Search

We present experimental findings and modeling insights into the expansion of bubbles within a Newtonian fluid, observed during an advanced process integrating additive manufacturing and physical foaming techniques to fabricate complex microcellular foams with orientation-graded morphologies. A physical and sustainable blowing agent (CO2) is solubilized into a biopolymer (PLA) that is 3D-printed through a cylindrical nozzle, and, at the nozzle outlet, the blowing agent foams inside the polymeric strand due to pressure drop or/and temperature rise. The experimental results show that, by engineering the temperature gradient at high printing velocities, corresponding to values of the Graetz number (i.e., the ratio of heat diffusion time and residence time inside the printer hot-end) larger than one, the microcellular foamed strands have a microstructure characterized by anisotropic bubbles oriented along two different directions. The microbubbles at the center of the strands are stretched in the extrusion direction, whereas those in the periphery are stretched radially. A foam morphology with microbubbles having two different orientations, smoothly changing within the cross section, has never been reported before. We investigate the formation mechanism of such a morphology by simplified modeling and numerical simulations. Simulation results support the experimental findings and rationalize the effects of the Graetz number on the microcellular foamed strands and on the expansion of gas bubbles in a Newtonian fluid, suggesting that the different orientations of the bubbles are due to the combined effect of high Graetz number and the radial expansion of the strand.

Solar photovoltaics offers a promising avenue for sustainable power generation, with perovskite solar cells gaining significant interest due to their cost effectiveness and remarkable performance. Lead-based perovskites, while possessing superior electron mobility and carrier properties, raise concerns due to environmental and health risks. Substituting lead with tin holds promise. Tin halide perovskites, particularly with iodine as the halide, exhibit lower band gaps, suggesting heightened efficiency. However, managing the crystallization process, crucial for achieving films with desired morphological properties and crystal phase purity, poses a significant challenge for perovskite materials. Although solvent and additive engineering are extensively explored, their specific effects on the colloidal properties of perovskite suspensions received relatively little attention. This review aims to provide an overview of the world of colloids, shedding light on how the manipulation of colloidal properties in perovskite suspensions can exert a substantial influence on the crystallization kinetics of halide perovskite thin films.

The widespread adoption of foam additive manufacturing (FAM) in industries ranging from biomedical to aerospace hinges on the precise control of foam morphology, a capability not fully realized with current technologies. This study explores the potential of the FAM process, employing polylactic acid (PLA) and carbon dioxide (CO2) as a blowing agent, to finely tune the microstructural characteristics of foamed materials through controlled manipulation of process parameters. By systematically varying the pressure of the blowing agent, the time of absorption and desorption, extrusion temperature, speed, and nozzle diameter, we provide a detailed analysis of their individual and collective impact on foam morphology at both macroscopic and microscopic levels. Our findings reveal how specific parameter adjustments can significantly influence the density, diameter, and bubble size distribution within the foamed strands. These insights not only bridge a critical knowledge gap in FAM process optimization but also empower designers and engineers across various sectors to engineer foams with tailored properties for enhanced performance in lightweighting, insulation, and shock absorption applications. This research serves as a foundational guide for advancing the practical utility and scientific understanding of FAM technologies in producing next-generation foamed materials.

In this study energy recovery of digestate from a biogas plant was investigated via air gasification. Gasification tests were executed in a pilot scale rotary kiln plant having a nominal biomass feeding rate of about 20 kg/h. The equivalence ratio was varied from 0.22 to 0.39 with the goal to approach the autothermal condition. Tests were carried out for 5 h in steady state condition. Syngas composition, char and gas yields were measured. To improve the cold gas efficiency of the process, a mixture of digestate and almond shells (60:40 wt%) was gasified. Autothermal condition was reached with the mixture using equivalence ratio of 0.30 where the corresponding cold gas efficiency achieved the maximum value of 55%. The raw gas had a lower heating value of 4–5 MJ/Nm3. To evaluate possible improvements in the produced gas properties, in this work the effect of steam injection was also investigated.

