Sand Point Research Articles

Grain Size Distribution and Provenance of Holocene Sand from the Sava River (Zagreb, Croatia)

This study involves an investigation into the grain size distribution and provenance of the sand deposited near Zagreb (Croatia) in the riverbed of the regionally important, almost 1000 km long Sava River, which connects several SE European countries. Recent research in the study area has mainly focused on the deposits forming the Zagreb alluvial aquifer system, rather on the Sava River sediment deposited in its riverbed, which is the focus of this study. The grain size distribution results obtained by dry sieving and laser granulometry showed a predominately fine and medium sand deposition at riverbanks and sand point bars. Medium sand increased downstream towards the east, within the artificially more channelized riverbed in the urban area. Fine sand prevailed 50 km further downstream in a more meandering low-relief area, near the city of Sisak and Lonjsko Polje Nature Park. Provenance analysis showed predominately carbonate sand in the western part of the city of Zagreb, originating from distant (Alpine) and local (Medvednica Mt. and Samobor Hills) sources. More siliciclastic sand was deposited in the Sava riverbed in the middle and eastern parts of Zagreb, originating mainly from the Medvednica Mt. The prevailing siliciclastic sand further downstream of the Sava River is probably sourced from the Kupa River tributary. Although various studies of the Zagreb alluvial aquifer system have been conducted so far, this study represents a novelty in its investigation into the grain size distribution of the Sava riverbed sand itself, setting the foundations for investigations in the future.

‘Double Puzzle’ at the Shumagin seismic gap, Alaska Peninsula: intraslab strike-slip faulting loaded by lateral variations in megathrust fault friction

SUMMARY Along the Aleutian megathrust, the Shumagin seismic gap (162° W–158.5° W) had not hosted a large megathrust earthquake during the observational period 1946–2020. Geodetic evidence suggests a prominent trench-parallel transition from strong to weak kinematic coupling in this segment, indicating varying frictional properties of the megathrust. In 2020 July and October, the occurrence of two large, but dissimilar earthquakes in this seismic gap (the Mw 7.8 Simeonof Island thrust event on 2020 July 22 followed by the Mw 7.6 Sand Point intraslab strike-slip event on 2020 October 19) presented a unique opportunity to examine the interaction between stresses on the megathrust and within the downgoing slab. We use geodetic and geophysical evidence to derive a more accurate kinematic coupling model of the megathrust in this area and show that the Mw 7.6 Sand Point earthquake within the downgoing Pacific slab, likely occurred as a result of both trench-perpendicular interseismic shear stress caused by variable kinematic coupling of the megathrust and coseismic stress changes resulting from the Simeonof Island event. Furthermore, we show that the location of the strike-slip event coincides with along-strike change in the megathrust gravitational anomaly and flexural bending of the downgoing plate, suggesting a long-term interaction between megathrust frictional properties and the structure of the plate interface and downgoing slab.

Coseismic Coulomb stress changes induced by a 2020–2021 MW > 7.0 Alaska earthquake sequence in and around the Shumagin gap and its influence on the Alaska-Aleutian subduction interface

Three MW > 7.0 earthquakes in 2020–2021 occurred in the Shumagin seismic gap and its adjacent area of the Alaska-Aleutian subduction zone, including the MW7.8 Simeonof thrust earthquake on July 22, 2020, the MW7.6 Sand Point strike-slip earthquake on October 19, 2020, and the MW8.2 Chignik thrust earthquake on July 29, 2021. The spatial and temporal proximity of these three earthquakes prompts us to probe stress-triggering effects among them. Here we examine the coseismic Coulomb stress change imparted by the three earthquakes and their influence on the subduction interface. Our results show that: (1) The Simeonof earthquake has strong loading effects on the subsequent Sand Point and Chignik earthquakes, with the Coulomb stress changes of 3.95 bars and 2.89 bars, respectively. The Coulomb stress change caused by the Sand Point earthquake at the hypocenter of the Chignik earthquake is merely around 0.01 bars, suggesting the negligible triggering effect on the latter earthquake; (2) The triggering effects of the Simeonof, Sand Point, and Chignik earthquakes on aftershocks within three months are not well pronounced because of the triggering rates of 38%, 14%, and 43% respectively. Other factors may have played an important role in promoting the occurrence of these aftershocks, such as the roughness of the subduction interface, the complicated velocity structure of the lithosphere, and the heterogeneous prestress therein; (3) The three earthquakes caused remarkable coseismic Coulomb stress changes at the subduction interface nearby these mainshocks, with an average Coulomb stress change of 3.2 bars in the shallow region directly inwards the trench.

