Role Of Density Research Articles

Response of Subpolar North Atlantic Meridional Overturning Circulation to Variability in Surface Winds on Different Timescales

Abstract A large part of the variability in the Atlantic meridional overturning circulation (AMOC) and thus uncertainty in its estimates on interannual time scales comes from atmospheric synoptic eddies and mesoscale processes. In this study, a suite of experiments with a 1/12° regional configuration of the MITgcm is performed where low-pass filtering is applied to surface wind forcing to investigate the impact of subsynoptic (<2 days) and synoptic (2–10 days) atmospheric processes on the ocean circulation. Changes in the wind magnitude and hence the wind energy input in the region have a significant effect on the strength of the overturning; once this is accounted for, the magnitude of the overturning in all sensitivity experiments is very similar to that of the control run. Synoptic and subsynoptic variability in atmospheric winds reduce the surface heat loss in the Labrador Sea, resulting in anomalous advection of warm and salty waters into the Irminger Sea and lower upper-ocean densities in the eastern subpolar North Atlantic. Other effects of high-frequency variability in surface winds on the AMOC are associated with changes in Ekman convergence in the midlatitudes. Synoptic and subsynoptic winds also impact the strength of the boundary currents and density structure in the subpolar North Atlantic. In the Labrador Sea, the overturning strength is more sensitive to the changes in density structure, whereas in the eastern subpolar North Atlantic, the role of density is comparable to that of the strength of the East Greenland Current. Significance Statement A key issue in understanding how well the Atlantic meridional overturning circulation is simulated in climate models is determining the impact of synoptic (2–10 days) and subsynoptic (shorter) wind variability on ocean circulation. We find that the greatest impact of wind changes on the strength of the overturning is through changes in energy input from winds to the ocean. Variations in winds have a more modest impact via changes in heat loss over the Labrador Sea, alongside changes in wind-driven surface currents. This study highlights the importance of accurately representing the density in the Labrador Sea, and both the strength and density structure of the East Greenland Current, for the correct representation of overturning circulation in climate models.

DEMOGRAPHIC DYNAMICS AND URBAN PROPERTY CRIME: A LINEAR REGRESSION ANALYSIS IN KUALA LUMPUR AND PUTRAJAYA (2015-2020)

In an era where urbanization is rapidly transforming the landscape of cities, this study provides a crucial overview of how demographic shifts influence property crime in metropolitan areas. The paper delves into the complex interplay between property crime rates and demographic characteristics in the urban settings of Kuala Lumpur and Putrajaya, Malaysia, over six years from 2015 to 2020. Employing linear regression analysis, the study meticulously examines the relationship between property crime and various demographic factors, including total population, male and female populations, and residential and household densities. The findings indicate a consistent positive correlation between total population and property crime, emphasizing urban density's role in crime propensity. Notably, the male population shows a stronger correlation with property crime than females. The study also highlights how residential and household densities influence property crime in these urban settings. These insights are invaluable for policymakers and urban planners, guiding targeted strategies to reduce property crime in growing cities.

Role of Density and Conformational Composition in the Surface-to-Bulk Molecular Dosing of Photosensitive Surfactant Monolayers.

Poorly water-soluble photosensitive monolayers might enable very precise control of the rate and number of desorbing molecules by controlling both the monolayer density and conformational composition. In this perspective, we systematically characterized the interfacial behavior of Langmuir monolayers consisting of a poorly water-soluble azobenzene-containing surfactant as a function of its trans/cis ratio. Precise control of the conformational ratio was achieved by controlling the UV irradiation time, allowing researchers to investigate compositions spanning from 100% trans to 90% cis. Our results demonstrate that in 100% trans monolayers, molecules do not desorb with compression until a threshold area is reached. Instead, the number of molecules desorbing in mixed trans-cis monolayers can be modulated by controlling both the composition and the compression rate. Additionally, the desorption rate at constant density is also strongly composition-dependent, and it accounts for two different regimes with two different characteristic times. We will show that trans molecules mostly desorb according to the slow regime while cis molecules conform to the fast one, but the two conformers mutually influence each other.

