Variations In Production Rates Research Articles

Global existence and boundedness in a two‐dimensional parabolic chemotaxis system with competing attraction and repulsion effects

In this paper, we investigate a chemotaxis system under homogeneous Neumann boundary conditions within a bounded domain with a smooth boundary. The system describes the movement of cells in response to two chemical signal substances: one acts as a chemoattractant, while the other serves as a chemorepellent, both produced by the cells. The system takes into account chemotactic sensitivity in the reaction movement when detecting these chemicals. Under certain assumptions, we demonstrate the existence of a unique global bounded classical solution for the proposed problem. To further understand the time evolution of the system's solutions, we conduct numerical experiments and analyze the dynamic properties of the norm of the solutions with respect to variations in chemical production rates.

Wearable Hydrogel SERS Chip Utilizing Plasmonic Trimers for Uric Acid Analysis in Sweat.

Uric acid is typically measured through blood tests, which can be inconvenient and uncomfortable for patients. Herein, we propose a wearable surface-enhanced Raman scattering (SERS) chip, incorporating a hydrogel membrane with integrated plasmonic trimers, for noninvasive monitoring of uric acid in sweat. The plasmonic trimers feature sub 5 nm nanogaps, generating strong electromagnetic fields to boost the Raman signal of surrounding molecules. Simultaneously, the hydrogel membrane pumps sweat through these gaps, efficiently capturing sweat biomarkers for SERS detection. The chip can achieve saturation adsorption of sweat within 5 min, eliminating variations in individual sweat production rates. Dynamic SERS tracking of uric acid and lactic acid levels during anaerobic exercise reveals a temporary suppression of uric acid metabolism, likely due to metabolic competition with lactic acid. Furthermore, long-term monitoring correlates well with blood test results, confirming that regular exercise helps reduce serum uric acid levels and supporting its potential in managing hyperuricemia.

Immediate auditory feedback regulates inter-articulator speech coordination in service to phonetic structure.

Research has shown that talkers reliably coordinate the timing of articulator movements across variation in production rate and syllable stress, and that this precision of inter-articulator timing instantiates phonetic structure in the resulting acoustic signal. We here tested the hypothesis that immediate auditory feedback helps regulate that consistent articulatory timing control. Talkers with normal hearing recorded 480 /tV#Cat/ utterances using electromagnetic articulography, with alternative V (/ɑ/-/ɛ/) and C (/t/-/d/), across variation in production rate (fast-normal) and stress (first syllable stressed-unstressed). Utterances were split between two listening conditions: unmasked and masked. To quantify the effect of immediate auditory feedback on the coordination between the jaw and tongue-tip, the timing of tongue-tip raising onset for C, relative to the jaw opening-closing cycle for V, was obtained in each listening condition. Across both listening conditions, any manipulation that shortened the jaw opening-closing cycle reduced the latency of tongue-tip movement onset, relative to the onset of jaw opening. Moreover, tongue-tip latencies were strongly affiliated with utterance type. During auditory masking, however, tongue-tip latencies were less strongly affiliated with utterance type, demonstrating that talkers use afferent auditory signals in real-time to regulate the precision of inter-articulator timing in service to phonetic structure.

A humidity resistant radon source developed by ion exchange of radium in a membrane

ObjectiveTo develop a humidity resistant radon source on a membrane based on the ion exchange technique. Methods226Ra in its standard solution was adsorbed in the HP membrane through cation exchange. The radioactivity of 226Ra in the membrane was determined through the measurements of 226Ra activities in the solution before and after the adsorption using a HPGe γ spectrometer. The emanation coefficients of radon from the membrane in different humidity conditions were quantified through the measurements of radon concentrations in a close loop mode using the AlphaGUARD DF2000 radon monitor. Long-term measurements of radon concentrations in the close loop and a standard chamber using the membrane as radon source were performed to verify the stability of radon emanation from the source. ResultsA piece (70 ​mm ​× ​20 ​mm) of the HP membrane could adsorb 51.2 kBq of 226Ra in about 30 ​min. The emanation coefficient of radon from the membrane could reach as high as 0.997, and it was hardly changed in a humidity range from 7.5% RH to 94.5 ​% RH. The variation of the radon production rate from the source was only ±1.2 ​% in two weeks at a general laboratory condition, and its emanation stability was also confirmed in a standard radon chamber by using the membrane source for one month. ConclusionThe radon membrane source developed in this study has a stable emanation coefficient regardless the environmental humidity. It can be used as a flow-through radon source in a standard radon chamber.

