Esthetic is a natural necessity among all human beings, and the reconstruction of the natural features of prosthesis is considered an important aspect in dentistry. Reconstruction of the natural features in removable prosthesis by characterization of denture base is one of the most important factors. In this regard esthetic, in removable prostheses, is achieved through different techniques such as: tooth selection and arrangement, designing the denture base and acrylic base color. The final goal for all these effects is to achieve a natural appearance for denture. However, other factors such as treatment limitations, different personal needs and general health principles, should be taken into consideration. This article not only reviews the natural appearance of oral mucosa that is replaced by the denture base, but also discusses about the materials used in tinting acrylic denture base and their application techniques.

Understanding the interaction of drought phenomenon and hydrological response of catchments can lead to obtaining some information for optimal water resource management. The aim of this study was to investigate the temporal relationship between drought and groundwater contribution to stream flow, in Kaka–Reza Sub-catchment. In this study, the common period of 1382-2017 was considered for the corresponding hydrometric and rain gauge stations. The Standardized Precipitation Index (SPI) was then calculated at time scales of three, six, nine, 12, 18 and 24 months. Base flow and related index were calculated by B-Flow-Line and Halick digital filter method in monthly, annual and total time bases. Then the Standardized Base Flow Index (SBFI), the Base Flow Duration Curve (BFDC) and the base flow duration curve shape index (SBFDC) was calculated. Changes in BFDC and the corresponding shape index and the relationships between SPI and SBFI were investigated and analyzed using the correlation method. The results showed that the average Base Flow Index during the research period was equal to 0.52 and its minimum and maximum were equal to 0.46 and 0.57, respectively. Also, the trend of bas flow changes is a decreasing trend with a low slope. The trend of changes SBFDC decreases over study period with a low slope. The rate of slope change is also from one to three percent, and close to the straight line, which indicates the tendency for base flow to be stable in the long time. The greatest impact of the drought phenomenon on the river base flow is in the time step of nine and twelve months. The correlation between SPI and SBFI with a coefficient of determination 0.87 confirms the increase in the groundwater contribution to base flow, with a delay of nine to twelve months.

The term hydrological drought is applied to represent low water levels in streams, reservoirs and lakes as well as a low groundwater level. Base flow index (BFI) as one of low flow indices gives the ratio of base flow to total flow and investigates basin’s ability to store and release of water in drought periods. The objectives of this study were to determine BFI and to validate this index in drought studies of Sefidrood Drainage Basin. To view of this, first three homogenous regions were identified based on the threshold level using cluster analysis. Then, daily BFI was calculated in 28 gauging stations of the homogenous regions. The results showed that the regional mean of BFI with value of 0.65 (SD=0.19) is stable during long-period data. BFI ranged between 0.17 and 0.86 and also based on the 25, 50 and 75 percentiles, river flow regime in the study area is divided into four categories that show more than 50 percent of the catchments in the study area have low or unstable regime. So it would be hard that the catchments able to provide river flow during drought periods. Therefore the results of this study can be used in assessment of groundwater recharge, water supply system, irrigation management, and hydrological drought monitoring as well as regional modeling of water resources storage and hydrological drought in ungauged areas.

The occurrence of drought is one of the natural phenomena and an inseparable part of climate change and natural hazards that can occur anywhere. Hydrological drought is used to indicate the reduction of surface flows and the drop in the levels of underground water reservoirs, lakes, and rivers. The present research was conducted to determine the values of the base flow index and to assess its effectiveness in identifying the type of flow regime and conducting a regional analysis of hydrological drought in the HalilRood watershed. For this purpose, three homogeneous hydrological drought zones were established based on the threshold level and cluster analysis. The base flow index was then calculated on a daily scale using daily discharge data from ten hydrometric stations within these homogeneous zones. The results showed that the regional average of the annual base flow index is 0. 38, with a standard deviation of 0. 193 over the long-term statistical period, and that the range of the base flow index is 0. 12–0. 29. Based on the 70th, 80th, and 90th percentiles, the river flow regime was divided into four classes, revealing that 100% of the watershed sub-basins in the study area exhibited an unstable regime. Additionally, the results of drought zoning indicated that hydrological drought occurred at a threshold level of 70 in the southeast of the region near the Dehroud hydrometric station, and at levels of 80 and 90 in the northwest near the Baft and Cheshme-Arus stations. The findings of this research can be utilized for assessing underground water supply, managing water supply systems, irrigation management, monitoring hydrological drought, and developing regional models for estimating water resource reserves in areas lacking statistical data.

