Synthesis and Characterization of Functional Triphenylphosphine‐Containing Microporous Organic Polymers for Gas Storage and Separation

Two kinds of novel triphenylphosphine‐containing microporous organic polymers are designed and synthesized via palladium‐catalyzed Sonogashira−Hagihara coupling condensation reaction of triphenylphosphine oxide‐ and sulfide‐based monomers with different arylethynylene linkers. The gas adsorption isotherms reveal that these polymers have strong binding affinity for CO₂ with high CO₂ adsorption capacity, although they have moderate Brunauer−Emmett−Teller surface area ranging from 684 to 883 m² g⁻¹. Among the resulting polymers, triphenylphosphine oxide–tris(4‐ethynylphenyl)amine exhibits the highest CO₂ uptake capacity of 2.61 mmol g⁻¹ at 273 K and 1.13 bar with relatively high gas selectivity of 60.2 for CO₂ over N₂ at 273 K.     

Preparation of Monodisperse Hyper‐Crosslinking Polymer Nanoparticles for Highly Efficient CO2 Adsorption

A facile and novel method for the synthesis of monodisperse hyper‐crosslinking polymer nanoparticles (HPNs) is reported in the combination of vesicle bilayer templating and hyper‐crosslinking technology. Monodisperse polymer nanoparticles (PNs) around 61 nm are first obtained through the confined reaction of vinylbenzyl chloride and divinylbenzene in the bilayers of the vesicles, and then the PNs are turned into HPNs through the Friedel–Crafts‐type hyper‐crosslinking reaction. The finally obtained HPNs demonstrate small and uniform size, high Brunauere–Emmette–Teller surface area up to ≈1300 m² g⁻¹, a very high micropore area above 1000 m² g⁻¹ and a micropore volume of 0.55 cm³ g⁻¹. In addition, they also show the carbon dioxide adsorption capacity of 2.87 mmol g⁻¹ (273 K, 1 bar), which is among the best CO₂ adsorption property for “Davankov Resins.”

     

Characterization of the Physical Properties and Biocompatibility of Polybenzoxazine-Based Aerogels for Use as a Novel Hard-Tissue Scaffold

Abstract

The process to successfully synthesize polybenzoxazine (PBO)-based aerogels has recently been optimized; however, the biocompatibility of these materials has never been investigated. PBO is synthesized from bisphenol A and aniline, which are both precursors to many commonly used biomaterials, including polyurethane. Surface-wise these new aerogels resemble the innate extracellular matrix of bone and if these new aerogels exhibit acceptable biocompatibility, they may be used as a scaffold for bone tissue engineering. Here, we aimed to characterize some of the physical properties of PBO aerogels, PBO aerogels co-polymerized with resorcinol and formaldehyde (RF) and their conversion to carbon aerogel, while determining the compatibility of all of these materials towards human osteoblasts. Biocompatibility was determined with a live/dead cell cytotoxicity assay, a metabolic activity assay, alkaline phosphatase activity and osteocalcin production, after incubation with PBO-based aerogels for up to 5 days. PBO aerogels co-polymerized with RF tended to have a low density, porosity and elastic modulus and provided the weakest substrate for bone cell growth. PBO-derived carbon aerogels tended to have a high density, a large porosity and improved mechanical properties and provided the best substrate for bone cell growth. These results suggest that PBO based carbon aerogels have a suitable biocompatibility towards osteoblasts and that they may be able to be used for bone tissue engineering scaffolds.     

