Association of obstructive sleep apnea severity with the composition of the upper airway microbiome.

STUDY OBJECTIVES: Although the airway mucosal system plays a pivotal role in the pathogenesis of obstructive sleep apnea (OSA), the underlying disease mechanism remains unclear. The microbiome greatly impacts human health and disease, particularly in the mucosa, where it can have direct interactions. In this study, we aimed to analyze the microbiome composition in the upper airway mucosa of individuals with and without OSA to identify potential disease severity-related microbial signatures. METHODS: This population-based cohort study involved 92 participants (mean age = 62.7 ± 5.8 years; male-to-female ratio = 0.74) who underwent a physical examination and sleep study. Upper airway swab samples were collected from the nasopharyngeal mucosa to evaluate the microbiome based on 16S rRNA gene pyrosequencing. The relationship between microbiome composition and sleep parameters was explored through bioinformatics analysis. RESULTS: The average apnea-hypopnea index was 7.75 ± 6.5 events/h. Proteobacteria, Firmicutes, and Actinobacteria were the predominant phyla in the nasopharyngeal microbiota in all participants. Simpson diversity indexes were higher in patients with OSA (0.6435 ± 0.2827) than in the control patients (0.6095 ± 0.2683); however, the difference was not significant (P = .1155). Specific anaerobes negatively correlated with the lowest oxygen saturation level during sleep (sum of powered score (1) = -117.47; P = .0052). CONCLUSIONS: The upper airway microbiome of older patients with mild-moderate OSA exhibited minor differences in composition compared with that of individuals without OSA, possibly owing to environmental changes in the upper airway mucosa resulting from recurrent airway obstruction and intermittent hypoxia in patients with OSA. CITATION: Hong S-N, Kim KJ, Baek M-G, et al. Association of obstructive sleep apnea severity with the composition of the upper airway microbiome. J Clin Sleep Med. 2022;18(2):505-515.

Phylogenetic tree-based microbiome association test.

MOTIVATION: Ecological patterns of the human microbiota exhibit high inter-subject variation, with few operational taxonomic units (OTUs) shared across individuals. To overcome these issues, non-parametric approaches, such as the Mann-Whitney U-test and Wilcoxon rank-sum test, have often been used to identify OTUs associated with host diseases. However, these approaches only use the ranks of observed relative abundances, leading to information loss, and are associated with high false-negative rates. In this study, we propose a phylogenetic tree-based microbiome association test (TMAT) to analyze the associations between microbiome OTU abundances and disease phenotypes. Phylogenetic trees illustrate patterns of similarity among different OTUs, and TMAT provides an efficient method for utilizing such information for association analyses. The proposed TMAT provides test statistics for each node, which are combined to identify mutations associated with host diseases. RESULTS: Power estimates of TMAT were compared with existing methods using extensive simulations based on real absolute abundances. Simulation studies showed that TMAT preserves the nominal type-1 error rate, and estimates of its statistical power generally outperformed existing methods in the considered scenarios. Furthermore, TMAT can be used to detect phylogenetic mutations associated with host diseases, providing more in-depth insight into bacterial pathology. AVAILABILITY AND IMPLEMENTATION: The 16S rRNA amplicon sequencing metagenomics datasets for colorectal carcinoma and myalgic encephalomyelitis/chronic fatigue syndrome are available from the European Nucleotide Archive (ENA) database under project accession number PRJEB6070 and PRJEB13092, respectively. TMAT was implemented in the R package. Detailed information is available at http://healthstat.snu.ac.kr/software/tmat. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

Photocurrent enhancement of dye-sensitized solar cells owing to increased dye-adsorption onto silicon-nanoparticle-coated titanium-dioxide films.

The inverse-micellar preparation of Si nanoparticles (Nps) was improved by utilizing sodium naphthalide. The Si Nps were subsequently functionalized with 4-vinylbenzoic acid for their attachment onto TiO(2) films of dye-sensitized solar cells (DSSCs). The average diameter of the COOH-functionalized Si (Si-COOH) Nps was 4.6(±1.7) nm. Depth profiling by secondary-ion mass spectrometry revealed that the Si Nps were uniformly attached onto the TiO(2) films. The number of Ru(II) dye molecules adsorbed onto a TiO(2) film that was treated with the Si-COOH Nps was 42 % higher than that on the untreated TiO(2) film. As a result, DSSCs that incorporated the Si-COOH Nps exhibited higher short-circuit photocurrent density and an overall energy-conversion efficiency than the untreated DSSCs by 22 % and 27 %, respectively. This enhanced performance, mostly owing to the intramolecular charge-transfer to TiO(2) from the dye molecules that were anchored to the Si-COOH Nps, was confirmed by comparing the performance with two different Ru(II) -bipyridine dyes (N719 and N749).

