Accumulation Of Debris Research Articles

The Plastic-Reduction Behavior of Chinese Residents: Survey, Model, and Impact Factors

The persistent generation of plastic waste represents a critical environmental challenge. Despite the implementation of various management policies spanning from usage to disposal that are aimed at incentivizing plastic reduction, the accumulation of plastic debris continues to pose a significant threat to both terrestrial and marine ecosystems. Moreover, this environmental issue adversely impacts economic development and human health. This study seeks to analyze the influencing factors of plastic-reduction behavior at the individual level. Through a diverse sample of 869 participants across 29 provincial-level administrative regions, this research utilizes structural equation modeling to elucidate the intricate factors influencing plastic-reduction behaviors. This study examines the factors influencing plastic-reduction behavior through the frameworks of economic savings and spiritual satisfaction, focusing on two specific behavioral intentions: economically driven behavior and spiritually driven persuasive behavior. Results show that the primary motivator for plastic reduction is the decrease in individual expenses. Environmental values and policy regulations have become important influencing factors, which also promote behaviors regarding plastic reduction through economic savings. The study distinguishes between the impacts of environmental knowledge and skills, highlighting the necessity of practical skills for effective behavior change. Moreover, the study reveals the pivotal role of local attachment in encouraging plastic-reduction actions. The urban natural environment, particularly when characterized by accessible and well-maintained features, such as lakes and rivers, can foster residents’ appreciation for the environment, thereby motivating them to engage in plastic-reduction actions to attain personal spiritual satisfaction.

Early depletion of gut microbiota shape oligodendrocyte response after traumatic brain injury

White matter injury (WMI) is thought to be a major contributor to long-term cognitive dysfunctions after traumatic brain injury (TBI). This damage occurs partly due to apoptotic death of oligodendrocyte lineage cells (OLCs) after the injury, triggered directly by the trauma or in response to degenerating axons. Recent research suggests that the gut microbiota modulates the inflammatory response through the regulation of peripheral immune cell infiltration after TBI. Additionally, T-cells directly impact OLCs differentiation and proliferation. Therefore, we hypothesized that the gut microbiota plays a critical role in regulating the OLC response to WMI influencing T-cells differentiation and activation. Gut microbial depletion early after TBI chronically reduced re-myelination, acutely decreased OLCs proliferation, and was associated with increased myelin debris accumulation. Surprisingly, the absence of T-cells in gut microbiota depleted mice restored OLC proliferation and remyelination after TBI. OLCs co-cultured with T-cells derived from gut microbiota depleted mice resulted in impaired proliferation and increased expression of MHC-II compared with T cells from control-injured mice. Furthermore, MHC-II expression in OLCs appears to be linked to impaired proliferation under gut microbiota depletion and TBI conditions. Collectively our data indicates that depletion of the gut microbiota after TBI impaired remyelination, reduced OLCs proliferation with concomitantly increased OLC MHCII expression, and required the presence of T cells. This data suggests that T cells are an important mechanistic link by which the gut microbiota modulate the oligodendrocyte response and white matter recovery after TBI.

Ayurvedic Management Of Sheetada With Special Reference To Gingivitis

Sheetada is one of the common problems of Dantamoola which is portrayed by the Raktasrava (Bleeding gum), Durghandha (halitosis), Krushnta (Discolouration of gums), Kledata (Excessive dischargre) Mruduta (Softnes of gums), Sheernata (gum downturn). It very well may be associated by Gingivitis. Gingivitis is caused mainly by the accumulation of debris, plaque, and calculus at the tooth margin, due to neglect of oral care . Among all periodontal disease Sheetada is an early stage of periodontal disease. It is caused by vitiated Kapha and Rakta which produces spontaneous bleeding from dark, slimy and soft gums with offensive odour and gum recession. In present study we have discussed a case of 52 year old female patient came to our OPD with chief complaints of foul smell from mouth,bleeding from gums on brushing,pain and swollen gums from last 6 months. This case was intervened with Dantamoola shodhana(dental scaling) followed by Pratisarana with Kushtadi Churna and Gandoosha with Lakshadi Taila.These intervention showed a potential improvement in the management of Sheetada.

