Saturation Patterns Research Articles

An Analytical Framework for the IEEE 802.15.4 MAC Layer Protocol under Periodic Traffic.

As the reference communication standard of wireless sensor networks (WSNs), the IEEE 802.15.4 standard has been adopted in various WSN-based applications. In many of these applications, one of the most common traffic pattern types is a periodic traffic patterns, however, the majority of existing analytical models target either saturated or unsaturated network traffic patterns. Furthermore, few of them can be directly extended to the periodic traffic scenario, since periodic traffic brings unstable load status to sensor nodes. To better characterize the WSNs with periodic traffic, we propose an accurate and scalable analytical framework for the IEEE 802.15.4 MAC protocol. By formulating the relationship between clear channel assessment (CCA) and its successful probability from the perspective of channel state and node state, single node’s behavior and whole network’s performance under different network scales and traffic loads can be derived. Extensive simulations are conducted to validate the proposed framework in terms of both local statistics and overall statistics, and the results show that the model can represent the actual behavior and the real performance of both single node and whole network. Besides, as the simplified version of double CCAs mode (DS mode), single CCA mode (SS mode), is also analyzed with simple modifications on the proposed analytical framework. Combining the analytical framework with simulation results, the applicable network scenarios of two modes are also demonstrated respectively. Finally, an approximate distribution of one data packet’s backoff duration is proposed. With this approximate distribution, a conservative estimation of data packet’s average transmission latency in networks with given configurations can be easily carried out.

Energy-Sufficiency for a Just Transition: A Systematic Review

Efforts to achieve an energy transition often neglect to account for the levelling of benefits realizable with higher levels of energy use, despite knowledge of a saturation effect and recognition of increasing harms of use. This research examines energy sufficiency as a maximum quantity of energy associated with improvements in human well-being to inform a recalibration of energy targets among high-energy societies. A systematic review of recent research was performed to identify the point at which increasing levels of energy use no longer correlate with meaningful increases in well-being. For selected studies (n = 18), energy sufficiency values range from 60–221 gigajoules per capita per year with a mean of 132 gigajoules per capita per year for associated measures of well-being. The review finds agreement in a pattern of saturation and provides a range of values for energy sufficiency maximums, suggesting that a relatively modest amount and a diverse quality of energy is needed to support high levels of human well-being. Beyond the conventional emphasis on energy efficiency and renewable energy, energy sufficiency therefore offers a necessary and complementary approach for supporting just and ecological energy transitions.

Characteristics of the air‒sea exchange of gaseous mercury and deposition flux of atmospheric mercury at an island near the boundary of the Bohai Sea and Yellow Sea

The variations of dissolved gaseous mercury (DGM, mainly Hg 0 ), air‒sea exchange of Hg 0 , and deposition of atmospheric mercury were very limited in nearshore regions of North China. Nearly two years measurements of DGM in surface seawater and gaseous elemental mercury (GEM or Hg 0 ) in the atmosphere over the Changdao Island were conducted to elucidate the characteristic of air‒sea exchange of Hg 0 based on meteorological parameters. Simultaneously, the wet deposition fluxes of atmospheric Hg were also calculated based on the precipitation amounts and concentrations of total mercury in precipitation (THg p ). The results show that both DGM and Hg 0 flux exhibit a distinct seasonal pattern with the order of summer (47.7 pg l −1 and 1.46 ng m −2 h −1 ), spring (24.6 pg l −1 and 0.82 ng m −2 h −1 ), fall (21.7 pg l −1 and 0.70 ng m −2 h −1 ), and winter (19.0 pg l −1 and 0.21 ng m −2 h −1 ). However, a striking feature in winter is that the study site and peripheral area sporadically act as a sink of atmospheric Hg 0 as a result of elevated GEM concentrations and low water temperature and solar radiation. The seasonal pattern of saturation was in line with that of DGM. In addition, a distinct diurnal cycle of DGM was observed with maximum concentrations at midday and minimum concentrations in nighttime during the whole study period, especially in summer. These remarkable seasonal and diurnal patterns indicate that the elevated DGM concentration in summer and midday appears mainly a photochemically driven. The mean unfiltered (UTHg) and dissolved (DTHg) seawater THg concentrations were 1.43 ± 0.94 and 0.53 ± 0.19 ng l −1 , respectively. On average, the mean DTHg/UTHg ratio was 0.45 ± 0.16, indicating that less than half of THg was concentrated in DTHg. There was no significant relationships between DGM and DTHg. Seasonal concentrations of THg p were 17.3, 7.4, 7.0, and 27.9 ng l −1 , whereas seasonal wet deposition fluxes were 1.28, 1.31, 0.82, and 0.62 μg m −2 yr −1 for spring, summer, fall, and winter, respectively. Overall, the THg p concentrations varied from 3.9 to 60.1 ng l −1 with a mean value of 16.4 ng l −1 , and the direct wet deposition flux was 4.03 μg m −2 yr −1 , representing approximately 57.4% of the annual evasion flux of Hg 0 (7.02 μg m −2 yr −1 ). • Similar distinct seasonal patterns of DGM, saturation, and Hg 0 flux were observed. • Diurnal DGM cycle was found with the highest values at midday especially in summer. • There were no significant relationships between DGM and DTHg as well as UTHg. • The seasonal patterns of DGM/UTHg and DGM/DTHg were opposite to that of UTHg. • Wet deposition flux of Hg constituted about 57.4% of the emission flux of gaseous Hg.

