Synthesis and characterization of photopolymerizable hydrogels based on poly (ethylene glycol) for biomedical applications

Hydrogels are polymeric materials widely used in medicine due to their similarity with the biological components of the body. Hydrogels are biocompatible materials that have the potential to promote cell proliferation and tissue support because of their hydrophilic nature, porous structure, and elastic mechanical properties. In this work, we demonstrate the microwave-assisted synthesis of three molecular weight varieties of poly(ethylene glycol) dimethacrylate (PEGDMA) with different mechanical and thermal properties and the rapid photo of them using 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184) as UV photoinitiator. The effects of the poly(ethylene glycol) molecular weight and degree of acrylation on swelling, mechanical, and rheological properties of hydrogels were investigated. The biodegradability of the PEGDMA hydrogels, as well as the ability to grow and proliferate cells, was examined for its viability as a scaffold in tissue engineering. Altogether, the biomaterial hydrogel properties open the way for applications in the field of regenerative medicine for functional scaffolds and tissues.     

A distributed requirements management framework for legal compliance and accountability

Increasingly, new regulations are governing organizations and their information systems. Individuals responsible for ensuring legal compliance and accountability currently lack sufficient guidance and support to manage their legal obligations within relevant information systems. While software controls provide assurances that business processes adhere to specific requirements, such as those derived from government regulations, there is little support to manage these requirements and their relationships to various policies and regulations. We propose a requirements management framework that enables executives, business managers, software developers and auditors to distribute legal obligations across business units and/or personnel with different roles and technical capabilities. This framework improves accountability by integrating traceability throughout the policy and requirements lifecycle. We illustrate the framework within the context of a concrete healthcare scenario in which obligations incurred from the Health Insurance Portability and Accountability Act (HIPAA) are delegated and refined into software requirements. Additionally, we show how auditing mechanisms can be integrated into the framework and how auditors can certify that specific chains of delegation and refinement decisions comply with government regulations.     

Grain fracture in rapid particulate media deformation and a particulate media research roadmap from the PMEE workshops

It is well known that grain fracture plays an important role in quasi-static compaction of particulate media (e.g. civil engineering applications). Grain fracture is frequently the energy-minimizing path which enables particulate media to support large stresses. Less well known is the role that fracture plays in higher-rate particulate media systems. This paper discusses grain-scale & macro-scale evidence for the role of fracture in high-pressure/rate particulate media deformation events. It also presents (Appendix) a related particulate materials research roadmap developed by feedback from the Particulate Materials in Extreme Environments (PMEE) workshops. Experimental evidence is presented from recent sand fracture experiments performed by launching hemispherical-nose projectiles into specially-prepared beds of sand. Particle size analysis, SEM images of virgin & fractured media, and images from the bulk sand fracture & flow are used to illustrate the role of sand fracture. It is shown that as-poured sand exhibits a dilatational response and that mechanically compacted sand exhibits a compaction response when each is stimulated by a high-speed hemi-nose projectile. For compacted sand, particle size analysis suggests that particles near the rear of the target (lower projectile velocities and pressures) are reduced more in size. Fractured sand is shown to exhibit abrasion, attrition and fracture modes with visual self-similarity limited to specific particle size range roughly divided into classes larger or smaller than ~50 microns. Initial particulate media density affects the bulk response to high-pressure/rate events. Varying the density can transition the flow from dilation to compaction-dominated, likely as a function of inter-grain stresses from compaction. Substantial particle fracture is an artifact of both flow cases.     