Oral Exposure to Microplastics Affects the Neurochemical Plasticity of Reactive Neurons in the Porcine Jejunum.

Plastics are present in almost every aspect of our lives. Polyethylene terephthalate (PET) is commonly used in the food industry. Microparticles can contaminate food and drinks, posing a threat to consumers. The presented study aims to determine the effect of microparticles of PET on the population of neurons positive for selected neurotransmitters in the enteric nervous system of the jejunum and histological structure. An amount of 15 pigs were divided into three groups (control, receiving 0.1 g, and 1 g/day/animal orally). After 28 days, fragments of the jejunum were collected for immunofluorescence and histological examination. The obtained results show that histological changes (injury of the apical parts of the villi, accumulations of cellular debris and mucus, eosinophil infiltration, and hyperaemia) were more pronounced in pigs receiving a higher dose of microparticles. The effect on neuronal nitric oxide synthase-, and substance P-positive neurons, depends on the examined plexus and the dose of microparticles. An increase in the percentage of galanin-positive neurons and a decrease in cocaine and amphetamine-regulated transcript-, vesicular acetylcholine transporter-, and vasoactive intestinal peptide-positive neurons do not show such relationships. The present study shows that microparticles can potentially have neurotoxic and pro-inflammatory effects, but there is a need for further research to determine the mechanism of this process and possible further effects.

Repositioning chair treatment procedure for cupulolithiasis: case report (with video)

IntroductionA cupulolithiasis of the lateral semicircular canal is an accumulation of otolithic debris at the level of the cupula of the same canal. Its pathophysiology generally generates a specific clinical presentation. This situation can be very disabling for the patient and tricky to treat for the clinician.Case reportThe patient was a 70-year-old man with cupulolithiasis of the right lateral semicircular canal. We present here the conversion of cupulolithiasis to canalolithiasis using the Thomas Richard Vitton (TRV) repositioning chair, as well as the treatment of this canalolithiasis through a mechanical liberation maneuver.ConclusionThe results of manual therapeutic maneuvers for Benign Paroxysmal Positional Vertigo (BPPV) are generally good regardless of the type of BPPV. It can sometimes be more challenging to resolve an ageotropic-type BPPV of the lateral semicircular canal and mechanically-assisted maneuvers using a repositioning chair may be required. Faced with symptom resistance despite attempts at multiple liberatory maneuvers, clinicians must be able to reconsider their initial diagnosis and investigate other potentially more serious origins of these symptoms. The TRV chair can be a treatment option in the management of cupulolithiasis, especially in cases where classic reduction maneuvers do not always yield good results.

Revue de la Littérature Traitement actuel du glaucome pseudo-exfoliatif et options thérapeutiques

Pseudoexfoliation glaucoma (PXFG) is known as the most common secondary open angle glaucoma. Accumulation of exfoliative debris in the angle and subsequent IOP elevations is thought to help make PXFG more recalcitrant to topical/medical therapy than primary open angle glaucoma. Laser therapy treatment in the form of selective laser trabeculoplasty for open angle PXFG is therefore discussed. Attention is also called however to the risk of an angle closure component in PXFG eyes and several possible mechanisms behind this. A literature-based discussion on the risks and benefits of laser peripheral iridotomy or cataract surgery to open the angle follows. Literature on the many microinvasive glaucoma surgery options (MIGS) available for PXFG is also reviewed. We provide an overview of MIGS subtypes and summarize study data on several of the better studied options for PXFG. The efficacy and risks of filtering procedures including trabeculectomy and tube shunts for PXFG is also examined.

