Range Of Slopes Research Articles

Full-field comparisons between strains predicted by QCT-derived finite element models of the scapula and experimental strains measured by digital volume correlation

Subject-specific finite element models (FEMs) of the shoulder can be used to evaluate joint replacement designs preclinically. However, to ensure accurate conclusions are drawn, experimental validation is critical. The objective of the current study was to evaluate the accuracy of strain predictions generated by subject-specific scapula FEMs through comparisons against full-field experimental strains measured using digital volume correlation (DVC). Three cadaveric scapulae were mechanically loaded using a custom-hexapod robot within a micro-CT scanner. BoneDVC was used to quantify resultant experimental full-field strains. Scapula FEMs were generated using three different density-modulus relationships to assign material properties. Two types of boundary conditions (BCs) were simulated: DVC-displacement-driven or applied-force-driven. Third principal strains were compared between the DVC measurements and FEM predictions. With applied-force BCs, poor agreement was observed between the predicted and measured strains (slope range: 0.16–0.19, r2 range: 0.04–0.30). Agreement was improved with the use of DVC-displacement BCs (slope range: 0.54–0.59, r2 range: 0.73–0.75). Strain predictions were independent of the density-modulus relationship used for DVC-displacement BCs, but differences were observed in the correlation coefficient and intercept for applied-force BCs. Overall, this study utilized full-field DVC-derived experimental strains for comparison with FEM predicted strains in models with varying material properties and BCs. It was found that fair agreement can be achieved in localized strain measurements between DVC measurements and FEM predictions when DVC-displacement BCs are used. However, performance suffered with use of applied-force BCs.

Combining wearable sensor signals, machine learning and biomechanics to estimate tibial bone force and damage during running.

There are tremendous opportunities to advance science, clinical care, sports performance, and societal health if we are able to develop tools for monitoring musculoskeletal loading (e.g., forces on bones or muscles) outside the lab. While wearable sensors enable non-invasive monitoring of human movement in applied situations, current commercial wearables do not estimate tissue-level loading on structures inside the body. Here we explore the feasibility of using wearable sensors to estimate tibial bone force during running. First, we used lab-based data and musculoskeletal modeling to estimate tibial force for ten participants running across a range of speeds and slopes. Next, we converted lab-based data to signals feasibly measured with wearables (inertial measurement units on the foot and shank, and pressure-sensing insoles) and used these data to develop two multi-sensor algorithms for estimating peak tibial force: one physics-based and one machine learning. Additionally, to reflect current running wearables that utilize running impact metrics to infer musculoskeletal loading or injury risk, we estimated tibial force using a commonly measured impact metric, the ground reaction force vertical average loading rate (VALR). Using VALR to estimate peak tibial force resulted in a mean absolute percent error of 9.9%, which was no more accurate than a theoretical step counter that assumed the same peak force for every running stride. Our physics-based algorithm reduced error to 5.2%, and our machine learning algorithm reduced error to 2.6%. Further, to gain insights into how force estimation accuracy relates to overuse injury risk, we computed bone damage expected due to a given loading cycle. We found that modest errors in tibial force translated into large errors in bone damage estimates. For example, a 9.9% error in tibial force using VALR translated into 104% error in estimated bone damage. Encouragingly, the physics-based and machine learning algorithms reduced damage errors to 41% and 18%, respectively. This study highlights the exciting potential to combine wearables, musculoskeletal biomechanics and machine learning to develop more accurate tools for monitoring musculoskeletal loading in applied situations.

Predicting Individualized Joint Kinematics over a Continuous Range of Slopes and Speeds.

Individuality in clinical gait analysis is often quantified by an individual's kinematic deviation from the norm, but it is unclear how these deviations generalize across different walking speeds and ground slopes. Understanding individuality across tasks has important implications in the tuning of prosthetic legs, where clinicians have limited time and resources to personalize the kinematic motion of the leg to therapeutically enhance the wearer's gait. This study seeks to determine an efficient way to predictively model an individual's kinematics over a continuous range of slopes and speeds given only one personalized task at level ground. We were able to predict the kinematics of able-bodied individuals at a wide variety of conditions that were not specifically tuned. Applied to 10 human subjects, the individualization method reduced the RMSE between the model and subject's kinematics over all tasks by an average of 2% (max 52%) at the ankle, 27% (max 59%) at the knee, and 45% (max 83%) at the hip. Our results indicate that knowing how an individual subject differs from the average subject at level ground alone is enough information to improve kinematic predictions across all tasks. This research offers a new method for personalizing robotic prosthetic legs over a variety of tasks without the need of an engineer, which could make these complex devices more clinically viable.

