1,721,158 research outputs found
Confinement effect on the viscoelastic particle ordering in microfluidic flows: Numerical simulations and experiments
Full text linkStrings of equally spaced particles, also called particle trains, have been employed in several applications, including flow cytometry and particle or cell encapsulation. Recently, the formation of particle trains in viscoelastic liquids has been demonstrated. However, only a few studies have focused on the topic, with several questions remaining unanswered. We here perform numerical simulations and experiments to elucidate the effect of the confinement ratio on the self-ordering dynamics of particles suspended in a viscoelastic liquid and flowing on the centerline of a microfluidic channel. For a fixed channel size, the particles self-order on shorter distances as the particle size increases due to the enhanced hydrodynamic interactions. At relatively low linear concentrations, the relative particle velocities scale with the fourth power of the confinement ratio when plotted as a function of the distance between the particle surfaces normalized by the channel diameter. As the linear concentration increases, the average interparticle spacing reduces and the scaling is lost, with an increasing probability to form strings of particles in contact. To reduce the number of aggregates, a microfluidic device made of an array of trapezoidal elements is fabricated and tested. The particle aggregates reduce down to 5% of the overall particle number, significantly enhancing the ordering efficiency. A good agreement between numerical simulations and experiments is found
Viscoelastic Particle Train Formation in Microfluidic Flows Using a Xanthan Gum Aqueous Solution
No full textViscoelastic polymer solutions have been widely employed as suspending liquids for a myriad of microfluidic applications including particle and cell focusing, sorting, and encapsulation. It has been recently shown that viscoelastic solutions can drive the formation of equally spaced particles called "particle trains"as a result of the viscoelasticity-mediated hydrodynamic interactions between adjacent particles. Despite their potential impact on applications such as droplet encapsulation and flow cytometry, only limited experimental studies on viscoelastic ordering are currently available. In this work, we demonstrate that a viscoelastic shear-thinning aqueous xanthan gum solution drives the self-assembly of particle trains on the centerline of a serpentine microfluidic device with a nearly circular cross section. After focusing, the flowing particles change their mutual distance and organize in aligned structures characterized by a preferential spacing, quantified in terms of distributions of the interparticle distance. We observe the occurrence of multi-particle strings, mainly doublets and triplets, that interrupt the continuity of the particle train. To account for the fluctuations in the number of flowing particles in the experimental window, we introduce the concept of local particle concentration, observing that an increase of the local particle concentration leads to an increase of doublets and triplets. We also demonstrate that using only a single tube to connect the sample to the microfluidic device results in a drastic reduction of doublets/triplets, thus leading to a more uniform particle train. Our findings establish the foundation for optimized applications such as deterministic droplet encapsulation in viscoelastic liquids and optimized flow cytometry
Interpretation and measurement of the spread between asking and selling prices in the Italian residential market
No full textThe lack of transparency in the property market and the resulting difficulty in finding comparables to use in property valuations, very often forces evaluators to substitute the asking prices with the selling prices in the market approach. This alternative is now also accepted by case law but has the limitation of having to quantify, albeit very roughly, the correction to be made in relation to the probable spread between the asking prices, taken as a reference, and future selling prices. The importance of the asking prices to understand the market, is acknowledged in international literature which has mainly focused (starting from the analysis of the prices themselves and the time spent on the market), on the search for the best sales strategies, or on the measurement of the illiquidity of the property market. This study, in an innovative way, also on the basis of the relationships already proven, instead, attempts to interpret and measure the difference between asking and selling prices, in order to build a reference for the adjustments made to the former in estimation practice. The target is pursued through the construction of a multivariate analysis model on a sample taken over a 12-year interval in the city of Potenza, Italy. The analysis allowed to measure and interpret the marginal contribution that macro and microeconomic variables provide to the explanation of the spread under investigation
The Key Role of Floors for the Sustainability of Retrofit Interventions in Older Existing Reinforced Concrete Buildings
