Assessment of Oxidative Stress in Patients with an Isolated Traumatic Brain Injury Using Disposable Electrochemical Test Strips

The barriers to using plasma redox potential as a measure of oxidative stress in patients are the use of specialized equipment, necessity of sterilization between tests, and inconsistent electrode surfaces and cell geometry. These problems are resolved using disposable test strips with built in electrochemical cells. Measuring the electrode potential at a small current yields a stable value that is ～50 mV higher for isolated traumatic brain injury (ITBI) patients than for healthy individuals. Even with natural variations within blood chemistry, this simple method may be clinically useful for assessing the degree of oxidative stress and injury severity in ITBI patients.     

Biomolecular Densely Grafted Brush Polymers: Oligonucleotides,Oligosaccharides and Oligopeptides

In this Minireview, we describe synthetic polymers densely functionalized with sequence-defined biomolecular sidechains. We focus on synthetic brush polymers of oligonucleotides, oligosaccharides, and oligopeptides, prepared via graft-through polymerization from biomolecule functionalized monomers. The resulting structures are brush polymers wherein a biomolecular graft is positioned at each monomer backbone unit. We describe key synthetic milestones, identify synthetic opportunities, and highlight recent advances in the field, including biological applications.     

The structure of ions and zwitterionic lipids regulates the charge of dipolar membranes

In pure water, zwitterionic lipids form lamellar phases with an equilibrium water gap on the order of 2 to 3 nm as a result of the dominating van der Waals attraction between dipolar bilayers. Monovalent ions can swell those neutral lamellae by a small amount. Divalent ions can adsorb onto dipolar membranes and charge them. Using solution X-ray scattering, we studied how the structure of ions and zwitterionic lipids regulates the charge of dipolar membranes. We found that unlike monovalent ions that weakly interact with all of the examined dipolar membranes, divalent and trivalent ions adsorb onto membranes containing lipids with saturated tails, with an association constant on the order of ～10 M(-1). One double bond in the lipid tail is sufficient to prevent divalent ion adsorption. We suggest that this behavior is due to the relatively loose packing of lipids with unsaturated tails that increases the area per lipid headgroup, enabling their free rotation. Divalent ion adsorption links two lipids and limits their free rotation. The ion-dipole interaction gained by the adsorption of the ions onto unsaturated membranes is insufficient to compensate for the loss of headgroup free-rotational entropy. The ion-dipole interaction is stronger for cations with a higher valence. Nevertheless, polyamines behave as monovalent ions near dipolar interfaces in the sense that they interact weakly with the membrane surface, whereas in the bulk their behavior is similar to that of multivalent cations. Advanced data analysis and comparison with theory provide insight into the structure and interactions between ion-induced regulated charged interfaces. This study models biologically relevant interactions between cell membranes and various ions and the manner in which the lipid structure governs those interactions. The ability to monitor these interactions creates a tool for probing systems that are more complex and forms the basis for controlling the interactions between dipolar membranes and charged proteins or biopolymers for encapsulation and delivery applications.     

Two-channel Kondo physics in two-impurity Kondo models

We consider the non-Fermi-liquid quantum critical state of the spin-S two-impurity Kondo model and its potential realization in a quantum dot device. Using conformal field theory and the numerical renormalization group, we show the critical point to be identical to that of the two-channel Kondo model with additional potential scattering, for any spin S. Distinct conductance signatures are shown to arise as a function of device asymmetry, with the square-root behavior commonly believed to arise at low-energies dominant only in certain regimes.     

