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Biological and artificial microswimmers often encounter fluid media with non-Newtonian rheological properties. In particular, many biological fluids such as blood and mucus are shear-thinning. Recent studies have demonstrated how shear-thinning rheology can impact substantially the propulsion performance in different manners. In this work, we examine the effect of geometrical shape upon locomotion in a shear-thinning fluid using a prolate spheroidal squirmer model. We use a combination of asymptotic analysis and numerical simulations to quantify how particle geometry impacts the speed and the energetic cost of swimming. The results demonstrate the advantages of spheroidal over spherical swimmers in terms of both swimming speed and energetic efficiency when squirming through a shear-thinning fluid. More generally, the findings suggest the possibility of tuning the swimmer geometry to better exploit non-Newtonian rheological behaviours for more effective locomotion in complex fluids.

The demand for corneal tissue replacements increases due to corneal diseases, prompting the exploration of tissue engineering (TE) solutions using biopolymers. Poly (glycerol sebacate) (PGS) is one of the promising biomaterials to be explored in the ocular TE, not only because of its biocompatibility, biodegradability, and elasticity, but also its transparency. However, its low molecular weight and low glass transition temperature (Tg) make PGS scaffold fabrication via electrospinning challenging. Here, we fabricated fibrous membranes by electrospinning of PGS and poly (vinyl alcohol) (PVA) blend and obtained a membrane composed of homogenous fibers with a diameter of 4 µm and a porosity of 28%. In addition, the membrane exhibited a stiffness of 12 MPa and strain of 20%. The permeability of the membrane closely resembled that of the natural cornea with 9.8E‐07 cm2/s. Most of the PVA was successfully washed off, resulting in biocompatible scaffold that was able to support the proliferation of human corneal epithelial cells (HCEC) and human corneal endothelial cells (HCEndC) for a week. According to the in vitro biocompatibility assay, HCEC has demonstrated an 88% and HCEndC a 96% viability on electrospun PGS membranes. These results demonstrate the suitability of electrospun PGS membrane for cornea tissue engineering. Fibrous PGS membranes that are composed of homogenous fibers are fabricated by electrospinning. Durability and permeability of the membranes closely resemble the natural cornea. Thereby, successfully supporting the proliferation of human corneal epithelial cells (HCEC) and human corneal endothelial cells (HCEndC). Consequently, this study demonstrates the suitability of electrospun PGS membrane for cornea tissue engineering.

In reward foraging tasks, prefrontal neurons track reward history, yet animals also show persistent choice-history biases. How these histories are represented in prefrontal circuits and guide animals’ decisions remains unknown. We asked whether past rewards and choices are incorporated by leaky integration or carried as discrete, history-specific codes, and how these codes are recruited under different task demands. We recorded medial prefrontal cortex (mPFC) activity while mice performed probabilistic reward foraging task and fit a reinforcement-learning model whose decision variable, combining reward and choice histories, captured behavior. Neurons represented history-specific rewards and choices while integrating them consistent with their behavioral impact. We then altered reward contingencies and inter-choice intervals and transiently inactivated mPFC. Neural representations adapted to changing task demands, yet the behavioral impact of inactivation was sensitive to inter-choice interval and reward contingencies. We conclude that mPFC hosts redundant computations whose influence is gated by timing and task structure. Neural basis of decision-making is not fully understood. Here authors show that mouse prefrontal neurons encode history-specific rewards and choices. However, their influence is gated by task structure and timing, affecting decisions primarily in variable interval tasks and when temporal delays separate events.

