An Euler-Bernoulli-type beam model of the vocal folds for describing curved and incomplete glottal closure patterns.

Incomplete glottal closure is a laryngeal configuration wherein the glottis is not fully obstructed prior to phonation. It has been linked to inefficient voice production and voice disorders. Various incomplete glottal closure patterns can arise and the mechanisms driving them are not well understood. In this work, we introduce an Euler-Bernoulli composite beam vocal fold (VF) model that produces qualitatively similar incomplete glottal closure patterns as those observed in experimental and high-fidelity numerical studies, thus offering insights into the potential underlying physical mechanisms. Refined physiological insights are pursued by incorporating the beam model into a VF posturing model that embeds the five intrinsic laryngeal muscles. Analysis of the combined model shows that co-activating the lateral cricoarytenoid (LCA) and interarytenoid (IA) muscles without activating the thyroarytenoid (TA) muscle results in a bowed (convex) VF geometry with closure at the posterior margin only; this is primarily attributed to the reactive moments at the anterior VF margin. This bowed pattern can also arise during VF compression (due to extrinsic laryngeal muscle activation for example), wherein the internal moment induced passively by the TA muscle tissue is the predominant mechanism. On the other hand, activating the TA muscle without incorporating other adductory muscles results in anterior and mid-membranous glottal closure, a concave VF geometry, and a posterior glottal opening driven by internal moments induced by TA muscle activation. In the case of initial full glottal closure, the posterior cricoarytenoid (PCA) muscle activation cancels the adductory effects of the LCA and IA muscles, resulting in a concave VF geometry and posterior glottal opening. Furthermore, certain maneuvers involving co-activation of all adductory muscles result in an hourglass glottal shape due to a reactive moment at the anterior VF margin and moderate internal moment induced by TA muscle activation. These findings have implications regarding potential laryngeal maneuvers in patients with voice disorders involving imbalances or excessive tension in the laryngeal muscles such as muscle tension dysphonia.

An Euler-Bernoulli-Type Beam Model of the Vocal Folds for Describing Curved and Incomplete Glottal Closure Patterns.

Incomplete glottal closure is a laryngeal configuration wherein the glottis is not fully obstructed prior to phonation. In this work, we introduce an Euler-Bernoulli composite beam vocal fold (VF) model that produces qualitatively similar incomplete glottal closure patterns as those observed in experimental and high-fidelity numerical studies, thus offering insights in to the potential underlying physical mechanisms. Refined physiological insights are pursued by incorporating the beam model into a VF posturing model that embeds the five intrinsic laryngeal muscles. Analysis of the combined model shows that co-activating the lateral cricoarytenoid (LCA) and interarytenoid (IA) muscles without activating the thyroarytenoid (TA) muscle results in a bowed (convex) VF geometry with closure at the posterior margin only; this is primarily attributed to the reactive moments at the anterior VF margin. This bowed pattern can also arise during VF compression (due to extrinsic laryngeal muscle activation for example), wherein the internal moment induced passively by the TA muscle tissue is the predominant mechanism. On the other hand, activating the TA muscle without incorporating other adductory muscles results in anterior and mid-membranous glottal closure, a concave VF geometry, and a posterior glottal opening driven by internal moments induced by TA muscle activation. In the case of initial full glottal closure, the posterior cricoarytenoid (PCA) muscle activation cancels the adductory effects of the LCA and IA muscles, resulting in a concave VF geometry and posterior glottal opening. Furthermore, certain maneuvers involving co-activation of all adductory muscles result in an hourglass glottal shape due to a reactive moment at the anterior VF margin and moderate internal moment induced by TA muscle activation.

Modeling the influence of the extrinsic musculature on phonation.

