Eubiotic effect of rifaximin is associated with decreasing abdominal pain in symptomatic uncomplicated diverticular disease: results from an observational cohort study.

BACKGROUND: Rifaximin effectively treats symptomatic uncomplicated diverticular disease (SUDD) and has shown eubiotic potential (i.e., an increase in resident microbial elements with potential beneficial effects) in other diseases. This study investigated changes in the fecal microbiome of patients with SUDD after repeated monthly treatment with rifaximin and the association of these changes with the severity of abdominal pain. METHODS: This was a single-center, prospective, observational, uncontrolled cohort study. Patients received rifaximin 400 mg twice a day for 7 days per month for 6 months. Abdominal pain (assessed on a 4-point scale from 0 [no pain] to 3 [severe pain]) and fecal microbiome (assessed using 16 S rRNA gene sequencing) were assessed at inclusion (baseline) and 3 and 6 months. The Spearman's rank test analyzed the relationship between changes in the gut microbiome and the severity of abdominal pain. A p-value ≤ 0.05 was considered statistically significant. RESULTS: Of the 23 patients enrolled, 12 patients completed the study and were included in the analysis. Baseline abdominal pain levels decreased significantly after 3 (p = 0.036) and 6 (p = 0.008) months of treatment with rifaximin. The abundance of Akkermansia in the fecal microbiome was significantly higher at 3 (p = 0.017) and 6 (p = 0.015) months versus baseline. The abundance of Ruminococcaceae (p = 0.034), Veillonellaceae (p = 0.028), and Dialister (p = 0.036) were significantly increased at 6 months versus baseline, whereas Anaerostipes (p = 0.049) was significantly decreased. The severity of abdominal pain was negatively correlated with the abundance of Akkermansia (r=-0.482; p = 0.003) and Ruminococcaceae (r=-0.371; p = 0.026) but not with Veillonellaceae, Dialister, or Anaerostipes. After 3 months of rifaximin, abdominal pain was significantly less in patients with Akkermansia in their fecal microbiome than in patients without Akkermansia (p = 0.022). CONCLUSION: The eubiotic effect of rifaximin was associated with decreased abdominal pain in patients with SUDD.

Preparation and properties of GC capillary column with hypercrosslinked stationary phase.

For the first time, highly porous hypercrosslinked polystyrene layer was synthesized within a gas chromatography capillary column and successfully deposited onto the capillary walls generating porous layer open-tubular capillary column. Elaborated three steps synthetic procedure provides tightly bonded porous polymeric layer and ensues complete elimination of particle shedding and the needs for particle traps. Due to highly developed surface area, porous layer open-tubular column provides strong solute retention that is useful for the separation of various volatile solvents and light gas compounds including ethane, ethylene, ethyne. Aqueous injections will not harm the column.

Reconstruction of the Image Metric of Periodic Structures in an Opto-Digital Angle Measurement System.

Measurement of the object angular position and its change is one of the important tasks in measurement technique. Our method is based on determination of the angular position of a 2D periodical optical pattern (2D mark) at the object, captured by the sensor of a digital camera. System performance can be frustrated by errors in determination of the spot coordinates on the camera sensor; by the presence of lens aberrations; by deviations from the parallelism of the pattern planes and the camera sensor; and by differences between the actual spots positions and the ideal grid. In the paper we discuss the effect of these errors and the way to correct or eliminate them. We have developed the mathematical routine and the corresponding numerical codes for correction of the said errors. The code and the routine we checked in a real experiment. It has shown that the correction decreases the standard deviation in 15 times.

Synthesis and evaluation of biological activity for dual-acting antibiotics on the basis of azithromycin and glycopeptides.

One of the promising directions of the combined approach is the design of dual-acting antibiotics - heterodimeric structures on the basis of antimicrobial agents of different classes. In this study a novel series of azithromycin-glycopeptide conjugates were designed and synthesized. The structures of the obtained compounds were confirmed using NMR spectroscopy and mass spectrometry data including MS/MS analysis. All novel hybrid antibiotics were found to be either as active as azithromycin and vancomycin against Gram-positive bacterial strains or have superior activity in comparison with their parent antibiotics. One compound, eremomycin-azithromycin conjugate 16, demonstrated moderate activity against Enterococcus faecium and Enterococcus faecalis strains resistant to vancomycin, and equal to vancomycin's activity for the treatment of mice with Staphylococcus aureus sepsis.