In this work, the efficiency of the updraft gasification of different biomass was analyzed using a 20 kg/h pilot facility. Eucalyptus wood chips, torrefied Eucalyptus wood chips, and torrefied Spruce chips were investigated. Absolute air, mixes of air with steam, and mixes of pure oxygen with steam were used as gasification media. The direct comparison between the parental and torrefied biomass emphasizes the positive effect of this pretreatment on syngas properties and plant performances. Typically, the use of torrefied feedstock resulted in a reduction to about 1/5of the tar load in the syngas and in 44% increment of the thermal power of the plant when compared to the performances obtained with the parental wood. The introduction of steam as co-gasifying stream was effective to avoid hot spots inside the reactive bed and to stabilize the process. Moreover, the use of steam positively affected the molar ratio of H2/CO that reached the value of 1.17 with the H2concentration in the syngas of 39 vol %. The cold gas efficiency was 0.85 with torrefied biomass and pure oxygen with steam (0.82 when taking into account the energy for steam production), whereas the use of parental wood in similar conditions gave a value of 0.67 (net of 0.65). The treatment capacity of the plant was directly proportional to the reactivity of the feedstock as assessed by thermogravimetric analysis when the feed was reported as volumetric flow.

Highlights: [•] We study the deformation of soft systems in fluids under unbounded shear flow. [•] The study is done with a finite element method based code for viscoelastic fluids. [•] To track the interface, a finite element method is defined on it. [•] Deformed shape of drops and elastic particles are nearly ellipsoidal. [•] Results on elastic particles in viscoelastic fluids are shown for the first time. [Copyright &y& Elsevier]

Abstract: In this work we present 2D numerical simulations on the migration of a particle suspended in a viscoelastic fluid under Poiseuille flow. A Giesekus model is chosen as constitutive equation of the suspending liquid. In order to study the sole effect of the fluid viscoelasticity, both fluid and particle inertia are neglected. The governing equations are solved through the finite element method with proper stabilization techniques to get convergent solutions at relatively large flow rates. An Arbitrary Lagrangian–Eulerian (ALE) formulation is adopted to manage the particle motion. The mesh grid is moved along the flow so as to limit particle motion only in the gradient direction to substantially reduce mesh distortion and remeshing. Viscoelasticity of the suspending fluid induces particle cross-streamline migration. Both large Deborah number and shear thinning speed up the migration velocity. When the particle is small compared to the gap (small confinement), the particle migrates towards the channel centerline or the wall depending on its initial position. Above a critical confinement (large particles), the channel centerline is no longer attracting, and the particle is predicted to migrate towards the closest wall when its initial position is not on the channel centerline. As the particle approaches the wall, the translational velocity in the flow direction is found to become equal to the linear velocity corresponding to the rolling motion over the wall without slip. [ABSTRACT FROM AUTHOR]

The interest in microfluidic applications based on complex fluids is a result of the unique fluid dynamics of these systems, which enable the creation of effective devices for health care or biological and chemical analysis. In this area, processing suspensions of rigid particles in viscoelastic liquids offers a variety of possible applications where the rheology plays a key role.

Purpose - To study optical resonances in metallic nanoparticles. Design/methodology/approach - The metallic nanoparticle is modeled as a dielectric body dispersive in frequency with assigned dielectric constant. The electric field is expressed as function of the charge distribution through an integral formulation. By imposing the boundary conditions on the nanoparticle surface, the equations for the induced charge in the nanoparticle is obtained. The numerical solution of such equations allows to treat arbitrary geometries and to estimate the effects of deviations from ideality on the resonance values. Findings - Plasmon resonances in metallic nanoparticles can be safely studied with an electro-quasistatic approximation. The resonance frequencies depend greatly on the details of the geometry of the nanoparticles. Research limitations/implications - The free-space wavelength is supposed to be much greater than the largest characteristic dimension of the nanoparticles. Consequently, a electro-quasistatic model is used to evaluate the distribution of the charges induced in the metallic nanoparticle. Originality/value - Two methods are presented for the evaluation of the resonance frequencies starting from the numerical solution for a given geometry. [ABSTRACT FROM AUTHOR]