Neck muscles play important roles in various physiological tasks, including swallowing, head stabilization, and phonation. The mechanisms by which neck muscles influence phonation are not well understood, with conflicting reports on the change in fundamental frequency for ostensibly the same neck muscle activation scenarios. In this work, we introduce a reduced-order muscle-controlled vocal fold model, comprising both intrinsic muscle control and extrinsic muscle effects. The model predicts that when the neck muscles pull the thyroid cartilage in the superior-anterior direction (with a sufficiently large anterior component), inferior direction, or inferior-anterior direction, tension in the vocal folds increases, leading to fundamental frequency rise during sustained phonation. On the other hand, pulling in the superior direction, superior-posterior direction, or inferior-posterior direction (with a sufficiently large posterior component) tends to decrease vocal fold tension and phonation fundamental frequency. Varying the pulling force location alters the posture and phonation biomechanics, depending on the force direction. These findings suggest potential roles of particular neck muscles in modulating phonation fundamental frequency, with implications for vocal hyperfunction.

Exploring the mechanics of fundamental frequency variation during phonation onset.

Fundamental frequency patterns during phonation onset have received renewed interest due to their promising application in objective classification of normal and pathological voices. However, the associated underlying mechanisms producing the wide array of patterns observed in different phonetic contexts are not yet fully understood. Herein, we employ theoretical and numerical analyses in an effort to elucidate the potential mechanisms driving opposing frequency patterns for initial/isolated vowels versus vowels preceded by voiceless consonants. Utilizing deterministic lumped-mass oscillator models of the vocal folds, we systematically explore the roles of collision and muscle activation in the dynamics of phonation onset. We find that an increasing trend in fundamental frequency, as observed for initial/isolated vowels, arises naturally through a progressive increase in system stiffness as collision intensifies as onset progresses, without the need for time-varying vocal fold tension or changes in aerodynamic loading. In contrast, reduction in cricothyroid muscle activation during onset is required to generate the decrease in fundamental frequency observed for vowels preceded by voiceless consonants. For such phonetic contexts, our analysis shows that the magnitude of reduction in the cricothyroid muscle activation and the activation level of the thyroarytenoid muscle are potential factors underlying observed differences in (relative) fundamental frequency between speakers with healthy and hyperfunctional voices. This work highlights the roles of sometimes competing laryngeal factors in producing the complex array of observed fundamental frequency patterns during phonation onset.

Modeling the influence of COVID-19 protective measures on the mechanics of phonation.

In an effort to mitigate the 2019 novel coronavirus disease pandemic, mask wearing and social distancing have become standard practices. While effective in fighting the spread of the virus, these protective measures have been shown to deteriorate speech perception and sound intensity, which necessitates speaking louder to compensate. The goal of this paper is to investigate via numerical simulations how compensating for mask wearing and social distancing affects measures associated with vocal health. A three-mass body-cover model of the vocal folds (VFs) coupled with the sub- and supraglottal acoustic tracts is modified to incorporate mask and distance dependent acoustic pressure models. The results indicate that sustaining target levels of intelligibility and/or sound intensity while using these protective measures may necessitate increased subglottal pressure, leading to higher VF collision and, thus, potentially inducing a state of vocal hyperfunction, a progenitor to voice pathologies.

Monolayer Graphene Radiation Sensor with Backend RF Ring Oscillator Transducer.

This paper proposes a new graphene gamma- and beta-radiation sensor with a backend RF ring oscillator transducer employed to convert the change in the graphene resistivity due to ionizing irradiation into a frequency output. The sensor consists of a CVD monolayer of graphene grown on a copper substrate, with an RF ring oscillator readout circuit in which the percentage change in frequency is captured versus the change in radiation dose. The novel integration of the RF oscillator transducer with the graphene monolayer results in high average sensitivity to gamma irradiation up to 3.82 kΩ/kGy, which corresponds to a percentage change in frequency of 7.86% kGy-1 in response to cumulative gamma irradiation ranging from 0 to 1 kGy. The new approach helps to minimize background environmental effects (e.g., due to light and temperature), leading to an insignificant error in the output change in frequency of the order of 0.46% when operated in light versus dark conditions. The uncertainty in readings due to background light was analyzed, and the error in the resistance was found to be of the order of 1.34 Ω, which confirms the high stability and selectivity of the proposed sensor under different background effects. Furthermore, the evolution of the graphene's lattice defect density due to radiation was observed using Raman spectroscopy and SEM, indicating a lattice defect density of up to 1.780 × 1011/cm2 at 1 kGy gamma radiation, confirming the increase in the graphene resistance and proving the graphene's sensitivity. In contrast, the graphene's defect density in response to beta radiation was 0.683 × 1011/cm2 at 3 kGy beta radiation, which is significantly lower than the gamma effects. This can be attributed to the lower p-doping effect caused by beta irradiation in ambient conditions, compared with that caused by gamma irradiation. Morphological analysis was used to verify the evolution of the microstructural defects caused by ionizing irradiation. The proposed sensor monitors the low-to-medium cumulative range of ionizing radiations ranging from 0 to 1 kGy for gamma radiation and 0 to 9 kGy for beta radiation, with high resolution and selectivity, filling the research gap in the study of graphene-based radiation sensors at low-to-medium ionizing radiation doses. This range is essential for the pharmaceutical and food industries, as it spans the minimum range for affecting human health, causing cancer and DNA damage.

