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The aim of this study is to examine the interactions of composite materials obtained by adding single-walled carbon nanotubes (SWCNT) to polyetherimide (ULTEM) in different weight ratios with various organic solvents, and to evaluate the solubility of composites in these organic solvents. The characterization of prepared composites was performed with SEM analysis. Thermodynamic properties of ULTEM/SWCNT composites were determined by the inverse gas chromatography (IGC) method at 260–285°C in infinite dilution. According to the IGC method, the retention behaviors were examined by passing different organic solvent vapors over the composites used as stationary phase, and retention diagrams were drawn using the obtained retention data. Thermodynamic parameters including Flory–Huggins interaction parameters (⁠|${\chi}_{12}^{\infty }$|⁠), equation of state interaction parameters (⁠|${\chi}_{12}^{\ast }$|⁠), weight fraction activity coefficients in infinite dilution (⁠|${\Omega}_1^{\infty }$|⁠), effective exchange energy parameters (⁠|${\chi}_{\mathrm{eff}}$|⁠), partial molar sorption enthalpies (⁠|$\Delta{\overline{H}}_1^S$|⁠), partial molar dissolution enthalpies in infinite dilution (⁠|$\Delta{\overline{H}}_1^{\infty }$|⁠) and molar evaporation enthalpies (⁠|$\Delta{\overline{H}}_v$|⁠) were calculated using the linear retention diagrams. According to |${\chi}_{12}^{\infty }$|⁠ , |${\chi}_{12}^{\ast }$|⁠ , |${\Omega}_1^{\infty }$| and |${\chi}_{\mathrm{eff}}$| values, organic solvents were found to be poor solvents for composites at all temperatures. Besides, the solubility parameters of composites were determined by IGC method at infinite dilution. [ABSTRACT FROM AUTHOR]

In this study, Phenylbenzoate-based calamitic liquid crystals (LCs) were synthesized and characterized, and then the thermodynamic properties and phase transition temperatures were investigated by inverse gas chromatography (IGC) at infinite dilution. The phase transition temperatures of the LCs were determined in the range of 40–170°C by the IGC method. Finally, in the thermodynamic equilibrium region (the range of 160–200°C), Flory-Huggins theory and the equation of state theory with the LC-solvent interaction parameters, the effective exchange energy parameters, the weight fraction activity coefficient, and also the partial molar heat of mixing at infinite dilution of solvent, the molar heat of vaporization of solvent, and the partial molar heat of sorption of solvent were calculated. [ABSTRACT FROM AUTHOR]

The boron-based ceramics namely hexagonal boron nitride (h-BN) and boron phosphate (BPO4) were synthesized and characterized by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The surface properties of h-BN and BPO4 were examined by inverse gas chromatography method. The dispersive surface energy and the acidic-basic character of h-BN, and BPO4 surfaces were estimated by the retention time with probes such as n -hexane, n -heptane, n -octane, n -nonane, n -decane, acetone, ethyl acetate, dichloromethane, chloroform and tetrahydrofuran at infinite dilution region. The dispersive surface free energies calculated using both Schultz and Dorris–Gray methods, decreased linearly with increasing temperature. The specific adsorption free energy and the specific adsorption enthalpy corresponding to acid–base surface interactions were determined. By correlating with the donor and acceptor numbers of the probes, the acidic and the basic parameters of the h-BN and BPO4 were calculated. The values obtained for and parameters indicated that h-BN has a basic character, whereas BPO4 has an acidic character. [ABSTRACT FROM AUTHOR]

The ability to separate isomer series and the surface properties of cholesteryl chloroformate (CC) liquid crystal were investigated by inverse gas chromatography (IGC). The retention diagrams of the selected solvents were plotted between 308.2 and 333.2 K using the IGC technique. The selectivity coefficients, α, of the structural isomers were determined for the CC liquid crystal in the infinite dilution. Besides, the dispersive energy, γ S D , the Gibbs specific energy, Δ G A S , the adsorption enthalpy, Δ H A S , the adsorption entropy, Δ S A S , of the selected solvents were also determined. The Δ H A S values were associated with the number of acidic and basic group to calculate the acidity constant ( K A ) and the basicity constant ( K D ). When the Δ H A S values calculated in experimental studies were examined, it was seen that the adsorption takes place exothermically. According to K A and K D constants, CC surface was found to be basic character ( K D / K A ≅ 3.11). [ABSTRACT FROM AUTHOR]