Purpose - To apply two different integral formulations of full-Maxwell's equations to the numerical study of interconnects in a low-frequency range and compare the results. Design/methodology/approach - The first approach consists of a surface formulation of the full-Maxwell's equations in terms of potentials, giving rise to a surface electric field integral equation. The equation, given in a weak form, is solved by using a finite element technique. The solenoidal and non-solenoidal components of the electric current density are separated using the null-pinv decomposition to avoid the low-frequency breakdown. The second model is an extension of partial element equivalent circuit technique to unstructured meshes allowing the use of triangular meshes. Two systems of meshes tied by duality relations are defined on multiconductor systems. The key point in the definition of the equivalent network is to associate the pair primal edge/dual face to a circuit branch. Solution of the resulting electrical network is performed by a modified nodal analysis method and regularization of the outcoming matrix is accomplished by standard techniques based on the addition of suitable resistors. Findings - Both the formulation have a regular behaviour at very low frequency. This is automatically achieved in the first approach by using the null-pinv decomposition. Research limitations/implications - Surface sources of fields. Originality/value - Two different integral formulations of full-Maxwell's equations for the numerical study of interconnects are compared in terms of low-frequency behaviour. [ABSTRACT FROM AUTHOR]

In this paper we report the results of a set of dedicated experiments carried out at JET, aimed at studying the spatial dependence of the excitation of the unstable mode following an edge localized mode (ELM). A dependence of the excitation of the unstable mode on the pre-ELM vertical position can indeed be found, although a neutral point is not present in the explored range. The CREATE_L linearized plasma response model is used to reliably estimate the growth rate and discuss a correct global characterization of ELMs from the point of view of simplified modelling for control. The results indicate that a drop of pressure energy alone is not sufficient but that an increase of magnetic energy should be included.

OBJECTIVE: The aim of this study was to investigate: (i) whether a persistent increase of cAMP interferes with the proliferation of transformed thyroid cells, and (ii) whether the degree of malignancy is correlated with the sensitivity to a transient and/or sustained increase in intracellular cAMP levels. DESIGN AND METHODS: To address these questions we used thyroid cell lines transformed with E1A oncogene from adenoviruses 5 (PC E1A cell line) or 2 (PC HE4 cell line), or infected with the polyoma murine leukemia virus (PC PyMLV cell line) carrying the middle T gene of the polyoma virus, or, finally, expressing both E1A and PyMLV. These cell lines present various degrees of malignancy: PC EIA and PC HE4 cells are not tumorigenic; PC PyMLV cells induce non-invasive tumors after a long latency period; and PC EIA+PyMLV cells are highly tumorigenic. RESULTS AND CONCLUSIONS: Thyroid cell proliferation required the transient increase of intracellular cAMP levels, while persistent elevation of cAMP blocked the proliferation of normal thyroid PC Cl 3 cells and of PC Cl 3 cells transformed by a variety of different oncogenes. In addition, sustained levels of cAMP induced apoptosis in cells carrying the adenovirus EIA oncogene, but not in cells transformed with other oncogenes or in the wild-type PC Cl 3 cells. Furthermore, middle T gene of the polyoma virus seemed to afford protection only from apoptosis induced by cAMP when middle T is present in thyroid cells along with the E1A gene.

In this paper an innovative technique is described to solve the electromagnetic problem in the presence of a cracked conductor. Both the direct problem (given the crack, compute the scattered field) and the inverse problem (given the external measurements, obtain the crack position and shape) are dealt with. The features of an integral formulation in terms of a two-component electric vector potential expanded over edge elements are fully exploited. The resulting method proves to be extremely efficient, also thanks to the binary nature of the unknown. In this paper we restrict our attention to a class of problems, namely the eddy current testing for thin cracks in non-magnetic metallic plates, but the method can be extended to more general cases.

