Intermediate Density Research Articles

Topology optimization of three-dimensional structures subject to self-weight loading

PurposeTopology optimization of structures under self-weight loading is a challenging problem which has received increasing attention in the past years. The use of standard formulations based on compliance minimization under volume constraint suffers from numerous difficulties for self-weight dominant scenarios, such as non-monotonic behaviour of the compliance, possible unconstrained character of the optimum and parasitic effects for low densities in density-based approaches. This paper aims to propose an alternative approach for dealing with topology design optimization of structures into three spatial dimensions subject to self-weight loading.Design/methodology/approachIn order to overcome the above first two issues, a regularized formulation of the classical compliance minimization problem under volume constraint is adopted, which enjoys two important features: (a) it allows for imposing any feasible volume constraint and (b) the standard (original) formulation is recovered once the regularizing parameter vanishes. The resulting topology optimization problem is solved with the help of the topological derivative method, which naturally overcomes the above last issue since no intermediate densities (grey-scale) approach is necessary.FindingsA novel and simple approach for dealing with topology design optimization of structures into three spatial dimensions subject to self-weight loading is proposed. A set of benchmark examples is presented, showing not only the effectiveness of the proposed approach but also highlighting the role of the self-weight loading in the final design, which are: (1) a bridge structure is subject to pure self-weight loading; (2) a truss-like structure is submitted to an external horizontal force (free of self-weight loading) and also to the combination of self-weight and the external horizontal loading; and (3) a tower structure is under dominant self-weight loading.Originality/valueAn alternative regularized formulation of the compliance minimization problem that naturally overcomes the difficulties of dealing with self-weight dominant scenarios; a rigorous derivation of the associated topological derivative; computational aspects of a simple FreeFEM implementation; and three-dimensional numerical benchmarks of bridge, truss-like and tower structures.

Optimum planting density of Amorpha fruticosa promotes the recovery of understory vegetation and the arbuscular mycorrhizal fungal community in plantations in arid coal mining areas

AbstractEstablishment of plantations may be a useful means of vegetation reconstruction in coal mining areas, especially in fragile environments. However, the influence of shrub planting on the relationship between understory vegetation and soil microorganisms remains poorly understood. Here, we describe a field experiment in which the relationships between understory vegetation and soil microorganisms under different planting densities of Amorpha fruticosa L. (A. fruticosa) were investigated. Compared with areas allowed to recover naturally, shrub planting changed the community and increased the biomass of understory vegetation and soil microbes, especially of arbuscular mycorrhizal fungi (AMF). Planting density was also a key factor that influenced understory vegetation and the soil AMF community and biomass. The maximum diversity of understory vegetation and the AMF community occurred at an intermediate density of introduced shrubs, which was considered to be the optimum density of A. fruticosa. The major soil nutrient cycles that influence understory vegetation and the AMF community were also investigated. An optimum density of introduced shrubs was important in the ecological reconstruction of vegetation in the coal mining area. There may also have been an optimum relationship between the understory vegetation and soil microorganisms especially with AMF in the experimental conditions.

An Unexpected Lewis Acid-Catalyzed Cascade during the Synthesis of the DEF-Benzoxocin Ring System of Nogalamycin and Menogaril: Mechanistic Elucidation by Intermediate Trapping Experiments and Density Functional Theory Studies.

An unexpected Lewis acid-catalyzed carbohydrate rearrangement of a 1,5-bis-glycopyranoside to the product of a formal intramolecular C-aryl glycosylation reaction is reported. Mechanistic studies based mainly on intermediate trapping experiments and density functional theory (DFT) calculations reveal a cascade process involving three transient (a)cyclic oxocarbenium cations, the breaking of three single C(sp3)-O bonds, and the formation of three single bonds (i.e., exo-, endo-, and C-glycosidic bonds), leading to the 2,6-epoxybenzoxocine skeleton of bioactive natural glycoconjugates related to serjanione A and mimocaesalpin E. DFT calculations established that the generation of the pyran moiety embedded in the bridged benzoxocin ring system is likely to proceed through an unusual ring-closure of an ortho-quinone methide intermediate in which the attacking nucleophile is a carbonyl oxygen.