Full text linkIn recent decades, the seismic performance of existing reinforced concrete (RC) buildings has played a key role. Nevertheless, the performance and reliability verification of important structural elements such as floors has often been neglected. Floors are primary structural elements that can affect the life cycle life of a building. However, the widespread lack of maintenance planning over time and the original construction practice (which was not always correct) are frequently the cause of unpredictable local or global collapse. In addition, although recent standards and codes recognize the importance of floors by prioritizing their verification with respect to gravitational load conditions, the verification of floor reliability with respect to the load combinations required by modern standards and codes is often not satisfied. Consequently, the intervention costs could be significantly affected by the floor conditions, and their overall amount might even discourage the implementation of interventions. The main purpose of this study is to evaluate the effects (in terms of sustainability) of interventions on residential RC buildings, considering the need to retrofit their existing floors. To this aim, the most vulnerable and potentially most degraded floor types are identified, and their capacity–demand relationships are evaluated. In the case of unverified floors, the main and most popular intervention methods are evaluated and related to the overall intervention costs, taking into account the main uncertainties in performance and cost predictions. The problems and critical issues of floors are key in determining the safety of the building and the cost-effectiveness (i.e., sustainability) of the retrofit intervention. Professionals and decision makers could benefit from the proposed study cost model to define intervention strategies on a regional or national scale
Reply to Charalampos Fragkoulis, Georgios Papadopoulos, and Konstantinos Ntoumas's letter to the editor re: Francesco Del Giudice, Giovanni Barchetti, Ettore De Berardinis, et al. Prospective assessment of vesical imaging reporting and data system (VI-RADS) and its clinical impact on the management of high-risk non–muscle-invasive bladder cancer patients candidate for repeated transurethral resection. Eur Urol 2020;77:101–9
No full textWe thank Fragkoulis and colleagues for their interest in our recently published paper on Vesical Imaging Reporting and Data System (VI-RADS) [1]. We acknowledge the issues raised and we hope to clarify the points of concern
Male fertility as a marker for health
No full textMale reproduction is a complex biological process, and male factor infertility is increasingly recognized as a biomarker for overall male health. Emerging data suggest associations between male reproduction and medical disease (genetic, infectious, chronic comorbid conditions), psychological disease, environmental exposures, dietary habits, medications and substances of abuse, and even socioeconomic factors. There is also evidence that a diagnosis of male fertility is associated with future disease risk including cancer, metabolic disease and mortality. As such, there is a growing view that the male fertility evaluation is an opportunity to improve a man's health beyond his immediate reproductive goals, and also highlights the necessity of a multidisciplinary approach
An Innovative Approach for the Enhancement of Public Real Estate Assets
No full textIn a context of dwindling resources and growing financial constraints for public administrations, available real estate assets can become an important economic resource both for debt reduction through their alienation, and for carrying out public works through rehabilitation and defunctionalisation using private capital. The latter requires the adoption of innovative policies and strategies to enhance the value of the assets, especially those that are disused or abandoned, which very often represent a critical element in the overall management of public administrations. This study proposes a strategy for the enhancement of public assets using a little-experimented contractual form of public–private partnership. This approach, through a complex exchange transaction, avoids the total disposal of the assets, thus guaranteeing the social and environmental sustainability of the intervention, and also allows for the enhancement of the property with a financially convenient solution for both partners. The balance between the benefits of the two parties is in fact the basis of the model proposed for the final solution
Microfluidic formation of crystal-like structures
No full textCrystal-like structures find application in several fields ranging from biomedical engineering to material science. For instance, droplet crystals are critical for high throughput assays and material synthesis, while particle crystals are important for particles and cell encapsulation, Drop-seq technologies, and single-cell analysis. Formation of crystal-like structures relies entirely on the possibility of manipulating with great accuracy the micrometer-size objects forming the crystal. In this context, microfluidic devices offer versatile tools for the precise manipulation of droplets and particles, thus enabling fabrication of crystal-like structures that form due to hydrodynamic interactions among droplets or particles. In this review, we aim at providing an holistic representation of crystal-like structure formation mediated by hydrodynamic interactions in microfluidic devices. We also discuss the physical origin of these hydrodynamic interactions and their relation to parameters such as device geometry, fluid properties, and flow conditions. This journal i
Analysis of the Difference Between Asking Price and Selling Price in the Housing Market
No full textIn Italy, the opacity of the real estate market, which often does not reveal the real consistency of selling prices, or, in relation to the phase of the economic cycle, the low number of transactions force appraisers to use asking prices as comparables in the market approach. The international literature recognizes the importance of analyzing the relationship between asking prices and selling prices or time on market for the interpretation of the real estate market. In this work, the analysis of the difference is aimed at interpreting its variance by identifying the variables that have greater weight. For this purpose, a multivariate analysis model is built on a sample of data over a 12 years interval recorded in the housing market of the city of Potenza, Italy
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