Slope control on ambient fluid entrainment of subaqueous density flows with steady sustained inflows

Entrainment of density flows is a key parameter in constructing predictive models of global climate, ocean flows, and turbidity currents. Our numerical experiment, which included 10 subaqueous dilute density flows with a steady sustained inflow (SSI) on a 2D channel bed slope varying from 0.1° to 90°, showed that in the slope range of 0.1–20°, there is a linear relationship between the ambient fluid entrainment and channel bed slope. We also found a power law relation between the bulk Richardson number and bed slope. On a larger slope bed, these relations broke down due to the strong head drag, which suggests that there exists a regime change from bed-supported to plunging flows at around 20° for SSI density flows on a slope bed. These findings may provide a way to quickly evaluate or parameterize subaqueous SSI density flows in the suggested slope range.

The effectiveness of fuel reduction burning for wildfire mitigation in sclerophyll forests

ABSTRACT The wildfires in south-eastern Australia in the 2019–20 fire season were some of the worst in recent memory. The effectiveness of fuel-reduction burning as a risk mitigation strategy is, once again, being scrutinised. Some argue that more fuel-reduction burning is needed, while others suggest that it is of limited use in such extreme fires. In this study, we tested the effectiveness of fuel-reduction burning at a landscape scale in terms of its ability to reduce the severity of subsequent wildfire. To achieve this, we selected all the recent (2015–2019) fuel-reduction burns undertaken in New South Wales and Victoria that intersected with the extent of the 2019–20 wildfires and evaluated whether the fire severity was significantly different in the recently treated areas to that of similar untreated areas in the vicinity. To determine fire severity, Sentinel 2 satellite imagery and the change in normalised burn ratio (a common metric used for rapid and broadscale fire severity mapping) was used. Our results showed that 48% of the 307 recent fuel-reduction burns resulted in statistically significant decreased fire severity. Our results also indicated that more recent fuel-reduction burns had a greater impact, with 66% of burns undertaken in 2019 significantly reducing severity, compared with 42% from 2015. We also analysed each fuel-reduction burn in the context of a range of metrics, including location, elevation, slope, aspect and forest heterogeneity, to assess whether these factors influenced the likelihood that a burn would be effective. Location and, to a lesser degree, forest heterogeneity were found to be significant factors. Our results support the view that recent fuel-reduction burns reduce fire severity. It is unclear, however, whether the differences would be operationally significant under extreme conditions, when wildfires are driven largely by weather, irrespective of fuel loads.

ZTF Early Observations of Type Ia Supernovae. III. Early-time Colors As a Test for Explosion Models and Multiple Populations

Abstract Colors of Type Ia supernovae (SNe Ia) in the first few days after explosion provide a potential discriminant between different models. In this paper, we present g − r colors of 65 SNe Ia discovered within 5 days from first light by the Zwicky Transient Facility in 2018, a sample that is about three times larger than that in the literature. We find that g − r colors are intrinsically rather homogeneous at early phases, with about half of the dispersion attributable to photometric uncertainties ( 0.18 mag). Colors are nearly constant starting from 6 days after first light (g − r ∼ −0.15 mag), while the time evolution at earlier epochs is characterized by a continuous range of slopes, from events rapidly transitioning from redder to bluer colors (slope of ∼−0.25 mag day−1) to events with a flatter evolution. The continuum in the slope distribution is in good agreement both with models requiring some amount of 56Ni mixed in the outermost regions of the ejecta and with “double-detonation” models having thin helium layers ( ) and varying carbon–oxygen core masses. At the same time, six events show evidence for a distinctive “red bump” signature predicted by double-detonation models with larger helium masses. We finally identify a significant correlation between the early-time g − r slopes and supernova brightness, with brighter events associated to flatter color evolution (p-value = 0.006). The distribution of slopes, however, is consistent with being drawn from a single population, with no evidence for two components as claimed in the literature based on B − V colors.

