Cyclic Variation Research Articles

Effects of estradiol, progesterone or cAMP on expression of PGRMC1 and progesterone receptor in a xenograft model of human endometrium and in endometrial cell culture

Estradiol and progesterone are key regulators of the menstrual cycle. In the human endometrium, progesterone induces morphological changes required for blastocyst implantation. Dysregulated response to progesterone can lead to endometrial pathologies including uterine bleeding and endometriosis. Besides the canonical nuclear progesterone receptor (encoded by the PGR gene), alternative response pathways include Progesterone Receptor Membrane Component 1 (PGRMC1), suspected to be involved in pathogenesis of endometrial diseases. We previously reported the spatiotemporal profile of PGRMC1 expression in the human endometrium along the menstrual cycle, highlighting progressive increase and decrease during the proliferative and secretory phases, respectively. Here we directly addressed its regulation by estradiol and progesterone, with systematic comparison with regulation of PGR expression. We found a direct correlation between expression of both genes during the proliferative and secretory phases in the cycling endometrium, but not during the menstrual phase. In a xenograft model mimicking the cycle phases, estradiol significantly increased and progesterone significantly decreased PGR expression but changes were not significant for PGRMC1. Finally, we did not find any significant effect of the ovarian steroids on expression of PGR or PGRMC1 in primary culture of endometrial stromal cells, except for a small increase in PGR expression by estradiol. Altogether, our experiments do not allow a major advance in our understanding of the mechanisms of cyclic variation of PGRMC1 expression, in particular regarding potential regulation by the ovarian steroids.

Cross Sectional Analysis of Impact of Seasonal Changes on Excimer Laser Ablation Performance on Polymethyl Methacrylate (PMMA).

Seasonal changes and varying degree of corneal hydration has been linked to excimer laser corneal ablation rates. The use of PMMA as a calibration material in refractive lasers is well established. However, PMMA ablation may be equally affected by seasonal variations in temperature and humidity, in turn affecting the calibration process. The aim of this work is to analyze the effect of seasonal changes in PMMA performance using SCHWIND AMARIS laser system. PET and PMMA ablations conducted in climate-controlled environment with 826 consecutive AMARIS systems manufactured over 6 years were retrospectively analyzed. Lasers were stratified depending on seasons and months of the year. Metrics like single laser pulse fluence, nominal number of laser pulses, mean performance, standard deviation, and technical performance of system were compared to global average values. Cyclic winter-summer variation was confirmed with seasons winter and summer showing statistically significant variations with respect to global values. Metric technical performance showed deeper PMMA ablation performance in summertime, with maximum seasonal deviation of 6%. Results were consistently confirmed in seasonal as well as monthly analyses. These findings could help minimize variance among laser systems by implementing compensation factors depending on seasons such that laser systems installed worldwide follow the same trend line of variation.

Experimental Characterization of Hydrocarbons and Nitrogen Oxides Production in a Heavy-Duty Diesel–Natural Gas Reactivity-Controlled Compression Ignition Engine

Reactivity-Controlled Compression Ignition (RCCI) combustion is considered one of the most promising Low-Temperature Combustion (LTC) concepts aimed at reducing greenhouse gases for the transportation and power generation sectors. Due to the spontaneous combustion of a lean, nearly homogeneous mixture of air and low-reactivity fuel (LRF), ignited through the direct injection of a small quantity of high-reactivity fuel (HRF), RCCI (dual-fuel) shows higher efficiency and lower pollutants compared to conventional diesel combustion (CDC) if run at very advanced injection timing. Even though a HRF is used, the use of advanced injection timing leads to high ignition delays, compared to CDC, and generates high cycle-to-cycle variability, limited operating range, and high pressure rise rates at high loads. This work presents an experimental analysis performed on a heavy-duty single-cylinder compression ignited engine in dual-fuel diesel–natural gas mode. The objective of the present work is to investigate and highlight the correlations between combustion behavior and pollutant emissions, especially unburned hydrocarbons (HC) and oxides of nitrogen (NOx). Based on the analysis of crank-resolved pollutants measurements performed through fast FID and fast NOx systems under different engine operating conditions, two correlations were found demonstrating a good accordance between pollutant production and combustion behavior: Net Cyclic Hydrocarbon emission—cyclic IMEP variations (R2 = 0.86), and Cyclic NOx—maximum value of the Rate of Heat Released (R2 = 0.82).

