Lead‐Chalcogenide Colloidal‐Quantum‐Dot Solids: Novel Assembly Methods,Electronic Structure Control,and Application Prospects

The quest for novel semiconductors with easy, cheap fabrication and tailorable properties has led to the development of several classes of materials, such as semiconducting polymers, carbon nanotubes, hybrid perovskites, and colloidal quantum dots. All these candidates can be processed from the liquid phase, enabling easy fabrication, and are suitable for different electronic and optoelectronic applications. Here, recent developments in the field of colloidal‐quantum‐dot solids are discussed, with a focus on lead‐chalcogenide systems. These include novel deposition methods; the recent growing understanding of their fundamental properties, driven by major successes in the control of the nanostructured assembly and surface chemistry; and selected reports on lab‐scale devices showing the technological prospects of these fascinating class of materials.     

Electron Mobility of 24 cm2 V−1 s−1 in PbSe Colloidal‐Quantum‐Dot Superlattices

Colloidal quantum dots (CQDs) are nanoscale building blocks for bottom‐up fabrication of semiconducting solids with tailorable properties beyond the possibilities of bulk materials. Achieving ordered, macroscopic crystal‐like assemblies has been in the focus of researchers for years, since it would allow exploitation of the quantum‐confinement‐based electronic properties with tunable dimensionality. Lead‐chalcogenide CQDs show especially strong tendencies to self‐organize into 2D superlattices with micrometer‐scale order, making the array fabrication fairly simple. However, most studies concentrate on the fundamentals of the assembly process, and none have investigated the electronic properties and their dependence on the nanoscale structure induced by different ligands. Here, it is discussed how different chemical treatments on the initial superlattices affect the nanostructure, the optical, and the electronic‐transport properties. Transistors with average two‐terminal electron mobilities of 13 cm² V^?1 s^?1 and contactless mobility of 24 cm² V^?1 s^?1 are obtained for small‐area superlattice field‐effect transistors. Such mobility values are the highest reported for CQD devices wherein the quantum confinement is substantially present and are comparable to those reported for heavy sintering. The considerable mobility with the simultaneous preservation of the optical bandgap displays the vast potential of colloidal QD superlattices for optoelectronic applications.     

Systemic Induction of Terpenoid Aldehydes in Cotton Pigment Glands by Feeding of Larval Spodoptera exigua

Pigment glands in cotton contain terpenoid aldehydes that are toxic and deterrent to feeding of several generalist lepidopteran insects. We hypothesized that previously observed systemically induced feeding deterrence may be associated with pigment glands. We conducted experiments to determine the dynamics and chemical nature of inducible feeding deterrents in leaves of cotton, Gossypium hirsutum L, to larvae of the beet armyworm, Spodoptera exigua. Production and/or filling of pigment glands was influenced by physiological age of Deltapine 90 cotton plants. In undamaged plants, successively formed leaves contained more pigment glands, up to the seventh or eighth true-leaf developmental stage. Feeding choice tests conducted one or seven days after initial feeding damage revealed that third instars of S. exigua consumed more of the two youngest leaves from control cotton plants than from plants whose two oldest leaves had been fed on previously for 24 hr by S. exigua. The preference for leaves from control plants was significant one day after initial damage and highly significant seven days after damage. Consumption of mature foliage (leaf immediately above initially damaged leaves) from control plants and damaged plants did not differ. More pigment glands were counted on the youngest leaf of damaged plants than on the youngest leaf of control plants one day after initial damage. HPLC analysis revealed greater amounts of hemigossypolone, heliocides 1 and 2 (H₁ and H₂), and total terpenoid aldehydes per gland in young foliage of damaged plants than control plants one day after initial injury. By seven days after initial injury, greater quantities of hemigossypolone and all heliocides except H₄ were detected in young foliage from damaged plants compared to control plants. Concentrations of H₁ per gland in young leaves from damaged plants increased the most of all terpenoid aldehydes measured (3.4× the amount found in leaves from control plants). Mature leaves from damaged plants did not contain more terpenoid aldehydes than mature leaves from control plants. We suggest that systemically induced feeding deterrence to S. exigua in young leaves of glanded cotton was due to increased amounts of terpenoid aldehydes in pigment glands.     

A Metamodel for the Web Services Standards

Web services provide distributed communication in a platform independent way. The WS-* standards define how middleware aspects (security, reliability, transactions, etc.) can be realized through web services. Although the WS-Policy standard family can be used to configure the various WS-* protocols, they are very hard to construct and to maintain manually. In addition, most SOA products and Grid systems implementing these standards provide their own methods for configuring these protocols, making it very difficult to match the various configuration options of different products. This fact inspired us to propose a platform independent metamodel for describing distributed systems of web services including the most important WS-* standards. The present article defines the full metamodel, it specifies the corresponding programming language formally, and it shows the productivity of the framework built around the metamodel through real-life examples. The framework is capable of generating product specific configuration files and source codes, resulting in directly interoperable applications even between different SOA products. The framework could also promote interoperability with Grid systems built on WS-* protocols.     