Intra-catchment variability of surface saturation – insights from physically based simulations in comparison with biweekly thermal infrared image observations

Abstract. In this study, we explored the spatio-temporal variability of surface saturation within a forested headwater catchment using a combined simulation–observation approach. We simulated the occurrence of surface saturation in the Weierbach catchment (Luxembourg) with the physically based model HydroGeoSphere. We confronted the simulation with thermal infrared images that we acquired during a 2-year mapping campaign for seven distinct riparian areas with weekly to biweekly recurrence frequency. Observations and simulations showed similar saturation dynamics across the catchment. The observed and simulated relation of surface saturation to catchment discharge resembled a power law relationship for all investigated riparian areas but varied to a similar extent, as previously observed between catchments of different morphological and topographical characteristics. The observed spatial patterns and frequencies of surface saturation varied between and within the investigated areas and the model reproduced these spatial variations well. The good performance of the simulation suggested that surface saturation in the Weierbach catchment is largely controlled by exfiltration of groundwater into local topographic depressions. However, the simulated surface saturation contracted faster than observed, the simulated saturation dynamics were less variable between the investigated areas than observed, and the match of simulated and observed saturation patterns was not equally good in all investigated riparian areas. These mismatches between observations and simulation highlight that the intra-catchment variability of surface saturation must also result from factors that were not considered in the model set-up, such as differing subsurface structures or a differing persistence of surface saturation due to local morphological features like perennial springs.

Bottle-feeding an infant feeding modality: An integrative literature review.

Bottle‐feeding is an infant feeding modality that has been in existence since ancient times, and currently, a significant number of infants are being fed via a bottle with either breastmilk or formula. Although research on bottle‐feeding has continued, it exists in fragmented, often small studies that focus on singular aspects of feeding an infant using a bottle, with limited information on the bottle‐feeding act. Systems theory was the approach used to define the act of bottle‐feeding and identify the parts within this act. Health databases were searched using MeSH terms. A summary of the studies are included. The findings of this review revealed that healthy term bottle‐feeding infants use similar tongue and jaw movements, can create suction and sequentially use teat compression to obtain milk, with minimal differences in oxygen saturation and SSB patterns, when compared with breastfeeding infants. Bottle and teat characteristics were revealed to affect infant feeding and milk intake. An infant's milk intake during feeding was shown to have a strong association with the interaction between the infant and parent/caregiver. With the issue of who controls the feed, mother or infant, likely to affect an infant's ability to self‐regulate their milk intake. Redefining bottle‐feeding as a holistic system identifies the interrelationship of the various parts which will improve the understanding of the reciprocal nature of infant feeding. To optimize bottle‐feeding outcomes, further research is required on parents' and health professionals' knowledge and understanding of the parts within the act of bottle‐feeding.

