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Online help-seeking refers to a learner's willingness to seek help in online learning environments. Counterintuitively, studies of help-seeking have found mixed results for the relationship between help-seeking and academic achievement. We hypothesized that these mixed findings might, in part, be accounted for by the confidence level of the learner. Utilizing a sample of 321 online university students (M = 32.78 years; SD = 9.53), we explored the moderating effect of self-efficacy in the help-seeking-academic achievement relationship. Aligned with the vulnerability hypothesis, when online learners were confident, they engaged in help-seeking more often than learners with low confidence. Importantly, however, when online learners were unconfident, we found that help-seeking behaviors were positively associated with academic success. Confident learners did not appear to gain any academic performance benefit from using help-seeking strategies. Our study highlights help-seeking's potential importance in improving academic success for our least confident learners, with no impact on confident learners.

Online help-seeking refers to a learner's willingness to seek help in online learning environments. Counterintuitively, studies of help-seeking have found mixed results for the relationship between help-seeking and academic achievement. We hypothesized that these mixed findings might, in part, be accounted for by the confidence level of the learner. Utilizing a sample of 321 online university students (M = 32.78 years; SD = 9.53), we explored the moderating effect of self-efficacy in the help-seeking–academic achievement relationship. Aligned with the vulnerability hypothesis, when online learners were confident, they engaged in help-seeking more often than learners with low confidence. Importantly, however, when online learners were unconfident, we found that help-seeking behaviors were positively associated with academic success. Confident learners did not appear to gain any academic performance benefit from using help-seeking strategies. Our study highlights help-seeking's potential importance in improving academic success for our least confident learners, with no impact on confident learners. [ABSTRACT FROM AUTHOR]

Irrigation reservoirs are widely used in parts of the Mississippi River alluvial floodplain to supplement limited groundwater resources. Constructed using local soils that are often low in clay content, the earthen embankments of these reservoirs are susceptible to wave erosion. In this study, laboratory experiments were performed to quantify wave-induced erosion and retreat of cohesive embankments. Erosion rates were measured for a model erodible embankment in a laboratory wave tank for a range of wave characteristics, and relationships were established between volume of embankment erosion, edge retreat rate, and incident wave height. An analytical model was developed to predict the embankment erosion and retreat rate. The model was calibrated using laboratory data and then compared with field measurements of erosion and retreat in an irrigation reservoir. The results show agreement between the field measurements and model predictions of bank retreat. [ABSTRACT FROM AUTHOR]

A study is conducted to examine the chemiluminescent reactions of ground state (Ca, Sr, and Ba) atoms with (Cl2, Br2, I2, ICl, and IBr) in a beam-gas arrangement. In order to identify the main reaction channels that contribute to MX2 formation and to obatin their relative contributions, kinetic models are fitted to the data.

On-farm irrigation reservoirs, together with tailwater recovery systems, are commonly used to store water in the Mississippi River Valley alluvial floodplain to supplement limited groundwater resources. The inner slopes of the earthen embankments that enclose these reservoirs are subjected to continuous erosion due to wind-generated waves. Various methods have been used to protect the embankments, but none of them have been shown to be both sustainable and cost-effective. In an effort to assess levee protection strategies, a range of treatment techniques, including levee configurations and surface treatments, were applied on the embankments of the University of Arkansas Pine Bluff (UAPB) Lonoke Demonstration Reservoir in 2007. The treatment techniques included 17 different slope configurations along the east and west embankments and five chemical and mechanical treatments along the north and south embankments. Embankment erosion was measured by comparing new surveys conducted in 2015 and 2017 with as-built information provided by the USDA Natural Resources Conservation Service (NRCS). The change in levee profile between the surveys and the as-built profiles was used to quantify the effectiveness of the treatment methods for protection against wave action. An artificial neural network (ANN) prediction model was developed to establish relationships between erosion parameters (eroded area and maximum retreat) and four independent variables (existence of berm, face slope, maximum effective fetch, and probability of wind speed). Data from 27 sections were used for training, and data from seven sections were used for testing. Almost all of the slope treatments were significantly eroded over the eight to ten years that elapsed between construction and the surveys. Although having a berm did not significantly reduce the total eroded volume, in most cases it delayed the bank retreat. For any two identical slope configurations, the one with the longest fetch typically had at least slightly higher erosion and retreat. In general, milder slopes performed better than steeper slopes. The survey results showed that geo-synthetic fabric, fly ash, and soil cement were more effective at reducing wave erosion than the other treatment methods. [ABSTRACT FROM AUTHOR]

