Background: Previously, we had shown that elevation of cerebral perfusion pressure, using pressors, improved short-term outcomes after traumatic brain injury and hemorrhagic shock in swine. The current study evaluates outcomes after resuscitation with diaspirin cross-linked hemoglobin (DCLHb)-a hemoglobin-based oxygen carrier with pressor activity-in the same swine model of traumatic brain injury and hemorrhagic shock. Methods: Anesthetized and ventilated swine received traumatic brain injury via cortical fluid percussion (6-8 atm) followed by 45% blood volume hemorrhage. One hour later, animals were randomized to either a control group (SAL) resuscitated with normal saline equal to three times shed blood volume or to one of two experimental groups resuscitated with DCLHb. The two experimental groups consisted of a low-dose group, resuscitated with 250 mL of DCLHb (Hb1), and a high-dose group, resuscitated with 500 mL of DCLHb (Hb2). Animals were observed for 210 minutes postresuscitation. Outcomes evaluated were cerebral oxygenation by measuring partial pressure and saturation of oxygen in cerebrovenous blood; cerebral function by evaluating the preservation and magnitude of cerebrovascular carbon dioxide reactivity; and brain structural damage by semiquantitatively assessing beta amyloid precursor protein positive axons. Results: Postresuscitation, cerebral perfusion pressure was higher in the DCLHb groups (p < 0.05, Hb1 and Hb2 vs. SAL), and intracranial pressure was lower in the Hb2 group (p < 0.05 vs. SAL). Cerebrovenous oxygen level was similar in all groups (p > 0.05). At baseline, 5% carbon dioxide evoked a 16 ± 1% increase in cerebrovenous oxygen saturation, indicating vasodilatation. At 210 minutes, this response was nearly absent in SAL (4 ± 4%) (p < 0.05 vs. baseline) and Hb1 (1 ± 5%), but was partially preserved in Hb2 (9 ± 5%). There was no intergroup difference in beta amyloid precursor protein positive axons. Five of 20 SAL and 0 of 13 DCLHb animals developed brain death (flat electroencephalogram) (p = 0.05, SAL vs. DCLhb). Postresuscitation, DCLHb animals maintained higher mean pulmonary arterial pressure (28 ± 1 mm Hg, SAL; 42 ± mm Hg, Hb1; 45 ± 1 mm Hg, Hb2) (p < 0.05, Hb1 and Hb2 vs. SAL) and lower cardiac output (3.9 ± 1.6 L/min, SAL; 2.6 ± 0.1 L/min, Hb1; 2.7 ± 0.1 L/min, Hb2) (p < 0.05, Hb1 and Hb2 vs. SAL). Three Hb2 animals died as a result of cardiac failure, and one SAL animal died as a result of irreversible shock. Conclusion: In this swine model of traumatic brain injury and hemorrhagic shock, resuscitation with DCLHb maintained a higher cerebral perfusion pressure. Low-dose DCLHb (minimal increase in oxygen carriage) failed to significantly improve short-term outcome. With high-dose DCLHb (significant improvement in oxygen carriage), intracranial pressure was lower and cerebrovascular carbon dioxide reactivity was partially preserved; however, this was at the cost of poorer cardiac performance secondary to high afterload.

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Genom ringöppningssampolymerisation av utvalda epoxider och anhydrider möjliggjordes en enkel strategi för att syntetisera funktionella sampolymerer. Sampolymererna hade förmågan att bilda tvärbundna material, och var dessutom benägna för både hydrolytisk och enzymatisk nedbrytning. Användning av organokatalysatorn PPNCl gjorde det möjligt att bilda sampolymerer genom alternerande ringöppning av epoxider och anhydrider. Utbytet var högt, och polymererna nådde molekylvikter i intervallet 0,7–7,6 kg mol-1. De omättade bindningarna i sampolymerernas sidokedjor gav dem förmågan att bilda tvärbundna nätverk. Graden av tvärbindning dikterades av sampolymerernas molekylära struktur och molekylvikt. De termiska egenskaperna hos sampolymererna reglerades genom att variera anhydriden, där strukturella skillnader mellan de valda anhydriderna hade en inverkan Tg och T5%. Tvärbindningsreaktionen resulterade i en ökning av både Tg och T5% i förhållande till de ursprungliga linjära sampolymererna. De klyvbara estergrupperna i sampolymerkedjorna gjorde det möjligt för sampolymererna att genomgå både hydrolytisk och enzymatisk nedbrytning. De nedbrutna sampolymererna påvisade en förändring i molekylvikt och dispersitet, samt en ökad viktminskning. De nedbrutna tvärbundna materialen visade på större svällning och lägre gelinnehåll än de initiala värdena före nedbrytning. Dessa resultat ger en ökad förståelse kring hur strukturen hos epoxid/anhydrid-baserade sampolyestrar påverkar deras egenskaper, så som förmågan att bilda tvärbundna material samt deras nedbrytbarhet. Förhoppningen är att denna studie ska gynna utvecklingen av nya material inom denna klass av polyestrar, och vara till hjälp för att förutse deras potentiella tillämpningar. / The ring-opening copolymerization of selected epoxides and anhydrides enabled a simple strategy to synthesize functional copolymers with the ability to form crosslinked materials and prone to hydrolytic and enzymatic degradation pathways. The synthesis utilized PPNCl as an organocatalyst and allowed the formation of copolymer chains by alternating ring-opening of epoxides and anhydrides in high yield and molar mass in the range of 0.7-7.6 kg mol-1. The pendant unsaturated bonds in the copolymer chains endowed the copolymers with the ability to form crosslinking networks. The degree of crosslinking was dictated by the molecular structure and molar mass of the copolymers. The thermal properties of the copolymers were regulated by varying the anhydrides, the difference in the structure of each anhydride influence the Tg and T5%. Crosslinking reaction indeed increased the Tg and T5% from the native copolymers. The presence of ester as cleavable groups in the copolymer chains allowed the copolymers to undergo hydrolytic and enzymatic degradation. The degraded copolymers showed a change in molar mass and dispersity and increased mass loss. The degraded crosslinked materials showed higher swelling ratio and lower gel content than the initial values before degradation. These results deliver a better understanding of the structure-property relationships, the ability to form crosslinked materials, and the degradation behavior of epoxides/anhydrides-based copolyesters. They should favor the design of new materials belonging to this class of polyesters and to envisage their potential applications.