High performance dye-sensitized solar cells with alkylpyridinium iodide salts in electrolytes.

Pyridinium iodide salts, which are competitive to the conventional imidazolium iodide salts, have been used for dye-sensitized solar cells as iodide sources and ionic conductivities. Pyridinium iodide series are easy to prepare and less expensive than the imidazolium series salts. In this research, quite comparable efficiencies were obtained from electrolytes with pyridinium iodide salts. For the experiments, pyridinium salts with a few different alkyl chains are applied. When a pyridinium head is modified to picolinium, which has a methyl group on the pyridinium head, a noticeable V(oc) drop has been observed. However, the length of the alkyl chains on the pyridinium head does not affect V(oc) effectively. The odd-numbered alkyl chains showed slightly lower V(oc) compared to that of the even-numbered alkyl chains. Finally, the performances of the cells with pyridinium salts are compared to those of the conventional cells with imidazolium salts.

Treatment of TiO2 with COOH-functionalized germanium nanoparticles to enhance the photocurrent of dye-sensitized solar cells.

A dye-sensitized solar cell (DSSC) containing a TiO(2) film treated with COOH-functionalized germanium nanoparticles (Ge-COOH Nps) exhibited a higher short-circuit photocurrent density (J(sc); 15.4 mA cm(-2)) compared to the corresponding untreated DSSC (13.4 mA cm(-2)) using N719 and a 12 µm thick TiO(2) film at 100 mW cm(-2). The amount of N719 attached to the treated TiO(2) film was 21% greater than that attached to the untreated TiO(2) film. Enhancement of the J(sc) value by 15% was attributed mostly to an intramolecular charge transfer from N719 attached to the Ge-COOH Nps to the TiO(2) conduction band through the Ge-COOH Nps.

Method to protect charge recombination in the back-contact dye-sensitized solar cell.

We prepared a back-contact dye-sensitized solar cell and investigated effect of the sputter deposited thin TiO2 film on the back-contact ITO electrode on photovoltaic property. The nanocrystalline TiO2 layer with thickness of about 11 µm formed on a plain glass substrate in the back-contact structure showed higher optical transmittance than that formed on an ITO-coated glass substrate, which led to an improved photocurrent density by about 6.3%. However, photovoltage was found to decrease from 817 mV to 773 mV. The photovoltage recovered after deposition of a 35 nm-thick thin TiO2 film on the surface of the back-contact ITO electrode. Little difference in time constant for electron transport was found for the back-contact ITO electrodes with and without the sputter deposited thin TiO2 film. Whereas, time constant for charge recombination increased after introduction of the thin TiO2 film, indicating that such a thin TiO2 film protected back electron transfer, associated with the recovery of photovoltage. As the result of the improved photocurrent density without deterioration of photovoltage, the back-contact dye-sensitized solar cell exhibited 13.6% higher efficiency than the ITO-coated glass substrate-based dye-sensitized solar cell.

Influence of nylon 6 in I3(-)/I(-) redox electrolyte on the photovoltaic performance and stability of dye-sensitized solar cells.

Nylon 6 fibers are used, for the first time, in dye-sensitized solar cells (DSSCs). The overall energy conversion efficiency obtained with 0.18 M nylon 6 reaches 6.2%, which is comparable to that (6.7%) obtained without adding nylon 6 on the day of cell fabrication. However, it is found that the long-term stability of the DSSCs with nylon 6 is superior to that of a reference electrolyte as a result of the complexation of nylon 6 with I(3)(-). Furthermore, nylon 6 is found to be a corrosion inhibitor for silver metal in the electrolyte containing I(3)(-).

High-performance quasi-solid-state dye-sensitized solar cell based on an electrospun PVdF-HFP membrane electrolyte.

