Utilizing a Second Flap to Address the Effect of Postradiotherapy Soft Tissue Fibrosis in Head and Neck Malignancy.

Background Late effects of adjuvant radiation therapy (RT) on soft tissues can lead to hair loss, pigmentary changes, loss of tissue volume, and fibrosis, which appear months to years after the treatment. These changes are often progressive and are because of tissue hypoxia due to radiation-induced capillary endothelial damage. Tissue hypoxia may be compounded by subclinical infection following minor trauma, exposed hardware, or associated osteoradionecrosis. The combined effect of these factors causes significant deformities in soft tissue, affecting both function and appearance. Such changes are also seen in primarily transferred flaps, which have been radiated, resulting in severe, progressive soft tissue fibrosis, compromising function and aesthetics. In selected cases, a second flap may be needed to restore function and volume. Methods Data of patients who underwent secondary soft tissue transfers for postradiotherapy-related soft tissue changes were collected from the hospital electronic medical records, from January 2019 to 2023. Details regarding the primary surgery, dose, duration of adjuvant RT, time interval between adjuvant RT and secondary soft tissue transfer, indications, and the choice of the second flap were analyzed. Results Twenty-one patients had undergone secondary soft tissue transfer for extensive soft tissue fibrosis. In addition, associated compounding features like exposed implant and volume loss were observed. Two patients with osteoradionecrosis also had associated extensive soft tissue fibrosis necessitating replacement. Out of these 21 patients, 13 had undergone free tissue transfers, while 7 locoregional tissue transfers. Conclusion Late sequelae of adjuvant RT changes usually present from 6 months onwards. The radiated hypoxic tissue, due to capillary damage, leads to a chronic progressive fibrotic stage, causing loss of soft tissue volume and fibrosis. Replacing this tissue with a vascularized flap helps to restore volume and correct these secondary changes, improving overall quality of life.

Head-On Collision of Dissimilar Viscosity Drops.

The head-on collision of drops is governed by the interfacial tension, viscosity, and inertia of the impacting drops. Earlier studies show that depending on the relative magnitude of these forces, the outcome of a head-on collision of two identical drops of the same liquid is likely to culminate in coalescence or reflexive separation. In this study, the head-on collision of drops of miscible liquids having dissimilar viscosity has been investigated numerically. As the two drop liquids are miscible, it is anticipated that the average viscosity of the two liquids will replicate the transition boundaries of coalescence and reflexive separation for a single fluid. However, numerical simulations reveal that this is true only for low-viscosity ratios. A high-viscosity ratio creates asymmetric flow; hence, the average viscosity does not accurately represent the local viscous effect. The asymmetric flow also facilitates the pinch-off of a thread without the separation of a satellite. The present investigation reveals that viscosity contrast leads to two additional outcomes of the head-on collision of drops: encapsulation and crossing separation. We have built a phase diagram identifying the outcome of a head-on collision of dissimilar viscosity drops on the viscosity ratio (µr)-Weber number (We) plane based on the results of approximately 450 simulations.

Transport Behavior of Commercial Anticancer Drug Protein-Bound Paclitaxel (Paclicad) in a Micron-Sized Channel.

Protein-bound paclitaxel has been developed clinically as one of the most successful chemotherapy drugs for the treatment of a wide variety of cancers. However, these medications, due to their nanoscale properties, may often induce capillary blocking while migrating through minute blood vessels. Considering the detrimental impact of this restriction, we investigated the transport of protein-bound paclitaxel, Paclicad, in a 7 µm microchannel mimicking the identical mechanical confinement of the blood capillaries. The drug was reported to migrate through a constricted microchannel without obstruction at a solution flow rate of 20-50 µL/h. The onset of an agglomeration site was observed at higher flow rates of 70-90 µL/h, while complete capillary obstruction was observed at 100 µL/h. The mobility of the particles was also calculated, and the results suggested that the presence of varying cross-sections affects the mobility of the drug particles. The trajectory of the particle migration was observed to be less tortuous at the higher flow rate, but the tortuous nature appeared to increase with the presence of agglomeration sites in the flow field. The experimental results were also compared with the computational model of the drug particle. The drug particle was modeled both as Newtonian and as an FENE-P viscoelastic drop. The drop interface tracking was done by the VOF method using the open source software Basilisk. The particle displacement was better estimated by both the FENE-P and Newtonian model at a flow rate of 30 µL/h, while deviation was observed at a flow rate of 50 µL/h. The FENE-P model was observed to show higher deformation than the Newtonian model at both flow rates. The experimental results provided better insight into the agglomeration tendency of Paclicad, migrating through a constricted microchannel at higher flow rates. The numerical model could be further employed to understand the more complex intravenous transport of drugs.

