Quantitative Study on Solubility Parameters and Related Thermodynamic Parameters of PVA with Different Alcoholysis Degrees

In recent years, inverse gas chromatography (IGC) and molecular dynamics simulation methods have been used to characterize the solubility parameters and surface parameters of polymers, which can provide quantitative reference for the further study of the surface and interface compatibility of polymer components in the future. In this paper, the solubility parameters and surface parameters of two kinds of common alcoholysis, PVA88 and PVA99, are studied by using the IGC method. The accuracy of the solubility parameters obtained by the IGC experiment is verified by molecular dynamics simulation. On the basis of this, the influence of repeated units of polyvinyl alcohol (PVA) on solubility parameters is studied, so as to determine the appropriate chain length of the PVA for simulation verification calculation. The results show that the solubility parameters are not much different when the PVA chain length is 30 and above; the numerical trends of the solubility parameters of PVA88 and PVA99 at room temperature are the same as the results of molecular dynamics simulation; the dispersive surface energy γsd and the specific surface energy γssp are scattered with the temperature distribution and have a small dependence on temperature. On the whole, the surface energy of PVA99 with a higher alcoholysis degree is higher than that of PVA88 with a lower alcoholysis degree. The surface specific adsorption free energy (ΔGsp) indicates that both PVA88 and PVA99 are amphoteric meta-acid materials, and the acidity of PVA99 is stronger.

Inverse gas chromatographic evaluation of polysiloxanes containing phenolic and fluorophenolic functional groups for use in gas sensors

The paper presents the results of inverse gas chromatographic (IGC) research on two novel polysiloxanes: poly{dimethylsiloxane-co -[4-(2,3-difluoro-4-hydroxyphenoxy)butyl]methylsiloxane} and poly{dimethylsiloxane-co -[4-(4-hydroxyphenoxy)butyl]methylsiloxane}, dubbed PMFOS and PMOS respectively, designed for use as chemosensitive coatings for acoustoelectronic sensors. These materials contain phenolic functional substituents that differ by the presence of fluorine atoms. The materials' solvation properties were identified by IGC with application of an LSER solvation model at temperatures ranging from 40 to 120 °C. In the case of both polysiloxanes, the research revealed that the dominant type of intermolecular interaction was the formation of acidic hydrogen bonds. The material with fluorine-activated hydroxyl groups, PMFOS, is much more acidic and less basic than the other one and thus more interesting. According to LSER, PMFOS exhibits high affinity and selectivity to hydrogen bond bases. In addition, the material retains its properties even at a temperature of 120 °C.

Application of finite inverse gas chromatography in hypromellose acetate succinate-water-acetone systems

A modification of a GC was developed to investigate both infinitely dilute and finite concentrations of solvents in polymers. Thermodynamic properties of hypromellose acetate succinate (HPMCAS-L)-acetone-water systems are important for the optimization of spray-drying processes used in pharmaceutical manufacturing of solid dispersion formulations. These properties, at temperatures below the glass transition temperature, were investigated using capillary column inverse gas chromatography (CCIGC). Water was much less soluble in the HPMCAS-L than acetone. Experiments were also conducted at infinitely dilute concentrations of one of the solvents in HPMCAS-L that was already saturated with the other solvent. Overall the partitioning of the water was not significantly affected by the presence of either water or acetone in the polymer. The acetone partition coefficient decreased as either acetone or water was added to the HPMCAS-L. A representation of the HPMCAS-L structure in terms of UNIFAC groups has been developed. With these groups, the UNIFAC-vdw-FV model did a reasonable job of predicting the phase equilibria in the binary and ternary systems. The Flory-Huggins correlation with fitted interaction parameters represented the data well.

Inverse gas chromatography applications: a review

Inverse gas chromatography (IGC) is a versatile, powerful, sensitive and relatively fast technique for characterizing the physicochemical properties of materials. Due to its applicability in determining surface properties of solids in any form such as films, fibres and powders of both crystalline and amorphous structures, IGC became a popular technique for surface characterization, used extensively soon after its development. One of the most appealing features of IGC that led to its popularity among analytical scientists in early years was its similarity in principle to analytical gas chromatography (GC). The main aspect which distinguishes IGC experiments from conventional GC is the role of mobile and stationary phases. Contrary to conventional GC, the material under investigation is placed in the chromatographic column and a known probe vapour is used to provide information on the surface. In this review, information concerning the history, instrumentation and applications is discussed. Examples of the many experiments developed for IGC method are selected and described. Materials that have been analysed include polymers, pharmaceuticals, minerals, surfactants, and nanomaterials. The properties that can be determined using the IGC technique include enthalpy and entropy of sorption, surface energy (dispersive and specific components), work of co/adhesion, miscibility and solubility parameters, surface heterogeneity, glass transition temperature, and specific surface area.

