Intra-day Variations Research Articles

Recalcitrant betas: Intraday variation in the cross‐sectional dispersion of systematic risk

We study the temporal behavior of the cross‐sectional distribution of assets' market exposure, or betas, using a large panel of high‐frequency returns. The asymptotic setup has the sampling frequency of returns increasing to infinity, while the time span of the data remains fixed, and the cross‐sectional dimension of the panel is either fixed or increasing. We derive functional limit results for the cross‐sectional distribution of betas evolving over time. We demonstrate, for constituents of the S&P 500 market index, that the dispersion in betas is elevated at the market open and gradually declines over the trading day. This intraday pattern varies significantly over time and reacts to information shocks such as clustered earning announcements and releases of macroeconomic news. We find that earnings news increase beta dispersion while FOMC announcements have the opposite effect on market betas.

Gas chromatography–mass spectrometry for quantitative and qualitative analysis of essential oil from Curcuma wenyujin rhizomes

Objectives: A rapid and sensitive gas chromatography–mass spectrometry (GC–MS) method for quantitative and qualitative analysis of essential oil from Curcuma wenyujin rhizomes was established. Methods: The essential oil of C. wenyujin rhizomes was extracted by supercritical CO2 extraction (SFE). Six main bioactive compounds (eucalyptol, β-elemene, curzerene, germacrone, curdione, and curcumol) were analyzed in selected ion monitoring mode (SIM). Results: Curzerene is not originally present in C. wenyujin rhizomes, but is a product of the transformation of furanodiene at high temperature. The six target components demonstrated good linearity (R2 > 0.9979) over a relatively wide concentration range. The interday and intraday variations had relative standard deviation values less than 5% and the average recovery ranged from 96.95% to 100.04%. The limit of quantitation ranged from 0.032 to 0.235 μg/mL. The developed method was successfully used to analyze the six compounds in 17 samples collected from different origins. Significant variation was observed for the concentrations of the six compounds. In addition, 51 constituents were identified in C. wenyujin rhizome essential oil, consisting of 87.66% of the total essential oil, including curdione, curzerene, dehydrocurdione, germacrone, 1,4-bis(2-benzimidazoyl)benzene, neocurdione, curcumenone, and β-elemene. Conclusions: The proposed method will be useful in the quality control of C. wenyujin rhizome essential oil production.

Intraday Herding and Attention Around the Clock

This paper analyzes return herding at the intraday level in the decentralized cryptocurrency market with its continuous, around the clock trading and dominance of retail investors. We first document substantial herding behavior that is stronger when market returns are positive. Herding is negatively related to both the level and cross-sectional dispersion of investor attention. Moreover, there are pronounced intraday variations: Market return herding exhibits similar patterns as attention and blockchain activity and is strongest during the overlap of hours when traders in major economic centers are likely awake.

Assessing the Intraday Variation of the Spillover Effect of Tweets-Derived Ambient Population on Crime

The spatial pattern of geotagged tweets reflects the dynamic distribution of the ambient population during day and night as a result of people’s routine activities. A few studies have assessed the impact of tweets-derived ambient population on crime and the spillover effect of such impact at different spatial and temporal scales. However, none has revealed the intraday variation of such spillover effect. This study analyzes both the direct and spillover effects of tweets-derived ambient population on crime and its intraday difference in day and night during weekdays and weekends. Four crime types, including assault, burglary, robbery, and theft, are examined at the neighborhood level. The analysis is based on negative binomial regression models, with the control of necessary socioeconomic and land-use variables driven by criminology theories. Results show (1) tweets-derived ambient population affects the magnitude of crime, but this effect varies by types of crime at different time periods of the day and week, and (2) the spillover effect of the tweets-derived ambient population exists for all four types of crime during most of the time periods at the neighborhood level and is particularly pronounced for thefts at all time periods. Similar results are seen in the block-level analysis. This study further confirms the utility of the count of geotagged tweets as a measure of the ambient population and its spatial lag for intraday analyses of crime, particularly theft.

