Therapeutic Strategies to Reduce Burn Wound Conversion.

Burn wound conversion refers to the phenomenon whereby superficial burns that appear to retain the ability to spontaneously heal, convert later into deeper wounds in need of excision. While no current treatment can definitively stop burn wound conversion, attempts to slow tissue damage remain unsatisfactory, justifying the need for new therapeutic interventions. To attenuate burn wound conversion, various studies have targeted at least one of the molecular mechanisms underlying burn wound conversion, including ischemia, inflammation, apoptosis, autophagy, generation of reactive oxygen species, hypothermia, and wound rehydration. However, therapeutic strategies that can target various mechanisms involved in burn wound conversion are still lacking. This review highlights the pathophysiology of burn wound conversion and focuses on recent studies that have turned to the novel use of biologics such as mesenchymal stem cells, biomaterials, and immune regulators to mitigate wound conversion. Future research should investigate mechanistic pathways, side effects, safety, and efficacy of these different treatments before translation into clinical studies.

The Role of Skin Substitutes in Acute Burn and Reconstructive Burn Surgery: An Updated Comprehensive Review.

Burns disrupt the protective skin barrier with consequent loss of cutaneous temperature regulation, infection prevention, evaporative losses, and other vital functions. Chronically, burns lead to scarring, contractures, pain, and impaired psychosocial well-being. Several skin substitutes are available and replace the skin and partially restore functional outcomes and improve cosmesis. We performed a literature review to update readers on biologic and synthetic skin substitutes to date applied in acute and reconstructive burn surgery. Improvement has been rapid in the development of skin substitutes in the last decade; however, no available skin substitute fulfills criteria as a perfect replacement for damaged skin.

Conchal Excision Techniques in Otoplasty: A Literature Review.

Prominent ears are a common congenital deformity of the head and neck. Correcting concha hypertrophy is an important step in otoplasty. Despite the risk of postoperative deformity due to the sharp edges created by excision, removing a section of cartilage is sometimes the only method to obtain a satisfying and long-lasting result. Multiple conchal excision techniques have been reported in the literature, with significant differences in approach, outcome evaluation, and complication classification. The objective was to review cartilage excision-based otoplasty procedures to offer plastic surgeons' insights into current data on outcomes and complications of conchal excision techniques. Methods: We conducted a literature search through the MEDLINE, EMBASE, Scopus, and Cochrane databases. Prospective and retrospective studies on otoplasty, including revision surgeries and conchal excision techniques involving concha cartilage resection, were included. Articles with no outcomes data, review articles, case reports, expert opinion or comment, and nonclinical studies were excluded. Results: There were a total of four manuscripts that fulfilled our criteria. Three out of four authors preferred posterior access that separates the skin excision from the cartilage excision. Following resection, cartilage edges can be approximated by placing cartilage sutures, or they can be allowed to collapse spontaneously. Although only two authors employed a systematic classification for complications, all the articles reviewed indicated a low complication rate and excellent postoperative cosmetic outcomes. Conclusion: Although the techniques and principles stated in the literature varied to some extent, the outcomes of all studies reviewed were comparable.

Stability bounds on superluminal propagation in active structures.

Active materials have been explored in recent years to demonstrate superluminal group velocities over relatively broad bandwidths, implying a potential path towards bold claims such as information transport beyond the speed of light, as well as antennas and metamaterial cloaks operating over very broad bandwidths. However, causality requires that no portion of an impinging pulse can pass its precursor, implying a fundamental trade-off between bandwidth, velocity and propagation distance. Here, we clarify the general nature of superluminal propagation in active structures and derive a bound on these quantities fundamentally rooted into stability considerations. By applying filter theory, we show that this bound is generally applicable to causal structures of arbitrary complexity, as it applies to each zero-pole pair describing their response. As the system complexity grows, we find that only minor improvements in superluminal bandwidth can be practically achieved. Our results provide physical insights into the limitations of superluminal structures based on active media, implying severe constraints in several recently proposed applications.

Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre.

The exotic physics emerging in non-Hermitian systems with balanced distributions of gain and loss has recently drawn a great deal of attention. These systems exhibit phase transitions and exceptional point singularities in their spectra, at which eigen-values and eigen-modes coalesce and the overall dimensionality is reduced. So far, these principles have been implemented at the expense of precise fabrication and tuning requirements, involving tailored nano-structured devices with controlled optical gain and loss. In this work, anti-parity-time symmetric phase transitions and exceptional point singularities are demonstrated in a single strand of single-mode telecommunication fibre, using a setup consisting of off-the-shelf components. Two propagating signals are amplified and coupled through stimulated Brillouin scattering, enabling exquisite control over the interaction-governing non-Hermitian parameters. Singular response to small-scale variations and topological features arising around the exceptional point are experimentally demonstrated with large precision, enabling robustly enhanced response to changes in Brillouin frequency shift.

Optomechanically Induced Birefringence and Optomechanically Induced Faraday Effect.

We demonstrate an optomechanical platform where optical mode conversion mediated by mechanical motion enables the arbitrary tailoring of polarization states of propagating light fields. Optomechanical interactions are realized in a Fabry-Pérot resonator, which naturally supports two polarization-degenerate states while an optical control field induces rotational symmetry breaking. Applying such principles, the entire Poincaré sphere is spanned by just optical control of the driving field, realizing reciprocal and nonreciprocal optomechanically induced birefringence for linearly polarized and circularly polarized control driving. A straightforward extension of this setup also enables all-optical tunable isolation and circulation. Our findings open new avenues to exploit optomechanics for the arbitrary manipulation of light polarization.