Macroscopic Components Research Articles

Mechanical and tribological characterization of wire and multi-wire arc additive manufactured thin-walled TC11 component

Multi-wire arc additive manufacturing (MWAAM) has higher deposition efficiency and material utilization than traditional wire arc additive manufacturing (WAAM), but its droplet transition mode is more complex and sensitive, which affects not only the forming quality but also the metallurgical quality. Therefore, it is necessary and urgent to explore and optimize its process. In this study, the macroscopic component formation mechanism and microstructure influence mechanism of WAAM and MWAAM processes were studied, and TC11 titanium alloy was taken as the target alloy considering its huge application prospect in the aerospace field. In addition, the effects of different processes on the morphology, microstructure, phase composition, mechanical properties and wear properties of the deposited samples were systematically studied through the deposition experiments controlled by different heat source velocities. The results show that the thin-walled TC11 components deposited by MWAAM exhibit good mechanical properties and excellent wear resistance. This study is of great significance for the intelligent and industrialized development of MWWAM technology.

Coupling theoretical analysis and FE framework for revealing the size effect on the deformation characteristics of 304 stainless steel microtubes manufactured via free-bending forming technology

The current study on free bending focuses on traditional macroscopic tubes and profile components. Nevertheless, as the geometric size of the tube decreases, the resulting size effect affects the free bending deformation behavior of the microtube in the less constrained state. In this investigation, a constitutive model of microtubes considering the surface layer model was established. The corresponding model parameters were determined by fitting the flow curves of surface single crystals and internal polycrystals. According to the principle of free bending, the springback internal bending moment of the microtube was derived to explain the phenomenon whereby the bending radius of the microtube decreases with decreasing size factor. With decreasing size factor, the influence of the surface layer grains on the bending behavior of the microtube becomes more intense. Furthermore, by comparing the results of the microscale free bending experiment and simulation, it can be concluded that the material properties of microtubes in the finite element (FE) simulation should be defined based on the surface layer and inner layer. With decreasing microtubule size factor, the bending radius of the tube decreases, and the wall thickness changes more significantly. The cross-sectional distortion of the microtubes decreases with increasing grain size and wall thickness. This study explored the feasibility of the free bending process to achieve bending of microtubes and revealed that the size effect on the deformation behavior of microtubes should be considered in the microscale free bending process.

Helical close-packing of anisotropic tubes

Helically close-packed states of filaments are common in natural and engineered material systems, ranging from nanoscopic biomolecules to macroscopic structural components. While the simplest models of helical close-packing, described by the ideal rope model, neglect anisotropy perpendicular to the backbone, physical filaments are often quite far from circular in their cross-section. Here, we consider an anisotropic generalization of the ideal rope model and show that cross-section anisotropy has a strongly non-linear impact on the helical close-packing configurations of helical filaments. We show that the topology and composition of the close-packing landscape depends on the cross-sectional aspect ratio and is characterized by several distinct states of self-contact. We characterize the local density of these distinct states based on the notion of confinement within a ‘virtual’ cylindrical capillary, and show that states of optimal density vary strongly with the degree of anisotropy. While isotropic filaments are densest in a straight configuration, any measure of anisotropy leads to helicity of the maximal density state. We show the maximally dense states exhibit a sequence of transitions in helical geometry and cross-sectional tilt with increasing anisotropy, from spiral tape to spiral screw packings. Furthermore, we show that maximal capillary density saturates in a lower bound for volume fraction of π/4 in the large-anisotropy, spiral-screw limit. While cross-sectional anisotropy is well-known to impact the mechanical properties of filaments, our study shows its strong effects to shape the configuration space and packing efficiency of this elementary material motif.