Physics of phonation offset: Towards understanding relative fundamental frequency observations.

Relative fundamental frequency (RFF) is a promising assessment technique for vocal pathologies. Herein, we explore the underlying laryngeal factors dictating RFF behaviours during phonation offset. To gain physical insights, we analyze a simple impact oscillator model and follow that with a numerical study using the well-established body-cover model of the vocal folds (VFs). Study of the impact oscillator suggests that the observed decrease in fundamental frequency during offset is due, at least in part, to the increase in the neutral gap between the VFs during abduction and the concomitant decrease in collision forces. Moreover, the impact oscillator elucidates a correlation between sharper drops in RFF and increased stiffness of the VFs, supporting experimental RFF studies. The body-cover model study further emphasizes the correlation between the drops in RFF and collision forces. The numerical analysis also illustrates the sensitivity of RFF to abduction initiation time relative to the phase of the phonation cycle, and the abduction period length. In addition, the numerical simulations display the potential role of the cricothyroid muscle to mitigate the RFF reduction. Last, simplified models of phonotraumatic vocal hyperfunction are explored, demonstrating that the observed sharper drops in RFF are associated with increased pre-offset collision forces.

Shape Memory Alloy Capsule Micropump for Drug Delivery Applications.

We introduce a shape memory alloy (SMA) actuated micropump optimized for drug delivery applications. The proposed novel design integrates a built-in replaceable drug reservoir within the pump package forming a self-contained preloaded capsule pump with an overall pump volume of 424.7 µL. The new design results in a compact, simple, and inexpensive micropump and reduces the probability of contamination with attained almost zero dead volume values. The pump consists of NiTi-alloy SMA wires coiled on a flexible polymeric enclosure and actuated by joule heating. Unlike diaphragm and peristaltic SMA micropump designs that actuate transversely, our design is actuated longitudinally along the direction of the highest mechanical compliance resulting in large strokes in the order of 5.6 mm at 27% deflection ratio, actuation speed up to 11 mm/s, and static head pressures up to 14 kPa (105 mmHg) at 7.1 W input power; thus, high throughputs exceeding 2524 µL/min under free convention conditions could be achieved. A model was developed to optimize the pump's geometrical parameters and the enclosure material. The model concluded that low stiffness enclosure material combined with thinner SMA wire diameter would result in the maximum deflection at the lowest power rating. To prove its viability for drug delivery applications, the pump was operated at a constant discharge volume at a relatively constant static head pressure. Furthermore, a design of bicuspid-inspired polymeric check-valves is presented and integrated onto the pump to regulate the flow. Since the built-in reservoir is replaceable, the pump capsule can be reused multiple times and for multiple drug types.

High-volume, multilevel local anesthetics-Epinephrine infiltration in kyphoscoliosis surgery: Intra and postoperative analgesia.