Phase Transitions and Pattern Formation in Chemo-Responsive Gels and Composites

Design of multifunctional materials often requires the chemical functionalization enabling the material to respond to a variety of stimuli. Herein, we focus on modeling of functionalized chemo-responsive gels and composites; functionalization alters the volume phase transitions allowing system to undergo structural reconfiguration. For instance, we consider the volume phase transitions in photo-sensitive hydrogels functionalized with two different types of chromophores that either alter the hydrophobicity of the illuminated sample or cause these samples to heat up. We then focus on gels that are driven by the oscillatory Belousov-Zhabotinsky reaction and show that chemically mediated interactions among these gels drive them to self-aggregate in a well-defined manner. Finally, we focus on the self-oscillating composite that does not contain oscillatory chemically reactions. In all these examples, effective control over the volume phase transitions is achieved through the combination of chemical functionalization and external stimuli, extending the potential utility of the host materials.     

High sodium continuous veno‐venous hemodialysis with regional citrate anticoagulation and online dialysate generation in patients with acute liver failure and cerebral edema

Introduction: Acute liver failure is associated with a high mortality rate. Induction of plasma hypertonicity with mannitol or hypertonic saline remains the cornerstone in the management of resultant cerebral edema. Significant disadvantages of this approach include poor or unpredictable control of serum sodium concentration and volume expansion, among others. Methods: We used high sodium continuous veno‐venous hemodialysis with regional citrate anticoagulation and online dialysate generation to accurately control the serum sodium in eleven patients with acute liver failure, renal failure, and cerebral edema. We used a Fresenius 2008 K/K2 machine in hemodialysis mode to deliver a blood flow of 60 ml/minute and dialysate flow of 400 ml/minute. Our previously published protocol results in complete removal of infused citrate by the dialyzer. On‐line clearance calculations were used to model the time required to reach the target serum sodium. Findings: All patients achieved serum sodium within 2 mEq/L of target without fluctuations or rebound. Nine patients survived without requiring liver transplantation and two died despite reaching the prescribed serum sodium target. We did not encounter any citrate toxicity. Discussion: We describe a novel approach for delivering continuous osmotherapy to patients with acute liver failure, renal failure, and cerebral edema. In comparison to standard therapy, the described modality enables precise titration of serum sodium without undesirable fluctuations in extracellular fluid volume. A particular advantage is zero delivery of citrate to this vulnerable group of patients with acute liver failure.     

Optimisation of microwave‐assisted extraction of phenolic compounds from broccoli and its antioxidant activity

The effect of independent variables of microwave‐assisted extraction (MAE), extraction temperature (50–90 °C), microwave power (100–200 W), solvent concentration (methanol/water, 50–90%, v/v) and extraction time (1–27 min) on total phenolics and flavonoids contents as well as antioxidant activity of broccoli extracts was investigated. Response surface methodology was successfully applied for optimisation and the high correlation of the mathematical model indicated that a quadratic polynomial model could be used for optimisation of investigated responses. Considering the maximum amount of extracted total phenolics, total flavonoids and antioxidant activity expressed as ORAC value, the optimal conditions for all three investigated responses were obtained (temperature ?71.11 °C; microwave power ?167.03 W; solvent concentration ?75.95%; and extraction time 16.34 min), which is in agreement with optimal conditions obtained for each investigated responses. The development of simultaneously MAE methods for total phenolics, total flavonoids and antioxidant activity of broccoli extracts might simplify assessment of broccoli as valuables source of antioxidants.     

A minimal element distortion strategy for computational mesh dynamics

Mesh motion strategy is one of the key points in many fluid–structure interaction (FSI) problems. Due to the increasing application of FSI to solve the current challenging engineering problems, this topic has become of great interest. There are several different strategies to solve this problem, some of them use a discrete and lumped spring–mass system to propagate the boundary motion into the volume mesh, and many others use an elastostatic problem to deform the mesh. In all these strategies there is always risk of producing an invalid mesh, i.e. a mesh with some elements inverted. Normally this condition is irreversible and once an invalid mesh is obtained it is difficult to continue. In this paper the mesh motion strategy is defined as an optimization problem. By its definition this strategy can be classified as a particular case of an elastostatic problem where the material constitutive law is defined in terms of the minimization of certain energy functional that takes into account the degree of element distortion. Some advantages of this strategy are its natural tendency to high quality meshes, its robustness and its straightforward extension to 3D problems. Several examples included in this paper show these capabilities. Even though this strategy seems to be very robust it is not able to recover a valid mesh starting from an invalid one. This improvement is left for future work. Copyright © 2006 John Wiley & Sons, Ltd.