Development of Generic Equivalence Margins for Early-Stage Implementation of Equivalence Testing for Potency Assays

Relative potency assays for biological therapeutics require statistical evaluation to demonstrate similarity between the dose-response curves of a reference standard and the test samples. We developed an equivalence testing approach that can be utilized for the complete potency assay life cycle, from early development until commercialization. This approach was based on the use of generic equivalence margins to enable equivalence testing at the beginning of assay development, when the body of assay-specific data is still very limited. Generic equivalence margins for equivalence testing of four-parameter logistic curve fits were established for bioassays and binding assays spanning a variety of designs, formats, and read-outs. We also established that equivalence testing using ratios of the reference standard and test sample was superior to equivalence testing using absolute differences. Based on a large body of historical data, generic equivalence margins were determined for the curve upper asymptote, slope, and dynamic range. Furthermore, we developed a road map to guide the implementation of generic or assay-specific margins to ensure the appropriate data analysis approach is being applied during the assay life cycle.

Variability of the Posterior Tibial Slope in Saudis: A Radiographic Study.

AimThe present study aimed to establish the normal range of the posterior tibial slope (PTS) angle in the Saudi adult population and to identify whether there was an association between the angle and gender or age.Materials and methodsA total of 524 normal knee radiographs of 410 patients aged 18-85 years were included in the study. The PTS was measured using the anterior tibial cortex method. Data were matched with gender and age for statistical analysis.Results The mean physiological PTS angle was 13.6 ± 3.4˚ (range: 3.8-23.9˚). Age and gender did not influence the PTS value (P >0.05). The two-way analysis of variance (ANOVA) test showed no interaction effect between age and gender on the PTS (P >0.05).ConclusionsThis study provided a reference range for the normal PTS among Saudis, which can assist in decision-making during different knee procedures. The PTS value did not significantly differ between male and female subjects, and there was no significant association between the PTS angle and age.

An application of posterior cervical and transoral approaches to treating primary malignant osseous tumors in craniovertebral junction

To investigate the surgical method for primary malignant osseous tumors in the craniovertebral junction (CVJ) and its effectiveness. The clinical data of 7 patients with primary malignant osseous spinal tumors in CVJ, which collected between September 2010 and April 2019, were retrospectively analyzed. There were 5 males and 2 females, aged 23 to 75 years (median, 56 years). All patients were diagnosed as chordoma in 4 cases, plasmacytoma in 2 cases, and fibrosarcoma in 1 case. The disease duration ranged from 0.7 to 36.0 months, with an average of 12.2 months. Lesion location: 1 case of C 0, 1, 3 cases of C 2, 1 case of C 1, 2, 1 case of C 2, 3, and 1 case of C 0-2. Preoperative visual analogue scale (VAS) score was 6.7±2.1, the Japanese Orthopaedic Association (JOA) score was 15.6±2.4. According to American Society of Spinal Cord Injury (ASIA) grading system, there was 1 case of grade C, 1 case of grade D, and 5 cases of grade E. According to Enneking stage of spinal malignant tumor, there was 1 case of stage ⅠB, 2 cases of stage ⅡB, and 4 cases of stage Ⅲ. According to Weinstein-Boriani-Biagini (WBB) stage, there was 1 case of 5-8/A-D, 1 case of 4-9/A-D, 1 case of 6-7/B-D, 1 case of 6-7/A-D, 2 cases of 1-12/A-D, and 1 case of 3-10/A-D. All these patients were treated with tumor extended resection, bone graft fusion, and internal fixation via posterior cervical approach, as well as tumor (stage Ⅰ or stage Ⅱ) boundary resection via transoral or submandibular approach. Meanwhile, anterior reconstructive fusion was procedured with bone grafting Cage needed to place the internal fixation. The operation time was 307-695 minutes (mean, 489.57 minutes), and the intraoperative blood loss was 400-2 000 mL (mean, 1 107.14 mL). There was no intraoperative injury in vertebral artery and spinal cord or any related postoperative complications, including incision infection, intracranial infection, and pulmonary infection. All the patients were followed up 3-57 months (mean, 21 months). Postoperative X-ray film and CT showed that the internal fixation screw was firm and in a satisfactory position, and the bone graft was fused at 3-6 months after operation. Symptoms such as neck pain, limb numbness, and fatigue relieved to different degrees after operation. At 3 months after operation, the VAS score improved to 1.7±0.8 ( t=7.638, P=0.000); while the JOA score improved to 16.1±1.5, but no significant difference was found when compared with preoperative score ( t=1.549, P=0.172). According to ASIA grading system, 1 patient with grade C had upgraded to grade D after operation, while the remaining patients had no change. There were 4 cases of recurrence after operation, in which those patients were with high malignancy of tumors before the first surgery. Their tumors also affected a wide range of slope or surrounding soft tissues and could not be completely removed. Among the 4 cases, 1 patient underwent transoral tumor removal operation again, while the other 3 cases gave up further treatment. There was no recurrence among the remaining 3 cases. Primary malignant osseous tumors in the CVJ can be completely exercised via means of trabsoral or submandibular approach. Meanwhile the anterior reconstruction can be achieved by placing special Cage specimen. These two methods together with postoperative adjuvant treatments such as radiotherapy and chemotherapy can improve the survival time of patients and reduce tumor recurrence.