Evaluation of variation of saliva iodine and recommendations for sample size and sampling time: Implications for assessing iodine nutritional status

Saliva iodine concentration (SIC) has been found to be a good indicator of iodine nutritional status. However, limited informationis available regarding saliva iodine characteristics. The study aimed to evaluate intra-day, intra-individual, and population SIC variation in order to provide information on optimal sample size and sampling time for assessing iodine nutritional status. Twenty-nine healthy school-aged students were recruited. Iodine intake from diet and water, and iodine excretion through urine and feces were assessed over a three-day period. Saliva samples were collected six times a day. Diurnal variations were observed in SIC corresponding to iodine intake. The mean CV in SIC was lower than that for 24-hour urinary iodine concentration (24-h UIC) and 24-hour urinary iodine excretion (24-h UIE) not only at the individual level (42.73% vs. 47.71% and 49.69%) but also at the population level (71.29% vs. 100.43% and 72.49%). The number of saliva samples needed to estimate the iodine level with 95% CI within precision ranges of ±10%, ±20% was 55, 14 in an individual, and 180, 45 in a population. There was a good correlation between post-lunch SIC and total daily iodine intake. Saliva iodine has utility for evaluating the recent iodine nutrition of individuals and populations. The variation in SIC was lower than that for 24-h UIC and 24-h UIE. Saliva may be preferred over urine because of its ease of collection. Fourteen samples are needed to assess individual iodine status and forty-five saliva samples for assessment of population iodine status with reasonable precision. We recommend that saliva samples be collected after 14:00 in a day.

Effects of demand control on the complex dynamics of electric power system blackouts.

The propagation of failures and blackouts in electric networks is a complex problem. Typical models, such as the ORNL-PSerc-Alaska (OPA), are based on a combination of fast and slow dynamics. The first describes the cascading failures while the second describes the grid evolution through line and generation upgrades as well as demand growth, all taking place in time scales from days to years. The growing integration of renewable energy sources, whose power fluctuates in time scales from seconds to hours, together with the increase in demand, which also presents fast fluctuations, requires the incorporation of distributed methods of control in the demand side to avoid the high cost of ordinary control in conventional power plants. In this work, we extend the OPA model to include fluctuations in the demand at time scales of the order of minutes, intraday demand variations, and the effect of demand control. We find that demand control effectively reduces the number of blackouts without increasing the probability of large-scale events.

Spatiotemporal Evaluation of PM10 Concentrations within the Greater Athens Area, Greece. Trends, Variability and Analysis of a 19 Years Data Series

This work investigates the spatiotemporal variation of suspended particles with aerodynamic diameter less than or equal to 10 μm (PM10) during a nineteen years period. Mean daily PM10 concentrations between 2001 and 2018, from five monitoring stations within the greater Athens area (GAA) are used. The aim is to investigate the impact of the economic crisis and the actions taken by the Greek state over the past decade on the distribution of PM10 within the GAA. Seasonality, intraweek, intraday and spatial variations of the PM10 concentrations as well as trends of data, are statistically studied. The work may assist the formation of PM10 forecasting models of hourly, daily, weekly, monthly and annual horizon. Innovations are alternative ways of statistical treatment and the extended period of data, which, importantly, includes major economic and social events for the GAA. Significant decreasing trend in PM10 series concentrations at all examined stations were found. This may be due to economic and social reasons but also due to measures taken by the state so as to be harmonised with the European Directives concerning the protection of public health and the atmospheric environment of the European Union (EU) members.

A multi-frequency and multi-GNSS method for the retrieval of the ionospheric TEC and intraday variability of receiver DCBs

As one of the important factors influencing the ionospheric total electron content (TEC) estimation accuracy, receiver differential code biases (DCBs) should be properly removed from global navigation satellite system (GNSS) measurements. The intraday variability in receiver DCBs (rDCBs), which is usually ignored in the commonly used ionospheric observable retrieval procedure, has been identified as one of the major errors degrading the accuracy of TEC estimation. The modified carrier-to-code leveling (MCCL) method can be adopted to eliminate the impact of the rDCB variability on the retrieval of the ionospheric TEC from dual-frequency (DF) GNSS observations. In this contribution, we extend the MCCL method from two aspects. First, the DF MCCL method is adapted to the multi-frequency (MF) case, in which DF, triple-frequency or even arbitrary-frequency observations can be readily processed to simultaneously estimate both the ionospheric TEC and rDCB variations. Second, the MCCL method is refined to enable the handling of GLONASS data by accounting for the effects of code inter-frequency biases induced by the frequency division multiple access (FDMA) technology. Based on the test results, the retrieval accuracy of the ionospheric TEC using our proposed method can be improved from 9.47 TECu to 2.67 TECu in the presence of significant intraday rDCB variations. We discovered that the maximum difference in the rDCB variations of the same satellite system between different frequency bands can be as large as 10 ns. The dependence of multi-GNSS and MF rDCB variations on the ambient temperature is further verified in this study. The results show that the temperature dependence of rDCB varies among different satellite systems and frequency bands. Compared to the Galileo, GPS and GLONASS satellite systems, the Beidou system (BDS) rDCB estimates exhibit a stronger correlation with the measured temperature. The percentages of stations with the mean absolute Pearson correlation coefficient value above 0.8 are 27.17% for GPS, 30.58% for GLONASS, 43.78% for BDS and 33.9% for Galileo, respectively.

