Polyimides and ionic liquids (ILs) are two classes of materials that have been widely studied as gas separation membranes, each demonstrating respective advantages and limitations. Both polyimides ...and ILs are amenable to modification/functionalization based on selection of the requisite precursors. However, there have been but a handful of reports considering how polyimides and ILs could be integrated to obtain fundamentally new materials with synergistic properties. In this manuscript, we demonstrate a new and versatile way to synthesize polyimides with imidazolium cations directly located within the polymer backbone to form polyimide–ionene hybrids, or “ionic polyimides”. Our strategy for synthesizing ionic polyimides does not require the use of amino-functionalized ILs. Instead, the imidization reaction occurs prior to polymerization in the formation of an imidazole-functionalized diimide monomer. This monomer is then reacted via step-growth (condensation) polymerization with p-dichloroxylene via Menshutkin reactions, simultaneously linking the monomers and creating the ionic components. The resultant ionic polyimide is amenable to thermal processing (e.g., extrusion, melt-pressing) and capable of forming thin films. Upon soaking thin films of the ionic polyimide in a widely used IL, 1-butyl-3-methylimidazolium bistriflimide (C4mimTf2N), a stoichiometric absorption of the IL into the ionic polyimide was observed, forming an ionic polyimide + IL composite. The gas separation performances of ionic polyimide and ionic polyimide + IL composite membranes were studied with respect to CO2, N2, CH4, and H2. The neat ionic polyimide exhibits low permeability to CO2 and H2 (∼0.9 and ∼1.6 barrers, respectively) and very low permeability to N2 and CH4 (∼0.03 barrers for both). For the ionic polyimide + IL composite, the permeabilities of CO2, N2, and CH4 increase by 1800–2700%, while H2 permeability only increased by ∼200%. The large increases in permeability for CO2, N2, and CH4 are due to greatly increased gas diffusivity through the material, with gas solubility essentially unchanged with the IL present. The ionic polyimide and ionic polyimide + IL composite were characterized using a number of techniques. Most interestingly, X-ray diffractometry (XRD) of the films reveals that the ionic polyimide + IL composite displays a sharp peak, indicating that the ionic polyimide may experience supramolecular assembly around the IL. Although the performances of these first ionic polyimide and ionic polyimide + IL composite membranes fall short of Robeson’s Upper Bounds, this work provides a strong foundation on which ionic polyimide materials with more sophisticated structural elements can be developed to understand the structure–property relationships underlying the ionic polyimide platform and ultimately produce high-performance gas separation membranes.
Etherification with high selectivity and yield has been one of the challenges for expanding the realm of glycerol transformations. In this work, a small glycerol triether molecule, ...1,2,3-triethoxypropane (1,2,3-TEP, CAS 162614-45-1), was designed and synthesized through a two-step strategy using epichlorohydrin as the starting material with ethanol and bromoethane as etherification reagents. The overall yield (after rigorous distillation) was 43.9%, higher than those of methods previously published in the literature. Thermophysical properties for 1,2,3-TEP are herein reported for the first time. Densities and viscosities measured at 1 atm from 20 to 80 °C show that 1,2,3-TEP is a less dense and less viscous liquid than glycerol and the corresponding 1,3-diether intermediate, 1,3-diethoxypropan-2-ol (1,3-DEP, CAS #4043-59-8). CO2 solubility in 1,2,3-TEP was investigated under pressures of 2–8 atm at 30, 45, 60, and 75 °C with respective K H values of 46.2, 57.4, 69.4, and 81.7 atm, enabling reliable predictions on CO2 solubility within this range of temperature and pressure conditions. Comparison of Henry’s law constants and vapor pressure between 1,2,3-TEP and diglyme from 0 to 75 °C has indicated its potential as an alternative CO2 capture solvent to those used in the Selexol process. 1,2,3-TEP showed broad miscibility with common solvents except water. The dipole moment of the minimum energy structure in the gas phase is calculated to be 1.47 D, but this value increases to 2.5–2.7 D in common solvents. The data obtained in this work are meaningful in guiding the further synthesis of a series of glycerol triether derivatives and developing uses for 1,2,3-TEP and related compounds.
