Does Open Rhinoplasty Alter Voice Quality?

PURPOSE: The voice can change after upper airway manipulation. The present study evaluated voice change after open rhinoplasty. MATERIALS AND METHODS: The present cross-sectional study was conducted on patients undergoing open rhinoplasty. Three acoustic parameters (frequency, bandwidth, and amplitude) were evaluated before open rhinoplasty and then 3, 7, and 10 months after the operation. Patients' sounds when pronouncing M, N, and A were examined. Acoustic factors were measured at the first and second nasal murmurs. Time was a predictive factor and multiple acoustic parameters were the outcome of the study. RESULTS: Twenty-five patients were studied. Amplitude and bandwidth decreased, whereas frequency increased, when pronouncing the vowel A after rhinoplasty. In contrast, for consonants M and N, amplitude decreased, whereas bandwidth and frequency increased, after rhinoplasty. CONCLUSION: Open rhinoplasty seems to affect voice quality. Open rhinoplasty altered the frequency, amplitude, and bandwidth of vowel and consonant sounds during 10-month follow-up.

Synthesis of Super-Long Carbon Nanotubes from Cellulosic Biomass under Microwave Radiation.

This study reports a novel method for synthesizing super-long carbon nanotubes (SL-CNTs) from cellulose via a microwave treatment process without an external catalyst. CNTs with a length of 0.7-2 mm were obtained via microwave treatment of cellulose biochar temperatures of 1200-1400 °C. Scanning electron microscope (SEM), together with high-resolution transmission electron microscope (HRTEM) results, were used to investigate the changes in the length and morphology of CNTs with respect to treatment temperature. The morphology of CNTs changed from twisted, curved, and threadlike to straight structures. The average length of CNTs after microwave pyrolysis at 600 °C was approximately 600-1800 nm, which after microwave treatment at 1300 °C and 1400 °C increased to about 1-2 mm. X-ray diffractometer (XRD) results confirmed the crystalline structure of CNTs with two prominent peaks at 2θ = 26.3° and 2θ = 43.2° correlating with the graphite (002) and (100) reflections. The ID/IG ratio obtained from Raman spectra of the CNTs decreased to the lowest value of 0.84 after microwave treatment at 1400 °C, implying a high degree of carbon order. The presence of Fe and trace amounts of other elements were confirmed by the energy-dispersive X-ray spectrometer (EDS) and were postulated to have catalyzed the growth of CNTs. The mechanism of the SL-CNTs growth under microwave treatment was proposed and discussed.

Structural Investigation of the Synthesized Few-Layer Graphene from Coal under Microwave.

This study focused on the structural investigation of few-layer graphene (FLG) synthesis from bituminous coal through a catalytic process under microwave heat treatment (MW). The produced FLG has been examined by Raman spectroscopy, XRD, TEM, and AFM. Coal was activated using the potassium hydroxide activation process. The FLG synthesis processing duration was much faster requiring only 20 min under the microwave radiation. To analyse few-layer graphene samples, we considered the three bands, i.e., D, G, and 2D, of Raman spectra. At 1300 °C, the P10% Fe sample resulted in fewer defects than the other catalyst percentages sample. The catalyst percentages affected the structural change of the FLG composite materials. In addition, the Raman mapping showed that the catalyst loaded sample was homogeneously distributed and indicated a few-layer graphene sheet. In addition, the AFM technique measured the FLG thickness around 4.5 nm. Furthermore, the HRTEM images of the P10% Fe sample contained a unique morphology with 2-7 graphitic layers of graphene thin sheets. This research reported the structural revolution with latent feasibility of FLG synthesis from bituminous coal in a wide range.

Structure of Coal-Derived Metal-Supported Few-Layer Graphene Composite Materials Synthesized Using a Microwave-Assisted Catalytic Graphitization Process.

Metal-supported few-layer graphene (FLG) was synthesized via microwave-assisted catalytic graphitization owing to the increasing demand for it and its wide applications. In this study, we quickly converted earth-abundant and low-cost bituminous coal to FLG over Fe catalysts at a temperature of 1300 °C. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and N2 adsorption-desorption experiments were performed to analyze the fabricated metal-supported FLG. The results indicated that the microwave-irradiation temperature at a set holding-time played a critical role in the synthesis of metal-supported FLG. The highest degree of graphitization and a well-developed pore structure were fabricated at 1300 °C using a S10% Fe catalyst for 20 min. High-resolution transmission electron microscopy analysis confirmed that the metal-supported FLG fabricated via microwave-assisted catalytic graphitization consisted of 3-6 layers of graphene nanosheets. In addition, the 2D band at 2700 cm-1 in the Raman spectrum of the fabricated metal-supported FLG samples were observed, which indicated the presence of few-layer graphene structure. Furthermore, a mechanism was proposed for the microwave-assisted catalytic graphitization of bituminous coal. Here, we developed a cost-effective and environmental friendly metal-supported FLG method using a coal-based carbonaceous material.