Modification of Concrete Composition Doped by Sewage Sludge Fly Ash and Its Effect on Compressive Strength.

The sustainable development of construction materials is an essential aspect of current worldwide trends. Reusing post-production waste in the building industry has numerous positive effects on the environment. Since concrete is one of the materials that people manufacture and use the most, it will continue to be an integral element of the surrounding reality. In this study, the relationship between the individual components and parameters of concrete and its compressive strength properties was assessed. In the experimental works, concrete mixes with different contents of sand, gravel, Portland cement CEM II/B-S 42.5 N, water, superplasticizer, air-entraining admixture, and fly ash from the thermal conversion of municipal sewage sludge (SSFA) were designed. According to legal requirements in the European Union, SSFA waste from the sewage sludge incineration process in a fluidized bed furnace should not be stored in landfills but processed in various ways. Unfortunately, its generated amounts are too large, so new management technologies should be sought. During the experimental work, the compressive strength of concrete samples of various classes, namely, C8/10, C12/15, C16/20, C20/25, C25/30, C30/37, and C35/45, were measured. The higher-class concrete samples that were used, the greater the compressive strength obtained, ranging from 13.7 to 55.2 MPa. A correlation analysis was carried out between the mechanical strength of waste-modified concretes and the composition of concrete mixes (the amount of sand and gravel, cement, and FA), as well as the water-to-cement ratio and the sand point. No negative effect of the addition of SSFA on the strength of concrete samples was demonstrated, which translates into economic and environmental benefits.

Class classification of glass products based on K-means clustering

The main raw material of glass is quartz sand, due to the high melting point of pure quartz sand, to reduce the melting temperature, it is necessary to add fluxes during refining. Different fluxes are added, and their main chemical composition is also different. To accurately classify high potassium glass and lead-barium glass, this paper establishes a K-means clustering model to classify glass types. High potassium glasses were classified into three subclasses by the content of iron oxide and barium oxide and lead barium glasses were classified into three subclasses by the content of magnesium oxide and barium oxide. Sensitivity analysis was performed on the model and the results remained significantly correlated.

Analysis of the composition of ancient glass objects based on cluster analysis and random forest methods

In ancient times fluxes were often added to the production of glass to lower the melting point of pure quartz sand. During the smelting process, the addition of different products resulted in significant changes in the internal composition of the glass products. This paper examines a sample of ancient glassworks, based on the data from several sources. The data are divided into 'weathered' and 'unweathered', and cluster analysis reveals significant differences between the categories, and random forest analysis is used to determine the non-linear relationship between the variables, resulting in a chemical composition correlation of the relationships were more variable for potassium chloride and lead chloride and smoother for the rest. This paper innovatively adopts a combination of K-means cluster analysis and random forest to evaluate the composition and identification problems of ancient glass objects. The model in this paper can also be extended to other studies related to the degree of weathering in ancient wooden shipwrecks, metals, ceramics, and other aspects.

Composition analysis of glass products based on correlation analysis

The main raw material of glass is quartz sand, and the main chemical composition is silica (SiO2). Due to the high melting point of pure quartz sand, in order to reduce the melting temperature, it is necessary to add flux in refining. The main chemical composition varies with the flux added. By comparing the chemical composition statistics of high-potassium glass and lead-barium glass before and after weathering, it is found that SiO2 content of high-potassium glass increases after weathering, while lead-barium glass increases after weathering. The content of SiO2 decreased after weathering. From the mapping relationship before and after weathering, the content of each chemical component before differentiation was calculated. The correlation of chemical components between high potassium and lead and barium glasses can be seen by Pearson correlation coefficient. By grey correlation analysis, it can be seen that lead oxide and barium oxide are the main factors to distinguish the two types of glass. Lead barium contains more lead oxide and barium oxide than high potassium, and high potassium contains more potassium oxide than lead barium.