The article focuses on the passive acoustic monitoring of bed load rates for fluvial applications. It mentions the use of passive acoustic technology for bed load monitoring using hydrophones deployed in the transporting flow to record interparticle collisions. It states that spectral composition of ensembles of particle sizes can be reasonably predicted from the particle size distribution.

Quantifying the effectiveness of erosion control practices in watersheds remains a difficult problem. Determination of recent sediment accumulation rates for lake sediments in agricultural watersheds using radioisotopes, such as lead-210 (210Pb) and cesium-137 (137Cs), is potentially a valuable means of assessing the effectiveness of soil conservation practices at the watershed scale. The predominance of sediment arriving in runoff from the watershed, variable sedimentation rates, and mechanical mixing of soil in nearby fields all present challenges in the conversion of radioisotope data to sedimentation rates. Four sediment cores from Beasley Lake, Mississippi, were used to demonstrate the application of the Constant Initial Concentration (CIC) model for calculating sediment age from the distribution of 210Pb bottom sediments. The activity of 137Cs was used to supplement the 210Pb data by providing a benchmark date within the core to calibrate the CIC model. Three of the four cores showed reductions in sediment accumulation rate within the 30 years prior to core collection in 2008 and 2011 by at least 50% relative to rates from before the adoption of soil conservation measures in the watershed. The most recently resolved rates were approximately 0.5 cm y-1 (0.2 in yr-1). The study demonstrates the application of the CIC model for developing sediment accumulation chronologies in agricultural catchments. [ABSTRACT FROM AUTHOR]

Increasing agricultural demands on limited groundwater resources in the Arkansas and Mississippi alluvial floodplain have created a growing need for the development of surface water resources. On-farm irrigation reservoirs are used to reduce dependence on groundwater supplies, but wind-induced wave erosion of levees creates an additional maintenance cost for producers. Measurements of levee erosion in a typical irrigation reservoir in east-central Arkansas were made with a ground-based LIDAR system and used to quantify erosion and estimate maintenance costs for irrigation reservoir levees. Approximately 1350 m³ of soil loss was measured from a 1530 m long levee during a seven-month period between December 2012 and July 2013. The damage was most severe in the northeast corner, where over 3 m of width were lost due to prevailing southerly winds blowing across the longest diagonal fetch length. Based on a typical cost (in 2014) for earth moving of $2.6 m-3, the cost to repair this loss would be approximately $3,500, resulting in a five-year maintenance cost of $17,500, which is about 16% of the initial cost of the levee. This research provides a basis for decision- making for producers who rely on irrigation reservoirs. Maintenance costs can be projected for a worst-casescenario of levee erosion, and the cost of protection can be balanced against expected erosion and repair costs. [ABSTRACT FROM AUTHOR]

