Stewart Method Research Articles

Acid base disturbances in leptospirosis patients: Comparison of conventional and Stewart method

Background: The Henderson-Hasselbalch equation is used in the conventional assessment of acid-base status. In 1983, P. Stewart put up an alternate strategy. The Henderson-Hasselbalch equation uses variations in PCO2 and bicarbonate to explain the acid-base state. On the other hand, the Stewart theory states that albumin, inorganic phosphate, PCO2, Strong Ion Difference (SID), and SID dictate acid-base status. Therefore, these variables have an important role in clinical management. The metabolic acidosis caused by unmeasured anions is accurately identified by the Stewart physiochemical approach, and it is a predictor of mortality in patients with leptospirosis. Aims and Objectives: Comparison of the leptospirosis patient’s S. albumin (requiring ABG analysis) and arterial blood gas (ABG) analysis parameters (pH, PO2, PCO2, HCO3-, BE, SaO2, S.Na+, S.K+, S.Cl, S.PO43-, and anion gap) to compare the conventional and Stewart methods and determine the type of acid-base disturbances present in leptospirosis patients in the intensive care unit. Materials and Methods: Following approval by the ethics committee, ABG and S. Albumin were taken from the clinical notes of fifty patients. The Henderson-Hasselbalch equation, in its conventional form, was unable to identify complex acid-base problems. Thus, we integrated this with the Stewart method. Results: The majority of leptospirosis patients had a mixed disorder characterized by respiratory alkalosis, metabolic acidosis, and metabolic alkalosis. The most prevalent conditions were metabolic acidosis, respiratory alkalosis, and metabolic alkalosis. Stewart’s method can help explain the cause of metabolic disorders. Stewart’s approach also made occult acid-base disorders visible. Conclusion: Stewart’s approach emphasizes the significance of Na+, K+, Cl-, Alb, and PO43- and clarifies their part in the development of metabolic abnormalities, particularly those involving Alb and PO43-. This demonstrates unequivocally that the cause of the metabolic abnormalities can be explained by Stewart’s method, which is highly helpful in planning the management.

Dynamics of Grain Yields in European Russia in the 19th — Early 20th Centuries: The Extent of Knowledge of the Issue

This article deals with the problems of research in national science of the dynamics of grain yields in European Russia between the nineteenth and early twentieth centuries. For the purpose of the article, the author refers to crop statistics. Disputes about their reliability have been going on for about two hundred years, however, no irrefutable evidence of their unreliability has been presented. This is also true about the discussion of the early twenty-first century, where the source was criticised by B. N. Mironov and M. A. Davydov, and their opponents were S. A. Nefedov, A. V. Ostrovsky, and I. A. Kuznetsov. Interest in the dynamics of productivity emerged in the late nineteenth century. The focus of attention was the question of whether there was an increase in productivity in the period under review or not. At the turn of the twentieth century, A. F. Fortunatov and R. I. Preger maintained that productivity had increased, and I. Kh. Ozerov argued that it had not. In the 1920s, three views on the character of yield dynamics formed. V. G. Mikhailovsky and M. I. Semenov talked about a growth in yield combined with cyclical and random fluctuations. F. Cherevanin wrote that the yield in European Russia changed exclusively cyclically. V. M. Obukhov and A. L. Weinstein argued that grain yields grew, obscured by random fluctuations, in the absence of a cyclical component. It was the third point of view that prevailed with B. S. Yastremsky, A. S. Nifontov, A. V. Ostrovsky, V. G. Rastyannikov, and I. V. Deryugina following it. Only N. O. Voskresenskaya questioned the widespread increase in productivity. However, the previously used research methods (interval enlargement, correlation-regression analysis) are imperfect, and therefore the findings require rechecking using methods that are not in demand by national science for the analysis of crop statistics (hypothesis of the averages, Foster — Stewart method), which will help to better understand the nature grain yield dynamics in European Russia in the nineteenth and early twentieth centuries.

McKern-Stewart method as a technique for analysing age related pubic symphyseal changes: A systematic review and meta-analysis.