Identification of glass products based on cluster analysis and random forest model

The main chemical composition of glass is silica (SiO2). Due to the high melting point of pure quartz sand in the raw material of glass production, flux should be added in order to reduce the melting temperature. The main chemical composition varies with the flux added. In this paper, through the grey correlation analysis can be concluded that the key factors influencing the classification to the content of lead oxide, and barium oxide, and through the random forest, hierarchical clustering, and K - Means method to classify different types of glass and the division of the class, the glass can be divided into high potassium, high potassium not weathering, lead, barium, lead, barium not weathering four categories of two classes, a total of eight classes, Through the test of classification sensitivity and reliability, it shows that the three models are reasonable and can be applied.

Restoring human and more-than-human relations in toxic riskscapes: “in perpetuity” within Lake Superior’s Keweenaw Bay Indian Community, Sand Point

Lake Superior’s Keweenaw Bay is the ancestral and contemporary homeland of the Anishinaabe Ojibwa and their relatives. It is also a toxic riskscape: Its waters, shorelines, and fish beings are polluted by an unknown tonnage of legacy mining waste rock called “stamp sands,” which contain unsafe levels of toxic compounds. This paper describes Ojibwa stewardship principles and reciprocal obligations, illustrating First Treaty With Gichi-Manitou practices of restoring relations within a toxic riskscape. Defined here, riskscapes are places and spaces where pollution/toxicity relations are continually reconfigured in literal, symbolic, and systemic ways. We share a story from Keweenaw Bay’s Sand Point restoration project (2002–present) to elucidate distinctly different approaches and challenges to restoring ecological relationships, including those between human and more-than-human beings. The restoration of 35 acres of barren shoreline into a thriving landscape concurrently created space for reclaiming Ojibwa stewardship obligations to land, water, and life. The goal was to restore Sand Point as a self-sustaining plant community, but maintenance remains demanding and costly. Lake Superior forces continually mobilize stamp sands, and recent extreme storm events have done so with even greater force. Thus measures of “success” are reconsidered annually, a reminder that “in perpetuity” toxic governance regimes are as unstable as riskscapes themselves. Yet Sand Point is a story of hope. Substantial transformations atop the surface reflect the restoration of many relationships between communities, institutional partners, and more-than-human beings. It is our Sand Point plant relatives who share the most valuable lessons of restoring sustainable livelihoods: resilience is inter-dependent communities caring for one another.

Evaluation of the freezing point of offshore saline sand based on the extended UNIQUAC model

Evaluation of the freezing point of offshore saline sand based on the extended UNIQUAC model

Structural Heterogeneity of the Alaska‐Aleutian Forearc: Implications for Interplate Coupling and Seismogenic Behaviors

AbstractWe determine high‐resolution 3‐D seismic images (Vp, Vs, and Vp/Vs) of the Alaska‐Aleutian forearc region, which are used to further estimate the serpentinization volume fraction of the subducting Pacific slab. Our results show that the hydration degree of the lower plate is high in the Shumagin Gap but relatively low in the Semidi and Kodiak segments, which roughly shows a trend of eastward decrease that is correlated with an increase of the interseismic slip deficit rate. The variation of slab serpentinization degree derived from our Vp model shows an uneven decreasing trend, well consistent with the along‐strike segmentation of interplate coupling and coseismic slip distributions of the 2020 Mw 7.8 Simeonof and 2021 Mw 8.2 Chignik megathrust earthquakes. The 2020 Mw 7.6 Sand Point earthquake took place within the strongly hydrated slab, whose occurrence was probably related to the variation of slip deficit rate that is probably affected by the changes in plate hydration. In addition, slow earthquakes occurred between the hydrated slab with pre‐subduction structures (e.g., bending faults, seamounts, and fracture zones) and the fluid‐saturated overriding crust and mantle wedge, where the intraslab seismicity and dehydration are intensive. These features suggest that lower‐plate hydration and dehydration may affect the interplate coupling and seismogenic behaviors in subduction zones.

