Percentage Change In Concentration Research Articles

Assessment of Air Quality Before and During COVID-19-Induced Lockdown in Jaipur, India

Air pollution is increasing at a frightening pace due to emissions from industrial plants and manufacturing activities and other anthropogenic activities affecting living beings, property, and environment. This study aims to monitor the impact of COVID-19-induced lockdown and unlock down phases on the air quality of Jaipur city, Rajasthan, India by assessing the change in ambient air quality during pre-COVID-19 (January 2018–December 2019) and COVID-19 (January 2020–December 2021) phases by evaluating air quality parameters (PM10, PM2.5, NO2, O3, Benzene and o-Xylene) using ground station data. Outcome of the study revealed that the ambient air quality improved significantly during lockdown phases (March–May 2020) as the percentage change in concentration of studied parameters declined by more than 100% at different sites. However, the concentrations tend to escalate with the introduction of unlock down phases (June–December 2020) and the onset of winter season (October–December 2020) aggravated the conditions. The AQI touched moderate and poor category many times during study period. Student’s t-test was conducted on the dataset. Results revealed significant difference in the concentration of air pollutants between pre-covid and covid period.

Impact of novel coronavirus disease (COVID-19) lockdown on ambient air quality of Saudi Arabia.

The outbreak of COVID-19 has spread globally affecting human activities but with improvement in ambient air quality. The first case of the virus in the Kingdom of Saudi Arabia was on the 2nd of March 2020. The impact of COVID-19 lockdown on the ambient air quality of the Kingdom of Saudi Arabia for the first time using data from nine cities was determined in this study. Hourly air quality data, based on concentrations of carbon monoxide (CO), particulate matter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2) and ozone (O3), and meteorological conditions (atmospheric temperature, relative humidity, and wind speed) of the nine cities studied were obtained from Saudi Arabian General Authority of Meteorology and Environmental Protection (GAMEP), for the period between January 2019 to May 2020. Significant variation (p < 0.05) was recorded for the five atmospheric pollutants across the cities before and during the lockdown, with lower concentrations during the lockdown except for the concentration of O3 in Tabuk, Al Qasim, and Haql. This can be a result of NO and O3 reaction, causing the inability of effective O3 depletion. The percentage changes in concentrations of CO (33.60%) and SO2 (44.16%) were higher in Jeddah; PM10 (91.12%) in Riyadh, while NO2 (44.35%) and O3 (18.98%) were highest in Makkah. However, even though there was a decrease in pollutants concentrations during the lockdown, the concentrations for CO, PM10, SO2, NO2, and O3 were still above WHO 24 h and annual mean limit levels. The COVID-19 lockdown in the Kingdom of Saudi Arabia revealed the possibility of significant atmospheric pollutant reduction by controlling traffic, activities by industries, and environmentally friendly transportation programs such as green commuting programs.

Effect of treatment with oral Ca boluses following calving on concentrations of Ca in serum in pasture-based dairy cows