Fine‐grained sediment production by endolithic sponges on Caribbean coral reefs

AbstractEndolithic sponges are key players in carbonate cycling on coral reef systems. While their bioerosion of reef framework is relatively well studied, their role in biogenic sediment generation is poorly understood. In this study, the sedimentary attributes and production rates of eight Caribbean endolithic sponge species were characterized. The findings revealed notable species‐specific variations in sediment production rates (range: 1.0–6.3 kg CaCO3 m−2 yr−1), alongside consistency in sediment characteristics (modal sizes ranging from 39 to 48 μm). The species‐specific rates were used to explore reef‐scale variations in sponge‐derived sediment generation across 50 reef sites in the Mexican Caribbean. Significant between‐site variability was observed, with estimated annual sediment production ranging from < 0.01 to 0.84 kg m−2 of reef. Production was primarily driven by sponge abundance, with discernible spatial variations in the contributions of different species, which could be related to variability in local environmental conditions. The rapidity at which these sediment producers can utilize dead coral substrates, coupled with their positive response to the changing marine environment, highlights the growing importance of these sponges in modern degraded Caribbean reef systems.

Holocene solar activity inferred from global and hemispherical cosmic-ray proxy records

Variations in solar activity have been proposed to play an important role in recent and past climate change. To study this link on longer timescales, it is essential to know how the Sun has varied over the past millennia. Direct observations of solar variability based on sunspot numbers are limited to the past 400 years, and beyond this we rely on records of cosmogenic radionuclides, such as 14C and 10Be in tree rings and ice cores. Their atmospheric production rates depend on the flux of incoming galactic cosmic rays, which is modulated by Earth’s and the Sun’s magnetic fields, the latter being linked to solar variability. Here we show that accounting for differences in hemispherical production rates, related to geomagnetic field asymmetries, helps resolve so far unexplained differences in Holocene solar activity reconstructions. We find no compelling evidence for long-term variations in solar activity and show that variations in cosmogenic radionuclide production rates on millennial timescales and longer, including the 2,400-year Hallstatt cycle, are explained by variations in the geomagnetic field. Our results also suggest an on-average stronger dipole moment during the Holocene, associated with higher field intensities in the Southern Hemisphere.

What controls the magma production rate along the Walvis Ridge, South Atlantic?

The Walvis Ridge is a volcanic chain with the most pronounced topographic anomaly in the South Atlantic. This study analyzes the factors influencing magma production rates along the ridge to provide insights into hotspot-lithosphere interactions. With the sub-lithospheric gravity effect excluded, we determine the crustal thickness in the South Atlantic via gravity inversion. By subtracting the age-averaged crustal thickness, we isolate the excess crustal thickness attributable to ridge magmatism and calculate the magma generation rate along the Walvis Ridge over the past 80 Ma. Our results reveal a relatively lower magma production rate in the Walvis Ridge (peaking at ∼2.5 m3/s) compared to other major hotspot tracks (e.g. Hawaii-Emperor seamount chain, Ninetyeast Ridge, or Deccan-Reunion hotspot). Furthermore, variations in magma production rate show a strong inverse correlation with lithospheric thickness (or crustal age) at the time of loading but no significant correlation with spreading rate. Extensively distributed fracture zones in the lithosphere also promote magma production during the period of ∼70–40 Ma. Together with previously identified spreading-type magmatism in the northeast Walvis Ridge, we infer that external tectonic factors, other than hotspot-related factors, play a crucial role in magma production rate across the entire Walvis Ridge.