Fabricating Flaps in the Forearm Prior to Tracheal Reconstruction.

Background The process of reconstruction of tracheal defects is complex and still not optimum. Options range from using staged reconstructions, combining flaps with autologous or alloplastic implants, as well as use of tissue-engineered constructs combined with vascularized tissues which are lined with cell cultures. Staged reconstructions using prelaminated epithelium, and prefabricated flaps, help in reconstruction of this complex structure. Prefabricating the flap at a different site allows for integration of the tissues prior to its transfer. Method This article reports two patients planned for tracheal reconstruction for the purpose of advanced papillary carcinoma of the thyroid invading the trachea. Staged reconstruction using a prefabricated radial artery forearm flap (RAFF) and split rib cartilage was performed. In the second patient, a young girl, a similar construct of the RAFF, prelaminated with buccal mucosa, was performed. However, in the latter case, an intraoperative decision by the head and neck team to limit excision of the trachea sparing the mucosa was taken; the reconstruct in the forearm was redundant and needed to be discarded, replacing the defect with a free superficial circumflex iliac artery perforator (SCIP) flap. Result At 3 years follow-up, both the patients are free of disease, with the construct serving its purpose in the older female.

Midface Reconstruction: Planning and Outcome.

Reconstruction of the complex anatomy and aesthetics of the midface is often a challenge. A careful understanding of this three-dimensional (3D) structure is necessary. Anticipating the extent of excision and its planning following oncological resections is critical. In the past over two decades, with the advances in microsurgical procedures, contributions toward the reconstruction of this area have generated interest. Planning using digital imaging, 3D printed models, osseointegrated implants, and low-profile plates, has favorably impacted the outcome. However, there are still controversies in the management: to use single composite tissues versus multiple tissues; implants versus autografts; vascularized versus nonvascularized bone; prosthesis versus reconstruction. This article explores the present available options in maxillary reconstruction and outlines the approach in the management garnered from past publications and experiences.

Optimistic metacognitive judgments predict poor performance in relatively complex visual tasks.

In some cases, people overestimate how much they can see. This can produce a metacognitive blind spot that may lead participants to devote fewer cognitive resources than a visual task demands. However, little research has tested whether individuals who are particularly optimistic about their visual capabilities are susceptible to poor visual performance. We tested whether optimistic metacognitive judgments would predict poor performance in a visual task, especially when it placed a large attentional load on the participant, and when it required balancing between multiple sources of information. We tested participants in a simplified battle command simulation in which they were asked to detect visual changes. Participants who predicted spatially expansive visual attention performance performed more poorly in the change detection task when the task required tracking larger numbers of aircraft, and when it included a secondary change-list display.

Electric field mediated separation of water-ethanol mixtures in carbon-nanotubes integrated in nanoporous graphene membranes.

We investigate the influence of an applied electric field on the separation of a water-ethanol solution inside a carbon nanotube (CNT) using a series of molecular dynamics simulations. The electric field is applied at an angle θ with respect to the axis of the CNT. The study uncovers that with the application of a 'small-angle' electric field (e.g. smaller θ), the water molecules exhibit preferential occupancy inside the CNT, whereas the application of the same electric field at a 'wide-angle' mode (e.g. higher θ) fills the CNT with ethanol molecules in place of water. Remarkably, the direction of the electric field plays a pivotal role because the field exerts a contrasting influence on the behaviours of the water and ethanol molecules. The water dipoles are favourably aligned at small values of θ creating an ordered water structure inside the CNT. Increasing θ disrupts the water dipole orientation and leads to the preferential occupancy of the CNT by ethanol molecules. An in-depth analysis on the simulated systems unveil that, at lower values of θ, multiple layers of water molecules are physically adsorbed near the CNT walls, which is found to diminish as θ is increased. In comparison, at higher magnitudes of θ, the ethanol molecules are preferentially adsorbed inside the CNT. The average interaction energy per ethanol (water) molecule is found to increase (reduce) when θ is monotonically increased, which can be ascribed to the increase (decrease) in the intermolecular hydrogen bonding capacity of the ethanol (water) molecules at larger values of θ. Consequently, inside the CNT, the average occupancy of water molecules decreases and ethanol molecules increases, as θ is monotonically increased, leading to the separation of the ethanol-water mixture. The proposed methodology can convert an equimolar mixture (1 : 1) of ethanol-water into a concentrated one (14 : 1) when the electric field is applied orthogonal to the axis of the CNT. The separation efficiency is found to improve with an increase in the intensity of the externally applied electric field.