Coordinated regulation of gene expression levels across a series of experimental conditions provides valuable information about the functions of correlated transcripts. The consideration of gene ...expression correlation over a time or tissue dimension has proved valuable in predicting gene function. Here, we consider correlations over a genetic dimension. In addition to identifying coregulated genes, the genetic dimension also supplies us with information about the genomic locations of putative regulatory loci. We calculated correlations among approximately 45,000 expression traits derived from 60 individuals in an F2 sample segregating for obesity and diabetes. By combining the correlation results with linkage mapping information, we were able to identify regulatory networks, make functional predictions for uncharacterized genes, and characterize novel members of known pathways. We found evidence of coordinate regulation of 174 G protein-coupled receptor protein signaling pathway expression traits. Of the 174 traits, 50 had their major LOD peak within 10 cM of a locus on Chromosome 2, and 81 others had a secondary peak in this region. We also characterized a Riken cDNA clone that showed strong correlation with stearoyl-CoA desaturase 1 expression. Experimental validation confirmed that this clone is involved in the regulation of lipid metabolism. We conclude that trait correlation combined with linkage mapping can reveal regulatory networks that would otherwise be missed if we studied only mRNA traits with statistically significant linkages in this small cross. The combined analysis is more sensitive compared with linkage mapping alone.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We previously mapped the type 2 diabetes mellitus-2 locus (T2dm2), which affects fasting insulin levels, to distal chromosome 19 in a leptin-deficient obese F2 intercross derived from C57BL/6 (B6) ...and BTBR T+ tf/J (BTBR) mice. Introgression of a 7-Mb segment of the B6 chromosome 19 into the BTBR background (strain 1339A) replicated the reduced insulin linked to T2dm2. The 1339A mice have markedly impaired insulin secretion in vivo and disrupted islet morphology. We used subcongenic strains derived from 1339A to localize the T2dm2 quantitative trait locus (QTL) to a 242-kb segment comprising the promoter, first exon and most of the first intron of the Sorcs1 gene. This was the only gene in the 1339A strain for which we detected amino acid substitutions and expression level differences between mice carrying B6 and BTBR alleles of this insert, thereby identifying variation within the Sorcs1 gene as underlying the phenotype associated with the T2dm2 locus. SorCS1 binds platelet-derived growth factor, a growth factor crucial for pericyte recruitment to the microvasculature, and may thus have a role in expanding or maintaining the islet vasculature. Our identification of the Sorcs1 gene provides insight into the pathway underlying the pathophysiology of obesity-induced type 2 diabetes mellitus.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
1,2,3-Trimethoxypropane (1,2,3-TMP) is the trimethyl ether of propane-1,2,3-triol, better known as glycerol, which can be derived from triglycerides originating from either plant or animal sources. ...Despite its simple structure and the ubiquity of its glycerol precursor, successful synthesis of 1,2,3-TMP was only recently reported in the literature, with studies suggesting it may be a “green” and nontoxic alternative to solvents such as diglyme, a constitutional isomer. However, no thermophysical properties of 1,2,3-TMP have yet been reported. Furthermore, the structure of 1,2,3-TMP is also analogous to polyether solvents used in the Selexol process for removal of CO2 and other “acid” gases from CH4, H2, etc. As such, examining the solubility of CO2 in 1,2,3-TMP is also of interest. This work details our initial studies and characterization of 1,2,3-TMP as a physical solvent for CO2 absorption, as well as the characterization of its density, viscosity, and vapor pressure with respect to temperature. 1,2,3-TMP exhibits favorable properties, and glycerol-derived triethers warrant deeper consideration as new solvents for CO2 absorption and other gas treating applications.