AIMSTo assess the effect of the administration of two oral Ca boluses on concentrations of total Ca, β-hydoxybutyrate (BHB) and non-esterified fatty acids (NEFA) in serum, and urine pH, in recently calved pasture-fed dairy cows.METHODSFriesian or Friesian cross Jersey cows from one dairy farm were blocked by age and randomly assigned to no treatment (control; n=14), or treatment (n=13) with two oral Ca boluses administered approximately 12 hours apart, with the first bolus being given within 14 hours of calving. Each bolus weighed 198 g and contained 43 g of Ca; 31 g of Ca from calcium chloride and 12 g of Ca from calcium sulfate. Cows were enrolled over three calendar days, and all cows were managed in one group during the 24-hour study period. Blood samples were collected at 0, 1, 2, 4, 8, 12, 13, 14, 16, 20 and 24 hours after the initial treatment. Serum from each time point was analysed for concentrations of total Ca, and from 0, 12, and 24 hours for NEFA and BHB. Urine was collected at 0, 12 and 24 hours for pH measurement and pH was categorised as <7 or ≥7. The effect of treatment on percentage change in concentrations of Ca in serum relative to 0 hours, and concentrations of NEFA, BHB and urine pH, was examined using multivariable repeated measures mixed models with cow as a random effect.RESULTSIn the final multivariable model for percentage change in concentrations of Ca, there was an interaction between time and treatment (p=0.004), with the percentage increase being higher in treatment than control cows at 1, 2, 4, 8 and 13 hours. At 12 hours, 5/13 (41%) treated cows had a urine pH <7compared to 0/12 (0%) control cows (p<0.001), and at 24 hours 13/13 (100%) treated cows had urine pH <7 compared to 0/12 (0%) control cows (p<0.001). Over the 24-hour period, mean concentrations of NEFA or BHB in serum were similar in treated and control cows (p>0.3).CONCLUSIONS AND CLINICAL RELEVANCEOral treatment with two Ca boluses increased concentrations of total Ca in serum and decreased urine pH in pasture-fed cows. This bolus has the potential to reduce the prevalence and duration of subclinical hypocalcaemia in recently calved cows.

Stability of Serum Carotene at Various Light and Temperature Conditions

To the Editor.—Carotenoids are brightly colored plant pigments that are essential for several metabolic functions including cell growth regulation and immune response. Carotene (previtamin A) is a slowly absorbed, fat-soluble, carotenoid pigment normally present in the diet. Serum carotene levels are used to determine the possibility of absorption defects that can lead to malabsorption. Decreased carotene levels are seen in several malabsorption syndromes, including, but not limited to, some pancreatic diseases, sprue, post–small intestine resection, and celiac disease.1Fat-soluble vitamins, such as carotene, are generally considered highly unstable when exposed to light, air, and ambient temperature.2 Therefore, serum carotene samples that are referred to core laboratories from satellite sites are required to be shipped frozen and protected from light at all times of handling and analysis. Recent studies indicate that fat-soluble vitamins, including carotene concentrations in whole blood, change insignificantly when stored for up to 7 days at room temperature in dark or light conditions; however, stability data for serum carotene remain scarce.3,4We prepared 5 different serum pools from healthy adult volunteers and from 7-day-old leftover laboratory specimens within our laboratory. Aliquots of 600 µL from each pool were maintained at various light and temperature conditions: room temperature–dark, room temperature–light, refrigerated-dark, refrigerated-light, frozen (−30°C)-dark, and frozen (−70°C)-dark for durations of 1 to 14 days. At the end of the timed conditions (Day 0, 1, 3, 7, 10, 14), the appropriate aliquots were removed and stored at −70°C until analysis. Serum carotene was then extracted with petroleum ether and analyzed using spectrophotometry at a wavelength of 440 nm. The procedure was performed under minimal lighting conditions. The stability of carotene under each storage condition was determined by calculating the percentage change in concentration from those of day 0, then calculating the mean percentage change (and standard error of the mean) of the 5 pools at each time point. Data were analyzed by 1-way analysis of variance using SPSS (Chicago, Illinois) and a P value < .05 was considered statistically significant.The analytic imprecision of this carotene assay is 6.6% at levels of 96.6 µg/dL (1.8 µmol/L) and 155.7 µg/dL (2.9 µmol/L). Carotene levels of the 5 serum pools ranged from 134.2 µg/dL (2.50 µmol/L) to 230.9 µg/dL (4.3 µmol/L). Serum stored at −70°C for 14 days (the end of study controls) demonstrated a minimal average change of only 3.04% compared with those measured freshly at day 0. Samples stored in the room temperature–light condition for 10 and 14 days demonstrated a significant decrease of 24.5% (P = .02) and 28.3% (P = .01) respectively in carotene levels when compared with the end-of-study controls. Except for room temperature, storage conditions did not induce clinically significant changes in serum carotene (Table).In conclusion, serum carotene levels are stable when stored at 4°C (in dark or light) or in the freezer for up to 14 days. Carotene stability is also acceptable at room temperature–dark for 7 days or room temperature–light for 3 days. In addition, repeated freezing to −70°C and thawing has been demonstrated to have no significant effects (less than 1% per freeze-thaw cycle) on the serum and plasma carotene concentrations.5 These results allow for less stringent storage, shipping, and handling conditions for serum carotene specimens.

