Impact of Functionalized Polystyrenes as the Electron Injection Layer on Gold and Aluminum Surfaces: A Combined Theoretical and Experimental Study

At metal/organic interfaces, the insertion of an organic monolayer can significantly modify the surface properties of the substrate, especially in terms of charge injection across the interface. Herein, we study the formation of an insulating monolayer of morpholine or amine-functionalized polystyrene on Al(111) and Au(111) surfaces and its impact on surface work-function and charge injection. First-principles calculations based on Density Functional Theory have been carried out and point to a significant decrease in the work-function of modified metal surfaces; this is in very good agreement with ultraviolet photoemission spectroscopy measurements performed on the Au(111) surface. In addition, a bilayer cathode, consisting of a thin film of high-work-function metal, such as Al and Au, and a layer of amine-functionalized polystyrene, was also fabricated and tested in organic light-emitting diodes. Such bilayer structures exhibit substantially enhanced efficiency when compared with controls without the functionalized polymers. Our combined theoretical and experimental investigation gives insight into how a thin layer of a commodity polymer can be used to transform rather high-work-function metals into high-performance cathodes to provide efficient electron injection.     

Influence of a metallic filler on polyurethane formation

The addition of metallic fillers is recognized to impart improvement of acoustic properties to polyurethane-based materials used for marine applications. The system under consideration was obtained by the reaction of a triisocyanateterminated prepolymer with 1,4-butanediol, in the presence of various concentrations of lead powder. With increasing lead content, gelation time is reduced and an Einstein-type law does not apply. The kinetics of the reaction were determined by Fourier transform infrared spectroscopy. Deviation from the classic second order is observed for the filled systems, and the higher the lead content, the more important the deviation is, showing undoubtedly the catalytic effect of the metallic powder.     

Microtribology,squeeze, and friction of the colloidal layer

Lubricant films containing colloidal overbased calcium salts have particular effects on detergency and on the wear process. The mechanical properties of such boundary films are very dependent on the process conditions, and are essentially a result of physico-chemical transformations of the colloid. Three types of films were compared: a film obtained by the drying of the base solvent, a film due to the compaction of the colloid between two steel surfaces, and a friction film obtained with this type of lubricant. Adsorption, compaction, and shear transformations induce a solid film. The pressure effect on the frictional behaviour of these colloidal films has been investigated using a surface force apparatus for low contact pressure (10⁴ to 10⁶ Pa), and using tribometers supporting heavy loads for the analysis of the high pressure domain. Above a critical pressure, evaluated at 10⁶ Pa, the colloidal film does not flow, but forms a compacted mattress sliding on the surface plane and squeezing a molecular layer of lubricant.     

Vascular Permeability in Diseases

Vascular permeability is a selective mechanism that maintains the exchange between vessels, tissues, and organs. The regulation was mostly studied during the nineteenth century by physiologists who defined physical laws and equations, taking blood, tissue interstitial, and oncotic pressure into account. During the last decades, a better knowledge of vascular cell functions and blood-vessel interactions opens a new area of vascular biology. Endothelial cell receptors vascular cell adhesion molecule (VCAM), intercellular cell adhesion molecule (ICAM), vascular endothelial growth factor receptor (VEGFR-2), receptor for advanced glycation end products (RAGE), and mediators were identified and their role in homeostasis and pathological situations was described. The molecular differences of endothelial cell junctions (tight, gap, and adherens junctions) and their role in vascular permeability were characterized in different organs. The main mediators of vasomotricity and permeability, such as prostaglandins, nitric oxide (NO), prostacyclin, vascular growth factor (VEGF), and cytokines, have been demonstrated to possess major functions in steady state and pathological situations. Leukocytes were shown to adhere to endothelium and migrate during inflammatory situations and infectious diseases. Increased vascular permeability is linked to endothelium integrity. Glycocalyx, when intact, may limit cancer cell metastasis. Biological modifications of blood and tissue constituents occurring in diabetes mellitus were responsible for increased permeability and, consequently, ocular and renal complications. Vascular pressure and fluidity are major determinants of pulmonary and cerebral edema. Beside the treatment of the infectious disease, of the blood circulation dysfunction and inflammatory condition, drugs (cyclooxygenase inhibitors) and specific antibodies anti-cytokine (anti-VEGF) have been demonstrated to reduce the severity and the mortality in diseases that exhibited enhanced vascular permeability.     

THE EFFECTS OF FEEDING ELEVATED LEVELS OF VITAMINS D3 AND E ON BEEF QUALITY

Yearling (12 Angus, 12 Wagyu ≥ Angus) and 2-year old heifers (12 Angus, 12 Wagyu ≥ Angus) were fed elevated levels of Vitamin D ₃ and/or Vitamin E to evaluate beef quality. Warner-Bratzler shear force (WBS) and sensory characteristics were determined on steaks from the Longissimus lumborum (LL) aged 21 days and on steaks from the Gluteus medius (GM) and Psoas major (PM) aged 7 days. Steaks were cut from all muscles, displayed for 5 days then L * value and hue angle were determined. Vitamin E supplemented heifers received the highest sensory tenderness and juiciness scores, while no differences were observed among other treatments. D ₃+ E supplemented Angus LL had higher WBS values than other treatments and breeds. Display time affected both color measures for all muscles, but especially hue angles of GM and PM. Vitamin treatment affected LL and GM color measures in yearlings to a greater extent than in 2-year olds.     