Introduction: Urtica dioica (nettle) is a plant species of the Urticaceae family that grows in various parts of the world and exerts antioxidant, antibacterial, antiulcer, antiviral, and anti‐inflammatory effects. Their leaves, roots, and seeds are used in various fields such as food, medicine, and cosmetics. Objectives: Inverse gas chromatography (IGC) was used to evaluate the surface characteristics and separation ability of U. dioica leaves, roots, and seeds. Characterization of these biomasses was performed by Fourier transform infrared spectroscopy (FTIR) analyses. Methodology: The surface properties of the biomasses including dispersive surface energy, adsorption enthalpy, Gibbs free energy, and acidity‐basicity constants were determined at infinite dilution using various organic solvents. These properties were compared with each other. Dispersive surface energies were calculated using the Dorris–Gray, Donnet–Park, and Schultz methods. The accuracy of these methods and their applicability were evaluated. In the last stage of this study, the separation of xylene isomers was investigated by using U. dioica biomasses as stationary phases. Results: The surface functional groups were determined by FTIR analysis. As a result of the IGC studies, it was found that the adsorption of polar solvents on biomasses occurred exothermically and spontaneously. Besides, it was found that the surfaces of biomasses were basic. From the retention diagrams and selectivity coefficients, it was determined that xylene isomers were effectively separated. Conclusion: IGC is a promising, low‐cost, easy‐to‐apply, and high‐accuracy technique for the investigation of the surface properties of biomasses and their ability to separate isomers. The surface properties and separation ability of xylene isomers of Urtica dioica leaves, roots and seeds were investigated using the inverse gas chromatography (IGC) technique. Characterization of biomass was carried out by FTIR analysis. The surfaces of biomasses were determined to be a basic by IGC. It was also observed that it effectively separate Xylene isomers. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of 4-(octyloxy) benzoic acid (OBA) liquid crystal (LC) were investigated at infinite dilution by inverse gas chromatography (IGC). The phase transition temperatures of OBA LC were determined by differential scanning calorimetry (DSC) and IGC. The thermodynamic region was determined to be between 160 and 170 °C. Specific retention volumes were calculated using IGC measurements to prepare retention diagrams. The results from the diagrams were used to characterize the thermodynamic properties of the OBA LCs. Based upon these properties, the solvents used in this study were determined to be unsuitable for OBA LCs. The separation of structural isomer series (butyl acetate, butyl alcohol, and amyl alcohol series) was studied by an OBA LC coated Chromosorb W stationary phase in the thermodynamic region. This system was able to distinguish the isomers according to the determined selectivity coefficients. [ABSTRACT FROM AUTHOR]

A highly ordered porous film was fabricated by the sol‐gel process using 3‐mercaptopropyltrimethoxysilane (MPTMS) precursor and polystyrene microspheres template. The liquid crystal (LC) (4‐(Octyloxy) benzoic acid) (OBA) was entrapped into the voids of the pre‐fabricated porous structure to obtain sensing materials that were characterized by scanning electron microscope (SEM) and fourier transform infrared spectroscopy (FT‐IR). The impedance of the films was measured and the capacitive reactance response (1/‐X) of LC‐based sensor exhibited satisfactory linear correlation (R2=0.9994) with the concentration of ammonia up to 50 ppm with a limit of detection (LOD) and quantification of 1.2 ppm and 4.0 ppm, respectively. The sensor exhibited high selectivity to ammonia compared to the different classes of solvent vapors, and satisfactory repeatability (RSD=4 %) and response time (10 min). Also, inverse gas chromatography (IGC) was used to confirm the acidic surface behavior of LC and its selectivity to ammonia. The results proved that the studied LC‐based sensor may be promise candidate for sensitive and selective determination of ammonia. [ABSTRACT FROM AUTHOR]

