Low-density Areas Research Articles

Multi-scale Experimental Investigations on the Deterioration Mechanism of Sandstone Under Wetting–Drying Cycles

The repeated wetting–drying (WD) cycles can cause the deterioration of rock and thus affect the service performance of the related rock engineering, e.g., the crushed-rock embankment and the reservoir. The study comprehensively investigated the deterioration mechanism of sandstone under the WD cycles based on a series of multi-scale experiments, including the microstructure, the meso–micro pore characteristics, and the macroscopic physical and mechanical properties. The results indicate that the content of dissolved minerals and the permeability are two key factors that determine the deterioration effect caused by the WD cycles. During the WD cycles, the pore size range of sandstone becomes wider due to the formation of new small pores and the connection of original pores. Thus, low-density area forms within the samples, which causes the increasing of density dispersion. The structure deterioration weakens the physical and mechanical properties of the samples. The ultrasonic test indicates that the decreasing rate of the P-wave velocity is larger than that of the S-wave velocity, especially in the first 5 cycles. Besides, the exponential equations of uniaxial compressive strength and elastic modulus with the number of WD cycles are established to describe the deterioration of mechanical characteristics.

Ultralight Bacterial Cellulose/Polypropylene-graft-Maleic Anhydride Composite Cryogel for Efficient Oil/Water Separation

Abstract An ultralight bacterial cellulose/polypropylene-graft-maleic anhydride (BC/PP-g-MA) composite cryogel was fabricated using a facile temperature induced phase separation (TIPS) method followed by freeze-drying. The presence of PP-g-MA endowed BC cryogel with the vital hydrophobicity for oil adsorption from water. With low density, high porosity, and high surface area, the obtained BC/PP-g-MA composite cryogel exhibited excellent adsorption capacity (up to 136 g/g) for a diversity of oils and organic solvents, making it a promising candidate for efficient oil/water separation.

RETRACTED ARTICLE: Distribution of rural tourism development in geographical space: a case study of 323 traditional villages in Shaanxi, China

ABSTRACT Spatial distribution of traditional village is the key factor for the sustainable development of rural tourism. Analyzing distribution characteristics and development conditions of traditional villages have profound implications for rural revitalization and all-for-one tourism. Firstly, this research introduced the characteristics and historic value of traditional villages in each region of Shaanxi province. Secondly, this paper analyzed the spatial distribution characteristics of 323 provincial-level traditional villages by using the method of quantitative geography through geographic information systems (GIS). Then, according to spatial type division, this research divided the spatial distribution of rural tourism in Shaanxi province into five areas, including linear tourist area, facial health area, distributed leisure area, low-density scenic area, self-driving tourist area. Finally, this paper summarized the development conditions of rural tourism in Shaanxi’s traditional villages and took case studies. The natural environment, social economy, and historical culture are crucial conditions for the sustainable development of traditional villages, influencing the spatial distribution of these villages. This paper summarized the spatial distribution of rural tourism development and proposed a guide for future space planning and construction for all-for-one tourism in other areas through empirical research on spatial distribution. Meanwhile, this research provides new ideas for rural revitalization.

High-purity foam-like micron-sized gold cage material with tunable plasmon properties

Herein, by growing mono dispersed gold nanoparticles (MNPAu) on the surface of polystyrene (PS)/nanogold (Au) core–shell composites (PS@Au), we successfully synthesized a micron-sized gold cage (2.6–10.7 μm), referred to as PS@Au@MNPAu for the first time. The new micron-gold cage materials exhibit broadband absorption range from near-ultraviolet to near-infrared, which is unlike the conventional nanogold core–shell structure. The uniform growth of MNPAu on the surface forms a new photonic crystal spectrum. The strong coupling of the spectra causes anomalous absorption in the ultraviolet-near infrared band (400–900 nm). Furthermore, by removing the PS core, a nanogold cavity structure referred to as Au@MNPAu was prepared. This structure demonstrated a high purity (> 97 wt%), low density (9–223 mg/cm3), and high specific surface area (854 m2/g). As the purification process progressed, the MNPAu coupling on the surface of the micro-gold cage strengthened, resulting in the formation of peaks around 370 nm, plasma resonant peaks around 495 nm, and structural bands of photonic crystal peaks around 850 nm. The micron-sized gold cage provides hybridized and tunable plasmonic systems. The theoretical simulations indicate that this plasmon anomalous absorption phenomena can be understood as the novel form of the topological structural transitions near the percolation threshold, which is consistent experimental measurements.

