A Virtual Reality Application of the Rubber Hand Illusion Induced by Ultrasonic Mid-air Haptic Stimulation

Ultrasonic mid-air haptic technologies, which provide haptic feedback through airwaves produced using ultrasound, could be employed to investigate the sense of body ownership and immersion in virtual reality (VR) by inducing the virtual hand illusion (VHI). Ultrasonic mid-air haptic perception has solely been investigated for glabrous (hairless) skin, which has higher tactile sensitivity than hairy skin. In contrast, the VHI paradigm typically targets hairy skin without comparisons to glabrous skin. The aim of this article was to investigate illusory body ownership, the applicability of ultrasonic mid-air haptics, and perceived immersion in VR using the VHI. Fifty participants viewed a virtual hand being stroked by a feather synchronously and asynchronously with the ultrasonic stimulation applied to the glabrous skin on the palmar surface and the hairy skin on the dorsal surface of their hands. Questionnaire responses revealed that synchronous stimulation induced a stronger VHI than asynchronous stimulation. In synchronous conditions, the VHI was stronger for palmar stimulation than dorsal stimulation. The ultrasonic stimulation was also perceived as more intense on the palmar surface compared to the dorsal surface. Perceived immersion was not related to illusory body ownership per se but was enhanced by the provision of synchronous stimulation.

Efficacy and Function of Feathers, Hair, and Glabrous Skin in the Thermoregulation Strategies of Domestic Animals

The objective of this review is to describe and analyze the effect of feathers, hair, and glabrous (hairless) skin on the thermoregulation of domestic and endotherm animals, especially concerning the uses and scope of infrared thermography (IRT), scientific findings on heat and cold stress, and differences among species of domestic animals. Clinical medicine considers thermoregulation a mechanism that allows animals to adapt to varying thermal environmental conditions, a process in which the presence of feathers, hair, or glabrous skin influences heat loss or heat retention, respectively, under hot and cold environmental conditions. Evaluating body temperature provides vital information on an individual’s physiological state and health status since variations in euthermia maintenance in vertebrates reflect a significant cellular metabolism deviation that needs to be assessed and quantified. IRT is a non-invasive tool for evaluating thermal responses under thermal stress conditions in animals, where the presence or absence of feathers, hair, and glabrous skin can affect readings and the differences detected. Therefore, anatomical regions, the characteristics of feathers, hair, glabrous skin such as structure, length, color, and extension, and strategies for dissipating or retaining heat together constitute a broad area of opportunity for future research into the phenomena of dermal thermoregulation in domestic species.

Mechanoreceptor synapses in the brainstem shape the central representation of touch

Mammals use glabrous (hairless) skin of their hands and feet to navigate and manipulate their environment. Cortical maps of the body surface across species contain disproportionately large numbers of neurons dedicated to glabrous skin sensation, potentially reflecting a higher density of mechanoreceptors that innervate these skin regions. Here, we find that disproportionate representation of glabrous skin emerges over postnatal development at the first synapse between peripheral mechanoreceptors and their central targets in the brainstem. Mechanoreceptor synapses undergo developmental refinement that depends on proximity of their terminals to glabrous skin, such that those innervating glabrous skin make synaptic connections that expand their central representation. In mice that do not sense gentle touch, mechanoreceptors innervating glabrous skin still make more powerful synaptic connections in the brainstem. We propose that the skin region a mechanoreceptor innervates controls refinement of its central synapses over development to shape the representation of touch in the brain.

Foxn1 Control of Skin Function

The forkhead box N1 (Foxn1) transcription factor regulates biological processes of the thymus and skin. Loss-of-function mutations in Foxn1 cause the nude phenotype in humans, mice, and rats, which is characterized by hairless skin and a lack of thymus. This review focuses on the role of Foxn1 in skin biology, including epidermal, dermal, and dermal white adipose tissue (dWAT) skin components. In particular, the role of Foxn1 in the scar-forming skin wound healing process is discussed, underscoring that Foxn1 inactivity in nude mice is permissive for scar-less cutaneous wound resolution.