Uncovering temporal changes in Europe\u2019s population density patterns using a data fusion approach

The knowledge of the spatial and temporal distribution of human population is vital for the study of cities, disaster risk management or planning of infrastructure. However, information on the distribution of population is often based on place-of-residence statistics from official sources, thus ignoring the changing population densities resulting from human mobility. Existing assessments of spatio-temporal population are limited in their detail and geographical coverage, and the promising mobile-phone records are hindered by issues concerning availability and consistency. Here, we present a multi-layered dasymetric approach that combines official statistics with geospatial data from emerging sources to produce and validate a European Union-wide dataset of population grids taking into account intraday and monthly population variations at 1 km2 resolution. The results reproduce and systematically quantify known insights concerning the spatio-temporal population density structure of large European cities, whose daytime population we estimate to be, on average, 1.9 times higher than night time in city centers.

Intraday effects of ambient PM1 on emergency department visits in Guangzhou, China: A case-crossover study

BackgroundShort-term exposure to PM2.5 has been widely associated with human morbidity and mortality. However, most up-to-date research was conducted at a daily timescale, neglecting the intra-day variations in both exposure and outcome. As an important fraction in PM2.5, PM1 has not been investigated about the very acute effects within a few hours. MethodsHourly data for size-specific PMs (i.e., PM1, PM2.5, and PM10), all-cause emergency department (ED) visits and meteorological factors were collected from Guangzhou, China, 2015–2016. A time-stratified case-crossover design with conditional logistic regression analysis was performed to evaluate the hourly association between size-specific PMs and ED visits, adjusting for hourly mean temperature and relative humidity. Subgroup analyses stratified by age, sex and season were conducted to identify potential effect modifiers. ResultsA total of 292,743 cases of ED visits were included. The effects of size-specific PMs exhibited highly similar lag patterns, wherein estimated odds ratio (OR) experienced a slight rise from lag 0–3 to 4–6 h and subsequently attenuated to null along with the extension of lag periods. In comparison with PM2.5 and PM10, PM1 induced slightly larger effects on ED visits. At lag 0–3 h, for instance, ED visits increased by 1.49% (95% confidence interval: 1.18–1.79%), 1.39% (1.12–1.66%) and 1.18% (0.97–1.40%) associated with a 10-μg/m3 rise, respectively, in PM1, PM2.5 and PM10. We have detected a significant effect modification by season, with larger PM1-associated OR during the cold months (1.017, 1.013 to 1.021) compared with the warm months (1.010, 1.005 to 1.015). ConclusionsOur study provided brand-new evidence regarding the adverse impact of PM1 exposure on human health within several hours. PM-associated effects were significantly more potent during the cold months. These findings may aid health policy-makers in establishing hourly air quality standards and optimizing the allocation of emergency medical resources.

Multi-objective optimization for an integrated renewable, power-to-gas and solid oxide fuel cell/gas turbine hybrid system in microgrid

Power-to-gas (P2G) using excess renewable sources is an effective method to reduce renewable curtailment issues in microgrid system. The produced hydrogen is versatile green fuel for different energy sectors, such as electricity, heat and mobility. In recent researches, fuel cell-based system is considered as a promising technology to consume hydrogen (H2) generated from P2G due to high efficiency and cleanness. However, its economic and thermodynamic adaptability when coupled with intermittent renewable sources remains an open question to be addressed carefully. One of the major challenges in optimizing such system is to simultaneously capture the intraday and seasonal variation of renewable sources & load, as well as the internal thermodynamic process of critical components in appropriate modeling detail. This paper presents a multi-energy system for microgrid in which a wind-powered P2G is coupled with a detailed thermoeconomic model of solid oxide fuel cell/gas turbine (SOFC/GT) hybrid system. A two-level multi-objective optimization of planning and operation together is proposed. For system planning, the optimal balance between the least wind curtailment rate and total life cycle cost (LCC) is determined. To facilitate the coordinate operation of system components, a power management strategy is proposed in response to fluctuations of wind power and electricity load with considerations of multiple thermodynamic safety criteria. Results show that in the selected case, the multi-energy system operates with low wind curtailment rate of 0.63% and high renewable penetration level of 90.1%. The optimized LCC of multi-energy system is £2,468,093 with wind power accounting for 68.35% of total capital investment. With the power management strategy applied, the SOFC/GT could operate under the maximum electrical efficiency of 67.1% with safety constraints satisfied, making up only half investment cost of P2G. To capture seasonal variations, both winter and summer scenarios are detailly analyzed, sensitivity analysis is also carried out to evaluate the interaction between capacities of MES components.