Scent's different directions Despite dramatic behavioural differences between the sexes, surprisingly few anatomic features have been observed that differentiate the male and female brain in any species. Work in the Drosophila fruit fly has now uncovered a striking difference in male and female responses to the insect pheromone cVA ( cis -vaccenyl acetate). Males release the pheromone, which is detected by both sexes via apparently identical neural circuits in their antennae. The scent induces females to become receptive to males, but in rival males it inhibits courtship behaviour. The single neuron tracing technique developed to make this discovery should be applicable to study the nervous systems of other genetically tractable species, such as the mouse. Despite marked behavioural differences between the sexes, surprisingly few anatomic features have been observed that differentiate the male and female brain in any species. But this study unveils a sexual dimorphism in the neuronal circuit responding to a pheromone, which induces different courtship behaviours in male and female fruitflies. The single neuron tracing technique that has been developed to do so should be useful to study the nervous systems of other genetically tractable species. Courtship is an innate sexually dimorphic behaviour that can be observed in naive animals without previous learning or experience, suggesting that the neural circuits that mediate this behaviour are developmentally programmed 1 . In Drosophila , courtship involves a complex yet stereotyped array of dimorphic behaviours that are regulated by Fru M , a male-specific isoform of the fruitless gene 2 , 3 , 4 , 5 . Fru M is expressed in about 2,000 neurons in the fly brain, including three subpopulations of olfactory sensory neurons and projection neurons (PNs). One set of Fru + olfactory neurons expresses the odorant receptor Or67d and responds to the male-specific pheromone cis -vaccenyl acetate (cVA) 6 , 7 , 8 , 9 , 10 . These neurons converge on the DA1 glomerulus in the antennal lobe. In males, activation of Or67d + neurons by cVA inhibits courtship of other males, whereas in females their activation promotes receptivity to other males 7 . These observations pose the question of how a single pheromone acting through the same set of sensory neurons can elicit different behaviours in male and female flies. Anatomical or functional dimorphisms in this neural circuit might be responsible for the dimorphic behaviour. We therefore developed a neural tracing procedure that employs two-photon laser scanning microscopy to activate the photoactivatable green fluorescent protein 11 . Here we show, using this technique, that the projections from the DA1 glomerulus to the protocerebrum are sexually dimorphic. We observe a male-specific axonal arbor in the lateral horn whose elaboration requires the expression of the transcription factor Fru M in DA1 projection neurons and other Fru + cells. The observation that cVA activates a sexually dimorphic circuit in the protocerebrum suggests a mechanism by which a single pheromone can elicit different behaviours in males and in females.

Eyes are one of the main critical organs of the body that provide our brain with the most information about the surrounding environment. Disturbance in the activity of this informational organ, resulting from different ocular diseases, could affect the quality of life, so finding appropriate methods for treating ocular disease has attracted lots of attention. This is especially due to the ineffectiveness of the conventional therapeutic method to deliver drugs into the interior parts of the eye, and the also presence of barriers such as tear film, blood-ocular, and blood-retina barriers. Recently, some novel techniques, such as different types of contact lenses, micro and nanoneedles and in situ gels, have been introduced which can overcome the previously mentioned barriers. These novel techniques could enhance the bioavailability of therapeutic components inside the eyes, deliver them to the posterior side of the eyes, release them in a controlled manner, and reduce the side effects of previous methods (such as eye drops). Accordingly, this review paper aims to summarize some of the evidence on the effectiveness of these new techniques for treating ocular disease, their preclinical and clinical progression, current limitations, and future perspectives.

Reinforcement learning control methods can impart robots with the ability to discover effective behavior, reducing their modeling and sensing requirements, and enabling their ability to adapt to environmental changes. However, it remains challenging for a robot to achieve navigation in confined and dynamic environments, which are characteristic of a broad range of biomedical applications, such as endoscopy with ingestible electronics. Herein, a compact, 3D‐printed three‐linked‐sphere robot synergistically integrated with a reinforcement learning algorithm that can perform adaptable, autonomous crawling in a confined channel is demonstrated. The scalable robot consists of three equally sized spheres that are linearly coupled, in which the extension and contraction in specific sequences dictate its navigation. The ability to achieve bidirectional locomotion across frictional surfaces in open and confined spaces without prior knowledge of the environment is also demonstrated. The synergistic integration of a highly scalable robotic apparatus and the model‐free reinforcement learning control strategy can enable autonomous navigation in a broad range of dynamic and confined environments. This capability can enable sensing, imaging, and surgical processes in previously inaccessible confined environments in the human body. A 3D‐printed three‐linked‐sphere robot integrated with a reinforcement‐learning algorithm can perform an adaptable, autonomous crawling in a confined channel. The scalable robot consists of three equally sized spheres that are linearly coupled and can learn the extension and contraction sequences that enable navigation across confined frictional surfaces without prior knowledge of the environment.