Sulfonated poly(arylene ether sulfone)s can exhibit several ideal features as potential desalination membranes for reverse osmosis applications, including chlorine resistance, low surface fouling, and high water flux. However, this class of polymer membranes has suffered from two major drawbacks that jeopardize effective levels of salt rejection in order to achieve high water flux. In mixed salt feed sources, monovalent salt rejection decreases when divalent cations such as Ca2+ bind with the anionic sulfonate groups to cause charge screening, and this can lead to too much salt passage for the membranes to be competitive with interfacially produced polyamides. Sulfonate fixed charge concentration must be high enough for sufficient membrane water uptake to obtain high membrane water flux, but if the water uptake is too high, this permits increased salt passage. The research described in this dissertation attempts to address both of these challenges through the design of a sulfonated monomer that strategically spaces the ionic groups along the polymer backbone chains to inhibit divalent ion binding. Free radical crosslinking further tunes the hydrated free volume in the RO membranes. A mono-sulfonated comonomer, sodium 3-sulfonate-4,4'-dichlorodiphenylsulfone (ms-DCDPS), was synthesized by stoichiometrically controlled electrophilic aromatic sulfonation of 4,4'-dichlorodiphenylsulfone (DCDPS). HPLC-UV revealed complete isolation of ms-DCDPS free of by-products after the 1st recrystallization and 1H NMR analysis confirmed the structure. A standard calibration curve was developed to accurately determine the leftover quantity of excess NaCl that was used for precipitation during the work-up procedures. A series of linear sulfonated poly(arylene ether sulfone)s with varying ms-DCDPS incorporation was synthesized. 1H NMR confirmed the structure of the polymers and size-exclusion chromatography confirmed that the intended molecular weights were achieved. The copolymers were cast into dense films and the mechanical and transport properties were measured in their fully hydrated states. Tensile tests revealed mechanically robust, tough membranes with glassy elastic moduli and high strains at break. The dense membrane prepared from sulfonated poly(arylene ether sulfone) with 51% of the repeat units sulfonated had NaCl rejection = 99.3% measured at 400 psi and 2000 ppm NaCl with a water permeability coefficient of 0.57 x 10-6 cm2/s. The salt rejection remained greater than 99% when a mixed salt feed source containing Ca2+ in the 0-200 ppm range together with the 2000 ppm NaCl was introduced. Crosslinked mono-sulfonated oligomers were synthesized with targeted molecular weights by utilizing stoichiometric quantities of monomers with the desired degrees of sulfonation, and the endgroups were functionalized with tetrafluorostryene. These end-functionalized sulfonated oligomers were crosslinked by both thermal and UV free radical methods in the presence of initiators without any additional crosslinking agents. Reaction conditions were thoroughly investigated and optimized to produce highly crosslinked membranes that yielded gel fractions greater than 87%, as measured by solvent extraction in dimethylacetamide. The hydrated crosslinked membranes were tested for both mechanical and transport properties, and the results were compared to their linear membrane counterparts. Crosslinking decreased the hydrated free volume and reduced water uptakes when compared to linear sulfonated membranes. Tensile tests of the fully hydrated crosslinked membranes showed good mechanical properties. The transport properties of a dense UV crosslinked membrane prepared with a 10,000 g/mol oligomer having 50% of the repeat units sulfonated was tested under RO cross-flow conditions at 400 psi and 2000 ppm NaCl in the feed. The membrane demonstrated a salt rejection = 98.4% with a water permeability coefficient of 0.49 x 10-6 cm2/s. / Doctor of Philosophy / Billions of individuals across the world lack clean, affordable drinking water, and the unavailability of fresh drinking water can be attributed to both physical and economic reasons. Several techniques have been utilized to produce potable water for human consumption that include both water desalination and recycling procedures. Water desalination is a process that allows for purifying salt contaminated water into drinking water. The two major desalination processes involve either distillation or passage through polymer membranes. Distillation separates water from salt by heating liquid water to form a gas, and collecting the vapor as condensate while impurities remain in the heated bulk material. Polymer membranes separate impurities through filtration where membranes allow water to pass through a physical barrier while rejecting the unwanted contaminants, including salt. Reverse osmosis desalination is the most common membrane separation process. Reverse osmosis membranes are comprised of either short-chain crosslinked oligomers or long-chain linear polymers. Commercial reverse osmosis membranes are largely poly(amide)s where a thin film is formed in an interfacial reaction. The membranes allow for almost quantitative salt rejection with high water fluxes. But, these membranes degrade over time from periodic cleaning with chlorine disinfectants. This dissertation primarily focuses on the implementation of an alternative polymer membrane material known as a mono-sulfonated polysulfone that strategically distributes the fixed sulfonate charged groups along the polymer backbone. Theses reverse osmosis mono-sulfonated polysulfones display comparable salt rejection with better chemical resistance than commercial poly(amide)-based membranes, and could potentially offer a replacement in the market.