Studies on twins with concordant acute lymphoblastic leukemia (ALL) have revealed that ETV6-RUNX1 gene fusion is a common, prenatal genetic event with other driver aberrations occurring subclonally and probably postnatally. The fetal cell type that is transformed by ETV6-RUNX1 is not identified by such studies or by the analysis of early B-cell lineage phenotype of derived progeny. Ongoing, clonal immunoglobulin (IG) and cross-lineage T-cell receptor (TCR) gene rearrangements are features of B-cell precursor leukemia and commence at the pro-B-cell stage of normal B-cell lineage development. We reasoned that shared clonal rearrangements of IG or TCR genes by concordant ALL in twins would be informative about the fetal cell type in which clonal advantage is elicited by ETV6-RUNX1. Five pairs of twins were analyzed for all varieties of IG and TCR gene rearrangements. All pairs showed identical incomplete or complete variable-diversity-joining junctions coupled with substantial, subclonal and divergent rearrangements. This pattern was endorsed by single-cell genetic scrutiny in one twin pair. Our data suggest that the pre-leukemic initiating function of ETV6-RUNX1 fusion is associated with clonal expansion early in the fetal B-cell lineage. [ABSTRACT FROM AUTHOR]

Experiments were conducted in a laboratory flume channel to evaluate the effects of increasing amounts of sand on its transport over and through an immobile coarse gravel bed. Detailed measurements of sand transport rate, bed texture, and bed topography were collected for four different discharges at approximately the same flow depth of 0.2 m for 11 different elevations of sand in the gravel bed. Sand transport was measured using both physical samples and a density cell. For a given flow rate, increases in the elevation of sand relative to gravel resulted in decreases of bed shear stress from 32-44% and increases in sand transport by three orders of magnitude. For the highest two discharges, the sand merged into a small number of long and low bed forms that translated through and over the gravel bed. A collapse of the transport data was accomplished by relating the sand transport rate to the bed shear stress scaled by the cumulative probability distribution function of the gravel surface evaluated at the height of the mean sand bed. [ABSTRACT FROM AUTHOR]

Floating breakwaters are typically used to protect small marinas or for shoreline erosion control on limited-fetch water bodies in which wavelengths are relatively short, such as lakes, reservoirs, and bays. In spite of the large amount of literature on floating breakwaters, there is still a lack of knowledge on the performance of cylindrical breakwaters, which, as a result of their simplicity, can minimize construction and material costs. In this paper, we describe a laboratory investigation of the hydrodynamic interaction of cylindrical breakwaters with monochromatic waves in deep and transitional water depths such as are found in small reservoirs. The tested breakwater models feature single- and multiple-cylinder cross sections combined with bottom-moored, arm-restrained (connected to shoreline), and pile-restrained configurations. When the breakwater models were fixed, the reflection was higher than in the partially restrained models, and the efficiency was strongly dependent on draft ratio (zd/d, where zd is the draft and d is the height of the structure). For partially restrained models, dissipation strongly influenced the transmission coefficients. For the measured range of waves, zd/d=0.7 was the best of the tested draft ratios for the pile-restrained model. Horizontal restraint was found to be more important than vertical restraint in terms of improving breakwater efficiency. [ABSTRACT FROM AUTHOR]

The effectiveness of erosion control methods is difficult to measure, hampering the development of management practices and preventing accurate assessment of the value of erosion control structures over time. Surface erosion can vary widely over an area, particularly if gully erosion is present, and the use of sediments transported in streams for quantifying erosion is hindered by the highly variable nature of fluvial sediment loads. When a watershed drains into a lake, accumulated sediments have the potential to yield information about historic rates of sedimentation that can be used to evaluate the effectiveness of previous erosion control measures. In the present study, sediments from five natural oxbow cutoff lakes in the Mississippi River alluvial floodplain were dated using lead-210 decay rates and bomb-pulse derived cesium-137 with the goal of relating trends in sedimentation rate to reductions in erosion due to management practices. It was found that the radioisotope dating methods were best used in concert with known dates for implementation of management practices. Changes in sedimentation rate over time frames as short as 12 years were detectable. Larger lakes showed smaller changes in sedimentation rate relative to smaller lakes. [ABSTRACT FROM AUTHOR]

