Intra-day Variations Research Articles

Fine-grained simulation model for PV power output interval based on two-stage scenario clustering and dual-ensemble compatible learning

Photovoltaic (PV) power simulation is indispensable for the planning and operation of renewable-rich power systems. Among various simulation methods, data-driven indirect simulation methods are the most efficient, primarily involving scenario extraction and power output generation. Typical scenario extraction methods often feature coarse characterizations, which also cannot be expressed by traditional power output generation models lacking the ability of quantifying the uncertainty of the output results. This paper proposes a fine-grained simulation model for PV power output interval, i.e., upper bound and lower bound, based on two-stage clustering of multiple typical scenarios and dual-ensemble compatible learning. The first stage of scenario extraction, considering the impact of total daily irradiance on PV output, employs a line distance index for preliminary scenario division of daily PV output. These scenarios are further divided into five characteristic scenarios with an angular distance index considering the impact of intra-day irradiance variations on power output. PV power output interval is generated from dual-ensemble compatible learning including Stacking and Bagging, which are adaptively selected with a Bias-Variance Selection Index (BS) calculated using the value of scenario characteristics. Stacking and Bagging are driven by three neural network base learners with Bayesian layers, which can output the lower bound and upper bound with confidence at a certain level, thus quantifying the uncertainty of the result accurately. The actual data of Daxing and Gangjialing power stations are used in case study. Results form case study show that compared with the existing methods, the proposed method can improve the Power Coverage Rate (PCR) and Average Power Simulation Accuracy (APA) of uncertainty simulation results by 27.44% and 5.39%, respectively. Meanwhile, the Average Daily Maximum Power Simulation Accuracy (AMPA) is similar to that of existing methods.

Skin tissue dielectric constant: Time of day and skin depth dependence.

Skin water measurements are used to investigate skin physiology, clinically study dermatological issues, and for conditions like diabetes, oedema, and lymphedema with measurements done at various times of day (TOD). One method used is skin's tissue dielectric constant (TDC), often clinically measured to a single depth of 2.5 mm. This report characterizes intraday variations measured to multiple depths to guide expected TOD and depth dependence. Twelve medical students self-measured TDC on their forearm to depths of 0.5, 1.5, 2.5, and 5.0 mm every 2 h from 08:00 to 24:00 h on 2 consecutive days. All were trained in the procedure. TDC declined slightly from morning through evening, mostly at 0.5 mm for which TDC was reduced by 4%. TDC values were not related to participants' whole-body fat or water percentages. The TDC decrease was less at 1.5 mm where the reduction was 2.7%. At depths of 2.5 or 5.0 mm, there was no significant decrease in TOD. Skin TDC shows a minor decreasing trend with an effect greater for shallower depths. In part, the clinical relevance of the findings relates to the confidence level associated with skin water estimates, based on TDC measurements, when measured at different TOD and depths during normal clinic hours. Based on the present data the TOD change is at most 4% and insignificant for measurement depths of 2.5 mm.

Mapping and assessment of harmonic voltage levels for railway traction supply stations in Sweden

Assessing harmonic distortion measurements in the electric railway power systems (ERPS) requires evaluating the time-varying behavior, interactions, and performance in different time scales. This paper aims to map and assess harmonic voltage levels in 13 traction converter stations for the Swedish railway power supply system, with findings that have direct practical implications. For that, measurements from the public and railway grid sides for 69 weeks are analyzed. Statistical values are explored for the harmonic voltage spectra and total harmonic distortion (THD) variation. The public grid side measurements are investigated using 95th percentile weekly values, and performance is evaluated by comparing the recommended planning levels of IEC 61,000–3–6. The intraweek variation complements the information about the time-varying behavior of the THD. The 95th percentile, minimum daily values, and intraday variation are explored to understand the time-based behavior since there are no reference limits from standards for comparison, looking to the railway grid side. Extended analysis is placed on the railway grid side to highlight some aspects of measurement time-aggregation based on 10-min values, and time-series trend analysis is used to confirm traffic planning impact. Discussion and findings regarding railway operation, the technology deployed at the traction converter station, time-varying behavior, traffic planning impact, measurement time-aggregation, and spectra patterns were presented.