Abstract: Most methods of measuring the interfacial tension between two immiscible polymers are based on the analysis of the shape that a drop of one polymer immersed in the other one exhibits under the action of flow or gravity. In such a situation, the small, yet nonzero mutual solubility between the two polymers acts toward mass transfer between the drop and the surrounding fluid. In this work, diffusion effects on the interfacial tension of the pair polyisobutylene/polydimethylsiloxane have been investigated by drop deformation under shear flow. When the drop was made of polyisobutylene, drop size decreased with time due to diffusion. Drop shrinkage was associated with a significant increase in interfacial tension, until an apparent plateau value was reached. The effect was attributed to a selective migration of molecular weights, which would act to enrich the drop with higher molar mass material. To support such an interpretation, drop viscosity was evaluated by drop shape analysis and it was actually found to increase with time. In some cases, the ratio between drop and continuous phase viscosity became higher than the critical value for drop breakup in shear flow. Upon inverting the phases (i.e., when the drop was made of polydimethylsiloxane), no significant transient effects were observed. In the light of these results, the problem of what are the correct values of interfacial tension and viscosity ratio for a polymer blend of a certain composition will also be discussed.

The retraction of a deformed drop back to the spherical, equilibrium shape at rest has been the subject of several studies in the literature with the aim of measuring the interfacial tension between the drop and the continuous phase. In this work, the retraction of a drop deformed under the action of a shear flow was analyzed by using the theoretical approach proposed by Rallison in the limit of small deformations. A single exponential decay was then obtained for the time evolution of the deformation parameter in the course of retraction. By fitting such expression to the experimental data the interfacial tension can be determined. Experiments of drop retraction were performed by using a parallel plate apparatus. The experimental trend of the deformation parameter during retraction was well represented by a single exponential decay and the calculated interfacial tension was in good agreement with values reported in the literature for the system investigated. A detailed comparison of the proposed analysis of drop retraction with other methods available in the literature is also presented.

Theoretical predictions for the 3D shape of a Newtonian drop immersed in a Newtonian fluid under slow flow have been available for a long time (C.E. Chaffey and H. Brenner, J. Colloid Interface Sci.24, 258 (1967); J.M. Rallison, J. Fluid Mech.98, 625 (1980)). The predictions contain four scalar coefficients, given in terms of the viscosity ratio of the component fluids. In this work, experimental values of such coefficients were measured for the case of two Newtonian fluids in simple shear flow. The experiments were carried out in a parallel plate apparatus, equipped with video-enhanced microscopy, and the measurements were performed by image analysis techniques. The results were also compared to theoretical calculations and provide the first complete assessment of shape predictions for the case of Newtonian fluids.

AbstractA high-order, multivariable, modern plasma controller has been designed using H∞optimal control techniques and tested on the Tokamak Configuration Variable (TCV) tokamak. An initial design for the control of the plasma current, position, and shape parameters is described. The design process was based on the CREATE-L linearized model of TCV, and the controller was implemented on a digital processor. The results demonstrated that the required performance was delivered and the controller response was in good agreement with predictions using the model.

Parental history of childhood physical/sexual abuse was examined among 68 parents of hospitalized middle-class adolescent alcohol/drug misusers and 68 parents of comparable nonhospitalized adolescents. Childhood physical and/or sexual abuse was reported by 54% of control and 48% of patient mothers and 46% of patient and 47% of control fathers, nonsignificant group and gender differences. Abused as compared to nonabused parents reported significantly greater alcohol dependency, more lifetime medical and childhood hyperactivity symptoms, lower levels of socialization, and greater levels of verbal ability, neuroticism, and addiction proneness.

An analysis of a staff planning group established to expedite "permanency planning" by the integration of services offered by two divisions within a public child welfare agency.