Variation in the diversity of bacterial communities and potential sources of fecal contamination of beaches in the Huron to Erie corridor

Understanding the diversity of bacteria and E.coli levels at beaches is important for managing health risks. This study compared temporal changes of the bacterial communities of Belle Isle Beach (Detroit, MI) and Sand Point Beach (Windsor, ONT), both located near the Lake St. Clair origin of the Detroit River. Water samples collected 4 days/week for 12 weeks in summer, were subjected to 16S rRNA analysis of amplicon sequencing and E. coli enumeration. Bacterial communities changed over time, as determined by cluster dendrogram analysis, exhibiting different communities in July and August than in June and different communities at the two beaches. After June, alpha diversity decreased and relative abundance of Enterobacter (Gammaproteobacteria) increased at Sand Point; whereas, Belle Isle maintained its alpha diversity and dominance by Betaproteobacteria and Actinobacteria. Contamination at both beaches is dominated by birds (23% to 50% of samples), while only ∼10% had evidence of human-associated bacteria. High E. coli at both beaches was often associated with precipitation. Nearshore sampling counts were higher than waist-deep sampling counts. Despite the dynamic changes in bacterial communities between the two beaches, this analysis based on 16S rRNA amplicon sequencing is able to provide information about bacterial types associated with high E. coli levels and to use bacterial sequences to more precisely determine sources and health relevance of contaminants.

Health Risk from Toxic Metals in Wild Rice Grown in Copper Mining-Impacted Sediments

Northern wild rice is of great dietary and cultural importance to the Native American population in the Upper Peninsula of Michigan. Millions of tons of mine tailings were discharged into Lake Superior and other inland lakes during the copper mining boom in the early 20th century in this area. This includes L’Anse Bay, located within the Keweenaw Bay Indian Community (KBIC) reservation. Since wild rice restoration is being encouraged by the KBIC, we investigated the distribution of toxic metals in sediments, water, and wild rice and their potential impact on human health from two locations. Sand Point sloughs on L’Anse Bay and a nearby inland lake, Lake Plumbago, were sampled for sediment, water, and wild rice, and the potential human health risk from dietary exposure to toxic metals in wild rice was assessed. Arsenic stood out as the element that had the highest bioaccumulation at both locations. Risk calculations showed that the hazard index (HI) value for wild rice seeds from both sites was high. Data indicate both carcinogenic and non-carcinogenic risks for As from wild rice in Sand Point sloughs and Lake Plumbago, and carcinogenic risks for Cd and Cr at Lake Plumbago.

Composition identification of ancient glass products based on cluster analysis

The Silk Road was a passage for the exchange of Chinese and Western cultures in ancient times, and glass was a valuable physical evidence of early trade exchanges. The main raw material of glass is quartz sand, and the main chemical composition is silicon dioxide (SiO2). Due to the high melting point of pure quartz sand, in order to reduce the melting temperature, it is necessary to add flux during refining. Since different materials can cause glass products to have different properties, the classification of glass products is worth studying. In this paper, a composition analysis and identification model of glass products is developed. First of all, the relationship between surface weathering and glass type, ornamentation and color of glass cultural relics is studied, and after the chemical composition content is counted, the chemical composition content before weathering is predicted according to the weathering point detection data.

Geomorphological Geometries and High-Resolution Seismic Sequence Stratigraphy of Malay Basin’s Fluvial Succession

This study identified the Pleistocene depositional succession of the group (A) (marine, estuarine, and fluvial depositional systems) of the Melor and Inas fields in the central Malay Basin from the seafloor to approximately −507 ms (522 m). During the last few years, hydrocarbon exploration in Malay Basin has moved to focus on stratigraphic traps, specifically those that existed with channel sands. These traps motivate carrying out this research to image and locate these kinds of traps. It can be difficult to determine if closely spaced-out channels and channel belts exist within several seismic sequences in map-view with proper seismic sequence geomorphic elements and stratigraphic surfaces seismic cross lines, or probably reinforce the auto-cyclic aggregational stacking of the avulsing rivers precisely. This analysis overcomes this challenge by combining well-log with three-dimensional (3D) seismic data to resolve the deposition stratigraphic discontinuities’ considerable resolution. Three-dimensional (3D) seismic volume and high-resolution two-dimensional (2D) seismic sections with several wells were utilized. A high-resolution seismic sequence stratigraphy framework of three main seismic sequences (3rd order), four Parasequences sets (4th order), and seven Parasequences (5th order) have been established. The time slice images at consecutive two-way times display single meandering channels ranging in width from 170 to 900 m. Moreover, other geomorphological elements have been perfectly imaged, elements such as interfluves, incised valleys, chute cutoff, point bars, and extinction surfaces, providing proof of rapid growth and transformation of deposits. The high-resolution 2D sections with Cosine of Phase seismic attributes have facilitated identifying the reflection terminations against the stratigraphic amplitude. Several continuous and discontinuous channels, fluvial point bars, and marine sediments through the sequence stratigraphic framework have been addressed. The whole series reveals that almost all fluvial systems lay in the valleys at each depositional sequence’s bottom bars. The degradational stacking patterns are characterized by the fluvial channels with no evidence of fluvial aggradation. Moreover, the aggradation stage is restricted to marine sedimentation incursions. The 3D description of these deposits permits distinguishing seismic facies of the abandoned mud channel and the sand point bar deposits. The continuous meandering channel, which is filled by muddy deposits, may function as horizontal muddy barriers or baffles that might isolate the reservoir body into separate storage containers. The 3rd, 4th, and 5th orders of the seismic sequences were established for the studied succession. The essential geomorphological elements have been imaged utilizing several seismic attributes.