A novel sustainable and ecofriendly UV-Spectrophotometric method for the determination of Naringenin in bulk and vaginal niosomal nanoformulation

Naringenin, a flavonoid found in several fruits like oranges, grapefruit, and bergamot, exhibits a wide range of biological effects. These include antidiabetic, antidepressant, antiatherogenic, antitumor, immunomodulatory, anti-inflammatory, hypolipidemic, antioxidant, peroxisome proliferator-activated receptors (PPARs) activation, hepatoprotective properties, memory enhancement and DNA protective properties. The aim of this current study is to develop a simple and precise UV spectrophotometric technique for measuring Naringenin Active Pharmaceutical Ingredient (API) in bulk and vaginal niosomal nanoformulation using PBS (Phosphate buffer solution) pH 4.5. The absorption peak of Naringenin was identified at 287 nm, and it adhered to Beer's law within the concentration range of 2 to 14 µg/ml. The calibration curve demonstrates a linear relationship between absorbance and concentration within the range of 2 to 14 µg/ml. The determined limit of detection and limit of quantification were found to be 0.587672µg/mL and 1.780824µg/mL, respectively. The validity of the method was assessed for repeatability, accuracy and precision. The results obtained indicated minimal intraday and interday variation. The excipients in the nanoformulation did not interfere the analysis. The developed analytical UV spectrophotometric method is simple, rapid and consistent, making it suitable for estimating the drug in both bulk and nanoformulation.

Interpretation of TSH results can be improved by reference values fluctuating in time.

The secretion of thyroid stimulating hormone (thyrotropin, TSH), is characterized by a marked circadian rhythm. Plasma or serum TSH values are significantly lower in the afternoon and in the evening as compared to the early morning. As in clinical practice, blood sampling time shows an important variation, a reliable assessment of thyroid status is often not an easy task for the clinician. The biological variation of TSH plays a major role in the intra-individual variability of TSH results in serum or plasma. The observed intra-day variation largely exceeds the reported inter-vendor variation and the coefficient of variation of clinical TSH assays. Therefore, a mathematical solution was sought for correcting interpretation of TSH results for sampling time. We have developed a cosinor model which allows to compensate TSH decision values for the fluctuating serum or plasma TSH concentrations throughout the day. The following mathematical function could be derived: corrected TSH cutoff_value (mIU/L)=0.40+0.24*cos(((π/12) *T)+6) in which T represents the time (hours). This mathematical function can be easily implemented into a laboratory's informatics system and furthermore allows a better tailored diagnosis of (subclinical) hyperthyroidism, regardless the blood sampling time. Implementing the corrected cut-off values result in a marked reduction of apparent (false positive) hyperthyroidism diagnosis, in particular in the afternoon.

Evaluating GreenFeed and respiration chambers for daily and intraday measurements of enteric gaseous exchange in dairy cows housed in tiestalls