Age estimation is one of the essential criteria in the identification process. The method of age estimation employed depends on the availability of skeletal material brought for forensic examination. McKern and Stewart's method constitutes one of the principal approaches towards pubic symphyseal age estimation. The method entails evaluating morphological changes within the pubic symphysis and subsequently allotting a specific score corresponding to the observed changes. Based on the obtained scores, an age range is then assigned to the remains presenting for examination. The present systematic review was undertaken to ascertain the applicability of the McKern-Stewart method for age estimation. Studies pertaining to the use of the McKern-Stewart method for age estimation in skeletal remains were retrieved by keying in a combination of MeSH terms and other free terms from four databases. The retrieved articles were subjected to a stringent inclusion and exclusion criteria, following which the risk of bias was assessed and the overall quality of evidence was established. Once the final tally of relevant articles was obtained, data specific to the mean age corresponding to each score was extracted. Non-parametric tests and boxplots were employed to compare the mean ages reported across multiple studies. The present systematic review concludes that the McKern-Stewart method can be applied for the purpose of age estimation in skeletal remains. Broader age cohorts for higher scores, as well as, overlapping values for age ranges in relation to the cumulative scores, however, can be considered a limitation for its applicability in forensic case work.

Evaluation of arterial blood gases of patients with type 1-2 respiratory failure diagnosed in intensive care using the quantitative Stewart method

Introduction: Arterial blood gases are tests that provide reliable information about the metabolic and respiratory status of patients. In traditional methods, arterial blood gases are evaluated by calculating the bicarbonate concentration and anion gap in the plasma. Since ICU patients almost always have protein and electrolyte disorders, a different method has been suggested instead of the traditional method that neglects electrolyte and protein in the evaluation. In the mathematical model described by Stewart and modified by Figge et al., 4 types of respiratory failure were defined according to their pathophysiology: hypoxemic (type 1), hypercapnic (type 2), perioperative (type 3), and hypoperfusion-induced respiratory failure in shock patients (type 4). The study aims to evaluate the arterial blood gases of intensive care patients with type 1 and type 2 respiratory failure with the Stewart method and compare them with the traditional method.
 Material and Method: In the study, serum BUN (blood urea nitrogen), creatinine, glucose, sodium, chlorine, serum BUN (blood urea nitrogen) of 106 patients diagnosed with type 1-2 respiratory failure. Together with potassium, magnesium, albumin values, pH, pCO2, pO2, HCO3, base deficit, and lactate values studied in arterial blood gas sample were determined and evaluated according to the Stewart method.
 Results: The length of stay of the patients in the intensive care unit was determined as 17.48±10.58 (minimum 6-maximum 68) days. It was determined that 74 (69.8%) of the patients were discharged and 32 (30.2%) died. When the blood gases and laboratory values of the patients were compared according to the clinical outcomes of the patients, no statistically significant correlation was found between the patients’ mean pH, pCO2, HCO3, base deficit, pO2, albumin, lactate, creatinine, glucose, potassium, and chlorine values and the patients’ discharge or death. BUN values of patients who died were found to be higher than those who were discharged. A statistically significant difference was found between the development of hypoalbuminemia and the length of stay in the intensive care unit. It has been determined that the treatment costs of patients with severe hypoalbuminemia are higher than other patients. The length of stay in the intensive care unit of the patients who did not develop acidosis was found to be statistically significantly lower than the patients who developed metabolic and respiratory acidosis.
 Conclusion: While a significant relationship was found between albumin levels, which has an important place in the Stewart method, and the length of stay in the intensive care unit, no relationship was found between albumin levels or lactate levels and mortality. However, increased BUN values were associated with mortality. As the albumin value decreases in patients with hypoalbuminemia, treatment costs increase. There is a need for larger multicenter studies with a larger sample group that will evaluate metabolic status with the Stewart method and investigate its relationship with mortality.