Pressure- and Rate-Transient Model for an Array of Interfering Fractured Horizontal Wells in Unconventional Reservoirs

Summary An analytical solution is presented for pressure- and rate-transient behavior of an array of n parallel and fractured horizontal wells in an unconventional reservoir. Wells are of equal length but otherwise of unidentical properties. Each well has an arbitrary number of uniformly spaced identical, finite-conductivity fractures and is surrounded by a stimulated reservoir volume (SRV). The properties of hydraulic fractures (HFs) and SRVs may vary from well to well. Different properties may also be assigned to the unstimulated reservoir sections between wells. Natural fractures in stimulated and unstimulated reservoir volumes are accounted for by transient dual-porosity idealization. The flow domain is divided into blocks of 1D flow under the trilinear-flow assumption. Solution for each block is obtained analytically and coupled with the solutions for the neighboring blocks by the continuity of pressure and flux at the block interfaces. Drainage volumes of wells are adjusted based on the variation of well production rates because of moving no-flow boundaries between wells. The superposition principle is applied to consider variable-production conditions as well as nonsynchronous production and shut-in schedules of wells. The final solution is in the form of a matrix-vector equation in the Laplace transform domain and inverted into the time domain numerically. The model is robust and reasonably accurate for most practical applications of single-phase oil and gas production from multiple wells in an unconventional reservoir. It is an efficient tool to assess well interference effects for different well completion designs and varying reservoir characteristics. The speed of the model makes it useful for pressure-transient and production-data analysis, as well as for the initial calibration and verification of more complex numerical models.

Synchronizing the Western Gotland Basin (Baltic Sea) and Lake Kälksjön (central Sweden) sediment records using common cosmogenic radionuclide production variations

Multi-archive studies of climate events and archive-specific response times require synchronous time scales. Aligning common variations in the cosmogenic radionuclide production rate via curve fitting methods provides a tool for the continuous synchronization of natural environmental archives down to decadal precision. Based on this approach, we synchronize 10Be records from Western Gotland Basin (WGB, Baltic Sea) and Lake Kälksjön (KKJ, central Sweden) sediments to the 14C production time series from the IntCal20 calibration curve during the Mid-Holocene period ~6400 to 5200 a BP. Before the synchronization, we assess and reduce non-production variability in the 10Be records by using 10Be/9Be ratios and removing common variability with the TOC record from KKJ sediments based on regression analysis. The synchronizations to the IntCal20 14C production time scale suggest decadal to multi-decadal refinements of the WGB and KKJ chronologies. These refinements reduce the previously centennial chronological uncertainties of both archives to about ± 20 (WGB) and ±40 (KKJ) years. Combining proxy time series from the synchronized archives enables us to interpret a period of ventilation in the deep central Baltic Sea basins from ~6250 to 6000 a BP as possibly caused by inter-annual cooling reducing vertical water temperature gradients allowing deep water formation during exceptionally cold winters.

HdC and EHe stars through the prism of Gaia DR3

Context. The Gaia DR3 release includes heliocentric radial velocity measurements and velocity variability indices for tens of millions of stars observed over 34 months. Aims. In this study, we utilise these indices to investigate the intrinsic radial velocity variations of Hydrogen-deficient Carbon (HdC) stars and Extreme Helium (EHe) stars across their large ranges of temperature and brightness. Methods. Taking advantage of the newly defined HdC temperature classes, we examine the evolution of the total velocity amplitude with effective temperature. Additionally, we analyse the variation in the dust production rate of R Coronae Borealis (RCB) stars with temperature using two different proxies for the photometric state of RCB stars: one from Gaia and another from the 2MASS survey. Results. Our observations revealed a trend in the evolution of the maximum radial velocity amplitude across each HdC temperature class. Similarly, we also observed a correlation between stellar temperature and the dust production rate. Conclusions. Interestingly, we possibly observed for the first time some variations of the intrinsic radial velocity amplitude and the dust production rate with HdC temperature class. If confirmed, these variations would indicate that the helium shell-burning giant stage starts with strong atmospheric motions that decrease in strength, up to ~6000 K, before picking up again as the HdC star atmosphere shrinks further in size and reaches warmer temperatures. Moreover, the dust formation rate appears to be much higher in colder RCB stars compared to warmer ones.