Surfactant-aided, matrix-assisted laser desorption/ionization mass spectrometry of hydrophobic and hydrophilic peptides

The analysis of hydrophobic and hydrophilic peptides in an aqueous medium using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is reported. The key development allowing for simultaneous analysis of both hydrophobic and hydrophilic components of the sample mixture is the use of surfactants to solubilize the hydrophobic components in the MALDI matrix solution. A wide variety of anionic, cationic, zwitterionic, and nonionic surfactants were evaluated for their ability to assist in the generation of an abundant pseudomolecular ion from a model hydrophobic peptide ([tert-butoxycarbonyl]Glu[gamma-O-benzyl]-Ala-Leu-Ala[O-phenacyl ester]). The results indicate that the most successful surfactant among those studied for analyzing the model hydrophobic peptide is sodium dodecyl sulfate (SDS). SDS exhibited no interfering surfactant background ions, little to no loss of the acid-labile protecting groups from the model hydrophobic peptide, and an abundant pseudomolecular ion of the analyte. In addition, the use of surfactants is shown to be compatible with hydrophilic peptides as well. Mixtures of hydrophobic and hydrophilic peptides were characterized using surfactant-aided (SA) MALDI-MS, and it is demonstrated that all components are detectable once the surfactant is included in the sample solution. We conclude that the key benefit of using SA-MALDI-MS is its ability to simultaneously analyze hydrophobic and hydrophilic peptides from a single sample mixture, including synthetic peptides containing acid- and base-labile protecting groups.     

Defect microstructure in single crystal silicon thin films grown at 150° C-305° C by remote plasma-enhanced chemical vapor deposition

Defect microstructure in terms of defect density and impurity concentration of epitaxial Si films grown by low temperature Remote Plasma-enchanced Chemical Vapor Deposition (RPCVD) in the temperature range of 150–305° C has been investigated using Transmission Electron Microscopy (TEM), Secondary Ion Mass Spectroscopy (SIMS), Reflection High Energy Electron Diffraction (RHEED) and defect etching/Nomarski microscopy. Defect density in the epitaxial Si films is found to be a strong function of growth temperature in the temperature range under study, indicating that thermal excitation is an important source of energy, in addition to plasma excitation, for driving surface reactions in the RPCVD expitaxial process. Impurity concentrations of H, O and C in the epitaxial films have been determined by SIMS analysis. The trace amounts (∼1 ppm) of oxygen and water vapor in the reactant gas (2%SiH₄/He) was identified to be an important source of oxygen in the epitaxial Si films. An oxygen concentration as low as 3 × 10¹⁸ cm^-3 in the epitaxial Si film grown at 150° C has been achieved through the use of a gas purifier. The higher hydrogen concentration in the films grown at lower temperatures is believed to be due to insufficiently rapid hydrogen desorption from the surface during growth. The results of characterization using TEM and SIMS are discussed to elucidate the atomistic mechanisms of Si epitaxial growth by RPCVD.     

Effects of induction versus deduction and discovery versus utilization on transfer of information.

Notes that discovery may be more complex than simple induction, yet the 2 are generally confounded in teaching concept chains. Transfer tasks generally contain a discovery component and thus are biased in favor of the discovery group. In a study with 72 undergraduates, a factorial design was employed to separate these effects and a no-feedback condition eliminated discovery on the transfer task. Fewer errors were found for the inductive-utilization group than the inductive-discovery group. Implications for cognitive structure, guided discovery, and the components of transfer are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Identifying incompleteness in privacy policy goals using semantic frames

Requirements Engineering - Companies that collect personal information online often maintain privacy policies that are required to accurately reflect their data practices and privacy goals. To be...     

A cross-domain empirical study and legal evaluation of the requirements water marking method

Companies that own, license, or maintain personal information face a daunting number of privacy and security regulations. Companies are subject to new regulations from one or more governing bodies, when companies introduce new or existing products into a jurisdiction, when regulations change, or when data are transferred across political borders. To address this problem, we developed a framework called “requirements water marking” that business analysts can use to align and reconcile requirements from multiple jurisdictions (municipalities, provinces, nations) to produce a single high or low standard of care. We evaluate the framework in two empirical case studies covering a subset of U.S. data breach notification laws and medical record retention laws. In these studies, applying our framework reduced the number of requirements a company must comply with by 76 % across 8 jurisdictions and 15 % across 4 jurisdictions, respectively. We show how the framework surfaces critical requirements trade-offs and potential regulatory conflicts that companies must address during the reconciliation process. We summarize our results, including surveys of information technology law experts to contextualize our empirical results in legal practice.