The objective of this study was to evaluate the GreenFeed (GF) and respiration chambers (RC) for daily and intraday measurements of the enteric gaseous exchange, as well as the metabolic heat production, lying behavior, and feed intake (FI) rate of dairy cows at these 2 respective housing conditions [tie-stall barn (TS) vs. RC] during the summer periods. Sixteen multiparous lactating dairy cows were recruited and arranged in a randomized complete block design with a baseline period established for each cow. Cows were given a basal diet (CON) for a baseline period of 7 d and were then fed a 3-nitrooxypropanol (3-NOP)-containing feed for the subsequent 26 d as experimental period. During both the baseline and the last 7 d of treatment period, gaseous exchanges of each animal were measured in the TS using GF for 8 6-hourly staggered measurements over 3 d, immediately followed by the measurement in RC for 2 d. Corresponding DMI, milk yield, and behavior parameters (e.g., lying behavior and FI rate) in TS and RC were recorded. The correlation coefficients of CH4 and H2 using raw data were 0.84 and 0.85, respectively. For all gases, correlation coefficients between GF and RC on individual cow level decreased when the marginal fixed effects (e.g., inhibitor and breed) were corrected by a mixed model. There were no differences in daily CH4 production or intensity between GF and RC (442 vs. 443 g CH4/d or 16.6 vs. 16.2 g CH4 /kg MY). However, greater CH4 yield was measured by GF than RC (19.0 vs. 17.8 g CH4/kg DMI), driven by a lower DMI (23.3 vs. 24.6 kg/d) when cows were housed in TS sampled by GF compared with cows being housed and sampled in RC. The correlations for CO2 production and O2 consumption were moderate and expected due to the variation associated with the mild heat stress condition during GF measurements in the TS (Thermal humidity index (THI) 56 vs. 68), as indicated by the reduced lying time (-2.1 h/d). At the intraday level, there was an interaction between techniques and hour-of-day for CH4 production, as indicated by the discrepancies in post-prandial CH4 emissions between techniques. In summary, this set of results showed that there were strong positive correlations for CH4 and H2 emissions between GF and RC based on individual cow data. However, such relationship should be interpreted with caution, given the data clustering resulting from the use of inhibitor 3-NOP. On treatment level, these 2 techniques detected similar inhibitor effect on the estimated daily CH4 emissions. The intraday patterns of CH4 and H2 production captured by GF provided a close approximation for those measured by RC. Nevertheless, potential underestimation may occur, especially following fresh feed delivery. For measuring CO2 production and O2 consumption, the GF captured similar intraday variations to those in the RC. However, the estimated daily production and consumption were not directly comparable, which was expected due to the variable thermal conditions during the summer. Further evaluations under the same weather conditions are warranted.

Development and validation of a bioanalytical method using LC-MS/MS to quantify Zanamivir in human plasma.

This study presents the development and validation of a highly sensitive and accurate LC-MS/MS method for the quantification of Zanamivir in human plasma. Utilizing a mobile phase of MeOH and Ammonium Formate (30:70 v/v) and a protein precipitation extraction technique, the method achieves excellent specificity and reproducibility. The calibration curve demonstrated linearity from 4-80 ng/ml with a correlation coefficient (r²) ≥ 0.9994. The method adheres to FDA guidelines, exhibiting high precision and accuracy with intra-day and inter-day variations of 0.81-1.98%. The developed method, requiring a minimal sample volume and a short run time, ensures robustness and stability across various analytical conditions, making it an ideal tool for Zanamivir plasma concentration studies.

Intraday Variations in Skin Water Parameters

Introduction: Three interrelated skin water assessments include stratum corneum hydration (SCH) via electrical measurements, skin water using tissue dielectric constant (TDC) measurements, and transepidermal water loss (TEWL). These are differentially used for skin physiology research, clinical assessments of dermatological conditions and to assess skin water in diabetes and lymphedema. Often volar forearm skin is used for assessments done at various times of day (TOD). The present goal was to assess the extent of intraday variability in SCH, TDC, and TEWL. Methods: Twelve medical students self-measured SCH, TDC, and TEWL on their forearm every 2 h from 08:00 to 24:00 h on 2 consecutive days. All participants were well trained and pre-certified in all procedures. Tests for parameter differences among TOD were via the nonparametric Friedman test. Results: No significant differences in SCH or TEWL were found among TOD over the 16-h interval for either day or combined. Contrastingly, TDC decreased slightly but significantly from morning through evening. There was no evidence of a diurnal pattern. Interestingly, a significant nonlinear relationship between TEWL and SCH was detected. Conclusion: Findings indicate only minor intraday variations with TOD trend except for TDC which decreases slightly from morning through evening. The clinical relevance relates to the confidence now gained associated with the parameter estimates when measured at different TOD during normal clinic hours or beyond. This should help in estimating the potential importance of small differences if measured at a different TOD. From a physiological viewpoint, the findings uncover and describe an interesting nonlinear relationship between TEWL and SCH which may serve to propel further investigations that might better characterize this process.