In the first part of this study, poly(methyl methacrylate) (PMMA)/multiwall carbon nanotube (MWCNT) nanocomposite was synthesized by adding carbon nanotube before polymerization with bulk polymerization. Surface morphology of the PMMA/MWCNT nanocomposite and the PMMA/MWCNT nanocomposite with Chromosorb W was characterized by scanning electron microscopy (SEM). Surface and thermodynamic properties of the PMMA/MWCNT nanocomposite were investigated by inverse gas chromatography (IGC). The surface acid base character and dispersed surface energy γSD of the PMMA/MWCNT were determined at infinite dilution. The entropy of adsorption, ∆SS, the specific free energy of adsorption, ∆GS, and the enthalpy of adsorption, ∆HS, of selected polar solvents were determined on the PMMA/MWCNT nanocomposite. The values of ∆HS were correlated with both the acceptor and donor numbers of the solvents to determine the Lewis acidic constant KA and the Lewis basic constant KD of the PMMA/MWCNT nanocomposite. The PMMA/MWCNT nanocomposite selectivity was investigated using the acetate and alcohol isomers by IGC at temperatures between 393.2 and 403.2 K. Glass transition temperature (Tg) was determined using differential scanning calorimetry (DSC) and IGC method. The interactions between the PMMA/MWCNT nanocomposite and 12 solvents were propped at a temperature range (423.2–448.2 K). The Flory–Huggins interaction parameter, χ12∞, and the weight fraction activity coefficient, Ω1∞, of the PMMA/MWCNT nanocomposite solvent system were estimated at temperatures between 423.2 and 448.2 K. The solubility parameter of the PMMA/MWCNT nanocomposite, δ2, was calculated as 14.0 (cal/cm3)1/2. [ABSTRACT FROM AUTHOR]

The novel chalcone modified poly (styrene) based polymer (PVBC-DMAC) has been prepared and characterized. By using the inverse gas chromatography method, we determined glass transition temperature and surface properties of PVBCDMAC. The obtained glass transition temperature, Tg, is a good agree with the one obtained by differential scanning calorimetry. Also considering some isomeric alcohol and acetate solvents in the temperature range from 303.2 K to 353.2 K, we investigated the polymer selectivity. The parameters KA (acidic) and KD (basic) of the PVBC-DMAC surface were calculated. The obtained KA, KD values reflected that PVBC-DMAC surface has a basic character. [ABSTRACT FROM AUTHOR]

The facultative human pathogen Vibrio cholerae changes its transcriptional profile upon oral ingestion by the host to facilitate survival and colonization fitness. Here, we used a modified version of recombination-based in vivo expression technology to investigate gene silencing during the in vivo passage, which has been understudied. Using a murine model of cholera, we screened a V. cholerae transposon library composed of 10,000 randomly generated reporter fusions and identified 101 in vivo repressed (ivr) genes. Our data indicate that constitutive expression of ivr genes reduces colonization fitness, highlighting the necessity to down-regulate these genes in vivo. For example, the ivr gene clcA, encoding an H+/Cl- transporter, could be linked to the acid tolerance response against hydrochloric acid. In a chloride-dependent manner, ClcA facilitates survival under low pH (e.g., the stomach), but its presence becomes detrimental under alkaline conditions (e.g., lower gastrointestinal tract). This pH-dependent clcA expression is controlled by the LysR-type activator AphB, which acts in concert with AphA to initiate the virulence cascade in V. cholerae after oral ingestion. Thus, transcriptional networks dictating induction of virulence factors and the repression of ivrgenes overlap to regulate in vivo colonization dynamics. Overall, the results presented herein highlight the impact of spatiotemporal gene silencing in vivo. The molecular characterization of the underlying mechanisms can provide important insights into in vivo physiology and virulence network regulation. [ABSTRACT FROM AUTHOR]