Thermal stability of poly[1-(trimethylsilyl)-1-propyne] and the gas chromatographic stationary phase based on it.

The thermal stability of poly[1-(trimethylsilyl)-1-propyne] is investigated by heating the capillary column with this polymer as the stationary phase with the subsequent separation of the test mixture of light hydrocarbons. It is shown that heating of the column up to 130°C does not cause a decrease in efficiency or in the retention time of solutes. A further increase in temperature results in both decrease in column efficiency and sorbate retention. However, a decrease in column retentivity goes in one way for all the tested hydrocarbons. At the same time, the efficiency of the column is changed to a lesser degree for methane and ethane up to the temperature of polymer degradation, while for propane, butane, and iso-butane the difference is rather sharp. The most expressed decrease in efficiency was found for iso-butane: the column efficiency for this sorbate versus temperature of heating had two stages. The diffusion coefficients for sorbates in the polymeric phase were also evaluated and the sharp decrease in their values was found after the column heating.

Investigation of poly[oligo(ethylene glycol)diacrylates] as potential stationary phases in GC.

Poly[oligo(ethylene glycol)diacrylate]s were investigated as potential candidates for application as stationary phases in capillary gas chromatography. Depending on the molar mass of the monomer, up to three different phase transitions were observed in calorimetric scans of the polymers. Two transitions have been identified as the glass transition and melting of crystallites while the nature of the third effect remains unknown. The new stationary phases demonstrate a good separating ability and selectivity in the viscous-elastic state, i.e. at temperatures above the glass transition and melting points. The new polymeric stationary phases possess selectivity similar to conventional PEG columns but provide better thermal stability than conventional PEG stationary phases.

Effect of Thermal Aging on Viscoelastic Behavior of Thermosetting Polymers under Mechanical and Cyclic Temperature Impact.

Development of load-bearing fiber reinforced plastic (hereinafter referred to as FRP) composite structures in civil engineering, exploited under high temperatures, such as industrial chimneys and gas ducts, requires the knowledge of their long-term behavior under constant and cyclic mechanical and temperature loads. Such conditions mean that the viscoelasticity of FRP should be considered along with the thermal aging effect. This research is devoted to the effects of thermal aging on the viscoelastic behavior of polymers. Two sets of experiments were conducted: creep tensile tests and cyclic heating in a constrained state. The Kelvin-Voigt viscoelasticity model was used to determine the rheological parameters of binder from experimental creep curves. Cyclic heating was used to compare the behavior of normal and thermally aged binders and to evaluate the possibility of temperature stress accumulation. Fourier-transform infrared spectroscopy was used for polymer's structural changes investigation. Both tests showed that non-aged glassed polymer (hereinafter referred to as GP) was prone to viscoelastic behavior, while the thermally aged GP lost viscosity and worked almost perfectly elastic. It was assumed that long heat treatment had caused changes in the inner structure of the GP, reducing the number of weak bonds and increasing the number of elastic ones. Therefore, the results show that the designing of FRP structures, exploited under thermomechanical load, requires using the elastic model while taking into account the properties of FRP after long-term heat treatment.

Cyclic Thermomechanical Loading of Epoxy Polymer: Modeling with Consideration of Stress Accumulation and Experimental Verification.

Developing a viscoelastic model for the cyclic thermomechanical loading of thermosetting polymers is the main goal of this study. The model includes memory for residual thermal stresses and can consider stress accumulation across many loading cycles. By considering stress accumulation, we can improve predictions and understand how thermosetting polymers' stress-strain state changes under cyclic thermomechanical loading. This approach was validated through experimental verification to ensure its applicability in practical engineering scenarios. The experiment showed that the thermosetting polymer can accumulate stress during cycles of heating and mechanical loading during use. The results of the modeling and experiment are compared. The results have led to corrections in the way this model is applied to thermosetting polymers like the epoxy resin in this study. The corrected results matched well with the experimental measurements of stress under cyclic thermomechanical load, with a difference of only 1 to 6%.

Synthesis and cytotoxicity of oligomycin A derivatives modified in the side chain.