Method development and validation for simultaneous estimation of amlodipine and Olmesartan in combined tablet dosage form by using RP-HPLC

The objective of the current study was to develop a simple, accurate, precise and rapid RP-HPLC method with subsequently validate as per ICH guidelines for the determination of Amlodipine (AML) and Olmesartan (OLM) using mobile phase [mixture of acetonitrile and methanol in the ratio of 60:40] as the solvent. The proposed method involves the measurement of Retention time at selected analytical wavelength. 260.0 nm was selected as the analytical wavelength. The retention time of AML and OLM was found to be 3.351 and 1.833 respectively. The linearity of the proposed method was investigated in the range of 5-25 µg/ml (r2 = 0.9999) for AML and 10-50 µg/ml (r2 = 0.9998) for OLM respectively. The method was statistically validated for its linearity, accuracy and precision. Both inter-day and intra-day variation was found to be showing less % RSD (Relative Standard Deviation) value indicating high grade of precision of the method.

Consistent retrieval of multiple parameters from GOES-R top of atmosphere reflectance data

ABSTRACT Current remote sensing products are mainly generated from polar-orbiting satellite data using parameter-specific algorithms. These products lack physical consistency and cannot accurately characterize intra-day variations of parameters, such as the fraction of absorbed photosynthetically active radiation (FAPAR) and surface albedo. In this study, a multi-parameter consistent retrieval method is proposed to simultaneously retrieve aerosol optical depth (AOD), leaf area index (LAI), photosynthetically active radiation (PAR), FAPAR, surface albedo, and incident shortwave radiation (ISR) from top of atmosphere (TOA) reflectance data acquired by the Advanced Baseline Imager (ABI) aboard the Geostationary Operational Environmental Satellite-R series (GOES-R). The retrieved parameter values were evaluated through comparisons with corresponding Moderate Resolution Imaging Spectroradiometer (MODIS), the second version of the Geoland2 (GEOV2), and GOES-R products and ground measurements over five surface radiation budget network (SURFRAD) sites with different vegetation types. The results demonstrate that the retrieved AOD, PAR, ISR, and surface albedo values have consistent intra-day variations with the ground measurements, and the retrieved parameter values achieve good performance against the ground measurements for all the five SURFRAD sites. The root mean square errors of the retrieved AOD, shortwave albedo, ISR, and PAR values against the ground measurements are 0.071, 0.032, 50.943 W m–2, and 27.975 W m–2, respectively.

Intra-day microplastic variations in wastewater: A case study of a sewage treatment plant in Hong Kong

Wastewater treatment plants (WWTPs) in coastal region play a primary role in transferring microplastics into the marine environment. Wastewater is closely related to anthropogenic activities, thus the intra-day variation of abundance of microplastics in the influent should be large and could have significant impact on their estimation of the daily mass load. In this study, a 2–hour interval sampling campaign was conducted at a secondary WWTP in Hong Kong to investigate the intra-day variations and daily loads of microplastics in influent. Results show that the average microplastic abundances increased from 7.1 ± 6.0 to 12.8 ± 5.8 particles/L over time, with predominant particle sizes ranging 1–5 mm. Approximately 80% of the microplastics in samples collected from 9:30–15:00 were polyethylene and polyester, while most samples collected at 17:00 were polypropylene and polyurethane. Microplastic loads exhibited large intra-day variations ranging 6.60 × 108–1.16 × 109 particles/day, indicating that calculated daily microplastic loads based on a specific sampling period may inaccurately estimate the actual daily load.