The miscibility behavior of binary mixtures of polymeric and low molecular weight molecule was studied using viscometric analysis, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The miscibility criteria of liquid crystal 4-[4-(tetradecyloxy) benzoyloxy]benzoic acid (TBBA) and poly(ether imide) (Ultem) was investigated at 30°C in dilute chloroform solutions by viscometric analysis. The intrinsic viscosity and viscometric parameters of this mixture system were determined for several TBBA/Ultem mixtures in compositions such as 80/20, 60/40, 40/60 and 20/80 in chloroform solutions. The miscibility criteria on the basis of the sign of Δbm, Δb′m, Δb″mand Δ[η]mwhich are the difference between their experimental and ideal values were calculated by applying equations proposed by Krigbaum–Wall, Catsiff–Hewett and Garcia et al. The methods were extended to the bulk state by obtaining the criteria from extrapolated experimental data to the zero of reciprocal of concentration. The miscibility of the mixtures was also studied by DSC and FTIR. [ABSTRACT FROM PUBLISHER]

Salmonella enterica serovar Typhimurium is an enteric pathogen associated with foodborne disease. Salmonella invades the intestinal epithelium using a type three secretion system encoded on Salmonella pathogenicity island 1 (SPI-1). SPI-1 genes are tightly regulated by a complex feed-forward loop to ensure proper spatial and temporal expression. Most regulatory input is integrated at HilD, through control of hilD mRNA translation or HilD protein activity. The hilD mRNA possesses a 310-nucleotide 3' untranslated region (UTR) that influences HilD and SPI-1 expression, and this regulation is dependent on Hfq and RNase E, cofactors known to mediate small RNA (sRNA) activities. Thus, we hypothesized that the hilD mRNA 3' UTR is a target for sRNAs. Here, we show that two sRNAs, SdsR and Spot 42, regulate SPI-1 by targeting different regions of the hilD mRNA 3' UTR. Regulatory activities of these sRNAs depended on Hfq and RNase E, in agreement with previous roles found for both at the hilD 3' UTR. Salmonella mutants lacking SdsR and Spot 42 had decreased virulence in a mouse model of infection. Collectively, this work suggests that these sRNAs targeting the hilD mRNA 3' UTR increase hilD mRNA levels by interfering with RNase E-dependent mRNA degradation and that this regulatory effect is required for Salmonella invasiveness. Our work provides novel insights into mechanisms of sRNA regulation at bacterial mRNA 3' UTRs and adds to our knowledge of post-transcriptional regulation of the SPI-1 complex feed-forward loop. IMPORTANCE Salmonella enterica serovar Typhimurium is a prominent foodborne pathogen, infecting millions of people a year. To express virulence genes at the correct time and place in the host, Salmonella uses a complex regulatory network that senses environmental conditions. Known for their role in allowing quick responses to stress and virulence conditions, we investigated the role of small RNAs in facilitating precise expression of virulence genes. We found that the 3' untranslated region of the hilD mRNA, encoding a key virulence regulator, is a target for small RNAs and RNase E. The small RNAs stabilize hilD mRNA to allow proper expression of Salmonella virulence genes in the host. [ABSTRACT FROM AUTHOR]

The inverse gas chromatography (IGC) method was used to obtain thermodynamic and surface properties of the thermotropic liquid crystalline material, 4-[4-((S)-citronellyloxy)benzoyloxy]benzoic acid (CBB). Liquid crystal (LC) selectivity was investigated using the alcohol and acetate isomers by the IGC method at temperatures between 338.2 K and 463.2 K. The retention diagrams of n-decane, undecane, dodecane, tridecane, n-butyl acetate, iso-butyl acetate, ethylbenzene and chlorobenzene onCBBwere plotted in the temperature range between 468.2 K and 493.2 K. The specific retention volume,, Flory–Huggins interaction parameter,, equation-of-state interaction parameter,, the partial molar heat of sorption,, the partial molar heat of mixing,, the molar heat of vaporization,and the weight fraction activity coefficient,, were determined. The dispersive component of the surface free energy,, of the studied adsorbent surface was estimated in the infinite dilution region. The specific free energy of adsorption,, the enthalpy of adsorption,and the entropy of adsorption,, of solvents on LC were determined. The values ofwere correlated with the donor and the acceptor numbers of the probes to quantify the acidicand the basicparameters of the LC surface. The values obtained forandparameters indicated an acidic character for the surface ofCBB. [ABSTRACT FROM PUBLISHER]