The formation of lamellar body-like structures may be a trigger of cetylpyridinium chloride-induced cell death and inflammatory response

Cetylpyridinium chloride (CPC) is a quaternary ammonium compound used widely in health and personal care products. Meanwhile, due to its increasing use, its potential adverse health effects are emerging as a topic of public concern. In this study, we first administered CPC by pharyngeal aspiration to determine the survival level (the maximum concentration at which no death is observed) and then administered CPC to mice repeatedly for 28 days using the survival level as the highest concentration. CPC increased the total number of pulmonary cells secreting pro- and anti-inflammatory cytokines and chemokines. Infiltration of inflammatory cells, production of foamy alveolar macrophages, and chronic inflammatory lesions were found in the lung tissue of male and female mice exposed to the highest dose of CPC. We also investigated the toxicity mechanism using BEAS-2B cells isolated from normal human bronchial epithelium. At 6 h after exposure to CPC, the cells underwent non-apoptotic cell death, especially at concentrations greater than 2 μg/mL. The expression of the transferrin receptor was remarkably enhanced, and the expression of proteins that contribute to intracellular iron storage was inhibited. The expression of both mitochondrial SOD and catalase increased with CPC concentration, and PARP protein was cleaved, suggesting possible DNA damage. In addition, the internal structure of mitochondria was disrupted, and fusion between damaged organelles was observed in the cytoplasm. Most importantly, lamellar body-like structures and autophagosome-like vacuoles were found in CPC-treated cells, with enhanced expression of ABCA3 protein, a marker for lamellar body, and a docking score between ABCA3 protein and CPC was considered to be approximately −6.8969 kcal/mol. From these results, we propose that mitochondrial damage and iron depletion may contribute to CPC-induced non-apoptotic cell death and that pulmonary accumulation of cell debris may be closely associated with the inflammatory response. Furthermore, we hypothesize that the formation of lamellar body-like structures may be a trigger for CPC-induced cell death.

Estimating the Temporal Impacts of Nearshore Fisheries on Coastal Ocean-Sourced Waste Accumulation in South Korea Using Stepwise Regression

Fishing activities have been recognized as one of the primary contributors to marine environmental pollution. Studies have been conducted on the impact of fishing activities on the accumulation of marine debris, but most of these studies have been conducted at specific points in time. This study collected marine debris data over four years in the coastal area of Korea. Data on the magnitude of nearshore fishing activities during the same period were collected and analyzed. Regression models were constructed to explore the impact of nearshore fishing activities on coastal waste accumulation over time. This research aimed to understand the influence of nearshore fishing activities on the accumulation of ocean-sourced coastal waste, leading to the development of a time series regression model. The results indicated that time series models have substantially more explanatory power compared to conventional models, emphasizing the importance of temporal considerations in quantifying the relationship between fishing activities and coastal litter over time.

Assessment of Oral Health Conditions Among Physically Disabled Patients in Saudi Arabia

ObjectivesThis study was undertaken to assess the oral health status among physically disabled Saudi patients. MethodsRecruitment took place in the Armed Forces Centre for Health Rehabilitation in Taif, Saudi Arabia. 124 patients living with a physical disability were enrolled and divided into three groups: hemiplegia, paraplegia and quadriplegia. Data was collected on demographics and different oral indices, including the Decayed Missing Filled Teeth (DMFT) index, the Mean Decayed Teeth score, the Community Periodontal Index (CPI), the Community Periodontal Index of Treatment Needs (CPITN), and the Simplified Oral Hygiene Index (OHI-S). ResultsHigh DMFT was observed among the hemiplegia group (mean = 22.61; P-value = .008) with no difference in the Mean Decayed Teeth. All groups showed signs of gingivitis in the form of gingival bleeding. The most compromised periodontal health in the form of pockets 6 mm or deeper was found in the hemiplegia group (53.7%; P-value = .001). This was also reflected in the CPITN (39.0%; P-value = .001), indicating the need for complex treatments in the same group. Regarding oral hygiene, all groups showed a “fair” oral hygiene condition (OHI-S < 3.0), with significantly poorer hygiene (mean = 2.49; P-value = .042) and greater debris accumulation (mean = 1.52; P-value = .024) among the quadriplegia group. In the regression analysis, both age and gender had significant effects on some indices, while disability type showed borderline effects. ConclusionThe findings indicate poor oral health in these individuals, mainly due to physical limitations, hindering effective self-care practices. Clinical significanceOral health is a critical aspect in people with physical disabilities, as it is intrinsically linked to overall health and well-being. Recognizing the clinical importance of oral health among physically disabled patients is essential to improve access and affordability of dental care for this vulnerable group of the population.