Electric field mediated spraying of miniaturized droplets inside microchannel.

We report a facile and noninvasive way to disintegrate a microdroplet into a string of further miniaturized ones under the influence of an external electrohydrodynamic field inside a microchannel. The deformation and breakup of the droplet was engendered by the Maxwell's stress originating from the accumulation of induced and free charges at the oil-water interface. While at smaller field intensities, for example less than 1 MV/m, the droplet deformed into a plug, at relatively higher field intensities, e.g. ∼1.16 MV/m, a pair of droplets having opposite surface charge was formed. The charged droplets showed an interesting periodic bridging and breakup during their translation motion across the channel. For even higher field intensities, for example more than 1.2 MV/m, the entire droplet underwent dielectrophoresis toward one of the electrodes before experiencing a strong attractive force from the other electrode to deform into a shape of a Taylor cone. With progress in time, mimicking the electrospraying phenomenon, the cone tip periodically ejected a string of miniaturized water droplets to form a microemulsion inside the channel. The frequency and size of the droplet ejection could be tuned by varying the applied field intensity. A water droplet of ∼214 µm diameter could continuously eject droplets of size ∼10 µm or even smaller to form a microemulsion inside the channel.

Computed tomography angiographic study of internal mammary perforators and their use as recipient vessels for free tissue transfer in breast reconstruction.

CONTEXT: The internal mammary artery perforator vessels (IMPV) as a recipient in free flap breast reconstruction offer advantages over the more commonly used thoracodorsal vessels and the internal mammary vessels (IMV). AIMS: This study was designed to assess the anatomical consistency of the IMPV and the suitability of these vessels for use as recipients in free flap breast reconstruction. PATIENTS AND METHODS: Data from ten randomly selected female patients who did not have any chest wall or breast pathology but had undergone a computed tomography angiography (CTA) for unrelated diagnostic reasons from April 2013 to October 2013 were analysed. Retrospective data of seven patients who had undergone mastectomy for breast cancer and had been primarily reconstructed with a deep inferior epigastric artery perforator free flap transfer using the IMPV as recipient vessels were studied. RESULTS: The CTA findings showed that the internal mammary perforator was consistently present in all cases bilaterally. In all cases, the dominant perforator arose from the upper four intercostal spaces (ICS) with the majority (55%) arising from the 2nd ICS. The mean distance of the perforators from the sternal border at the level of pectoralis muscle surface on the right side was 1.86 cm (range: 0.9-2.5 cm) with a mode value of 1.9 cm. On the left side, a mean of 1.77 cm (range: 1.5-2.1 cm) and a mode value of 1.7 cm were observed. Mean perforator artery diameters on the right and left sides were 2.2 mm and 2.4 mm, respectively. CONCLUSIONS: Though the internal mammary perforators are anatomically consistent, their use as recipients in free tissue transfer for breast reconstruction eventually rests on multiple variables.

Evaporation of water droplets on Pt-surface in presence of external electric field--A molecular dynamics study.

Evaporation of a sessile droplet on a hot solid substrate is an important problem in fluid mechanics. It is relevant to theoretical issues in heat transfer as well as several practical applications. This study investigates the spreading and evaporation of a nanoscale water droplet on a solid platinum surface. The major objective was to analyze the effect of an external electric field on these phenomena. Varying the intensity and direction of the external electric field, a series of molecular dynamics simulations were carried out to understand these phenomena at a molecular level. The results reveal that a horizontal electric field assists in droplet spreading, whereas a vertical electric field enhances the rate of evaporation for a certain range of field intensities. It also shows that the substrate temperature plays an important role in such processes. It is seen that the effect of an external electric field on droplet evaporation becomes significant at an intermediate range of surface temperatures and this effect is not clearly visible for either very high or very low range of surface temperatures.

Model-Based Design of Tree WSNs for Decentralized Detection.

The classical decentralized detection problem of finding the optimal decision rules at the sensor and fusion center, as well as variants that introduce physical channel impairments have been studied extensively in the literature. The deployment of WSNs in decentralized detection applications brings new challenges to the field. Protocols for different communication layers have to be co-designed to optimize the detection performance. In this paper, we consider the communication network design problem for a tree WSN. We pursue a system-level approach where a complete model for the system is developed that captures the interactions between different layers, as well as different sensor quality measures. For network optimization, we propose a hierarchical optimization algorithm that lends itself to the tree structure, requiring only local network information. The proposed design approach shows superior performance over several contentionless and contention-based network design approaches.