Response of soil bacterial community and geochemical parameters to cyclic groundwater‐level oscillations in laboratory columns

AbstractGroundwater‐level oscillations change geochemical conditions, C cycling processes, and bacterial community composition, and these changes may vary vertically with depth in a soil. In this study, soil column experiments were conducted to explore variations in soil bacterial community composition and its associated geochemical parameters to rapid short‐term cyclic groundwater‐level oscillations driven by natural fluctuations (NF) and rainfall infiltration (RI), and the results are compared with a quasistatic (QS) column. Water saturation patterns in vadose and oscillated zones, and O2 level patterns, soil total organic C (TOC) removal rates, and soil bacterial community composition in vadose, oscillated, and saturated zones were evaluated. Results showed that water saturation and O2 level oscillated with groundwater level in NF and RI columns. Total organic C removal rates in RI column were the highest across vadose (∼38.4%), oscillated (∼35.8%), and saturated (∼35.2%) zones. Deltaproteobacteria, which were significantly correlated with TOC removal (p < .05), were found in higher abundance in the vadose and oscillated zones of the RI column than in the QS and NF columns. Soil bacterial community structure was dynamic at the class level due to water saturation, O2 level, and TOC removal. Total organic C removal was the driver to separate the distribution of bacterial community structure in the vadose and oscillated zones of the RI column from those of the QS and NF columns. This study suggests that RI induced rapid, short‐term, cyclic, groundwater‐level oscillations could significantly influence both the soil C cycle and bacterial community structure in the vadose and oscillated zones.

Near‐Infrared Spectroscopy Reveals Brain Hypoxia and Cerebrovascular Dysregulation in Primary Biliary Cholangitis

Primary biliary cholangitis (PBC) is an autoimmune cholestatic liver disease linked to symptoms including fatigue and altered mood/cognition, indicating that chronic liver inflammation associated with PBC can impact brain function. We employed near-infrared spectroscopy (NIRS), a noninvasive neuroimaging technique, to determine whether patients with PBC exhibit reduced cerebral oxygen saturation (StO2 ) and altered patterns of microvascular cerebral blood perfusion and whether these alterations were associated with clinical phenotype. This observational case-control study was conducted at a tertiary hospital clinic (University of Calgary Liver Unit). Thirteen female patients with noncirrhotic PBC, seven female patients with cirrhotic PBC, and 11 healthy female controls were recruited by physician referral and word of mouth, respectively. NIRS was used to measure cerebral hemoglobin and oxygen saturation. A wavelet phase coherence method was used to estimate the coherent frequency coupling of temporal changes in cerebral hemodynamics. The PBC group demonstrated significantly reduced cerebral StO2 (P=0.01, d=0.84), indicating cerebral hypoxia, significantly increased cerebral deoxygenated hemoglobin concentration (P<0.01, d=0.86), and significantly reduced hemodynamic coherence in the low-frequency band (0.08-0.15 Hz) for oxygenated hemoglobin concentration (P=0.02, d=0.99) and total hemoglobin (tHb) concentration (P=0.02, d=0.50), indicating alterations in cerebrovascular activity. Complete biochemical response to ursodeoxycholic acid (UDCA) therapy in early patients with PBC was associated with increased cerebral tHb concentration and decreased hemodynamic coherence. Using NIRS, patients with PBC were found to have hypoxia, increased cerebral hemoglobin concentration, and altered cerebrovascular activity, which were reversed in part in UDCA responders. In addition, symptoms and quality-of-life measures did not correlate with brain hypoxia or cerebrovascular dysregulation in patients with PBC.

Finding indications of lag time, saturation and trading inflow in the emergence record of exotic agricultural insect pests in Japan

Agricultural imports are the primary pathway for the introduction of exotic insect pests. The invasion records of exotic insect pests are also influenced by the lag time before detection and saturation caused by the limited species pool of potential invaders. We compiled an exhaustive list of exotic insect species in mainland Japan and tried to evaluate the connection between the commodity types of agricultural imports and insect types of agricultural pests, in addition to the effects of lag time and saturation. We found that lag time was prominent when all pest types were merged into one group, whilst saturation always existed when we divided the records into the four agricultural pest types. Saturation was especially prominent in stored product pests because this group contained many cosmopolitan insect pests that could have easily inhabited the newly built mills throughout Japan in the 1950s. We suspect that the saturation effect was masked by admixture amongst pests with different saturation patterns. Our findings indicate that all commodities, i.e. flowers, fruits, vegetables, cereal and timber, contributed to the invasion of pest insects as potential pathways. However, it was unclear if certain items had comparatively greater significance in this process.

