Dual zinc catalysts for L‐lactide polymerization and reaction of CO2 with cyclohexene oxide

A series of zinc complexes, [ L ^X ZnEt] ( 1–5 ) and [ L ^X Zn ₂ (OAc) ₃ ] (6–9) , associated with NNO‐tridentate Schiff base ligands (2‐(((2‐((cyclohexyl[methyl]amino)methyl)phenyl)imino)methyl)phenolate (CAP) derivatives), were synthesized, and their activity toward ring‐opening polymerization (ROP) of L‐lactide (LA) and the reaction of CO₂ with cyclohexene oxide were also investigated. All of [ L ^X ZnEt] revealed excellent catalytic activity to ring‐opening polymerization (ROP) of LA in the presence of benzyl alcohol. Among them, [ L ^H ZnEt] (1) showed the highest activity with 82% conversation within 45 s. In contrast, [L ^X Zn ₂ (OAc) ₃ ] (6–9) were inactive in ROP of L‐lactide. In addition, all of these Zn complexes demonstrated moderate activity in the reaction of CO₂ with cyclohexene oxide in the presence of Bu₄NCl.     

Chalcogen-Containing Manganese Carbonyl Clusters: Synthesis and Structural Transformations

Recently, we have developed several synthetic routes to the new classes of chalcogen-containing manganese carbonyl clusters, and the interesting structural transformations and reactivity of the resultant clusters have been investigated as well. In this short review, the syntheses and bonding modes of the sulfur, selenium, and tellurium-containing manganese carbonyl complexes reported by our laboratory will be presented, and the cluster growth and transformation will be systematically compared and discussed.     

Molecular orientation of evaporated pentacene films on gold: alignment effect of self-assembled monolayer

Pentacene films deposited on self-assembled monolayers (SAMs) bearing different terminal functional groups have been studied by reflection-absorption IR, grazing angle XRD, NEXAFS, AFM, and SEM analyses. A film with pentacene molecules nearly perpendicularly oriented was observed on Au surfaces covered with an SAM of alkanethiol derivative of X-(CH2)(n)-SH, with X = -CH(3), -COOH, -OH, -CN, -NH(2), C(60), or an aromatic thiol p-terphenylmethanethiol. On the other hand, a film with the pentacene molecular plane nearly parallel to the substrate surface was found on bare Au surface. A similar molecular orientation was found in thinner ( approximately 5 nm) and thicker (100 nm) deposited films. Films deposited on different surfaces exhibit distinct morphologies: with apparently smaller and rod-shaped grains on clean bare Au surface but larger and islandlike crystals on SAM-modified surfaces. X-ray photoemission electron microscopy (X-PEEM) was used to analyze the orientation of pentacene molecules deposited on a SAM-patterned Au surface. With the micro-NEXAFS spectra and PEEM image analysis, the microarea-selective orientation control on Au was characterized. The ability to control the packing orientation in organic molecular crystals is of great interest in fabricating organic field effect transistors because of the anisotropic nature of charge transport in organic semiconducting materials.     

Controlling the shape of the molecular weight distribution for tailored tensile and rheological properties in thermoplastics and thermoplastic elastomers

Thermoplastics and thermoplastic elastomers compose roughly 80 percent of all polymeric materials manufactured today and play an important role in numerous sectors of modern society. While the effects of molecular weight and dispersity (Ð) on the tensile and rheological properties of these materials are well-known, only recent studies have evidenced the profound influence of the shape of the molecular weight distribution (MWD) on polymer properties. This development is largely due to the emergence of new synthetic strategies to control higher moments of the MWD. In this Perspective, we describe recent advancements by our group in understanding the effect of MWD shape on the mechanical and rheological properties of thermoplastics and thermoplastic elastomers. We highlight means to exploit MWD shape for improved processability and performance and discuss future directions in this field.     

Pharmacological Role of Functionalized Gold Nanoparticles in Disease Applications