Towards moss biocrust effects on surface soil water holding capacity: Soil water retention curve analysis and modeling

As ecosystem engineers in drylands, biocrusts possibly generate great influences on surface soil water holding capacity and availability, but these effects have not yet been sufficiently investigated, especially through analyzing and modeling their soil water retention curve (SWRC). On the Loess Plateau of China, the naturally developed moss biocrusts and surface bare soil were sampled in five replicates on loess soil and aeolian sand respectively, and their SWRCs from saturation (soil water potential = 0 hPa) to dry (soil water potential = −15,000 hPa) were measured with a sandbox (low water potential range) in combination with a pressure plate (high water potential range). The measured SWRCs were compared to the van Genuchten (VG), Brooks and Corey (BC), and Log-Normal Distribution (LND) models, and the model with best performance was adopted to further determine the effects of biocrusts on surface soil water holding capacity and water availability through comparing the differences in soil water content (θ) at specific water potentials between the biocrusts and uncrusted soil. Our results showed that (i) the biocrusts always had higher θ as compared with the bare soil across the whole water potential range, and the increasing effects of the biocrusts was much stronger on aeolian sand (165%) in comparison to that on loess soil (15%). (ii) As compared with the bare soil, the saturated water content, field capacity, wilting point, and available water content of the aeolian sand increased by 52%, 256% (0.192 vs. 0.054 cm3 cm−3), 65%, and 1000% by the biocrusts, respectively; while that of the loess soil increased by 28%, 9% (0.240 vs.0.220 cm3 cm−3), 27%, and 8% by the biocrusts, respectively. (iii) The increased water holding capacity of the biocrusts was possibly attributed to their higher percentage (18% vs. 16%) of microscopic pores (0.3–5 μm) on the loess soil and their increasing (16% vs. 1%) microscopic pores and decreasing (18% vs. 50%) medium pores (30–75 μm) on the aeolian sand. (iv) The VG and LND models performed better (R2 > 0.98, RMSE ≤ 0.019 cm3 cm−3, RE ≤ 7.4%) than the BC model in simulating the SWRCs of the biocrusts and bare soil, and their fitting errors were mostly distributed in the high (−500 to −1000 hPa) and low (<−5000 hPa) water potential ranges. As indicated by SWRCs, we conclude that biocrusts greatly increase surface soil water holding capacity and water availability, leading in turn to a positive feedback mechanism of the biocrusted layer, which may affect surface hydropedological process (e.g., infiltration and evaporation) in drylands.