Coating Cutting Blades with Thin-Film Metallic Glass to Enhance Sharpness

In this study, we sought to enhance the cutting properties of the various blades by coating them with Zr- and Fe-based thin film metallic glasses (TFMGs) to a thickness of 234–255 nm via sputter deposition. In oil-repellency/sliding tests on kitchen blades, the sliding angle and friction forces were as follows: bare blades (31.6°) and (35 µN), Ti-coated blades (20.3°) and (23.7 µN), and Z-TFMG coated blades (16.2°) and (19.2 µN). Comparisons were conducted with bare blades and those with a Teflon coating (a low-friction material commonly used for the coating of microtome blades). We also found that the Teflon coating reduced the cutting forces of an uncoated microtome blade by ~80%, whereas the proposed Z-TFMG achieved a ~51% reduction. The Z-TFMG presented no indications of delamination after being used 30 times for cutting; however, the Teflon coating proved highly susceptible to peeling and the bare blade was affected by surface staining. These results demonstrate the efficacy of the TFMG coating in terms of low friction, non-stick performance, and substrate adhesion. The performance of Z-TFMG and F-TFMG was also evaluated in split-thickness skin graft surgery using dermatome blades aimed at elucidating the influence of TFMG coatings on the healing of surgical incisions. When tested repeatedly on hairless skin, the surface roughness of uncoated blades increased by approximately 70%, whereas the surface roughness of TFMG-coated blades increases by only 8.6%. In the presence of hair, the surface roughness of uncoated blades increased by approximately ~108%, whereas the surface roughness of TFMG-coated blades increases by only ~23%. By Day 7, the wounds produced using TFMG-coated blades were noticeably smaller than those produced using uncoated blades, and these effects were particularly evident in hairy samples. This is a clear demonstration of the efficacy of TFMG surface coatings in preserving the cutting quality of surgical instruments.

Quantitative Analysis of Glabrous Skin Blood Flow and its Role in Human Thermoregulation

Glabrous (hairless) skin found on the hands, feet, face, and ears is a unique component of the thermoregulatory system. Its anatomy and control physiology differ markedly from those of the rest of the skin. Glabrous regions contain vascular networks capable of supporting large blood flows due to the presence of highly tortuous and densely packed arteriovenous anastomoses (AVAs) and associated venous collecting networks [1]. When dilated, these vessels bring large volumes of blood close to the body surface where they function as highly efficient heat exchangers. Furthermore, the manner in which this blood flow is controlled is very unique, exhibiting, for example, rapid and high-magnitude responses, as well as a greater sensitivity to central core signals [1]. In this light, glabrous skin is an important but often overlooked tool the body uses to rapidly and finely adjust energy balance to maintain thermal equilibrium.

The beautiful woman in medieval Iberia: rhetoric, cosmetics, and evolution

Literary portraits of the beautiful woman in medieval Iberia tend to emphasize several physical features, such as long, blond hair, or light-colored and hairless skin. This study examines the specific features of the beautiful woman in several major works and genres from medieval Iberia. It also traces the rhetorical sources of these portraits to the Classical and medieval Latin traditions, whose influence is evident in other early vernacular literatures of Europe. It then analyzes several medieval cosmetic treatises in Latin and in vernacular languages that attest to medieval women's beautifying practices, such as the use of hair-dyes, depilatories, and skin-whitening creams. The comparison of the literary and cosmetic evidence shows a canonical view of feminine beauty that encompasses different cultural areas in medieval Iberia. This view is also consistent with ancient as well as with twenty-first century conceptions of beauty. The findings suggest that the ideal of feminine beauty in medieval Iberia is not unique, but rather a manifestation of near-universal male preferences shaped by sexual selection in the course of human evolution.