Microfluidic chips for microbially induced calcium carbonate precipitation: Advantages, challenges, and insights

Microbially induced calcium carbonate precipitation (MICP) has garnered significant attention as a biomineralization process with diverse applications spanning from construction to environmental remediation. To propel MICP research and deepen our comprehension of MICP mechanisms, microfluidic chips have emerged as potent tools offering precise control over environmental parameters and real-time observations. Herein, we explore the benefits and challenges associated with employing microfluidic chips as a platform for investigating MICP. The advantages of microfluidic chips lie in their capacity to create controlled microenvironments conducive to emulating specific conditions crucial for MICP. The high-throughput nature of these devices accelerates experimentation by facilitating simultaneous testing of various microbial strains and nutrient compositions. Throughout the MICP process, observations were made on the behaviors of both bacterial cells and CaCO3 cementation. The inherent reduction in reagent consumption offered by microfluidics is both cost-effective and environmentally friendly. However, scaling up from microscale findings to practical applications necessitates careful consideration. Fully replicating the three-dimensional complexity and heterogeneous structures of the soil matrix, which influence microbial behavior, mineral distribution, and overall precipitation dynamics, using microfluidic chips remains challenging. Additionally, certain environmental complexities, including macroscopic soil components such as organic matter and various particle types, which significantly affect microbial activities and mineral precipitation patterns, may be difficult to replicate in microfluidic setups. However, microfluidic chips stand as invaluable tools for advancing MICP research. By addressing the advantages and disadvantages outlined here, researchers can harness the capabilities of microfluidic systems to unravel the intricacies of MICP, ultimately bridging the gap between fundamental understanding and real-world applications.

Understanding and Controlling Electrostatic Discharge in Triboelectric Nanogenerators.

Triboelectric nanogenerators (TENGs) have been widely used to harness various forms of mechanical energy for conversion to electrical energy. However, the contentious challenge in characterising TENGs is the lack of standard protocols for assessing mechanical-to-electrical energy conversion processes. Herein, macroscopic signal analysis is used to identify three key charging events within triboelectric signals: charge induction (CI), contact electrification (CE), and electrostatic discharge (ESD). By considering two phases of motion during contact-separation (approach and departure of the contact materials), CI arising from the motion of bound surface charge (varying electric field) between opposing contact materials is shown to dominate the measured displacement current signal, rather than the process of CE itself. Furthermore, the conventional signal (i. e., voltage, current, charge) interpretation of CE and CI during approach and departure phases is re-assessed, to indicate that the sudden spike of current often observed immediately prior to contact (or after separation) arises from polarity inverting electrostatic discharge (ESD). This aspect of the measured triboelectric effect, which is often ignored, is crucial for the design of TENGs and hence, techniques to enhance the understanding and control over the stochastic occurrence of ESDs is explored. The methods proposed for the deconvolution of the macroscopic signal components of TENGs, and mitigation of ESD occurrences, will allow for precise quantification of the associated charging events. The applications of this study will template the design and development of future super-TENGs with optimised energy conversion capabilities.

Salvage high-dose rate brachytherapy for local recurrence of prostate cancer after radical prostatectomy

Background. The current need for optimization of salvage treatment methods is dictated by the growing expansion of indications for radical prostatectomy in many centers in the developed countries of the world.Aim. To evaluate the effectiveness, toxicity, and technical characteristics of high-dose rate brachytherapy in treatment of local prostate cancer (PCa) recurrences after radical prostatectomy.Materials and methods. Between January 2015 and December 2020, salvage high-dose rate brachytherapy was performed in 17 patients at the Russian Scientific Center of Roentgenology and Radiology for local recurrence of PCa after radical prostatectomy. All patients underwent multiparametric magnetic resonance imaging of the pelvis at the stage of primary diagnosis in order to determine macroscopic tissue component in the prostate bed area. To rule out regional and distant metastases, all patients underwent positron emission tomography with 18F- or 68Ga-labeled prostate-specific membrane antigen. All patients included in the study underwent perineal biopsy of the prostate bed and seminal vesicles.Results. Median follow-up in the treatment group was 35.7 (24–54) months. Overall survival was 100 %. Prostatespecific antigen-specific survival was 88.2 %. There were no local recurrences of PCa in the treatment group. In patients with local PCa recurrence, significant predictors of treatment failure were the presence of clinically extremely high risk of progression at initial diagnosis (p = 0.003), development of biochemical relapse up to 24 months after main treatment (p = 0.001), and increased blood level of prostate-specific antigen above 10 ng/mL during registration of biochemical relapse (p = 0.002).Conclusion. High-dose rate brachytherapy is a safe and effective salvage treatment for local recurrence of PCa after radical prostatectomy. In addition to the brachytherapy technique, the diagnostic stage is also of great importance providing visualization of the exact location of tumor recurrence.