A comparison of traditional and quantitative analysis of acid-base and electrolyte imbalance in 87 cats

Acid–base disorder is a common problem in veterinary emergency and critical care. Traditional methods, as well as the Stewart method based on strong ion difference concepts and the Fencl–Stewart method, can be used to analyze the underlying causes. On the other hand, there are insufficient comparative study data on these methods in cats. From 2018 to 2020, 327 acid–base analysis data were collected from 69 sick and 18 healthy cats. The three most well-known methods (traditional method, Stewart method, and Fencl–Stewart method) were used to analyze the acid–base status. The frequency of acid–base imbalances and the degree of variation according to the disease were also evaluated. In traditional acid–base analysis, 5/69 cats (7.2%) showed a normal acid–base status and 23.2% and 40.6% of the mixed and straightforward disorders, respectively. The Fencl–Stewart method showed changes in both the acidotic and alkalotic processes in 64/69 (92.8%), whereas all cats showed an abnormal status in the Fencl–Stewart method (semiquantitative approach). Different acid–base imbalances were identified according to the analysis method. These findings from the disease categories are anticipated to assist in analyzing the underlying causes of acid–base imbalance and developing the appropriate treatment.

Describing acid-base balance using three different methods of analysis in a feline acute haemorrhage-resuscitation model

ObjectiveTo describe acid-base status using the Henderson-Hasselbalch, Stewart and semi-quantitative methods of analysis in a feline haemorrhage-resuscitation model. Study designRandomized crossover study. AnimalsA total of six domestic cats (mean age, 21 months; weight, 4.9 kg). MethodsVenous blood samples were taken before haemorrhage, after haemorrhage at 30 minute intervals during fluid resuscitation and at 24 hours. The cats were anaesthetized and underwent following treatments: no purposeful haemorrhage and resuscitation (NoPHR), purposeful haemorrhage followed by either lactated Ringer’s solution (LRS) or 6% tetrastarch 130/0.4 (Voluven) for resuscitation. LRS and Voluven were administered at 60 and 20 mL kg–1 hour–1, respectively, for 120 minutes. Variables used for the analysis methods were measured or calculated from the blood samples and then compared among treatments over time using a general linear mixed model (p < 0.05; data reported as mean and standard deviation). ResultsThe total blood loss at 120 minutes was 10.2 ± 2.3, 29.3 ± 9.0 and 29.1 ± 6.3 mL kg–1 for NoPHR, LRS and Voluven, respectively. Total volumes of LRS and Voluven administered were 120 and 40 mL kg–1, respectively. All cats became acidaemic during anaesthesia regardless of treatment. The Henderson-Hasselbalch method indicated that anaesthetized cats undergoing severe haemorrhage and resuscitation manifest a mixed acidosis. The Stewart method indicated two counter metabolic processes that contributed to the overall pH—decrease in apparent strong ion difference (acidosis) and decrease in total weak acids (alkalosis). The semi-quantitative method identified the free water and chloride effects as variables causing acidosis and the albumin effect causing alkalosis. Conclusions and clinical relevanceIn an experimental haemorrhage and resuscitation model in cats, blood pH was similar among treatments over time regardless of severe haemorrhage and resuscitation with LRS or Voluven or mild haemorrhage and no resuscitation.

Age estimation from morphological changes in pubic symphysis

The present study was carried out to examine if Mckern and Stewart method (1957) could be used to assess the age from pubic symphysis of male individuals of the Dakshina Kannada District. Samples of pubic bones were collected from 50 deceased males of known age who were brought for autopsy to the Department of Forensic Medicine and Toxicology at a Tertiary care centre after obtaining a written informed consent from the relatives of the deceased. The analysis showed that the component based method of McKern and Stewart cannot be applied in its original form to the Indian population. The study established that the changes aiding in age analysis were more defined in the younger age groups and were obscured as the age advanced. It is also observed that the changes categorizing the bone in a particular age group commence at a later stage in the present study when compared to the reference studyThe likelihood of changes in each component of analysis being more pronounced in early stages are high compared to the older age groupThough analysis of pubic symphysis is useful in age estimation a study in bigger sample size will further prove the above hypothesis.

Comparison of a modified Story approach to traditional evaluation of acid-base disturbances in patients with shock: a cohort study.