A novel electric field-assisted material extrusion process for clean additive manufacturing

Material extrusion (MEX) is a type of additive manufacturing technique that is widely used in a variety of applications. However, the issue of reduced quality of printed parts caused by degraded polymer debris accumulation on the nozzle surface during the MEX process has received very limited attention. This work presents a novel electric field-assisted MEX (E-MEX) method to solve the quality issue by significantly reducing the accumulations of polymer debris on the nozzle. By applying a high-voltage power source between the nozzle and the build plate, an electrostatic force was generated to overcome the which showed great potential to reduce the accumulation of molten thermoplastic material on the nozzles. Both the E-MEX and conventional MEX methods were used to print test specimens for specific amounts of time to confirm the efficacy of the E-MEX method. 3D scanning was used to quantify the volumes of debris that had accumulated on the nozzle. Compared to the conventional MEX method, the E-MEX printing reduced debris accumulation by 47 % after about 5 h and over 80 % after about 15 h of the printing process. The changes in electric field intensity over orienting height were analyzed using numerical simulations. The relationship between electric field intensity and time spent by the nozzle during the printing process at a specific height was established. The polymer accumulation in the E-MEX process was found to be dependent on the electric field intensity and the continuous time spent by the nozzle in the weaker electric field enhanced polymer debris accumulations on the nozzle surfaces. The presented study integrates experimental observations with simulation results, revealing the mechanism of debris accumulation on the nozzle when the electric field decreased to a certain level during printing process. A numerical simulation model was developed to understand the traveling of accumulated polymer debris from the nozzle's outer surface to the printing layer under the influence of electrostatic force. The simulation results showed that the dragging of polymer debris towards the build plate occurs when the electric force acting in the tangential and normal direction is sufficient to overcome the viscous force and normal force in the polymer debris. The simulation results also showed some part of the debris remained in the crease area of the nozzle surface due to the viscous and surface tension forces prevailing over the electric force.

Deficiency of galactosyl-ceramidase in adult oligodendrocytes worsens disease severity during chronic experimental allergic encephalomyelitis

Galactosyl-ceramidase (GALC) is a ubiquitous lysosomal enzyme crucial for the correct myelination of the mammalian nervous system during early postnatal development. However, the physiological consequence of GALC deficiency in the adult brain remains unknown. In this study, we found that mice with conditional ablation of GALC activity in post-myelinating oligodendrocytes were lethally sensitized when challenged with chronic experimental allergic encephalomyelitis (EAE), in contrast to the non-lethal dysmyelination observed in GALC-ablated mice without the EAE challenge. Mechanistically, we found a strong inflammatory demyelination without remyelination and an impaired fusion of lysosomes and autophagosomes with accumulation of myelin debris following a TFEB-dependent increase in the lysosomal autophagosome flux. These results indicate that the physiological impact of GALC deficiency is highly influenced by the cell context (oligodendroglial vs global expression), the presence of inflammation, and the developmental time when it happens (pre-myelination vs post-myelination). We conclude that GALC expression in adult oligodendrocytes is crucial for the maintenance of adult central myelin and to reduce vulnerability to additional demyelinating insults.

KELIMPAHAN MAKRO DEBRIS DI EKOSISTEM MANGROVE MUARA TUKAD MATI, BALI

Macro debris refers to waste materials ranging in size from 2.5 cm to 1 m, commonly found both on the water's surface and on the seabed. The accumulation of such large debris in coastal and marine environments can lead to various consequences, including disturbances to ecosystem stability and threats to the survival of organisms. Additionally, it diminishes the aesthetic quality of the environment. Among the ecosystems most susceptible to becoming repositories for this waste is the mangrove ecosystem. This study aims to quantify the amount, types, and abundance of macro debris scattered in the Tukad Mati Estuary Mangrove Area, Badung Regency, Bali. The research methodology involved several steps, starting with the selection of research stations. Transects measuring 5 x 5 meters were established. Within these designated areas, samples of macro debris were collected and categorized according to their composition, including materials such as plastic, fabric, glass, metal, and rubber. The results revealed that the total mass of macro debris collected in the Tukad Mati Estuary area amounted to 42,630 grams. The types of macro debris found in the Tukad Mati Estuary mangrove ecosystem consist of plastic, fabric, glass, metal, and rubber. Based on their quantity, the composition of macro debris is dominated by plastic at 87.02%, followed by fabric at 4.24%, rubber at 4.17%, glass at 2.67%, and metal being the least at 1.89%. Based on their weight, the composition of macro debris is highest for plastic at 32.33%, followed by rubber at 27.29%, fabric at 20.23%, glass at 14.36%, and metal being the lowest at 5.78%. The abundance of macro debris in the Tukad Mati Estuary mangrove ecosystem ranges from 0.85 items/m² to 10.68 items/m². Keywords: Marine Debris; Pollution; Tukad Mati Estuary; Mangrove