Experimental and numerical study of the impact of viscosity ratio and velocity on the multiphase flow in micromodels

The process of fluid displacement in a microscale of porous media in oil reservoirs rock is affected by several factors. Understanding the effects of factors in multiphase flow mechanisms in porous media through numerical investigations allows us to estimate the flow behavior. In this study, the effect of important parameters like viscosity ratio and velocity on displacement in porous media was investigated using the volume of fluid method as a numerical model. So, a set of governing equations were calculated under a wide range of injection velocities and viscosity ratios to characterize displacing pattern. A similar experiment was done on a micromodel to validate the numerical method, and a rational agreement was reached between the experimental and numerical results. Saturation, velocity, pressure, breakthrough times, displacement efficiencies and displacement patterns were studied. Results show that the effect of viscosity ratio is more important than the effect of velocity. If the viscosity ratio increases five times, injection rate has to decrease 10 times to recover the same amount of oil. However, in a homogeneous porous media, fingering takes place due to the interaction of some forces where in a heavy oil reservoir the viscous forces play the main role. Also, pore scale events were investigated to better understanding the role of film rupture, coalescence, pinch off and splitting in meniscus displacement through the throat of the pore.

Hue, chroma, and lightness preference in Chinese adults: Age and gender differences

AbstractRecent studies have shown cultural differences in color preference. However, the color preference of people in China, which was found to have its own pattern, was yet to be studied in depth. The current study investigated color preference and the associated age and gender differences in an adult national sample (N = 1290) to provide a culture‐specific characteristic of color perception. Participants rated how much they liked each of 31 colors (four chroma‐lightness levels of red, orange, yellow, green, cyan, blue, and purple, plus three achromatic colors). We found a unique saturated color preference pattern characterized by red, cyan, and blue being preferred the most and orange as the least preferred chromatic color. The “red preference” phenomenon was observed in Chinese adults. Light colors were preferred the most in terms of chroma‐lightness level, followed by saturated, muted, and dark colors. The results of a principal component analysis of the 28 chromatic colors showed that blue‐green‐like colors (cool colors) constituted the largest proportion of color preference. The preference for orange and several dark colors increased with age, while that for bluish colors, purple, yellow, white, black, and light colors decreased. In terms of gender, women liked cyan, white, pink, and light colors and disliked red, orange, and dark colors more than men did. Our findings provide new empirical evidence about the color preference of Chinese and may offer some insight into the study of color preference and lay the foundations for future theoretical and practical research.

149 Does discharging infants home on caffeine affect the pattern of oxygen saturation?

149 Does discharging infants home on caffeine affect the pattern of oxygen saturation?

Non-Embedded Ultrasonic Detection for Pressure Cores of Natural Methane Hydrate-Bearing Sediments

An apparatus for the analysis of pressure cores containing gas hydrates at in situ pressures was designed, and a series of experiments to determine the compressional wave response of hydrate-bearing sands were performed systematically in the laboratory. Considering the difficulties encountered in performing valid laboratory tests and in recovering intact hydrate bearing sediment samples, the laboratory approach enabled closer study than the marine environment due to sample recovery problems. The apparatus was designed to achieve in situ hydrate formation in bearing sediments and synchronous ultrasonic detection. The P-wave velocity measurements enabled quick and successive ultrasonic analysis of pressure cores. The factors influencing P-wave velocity (Vp), including hydrate saturation and formation methodology, were investigated. By controlling the initial water saturation and gas pressure, we conducted separate experiments for different hydrate saturation values ranging from 2% to 60%. The measured P-wave velocity varied from less than 1700 m/s to more than 3100 m/s in this saturation range. The hydrate saturation can be successfully predicted by a linear fitting of the attenuation (Q−1) to the hydrate saturation. This approach provided a new method for acoustic measurement of the hydrate saturation when the arrival time of the first wave cannot be directly distinguished. Our results demonstrated that the specially designed non-embedded ultrasonic detection apparatus could determine the hydrate saturation and occurrence patterns in pressure cores, which could assist further hydrate resource exploration and detailed core analyses.