Microwave-Assisted Coal-Derived Few-Layer Graphene as an Anode Material for Lithium-Ion Batteries.

A few-layer graphene (FLG) composite material was synthesized using a rich reservoir and low-cost coal under the microwave-assisted catalytic graphitization process. X-ray diffraction, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used to evaluate the properties of the FLG sample. A well-developed microstructure and higher graphitization degree were achieved under microwave heating at 1300 °C using the S5% dual (Fe-Ni) catalyst for 20 min. In addition, the synthesized FLG sample encompassed the Raman spectrum 2D band at 2700 cm-1, which showed the existence of a few-layer graphene structure. The high-resolution TEM (transmission electron microscopy) image investigation of the S5% Fe-Ni sample confirmed that the fabricated FLG material consisted of two to seven graphitic layers, promoting the fast lithium-ion diffusion into the inner surface. The S5% Fe-Ni composite material delivered a high reversible capacity of 287.91 mAhg-1 at 0.1 C with a higher Coulombic efficiency of 99.9%. In contrast, the single catalyst of S10% Fe contained a reversible capacity of 260.13 mAhg-1 at 0.1 C with 97.96% Coulombic efficiency. Furthermore, the dual catalyst-loaded FLG sample demonstrated a high capacity-up to 95% of the initial reversible capacity retention-after 100 cycles. This study revealed the potential feasibility of producing FLG materials from bituminous coal used in a broad range as anode materials for lithium-ion batteries (LIBs).

Catalytic reforming of palm kernel shell microwave pyrolysis vapors over iron-loaded activated carbon: Enhanced production of phenol and hydrogen.

This study addresses the in-situ microwave catalytic reforming of volatile matter from palm kernel shell (PKS) over iron-loaded activated carbon (Fe/AC) catalysts. The impacts of catalyst composition on the secondary gas-phase reactions and distribution of products were studied at 500 °C. It was found that the Fe/AC catalyst promoted the yield of light gases. Using the 1%-Fe/AC catalyst, the yield of gaseous fraction peaked at 37.09 wt%. The selectivity of the deoxygenated products was promoted in the presence of Fe. Catalytic reforming of PKS pyrolysis vapors over Fe/AC drastically enhanced the generation of phenol and H2, the concentrations of which reached 75.09 area% and 75.12 vol%, respectively. Catalytic pyrolysis of syringol and guaiacol as model compounds showed that Fe/AC catalyst promoted the demethoxylation and deoxygenation reactions to selectively generate phenol which was explained by oxophilic reactivity of the active Fe sites.

Mechanistic Study on the Removal of NO2 from Flue Gas Using Novel Ethylene Glycol-tetrabutylammonium Bromide Deep Eutectic Solvents.

The removal of NO x (approximately 90% of which is NO) from flue gas is a crucial process for clean power generation from coal combustion. Oxidation of NO to NO2 followed by NO2 absorption using sorbents is considered to be a promising technology alternative to selective catalytic reduction (SCR). This study investigated the absorption of NO2 in flue gas by ethylene glycol (EG)-tetrabutylammonium bromide (TBAB) deep eutectic solvents (DESs) under a range of experimental conditions. The effects of experimental conditions including molar ratio of EG to TBAB, operating temperature, residence time, and the O2 and steam partial pressure in the flue gas on the denitrification performance of EG-TBAB DESs were systematically analyzed. The concentrations of NO2 in the inlet and outlet were evaluated using a flue gas analyzer. The chemical structure changes of DESs after denitrification were characterized using Fourier transform infrared (FT-IR) spectroscopy. The obtained analysis signified that maximum denitrification efficiency and capacity were achieved at a EG/TBAB molar ratio of 5:1, 50 °C, and 6 s residence time. EG-TBAB DESs were able to maintain a stable denitrification performance after five absorption-desorption cycles. The results of quantum chemical calculation and 1H NMR spectra of EG-TBAB DES show that bromide anions in the EG-TBAB DES maintained strong interactions with NO2 via hydrogen bonding, leading to increased NO2 adsorption. The presence of O2 and steam in the flue gas improved the absorption of NO2 in EG-TBAB DESs due to chemical reactions and formation of nitrate.