Quantitative prediction of wear failure based on dissipative methodology under dry friction

The evaluation and prediction on failure of friction pair are important for improving equipment reliability and life span. In engineering practice, researchers often determine the severe-wear stage by monitoring changes in wear and the friction coefficient. However, existing criteria for evaluating the wear process are nebulous, leading to the ambiguous relationship between the measured parameters and the wear process which cannot be precisely quantified. In this study, based on dissipation theory, an exploration into the system entropy production rate variations throughout the wear process has been conducted. This investigation reveals that entropy production rate variations at different wear stages, providing a basis for segmenting the wear process. Through experimental methods, a clear transitional stage with substantial entropy production rate variations between the mild-wear and severe-wear stages has been discovered. These findings gave a novel method for predicting wear failure. The efficacy of this proposed approach has been validated by experiment, thus laying a theoretical groundwork for early failure prediction of critical components principally prone to wear failure. Furthermore, this work provides the foundation for the construction of visual data system in friction-wear digital twin systems.

Generalization of inter-articulator timing control: Evidence from tongue-jaw and lip-jaw kinematics using electromagnetic articulography

Recent research in speech production indicates that talkers reliably control the relative timing of articulator movement onsets across variation in production rate, syllable stress, and segmental makeup and that this precision of inter-articulator timing control instantiates phonetic structure. To date, these timing relations have been highly reliable for tongue-jaw kinematics. In the present study, we address the generality of these timing relations to lip-jaw kinematics. Eleven talkers recorded 240 /tV#Cat/ and 240 / bV#Cab/ utterances using electromagnetic articulography, with alternative V (/ɑ/-/ɛ/) and C (/t/−/d/ or /p/−/b/), across changes in production rate (fast-normal) and stress (first syllable stressed-unstressed). To quantify inter-articulator temporal coordination, the timing of either tongue-tip or lower-lip raising onset for the intervocalic C, relative to the jaw opening-closing cycle for V, was obtained. Results indicate that the same kinematic pattern occurred among both sets of articulators: any manipulation that shortened the jaw opening-closing cycle reduced the latency of either tongue-tip or lower-lip movement onset, relative to the onset of jaw opening. Furthermore, the movement onset latencies of the tongue-tip and lower-lip were both highly differentiated by utterance type, bolstering the view that inter-articulator timing relations instantiate phonetic structure in the resulting acoustic signal.

An investigation of the effect of drawdown pressure on sand production in an Iranian oilfield using a hybrid numerical modeling approach

AbstractReservoir pressure reduction due to continuous production from oil and gas wells affects the sand production rate. An increase in drawdown pressure and/or a decrease in reservoir pressure increases the sand production rate. Since the problem of sand production is one of the main issues in the Asmari sandstone formation located in one of the oilfields in the southwest of Iran, therefore, in this research, the variations in the sand production rate due to the changes in the reservoir and drawdown pressures were investigated. So, for the first time, a hybrid numerical model of finite difference method (FDM)—discrete element method (DEM)—finite element method (FEM)—computational fluid dynamics (CFD) was developed. This numerical model investigated the increase in the sand production rate due to variations in reservoir pressure with a constant bottom-hole flowing pressure. Then, by performing an extensive sensitivity analysis on different values of reservoir pressure and drawdown pressure, the changes in the sanding rate, the critical drawdown pressure, and the safe drawdown line were determined. The results showed that, if the production flow rate of the well is constant, increasing the drawdown pressure can change the sand production rate only to a certain extent, and more than that, will be produced at a constant rate. Also, adjusting the drawdown pressure within a safe range does not necessarily keep the sand production rate constant at a permissible value for a long time, while by keeping the bottom hole flowing pressure constant within an acceptable range, the sand production rate can be controlled for a longer period.

Virus production in shallow groundwater at the bank of the Danube River.