Micro-CT studies on 3-D bioactive glass–ceramic scaffolds for bone regeneration

The aim of this study was the preparation and characterization of bioactive glass–ceramic scaffolds for bone tissue engineering. For this purpose, a glass belonging to the system SiO₂–P₂O₅–CaO–MgO–Na₂O–K₂O (CEL2) was used. The sponge-replication method was adopted to prepare the scaffolds; specifically, a polymeric skeleton was impregnated with a slurry containing CEL2 powder, polyvinyl alcohol (PVA) as a binding agent and distilled water. The impregnated sponge was then thermally treated to remove the polymeric phase and to sinter the inorganic one. The obtained scaffolds possessed an open and interconnected porosity, analogous to cancellous bone texture, and with a mechanical strength above 2 MPa. Moreover, the scaffolds underwent partial bioresorption due to ion-leaching phenomena. This feature was investigated by X-ray computed microcomputed tomography (micro-CT). Micro-CT is a three-dimensional (3-D) radiographic imaging technique, able to achieve a spatial resolution close to 1 μm³. The use of synchrotron radiation allows the selected photon energy to be tuned to optimize the contrast among the different phases in the investigated samples. The 3-D scaffolds were soaked in a simulated body fluid (SBF) to study the formation of hydroxyapatite microcrystals on the scaffold struts and on the internal pore walls. The 3-D scaffolds were also soaked in a buffer solution (Tris–HCl) for different times to assess the scaffold bioresorption according to the ISO standard. A gradual resorption of the pores walls was observed during the soakings both in SBF and in Tris–HCl.     

Diaphragm and genioglossus corticomotor excitability in patients with obstructive sleep apnea and control subjects

Corticomotor excitability of peripheral muscles appears to be altered in patients with obstructive sleep apnea. However, there is no evidence of such alteration for upper airway/respiratory muscles that are involved in the pathophysiology of this disease. The aim of this study was to compare the effects of hypercapnic stimulation on diaphragm and genioglossus corticomotor excitability in awake healthy subjects versus patients with obstructive sleep apnea. Corticomotor excitability was assessed by transcranial magnetic stimulation in 12 untreated apneic men (48 ± 10 years; body mass index = 28.9 ± 4.7 kg m⁻²; apnea–hypopnoea index = 41 ± 23 events per hour) and nine control men (45 ± 10 years; body mass index = 27.3 ± 3.3 kg m⁻²; apnea–hypopnoea index = 7 ± 4 events per hour). Assessments included diaphragm and genioglossus expiratory motor thresholds, and transcranial magnetic stimulation‐induced motor‐evoked potential characteristics obtained while breathing room air or 5% CO₂ (random order) and then 7% CO₂ both balanced with pure O₂. Transcranial magnetic stimulation twitches were applied during early inspiration and end expiration. Diaphragm motor‐evoked potential amplitudes increased and expiratory diaphragm motor‐evoked potential latencies decreased during CO₂‐induced increase in ventilatory drive, with no difference in these responses between patients with obstructive sleep apnea and control subjects. Expiratory genioglossus motor‐evoked potential amplitudes were significantly lower in patients with obstructive sleep apnea than in control subjects. Baseline activity of the genioglossus increased with increasing FiCO₂, this effect being significantly higher in patients with obstructive sleep apnea than in control subjects. However, neither genioglossus motor‐evoked potential amplitudes nor latencies were significantly modified with increasing FiCO₂ both in patients with obstructive sleep apnea and in control subjects. Corticomotor excitability of genioglossus and diaphragm are not altered during CO₂‐induced increase in ventilatory drive in patients with obstructive sleep apnea.     

Varying the Hydrogen Bonding Strength in Phenolic/PEO‐b‐PLA Blends Provides Mesoporous Carbons Having Large Accessible Pores Suitable for Energy Storage

In this study, mesoporous carbons are prepared by using a resol‐type phenolic resin as the carbon source and poly(ethylene oxide‐b‐lactic acid) (PEO‐b‐PLA) copolymer as the template, with a process of thermal curing, calcination, carbonization, and activation. The structures of these mesoporous carbons are strongly influenced by the self‐assembled structures formed from phenolic/PEO‐b‐PLA blends, varying from double‐gyroid, to cylinder, and finally to spherical micelle structures upon increasing the phenolic concentrations. The large pores (>20 nm) and high surface areas (>1000 m² g^?1) of these activated mesoporous carbons arise because the phenolic resin interacts only with the PEO segment (i.e., not with the PLA segment) through hydrogen bonding; thus, the relative wall thickness of the phenolic matrix decreases after template removal (thereby increasing the pore size), similar to the behavior of the poly(ethylene oxide‐b‐styrene) template system. Furthermore, these mesoporous carbons display efficient energy storage capacities of up to 200 F g^?1 at 5 mV s^?1, with excellent stabilities after 5000 charge/discharge cycles at 20 A g^?1. Thus, this facile approach provides large and well‐ordered mesoporous carbons suitable for energy storage applications.     