BACKGROUND AND AIMS: Local anesthetic (LA) infiltration is one of the analgesic techniques employed during scoliosis correction surgery. However, its efficacy is controversial. In the present study for optimizing analgesia using the infiltration technique, we proposed two modifications; first is the preemptive use of high volume infiltration, second is applying three anatomical multilevel infiltrations involving the sensory, motor, and sympathetic innervations consecutively. MATERIAL AND METHODS: This prospective study involved 48 patients randomized into two groups. After general anesthesia (GA), the infiltration group (I) received bupivacaine 0.5% 2 mg/kg, lidocaine 5 mg/kg, and epinephrine 5 mcg/mL of the total volume (100 mL per 10 cm of the wound length) as a preemptive infiltration at three levels; subcutaneous, intramuscular, and the deep neural paravertebral levels, timed before skin incision, muscular dissection, and instrumentation consecutively. The control group (C) received normal saline in the same manner. Data were compared by Mann-Whitney, Chi-square, and t-test as suitable. RESULTS: Intraoperatively, the LA infiltration reduced fentanyl, atracurium, isoflurane, nitroglycerine, and propofol consumption. Postoperatively, there was a 41% reduction in morphine consumption, longer time to the first analgesic request, lower VAS, early ambulation, and hospital discharge with high-patient satisfaction. CONCLUSION: The preemptive, high-volume, multilevel infiltration provided a significant intra and postoperative analgesia in scoliosis surgery.

Performance-Enhanced Non-Enzymatic Glucose Sensor Based on Graphene-Heterostructure.

Non-enzymatic glucose sensing is a crucial field of study because of the current market demand. This study proposes a novel design of glucose sensor with enhanced selectivity and sensitivity by using graphene Schottky diodes, which is composed of graphene (G)/platinum oxide (PtO)/n-silicon (Si) heterostructure. The sensor was tested with different glucose concentrations and interfering solutions to investigate its sensitivity and selectivity. Different structures of the device were studied by adjusting the platinum oxide film thickness to investigate its catalytic activity. It was found that the film thickness plays a significant role in the efficiency of glucose oxidation and hence in overall device sensitivity. 0.8-2 µA output current was obtained in the case of 4-10 mM with a sensitivity of 0.2 A/mM.cm2. Besides, results have shown that 0.8 A and 15 A were obtained by testing 4 mM glucose on two different PtO thicknesses, 30 nm and 50 nm, respectively. The sensitivity of the device was enhanced by 150% (i.e., up to 30 A/mM.cm2) by increasing the PtO layer thickness. This was attributed to both the increase of the number of active sites for glucose oxidation as well as the increase in the graphene layer thickness, which leads to enhanced charge carriers concentration and mobility. Moreover, theoretical investigations were conducted using the density function theory (DFT) to understand the detection method and the origins of selectivity better. The working principle of the sensors puts it in a competitive position with other non-enzymatic glucose sensors. DFT calculations provided a qualitative explanation of the charge distribution across the graphene sheet within a system of a platinum substrate with D-glucose molecules above. The proposed G/PtO/n-Si heterostructure has proven to satisfy these factors, which opens the door for further developments of more reliable non-enzymatic glucometers for continuous glucose monitoring systems.

High-volume, Multilevel Local Anesthetics-Epinephrine Infiltration in Kyphoscoliosis Surgery: Blood Conservation.

INTRODUCTION: Scoliosis surgery is usually associated with severe bleeding. Various systemic strategies for blood conservation were applied, while the local techniques get less attention. The preemptive use of sufficient volume for proper tissue infiltration at two levels was applied. The local epinephrine may control bleeding without reliance upon deliberate hypotension, permitting a higher tissue perfusion. MATERIALS AND METHODS: This prospective study included 46 patients scheduled for posterior spinal fusion for scoliosis correction. Patients were randomized into two groups. group I received a cocktail of high volume (100 ml/each 10 cm of wound length) of local anesthetics and epinephrine tumescent infiltration at the subcutaneous (SC) followed by intramuscular level bilaterally. Group C received saline infiltration in the same technique. Statistically, data were analyzed according to its distribution using the t-test, Mann-Whitney, and Chi-square tests as appropriate. RESULTS: There was a significant reduction in blood loss (38%), reduced blood and fluid transfusion (36% and 23%), and reduced operative time (23%), with higher surgeon satisfaction. The surgical field visibility (Fromme's scale) was much better during SC and muscular dissection in Group I, while it was fair during the bony work. The satisfactory field in spite of higher mean blood pressure in Group I greatly omitted the reliance upon deliberate hypotension. CONCLUSION: The high-volume multilevel infiltration of epinephrine cocktail can provide a significant blood and operative time conservation in kyphoscoliosis surgery.