Predation of Raoiella indica (Acari: Tenuipalpidae) by Stethorus tridens Gordon (Coleoptera: Coccinellidae)

The red palm mite (RPM), Raoiella indica Hirst (Acari: Tenuipalpidae), is an invasive species in several American countries and has a wide range of hosts, causing significant damage, mainly to coconut and banana crops. Previous studies conducted in America have focused on the biological control of RPM through predatory mites and insects. Stethorus tridens Gordon (Coleoptera: Coccinellidae) is considered a promising biocontrol agent of phytophagous mites it has been observed on several cultures, and has a high predatory capacity. The aim of this study was to investigate S. tridens preferences among different developmental stages of RPM and estimating the functional and numerical responses of S. tridens over its most preferred prey-stage. Furthermore, the prey preference of S. tridents was examined between eggs of Tetranychus evansi Baker and Pritchard (its natural prey) and eggs of RPM through two-choice and non-choice experiments. The results showed that S. tridens prey on all developmental stages of RPM, with a marked preference for eggs over other stages of RPM. The functional response of this predator was type III, as consumption increased rapidly at intermediate egg densities. Predation on RPM eggs was unable to stimulate S. tridens reproduction, even at the highest densities. When we compared the food preference of S. tridens to eggs of T. evansi and RPM, we found that the predator preferred tetranychids. The results of this study suggested that RPM can be used as alternative prey to S. tridents, serving as a source of energy and allows for maintenance but not its reproduction.

Molecular dynamics simulation study of oil slippage on polymer grafted surface: The role of grafting density

AbstractThe polymer grafted materials are frequently used in antifouling and oil–water separation, while the microscopic mechanism of liquid slippage on this surface remains unclear. This study uses molecular dynamics (MD) simulations to explore the structure and transport of oil (n‐hexadecane) on polydimethylsiloxane (PDMS) grafted surface as a function of grafting density. Simulation results indicate that PDMS chain structure undergoes a transition from liquid‐like to solid‐like structure when the grafting density increases. As a result, the entanglement between the PDMS and n‐hexadecane is also weakened. The direct consequence of this structural change is that the slip length of n‐hexadecane shows a non‐monotonic dependence on the grafting density, and a maximum slip length appears at intermediate grafting density. Further analysis indicate that the slip length also increases as the applied shear rate increases, which facilitates the transport of fluid at the grafted surface. These simulation results illustrate the subtle interplay between polymer–alkane interface structure and the transport property of the fluids, which are consistent with recent experimental studies, and will be helpful for rational design of polymer grafted materials in separation technologies.

The intermediate neutron capture process

Context. The observed surface abundance distributions of carbon-enhanced metal-poor (CEMP) r/s stars suggest that these stars could have been polluted by an intermediate neutron capture process (the so-called i-process) occurring at intermediate neutron densities between the r- and s-processes. Triggered by the ingestion of protons inside a convective He-burning zone, the i-process could be hosted in several sites, a promising one being the early AGB phase of low-mass, low-metallicity stars. The i-process remains affected however by many uncertainties, including those of nuclear origin, since it involves hundreds of nuclei for which reaction rates have not yet been determined experimentally. Aims. We investigate both the systematic and statistical uncertainties associated with theoretical nuclear reaction rates of relevance during the i-process and explore their impact on the i-process elemental production, and subsequently on the surface enrichment, of a low-mass, low-metallicity star during the early AGB phase. Methods. We used the TALYS reaction code to estimate both the model and parameter uncertainties affecting the photon strength function and the nuclear level densities, and hence the radiative neutron capture rates. The impact of correlated systematic uncertainties was estimated by considering different nuclear models, as was detailed in Paper II. In contrast, the uncorrelated uncertainties associated with local variation in model parameters were estimated using a variant of the backward-forward Monte Carlo method to constrain the parameter changes to experimentally known cross sections before propagating them consistently to the neutron capture rates. The STAREVOL code (Siess 2006, A&A, 448, 717) was used to determine the impact of nuclear uncertainties on the i-process nucleosynthesis in a 1 M⊙ [Fe/H] = –2.5 model star during the proton ingestion event in the early AGB phase. A large nuclear network of 1160 species coherently coupled to the transport processes was solved to follow the i-process nucleosynthesis. Results. We find that the uncorrelated parameter uncertainties lead the surface abundance uncertainties of elements with Z ≥ 40 to range between 0.5 and 1.0 dex, with odd-Z elements displaying higher uncertainties. The correlated model uncertainties are of the same order of magnitude, and both model and parameter uncertainties have an important impact on potential observable tracers such as Eu and La. We find around 125 important (n, γ) reactions impacting the surface abundances, including 28 reactions that have a medium to high impact on the surface abundance of elements that are taken as observable tracers of i-process nucleosynthesis in CEMP stars. Conclusions. Both the correlated model and uncorrelated parameter uncertainties need to be estimated coherently before being propagated to astrophysical observables through multi-zone stellar evolution models. Many reactions are found to affect the i-process predictions and will require improved nuclear models guided by experimental constraints. Priority should be given to the reactions influencing the observable tracers.