To compare whether the diagnostic evaluation of metabolic acidosis can be improved by using a modified Story method compared to the traditional evaluation in a population of critically ill patients with shock. This prospective cohort study included shock patients admitted to the ICU of a tertiary hospital in Brazil between May 2018 and November 2019. We collected laboratory data necessary for traditional evaluation and the simplified Stewart's method. During the study period, 149 patients were included in the final analysis. Of the 17 patients with a normal SBE and AGcorrected, 13 (76.5%) presented with metabolic acidosis according to the modified Story assessment. Therefore, of the 149 patients included in the study, the traditional approach failed to identify metabolic acidosis that was identified by the modified Story assessment in 13 (8.7%) patients. In addition, the determination of the severity of metabolic acidosis also differed between the two methods by a mean of - 7.8mEq/L. We found that a modified Story method can identify and quantify metabolic acidosis in patients with disorders that were not revealed by the traditional approach.

Modulatory Role of Vitamin E on Proton Pump (ATPase) Activity of Cadmium Chloride-Induced Testicular Damage in Wistar Rats.

Proton pumps are membrane-bound enzymes important in generating gradients that help in maintaining cellular ion homeostasis, cell membrane potential, water, and solute transport across the cell surface. This study investigated the modulatory role of vitamin E on proton pump activity and reproductive parameters in cadmium-induced testicular damage. Twenty (20) male Wistar rats weighing between 180 and 200 g were sorted into 4 groups of five rats each. Group I served as the control and was given normal saline orally, Group II rats were treated with a single dose of 2 mg/kg BW cadmium chloride (CdCl2) intraperitoneally, Group III rats were given 100 mg/kg BW of vitamin E orally, and Group IV rats were given 100 mg/kg BW of vitamin E orally for 30 days prior to intraperitoneal administration of single dose of 2 mg/kg BW of cadmium chloride. The rats were anaesthetized with diethyl ether, and blood samples were obtained for sex hormonal analysis; caudal epididymis was dissected for sperm count, motility, and viability, and the testis were homogenized for lipid peroxidation and proton pump (Na+/K+ ATPase, Ca2+ ATPase, and Mg2+ ATPase) activity. Proton pump activity was assayed spectrophotometrically using the Stewart method to determine the inorganic phosphate level. Histopathological changes of the testis were also studied. The group treated with CdCl2 showed a significant (p < 0.05) decrease in proton pump activity, sperm count, and motility and a significant (p < 0.05) increase in malondialdehyde level when compared with the control group. The CdCl2-treated group also showed decrease reproductive organ weights and hormonal levels and cause necrosis of spermatogonia lining the seminiferous tubules. Rats treated with vitamin E orally for 30 days prior to CdCl2 exposure showed improvement in proton pump activity, a significant (p < 0.05) increase in sperm parameters and luteinizing hormonal level, and a decrease in the lipid peroxidation level as compared with the CdCl2 group. This study showed that vitamin E ameliorated the toxic effect of CdCl2 on proton pump activity in the testes, hence improving testicular integrity, structures, and functions.

Short communication: First record of Arapaima gigas (Schinz, 1822) (Teleostei: Osteoglossomorpha), in the Brantas River, Sidoarjo, East Java, Indonesia

Abstract. Fadjar M, Islamy RA, Herawati EY. 2019. Short communication: First record of Arapaima gigas (Schinz, 1822) (Teleostei: Osteoglossomorpha), in the Brantas River, Sidoarjo, East Java, Indonesia. Biodiversitas 20: 3527-3531. The arapaima (= Arapaima gigas) is the largest freshwater fish in the Neotropical region, obligate air-breathing fish that known to reach up to 3 m - 3.90 m in length and 200 kg in weight endemic to the Amazon basin. Arapaima gigas is giant osteoglossomorph and obligate air‐breathing fish and also a native species of the Amazon basin. We present the first record of Arapaima gigas (Schinz, 1822) in Brantas River, Sidoarjo, East Java, Indonesia with diagnostic meristic and morphometrics of the specimens analyzed following Stewart method. Herein, it recorded from the Brantas River basin. This record based on the finding of one live specimen on the tributary of Brantas River basin, and in situ observation of juveniles and adults in the river).