Internal mammary artery perforator flap in the management of tracheoesophageal fistulae.

BACKGROUND: A pathological communication between the trachea and oesophagus - a tracheoesophageal fistula - may be congenital or acquired, benign or malignant, necessitating a multidisciplinary approach. Conservative attempts at closure of this abnormal connection are ineffective; the interposition of healthy vascular tissue offers the least chance of recurrence. METHODS: Outcomes of an islanded fasciocutaneous internal mammary artery perforator flap applied for tracheoesophageal fistula management were assessed in four radiated patients with laryngeal carcinoma using retrospective records. RESULTS: Four male patients, with an average age of 60.75 years, underwent tracheoesophageal fistula closure between September 2017 and February 2021. A left-sided second internal mammary artery perforator flap was used in all cases, with an average dimension of 10.5 × 4.5 cm. There were no complications of tracheoesophageal leak, flap issues or donor site morbidity on follow up. CONCLUSION: Recent advances in angiosomal territory mapping and microvascular dissection techniques, combined with an understanding of tracheoesophageal fistula pathology, have changed management perspectives in these difficult-to-treat patients.

Chronic discharging ear in a child: are we missing something?

Chronic discharging ear, mostly due to middle or external ear infection, is one of the leading causes for seeking healthcare among the paediatric population in a developing country. However, a long-standing forgotten middle ear foreign body forms a rare cause for such presentation demanding a high index of suspicion from the clinicians. Most of them are iatrogenic or accidental, and are removed by conventional permeatal approach; need for tympanotomy is rarely documented in the recent literature. We report the first case where a large stone was introduced into the middle ear through a pre-existing tympanic membrane perforation by the child himself, and only the second documentation of removal of a middle ear foreign body by tympanotomy in a child.

Ocular morbidity among children at a tertiary eye care hospital in Kolkata, West Bengal.

Eye diseases in childhood are important causes of medical consultation and it affects learning ability, adjustment in school and personality. To determine the pattern of ocular morbidity a cross-sectional observational study was conducted among 714 children, attending Ophthalmology department at a tertiary eye care center in Kolkata, West Bengal. All the children less than 15 years of age, attending in Unit II outpatient department were selected by complete enumeration method for duration of one year (January-December 2010). Distribution of association was analyzed by Chi-square test and difference between two proportions was calculated by z test for proportions. The common ocular morbidity were refractive errors (23.67%) followed by allergic conjunctivitis (17.23%), infection of the eye and adnexa (15.13%), ocular trauma (12.74%), and congenital eye diseases (13.59%). Majority of ocular morbidity is treatable and need early attention through eye screening cum intervention program beginning right from the childhood.

Using the DiCoT framework for integrated multimodal analysis in mixed-reality training environments.

Simulation-based training (SBT) programs are commonly employed by organizations to train individuals and teams for effective workplace cognitive and psychomotor skills in a broad range of applications. Distributed cognition has become a popular cognitive framework for the design and evaluation of these SBT environments, with structured methodologies such as Distributed Cognition for Teamwork (DiCoT) used for analysis. However, the analysis and evaluations generated by such distributed cognition frameworks require extensive domain-knowledge and manual coding and interpretation, and the analysis is primarily qualitative. In this work, we propose and develop the application of multimodal learning analysis techniques to SBT scenarios. Using these analysis methods, we can use the rich multimodal data collected in SBT environments to generate more automated interpretations of trainee performance that supplement and extend traditional DiCoT analysis. To demonstrate the use of these methods, we present a case study of nurses training in a mixed-reality manikin-based (MRMB) training environment. We show how the combined analysis of the video, speech, and eye-tracking data collected as the nurses train in the MRMB environment supports and enhances traditional qualitative DiCoT analysis. By applying such quantitative data-driven analysis methods, we can better analyze trainee activities online in SBT and MRMB environments. With continued development, these analysis methods could be used to provide targeted feedback to learners, a detailed review of training performance to the instructors, and data-driven evidence for improving the environment to simulation designers.

Identifying and describing subtypes of spontaneous empathic facial expression production in autistic adults.