An electrospun membrane was prepared from a 16 wt % solution of poly(vinylidenefluoride- co-hexafluoropropylene) (PVdF-HFP) in a mixture of acetone/ N, N-dimethylacetamide (7:3 wt %) at an applied voltage of 12 kV. It was then activated by immersing it in 0.6 M 1-hexyl-2,3-dimethylimidazolium iodide, 0.1 M LiI, 0.05 M I 2, and 0.5 M 4- tert-butylpyridine in ethylene carbonate/propylene carbonate (1:1 wt %) to obtain the corresponding membrane electrolyte with an ionic conductivity of 10 (-5) S cm (-1) at 25 degrees C. On the basis of this electrospun membrane electrolyte, quasi-solid-state dye-sensitized solar cells were fabricated, which showed an open-circuit voltage ( V oc) of 0.76 V, a fill factor of 0.62, and a short-circuit current density ( J sc) of 15.57 mA cm (-2) at an incident light intensity of 100 mW cm (-2). This yields a light-to-electricity conversion efficiency of 7.3%. Moreover, this cell possessed better long-term stability than that fabricated with conventional liquid electrolyte.

Determination of polychlorinated biphenyls in transformer oil using various adsorbents for solid phase extraction.

Various adsorbents for a solid phase extraction (SPE) method were used to study their ability to separate PCBs from transformer oil to rapidly determine their sub-ppm concentration in the transformer oil. Approximately 90% of the transformer oil could be removed from the PCBs by using a hydrophilic-lipophilic balanced copolymer (HLB) adsorbent, but the recovery of deca-chlorobiphenyl (deca-CB) used as a surrogate was only 24.5% due to lose during this cleanup process. The use of a silica adsorbent gave good results with 89.9% recovery of the deca-CB. The recovery of Aroclor 1242 and 1260 were 95.4 and 90.3% on silica, and 98.9 and 83.5% on HLB, respectively. Acid treatment was an essential step in removing the ambiguous interference peaks to help identify the PCBs. A decreased sensitivity of the electron capture detection (ECD) for PCBs was observed due to the presence of the remaining trace oil after the workup procedure. This loss in sensitivity was allowed for by using tetrachloroxylene as an internal standard, and this was found to be reliable for the criteria of quality control by employing an experiment in which LCS was spiked with 2mg/l of Aroclor 1260 and analyzed each day over a 25 day period. The MDL for the analytical method established in this study is 0.05 mg/l.

CTAB-promoted prussian blue-modified electrode and its cation transport characteristics for K+, Na+, Li+, and NH4+ ions.

A Prussian blue (PB) film was deposited on a glassy carbon (GC) electrode by cyclic voltammetry in the presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB). The electrode thus formed showed 4-fold enhancements in redox current and charge values in pure KCl electrolyte as well as greater stability than an electrode prepared in the absence of CTAB. This improved performance of a PB+CTAB electrode versus a PB electrode was further demonstrated using SEM, XRD, and electrochemical impedance spectroscopy (EIS) measurements. A comparative study was undertaken on the cation transport characteristics of PB and PB+CTAB electrodes for Na+, Li+, and NH4+ ions. We obtained a CV pattern for a CTAB-promoted PB film, which showed ideal Nernstian behavior at all scan rates from 5 to 140 mV s(-1). Conditions for the formation and preservation of these ideal and stable PB films are discussed. Possible mechanisms for the beneficial effects of CTAB are proposed.

Structural analysis of platycosides in Platycodi Radix by liquid chromatography/electrospray ionization-tandem mass spectrometry.

Platycosides extracted from Platycodi Radix were analyzed by HPLC coupled with electrospray ionization multistage tandem mass spectrometry (HPLC/ESI-MS(n)). Predominant [M+Na](+) ions in positive mode and [M-H](-) ions in negative mode in the direct ESI-MS spectra of extract provided information on molecular weights, but minor components and isomers could not be discriminated. However, combining HPLC and ESI-MS(n), allowed eleven platycosides, including four acetylated platycodin isomers and two prosapogenines to be analyzed. During MS(2) analysis conducted to elucidate the structures of platycosides, fragment ions provided information on sugar moieties attached at C-28 of triterpene structure of the platycosides. Glycosidic bond cleavages at C-3 were revealed by fragment ions in MS(3) spectra. Some characteristic fragment ions not related to sugar bond cleavage revealed that an esterified triterpene is linked to sugars at C-28. The only sugar ring-cross cleavage corresponding to 90 Da in the negative MS(2) spectrum took place at an arabinosyl sugar moiety. By using HPLC/ESI-MS(n), three acetylated platycosides in Platycodi Radix extract were newly identified.