Analysis of A Second-Generation Tetracycline Antibiotic Minocycline in Human Plasma by LC–MS/MS

A simple, selective and sensitive LC-MS/MS assay has been developed for the determination of minocycline in human plasma. Plasma samples were prepared by protein precipitation, followed by chromatographic separation on a HyPURITY™ C8 (100 mm × 4.6 mm, 5 µm) column under isocratic conditions. The LOD and LLOQ of the method were 0.50 and 20.0 ng/ml, respectively. The intra-batch and inter-batch precision (% coefficient of variation) across quality control levels was less than 8.0%. For a set of incurred samples the percentage change in concentration was within ± 9.0%. The method was successfully applied to a bioequivalence study of 135 mg minocycline tablet formulation in 14 healthy Indian males. The reproducibility in the measurement of study data was demonstrated by incurred sample reanalysis.

Trends in Inhalation Exposure—A Review of the Data in the Published Scientific Literature

As part of a larger study aimed at identifying the long-term changes in inhalation exposure for selected hazardous substances in a number of industrial sectors within the UK, we have reviewed the published literature on temporal changes in inhalation exposure. Scientific papers and reports of interest were identified using standard literature review techniques. Most studies did not express the results as relative annual trends in exposure, and so where possible the data were reanalysed using regression methods to produce estimates of the average annual percentage change in concentration. In the majority of instances, there were significant reductions in exposure, with percentage yearly declines up to 32%. In many studies, information about changes in the working environment, process conditions or other factors that may have influenced the change in exposure over time was lacking. Factors commonly cited as being responsible for exposure reductions included the introduction of new standards and response to regulatory requirements as well as changes in production methods. A large number of exposure measurement datasets exist for many industrial sectors for most of the second half of the 20th century and this resource has allowed us to identify trends in occupational exposure. It is most important that longitudinal exposure data continue to be collected along with relevant contextual information to enable future changes to be adequately assessed.

Prediction of foaling using mammary secretion constituents

AIMS: To test published models for predicting time of foaling using data derived from prepartum mammary secretions and to develop a new model based on concentrations of mammary secretion constituents that accurately predicts time of foaling in Thoroughbred mares. METHODS: Concentrations of sodium, potassium, calcium, citrate and lactose were measured in prepartum mammary secretions of 20 Thoroughbred mares in the 2 weeks before expected date of foaling. Models to predict time of foaling were fitted to data based on absolute concentration, change in concentration, and percentage change in concentration of mammary secretion constituents in relation to actual intervals to foaling. RESULTS: Concentrations of potassium, calcium, citrate and lactose increased, and concentration of sodium decreased as foaling approached but variation between mares was large. Models to predict time of foaling based on percentage change in electrolyte concentrations were less accurate than those based on absolute concentration and change in concentration. When data from this study were fitted to two previously published models, the statistical sensitivity, specificity, and positive and negative predictive values of both models were lower than those originally reported. CONCLUSIONS: The use of prepartum equine mammary secretion electrolyte concentrations for prediction of time of foaling is unreliable, due to large variation in both absolute concentrations and change in concentrations between mares. Models that use a combination of mammary secretion electrolytes and physical and behavioural factors may better predict foaling than those based on mammary secretions alone.