FRTL5 rat thyroid cells possess separate high affinity receptors for insulin and insulin-like growth factor I (IGF I) that undergo β-subunit phosphorylation upon interaction with the specific ligand. Phosphorylation is rapid and dose-dependent and occurs primarily on tyrosine residues. Within 2 min, both insulin and IGF I also give rise to a Mr175,000 phosphoprotein (pp175) that can be immunoprecipitated by anti-phosphotyrosine antibody (α-Tyr(P)). Phosphorylation of pp175 occurs on serine and threonine as well as tyrosine residues. When FRTL5 cells are solubilized with 1% Triton X-100, α-Tyr(P) immunoprecipitates phosphorylated insulin and IGF I receptors but little pp175 from the Triton-soluble fraction. After treatment of the Triton-insoluble portion with 1% sodium dodecyl sulfate at 100 °C, ppl75 can be identified by immunoprecipitation with α-Tyr(P). The fraction of FRTL5 cells that remains after extraction of an attached monolayer with 1% Triton for 5 min at 22 °C contains most of the cytoskeleton and also nuclei. Extraction of this 32P-labeied cytoskeleton preparation with sodium dodecyl sulfate followed by α-Tyr(P) immunoprecipitation results in almost complete recovery of the pp175 content of the cells. When a nuclear fraction was prepared from FRTL5 cells by differential centrifugation, pp175 was not found in the nuclear pellet from labeled cells, but >80% of pp175 was recovered in the supernatant. We conclude that pp175 is a common substrate for insulin and IGF I receptor kinases which, in FRTL5 cells, is associated with the cytoskeleton. It is suggested that phosphorylation of proteins associated with cytoskeletal elements could be involved in insulin and IGF I action in cells.

Thyroid stimulating hormone (TSH) and insulin-like growth factors type 1 (IGF-I) regulate the proliferation and differentiation of cultured thyroid cells but not of cultured liver cells. We have examined the influence of TSH and IGF-I on the metabolic functions and proliferation of somatic hybrids obtained by fusing rat thyroid cells (FRTL5) with rat liver cells (BRL). While IGF-I is able to stimulate the proliferation of the hybrid cells (TxL) TSH fails to induce their growth. However, the hybrid TxL cells have surface TSH receptors with normal ligand characteristics. The addition of TSH to TxL cells led to typical enhancement of cAMP production and depolymerization of actin filaments. Yet, TSH failed to stimulate iodine uptake in the hybrid cells. Interestingly, iodine inhibited TxL proliferation induced by IGF-I but not by serum. It is concluded that the hybrid TxL cells inherited from the parental thyroid cells several important differentiated traits including mitogenic pathways induced and used by IGF-I, functional TSH receptors, and sensitivity to the inhibitory action of iodine.

Abstract. Thyroid cell proliferation has been studied using an in vitro system of rat thyroid follicular cell strain (FRTL-5). While growing in continuous culture, this strain is still differentiated and non-tumourigenic. Both advantages and limitations in the use of such system for studies of thyroid cell growth should be considered. Some obvious limitations should be considered, such as the species (rat) from which FRTL-5 cells were originated, their long-term growth outside the animals, the presence of a chronic TSH stimulation. On the other hand, several advantages as the growth in hormonally and chemically defined media, their dependence upon TSH in the medium, their genetic homogeneity and their widespread use in many laboratories render the FRTL-5 strain a useful experimental tool. Studies on cell proliferation and mechanism of action of hormones, growth factors and human autoimmune IgG have been and are being performed, with the assumption that FRTL-5 cells are the in vitro equivalent of thyroid follicular cells.

Expression of the soluble lectin L-14 is low in normal and very high in transformed thyroid cells. We show that L-14 gene expression is transiently induced upon thyrotropin stimulation of normal quiescent FRTL-5 rat thyroid cells. Permanent activation of L-14 gene expression is obtained in the same cells infected with a wild-type and a temperature sensitive mutant of Kirsten murine sarcoma virus, both at the permissive and non permissive temperature for transformation. We also find that L-14 mRNA is undetectable in rat brain but is abundant in rat oligodendrocytes precursors transformed by polyoma middle T oncogene. Retinoic acid treatment of these transformed cells leads to acquisition of a differentiated phenotype accompanied by a 30-fold decrease of L-14 mRNA levels. Removal of retinoic acid restores both the transformed undifferentiated phenotype and high L-14 expression. Taken together these results indicate that growth stimulation and induction of cell differentiation are accompanied by strong modulation of L-14 gene expression.