Symmetry and reactivity of π-systems in electric and magnetic fields: a perspective from conceptual DFT.

The extension of conceptual density-functional theory (conceptual DFT) to include external electromagnetic fields in chemical systems is utilised to investigate the effects of strong magnetic fields on the electronic charge distribution and its consequences on the reactivity of π-systems. Formaldehyde, H2CO, is considered as a prototypical example and current-density-functional theory (current-DFT) calculations are used to evaluate the electric dipole moment together with two principal local conceptual DFT descriptors, the electron density and the Fukui functions, which provide insight into how H2CO behaves chemically in a magnetic field. In particular, the symmetry properties of these quantities are analysed on the basis of group, representation, and corepresentation theories using a recently developed automatic program for symbolic symmetry analysis, QSYM2. This allows us to leverage the simple symmetry constraints on the macroscopic electric dipole moment components to make profound predictions on the more nuanced symmetry transformation properties of the microscopic frontier molecular orbitals (MOs), electron densities, and Fukui functions. This is especially useful for complex-valued MOs in magnetic fields whose detailed symmetry analyses lead us to define the new concepts of modular and phasal symmetry breaking. Through these concepts, the deep connection between the vanishing constraints on the electric dipole moment components and the symmetry of electron densities and Fukui functions can be formalised, and the inability of the magnetic field in all three principal orientations considered to induce asymmetry with respect to the molecular plane of H2CO can be understood from a molecular perspective. Furthermore, the detailed forms of the Fukui functions reveal a remarkable reversal in the direction of the dipole moment along the CO bond in the presence of a parallel or perpendicular magnetic field, the origin of which can be attributed to the mixing between the frontier MOs due to their subduced symmetries in magnetic fields. The findings in this work are also discussed in the wider context of a long-standing debate on the possibility to create enantioselectivity by external fields.

Brushed Nano‐Stirbars for Measuring Viscosity in Microscopic Systems

AbstractConventional methods for measuring viscosity rely on macroscopic device components, which are difficult to miniaturize. The magnetic nano‐stirbars are small enough to enter tiny spaces and can spin without precise installation, making them an ideal candidate for exploring new methods. It is shown that a dense layer of Au nanowires can be grown on the silica surface of the nano‐stirbars, as a means to modulate the viscous resistance during their spinning and to make them visible under an optical microscope. The uniform growth of Au nanowires and the slight fluctuation of the spinning rates are investigated. It is shown that the nano‐stirbars with the hairy layer of Au nanowires can be used to measure the viscosity in microscopic liquid systems, such as microfluidic chambers and capillary tubes, involving cell media and blood samples. It is believed that the success with the proof‐of‐concept tests will open a window for further miniaturization of the nano‐stirbars for measuring in ultrasmall systems.

Catastrophic magnetic flux avalanches in NbTiN superconducting resonators

Macroscopic superconducting components are an important building block of various quantum circuits. Since several of the envisioned applications require exposure to magnetic fields, it is of utmost importance to explore the impact of magnetic fields on their performance. Here we explore the complex pattern of magnetic field penetration and identify its impact on the resonance frequency of NbTiN superconducting resonators by combining magneto-optical imaging and high-frequency measurements. At temperatures below approximately half of the superconducting critical temperature, the development of magnetic flux avalanches manifests itself as a noisy response in the field-dependent resonance frequency. Magneto-optical imaging reveals different regimes and distinguishes the impact of avalanches in the ground plane and resonator. Our findings demonstrate that superconducting resonators represent a valuable tool to investigate magnetic flux dynamics. Moreover, the current blooming of niobium-based superconducting radio-frequency devices makes this report timely by unveiling the severe implications of magnetic flux dynamics.