Major and minor hysteresis loops in the enthalpy-temperature and phase fraction-temperature diagrams of solid/liquid phase change materials

A rate-independent hysteresis model originally proposed by Ivshin and Pence (1994) is extended to describe thermal hysteresis in enthalpy, specific heat capacity and phase fraction of solid/liquid phase transitions. It turns out that, even for smooth cyclic temperature variations, major and minor loops in the enthalpy-temperature diagram are not necessarily closed. Jump discontinuities may occur upon switches between heating and cooling. This issue is highly problematic: the model does not obey the law of conservation of energy. This problem particularly concerns the frequently found setting that solid and liquid heat capacities do not coincide and the phase transition enthalpy is assumed constant, i.e. independent of temperature. Two possible solutions are proposed. They follow the idea of Kirchhoff’s Law and relate temperature variations of the phase transition enthalpy to the difference in specific heat capacities of the distinct phases. Conditions for path reversibility and for the existence of closed major and minor loops (limit cycles) are given. The models show good agreement with experimental data generated by differential scanning calorimetry (DSC) of three types of paraffin-based solid/liquid phase change materials (PCM). These materials are increasingly adopted for storing thermal energy in building applications and show thermal hysteresis for complete and partial melting/solidification cycles.

Determination of combustion and emission characteristics of liquid Fischer-Tropsch diesel fuel synthesized from coal in a diesel engine

Fischer–Tropsch (FT) synthesis is a production method that processes a liquid diesel fuel from heavy carbon-containing organic compounds such as coal and biomass. FT synthesis is an essential process in demonstrating the usability of coal-to-liquid fuel in internal combustion engines. This study investigates the effects of using FT diesel fuel synthesized from coal on the combustion characteristics of a single-cylinder common-rail direct-injection diesel engine. The engine tests were conducted at 50% of the wide-open throttle position and fixed engine control parameters (cycle duration, fuel amount, start of injection timing, etc.). As a result of the study, it was observed that the combustion with the use of FT diesel fuel started (almost 1.5 °CA) and completed earlier according to the petroleum-based diesel (D100). The cyclic variations were more stable with FT diesel fuel. With the use of FT diesel fuel, the indicated mean effective pressure was 3% lower, peak cylinder gas pressure was slightly lower, and the combustion noise was 2–3 dB quieter compared to D100. The heat release was higher during the premixed combustion phase at the cycle durations of 67 ms and 55 ms, while it occurred very small at the cycle duration of 86 ms. Significant reductions in CO2 and NOx emissions, which are complete oxidation products, were obtained with FT diesel fuel compared to D100. The fuel properties, combustion characteristics and emission results showed that no further measures should be taken to use FT diesel in compression ignition engines. FT diesel fuel can be safely used as an alternative fuel.

A DEM Investigation on the Influence of Cyclic and Static Stress Ratios and State Variables on the Pore Water Pressure Generation in Granular Materials

A granular soil may undergo liquefaction failure due to excess pore water pressure (Δu) generation when subjected to cyclic loading such as an earthquake. Several past studies indicated Δu generation may be independent of cyclic stress ratio (CSR), whereas others contradicted this observation. A soil element in its natural state often remains in K0 consolidation state, i.e., subjected to nonzero static shear stress ratio (SSR). Using the discrete element method (DEM), this study performs a large number of cyclic triaxial tests and evaluates various factors influencing the magnitude and rate of Δu generation under symmetric and nonsymmetric cyclic loading conditions. The study also evaluates the capabilities of several existing Δu generation models to predict the development of Δu under different failure scenarios. It was observed that the generation of Δu can be influenced by CSR for specimens subjected to symmetrical cyclic loading and by both CSR and SSR for nonsymmetric cyclic loading conditions. A new prediction model for Δu generation was developed along with an objective framework to estimate its input parameters. The model showed good agreement with the DEM simulation results.