Solid-Phase Synthesis of Substrate-Based Dipeptides and Heterocyclic Pseudo-dipeptides as Potential NO Synthase Inhibitors

More than 160 arginine analogues modified on the C-terminus via either an amide bond or a heterocyclic moiety (1,2,4-oxadiazole, 1,3,4-oxadiazole and 1,2,4-triazole) were prepared as potential inhibitors of NO synthases (NOS). A methodology involving formation of a thiocitrulline intermediate linked through its side-chain on a solid support followed by modification of its carboxylate group was developed. Finally, the side-chain thiourea group was either let unchanged, S-alkylated (Me, Et) or guanidinylated (Me, Et) to yield respectively after TFA treatment the corresponding thiocitrulline, S-Me/Et-isothiocitrulline and N-Me/Et-arginine substrate analogues. They all were tested against three recombinant NOS isoforms. Several compounds containing a S-Et- or a S-Me-Itc moiety and mainly belonging to both the dipeptide-like and 1,2,4-oxadiazole series were shown to inhibit nNOS and iNOS with IC₅₀ in the 1–50 μM range. Spectral studies confirmed that these new compounds interacted at the heme active site. The more active compounds were found to inhibit intra-cellular iNOS expressed in RAW264.7 and INS-1 cells with similar efficiency than the reference compounds L-NIL and SEIT.     

Reactions of Recombinant Neuronal Nitric Oxide Synthase with Redox Cycling Xenobiotics: A Mechanistic Study

Neuronal nitric oxide synthase (nNOS) catalyzes single-electron reduction of quinones (Q), nitroaromatic compounds (ArNO₂) and aromatic N-oxides (ArN → O), and is partly responsible for their oxidative stress-type cytotoxicity. In order to expand a limited knowledge on the enzymatic mechanisms of these processes, we aimed to disclose the specific features of nNOS in the reduction of such xenobiotics. In the absence or presence of calmodulin (CAM), the reactivity of Q and ArN → O increases with their single-electron reduction midpoint potential (E¹₇). ArNO₂ form a series with lower reactivity. The calculations according to an “outer-sphere” electron transfer model show that the binding of CAM decreases the electron transfer distance from FMNH₂ to quinone by 1–2 Å. The effects of ionic strength point to the interaction of oxidants with a negatively charged protein domain close to FMN, and to an increase in accessibility of the active center induced by high ionic strength. The multiple turnover experiments of nNOS show that, in parallel with reduced FAD-FMN, duroquinone reoxidizes the reduced heme, in particular its Fe²⁺-NO form. This finding may help to design the heme-targeted bioreductively activated agents and contribute to the understanding of the role of P-450-type heme proteins in the bioreduction of quinones and other prooxidant xenobiotics.     

Sequestration of Host Plant Glucosinolates in the Defensive Hemolymph of the Sawfly Athalia rosae

Interactions between insects and glucosinolate-containing plant species have been investigated for a long time. Although the glucosinolate–myrosinase system is believed to act as a defense mechanism against generalist herbivores and fungi, several specialist insects use these secondary metabolites for host plant finding and acceptance and can handle them physiologically. However, sequestration of glucosinolates in specialist herbivores has been less well studied. Larvae of the turnip sawfly Athalia rosae feed on several glucosinolate-containing plant species. When larvae are disturbed by antagonists, they release one or more small droplets of hemolymph from their integument. This reflex bleeding is used as a defense mechanism. Specific glucosinolate analysis, by conversion to desulfoglucosinolates and analysis of these by high-performance liquid chromatography coupled to diode array UV spectroscopy and mass spectrometry, revealed that larvae incorporate and concentrate the plant's characteristic glucosinolates from their hosts. Extracts of larvae that were reared on Sinapis alba contained sinalbin, even when the larvae were first starved for 22 hr and, thus, had empty guts. Hemolymph was analyzed from larvae that were reared on either S. alba, Brassica nigra, or Barbarea stricta. Leaves were analyzed from the same plants the larvae had fed on. Sinalbin (from S. alba), sinigrin (B. nigra), or glucobarbarin and glucobrassicin (B. stricta) were present in leaves in concentrations less than 1 mol/g fresh weight, while the same glucosinolates could be detected in the larvae's hemolymph in concentrations between 10 and 31 mol/g fresh weight, except that glucobrassicin was present only as a trace. In larval feces, only trace amounts of glucosinolates (sinalbin and sinigrin) could be detected. The glucosinolates were likewise found in freshly emerged adults, showing that the sequestered phytochemicals were transferred through the pupal stage.     

Chalcogenide Glasses for Infrared Photonics

The last advances in the synthesis and shaping techniques of chalcogenide glasses suitable for infrared photonics are reported. Ball milling combined with spark plasma sintering allows the preparation of bulk chalcogenide glasses at lower temperature and at lower cost. Microstructuring of optical fibers results in enhanced nonlinear properties leading to the demonstration of low-threshold Brillouin laser at 1.55 μm, all-optical wavelength conversion and time-domain demultiplexing with a 170 Gb/s rate, and supercontinuum between 1.5 and 2.8 μm. The potential of integrated waveguides for functions such as near-IR sensing, mid-IR injection, and (bio)-chemical functionalization is shown.     

Current–Voltage Characteristics in Individual Polypyrrole Nanotube, Poly(3,4-ethylenedioxythiophene) Nanowire, Polyaniline Nanotube, and CdS Nanorope

In this paper, we focus on current–voltage (I–V) characteristics in several kinds of quasi-one-dimensional (quasi-1D) nanofibers to investigate their electronic transport properties covering a wide temperature range from 300 down to 2 K. Since the complex structures composed of ordered conductive regions in series with disordered barriers in conducting polymer nanotubes/wires and CdS nanowires, all measured nonlinear I–V characteristics show temperature and field-dependent features and are well fitted to the extended fluctuation-induced tunneling and thermal excitation model (Kaiser expression). However, we find that there are surprisingly similar deviations emerged between the I–V data and fitting curves at the low bias voltages and low temperatures, which can be possibly ascribed to the electron–electron interaction in such quasi-1D systems with inhomogeneous nanostructures.