Wood warping is a phenomenon known as a deformation in wood that occurs when changes in moisture content cause an unevenly volumetric change due to fiber orientation. Here we present an investigation of wood warped objects that were fabricated by 3D printing. Similar to natural wood warping, water evaporation causes volume decrease of the printed object, but in contrast, the printing pathway pattern and flow rate dictate the direction of the alignment and its intensity, all of which can be predesigned and affect the resulting structure after drying. The fabrication of the objects was performed by an extrusion-based 3D printing technique that enables the deposition of water-based inks into 3D objects. The printing ink was composed of 100% wood-based materials, wood flour, and plant-extracted natural binders cellulose nanocrystals, and xyloglucan, without the need for any additional synthetic resins. Two archetypal structures were printed: cylindrical structure and helices. In the former, we identified a new length scale that gauges the effect of gravity on the shape. In the latter, the structure exhibited a shape transition analogous to the opening of a seedpod, quantitatively reproducing theoretical predictions. Together, by carefully tuning the flow rate and printing pathway, the morphology of the fully dried wooden objects can be controlled. Hence, it is possible to design the printing of wet objects that will form different final 3D structures.
2022. “אחרית דבר [Afterword].” In אדה: כרוניקה משפחתית [Ada or Ardor: A Family Chronicle], by Vladimir Nabokov; trans. Daphna Rosenbluth, Pp. 547-555. Jerusalem: Carmel.
This paper studies whether crony governance affects the logic behind governments’ targeting of violence, and how the deployment of violence allows politically connected firms to benefit from crony governance. We address these issues in the context of the Argentine military junta that took power on March 24, 1976. Specifically, we examine the logic driving the choice of firm level union representatives who were subjected to violence following the coup. Using an original dataset assembled and digitized by us, we find that political, business and social connections to the regime are associated with an increase of 2 to 3 times in the number of firm level union representatives arrested and/or disappeared. This is the case even after controlling for a battery of firms’ characteristics that capture alternative explanations for the targeting of violence. The effect is particularly pronounced in privately owned (as opposed to state-owned) firms, suggesting that the correlation is driven by cronyism for financial gain rather than ideology or information transmission. We also show that connected firms benefited from violence against union representatives by subsequently having less strikes and a higher market valuation. Our findings highlight the pervasiveness of ties to the government, even in cases where one of the main stated goals of the regime is to curb cronyism.
Soft robotics is a growing field of research, focusing on constructing motor-less robots from highly compliant materials, some are similar to those found in living organisms. Soft robotics has a high potential for applications in various fields such as soft grippers, actuators, and biomedical devices. 3D printing of soft robotics presents a novel and promising approach to form objects with complex structures, directly from a digital design. Here, recent developments in the field of materials for 3D printing of soft robotics are summarized, including high-performance flexible and stretchable materials, hydrogels, self-healing materials, and shape memory polymers, as well as fabrication of all-printed robots (multi-material printing, embedded electronics, untethered and autonomous robotics). The current challenges in the fabrication of 3D printed soft robotics, including the materials available and printing abilities, are presented and the recent activities addressing these challenges are also surveyed.
New ink compositions for direct ink writing (DIW) printing of hydrogels, combining superior rheological properties of cellulose nanocrystals (CNCs) and a water-compatible photoinitiator, are presented. Rapid fixation was achieved by photopolymerization induced immediately after the printing of each layer by 365 nm light for 5 s, which overcame the common height limitation in DIW printing of hydrogels, and enabled the fabrication of objects with a high aspect ratio. CNCs imparted a unique rheological behavior, which was expressed by orders of magnitude difference in viscosity between low and high shear rates and in rapid high shear recovery, without compromising ink printability. Compared to the literature, the presented printing compositions enable the use of low photoinitiator concentrations at a very short build time, 6.25 s/mm, and are also curable by 405 nm light, which is favorable for maintaining viability in bioinks.
Hydrogel-polymer hybrids have been widely used for various applications such as biomedical devices and flexible electronics. However, the current technologies constrain the geometries of hydrogel-polymer hybrid to laminates consisting of hydrogel with silicone rubbers. This greatly limits functionality and performance of hydrogel-polymer–based devices and machines. Here, we report a simple yet versatile multimaterial 3D printing approach to fabricate complex hybrid 3D structures consisting of highly stretchable and high–water content acrylamide-PEGDA (AP) hydrogels covalently bonded with diverse UV curable polymers. The hybrid structures are printed on a self-built DLP-based multimaterial 3D printer. We realize covalent bonding between AP hydrogel and other polymers through incomplete polymerization of AP hydrogel initiated by the water-soluble photoinitiator TPO nanoparticles. We demonstrate a few applications taking advantage of this approach. The proposed approach paves a new way to realize multifunctional soft devices and machines by bonding hydrogel with other polymers in 3D forms.