New evidence for the precession of tilted disc in SDSS J081256.85+191157.8

ABSTRACT Superorbital signals and negative superhumps are thought to be related to the reverse precession of the nodal line in a tilted disc, but the evidence is lacking. Our results provide new evidence for the precession of the tilted disc. Based on the TESS and K2 photometry, we investigate the superorbital signals, negative superhumps, positive superhumps, and eclipse characteristics of the long-period eclipsing cataclysmic variable star SDSS J0812. We find superorbital signals, negative superhumps, and positive superhumps with periods of 3.0451(5) d, 0.152047(2) d, and 0.174686 (7) d, respectively, in the K2 photometry, but all disappear in the TESS photometry, where the positive superhumps are present only in the first half of the same campaign, confirming that none of them is permanently present in SDSS J0812. In addition, we find for the first time a cyclic variation of the O-C of minima, eclipse depth, and negative superhumps amplitudes for 3.045 (8) d, 3.040(6) d, and 3.053 (8) d in SDSS J0812, respectively, and all reach the maximum at ∼0.75 precession phases of the tilted disc, which provides new evidence for the precession of the tilted disc. We suggest that the O-C and eclipse depth variations may come from a shift of the brightness centre of the precession tilted disc. Our first finding on the periodic variation of negative superhumps amplitude with the superorbital signals is significant evidence that the origin of negative superhumps is related to the precession of the tilted disc.

Optical Study on Spark Plug Gap in Extending Methane Lean Combustion Limits under High Ignition Energy Conditions

<div>Lean combustion has the potential to achieve high thermal efficiency for internal combustion engines. However, natural gas (NG) engines often suffer from slow burning rates and large cyclic variations when adopting lean combustion. In this study, the effects of spark plug gaps (SPGs) on methane lean combustion are optically investigated under high ignition energy conditions. Synchronization measurements of in-cylinder pressure and high-speed photography are performed for combustion analysis. The results show that large SPGs with high ignition energy exhibit great improvement in engine combustion stability and power capability. Under ultra-lean conditions, a large SPG with a high ignition energy of 150–200 mJ can extend the lean limit to 1.55. Combustion images indicate that this is contributed by the enlarged initial flame kernel, which promotes early flame propagation. Besides, an empirical criterion is adopted to quantify the underlying mechanism, and the results confirm that a more stable early flame development with a faster burning rate can be obtained by a larger SPG and higher ignition energy under lean conditions. Therefore, a large SPG is an effective way to improve combustion stability and thermal efficiency for NG engines.</div>

Effect of hydrogen blending on the combustion performance, emission, and cycle-to-cycle variation characteristics of a single-cylinder GDI spark ignition dual-fuel engine

The effect of hydrogen addition on combustion, performance, emission and cyclic variation under different hydrogen flow rates (2, 5, 8, 11, and 14 LPM) were investigated based on a SI engine with hydrogen port induction and gasoline direct injection. The in-cylinder pressure increases by 52.04% with an 8LPM of hydrogen flow rate. The rate of pressure rise and heat release from the hydrogen-gasoline mixture combustion are more concentrated and 95.53% increase in the engine torque. For the specified hydrogen flow rate, brake specific energy consumption was reduced by 92.27% and brake thermal efficiency increased by 25%. Moreover, CO emission was improved after hydrogen addition under all operating conditions. CO2 and NOX emissions were continuously increased with hydrogen addition. The cyclic variation was increased with the increase in the hydrogen flow rate and reduced with the increase in gasoline injection quantity.