Renal abscess with bacteremia caused by extended-spectrum \u03b2-lactamase-producing Escherichia coli: a case report

BackgroundRenal abscess in children is a rare and severe form of infectious kidney disease that is responsible for several serious complications. In this report, we describe a previously healthy 5-year-old girl with a renal abscess caused by extended-spectrum β-lactamase (ESBL)-producing Escherichia coli (E. coli), which led to bacteremia and renal scarring.Case presentationThe patient presented to our department with high fever, headache, vomiting for 2 days and high inflammatory response. We diagnosed her with a urinary tract infection and initiated treatment with ampicillin and cefotaxime. Gram-negative bacilli bacteremia was noted on day 3. On day 4, her fever persisted, and a computed tomography (CT) scan revealed a renal abscess in the left kidney. After identifying the bacteria as ESBL-producing E. coli from the blood culture, we switched to the antibiotic meropenem and continued treatment for 3 weeks. The renal abscess was not drained. Although the renal abscess was successfully treated and it disappeared, a low-density area remained in same lesion on subsequent CT scans and a dimercaptosuccinic acid renal scan performed 4 months after onset revealed renal scarring.ConclusionGiven the increasing prevalence of ESBL-producing microorganisms, clinicians should be aware of the possibility of renal abscesses caused by community-acquired ESBL-producing organisms even in previously healthy children. Once a renal abscess is suspected, early diagnosis and management are important for reducing the risk of life-threating complications and renal scarring.

Quantifying the employment accessibility benefits of shared automated vehicle mobility services: Consumer welfare approach using logsums

Abstract The goal of this study is to assess and quantify the potential employment accessibility benefits of shared-use automated vehicle (AV) mobility service (SAMS) modes across a large diverse metropolitan region considering heterogeneity in the working population. To meet this goal, this study proposes employing a welfare-based (i.e. logsum-based) measure of accessibility, obtained via estimating a hierarchical work destination-commute mode choice model. The employment accessibility logsum measure incorporates the spatial distribution of worker residences and employment opportunities, the attributes of the available commute modes, and the characteristics of individual workers. The study further captures heterogeneity of workers using a latent class analysis (LCA) approach to account for different worker clusters valuing different types of employment opportunities differently, in which the socio-demographic characteristics of workers are the LCA model inputs. The accessibility analysis results in Southern California indicate: (i) the accessibility benefit differences across latent classes are modest but young workers and low-income workers do see higher benefits than high- and middle-income workers; (ii) there are substantial spatial differences in accessibility benefits with workers living in lower density areas benefiting more than workers living in high-density areas; (iii) nearly all the accessibility benefits come from the SAMS-only mode as opposed to the SAMS+Transit mode; and (iv) the SAMS cost per mile assumption significantly impacts the magnitude of the overall employment accessibility benefits.

Assembly of three-dimensional ultralight poly(amidoxime)/graphene oxide nanoribbons aerogel for efficient removal of uranium(VI) from water samples

Assembling graphene oxide nanoribbons (GONRs) into three-dimensional (3D) materials with controllable and desired structure is an effective way to expand their structural features and enable their practical applications. In this work, an ultralight 3D porous amidoxime functionalized graphene oxide nanoribbons aerogel (PAO/GONRs-A) was prepared via solvothermal polymerization method using acrylonitrile as monomer and GONRs as solid matrices for selective separation of uranium(VI) from water samples. The PAO/GONRs-A possessed a high nitrogen content (13.5%), low density (8.5 mg cm−3), and large specific surface area (494.9 m2 g−1), and presented an excellent high adsorption capacity of uranium, with a maximum capacity of 2.475 mmol g−1 at a pH of 4.5, and maximum uranium-selectivity of 65.23% at a pH of 3.0. The results of adsorption experiments showed that U(VI) adsorption on PAO/GONRs-A was a pH-dependent, spontaneous and endothermic process, which was better fitted to the pseudo-second-order kinetic model and Langmuir isotherm model. Both X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations revealed that U(VI) adsorption on PAO/GONRs-A mainly did rely on the amidoxime groups anchored on the aerogel while UO2(PAO)2(H2O)3 was dominant after interaction of uranyl with PAO/GONRs-A. Therefore, as a candidate adsorbent, PAO/GONRs-A has a high potential for the removal of uranium from aqueous solutions.