Biofloc based farming of Nile tilapia (Oreochromis niloticus) in tanks under different stocking densities

This experiment was conducted to optimize the stocking density of Nile tilapia (Oreochromis niloticus) in biofloc based farming system in tanks for a period of 90 days from 23 December to 22 March 2022 in Mohanpur upazilla, Rajshahi district, Bangladesh. The experiment was conducted in 5000 L cemented tanks (5m3) under three different of stocking densities (T1: 200 fishes/m3, T2: 150 fishes/m3 and T3: 100 fishes/m3) having three replicates each. The initial weight of fish was 11.50±0.35 g and fishes were fed (34% protein content) twice a day @ 5-3 % body weight. Among three treatments, a significantly higher (P<0.05) average daily gain (ADG) of 1.15±0.07 g with specific growth rate (SGR) of 2.44±0.09 % day-1 were recorded in T3 treatment but a significantly higher (P<0.05) average yield of 118907.70 and 114914.20 kg/ha/3 months were obtained in T1 and T2 treatment, respectively. Higher average net benefit of 1231671.90 BDT/ha/3 months and BCR of 0.12 were obtained in T2 treatment which is significantly higher (p<0.05) than T1 and T3 treatment. By an economical assessment, if the sales price is influenced by the final body weight, the reduced average harvest weight in higher stocking densities could lead to low profitability. Therefore, it is concluded that the use of intermediate stocking density, around 150 fishes/m3, has higher profitability since it produces a large proportion of harvested fish that reach high body weights, and possible high selling prices, combined with desirable biomass.

DPA-P2PNet: Deformable Proposal-Aware P2PNet for Accurate Point-Based Cell Detection

Point-based cell detection (PCD), which pursues high-performance cell sensing under low-cost data annotation, has garnered increased attention in computational pathology community. Unlike mainstream PCD methods that rely on intermediate density map representations, the Point-to-Point network (P2PNet) has recently emerged as an end-to-end solution for PCD, demonstrating impressive cell detection accuracy and efficiency. Nevertheless, P2PNet is limited to decoding from a single-level feature map due to the scale-agnostic property of point proposals, which is insufficient to leverage multi-scale information. Moreover, the spatial distribution of pre-set point proposals is biased from that of cells, leading to inaccurate cell localization. To lift these limitations, we present DPA-P2PNet in this work. The proposed method directly extracts multi-scale features for decoding according to the coordinates of point proposals on hierarchical feature maps. On this basis, we further devise deformable point proposals to mitigate the positional bias between proposals and potential cells to promote cell localization. Inspired by practical pathological diagnosis that usually combines high-level tissue structure and low-level cell morphology for accurate cell classification, we propose a multi-field-of-view (mFoV) variant of DPA-P2PNet to accommodate additional large FoV images with tissue information as model input. Finally, we execute the first self-supervised pre-training on immunohistochemistry histopathology image data and evaluate the suitability of four representative self-supervised methods on the PCD task. Experimental results on three benchmarks and a large-scale and real-world interval dataset demonstrate the superiority of our proposed models over the state-of-the-art counterparts. Codes and pre-trained weights are available at https://github.com/windygoo/DPA-P2PNet.