Applicability of Three Component System of Age Estimation in Haryana Population

Various methods has been postulated to estimate the age of skeletonised remains which is a very essential aspect in forensic medicine. Mc Kern and Stewart formulated three component system of age estimation in pubic bones. Component I, II and III were based on development of dorsal half, ventral half and outline of the pubic symphysis respectively. A total of 300 pubic bones were evaluated of which 225 were male send 75 were females. Each pubic bone was given a score based on Mc Kern and Stewart method. The observation were tabulated according to the Mc Kern Stewart score. Suitable adjustments in the age range should be made in the Mc Kern and Stewart method for using it in different population

Comparison between bicarbonate-based and Stewart methods to assess metabolic acid-base disorders in internistic patients. A pilot study

Aim: To assess the acid-base status in a cohort of internistic patients, using traditional and “modern” methods, to compare their different sensitivity to detect metabolic disorders and to evaluate a possible relationship between classical and alternative parameters.Patients and Methods: 143 assessment of acid-base and electrolytes balance on 121 internistic patients (76 males and 45 females, mean age 73.9 ± 10,8 years) were examined according to bicarbonate-based and Stewart methods.Results: The traditional method detected 81 cases (56.6 %) of metabolic alkalosis and 15 cases (10.4 %) of metabolic acidosis. The Stewart method detected 92 cases (64.3 %) of metabolic alkalosis and 22 cases (15.3%) of metabolic acidosis.Traditional method failed to detect 11 cases of metabolic alkalosis (chi square = 1.443; p = 0.226), and 7 cases of metabolic acidosis (chi square = 1.118; p = 0.290) when compared to Stewart's method. A significant relationship was observed between Strong Ion Gap (SIG) and Anion Gap corrected for albumin concentration (AGcorr) (r= 0.53; p &lt;0.001).Conclusions: Our result showed that traditional method is useful to assess acid-base status in internistic clinical setting as well as Stewart's method because no significant difference was found between the two approaches. Nevertheless, the light disagreement observed between the two methods suggests that in a small percentage of cases the traditional method can fail to detect metabolic acid-base abnormalities.

Evaluation of accuracy of literature gasoline blending models to predict octane numbers of gasoline blends

ABSTRACTThe gasoline blending prediction models available in the open literature: Linear method, Ethyl method, Stewart method, Zahed method, and Twu method were tested on 25 gasoline blends prepared from 14 components used by LUKOIL Neftohim Burgas (LNB) refinery to produce commercial gasoline grades. The performed tests with these models showed prediction accuracy outside of the acceptable ASTM D 2699 and ASTM D 2700 reproducibility limits. However, the LNB-modified regression model of Zahed method turned out to predict RON and MON of studied gasoline blends with accuracy equivalent to the reproducibility of the standard methods for measurement of RON and MON.

Metabolic acidosis in medical intensive care unit with indicators and their prognostic value- A prospective observational study

Background: Metabolic acidosis is a common abnormality in the intensive care unit. There has recently been a surge of interest in nontraditional approaches to the analysis of acid base disorders.Aims and Objectives: This study was undertaken to compare the application of the physicochemical method of Stewart and the traditional Henderson-Hasselbach equation withcorrection for albumin in quantification of acid base disorders.Materials and Methods: All patients with metabolic acidosis admitted to the ICU as defined by a base deficit of &gt;2.5 were included in the study. The APACHE II score was calculated at admission and the predicted mortality was defined. The acid base disorders were quantified by the traditional approach with anion gap correction for serum albumin as well as by the Stewart method with calculation of the strong anion gap acidosis.Results: One-hundred forty patients were included in the study of which 58% were males. In 125 subjects (89%) acidosis was discovered by the Stewart method. The traditional method detected increased anion gap in 109 subjects (78%) but this increased to 124 (88.5%) when corrected for albumin. Both the strong ion gap (SIG) and the albumin corrected anion gap correlated strongly. Serum lactate levels and SIG predicted mortality as did albumin corrected anion gap.Conclusion: Albumin correction of the anion gap correlates well with acidosis as discovered by the SIG and therefore should be used in the ICUs rather than the traditional anion gap. With this modification, we can thus depend on the application of the intuitive traditional method rather than the more difficult to apply Stewart method for analysis of the acid base abnormalities in the ICU.Asian Journal of Medical Sciences Vol.8(3) 2017 60-67