Are Transit-Oriented Development and Travel Characteristics Influencing Residential Dissonance? Analysis From a Developing Country’s Perspective

The success of transit-oriented development (TOD) could hinge on reduced residential dissonance among the people living in TOD neighborhoods. Understanding the factors that could be associated with residential dissonance would be crucial in different contexts. Therefore, this study focused on exploring the various factors, such as TOD indicators, travel, and socio-demographic characteristics, that could influence the level of dissatisfaction of people living in TODs in Hyderabad, India. An ordered logit model was developed, which used data collected from primary as well as secondary sources. Results showed negative impacts of gender (male) and income on levels of dissatisfaction about neighborhoods, prompting policy interventions to address the disparities in gender and income groups. Further, it outlined the need to fulfill the varying requirements of larger households to reduce the dissonance. The roles of density, horizontal land-use diversity, and proximity to transit are very significant in improving living-satisfaction levels among people in TODs. More findings suggested the need for well-designed and maintained public spaces to address concerns related to safety and security and improve levels of satisfaction with TOD neighborhoods. The study also suggested that travel distances for educational trips, trip frequencies for work and shopping, and the use of private vehicles for work trips have positive influences on residential dissonance. It would be important to look for ways to provide convenient and sustainable alternative modes along with compact and diverse development, even though a longer commute may be acceptable.

Toward Better Pedestrian Trajectory Predictions: The Role of Density and Time-to-Collision in Hybrid Deep-Learning Algorithms.

Predicting human trajectories poses a significant challenge due to the complex interplay of pedestrian behavior, which is influenced by environmental layout and interpersonal dynamics. This complexity is further compounded by variations in scene density. To address this, we introduce a novel dataset from the Festival of Lights in Lyon 2022, characterized by a wide range of densities (0.2-2.2 ped/m2). Our analysis demonstrates that density-based classification of data can significantly enhance the accuracy of predictive algorithms. We propose an innovative two-stage processing approach, surpassing current state-of-the-art methods in performance. Additionally, we utilize a collision-based error metric to better account for collisions in trajectory predictions. Our findings indicate that the effectiveness of this error metric is density-dependent, offering prediction insights. This study not only advances our understanding of human trajectory prediction in dense environments, but also presents a methodological framework for integrating density considerations into predictive modeling, thereby improving algorithmic performance and collision avoidance.

The Role of Density in Achieving Volume and Weight Symmetry in Breast Reconstruction.

Knowledge of tissue and implant density is crucial in obtaining both volume and weight symmetry in unilateral breast reconstruction. Therefore, the aim of this study was to determine and compare the density of abdominal and breast tissue specimens as well as of 5th generation breast implants. Thirty-one breast tissue and 30 abdominal tissue specimens from 61 patients undergoing either mammaplasty or abdominoplasty as well as five different 5th generation breast implants were examined. Density (g/mL) was calculated by applying the water displacement method. The mean specimen density was 0.94 ± 0.02 g/mL for breast tissue and 0.94 ± 0.02 g/mL for abdominal tissue, showing no significant difference (p = 0.230). Breast tissue density significantly (p = 0.04) decreased with age, while abdominal tissue did not. A regression equation to calculate the density of breast tissue corrected for age (breast density [g/mL] = 0.975-0.0007 * age) is provided. Breast tissue density was not related to body mass index, past pregnancy, or a history of breastfeeding. The breast implants had a density ranging from 0.76 to 1.03 g/mL which differed significantly from breast tissue density (-0.19 g/mL [-19.8%] to +0.09 g/mL [+9.58%]; p ≤ 0.001). Our results support the suitability of abdominal-based perforator flaps in achieving both volume and weight symmetry in unilateral autologous breast reconstruction. Abdominal flap volume can be derived one-to-one from mastectomy weight. Further, given significant brand-dependent density differences, the potential to impose weight disbalances when performing unilateral implant-based reconstructions of large breasts should be considered.