The adsorption of preferential binding peptides to apatite-based materials

The objective of this work was to identify peptide sequences with high affinity to bone-like mineral (BLM) to provide alternative design methods for functional bone regeneration peptides. Adsorption of preferential binding peptide sequences on four apatite-based substrates [BLM and three sintered apatite disks pressed from powders containing 0% CO₃^2? (HA), 5.6% CO₃^2? (CA5), 10.5% CO₃^2? (CA10)] with varied compositions and morphologies was investigated. A combination of phage display, ELISA, and computational modeling was used to elucidate three 12-mer peptide sequences APWHLSSQYSRT (A), STLPIPHEFSRE (S), and VTKHLNQISQSY (V), from 243 candidates with preferential adsorption on BLM and HA. Overall, peptides S and V have a significantly higher adsorption to the apatite-based materials in comparison to peptide A (for S vs. A, BLM p = 0.001, CA5 p < 0.001, CA10 p < 0.001, HA p = 0.038; for V vs. A, BLM p = 0.006, CA5 p = 0.033, CA10 p = 0.029). FT-IR analysis displayed carbonate levels in CA5 and CA10 dropped to approximately 1.1–2.2% after sintering, whereas SEM imaging displayed CA5 and CA10 possess distinct morphologies. Adsorption results normalized to surface area indicate that small changes in carbonate percentage at a similar morphological scale did not provide enough carbonate incorporation to show statistical differences in peptide adsorption. Because the identified peptides (S and V) have preferential binding to apatite, their use can now be investigated in bone and dentin tissue engineering, tendon and ligament repair, and enamel formation.     

Combined spiroergometry and 31P–MRS of human calf muscle during high‐intensity exercise

Simultaneous measurements of pulmonary oxygen consumption (VO₂), carbon dioxide exhalation (VCO₂) and phosphorus magnetic resonance spectroscopy (³¹P–MRS) are valuable in physiological studies to evaluate muscle metabolism during specific loads. Therefore, the aim of this study was to adapt a commercially available spirometric device to enable measurements of VO₂ and VCO₂ whilst simultaneously performing ³¹P–MRS at 3 T. Volunteers performed intense plantar flexion of their right calf muscle inside the MR scanner against a pneumatic MR‐compatible pedal ergometer. The use of a non‐magnetic pneumotachograph and extension of the sampling line from 3 m to 5 m to place the spirometric device outside the MR scanner room did not affect adversely the measurements of VO₂ and VCO₂. Response and delay times increased, on average, by at most 0.05 s and 0.79 s, respectively. Overall, we were able to demonstrate a feasible ventilation response (VO₂ = 1.05 ± 0.31 L/min; VCO₂ = 1.11 ± 0.33 L/min) during the exercise of a single calf muscle, as well as a good correlation between local energy metabolism and muscular acidification (τ_{PCr fast} and pH; R² = 0.73, p < 0.005) and global respiration (τ_{PCr fast} and VO₂; R² = 0.55, p = 0.01). This provides improved insights into aerobic and anaerobic energy supply during strong muscular performances.     

Novel Sulfur‐Containing Cross‐Linking Agent for Si‐Based Preceramic Polymers

Cross‐linking polymethylhydrosiloxane (PMHS) with divinylthiophene (DVT) via hydrosilylation in highly dilute conditions and subsequent supercritical drying in CO₂ yield a polymeric aerogel containing aromatic sulfur integrally and uniformly distributed throughout the monolith. Fourier‐transform infrared (FT‐IR) spectroscopy indicates almost complete consumption of vinyl groups and Si? H bonds in the product. Both FT‐IR and Raman spectroscopic analyses support loss of conjugation of vinyl groups with the retained double bonds of the thiophene ring. Scanning electron microscopy (SEM) indicates a condensed colloidal structure with characteristic particulate diameters of about 165 nm. SEM coupled with energy dispersive X‐ray spectroscopy elemental mapping shows that sulfur is distributed homogeneously in the polymeric aerogel. Porosimetry of the mesoporous aerogel indicates the effective average pore diameters are about 12 nm. Thermogravimetric analysis (TGA) establishes greater thermal stability of the PMHS‐DVT product than either of the pure unreacted components. TGA coupled with mass spectrometric (TG‐MS) identification of the volatiles released during pyrolysis shows that sulfur is driven from the cross‐linked polymer as thiophene and its derivatives. Recorded mass spectra support the hypothesis that cross‐linking DVT bridges between PMHS chains in the polymeric aerogel, and that this results in a more thermally stable monolith.     