Viruses play a crucial role in regulating prokaryotic populations, yet their impact on subsurface environments, specifically groundwater habitats, remains poorly understood. In this study, we employed the virus-dilution approach to measure lytic virus production rates in shallow groundwater located near the city of Vienna (Austria) during the period from July-November 2020. Physico-chemical parameters (pH, electrical conductivity, water temperature, concentration of dissolved oxygen), prokaryotic, and viral abundance, and viral decay rates were monitored as well. Our findings revealed low virus-to-prokaryote ratios varying between 0.9-3.9 throughout the study period and a lack of correlation between prokaryotic and viral abundance in groundwater. Virus production rates varied between 9-12% of viral abundance h-1 in July-August and between 34-36% of viral abundance h-1 in October-November. Seasonal variations in virus production rates were found to be correlated with electrical conductivity, revealing ~3.5 times higher virus production rates during periods with high electrical conductivity and low groundwater recharge in October-November compared to July-August with higher groundwater recharge and lower electrical conductivity. Our data indicate that groundwater recharge disrupts the balance between virus and prokaryotic host communities, resulting in a deficiency of suitable prokaryotic host cells for viral proliferation.

Variation in Cerebrospinal Fluid Production Rate During Asleep and Awake States

Variation in Cerebrospinal Fluid Production Rate During Asleep and Awake States

Local scale extreme low pH conditions and genetic differences shape phenotypic variation in a broad dispersal copepod species

Extreme low pH events in estuaries and upwelling areas can modulate the phenotypic and genetic diversity of natural populations. To test this hypothesis, we explored the linkage between local scale extreme low pH events, genetic diversity, and variation in fecundity-related traits (body size, egg size, and egg production rate) in the broad-dispersal copepod Acartia tonsa. We assessed genetic and phenotypic characteristics of populations by contrasting extreme low pH environments (upwelling and temperate estuary) in the coastal Southeast Pacific, under natural and experimental conditions. These populations showed significant genetic differentiation with higher diversity in mitochondrial and nuclear loci (encoding mtCOI and 18S rRNA) in the estuarine population. Copepods from this population are exposed to more frequent extreme low pH events (< 7.7), and the adult females exhibit consistent phenotypic variation in body size, egg size, and egg production rate across different cohorts. Experimental acclimation to extreme low pH conditions revealed no significant differences in fecundity-related traits between A. tonsa populations. Although these results partially support our hypothesis, the experimental findings suggest other drivers might also influence phenotypic differences in the local environments.

Spatial Variability in the Primary Production Rates and Biomasses (Chl a) of Sea Ice Algae in the Canadian Arctic–Greenland Region: A Review

The aims of this review are to elucidate the spatial variation in the primary production rates and biomasses (Chl a) of sea ice algae in the Canadian Arctic–Greenland region, characterized by its comparable physical settings. A database was compiled from 30 studies of the production rates and biomasses (Chl a) of sea ice algae, the snow and ice thicknesses, ice types, nutrients (Si(OH)4, PO4, (NO3 + NO2)), and NH4 concentrations in the ice and below the ice from the region. Production rates were significantly higher (463 mg C m−2 d−1) in Resolute Bay and Northern Baffin Bay (317 mg C m−2 d−1), both in the Canadian Arctic, compared to a rate of 0.2 mg C m−2 d−1 in northeast Greenland. The biomasses reached 340 mg Chl a m−2 in Resolute Bay in comparison to 0.02 mg Chl a m−2 in southwest Greenland. Primary production at other Canadian and Greenland sites was comparable, but sea ice Chl a was higher (15.0 ± 13.4 mg Chl a m−2) at Canadian sites compared to Greenland ones (0.8 ± 0.5 mg Chl a m−2). Resolute and Northern Baffin Bay production rates were significantly higher when compared to other Arctic Ocean sites outside the studied region. The review concludes that the high production rates and biomasses in Resolute and Northern Baffin Bay are related to the inflow and mixing of nutrient-rich waters of Pacific origin. A conceptual model with drivers and inhibitors of the primary production of sea ice algae is proposed, and the database is compiled into a dataset of published data for further studies.