A novel method to efficiently differentiate human osteoclasts from blood-derived monocytes

BackgroundOsteoclasts are the tissue-specific macrophage population of the bone and unique in their bone-resorbing activity. Hence, they are fundamental for bone physiology in health and disease. However, efficient protocols for the isolation and study of primary human osteoclasts are scarce. In this study, we aimed to establish a protocol, which enables the efficient differentiation of functional human osteoclasts from monocytes.ResultsHuman monocytes were isolated through a double-density gradient from donor blood. Compared to standard differentiation schemes in polystyrene cell culture dishes, the yield of multinuclear osteoclasts was significantly increased upon initial differentiation of monocytes to macrophages in fluorinated ethylene propylene (FEP) Teflon bags. This initial differentiation phase was then followed by the development of terminal osteoclasts by addition of Receptor Activator of NF-κB Ligand (RANKL). High concentrations of RANKL and Macrophage colony-stimulating factor (M-CSF) as well as an intermediate cell density further supported efficient cell differentiation. The generated cells were highly positive for CD45, CD14 as well as the osteoclast markers CD51/ITGAV and Cathepsin K/CTSK, thus identifying them as osteoclasts. The bone resorption of the osteoclasts was significantly increased when the cells were differentiated from macrophages derived from Teflon bags compared to macrophages derived from conventional cell culture plates.ConclusionOur study has established a novel protocol for the isolation of primary human osteoclasts that improves osteoclastogenesis in comparison to the conventionally used cultivation approach.

Empirical phenotyping and genome-wide association study reveal the association of panicle architecture with yield in Chenopodium quinoa.

Chenopodium quinoa manifests adaptability to grow under varying agro-climatic scenarios. Assessing quinoa germplasm's phenotypic and genetic variability is a prerequisite for introducing it as a potential candidate in cropping systems. Adaptability is the basic outcome of ecological genomics of crop plants. Adaptive variation predicted with a genome-wide association study provides a valuable basis for marker-assisted breeding. Hence, a panel of 72 quinoa plants was phenotyped for agro morphological attributes and association-mapping for distinct imperative agronomic traits. Inter simple sequence repeat (ISSR) markers were employed to assess genetic relatedness and population structure. Heatmap analysis showed three genotypes were early maturing, and six genotypes were attributed for highest yield. The SD-121-07 exhibited highest yield per plant possessing green, glomerulate shaped, compact density panicle with less leaves. However, SJrecm-03 yielded less exhibiting pink, intermediate shape, intermediate density panicles with less leaves. The phenotyping revealed strong correlation of panicle architecture with yield in quinoa. A genome-wide association study unraveled the associations between ISSR makers and agro-morphological traits. Mixed linear modes analysis yielded nine markers associated with eight traits at p ≤ 0.01. Moreover, ISSR markers significantly associated with panicle shape and leafiness were also associated with yield per plant. These findings contribute to the provision of authenticity for marker-assisted selection that ultimately would support quinoa breeding programs.

Inverse design of periodic microstructures with targeted nonlinear mechanical behaviour

This paper introduces an inverse design framework for the precise tailoring of desired nonlinear mechanical responses in periodic microstructures, with particular focus on prescribed nonlinear stress–strain relationships. The topology optimization hinges on minimizing the error between the target and realized properties of the microstructures. A deformation-driven homogenization framework is setup. The periodic constraints needed for the microscale equilibrium equation are imposed through strongly enforced periodic boundary conditions and the removal of the translational nullspace, avoiding the need for Lagrange multipliers, greatly simplifying the implementation. Automatic differentiation is leveraged to efficiently calculate the necessary sensitivities for the gradient-based optimization. To further aid the design of discrete designs a intermediate density penalty constraint is proposed. Numerical examples underscore the efficacy of our methodology, showcasing microstructures that demonstrate targeted softening and stiffening as well as distinctive directional behaviour.