Latency to CNS oxygen toxicity in rats as a function of PCO2 and PO2

Central nervous system (CNS) oxygen toxicity can occur as convulsions and loss of consciousness, without any premonitory symptoms. We have made a quantitative study of the effect of inspired carbon dioxide on sensitivity to oxygen toxicity in the rat. Rats were exposed to four oxygen pressures (PO₂; 456, 507, 608 and 709?kPa) and an inspired partial pressure of carbon dioxide (PCO₂) in the range 0–12?kPa until the appearance of the electroencephalograph first electrical discharge (FED) that preceds the clinical convulsions. Exposures were conducted at a thermoneutral temperature of 27°C. Latency to the FED decreased linearly with the increase in PCO₂ at all four PO₂ values studied. This decrease, which is probably related to the cerebral vasodilatory effect of carbon dioxide, reached a minimal value that remained constant on further elevation of PCO₂. The slopes (absolute value) and intercepts of latency to the FED as a function of carbon dioxide decreased with the increase in PO₂. This log-linear relationship made possible the derivation of equations that describe latency to the FED as a function of both PO₂ and PCO₂ in the PCO₂– dependent range: Latency (min)?=?e^{(5.19?0.0040 P O2)}?e^{(2.77?0.0034 P O2)}?×?PCO₂ (kPa), and in the PCO₂-independent range: Latency(min) =?e^{(2.44?0.0009 P O2)}. A PCO₂ as low as 1?kPa significantly reduced the latency to the FED. It is suggested that in closed-circuit oxygen diving, any accumulation of carbon dioxide should be avoided in order to minimize the risk of CNS oxygen toxicity.     

Polycyclotrimers of 1,4‐Diethynylbenzene, 2,6‐Diethynylnaphthalene,and 2,6‐Diethynylanthracene: Preparation and Gas Adsorption Properties

Hyperbranched partly cross‐linked polycyclotrimers of 1,4‐diethynylbenzene, 2,6‐diethynyl­naphthalene, and 2,6‐diethynylanthracene, Pc(1,4‐DEB), Pc(2,6‐DEN), and Pc(2,6‐DEA), respectively, are prepared using TaCl₅/Ph₄Sn catalyst. Brunauer–Emmett–Teller (BET) surface area, microporosity, and maximum sorption capacity for H₂ and CO₂ decrease in the order of decreasing relative content of branching points in polycyclotrimers Pc(1,4‐DEB) > Pc(2,6‐DEN) > Pc(2,6‐DEA), the highest values for Pc(1,4‐DEB) being S_BET = 1299 m² g^?1, a_H2 = 1.26 wt% (100 kPa, 77 K), and a_CO2 = 10.8 wt% (100 kPa, 273 K). N₂ isotherms show that adsorption/desorption hysteresis occurs already at low equilibrium pressures. CO₂ isotherms show that the time allotted to the measurement influences both the maximum adsorption capacity and the hysteresis upon desorption.

     

Fluorinated methacrylamide chitosan hydrogel systems as adaptable oxygen carriers for wound healing

In this study a series of novel, biocompatible hydrogels able to repeatedly takeup and deliver oxygen at beneficial levels have been developed by conjugating various perfluorocarbon (PFC) chains to methacrylamide chitosan via Schiff base nucleophilic substitution, followed by photopolymerization to form hydrogels. The synthesized fluorinated methacrylamide chitosan (MACF) hydrogels were confirmed by high resolution ¹⁹F NMR. Synthesized MACF hydrogels were tested for their ability to takeup and then release oxygen for future use in dermal wound healing. Depending on the PFC substitution type maximum O₂ uptake was observed within 2–6 h, followed by complete release to the surrounding environment (5% CO₂) within 12–120 h at oxygen partial pressures of 1–25 mm Hg h^?1, providing outstanding system tuning for wound healing and regenerative medicine. MACFs with the most fluorines per substitution showed the greatest uptake and release of oxygen. Interestingly, adding PFC chains with a fluorinated aromatic group considerably enhanced oxygen uptake and extended release compared with a linear PFC chain with the same number of fluorine molecules. MACF hydrogels proved to be readily reloaded with oxygen once release was complete, and regeneration could be performed as long as the hydrogel was intact. Fibroblasts were cultured on MACFs and assays confirmed that materials containing more fluorines per substitution supported the most cells with the greatest metabolic activity. This result was true, even without oxygenation, suggesting PFC-facilitated oxygen diffusion from the culture medium. Finally, MACF gradient hydrogels were created, demonstrating that these materials can control oxygen levels on a spatial scale of millimeters and greatly enhance cellular proliferative and metabolic responses.     