Planning and management of water resources in watersheds require data, including, base flow and its index. These parameters are influenced by morphometric, geologic and hydro climatologic factors and have always been of the most important issues in hydrology. In this research, base flow and related index were extracted from daily stream flow data using two parameters recursive digital filters in 43 hydrometric stations of Kerman Province. Physiographic, climatic and hydrological parameters were calculated in GIS environment. Using factor analysis of 14 parameters, six factors were chosen as the most important independent factors. Then the regional equations were determined, using linear regression at 1% significant level. To compare and evaluate the accuracy and efficiency of the models, independence errors, colinerity and normal distribution of error were tested. Among the factors investigated, multivariate regressions were identified as the best estimator of base flow index in the study area.

This study, using conditional turbulence method, investigates the factors affecting on instability index in base metals industry sector of Tehran Stock Exchange. For this purpose, monthly data from April 2009 to April 2020 were used. The results show that fluctuations in the industrial sector are caused by factors such as political conflicts and international problems in Iran and are strengthened by fluctuations in parallel markets such as oil, gold and currency. According to the results of the research, factors outside the stock market industry, due to the underdevelopment of the stock market in Iran, have a greater impact than in-company factors on instability of the stock market. From the point of view of the analyzes performed, the most important effect and factor causing fluctuations is the section of political tensions and international relations in Iran, which has uncontrollable effects on parallel markets in Iran and ultimately the effect of all of them is reflected in the stock market.

River flow is one of the most important water resources for uses in agriculture, industry and sanitary sectors. In this regard, analysis of temporal trend in river flow is essential in management of water resource. Better understanding of base flow can be used in analysis of river flow pattern and discharge regime and management of water resources in the low flow periods. Water withdrawals alter the natural patterns of stream flow regime and flow conditions. The main aim of the present research is to investigate the spatio-temporal variations of surface flow and base flow over Ardabil Province through 22 river gauge stations considering rainfall variability. Therefore, the daily discharge and rainfall records were analyzed over the period 1989-2012. A common approach to quantify the base flow components of stream flow is to use a graphical hydrograph separation approach, as the discharge data is the only requirement. The stream discharge records are widely available, and therefore, the graphical approach can be employed in different spatial scales. The base flow component of the hydrograph was estimated at a daily time step for the period of record at each station. The amount of surface run off was calculated and the local minima technique was used to separate the base flow contribution and then the base flow index (BFI) values were calculated in each station and were interpolated to detect the spatial variation pattern. The recorded data length were divided into 5-year periods and the variations of base flow and BFI were analyzed and its relationship with total runoff and rainfall amounts was investigated to detect the temporal changes in the base flow amount and base flow index. The results showed that the decreasing changes was dominant through study area. Also relationships of monthly precipitation and base flow amount indicated that the precipitation variations had low impact on the base flow decreasing pattern. Based on the results, the spatial pattern of total runoff, base flow and base flow index follows a similar regime and the highest values in three variables is related to West and South-west parts of the Ardabil Province and the South-East parts of the study area had the lowest values of interpolated amounts. The highest values of base flow index varies from 0.05 to 0.88 in the study area and highest values are concentrated in the West part of the study area. It was determined that the highest values of base flow is related to the amount of 30 cubic meter per second in the Doost Beigloo station. Also, it can be concluded that the maximum of base flow was observed in Gilandeh station. It can be noted that the West parts of the study area is snowmelt-dominated rivers where there is a persistent flow discharge during snowmelt in late spring or early summer and low-flow periods. The impacts of rainfall variations and water uses on the river flow is clearly reflected in the timing and quantity of river flow. It should be noted that the base flow and base flow amount have decreased and the rate of decreasing intensity was more intense in three months of autumn season.