Unsaturated water flow-induced the structure variation of gas hydrate reservoir and its effect on fluid migration and gas production

Multi-phase (gas, saturated water, and unsaturated water) seepage is bound to exist in natural gas hydrates (NGHs) production process. The effect of water flow, especially for unsaturated water flow, on the permeability variation of hydrate reservoir and gas production behavior do not appear well understood. In this study, the unsaturated water flow in hydrate-bearing sediment and hydrate-free sediment is simulated by controlling water flow velocity. The hydrate phase distribution was monitored using visualization magnetic resonance imaging system. The variation of temperature, pressure, and gas production rate during the unsaturated water flow were analyzed. The results show that the changing trend of the pressure difference presented the three stages for the hydrate-free sediment. In contrast, the pressure difference followed a five-stage change for the hydrate-bearing sediment in the unsaturated water flow process due to the hydrate dissolution. The hydrate dissolution caused an increase in permeability (maximum of log10(Kr) was 0.5) and formed the obvious unsaturated water flow channel. Moreover, the higher water flow velocity, which increased the chemical potential difference between hydrate phase and water phase, accelerated the MH dissolution, and further induced the faster increase rate of permeability and gas production. Surprisingly, when the unsaturated water flow velocity was improved to 15 mL/min from 0.5 mL/min, the gas production rate increased by 35 times. Furthermore, the average gas production rate was mainly determined by the unsaturated water flow velocity, it was changing in a linear fashion with the increasing water flow velocity. The findings could provide new knowledge on the strategy design on NGHs production with high efficiency.

Assessment of Oil Chromatography Sensor Failure for Transformer Based on Multi-dimensional Data-driven

Online monitoring and analysis of transformer oil chromatography is of great significance for the assessment of internal insulation with transformer operation. The existence of numerous invalid monitoring sensors in the field makes the quality of online monitoring data degraded, which makes the online monitoring system unable to monitor the operating status of transformers in a timely and accurate manner. This paper propose a data-driven method for evaluating the effectiveness of oil chromatography monitoring sensors by selecting a fixed-length feature data set from online data for evaluation, and then using the distribution of abnormal values, the distribution of consecutive identical values, the variation of coefficient of variation and the variation of gas production rate in the feature data set as criteria to judge the feature data set and obtain the corresponding discriminant values. Afterwards, the discriminant values are assigned weights according to the focus of each criterion to obtain the sensor status values, which are compared with the preset tolerance level to obtain the sensor evaluation results. The method proposed evaluates the effectiveness of online monitoring sensors from several aspects, which can detect faulty sensors in time and is of great significance for improving the accuracy of online monitoring data and the reliability of monitoring device.

Seasonal Dynamics of Primary Production in the Southeastern Bering Sea Assessed Using Continuous Temporal and Vertical Dissolved Oxygen and Chlorophyll‐a Measurements

AbstractThe Bering Sea and other high‐latitude systems are experiencing unprecedented changes related to climate warming and the consequent loss of sea ice. Understanding how such changes influence primary production is a pressing question. Here, we quantify primary production rates in the southeastern Bering Sea over 4 years (2016–2019) at daily to weekly time resolution. A moored high‐resolution Profiling Crawler was used in combination with in situ sampling to collect physical and biological data in the ocean's upper 50 m. We used dissolved oxygen (O2) data to estimate gross and net primary production (NPP), and chlorophyll‐a (Chl‐a), temperature, and irradiance data to model NPP rates. We then assessed seasonal variation in phytoplankton production rates, phytoplankton community growth rates () and explored to what extent summer phytoplankton community growth rates may be influenced by nitrogen limitation. Our analyses revealed that the majority of gross primary production (GPP) and net community production occurs in association with the spring phytoplankton bloom. After the bloom, the water column generally experienced low GPP and net biological carbon consumption. Phytoplankton growth rates were commonly suppressed in late summer due to apparent nitrogen depletion. Using high temporal resolution vertically resolved measurements of O2 and Chl‐a, our analyses provides important insight into how biogeochemical cycles, phytoplankton community growth rates, and carbon available for export vary seasonally in the southeastern Bering Sea.