Initial investigation of glucose metabolism in mouse brain using enriched 17O‐glucose and dynamic 17O‐MRS

In this initial work, the in vivo degradation of ¹⁷O‐labeled glucose was studied during cellular glycolysis. To monitor cellular glucose metabolism, direct ¹⁷O‐magnetic resonance spectroscopy (MRS) was used in the mouse brain at 9.4 T. Non‐localized spectra were acquired with a custom‐built transmit/receive (Tx/Rx) two‐turn surface coil and a free induction decay (FID) sequence with a short TR of 5.4 ms. The dynamics of labeled oxygen in the anomeric 1‐OH and 6‐CH₂OH groups was detected using a Hankel–Lanczos singular value decomposition (HLSVD) algorithm for water suppression. Time‐resolved ¹⁷O‐MRS (temporal resolution, 42/10.5 s) was performed in 10 anesthetized (1.25% isoflurane) mice after injection of a 2.2 M solution containing 2.5 mg/g body weight of differently labeled ¹⁷O‐glucose dissolved in 0.9% physiological saline. From a pharmacokinetic model fit of the H₂¹⁷O concentration–time course, a mean apparent cerebral metabolic rate of ¹⁷O‐labeled glucose in mouse brain of CMR_Glc = 0.07 ± 0.02 μmol/g/min was extracted, which is of the same order of magnitude as a literature value of 0.26 ± 0.06 μmol/g/min reported by ¹⁸F‐fluorodeoxyglucose (¹⁸F‐FDG) positron emission tomography (PET). In addition, we studied the chemical exchange kinetics of aqueous solutions of ¹⁷O‐labeled glucose at the C1 and C6 positions with dynamic ¹⁷O‐MRS. In conclusion, the results of the exchange and in vivo experiments demonstrate that the C6‐¹⁷OH label in the 6‐CH₂OH group is transformed only glycolytically by the enzyme enolase into the metabolic end‐product H₂¹⁷O, whereas C1‐¹⁷OH ends up in water via direct hydrolysis as well as glycolysis. Therefore, dynamic ¹⁷O‐MRS of highly labeled ¹⁷O‐glucose could provide a valuable non‐radioactive alternative to FDG PET in order to investigate glucose metabolism.     

Application of bioreactance for cardiac output assessment during exercise in healthy individuals

In patients with cardiac failure, bioreactance-based cardiac output (CO) monitoring provides a valid non-invasive method for assessing cardiac performance during exercise. The purpose of this study was to evaluate the efficacy of this technique during strenuous exercise in healthy, trained individuals. Fourteen recreational cyclists, mean (SD) age of 34 (8) years and relative peak oxygen uptake of (VO₂) 56 (6) ml kg⁻¹ min⁻¹, underwent incremental maximal exercise testing, whilst CO was recorded continuously using a novel bioreactance-based device (CO_bio). The CO_bio was evaluated against relationship with VO₂, theoretical calculation of arterial-venous oxygen difference (C(a − v) O₂) and level of agreement with an inert gas rebreathing method (CO_rb) using a Bland–Altman plot. Bioreactance-based CO measurement was practical and straightforward in application, although there was intermittent loss of electrocardiograph signal at high-intensity exercise. At rest and during exercise, CO_bio was strongly correlated with VO₂ (r = 0.84; P < 0.001), however, there was evidence of systematic bias with CO_bio providing lower values than CO_rb; mean bias (limits of agreement) −19% (14.6 to −53%). Likewise, calculated (C(a − v) O₂) was greater when determined using CO_bio than CO_rb (P < 0.001), although both devices provided values in excess of those reported in invasive studies. Bioreactance-based determination of CO provides a pragmatic approach to the continuous assessment of cardiac performance during strenuous exercise in trained individuals. Our findings, however, suggest that further work is needed to refine the key measurement determinants of CO using this device to improve measurement accuracy in this setting.     

