Serve (NRCS) and Kirpich. That results is compared to with HEC RAS and observation method. That research location is in Ciliwung watershed, with tc calculation of Katulampa (Bogor) to MT. Haryono (Jakarta). That results show that results from design flood discharge using the HSS Nakayasu method for Q2 of 161.04 m3/s, Q5 of 187.07 m3/s, Q 10 of 215.08 m3/s, Q25 of 263.11m3/s, Q50 of 308.91m3/s and Q100 of 364.34m3/s. Time of concentration using the Time Travel method from Katulampa to MT. Haryono 12 hours 32 minutes, while using the NRCS method is 12 hours and 31 minutes while the Kirpich method is 12 hours 52 minutes. That time of concentration using observations is about 13 hour and using the HEC RAS is 14 hours. The closest method to calculate the time of concentration under actual conditions is the Kirpich method.

Exploring the Insecticidal Potential of Gaseous and Aqueous Ozone to Control Spotted-Wing Drosophila, Drosophila suzukii (Diptera: Drosophilidae).

Over the last decade, numerous companies have marketed aqueous ozone sprayers for insect and disease management, but little to no data has been published on their efficacy. Thus, we evaluated the potential of both gaseous and aqueous ozone as a potential preharvest insecticide against the adult life stage of the invasive fruit pest, spotted-wing drosophila, Drosophila suzukii (Matsumura). Gaseous ozone was applied at two dosages, 14,600 and 30,100 ppmv, for varying durations and the respective concentration-time (CT) exposure responses were modeled for sex-specific mortalities recorded at 0, 24, 48, and 72 h following treatment. We found that gaseous ozone primarily caused mortality immediately following exposure, with slight increases 72 h following ozone treatments. The female and male lethal concentration-time (LCT) 50 estimates were significantly different at 0, 24, 48, and 72 h after 30,100 ppmv treatments, where males observed an increased mortality response. However, the LCT 99 estimates confidence intervals (95%) of adult female and male D. suzukii were similar at 0, 24, 48, and 72 h after 14,600 or 30,100 ppmv ozone treatments. In contrast, ozone dissolved in distilled water at 18.52 ppm (mg/L) did not provide any mortality after total immersion of subjects for 30 s. While gaseous ozone may have some utility as a fumigant for D. suzukii in closed vessels where concentrations could be maintained, we did not identify any insecticidal potential for ozone dissolved in aqueous solution when simulating a preharvest treatment under optimal laboratory conditions.

Physiologically-Based Pharmacokinetics Modeling for Hydroxychloroquine as a Treatment for Malaria and Optimized Dosing Regimens for Different Populations.

Malaria is a severe parasite infectious disease with high fatality. As one of the approved treatments of this disease, hydroxychloroquine (HCQ) lacks clinical administration guidelines for patients with special health conditions and co-morbidities. This may result in improper dosing for different populations and lead them to suffer from severe side effects. One of the most important toxicities of HCQ overdose is cardiotoxicity. In this study, we built and validated a physiologically based pharmacokinetic modeling (PBPK) model for HCQ. With the full-PBPK model, we predicted the pharmacokinetic (PK) profile for malaria patients without other co-morbidities under the HCQ dosing regimen suggested by Food and Drug Administration (FDA) guidance. The PK profiles for different special populations were also predicted and compared to the normal population. Moreover, we proposed a series of adjusted dosing regimens for different populations with special health conditions and predicted the concentration-time (C-T) curve of the drug plasma concentration in these populations which include the pregnant population, elderly population, RA patients, and renal impairment populations. The recommended special population-dependent dosage regimens can maintain the similar drug levels observed in the virtual healthy population under the original dosing regimen provided by FDA. Last, we developed mathematic formulas for predicting dosage based on a patient’s body measurements and two indexes of renal function (glomerular filtration rate and serum creatine level) for the pediatric and morbidly obese populations. Those formulas can facilitate personalized treatment of this disease. We hope to provide some advice to clinical practice when taking HCQ as a treatment for malaria patients with special health conditions or co-morbidities so that they will not suffer from severe side effects due to higher drug plasma concentration, especially cardiotoxicity.