Bright and dark Talbot pulse trains on a chip

Temporal Talbot effect, the intriguing phenomenon of the self-imaging of optical pulse trains, is extensively investigated using macroscopic components. However, the ability to manipulate pulse trains, either bright or dark, through the Talbot effect on integrated photonic chips to replace bulky instruments has rarely been reported. Here, we design and experimentally demonstrate a proof-of-principle integrated silicon nitride device capable of imprinting the Talbot phase relation onto in-phase optical combs and generating the two-fold self-images at the output. We show that the GHz-repetition-rate bright and dark pulse trains can be doubled without affecting their spectra as a key feature of the temporal Talbot effect. The designed chip can be electrically tuned to switch between pass-through and repetition-rate-multiplication outputs and is compatible with other related frequencies. The results of this work lay the foundations for the large-scale system-on-chip photonic integration of Talbot-based pulse multipliers, enabling the on-chip flexible up-scaling of pulse trains’ repetition rate without altering their amplitude spectra.

Fission fragment mass distribution of 187Ir

The fission fragment mass and total kinetic energy (TKE) distributions were studied for 187Ir populated using 12C + 175Lu reaction at excitation energies 24.8, 23.3, 20.8, and 16.7 MeV above the saddle point. Fission fragments (FF) were detected using position sensitive MWPC’s kept at a folding angle. The mass of the fragment was calculated using Time-of-Flight (TOF) difference method. The multi Gaussian fit to the extracted mass distributions shows the presence of narrower microscopic components corresponding to Z = 38 and 45 in addition to the liquid drop component at lower excitation energies. The GEF model predicts significant asymmetric components at all the measured energies. The TKE distribution investigations suggest the dominance of macroscopic liquid drop components at all energies.

Algal Nanoparticles and Their Antibacterial Activity: Current Research Status and Future Prospectives

Green nanotechnology is a promising technology that has a wide range of applications in pharmaceuticals today because they offer a higher surface-area-to-volume ratio. Algal-based nanoparticles (NPs) are the subject of intense research interest today for their potential to treat and prevent infections caused by infectious microorganisms that are antibiotic resistant. Algae contain a variety of therapeutically potential bioactive ingredients, including chlorophyll, phycobilin, phenolics, flavonoids, glucosides, tannins, and saponins. As a result, NPs made from algae could be used as therapeutic antimicrobials. Due to their higher surface-area-to-volume ratios compared to their macroscopic components, metallic nanoparticles are more reactive and have toxic effects on their therapy. For pharmaceutical and biomedical applications, green synthesis restricts the use of physical and chemical methods of metallic nanoparticle synthesis, and it can be carried out in an environmentally friendly and relatively low-cost manner. The majority of macroalgae and some microalgae have latent antimicrobial activity and are used in the synthesis of metallic nanoparticles. A potential application in the field of nanomedicine and the establishment of a potential pharmacophore against microorganisms may result from the synthesis of algal-based NPs. Only a few studies have been done on the potential antimicrobial, antifungal, and antibacterial activity of algae-based NPs. As a result, the study will concentrate on the environmentally friendly synthesis of various NPs and their therapeutic potential, with a focus on their antibacterial activity. Thus, the aim of this study is to review all the literature available on the synthesis and characterization of the algal nanoparticles and their potential application as an antibacterial agent.