A novel way of chemical modification of the macrolide antibiotic oligomycin A (1) at the side chain was developed. Mesylation of 1 with methane sulfonyl chloride in the presence of 4-dimethylaminopyridine produced 33-O-mesyl oligomycin in 56% yield. Reactions of this intermediate with sodium azide produced the key derivative 33-azido-33-deoxy-oligomycin A in 60% yield. 1,3-Dipolar cycloaddition reaction with propiolic acid, methyl ester of propiolic acid, and phenyl acetylene resulted in 33-deoxy-33-(1,2,3-triazol-1-yl)oligomycin A derivatives substituted at N4 of the triazole cycle. The mesylated oligomycin A and 33-deoxy-33-azidooligomycin A did not inhibit F0F1 ATFase ATPase; however, 33-azido-33-deoxy-oligomycin A and the derivatives containing 4-phenyltriazole, 4-methoxycarbonyl-triazole and 3-dimethylaminoethyl amide of carboxyltriazole substituents demonstrated a high cytotoxicity against K562 leukemia and HCT116 human colon carcinoma cell lines whereas non-malignant skin fibroblasts were less sensitive to these compounds. Novel series of oligomycin A derivatives allow for the search of intracellular molecules beyond F0F1 ATP synthase relevant to the cytotoxic properties of this perspective chemical class.

Relaxation Model of the Relations between the Elastic Modulus and Thermal Expansivity of Thermosetting Polymers and FRPs.

This research was completed in the development of studies devoted to relations between the elastic modulus (MoE) and thermal expansivity (CTe) of different materials. This study, based on experimental data, confirmed the models of the relations between MoE and CTe under normal and heating temperatures for thermosetting epoxy polymers and glass-fiber FRPs in two variants (unfilled and filled by mineral additives), after the usual glassing and prolonged thermal conditioning (thermo-relaxation). The experiment was based on dilatometric and elastic deformation testing. Two models of MoE/CTe were tested: Barker's model and our authors relaxation model (MoE = f(CTe)), which is based on previous modelling of the non-linearity of the physical properties of polymers' supramolecular structures. The result show that the models' constants depend on composition; Barker's model is applicable only to polymers with satisfying agreement degrees in the range 10-20%; our model is applicable to polymers and FRPs with satisfying agreement degrees in the range of 6-18%.

Monolithic columns with optimized pore structure for molecular size-based separations of synthetic polymers.

Monolithic capillary columns based on divinylbenzene were synthesized using different alcanols as porogens. Prepared columns were tested in separation of polystyrene standards according to their molar mass (MM) and were characterized by corresponding calibration graphs. It was demonstrated that a decrease of alcanol chain length from dodecanol to octanol resulted in a decrease of column permeability and in an improved column ability to separate polystyrene standards. In contrast, removing a good solvent from porogen mixture results in an increase of column permeability and in a decrease of column performance toward polystyrene standards. Optimized synthetic conditions included porogen composed of nonanol and toluene or mesytilene, and the column prepared with this porogen was capable of separating a mixture of 14 polystyrene standards with MM ranged from several millions to oligomers.

Separation of polystyrenes by means of open tubular capillary chromatography.

Simulating polymer separation in flow-through channels of monolithic columns, separation of a mixture of polystyrene standards was investigated using open tubular capillary column of 2 µm inner diameter. High column efficiency was observed for polymers of molar mass ranged from few tens to few hundred kDas. Column efficiency significantly decreased for polymers with molar mass larger than 500 kDa nevertheless preserving value of few tens of thousands theoretical plates. Calibration curve observed for open capillary column is rather steep and can be well described by simple equation without quadratic term. In spite of low selectivity, capillary columns were able in separating wide range of polystyrene standards due to column high efficiency and in such a way supported an idea of hydrodynamic mechanism of polymer separation in flow-through channel of monolithic packings.

Effect of Long-Term Thermal Relaxation of Epoxy Binder on Thermoelasticity of Fiberglass Plastics: Multiscale Modeling and Experiments.

The work is devoted to the prediction and experimental research of the elastic bending modulus of glass-reinforced plastics with an epoxy matrix on anhydride hardener reinforced with different glass fabrics. Experimental studies have been carried out to assess the effect of thermal relaxation of the polymer matrix structure due to long-term exposure to elevated temperatures (above the glass transition temperature of the polymer matrix) on the GRP elastic bending modulus at temperatures ranging from 25 to 180 °C. It has been shown that due to the thermal relaxation of the polymer matrix structure, the GRP modulus increases significantly at temperatures above 110 °C and decreases slightly at lower temperatures. Using a multiscale simulation based on a combination of the finite-element homogenization method in the Material Designer module of the ANSYS software package and three-point bending simulation in the ANSYS APDL module, the elastic modulus of FRP was predicted concerning the temperature, its averaged structural properties, and thermal relaxation of the polymer matrix structure. We have also carried out the prediction of the temperature dependences of the modulus of elasticity of glass-reinforced plastics on different types of glass fabrics in the range from 25 to 200 °C by using the entropic approach and the layered model.