A new chiral calamitic liquid crystal 4′-((S)-3,7-dimethyloctyloxy)phenyl 4-(10-undecen-1-yloxy)benzoate (DOPUB) has been synthesized and characterized by spectroscopic methods (1H-NMR and13C-NMR). The focus is on the preparation of the nanocomposites of new chiral calamitic liquid crystal DOPUB/Organo-montmorillonite clay (OMMT) by solution intercalation method addition with OMMT contents 2.5, 5, and 7.5 wt% and determination of the morphology, thermal behavior, and crystalline properties of liquid crystal DOPUB/OMMT. Montmorillonite (MMT) modified by cationic surfactant cetyltrimethylammonium bromide (CTAB) for increasing the interaction of clay with DOPUB liquid crystal. The characterization of clay minerals and nanocomposites was investigated by X-ray diffraction. The mesomorphic behavior of liquid crystal (DOPUB) and the nanocomposites was investigated by differential scanning calorimetry (DSC) and optical polarizing microscopy (PM). [ABSTRACT FROM AUTHOR]

The inverse gas chromatography method was used to obtain thermodynamic and surface properties of the thermotropic liquid crystalline material, 4-[4-(2-ethylhexyloxy)benzoyloxy]benzoic acid (EBBA). The retention diagrams of undecane, dodecane, tridecane, ethyl acetate,n-butyl acetate, iso-butyl acetate, toluene, ethylbenzene, iso-propylbenzene,n-propylbenzene and chlorobenzene onEBBAwere plotted at temperatures between 443.2 and 468.2 K. The specific retention volume,, Flory–Huggins interaction parameter,, equation-of-state interaction parameter,, and effective exchange energy parameter,, were determined. The dispersive component of the surface free energy,, of the studied adsorbent surface was estimated using retention times of different nonpolar organic solvents in the infinite dilution region. The specific free energy of adsorption,the enthalpy of adsorption,, and the entropy of adsorption,, of solvents on liquid crystal were determined. The values ofwere correlated with the donor and the acceptor numbers of the probes to quantify the acidicand the basicparameters of the liquid crystal surface. The values obtained forandparameters indicated an acidic character for the surface ofEBBA. [ABSTRACT FROM AUTHOR]

An inverse gas chromatographic (IGC) study of the sorption properties of poly(ethylene glycol) modified with tosylate (PEG-TOS) was presented. PEG-TOS was synthesized via the tosylation of the corresponding poly(ethylene glycol) (PEG) with p-toluenesulfonyl chloride in the basic medium. The synthesized PEG-Tos was characterized by FTIR-ATR and ¹HNMR techniques. The retention diagrams of n-hexane, n-heptane, n-octane, n-nonane, n-decane, dichloromethane, chloroform, acetone, tetrahydrofuran, ethyl acetate, and ethanol on the PEG and PEG-Tos were plotted at temperatures in K between 303 and 373 by inverse gas chromatography technique. The dispersive component of the surface-free energy, γsD, of studied adsorbent surface was estimated using retention times of different nonpolar organics in the infinite dilution region. Thermodynamic parameters of adsorption (free energy, ΔGAS, enthalpy, ΔHAS, and entropy, ΔSAS), dispersive components of the surface energies, γSD, and the acid, KA, and base, KD, constants for the PEG and PEG-Tos were calculated and the results were discussed. [ABSTRACT FROM AUTHOR]