Polyimides (PI) synthesized from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with various diamines have been frequently studied as gas separation membranes. The use of 6FDA in ...polyimides creates a bent structure than can increase fractional free volume (FFV) and gas permeability. Here, we demonstrate that 6FDA is also a useful building block for PI‐ionene materials, which contain cations directly within the polymer backbone. These new 6FDA‐containing PI‐ionenes were combined with several different imidazolium ionic liquids (ILs) to form thin membranes. The thermal properties of all the derivatives were investigated to determine the relationship between regiochemistry and degradation as well as the intermolecular forces that are present within these structures. The gas separation properties of these 6FDA‐containing PI‐ionene + IL materials were investigated, showing modest CO2 permeabilities similar to other polyimide‐ionenes and CO2/CH4 and CO2/N2 permselectivities that were relatively higher than other polyimide‐ionenes.
The synthesis of polyimide membranes for energy‐efficient gas separations typically relies on the reaction of a dianhydride with a diamine. Although effective, this conventional approach limits the number of potential structures and compositions available to study. However, 6FDA‐containing polyimide‐ionenes and composites with ionic liquids open vast new opportunities in the design of polymer gas‐separation membranes for applications such as the removal of CO2 from industrial processes.
In the past, the authors performed a comprehensive literature review to identify all randomized controlled trials assessing the impact of early tracheostomy on severe brain injury outcomes. The ...search produced only two trials, one by Sugerman and another by Bouderka.
The current authors initiated an Institutional Review Board-approved severe brain injury randomized trial to evaluate the impact of early tracheostomy on ventilator-associated pneumonia rates, intensive care unit (ICU)/ventilator days, and hospital mortality. Current study results were compared with the other randomized trials and a meta-analysis was performed.
Early tracheostomy pneumonia rates were Sugerman-48.6%, Bouderka-58.1%, and current study-46.7%. No early tracheostomy pneumonia rates were Sugerman-53.1%, Bouderka-61.3%, and current study-44.4%. Pneumonia rate meta-analysis showed no difference for early tracheostomy and no early tracheostomy (OR 0.89; p = 0.71). Early tracheostomy ICU/ventilator days were Sugerman-16 ± 5.9, Bouderka-14.5 ± 7.3, and current study-14.1 ± 5.7. No early tracheostomy ICU/ventilator days were Sugerman-19 ± 11.3, Bouderka-17.5 ± 10.6, and current study-17 ± 5.4. ICU/ventilator day meta-analysis showed 2.9 fewer days with early tracheostomy (p = 0.02). Early tracheostomy mortality rates were Sugerman-14.3%, Bouderka-38.7%, and current study-0%. No early tracheostomy mortality rates were Sugerman-3.2%, Bouderka-22.6%, and current study-0%. Randomized trial mortality rate meta-analysis showed a higher rate for early tracheostomy (OR 2.68; p = 0.05). Because the randomized trials were small, a literature assessment was undertaken to find all retrospective studies describing the association of early tracheostomy on severe brain injury hospital mortality. The review produced five retrospective studies, with a total of 3,356 patients. Retrospective study mortality rate meta-analysis demonstrated a larger mortality for early tracheostomy (OR 1.97; p < 0.0001).
For severe brain injury, analyses indicate that ventilator-associated pneumonia rates are not decreased with early tracheostomy. Further, this study implies that mechanical ventilation is reduced with early tracheostomy. Both the randomized trial and retrospective meta-analysis indicate that risk for hospital death increases with early tracheostomy. Findings imply that early tracheostomy for severe brain injury is not a prudent routine policy.
The purpose of this study was to determine if noninvasive transcranial oxygen saturation (StcO2) and Bispectral Index (BIS) correlate with severe traumatic brain injury intensive care unit (ICU) ...outcomes.
This is a prospective observational study. Values of intracranial pressure (ICP), mean arterial pressure (MAP), BIS, and StcO2 were recorded hourly for the first six, post-injury days in 18 patients with severe brain injury. Included in the analyses was the Cranial-Arterial Pressure (CAP) Index, which is ICP/(MAP-ICP).