Identification of spatial coupling between cultivated land functional transformation and settlements in Three Gorges Reservoir Area, China

Understanding the relationship between cultivated land transformation and settlement development is of considerable significance to the agricultural utilization and rural development in the context of global rural revitalization. This paper tries to reveal intensive land use under the background of population contraction in China's mountainous areas and its transformation trend by defining the cultivated land functional transformation (CLFT). Given the representativeness of land-use change in mountains, Caotangxi watershed in the Three Gorges Reservoir Area (TGRA) was taken as a case study, and ArcGIS spatial analysis techniques were used to explore the spatial coupling relationship between CLFT and settlements development in mountainous areas. The results show that: (1) CLFT shifts from the low elevation area of <800m to the high elevation area of 800–1000m, and the transformation process remains within the range of slope 15–30°. (2) The decline-type settlements with high elevation gradually moved to the vigor-type settlements in low elevation, and CLFT location is closest to the settlements with great ecological vitality. (3) The coupling types between CLFT and settlements can be divided into four patterns, the spatial distribution of various patterns shows significant differential characteristics with terrain changes. (4) The spatial coupling relationship between CLFT and settlements can reflect the general law of rural land use transition in mountainous areas, and thereby provide policy ideas for mountainous development. Overall, this study's content can provide scientific guidance for rural development, agricultural production, and land consolidation in mountainous areas.

Influence of slope of grain on the mechanical properties of tropical hardwoods and the consequences for grading

The main parameter that influences the bending strength of timber from tropical hardwood is the slope of grain. Although, in the grading rules, a specific threshold value is given, in these hardwoods, the global slope of grain is very difficult to quantify by visual assessment. The slope of grain measured after testing gives a better indication, but still it can only poorly describe the Hankinson relations. By rewriting the Hankinson relations, the slope of grain can be determined from the bending strength test values and from the MOE test value, both in combination with the density values and constants derived by non-linear regression analysis. These two values correlate very well, and the average value is designated as the theoretical slope of grain. With the theoretical slope of grain, five test samples of the tropical wood species okan were evaluated, and slope of grain values of 0.3 were observed, where 0.1 is the limit value. Because all pieces passed the visual grading method as applied in practice, slope of grain values should be incorporated in the strength class assignment test program, when these qualities cannot be ruled out for coming on the market. The (dynamic) modulus of elasticity can be used to evaluate the occurrence of the desired range of slope of grain values in the test samples.

Determination of Semi-Empirical Models for Mean Wave Overtopping Using an Evolutionary Polynomial Paradigm

The present work employs the so-called Evolutionary Polynomial Regression (EPR) algorithm to build up a formula for the assessment of mean wave overtopping discharge for smooth sea dikes and vertical walls. EPR is a data-mining tool that combines and integrates numerical regression and genetic programming. This technique is here employed to dig into the relationship between the mean discharge and main hydraulic and structural parameters that characterize the problem under study. The parameters are chosen based on the existing and most used semi-empirical formulas for wave overtopping assessment. Besides the structural freeboard or local wave height, the unified models highlight the importance of local water depth and wave period in combination with foreshore slope and dike slope on the overtopping phenomena, which are combined in a unique parameter that is defined either as equivalent or imaginary slope. The obtained models aim to represent a trade-off between accuracy and parsimony. The final formula is simple but can be employed for a preliminary assessment of overtopping rates, covering the full range of dike slopes, from mild to vertical walls, and of water depths from the shoreline to deep water, including structures with emergent toes.