A new banana-shaped liquid crystal compound, i.e., the bent-core mesogen, 4-Bromo-1,3-phenylene-bis[4-[4'-(10-undecenyloxy)-benzoyloxy]]benzoate (BPUBB), has been synthesized and characterized. Phase transition temperatures of BPUBB were determined by polarizing microscopy and differential scanning calorimetry. The inverse gas chromatography method was utilized to obtain the surface characterization of BPUBB. This compound was used as a stationary phase in the chromatographic column and nine solutes with a different chemical nature were used as eluents. The dispersive component of the surface free energy, γDS, of studied adsorbent surface was estimated using retention times of different nonpolar organics in the infinite dilution region. The specific free energy of adsorption, ΔGSA, the enthalpy of adsorption, ΔHS A, and the entropy of adsorption, ΔSSA, of solvents on liquid crystal were determined. The values of the ΔHSA were correlated with both the donor and the acceptor numbers of the probes to quantify the acid KA and the basic KD parameters of the liquid crystal surface. The values obtained for the KA and KD parameters indicated a basic character for the surface of the BPUBB. [ABSTRACT FROM AUTHOR]

Salmonella enterica serovar Typhimurium invades the intestinal epithelium and induces inflammatory diarrhea using the Salmonella pathogenicity island 1 (SPI1) type III secretion system (T3SS). Expression of the SPI1 T3SS is controlled by three AraC-like regulators, HilD, HilC, and RtsA, which form a feed-forward regulatory loop that leads to activation of hilA, encoding the main transcriptional regulator of the T3SS structural genes. This complex system is affected by numerous regulatory proteins and environmental signals, many of which act at the level of hilD mRNA translation or HilD protein function. Here, we show that the sRNA MicC blocks translation of the hilD mRNA by base pairing near the ribosome binding site. MicC does not induce degradation of the hilD message. Our data indicate that micC is transcriptionally activated by SlyA, and SlyA feeds into the SPI1 regulatory network solely through MicC. Transcription of micC is negatively regulated by the OmpR/EnvZ two-component system, but this regulation is dependent on SlyA. OmpR/EnvZ control SPI1 expression partially through MicC but also affect expression through other pathways, including an EnvZ-dependent, OmpR-independent mechanism. MicC-mediated regulation plays a role during infection, as evidenced by an SPI1 T3SS-dependent increase in Salmonella fitness in the intestine in the micC deletion mutant. These results further elucidate the complex regulatory network controlling SPI1 expression and add to the list of sRNAs that control this primary virulence factor. [ABSTRACT FROM AUTHOR]

The article presents a study on the swelling behavior of poly(p-chloro styrene) or PPCS networks in aromatic hydrocarbons and linear PPCS (LPPCS) solutions. It investigated the variation of interaction parameter between crosslinked networks NPPCS and LPPCs with molecular weight and concentration of the linear polymer. It found that the parameter X'23 decreased with molecular weight but increased with concentration of LPPCS in outer solution.

A new liquid crystalline compound, i.e. (S)-5-(2-methylbutoxy)-2-{[(4-dodecyloxyphenyl)imino]methyl}phenol (MBDOPIMP), was prepared and characterised. Phase transition temperatures of MBDOPIMP were determined by polarising optical microscopy and differential scanning calorimetry. Trace amounts of ethyl acetate, butyl acetate, isobutyl acetate, hexane, heptane, octane, nonane and decane were passed through a chromatographic column loaded with MBDOPIMP coated on Chromosorb W. The retention diagrams of the solvents on MBDOPIMP were plotted using specific retention volumes at temperatures between 105 and 125°C. Thermodynamic parameters, such as Flory-Huggins liquid-solvent interaction, [image omitted] , equation-of-state liquid-solvent interaction, [image omitted] , effective exchange energy, X eff, the exchange enthalpy, X 12 and exchange entropy, Q 12, were determined for the liquid crystal-solvent systems. Subsequently, the partial molar heats of sorption, ΔH1,sorp and mixing, [image omitted] , were determined from the slopes of the plots of the logarithm of the specific retention volume, ln [image omitted] , versus 1/T and logarithm of the weight fraction activity coefficients, ln [image omitted] , versus 1/T, respectively. [ABSTRACT FROM AUTHOR]