Pressurized entrained-flow pyrolysis of microalgae: Enhanced production of hydrogen and nitrogen-containing compounds.

Pressurized entrained-flow pyrolysis of Chlorella vulgaris microalgae was investigated. The impact of pressure on the yield and composition of pyrolysis products were studied. The results showed that the concentration of H2 in bio-gas increased sharply with increasing pyrolysis pressure, while those of CO, CO2, CH4, and C2H6 were dramatically decreased. The concentration of H2 reached 88.01 vol% in bio-gas at 900 °C and 4 MPa. Higher pressures promoted the hydrogen transfer to bio-gas. The bio-oils derived from pressurized pyrolysis were rich in nitrogen-containing compounds and PAHs. The highest concentration of nitrogen-containing compounds in bio-oil was achieved at 800 °C and 1 MPa. Increasing pyrolysis pressure promoted the formation of nitrogen-containing compounds such as indole, quinoline, isoquinoline and phenanthridine. Higher pyrolysis pressures led to increased sphericity, enhanced swelling, and higher carbon order of bio-chars. Pressurized pyrolysis of biomass has a great potential for poly-generation of H2, nitrogen containing compounds and bio-char.

A review on the production of nitrogen-containing compounds from microalgal biomass via pyrolysis.

Nitrogen-containing compounds (NCCs) which may be produced from nitrogen-rich biomass such as microalgae, may find important biochemical and biomedical applications. This review summarizes the recent knowledge about the formation mechanism of NCCs during pyrolysis of microalgae. The key technical and biological aspects of microalgae and pyrolysis process parameters, which influence the formation of NCCs, have been analyzed. The mechanism of formation of NCCs such as indole, pyridine, amides, and nitriles during primary and secondary pyrolysis reactions are elaborated. It has been emphasized that the pyrolysis conditions and the use of catalysts had significant impacts on the yields and compositions of NCCs. The available information shows that the transformation of nitrogen and nitrogen functionalities during pyrolysis are strongly associated with the formation process of NCCs. The challenges in the development of pyrolysis technologies for the production of NCCs from microalgae are identified with future research needs identified.

Effects of pressure on morphology and structure of bio-char from pressurized entrained-flow pyrolysis of microalgae.

The present dataset describes the entrained-flow pyrolysis of Microalgae Chlorella vulgaris and the results obtained during bio-char characterization. The dataset includes a brief explanation of the experimental procedure, experimental conditions and the influence of pyrolysis conditions on bio-chars morphology and carbon structure. The data show an increase in sphericity and surface smoothness of bio-chars at higher pressures and temperatures. Data confirmed that the swelling ratio of bio-chars increased with pressure up to 2.0 MPa. Consequently, changes in carbon structure of bio-chars were investigated using Raman spectroscopy. The data showed the increase in carbon order of chars at elevated pressures. Changes in the chemical structure of bio-char as a function of pyrolysis conditions were investigated using FTIR analysis.

The transformation of nitrogen during pressurized entrained-flow pyrolysis of Chlorella vulgaris.

The transformation of nitrogen in microalgae during entrained-flow pyrolysis of Chlorella vulgaris was systematically investigated at the temperatures of 600-900 °C and pressures of 0.1-4.0 MPa. It was found that pressure had a profound impact on the transformation of nitrogen during pyrolysis. The nitrogen retention in bio-char and its content in bio-oil reached a maximum value at 1.0 MPa. The highest conversion of nitrogen (50.25 wt%) into bio-oil was achieved at 1.0 MPa and 800 °C, which was about 7 wt% higher than that at atmospheric pressure. Higher pressures promoted the formation of pyrrolic-N (N-5) and quaternary-N (N-Q) compounds in bio-oil at the expense of nitrile-N and pyridinic-N (N-6) compounds. The X-Ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) results on bio-chars clearly evidenced the transformation of N-5 structures into N-6 and N-Q structures at elevated pressures. The nitrogen transformation pathways during pyrolysis of microalgae were proposed and discussed.

Formation of nitrogen-containing compounds during microwave pyrolysis of microalgae: Product distribution and reaction pathways.