Density affects rearing performance of juvenile landlocked fall Chinook Salmon

AbstractObjectiveDensity‐related information for landlocked fall Chinook Salmon Oncorhynchus tshawytscha shortly after first feeding is poorly understood. This study was undertaken to determine the effects of a range of rearing densities (low, intermediate, and high) on rearing performance and survival of newly feed‐trained juvenile landlocked fall Chinook Salmon.MethodsThe fish were reared for 66 days in 1.8‐m (diameter) tanks with approximate volume of 2036 L at one of three loadings of approximately 2500, 5000, or 10,000 fish/tank.ResultThe initial and final densities for each of the three loadings were 0.73 and 8.93, 1.45 and 16.41, and 2.90 and 26.86 kg/m3, respectively. At the end of the study, the specific growth rates were significantly lower, total lengths were significantly shorter, and feed conversion ratios were significantly greater in the fish from the highest‐density treatment relative to the fish in the other treatments. Percentage of weight gain, final weights, and condition factor were significantly reduced in fish from the highest‐density treatment relative those at the lowest density. There were no significant differences in any growth metrics between fish that were reared at the lowest and intermediate densities. The intermediate density (5000 fish/tank) produced intermediate results that did not significantly differ from either the highest or lowest densities. Mortality was not significantly different among the density treatments.ConclusionAn initial loading of 5000 fish in 1.8‐m (diameter) circular tanks, corresponding to initial and final densities of 1.45 and 16.41 kg/m3, respectively, is recommended to minimize the detrimental effects of density on newly feeding Chinook Salmon while maximizing their production in often limited hatchery space.

Hydrogen Production through Distinctive C-C Cleavage during Acetic Acid Reforming at Low Temperature.

Acetic acid reforming is a green method for sustainable hydrogen production owing to its renewable source from biomass conversion. However, conventional acetic acid reforming would produce various byproducts, including CO, CH4 and so on. Here, we develop a distinctive method for selective hydrogen production from C-C directional cleavage during acetic acid reforming. Completely different from conventional acetic acid reforming process, acetic acid would react with water over organoruthenium catalyst during its C-C cleavage at low temperature, then produce methanol and formic acid (CH3COOH+H2O→CH3OH+HCOOH). Lastly, methanol and formic acid could further decompose into hydrogen and carbon dioxide over organoruthenium selectively. As a result, there is little CO and CH4 produced in the first step of C-C bond cleavage during acetic acid reforming at 100 °C. Hydrogen production rate is up to 26.8 molH2/(h-1*mol-1 Ru) at 150 °C through a tandem catalysis. A mechanism for C-C cleavage of acetic acid is proposed based on intermediate product analysis and density functional theory (DFT) calculation. Firstly, the C-C single bond was transformed into C=C double bond by dropping one H atom to organoruthenium. Then the coming H2O molecule reacted with the C=C bond by an addition reaction, forming methanol and formic acid. This research not only proposes distinctive reaction pathway for hydrogen production from acetic acid reforming, but also provides some inspiration for selective C-C bond cleavage during ethanol reforming.

Density-dependent facilitation and inhibition between submerged and free-floating plants

This study aimed at testing the hypothesis that free-floating plants may facilitate the growth of submerged plants under hypertrophic conditions and intermediate plant density. The effects of Lemna presence on the growth of two submerged plants (Elodea nuttallii and Ceratophyllum demersum) over a nitrogen gradient were experimentally investigated. This was complemented with analysing the presence of C. demersum and E. nuttallii in Hungary and in Germany in relation to the density of free-floating plants. Results showed a negative exponential pattern between underwater light intensity and Lemna cover. Ceratophyllum and Elodea relative growth rate decreased with increasing nitrogen concentrations and additional low Lemna density stimulated Ceratophyllum and suppressed Elodea. Elodea decreased linearly with Lemna density while Ceratophyllum showed a unimodal response. Total algal biomass (epiphytic and planktonic) was higher in Ceratophyllum than in Elodea treatments and decreased rapidly with increasing Lemna density. The field studies showed a positive relationship between Ceratophyllum and a negative one between Elodea and free-floating plant cover. This study clearly showed that free-floating plants can have either facilitating or inhibiting impact on the growth of submerged plants depending on cover density and macrophyte species. The facilitating effect on Ceratophyllum is most likely due to suppressing epiphytic algal growth.

An improved proportional topology optimization method combining a polarized material interpolation scheme and Heaviside threshold function

An improved proportional topology optimization (IPTO) method is proposed in this work. The main improvement of this method is that the conventional solid isotropic material with penalization (SIMP)-based material interpolation scheme is replaced by a polarized material interpolation scheme, and the Heaviside threshold function is adopted based on the original proportional topology optimization (PTO) method. By using this approach, the minimum compliance problem can be solved without requiring the numerical derivation of the sensitivity function. To verify the feasibility and effectiveness of the proposed method, two-dimensional (2D) and three-dimensional (3D) cantilevers and L-bracket beams are used as examples. The 2D results obtained by the IPTO method are compared with those obtained by the PTO and SIMP methods. Numerical examples demonstrate that IPTO can acquire better objective function values and more ideal topology structures compared to PTO and SIMP. Furthermore, IPTO offers significant advantages over PTO and SIMP in terms of convergence speed and the ability to suppress intermediate density elements. Additionally, this method enables topology optimization design under multiple working conditions. Therefore, it provides an effective approach for structural topology optimization in research and engineering applications. With appropriate adjustment, this method can also be applied to composite material design and heat conduction design.