Le rôle de l'estime de soi dans les choix compétitifs - Un programme transnational de recherche sur les déterminants des processus de décision s'est concentré dans une première phase sur la relation entre l'estime de soi et le comportement compétitif dans un jeu de type <>. Des étudiants américains, chez lesquels une grande estime de soi avait étaé induite, firent davantage de choix compétitifs que les sujets chez lesquels on avait induit une faible estime de soi. Une des deux expériences avec des étudiants français a reproduit les memes résultats, alors que des expériences avec des sujets italiens ont produit des résultats inverses. Différentes interprétations théoriques des résultats sont proposées et critiquées.

Une série d'études inter-culturelles a été consacrée à l'effet de l'équité sur le comportement de choix, dans un jeu de type Dilemme du Prisonnier. Les résultats antérieurement collectés montrent que les sujets américains choisissent de maximiser leur gain en fonction de leur niveau d'estime de soi: une distribution des recompenses en fonction du mérite semble correspondre à un besoin d'équité; mais les sujets italiens qui ont une faible estime d'eux-memes tendent à maximiser plus fréquemment leur gain: ils ont tendance à etre "ego-défensifs". Dans les études qui sont présentées ici, une récompense initiale est donnée à l'un des deux partenaires, sur la base d'un "test" d'aptitude à la prédiction (Distribution Juste), ou bien la récompense est donnée arbitrairement, sans tenir compte du test (Distribution Injuste). Les sujets doivent ensuite faire une série de cinquante choix. Les choix des sujets américains reflètent un besoin d'équité dans la condition Distribution Injuste, le sujet qui a reçu une récompense choisit moins souvent de maximiser ses gains que le sujet qui n'a pas reçu de récompense; dans la condition Distribution Juste, les sujets maintiennent l'inégalité créée par la récompense initiale. Sur l'ensemble des trois échantillons italiens qui ont été étudiés séparément, on observe une tendance à minimiser l'injustice dans la condition Distribution Injuste; mais dans la condition Distribution Juste, on observe un effet de défense du moi. Diflérentes interprétations théoriques des résultats sont discutées.

In article number 20200034, Pietro Ferraro and co‐workers emphasize that early detection in cancer diseases is a key issue. The current state of the art of technology could allow a great opportunity for this purpose, to develop systems for detecting circulating cancer cells (CTC) in the blood. The challenge is to recognize and classify cancer cells and detect them non‐invasively through a lab‐on‐chip device as they flow. Single‐cell holographic phase contrast tomography offers the possibility in the real world to detect CTC in a label‐free mode by means of morphological analyzes when combined with artificial intelligence (AI). The cover summarizes and depicts the main concepts and the technological ingredients necessary to achieve such an ambitious goal, namely the recognition and sorting of cells, 3D‐imaging by microscope and complete morphological analysis of 3D‐phase‐contrast tomograms by AI tools.

Circulating tumor cells (CTCs) are rare tumor cells released from primary, metastatic, or recurrent tumors in the peripheral blood of cancer patients. CTCs isolation from peripheral blood and their molecular characterization represent a new marker in cancer screening, a diagnostic tool called “liquid biopsy” (LB). Compared to traditional tissue biopsy that is invasive and does not reveal tumor heterogeneity, LB is noninvasive and reflects in “real‐time” tumor dynamism and drug sensitivity. In the frame of LB, a new paradigm based on single‐cell and label‐free analysis based on morphological analysis is emerging. Here, we review the latest research developments in this emerging vision of LB. In particular, we survey and discuss recent improvements in microfluidics, imaging label‐free diagnosis and cell classification by artificial intelligence and how to combine them to realize an intelligent platform based on lab‐on‐chip technology. This prospect appears to open up promising and intriguing new scenarios for cancer management through single‐cell analysis that will revolutionize the future of early cancer diagnosis and therapeutic choice with disruptive impact on the society. The most promising approach to liquid biopsy has its roots in the smart integration between label‐free quantitative phase microscopy, accurate manipulation of microfluidic streams, and artificial intelligence. Lab‐on‐a‐chip devices with embedded imaging functions can now rely on robust deep learning architectures to generate accurate classification results from single‐cell analysis of blood flows. Flow engineering allows sorting and controlling the rotation of blood components, thus permitting added‐value high‐throughput tomographic inspection of circulating tumor cells.