The formation of nitrogen-containing compounds in bio-oil during microwave pyrolysis of Chlorella and Spirulina microalgae has been investigated in this study. Activated carbon (AC) and magnetite (Fe3O4) were used as microwave receptors during microwave pyrolysis experiments. It has been found that the use of Fe3O4 increased the total yield of bio-oil. The use of different microwave receptors did not seem to have affected the total yield of nitrogen-containing compounds in the bio-oil. However, Fe3O4 promoted the formation of nitrogen-containing aliphatics, thereby reducing the formation of nitrogen-containing aromatics. The use of AC promoted the dehydration reactions during amino acid decomposition, thereby enhancing the formation of nitrogen-containing aromatics during pyrolysis. From the gas chromatography-mass spectrometry (GC-MS) analysis results, the major high-value nitrogen-containing compounds in the pyrolysis bio-oil of Chlorella and Spirulina were identified as indole and dodecamide. The formation mechanisms of nitrogen-containing compounds were proposed and discussed.

An experimental study on the formation of methoxyaromatics during pyrolysis of Eucalyptus pulverulenta: Yields and mechanisms.

The production of bio-oil rich in methoxyaromatics during catalytic pyrolysis of Eucalyptus pulverulenta (EP) was studied using a fixed-bed reactor in the temperature range of 300-500°C and the bio-oil composition was analyzed by using a GC-MS. The results showed that the highest bio-oil yield of 38.45wt% was obtained at 400°C in the presence of Na2CO3, and the concentration of methoxyaromatics reached the maximum value of 63.4%(area) in the bio-oil. The major methoxyaromatics identified in bio-oil were guaiacol, syringol, 4-ethyl-2-methoxy phenol, and 1,2,4-trimethoxybenzene. The analysis of gaseous products indicated that CO2 was the major gas at low-temperatures and concentrations of H2 and CH4 increased with increasing pyrolysis temperature. Na2CO3 promoted the formation of methoxyaromatics, while NaOH seems to have enhanced the formation of phenolics. The mechanism of the formation of methoxyaromatics during pyrolysis of EP was proposed.

The effects of pore structure on the behavior of water in lignite coal and activated carbon.

The effects of physical structure (pore structure) on behavior of water in lignite coal and activated carbon (AC) samples were investigated by using Differential Scanning Calorimetry (DSC) and low-temperature X-ray diffraction (XRD) techniques. AC samples with different pore structures were prepared at 800°C in steam and the results were compared with that of parent lignite coal. The DSC results confirmed the presence of two types of freezable water that freeze at -8°C (free water) and -42°C (freezable bound water). A shift in peak position of free water (FW) towards lower temperature was observed in AC samples compared to the lignite coal with decreasing water loading. The amount of free water (FW) increased with increasing gasification conversion. The amounts of free and freezable bound water (FBW) in AC samples were calculated and correlated to pore volume and average pore size. The amount of FW in AC samples is well correlated to the pore volume and average pore size of the samples, while an opposite trend was observed for FBW. The low-temperature XRD analysis confirmed the existence of non-freezable water (NFW) in coal and AC with the boundary between the freezable and non-freezable water (NFW) determined.

Microwave-assisted catalytic pyrolysis of lignocellulosic biomass for production of phenolic-rich bio-oil.

Catalytic microwave pyrolysis of peanut shell (PT) and pine sawdust (PS) using activated carbon (AC) and lignite char (LC) for production of phenolic-rich bio-oil and nanotubes was investigated in this study. The effects of process parameters such as pyrolysis temperature and biomass/catalyst ratio on the yields and composition of pyrolysis products were investigated. Fast heating rates were achieved under microwave irradiation conditions. Gas chromatography-mass spectrometry (GC-MS) analysis of bio-oil showed that activated carbon significantly enhanced the selectivity of phenolic compounds in bio-oil. The highest phenolics content in the bio-oil (61.19 %(area)) was achieved at 300°C. The selectivity of phenolics in bio-oil was higher for PT sample compared to that of PS. The formation of nanotubes in PT biomass particles was observed for the first time in biomass microwave pyrolysis.

Production of phenol-rich bio-oil during catalytic fixed-bed and microwave pyrolysis of palm kernel shell.

Catalytic fixed-bed and microwave pyrolysis of palm kernel shell using activated carbon (AC) and lignite char (LC) as catalysts and microwave receptors are investigated. The effects of process parameters including temperature and biomass:catalyst ratio on the yield and composition of pyrolysis products were studied. The addition of catalyst increased the bio-oil yield, but decreased the selectivity of phenol in fixed-bed. Catalytic microwave pyrolysis of PKS significantly enhanced the selectivity of phenol production. The highest concentration of phenol in bio-oil of 64.58 %(area) and total phenolics concentration of 71.24 %(area) were obtained at 500°C using AC. Fourier transform infrared spectroscopy (FTIR) results indicated that concentration of OH, CH, CO and CO functional groups in char samples decreased after pyrolysis. Scanning electron microscopy (SEM) analysis clearly indicated the development of liquid phase in biomass particles during microwave pyrolysis, and the mechanism is also discussed.