Rheological properties and phase behaviour degradation of asphalt mastics under cyclic temperature variations

ABSTRACT Asphalt pavements are continuously subjected to cyclic temperature variations induced by varying day–night and seasonal temperatures. However, the effect of thermal cycling on asphalt materials has not been thoroughly documented. This study conducted accelerated thermal cycling tests on asphalt mastics to simulate the environmental temperature variation. The evolution of the rheological properties and phase behaviors under cyclic temperature variations was clarified. The temperature factors sensitive to damage were identified by establishing the quantitative relationship between the cyclic temperature parameters and these properties. Results demonstrated that, as the expansion of cyclic temperature ranges, the three asphalt mastics gradually lost their viscosity properties and became increasingly elastic. Thermal cycling increased the stiffness and high temperature deformation resistance of the three asphalt mastics, but significantly reduced their stress relaxation capability. The phase structures were degraded upon thermal cycling, weakening the asphalt-aggregate interaction. The temperature difference and cyclic high temperature were the primary factors affecting the rheological performance of the asphalt mastics. SBS modified asphalt mastic displayed remarkable resistance to thermal cycling, demonstrating its potential for application in regions with frequent temperature fluctuations. This research can help us understand the evolution of asphalt pavement performance in areas with frequent temperature changes at a macro-level.

Eclipse timing variations in the WD + dM eclipsing binary RR Cae

ABSTRACT We present the binary model and the eclipse timing variations of the eclipsing binary RR Cae, which consists of a white dwarf eclipsed by an M-type dwarf companion. The multiwavelength optical photometry from the Transiting Exoplanet Survey Satellite (TESS), the 0.6-m PROMPT-8 telescope, and the 0.7-m Thai Robotic Telescope at Spring Brook Observatory, combined with archive H α radial velocities from the Very Large Telescope (VLT) are analysed. From the data, the physical parameters of the system are obtained along with 430 new times of minima. The TESS light curves in 2018 and 2020 show out-of-eclipse variations, which might be caused by a large spot on the secondary component. The light travel time effect models due to the gravitational interaction of one or two circumbinary objects are adopted to fit the cyclic variations in the RR Cae’s O-C curve. The fitting solution of the O-C curve with one circumbinary object model shows a periodic variation with a period of 16.6 ± 0.2 yr and an amplitude of 14 ± 1 s, which can be caused by a planet with a minimum mass of 3.4 ± 0.2 MJup. When we consider the model with two circumbinary objects, the O-C curve shows cyclic variations with periods of 15.0 ± 0.5 yr and 39 ± 5 yr and amplitudes of 12 ± 1 s and 20 ± 5 s, respectively, corresponding to minimum masses of 3.0 ± 0.3 MJup and 2.7 ± 0.7 MJup.

Fuzzy-based global water quality assessment and water quality cells identification using satellite data

The water environmental impact assessment and management programs increasingly rely on accurate and quantitative estimates of water quality parameters through remote sensing, owing to the limitation of the time-consuming field-based approaches. Numerous studies have utilised the remote-derived water-quality products and existing water quality index WQI models, but they are typically site-specific and yield significant errors for the accurate assessment and monitoring of coastal and inland water bodies. This study presents a generalized WQI model that incorporates a flexible number of parameters, simplifying them to produce comprehensive water quality index values with the fuzzy logic approach. To derive these index values, three major water quality parameters such as Chl, TSS and aCDOM443 were estimated using new remote-sensing models, and the corresponding indices Trophic State Index (TSI), Total Suspended Solids Index (TSSI) and CDOM Index (CI) were produced by a generalized index model. Finally, WQI products were derived based on the Mamdani-based Fuzzy Inference System (FIS) and individual contribution of the water quality parameters to WQI was analysed to establish ‘Water Quality Cells’ WQcells, which are represented by the dominant WQ parameter. The new models were tested on MODIS-Aqua and Sentinel-3 OLCI data in different regional and global oceanic waters. Further, a time series analysis was performed in regional coastal oceanic waters (along the Indian coast) to study the seasonal variations of individual water quality parameters and WQI over the period from 2011 to 2020. The results demonstrated that the FIS is efficient in handling the parameters with varying units and their relative importance. The water quality cells were identified in the bloom-dominated (Arabian Sea), TSS-dominated (Point Calimere, India and Yangtze River estuary, China) and CDOM-dominated (South Carolina coast, USA) regions. The time series analysis revealed that the water quality of the Indian coast exhibits cyclic seasonal variations due to the annual occurrence of the south-west and north-east monsoons. These results are critical for monitoring and assessing the quality of surface waters in coastal and inland environments and enabling water resources managers to formulate and implement management plans for a variety of water bodies cost-effectively.