Soil Structure Interaction Using Silt Clay by Direct Shear Test: A Review Paper

Direct shear test is a type of laboratory test which is used to determine shear strength parameters such as cohesion c (kPa) and angle of internal friction φ (°). For performing this test various conditions should be considered. The conditions are such that there must have constant vertical pressure at the top of the sample and the volume of the sample must be constant to estimate shear strength parameters of loose and dense soils. A constant horizontal displacement rate is utilized to determine shear strength parameters. The researchers also found some factors which control these shear strength parameters. These controlling factors are surface roughness, soil composition, the magnitude of normal loading, and moisture content. In the direct shear test, the surface thickness of the sample influences shear strength parameters. The researchers have given a different report based on their analysis. They showed the different modes of shear strength parameters in different conditions of sand, clay, soil, etc. for the interaction of soil structure. By mixing geo-membrane, geotextile, etc. with soil, sand, clay greatly affects shear strength parameters. When horizontal displacement is applied, vertical deformation of the shear plane of soil increases up to the yielding point of sand. The direct shear box contains a gap between the upper and lower ring but it is not constant. But, there are some drawbacks to their research. They did not show how shear strength parameters behave in silty clay. In this paper, a relative review of soil-structure interaction using silty clay is shown. In the direct shear test, cohesion is increased due to an increase in moisture content. To determine shear strength parameters, the conditions of silty clay are unsaturated. For this investigation, a shear box is used. Different loading is applied to see the deflection in a specific time interval.

One-sided Social Media Relationships and the Impact of Advertising on Children.

* Abbreviation: PSR — : parasocial relationship In this issue of Pediatrics, Alruwaily et al1 provide an update on advertising to children by evaluating the presence of food product placements in user-created content on the social media platform YouTube. At a time when social media companies are creating spaces specifically for children (eg, YouTube Kids and Messenger Kids), this study offers an important start to needed research on the impacts of advertising and marketing to children by “kid influencers.” The authors define social media influencers as “‘everyday people’ whose primary tool for building fame involves creating entertaining or engaging YouTube videos or social media posts that help them attract large numbers of social media followers. Kid influencers are children whose parents film videos of the child playing with toys or engaging in family-friendly activities.” Social media celebrity influencers are well known, have large viewing audiences, and continually generate new content that is always available. This user-generated content often includes activities such as unboxing and playing with toys, interacting with siblings, making food items, and activities that seem ordinary. In general, influencers are more diverse (eg, underrepresented minority or lesbian, gay, bisexual, transgender, or queer) than more traditional entertainers, thus increasing their relatability and appeal to diverse populations and their consumer reach.2 Digital marketing campaigns have exploited … Address correspondence to Yolanda N. Evans, MD, MPH, Seattle Children’s Hospital, 4540 Sand Point Way NE, Suite 200, Seattle, WA 98105. E-mail: yolanda.evans{at}seattlechildrens.org

The Toils, Trials, and Tribulations of Research on Childhood Vaccine Acceptance.

* Abbreviation: VHP — : vaccine-hesitant parent The severe acute respiratory syndrome coronavirus 2 pandemic has put into sharp perspective the paucity of our understanding of how to influence immunization behavior. If we must achieve herd immunity to halt this pandemic, how can that be accomplished? What could we do now to ensure almost universal acceptance of a vaccine determined by the US Food and Drug Administration to be safe and effective in preventing coronavirus disease? Furthermore, recent experience with measles in the United States has demonstrated that even the ready availability of an indisputably effective and demonstrably safe vaccine is no longer sufficient to prevent outbreaks. We need to figure out how to achieve and sustain vaccine acceptance by a high proportion of our population. The investment required to bring a new vaccine to licensure in the United States (estimated to cost ∼$1 billion)1 warrants a substantial commitment to funding research on how and when attitudes and beliefs about vaccines are formed and how best to communicate about vaccines to parents and the public to promote vaccine acceptance. The good news is that this work is well on its way for childhood vaccines. There is a robust literature on parents’ vaccine attitudes … Address correspondence to Edgar K. Marcuse, MD, MPH, FPIDS, Department of Pediatrics, University of Washington School of Medicine, 4800 Sand Point Way NE Seattle, Washington, 98105. E-mail: emarcuse{at}uw.edu

Arthroscopic anterior capsular release for posttraumatic elbow flexion contracture in pediatric patients: a case report of two patients with treatment protocol

aUniversity of Washington School of Medicine, Seattle, WA bDepartment of Orthopaedics and Sports Medicine, University of Washington, Seattle, WA cSeattle Children’s, Department of Orthopedics and Sports Medicine, Seattle, WA Financial Disclosure: Dr. Saper reports money paid outside of this study to him and his institution by Arthrex. Dr. Welling has no disclosures. The authors report no conflicts of interest. Correspondence to Michael Saper, DO, ATC, CSCS, 4800 Sand Point Way NE, Seattle, WA 98105 Tel: +1-206-987-5678; fax: +1-206-987-3852; e-mail: [email protected].