Recommendations for clinical GnRH challenge testing of stallions

Eight mature light-breed stallions with normal testes size, sperm output and semen quality were used to evaluate response to 3 GnRH challenge regimens in the summer in southeast Texas. Gonadotropin releasing hormone (50 μg) was administered intravenously once to each of eight stallions after three days of sexual rest (50 μg GnRH-1X). The same stallions were administered either 5μg GnRH intravenously once hourly for three injections (5 μg GnRH-3X) and 15μg GnRH intravenously once (15μg GnRH-1X) one and two weeks later. Blood samples were collected prior to and at intervals after GnRH administration. Plasma was immediately separated from blood samples and was frozen until assayed for LH, FSH, estradiol and testosterone concentrations. Percentage changes in hormone concentrations from pre-treatment values (baseline) were analyzed by paired studient'st-test to detect significant rises in hormone concentrations. Group mean percentage changes in hormone concentrations were analyzed by analysis of variance to compare responses among treatments. A computerized peak-detection algorithm (PC Pulsar) was used to detect peaks in LH and testosterone concentrations following 5 μg GnRH-3X and 15 μg GnRH-1X treatment. No differences (P>0.10) were detected in percentage change from baseline concentration for LH, FSH, or testosterone at one or two hours after administration of any of the three regimens of GnRH. When more frequent sampling intervals were analyzed for 5 μg GnRH-3X or 15 μg GnRH-1X treatments, no differences were detected in percentage change from baseline concentration for any hormone at 15, 30 or 60 minutes. Thereafter, percentage changes in concentrations of LH and FSH remained increased for 5μg GnRH-3X compared to 15 μg GnRH-1X treated stallions (P<0.05). Percentage changes in concentrations of testosterone were increased for 5μg GnRH-3X compared to 15 μg GnRH-1X treated stallions from 180–300 min (P<0.05), while no differences (P>0.10) were detected between 5 μg GnRH-3X and 15 μg GnRH-1X treated stallions for changes in concentrations of estradiol throughout the experiment. For 15 μg GnRH-1X treated stallions, maximum concentrations of LH in PC Pulsar-detected peaks occurred most commonly at 15 to 30 minutes (7/8 treatment periods) after GnRH injection. Maximum concentrations of testosterone in PC Pulsar-detected peaks occurred most commonly at 60–120 min (7/8 treatment periods) after GnRH injection. A protocol of blood sampling prior to, and 15, 30, 60 and 120 minutes after, intravenous administration of small doses of GnRH would be practical for challenge testing of stallions during the breeding season. In order to reduce cost of hormone assays, we suggest assay of the pre-challenge blood sample (baseline) could include LH, FSH, testosterone and estradiol concentrations (to assess overall hypothalamic-pituitary-testicularfunction), while only LH and testosterone concentrations need be determined after GnRH administration (to assess pituitary and testicular responsiveness). Assay for LH could be done on only the 15 and 30 minute post-GnRH samples, and assay for testosterone could be done on only the 60 and 120 minute post-GnRH samples. Failure to achieve approximately a 50% increase in LH concentration by 30 minutes after GnRH administration, and/or failure to achieve approximately a 100% increase in testosterone concentration by two hours after GnRH administration, could be further pursued either by treatment with increasing dosages of GnRH, or repeated administration of GnRH at hourly intervals, as has been suggested by other workers.

Diffusion in axon guidance.

Axon guidance by target-derived diffusible factors plays an important role in the development of the nervous system. This paper considers the constraints imposed on this process by the mathematics of diffusion. A point source continuously producing a factor into an infinite three-dimensional volume is considered as a model for both the in vivo and in vitro situation. Basic constraints for effective guidance are assumed to be that the concentration falls between certain maximum and minimum limits, and that the percentage change in concentration across the width of the growth cone exceeds a certain minimum value. The evolution of the shape of the gradient over time is analysed. Using biologically reasonable parameter values, it is shown that the maximum range over which growth cone guidance by a diffusible factor is possible for large times (several days) after the start of the production of the factor is 500-1000 microm. This maximum distance is independent of the diffusion constant of the diffusing molecule, applies to both chemoattractants and chemorepellents, and agrees with experimental data. At earlier times, however, the constraints may be satisfied for distances up to several millimetres. The time it takes for this maximum guidance distance to fall to the asymptotic value depends on the diffusion constant. This time is a few hours for a small molecule but as much as a few days for a large molecule. The model therefore predicts that guidance over distances larger than 1000 microm is possible if the start of production of the factor is carefully matched to the time when guidance is required.