Investigating Optical Variability of the Blazar S5 0716+714 on Diverse Timescales

We present the results of the observational study of the blazar S5 0716+716 in the optical bands B, V, R, and I between 2019 March and 2023 August to investigate its variability on diverse timescales. The blazar was followed up by the T60 robotic telescope in Türkiye for 416 nights to obtain long-term variability during this period. In order to search for the intraday variability of the object, we have carried out 21 nights of observations with the T100 telescope for at least 1 hr. The blazar showed a ∼2.47 mag variation in the optical R band during our monitoring period, the brightest state on 2020 January 18 (MJD 58866) as R = 12.109 ± 0.011 mag and the faintest state on 2019 March 23 (MJD 58565) as R = 14.580 ± 0.013 mag. We employed the nested ANOVA test and the power-enhanced F-test to quantify intraday variability, which showed that the blazar was significantly variable in the R band on 12 out of 21 nights. Correlation analysis of the light curves shows that the emission in the BVRI optical bands was strongly correlated both in the short and long term without any time lag. The blazar has likely quasiperiods of 186 ± 30 and 532 ± 76 days in the optical R-band light curve according to the weighted wavelet Z-transform and Lomb–Scargle periodogram. The intraday variation and long-term variation features are discussed within the frame of prospective scenarios.

Intraday Variation of Ankle Dorsiflexion in Short-Track Speed Skaters.

Optimal ankle dorsiflexion range of motion plays a vital role in attaining the essential crouched posture necessary for excelling in speed skating. The purpose of this study was to determine how the ankle dorsiflexion angle evolves throughout a day of training and to identify the factors that influence this angle. Thirty short-track speed skaters, from 2 teams, participated in this study. The maximum ankle dorsiflexion angle was obtained in a lunge position facing a wall, using a digital inclinometer. All measures were obtained 3 times per side, 6 times per day, on 2 training days separated by at least a week. We conducted multiple tests to study the impact of repetition, day, side, team level, sex, and moment on the ankle dorsiflexion angle. The 3 times repeated measures and the 2days of training did not have a significant influence on the results. There was a statistically significant difference between the first time point of the day and the 5 other time points for both ankles. Moreover, the influence of sex and team level was not statistically significant. The results indicate that there are significant changes in ankle dorsiflexion range of motion but only after the first warm-up of the day. Such findings could enable team staff to enhance athletes' precompetition preparation and tailor ankle mobility training regimens more effectively.

Assessment of Intraday Variations in Skin Indentation Resistance.

Information about the mechanical properties of skin and their changes with age and other conditions is important to help characterize skin physiology and pathological changes. One method to obtain this information is to measure the force required to indent the skin to a specified indentation depth (FORCE). This process measures the tissue's resistance to indentation or its compressibility and is related to the tissue's elastic modulus. Since such measurements are made in clinical and other settings at various times of day (TOD), it is useful to estimate the extent of intraday variations in FORCE that may be expected. This report focuses on this issue. FORCE was self-measured on the volar forearm, 5 cm distal to the antecubital fossa, every two hours from 08:00 to 24:00 hours on two consecutive days by 12 medical students (six females and six males) who were trained in the measurement process using an indentation device (SkinFibroMeter). Variability in FORCE versus TOD was analyzed using the nonparametric Friedman test and differences between genders by the nonparametric Wilcoxon test. Differences between the first day (day 1) and the second day (day 2) were tested at each TOD. The whole-body fat percentage (FAT%) and water percentage (H2O%) were determined for each participant via bioimpedance measurements at 50 KHz. The age and BMI of the combined group (mean ± SD) were 24.5 ± 1.5 years and 23.2 ± 3.3 kg/m2.The overall average FORCE (mean ± SD) for the day over the 16 hours was 84.1 ± 22.7 mN and for day 2, it was 83.4 ± 28.5 mN with no significant difference between day 1 and day 2. For females, the overall two-day average FORCE (mean ± SD) over the 16 hours was 81.8 ± 20.3 mN and for males, it was 85.7 ± 30.1 mN with no significant difference between them (p = 0.271). Overall, there was no statistically significant difference in FORCE among TOD (p = 0.568). FORCE was not correlated with either FAT%, HTO%, or BMI. The findings indicate no statistically significant variation in indentation force in females, males, or combined concerning the TODof the measurement or differences between consecutive days at corresponding times. This suggests that whether such measurements are done in a research setting or within a clinic, they can be done at various TODwith minimal expected variation for a given subject. However, an extension of these findings to persons with skin conditions or ages not herein evaluated must await further study.

