Biodegradable nanoparticle flocculates for dry powder aerosol formulation

Uncontrolled agglomeration presents a formidable encumbrance to nanoparticle formulation as a dry powder for inhalation therapy. Spray-drying and freeze-drying of nanosuspensions has demonstrated some success in creating dry powders composed of agglomerated nanoparticles with appropriate aerodynamic properties. These controlled drying processes, however, may require an undesirable amount of excipient to maintain an active therapeutic while generating dry powders and may not offer the desired control over agglomerate size and aerosolizability. As a potential alternative approach, a method for flocculating nanoparticles in solution followed by freeze-drying is reported. Biodegradable poly(DL-lactic-co-glycolic acid) nanoparticles were self-assembled into flocs via electrostatic interactions between nanoparticles coated with oppositely charged polyelectrolytes. The size of the nanoparticle flocs was readily controlled by manipulating the mixing ratio of charged nanoparticles. Freeze-drying the flocculated nanoparticles produced dry powders exhibiting low density (approximately 0.1 g/cm3), a weblike morphology, and desirable aerodynamic properties suited for dry powder aerosols.     

A regio- and stereoselective approach to quaternary centers from chiral trisubstituted aziridines

A thorough investigation of a regio- and stereospecific aziridine ring opening reaction presents new synthetic technology for the construction of a variety of quaternary beta-substituted-alpha-amino functional groups. Mild, metal-free reaction conditions allow for application in highly functionalized systems. This reaction has been applied to the challenging stereoselective formation of tertiary alkyl-aryl ethers. The strategy for the formation of these hindered ethers has been investigated using a variety of functionalized aziridines and phenols to determine the scope of the reaction. Other nucleophiles, such as thiolate, azide, and chloride, have also been examined to encompass the synthesis of a broader range of functionalities. This aziridine ring opening reaction manifold has demonstrated utility in assembling: beta-substituted-alpha-amino carboxamides, beta-substituted-alpha-amino esters, beta-substituted-alpha-amino silyl ethers, beta-thio-alpha-amino carboxamides, beta-azido-alpha-amino carboxamides, and beta-halo-alpha-amino carboxamides. Studies to probe the effect of the aziridine substitution patterns show that alkyl aziridines display similar reactivity to alkynyl aziridines, giving insight into mechanistic possibilities.     

Pincer-Supported Gallium Complexes for the Catalytic Hydroboration of Aldehydes,Ketones and Carbon Dioxide

Gallium hydrides stabilised by primary and secondary amines are scarce due to their propensity to eliminate dihydrogen. Consequently, their reactivity has received limited attention. The synthesis of two novel gallium hydride complexes HGa(THF)[ON(H)O] and H₂Ga[μ²-ON(H)O]Ga[ON(H)O] ([ON(H)O]²⁻=N,N-bis(3,5-di-tert-butyl-2-phenoxy)amine) is described and their reactivity towards aldehydes and ketones is explored. These reactions afford alkoxide-bridged dimers through 1,2-hydrogallation reactions. The gallium hydrides can be regenerated through Ga−O/B−H metathesis from the reaction of such dimers with pinacol borane (HBpin) or 9-borabicyclo[3.3.1]nonane (9-BBN). These observations allowed us to target the catalytic reduction of carbonyl substrates (aldehydes, ketones and carbon dioxide) with low catalyst loadings at room temperature.     

A coordination polymer strategy for anion encapsulation: anion-pi interactions in (4,4) nets formed from Ag(I) salts and a flexible pyrimidine ligand

Anions encapsulated by a uniform mode of anion-pi binding in isomorphous (4,4) nets formed from Ag(I) salts and bis(4-pyrimidylmethyl)sulfide appear to be structurally directing.     

Fidelity enhancement by logical qubit encoding

We demonstrate coherent control of two logical qubits encoded in a decoherence free subspace (DFS) of four dipolar-coupled protons in an NMR quantum information processor. A pseudopure fiducial state is created in the DFS, and a unitary logical qubit entangling operator evolves the system to a logical Bell state. The four-spin molecule is partially aligned by a liquid crystal solvent, which introduces strong dipolar couplings among the spins. Although the system Hamiltonian is never fully specified, we demonstrate high fidelity control over the logical degrees of freedom. In fact, the DFS encoding leads to higher fidelity control than is available in the full four-spin Hilbert space.     

Rapid quick,easy, cheap,effective, rugged,and safe extraction with novel phospholipid cleanup: A streamlined ultra high performance liquid chromatography with ultraviolet detection approach for screening polycyclic aromatic hydrocarbons in avian blood cells and plasma

A streamlined method has been developed for the isolation and analysis of polycyclic aromatic hydrocarbons in avian blood cells and plasma utilizing quick, easy, cheap, effective, rugged, and safe extraction in combination with novel phospholipid cleanup technology. A variety of traditional extraction and cleanup techniques have been employed in the preparation and analysis of polycyclic aromatic hydrocarbonsin a variety of matrices; liquid–liquid partitioning, solid‐phase extractions, gel permeation chromatography, and column chromatography are all effective techniques, however they are laborious and time consuming processes that require large amounts of solvent. Using quick, easy, cheap, effective, rugged, and safe extraction coupled with phospholipid cleanup, samples can be quickly screened while maintaining high throughput and sensitivity. With a liquid chromatography approach, analysis times may be kept short at 16 min while maintaining high analyte recovery. Recoveries in quality control samples ranged from 70 to 109%, with average surrogate recoveries of 80.6 ± 1.10%. The result of using a quick, easy, cheap, effective, rugged, and safe extraction approach in conjunction with phospholipid cleanup is a methodology that significantly reduces sample preparation time and solvent use while maintaining high sensitivity and reproducibility.     

The Influence of C(sp3)H–Selenium Interactions on the 77Se NMR Quantification of the π-Accepting Properties of Carbenes

Selenium NMR has become a standard tool for scaling the π-accepting character of carbenes. Herein, we highlight that non-classical hydrogen bonding (NCHB), likely resulting from hyperconjugation, can play a significant role in the carbene–selenium ⁷⁷Se NMR chemical shift, thus triggering a non-linear behavior of the Se-Scale.     

Practical aspects of using Hertzian ring crack initiation to measure surface flaw densities in glasses: influence of humidity,friction and searched areas

Ring crack initiation loads on glass, using spherical Tungsten carbide (WC) and glass (G) indenters, are measured and analysed. Our measurements demonstrate that environmental humidity plays a key role in determining the load to fracture; experiments conducted without controlling this variable cannot be used to obtain material properties. The role of friction is explicitly considered for dissimilar (WC–G) elastic contacts. For this material pair, the stresses at fracture are well described by a boundary lubrication value of friction coefficient. The fracture loads are used in a fracture-mechanics formulation to calculate crack sizes on glass surfaces. The ‘searched-area’ concept for dissimilar contacts is described, and used to provide crack density values for these surfaces.     

An analysis of SCF and geometry convergence for diatomic molecules

A geometry and SCF convergence study of Hartree-Fock calculations using the 6-31G* basis set is carried out on the set of all possible diatomic molecules formed from atoms with Z≤36. The utility of Hartree-Fock calculations using the smaller STO-3G basis set to improve the convergence behavior is demonstrated.