Rural and agri-entrepreneurial networks: A qualitative case study

The Queijo Serra da Estrela, DOP is the oldest Portuguese cheese recognized internationally. The objective of this paper is to analyse a rural, agri-entrepreneurial network created by a young, female, craft cheese producer located in an area of low population density in the inland central region of Portugal. For data collection, several qualitative semi-structured phone and face-to-face interviews were held with the partners of the network. This paper contributes by helping to understand how a rural agricultural network in the specific sector of a Protected Denomination of Origin (PDO) product works and what its motives, success factors and benefits are. The results indicate that trust, confidence and regular payments are essential to make this network viable and create added value for business in a traditional sector threatened by climate changes, the age of shepherds and importation of exotic breeds of sheep. Some theoretical and practice contributions will be also presented.

Spatial Distribution of Local Forest Products at the End of the 19th Century: A Case Study of Former Villages in Iwate Prefecture

Recent research in Japan has investigated how local people historically utilized natural resources, using geographic information systems (GIS). These works have helped to clarify the role of forest provisioning services in the past, and have shown how modern landscapes were formed. The aim of this study was to elucidate the utilization of plant resources in forest landscapes of both fields and mountains, in the late 19th century in Iwate Prefecture, located in northeastern Japan. This study focused on a different area and a larger scale than previous studies, and included information from 642 villages. This study specifically focused on what kinds of forest products were historically used and shipped, which species were used, and how these uses were distributed around the prefecture. A combination of historical documents and GIS mapping, named MANDARA, was employed. The primary historical document was “The topography of Iwate Prefecture” that was published from 1876 to 1885, and recorded the products used in each village. A wide range of forest products were recorded, which contained both edible and inedible plants further split into 10 primary categories: edible wild plants, mushrooms, nuts and berries, medical herbs, timber, agricultural and construction materials, fuel, tree sap, bark, and others. Many villages also produced various secondary processed goods. Fifty-two species were specified as forest products, which included some estimation, and were composed of 19 herbaceous and 23 arboreal species. GIS mapping of each village indicated that firewood and charcoal were shipped to towns located in southern Iwate, from around Kesen County. People might trade these fuel woods on markets. On the other hand, chestnut (Castanea crenata S. et Z.) and acorn were produced in the low-density populated area all around Iwate.

An animal model of early-stage femoral head osteonecrosis induced by cryo-insult in small tailed Han sheep.

SummaryPurposeThis study investigated the ability of liquid nitrogen cryo-insults to induce early-stage osteonecrosis of the femoral head (ONFH) in small tail Han sheep.Methods16 animals were subjected to unilateral cryo-insult using cryogen equipment with a cryo-insult probe, followed 1, 3, and 6 months later by X-ray, CT scanning, micro-CT scanning, and histological evaluation.ResultsX-ray evaluation of operative femoral heads (Op-FHs) at each time point showed low density areas under the cartilage surface that paralleled sclerosis belts, and CT scans showed sclerosis and cyst areas in Op-FHs. Micro-CT analysis showed that the ratio of bone to total volume and mean trabecular thickness of regions of interest (ROIs) were lower in Op-FHs than in normal femoral heads (No-FHs) at each time point (n = 4, p < 0.05). Histological evaluation at 1 month showed that necrotic changes were dominant as evidenced by moderate empty lacunae, decreases in the number of hematopoietic cells, and moderate increases in the number of fibroblasts. At 3 and 6 months, fractured trabeculae, fibroblasts, and new blood capillaries were increased, indicating an absorption and repair process. Bone volume fraction of ROIs of Op-FHs was lower than in No-FHs at each time point (n = 4, p < 0.05) in histological evaluation. At 6 months, the maximum load of No-FHs was higher than Op-FHs (n = 4, p < 0.05).ConclusionThese findings indicate that early-stage ONFH can be induced in small tail Han sheep using cryogenic equipment.The translational potential of this articleThis animal model may be helpful in developing new treatment modalities for human ONFH.