The role of density in the energy conservation for the isentropic compressible Euler equations

In this paper, we study Onsager’s conjecture on the energy conservation for the isentropic compressible Euler equations via establishing the energy conservation criterion involving the density ϱ∈Lk(0,T;Ll(Td)). The motivation is to analyze the role of the integrability of density in energy conservation of weak solutions in this system, since almost all known corresponding results require ϱ∈L∞(0,T;L∞(Td)). Our results imply that the lower integrability of density ϱ means that more integrability of the velocity v is necessary in energy conservation. The proof relies on the Constantin–Weinan–Titi type and Lions type commutators on the mollifying kernel.

The COVID-19 pandemic and urban density: a systematic literature review

The role of density in the spread of the coronavirus pandemic is among the most critical concerns of urban designers and planners. To clarify this role, this systematic literature review is conducted on urban density and the COVID-19 infection and mortality rates in the context of urban design and planning. The studies were searched through three databases including Scopus, PubMed, and Web of Science in March 2022 and were screened and reviewed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. In total, 58 of the 3344 studies had pre-defined criteria. The results were categorised into four sections: population density, building density, built environment factors, and sociodemographic factors. Finally, directions are provided for future studies due to research gaps.

Modeling of laser-assisted micro-milling

The difficulties in the mechanical micro-machining process regarding the tool deflection, size effect and tool wear are much more pronounced than those in mechanical macro-machining. However, the role of mechanical micro-machining cannot be overestimated as an alternative against the non-traditional machining methods in manufacturing complex micro-parts with high dimensional and geometrical accuracies. Laser-Assisted Machining (LAM) can be used as a promising method by reducing the cutting forces and providing the possibility of increasing the Material Removal Rate (MRR) to enhance the productivity of mechanical micro-machining of difficult-to-cut material. Unlike common LAM, the parts are structured before machining using the ultra-short pulsed laser, followed by removing some parts of the material and consequently changing uncut chip thicknesses at the machining process. A model has been developed to understand how the structuring of the parts before micro-milling affects the uncut chip thicknesses at the micro-milling process. The model includes a variety of input parameters in terms of structure, tool, and process parameters to investigate this novel LAM comprehensively. Based on model results, the uncut chip thicknesses are reduced through the structuring of the part. The structure density was found as the most crucial parameter in uncut chip thickness reduction. The influence of structure density on cutting force reduction was also studied in the experiment. Workpieces made of titanium alloy (Ti6Al4V) were structured using a pico-second laser at different structure densities. The structured parts were machined at two feeds of 10 and 50 µm/tooth with a 35 m/min constant cutting speed. Structure density's role in reducing cutting force was also considerable. In addition, the contribution of different factors affecting cutting force reduction in this novel LAM process is discussed.

Poly(β‐hydroxythioether)s as shape memory polymer foams for oil sorption in aquatic environments

AbstractOil spills in aquatic environments represent a significant ongoing threat to aquatic life due to the persistence of oil films or slick. While many methods are available for open ocean waterways, interior waterways represent a different set of challenges. To that end, we propose the use of poly(β‐hydroxythioether) (PBHTE) shape memory polymer foams as a highly porous, low density solid for environmental remediation through oil collection. PBHTE foams are produced through thiol‐epoxy “click” reactions in the presence of an organobase, with gas blown foaming producing the highly porous scaffold with tunable pore sizes and salt‐leaching yielding smaller pore sizes (~400 μm). The different porosities are used here for studying the oil sorption as functions of time and environmental temperature for different pore sizes and compositions. The PBHTE material demonstrated two different Tgs when dry versus wet to compare against environmental differences. While dry the foam showed a Tgof 51.5°C and conversely when wet the Tgwas at 25°C. The foams were compared to see how the pore size will affect the oil sorption of the material and how it can be optimized for oil spills in interior water ways. The pore sizes analyzed were 400 μm, 800 μm, and 1100 μm. The relationship of pore size, temperature of the oil system during sorption, and time in the oil system seemed to have the largest impact on the sorption of oil during this study. The peak conditions for maximum oil sorption yielded the best performer being the 800 μm foam at 10°C after 15 h of sorption yielding a 2250% sorption, comparable with graphene and other low density sorption materials. Ultimately, the role of density in scavenging, along with a literature review, is used to assemble a density vs sorption Ashby chart to provide insight into the different materials available for such environmental remediation. In this context, PBHTE foams represent a new, promising class of material capable of absorbing oil in aquatic environments.