Structural determination of monoacylglycerols extracted from marine sponge by fast atom bombardment tandem mass spectrometry.

Five new monoacylglycerols (MAGs) were isolated from the marine sponge Stelletta sp. by reversed-phase high-performance liquid chromatography and analyzed by positive ion fast atom bombardment mass spectrometry (FAB-MS). FAB mass spectra of these compounds produced abundant sodium-adducted molecules [M+Na]+ from a mixture of 3-nitrobenzyl alcohol and sodium iodide. The structural elucidation of these sponge MAGs was carried out by FAB tandem mass spectrometry (MS/MS). To find diagnostic ions for the characterization of the MAGs, authentic MAGs were initially analyzed by collision-induced dissociation (CID) MS/MS. The CID MS/MS of [M+Na]+ precursor ions resulted in the formation of numerous characteristic product ions via a series of dissociative processes. The product ions formed by charge-remote fragmentation (CRF) provided important information for the characterization of acyl chains substituted at the glycerol backbone, and product ions at m/z 84, 97, 113 and 139 were diagnostic for the sodiated glycerol backbone. On the basis of these fragmentation patterns, the structures of five MAGs extracted from marine sponge were elucidated. In addition, high-resolution mass measurement was performed to obtain the elemental compositions of the MAGs.

Structural determination of saponins extracted from starfish by fast atom bombardment collision-induced dissociation mass spectrometry.

Three saponins were extracted and isolated from starfish by reversed-phase high performance liquid chromatography (HPLC), and analyzed by fast atom bombardment mass spectrometry (FAB-MS). Their molecular weight information could be obtained by the presence of abundant [M+Na]+ ions and weak [M+H]+ ions in FAB-MS spectra. Moreover, high resolution mass measurements of their [M+Na]+ ions were performed at the resolution of 10000 to elucidate the element composition of extracted saponins. The collision-induced dissociation (CID) of sodium-adducted molecules [M+Na]+ yielded diverse product ions via dissociated processes. In the collision-induced dissociation (CID)-MS/MS analysis of [M+Na]+ ion, the sulfate-containing saponins produced characteristic ions such as SO4Na+, [NaHSO4+Na]+, [M+Na-sugar]+ and [M+Na-2sugar]+ ions, whereas the sulfate-free compound showed characteristic ions produced by cleavage of sugar moiety and side chain of aglycone. The fragmentation patterns could provide information on the linkage position of sugar groups in aglycone and sulfate groups.

Structural determination of cyclitol derivatives by fast-atom bombardment tandem mass spectrometry.

Three cyclitol derivatives were isolated from the marine sponge Sarcotragus sp. by reversed-phase high-performance liquid chromatography and analyzed by fast-atom bombardment mass spectrometry (FAB-MS). Their structural elucidation was carried out with FAB tandem mass spectrometry (FAB-MS/MS). FAB-MS spectra produced a significant abundance of the sodium adducts [M+Na]+ and [M+2Na-H]+ from a mixture of m-NBA and NaI. In addition, trifluoroacetylation of the cyclitol derivatives was used for confirmation of the presence of the cyclitol ring. High abundance [M-5H+5CF3CO+Na]+ ions were observed in the FAB-MS spectra of the trifluoroacetyl-cyclitol derivatives. Collision-induced dissociation (CID) of the [M+Na]+ ions produced diverse product ions via a series of dissociative processes. Charge-remote fragmentation (CRF) patterns of [M+Na]+ ions were very useful for the identification of product ions which are characteristic for the cyclitol ring and long hydrocarbon chains substituted at the glycerol backbone. Moreover, the CID-MS/MS spectra of the [M+Na]+ ions yielded characteristic product ions at m/z 53, 83, 113, 155 and 171 for the cyclitol moiety, and at m/z 213, 229 and 245 for the glycerol backbone attached to the cyclitol ring.

Beneficial role of surfactants in electrochemistry and in the modification of electrodes.