ECOfast – An integrative ecological evaluation index for an ecosystem-based assessment of shallow rocky reefs

The degradation of marine ecosystems is a growing concern worldwide, emphasizing the need for efficient tools to assess their ecological status. Herein, a novel ecosystem-based ecological evaluation index of shallow rocky reefs is introduced and tested in the Aegean and Ionian Seas (NE Mediterranean). The index focuses on a specific set of pre-selected species, including habitat-forming, key, commercially important, and non-indigenous species, across a wide range of trophic levels (1.00–4.53). Data acquisition is conducted through rapid non-destructive SCUBA diving surveys to assess all macroscopic food web components (macroalgae, invertebrates, and fish). Two versions of the index, ECOfast and ECOfast-NIS, were developed, each applying a different approach to account for the impact of non-indigenous species. In our case study, the correlations between the two versions of the index and sea surface temperature, protection status, occurrence of carnivorous fish, and non-indigenous herbivores were assessed through generalized additive models (GAMs). The assessment assigned 93% (ECOfast) or 96% (ECOfast-NIS) of the sites to a moderate to bad ecological status, indicating an alarming situation in the shallow rocky reefs of the NE Mediterranean. Sites evaluated as poor or bad were characterized by extensive coverage of ephemeral macroalgae, absence or minimal presence of large indigenous carnivorous fish, and complete absence of one to three out of five invertebrate functional trophic groups. The community composition of macroalgae, herbivorous species, and carnivorous fishes differed between the 5 m and 15 m depth zones. Surface temperature and carnivorous fish occurrence were the most important tested predictors of the ecological status of shallow rocky reefs. The best GAMs showed that the ECOfast score declined with sea surface temperature and increased with the occurrence of carnivorous fish; ECOfast-NIS declined with sea surface temperature and the occurrence of non-indigenous fish and increased with the occurrence of carnivorous fish. The non-destructive and integrative nature of this approach, its speed of data acquisition and analysis, and its capacity to account for highly mobile predatory fish and non-indigenous species render the ECOfast index a novel, robust, and valuable tool for assessing the ecological status of shallow rocky reefs.

Fibrous hamartoma of infancy: imaging findings.

Fibrous hamartoma of infancy is a benign tumor that typically arises within the first 2years of life in the subcutaneous and lower dermal layers. Diagnosis can be challenging as it is a rare tumor, and the imaging appearance is not well known. To describe the imaging features in 4 cases of fibrous hamartoma of infancy focusing on ultrasound (US) and magnetic resonance (MR) findings. In this retrospective IRB-approved study, informed consent was waived. We searched patient charts for histopathology-confirmed fibrous hamartoma of infancy diagnosis between November 2013 and November 2022. We found four cases, three boys and one girl, and the mean age was 1.4years (5months-3years). The lesions were located in the axilla, posterior elbow, posterior neck, and lower back. All four patients underwent ultrasound evaluation of the lesion, and two patients also underwent MRI evaluation. The imaging findings were reviewed by consensus by two pediatric radiologists. US imaging revealed subcutaneous lesions with variably defined hyperechoic regions and intervening hypoechoic bands resulting in a linear "serpentine" pattern or a "multiple semicircle" pattern. MR imaging evidenced heterogeneous soft tissue masses, localized in the subcutaneous fat, and showed hyperintense fat interspersed with hypointense septations on both T1- and T2-weighted images. Fibrous hamartoma of infancy has a suggestive appearance on US with heterogeneous, echogenic subcutaneous lesions with intervening hypoechoic portions, in parallel or circumferential arrangement that can be seen as a serpentine or semicircular pattern. On MRI, interspersed macroscopic fatty components show high signal intensity on T1- and T2-weighted images and reduced signal on fat-suppressed inversion recovery images, with irregular peripheral enhancement.

Ventriculo-arterial (un)coupling in septic shock: Impact of current and upcoming hemodynamic drugs.