After 1,883 hours of data were analyzed, we found that StcO2 and BIS are associated with survival, good neurological outcome, ICP </=20, cerebral perfusion pressure (CPP) > or =60, and CAP index < or =0.30 (p < or = 0.001). Survival and good outcome are independently associated with BIS > or =60, StcO2 > or =70, and ICP < or =20 (p < 0.0001). BIS > or =60 or StcO2 > or =70 is associated with survival, good outcome, CPP > or =60, ICP < or =20, CAP index < or =0.30, and fewer ICP interventions (p < 0.0001). With BIS > or =60 or StcO2 > or =70, the rate of CPP > or =60 is 97.2% and the rate of ICP< or = 25 is 97.1%. An increased CAP index is associated with death, poor neurological outcome, and increased ICP interventions (p < 0.0001). With CAP index >0.25, MAP is not related to ICP (p = 0.16).
Numerous significant associations with ICU outcomes indicate that BIS and StcO2 are clinically relevant. The independent associations of BIS, StcO2, and ICP with outcomes suggest that noninvasive multi-modal monitoring may be beneficial. Future studies of patients with BIS > or =60 or StcO2 > or =70 will determine if select patients can be managed without ICP monitoring and whether marginal ICP can be observed. An increased CAP index is associated with poor outcome.
The manipulation of particulates in microfluidics is a challenge that continues to impact applications ranging from fine chemicals manufacturing to the materials and the life sciences. Heterogeneous ...operations carried out in microreactors involve high surface-to-volume characteristics that minimize the heat and mass transport resistances, offering precise control of the reaction conditions. Considerable advances have been made towards the engineering of techniques that control particles in microscale laminar flow, yet there remain tremendous opportunities for improvements in the area of chemical processing. Strategies that have been developed to successfully advance systems involving heterogeneous materials are reviewed and an outlook provided in the context of the challenges of continuous flow fine chemical processes.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Departments of 1 Nutritional Sciences, 2 Biochemistry, 3 Statistics and Horticulture, and 4 Biostatistics and Medical Informatics, University of WisconsinMadison, Madison, Wisconsin
Submitted 24 ...July 2006
; accepted in final form 13 November 2006
Insulin resistance is a common feature of obesity. BTBR mice have more fat mass than most other inbred mouse strains. On a chow diet, BTBR mice have elevated insulin levels relative to the C57BL/6J (B6) strain. Male F1 progeny of a B6 x BTBR cross are insulin resistant. Previously, we reported insulin resistance in isolated muscle and in isolated adipocytes in this strain. Whereas the muscle insulin resistance was observed only in male F1 mice, adipocyte insulin resistance was also present in male BTBR mice. We examined in vivo mechanisms of insulin resistance with the hyperinsulinemic euglycemic clamp technique. At 10 wk of age, BTBR and F1 mice had a >30% reduction in whole body glucose disposal primarily due to insulin resistance in heart, soleus muscle, and adipose tissue. The increased adipose tissue mass and decreased muscle mass in BTBR and F1 mice were negatively and positively correlated with whole body glucose disposal, respectively. Genes involved in focal adhesion, actin cytoskeleton, and inflammation were more highly expressed in BTBR and F1 than in B6 adipose tissue. The BTBR and F1 mice have higher levels of testosterone, which may be related to the pathological changes in adipose tissue that lead to systemic insulin resistance. Despite profound peripheral insulin resistance, BTBR and F1 mice retained hepatic insulin sensitivity. These studies reveal a genetic difference in body composition that correlates with large differences in peripheral insulin sensitivity.
mouse genetics; adipose; insulin sensitivity
Address for reprint requests and other correspondence: A. D. Attie, Dept. of Biochemistry, Univ. of WisconsinMadison, 433 Babcock Dr., Madison, WI 53706 (e-mail: attie{at}biochem.wisc.edu )
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