In diesem Beitrag wird eine Organisationsanalyse hinsichtlich der Kooperation vernetzter Kleinunternehmen und Freelancer dargestellt. Ziel ist, den Begriff der virtuellen Organisation zu definieren und die verschiedenen Kooperationsformen und Besonderheiten vernetzter Kleinunternehmen und Freelancer zu beschreiben. Neben einer Literaturstudie wurden dazu Projektausschreibungen auf einer Kooperationsplattform im Internet analysiert und eine Reihe von felderkundenden Interviews durchgeführt. Daraufhin wurde eine detaillierte Analyse der Arbeitsorganisation in einem Projekt eines virtuellen Netzwerkunternehmens vorgenommen. Die Ergebnisse verschaffen einen Einblick in die Rollenvergabe und Arbeitsteilung zwischen den Partnern und in die Rolle(n) des Koordinationsunternehmens sowie in die potentiellen Vor- und Nachteile einer solchen zentralen Koordination der autonomen Partner.

Polymer networks are an important class of materials that are ubiquitously found in natural, biological, and man-made systems. The complex mesoscale structure of these soft materials has made it difficult for researchers to fully explore their properties. In this dissertation, we introduce a coarse-grained computational model for permanently cross-linked polymer networks than can properly capture common properties of these materials. We use this model to study several practical problems involving dry and solvated networks. Specifically, we analyze the permeability and diffusivity of polymer networks under mechanical deformations, we examine the release of encapsulated solutes from microgel capsules during volume transitions, and we explore the complex tribological behavior of elastomers. Our simulations reveal that the network transport properties are defined by the network porosity and by the degree of network anisotropy due to mechanical deformations. In particular, the permeability of mechanically deformed networks can be predicted based on the alignment of network filaments that is characterized by a second order orientation tensor. Moreover, our numerical calculations demonstrate that responsive microcapsules can be effectively utilized for steady and pulsatile release of encapsulated solutes. We show that swollen gel capsules allow steady, diffusive release of nanoparticles and polymer chains, whereas gel deswelling causes burst-like discharge of solutes driven by an outward flow of the solvent initially enclosed within a shrinking capsule. We further demonstrate that this hydrodynamic release can be regulated by introducing rigid microscopic rods in the capsule interior. We also probe the effects of velocity, temperature, and normal load on the sliding of elastomers on smooth and corrugated substrates. Our friction simulations predict a bell-shaped curve for the dependence of the friction coefficient on the sliding velocity. Our simulations also illustrate that at low sliding velocities, the friction decreases with an increase in the temperature. Overall, our findings improve the current understanding of the behavior of polymer networks in equilibrium and non-equilibrium conditions, which has important implications for synthesizing new drug delivery agents, designing tissue engineering systems, and developing novel methods for controlling the friction of elastomers.

Robust industrially relevant membranes for CO₂ removal from aggressive natural gas feed streams were developed and characterized. Asymmetric hollow fiber membranes with defect-free selective skin layers on an optimized porous support substructure were successfully spun and subsequently stabilized by covalent crosslinking within the economical membrane formation process. Thermal treatment conditions, which promote sufficient crosslinking without introducing defects or undesired substructure resistance, were identified. It was found that crosslinking improves membrane efficiency and plasticization resistance as well as mechanical strength of fibers. The capability to maintain attractive separation performance under realistic operating conditions and durability against deleterious impurities suggests that the crosslinked fibers have great potential for use in diverse aggressive applications, even beyond the CO₂/CH₄ example explored in this work.