A Novel Route for the Preparation of Discrete Nanostructured Carbons from Block Copolymers with Polystyrene Segments

Well‐defined nanostructured carbon was prepared by pyrolysis of core cross‐linked micelles formed from block copolymers containing polystyrene segments. These micelles were obtained by self‐assembly of poly(ethylene oxide)‐block‐polystyrene (PEO₁₁₃‐b‐PS₅₂) diblock copolymer or brush macromolecules containing polymethacrylate backbone and side chains with PS and poly(acrylic acid) block segments (PBPEM₃₃₀‐g‐PS₄₀‐b‐PAA₁₁₁) in selective solvents. UV irradiation was used to induce cross‐linking of the PS core in the micelles. After pyrolysis, the cross‐linked PS cores were converted to a partially graphitic carbon, while the shells were sacrificed, resulting in the formation of discrete carbon nano‐objects. The formation of carbon material was confirmed by Raman scattering spectroscopy while the morphology of the precursor and the resulting pyrolyzed product was studied by atomic force microscope (AFM).

     

Differential CD4+ T‐cell responses of allergic and non‐allergic subjects to the immunodominant epitope region of the horse major allergen Equ c 1

The responses of allergen‐specific CD4⁺ T cells of allergic and healthy individuals are still incompletely understood. Our objective was to investigate the functional and phenotypic properties of CD4⁺ T cells of horse‐allergic and healthy subjects specific to the immunodominant epitope region of the major horse allergen Equ c 1. Specific T‐cell lines (TCLs) and clones were generated from peripheral blood mononuclear cells with Equ c 1_143–160, the peptide containing the immunodominant epitope region of Equ c 1. The frequency, proliferative response, cytokine production and HLA restriction of the cells were examined. The frequency of Equ c 1‐specific CD4⁺ T cells was low (approximately 1 per 10⁶ CD4⁺ T cells) in both allergic and non‐allergic subjects. The cells of allergic subjects had a stronger proliferative capacity than those of non‐allergic subjects, and they predominantly emerged from the memory T‐cell pool and expressed the T helper type 2 cytokine profile, whereas the cells of non‐allergic subjects emerged from the naive T‐cell pool and produced low levels of interferon‐γ and interleukin‐10. T‐cell response to Equ c 1_143–160 was restricted by several common HLA class II molecules from both DQ and DR loci. As the phenotypic and functional properties of Equ c 1‐specific CD4⁺ T cells differ between allergic and non‐allergic subjects, allergen‐specific T cells appear to be tightly implicated in the development of diseased or healthy outcome. Restriction of the specific CD4⁺ T‐cell response by multiple HLA alleles suggests that Equ c 1_143–160 is a promising candidate for peptide‐based immunotherapy.     

Thermodynamics of 2‐Methyltrimethylene Urethane,its Polymerization in Bulk and of Poly(2‐methyl‐trimethylene urethane) Between 0 and 335 K

In an adiabatic vacuum calorimeter the temperature dependence of the heat capacity C ⁰_p of crystalline 2‐methyltrimethylene urethane (MTU; systematic name: 5‐methylperhydro‐1,3‐oxazin‐2‐one) and of amorphous poly(2‐methyltrimethylene urethane) [PMTU; systematic name: poly(5‐methyl‐2‐oxo‐1‐oxa‐3‐azahexamethylene)] was studied between 6 and 335 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield the energies of combustion ΔU_comb of the monomer and of the polymer were measured. From the experimental data the thermodynamic functions C ⁰_p (T), H ⁰(T)–H ⁰(0), S ⁰(T), G ⁰(T)–H ⁰(0) were calculated in the range of 0 to 340 K, and enthalpies of combustion ΔH⁰_comb and thermodynamic parameters of formation ΔH ⁰_f, ΔS ⁰_f, ΔG ⁰_f of the substances studied were estimated at T = 298.15 K and standard pressure. The configurational entropy S ⁰_conf of the polymer was estimated. The results were used to calculate the thermodynamic characteristics of MTU polymerization in bulk (ΔH ⁰_pol, ΔS ⁰_pol, ΔG ⁰_pol) with ring‐opening and formation of linear PMTU in the range of 0 to 340 K.     