Optical microscopy evaluation of root canal filling removal by beginner operators in posterior teeth.

This study analyzed the effectiveness of root canal filling removal in lower molars performed by beginner operators using optical microscopy. A total of 55 mandibular first and second molars with mesial roots exhibiting an average curvature of 10-20° were selected based on preoperative radiographs. Instrumentation was done with ProTaper Gold (Dentsply Sirona) up to F2 (25/.08), using 2ml of 2.5% NaOCl irrigation solution after each file. Root canal obturation was performed using gutta-percha points with cold lateral condensation and Sealapex (Kerr Dental). Coronal fillings were made with composite resin and stored in distilled water for two years. Removal of the root canal fillings was performed with AF Retreatment Rotary (AFRR) and AF Blue R3 (AFBR3) (Fanta Dental Materials) under reciprocating motion with 2.5% NaOCl irrigation. Cross-sections of the coronal, middle, and apical thirds were analyzed at 40x magnification using a STEINDORFF POL microscope with a digital camera. Image analysis was conducted using Image J software, version 1.54, to determine the efficiency of root canal filling removal by percentage. Statistical analysis via one-way ANOVA revealed significant differences between distal and mesial roots (P < 0.05). Specifically, for mesial roots, the removal efficiency was 70.65% in the coronal third, 54.66% in the middle third, and 21.32% in the apical third. Significant difficulties were noted due to fractured files, calcifications, and debris accumulation in the isthmuses. The study concluded that the protocol using Fanta files demonstrated significant differences in removal efficiency correlated with root curvature, compounded by the inexperience of beginner operators. The findings highlight the challenges faced by novice practitioners in achieving effective root canal filling removal.

Trajectory planning and control of spacecraft avoiding dynamic debris swarm

The continuous accumulation of space debris poses a significant threat to spacecraft on orbit. This paper introduces a dynamic trajectory planning and control framework aimed at ensuring the safe traversal of spacecraft through space debris swarms. Initially, a threat model is established, considering the movement of the debris swarm and the constraints of spacecraft detection range. This model utilizes a dynamically updated, redefined Gaussian mixture model to characterize the threat posed by the debris swarm to spacecraft, with proximity to debris correlating to increased threat levels. Building upon this threat model, four guidance rules are defined, including target guidance, minimal threat, threat threshold, and local path optimization, to facilitate the generation of the shortest collision-free local trajectory for spacecraft. Combining the concept of receding horizon control, an online real-time planning and control framework is formulated for spacecraft navigating through debris swarms. Finally, numerical and semi-physical simulations verify that the proposed framework can stably generate spacecraft safe trajectories and control commands under the threat of numerous dynamic space debris, showing the characteristics of optimal planning trajectory, rapid computation speed and robust safety features.