Determination of tissue hypoxia by physicochemical approach in premature anemia

Anemia is a common problem in premature infants and its most rapid and effective therapy is erythrocyte transfusion. However, owing to inherent risks of transfusion in this population, transfusions should be administered only when adequate oxygen delivery to tissues is impaired. The aim of this study was to determine tissue acid levels using Stewart method in an attempt to evaluate the tissue oxygenation level and thereby the accuracy of transfusion timing. This study included 47 infants delivered at gestational age below 34 weeks who required erythrocyte transfusion for premature anemia. Strong ion gap (SIG), unmeasurable anions (UMA), tissue acid levels (TA), and Cl/Na ratios were calculated before and after transfusion. The mean birth weight and gestational age of the study population were 1210 ± 365 g and 29.2 ± 2.7 weeks, respectively. Tissue acid levels were increased (TA ≥ 4) and tissue hypoxia developed in 10 (16.6%) of 60 erythrocyte transfusions administered according to the restrictive transfusion approach. The patients were divided into two groups according to tissue acid levels as low (<4) and high (≥4) tissue acid groups. The group with tissue hypoxia (TA ≥ 4) had significantly higher UMA levels but a significantly lower Cl/Na ratio; and UMA levels decreased and Cl/Na ratio increased after transfusion in this group. Tissue hypoxia secondary to anemia was shown to be improved by erythrocyte transfusion. The results of the present study suggest that the determination of the level of tissue hypoxia by the Stewart approach may be an alternative to restrictive transfusion guidelines for timing of transfusion in premature anemia. It also showed that a low Cl/Na ratio can be used as a simple marker of tissue hypoxia.

Effectiveness of the Stewart Method in the Evaluation of Blood Gas Parameters

SUMMARYObjectivesIn 1981, Peter A. Stewart published a paper describing his concept for employing Strong Ion Difference. In this study we compared the HCO3 levels and Anion Gap (AG) calculated using the classic method and the Stewart method.MethodsFour hundred nine (409) arterial blood gases of 90 patients were collected retrospectively. Some were obtained from the same patients in different times and conditions. All blood samples were evaluated using the same device (ABL 800 Blood Gas Analyzer). HCO3 level and AG were calculated using the Stewart method via the website AcidBase.org. HCO3 levels, AG and strong ion difference (SID) were calculated using the Stewart method, incorporating the parameters of age, serum lactate, glucose, sodium, and pH, etc.ResultsAccording to classic method, the levels of HCO3 and AG were 22.4±7.2 mEq/L and 20.1±4.1 mEq/L respectively. According to Stewart method, the levels of HCO3 and AG were 22.6±7.4 and 19.9±4.5 mEq/L respectively.ConclusionsThere was strong correlation between the classic method and the Stewart method for calculating HCO3 and AG. The Stewart method may be more effective in the evaluation of complex metabolic acidosis.

Chloride and its Clinical Implications in Today’s Clinical Practice: Not an Orphan Electrolyte

Though chloride is the predominant extracellular anion, it is mostly seen just as an anion accompanying sodium and hardly receives attention in textbooks. But independent evaluation of serum chloride may unearth several clinical and acid-base disorders. It is used in formulas to estimate serum anion gap, urine anion gap, and strong ion difference (Stewart method). Several critical functions of a cell such as maintenance of cell volume, neutralization of H+ in lysosomal vesicles, epithelial fluid transport, change in cell membrane potential and ligand-gated transmission in the post-synaptic membrane utilize chloride channels. In addition, chloride forms an integral part of anion exchanger proteins coded by SLC26A gene family. Chloride is an essential component of intravenous fluids used in day-to-day clinical practice. The role and contribution of chloride rich fluids and resulting acidosis in causing inferior outcomes in sepsis, renal vasoconstriction, and acute kidney injury has been debated. Numerous genetic diseases are known to be related with chloride channels and proteins abnormalities. In the following review, I would like to bring much needed attention towards importance of chloride in human physiology. The following hypothetical clinical case will be just a spark for fiery chloride.