Quantitative analyses of cirques on the Faroe Islands: evidence for time transgressive glacier occupation

This study presents the first analysis of ice‐free cirques on the Faroe Islands using a Geographical Information System (GIS) and the Automated Cirque Metric Extraction (ACME) tool. The length, width, area, circularity, mean aspect, mean slope, and elevation range, minimum, and maximum were calculated using ACME. Cirque distance to coastline was measured using ArcGIS. A total of 116 cirques were identified. Mean cirque length is 950 m and mean cirque width is 890 m. Average cirque area is 0.8 km2 and mean elevation is 386 m a.s.l. The modal orientation of the aspect of cirques is north‐northeast, with a vector mean of 7° and mean resultant length of 0.09. Aspect data have large dispersion, which shows evidence of cloudy ablation seasons in the past. The dispersion in aspect may also be related to the time transgressive nature of glacier occupation in these cirques. Past equilibrium‐line altitudes (ELAs) of cirque glaciers reconstructed with the minimum point method resulted in a mean palaeo‐ELA of 213 m a.s.l. Positive, linear relationships are observed between palaeo‐ELA and cirque distance to coastline. There are at least two possible interpretations of this relationship: (i) that the cirque formation is dependent on pre‐existing topography with cirques forming at the head of valleys, which occurs at higher elevations further inland, and (ii) that this relationship demonstrates the importance of access to moisture for glacier survival. A combination of both interpretations is also possible. Positive linear relationships are also observed between longitude and palaeo‐ELA indicative of palaeo‐precipitation patterns along an east–west gradient. Cirques on the Faroe Islands are smaller in length and width and present at lower elevations compared to cirques located in other regions of the world. The timing of glacial occupation in these cirques is not known, and the landforms likely formed over multiple glaciations.

Effect of Slope on the Analysis of Forest Fire Risk

The main cause of forest fires is human activities. For this reason, when talking about the risk of forest fire in an area, it is mentioned about the intensity of human activities that can cause forest fire when vegetation and topographic compatibility are provided. In other words, although the type, amount, humidity and intensity of the combustible material is suitable with the effect of topographic factors in an area, if there is no human activity that will cause fire, only lightning caused forest fires can be mentioned. While evaluating the impact of slope on forest fire risk in our study, the starting points of the last 10 years forest fires have occurred in Turkey were analyzed with geographic information systems (GIS). Thus, it has been tried to make an objective assessment of the impact of the slope on forest fire risk. According to the results of the analysis, 40.53% of the forest fires which examined in Turkey occured in the range of slope between 0-10%. Therewithal, 87.16% of these fires occured in the range of slope between 0-30%. As a result, contrary to the general opinion, it is thought that the forest fire risk decrease as the slope increases.

Experimental investigation on the effects of bed slope and tailwater on dam-break flows

Understanding of the characteristics of dam-break flows moving along a sloping wet bed can help to timely issue flood warning and risk mitigation. In this study, laboratory experiments are carried out in a large flume for a wide range of upstream water depth, bed slopes and tailwater depth. The water level is recorded and processed to calculate the mean velocity and wave celerity. Results show that the increase of the bed slope will significantly accelerate the wave-front celerity for the downstream dry bed, while the negative wave celerity will decrease. When water depth ratio α ≥ 0.3 (defined as the ratio of initial downstream water depth over the upstream water depth of dam), there are extra negative waves propagating towards the reservoir area after the flow has developed for a period of time. When α ≥ 0.6, there are the Favre waves propagating downstream. The water level and the mean velocity fluctuate due to the influence of the extra negative waves and the Favre waves. Such fluctuant frequency increases with the increase of the water depth ratio. The empirical formulas are obtained for the celerity of the first extra negative wave and the first downstream wave. The variation of wave-front height is very similar under three bed slopes investigated in this study, while the maximum wave-front height occurs when α = 0.2. The present study broadens the understanding of the effects of the bed slope and the tailwater level on the movement of the dam-break flows. Furthermore, experimental results are also compared with some analytical solutions. The validity of the assumptions made during the development of these analytical solutions and their limitations are discussed by comparing with the experimental measurements.