BACKGROUND: It is unclear whether atypical patterns of facial expression production metrics in autism reflect the dynamic and nuanced nature of facial expressions across people or a true diagnostic difference. Furthermore, the heterogeneity observed across autism symptomatology suggests a need for more adaptive and personalized social skills programs. Towards this goal, it would be useful to have a more concrete and empirical understanding of the different expressiveness profiles within the autistic population and how they differ from neurotypicals. METHODS: We used automated facial coding and an unsupervised clustering approach to limit inter-individual variability in facial expression production that may have otherwise obscured group differences in previous studies, allowing an "apples-to-apples" comparison between autistic and neurotypical adults. Specifically, we applied k-means clustering to identify subtypes of facial expressiveness in an autism group (N = 27) and a neurotypical control group (N = 57) separately. The two most stable clusters from these analyses were then further characterized and compared based on their expressiveness and emotive congruence to emotionally charged stimuli. RESULTS: Our main finding was that a subset of autistic adults in our sample show heightened spontaneous facial expressions irrespective of image valence. We did not find evidence for greater incongruous (i.e., inappropriate) facial expressions in autism. Finally, we found a negative trend between expressiveness and emotion recognition within the autism group. CONCLUSION: The results from our previous study on self-reported empathy and current expressivity findings point to a higher degree of facial expressions recruited for emotional resonance in autism that may not always be adaptive (e.g., experiencing similar emotional resonance regardless of valence). These findings also build on previous work indicating that facial expression intensity is not diminished in autism and suggest the need for intervention programs to focus on emotion recognition and social skills in the context of both negative and positive emotions.

Opportunities and Challenges in Developing Technology-Based Social Skills Interventions for Adolescents with Autism Spectrum Disorder: A Qualitative Analysis of Parent Perspectives.

Interest continues to be high in technology-based interventions for individuals with autism spectrum disorder (ASD). Understanding the preferences and challenges of technology use among individuals with ASD can inform the design of such interventions. Through 18 interviews with parents, we used an iterative inductive-deductive approach to qualitative analysis and explored uses of technology for social skills development among adolescents with ASD. Our findings include parents' observations about their adolescent's preferences in types of technology devices and digital content, as well as both positive and negative effects of technology use on mood and behavior. Parents highlighted several avenues of technological preferences and risks that may inform intervention design, enhance user engagement, and capitalize on users' strengths while buttressing areas for growth.

Surface instability of a thin electrolyte film undergoing coupled electroosmotic and electrophoretic flows in a microfluidic channel.

We consider the stability of a thin liquid film with a free charged surface resting on a solid charged substrate by performing a general Orr-Sommerfeld (O-S) analysis complemented by a long-wave (LW) analysis. An externally applied field generates an electroosmotic flow (EOF) near the solid substrate and an electrophoretic flow (EPF) at the free surface. The EPF retards the EOF when both the surfaces have the same sign of the potential and can even lead to the flow reversal in a part of the film. In conjunction with the hydrodynamic stress, the Maxwell stress is also considered in the problem formulation. The electrokinetic potential at the liquid-air and solid-liquid interfaces is modelled by the Poisson-Boltzmann equation with the Debye-Hückel approximation. The O-S analysis shows a finite-wavenumber shear mode of instability when the inertial forces are strong and an LW interfacial mode of instability in the regime where the viscous force dominates. Interestingly, both the modes are found to form beyond a critical flow rate. The shear (interfacial) mode is found to be dominant when the film is thick (thin), the electric field applied is strong (weak), and the zeta-potentials on the liquid-air and solid-liquid interfaces are high (small). The LW analysis predicts the presence of the interfacial mode, but fails to capture the shear mode. The change in the propagation direction of the interfacial mode with the zeta-potential is predicted by both O-S and LW analyses. The parametric range in which the LW analysis is valid is thus demonstrated.

Instability and dewetting of ultrathin solid viscoelastic films on homogeneous and heterogeneous substrates.

Instability and dewetting engendered by the van der Waals force in soft thin (<100 nm) linear viscoelastic solid (e.g., elastomeric gel) films on uniform and patterned surfaces are explored. Linear stability analysis shows that, although the elasticity of the film controls the onset of instability and the corresponding critical wavelength, the dominant length-scale remains invariant with the elastic modulus of the film. The unstable modes are found to be long-wave, for which a nonlinear long-wave analysis and simulations are performed to uncover the dynamics and morphology of dewetting. The stored elastic energy slows down the temporal growth of instability significantly. The simulations also show that a thermodynamically stable film with zero-frequency elasticity can be made unstable in the presence of physico-chemical defects on the substrate and can follow an entirely different pathway with far fewer holes as compared to the viscous films. Further, the elastic restoring force can retard the growth of a depression adjacent to the hole-rim and thus suppress the formation of satellite holes bordering the primary holes. These findings are in contrast to the dewetting of viscoelastic liquid films where nonzero frequency elasticity accelerates the film rupture and promotes the secondary instabilities. Thus, the zero-frequency elasticity can play a major role in imposing a better-defined long-range order to the dewetted structures by arresting the secondary instabilities.