Sepsis is an archetype of distributive shock and combines different levels of alterations in preload, afterload, and often cardiac contractility. The use of hemodynamic drugs has evolved over the past few years, along with the invasive and non-invasive tools used to measure these components in real time. However, none of them is impeccable, which is why the mortality of septic shock remains too high. The concept of ventriculo-arterial coupling (VAC) allows for the integration of these three fundamental macroscopic hemodynamic components. In this mini review, we discuss the knowledge, tools, and limitations of VAC measurement, along with the evidence supporting ventriculo-arterial uncoupling in septic shock. Finally, the impact of recommended hemodynamic drugs and molecules on VAC is detailed.

Novel bottom-up methodology to build the lifecycle inventory of unit operations: the impact of macroscopic components

Novel bottom-up methodology to build the lifecycle inventory of unit operations: the impact of macroscopic components

A large-deviations principle for all the components in a sparse inhomogeneous random graph

We study an inhomogeneous sparse random graph, {mathcal G }_N, on [N]={1,dots ,N} as introduced in a seminal paper by Bollobás et al. (Random Struct Algorithms 31(1):3–122, 2007): vertices have a type (here in a compact metric space {mathcal S }), and edges between different vertices occur randomly and independently over all vertex pairs, with a probability depending on the two vertex types. In the limit Nrightarrow infty , we consider the sparse regime, where the average degree is O(1). We prove a large-deviations principle with explicit rate function for the statistics of the collection of all the connected components, registered according to their vertex type sets, and distinguished according to being microscopic (of finite size) or macroscopic (of size asymp N). In doing so, we derive explicit logarithmic asymptotics for the probability that {mathcal G }_N is connected. We present a full analysis of the rate function including its minimizers. From this analysis we deduce a number of limit laws, conditional and unconditional, which provide comprehensive information about all the microscopic and macroscopic components of {mathcal G }_N. In particular, we recover the criterion for the existence of the phase transition given in Bollobás et al. (2007).

The mean-field limit for particle systems with uniform full-rank constraints

We consider a particle system with uniform coupling between a macroscopic component and individual particles. The constraint for each particle is of full rank, which implies that each movement of the macroscopic component leads to a movement of all particles and vice versa. Skeletal muscle tissues share a similar property which motivates this work.We prove convergence of the mean-field limit, well-posedness and a stability estimate for the mean-field PDE. This work generalises our previous results from [25] to the case of nonlinear constraints.

Упрочнение поликристаллического льда наночастицами диоксида кремния

Ice as a construction material has a number of advantages in Arctics. It is local renewable ecologically safe resource, and it does not require supplying from mainland. However, mechanical characteristics of natural ice is rather low. Potential of known techniques of ice strengthening employing reinforcement by microfibers or macroscopic components is limited. The paper describes strengthening of ice matrix using nanodisperce silica particles. Sixfold reduction of grain size induced by adding 10% wt of SiO2 nanoparticles results in 2.5 times increase in strength limit in uniaxial compression test and more than an order of magnitude increase in fracture energy.

Effects of kneading and impact action on the movement of aggregates in asphalt mixtures during compaction

Current studies on the movement of asphalt mixture components and the formation of internal structures during compaction are lacking. Therefore, this article focuses on the effect of compaction and compaction methods on the movement and contact of mixture components. First, models of asphalt mixtures were established based on X-ray computed tomography (X-CT) and the discrete element method (DEM). Subsequently, compaction processes of the Marshall and Superpave gyratory compactor (SGC) method were simulated, and the model was verified using monitoring results of the smart rock. Finally, the macroscopic air voids, component contacts, and coarse aggregate trajectories were recorded and analyzed. The results showed that, in the early compaction stages, the compactness of the Marshall specimen increased rapidly, which also led to more resistance. The number of contact points and the contact force inside specimens gradually increased with compaction; however, the rate of this increase was different. The trajectories of coarse aggregates were affected by their location and compaction methods, especially the distance to the impacted side and to the center of the cross-section. An edge effect, namely lower compactness at the edges may also be caused by this difference. The movement of aggregates inside the Marshall specimen mainly occurred in the direction of impact. The kneading effect of the SGC method made aggregate particles move and rotate periodically, and compaction efficiency in the later stages was higher.