Electrocardiogram Derived Respiration for Tracking Changes in Tidal Volume from a Wearable Armband.

A pilot study on tracking changes in tidal volume (TV) using ECG signals acquired by a wearable armband is presented. The wearable armband provides three ECG channels by using three pairs of dry electrodes, resulting in a device that is convenient for long-term daily monitoring. An additional ECG channel was derived by computing the first principal component of the three original channels (by means of principal component analysis). Armband and spirometer signals were simultaneously recorded from five healthy subjects who were instructed to breathe with varying TV. Three electrocardiogram derived respiration (EDR) methods based on QRS complex morphology were studied: the QRS slopes range (SR), the R-wave angle (Փ), and the R-S amplitude (RS). The peak-to-peak amplitudes of these EDR signals were estimated as surrogates for TV, and their correlations with the reference TV (estimated from the spirometer signal) were computed. In addition, a multiple linear regression model was calculated for each subject, using the peak-to-peak amplitudes from the three EDR methods from the four ECG channels. Obtained correlations between TV and EDR peak-to-peak amplitude ranged from 0.0448 up to 0.8491. For every subject, a moderate correlation (>0.5) was obtained for at least one EDR method. Furthermore, the correlations obtained for the subject-specific multiple linear regression model ranged from 0.8234 up to 0.9154, and the goodness of fit was 0.73±0.07 (median ± standard deviation). These results suggest that the peak-to-peak amplitudes of the EDR methods are linearly related to the TV. opening the possibility of estimating TV directly from an armband ECG device.Clinical Relevance- This opens the door to possible continuous monitoring of TV from the armband by using EDR.

Local-level emergence of network governance within the U.S. Forest Service: A case study of mountain pine beetle outbreak from Colorado, USA

In the U.S. and around the world, governmental and non-governmental actors are piloting network governance approaches to fill gaps in governance resources (management capacity, local legitimacy) that cannot be met by a single entity alone. Such resources are needed to respond adaptively to changing conditions, such as those posed by severe disturbance. The purpose of this study is to provide insight into the drivers, pathways, and outcomes of network governance emergence within a federal bureaucracy, that of the U.S. Forest Service. We aim to shed light on the local variability of emergent network types (partnerships, collaboratives, combination types). We conducted case study research on responses to a severe mountain pine beetle (MPB, Dendroctonus ponderosae Hopkins) infestation (~1996–2012) on the Arapaho and Roosevelt National Forests in northern Colorado, USA. We applied a multi-level analysis, comprised of bottom-up, top-down, and “from around” (pre-existing network) factors, to three examples of MPB outbreak-driven network emergence. The examples vary in their combination of geographic location (Western Slope vs. Front Range) and scale (local vs. regional). Our analysis revealed: (1) network type and governance outcomes varied due to interlinked, multi-level factors (predominant gaps in governance resources, bottom-up factors, and pre-existing networks); (2) USFS managers and counterparts exercised agency in navigating top-down bureaucratic constraints on network governance emergence; (3) state, local, industry, and NGO entities, along with federal counterparts, co-initiated network governance of federal lands; (4) emergent networks generally did not persist in the large bureaucracy after the aftermath subsided. This study's findings are applicable to governance networks associated with land management bureaucracies in the U.S. and around the world.