Phase Diagram of Nuclear Pastas in Neutron Star Crusts

Two neural networks were trained to predict, respectively, the Euler characteristic and the curvature of nuclear pastas in neutron star crust conditions generated by molecular dynamics simulations of neutron star matter with 0.1 < x < 0.5, 0.040 fm−3 < ρ < 0.085 fm−3 (0.68 × 1014 g/cm3 < ρ < 1.43 × 1014 g/cm3), and 0.2 MeV < T < 4.0 MeV, where x is proton content, the density is ρ, and the temperature is T. The predictions of the two networks were combined to determine the nuclear pasta phase that is thermodynamically stable at a given x, ρ, and T, and a three-dimensional phase diagram that extrapolated slightly the regions of existing molecular dynamics data was computed. The jungle gym and anti-jungle gym structures are prevalent at high temperature and low density, while the anti-jungle gym and anti-gnocchi structures dominate at high temperature and high density. A diversity of structures exist at low temperatures and intermediate density and proton content. The trained models used in this work are open access and available at a public repository to promote comparison to pastas obtained with other models.

An integrated population model reveals source-sink dynamics for competitively subordinate African wild dogs linked to anthropogenic prey depletion.

Many African large carnivore populations are declining due to decline of the herbivore populations on which they depend. The densities of apex carnivores like the lion and spotted hyena correlate strongly with prey density, but competitively subordinate carnivores like the African wild dog benefit from competitive release when the density of apex carnivores is low, so the expected effect of a simultaneous decrease in resources and dominant competitors is not obvious. Wild dogs in Zambia's South Luangwa Valley Ecosystem occupy four ecologically similar areas with well-described differences in the densities of prey and dominant competitors due to spatial variation in illegal offtake. We used long-term monitoring data to fit a Bayesian integrated population model (IPM) of the demography and dynamics of wild dogs in these four regions. The IPM used Leslie projection to link a Cormack-Jolly-Seber model of area-specific survival (allowing for individual heterogeneity in detection), a zero-inflated Poisson model of area-specific fecundity and a state-space model of population size that used estimates from a closed mark-capture model as the counts from which (latent) population size was estimated. The IPM showed that both survival and reproduction were lowest in the region with the lowest density of preferred prey (puku, Kobus vardonii and impala, Aepyceros melampus), despite little use of this area by lions. Survival and reproduction were highest in the region with the highest prey density and intermediate in the two regions with intermediate prey density. The population growth rate ( ) was positive for the population as a whole, strongly positive in the region with the highest prey density and strongly negative in the region with the lowest prey density. It has long been thought that the benefits of competitive release protect African wild dogs from the costs of low prey density. Our results show that the costs of prey depletion overwhelm the benefits of competitive release and cause local population decline where anthropogenic prey depletion is strong. Because competition is important in many guilds and humans are affecting resources of many types, it is likely that similarly fundamental shifts in population limitation are arising in many systems.

The limiting behavior of Riemann solutions to the Euler equations of compressible fluid flow for the modified Chaplygin gas with the body force

In this paper, we investigate the limiting behavior of Riemann solutions to the Euler equations of compressible fluid flow for modified Chaplygin gas with the body force as the two parameters tend to zero. The formation of delta shock waves and the vacuum states is identified and analyzed during the process of vanishing pressure in the Riemann solutions. The concentration and cavitation are fundamental and physical phenomena in fluid dynamics, which can be mathematically described by delta shock waves and vacuums, respectively. In this paper, our main objective is to rigorously investigate the formation of delta shock waves and vacuums and observe the concentration and cavitation phenomena. First, the Riemann problem of the Euler equations of compressible fluid flow for the modified Chaplygin gas with the body force is solved. Second, we rigorously confirm that, as the pressure vanishes, any two shock Riemann solution to the Euler equations of compressible fluid flow for the modified Chaplygin gas with the body force tends to a δ-shock solution to the pressureless gas dynamics model with a body force, and the intermediate density between the two shocks tends to a weighted δ-measure that forms the δ-shock; any two-rarefaction-wave Riemann solution to the Euler equations of compressible fluid flow for the modified Chaplygin gas with the body force tends to a solution consisting of four contact discontinuities together with vacuum states with three different virtual velocities in the limiting situation.