The Impact of Rainfall -Runoff on the Performance of Main Irrigation Canal and Cross Drainage of Omo-Kuraz I and II Sugar Project (The Case of Omo-Gibe Basin)

Flood is serious economic losses like damage main irrigation canal and installed infrastructure on sugar project. The objective of this research was to provide an estimation of rainfall-runoff effect on main canal irrigation scheme. The hydrograph characteristics of observed and simulated events are compared using various evaluation criteria consisting of Nash-Sutcliffe coefficient (NSE) is between 0.8 and 0.9, relative volume error (RVE) between -10 and 10%, and coefficient of determination (r2) is between 0.8 and 0.9 during calibration and validation period. Among the catchments of the basin that are used in the regional modeling work and nine Model Parameters are selected among those commonly used in regionalization studies. Four parameter regionalization methods (linear regression, spatial proximity, area ratio and sub-basin mean) were applied to transfer model parameter values from the gauged to the un-gauged catchments except area ratio method. In regional model, gauged catchments Model Parameters and Physical catchment characteristics of un-gauged catchments were used to develop the equations in order to predict discharge of un-gauged catchments. To have better understanding of model parameter performance, the sensitivity analysis of nine model parameters were performed manually by trial and error. The evaluation demonstrations that time of concentration (TC), storage coefficient(R), maximum storage (MS) and constant rate (CR) are more sensitive than others. Therefore, spatial proximity method is recommended in predicting discharge for un-gauged catchments for this research and obtained 85.1m3/s, 1.6m3/s, 9m3/s, 0.6m3/s,1.1m3/s, 14.3m3/s and 28.2m3/s peak flow for cross drainage three, culvert outlet four, culvert outlet three, culvert outlet two, culvert outlet one, cross drainage thirteen and cross drainage fourteen un-gauged sub catchments respectively. To determined predicted peak discharge using L-moment method in flood frequency analysis of selected gauged catchment. Finally, flood damage protection structures like dyke must be recommended for temporary, but redesign depend on peak discharge is necessary. Keywords: HEC-HMS, Regionalization, Stream flow simulation, L-moment, un-gauged catchments, Omo-Gibe sub-basin DOI: 10.7176/CER/14-2-02 Publication date: April 30 th 2022

In Silico Prediction of Pharmacokinetic Profile for Human Oral Drug Candidates Which Lack Clinical Pharmacokinetic Experiment Data.

In silico methods which can generate high-quality physiologically based pharmacokinetic (PBPK) models for arbitrary drug candidates are greatly needed to select developable drug candidates that escape drug attrition because of the poor pharmacokinetic profile. The purpose of this study is to develop a novel protocol to preliminarily predict the concentration profile of a target drug based on the PBPK model of a structurally similar template drug by combining two software platforms for PBPK modeling, the SimCYP simulator and ADMET Predictor. The method was evaluated by utilizing 13 drug pairs from 18 drugs in the built-in database of the SimCYP software. All drug pairs have Tanimoto scores (TS) no less than 0.5. As each drug in a drug pair can serve as both target and template, 26 sets were studied in this work. Three versions (V1, V2 and V3) of models for the target drug were constructed by replacing the corresponding parameters of the template drug step by step with those predicted by ADMET Predictor for the target drug. V1 represents the replacement of molecular weight (MW), V2 includes the replacement of parameter MW, fraction unbound in plasma (fu), blood-to-plasma partition ratio (B/P), logarithm of the octanol-buffer partition coefficient (log Po:w) and acid dissociation constant (pKa). In V3, all above-mentioned parameters as well as human jejunum effective permeability (Peff), Vd and cytochrome P450 (CYP) metabolism parameters (Km, Vmax or CLint) are modified. Normalized root mean square error (NRMSE) was used for the evaluation of the model performance. We found that the performance of the three versions of the models depends on structural similarity of the drug pairs. For Group I drug pairs (TS ≤ 0.7), V2 and V3 performed better than V1 in terms of NRMSE; for Group II drug pairs (0.7 < TS ≤ 0.9), 8 out of 10 V3 models had NRMSE < 0.2, the cutoff we applied to judge whether the simulated concentration-time (C-T) curve was satisfactory or not. V3 outperformed the V1 and V2 versions. For the two drug pairs belonging to Group III (TS > 0.9), V2 outperformed V1 and V3, suggesting more unnecessary replacement can lower the performance of PBPK models. We also investigated how the prediction accuracy of ADMET Predictor as well as its collaboration with SimCYP influences the quality of PBPK models constructed using SimCYP. In conclusion, we generated practical guidance on applying two mainstream software packages, ADMET Predictor and SimCYP, to construct PBPK models for drugs or drug candidates that lack ADME parameters in model construction.