Stay at (which) home: second homes during and after the COVID-19 pandemic

Purpose This viewpoint paper aims to provide reflections on the role of second homes in the tourism and housing markets together with future lines of research during and after the first outbreak of the COVID-19 (coronavirus disease 2019) pandemic. The authors aim to review the epistemological evolution of the term “second homes” because of the pandemic, as well as to unfold possible short-, medium- and long-term effects that could place second homes at the center of tourist activity and of the tourist rental market profitability. Design/methodology/approach This paper is based on published research studies about the definition of the term “second homes”, as well as media sources related to their role during the current situation of the first outbreak of the COVID-19 pandemic. Findings In the early stages of the pandemic, second-home owners migrated from crowded cities to low-density areas, being vectors of transmission of the virus. Now, a potential shift in tourist preferences could position second homes at the center of tourist activity as soon as travel restrictions are reduced. This could intensify existing processes of commodification of housing, empowering accommodation platforms and situating the potential for profiteering around the tourist rental market. Parallely, international interests in migrating from crowded cities to low-density areas could also be triggered. Originality/value This viewpoint is presented as the confinement measures associated with the new pandemic are being de-escalated in most of the western countries. It is expected that sharing it will provide insights to researchers and practitioners to better plan their research around secondary housing. Its role should be analysed from different perspectives: in the spread of the virus to low-density areas to anticipate mitigation actions in future outbreaks; in the recovery process of (domestic) tourism; in the processes of commodification and financialization of housing in tourist areas; and their impacts on local residents.

Detection of spatio-temporal changes of vegetation in coastal areas subjected to soil erosion issue

Coastal soil erosion can be recognized as the most alarming environmental issue since, causing shoreline retreat, reduces the area available for plant habitat survival, highly influencing their health status, and, consequently, limiting their ability in beach front properties protection. A deep knowledge of vegetation changes is required to identify the proper strategy to be adopted to face soil erosion problems in coastal areas. Therefore, the current paper is aimed to quantitatively examine the spatio-temporal changes suffered by the vegetation in the coastline of Siponto in Apulia Region (Southern Italy) covering a time period of about forty years. LANDSAT images from 1975, 2006, 2011 and 2018 were collected, atmospherically corrected and, finally, processed to generate binary classification maps of vegetation by applying the Composite Vegetation Index, a novel index based on the interpolation of Red, Green and Near-Infrared bands, suitable for catching both cellular and metabolic features of vegetation. Then, the generated binary classification maps were compared using the Vegetation Index Differencing technique, a post-classification change detection technique. The results showed an increase in vegetation extension cover and density overall the entire examined period. That phenomenon appeared more and more prominent between 1975 and 2006, where an increment of vegetated areas extension of about 88% were registered. Combining of the novel vegetation index, developed ad-hoc in the current research, and Vegetation Index Differencing approach shows promising results in vegetation classification and comparison over the time. Indeed, the method allows the fast vegetation extraction, great processing time saver. Nevertheless, spatial resolution of Landsat Images limits the classification of small and low-density vegetated areas. Therefore, future work should plan to test the proposed approach at a more detailed scale.