Mixed chromium(III) complexes with pyridinedicarboxylato and oxalato ligands: kinetic studies in HClO<Subscript>4</Subscript> solutions

Three chromium(III) complexes of general formula [Cr(ox)₂(pdaH)]²⁻ (where ox = C₂O₄ ²⁻ and pdaH⁻ is N,O-bonded 2,3-, 2,4- or 2,5-pyridinedicarboxylic acid anion) were obtained and characterized in solution. Acid-catalysed aquation of [Cr(ox)₂(pdaH)]²⁻ gave two products: [Cr(ox)(pdaH)(H₂O)₂]⁰ (P₁) and cis-[Cr(ox)₂(H₂O)₂]²⁻ (P₂). The kinetics of these reactions were studied spectrophotometrically, within the 0.1–1.0 M HClO₄ range, and the pseudo-first-order rate constants for the oxalato (k _obs1) and pdaH⁻ (k _obs2) ligands dissociation were calculated based on the determined pseudo-first-order rate constants (k _obs) and P₁:P₂ molar ratio. The dependencies of the pseudo-first-order rate constants on [H⁺] are as follows: k _obs1 = b ₁[H⁺] and k _obs2 = b ₂[H⁺], where b ₁ and b ₂ are the second-order rate constants for the oxalato and pdaH⁻ ligands dissociation, respectively. Kinetic parameters were determined and the mechanism of the pdaH⁻ ligand dissociation is proposed.     

Multisoliton ejection from an amplifying potential trap

We study theoretically the dynamics of a beam launched inside an amplifying trap potential. Raising the amplification transforms the dynamics from linear tunneling at low amplification to periodic ejection of a sequence of identical solitons (when the amplification rate exceeds the tunneling rate) and, at strong amplification, to nonperiodic multisoliton ejection.     

Dehn fillings that reduce Thurston norm

We construct examples for which more than one Dehn filling reduces the Thurston norm of (distinct) second homology classes of Φ _P -atoroidal 3-manifolds. We bound the number of these Dehn fillings by the number of faces of the Thurston Ball. This work is part of a thesis under the supervision of Eliahu Rips at the Hebrew University of Jerusalem. Sponsored in part by the Landau Center for Mathematical Research.     

Structure and rigidity in hyperbolic groups I

We introduce certain classes of hyperbolic groups according to their possible actions on real trees. Using these classes and results from the theory of (small) group actions on real trees, we study the structure of hyperbolic groups and their automorphism group.The second author was partially supported by an NSF grant.     

Newly designed polysiloxane-graft-poly (oxyethylene) copolymeric surfactants: preparation,surface activity and emulsification properties

Two sets of comb-grafted polymeric surfactants based on poly-(methylhydrogen siloxane) (PHMS) and/or poly(dimethylsiloxane) (PHMS-PDMS) were prepared by sililation of the active Si-H group with an active omega-vinyl group of specially designed undecenoic-polyethyleneglycol esters (UPEG) to form newly-designed polysiloxane-grafted-polyethyleneglycol comb-copolymeric surfactants.The hydrophilic moieties are hooked to the hydrophobic backbone through a spacer (undecenoic acid). The variations in the surfactants' structures were in the length and density of the grafted hydrophilic moieties, the chain length (DP) and nature of the hydrophobic backbone.The first 12 different polymeric surfactants (set 1), termed PHMS-UPEG, were found to be ineffective emulsifiers with limited ability to stabilize oil-in-water emulsions. The second set of surfactants, named PHMS-PDMS-UPEG comb-grafted copolymers, significantly reduced the oil-water interfacial tension and effectively stabilized several types of oil-in-water emulsions. The best emulsifier of this set (PHMS-PDMS-52-UPEG-45), seems to be the one whose anchor backbone (PHMS-PDMS) dissolves (rather than spreads) in the oil phase, and whose stabilizing moieties are sufficiently long (45 EO units) and hooked to the silicone backbone at high density (52% substitution).     

Mean-risk optimal decision of a steel company under emission control

We propose a mean-risk decision model for a steel company facing emission limits and trading with emission allowances. The model is calibrated using data of a real-life steel company and is subsequently solved for five different scenarios of demand and different levels of risk aversion. It is found that while the limits are never reached, permit trading influences the decision to a great extent, especially given extremely low or extremely high demand, i.e., when large amounts of permits need to be traded. We demonstrate that the risk caused by emission trading may increase not only with an increasing demand but also when the demand is low and a great amount of allowances must be sold.