Plant Species and Hydrology as Controls on Constructed Wetland Methane Fluxes

Core IdeasWetland plant species and site hydrology affect methane fluxes.Plant species effects were clearer under stable hydrology in mesocosm experiments.Species was not as important as the long‐term saturation pattern under variable field hydrologic conditions.Plants which emit methane under isolated mesocosm conditions do not necessarily do so under field conditions.Water table height and fluctuation may be a more dominant control over methane fluxes in wetland soils.Wetlands are the largest natural source of atmospheric methane (CH4), a potent greenhouse gas. Hydrology and species composition are important controls on wetland CH4emissions. Few studies target interactive effects on CH4fluxes, but rather study variables in isolation. Therefore, we asked: How do hydrology and plant species interact to affect CH4fluxes from wetland soils? We measured CH4fluxes under stable water tables in mesocosms planted withAsclepias incarnataL. and mesocosms planted withAlisma trivialePursh. We then tested the interactive effects in saturated and unsaturated restored field locations by measuring CH4fluxes from the plants and the surrounding soil. In mesocosms, CH4fluxes fromA. incarnatawere 8‐fold greater than fluxes from control (no plant) orA. trivialemesocosms.Alisma trivialemesocosms had higher CO2to CH4ratio (less methanogenic dominance) than control mesocosms but did not differ significantly fromA. incarnatamesocosms. In the field, hydrology was the dominant control of CH4flux; both plant species produced approximately 10‐fold more CH4in saturated plots than in unsaturated plots. Incorporating hydrology and species composition into modeling will better predict CH4fluxes from wetland soils, which in turn could aid in designing restored wetlands that offset greenhouse gas emissions.

Calibration of 2‐D soil zymography for correct analysis of enzyme distribution

Soil zymography is a new technique developed to visualize two‐dimensional distributions of enzyme activities. The method consists of incubating a membrane saturated with an enzyme‐specific fluorogenic substrate on a surface of the soil sample, followed by recording the membrane image generated by a fluorescent product (e.g. MUF: methylumbelliferone) in ultraviolet light. Despite its relative ease of use, performing zymography involves multiple user‐made decisions that might affect the accuracy of enzyme activity estimates. Therefore, unification of the zymography methodology is required for correct estimations and comparisons of various studies. We evaluated the following methodological aspects of the implementation of zymography: (a) camera settings and image processing, (b) effects of evaporation and (c) calibration procedures. Camera settings (shutter speeds or exposure time) affected the intensity of background fluorescence and signal‐to‐noise ratios (SNR). However, because their combined effects varied depending on MUF concentrations, light and camera setting need to be optimized for the expected range of MUF concentrations prior to zymography. Evaporation of MUF solution from the membrane had no effect on fluorescence. Relations between MUF concentration and intensity of fluorescence during calibrations demonstrated a saturated pattern and were strongly affected by image noise outside the optimal range (e.g. 8–14 μm MUF pixel−1). We developed a new calibration approach that is based on a piecewise linear regression. The new approach accounted for specific ranges of MUF concentration and uses nonuniformly saturated membranes, reflecting the real distribution of enzyme activities in soil. The new calibration algorithm eliminated biases of the standard calibration and resulted in greater accuracy in predicting MUF concentrations.Highlights We developed a new approach to calibration for 2‐D soil zymography. The approach accounted for spatial nonuniformity of soil zymograms. Standard calibration resulted in systematic underestimation of enzyme activity. Soil zymography requires pixel‐based calibration with nonuniformly saturated membranes.

Pore-scale characteristics of multiphase flow in heterogeneous porous media using the lattice Boltzmann method

This study provides a pore-scale investigation of two-phase flow dynamics during primary drainage in a realistic heterogeneous rock sample. Using the lattice Boltzmann (LB) method, a series of three-dimensional (3D) immiscible displacement simulations are conducted and three typical flow patterns are identified and mapped on the capillary number (Ca)-viscosity ratio(M) phase diagram. We then investigate the effect of the viscosity ratio and capillary number on fluid saturation patterns and displacement stability in Tuscaloosa sandstone, which is taken from the Cranfield site. The dependence of the evolution of saturation, location of the displacement front, 3D displacement patterns and length of the center of mass of the invading fluid on the viscosity ratio and capillary number have been delineated. To gain a quantitative insight into the characteristics of the invasion morphology in 3D porous media, the fractal dimension Df of the non-wetting phase displacement patterns during drainage has been computed for various viscosity ratios and capillary numbers. The logarithmic dependence of Df on invading phase saturation appears to be the same for various capillary numbers and viscosity ratios and follows a universal relation.