Evaluation of lag time and time of concentration estimation methods in small tropical watersheds in Ethiopia

Study regionSix small agricultural watersheds in three tropical climatic regions of Ethiopia. Three regions of contrasting climate: highland, midland, and lowland regions with respectively high, middle, and low elevations and rainfalls. Study focusLag time (TL) and time of concentration (TC) are two measures of how quickly a stream responds to runoff-producing rainfall. These parameters are the main inputs used to estimate peak flow under flood conditions in ungauged watersheds. Many empirical methods have been proposed to estimate TL and TC, but the validity of none of them has been tested. This study compared 10 commonly used methods by using measured TL and TC. New hydrological insightsMeasured median values of TL and TC for 176 rainfall–runoff events were used to evaluate the performance of empirical methods. For individual watersheds, the estimates of TL and TC differed by up to 2.6 h and 4.4 h, respectively. Most of the empirical methods tended to substantially underestimate TL and TC, which would lead to overestimation of runoff volume. TL and TC computed by two methods that consider both overland and channel flow were closest to the measured values of TL and TC, because such mixed flow is typical of tropical climate regions. Our results show the need for caution when empirical methods developed in regions with a particular climatic and geomorphological conditions are applied elsewhere.

A Combination Sulfuryl Fluoride and Propylene Oxide Treatment for Trogoderma granarium (Coleoptera: Dermestidae).

The khapra beetle, Trogoderma granarium, is an important quarantine pest of stored-products. While it is not established in the North America, frequent interceptions highlight the need for treatments to eradicate isolated populations if they occur. Methyl bromide has long been the standard fumigant used for this purpose; however, increasing restrictions on its use necessitate the development of new treatment options. Here we evaluate a treatment for khapra beetle using a combination of sulfuryl fluoride (SF) and propylene oxide (PPO). Experiments were conducted to determine the most tolerant stages and the effective rates for each compound. Combination treatments using both products were then evaluated at several temperatures to determine effective doses for quarantine level control. The egg stage was by far the most tolerant to SF, requiring concentration × time (CT) products roughly 10-fold greater than the next most tolerant stage, diapausing larvae. Diapausing larvae were significantly more tolerant to SF than non-diapausing larvae in a recently collected 'field' strain, but not in a more than 30-yr-old 'laboratory' culture. PPO treatments were shown to completely control the egg stage at CTs greater than 155 hr-mgL-1 at both 10 and 20°C. Resulting combination treatments with initial dose rates of 96 and 40 mgL-1 at 10°C and 80 and 40 mgL-1 at 20°C are proposed for SF and PPO, respectively. These combination treatments utilize SF's efficacy against the larval stage along with PPO's superior ovicidal properties to provide enhanced treatment efficacy over each product alone against all life stages of khapra beetle.

Comparative Analysis of Some Existing Models for Estimating the Time of Concentration for Watersheds in Anambra State, Nigeria

This study considered the estimation of the time of concentration (TC) using 30 different watersheds in Anambra State, Nigeria. The study assessed the performance of some existing models for the estimation of time of concentration in the study area. Data for this research were collected from watersheds located at Awka-South Local Government in Anambra State. A measured time of concentration values was also obtained by using a tracer at the watershed divide and the time it took the tracer to get the outlet of the watershed was recorded. This was carried out on all the 30 watersheds at the same time. The length, slope and area of the 30 watersheds were also measured. Thereafter, the time of concentration was estimated using the 30 existing models. The extent of linear association between the observed and estimated time of concentration for the different models was determined. The outcome of the study revealed that the Ventura model (Tc12) developed in Italy recorded the highest correlation coefficient with a measure of 0.681, followed by DNOS model (Tc14) with a coefficient measure of 0.661 while the least performing model was Picking model (Tc13) with -0.423 correlation measure. There was also an obvious difference in the values of the time of concentration calculated using the different models. Therefore there is always a need to verify any model to be used for estimating the time of concentration in other to have a more robust design.