Accurate determination of type B trichothecenes and conjugated deoxynivalenol in grains by isotope dilution–liquid chromatography tandem mass spectrometry

An isotope dilution-liquid chromatography tandem mass spectrometry method (ID-LC/MS/MS) has been developed as a candidate reference method for the accurate measurement of major type B trichothecenes and conjugated deoxynivalenol mycotoxins in grain samples. 13C15-deoxynivalenol, 13C15-nivalenol, 13C17-3-acetyldeoxynivalenol, and 13C17-15-acetyldeoxynivalenol were used as internal standards, and the immunoaffinity columns and MycoSep 227 cartridges were employed for sample clean-up. The ID-LC/MS/MS method was validated by the analysis of samples fortified with the target mycotoxins at three concentration levels. The results exhibited sufficient accuracy of 98.2 ̶102.6% with a relative expanded uncertainty of 1.3 ̶3.8%. Moreover, the developed method was applied to the analysis of deoxynivalenol in the reference material and quality control samples (corn and wheat). Intraday and interday variations were also evaluated for the assessment of the metrological quality of the established method. This analytical method was proved to have a higher order metrological quality and exhibited greatly enhanced performance compared to other methods reported in literatures. Furthermore, the method will be applied to the value-assignment of certified reference materials that are under development in this laboratory.

Human impact on suspended particulate matter in the Yellow River Estuary, China: Evidence from remote sensing data fusion using an improved spatiotemporal fusion method

Transport of suspended particulate matter (SPM) in estuarine waters plays an important role in regulating erosion-accretion and biogeochemical processes. In the Yellow River Estuary (YRE), artificial water and sediment regulation scheme (WSRS) and coastal engineering structures are the 2 typical anthropogenic activities affecting the spatiotemporal dynamics of estuarine SPM. The monitoring of SPM transport affected by such human activities requires SPM mapping at both high spatial and high temporal resolutions. In this study, we presented an improved Flexible Spatiotemporal Data Fusion (FSDAF) strategy with consideration of highly dynamic SPM variations in estuarine waters, and generated 30-m hourly SPM concentrations based on Landsat 8 OLI and GOCI datasets. The new strategy produced higher SPM estimation accuracy than the original FSDAF, with the relative percentage difference (RPD) decreasing from 29.75% to 5.31% using GOCI-derived hourly SPM as reference. With in situ SPM measurements as reference, the fused SPM concentrations had an RMSE of 12.09 mg/L and an RPD of 27.17%. Investigation of interday SPM variations before, during, and after the WSRS in 2018 revealed that the first WSRS significantly increased the SPM concentration and plume extent; new wetland with an area of 12.56 km2 was formed due to sediment accretion near the river mouth. The two groins offshore from the coastlines on the north and south sides of YRE exhibited obvious sediment trapping effects in that higher SPM concentrations on one side of each groin were found regardless of the turbidity modes and diurnal SPM variations; the trapping effects were associated with the number of groins and groin length. Intraday variations of SPM were influenced by tidal currents, with plume direction following the ebb and flooding tidal current direction. The inter- and intraday characteristics of the 30-m hourly SPM dynamics facilitate the detailed analysis of the sediment transport associated with human activities.

UV Spectroscopic Method for Optimization and Determination of Glibenclamide in Bulk, Pharmaceutical Dosage Form and its Application for In Vitro Interaction Studies

A simple, easy and cost-efficient UV spectroscopic method was developed and validated for glibenclamide, the second generation of sulfonylureas, using 0.1 N NaOH as a solvent. The proposed method is linear (R2 > 0.999) with the range 5–25 µg mL−1, accurate (99.60%), precise (inter and intraday variation 0.241 and 0.019%, respectively) and robust (< 1%). The quantification and detection limit were 1.46 and 0.48 μg mL−1, respectively. The validated method was applied for in vitro interaction studies of glibenclamide (GLB) with commonly prescribed quinolones (ciprofloxacin, levofloxacin, moxifloxacin, and gemifloxacin) and nonsteroidal anti-inflammatory drugs (NSAIDs) (diclofenac sodium, ibuprofen, mefenamic acid, and aspirin) using UV spectrophotometer. The in vitro interaction studies were carried out in different artificially prepared physiological buffers at 37 °C for 2 h. Results showed raised level of glibenclamide when interacted with gemifloxacin (pH 7.4), levofloxacin (pH 9), ciprofloxacin (pH 4.5) and with moxifloxacin (pH 4.5, 7.4 and 9). Interaction with NSAIDs results in increased %availability of glibenclamide in the presence of diclofenac sodium, ibuprofen, and mefenamic acid at pH 4.5. The anticipated method can be successfully applied for the routine analysis and also for the interaction of glibenclamide with other drugs.