Comparing ERT- and scaling-based approaches to parameterize soil hydraulic properties for spatially distributed model applications

Optimal management of water resources depends on the prediction capability of process-based hydrological models. New generation Richards equation-based distributed models provide detailed descriptions of hydrological processes that, however, depend highly on the proper assessment of the spatial variability of soil hydraulic properties (SHPs). Field surveys and sampling campaigns commonly provide sparse local scale measurements of SHPs. Nevertheless, the challenge is to transfer this information from the “observation scale” to the “model scale” by increasing as much as possible the prediction efficiency with affordable practical burdens. The performances of two parameterization approaches are compared in this study in terms of outputs of water budget simulated by the HydroGeoSphere (HGS) model in a small catchment. The first approach relies on knowledge of soil hydraulic data from soil cores (centimeter scale) collected in many locations of the study site and the application of the Miller-Miller scaling technique enabling the spatial variability of the so-called “aggregated” SHPs to be described over the spatial domain of interest. The second approach, instead, estimates a set of “equivalent” SHPs through the numerical inversion of geophysical data measured with the electrical resistivity tomography (ERT) during an infiltration experiment (meter scale) performed in only one plot-transect of the study catchment. The SHPs obtained by these two approaches are then assigned to each numerical grid cell in HGS to simulate the catchment-scale soil water budget at daily time resolution. Within the framework of a functional evaluation, we compare the performance of these two soil hydraulic parameterization approaches in terms of streamflow (viewed as a lumped flux) and near-surface soil effective saturation patterns (viewed as distributed state variables). Better comparisons between observed and simulated streamflow values are obtained when the study site is parameterized using the “equivalent” SHPs. Conversely, the HGS water budget simulations using the “aggregated” SHPs are more effective when one should describe the spatial patterns of near-surface soil moisture values. This study highlights the pros and cons and potential flaws when choosing two different parameterization techniques in spatially distributed modeling applications.

Correlation Between Oxygen Saturation and Pulse Tracing Patterns on Overnight Oximetry With Normal Desaturation Index Is an Independent Predictor of Obstructive Sleep Apnea.

Overnight pulse oximetry (OPO) is commonly used as a screening test for obstructive sleep apnea. Heart rate variability (HRV) correlates well with apnea-hypopnea index during polysomnography (PSG). We hypothesized that visual correlation of episodic increase in HRV with minimal oxygen desaturations on normal OPO (oxygen desaturation index less than 5 events/h) is predictive of OSA. A retrospective analysis of patients undergoing OPO and PSG in 1 year was performed. We included only OPO performed on room air and interpreted as normal. Visual correlation between simultaneous increase in HRV and minimal oxygen desaturation was independently assessed by three raters, resulting in the consensus agreement. The primary outcome was presence of OSA on the subsequent PSG. Of 936 patients with OPO and PSG, 109 patients had normal overnight oximetry study on room air. Of these, 65 (60%) were females, median (interquartile range) age was 54 years (44, 67), body mass index was 29 kg/m2 (25, 32), and the median oxygen desaturation index was 1.8 events/h (1, 2.7). Consensus agreement identified 54 patients with visual correlation between pulse and minimal oxygen desaturations. Thirty-two patients (29%) were found to have OSA on PSG, of which 24 (75%) could have been accurately predicted by the consensus agreement (odds ratio 4.70, 95% confidence interval 1.87-11.8, P < .001). When adjusted for pertinent clinical and demographic variables, consensus agreement was independently associated with diagnosis of OSA on subsequent PSG (odds ratio 5.6, 95% confidence interval 1.76-20.9, P = .003). Visual correlation between episodic increase in HRV and minimal oxygen desaturations on OPO is an independent predictor of OSA, and promising marker for clinical use.