Pharmacokinetics and hemorheology of phosphocreatine and creatine in rabbits: A directly comparative study between parent drug and active metabolite

This study is to investigate pharmacokinetics (PK) and hemorheology (HR) of exogenous phosphocreatine (PCr), a cardio-protective agent, and its active metabolite creatine (Cr), with particular focus on the PK and PD comparison between PCr and Cr. A specific ion-pair reversed-phase HPLC-UV assay was used to simultaneously measure PCr, Cr and ATP concentrations in plasma and red blood cells (RBC) samples of rabbits. PK and HR parameters were calculated based on concentration-time (C-T) curves and effect-time (E-T) curves, respectively, obtained after i.v. dosing. Meanwhile the apparent pharmacological activity ratio (Rapp) and real pharmacological activity ratio (Rreal) of Cr to PCr were calculated. The PCr disappeared from plasma rapidly and in a biphasic manner; plasma PCr was converted to Cr fast and largely with the elimination rate limited metabolite disposition in vivo (Km < K). The i.v. administration of PCr led to a markedly elevated and long-lasting ATP level in RBC. After i.v. administration of preformed Cr, plasma Cr displayed similar elimination kinetics behaviors to that of Cr generated metabolically after i.v. PCr. The Cr could also raise ATP level in RBC, but to less extent than PCr. Approximately 43% of PCr-derived ATP came from Cr-derived ATP in RBC. PCr could significantly reduce whole blood viscosity and RBC osmotic fragility and Cr could do so, but weakly with estimated Rapp of 0.53–0.68 and Rreal of 0.38–0.48. PCr also inhibited platelet aggregation significantly, as opposed to Cr. The PCr-caused improvement of HR is related to the rise in ATP level in RBC. Cr is likely to partially mediate HR effect of PCr.

A Comparative Pharmacokinetic Profile of Trahydropalmatine After Oral Administration of its Monomer, Rhizoma Corydalis Alkaloid Extracts and Tong-Bi-Si-Wei-Fang to Rats

Background: Tong-Bi-Si-Wei-Fang (TBSWF) is a candidate formula of Traditional Chinese Medicine (TCM) for treating rheumatoid bone diseases, which is composed of rhizoma corydalis alkaloids, saponins of glycyrrhiza uralensis and panax notoginseng, flavonoids of rhizoma drynariae and glycyrrhiza uralensis. &lt;/P&gt;&lt;P&gt; Objective: Trahydropalmatine (THP), the main active ingredient of rhizoma corydalis alkaloids, was selected to study in vivo pharmacokinetics and druggability of TBSWF. Methods: The plasma concentration-time (C-T) profiles of THP and the pharmacokinetic property parameters after oral administration of THP monomer, extract of corydalis alkaloids (ECA) and TBSWF to rats, respectively were compared by a fully-validated HPLC method. Results: Compared to the THP monomer, the THP in TBSWF is absorbed faster, resides in the plasma longer and has a similar apparent volume of distribution Vz/F (10~20 L/kg). Compared to THP monomer and THP in TBSWF, the area under the concentration-time curve AUC 0-t of THP in ECA decreases two-third; Vz/F of THP in ECA (85.02 L/kg) is significantly higher than that of THP in TBSWF(p &lt;0.05). Unlike THP monomer and THP in ECA, double peaks are observed in the C-T profile of THP after oral administration of TBSWF. THP in TBSWF exhibits slow release to a certain degree. Conclusion: The interactions among the ingredients of TBSWF promote the adsorption and prolong the residence time of THP in vivo, and provide an explanation for the advantages of TBSWF from the point of pharmacokinetics.