Pharmacokinetics, Pharmacodynamics, and Rational Opioid Selection

Fentanyl, alfentanil, and sufentanil have important pharmacokinetic and pharmacodynamic differences. Selecting one of these opioid analgesics as an adjunct to general anesthesia requires appreciation of the relationship between the pharmacokinetic and pharmacodynamic characteristics of these drugs and the onset of and recovery from drug effect. Using a pharmacokinetic-pharmacodynamic model, the authors simulated the decrease in plasma fentanyl, alfentanil, and sufentanil concentration after intravenous administration by either bolus injection, brief infusion, or prolonged infusion. The percentage change in concentration, rather than absolute concentration, was simulated to permit comparison of the relative opioid concentration independently of drug potency. These computer simulations quantified the relationship between infusion duration and the time required for recovery after termination of the infusion. The analysis suggests that alfentanil is best used for operations longer than 6-8 h when a rapid decrease in effect site (i.e., biophase) opioid concentration is desired after discontinuation of the infusion. Alfentanil may also be the most appropriate drug to provide a transient peak effect after a single bolus. Although sufentanil has longer distribution and elimination half-lives than alfentanil, recovery from sufentanil infusions may be more rapid than recovery from alfentanil infusions for operations shorter than 6-8 h. These computer simulations demonstrate that simply comparing pharmacokinetic parameters (e.g., half-lives) of different drugs will not predict the relative rates of decrease in effect site concentrations after either an intravenous bolus or a continuous infusion.

Photochemical oxidant formation and the effects of vehicle exhaust emission controls in the U.K. the results from 20 different chemical mechanisms

Twenty different chemical mechanisms have been used in a photochemical trajectory model, to examine the effects of motor-vehicle exhaust emission controls on the formation of photochemical oxidants downwind of London. Three different cases were studied: 1984 baseline calculations; year 2000, with high growth in the use of motor vehicles, and all petrol-engined vehicles complying with the emissions limits set in the Luxembourg Agreement; year 2000, with high growth in the use of motor vehicles, and all vehicles complying with stringent limits on exhaust emissions. All other emissions were held constant. In each of the three cases, the model was used to study the formation of photochemical oxidants downwind (to the west) of London, during clear sky, midsummer, anticyclonic conditions with a low wind speed. The 20 chemical mechanisms were modified from their published forms, so that they all included the same inorganic processes, and so that the rate constants of most organic reactions were the same throughout the set of mechanisms. In each of the three cases, the results of the different mechanisms varied significantly, both in the peak concentrations of photochemical oxidants, and in their integrated concentrations over a 24-h period. These variations were rather greater for PANs and hydrogen peroxide than for ozone and nitric acid. For ozone, nitric acid and hydrogen peroxide, the variation was rather smaller among the results of the nine most recent mechanisms than among those of the whole set. However, the pattern of variation was the same for each of the three scenarios, so that the percentage changes in concentration on moving from 1984 to either scenario set in the year 2000 were rather better determined than the concentrations themselves. These results indicate that concentrations of ozone, PANs and hydrogen peroxide will be lower in the year 2000 than in 1984, if all vehicles comply with the Luxembourg Agreement. Stringent emission controls similar to those possible by the use of three-way catalysts would cause further significant reductions in the concentrations of ozone and of PANs, and would also reduce the concentration of nitric acid.