P-572 Circadian serum progesterone variations on the day of frozen embryo transfer in a modified natural cycle protocol

Abstract Study question Does a circadian variation of serum progesterone (P) on the frozen embryo transfer (FET) day in a modified natural cycle (mNC) exist? Summary answer A statistically significant diurnal variation of serum P on the day of a FET in a mNC protocol exists. What is known already In recent years, the proportion of FET cycles has increased dramatically. To further optimize pregnancy outcomes after FET, recent studies have focused on serum luteal P levels in both natural and artificially prepared FET cycles. Despite the different cut-off values proposed to define low serum P in the natural cycle, it is generally accepted that lower serum P values (<10ng/ml) around the day of FET are associated with negative reproductive outcomes. However, a single serum P measurement on the day of FET is not reliable given that P levels are prone to diurnal fluctuations and are impacted by patients’ characteristics. Study design, size, duration A prospective cohort study was conducted in a single fertility center including 22 patients performing a single blastocyst mNC-FET from August 2022 to August 2023.Serum P levels were measured on the day of transfer at 08:00h,12:00h,16:00h and 20:00h.Differences between P levels were compared using the Wilcoxon signed-rank test.The sample size was calculated to detect a difference of 15% between the first and last P measurements with a 5% false-positive rate and a 95% confidence interval. Participants/materials, setting, methods Patients with a normal BMI, between 18 and 40 years old, without uterine diseases were eligible. Patients utilizing donated oocytes were excluded. The mNC-FET protocol implied monitoring the normal ovarian cycle and triggering ovulation with an injection of 250 mcg of choriogonadotropin alfa when a pre-ovulatory follicle (16-20 mm diameter)was visualized. The blastocyst was transferred seven days later. The patients were not supplemented with exogenous P at any moment before the day of the FET. Main results and the role of chance The mean age and BMI of the study population were 33.6 ± 3.8 years and 22.7 ± 1.8 kg/m2, respectively. Mean P values at 08:00h,12:00h,16:00h, and 20:00h were 14.6 ± 4.5ng/ml, 14.7 ± 4.1ng/ml, 12.9 ± 3.5ng/ml, and 14.6 ± 4.3ng/ml, respectively. The mean P levels at 16:00h were statistically significantly lower compared to all other time points (p < 0.05:p= 0.007 between P at 8:00h and 16:00h;p = 0.003 between P at 12:00h and 16:00h;p=0.007 between P at 16:00h and 20:00h). Absence of a statistically significant fluctuation was observed between P values at the other time points (p = 0.88 between P at 8:00h and 12:00h;p=0.96 between P at 8:00h and 20:00h;p=0.83 between P at 12:00h and 20:00h). This study confirms the existence of an intra-day variation of serum P on the day of mNC-FET, with lower values at 16:00h. This highlights the importance of standardizing P measurement on the day of FET; we propose this should always be assessed in the morning to be more reliable and to allow the time to prescribe additional exogenous progesterone if lower P values (<10ng/ml) are detected. This standardization would allow fertility clinics around the world to compare their results and develop internationally recognized treatment protocols. Limitations, reasons for caution The study’s main limitation include the small sample size that may cause a bias when results are extrapolated to a larger subfertile population undergoing mNC-FET. Ideally, larger prospective trials including a more heterogeneous patient population would be necessary to validate our findings. Wider implications of the findings This study demonstrates the existence of a diurnal fluctuation of serum P on the mNC-FET day highlighting the importance of a standardized time point for its measurement.This is important when clinical actions, like additional exogenous P supplementation, are considered when encountering P values lower than 10ng/ml on the FET day. Trial registration number NCT05511272

Intra-day variations in volar forearm skin hydration.