Rock glacier distribution across the Himalaya

In High Mountain Asia, human-induced climate warming threatens the cryosphere. Expected long-term reductions in future runoff from glacial catchments raises concerns regarding the sustainability of these natural ‘water towers’ and the implications of reduced water availability for regional human and ecological systems. Ice-debris landforms (I-DL), containing ice whether moving or not include rock glaciers and ice-cored moraines, and are likely to be climatically more resilient than debris-covered and debris-free glaciers. Recent work has shown that rock glaciers contain globally valuable water supplies yet over High Mountain Asia information regarding their number, spatial distribution, morphometric characteristics and water content are scarce. Here, we present the first systematic estimate of the current extent and distribution of rock glaciers for a subset of High Mountain Asia (the Himalaya). A sample of 2070 intact and relict rock glaciers were digitized on Google Earth imagery from the Western, Central and Eastern Himalaya regions and then quantitative and qualitative characteristics were analysed regionally based on topographic data from the NASA Shuttle Radar Topography Mission (SRTM) Version 3.0 and then aggregated across the Himalaya using an “upscaling” method. The majority of the digitized landforms (∼65%) were categorised as intact rock glaciers (i.e., ice-debris Landforms, or I-DLs, containing ice) and the remainder as relict rock glaciers (i.e., discrete debris accumulations or DDAs, not containing ice). They range in elevation from 3225 to 5766 m a.s.l., with the lowest in the Central Himalaya. Sampled relict and intact rock glaciers are primarily situated on northern quadrants. Over the entire Himalaya, we identified ∼25,000 landforms, with a total estimated areal coverage of 3747 km2. The area upscaling method was validated in the Manaslu region of Nepal using high-resolution Planet data (5 m) and freely available, fine spatial resolution optical satellite data accessed through Google Earth Pro and ESRI basemaps. In absence of complete rock glacier inventories over the Himalaya, our approach proves useful to investigate the nature, distribution and infer potential future behaviour of these landforms across the Himalaya in a changing climate.

De-orbiting space debris via interaction between a permanent magnet and Earth’s magnetic field: A feasibility study

The accumulation of space debris is an ever-increasing problem. Systems that can reliably de-orbit (i.e., decrease the time to re-entry for) an inactive resident space object (RSO) are highly sought after. In this paper, we investigate the feasibility of utilizing the forces owing to the interaction of Earth’s magnetic field with a permanent magnet that has been attached to an RSO in low Earth orbit. We consider an actively controlled permanent magnet that is optimally oriented to remove energy from the system, and the most favorable magnet-to-RSO mass ratio. We show that, even under these best-case assumptions, the interaction between a permanent magnet and Earth’s magnetic field is not a viable means of de-orbiting an RSO.

Machine Learning-Based Control of Autonomous Vehicles for Solar Panel Cleaning Systems in Agricultural Solar Farms

This paper presents a machine learning (ML)-based approach for the intelligent control of Autonomous Vehicles (AVs) utilized in solar panel cleaning systems, aiming to mitigate challenges arising from uncertainties, disturbances, and dynamic environments. Solar panels, predominantly situated in dedicated lands for solar energy production (e.g., agricultural solar farms), are susceptible to dust and debris accumulation, leading to diminished energy absorption. Instead of labor-intensive manual cleaning, robotic cleaners offer a viable solution. AVs equipped to transport and precisely position these cleaning robots are indispensable for the efficient navigation among solar panel arrays. However, environmental obstacles (e.g., rough terrain), variations in solar panel installation (e.g., height disparities, different angles), and uncertainties (e.g., AV and environmental modeling) may degrade the performance of traditional controllers. In this study, a biologically inspired method based on Brain Emotional Learning (BEL) is developed to tackle the aforementioned challenges. The developed controller is implemented numerically using MATLAB-SIMULINK. The paper concludes with a comparative analysis of the AVs’ performance using both PID and developed controllers across various scenarios, highlighting the efficacy and advantages of the intelligent control approach for AVs deployed in solar panel cleaning systems within agricultural solar farms. Simulation results demonstrate the superior performance of the ML-based controller, showcasing significant improvements over the PID controller.

Fourier-transform infrared spectroscopy imaging is a useful adjunct to routine histopathology to identify failure of polyethylene inlays in revision total hiparthroplasty.