The earthen levees commonly used to form irrigation reservoirs are subjected to significant embankment erosion due to wind-generated waves. The design of bank protection measures relies on adequate prediction of wave characteristics based on wind conditions and fetch length. Current formulations are based primarily on winds and waves in large water bodies and do not provide an optimal fit to waves in small water bodies such as irrigation ponds. Based on wind and wave data collected in an irrigation reservoir near Carlisle, Arkansas, the coefficients in a commonly used equation for wind wave prediction were improved for use in irrigation reservoirs. Details of the development of the new coefficients as well as data collection procedures are presented here. With the new empirical coefficients, the RMS error is 0.01 m for energy-based significant wave height and 0.06 s for peak wave period. [ABSTRACT FROM AUTHOR]

The earth levees commonly used for irrigation reservoirs are subjected to significant embankment erosion due to wind-generated waves. Large seasonal fluctuations in water level make vegetative bank protection impractical, and other stabilization methods, such as the use of stone or discarded tires, are not acceptable due to ecological or economic concerns. Here, a floating wave barrier made of polyethylene irrigation tubing is designed through a laboratory model study and subjected to a short-term prototype-scale field test. Based on wave characteristics measured in an irrigation pond near Carlisle, Arkansas, a laboratory-scale wave generating flume was designed, constructed, and used to test multiple wave barrier configurations for regular waves in deep and transitional water depths. Wave transmission characteristics were investigated for the following breakwater arrangements: (1) fully restrained, (2) vertically restrained with a single mooring line, and (3) horizontally restrained with piles at both sides of the wave barrier. The test results show that cylindrical pipes can be used effectively and that wave transmission characteristics strongly depend on the draft and mooring configuration of the wave barrier. The use of multiple small cylinders to replace a single large one is validated. A composite design made of two sizes of cylinders joined at the top was chosen for field testing. In the prototype-scale field test, wave amplitudes were reduced by an average of approximately 50%, which translates into a 75% reduction in wave energy. [ABSTRACT FROM AUTHOR]

The history of sediment accumulation in an oxbow lake located on the Mississippi alluvial floodplain was reconstructed based on sedimentation rates determined using 14C activities from bulk sediment fractions and from 210Pb and 137Cs measurements. Higher rates of sediment accumulation consistent with frequent flooding when first abandoned 3,800 to 5,000 years before the present were followed by slower sedimentation rates consistent with migration of the Mississippi river away from the oxbow and less frequent flooding. This low sedimentation rate persisted for several thousand years until the surrounding land was cleared for agricultural use in the late 19th century. A 50-fold increase in the rate of sediment accumulation has persisted from the time of land clearing to the present, doubling the total mass of accumulated sediment in a single century. [ABSTRACT FROM AUTHOR]

The clinical diagnosis of mixed cryoglobulinaemia is difficult due to heterogeneity in presentation. Symptoms include the classical triad of purpura, arthralgia and weakness, with one or more other organs involved. We discuss a case of cryoglobulinaemia that presented with sensory motor neuropathy and with features of mononeuritis multiplex syndrome, but which lacked other classical features. Laboratory testing revealed a profile typical of mixed cryoglobulins: immunoglobulin M (IgM) paraprotein, low fourth carbon (C4) and positive rheumatoid factor. Subsequent investigations failed to reveal an underlying infectious or neoplastic cause. This case demonstrates the need to include cryoglobulinaemia in the differential diagnosis for peripheral neuropathy, and the critical importance of using the correct collection procedure to isolate cryoglobulins. [ABSTRACT FROM AUTHOR]