Combustion characteristics and air pollutant formation during oxy-fuel co-combustion of microalgae and lignite.

Oxy-fuel combustion of solid fuels is seen as one of the key technologies for carbon capture to reduce greenhouse gas emissions. The combustion characteristics of lignite coal, Chlorella vulgaris microalgae, and their blends under O2/N2 and O2/CO2 conditions were studied using a Thermogravimetric Analyzer-Mass Spectroscopy (TG-MS). During co-combustion of blends, three distinct peaks were observed and were attributed to C. vulgaris volatiles combustion, combustion of lignite, and combustion of microalgae char. Activation energy during combustion was calculated using iso-conventional method. Increasing the microalgae content in the blend resulted in an increase in activation energy for the blends combustion. The emissions of S- and N-species during blend fuel combustion were also investigated. The addition of microalgae to lignite during air combustion resulted in lower CO2, CO, and NO2 yields but enhanced NO, COS, and SO2 formation. During oxy-fuel co-combustion, the addition of microalgae to lignite enhanced the formation of gaseous species.

Comparative study on pyrolysis of lignocellulosic and algal biomass using a thermogravimetric and a fixed-bed reactor.

Pyrolysis characteristics of four algal and lignocellulosic biomass samples were studied by using a thermogravimetric analyzer (TGA) and a fixed-bed reactor. The effects of pyrolysis temperature and biomass type on the yield and composition of pyrolysis products were investigated. The average activation energy for pyrolysis of biomass samples by FWO and KAS methods in this study were in the range of 211.09-291.19kJ/mol. CO2 was the main gas component in the early stage of pyrolysis, whereas H2 and CH4 concentrations increased with increasing pyrolysis temperature. Bio-oil from Chlorellavulgaris showed higher content of nitrogen containing compounds compared to lignocellulosic biomass. The concentration of aromatic organic compounds such as phenol and its derivatives were increased with increasing pyrolysis temperature up to 700°C. FTIR analysis results showed that with increasing pyrolysis temperature, the concentration of OH, CH, CO, OCH3, and CO functional groups in char decreased sharply.

A Comparative study of microwave-induced pyrolysis of lignocellulosic and algal biomass.

Microwave (MW) pyrolysis of algal and lignocellulosic biomass samples were studied using a modified domestic oven. The pyrolysis temperature was recorded continuously by inserting a thermocouple into the samples. Temperatures as high as 1170 and 1015°C were achieved for peanut shell and Chlorella vulgaris. The activation energy for MW pyrolysis was calculated by Coats-Redfern method and the values were 221.96 and 214.27kJ/mol for peanut shell and C. vulgaris, respectively. Bio-oil yields reached to 27.7wt.% and 11.0wt.% during pyrolysis of C. vulgaris and peanut shell, respectively. The bio-oil samples from pyrolysis were analyzed by a gas chromatography-mass spectrometry (GC-MS). Bio-oil from lignocellulosic biomass pyrolysis contained more phenolic compounds while that from microalgae pyrolysis contained more nitrogen-containing species. Fourier transform infrared spectroscopy (FTIR) analysis results showed that concentration of OH, CH, CO, OCH3, and CO functional groups in char samples decreased significantly after pyrolysis.

Co-pyrolysis of pine sawdust and lignite in a thermogravimetric analyzer and a fixed-bed reactor.

Co-pyrolysis characteristics of lignite and pine sawdust were studied in a TGA and a fixed-bed reactor. The effects of pyrolysis temperature and blending ratio on the yield and composition of pyrolysis products (gas, tar, and char) were investigated. TGA experiments showed that pine sawdust decomposition took place at lower temperatures compared to lignite. With increasing the pine sawdust content in the blend, the DTG peaks shifted towards lower temperatures due to synergetic effect. In fixed-bed experiments, the synergetic effect increased the yield of volatile matter compared to the calculated values. The major gases released at low temperatures were CO2 and CO. However, hydrogen was the primary gaseous product at higher temperatures. During co-pyrolysis, concentrations of benzene, naphthalene, and hydrocarbons in the tar decreased, accompanied by an increase in phenols and guaiacol concentrations. With increasing pyrolysis temperature, the OH, aliphatic CH, CO, and CO functional groups in char decomposed substantially.