D-phenylglycine improves L-dopa binding to serum albumin

D-phenylglycine-L-dopa, a dipeptide synthesized in this laboratory for improving the oral absorption of L-dopa, showed better absorption and distribution in rats. We assumed that the extensive distribution might explain its sustained release of brain dopamine. Since protein binding is a main factor of drug distribution, we investigated the effect of D-phenylglycine on the binding of L-dopa to human serum albumin. The degree of the binding of D-phenylglycine, L-dopa and D-phenylglycine-L-dopa to serum albumin was determined. Free and bound portion of test compounds were separated with ultrafiltration method and the assay of free drug portion was conducted with reversed phase HPLC. The LOQ for D-phenylglycine, L-dopa and D-phenylglycine-L-dopa was 0.5 μg/mL, 0.1 μg/mL and 0.5 μg/mL, respectively. Assay methods were validated by determining the precision and accuracy of interday and intraday variations. The coefficient of variation (CV) was within 12% and the relative error (RE) was within 10% (n = 3). The recovery rate was 95.4% - 98.1% for D-phenylglycine, 91.9 % - 98.8% for L-dopa and 96.8% - 97.9% for D-phenylglycine-L-dopa, respectively (n = 3). D-Phenylglycine showed higher serum albumin binding than L-dopa did at various concentrations. At a concentration of 600 μM, the degree of albumin binding of D-phenylglycine, L-dopa, D-phenylglycine-L-dopa was 27.98%, 8.20% and 19.18%, respectively. The albumin binding of L-dopa at this concentration increased by 2.4 folds when chemically bound to D-phenylglycine. The number of the binding sites of L-dopa increased by 5.8 folds and the binding constant Kal increased by 3.8 folds when L-dopa was chemically bound to D-phenylglycine. With the affinity to serum albumin, D-phenylglycine showed its possibility as a delivery moiety for drugs with limited distribution to use the body protein as a reservoir.

New HPTLC methods for analysis of major bioactive compounds in mate (Ilex paraguariensis) tea

New HPTLC (high-performance thin-layer chromatography) methods to evaluate major bioactive compounds in mate (Ilex paraguariensis) tea were developed. Identification of compounds was based on HPTLC-MS (high-performance thin-layer chromatography–mass spectrometry), parallel to other techniques. Quantitative evaluation of the main methylxanthines and phenolic compounds in this species was accomplished by two HPTLC methods which can be performed consecutively on one single plate. A solvent system for the separation of the identified saponins is also described for qualitative evaluations. The methods for quantification were validated in terms of: robustness; LOD and LOQ (limits of detection and quantification); repeatability; intra-day and inter-day variation; ruggedness; and accuracy. The methods have proven to be suitable for evaluation of mate tea aqueous and methanolic extracts, with the advantages of: high-throughput; reduced need of plates and application procedures; and high sensitivity – low LODs and LOQs were achieved. Aqueous extracts of nineteen mate teas of different type, geographical origin and age were evaluated in terms of methylxanthines, phenolic compounds and pH. By means of principal component analysis, distinctive characteristics between mate teas could be observed.

Optical variability of three extreme TeV blazars

ABSTRACT We present the results of optical photometric observations of three extreme TeV blazars, 1ES 0229+200, 1ES 0414+009, and 1ES 2344+514, taken with two telescopes (1.3 m Devasthal Fast Optical Telescope, and 1.04 m Sampuranand Telescope) in India and two (1.4 m Milanković telescope and 60 cm Nedeljković telescope) in Serbia during 2013–2019. We investigated their flux and spectral variability on diverse time-scales. We examined a total of 36 intraday R-band light curves of these blazars for flux variations using the power-enhanced F-test and the nested ANOVA test. No significant intraday variation was detected on 35 nights, and during the one positive detection the amplitude of variability was only 2.26 per cent. On yearly time-scales, all three blazars showed clear flux variations in all optical wavebands. The weighted mean optical spectral index (αBR), calculated using B − R colour indices, for 1ES 0229+200 was 2.09 ± 0.01. We also estimated the weighted mean optical spectral indices of 0.67 ± 0.01 and 1.37 ± 0.01 for 1ES 0414+009, and 1ES 2344+514, respectively, by fitting a single power law (Fν ∝ ν−α) in their optical (VRI) spectral energy distributions. A bluer-when-brighter trend was only detected in the blazar 1ES 0414+009. We briefly discuss different possible physical mechanisms responsible for the observed flux and spectral changes in these blazars on diverse time-scales.