Skin hydration (SKH) measurements are used for multiple purposes: to study skin physiology, to clinically investigate dermatological issues, and to assess localized skin water in pathologies like diabetes and lymphedema. Often the volar forearm is measured at various times of day (TOD). This report aims to characterize intra-day variations in volar forearm SKH to provide guidance on expected TOD dependence. Forty medical students (20 male) self-measured tissue dielectric constant (TDC) on their non-dominant forearm in triplicate as an index of local skin tissue water every 2 h starting at 0800 and ending at 2400h. All were trained and pre-certified in the procedure and had whole-body fat (FAT%) and water (H2O%) measured. Day average TDC (TDCAVG) was determined as the average of all time points expressed as mean±SD. Males versus females had similar ages (25.1±2.2 yearsvs. 25.1±1.5 years), higher H2O% (56.6±5.0vs. 51.8±5.7, p=0.002), and higher TDCAVG (32.7±4.1vs. 28.5±5.1, p=0.008). TDC values were not significantly impacted by H2O% or FAT%. Female TDC exhibited a significant decreasing trend from morning to night (p=0.004); male TDC showed no trend. Skin water assessed by TDC shows some intra-day variations for females and males but with quite different temporal patterns. Clinical relevance relates to the confidence level associated with skin hydration estimates when measured at different times of day during normal clinic hours which, based on the present data, is expected to be around 5% for both males and females.

A novel ultra-performance liquid chromatography detection method development and validation for paclitaxel and its major metabolite in human plasma.

Paclitaxel is a promising anticancer drug for patients with ovarian, breast, lung, gastrointestinal, genitourinary, prostate, and head-and-neck cancers. Paclitaxel follows nonlinear pharmacokinetics. The major metabolite of paclitaxel is 6-alpha-hydroxy paclitaxel, mediated by CYP2C8, while metabolism to two of its minor metabolites, 3'-p-hydroxypaclitaxel and 6a, 3'- p-dihydroxypaclitaxel, is catalyzed by CYP3A4. Therapeutic drug monitoring of paclitaxel could be a promising approach to improve the efficacy and safety of paclitaxel correct personalized doses and improve the overall benefit-risk ratio. A novel and highly sensitive chromatographic method for the detection of paclitaxel and its metabolite has been proposed that allows quantification in human plasma with 100% accuracy in terms of recovery without significant intraday or interday variations. The present study was planned following bioanalytical method validation guidance according to the U.S. Food and Drug Administration requirements. The validation of the analytical procedure was performed as per ICH Q2(R1) guidelines. It was done to assure the reliability of the results obtained for various parameters such as linearity, accuracy, precision, limit of detection (LOD), limit of quantification, robustness, stability, and system suitability. The specificity of the method was established by ensuring no interference with peak obtained from paclitaxel and 6-alpha-hydroxy paclitaxel. LOD was found to be 0.05 and 0.033 while the limit of quantitation was 0.14 and 0.099 for paclitaxel and 6-alpha-hydroxy paclitaxel, respectively. Median (±interquartile range) accuracy for paclitaxel and 6-alpha-hydroxy paclitaxel was found to be 102.73 (±13.581) and 100.87 (±7.573), respectively. This novel method of simultaneous detection of paclitaxel and its major metabolite 6-alpha-hydroxy paclitaxel demonstrated significant resolution and was sensitive enough for its quantification in human plasma.