Discussion on the potential of methane-hydrogen dual-fueled Wankel rotary engine

Wankel rotary engine (WRE) is welcomed due to its high power density and compact layout and is criticized due to its low efficiency and poor emission. To develop low-carbon emission and high-efficiency WRE, the present work discusses the potential of hydrogen/methane dual-fueled WRE with varied fuel components. The test was conducted at 1500 r/min, 80 kPa manifold absolute pressure and stoichiometric ratio. The results indicate that compared with pure hydrogen or pure methane WRE, hydrogen/methane dual-fueled WRE can achieve higher thermal efficiency and output power, the maximum values of which are 30.7% and 12.4 kW under test conditions, respectively. Besides, it also has satisfactory NO, CO2 and HC emissions. In particular, there is a linear relationship between NO emission and methane volumetric percentage with a 0.9949 determination coefficient in logarithmic coordinates, which means that the NO emission can be easily predicted. In addition, the cyclic variation is acceptable at maximum-efficiency CH4% and the knock can be almost eliminated in hydrogen-methane dual-fueled WRE when the volume ratio of methane exceeds about 40%. In general, WRE is recommended to be fueled by a mixture of hydrogen and methane with a high methane volumetric percentage.

Experimental Investigation of Cyclic Variation of the In-Cylinder Flow in a Spark-Ignition Engine with a Charge Motion Control Valve

Experimental Investigation of Cyclic Variation of the In-Cylinder Flow in a Spark-Ignition Engine with a Charge Motion Control Valve

House Condition Scoring Scale as a Risk Indicator of Infestation by Aedes in Two Mexican Localities.

Mexico has shown an increase in dengue incidence rates. There are factors related to the location that determine housing infestation by Aedes. This study aimed to determine factors associated with housing infestation by immature forms of Aedes spp. in the dengue endemic localities of Axochiapan and Tepalcingo, Mexico, from 2014 to 2016. A cohort study was carried out. Surveys and inspections of front- and backyards were conducted every 6 months, looking for immature forms of Aedes spp. A house condition scoring scale was developed using three variables (house maintenance, tidiness of the front- and backyards, and shading of the front- and backyards). Multiple and multilevel regression logistic analysis were conducted considering the housing infestation as the outcome and the household characteristics observed 6 months before the outcome as factors; this was adjusted by time (seasonal and cyclical variations of the vector). The infestation oscillated between 5.8% of the houses in the second semester of 2015 and 29.3% in the second semester of 2016. The factors directly associated with housing infestation by Aedes were the house condition score (adjusted odds ratio [aOR]: 1.64; 95% CI: 1.40-1.91) and the previous record of housing infestation (aOR: 2.99; 95% CI: 2.00-4.48). Moreover, the breeding-site elimination done by house residents reduced the housing infestation odds by 81% (95% CI: 25-95%). These factors were independent of the seasonal and cyclical variations of the vector. In conclusion, our findings could help to focalize antivectorial interventions in dengue-endemic regions with similar demographic and socioeconomic characteristics.

Orbital Period Variations of the Eclipsing Binaries RX Ari and V449 Oph

The variations in the orbital period of the eclipsing binaries RX Ari and V449 Oph have been analyzed. It has been shown that the variations in the period of RX Ari can be represented by a superposition of a secular period increase and two cyclic variations. The secular increase in the period can be explained by the exchange of matter between the components. Cyclic variations in the period may be due to the presence of two additional bodies in the system, or only one additional body in combination with the magnetic activity of the main component. The variations in the orbital period of V449 Oph can be represented with almost equal accuracy either as a superposition of two cyclic variations, or as a superposition of a secular period increase and two cyclic variations. The obtained parameters of the light-time effects and magnetic quantities lead to the conclusion that it is preferable to use linear elements to represent the variations in the orbital period of V449 Oph. In this case, one of the cyclic variations can be a consequence of the light-time effect, and the second one can be a consequence of the magnetic activity of the secondary component. Both types of variations can also be a consequence of the magnetic activity of the secondary component.