Role of Density and Grain Size on the Electrocaloric Effect in Ba0.90Ca0.10TiO3 Ceramics.

Pure perovskite Ba0.90Ca0.10TiO3 ceramics, with a relative density of between 79 and 98% and grain sizes larger than 1 µm, were prepared by solid-state reaction. The dielectric and electrocaloric properties were investigated and discussed considering the density and grain size of the samples. Room temperature impedance measurements show good dielectric properties for all ceramics with relative permittivity between 800 and 1100 and losses of <5%. Polarization vs. E loops indicates regular variation with increasing sintering temperature (grain size and density), an increase in loop area, and remanent and saturation polarization (from Psat = 7.2 µC/cm2 to Psat = 16 µC/cm2). The largest electrocaloric effect was 1.67 K for ceramic with GS = 3 µm at 363 K and electrocaloric responsivity (ζ) was 0.56 K mm/kV. These values are larger than in the case of other similar materials; thus, Ba0.90Ca0.10TiO3 ceramics with a density larger than 90% and grain sizes of a few µms are suitable materials for electrocaloric devices.

Role of additives in influencing heating and melting of polymers during thermoforming

AbstractThe heating stage in thermoforming of amorphous and semi‐crystalline polymers was analyzed for constant heat flux conditions using an energy balance model; candidate polymers were high impact polystyrene and isotactic polypropylene. Using an analytical solution, temperature differences as large as 100°C were predicted to arise between the surface and the interior of the sheet being thermoformed for conditions chosen in this work, and these can limit the heat flux being used. A Matlab program was used to compute temperature and crystallinity profiles for crystal melting. Melting took almost as much time as required to heat the surface of the film to the crystal melting point. High thermal conductivity additives, such as calcium carbonate and graphene, can provide temperature uniformity, and the additive uniformity can be verified using thermogravimetric analysis. The ability of these additives to provide temperature uniformity and to reduce energy consumption and heating time is determined in a quantitative manner. Both additives improve heat transfer, and, at the same added volume fraction, graphene is more effective. However, calcium carbonate has a lower cost. The role of density, specific heat, thermal conductivity, and amount of the polymers and additives in influencing temperature and crystallinity profiles was explored, and methods of carrying out thermoforming in an energy efficient manner are proposed.

How does resource dependence relate cities' technology diversification? The role of density and complexity

This study investigates the relationship between resource dependence and technology diversification with a territorial perspective, considering heterogeneity of different technologies, based on the patent application data of 641 categories in 341 cities in China. Using a linear probability model with fixed effects, the result shows that regional natural resources dependence is negatively related to the probability of diversifying into new technologies and the growth of a technology, providing evidence of “resource curse”. However, the probability of diversifying into less related and more complex technology spaces is less likely to be hindered by reliance on natural resources. Cities with higher complex knowledge structure are inclined to develop new technologies, and also experience a less negative effect of resource dependence on the probability of entering new technology space. Moreover, for technologies of different position in a city, reliance on natural resource also affects their growth distinctively. This study provides significant policy implications for the development of resource-dependent cities and the transformation of old industrial regions. Governments can manage existing resources to make a strategy and develop technical fields that have higher complexity or lower relatedness, which is vital to convert resource curse to resource blessing, thereby improving the sustainability and productivity of resource use.