Impact of COVID-19 on foreign population resident in urban areas of Italy: selection of indicators, data sources, and definition of geographical stratification levels

to describe indicators, data sources, and levels of geographical stratification used within the framework of the CCM project "Epidemiological Surveillance and Control of COVID-19 in Metropolitan Urban Areas and for the containment of SARS-CoV-2 circulation in the immigrant population in Italy". population-based observational study based on data from the Integrated Covid-19 Surveillance System and the archive of hospital discharge records. interregional collaborative project. Resident population in 5 Italian Regions (Piedmont, Emilia-Romagna, Tuscany, Lazio, and Sicily). crude and age-standardized rates of diagnostic test utilization and positivity, hospitalization (in any department and in intensive care unit), and mortality in COVID-19 cases. starting from the set of 11 indicators from the Italian National Institute for Health, Migration and Poverty (INMP) project "Epidemiology of SARS-CoV-2 Infection (COVID-19) and Use of Health Services in the Immigrant Population and Vulnerable Population Groups in Italy", the five most effective indicators for CCM purposes were identified. The INMP project highlighted higher rates of test access and positivity among Italians compared to foreigners, higher standardized hospitalization rates among foreigners, and higher standardized mortality rates among Italians, with geographical and temporal heterogeneity. The intersection between the DEGURBA (degree of urbanisation) classification and altimetric zones defined five levels of territorial stratification characterized by decreasing population density. Approximately 81% of the population involved in the CCM project resided in the first two levels; 43% of Italians lived in areas with intermediate population density in hilly or plain areas, while 48% of foreigners were concentrated in densely populated areas. sharing the collaborative approach and a research methodology already tested, integrated with the analysis of disaggregated indicators by morphological, functional, and administrative characteristics of the residential territory, allowed for assessing differences in the impact of the pandemic between Italians and foreigners residing in more or less densely populated areas.

Remnant cholesterol traits and risk of stroke: A multivariable Mendelian randomization study.

Observational epidemiological studies have reported a relationship between remnant cholesterol and stroke. However, the results are inconclusive, and causality remains unclear due to confounding or reverse causality. Our objective in this study was to investigate the causal relevance of remnant cholesterol and the risk of stroke and its subtypes using the Mendelian randomization (MR) approach. Genome-wide association studies (GWASs) including 115,082 European individuals (UK Biobank) were used to identify instruments for remnant cholesterol, including intermediate-density lipoprotein (IDL) cholesterol and very-low-density lipoprotein (VLDL) cholesterol. Summary-level data for total stroke, intracerebral hemorrhage, subarachnoid hemorrhage, ischemic stroke (IS), and IS subtypes were obtained from GWAS meta-analyses conducted by the MEGASTROKE consortium. Univariable and multivariable MR analyses were performed. The GWAS identified multiple single-nucleotide polymorphisms after clumping for remnant cholesterol (n = 52), IDL cholesterol (n = 62), and VLDL cholesterol (n = 67). Assessed individually using MR, remnant cholesterol (weighted median: odds ratio [OR] 1.32 per 1-SD higher trait; 95% CI: 1.04-1.67; P = 0.024) had effect estimates consistent with a higher risk of LAS-IS, driven by IDL cholesterol (OR 1.32; 95% CI: 1.04-1.68; P = 0.022). In multivariable MR, IDL cholesterol (OR 1.46; 95% CI: 1.10-1.93; P = 0.009) retained a robust effect on LAS-IS after controlling for VLDL cholesterol and high-density lipoprotein cholesterol. The MR analysis did not indicate causal associations between remnant cholesterol and other stroke subtypes. This study suggests that remnant cholesterol is causally associated with the risk of LAS-IS driven by IDL cholesterol.