Studying the cyclic variability (CCV) of performance and NO and CO emissions in a methane-run high-speed SI engine via quasi-dimensional turbulent combustion modeling and two CCV influencing mechanisms

Studying the cyclic variability (CCV) of performance and NO and CO emissions in a methane-run high-speed SI engine via quasi-dimensional turbulent combustion modeling and two CCV influencing mechanisms

The correlation between unemployment and economic growth in Latin America – Okun's law estimates by country

The authors question the validity of Okun's law in Latin America in this paper. Based on several econometric models, they show that fluctuations in economic activity have a lesser impact on unemployment rates in Latin American countries than in other, more advanced economies. Instead of stimulus policies focused on reducing unemployment in general, these countries need targeted policies that encourage job creation in specific sectors. That being said, the unemployment—output ratio differs from one Latin American country to another. Where the ratio is weak or non‐existent, cyclical variations adversely affect the quality of employment – another aspect that must also be addressed by economic policy.

A novel multiple spark ignition strategy to achieve pure ammonia combustion in an optical spark-ignition engine

Ammonia is an attractive carbon-free fuel that has the potential to reduce the need for conventional hydrocarbons (HC) and reduce emissions of undesirable pollutants such as CO, CO2, particulates, and unburned hydrocarbons. However, ammonia has different combustion characteristics than conventional HC fuel. Ammonia is difficult to ignite and has a low combustion rate, resulting in large cyclic variations. In addition, nitrogen oxides (NOx) emissions in the exhaust tract are a major challenge when using ammonia as a fuel directly in engines. In this study, the effect of multiple spark ignition sites on the combustion of pure ammonia in an optical spark ignition engine (SI) was investigated. The experiment was conducted with four spark plugs mounted equidistantly on a special metal liner and one spark plug fitted at the top of the cylinder head. The multiple flames emitted from the different spark ignition sites were captured by natural flame luminosity (NFL) imaging. In the results, the conventional single spark ignition is compared with multiple ignitions. It was found that single spark ignition resulted in lower in-cylinder pressure, longer combustion duration, and higher combustion instability due to the poor ammonia fuel combustion rate. However, firing multiple spark plugs significantly improved combustion stability, increased engine power, and shortened the combustion period under the same operating conditions. In addition, the flame kernels produced by multiple ignition sites resulted in higher NOx emissions in the exhaust tract due to the higher temperatures in the cylinder. In addition, this study also investigated the effect of three different air–fuel equivalence ratios (λ) of 1.0, 1.2, and 1.4 on the combustion characteristics of ammonia fuel. The maximum NOx level was obtained for λ: 1.2 because the excess air in the mixture oxidizes the ammonia and provides abundant oxygen to generate more NOx. Further reducing the ammonia fuel and increasing the excess air to λ: 1.4 dramatically reduced NOx emissions due to the lower pressures and temperatures in the cylinder resulting from the longer combustion period.

Investigation of crack propagation driving force based on crystal plasticity and cyclic J-integral

The fatigue indicator parameter (FIP) is evaluated with cyclic J-integral in single crystal and polycrystal models as the crack driving force for microstructurally fatigue crack growth. A multiscale model is employed with the crack front tip reconstructed with a grain-based crystal plasticity model. The material parameters are selected based on high-strength low-alloy (HSLA) steel, which is widely used as a structure or mechanical device, such as bridges, pipes, or ships. The calculation of cyclic J-integral is implemented and validated with analytical results. In order to investigate the evolutions of FIP and cyclic J-integral on small-scale and large-scale yielding conditions, the nominal strain applied to the model varies from high cycle fatigue (HCF) to low cycle fatigue (LCF). Three modes of fracture, namely, Mode I, Mode II, and Mixed mode, are analyzed by applying corresponding boundary conditions. With the simulation results, the FIP and cyclic J-integral variations are evaluated as the increase of nominal strain. Furthermore, the maximum FIP and averaged FIP are selected as two parameters to correlate with cyclic J-integral by linear regression in logarithm coordinates. The correlation results show a bilinear relation between FIP and cyclic J-integral. The regression parameters indicate the maximum FIP and cyclic J-integral have good correlations in both the single crystal and polycrystal models. For the nonlocal measurement of FIP, the associated values of regression parameters are provided.