Non-Linearity of Thermosetting Polymers' and GRPs' Thermal Expanding: Experimental Study and Modeling.

Thermal expanding is the important property that defines the stress-strain condition of GRP structures exploited under heating and having limited thermal resistance. So, the GRPs' thermal expanding prediction is the actual requirement of such structures design. The experimental accurate dilatometric study resulted in the non-linearity of thermosetting polymers and plastics thermal expanding under heating. The polymers and plastics thermal expanding coefficient (CTE) is non-linearly increasing under heating before glassing temperature (Tg). Using the previous polymers and GRPs modelling experience and experimental dilatometric results, the non-linear adequate prediction models of their CTE were proposed and proved. The new compensative wave model of polymers' CTE and multi-layer model of GRPs' CTE were proposed and successfully tested. A prediction of the temperature dependences of the thermal expansion coefficients of various thermoset polymer binders and data on the reinforcement structure was performed based on the experimentally obtained temperature dependences of the CTEs of GRPs. The prediction was performed using the finite-element homogenization method in the Material Designer module of the academic version of the Ansys package. A satisfactory concurrence of the numerical results of the prognosis and the experiment for all considered cases is observed in the temperature range from 50 to 100 °C, after glass transition temperature best coincidence of numerical values of CTE is obtained for glass-reinforced plastics on epoxy resin, which were not subjected to thermal aging.

Solid Particle Erosion of Filled and Unfilled Epoxy Resin at Room and Elevated Temperatures.

Solid particle erosion at room and elevated temperatures of filled and unfilled hot-cured epoxy resin using an anhydride hardener were experimentally tested using an accelerated method on a special bench. Micro-sized dispersed industrial wastes were used as fillers: fly ash from a power plant and spent filling material from a copper mining and processing plant. The results showed that the wear of unfilled epoxy resin significantly decreases with increasing temperature, while the dependence on the temperature of the wear intensity at an impingement angle of 45° is linear and inversely proportional, and at an angle of 90°, non-linear. The decrease in wear intensity is probably due to an increase in the fracture limit because of heating. Solid particle erosion of the filled epoxy compounds is considerably higher than that of unfilled compounds at impingement angles of 45° and 90°. Filled compounds showed ambiguous dependences of the intensity of wear on temperature (especially at an impingement angle of 45°), probably as the dependence is defined by the filler share and the structural features of the samples caused by the distribution of filler particles. The intensity of the wear of the compounds at impingement angles of 45° and 90° has a direct and strong correlation with the density and the modulus of elasticity, and a weak correlation with the bending strength of the materials. The data set for determining the correlation between the mechanical properties and the wear included compound filling characteristics and temperature.

Impact of the Polymer Backbone Structure on the Separation Properties of New Stationary Phases Based on Tricyclononenes.

The main purpose of this paper is to compare the chromatographic properties of capillary columns prepared with polymers with different backbone structures and to demonstrate the possibility of polymer differentiation via inverse gas chromatography. With the use of addition and metathesis types of polymerization of tricyclononenes, two new stationary phases were prepared. The metathesis polymer contained double bonds in the polymeric backbone while the backbone of the addition polymer was fully saturated and relatively mobile. A comparison of the separation and adsorption properties of new phases with conventional gas chromatography (GC) stationary phases clearly indicated their non-polar characteristics. However, the difference in the polymer structure appeared to have very little effect on the stationary phase separation properties, so other parameters were used for polymer characterization. The thermodynamic parameters of the sorption of alkanes and aromatic compounds in both polymeric stationary phases were also very similar; however, the entropy of sorption for hydrocarbons with seven or more carbon atoms was different for the two polymers. An evaluation of the specific surface energy of the stationary phases also allowed us to discriminate the two stationary phases.

Enthalpy-entropy compensation effect on adsorption of light hydrocarbons on monolithic stationary phases.