Gold has always been regarded as a symbol of nobility, and its shiny golden appearance has always attracted the attention of many people. Gold has good ductility, molecular recognition properties, and good biocompatibility. At present, gold is being used in many fields. When gold particles are as small as several nanometers, their physical and chemical properties vary with their size in nanometers. The surface area of a nano-sized gold surface has a special effect. Therefore, gold nanoparticles can, directly and indirectly, give rise to different biological activities. For example, if the surface of the gold is sulfided. Various substances have a strong chemical reactivity and are easy to combine with sulfhydryl groups; hence, nanogold is often used in biomedical testing, disease diagnosis, and gene detection. Nanogold is easy to bind to proteins, such as antibodies, enzymes, or cytokines. In fact, scientists use nanogold to bind special antibodies, as a tool for targeting cancer cells. Gold nanoparticles are also directly cytotoxic to cancer cells. For diseases caused by inflammation and oxidative damage, gold nanoparticles also have antioxidant and anti-inflammatory effects. Based on these unique properties, gold nanoparticles have become the most widely studied metal nanomaterials. Many recent studies have further demonstrated that gold nanoparticles are beneficial for humans, due to their functional pharmacological properties in a variety of diseases. The content of this review will be the application of gold nanoparticles in treating or diagnosing pressing diseases, such as cancers, retinopathy, neurological diseases, skin disorders, bowel diseases, bone cartilage disorders, cardiovascular diseases, infections, and metabolic syndrome. Gold nanoparticles have shown very obvious therapeutic and application potential.     

Liquid Chromatography of Aspirin,Salicylic Acid and Acetic Acid on Cation Exchange Resin

A 8% cross-linked sulfonated polystyrene cation exchanger in the hydrogen or sodium form was used as stationary phase for the chromatography of aspirin, salicylic acid and acetic acid. The eluent is 0.02 M mineral acids or their sodium salts in aqueous ethanol. Phosphoric acid, nitric acid or sulfuric acid added in aqueous ethanol eluent made successful separation of aspirin, salicylic acid and acetic acid on hydrogen form cation exchanger.     

Dynamic kinetic asymmetric synthesis of five contiguous stereogenic centers by sequential organocatalytic stetter and Michael-aldol reaction: enantioselective synthesis of fully substituted cyclopentanols bearing a quaternary stereocenter

A synthesis of fully substituted cyclopentanes bearing a quaternary carbon center and five contiguous stereogenic centers has been achieved by sequential organocatalyzed Stetter and Michael-Aldol reactions of heteroaromatic aldehydes, nitroalkenes, and α,β-unsaturated aldehydes via the [1 + 2 + 2] annulation strategy with dynamic kinetic asymmetric transformation and excellent enantioselectivities (up to >99% ee).     

Considerations of single-machine scheduling with deteriorating jobs

This paper considers some scheduling problems with deteriorating jobs. The objectives are to minimize the makespan, the total completion time, the total absolute deviation of completion time, the earliness, tardiness, and due date penalty, the sum of earliness penalties subject to no tardy jobs, respectively. We also explore two resource constrained scheduling problems: how to minimize the resource consumption with makespan constraints and how to minimize the makespan with the total resource consumption constraints. Several polynomial time algorithms are proposed to optimally solve the problems with the above objective functions.     

Polarization-dependent optical tuning of focal intensity of liquid crystal polymer microlens array

This work demonstrates the feasibility of a microlens array (MLA) with a focal intensity that can be optically tuned by controlling the polarization of incident light. The proposed MLA has a focusing unit based on birefringent liquid crystalline polymer (LCP) and a tuning unit with a photo-alignment layer for controlling the polarization state of incident laser light. The optically variable refractive indices of LCP allow a positive or negative MLA to be realized by controlling the polarization of the incident light.     

Gold nanoparticle-based inductively coupled plasma mass spectrometry amplification and magnetic separation for the sensitive detection of a virus-specific RNA sequence

We have developed a sensitive gold nanoparticle (AuNP)-based inductively coupled plasma mass spectrometry (ICP-MS) amplification and magnetic separation method for the detection of oligonucleotide sequences. The assay relies on (i) the sandwich-type binding of two designed probe sequences that specifically recognize the target oligonucleotide sequences, (ii) magnetic bead separation, and (iii) AuNP-based ICP-MS amplification detection. To enhance the analytical signal and minimize the background signal resulting from nonspecific binding, we performed a series of experiments to evaluate the effects of various parameters (the concentration of the capture probe; the time required for hybridization; the number of washings required to eliminate nonspecific binding) on the oligonucleotide detection. Under the optimized conditions, the detection limit was 80zmol (corresponding to 1.6fM of the target sequence in a sample volume of 50μL). Moreover, it employs a shorter hybridization step and ICP-MS, this procedure is relatively simple and rapid (ca. 1.5h). Based on the analytical results obtained using complementary and mismatched sequences, our method exhibits good performance in distinguishing complementary and random oligonucleotides. Compared with the "gold standard" methodology (plaque assay) for the quantification of dengue virus, our method has the capability to allow early detection of dengue virus in complicated and small-volume samples, with high specificity, good analytical sensitivity, and superior time-effectiveness.