Climate change impacts on rainfed agriculture in the Guadiana river basin (Portugal)

In this study, the crop yield response of rainfed crops to climate change was evaluated focusing on the most representative crops in the Guadiana river basin. The quantification of crop yields was performed using a simple soil water balance model framework. The herbaceous crop yields were evaluated with the ISAREG model, implementing a water balance approach combined with the Stewart method. A similar water balance approach was used to estimate the yields for the most representative permanent rainfed woody crops in the region using an alternative spreadsheet-based model, but implementing a more detailed water stress evaluation through the crop cycles. Yields were simulated for two future periods (2011–2040) and (2041–2070) using, as climate inputs, temperature and precipitation series, reflecting a combination of five climate change scenarios (CCS) created using the ensemble-delta technique applied to CMIP3 climate projections datasets to represent different alternative climate change bracketing conditions for rainfall and air temperature. The results showed that comparatively with the reference period climate (1961–1990) rainfed crop yields will decrease in future period 1 (2011–2040) and reach even higher losses in future period 2 (2041–2070). Within the herbaceous crops, sunflower and winter wheat were the most susceptible to yield losses under climate change, reaching estimated maximum losses for future period 2 of respectively 18.5% and 13.6%, followed by natural grown pastures with 11.5%. For woody crops, maximum estimated yields losses were considerably higher for almond (27.2%) than grapevine (5.4%) and olive (14.9%).

Study of different climatic conditions to assess the role of solar radiation in reference crop evapotranspiration equations

This study aims to assess radiation-based models versus the FAO Penman–Monteith (FPM) model to determine the best model using linear regression under different weather conditions. The reference evapotranspiration was estimated using 22 radiation-based methods and was compared with the FPM. The results showed that the Stephens method estimates the reference evapotranspiration better than other methods in the most provinces of Iran (nine provinces). However, the values of R2 were more than 0.9930 for 24 provinces of Iran. The radiation-based methods estimated the reference evapotranspiration near the Caspian Sea better than other regions. The most precise methods were the Berengena–Gavilan, Modified Priestley–Taylor, and Priestley–Taylor methods for the provinces ES (center of Iran), GI and GO (north of Iran) and the Stephens–Stewart method for IL (west of Iran). Finally, a list of the best performance of each method has been presented to use other regions and next research steps according to the values of mean, maximum, and minimum temperature, relative humidity, solar radiation, elevation, sunshine, and wind speed. The best weather conditions to use radiation-based equations are 23.6–24.6 MJ m−2 day−1, 12–20°C, 18–24°C, 5–13°C, and <180 hour month−1 for solar radiation, mean, maximum, and minimum temperature, and sunshine, respectively.

Modeling of daily pan evaporation in sub tropical climates using ANN, LS-SVR, Fuzzy Logic, and ANFIS

This paper investigates the abilities of Artificial Neural Networks (ANN), Least Squares – Support Vector Regression (LS-SVR), Fuzzy Logic, and Adaptive Neuro-Fuzzy Inference System (ANFIS) techniques to improve the accuracy of daily pan evaporation estimation in sub-tropical climates. Meteorological data from the Karso watershed in India (consisting of 3801 daily records from the year 2000 to 2010) were used to develop and test the models for daily pan evaporation estimation. The measured meteorological variables include daily observations of rainfall, minimum and maximum air temperatures, minimum and maximum humidity, and sunshine hours. Prior to model development, the Gamma Test (GT) was used to derive estimates of the noise variance for each input–output set in order to identify the most useful predictors for use in the machine learning approaches used in this study. The ANN models consisted of feed forward backpropagation (FFBP) models with Bayesian Regularization (BR), along with the Levenberg–Marquardt (LM) algorithm. A comparison was made between the estimates provided by the ANN, LS-SVR, Fuzzy Logic, and ANFIS models. The empirical Hargreaves and Samani method (HGS), as well as the Stephens–Stewart (SS) method, were also considered for comparison with the newer machine learning methods. The Root Mean Square Error (RMSE) and Correlation Coefficient (CORR) were the statistical performance indices that were used to evaluate the accuracy of the various models. Based on the comparison, it was found that the Fuzzy Logic and LS-SVR approaches can be employed successfully in modeling the daily evaporation process from the available climatic data. In addition, results showed that the machine learning models outperform the traditional HGS and SS empirical methods.