An improved global Tm stratification model for GNSS-PWV retrieval

The atmospheric weighted mean temperature (Tm) is a key parameter for converting tropospheric wet delay (ZWD) into precipitable water vapor (PWV) and plays a vital role in Global Navigation Satellite System (GNSS) meteorology. Existing Tm models suffer from limitations such as the lack of consideration of full periodicity, poor accuracy at high altitudes, and the adoption of single-resolution grid data for modeling. Hence, an improved global Tm stratification model is developed based on ERA5 hourly reanalysis data from 2015 to 2019, called IGTmS, which takes seasonal and intraday variations into consideration and adopts a stratification mode to improve the vertical accuracy of Tm estimation. The accuracy and applicability of the IGTmS model are evaluated using Tm data at 417 radiosonde stations in 2020. The results show that the mean bias and RMS of Tm for the IGTmS model are −0.34 K and 3.53 K, and the accuracy is improved by approximately 7.8 %, 4.6 % and 2.5 % compared with that of GPT3, GTm-III and GTrop models on a global scale, respectively. IGTmS model can achieve the mean σPWV and σPWV/PWV values of 0.38 mm and 1.3 %, respectively, which shows optimal performance among the four models, especially in the Antarctic and Tibetan Plateau regions. Furthermore, three resolutions of the IGTmS models have been developed and all show high accuracy compared to GPT3 models. Users can choose the suitable model according to the desired accuracy and resolution. The developed stratification model IGTmS can effectively weaken the influence of large height difference on Tm estimation and can obtain high-accuracy and stable Tm over the globe and provide data support for real-time GNSS PWV retrieval.

Adaptive Design of Solar-Powered Energy Systems Based on Daily Clearness State Evolution

The optimal designing of the hybrid energy system (HES) is a challenging task due to the multiple objectives and various uncertainties. Especially for HES, primarily powered by solar energy, the reference solar radiation data directly impact the result of the optimization design. To incorporate the stochastic characteristics of solar radiation into the sizing process, a data-driven stochastic modeling method for solar radiation is proposed. The method involves two layers of stochastic processes that capture the intraday variation and daily evolution of solar radiation. First, the clearness index (CI) is introduced to describe the radiation intensity at different times. Then, the daily clearness state (DCS) is proposed, based on the statistical indicators of the intraday CI. The Markov model is used to describe the stochastic evolutionary characteristics between different DCSs. The probabilistic distribution of the CI under different DCS is obtained based on the diffusion kernel density estimation (DKDE), which is used for the stochastic generation of the CI at various times of the day. Finally, the radiation profile required for the optimal design is obtained by the stochastic generation of the DCS sequences and the intraday clearness index under corresponding states. A case study of an off-grid solar-powered HES is provided to illustrate this methodology.

Comparison of ELSD and RID combined with HPLC for simultaneous determination of six rare sugars in food components

Evaporative light scattering detection (ELSD) and refractive index detection (RID) are two methods commonly used in high-performance liquid chromatography (HPLC) to quantitatively analyze sugars. The performance of two detectors for the detection and quantification of six rare sugars in food samples is systematically compared in this paper. Erythritol, allulose, tagatose, mannitol, isomaltulose and trehalose were separated by HPLC on an NH2 chromatographic column using a flow gradient or isocratic composition acetonitrile–water (80:20, v/v) as mobile phase. The analytical signals for six rare sugars were obtained using ELSD and RID. The intra-day and inter-day variations were lower 3.9 % and 3.5 % for ELSD and 2.4 % and 3.6 % for RID, respectively. The limits of detection (LODs) were between 0.02 mg·mL−1 and 0.06 mg·mL−1 for ELSD in the range of 0.06–0.6 mg·mL−1. The LODs of RID were between 0.1 mg·mL−1 and 1.0 mg·mL−1 within a wider dynamic range (0.4–80 mg·mL−1). The optimized method was used to analyze seven samples. Although both methods can be used for the detection of six rare sugars, the selectivity of isomaltulose and the detection results of six rare sugars under the HPLC-RID method are not as good as the HPLC-ELSD method. Therefore, the HPLC-ELSD method is more suitable for the detection of six rare sugars in food.