The water storage capacity and dam integrity of thousands of flood control reservoirs built since 1950 may be compromised by excessive stored sediments. The fate of these structures depends on the amount and characteristics of accumulated material. To aid in understanding the scope of impairment of small reservoirs in the hill lands of northern Mississippi, physical sediment characteristics and reservoir storage capacity were evaluated in three small reservoirs (<8 ha [<20 acres]) built in the early 1960s as part of the Yazoo-Little Tallahatchie erosion control project. A vibrating corer was used to collect continuous cores of deposited sediment and preimpoundment soil. Bulk density, grain size, and activity of 137Cs were used to identify the boundary between preimpoundment soil and postimpoundment sediment. Mean local sediment accumulation rates ranged from 5.6 to 7.9 mm yr-1 (0.22 to 0.31 in yr-1) with reductions in storage capacity of 7% to 18% since construction. Selected cores were tested for pre-1972 residual pesticides and more recently used pesticides. Results suggest that some currently used pesticides are being transported by prevailing winds from the heavily farmed Mississippi Delta area. [ABSTRACT FROM AUTHOR]

Mechanical heart valves are associated with a risk of thromboembolism and anticoagulation is generally recommended. However, this is inevitably associated with a risk of intracranial bleeding. The case of a patient who sustained an intracranial bleed while taking warfarin for a prosthetic aortic valve and a further two intracranial bleeds while on heparin as an inpatient is discussed and the literature on the management of intracranial haemorrhage in patients on warfarin with prosthetic valves is reviewed. [ABSTRACT FROM AUTHOR]

A series of laboratory flume experiments were conducted to characterize lateral variations of suspended sediment over dunes. Forty experimental runs were made using flow depths of 0.328 and 0.127 m in a 1.2-m-wide channel. The Froude number was 0.47 and the median diameter of the bed material was 0.52 mm. Point samples of suspended sediment and depth-integrated values calculated using acoustic backscatter data were collected simultaneously at two lateral positions at spacings of 0.41, 0.20, 0.10, and 0.05 m. Root mean square differences between the paired samples increased from 30 to 94% and from 20 to 45% of the mean concentration for point samples and depth-integrated samples, respectively, as the lateral spacing between samples was increased. Lateral variations in the concentration of suspended sediment should be considered when designing sediment sampling strategies over dune beds. [ABSTRACT FROM AUTHOR]

Lateral and longitudinal variability in suspended-sediment concentration was investigated over dune and upper-regime plane beds under steady, uniform flow in a laboratory flume. A much greater sampling time was required to reliably predict mean concentration in a dune bed than for an upper-regime plane bed. Laterally separated, simultaneous samples over both dune and upper-regime plane beds were poorly correlated. [ABSTRACT FROM AUTHOR]

In this paper we describe the previously unreported phenomenon of a carbamazepine-induced mucocutaneous syndrome in identical twins. These twins had developed primary generalised epilepsy within 2 months of each other. [ABSTRACT FROM AUTHOR]

Many sampling projects have been initiated or modified in recent years to quantify the effects of water quality protection and enhancement programs. Although comprehensive references on the theory and procedures related to discharge data collection have been published, similar guides to water quality sampling are not available. Several sources provide general guidance on sampling project design and on manual sampling procedures, but only recently has detailed information on automated storm water quality sampling been developed. As a result, a compilation of available information on the design of water quality sampling projects is needed to support sound decision-making regarding data collection resources and procedural alternatives. Thus, the objective of this article is to compile and present practical guidance for collection of discharge and water quality constituent data at the field and small watershed scale. The guidelines included are meant to increase the likelihood of project success, specifically accurate characterization of water quality within project resource constraints. Although many considerations are involved in establishing a successful sampling project, the following recommendations are generally applicable to field and small watershed studies: (1) consider wet-weather access, travel time, equipment costs, and sample collection method in the selection of sampling site numbers and locations; (2) commit adequate resources for equipment maintenance and repair; (3) assemble a well-trained, on-call field staff able to make frequent site visits; (4) establish reliable stage-discharge relationships for accurate discharge measurement; (5) use periodic manual grab sample collection with adequate frequency to characterize baseflow water quality; (6) use flow-interval or time-interval storm sampling with adequate frequency to characterize storm water quality; and (7) use composite sampling to manage sample numbers without substantial increases in uncertainty. [ABSTRACT FROM AUTHOR]