In situ fabrication of robust three dimensional ordered macroporous γ-MnO2/LaMnO3.15 catalyst for chlorobenzene efficient destruction

Catalytic activity of perovskite oxides as LaMnO3+δ is greatly limited by their low surface area and deficient active site density though they are thought to be one category of desired candidates for noble metal-based catalysts. Here, a robust three dimensional ordered macroporous (3DOM) γ-MnO2/LaMnO3.15 (Mn/3DLM) was in situ fabricated by the strategy of selectively dealloyed surface La cations. Mn/3DLM displayed excellent activity with 90% of chlorobenzene destructed at 207 °C (apparent activation energy of 45.4 kJ/mol), obviously lower than those of γ-MnO2 (244 °C; 51.9 kJ/mol) and bulk LaMnO3.15 (311 °C; 70.2 kJ/mol) owing to large surface area, excellent reducibility, and improved surface active oxygen concentration. Nucleophilic substitution was the main process for active oxygen attacking, while electrophilic substitution mainly contributed to chlorinated byproducts formation. Remarkably, reaction byproducts as phenol, o-dichlorobenzene, trichloroethylene, and bichloroethylene over Mn/3DLM can be efficiently inhibited during the long-term operations via weakened the electrophilic substitution effect.

Assessment of Rainwater Harvesting Potential from Roof Catchments through Clustering Analysis

Rainwater harvesting from rooftop catchments represents a climate change adaptation measure that is especially significant in areas affected by water scarcity. This article develops a Geographic Information Systems-based methodology to evaluate the spatial distribution of rainwater catchment potential to identify the most favorable urban areas for the installation of these infrastructures. Since performance and water saving potential of rainwater harvesting systems greatly depends on population density and roof size, this assessment was performed for each residential plot on a per capita basis, based on cadastral data and a method of demographic disaggregation. Furthermore, to evaluate spatial variation of runoff coefficient per building, a supervised classification was carried out to consider the influence of roof types on the rainwater catchment potential. After calculating rainwater catchment potential per capita for each residential plot, the spatial clustering of high (hot spots) and low values (cold spots) was assessed through the Getis-Ord General G statistic. Results indicate a spatial pattern of high rainwater catchment potential values in low-density urban areas, where rainwater catchment systems are expected to offer a better performance and a shorter amortization period. These results may be useful for the enactment of local legislation that regulates the obligation to install these infrastructures or offers subsidies for their implementation.

Integrating Affordable Housing with Transit: Where are the Transit Deserts?

This study analyzed transit deserts in Seattle using spatial principal component analysis. We ranked factors related to transit deserts and incorporated the spatial and temporal features of transit services. We found that transit access was the main factor that contributed to transit deserts. We identified clustered and scattered transit deserts. The clustered ones were in dense areas outside of transit corridors, and the scattered ones were located across low-density areas. These findings imply that transit planning and affordable housing should be integrated, and that micro-transit can fulfill the mobility needs of people living in transit deserts.

Plant Counting of Cotton from UAS Imagery Using Deep Learning-Based Object Detection Framework

Assessing plant population of cotton is important to make replanting decisions in low plant density areas, prone to yielding penalties. Since the measurement of plant population in the field is labor intensive and subject to error, in this study, a new approach of image-based plant counting is proposed, using unmanned aircraft systems (UAS; DJI Mavic 2 Pro, Shenzhen, China) data. The previously developed image-based techniques required a priori information of geometry or statistical characteristics of plant canopy features, while also limiting the versatility of the methods in variable field conditions. In this regard, a deep learning-based plant counting algorithm was proposed to reduce the number of input variables, and to remove requirements for acquiring geometric or statistical information. The object detection model named You Only Look Once version 3 (YOLOv3) and photogrammetry were utilized to separate, locate, and count cotton plants in the seedling stage. The proposed algorithm was tested with four different UAS datasets, containing variability in plant size, overall illumination, and background brightness. Root mean square error (RMSE) and R2 values of the optimal plant count results ranged from 0.50 to 0.60 plants per linear meter of row (number of plants within 1 m distance along the planting row direction) and 0.96 to 0.97, respectively. The object detection algorithm, trained with variable plant size, ground wetness, and lighting conditions generally resulted in a lower detection error, unless an observable difference of developmental stages of cotton existed. The proposed plant counting algorithm performed well with 0–14 plants per linear meter of row, when cotton plants are generally separable in the seedling stage. This study is expected to provide an automated methodology for in situ evaluation of plant emergence using UAS data.

