RESUMO
Electrospinning has been applied to produce ceramic fibers using sol gel-based spinning solutions consisting of ceramic precursors, a solvent, and a polymer to control the viscosity of the solution. However, the addition of polymers to the spinning solution makes the process more complex, increases the processing time, and results in porous mechanically weak ceramic fibers. Herein, we develop a coelectrospinning technique, where a nonspinnable sol (<10 mPa s) consisting of only the ceramic precursor(s) and solvent(s) is encapsulated inside a polymeric shell, forming core-shell precursor fibers that are further calcined into ceramic fibers with reduced porosity, decreased surface defects, uniform crystal packing, and controlled diameters. We demonstrate the versatility of this method by applying it to a series of nonspinnable sols and creating high-quality ceramic fibers containing TiO2, ZrO2, SiO2, and Al2O3. The polycrystalline TiO2 fibers possess excellent flexibility and a high Young's modulus reaching 54.3 MPa, solving the extreme brittleness problem of the previously reported TiO2 fibers. The single-component ZrO2 fibers exhibit a Young's modulus and toughness of 130.5 MPa and 11.9 KJ/m3, respectively, significantly superior to the counterparts prepared by conventional sol-gel electrospinning. We also report the creation of ceramic fibers in micro- and nanospring morphologies and examine the formation mechanisms using thermomechanical simulations. The fiber assemblies constructed by the helical fibers exhibit a density-normalized toughness of 3.5-5 times that of the straight fibers due to improved fracture strain. This work expands the selection of the electrospinning solution and enables the development of ceramic fibers with more attractive properties.
RESUMO
INTRODUCTION: Human development includes lots of physical and emotional changes. The human voice depends on age. Voice production is a complex physiological and acoustic phenomenon that depends on many factors such as structure, hormone level, degree of fatigue or nutrition and hydration of the body, systemic diseases, and emotional state. All these factors can be present in anorexia nervosa (AN), such as excessive weight loss, generated hydro-electrolytic changes, nutritional deficiencies, hormonal disturbances in the function of the hypothalamic-pituitary-adrenal axis, the hypothalamic-pituitary-thyroid axis, the hypothalamic-pituitary-ovarian axis, and emotional distress. The prevalence of AN ranges between 0.3% and 3%, and it is the third most common chronic disease affecting adolescent girls. However, voice changes related to AN have not been fully investigated. OBJECTIVE: The purpose of this study was to evaluate the impact of AN on age-related changes in the voice of adolescent women-before and after puberty, particularly through acoustic analysis. An additional objective was to evaluate estrogen substitution in female patients with AN in order to investigate their effect on voice condition. MATERIALS AND METHODS: 126 girls diagnosed with AN (15.32 ± 2.12 years, range 12-19, BMI = 14.38 ± 1.67), were assessed for the condition of the voice such as perceptual voice evaluation on the GRBAS scale, maximal phonation time (MPT), laryngoscopy, with special attention to voice acoustic analysis-Multi-Dimensional Voice Program (MDVP). The control group (B) included 93 girls without eating disturbances (aged 12-19, mean age 15.52 ± 2.40, BMI = 21.50 ± 1.54). Perceptual voice assessment, aerodynamic test MPT, and acoustic parameters were analyzed in age groups (≤16 years and >16 years). The human vocal tract is sensitive to sex hormones, so the analysis was carried out in the group up to the age of 16 and above 16 to check possible effects. RESULTS: GRBAS scale was higher in girls with AN compared to the control group for breathiness (B) (P = 0.0002) and asthenia (A) (P < 0.05). The median GRBAS scale for the older group of anorexic women was the highest (2.0). The mean MPT for group A was significantly lower (15.40 ± 3.51 seconds). Comparing age subgroups there was a prolongation of MPT in the healthy group (in groups ≤16 years and >16 years respectively 21.13 seconds versus 25.40 seconds) and a shortening in the anorectic group (≤16 years versus >16 years: 17.06 seconds versus 14.17 seconds). There was no difference between groups A and C up to 16 years of age, but above 16 years of age appeared (14.17 seconds versus 25.40 seconds). Acoustic analysis revealed lower F0 values in group A and C in older subgroups (215,85 Hz versus 236,01 Hz-statistically significant), as well as between subgroups both groups (A: 251,38 Hz versus 215,85 Hz; C: 248,20 Hz versus 236,01 Hz). A narrowing of the vocal range in girls over 16 years in group A was observed. There were no statistically significant differences in F0 between subgroups ≤16 years in groups A and C (251.38 Hz versus 248.20 Hz). The ENT study found that more than half of the girls (54.55%) over the age of 16 who took hormone supplementation manifested laryngeal structure that was normal for their age, there was no effect of hormone supplementation on any of the MDVP parameters between the drug-taking and non-drug-taking groups. CONCLUSIONS: The acoustic results of the voice in MDVP measurements in adolescent women with AN are not within the normal range and do not mimic the normal developmental changes of the voice. The most important acoustic characteristics of the voice are changes in the fundamental frequency F0 and the range of the voice tended to be more severe in anorectic women >16 years of age and to increase with age, indicating a possible cumulative effect of malnutrition-related disorders as well as hormonal dysfunctions. MDVP can be considered a simple, non-invasive method of assessing the voice organ in AN. MPT differentiated the study groups well: statistically significant differences were noted both between the groups, as well as between age groups. There was no significant effect of oral hormone supplementation on any parameters of the voice. In conclusion, body mass and fat volume in AN may be related to voice production/physiology, affecting voice quality, voice acoustic parameters, voice aerodynamics, and phonatory range in an age-dependent manner. Future studies are needed to assess the long-term efficacy of estrogen treatment in AN.