Development of a Simultaneous Normal-Phase HPLC Analysis of Lignans, Tocopherols, Phytosterols, and Squalene in Sesame Oil Samples.

The objective of this study was to develop a simultaneous analytical method for the determination of lignans, tocols, phytosterols, and squalene using high-performance liquid chromatography coupled with a diode array and fluorescence detector (HPLC-DAD-FLD). The method employed a VertisepTM UPS silica HPLC column (4.6 × 250 mm, 5 µm) with a mobile phase mixture of n-hexane/tetrahydrofuran/2-propanol. This approach enabled the simultaneous analysis of ten compounds within 22 min. The linear correlation (R2) exceeded 0.9901. The limit of detection (LOD) and limit of quantitation (LOQ) were up to 0.43 µg mL-1 for lignans and tocopherols and up to 326.23 µg mL-1 for phytosterol and squalene. The precision and accuracy of the intra-day and inter-day variation were less than 1.09 and 3.32% relative standard deviations (RSDs). Furthermore, the developed method was applied for the analysis of targeted compounds in twenty-eight sesame oil samples (1775-8965 µg g-1 total lignans, 29.7-687.9 µg g-1 total tocopherols, 2640-9500 µg g-1 phytosterol, and 245-4030 µg g-1 squalene). The HPLC method that has been developed was proven to be a reliable and effective tool for the determination of those functional compounds among sesame oil samples.

QbD Assisted Development and Validation of UV Spectroscopic Method in Estimation of Silymarin

Background: Silymarin is a flavonoid utilised in liver dysfunction for years; new studies have emphasised its potential utility as a therapy for nanoparticulate targeting in many other disorders. In order to establish the product quality of such compounds, researchers have been trying to develop a robust method of analysis, but the methods developed till now are too expensive and time-consuming. Here we proposed quality by design-assisted development and validation of the UV spectroscopic method using Design-Expert® software in the estimation of Silymarin for fabrication of nanoparticulate formulations, which is simple, accurate, cost-effective and non-tedious. Aim: The proposed method is a simple, new, robust, accurate, and precise UV visible spectroscopic technique for estimating silymarin produced in nano-formulations utilising an analytical quality by design (AQbD) approach. Methods: A UV spectrophotometric technique was established, as maximum absorption (287.7) was measured using a Shimadzu UV-1800 double-beam UV visible spectrophotometer. The characterization of silymarin was done by melting point, DSC and FTIR techniques. The two critical method variables chosen were scanning speed and sample interval to be analysed by the design of experiment methodology utilizing the central composite design principle, which shows robustness and optimized technique involved in this work. Results: The spectroscopy technique was developed and validated as per International Conference of Harmonization recommendations. The Beer's-Lambert rule was followed in a series of 2-12 μg/ml dilution increments, with a correlation value of R2 = 0.999. The method's linearity was shown to be excellent across the concentration range. The percent recovery of the current method approach was determined to be within the confidential limitations, i.e., less than 2% expressed as % RSD, and the methodology was proved to be precise at inter and intraday variations (% RSD). The LOD and LOQ were found to be 0.264 μg/ml and 0.801 μg/ml which were also determined correctly. During specificity testing, no interfering peaks were found. Conclusion: This UV approach has been used successfully to determine the quantity of silymarin present in the nanoparticulate formulation, which can be used for testing its other pharmaceutical dosage forms.

Intraday variation in trading costs: Evidence from the TSPP

AbstractWe examine changes in the intraday pattern of trading costs between pilot and control stocks during the US Securities and Exchange Commission tick size pilot program (TSPP). We find that intraday trading costs are relatively unchanged between pilot and control stocks in pre‐ and post‐TSPP periods. We find that differences in trading costs between pilot and control stocks during the TSPP are lower in the morning and greater toward the close. We also find that intraday differences in quoted depth between pilot and control stocks during the TSPP is lower at the beginning of the day, increases during the day, and falls toward the close of trading.