Rotating spheres in cylindrical channels roll or slide along the channel depending on the physical and geometric conditions. For a thorough investigation of the phenomenon, finite-element modelling is utilized to obtain the resistance coefficients for the motion of a sphere in a cylindrical channel, with an emphasis on near-wall motion. Extracted coefficients are compared with the data in the literature and utilized in exploring the conditions for rolling versus sliding along the channel. Sliding occurs due to the pressure build-up in the nip region between the wall and the rotating sphere in small confinement ratios, whereas rolling occurs when the shearing forces on the sphere are dominant in larger ratios. According to numerical results, a flow reversal takes place in the nip region and reduces the shear as well. Rolling versus sliding is demonstrated in experiments by using magnetic spherical particles, which are rotated by means of an external magnetic field inside cylindrical channels filled with viscous fluids. Faster axial velocities are observed in narrow channels while sliding than in wider channels while rolling for the same rotation rate of the sphere. Experiment observations are compared with the velocities evaluated from the resistance coefficients, showing that the distance between the sphere and the wall, which is dominated by roughness, plays an important role in the velocity of the sphere.

This article examines whether incorporating the Women, Peace, and Security Agenda of the United Nations Security Council into the international refugee regime may give refugee women greater potential to participate in decision-making processes. In addition to recognizing the need to protect women in conflict settings, the Women, Peace, and Security Agenda also promotes women's participation in order to achieve sustainable peace. The article focuses on Turkey, which hosts the largest number of refugees globally. The article explores the extent to which the protection and participation of refugee women in Turkey are balanced in the activities of national and international actors, and it advises adopting a national action plan on refugee women in line with the Women, Peace, and Security Agenda. We conducted qualitative research and carried out a field study in Turkey to engage with the article's main research question. In the field study, we conducted semi-structured interviews with participants from international organizations, international and national non-governmental organizations, and state institutions. We argue that refugee women's participation is frequently reduced to a formality and is constrained by the restrictions imposed by governmental and humanitarian agencies. A national action plan that considers the rights, ambitions, and expectations of refugee women in Turkey would not only strengthen their protection from violence but also encourage their agency. Under a legally binding framework, all stakeholders–refugee women, international organizations, donors, nongovernmental organizations, and the state–would be obliged to encourage refugee women's participation in decision-making processes and mechanisms at varying levels and fields. We argue that a national action plan would challenge the traditional and patriarchal stereotypes regarding refugee women and enable all relevant stakeholders to promote refugee women's agency in a systematic way.

Organisms have evolved diverse behavioural strategies that enhance the likelihood of encountering and assessing mates 1 . Many species use pheromones to communicate information about the location, sexual and social status of potential partners 2 . In mice, the major urinary protein darcin—which is present in the urine of males—provides a component of a scent mark that elicits approach by females and drives learning 3 , 4 . Here we show that darcin elicits a complex and variable behavioural repertoire that consists of attraction, ultrasonic vocalization and urinary scent marking, and also serves as a reinforcer in learning paradigms. We identify a genetically determined circuit—extending from the accessory olfactory bulb to the posterior medial amygdala—that is necessary for all behavioural responses to darcin. Moreover, optical activation of darcin-responsive neurons in the medial amygdala induces both the innate and the conditioned behaviours elicited by the pheromone. These neurons define a topographically segregated population that expresses neuronal nitric oxide synthase. We suggest that this darcin-activated neural circuit integrates pheromonal information with internal state to elicit both variable innate behaviours and reinforced behaviours that may promote mate encounters and mate selection. A neural circuit activated by the male pheromone, darcin, mediates a complex and variable array of innate and reinforced behaviours that may promote mate encounters and mate selection.