Experimental and Numerical Studies of Saturation Overshoot during Infiltration into a Dry Soil

Core Ideas Experiments measured saturation overshoot during infiltration of water into dry soil. Two models based on Richards' equation with a dynamic capillarity term simulated the data. The IFA model is an alternative approach to simulate saturation overshoot. The IFA model and dynamic capillarity equation were combined to simulate experiments. Downward infiltration of water into almost dry soil, when there is no ponding at the soil surface, often occurs in the form of fingers, with saturation overshoot at the finger tips. While this is well known, there is still uncertainty about the exact saturation pattern within fingers. We performed a series of one‐dimensional water infiltration experiments into a dry soil to study the non‐monotonicity of the saturation. We observed that saturation showed a non‐monotonic behavior as a function of time. The overshoot was somewhat plateau shaped at relatively low flow rates but was quite sharp at higher flow rates. Two mathematical models, referred to as the extended standard (ESD) model and the interfacial area (IFA) model, were used to simulate the experimental results. Both models were based on extended forms of the Richards equation by including a dynamic capillary term. In the ESD model, standard equations for hysteresis were used. In the IFA model, the specific interfacial area was introduced to simulate hysteresis. Parameter values for both models were obtained from preliminary experiments or using empirical formulas. Only one parameter, the dynamic capillarity coefficient τ, was optimized to model saturation overshoot. While the ESD model did not reproduce the form of saturation overshoot for any combination of parameter values, the IFA model could provide good agreement with the data. To our knowledge, this is the first time where a combination of the IFA model and the dynamic capillarity equation has been used to simulate a set of experiments.

Plasma-membrane electrical responses to salt and osmotic gradients contradict radiotracer kinetics, and reveal Na+-transport dynamics in rice (Oryza sativa L.).

A systematic analysis of NaCl-dependent, plasma-membrane depolarization (∆∆Ψ) in rice roots calls into question the current leading model of rapid membrane cycling of Na+ under salt stress. To investigate the character and mechanisms of Na+ influx into roots, Na+-dependent changes in plasma-membrane electrical potentials (∆∆Ψ) were measured in root cells of intact rice (Oryza sativa L., cv. Pokkali) seedlings. As external sodium concentrations ([Na+]ext) were increased in a step gradient from 0 to 100mM, membrane potentials depolarized in a saturable manner, fitting a Michaelis-Menten model and contradicting the linear (non-saturating) models developed from radiotracer studies. Clear differences in saturation patterns were found between plants grown under low- and high-nutrient (LN and HN) conditions, with LN plants showing greater depolarization and higher affinity for Na+ (i.e., higher Vmax and lower Km) than HN plants. In addition, counterion effects on ∆∆Ψ were pronounced in LN plants (with ∆∆Ψ decreasing in the order: Cl- > SO42- > HPO 4 2- ), but not seen in HN plants. When effects of osmotic strength, Cl- influx, K+ efflux, and H+-ATPase activity on ∆∆Ψ were accounted for, resultant Km and Vmax values suggested that a single, dominant Na+-transport mechanism was operating under each nutritional condition, with Km values of 1.2 and 16mM for LN and HN plants, respectively. Comparing saturating patterns of depolarization to linear patterns of 24Na+ radiotracer influx leads to the conclusion that electrophysiological and tracer methods do not report the same phenomena and that the current model of rapid transmembrane sodium cycling may require revision.

Technical note: Mapping surface-saturation dynamics with thermal infrared imagery

Abstract. Surface saturation can have a critical impact on runoff generation and water quality. Saturation patterns are dynamic, thus their potential control on discharge and water quality is also variable in time. In this study, we assess the practicability of applying thermal infrared (TIR) imagery for mapping surface-saturation dynamics. The advantages of TIR imagery compared to other surface-saturation mapping methods are its large spatial and temporal flexibility, its non-invasive character, and the fact that it allows for a rapid and intuitive visualization of surface-saturated areas. Based on an 18-month field campaign, we review and discuss the methodological principles, the conditions in which the method works best, and the problems that may occur. These considerations enable potential users to plan efficient TIR imagery-mapping campaigns and benefit from the full potential offered by TIR imagery, which we demonstrate with several application examples. In addition, we elaborate on image post-processing and test different methods for the generation of binary saturation maps from the TIR images. We test the methods on various images with different image characteristics. Results show that the best method, in addition to a manual image classification, is a statistical approach that combines the fitting of two pixel class distributions, adaptive thresholding, and region growing.