Effects of built environment on activity participation under different space-time constraints: A case study of Guangzhou, China

Conventional facility planning seeks to provide service facilities to meet population demand in an aggregate manner. However, recent studies reveal that the provision of facilities in residential neighborhoods does not necessarily mean easy service access for certain groups. This issue is approached through the lens of space–time constraints in this study, which asserts that because people with different socioeconomic attributes experience different space–time constraints, the effects of the same built environment on actual access can considerably vary. Based on the activity-diary data from 493 respondents in Guangzhou, China, this study conducts a quasi-experiment facilitated by the propensity score matching approach. Residents in low-density suburban areas and those in high-density central city areas are considered as the control and treatment groups, respectively. By comparing the activity-travel behavior between these two groups, this work presents an analysis of the effects of service density improvement on residents’ actual service access. Moreover, the differences of such effects are examined through separate quasi-experiments for residents with the largest, medium and smallest space–time constraints. Residents who originally experience the smallest space–time constraints could further benefit from the enhancement of service density, whereas those who originally suffer from the largest and medium space–time constraints could not. These findings imply that conventional facility planning may not provide equitable outcomes. Therefore, facility planning and management should address and integrate residents’ unequal experiences of space–time constraints into time-sensitive policies (e.g., flextime policies).

Road traffic crash characteristics of drivers who take prescription medicines that carry a risk to driving

BackgroundThe specific features of crashes involving an alcohol-intoxicated driver have been extensively characterized, but no such data are available for crashes involving a driver who has used a prescription medicine, which could help to plan and target prevention and control initiatives. This study aimed to describe the characteristics of crashes involving drivers under the influence of prescription medicines. MethodsWe took advantage of CESIR, a French record linkage study for which data were extracted and matched from three French national databases: police reports, the national police database of injurious crashes and the national health care insurance database (HCI database). The drivers included in the study were those involved in an injurious road crash in France from July 1, 2005 to December 31, 2015, whose national identity number, date of birth and sex allowed matching. Prescription medicines considered were those with the two highest levels of warning. ResultsSimilar crash profiles were found when drivers used alcohol or medicines, particularly with respect to injury severity, type of vehicle, type of collision, type of road and cross-track profile. Alcohol-related crashes were over-represented during weekends and in low-density areas and medicine-related crashes were over-represented during weekdays and in cities of fewer than 300 000 inhabitants. While a much higher strength of association with responsibility was found for alcohol than for medicines, the proportion of crashes with drivers using medicines was twice as high as crashes with drivers using alcohol. ConclusionThe lower risk carried by medicines is therefore in part compensated by a higher prevalence of use, making medicines one of the hidden factors of road risk. Characterizing these crashes will therefore be useful to better focus road safety intervention on the prevention of driving under the influence of psychotropic medicines.

Synchrotron X-ray Topography Characterization of Commercial GaN Substrates for Power Electronic Applications

Commercial GaN substrates from different vendors were characterized by synchrotron X-ray topography (XRT) as well as high resolution X-ray diffraction (HRXRD) to evaluate their defect and strain distributions. Synchrotron monochromatic beam X-ray topographs reveal the various dislocation types and their distribution in the GaN materials grown by different methods. By correlating the dislocation contrast with ray-tracing simulation results, the Burgers vectors of dislocations were successfully determined. The ammonothermal-grown GaN material using native seed show the highest quality with low dislocation densities. Patterned HVPE GaN wafers have heterogeneous distribution of dislocations with large areas of low threading dislocation densities. Regular HVPE GaN substrate and ammonothermal GaN grown on an HVPE GaN seed show a very high level of strain, and the dislocation densities are much higher than ammonothermal and patterned HVPE samples.

The Geography of Unconventional Innovation

Using a newly assembled dataset of U.S. patents, we show that overall innovation activity is less concentrated in high-density urban areas than commonly believed, but inventions based on atypical combinations of knowledge are indeed more prevalent in high-density cities. To interpret this relation, we propose that informal interactions in densely populated areas help knowledge flows between distant fields, but are less relevant for flows between close fields. We build a model of innovation in a spatial economy that endogenously generates the pattern observed in the data: specialized clusters emerge in low-density areas, whereas high-density cities diversify and produce unconventional ideas.