The use of highly crosslinked ultra-high molecular weight polyethylene (XLPE) has significantly reduced the volumetric wear of acetabular liners, thereby reducing the incidence of osteolysis. However, contemporary components tend to generate smaller wear particles, which can no longer be identified using conventional histology. This technical limitation can result in imprecise diagnosis. Here, we report on two uncemented total hip arthroplasty cases (~7 years in situ) revised for periprosthetic fracture of the femur and femoral loosening, respectively. Both liners exhibited prominent wear. The retrieved pseudocapsular tissue exhibited a strong macrophage infiltration without microscopically identifiable polyethylene particles. Yet, using Fourier-transform infrared micro-spectroscopic imaging (FTIR-I), we demonstrated the prominent intracellular accumulation of polyethylene debris in both cases. This study shows that particle induced osteolysis can still occur with XLPE liners, even under 10 years in situ. Furthermore, we demonstrate the difficulty of determining the presence of polyethylene debris within periprosthetic tissue. Considering the potentially increased bioactivity of finer particles from XLPE compared to conventional liners, an accurate detection method is required, and new histopathological hallmarks of particle induced osteolysis are needed. FTIR-I is a great tool to that end and can help the accurate determination of foreign body tissue responses.

Geoecology of limestone-hosted dryland calcicolous plants, North Otago, New Zealand

ABSTRACT Dryland calcicolous plants are drought-tolerant species that are adapted to survive on alkaline low-nutrient bare substrates derived from limestone around the world. Outcrops of the Otekaike Limestone of North Otago host some rare low-growing (<10 cm) endemic calcicoles, and conservation reserves have been created at some localities. The calcicoles occupy microhabitats in solution cavities in limestone outcrops, growing in thin (<10 cm) limestone debris accumulations, including detrital sand and silt. Calcicoles also grow in coarse and fine disaggregated limestone talus deposits at tops and bottoms of outcrops, commonly with the low-growing exotic hawkweed but the calcicoles are displaced by taller species, especially grasses. Calcicole substrates have pH 8 to 9, with a balance between calcite dissolution and calcite re-precipitation. Electrical conductivity is typically <500 µS/cm, but can be as high as 7 mS/cm with evaporative salts and salt weathering enhancing porosity. The limestone contains variably oxidised authigenic glaucony and pyrite, which provide some plant nutrients (K, Mg, Fe, S, N) as roots penetrate porous limestone, with apatite providing phosphate. Persistence of these rare calcicolous communities in soil-free settings is strongly affected by the underlying mineralogy and geochemistry, and some similar microhabitats may occur on other rock types.

Tsunami Debris Damming Drag Forces And Associated Coefficients On Elevated Coastal Structure Columns

Tsunami overland flow induces hydrodynamic loads on coastal structures and may transport various objects located within the inundation zone, which could become debris and exacerbate hydrodynamic loading. In the process of adopting “the first national, consensus-based standard for tsunami resilience” (Chock, 2016) in the form of ASCE 7-16 Chapter 6: Tsunami Loads and Effects, emphasis was placed on evaluating debris transport and impact forces. This is evidenced by the robust body of literature regarding physical model experiments of these processes and thorough design procedures for both load considerations in current structural engineering standards (ASCE, 2022). Debris damming forces, resultant of debris being transported and accumulating against structures, are less thoroughly studied, having only recently begun to transition from steady flow experiments to transient flow conditions representative of coastal inundation events. A recent pair of experiments bridges this gap, comparing debris damming via steady-state, subcritical flow conditions to that caused by a dam-break style hydraulic bore (Stolle et al., 2018). That paper aimed to study debris dam formation, stability, and loading as well as runup of the flow onto idealized structural columns. Another study varied debris quantity, orientation, and arrangement to determine the effect had on damming and impact loads (Shekhar et al., 2020), however neither compared findings to current standards. The experimental work presented herein represents initial findings of a multi-year experimental campaign to better understand the mechanisms that lead to debris damming and increased structural loading. This work builds upon previous studies by using larger scale debris elements, more numerous debris fields, and more trials to better model such a stochastic process as debris damming. Three different incident wave conditions also led to varied hydrodynamics at the column specimen. In later phases, this campaign will also investigate the debris damming consequences of heterogeneous debris, which more accurately represent highly variable debris fields observed in post-event site surveys (Nistor et al., 2017). This paper aims to compare experimental debris dam loading parameters to those in the current ASCE 7-22 standard (ASCE, 2022). Namely, evaluating conservatism of ASCE 7-22 design values for: overall drag force on buildings, minimum closure ratios used in load determination, and empirical rectilinear structure drag coefficients during both debris accumulation and quasi-steady debris damming phases.