A perspective on the fragility of glass-forming liquids

We discuss possible extraneous effects entering in the conventional measures of "fragility" at atmospheric pressure that may obscure a characterization of the genuine super-Arrhenius slowdown of relaxation. We first consider the role of density, which increases with decreasing temperature at constant pressure, and then the potential influence of the high-temperature dynamical behavior and of the associated activation energy scale. These two effects involve both thermodynamic parameters and the strength of the "bare" activation energy reflecting the specific bonding between neighboring molecules. They vary from system to system with, most likely, little connection with any putative collective behavior associated with glass formation. We show how to scale these effects out by refining the definition of fragility and modifying the celebrated Angell plot. We dedicate this note to our great and so inspiring friend, Austen Angell, and associate in this tribute another dear colleague who died too soon, Daniel Kivelson.

Abstract P5-13-05: Multiplex spatial systems analysis of responses to spatially separate nanoliter doses of drug predicts systemic immune-modulating combination treatments in breast cancer

Abstract Most targeted and chemotherapeutic agents in use today affect both the tumor and the associated tumor microenvironment (TME) and should be combined to achieve effective control by simultaneously attacking tumor intrinsic vulnerabilities, enhancing immune surveillance, and mitigating stromal mediators of resistance. We have developed an integrated technological platform that enables rapid identification of such combinations by effective, fast and harmless assessment of TME responses to multiple drugs or drug combinations. This approach uses an implantable microdevice for delivery of dozens of treatments into spatially separated regions of a single living tumor and multiplexed histology analyses with probes for 30+ proteins to interrogate the responses of tumor epithelial cells, cancer associated fibroblasts, endothelial cells, lymphoid and myeloid immune lineages. Responses of interest include changes in differentiation state, antigenicity and immunogenic cell death. We demonstrated the utility of this platform by performing an unbiased in vivo screen to assess the effects of seven FDA approved drugs and combinations thereof on two late-stage mouse models of breast cancer with intact immunity. These studies indicated that the most effective, immunogenic, tumor cell kill was produced by the epigenetic modulator, panobinostat, and was linked with upregulation of MHC-I expression on tumor cells, and recruitment of antigen presenting macrophages and cytotoxic neutrophils. Increased expression of Galectin-3 and Neuropilin-1 on cancer stem cells and neutrophils, respectively, correlated with the therapeutic response three days after drug exposure, suggesting a functional role of these two proteins in early events of induced anti-tumor immunity. Our spatial systems analyses also revealed a key role for density of cancer stem cells (CSCs) and formation of fibroblasts/ECM barriers as potential resistance mechanisms. Addition of the BCL2 inhibitor, venetoclax, enhanced panobinostat anti-tumor activity, and the local phenotypic cell responses involving dendritic cell recruitment and clustering to CSC microculture suggested the use of anti-CD40 immunotherapy to induce maximum therapeutic effect. We demonstrated that a panobinostast-venetoclax-anti-CD40 therapeutic combination predicted from microdevice analyses was effective in whole animal studies in multiple models of breast cancer and often resulted in complete tumor control. Generalization of this approach promises to enable rapid design of personalized drug combination regimens that maximize tumor cell eradication by direct action on the tumor cells and by creating effective antitumor microenvironments. We demonstrated the utility of the approach in model systems but application in humans is now underway. Citation Format: Zuzana Tatarova, Dylan C Blumberg, Lisa M Coussens, Gordon B Mills, Oliver Jonas, Joe W Gray. Multiplex spatial systems analysis of responses to spatially separate nanoliter doses of drug predicts systemic immune-modulating combination treatments in breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-05.

Role of density and electrostatic interactions in the viscosity and non-newtonian behavior of ionic liquids - a molecular dynamics study.