Thermodynamics of Aliphatic Cyclic Urethanes,of Their Ring‐Opening Polymerization,and of Corresponding Polyurethanes

For some cyclic aliphatic urethanes (dimethylene urethane, trimethylene urethane, 2‐methyltrimethylene urethane, 2,2‐dimethyltrimethylene urethane, tetramethylene urethane) and the corresponding linear polyurethanes (poly(dimethylene urethane), poly(trimethylene urethane), poly(2‐methyltrimethylene urethane), poly(2,2‐dimethyltrimethylene urethane), poly(tetramethylene urethane)) the temperature dependence of the heat capacity, C⁰_p, were investigated in the range of 5–10 K to 300–450 K, and temperatures and enthalpies of physical transitions were determined at standard pressure. From the experimental data the standard thermodynamic functions, i. e., enthalpies H ⁰ (T)–H ⁰ (0), entropies S ⁰ (T), and Gibbs functions G ⁰ (T)–H ⁰ (0) were calculated in the range of 0 to 300–450 K for all compounds studied. The configurational entropies, S⁰_conf, of the polymers in the glassy and partly crystalline state were estimated. The energies of combustion of the substances were determined experimentally and the standard enthalpies of combustion Δ_comb H ⁰ and thermodynamic parameters of formation Δ_f H ⁰, Δ_f S ⁰, Δ_f G ⁰, were calculated at T = 298.15 K. The results obtained were used to calculate the standard thermodynamic parameters of ring‐opening polymerization of cyclourethanes in bulk with in the range of 0 to 300–450 K. From the thermodynamic functions, the energies of combustion and the thermodynamic parameters of formation of cyclic monomers and polymers, and the dependence of the above properties on the chemical structure of the compounds were obtained. Estimations of the corresponding properties were made for the monomers and polymers not yet studied experimentally.     

A comparison of pulse oximetry and cerebral oxygenation in children with severe sleep apnea–hypopnea syndrome: a pilot study

Near infrared spectroscopy (NIRS) has been used to assess the impact of obstructive sleep apnea–hypopnea syndrome (OSAHS) on cerebral oxygenation. However, the relationship between the variations in the cerebral tissue oxygen saturation (ΔTOI) and pulse oximetry (ΔSpO₂) has not been assessed in children with OSAHS. Consecutive clinically stable children with severe OSAHS [apnea–hypopnea index (AHI) >15 events h⁻¹] diagnosed during a night‐time polygraphy with simultaneous recording of cerebral oxygenation with NIRS (NIRO‐200NX, Hamamatsu Photonics KK) were included between September 2015 and June 2016. Maximal ΔSpO₂ (SpO₂ drop from the value preceding desaturation to nadir) and concomitant variations in transcutaneous carbon dioxide (ΔPtcCO₂), maximal ΔTOI and maximal variations in cerebral oxygenated (O₂Hb) and deoxygenated (HHb) haemoglobin were reported. The relationships between ΔSpO₂, ΔPtcCO₂ and ΔTOI, ΔO₂Hb and ΔHHb were investigated. The data from five children (three boys, aged 9.6 ± 6.7 years, AHI 16–91 events h⁻¹) were analysed. Strong correlations were found between ΔSpO₂ and ΔTOI (r = 0.887, P < 0.001), but also with ΔO₂Hb and ΔHHb with a particular pattern in the youngest child with a dark skin pigmentation. Mean ΔSpO₂ was 20 ± 17% and mean ΔTOI was 8 ± 7%. Maximal ΔSpO₂ of approximately 70% were coupled with ΔTOI of no more than 35%. ΔPtcCO₂ correlated only weakly with the cerebral oxygenation indexes. This pilot study shows a strong relationship between pulse oximetry and cerebral oxygenation in children with OSAHS, with lower changes in TOI compared to SpO₂. Future studies should address the clinical impact of respiratory events on cerebral oxygenation and its consequences.