Influence of Historical Climate Patterns on Streamflow and Water Demand in Wales, UK

Ensuring reliable drinking water supplies is anticipated to be a key future challenge facing water service providers due to fluctuations in rainfall patterns and water demand caused by climate change. This study investigates historical trends and relationships between precipitation, air temperature and streamflow in five catchments in Wales, before correlating these with actual total abstraction data provided by the water company, to give insight into the supply-demand balance. Changes in seasonal and annual averages, as well as extreme events, are assessed for a 34-year period (1982–2015) and a breakpoint analysis is performed to better understand how climate has already changed and what this might mean for the future of water supply. Results show a north-south divide in changes in extreme temperature and streamflow; a strong warming trend in autumn average temperatures across Wales (Sen’s slope range: 0.38–0.41, p &lt;0.05), but little change in precipitation. Abstraction, as a proxy for overall water demand, is shown to be positively correlated to temperature (Spearman’s ρ value range: 0.094–0.403, p &lt;0.01; Pearson’s r value range 0.073–0.369, p &lt;0.01) in four of five catchments. Our study provides new insight into the relationship between abstraction volume and hydroclimatic factors and highlights the need for catchment-scale water resource planning that accounts for hydroclimatic variations over small spatial distances, as these nuances can be vital.

Micro-Watershed Management for Erosion Control Using Soil and Water Conservation Structures and SWAT Modeling

This study evaluated the effectiveness of soil and water conservation structures for soil erosion control by applying a semi-distributed Soil and Water Assessment Tool (SWAT) model in various small watersheds of the Chakwal and Attock districts of Pothwar, Pakistan. The validated model without soil conservation structures was applied to various ungauged small watershed sites with soil conservation stone structures. The stone bund-type structure intervention was used in the model through the modification of the Universal Soil Loss Equation (USLE) to support the practice factor (P-factor), the curve number, and the average slope length for the sub-basin (SLSUBBSN). The structures had significant effects, and the average sediment yield reduction caused by the soil conservation stone structures at these sites varied from 40% to 90%. The sediment yield and erosion reductions were also compared under conditions involving vegetation cover change. Agricultural land with winter wheat crops had a higher sediment yield than fallow land with crop residue. The fallow land facilitated sediment yield reduction, along with soil conservation structures. The slope classification analysis indicated that 60% of the agricultural area of the Chakwal and Attock districts lie in a slope range of 0–4%, where considerable potential exists for implementing soil conservation measures by installing soil conservation stone structures. The slope analysis measured the suitability of conservation structures in the semi-mountainous Pothwar area in accordance with agriculture practice on land having a slope of less than 5%. The SWAT model provides reliable performance for erosion control and watershed management in soil erosion-prone areas with steep slopes and heavy rainfall. These findings can serve as references for policymakers and planners.

Constraints on the engines of fast radio bursts

ABSTRACT We model the sample of fast radio bursts (FRBs), including the newly discovered CHIME repeaters, using the decelerating synchrotron maser blast wave model of Metzger, Margalit &amp; Sironi (2019), which built on earlier work by Lyubarsky (2014), Beloborodov (2017). This model postulates that FRBs are precursor radiation from ultrarelativistic magnetized shocks generated as flare ejecta from a central engine collides with an effectively stationary external medium. Downward drifting of the burst frequency structure naturally arises from the deceleration of the blast wave coupled with the dependence of the maser spectral energy distribution, and induced Compton scattering depth, on the upstream medium. The data are consistent with FRBs being produced by flares of energy Eflare ∼ 1043–1046(fξ/10−3)−4/5 erg, where fξ is the maser efficiency, and minimum bulk Lorentz factors Γ ≈ 102–103, which generate the observed FRBs at shock radii rsh ∼ 1012–1013 cm. We infer upstream densities next(rsh) ∼ 102–104 cm−3 and radial profiles next ∝ r−k showing a range of slopes k ≈ [ − 2, 1] (which are seen to evolve between bursts), both broadly consistent with the upstream medium being the inner edge of an ion-loaded shell released by a recent energetic flare. The burst time-scales, energetics, rates, and external medium properties are consistent with repeating FRBs arising from young, hyperactive flaring magnetars, but the methodology presented is generally applicable to any central engine which injects energy impulsively into a dense magnetized medium. Several uncertainties and variations of the model regarding the composition and magnetization of the upstream medium, and the effects of the strong electric field of the FRB wave (strength parameter a ≫ 1) on the upstream medium and its scattering properties, are discussed. One-dimensional particle-in-cell simulations of magnetized shocks into a pair plasma are presented which demonstrate that high maser efficiency can be preserved, even in the limit a ≫ 1 in which the FRB wave accelerates the upstream electrons to ultrarelativistic speeds.