Strong ionic interactions, as well as the consequent correlations between cation and anion dynamics, give ionic liquids various physical features that set them apart from ordinary organic solvents. In particular, they result in larger viscosities and larger densities than mixtures of neutral compounds with similar molecular structures. However, both the direct effect of electrostatic interactions and the increase of liquid density contribute to the high viscosity and so far no experimental or computational work enabled a clear quantification of those effects. Also, the effects over the shear thinning behavior, which may have important consequences for application as lubricants, were not considered yet. Here, these questions were tackled by performing non-equilibrium molecular dynamics (NEMD) simulations changing both the strength of ionic interactions and liquid density at several shear rates using a coarse grained model. The relative dielectric constant was adjusted to reproduce viscosity data from all-atoms simulations on both zero shear and high shear conditions. Elimination of ionic interactions results in a reduction of density and zero shear viscosity and also delays the beginning of shear thinning to higher shear rates. Restoring density to the ionic liquid's value only partially reverses the alterations. Correlations of the non-newtonian behavior and changes in the intermolecular structure and contact lifetimes were also explored.

The Role of Density of Physical Variable

The Role of Density of Physical Variable

On the relations between large-scale models of superfluid helium-4

Superfluid helium-4 is characterized by extremely small values of kinematic viscosity, and its thermal conductivity can be huge, orders of magnitude larger than that of water or air. Additionally, quantum vortices may exist within the fluid. Therefore, its behavior cannot be explained by using the classical tools of Newtonian fluid mechanics, and, over the years, a few alternative models have been proposed. In order to highlight similarities and differences between these models, we recast them within a unifying framework, the general equation for non-equilibrium reversible-irreversible coupling (GENERIC). We begin by comparing the original two-fluid model, developed by Tisza and Landau, with the Hall–Vinen–Bekarevich–Khalatnikov model, both prescribing two types of fluid motion and two fluid densities, at flow scales appreciably larger than the typical distance between quantum vortices. We find from the geometrical structure of the models that only one fluid density plays the role of state variable, which should be taken into account when choosing an adequate expression for the free energy. We also recast within the GENERIC framework the one-fluid model of superfluid helium-4, where the inviscid component of two-fluid models is replaced by a caloric quantity, such as entropy. We find that the corresponding geometrical structures are analogous, with the roles of density and entropy swapped. In short, our work demonstrates that the studied models are compatible with each other, at least when focusing on the reversible parts of the models.

Climate change and indoor temperature variation in Venetian buildings: the role of density and urban form

Although the influence of urban form on microclimate and building thermal processes has been acknowledged, few studies have addressed the influence of overheating mechanisms on heterogeneous urban fabrics for existing historical cities. This study investigates the impact of changing urban climate on indoor temperatures by focusing on three Venice morphological patterns. Through microclimate modelling techniques, outdoor and indoor temperatures are simulated in 2020 and 2050 scenarios. Results show that the compactness of the urban fabric contributes to reducing indoor building temperatures. The analysis suggests that the increased density of shadow areas can mitigate the outdoor temperature values and reduce direct radiation on façades. When comparing the two climate scenarios 2020 and 2050, average indoor temperatures increase in the latter. However, the analysis highlights that the absence of insulation and the relatively high thermal mass of typical Venetian envelopes plays a crucial role in the building thermal processes preserving indoor comfort in a warmer climate future.

Role of hydrogen and its implications to decarbonise India

Hydrogenis gaining attentionas a promising future energy source. It has the potential to be a clean alternative to fossil fuels, particularly if it is produced using renewable resources. Two key concerns will be addressed by hydrogen energy, viz, reduce reliance on fossil fuels, Cut down on pollutants and greenhouse gas emissions. This paper discusses various production methodologies, as well as challenges, consequences, and control measures, as well as methods for storing and transporting hydrogen, the role of density in storage, the use of existing pipelines and mapping for transportation, and the transition to cryogenic tanks and embrittlement resistant materials in the near future. India has a favourable geographical location and vast reserves for renewable energy which makes it a suitable candidate to emerge as a green hydrogen exporter by 2030. It also discusses how India can use its resources effectively, implement policies and measures and seek international collaborationfor R&D in production technology and storage capabilities and materials in order to reduce Green House Gas (GHG) emissions, cost of production, replace fossil fuels with clean energy fuels and achieve its ambitious target of decarbonising by 2050.