Self-healing hydrogels may mimic the behavior of living tissues, which can autonomously repair minor damages, and therefore have a high potential for application in biomedicine. So far, such hydrogels have been processed only via extrusion-based additive manufacturing technology, limited in freedom of design and resolution. Herein, we present 3D-printed hydrogel with self-healing ability, fabricated using only commercially available materials and a commercial Digital Light Processing printer. These hydrogels are based on a semi-interpenetrated polymeric network, enabling self-repair of the printed objects. The autonomous restoration occurs rapidly, at room temperature, and without any external trigger. After rejoining, the samples can withstand deformation and recovered 72% of their initial strength after 12 hours. The proposed approach enables 3D printing of self-healing hydrogels objects with complex architecture, paving the way for future applications in diverse fields, ranging from soft robotics to energy storage.
Aerogels, the lightest solid material known, are low-density nanoporous solids that have found a wide range of applications such as thermal insulation, scaffolds for tissue engineering, catalysts supports, and micrometeorite collectors. Many types of materials have been used for their preparation, and ceramic/oxide aerogels are by far the most studied and applied family. Here we propose a new comprehensive solution to prepare these materials photochemically and fabricating them in highly complex shapes at all scales, from the macro scale down to the microns scale. The solution to these two challenges is linked, shown in the three photochemical approaches developed, allow unprecedented complexity in shape. The processes are mold irradiation, digital light processing (DLP) 3D printing, and a two-photon printing (TPP) process. The obtained 3D complex silicate objects display low density, high porosity, large surface area, and low thermal conductivity. The fabrication process also enables easy functionalization of the aerogels as inducing in them luminescence or making the printed object superhydrophobic by post printing process. The photochemical approach is ideal for the preparation of components of miniature devices, where low weight is a governing requirement.
4D printing is based on 3D printing of objects that can change their shape upon a proper triggering. Here, a novel approach is reported for fabricating programmable 3D printed objects composed of shape-memory polymers (SMPs) that are activated by light. The light activation of the movement and shape morphing are based on combining gold nanoparticles (AuNPs) as photothermal converters with acrylate-based printing compositions that form an SMP with tunable transition temperatures. The shape change of the printed objects is triggered by remote irradiation with a low-cost LED light at a wavelength specific to the surface plasmon resonance of the embedded AuNPs. The light is converted to heat which enables the shape transition when the temperature reaches the Tg of the polymer. Excellent SMP properties are achieved with shape fixity and recovery ratios over 95%. This material composition and triggering approach enable fabricating programmable light-activated 3D printed structures with a dual transition while tuning the concentration. Furthermore, numerical simulations performed by finite-element analysis result in the excellent prediction of the shape-memory recovery. The presented approach can be applied in remotely controlling morphing, mainly for applications in the fields of actuators and soft robotics.
Acousto-optic imaging (AOI) enables optical-contrast imaging deep inside scattering samples via localized ultrasound-modulation of scattered light. While AOI allows optical investigations at depths, its imaging resolution is inherently limited by the ultrasound wavelength, prohibiting microscopic investigations. Here, we propose a computational imaging approach that allows optical diffraction-limited imaging using a conventional AOI system. We achieve this by extracting diffraction-limited imaging information from speckle correlations in the conventionally detected ultrasound-modulated scattered-light fields. Specifically, we identify that since ``memory-effect'' speckle correlations allow estimation of the Fourier magnitude of the field inside the ultrasound focus, scanning the ultrasound focus enables robust diffraction-limited reconstruction of extended objects using ptychography (i.e., we exploit the ultrasound focus as the scanned spatial-gate probe required for ptychographic phase retrieval). Moreover, we exploit the short speckle decorrelation-time in dynamic media, which is usually considered a hurdle for wavefront-shaping- based approaches, for improved ptychographic reconstruction. We experimentally demonstrate noninvasive imaging of targets that extend well beyond the memory-effect range, with a 40-times resolution improvement over conventional AOI.
Political choices are all about the future. Through democratic elections, citizens select which political personnel, what policies and which values will guide societies into the times that lie ahead. Yet, it remains uncertain what futures await a society, which policies will deliver what outcomes, or how elected officials will behave. To exercise their democratic rights, citizens need to imagine possible futures and evaluate these to inform their political choices.
In the present study, we investigate how voters rely on a wide range of resources and strategies to project their collective futures. We draw upon data from 25 focus group interviews, conducted over the duration of the two rounds of Israeli general elections in April and September 2019, which were marked by substantially different levels of political uncertainty. Five groups of 7-12 participants with heterogeneous political views (four groups of Jewish Israeli voters, thereof one with young adults, and one group of Arab Israeli voters) were reconvened five times each to discuss their expectations for the elections and the future course of the country. Applying an abductive discourse analytic approach, we studied participants’ discursive strategies for presenting, justifying and negotiating their respective expectations. Specifically, we identified how participants anchored their projections in available evidence, knowledge and experience, how these anchoring strategies differed under higher or lower uncertainty, and how participants’ projections, in turn, enabled them to derive political orientation and efficacy. In order to link participants’ projections to the available information environment offering possible anchors and projections, we additionally analyzed a broad repertoire of news coverage and social media feeds (by political actors, journalists, experts, other public figures).