This review deals with the beneficial use of surfactants in various fields of electrochemistry, in general and in the modification of electrodes with immobilized electroactive species, in particular. Special emphasis is laid on the modification of electrodes with metal hexacyanoferrates (MHCFs). After an introduction and brief notes on fundamentals of surfactants, and their applications in electrochemistry, covering some of the very important works in the past two decades involving beneficial use of surfactants, the article gives a brief account on metal hexacyanoferrate modified electrodes and the salient features of our published results on the beneficial role of cetyltrimethylammonium bromide (CTAB), a cationic surfactant, in the modification of electrodes with MHCFs and their derivatized oxides, and with titanium dioxide.

Linkage of N3 dye to N3 dye on nanocrystalline TiO2 through trans-1,2-bis(4-pyridyl)ethylene for enhancement of photocurrent of dye-sensitized solar cells.

Linking of N3 dye to another TiO2-attached N3 dye rendered an enhanced short-circuit photocurrent and thereby higher efficiency for the dye-sensitized solar cell with the pertinent TiO2 film electrode.

Coordinatively induced length control and photoluminescence of W18O49 nanorods.

A coordinatively induced length control of W18O49 nanorods has been developed using thermal decomposition of W(CO)6 in octyl ether solutions of single or mixed capping agents, oleic acid (OA), oleic acid/hexadecylamine (HDA), and oleic acid/trioctylphosphine oxide (TOPO). The order of length for nanorods synthesized with different capping agents was OA > OA/HDA > OA/TOPO, which was the opposite of order of their coordinating power. The order of crystalline size (diameter x length) from the TEM image was OA/HDA > OA > OA/TOPO and matched exactly with the order of crystallinity from the XRD pattern. The order of photoluminescence intensity was OA/HDA < OA < OA/TOPO and was the opposite of the order for the crystalline size or crystallinity. The strong coordinating power and steric bulkiness of TOPO is thought to interrupt the growth of the nanorods, the rearrangement of the end face atoms, and the fusion of the lateral faces and, thereby, increase the oxygen defects and the photoluminescence intensity.

Incorporation of functionalized single-wall carbon nanotubes in dye-sensitized TiO2 solar cells.

Effects of incorporation of acid-treated single-wall carbon nanotubes (a-SWCNs) in TiO(2) film and of anchorage of dye-linked, a-SWCNs (hereafter dye-SWCNs) to the TiO(2)/electrolyte interface on photocurrent-voltage characteristics of dye-sensitized solar cells were studied. Compared with an unmodified cell, the modified cell with the a-SWCNs in TiO(2) film showed a 25% increase in short-circuit photocurrent (J(sc)). The J(sc) increase is correlated with improved connectivity between the a-SWCNs and the TiO(2) particles and with enhanced light scattering by TiO(2) clusters formed in the presence of the a-SWCNs. In the case of anchoring dye-SWCNs to the TiO(2)/electrolyte interface, the open-circuit voltage (V(oc)) increased by as much as 0.1 V, possibly due to the basicity of the TiO(2) surface from NH groups of ethylenediamine moieties of the anchored dye-SWCNs.

Beneficial role of cetyltrimethylammonium bromide in the enhancement of photovoltaic properties of dye-sensitized rutile TiO2 solar cells.

A new approach involving the introduction of the common cationic surfactant cetyltrimethylammonium bromide (CTAB) for modifying a rutile TiO2 film during its formation from hydrolyzed TiCl4 solution has been adopted, intending to improve the photoelectrochemical properties of the pertinent dye-sensitized solar cell. CTAB-routed films were found to consist of smaller clusters of near-spherical TiO2 particles, compared with larger clusters of long rod-shaped particles in the absence of CTAB. As a consequence, the photocurrent and photovoltage of the cell fabricated by using CTAB have increased significantly, leading to a conversion efficiency increase, compared with those of the cell prepared without CTAB. On the basis of FE-SEM, BET, and XRD analyses, the increases are attributed to decreased particle size, improved interparticle connectivity, and enhanced crystallinity of the CTAB-promoted TiO2 particles and decreased void volume in the film. Faster growth of the TiO2 film was another beneficial effect of CTAB. A mechanism is proposed for the beneficial role of CTAB during the film formation.