Enthalpy and entropy of adsorption of light hydrocarbons C1-C4 have been measured for three monoliths of different polarity and for five different carrier gases: helium, hydrogen, nitrogen, carbon dioxide and dinitrogen oxide. Using carrier gas helium the highest values of enthalpy and entropy were observed for monolith based on ethylenedimethacrylate and the lowest values were observed for monolith based on silica, while monolith based on divinylbenzene demonstrated intermediate values. Entropy-enthalpy correlations were observed with carrier gas helium for all thee monoliths and possess similar slope indicating similar adsorption mechanism on all monoliths studied. Comparing different carrier gases entropy-enthalpy correlations within a homological series of solutes were observed for light carrier gases (He, H2 and N2) and were not observed for heavy carrier gases (CO2 and N2O). Instead, entropy-enthalpy correlations for heavy carrier gases were observed with pressure as variable and the higher the carrier gas pressure the lower the values of enthalpy and entropy observed. The observed changes in entropy-enthalpy correlations were explained by competitive adsorption of heavy carrier gas on monoliths.

The Struggle for Certainty: Ontological Security, the Rise of Nationalism, and Australia-China Tensions after COVID-19.

Australia-China relations have been relatively stable over the last decade. However, soon after the outbreak of COVID-19, Australia took an increasingly assertive stance toward China, one that is arguably even more assertive than those of its Western allies. What prompted Australia to adopt a tougher policy against China? This article argues that COVID-19 has brought significant uncertainty to the international system and, hence, to Australia's external environment, which has affected the country's decision-making, accelerating the formation of a hardline policy toward China. A contributing factor behind this policy is Australia's quest for ontological security, which, in the context of COVID-19, has triggered a rise in anti-China sentiment. Meanwhile, this strategy backfired when it encountered China's own nationalism, which exacerbated the widening political chasm, dragging the two countries into an unprecedented diplomatic confrontation. The core of ontological security lies in maintaining the stability of the identity needed for the formation of consistent policy. The uncertainties created by the COVID-19 pandemic have changed the familiar external environment and challenged Australia's ability to interpret this new environment and adjust to it, which has triggered ontological insecurity. By analyzing Australia's identity as a middle power in the context of changing regional security and its commitment to certain values, the article shows how COVID-19 has accelerated Australia's quest for ontological security, which has changed the country's China policy.

Prolonged Thermal Relaxation of the Thermosetting Polymers.

The rigidity of structures made of polymer composite materials, operated at elevated temperatures, is mainly determined by the residual rigidity of the polymer binder (which is very sensitive to elevated temperatures); therefore, the study of ways to increase the rigidity of polymer materials under heating (including prolonged heating) is relevant. In the previous research, cured thermosetting polymer structure's non-stability, especially under heating, is determined by its supra-molecular structure domain's conglomerate character and the high entropy of such structures. The polymer elasticity modeling proved the significance of the entropy factor and layer (EPL) model application. The prolonged heating makes it possible to release adsorptive inter-layer bonds and volatile groups. As a result, the polymer structure is changing, and inner stress relaxation occurs due to this thermo-process, called thermo-relaxation. The present study suggests researching thermo-relaxation's influence on polymers' deformability under load and heating. The research results prove the significant polymer structure modification due to thermo-relaxation, with the polymer entropy parameter decreasing, the glassing onset temperature point (Tg) increasing by 1.3-1.7 times, and the modulus of elasticity under heating increasing by 1.5-2 times.

Chromatographic Method for Evaluation of Polymeric GC Stationary Phases Ageing Using the Novel Non-Cross-Linked Poly(3-(Tributoxysilyl)Tricyclononene-7) as the Model Stationary Phase.

The chromatographic properties and thermal stability are investigated for the polymeric stationary phase based on the norbornene polymer. It was shown that without additional cross-linking, poly(3-(tributoxysilyl)tricyclononene-7) demonstrates properties similar to liquid chromatographic stationary phases. It was also found to be more thermally stable than previously studied trimethylsilyl- and trimethoxysilyl- derivatives. The long-term heating at 170 °C resulted in an increase of mass transfer rate between stationary and mobile phases which could be observed as a decrease of parameter C of Van Deemter equation. This effect is rather unusual, as the polymeric stationary phases tend in decrease of the layer volume and porosity while ageing. Additionally, the values of thermodynamic parameters of sorption are calculated for the polymeric stationary phase: enthalpy of sorption varied -28 to -37 kJ/mol, entropy change was -41 to -51 J/mol K. The compensation curves were plotted for the alkanes, arenes, and alcohols, and the parameters of compensation plot were calculated, demonstrating the different sorption mechanisms both for hydrocarbons and oxygen-containing compounds, and different classes of organic compounds.