Our analysis documents that voters rely on a broad range of anchors and inferencing strategies, routinely combining personal observations and convictions with a creative use of media narratives (or fragments thereof). Depending on the use of narrower or broader anchors, as well as the degree of political uncertainty, distinct implications arise for the specific kinds of projections that can be derived, and the degree of confidence that they inspire in the formed expectations. Given low uncertainty during the first election campaign, for instance, knowledge about the agendas and character of individual leaders sufficed to project broad governmental programs and their implementation. After the political crisis that led to the second election round, by contrast, the same knowledge carried no further than predicting parties' negotiation strategies; numerous additional anchors had to be mobilized to project broader implications for government formation and beyond. Media reliance increased with raised uncertainty, but served more to interpret present observations than to infer their future implications. Other anchors were resilient against raised uncertainty: For instance, the exaltation of specific leaders as political ‘saviors’ inspired unbroken confidence in their prowess to effect far-reaching implications. Likewise, most continuity heuristics withstood the raised uncertainty (e.g., predicting rising religious influence, stable democratic institutions, or politicians’ unchanging characters). Reviewing the underlying heuristics and interrogating those cultural scripts enabling the formation of different projections, we discuss implications of future-oriented discourse for political communication scholarship.
Plasmonic thermochromic films are promising for smart window applications. Hereby, we develop a flexible plasmonic thermochromic film towards multifunctionality. The double-layer film consists of a bottom layer of W/Mg co-doped vanadium dioxide (VO2) rods in a polyurethane acrylate matrix and a top layer of hollow silica spheres (HSSs). Based on the finite-difference time-domain (FDTD) method, we demonstrate for the first time, a transverse and a longitudinal mode of VO2 localized surface plasmonic resonance (LSPR) in near- and mid-infrared bands, respectively, and only the transverse mode contributes to the solar energy modulation performance. The film shows a luminous transmittance of 46.2%, a solar energy modulation of 10.8%, and a critical transition temperature of 36.9 °C. The HSSs overcoating enhances the surface hydrophilicity and thermal insulation, which give rise to more favored functionalities for windows.
BACKGROUND: Antisense oligonucleotide (ASO)-based drugs for splicing modulation were recently approved for various genetic diseases with unmet need. Here we aimed to develop an ASO-based splicing modulation therapy for Cystic Fibrosis (CF) patients carrying the 3849+10 kb C-to-T splicing mutation in the CFTR gene.
METHODS: We have screened, in FRT cells expressing the 3849+10 kb C-to-T splicing mutation, ~30 2'-O-Methyl-modified phosphorothioate ASOs, targeted to prevent the recognition and inclusion of a cryptic exon generated due to the mutation. The effect of highly potent ASO candidates on the splicing pattern, protein maturation and CFTR function was further analyzed in well differentiated primary human nasal and bronchial epithelial cells, derived from patients carrying at least one 3849+10 kb C-to-T allele.
RESULTS: A highly potent lead ASO, efficiently delivered by free uptake, was able to significantly increase the level of correctly spliced mRNA and completely restore the CFTR function to wild type levels in cells from a homozygote patient. This ASO led to CFTR function with an average of 43% of wild type levels in cells from various heterozygote patients. Optimized efficiency of the lead ASO was further obtained with 2'-Methoxy Ethyl modification (2'MOE).
CONCLUSION: The highly efficient splicing modulation and functional correction, achieved by free uptake of the selected lead ASO in various patients, demonstrate the ASO therapeutic potential benefit for CF patients carrying splicing mutations and is aimed to serve as the basis for our current clinical development.
Bottlebrush block copolymers offer unique advantages for polymer-nanoparticle assembly, arising from the stiffness of their backbones and the compositional tunability afforded by the lengths of the grafts in each block independently. The morphologies of ultrathin bottlebrush block copolymer films are extremely sensitive to the chemistry of the substrate. Modifying the substrate with a polymer brush that corresponds to one of the blocks of the bottlebrush copolymer leads to different, often non-bulk morphologies that relate to the interaction of the copolymer with the substrate, which is dictated by the bottlebrush polymer composition. In this work, we investigate the assembly of bottlebrush block copolymers of different compositions with gold nanoparticles, which are modified with polymeric ligands that correspond to one of the blocks. Our results show that the net interaction of the copolymer with the substrate influences the self-assembly process, leading to two types of routes: the co-assembly route, in which the nanoparticles are organized by the polymer into periodic structures, or macrophase separation. In the co-assembly route, selective substrates slightly distort the shape of the domains. The nanoparticles, in turn, influence the kinetics of the process by their interaction with the substrate.
We explore how problem framing shapes teacher dialogue in teacher-led, school-based peer consultations. Twenty audio-recorded workgroup conversations were analyzed using a mixed-methods approach. Three different frames for presenting problems of practice were identified: teaching-, student- and classroom composition-oriented. Quantitative analyses showed associations between problem frames and the ensuing positioning of teachers as main agentive actors. In-depth qualitative analysis of two focal cases of low-teacher-agency problem frames (student- and classroom composition-oriented) revealed that psychologized discourses and attribution of responsibility to parents contributed to reduction of teacher responsibility and concomitant limited agency, and that initial problem frames were resistant to reframing.