Peri-procedural tight glycemic control during early percutaneous coronary intervention up-regulates endothelial progenitor cell level and differentiation during acute ST-elevation myocardial infarction: effects on myocardial salvage

BACKGROUND

We examined the effects of peri-procedural intensive glycemic control during early percutaneous coronary intervention (PCI) on the number and differentiation of endothelial progenitor cells (EPCs) and myocardial salvage (MS) in hyperglycemic patients with first ST-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

We conducted a randomized, prospective, open label study on 194 patients with STEMI undergoing PCI: 88 normoglycemic patients (glucose < 140 mg/dl) served as the control group. Hyperglycemic patients (glucose ≥140 mg/dl) were randomized to intensive glycemic control (IGC) for almost 24 h after PCI (n = 54; 80-140 mg/dl) or conventional glycemic control (CGC, n = 52; 180-200 mg/dl). EPC number, differentiation, and SIRT1expression were assessed immediately before, 24 h, 7, 30 and 180 days after PCI. The primary end point of the study was salvage index, measured as the proportion of initial perfusion defect (acute technetium-99m sestamibi scintigraphy, performed 5 to 7 days after STEMI) and myocardium salvaged by therapy (6 months after STEMI). Hyperglycemic patients had lower EPC number and differentiation and lower SIRT1 levels than normoglycemic patients (P < 0.01). After the insulin infusion, mean plasma glucose during peri-procedural period was greater in CGC group than in IGC group (P < 0.001). The EPC number, their capability to differentiate, and SIRT1 levels were significantly higher in IGC group than in CGC, peaking after 24 h (P < 0.01). In the IGC group, the salvage index was greater than in patients treated with CGC (P < 0.001).

CONCLUSIONS

Optimal peri-procedural glycemic control, by increasing EPC number and their capability to differentiate, may improve the myocardial salvage.

Longitudinal description of the glasgow outcome scale-extended for individuals in the traumatic brain injury model systems national database: a National Institute on Disability and Rehabilitation Research traumatic brain injury model systems study

OBJECTIVE

To comprehensively describe the temporal patterns of global outcome after traumatic brain injury (TBI) in the Traumatic Brain Injury Model Systems National Database (TBIMS NDB).

DESIGN

Longitudinal prospective cohort study.

SETTING

TBI Model Systems centers.

PARTICIPANTS

Patients (N=3870) ≥16 years of age with moderate or severe TBI enrolled in the TBIMS NDB.

INTERVENTIONS

None.

MAIN OUTCOME MEASURE

Glasgow Outcome Scale-Extended (GOS-E).

RESULTS

The trajectory of the GOS-E scores is best described with a model of quadratic change, in which scores initially increase and peak approximately 10 years after the first GOS-E assessment, and then decrease. Change occurs most rapidly in the initial and final years of the timeline. There was significant variability in each growth parameter (P<.05). A reduced multilevel model was built, including all covariates (age at first GOS-E assessment, FIM, race, sex, rehabilitation length of stay) that related significantly to the growth parameters. An interactive tool was created to generate individual level trajectories based on various combinations of covariate values. Results provide an individual level account of the chronological progression of TBI outcomes, as measured by the GOS-E.

CONCLUSIONS

Individual growth curve analysis is a statistically rigorous approach to describe temporal change with respect to the GOS-E at the individual level for participants within the TBIMS NDB. Results indicated that, for individuals in the TBIMS NDB as a group, functional status as measured by the GOS-E initially improves, plateaus, and then begins to decline. Factors such as age at first GOS-E assessment, race, FIM score at rehabilitation admission, and rehabilitation length of stay were found to influence baseline GOS-E scores, as well as the rate and extent of both improvement and decline over time. Additional research may be required to determine the generalizability of these findings and the usefulness of this tool for clinical applications.

Longitudinal description of the disability rating scale for individuals in the National Institute on Disability and Rehabilitation Research traumatic brain injury model systems national database

OBJECTIVE

To develop a detailed understanding of temporal change (ie, estimated trajectories) at the individual level as measured by the Disability Rating Scale (DRS).

DESIGN

Individual growth curve (IGC) analysis of retrospective data obtained from the National Institute on Disability and Rehabilitation Research Traumatic Brain Injury (TBI) Model Systems National Database.

SETTING

Multicenter longitudinal database study.

PARTICIPANTS

Individuals with TBI (N=8816) participating in the TBI Model Systems National Database project.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURE DRS RESULTS

The negative exponential consisting of 3 growth parameters (pseudointercept, asymptote, rate) was successfully used to predict trajectory of recovery on the DRS qualified by the following covariates: race, sex, level of education and age at admission, rehabilitation length of stay, and cognitive and motor FIM scores at rehabilitation admission. Based on these results, an interactive tool was developed to allow prediction of the trajectory of recovery for individuals and subgroups with specified characteristics on the selected covariates.

CONCLUSIONS

With the use of IGC analysis, the longitudinal trajectory of recovery on the DRS for individuals sharing common characteristics and traits can be described. This methodology allows researchers and clinicians to predict numerous individual-level trajectories through use of a web-based computer automated interactive tool.